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Sample records for neretva river delta

  1. Coastal aquifer groundwater dynamics and salt intrusion: Monitoring system of river Neretva delta

    NASA Astrophysics Data System (ADS)

    Srzić, Veljko; Vranješ, Mijo; Deković, Jure; Romić, Davor; Zovko, Monika; Milin, Marin

    2017-04-01

    River Neretva delta is located in southern part of Croatia and creates a complex surface- groundwater system influenced by tidal forces characteristic for Adriatic Sea and river Neretva whose discharge varies from 70 - 2700 m3/s over the year. From agricultural point of view, area is used widely for fruit production which implies existence and functionality of complex drainage system consisted of a net of lateral channels and pumping station plants with the capacity of app. 25 m3/s. Area of interest covers app 3500 ha and is bounded by river Neretva from North and Adriatic sea from West. Southern and eastern boundaries are dominantly karstic hills. Lover aquifer is confined with app depth of 65 m, made of fine gravel. Aquitard is a 15 m height layer of clay. Upper aquifer in unconfined with depth of app 10-20 m. Inside the area of interest there are 8 wells installed (each aquifer 4) measuring piezometric head on hourly/daily temporal scale. Sea level measurements are also made capturing for long term tidal oscillations. Discharge measurements are made few km downstream from hydropower plant Mostar (Bosnia and Herzegovina), while three meteorological stations for rainfall measurements are located at the area boundaries. Salt water concentration, pH and resistivity values have been measured locally, app 6 times per year for last 10 years. Results imply confined aquifer is dominantly influenced by the sea level while tidal effects are noticed 9 km upstream the river Neretva with delay of 9-12 minutes compared to sea level. Salt water cline inside the river is related to tidal effects and river discharge, with potential presence at distances of more than 15 km upstream from the sea. Salt water intrusion dominantly occurs through confined aquifer while vertical transport of salt is supposed to be enhanced by the effects of drainage system.

  2. Growth of Cobitis narentana Karaman, 1928 in the Neretva River, Croatia.

    PubMed

    Zanella, Davor; Mrakovcić, Milorad; Schneider, Daniela; Mustafić, Perica; Caleta, Marko; Radić, Ivana

    2003-01-01

    Age and growth of Cobitis narentana were examined in the delta of Neretva River in Croatia. Maximum observed length was 100.4 mm for females and 63.5 for males. Five age classes were determined, from 0+ to 4+. For both females (61.0%) and males (53.8%), the greatest proportion of specimens were in the 1+ age category. Growth was faster in males in the first year of life, while females grew at a faster rate than males after the first year. The Fulton condition factor was determined (CF=0.588 for males and CF=0.618 for females). The length-weight relationship was determined for females (W=8xl0(-5)L2.9325) and males (W=2x l0(-5)L2.6431). The parameter b was calculated as less than b=3.0, thus establishing that growth in both males and females was allometric. Growth rate was determined using the von Bertalanffy growth rate curves for females (Lt=101.1[ 1-e(-0.5(t-0.94)]; r2=0.99) and for males (Lt=65.3[1-e(-0.54(t-2.27)]; r2=0.97). The resulting growth rate coefficient (K) was found to be slightly higher in males (0.54) than in females (0.5).

  3. Nile River Delta, Egypt

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The Nile River Delta of Egypt (30.0N, 31.0E) irrigated by the Nile River and its many distributaries, is some of the richest farm land in the world and home to some 45 million people, over half of Egypt's population. The capital city of Cairo is at the apex of the delta. Just across the river from Cairo can be seen the ancient three big pyramids and sphinx at Giza and the Suez Canal is just to the right of the delta.

  4. Nile River Delta, Egypt

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The Nile River Delta of Egypt (30.0N, 31.0E) irrigated by the Nile River and its many distributaries, is some of the richest farm land in the world and home to some 45 million people, over half of Egypt's population. The capital city of Cairo is at the apex of the delta. Just across the river from Cairo can be seen the ancient three big pyramids and sphinx at Giza and the Suez Canal is just to the right of the delta.

  5. Modeling river delta formation

    PubMed Central

    Seybold, Hansjörg; Andrade, José S.; Herrmann, Hans J.

    2007-01-01

    A model to simulate the time evolution of river delta formation process is presented. It is based on the continuity equation for water and sediment flow and a phenomenological sedimentation/erosion law. Different delta types are reproduced by using different parameters and erosion rules. The structures of the calculated patterns are analyzed in space and time and compared with real data patterns. Furthermore, our model is capable of simulating the rich dynamics related to the switching of the mouth of the river delta. The simulation results are then compared with geological records for the Mississippi River. PMID:17940031

  6. Nile River Delta, Egypt

    NASA Image and Video Library

    1984-10-13

    The Nile River Delta of Egypt (30.0N, 31.0E) irrigated by the Nile River and its many distributaries, is some of the richest farm land in the world and home to some 45 million people, over half of Egypt's population. The capital city of Cairo is at the apex of the delta. Just across the river from Cairo can be seen the ancient three big pyramids and sphinx at Giza and the Suez Canal is just to the right of the delta.

  7. Connectivity in river deltas

    NASA Astrophysics Data System (ADS)

    Passalacqua, P.; Hiatt, M. R.; Sendrowski, A.

    2016-12-01

    Deltas host approximately half a billion people and are rich in ecosystem diversity and economic resources. However, human-induced activities and climatic shifts are significantly impacting deltas around the world; anthropogenic disturbance, natural subsidence, and eustatic sea-level rise are major causes of threat to deltas and in many cases have compromised their safety and sustainability, putting at risk the people that live on them. In this presentation, I will introduce a framework called Delta Connectome for studying connectivity in river deltas based on different representations of a delta as a network. Here connectivity indicates both physical connectivity (how different portions of the system interact with each other) as well as conceptual (pathways of process coupling). I will explore several network representations and show how quantifying connectivity can advance our understanding of system functioning and can be used to inform coastal management and restoration. From connectivity considerations, the delta emerges as a leaky network that evolves over time and is characterized by continuous exchanges of fluxes of matter, energy, and information. I will discuss the implications of connectivity on delta functioning, land growth, and potential for nutrient removal.

  8. Zambezi River Delta

    NASA Image and Video Library

    2013-08-29

    It drains a watershed that spans eight countries and nearly 1.6 million square kilometers 600,000 square miles. The Zambezi also Zambeze is the fourth largest river in Africa, and the largest east-flowing waterway. The Operational Land Imager on the Landsat 8 satellite acquired this natural-color image of the Zambezi Delta on August 29, 2013. Sandbars and barrier spits stretch across the mouths of the delta, and suspended sediment extends tens of kilometers out into the sea. The sandy outflow turns the coastal waters to a milky blue-green compared to the deep blue of open water in the Indian Ocean. The Zambezi Delta includes 230 kilometers of coastline fronting 18,000 square kilometers (7,00 square miles) of swamps, floodplains, and even savannahs (inland). The area has long been prized by subsistence fishermen and farmers, who find fertile ground for crops like sugar and fertile waters for prawns and fish. Two species of endangered cranes and one of the largest concentration of buffalo in Africa -- among many other species of wildlife -- have found a haven in this internationally recognized wetland. However, the past six decades have brought great changes to the Zambezi Delta, which used to pour more water and sediment off of the continent. Hydropower dams upstream-most prominently, the Kariba and the Cahora Bassa-greatly reduce river flows during the wet season; they also trap sediments that would otherwise flow downstream. The result has been less water reaching the delta and the floodplains, which rely on pulses of nutrients and sediments from annual (and mostly benign) natural flooding. The change in the flow of the river affects freshwater availability and quality in the delta. Strong flows push fresh water further out into the sea and naturally keep most of a delta full of fresh (or mostly fresh) water. When that fresh flow eases, the wetlands become drier and more prone to fire. Salt water from the Indian Ocean also can penetrate further into the marsh

  9. Mississippi River Delta

    NASA Image and Video Library

    2002-06-11

    As the Mississippi River enters the Gulf of Mexico, it loses energy and dumps its load of sediment that it has carried on its journey through the mid continent. This pile of sediment, or mud, accumulates over the years building up the delta front. As one part of the delta becomes clogged with sediment, the delta front will migrate in search of new areas to grow. The area shown on this image is the currently active delta front of the Mississippi. The migratory nature of the delta forms natural traps for oil. Most of the land in the image consists of mud flats and marsh lands. There is little human settlement in this area due to the instability of the sediments. The main shipping channel of the Mississippi River is the broad stripe running northwest to southeast. This image was acquired on May 24, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet. http://photojournal.jpl.nasa.gov/catalog/PIA03497

  10. Mackenzie River Delta, Canada

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The Mackenzie River in the Northwest Territories, Canada, with its headstreams the Peace and Finley, is the longest river in North America at 4241 km, and drains an area of 1,805,000 square km. The large marshy delta provides habitat for migrating Snow Geese, Tundra Swans, Brant, and other waterfowl. The estuary is a calving area for Beluga whales. The Mackenzie (previously the Disappointment River) was named after Alexander Mackenzie who travelled the river while trying to reach the Pacific in 1789.

    The image was acquired on August 4, 2005, covers an area of 55.8 x 55.8 km, and is located at 68.6 degrees north latitude, 134.7 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  11. Colorado River Delta

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Colorado River ends its 2330 km journey in the Gulf of Mexico in Baja California. The heavy use of the river as an irrigation source for the Imperial Valley has dessicated the lower course of the river in Mexico such that it no longer consistently reaches the sea. Prior to the mid 20th century, the Colorado River Delta provided a rich estuarine marshland that is now essentially desiccated, but nonetheless is an important ecological resource.

    The image was acquired May 29, 2006, covers an area of 44.3 x 57.5 km, and is located at 32.1 degrees north latitude, 115.1 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  12. Colorado River Delta

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Colorado River ends its 2330 km journey in the Gulf of Mexico in Baja California. The heavy use of the river as an irrigation source for the Imperial Valley has dessicated the lower course of the river in Mexico such that it no longer consistently reaches the sea. Prior to the mid 20th century, the Colorado River Delta provided a rich estuarine marshland that is now essentially desiccated, but nonetheless is an important ecological resource.

    The image was acquired May 29, 2006, covers an area of 44.3 x 57.5 km, and is located at 32.1 degrees north latitude, 115.1 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  13. Mackenzie River Delta, Canada

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The Mackenzie River in the Northwest Territories, Canada, with its headstreams the Peace and Finley, is the longest river in North America at 4241 km, and drains an area of 1,805,000 square km. The large marshy delta provides habitat for migrating Snow Geese, Tundra Swans, Brant, and other waterfowl. The estuary is a calving area for Beluga whales. The Mackenzie (previously the Disappointment River) was named after Alexander Mackenzie who travelled the river while trying to reach the Pacific in 1789.

    The image was acquired on August 4, 2005, covers an area of 55.8 x 55.8 km, and is located at 68.6 degrees north latitude, 134.7 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  14. Ganges River Delta

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Ganges River forms an extensive delta where it empties into the Bay of Bengal. The delta is largely covered with a swamp forest known as the Sunderbans, which is home to the Royal Bengal Tiger. It is also home to most of Bangladesh, one of the world's most densely populated countries. Roughly 120 million people live on the Ganges Delta under threat of repeated catastrophic floods due to heavy runoff of meltwater from the Himalayas, and due to the intense rainfall during the monsoon season. This image was acquired by Landsat 7's Enhanced Thematic Mapper plus (ETM+) sensor on February 28, 2000. This is a false-color composite image made using green, infrared, and blue wavelengths. Image provided by the USGS EROS Data Center Satellite Systems Branch

  15. Hugli River Delta, India

    NASA Image and Video Library

    2001-10-22

    The western-most part of the Ganges Delta is seen in this 54.5 by 60 km ASTER sub-scene acquired on January 6, 2005. The Hugli River branches off from the Ganges River 300 km to the north, and flows by the city of Calcutta before emptying into the Bay of Bengal. High sediment load is evident by the light tan colors in the water, particularly downstream from off-shore islands. The deep green colors of some of these islands are mangrove swamps. The image is centered at 21.9 degrees north latitude, 88 degrees east longitude. http://photojournal.jpl.nasa.gov/catalog/PIA11158

  16. Mississippi River Delta

    NASA Technical Reports Server (NTRS)

    2002-01-01

    As the Mississippi River enters the Gulf of Mexico, it loses energy and dumps its load of sediment that it has carried on its journey through the mid continent. This pile of sediment, or mud, accumulates over the years building up the delta front. As one part of the delta becomes clogged with sediment, the delta front will migrate in search of new areas to grow. The area shown on this image is the currently active delta front of the Mississippi. The migratory nature of the delta forms natural traps for oil. Most of the land in the image consists of mud flats and marsh lands. There is little human settlement in this area due to the instability of the sediments. The main shipping channel of the Mississippi River is the broad stripe running northwest to southeast.

    This image was acquired on May 24, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet.

    ASTER is one of five Earth-observing instruments launched December 18,1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. The Terra mission is part of NASA's Earth Science Enterprise, a long-term research and technology program designed to examine Earth's land, oceans, atmosphere, ice and life as a total integrated system.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping

  17. Ganges River Delta, Bangladesh, India

    NASA Image and Video Library

    1994-11-14

    The Ganges River Delta is the largest inter-tidal delta in the world. With its extensive mangrove mud flats, swamp vegetation and sand dunes, it is characteristic of many tropical and subtropical coasts. As seen in this photograph, the tributaries and distributaries of the Ganges and Brahmaputra Rivers deposit huge amounts of silt and clay that create a shifting maze of waterways and islands in the Bay of Bengal.

  18. Ganges River Delta, Bangladesh, India

    NASA Technical Reports Server (NTRS)

    1994-01-01

    The Ganges River Delta is the largest inter-tidal delta in the world. With its extensive mangrove mud flats, swamp vegetation and sand dunes, it is characteristic of many tropical and subtropical coasts. As seen in this photograph, the tributaries and distributaries of the Ganges and Brahmaputra Rivers deposit huge amounts of silt and clay that create a shifting maze of waterways and islands in the Bay of Bengal.

  19. Mackenzie River Delta, Canada

    NASA Image and Video Library

    2007-12-11

    The Mackenzie River in the Northwest Territories, Canada, with its headstreams the Peace and Finley, is the longest river in North America. This image was acquired by NASA Terra satellite on August 4, 2005.

  20. Yellow River Delta, China

    NASA Image and Video Library

    2009-12-08

    The Yellow River is the second-longest river in China, and the sixth longest in the world and makes many dramatic shifts over time. This image was taken with the ASTER instrument aboard NASA Terra spacecraft in 2009.

  1. The Mechanics of River Avulsions on Deltas

    NASA Astrophysics Data System (ADS)

    Ganti, Vamsi; Chadwick, Austin; Hassenruck-Gudipati, Hima; Lamb, Michael

    2017-04-01

    River deltas are highly dynamic, often fan-shaped depositional systems that form when rivers drain into a standing body of water. They host over a half billion people worldwide and are currently under threat of drowning and destruction by relative sea-level rise, subsidence, and anthropogenic interference. Many river deltas develop planform fan shapes through avulsions, whereby major river channel shifts occur via "channel jumping" about a persistent spatial node, thus determining their fundamental length scale. Emerging theories suggest that the size of deltas is set by backwater hydrodynamics; however, these ideas are difficult to test on natural deltas, which evolve on centennial to millennial timescales. Here, using physical experiments coupled with observations of the dynamics of modern deltaic evolution, we show that deltas grow through successive deposition of lobes that maintain a constant size that scales with backwater hydrodynamics. The preferential avulsion node in our experiments is a consequence of multiple river floods and Froude-subcritical flows that produce persistent nonuniform flows and a peak in net channel deposition within the backwater zone of the coastal river. Moreover, because the backwater hydrodynamics are controlled by the downstream boundary condition of constant sea level, the backwater-mediated avulsion sites translate seaward in step with shoreline progradation. In contrast, experimental deltas without multiple floods produce flows with uniform velocities and delta lobes that lack a characteristic size. Results have broad applications to sustainable management of deltas and for decoding their stratigraphic record on Earth and Mars.

  2. Tidal controls on river delta morphology

    NASA Astrophysics Data System (ADS)

    Hoitink, A. J. F.; Wang, Z. B.; Vermeulen, B.; Huismans, Y.; Kästner, K.

    2017-09-01

    River delta degradation has been caused by extraction of natural resources, sediment retention by reservoirs, and sea-level rise. Despite global concerns about these issues, human activity in the world’s largest deltas intensifies. Harbour development, construction of flood defences, sand mining and land reclamation emerge as key contemporary factors that exert an impact on delta morphology. Tides interacting with river discharge can play a crucial role in the morphodynamic development of deltas under pressure. Emerging insights into tidal controls on river delta morphology suggest that--despite the active morphodynamics in tidal channels and mouth bar regions--tidal motion acts to stabilize delta morphology at the landscape scale under the condition that sediment import during low flows largely balances sediment export during high flows. Distributary channels subject to tides show lower migration rates and are less easily flooded by the river because of opposing non-linear interactions between river discharge and the tide. These interactions lead to flow changes within channels, and a more uniform distribution of discharge across channels. Sediment depletion and rigorous human interventions in deltas, including storm surge defence works, disrupt the dynamic morphological equilibrium and can lead to erosion and severe scour at the channel bed, even decades after an intervention.

  3. Paraiba do Sul river delta, Brazil

    NASA Image and Video Library

    1996-01-20

    STS072-738-019 (11-20 Jan. 1996) --- The Delta of the Paraiba do Sul River, northeast of Rio de Janeiro, Brazil, stands out in this 70mm frame exposed from the Earth-orbiting Space Shuttle Endeavour. The brown color of the river water and offshore sediment plume show that the river is in flood stage. This delta attracts much attention from orbit because of its prominent beach ridges either side of the river mouth. River sediment from inland supplies the material which is redistributed by coastal currents to form the parallel beach ridges. The lower 20 miles of the river appear in this scene. The river flows into the Atlantic in an easterly direction.

  4. From Natural to Design River Deltas

    NASA Astrophysics Data System (ADS)

    Giosan, Liviu

    2016-04-01

    Productive and biologically diverse, deltaic lowlands attracted humans since prehistory and may have spurred the emergence of the first urban civilizations. Deltas continued to be an important nexus for economic development across the world and are currently home for over half a billion people. But recently, under the double whammy of sea level rise and inland sediment capture behind dams, they have become the most threatened coastal landscape. Here I will address several deceptively simple questions to sketch some unexpected answers using example deltas from across the world from the Arctic to the Tropics, from the Danube to the Indus, Mississippi to Godavari and Krishna, Mackenzie to Yukon. What is a river delta? What is natural and what is not in a river delta? Are the geological and human histories of a delta important for its current management? Is maintaining a delta the same to building a new one? Can we design better deltas than Nature? These answers help us see clearly that survival of deltas in the next century depends on human intervention and is neither assured nor simple to address or universally applicable. Empirical observations on the hydrology, geology, biology and biochemistry of deltas are significantly lagging behind modeling capabilities endangering the applicability of numerical-based reconstruction solutions and need to be ramped up significantly and rapidly across the world.

  5. Lena River delta formation during the Holocene

    NASA Astrophysics Data System (ADS)

    Bolshiyanov, D.; Makarov, A.; Savelieva, L.

    2015-01-01

    The Lena River delta, the largest delta of the Arctic Ocean, differs from other deltas because it consists mainly of organomineral sediments, commonly called peat, that contain a huge organic carbon reservoir. The analysis of delta sediment radiocarbon ages showed that they could not have formed as peat during floodplain bogging; rather, they accumulated when Laptev Sea water level was high and green mosses and sedges grew and were deposited on the surface of flooded marshes. The Lena River delta formed as organomineral masses and layered sediments accumulated during transgressive phases when sea level rose. In regressive phases, the islands composed of these sediments and other, more ancient islands were eroded. Each new sea transgression led to further accumulation of layered sediments. As a result of alternating transgressive and regressive phases, the first alluvial-marine terrace formed, consisting of geological bodies of different ages. Determining the formation age of different areas of the first terrace and other marine terraces on the coast allowed the periods of increasing (8000-6000 BP (years before present), 4500-4000, 2500-1500, and 400-200 BP) and decreasing (5000, 3000, and 500 BP) Laptev Sea levels to be distinguished in the Lena Delta area.

  6. Coastal Zone and River Delta Studies

    NASA Technical Reports Server (NTRS)

    1971-01-01

    Remote sensing techniques are proposed for the development of a California coastal land use classification system which depicts and reflects essential parameters of environmental conditions and quality. Included in the earth resources survey is the Sacramento - San Joaquin River Delta and its complex hydrologic system which links saline waters of the San Francisco Bay with the Central Valley watershed.

  7. Tidal river dynamics: Implications for deltas

    NASA Astrophysics Data System (ADS)

    Hoitink, A. J. F.; Jay, D. A.

    2016-03-01

    Tidal rivers are a vital and little studied nexus between physical oceanography and hydrology. It is only in the last few decades that substantial research efforts have been focused on the interactions of river discharge with tidal waves and storm surges into regions beyond the limit of salinity intrusion, a realm that can extend inland hundreds of kilometers. One key phenomenon resulting from this interaction is the emergence of large fortnightly tides, which are forced long waves with amplitudes that may increase beyond the point where astronomical tides have become extinct. These can be larger than the linear tide itself at more landward locations, and they greatly influence tidal river water levels and wetland inundation. Exploration of the spectral redistribution and attenuation of tidal energy in rivers has led to new appreciation of a wide range of consequences for fluvial and coastal sedimentology, delta evolution, wetland conservation, and salinity intrusion under the influence of sea level rise and delta subsidence. Modern research aims at unifying traditional harmonic tidal analysis, nonparametric regression techniques, and the existing understanding of tidal hydrodynamics to better predict and model tidal river dynamics both in single-thread channels and in branching channel networks. In this context, this review summarizes results from field observations and modeling studies set in tidal river environments as diverse as the Amazon in Brazil, the Columbia, Fraser and Saint Lawrence in North America, the Yangtze and Pearl in China, and the Berau and Mahakam in Indonesia. A description of state-of-the-art methods for a comprehensive analysis of water levels, wave propagation, discharges, and inundation extent in tidal rivers is provided. Implications for lowland river deltas are also discussed in terms of sedimentary deposits, channel bifurcation, avulsion, and salinity intrusion, addressing contemporary research challenges.

  8. Quantitative Metrics of Robustness in River Deltas

    NASA Astrophysics Data System (ADS)

    Foufoula-Georgiou, E.; Tejedor, A.; Longjas, A.; Zaliapin, I. V.

    2014-12-01

    Deltas are landforms with channels that deliver water, sediment and nutrient fluxes from rivers to oceans or inland water bodies via multiple pathways. We conceptualize a delta channel network as a rooted acyclic directed graph where channels are modeled by edges and junctions by vertices. We use spectral graph theory - mainly the geometry of the null space of the directed weighted graph Laplacian - to establish a quantitative framework for extracting important structural and dynamics-related information from river deltas. Using this information, we introduce refined metrics of system complexity, such as entropy. Entropy has been proven to be an important measure of the amount of uncertainty in stochastic systems, and therefore a surrogate of the capacity of the system to undergo changes. Here we present an entropic approach to evaluate the robustness of deltas, showing how the two components of entropy: mutual information and conditional entropy can be interpreted in this framework. We also present other metrics that include, among others, resistance distance and number of alternative paths, which quantify the structural complexity of the system. We use these metrics to better classify deltaic systems, quantify their resilience and propose possible management scenarios.

  9. The Atchafalaya River Delta. Report 7. Analytical Analysis of the Development of the Atchafalaya River Delta.

    DTIC Science & Technology

    1985-09-01

    guide. Statistical Analysis System SAS Institute Inc., Cary, N. C. Scheid, F. 1968. Numerical analysis . Schaum’s Outline Series, Schaum Publishing Co...rD-i64 931 THE ATCHAFALAYA RIVER DELTA REPORT 7 ANALYTICAL 113 ANALYSIS OF THE DEVELOPHE..(U) LOUISIANA S ATE UNIV U UtjBATON ROUGE COASTAL...Field data per- taining to our analytical analysis of delta development were gathered from various sources and are outlined in the following sections

  10. Zooplankton community and hydrographical properties of the Neretva Channel (eastern Adriatic Sea)

    NASA Astrophysics Data System (ADS)

    Vidjak, Olja; Bojanić, Natalia; Kušpilić, Grozdan; Ninčević Gladan, Živana; Tičina, Vjekoslav

    2007-12-01

    Temporal and spatial variability of micro and mesozooplankton was studied in 1998 and 1999 at four stations in the Neretva Channel area influenced by the Neretva river and the open waters of the south Adriatic Sea. The area is orthophosphate limited, but an excessive accumulation of land derived nitrogen is prevented by phytoplankton uptake and the general circulation pattern. Microzooplankton was dominated by ciliates, with average abundances comparable to other Adriatic channel areas (122 543 ind. l-1). Non-loricate ciliates (NLC) generally peaked in the warmer periods, but a winter increase was evident towards the inner part of the channel. Tintinnid abundances generally increased in autumn. A significant relationship with temperature was not recorded for either protozoan group. An inverse relationship between NLC and salinity might be indirectly caused by their preference for the food abundant surface layer. Mesozooplankton was dominated by copepods, with distinct summer maxima throughout the area and pronounced winter maxima of >10,000 ind. m-3 at the inner stations. The community was predominantly neritic but the open sea waters were important in structuring the mesozooplankton assemblage at all stations during the autumn winter period. Although temperature regulated the seasonal dynamics of most metazoans and the species succession in the copepod community, small omnivorous copepods ( Oncaea media complex, Oithona nana and Euterpina acutifrons) dominated regardless of the season. A trophic link between copepods and ciliates was evident in winter during low phytoplankton biomass.

  11. Elwha River Delta: Geomorphology of a Mixed-Sediment Beach

    NASA Astrophysics Data System (ADS)

    George, D. A.; Warrick, J. J.

    2007-12-01

    The Elwha River drains the Olympic Peninsula of Washington and forms a mixed grain-size delta in the Strait of Juan de Fuca. The Elwha River has been dammed for almost a century, and a pending dam removal project is expected to reconnect upstream sediment sources to the river mouth. Topographic and grain-size mapping of the delta during 1939-2007 is synthesized and the geomorphology and shoreline changes of this system are described. Data sources include historical aerial photographs, airborne LIDAR, semiannual RTK DGPS topographic surveys and grain-size analyses from digital photographs. The delta is divided into three geomorphic regions: west delta, river mouth and east delta. The river mouth is the most complex region due to the river channel movement, side-channels, and bars immediately offshore of the mouth. The east and west delta differ in beach profile and shoreline change rates. The west delta is steep, cuspate and lacks a low-tide terrace. Further, the west delta has exhibited little semi-annual or inter-annual shoreline change. In contrast, the east delta has a steep foreshore, flat low tide terrace that is dominated by cobble, and a consistent trend of erosion during the surveys. These observations can be used to track coastal changes following dam removal on the Elwha River..

  12. Landsat View: Pearl River Delta, China

    NASA Image and Video Library

    2017-09-27

    In 1979, China established two special economic zones around the Pearl River Delta, north of Hong Kong. This image, taken by Landsat 3 on October 19, 1973, shows that the region was rural when the zone was established. Plant-covered land, which is red in this false-color image, dominates the scene. Square grids are agriculture. By January 10, 2003, when Landsat 7 took this image, the Pearl River Delta was a densely populated urban corridor with several large cities. The urban areas are gray in this image. The region is a major manufacturing center with an economy the size of Taiwan’s. As of 2010, the Pearl River Economic Zone had a population of 36 million people. ---- NASA and the U.S. Department of the Interior through the U.S. Geological Survey (USGS) jointly manage Landsat, and the USGS preserves a 40-year archive of Landsat images that is freely available over the Internet. The next Landsat satellite, now known as the Landsat Data Continuity Mission (LDCM) and later to be called Landsat 8, is scheduled for launch in 2013. In honor of Landsat’s 40th anniversary in July 2012, the USGS released the LandsatLook viewer – a quick, simple way to go forward and backward in time, pulling images of anywhere in the world out of the Landsat archive. NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  13. The wave-tide-river delta classification revisited: Introducing the effects of Humans on delta equilibriu

    NASA Astrophysics Data System (ADS)

    Besset, M.; Anthony, E.; Sabatier, F.

    2016-12-01

    The influence of physical processes on river deltas has long been identified, mainly on the basis of delta morphology. A cuspate delta is considered as wave-dominated, a delta with finger-like extensions is characterized as river-dominated, and a delta with estuarine re-entrants is considered tide-dominated (Galloway, 1975). The need for a more quantitative classification is increasingly recognized, and is achievable through quantified combinations, a good example being Syvitski and Saito (2007) wherein the joint influence of marine power - wave and tides - is compared to that of river influence. This need is further justified as deltas become more and more vulnerable. Going forward from the Syvitski and Saito (2007) approach, we confront, from a large database on 60 river deltas, the maximum potential power of waves and the tidal range (both representing marine power), and the specific stream power and river sediment supply reflecting an increasingly human-impacted river influence. The results show that 45 deltas (75%) have levels of marine power that are significantly higher than those of specific stream power. Five deltas have sufficient stream power to counterbalance marine power but a present sediment supply inadequate for them to be statistically considered as river-dominated. Six others have a sufficient sediment supply but a specific stream power that is not high enough for them to be statistically river-dominated. A major manifestation of the interplay of these parameters is accelerated delta erosion worldwide, shifting the balance towards marine power domination. Deltas currently eroding are mainly influenced by marine power (93%), and small deltas (< 300 km2 of deltaic protuberance) are the most vulnerable (82%). These high levels of erosion domination, compounded by accelerated subsidence, are related to human-induced sediment supply depletion and changes in water discharge in the face of the sediment-dispersive capacity of waves and currents.

  14. River diversion could change climate in delta ecosystems

    NASA Astrophysics Data System (ADS)

    When humans divert excessive amounts of water from their natural courses, ensuing impacts on regional and global climate may threaten the fragile ecosystems around the mouths of rivers. David Smith, a geographer at the National Center for Atmospheric Research in Boulder, Colo., is researching this problem by concentrating on river deltas, which are recognized for their fertile soils and abundance of water. As a result, river deltas are also sites of intense agricultural production and high population density.

  15. Growth laws for delta crevasses in the Mississippi River Delta: observations and modeling

    NASA Astrophysics Data System (ADS)

    Yocum, T. A.; Georgiou, I. Y.

    2016-02-01

    River deltas are accumulations of sedimentary deposits delivered by rivers via a network of distributary channels. Worldwide they are threatened by environmental changes, including subsidence, global sea level rise and a suite of other local factors. In the Mississippi River Delta (MRD) these impacts are exemplified, and have led to proposed solutions to build land that include sediment diversions, thereby reinitiating the delta cycle. While economically efficient, there are too few analogs of small deltas aside from laboratory studies, numerical modeling studies, theoretical approaches, and limited field driven observations. Anthropogenic crevasses in the modern delta are large enough to overcome limitations of laboratory deltas, and small enough to allow for "rapid" channel and wetland development, providing an ideal setting to investigate delta development mechanics. Crevasse metrics were obtained using a combination of geospatial tools, extracting key parameters (bifurcation length and width, channel order and depth) that were non-dimensionalized and compared to river-dominated delta networks previously studied. Analysis showed that most crevasses in the MRD appear to obey delta growth laws and delta allometry relationships, suggesting that crevasses do exhibit similar planform metrics to larger Deltas; the distance to mouth bar versus bifurcation order demonstrated to be a very reasonable first order estimate of delta-top footprint. However, some crevasses exhibited different growth metrics. To better understand the hydrodynamic and geomorphic controls governing crevasse evolution in the MRD, we assess delta dynamics via a suite of field observations and numerical modeling in both well-established and newly constructed crevasses. Our analysis suggests that delta development is affected by the relative influence of external (upstream and downstream) and internal controls on the hydrodynamic and sediment transport patterns in these systems.

  16. Water pollution remote sensing for Pearl River Delta

    NASA Astrophysics Data System (ADS)

    Deng, Ruru; Xiong, Shouping; Qin, Yan

    2008-10-01

    Water pollution on the Delta of Pearl River is increasingly serious and to command the fact of pollution is the key of the control. A remote sensing model for water pollution base on single scattering is deduced in this paper. To avoid the effect by turbidity of water, by analysis the characteristics of the energy composition of multiple scattering, a factor of second scattering is deduced to build a double scattering model, and the practical arithmetic for the calculation of the model is put forwarded and then used to the pollution remote sensing over the Pearl River Delta. The precision of the result is validated by the synchronous measured data on water surface. The result of remote sensing showed that all of the North River, East River and West River are polluted in Pearl River Delta, and the most serious pollution is take place around Guang Zhou City and Dong Guan City.

  17. Mississippi River Delta, Louisiana as seen from STS-62

    NASA Image and Video Library

    1994-03-05

    STS062-85-021 (4-18 March 1994) --- The Mississippi River is the largest river system in North America. Its delta is a typical example of the bird's foot class of river deltas. It drains nearly 3 1/2 million square kilometers of real estate and is estimated to carry 2.4 billion kilograms (more than 500 million tons) of sand, silt, and clay to the Gulf of Mexico annually. Most of this sediment is deposited as a delta at the mouth of the river where the velocity of the river water is slowed and its ability to transport sediment is accordingly diminished. Continued deposition at such a site progrades the delta or extends it seaward into the Gulf as much as 150 meters each year until such time as a flooding episode finds a shorter more efficient channel to deliver sediment-laden river waters to the Gulf. At that time the old delta is abandoned and the river begins to build a new delta. In time, compaction of the sediment in the old delta causes it to subside forming first marshes, then bays. This and the modifying effects of coastal waves eventually allow the sea to reclaim much of the temporary land area of the delta. This sequence has repeated itself over and over again at the Mississippi Delta. In this photograph, the present day active Balize delta is shown. According to NASA scientists it is the youngest of the recent delta lobes having begun its seaward pro-gradation only some 600 - 800 years ago. The main channel of the river is 2 kilometers wide and 30 - 40 meters deep. Natural levees here are almost 1 kilometer wide and 3 to 4 meters above sea level. Along the active distributaries of the lower delta, natural levees are less than 100 meters wide and generally less than 0.5 meters above sea level. The bird's foot appearance of deltas such as this is characteristic of low coastal energy conditions - that is, low levels of tidal fluctuation and generally low wave energy. The interdistributary bays are extremely shallow, usually less than a few meters, and contain

  18. Stereo Anaglyphs of River Meanders in Eberswalde Delta

    NASA Image and Video Library

    2007-01-10

    This anaglyph from NASA Mars Reconnaissance Orbiter spacecraft, shows that Eberswalde Delta contains river meanders, which indicate that flowing water was present for an extended period of time. 3D glasses are necessary to view this image.

  19. Ecosystem Services Assessment of the Nemunas River Delta

    EPA Science Inventory

    The concept of ecosystem services recognizes the services, and benefits, provided to people by ecosystems. The Nemunas River Delta, in Lithuania, provides many ecosystem services to the people of the area, including food, fuel, transportation, climate regulation, water purificati...

  20. Ecosystem Services Assessment of the Nemunas River Delta

    EPA Science Inventory

    The concept of ecosystem services recognizes the services, and benefits, provided to people by ecosystems. The Nemunas River Delta, in Lithuania, provides many ecosystem services to the people of the area, including food, fuel, transportation, climate regulation, water purificati...

  1. Altamaha River Delta, Georgia Sea Islands

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The history of sea islands in the Altamaha River delta on the coast of Georgia is revealed in this image produced from data acquired by the Airborne Synthetic Aperture Radar (AIRSAR), developed and operated by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The outlines of long-lost plantation rice fields, canals, dikes and other inlets are clearly defined. Salt marshes are shown in red, while dense cypress and live oak tree canopies are seen in yellow-greens.

    Agricultural development of the Altamaha delta began soon after the founding of the Georgia Colony in 1733. About 25 plantations were located on the low-lying islands and shores by the 19th century, taking advantage of the rich alluvial flow and annual inundation of water required by some crops. The first major crop was indigo; when demand for that faded, rice and cotton took its place. A major storm in 1824 destroyed much of the town of Darien (upper right) and put many of the islands under 20 feet of water. The Civil War ended the plantation system, and many of the island plantations disappeared under heavy brush and new growth pine forests. Some were used as tree farms for paper and pulp industries, while the Butler Island (center left) plantation became a wildlife conservation site growing wild sea rice for migrating ducks and other waterfowl. Margaret Mitchell is reputed to have used the former owner of the Butler Plantation as a basis for the Rhett Butler character in her novel 'Gone With The Wind,' taking the first name from Rhett's Island (lower right).

    These data were obtained during a 1994-95 campaign along the Georgia coast. AIRSAR's ability to detect vegetation canopy density, hydrological features and other topographic characteristics is a useful tool in landscape archaeology. AIRSAR flies aboard a NASA DC-8 based at NASA's Dryden Flight Research Center, Edwards, Calif. The analysis on the data shown was accomplished by Dr. Gary Mckay, Department of Archaeology and Geography, and Ian

  2. Altamaha River Delta, Georgia Sea Islands

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The history of sea islands in the Altamaha River delta on the coast of Georgia is revealed in this image produced from data acquired by the Airborne Synthetic Aperture Radar (AIRSAR), developed and operated by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The outlines of long-lost plantation rice fields, canals, dikes and other inlets are clearly defined. Salt marshes are shown in red, while dense cypress and live oak tree canopies are seen in yellow-greens.

    Agricultural development of the Altamaha delta began soon after the founding of the Georgia Colony in 1733. About 25 plantations were located on the low-lying islands and shores by the 19th century, taking advantage of the rich alluvial flow and annual inundation of water required by some crops. The first major crop was indigo; when demand for that faded, rice and cotton took its place. A major storm in 1824 destroyed much of the town of Darien (upper right) and put many of the islands under 20 feet of water. The Civil War ended the plantation system, and many of the island plantations disappeared under heavy brush and new growth pine forests. Some were used as tree farms for paper and pulp industries, while the Butler Island (center left) plantation became a wildlife conservation site growing wild sea rice for migrating ducks and other waterfowl. Margaret Mitchell is reputed to have used the former owner of the Butler Plantation as a basis for the Rhett Butler character in her novel 'Gone With The Wind,' taking the first name from Rhett's Island (lower right).

    These data were obtained during a 1994-95 campaign along the Georgia coast. AIRSAR's ability to detect vegetation canopy density, hydrological features and other topographic characteristics is a useful tool in landscape archaeology. AIRSAR flies aboard a NASA DC-8 based at NASA's Dryden Flight Research Center, Edwards, Calif. The analysis on the data shown was accomplished by Dr. Gary Mckay, Department of Archaeology and Geography, and Ian

  3. A global analysis of human habitation on river deltas

    NASA Astrophysics Data System (ADS)

    Edmonds, Douglas; Caldwell, Rebecca; Baumgardner, Sarah; Paola, Chris; Roy, Samapriya; Nelson, Amelia; Nienhuis, Jaap

    2017-04-01

    River deltas are ideal sites for human habitation because of their fertile floodplains, easy access to the ocean, and abundant land. But anthropogenic and natural processes are causing deltas to sink, which increases the probability of coastal flooding and human exposure to risk. The full extent of the risk posed to humans is unclear because the number of people living on river deltas is unknown. Towards this end we mapped the locations and areas of all deltas in the world (n= 1813). Using Google Earth we identified all river mouths (≥ 50 m wide) on marine coastlines that are also connected to an upstream catchment. Rivers that split into two or more active or relict distributary channels, end in a depositional protrusion from the shoreline, or do both, are defined as deltas. The depositional protrusion and distributary channel network define the geomorphic area of each delta. We mark the position of the delta apex at the first bifurcation, or for a single channel delta at the intersection of the regional shoreline and the main channel. We mark three lateral extents, one on either side of the main channel at the maximum displacement of the depositional protrusion or the distributary network, and one on the most basinward position of the delta. We define delta area as the convex hull around these extent points and the delta apex. For each delta area polygon we extract elevation from the Shuttle Radar Topography Mission dataset and population count in years 2000, 2005, 2010, 2015, and 2020 from Gridded Population of the World, version 4. In total, deltas cover 0.56% of the total area of the world yet contain 4.1% of the world's population. The population on deltas has grown from 237 million in 2000 to projected values of 322 million in 2020. Deltaic population is growing at 1.59% per year, which outpaces the world growth rate of 1.11%. Additionally, population density is increasing with time from 322 people per km2 in year 2000 to projected values of 422 people per

  4. Mississippi River Delta, Louisiana as seen from STS-62

    NASA Technical Reports Server (NTRS)

    1994-01-01

    The Mississippi River Delta, Louisiana as seen from STS-62, is the largest river system in North America. The interdistributary bays are extremely shallow, usually less than a few meters, and contain brackish to normal marine waters except during times of flooding, when fresh water fills the bays. Sedimentation within the bays is very low, occurring only during flood periods. Along the west side of the river, a highway has been built southeastward to Venice.

  5. New depositional model for Mississippi River delta plain

    SciTech Connect

    Penland, S.; Kosters, E.C.; Suter, J.R.

    1987-05-01

    The current Mississippi River delta plain model depicts a single Holocene delta plain consisting of six delta complexes sequentially deposited over the last 7000 years by the classic delta switching process. In order of increasing age, these complexes are the Atchafalaya, Balize, Lafourche, St. Bernard, Teche, and Maringouin. Between 1981 and 1986, the Louisiana Geological Survey has acquired more than 10,000 km of high-resolution seismic profiles, 248 offshore vibracores, 397 onshore vibracores, 234 soil borings, and 226 new radiocarbon dates throughout south Louisiana. Analysis of this data set led to the development of a new, more precise stratigraphic model which depicts the Mississippi delta plain as actually two individual, imbricated shelf-phase delta plains deposited at different sea level stillstands. Termed the Modern and Late Holocene, these two delta plains are separated by a ravinement surface several hundred kilometers in extent that can be traced updip to a relict-transgressive shoreline, termed the Penchant Shoreline. The Late Holocene delta plain consists of a set of delta complexes 15-20 m thick deposited during a sea level stillstand 6 m below the present, 4500-7000 y.B.P. This unit consists of the exposed Maringouin and Teche delta complexes offshore of south-central Louisiana and an unnamed delta complex buried by the Modern delta plain in southeast Louisiana. A relative sea level rise between 2800-4500 y.B.P. to about present sea level led to the transgressive submergence of the Late Holocene delta plain, generating Trinity Shoal, Ship Shoal, and the Penchant Shoreline, which represents the subsurface eastern extension of the Vermilion Bay shoreline. The 10-15-m thick Modern delta plain began building seaward of the penchant Shoreline about 2800 y.B.P.

  6. Asymmetric Erosion of the Thu Bon River Delta, Central Vietnam

    NASA Astrophysics Data System (ADS)

    Tanaka, Hitoshi; Van Duy, Dinh; Viet, Nguyen Trung

    2017-04-01

    The shape of an estuarine delta is determined based on the steady state between sediment supply from the river and the longshore flux which transports the sediment away from the river mouth. Therefore, significant change in the delta landform will occur where there is imbalance between the sediment supply and the longshore sediment transport. Coastal erosion at Cua Dai Beach which is located on the left of Thu Bon River estuary in central Vietnam can be considered as an example. On the left side of the river mouth, the significant retreat of shoreline positions (around 170m) clearly indicates severe erosion at Cua Dai Beach. Along this coastline, erosion zone extends from the river mouth to a distance approximate to 4km and no erosion is observed beyond that. On the other hand, except for the variation of the cuspate shoreline's tip, there is almost no significant change of shoreline position on the right side of the river mouth. In order to study the propagation of the erosion wave on Cua Dai Beach, analytical solution of one-line model for delta shape was applied. The applicability of this theory can be confirmed by the protruding shape of the Thu Bon River estuary which indicates the typical type of estuarine delta formed by the sediment supply from the river. In addition, a method for determination of a model's constant was also proposed using the basis of dimensionless representation of analytical solution of one-line model for delta shape. The comparison between the measured data and the theoretical one in terms of the propagation speed of the erosion wave shows good agreement which confirms the reliability of the model's constant value. (275 words)

  7. Morphology of river deltas on Titan and Earth

    NASA Astrophysics Data System (ADS)

    Witek, Piotr; Czechowski, Leszek

    2016-07-01

    The Cassini-Huygens mission is entering its final phase. The landing of Huygens on Titan and flybys performed by the Cassini probe during the last ten years revolutionized our knowledge about that moon, revealing a complex fluvio-lacustrine environment. Despite significant differences in composition, temperature and gravity, the processes of sediment transport and deposition are similar on Earth and Titan. We performed numerical simulations of development of river deltas in Titanian and terrestrial conditions, under various discharges and with different dominant grain sizes. We found that evolution of deltaic deposits is more rapid on Titan due to higher efficiency of transport, but the flat, lobate river deltas may form in narrower range of parameters than on Earth. Our results help in understanding the evolution of sedimentary deposits and may partially explain the paucity of river deltas in Titan's lakes.

  8. Holocene sand shoals offshore of Mississippi River delta plain, Louisiana

    SciTech Connect

    Penland, S.; McBride, R.A. ); Suter, J.R. ); Williams, S.J. ); Kindinger, J.L. ); Boyd, R. )

    1989-09-01

    Offshore of the Mississippi River delta plain lies a series of Holocene sand shoals marking the position of ancient submerged shorelines. These ancient shorelines represent stillstand positions during which the Holocene transgression drove sea level across the former lowstand subaerial erosion surface of the Mississippi River delta plain. Short periods of rapid sea level rise led to the transgressive submergence of these sandy shorelines. Two shoreline trends can be recognized at the {minus}10-m and {minus}20-m isobaths on the continental shelf.

  9. Sandy River Delta Habitat Restoration Project, Annual Report 2001.

    SciTech Connect

    Kelly, Virginia; Dobson, Robin L.

    2002-11-01

    The Sandy River Delta is located at the confluence of the Sandy and Columbia Rivers, just east of Troutdale, Oregon. It comprises about 1,400 land acres north of Interstate 84, managed by the USDA Forest Service, and associated river banks managed by the Oregon Division of State Lands. Three islands, Gary, Flag and Catham, managed by Metro Greenspaces and the State of Oregon lie to the east, the Columbia River lies to the north and east, and the urbanized Portland metropolitan area lies to the west across the Sandy River. Sandy River Delta was historically a wooded, riparian wetland with components of ponds, sloughs, bottomland woodland, oak woodland, prairie, and low and high elevation floodplain. It has been greatly altered by past agricultural practices and the Columbia River hydropower system. Restoration of historic landscape components is a primary goal for this land. The Forest Service is currently focusing on restoration of riparian forest and wetlands. Restoration of open upland areas (meadow/prairie) would follow substantial completion of the riparian and wetland restoration. The Sandy River Delta is a former pasture infested with reed canary grass, blackberry and thistle. The limited over story is native riparian species such as cottonwood and ash. The shrub and herbaceous layers are almost entirely non-native, invasive species. Native species have a difficult time naturally regenerating in the thick, competing reed canary grass, Himalayan blackberry and thistle. A system of drainage ditches installed by past owners drains water from historic wetlands. The original channel of the Sandy River was diked in the 1930's, and the river diverted into the ''Little Sandy River''. The original Sandy River channel has subsequently filled in and largely become a slough. The FS acquired approximately 1,400 acres Sandy River Delta (SRD) in 1991 from Reynolds Aluminum (via the Trust for Public Lands). The Delta had been grazed for many years but shortly after FS

  10. Underground and Previously Undiscovered Rivers in the Mississippi Delta

    NASA Astrophysics Data System (ADS)

    Kolker, A.; Breaux, A.; Coleman, D.; Inniss, L. V.; Telfeyan, K.; Kim, J.; Schneider, A.; Allison, M. A.; Cable, J. E.; Johannesson, K. H.

    2013-12-01

    In this study we show that there are large, and previously undiscovered, groundwater pathways by which water from the Mississippi River is transported to the wetlands and estuaries of the Mississippi River Delta. Results from multiple methodologies suggest that the total flux of groundwater to the coastal zone in the Mississippi River Delta averages 1,000 m3 s-1, and can reach 5,000 m3 s-1 at high flow. We suggest that flow preferentially occurs through paleo-crevasse channels, relict bayous, and other buried deposits of permeable and coarse grained material. These conduits were formed during the present and previous stages of the delta cycle, which occurred in historical (102 y) and late Holocene(103 y) times, respectively. Flow is driven by the hydrological head difference between the river and the estuary, which is seasonally variable in magnitudeand can reach 5-8 m during peak river floods. This talk will present data from hydrological budgets that show a missing fraction in the Mississippi River water budget, and a missing source of fresh water to a large estuary. We will show that water levels in wells in New Orleans fluctuate with the stage of the Mississippi River. Data of Rn concentration indicate advective submarine groundwater flow, whereas Ba concentrations suggest geochemical leachates are entering the estuary. Furthermore, seismic data indicate the prevalence of paleochannels and other buried features that could carry flow. Given the importance of deltas to global geochemical budgets, we suggest that these results may be generalizable: submarine groundwater discharge in deltas may prove to be an important but understudied pathway by which dissolved materials are transported from the continents to the ocean.

  11. Is there a self-organization principle of river deltas?

    NASA Astrophysics Data System (ADS)

    Tejedor, Alejandro; Longjas, Anthony; Foufoula-Georgiou, Efi

    2017-04-01

    River deltas are known to possess a complex topological and flux-partitioning structure which has recently been quantified using spectral graph theory [Tejedor et al., 2015a,b]. By analysis of real and simulated deltas it has also been shown that there is promise in formalizing relationships between this topo-dynamic delta structure and the underlying delta forming processes [e.g., Tejedor et al., 2016]. The question we pose here is whether there exists a first order organizational principle behind the self-organization of river deltas and whether this principle can be unraveled from the co-evolving topo-dynamic structure encoded in the delta planform. To answer this question, we introduce a new metric, the nonlocal Entropy Rate (nER) that captures the information content of a delta network in terms of the degree of uncertainty in delivering fluxes from any point of the network to the shoreline. We hypothesize that if the "guiding principle" of undisturbed deltas is to efficiently and robustly build land by increasing the diversity of their flux pathways over the delta plane, then they would exhibit maximum nonlocal Entropy Rate at states at which geometry and flux dynamics are at equilibrium. At the same time, their nER would be non-optimal at transient states, such as before and after major avulsions during which topology and dynamics adjust to each other to reach a new equilibrium state. We will present our results for field and simulated deltas, which confirm this hypothesis and open up new ways of thinking about self-organization, complexity and robustness in river deltas. One particular connection of interest might have important implications since entropy rate and resilience are related by the fluctuation theorem [Demetrius and Manke, 2005], and therefore our results suggest that deltas might in fact self-organize to maximize their resilience to structural and dynamic perturbations. References: Tejedor, A., A. Longjas, I. Zaliapin, and E. Foufoula

  12. Ecosystem Services Assessment of the Nemunas River Delta

    EPA Science Inventory

    The concept of ecosystem services recognizes the services, and benefits, provided to people by ecosystems. The Nemunas River Delta, in Lithuania, is a valued area that can provide a range of services. We conducted a meta-analysis of existing studies done on the region to identify...

  13. Ecosystem Services Assessment of the Nemunas River Delta

    EPA Science Inventory

    The concept of ecosystem services recognizes the services, and benefits, provided to people by ecosystems. The Nemunas River Delta, in Lithuania, is a valued area that can provide a range of services. We conducted a meta-analysis of existing studies done on the region to identify...

  14. Seismic stability of the Duwamish River Delta, Seattle, Washington

    USGS Publications Warehouse

    Kayen, Robert E.; Barnhardt, Walter A.

    2007-01-01

    The delta front of the Duwamish River valley near Elliott Bay and Harbor Island is founded on young Holocene deposits shaped by sea-level rise, episodic volcanism, and seismicity. These river-mouth deposits are highly susceptible to seismic soil liquefaction and are potentially prone to submarine landsliding and disintegrative flow failure. A highly developed commercial-industrial corridor, extending from the City of Kent to the Elliott Bay/Harbor Island marine terminal facilities, is founded on the young Holocene deposits of the Duwamish River valley. The deposits of this Holocene delta have been shaped not only by relative sea-level rise but also by episodic volcanism and seismicity. Ground-penetrating radar (GPR), cores, in situ testing, and outcrops are being used to examine the delta stratigraphy and to infer how these deposits will respond to future volcanic eruptions and earthquakes in the region. A geotechnical investigation of these river-mouth deposits indicates high initial liquefaction susceptibility during earthquakes, and possibly the potential for unlimited-strain disintegrative flow failure of the delta front.

  15. Management needs assessment for the Copper River Delta, Alaska.

    Treesearch

    L.E. Kruger; C.B. Tyler

    1995-01-01

    This report assesses needs, problems, and perceptions relevant to management for the Copper River Delta (Alaska)—the largest coastal wetland on the Pacific coast of North America. The assessment provides a basis for planning and decisionmaking and a framework for ongoing research, development, and application. It also underscores concerns about human impacts...

  16. Godavari River Delta Panorama, Bay of Bengal, India

    NASA Image and Video Library

    1993-01-19

    STS054-80-024 (13-19 Jan 1993) --- As the Shuttle was passing southeast over the coast of India, approaching the Bay of Bengal, Endeavour's crew took this picture of the Godavari River Delta. The sun glint pattern was centered directly over the delta and highlighted well the intricate drainage pattern. Offshore, water features associated with current boundaries and river plumes are readily visible. The line of clouds along the coast south of the delta suggest that surface winds are blowing onshore from the Bay of Bengal. As the air passes over the warmer coastal water and land, it is warmed and begins to rise. The moisture in the air condenses, forming a line of low-level clouds.

  17. Sand shoal development on muddy Mississippi river delta shelf

    SciTech Connect

    Penland, S.; Suter, J.R.; Moslow, T.F.

    1984-04-01

    Trinity and Ship Shoals are transgressive sand bodies on the Louisiana inner continental shelf, and they represent the reworked sands of the abandoned Holocene Teche and Maringouin deltas. The development of these shoals is initiated by an episode of delta abandonment followed by subsidence-enhanced sea level rise. Through the process of shoreface retreat, the abandoned delta lobe evolves from an erosional headland with flanking barrier islands to a barrier-island arch and finally into a submerged inner-shelf shoal system. Trinity and Ship Shoals represent the final stage in the Mississippi River delta barrier shoreline cycle and provide a possible modern analogue for some Cretaceous shelf sandstones of the Western Interior. More than 1000 km (620 mi) of high-resolution seismic profiles correlated with cores provide the data base for interpretation of the depositional history of sand-body development on the muddy Louisiana shelf.

  18. Pen Branch Delta and Savannah River Swamp Hydraulic Model

    SciTech Connect

    Chen, K.F.

    1999-05-13

    The proposed Savannah River Site (SRS) Wetlands Restoration Project area is located in Barnwell County, South Carolina on the southwestern boundary of the SRS Reservation. The swamp covers about 40.5 km2 and is bounded to the west and south by the Savannah River and to the north and east by low bluffs at the edge of the Savannah River floodplain. Water levels within the swamp are determined by stage along the Savannah River, local drainage, groundwater seepage, and inflows from four tributaries, Beaver Dam Creek, Fourmile Branch, Pen Branch, and Steel Creek. Historic discharges of heated process water into these tributaries scoured the streambed, created deltas in the adjacent wetland, and killed native vegetation in the vicinity of the delta deposits. Future releases from these tributaries will be substantially smaller and closer to ambient temperatures. One component of the proposed restoration project will be to reestablish indigenous wetland vegetation on the Pen Branch delta that covers about 1.0 km2. Long-term predictions of water levels within the swamp are required to determine the characteristics of suitable plants. The objective of the study was to predict water levels at various locations within the proposed SRS Wetlands Restoration Project area for a range of Savannah River flows and regulated releases from Pen Branch. TABS-MD, a United States Army Corps of Engineer developed two-dimensional finite element open channel hydraulic computer code, was used to model the SRS swamp area for various flow conditions.

  19. River delta self-organization via entropy rate analysis

    NASA Astrophysics Data System (ADS)

    Tejedor, A.; Longjas, A.; Foufoula-Georgiou, E.

    2016-12-01

    Previous work [Tejedor et al., 2015a,b; 2016] has shown that network topologic characteristics for a wide range of field and simulated delta channel networks vary significantly reflecting to some extend the different underlying physical processes. While more work remains to be done in this direction to advance quantitative delta classification, a problem of parallel interest is that of unraveling whether deltas evolve and attain topologies and flow partitions that are consistent with an underlying principle of optimization, as for example has been examined for tributary river networks. Here we study concepts of Entropy as applied to directed acyclic graphs such as river deltas, and specifically the concept of Entropy rate that measures the rate at which a stochastic process generates information. For deltas, Entropy rate can be interpreted as the amount of information we need to acquire at each time step to probabilistically track the position of the particles on the network. We propose a new Entropy metric, the non-local Entropy Rate (nER), which we argue is more pertinent to deltas as it captures the averaged information content of a delta network in terms of the degree of uncertainty in delivering fluxes from any point of the network to the shoreline. We interpret nER as measuring delta's capacity to optimally grow by spreading water and sediment over its delta top in a non-preferential way. We present results for field and simulated deltas, showing that conditional on a network topology, channel widths self-adjust such that the delivery of fluxes from the delta top to the shoreline has a maximal value of non-local Entropy Rate. Drawing on the connection between Entropy and resilience via the fluctuation theorem [Demetrius and Manke, 2005], we also suggest that deltas might in fact self-organize to maximize their resilience to perturbations. Tejedor, A., A. Longjas, I. Zaliapin, and E. Foufoula-Georgiou (2015), Water Resour. Res., 51, 3998-4018 Tejedor, A., A

  20. Using Modern Processes to Understand Postglacial Delta Evolution: Elwha River Delta

    NASA Astrophysics Data System (ADS)

    Lee, K. M.; Ogston, A. S.; Nittrouer, C. A.; Holmes, M.

    2008-12-01

    The post-glacial shoreline of the Elwha River delta in the Strait of Juan de Fuca, Washington State, is thought to have been 4 km seaward and approximately 50 m lower than the modern shoreline. Nearshore transport processes throughout this rapid transgression are poorly constrained. Previous work suggests storm-driven waves and relative sea level are the primary forcings of the Elwha River delta over the past 10,000 years. Net eastward sediment transport formed a series of drowned paleospits at -25 m, -8 m, and -6 m depths in the Strait of Juan de Fuca. Sea-level rise slowed at 4,500 years BP and created the well- developed modern spit, Ediz Hook. In recent times, the Elwha River was dammed (starting in 1916) and later the surrounding coastal bluffs were armored. The resulting cutoff of sediment to the nearshore created a period of net shoreline erosion, when storm waves, tidal currents, and sediment supply shaped the modern delta morphology. We created a base map of the subaqueous delta morphology using multibeam swath mapping and seismic reflection profiles to test the conceptual model (Galster, 1978) of shoreline evolution over the past 10,000 years. In addition, we quantified the modern sediment-transport pathways and mapped the seasonal surface plume of the river along with current measurements and suspended-sediment concentrations collected in the bottom boundary layer using an instrumented tripod. The modern sediment- transport system can be linked to the ancient morphology and stratigraphy though the pairing of the water- column energetics with high-resolution bathymetry and seismic-reflection data. Data indicate that sediment is focused by a tidally-driven, thin bidirectional surface plume and an eddy in the lee of the protruding delta. The strong currents (over 1 m/s) direct net transport to the east and may smooth the delta morphology. Newly acquired seismic-reflection data show outbuilding foresets on the subaqueous delta front and accretionary features

  1. Urban growth and environmental impacts in Jing-Jin-Ji, the Yangtze, River Delta and the Pearl River Delta

    NASA Astrophysics Data System (ADS)

    Haas, Jan; Ban, Yifang

    2014-08-01

    This study investigates land cover changes, magnitude and speed of urbanization and evaluates possible impacts on the environment by the concepts of landscape metrics and ecosystem services in China's three largest and most important urban agglomerations: Jing-Jin-Ji, the Yangtze River Delta and the Pearl River Delta. Based on the classifications of six Landsat TM and HJ-1A/B remotely sensed space-borne optical satellite image mosaics with a superior random forest decision tree ensemble classifier, a total increase in urban land of about 28,000 km2 could be detected alongside a simultaneous decrease in natural land cover classes and cropland. Two urbanization indices describing both speed and magnitude of urbanization were derived and ecosystem services were calculated with a valuation scheme adapted to the Chinese market based on the classification results from 1990 and 2010 for the predominant land cover classes affected by urbanization: forest, cropland, wetlands, water and aquaculture. The speed and relative urban growth in Jing-Jin-Ji was highest, followed by the Yangtze River Delta and Pearl River Delta, resulting in a continuously fragmented landscape and substantial decreases in ecosystem service values of approximately 18.5 billion CNY with coastal wetlands and agriculture being the largest contributors. The results indicate both similarities and differences in urban-regional development trends implicating adverse effects on the natural and rural landscape, not only in the rural-urban fringe, but also in the cities' important hinterlands as a result of rapid urbanization in China.

  2. Intertidal benthic resources of the Copper River Delta, Alaska, USA

    NASA Astrophysics Data System (ADS)

    Powers, Sean P.; Bishop, Mary Anne; Grabowski, Jonathan H.; Peterson, Charles H.

    2002-02-01

    The Copper River Delta, Alaska is the largest contiguous coastal wetland system along the West Coast of North America. Vast expanses of tidal mud flats formed by sediments carried by the suspended load of the Copper River serve as a connection between the Gulf of Alaska and the extensive network of wetlands, rivers and sloughs of the delta system. In addition to providing habitat for resident fish, shrimp and crabs, these tidal flats serve as critical feeding grounds for up to 5 million migratory shorebirds as well as an entry and exit corridor for three species of commercially fished salmonids. Here we report the first description of the benthic community of these intertidal flats. Between April and September 2000, we conducted three samplings on the Copper River Delta in which we quantified benthic macro-invertebrates inhabiting silt-clay sediments, the dominant substrate in the system, over a range of tidal inundation. Specifically, sampling was performed in two areas on the delta: near the outflows of the Eyak River and Pete Dahl Slough. Pore-water salinity of surficial sediment ranged from 4 psu during peak summer flow of the Copper River to 14 psu in April prior to increased riverine input. Sediment temperatures corresponded to ambient air temperatures with lowest temperatures during the April-September observation period recorded in April (4°C) and warmest in August (16°C). The benthic community of the delta's tidal flats was characterised by low species diversity and was dominated by the tellinid bivalve Macoma balthica, which reached densities greater than 4000 m -2. Age-length relationship of M. balthica indicated slow growth and longevity of up to 8 years. Polychaete densities, primarily the phyllodocid Eteone longa, were low throughout the study period, reaching a maximum of only 700 m -2 in August. Amphipod densities, primarily the corophid amphipod Corophium salmonis, were high (up to 7000 m -2) only during the August sampling. Spatial patterns of

  3. Mackenzie River Delta morphological change based on Landsat time series

    NASA Astrophysics Data System (ADS)

    Vesakoski, Jenni-Mari; Alho, Petteri; Gustafsson, David; Arheimer, Berit; Isberg, Kristina

    2015-04-01

    Arctic rivers are sensitive and yet quite unexplored river systems to which the climate change will impact on. Research has not focused in detail on the fluvial geomorphology of the Arctic rivers mainly due to the remoteness and wideness of the watersheds, problems with data availability and difficult accessibility. Nowadays wide collaborative spatial databases in hydrology as well as extensive remote sensing datasets over the Arctic are available and they enable improved investigation of the Arctic watersheds. Thereby, it is also important to develop and improve methods that enable detecting the fluvio-morphological processes based on the available data. Furthermore, it is essential to reconstruct and improve the understanding of the past fluvial processes in order to better understand prevailing and future fluvial processes. In this study we sum up the fluvial geomorphological change in the Mackenzie River Delta during the last ~30 years. The Mackenzie River Delta (~13 000 km2) is situated in the North Western Territories, Canada where the Mackenzie River enters to the Beaufort Sea, Arctic Ocean near the city of Inuvik. Mackenzie River Delta is lake-rich, productive ecosystem and ecologically sensitive environment. Research objective is achieved through two sub-objectives: 1) Interpretation of the deltaic river channel planform change by applying Landsat time series. 2) Definition of the variables that have impacted the most on detected changes by applying statistics and long hydrological time series derived from Arctic-HYPE model (HYdrologic Predictions for Environment) developed by Swedish Meteorological and Hydrological Institute. According to our satellite interpretation, field observations and statistical analyses, notable spatio-temporal changes have occurred in the morphology of the river channel and delta during the past 30 years. For example, the channels have been developing in braiding and sinuosity. In addition, various linkages between the studied

  4. Delta Morphodynamics from River Sediment Input: Dam Removal, Elwha River, Washington, USA.

    NASA Astrophysics Data System (ADS)

    Warrick, J. A.; Gelfenbaum, G. R.; Stevens, A. W.; Miller, I. M.; Kaminsky, G. M.; Ritchie, A.

    2015-12-01

    Sediment supply plays an important role in river delta morphodynamics and sustainability, and it is important to evaluate how deltas respond to the restoration or enhancement of sediment supplies. Here we report on the morphodynamic responses of the Elwha River delta to large increases in river sediment loads from the removal of two large dams beginning in 2011. The dam removal project exposed ~30 million tonnes of sediment stored within the former reservoirs to natural erosion by the river, and roughly half of this reservoir sediment was eroded during the first four years of the project. Coastal surveys with GPS-based mapping systems, sonar, and aerial photography have revealed that the Elwha River mouth has expanded seaward by ~500 m with the introduction of new supplies of sediment. Approximately 3.5 million cubic meters (or ~5 million tonnes) of sediment were deposited at the river mouth delta between 2011 and 2015. This newly deposited sediment has been shaped by waves and currents into a series of dynamic bars that have greatly expanded the estuarine habitats of the delta.

  5. On river cross-sectional change in the Niger Delta

    NASA Astrophysics Data System (ADS)

    Abam, T. K. S.; Omuso, W. O.

    2000-08-01

    A network of dominantly distributary river systems dissects the superficial deposits of the Niger Delta comprising alluvial sediments. Changes in river cross-sections are instigated mainly by bank failures, fluctuations in discharge, and bed degradation by fluvial processes. The relative importance of factors causing river cross-sectional change was ranked, based on a deterministic sensitivity technique involving partial differentiation of soil properties, flow characteristics, and geometrical parameters of the river channels. Analysis suggests that steep bank inclination and high flow velocity/discharge are the major causes of cross-sectional change, while interlocking of soil grains is the major erosion-restraining factor. Sensitivity coefficients were used further to generate susceptibility indices, indicating the vulnerability of channel cross-sections to change. Based on this, the risks of channel cross-sectional change were compared at different sites.

  6. Fluvial transport on Titan: formation and evolution of river deltas

    NASA Astrophysics Data System (ADS)

    Witek, Piotr Przemyslaw; Czechowski, Leszek

    2016-10-01

    The Cassini-Huygens mission provided numerous observations indicating that processes of sediment transport are currently operating on the surface of Titan. We performed numerical simulations of flow and sediment transport on Titan with particular emphasis on formation of sedimentary landforms in Titan's lakes. We compared the morphology and evolution of landforms formed in Titanian and terrestrial conditions, under various discharges and with different dominant grain sizes. The processes are similar in both environments; in some cases we observed bifurcation of the flow and switching of the active distributaries. Such processes may lead to abandonment of some delta lobes, as hypothesized for the delta observed in Ontario Lacus on Titan. The lower gravity of Titan and higher buoyancy of the most plausible kinds of sediment result in higher efficiency of transport and generally faster evolution of the deltaic deposits. Our results suggest also that the flat, lobate river deltas may form in narrower range of parameters than on Earth.

  7. Large infrequently operated river diversions for Mississippi delta restoration

    NASA Astrophysics Data System (ADS)

    Day, John W.; Lane, Robert R.; D'Elia, Christopher F.; Wiegman, Adrian R. H.; Rutherford, Jeffrey S.; Shaffer, Gary P.; Brantley, Christopher G.; Kemp, G. Paul

    2016-12-01

    Currently the Mississippi delta stands as a highly degraded and threatened coastal ecosystem having lost about 25% of coastal wetlands during the 20th century. To address this problem, a 50 billion, 50-year restoration program is underway. A central component of this program is reintroduction of river water back into the deltaic plain to mimic natural functioning of the delta. However, opposition to diversions has developed based on a number of perceived threats. These include over-freshening of coastal estuaries, displacement of fisheries, perceived water quality problems, and assertions that nutrients in river water leads to wetland deterioration. In addition, growing climate impacts and increasing scarcity and cost of energy will make coastal restoration more challenging and limit restoration options. We address these issues in the context of an analysis of natural and artificial diversions, crevasse splays, and small sub-delta lobes. We suggest that episodic large diversions and crevasses (>5000 m3 s-1) can build land quickly while having transient impacts on the estuarine system. Small diversions (<200 m3 s-1) that are more or less continuously operated build land slowly and can lead to over-freshening and water level stress. We use land building rates for different sized diversions and impacts of large periodic inputs of river water to coastal systems in the Mississippi delta to conclude that high discharge diversions operated episodically will lead to rapid coastal restoration and alleviate concerns about diversions. Single diversion events have deposited sediments up to 40 cm in depth over areas up to 130-180 km2. This approach should have broad applicability to deltas globally.

  8. River-Ocean Interactions: A Coupled Morphodynamic Delta Model

    NASA Astrophysics Data System (ADS)

    Ratliff, K. M.; Hutton, E. W. H.; Murray, A. B.

    2015-12-01

    Society has become increasingly reliant on deltas for agriculture, resource extraction, transportation and trade, yet these landforms and their inhabitants have become increasingly vulnerable to submergence and natural disasters (e.g., flooding, storm surges). Although we know that many 'natural' processes influence large-scale delta morphology, we do not yet know the relative importance of anthropogenic influences (e.g., climate and land-use change) in shaping modern deltas. In particular, the processes and feedbacks that shape delta morphology over large space and timescales (i.e. timescales of multiple river avulsions and the evolution of multiple delta lobes) are not well understood. To explore the long-term combined effects of sea-level rise, subsidence and anthropogenic manipulations, we have developed a new morphodynamic delta model that links fluvial, floodplain, and deltaic dynamics over large space and timescales. Using the framework and tools of the Community Surface Dynamics Modeling System, we couple a new river and floodplain module to the Coastline Evolution Model (CEM, Ashton and Murray, 2001). In the fluvial module, cell width is assumed to be larger than the channel belt width (including natural levees that are maintained at a bankfull channel-depth above the riverbed elevation). The river course is determined using a steepest-descent methodology, and erosion and deposition along the course is modeled as a linear diffusive process. An avulsion occurs when the riverbed becomes super-elevated above the surrounding floodplain, and the new steepest-descent path to sea level is shorter than the previous course. Floodplain deposition is modeled by blanket (uniform) deposition and crevasse splay deposition (after a 'failed' avulsion; if the riverbed is super-elevated, but the new steepest path to sea level is longer than the prior path). Preliminary results indicate that anthropogenic manipulations of the river (e.g., levees) can propagate hundreds of

  9. Reading Ombrone river delta evolution through beach ridges morphology

    NASA Astrophysics Data System (ADS)

    Mammi, Irene; Piccardi, Marco; Pranzini, Enzo; Rossi, Lorenzo

    2017-04-01

    The present study focuses on the evolution of the Ombrone River delta (Southern Tuscany, Italy) in the last five centuries, when fluvial sediment input was huge also as a consequence of the deforestation performed on the watershed. The aim of this study is to find a correlation between river input and beach ridges morphology and to explain the different distribution of wetlands and sand deposits on the two sides of the delta. Visible, NIR and TIR satellite images were processed to retrieve soil wetness associated to sand ridges and interdune silty deposits. High resolution LiDAR data were analysed using vegetation filter and GIS enhancement algorithms in order to highlight small morphological variations, especially in areas closer to the river where agriculture has almost deleted these morphologies. A topographic survey and a very high resolution 3D model obtained from a set of images acquired by an Unmanned Aerial Vehicle (UAV) were carried out in selected sites, both to calibrate satellite LiDAR 3D data, and to map low relief areas. Historical maps, aerial photography and written documents were analysed for dating ancient shorelines associated to specific beach ridges. Thus allowing the reconstruction of erosive and accretive phases of the delta. Seventy beach ridges were identified on the two wings of the delta. On the longer down-drift side (Northern wing) beach ridges are more spaced at the apex and gradually converge to the extremity, where the Bruna River runs and delimits the sub aerial depositional area of the Ombrone River. On the shorter up-drift lobe (Southern wing), beach ridges are closer, but run almost parallel each other. In this case, a rocky headland called Collelungo promontory closes and cuts the beach ridges sequence but shallow water depth allows sediment by pass. One kilometre to the south a more pronounced promontory encloses a small pocket beach (Cala di Forno) and identifies the limit of the subaerial depositionary area. Beach ridges

  10. It takes more than water: Restoring the Colorado River Delta

    USGS Publications Warehouse

    Pitt, Jennifer; Kendy, Eloise; Schlatter, Karen; Hinojosa-Huertaf, Osvel; Flessa, Karl W.; Shafroth, Patrick B.; Ramirez-Hernandez, Jorge; Nagler, Pamela L.; Glenn, Edward P.

    2017-01-01

    Environmental flows have become important tools for restoring rivers and associated riparian ecosystems (Arthington, 2012; Glenn et al., 2017). In March 2014, the United States and Mexico initiated a bold effort in restoration, delivering from Morelos Dam a “pulse flow” of water into the Colorado River in its delta for the purpose of learning about its environmental effects (Flessa et al., 2013; Bark et al., 2016). Specifically, scientists evaluated whether the pulse flow, albeit miniscule compared to historical floods, could provide the ecological functions needed to establish native, flood-dependent vegetation to restore natural habitat along the riparian corridor.

  11. Volga River Delta and Caspian Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color MODIS image from May 10, 2002, captures Russia's Volga River (running south through the center) emptying into the northern portion of the Caspian Sea. The waters of the Caspian Sea are quite murky in this image, highlighting the water quality problems plaguing the sea. The sea is inundated with sewage and industrial and agricultural waste, which is having measurable impact on human health and wildlife. According reports from the Department of Energy, in less than a decade the sturgeon catch dropped from 30,000 tons to just over 2,000 tons. National and international groups are currently joining together to find strategies of dealing with the environmental problems of the Caspian Sea. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  12. Variance in Dominant Grain Size Across the Mississippi River Delta

    NASA Astrophysics Data System (ADS)

    Miller, K. L.; Chamberlain, E. L.; Esposito, C. R.; Wagner, R. W.; Mohrig, D. C.

    2016-02-01

    Proposals to restore coastal Louisiana often center on Mississippi River diversion projects wherein water and sediment are routed into wetlands and shallow waters in an effort to build land. Successful design and implementation of diversions will include consideration of behavior and characteristics of sediment, both in the river and in the receiving basin. The Mississippi River sediment load is primarily mud (roughly 75%), with the remainder being very-fine to medium sand or organic detritus. The dominance of muds leads many to suggest that diversions should focus on capturing the mud fraction despite the smaller size and longer settling times required for these particles compared to sand; others believe that sand should be the focus. We present a systemic analysis of the texture of land-building sediment in the Mississippi Delta using borehole data from various depositional environments representing a range of spatial scales, system ages, and fluvial and basin characteristics. We include subdelta-scale data from the incipient Wax Lake Delta and from the distal plain of the abandoned Lafourche subdelta, as well as crevasse-scale data from modern Cubit's Gap and the Attakapas splay, an inland Lafourche crevasse. Comparison of these sites demonstrates a large variance in the volumetric mud to sand ratios across the system. We consider the differences to be emblematic of the various forcings on each lobe as it formed and suggest that the most efficient building block for a diversion is a function of the receiving basin and is not uniform across the entire delta.

  13. Groundwater - surface water interactions in the Ayeyarwady river delta, Myanmar

    NASA Astrophysics Data System (ADS)

    Miyaoka, K.; Haruyama, S.; Kuzuha, Y.; Kay, T.

    2012-12-01

    Groundwater is widely used as a water resource in the Ayeyarwady River delta. But, Groundwater has some chemical problem in part of the area. To use safety groundwater for health, it is important to make clear the actual conditions of physical and chemical characteristics of groundwater in this delta. Besides, Ayeyarwady River delta has remarkable wet and dry season. Surface water - groundwater interaction is also different in each season, and it is concerned that physical and chemical characteristics of groundwater is affected by the flood and high waves through cyclone or monsoon. So, it is necessary to research a good aquifer distribution for sustainable groundwater resource supply. The purposes of this study are evaluate to seasonal change of groundwater - surface water interactions, and to investigate the more safety aquifer to reduce the healthy risk. Water samples are collected at 49 measurement points of river and groundwater, and are analyzed dissolved major ions and oxygen and hydro-stable isotope compositions. There are some groundwater flow systems and these water qualities are different in each depth. These showed that physical and chemical characteristics of groundwater are closely related to climatological, geomorphogical, geological and land use conditions. At the upper Alluvium, groundwater quality changes to lower concentration in wet season, so Ayeyarwady River water is main recharge water at this layer in the wet season. Besides, in the dry season, water quality is high concentration by artificial activities. Shallower groundwater is affected by land surface conditions such as the river water and land use in this layer. At lower Alluvium, Arakan and Pegu mountains are main recharge area of good water quality aquifers. Oxygen18 value showed a little affected by river water infiltration in the wet season, but keep stable good water quality through the both seasons. In the wet season, the same groundwater exists and water quality changes through

  14. Cohesive Sedimentary Processes on River-Dominated Deltas: New Perspectives from the Mississippi River Delta Front, Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Bentley, S. J.; Keller, G. P.; Obelcz, J.; Maloney, J. M.; Xu, K.; Georgiou, I. Y.; Miner, M. D.

    2016-12-01

    On river deltas dominated by proximal sediment accumulation (Mississippi, Huang He, others), the delta front region is commonly dominated by rapid accumulation of cohesive fluvial sediments, and mass-wasting processes that remobilize recently deposited sediments. Mass transport is preconditioned in sediments by high water content, biogenic gas production, over steepening, and is commonly triggered by strong wave loading and other processes. This understanding is based on extensive field studies in the 1970's and 80's. Recent studies of the Mississippi River Delta Front are yielding new perspectives on these processes, in a time of anthropogenically reduced sediment loads, rising sea level, and catastrophic deltaic land loss. We have synthesized many industry data sets collected since ca. 1980, and conducted new pilot field and modeling studies of sedimentary and morphodynamic processes. These efforts have yielded several key findings that diverge from historical understanding of this dynamic setting. First, delta distributary mouths have ceased seaward progradation, ending patterns that have been documented since the 18th century. Second, despite reduced sediment supply, offshore mass transport continues, yielding vertical displacements at rates of 1 m/y. This displacement is apparently forced by wave loading from storm events of near-annual return period, rather than major hurricanes that have been the focus of most previous studies. Third, core analysis indicates that this vertical displacement is occurring along failure planes >3 m in the seabed, rather than in more recently deposited sediments closer to the sediment-water interface. These seabed morphodynamics have the potential to destabilize both nearshore navigation infrastructure, and seabed hydrocarbon infrastructure offshore. As well, these findings raise more questions regarding the future seabed evolution offshore of major river deltas, in response to anthropogenic and climatic forcing.

  15. Changes in the areal extents of the Athabasca River, Birch River, and Cree Creek Deltas, 1950-2014, Peace-Athabasca Delta, Canada

    NASA Astrophysics Data System (ADS)

    Timoney, Kevin; Lee, Peter

    2016-04-01

    Deltas form where riverborne sediment accumulates at the interface of river mouths and their receiving water bodies. Their areal extent is determined by the net effect of processes that increase their extent, such as sediment accumulation, and processes that decrease their extent, such as erosion and subsidence. Through sequential mapping and construction of river discharge and sediment histories, this study examined changes in the subaerial extents of the Cree Creek and Athabasca River Deltas (both on the Athabasca River system) and the Birch River Delta in northern Canada over the period 1950-2014. The purpose of the study was to determine how, when, and why the deltas changed in areal extent. Temporal growth patterns were similar across the Athabasca and Birch River systems indicative of a climatic signal. Little or no areal growth occurred from 1950 to 1968; moderate growth occurred between 1968 and the early to mid-1980s; and rapid growth occurred between 1992 and 2012. Factors that affected delta progradation included dredging, sediment supply, isostatic drowning, delta front bathymetry, sediment capture efficiency, and storms. In relation to sediment delivered, areal growth rates were lowest in the Athabasca Delta, intermediate in the Birch Delta, and highest in the Cree Creek Delta. Annual sediment delivery is increasing in the Cree Creek Delta; there were no significant trends in annual sediment delivery in the Birch and Athabasca Deltas. There was a lag of up to several years between sediment delivery events and progradation. Periods of delta progradation were associated with low water levels of the receiving basins. Predicted climate-change driven declines in river discharge and lake levels may accelerate delta progradation in the region. In the changing ecosystems of northeastern Alberta, inadequate monitoring of vegetation, landforms, and sediment regimes hampers the elucidation of the nature, rate, and causality of ecosystem changes.

  16. Morphodynamics and Stratigraphy of Essex River EBB-Tidal Delta: Massachusetts

    DTIC Science & Technology

    1991-08-01

    AD-A241 424 TECHNICAL REPORT CERC-91 -11 --- "MORPHODYNAMICS AND STRATIGRAPHY OF ESSEX RIVER EBB-TIDAL DELTA: MASSACHUSETTS by J. Bailey Smith...COVERED I August 1991 Final report 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Morphodynamics and Stratigraphy of Essex River Ebb-Tidal Delta...12b. DISTRIBUTION CODE Approved for public release; distribution is unlimited 13. ABSTRACT (Maximum 200 words) The Essex River Inlet ebb-tidal delta

  17. Morphology of river deltas on Earth and Titan

    NASA Astrophysics Data System (ADS)

    Witek, Piotr; Czechowski, Leszek

    2016-04-01

    Presently volatile cycles are known to operate on surfaces of two planetary bodies in the Solar System, Earth and Titan. Fluvial erosion, transport and deposition of rocky material modify parts of the surface. Numerous indications of geologically recent sediment transport have been discovered on Titan by the Cassini-Huygens mission. Theoretical calculations suggest greater mobility of Titanian sediments in comparison to terrestrial, due to lower gravity and lower density of typical crustal material. Using numerical model of flow and sediment transport, we compare the development and morphology of deposits forming in lakes in terrestrial and Titanian conditions. We explore the range of possible river discharges, including natural variability, and several dominant grain sizes. We consider several compositions of sediments on Titan, on Earth we model the transport of quartz grains by water. We perform simulations for the same initial geometry of river channel and lake basin, for a given discharge and dominant grain diameter in each environment. Morphology and evolution of the deltaic deposits are compared. We observe that the erosion has dominant role for the smallest grains, and the effect is more pronounced on Titan than on Earth. The largest grains usually form steep-sloped fan-like deltas on both planetary bodies. The processes of formation and development of the sedimentary landforms are generally similar in both environments. Particular types of deposits may however form in different ranges of discharge and grain size, due to differences in environmental parameters. Greater mobility of sediments on Titan result in easier displacement of loose granular material, especially for smallest considered grains. The flat, lobate deltas can form in narrower range of discharges and grain sizes than on Earth. This fact might be partially responsible for scarcity of river deltas on that active moon, where other signs of fluvial processes are widespread.

  18. Biogeochemical features of aquatic plants in the Selenga River delta

    NASA Astrophysics Data System (ADS)

    Shinkareva, Galina; Lychagin, Mikhail

    2014-05-01

    The Selenga River system provides more than a half of the Lake Baikal total inflow. The river collects a significant amount of pollutants (e.g. heavy metals) from the whole basin. These substances are partially deposited within the Selenga delta, and partially are transported further to the lake. A generous amount of aquatic plants grow in the delta area according to its favorable conditions. This vegetation works as a specific biofilter. It accumulates suspended particles and sorbs some heavy metals from the water. The study aimed to reveal the species of macrophytes which could be mostly important for biomonitoring according to their chemical composition. The field campaign took place in the Selenga River delta in July-August of 2011 (high water period) and in June of 2012 (low water period). 14 species of aquatic plants were collected: water starwort Callitriche hermaphroditica, small yellow pond lily Nuphar pumila, pondweeds Potamogeton crispus, P. pectinatus, P. friesii, broadleaf cattail Typha latifolia, hornwort or coontail Ceratophyllum demersum, arrowhead Sagittaria natans, flowering rush (or grass rush) Butomus umbellatus, reed Phragmites australis, parrot's feather Myriophyllum spicatum, the common mare's tail Hippuris vulgaris, Batrachium trichophyllum, canadian waterweed Elodea canadensis. The samples were dried, grinded up and digested in a mixture of HNO3 and H2O2. The chemical composition of the plant material was defined using ICP-MS and ICP-AES methods. Concentrations of Fe, Mn, Cr, Ni, Cu, B, Zn, V, Co, As, Mo, Pb, and U were considered. The study revealed that Potamogeton pectinatus and Myriophyllum spicatum concentrate elements during both high and low water periods. Conversely the Butomus umbellatus and Phragmites australis contain small amount of heavy metals. The reed as true grasses usually accumulates fewer amounts of elements than other macrophytes. To compare biogeochemical specialization of different species we suggest to use

  19. Bathymetry of the Hong and Luoc River Junction, Red River Delta, Vietnam, 2010

    USGS Publications Warehouse

    Kinzel, Paul J.; Nelson, Jonathan M.; Toan, Duong Duc; Thanh, Mung Dinh; Shimizu, Yasuyuki

    2012-01-01

    The U.S. Geological Survey, in collaboration with the Water Resources University in Hanoi, Vietnam, conducted a bathymetric survey of the junction of the Hong and Luoc Rivers. The survey was done to characterize the channel morphology of this delta distributary network and provide input for hydrodynamic and sediment transport models. The survey was carried out in December 2010 using a boat-mounted multibeam echo sounder integrated with a global positioning system. A bathymetric map of the Hong and Luoc River junction was produced which was referenced to the datum of the Trieu Duong tide gage on the Luoc River.

  20. Sediment Trapping Pathways and Mechanisms through the Mekong Tidal River and Subaqueous Delta

    DTIC Science & Technology

    2013-09-30

    Walfir, P. W.; Silva, M. S.; Silveira, O. F.; Fricke, A. T.; Water and sediment transport in the Amazon tidal river and its tributaries (Abstract ID...transport dynamics that act to effect the delivery and retention of fine-grained sediment through tidal rivers and in shallow- water coastal regions. We...system. We report here on preliminary results from the Tropical Deltas DRI on the Mekong River , along with results from the Amazon River delta system

  1. Perfluoroalkyl acids (PFAAs) in sediments from rivers of the Pearl River Delta, southern China.

    PubMed

    Liu, Baolin; Zhang, Hong; Li, Juying; Dong, Weihua; Xie, Liuwei

    2017-05-01

    Having been largely used in industrial and household products, perfluoroalkyl acids (PFAAs) appear in environmental and biological systems with prevalence and persistence and have raised great concern in recent years. The present study is aimed at studying concentrations and composition profiles of 16 PFAAs in surface sediments collected from 51 sampling locations in 4 main rivers of the Pearl River Delta, one of the economy-developed areas in China. The total PFAA concentrations (∑ PFAAs) were determined in a wide range of 1.89-15.1 ng g(-1) dw (dry weight) with an average concentration to be 3.54 ng g(-1) dw. Higher ∑ PFAAs were observed in the downstream of Dongjiang River and the Pearl River, possibly due to the discharge of industrial wastewater. Perfluoropentanoic acid (PFPeA) and perfluorooctane sulfonate (PFOS) were the dominant PFAAs, accounting for 51 to 85% of ∑ PFAAs in 27% of the samples. High PFPeA concentrations in sediments of urban river were scarcely observed in previous studies worldwide. The sources of short-chain perfluoroalkyl carboxylic acids (PFCAs) were significantly different from those of other PFAAs. Preliminary hazard assessment proved negligible for PFOS, perfluorooctanoic acid (PFOA), PFPeA, and perfluorohexanoic acid (PFHxA) concentrations in sediments from rivers of the Pearl River Delta.

  2. Hydrodynamic modeling for river delta salt marshes using lidar topography

    NASA Astrophysics Data System (ADS)

    Hodges, Ben R.

    2014-05-01

    Topographic data from lidar and multi-beam sonar create new challenges for hydrodynamic models of estuaries, tidelands, and river deltas. We now can readily obtain detailed elevation data on 1 m scales and finer, but solving hydrodynamics with model grid cells at these small scales remains computationally prohibitive (primarily because of the small time step required for small grid cells). Practical estuarine models for the next decade or so will likely have grid scales in the range of 5 to 15 m. So how should we handle known subgrid-scale features? Simply throwing out known data does not seem like a good idea, but there is no consensus on how best to incorporate knowledge of subgrid topography into either hydrodynamic or turbulence models. This presentation discusses both the theoretical foundations for modeling subgrid-scale features and the challenges in applying these ideas in the salt marshes of a river delta. The subgrid problem highlights some important areas for field and laboratory research to provide calibration parameters for new models that upscale the effects of known subgrid features.

  3. River, delta and coastal morphological response accounting for biological dynamics

    NASA Astrophysics Data System (ADS)

    Goldsmith, W.; Bernardi, D.; Schippa, L.

    2015-03-01

    Management and construction can increase resilience in the face of climate change, and benefits can be enhanced through integration of biogenic materials including shells and vegetation. Rivers and coastal landforms are dynamic systems that respond to intentional and unintended manipulation of critical factors, often with unforeseen and/or undesirable resulting effects. River management strategies have impacts that include deltas and coastal areas which are increasingly vulnerable to climate change with reference to sea level rise and storm intensity. Whereas conventional assessment and analysis of rivers and coasts has relied on modelling of hydrology, hydraulics and sediment transport, incorporating additional biological factors can offer more comprehensive, beneficial and realistic alternatives. Suitable modelling tools can provide improved decision support. The question has been whether current models can effectively address biological responses with suitable reliability and efficiency. Since morphodynamic evolution exhibits its effects on a large timescale, the choice of mathematical model is not trivial and depends upon the availability of data, as well as the spatial extent, timelines and computation effort desired. The ultimate goal of the work is to set up a conveniently simplified river morphodynamic model, coupled with a biological dynamics plant population model able to predict the long-term evolution of large alluvial river systems managed through bioengineering. This paper presents the first step of the work related to the application of the model accounting for stationary vegetation condition. Sensitivity analysis has been performed on the main hydraulic, sedimentology, and biological parameters. The model has been applied to significant river training in Europe, Asia and North America, and comparative analysis has been used to validate analytical solutions. Data gaps and further areas for investigation are identified.

  4. Impacts of the Indian Rivers Inter-link Project on Sediment Transport to River Deltas

    NASA Astrophysics Data System (ADS)

    Higgins, S.; Overeem, I.; Syvitski, J. P.

    2015-12-01

    The Indian Rivers Inter-link project is a proposal by the Indian government to link several of India's major rivers via a network of reservoirs and canals. Variations of the IRI have been discussed since 1980, but the current plan has recently received increased support from the Indian government. Construction on three canals has controversially begun. If the Inter-link project moves forward, fourteen canals will divert water from tributaries of the Ganges and Brahmaputra rivers to areas in the west, where fresh water is needed for irrigation. Additional canals would transport Himalayan sediments 500 km south to the Mahanadi delta and more than 1000 km south to the Godavari and Krishna deltas. We investigate the impacts of the proposed diversions on sediment transport to the Mahanadi/Brahmani, Godavari, and Krishna deltas in India and the Ganges-Brahmaputra Delta in Bangladesh. We map the entire river network and the proposed new nodes and connections. Changing watersheds are delineated using the Terrain Analysis Using Digital Elevation Models (TauDEM) Suite. Climate data comes from interpolation between observed precipitation stations located in China, Nepal, India, Bhutan and Bangladesh. Changes in water discharge due to the proposed canals are simulated using HydroTrend, a climate-driven hydrological water balance and transport model that incorporates drainage area, discharge, relief, temperature, basin-average lithology, and anthropogenic influences. Simulated river discharge is validated against observations from gauging stations archived by the Global Runoff Data Center (GRDC). HydroTrend is then used to investigate sediment transport changes that may result from the proposed canals. We also quantify changes in contributing areas for the outlets of nine major Indian rivers, showing that more than 50% of the land in India will contribute a portion of its runoff to a new outlet should the entire canal system be constructed.

  5. Space Radar Image of Nile River Delta, Egypt

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This spaceborne radar image shows the area just north of the city of Cairo, Egypt, where the Nile River splits into two main branches. The Rosetta Branch is the curving dark line in the center of the image and the Damietta Branch is the curving dark line in the lower right of the image. The light blue area on the right half of the image is a portion of the Nile River Delta. The thinner, straighter lines and the small network of gold lines are irrigation canals. There are more than 10,000 kilometers of canals throughout the Nile Delta. A transition zone of irrigated fields is shown in blue and yellow between the irrigated delta and the surrounding desert. The desert is the dark blue area on the left side of the image lacking the pattern of irrigated fields. This image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) on October 4, 1994, onboardthe space shuttle Endeavour. The image is 75 kilometers by 60 kilometers (46 miles by 37 miles) and is centered at 30.2 degreesnorth latitude, 31.1 degrees east longitude. North is toward the upper right. The colors are assigned to different radar frequencies and polarizations as follows: red is L-band, horizontally transmitted and received; green is C-band, horizontally transmitted and received; and blue is the ratio of C-band and L-band, horizontally transmitted and received. SIR-C/X-SAR, a joint mission of the German, Italian and United States space agencies, is part of NASA's Mission to PlanetEarth program.

  6. Process connectivity in a naturally prograding river delta

    NASA Astrophysics Data System (ADS)

    Sendrowski, Alicia; Passalacqua, Paola

    2017-03-01

    River deltas are lowland systems that can display high hydrological connectivity. This connectivity can be structural (morphological connections), functional (control of fluxes), and process connectivity (information flow from system drivers to sinks). In this work, we quantify hydrological process connectivity in Wax Lake Delta, coastal Louisiana, by analyzing couplings among external drivers (discharge, tides, and wind) and water levels recorded at five islands and one channel over summer 2014. We quantify process connections with information theory, a branch of mathematics concerned with the communication of information. We represent process connections as a network; variables serve as network nodes and couplings as network links describing the strength, direction, and time scale of information flow. Comparing process connections at long (105 days) and short (10 days) time scales, we show that tides exhibit daily synchronization with water level, with decreasing strength from downstream to upstream, and that tides transfer information as tides transition from spring to neap. Discharge synchronizes with water level and the time scale of its information transfer compares well to physical travel times through the system, computed with a hydrodynamic model. Information transfer and physical transport show similar spatial patterns, although information transfer time scales are larger than physical travel times. Wind events associated with water level setup lead to increased process connectivity with highly variable information transfer time scales. We discuss the information theory results in the context of the hydrologic behavior of the delta, the role of vegetation as a connector/disconnector on islands, and the applicability of process networks as tools for delta modeling results.

  7. Research on vulnerability assessments of the Huanghe (Yellow River) delta

    NASA Astrophysics Data System (ADS)

    qiao, shuqing; shi, xuefa

    2014-05-01

    Coastal zone located at the juncture of the sea, river and land, and under the influence of both land and ocean (including atmosphere), especially the sea-level rise and human activities, are vulnerable to environment and ecology. At highest risk are coastal zone of South, Southeast and East Asia with dense populations, low elevations and inadequate adaptive capacity. In China, more than 40% of the population live on the 15% of the land in coastal area and more than 70% cities located around the coastal area. The Chinese coastal region, especially river delta area has been experienced erosion, seawater intrusion and decrease in biodiversity under the combined influence of sea-level rise, tectonic subsidence and flooding. Furthermore, some kinds of human activity, such as land use, building, dam construction, reclamation from the sea and waste dumping strengthen the vulnerability of environment and ecosystem in coastal region. The coastal hazards (e.g. coastal erosion, seawater intrusion, land subsidence) and vulnerability of the Huanghe (Yelllow River) delta area are studied during the past several years. A systematic coastal assessment index is built and an evaluation model is developed using the development platform of Visual studio.Net 2005. The assessment index system includes two parts, inherent (sea level rise rate, elevation, morphology, water and sediment discharge, mean tidal range, mean wave height etc) and specific vulnerability index (population density, GDP, land utilization, protection structures etc). The assessment index are determined the weight using Analytic hierarchy process (AHP) method. Based on the research results, we better understand the current status and future change of coastal vulnerability and hazards, discuss the impact of the natural possess and human activities. Furthermore, we provide defending strategies for coastal zone vulnerability and typical coastal hazards.

  8. Phytosociology and succession on earthquake-uplifted coastal wetlands, Copper River Delta, Alaska.

    Treesearch

    T.F. Thilenius

    1995-01-01

    The delta formed by the Copper River stretches more than 75 kilometers along the south-central coastline of Alaska. It is the terminus of the outwash deposits from a large part of the most heavily glaciated region of North American, and all major rivers that flow into the delta carry extremely high levels of suspended sediments. Coastal wetlands extend inland for as...

  9. The Riverbed Evolution, Avulsions and Backwater Hydrodynamics on the Huanghe River Delta

    NASA Astrophysics Data System (ADS)

    Chu, Z.; Ganti, V.; Lamb, M. P.

    2013-12-01

    The Huanghe River is known for high suspended sediment concentration and resultant heavy sedimentation and frequent channel-shifting among major rivers in the world. This plain coastal river is the main contributor of terrestrial sediment to the Bohai Sea and the Yellow Sea. Since 1855, there have been 11 major avulsions (versus 4 avulsions on the Mississippi River during the Holocene) on the lower reach with an recurrence interval of ~10 years, developing individual lobes that build up the modern Huanghe River delta. We summarize the main features of riverbed evolution on the delta with a database of measured data. The observed avulsions on the delta often occurred along a persistent spatial node, whose distance from the shoreline scales with the computed backwater length. In order to explain the avulsion locations on the delta, and meanwhile to test the viewpoint of river backwater controls on avulsion locations on deltas, we simulate the long profile evolution of the riverbed on the delta considering river discharge, river plume spreading, land subsidence and sea level rise, with a 1D fluvial morphodynamic model. The main results from the numerical simulations provide insights into how the long profile of the river on the delta evolves at the time scales of flood events and avulsions.

  10. Assessing impact of urbanization on river water quality in the Pearl River Delta Economic Zone, China.

    PubMed

    Ouyang, Tingping; Zhu, Zhaoyu; Kuang, Yaoqiu

    2006-09-01

    The Pearl River Delta Economic Zone is one of the most developed regions in China. It has been undergoing a rapid urbanization since the reformation and opening of China in 1978. This process plays a significant impact on the urban environment, particularly river water quality. The main goal of this present study is to assess the impact of urban activities especially urbanization on river water quality for the study area. Some Landsat TM images from 2000 were used to map the areas for different pollution levels of urban river sections for the study area. In addition, an improved equalized synthetic pollution index method was utilized to assess the field analytical results. The results indicate that there is a positive correlation between the rapidity of urbanization and the pollution levels of urban river water. Compared to the rural river water, urban river water was polluted more seriously. During the urban development process, urbanization and urban activities had a significant negative impact on the river water quality.

  11. Reliability characteristics of a platform in the Mississippi River delta

    SciTech Connect

    Bea, R.G.

    1998-08-01

    In August 1995, the Energy Development Corporation installed a conventional drilling and production platform in South Pass Block 47. Due to its proximity to the delta of the Mississippi River, this platform is exposed to the environmental forces developed by hurricanes and movements of the seafloor. This paper summarizes results from probability-based study of the oceanographic, geotechnical, and structural reliability characteristics of a conventional platform installed in South Pass Block 47. Experience with other structures installed in this area that have failed due to seafloor slides is correlated with results from these analyses. The analyses indicated that a conventional platform could be safely installed at the proposed location. The platform has experienced several severe hurricanes without signs of distress.

  12. Water management in the Senegal River Delta: a continuing uncertainty

    NASA Astrophysics Data System (ADS)

    Mietton, M.; Dumas, D.; Hamerlynck, O.; Kane, A.; Coly, A.; Duvail, S.; Pesneaud, F.; Baba, M. L. O.

    2007-11-01

    Water management is the driving force behind the productivity of the ecosystems of the Senegal River Estuary and floodplains. It is dependent on human decision-making, but has been separated from the River's flooding since the building of the Diama Dam. The current objectives of the Office de Mise en Valeur du fleuve Sénégal (OMVS: Senegal River Development Agency) are mainly turned towards the development of irrigated agriculture on the former floodplains and since 2002 the production of hydroelectric power at Manantali. In October 2003, a four-metre-wide runoff canal, which quickly widened into a breach several hundred metres across, was dug in the Barbary Spit area to protect the city of Saint-Louis from heavy flooding. The hydraulic quality of the area downstream from the dam has improved to the extent that there is no longer any flooding there, but as the management of the dams concerns only the section of the river between Manantali and Diama, a certain amount of flood risk probably still persists. The intrusion of seawater into the estuary is also threatening ecosystems and fresh water supplies, and abruptly altering agricultural practices such as fruit and vegetable growing in the Gandiolais district. When added to the tentative efforts to coordinate the management of the two dams, with no management objective downstream from Diama, such permanent modifications impose serious constraints on the managers and residents of the lower delta. This paper presents an overview of the constraints and uncertainties at different levels and scales. This wholly human-wrought environment can be considered as a learning experience, where a large number of variables need to be monitored closely and an ongoing process of participatory analysis should be backed up by multidisciplinary research.

  13. Acoustical facies analysis at the Ba Lat delta front (Red River Delta, North Vietnam)

    NASA Astrophysics Data System (ADS)

    van den Bergh, G. D.; van Weering, Tj. C. E.; Boels, J. F.; Duc, D. M.; Nhuan, M. T.

    2007-02-01

    A shallow penetrating, high-resolution acoustic study was performed in the Ba Lat delta, the major distributary of the Red River System in Northern Vietnam. An acoustic facies map was constructed and the various facies types were validated through analysis of bottom sediments, by a study of gravity cores collected at 22 stations. Analysis of the acoustic profiles and gravity cores revealed the presence of an asymmetrical, S to SW prograding prodelta lobe, in accordance with the prevailing longshore currents to the S. The southern part of this prodelta is detached from the protruding Ba Lat delta front. The prodelta is dominated by muddy sediments with minor thin (<5 cm) sandy and silty layers. The coarser-grained layers decrease in abundance away from the Ba Lat river mouth. Offshore, the modern delta deposits are characterized by an off-lapping contact over a semi-prolonged bottom reflector lacking any sub-bottom reflectors. This semi-prolonged bottom reflector is correlated with sandy deposits of presumably Early Holocene age. Bottom and coastal erosion is restricted to two areas N and SW of the Ba Lat. Erosion in the North is inferred to be due to reduced sediment supply as a result of shifting in 1971 of the main outlet to its present, more southern location. The erosional area along the Hai Hau coast SW of the Ba Lat also has experienced a reduction in sediment supply in the course of the 20th century, when the local Song Vop distributary channel became less active and was completely dammed in the 1970s. Most sediment supplied by the Ba Lat at present bypasses the Hai Hau erosional coastal zone, as the active part of the Ba Lat prodelta is detached from the coast SW of the Ba Lat. An active, NNE-SSW trending fault system with surface expression is located along the offshore edge of the prodelta, and is linked to deeper fault structures in this active neotectonic region. Subsurface reflectors are folded in the vicinity of the fault.

  14. Natural and Human Impacts on Recent Development of Asian Large Rivers and Deltas

    NASA Astrophysics Data System (ADS)

    Liu, P.; Lu, C.

    2014-12-01

    Most recent data analysis indicates sediment loads in most of Asian large rivers (like, Yellow, Yangtze, Pearl, Chao Phraya, Indus, Krishna, Godavari, etc) have decreased up to 80-90% in the past 60 years. Correspondingly, most of Asian large river deltas are facing severe sediment starving; delta shoreline comparisons indicate that some are under strong coastal erosion. For examples, the Yellow River Delta has been retreating since 1990s when its annual sediment load has kept below 300 million tons. The Yangtze River delta kept growing before Three Gorges Dams was operating, and began to be eroded from the year 2003 to 2009, and then prograded locally due to the Deep Water Navigation Project. The Mekong Delta shoreline has also been dynamically changing with the sediment flux variation, eroding from 1989 to 1996 and prograding from 1996 to 2002. More information is available at http://www.meas.ncsu.edu/sealevel

  15. Integrating Delta Building Physics & Economics: Optimizing the Scale of Engineered Avulsions in the Mississippi River Delta

    NASA Astrophysics Data System (ADS)

    Kenney, M. A.; Mohrig, D.; Hobbs, B. F.; Parker, G.

    2011-12-01

    Land loss in the Mississippi River Delta caused by subsidence and erosion has resulted in habitat loss, interference with human activities, and increased exposure of New Orleans and other settled areas to storm surge risks. Prior to dam and levee building and oil and gas production in the 20th century, the long term rates of land building roughly balanced land loss through subsidence. Now, however, sediment is being deposited at dramatically lower rates in shallow areas in and adjacent to the Delta, with much of the remaining sediment borne by the Mississippi being lost to the deep areas of the Gulf of Mexico. A few projects have been built in order to divert sediment from the river to areas where land can be built, and many more are under consideration as part of State of Louisiana and Federal planning processes. Most are small scale, although there have been some proposals for large engineered avulsions that would divert a significant fraction of the remaining available sediment (W. Kim, et al. 2009, EOS). However, there is debate over whether small or large diversions are the economically optimally and socially most acceptable size of such land building projects. From an economic point of view, the optimal size involves tradeoffs between scale economies in civil work construction, the relationship between depth of diversion and sediment concentration in river water, effects on navigation, and possible diminishing returns to land building at a single location as the edge of built land progresses into deeper waters. Because land building efforts could potentially involve billions of dollars of investment, it is important to gain as much benefit as possible from those expenditures. We present the result of a general analysis of scale economies in land building from engineered avulsions. The analysis addresses the question: how many projects of what size should be built at what time in order to maximize the amount of land built by a particular time? The analysis

  16. Characteristics of soil salinity in the typical area of Yellow River Delta and its control measures

    NASA Astrophysics Data System (ADS)

    Zhang, Mingliang; Wang, Haixia; Pang, Xiaoke; Liu, Hui; Wang, Qun

    2017-05-01

    The Yellow River Delta is one of important ecological areas in eastern China, however sustainable development of the Yellow River Delta is seriously restricted because of severe soil salinization. The main sources of soil salinity are chloride, sodium and sulfate ions. The distribution of soil salinity in soil profiles showed that surface accumulation of soil salt was significant in the Yellow River Delta. Some control measures including soil improvement and regulation, reasonable combination of salt-fresh water irrigation in farmland, land cover and effective drainage were put forward for soil salinity control.

  17. Experimental river delta size set by multiple floods and backwater hydrodynamics

    PubMed Central

    Ganti, Vamsi; Chadwick, Austin J.; Hassenruck-Gudipati, Hima J.; Fuller, Brian M.; Lamb, Michael P.

    2016-01-01

    River deltas worldwide are currently under threat of drowning and destruction by sea-level rise, subsidence, and oceanic storms, highlighting the need to quantify their growth processes. Deltas are built through construction of sediment lobes, and emerging theories suggest that the size of delta lobes scales with backwater hydrodynamics, but these ideas are difficult to test on natural deltas that evolve slowly. We show results of the first laboratory delta built through successive deposition of lobes that maintain a constant size. We show that the characteristic size of delta lobes emerges because of a preferential avulsion node—the location where the river course periodically and abruptly shifts—that remains fixed spatially relative to the prograding shoreline. The preferential avulsion node in our experiments is a consequence of multiple river floods and Froude-subcritical flows that produce persistent nonuniform flows and a peak in net channel deposition within the backwater zone of the coastal river. In contrast, experimental deltas without multiple floods produce flows with uniform velocities and delta lobes that lack a characteristic size. Results have broad applications to sustainable management of deltas and for decoding their stratigraphic record on Earth and Mars. PMID:27386534

  18. Experimental river delta size set by multiple floods and backwater hydrodynamics.

    PubMed

    Ganti, Vamsi; Chadwick, Austin J; Hassenruck-Gudipati, Hima J; Fuller, Brian M; Lamb, Michael P

    2016-05-01

    River deltas worldwide are currently under threat of drowning and destruction by sea-level rise, subsidence, and oceanic storms, highlighting the need to quantify their growth processes. Deltas are built through construction of sediment lobes, and emerging theories suggest that the size of delta lobes scales with backwater hydrodynamics, but these ideas are difficult to test on natural deltas that evolve slowly. We show results of the first laboratory delta built through successive deposition of lobes that maintain a constant size. We show that the characteristic size of delta lobes emerges because of a preferential avulsion node-the location where the river course periodically and abruptly shifts-that remains fixed spatially relative to the prograding shoreline. The preferential avulsion node in our experiments is a consequence of multiple river floods and Froude-subcritical flows that produce persistent nonuniform flows and a peak in net channel deposition within the backwater zone of the coastal river. In contrast, experimental deltas without multiple floods produce flows with uniform velocities and delta lobes that lack a characteristic size. Results have broad applications to sustainable management of deltas and for decoding their stratigraphic record on Earth and Mars.

  19. The Potential of Time Series Based Earth Observation for the Monitoring of Large River Deltas

    NASA Astrophysics Data System (ADS)

    Kuenzer, C.; Leinenkugel, P.; Huth, J.; Ottinger, M.; Renaud, F.; Foufoula-Georgiou, E.; Vo Khac, T.; Trinh Thi, L.; Dech, S.; Koch, P.; Le Tissier, M.

    2015-12-01

    Although river deltas only contribute 5% to the overall land surface, nearly six hundred million people live in these complex social-ecological environments, which combine a variety of appealing locational advantages. In many countries deltas provide the major national contribution to agricultural and industrial production. At the same time these already very dynamic environments are exposed to a variety of threats, including the disturbance and replacement of valuable ecosystems, increasing water, soil, and air pollution, human induced land subsidence, sea level rise, as well upstream developments impacting water and sediment supplies. A constant monitoring of delta systems is thus of utmost relevance for understanding past and current land surface change and anticipating possible future developments. We present the potential of Earth Observation based analyses and derived novel information products that can play a key role in this context. Along with the current trend of opening up numerous satellite data archives go increasing capabilities to explore big data. Whereas in past decades remote sensing data were analysed based on the spectral-reflectance-defined 'finger print' of individual surfaces, we mainly exploit the 'temporal fingerprints' of our land surface in novel pathways of data analyses at differing spatial-, and temporally-dense scales. Following our results on an Earth Observation based characterization of large deltas globally, we present in depth results from the Mekong Delta in Vietnam, the Yellow River Delta in China, the Niger Delta in Nigeria, as well as additional deltas, focussing on the assessment of river delta flood and inundation dynamics, river delta coastline dynamics, delta morphology dynamics including the quantification of erosion and accretion processes, river delta land use change and trends, as well as the monitoring of compliance to environmental regulations.

  20. Barrier island arcs along abandoned Mississippi River deltas

    USGS Publications Warehouse

    Penland, S.; Suter, J.R.; Boyd, Ron

    1985-01-01

    Generation of transgressive barrier island arcs along the Mississippi River delta plain and preservation of barrier shoreline facies in their retreat paths on the inner shelf is controlled by: (1) shoreface translation; (2) age of the transgression; and (3) the thickness of the barrier island arc sediment package. Barrier island arcs experience an average relative sea level rise of 0.50-1.00 cm yr-1 and shoreface retreat rates range from 5-15 m yr-1. Young barrier island arc sediment packages (Isles Dernieres) are thin and have experienced limited landward retreat of the shoreface. Older barrier island arcs (Chandeleur Islands) are thicker and have experienced significant landward movement of the shoreface because of the greater time available for retreat. If the transgressed barrier shoreline sediment package lies above the advancing ravinement surface, the entire sequence is truncated. A thin reworked sand sheet marks the shoreface retreat path. The base of the transgressive sediment package can lie below the ravinement surface in older barrier shorelines. In this setting, the superstructure of the barrier shoreline is truncated, leaving the basal portion of the transgressive sequence preserved on the inner shelf. A variety of transgressive stratigraphic sequences from sand sheets to truncated barrier islands to sand-filled tidal inlet scars have been identified by high resolution seismic profiling across the shoreface retreat paths of Mississippi delta barrier island arcs. One of these examples, the Isles Dernieres, represents a recently detached barrier island arc in the early stages of transgression. An older example, the Chandeleur Islands, represents a barrier island arc experiencing long-term shoreface retreat. This paper describes the stratigraphic character and preserved transgressive facies for the Isles Dernieres and Chandeleur Islands. ?? 1985.

  1. The evolution of a subaqueous delta in the Anthropocene: A stratigraphic investigation of the Brazos River delta, TX USA

    NASA Astrophysics Data System (ADS)

    Carlin, Joseph A.; Dellapenna, Timothy M.

    2015-12-01

    Globally, deltas are increasingly threatened by anthropogenic activities. As a result, deltas now evolve through the combined effects of natural and human-induced processes occurring throughout the fluvial-deltaic system. The Brazos River delta, located along the Texas coast in the northwestern Gulf of Mexico, and its watershed have been impacted by direct and indirect human activities since the late 19th century. This provides an opportunity to investigate how such alterations have shaped the evolution of a delta in the Anthropocene, a time when humans are drivers of geological change. Historic alteration to the delta and watershed include extensive agricultural activity, jetty construction at the mouth in the late 1890s, mouth diversion ~10 km to the southwest in 1929, and reservoir construction throughout the early and mid 20th Century. Three subaerial deltaic geometries provided the framework to connect subaerial deltaic responses, to the anthropogenic alterations, to the resulting stratigraphic characteristics observed in the subaqueous delta. This study utilized high-resolution geophysical data (swath bathymetry, side scan sonar, CHIRP subbottom profiling) on the subaqueous delta to investigate the subaqueous delta stratigraphy and infer the processes that shaped the deltaic record over time. The results showed distinct areas across the subaqueous delta that were dominated by erosion and deposition. Erosional areas corresponded to earlier growth phase depocenters being exposed at the surface, while the depositional areas corresponded to areas with the most recent growth phase depocenter overlying the earlier depocenters. These results highlight that the subaqueous depocenter has migrated westward over time, consistent with the observed changes to the subaerial delta. Additionally, the data showed that evidence for these past growth phases and depocenters may be preserved within the subaqueous delta, even after subaerial portions of the delta returned to pre

  2. Heavy metal flows in aquatic systems of the Don and Kuban river deltas

    NASA Astrophysics Data System (ADS)

    Tkachenko, A. N.; Tkachenko, O. V.; Lychagin, M. Yu.; Kasimov, N. S.

    2017-05-01

    This paper presents the calculated heavy metal (Fe, Mn, Zn, Ni, Cu, Cr, Co, Cd, and Pb) flows in suspended and dissolved forms in the main navigable branches of the Don and Kuban river deltas during the low-water period of 2013-2014. This work is based on the data of field studies in which water and suspended matter samples were collected and the turbidity and water discharge in deltas were measured. A quantitative estimate of heavy metal inflows into the deltas of the Don and Kuban rivers is provided. Transformation of flows of suspended and dissolved metal forms from the delta top to the sea edge is discussed. The influence of localities (Rostov-on-Don, Temryuk) on the increase in heavy metal flows downstream is shown, and the heavy metal flows in the deltas of the Don and Kuban rivers are compared.

  3. Land Creation in the Pearl River Delta, Macau's Case

    NASA Astrophysics Data System (ADS)

    Balsas, C.

    2016-02-01

    Macau has a long tradition of reclaiming land to the Pearl River. In approximately 100 years, the territory more than doubled its landmass from 11.6 square kilometer in 1912 to its current area of about 29 square kilometer. The latest reclamation phase plans to add another 3.5 square kilometer to the territory in five designated areas along the Peninsula's northeastern shore and Taipa's coastline. These projects continue the most emblematic land reclamation projects built during the last decades of the Portuguese administration. Landfill-based expansion has provided the substrate needed to urbanize the territory and enable its continuous growth. This paper examines the context and potential impacts of the most recent land reclamation projects, the first under PRC's jurisdiction. The neoliberal expansionist policies of the last decade have turned Macau in the gambling and entertainment hub of Asia. I argue that nature's uncontrollable forces and the idiosyncrasies of anticipatory planning may change the path (or at least the borders) of the territory, if climate change and sea level rise phenomena are not properly accommodated in the physical designs and long-range regional governance strategies for the Pearl River Delta estuary. The paper utilizes a climate change adaptation and mitigation framework to analyze future territorial impacts on the hydrographic-terrestrial interface. This paper continues a line of research, which started in the late 1990s and culminated with the publication of two research papers: Balsas, C. (1999) Macau: A Story of Land Reclamation. Portuguese Studies Review, 7(2): 80-92 and Balsas, C. (2000) Developing a Transport Infrastructure in a Context of Political Change, the Example of Macau. Third World Planning Review, 22(3): 261-288. The paper attempts to place the most recent land reclamation efforts in the context of other waterfront expansion and regeneration projects in southeastern Asian cities.

  4. River salinity on a mega-delta, an unstructured grid model approach.

    NASA Astrophysics Data System (ADS)

    Bricheno, Lucy; Saiful Islam, Akm; Wolf, Judith

    2014-05-01

    With an average freshwater discharge of around 40,000 m3/s the BGM (Brahmaputra Ganges and Meghna) river system has the third largest discharge worldwide. The BGM river delta is a low-lying fertile area covering over 100,000 km2 mainly in India and Bangladesh. Approximately two-thirds of the Bangladesh people work in agriculture and these local livelihoods depend on freshwater sources directly linked to river salinity. The finite volume coastal ocean model (FVCOM) has been applied to the BGM delta in order to simulate river salinity under present and future climate conditions. Forced by a combination of regional climate model predictions, and a basin-wide river catchment model, the 3D baroclinic delta model can determine river salinity under the current climate, and make predictions for future wet and dry years. The river salinity demonstrates a strong seasonal and tidal cycle, making it important for the model to be able to capture a wide range of timescales. The unstructured mesh approach used in FVCOM is required to properly represent the delta's structure; a complex network of interconnected river channels. The model extends 250 km inland in order to capture the full extent of the tidal influence and grid resolutions of 10s of metres are required to represent narrow inland river channels. The use of FVCOM to simulate flows so far inland is a novel challenge, which also requires knowledge of the shape and cross-section of the river channels.

  5. [Numerical simulation study of SOA in Pearl River Delta region].

    PubMed

    Cheng, Yan-li; Li, Tian-tian; Bai, Yu-hua; Li, Jin-long; Liu, Zhao-rong; Wang, Xue-song

    2009-12-01

    Secondary organic aerosols (SOA) is an important component of the atmospheric particle pollution, thus, determining the status and sources of SOA pollution is the premise of deeply understanding the occurrence, development law and the influence factors of the atmospheric particle pollution. Based on the pollution sources and meteorological data of Pearl River Delta region, the study used the two-dimensional model coupled with SOA module to stimulate the status and source of SOA pollution in regional scale. The results show: the generation of SOA presents obvious characteristics of photochemical reaction, and the high concentration appears at about 14:00; SOA concentration is high in some areas of Guangshou and Dongguan with large pollution source-emission, and it is also high in some areas of Zhongshan, Zhuhai and Jiangmen which are at downwind position of Guangzhou and Dongguan. Contribution ratios of several main pollution sources to SOA are: biogenic sources 72.6%, mobile sources 30.7%, point sources 12%, solvent and oil paint sources 12%, surface sources less than 5% respectively.

  6. Chemical weather forecasting for the Yangtze River Delta

    NASA Astrophysics Data System (ADS)

    Xie, Y.; Xu, J.; Zhou, G.; Chang, L.; Chen, B.

    2016-12-01

    Shanghai is one of the largest megacities in the world. With rapid economic growth of the city and its surrounding areas in recent years, air pollution has posed adverse effects on public health and ecosystem. In winter heavy pollution episodes are often associated with PM exceedances under stagnant conditions or transport events, whereas in summer the region frequently experiences elevated O3 levels. Chemical weather prediction systems with the WRF-Chem and CMAQ models are being developed to support air quality and haze forecasting for Shanghai and the Yangtze River Delta region. We will present main components of the modeling system, forecasting products, as well as evaluation results. Evaluation of the WRF-Chem forecasts show the model has generally good ability to capture the temporal variations of O3 and PM2.5. Substantial regional differences exist, with the best performance in Shanghai. Meanwhile, the forecasts tend to degrade during highly polluted episodes and transitional time periods, which highlights the need to improve model representation of key process (e.g. meteorological fields and formation of secondary pollutants). Recent work includes using the ECMWF global model forecasts as chemical boundary conditions for our regional model. We investigate the impact of chemical downscaling, and also compare the results from different models participated in the PANDA (PArtnership with chiNa on space Data) project. Results from ongoing efforts (e.g. chemical weather forecasting driven by SMS regional high resolution NWP) will also be presented.

  7. Plant community succession in modern Yellow River Delta, China*

    PubMed Central

    Zhang, Gao-sheng; Wang, Ren-qing; Song, Bai-min

    2007-01-01

    Data were collected in different successional stages using a simultaneous sampling method and analyzed through quantitative classification method. Three large groups and 12 classes were made to represent the community patterns of three succession stages and 12 succession communities. The succession series of plant community in the study area was as follows: saline bare land→community Suaeda salsa→community Tamarix chinensis→grassland. Succession degree and succession process of 12 succession communities were calculated. Most of these communities were in the lower succession stage, however, community Phragmites communis+Glycine soja and community Imperata cylindrica+G. soja were close to the succession stage of grassland climax. Five species diversity indices were used to study the changes in species richness, species evenness and diversity during succession of community. Heterogeneity index and richness index increased gradually during the community succession process, but species evenness tended to decrease with succession development. The relation between succession and environment was studied by ordination technique, and the results showed that the soil salt content was an important factor to halarch succession of the modern Yellow River Delta. It affected community structure, species composition and succession process. PMID:17657854

  8. Latest Quaternary stratigraphic framework of the Mississippi River delta region

    USGS Publications Warehouse

    Kulp, Mark; Howell, Paul; Adiau, Sandra; Penland, Shea; Kindinger, Jack; Williams, S. Jeffress

    2002-01-01

    Previous researchers separated the uppermost Quaternary stratigraphy of the Mississippi River delta region into two major lithofacies. The stratigraphically lower of these, "substratum," primarily consists of coarse-grained sediment deposited within lowstand-incised stream valleys. Relatively finer-grained "topstratum" overlies substratum; above interfluves, topstratum directly overlies weathered late Pleistocene sediments. However, the onshore to offshore distribution and architecture of these lithofacies was not well constrained. This study integrates published and unpublished lithostratigraphic data with high-resolution seismic profiles from the continental shelf to aid in mapping the regional distribution of major substratum deposits and thickness of topstratum sediments. A transgressive sand sheet commonly marks the base of the topstratum deposits, providing a stratigraphic marker to aid in regional lithostratigraphic correlations. Radiocarbondated deposits and boreholes tied to oxygen isotope chronologies provide chronostratigraphic control. Excellent correlation between these multiple datasets has been found to exist, enabling construction of regional isopachous and structural elevation maps and cross sections detailing elements of the Late Quaternary stratigraphy.

  9. Site Response in the San Joaquin/Sacramento River Delta

    NASA Astrophysics Data System (ADS)

    Fletcher, J. B.; Boatwright, J.

    2007-12-01

    The Sacramento/San Joaquin River Delta lies on the western edge of the Great Valley and contains a system of levees that are thought to be prone to catastrophic failure from a major earthquake in the San Francisco Bay area or on faults along the western border of the Great Valley. To assess this risk we deployed digital recorders and broadband sensors in late 2006 and 2007 at 3 levee sites in the Delta (each site had a top and base sensor) and at one reference site to the west. Cone penetrometer data show that at the base, the soils have low S-wave velocities of 170 to 240 m/s. Upper soil layers are typically peats and aeolian sands. During the nine months of deployment, we recorded 3 local events (45kmDelta (Byron Hot Springs , BYR) or Black Diamond Mine (BDM, part of the Berkeley Digital Seismic Network). Spectra are normalized for distance. Each spectrum is smoothed with an algorithm that tries to preserve peaks; a running mean filter is also applied to the spectra from the reference site to reduce the possibility of holes in the reference spectrum appearing as a resonance in the ratio. Our primary observation is that many of the spectral ratios show large resonances, typically at 1-3 Hz and may represent a substantial risk to the levees. Sites at the tops of levees typically have stronger resonances in the 1-3 Hz range compared to base sites. The character of these ratios, however, differs substantially for each event. For example, the top site at Bethel Isl. has peaks in the site response with amplitudes between 6 and 15 (2-3Hz) for an earthquake located near Berkeley using either reference site, but is only apparent in the ratios using BDM for the other two events. This is because BYR has more amplitude in the 2- 3

  10. Sediment and water chemistry of the San Juan River and Escalante River deltas of Lake Powell, Utah, 2010-2011

    USGS Publications Warehouse

    Hornewer, Nancy J.

    2014-01-01

    Recent studies have documented the presence of trace elements, organic compounds including polycyclic aromatic hydrocarbons, and radionuclides in sediment from the Colorado River delta and from sediment in some side canyons in Lake Powell, Utah and Arizona. The fate of many of these contaminants is of significant concern to the resource managers of the National Park Service Glen Canyon National Recreation Area because of potential health impacts to humans and aquatic and terrestrial species. In 2010, the U.S. Geological Survey began a sediment-core sampling and analysis program in the San Juan River and Escalante River deltas in Lake Powell, Utah, to help the National Park Service further document the presence or absence of contaminants in deltaic sediment. Three sediment cores were collected from the San Juan River delta in August 2010 and three sediment cores and an additional replicate core were collected from the Escalante River delta in September 2011. Sediment from the cores was subsampled and composited for analysis of major and trace elements. Fifty-five major and trace elements were analyzed in 116 subsamples and 7 composited samples for the San Juan River delta cores, and in 75 subsamples and 9 composited samples for the Escalante River delta cores. Six composited sediment samples from the San Juan River delta cores and eight from the Escalante River delta cores also were analyzed for 55 low-level organochlorine pesticides and polychlorinated biphenyls, 61 polycyclic aromatic hydrocarbon compounds, gross alpha and gross beta radionuclides, and sediment-particle size. Additionally, water samples were collected from the sediment-water interface overlying each of the three cores collected from the San Juan River and Escalante River deltas. Each water sample was analyzed for 57 major and trace elements. Most of the major and trace elements analyzed were detected at concentrations greater than reporting levels for the sediment-core subsamples and composited

  11. The Selenga River delta - a geochemical barrier for the waters of Lake Baikal

    NASA Astrophysics Data System (ADS)

    Chalov, Sergey; Thorslund, Josefin; Pietron, Jan; Jarsjö, Jerker

    2016-04-01

    Delta systems play an important role in retention of sediments and contaminants to downstream recipients, through processes such as gravitational sedimentation, flocculation and biofiltration. The Selenga river delta is one of the world's largest inland deltas, providing a huge buffer zone between Lake Baikal and upstream waters of the Selenga river basin. Understanding the delta functioning is critical for the planning of water management measures in the Selenga River Basin and for protection of the waters of Lake Baikal. We here study the current state and functioning of the delta's ecosystem and hydrogeochemical processes. More specifically, we considered spatio-temporal changes in water flow, morphology and transport of sediments and metals within the delta and what potential impacts these changes may have on the delta functions. Results show that the delta network has a large influence on the mass of metals reaching the Lake Baikal at the delta outlet. Regions with high density of wetlands and small channels, in contrast to main channel regions, show a consistent pattern of considerable contaminant filtering and removal (between 77-99% for key metals), during both high and low flow conditions, following with a significant increase (2-3 times) of bottom sediment pollution. Geomorphological processes also governs the barrier function of the delta, due to partitioning of flow between different channel systems. These results are particularly relevant in the light of recent and expected future changes involving both the hydrology and water quality in the Lake Baikal basin. Taken together, this emphasizes the importance of understanding the interface between flow partitioning, delta morphology, and sediment and metal patterns and storage rates for fully capturing and quantifying the variety in delta functions. This is particularly relevant coupled to hydroclimatic changes in the region, which could lead to significant decline in barrier functions of the delta due to

  12. 78 FR 39314 - Notice of Availability of the Decision Record for the Delta River Special Recreation Management...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-01

    ....AL0000] Notice of Availability of the Decision Record for the Delta River Special Recreation Management... of the Decision Record (DR) for the Delta River Special Recreation Management Area and East Alaska..., Glennallen, AK 99588 or by calling 907-822-3217. The Environmental Assessment (EA) for the Delta...

  13. Fractionation and ecological risk of metals in urban river sediments in Zhongshan City, Pearl River Delta.

    PubMed

    Cai, Jiannan; Cao, Yingzi; Tan, Haijian; Wang, Yanman; Luo, Jiaqi

    2011-09-01

    Surface sediments collected from nine urban rivers located in Zhongshan City, Pearl River Delta, were analyzed for total concentration of metals with digestion and chemical fractionation adopting the modified European Community Bureau of Reference (BCR) sequential extraction procedure. The results showed that concentration and fractionation of metals varied significantly among the rivers. The total concentration of eight metals in most rivers did not exceed the China Environmental Quality Standard for Soil, Grade III. The potential ecological risk of metals to rivers were related to the land use patterns, in the order of manufacturing areas > residential areas > agriculture areas. The concentration of Pb in the reducible fraction was relatively high (60.0-84.3%). The dominant proportions of Cd, Zn and Cu were primary in the non-residual fraction (67.0%, 71.8% and 81.4% on average respectively), while the percentages of the residual fractions of Cr and Ni varied over a wide range (43-85% and 24-71% respectively). The approaches of the Håkanson ecological risk index and Secondary Phase Enrichment Factor were applied for ecological risk assessment and metal enrichment calculation. The results indicated Hg and Cd had posed high potential ecological risk to urban rivers in this region. Meanwhile, there was widespread pollution and high enrichment of Cu in river sediments in this region. Multiple regression analysis showed that five water quality parameters (pH, DO, COD(Mn), NH(4)(+)-N, TP) had little influence on the distribution of metal fractionation. This result revealed that the ecological risk of metals was not eliminated along with the improvement in water quality. Correlation studies showed that among the metals, Group A (Cd, As, Pb, Zn Hg, r = 0.730-0.924) and Group B (Cr, Cu, Ni, r = 0.815-0.948) were obtained, and the metal contaminations were from industrial activities rather than residential.

  14. The sediment-starved Yellow River Delta as remotely controlled by human activities in the river basin

    NASA Astrophysics Data System (ADS)

    Wang, H.; Saito, Y.; Bi, N.; Syvitski, J. P.; Yang, Z.

    2016-02-01

    Human presented significant disturbances on the natural processes of land-ocean interactions in context of global change. Here we illustrate how the signals of human activities in the river basin have been transferred to the coastal ocean along the hydrological pathway and remotely controlled the Yellow River Delta. Dam-orientated water and sediment regulation scheme (WSRS) has resulted in effective erosion of the lower channel and mitigation of siltation within the reservoirs. However, significant impacts have been identified on the delta morphology and coastal ecosystem ten years after the WSRS, which was unexpected at the beginning of engineering efforts. The coarser sediment derived from the channel erosion during the first phase of WSRS was directly contributed to the rapid accretion of present river mouth, whereas the delta was starved and declined due to insufficient sediment supply and regime shift of sediment transport. The fine-grained sediment exported from the Xiaolangdi Reservoir during the second phase of WSRS seemed to be a critical carrier for the nutrients and pollutants. The human-altered hydrological cycle, enhanced delivery of nutrient and pollutants and the changing estuarine environment present unpredictable impacts on both terrestrial and aquatic ecosystem in the delta region. These confirm that humans are modifying the river-coast system in ways that go well beyond climate change, and an integrated management of the river-coast continuum is crucially important for the sustainability of the river-delta system.

  15. The sediment-starved Yellow River Delta as remotely controlled by human activities in the river basin

    NASA Astrophysics Data System (ADS)

    Wang, H.; Bi, N.

    2015-12-01

    Human presented significant disturbances on the natural processes of land-ocean interactions in context of global change. Here we illustrate how the signals of human activities in the river basin have been transferred to the coastal ocean along the hydrological pathway and remotely controlled the Yellow River Delta. Dam-orientated water and sediment regulation scheme (WSRS) has resulted in effective erosion of the lower channel and mitigation of siltation within the reservoirs. However, significant impacts have been identified on the delta morphology and coastal ecosystem ten years after the WSRS, which was unexpected at the beginning of engineering efforts. The coarser sediment derived from the channel erosion during the first phase of WSRS was directly contributed to the rapid accretion of present river mouth, whereas the delta was starved and declined due to insufficient sediment supply and regime shift of sediment transport. The fine-grained sediment exported from the Xiaolangdi Reservoir during the second phase of WSRS seemed to be a critical carrier for the nutrients and pollutants. The human-altered hydrological cycle, enhanced delivery of nutrient and pollutants and the changing estuarine environment present unpredictable impacts on both terrestrial and aquatic ecosystem in the delta region. These confirm that humans are modifying the river-coast system in ways that go well beyond climate change, and an integrated management of the river-coast continuum is crucially important for the sustainability of the river-delta system.

  16. A source-to-sink study of the Mekong River Delta: Hydrology, delta evolution, and sediment transport modeling

    NASA Astrophysics Data System (ADS)

    Xue, Zuo

    The Mekong River is the third largest river in the Western Pacific. As the population and economy of the area booms, more and more dams are built in the Mekong basin. Concerns about negative impacts on downstream and the delta plain from upstream damming have been raised ever since the completion of the Manwan Dam, the first of the 13 major dams designed on the Upper Mekong, in 1993. The runoff of the Lower Mekong has a closer connection with the regional precipitation and El Nino Southern Oscillation during the post-dam period (1994-2005) than the pre-dam period (1950-1993). With ˜200 new dams to be added to the basin in the next couples of decades, changes are expected in both hydrological regime and delta dynamics. The Mekong River delivers ˜160 million tons of sediment per year to the South China Sea (SCS). The Mekong River Delta (MRD) has the third largest delta plain in the world. High-resolution seismic profiling and coring during 2006 and 2007 cruises reveals a low gradient, subaqueous delta system, up to 20 m thick, surrounding the modern MRD in the west of the SCS. A late Holocene sediment budget for the MRD has been determined, based on the area and thickness of deltaic sediment. Approximately 80% of Mekong delivered sediment has been trapped within the delta area, which, together with a falling sea-level, resulted in a rapidly prograding MRD over the past 3000 yr. The late Holocene evolution of the MRD has shown a morphological asymmetry indicated by a large down-drift area and a rapid progradation around Cape Camau, ˜200 km downstream from the river mouth. The coupled hydrodynamic-sediment transport modeling using the Regional Ocean Modeling System (ROMS) and Community Sediment Transport Model System (CSTMS) showed that wind is a most important factor influencing the along-shelf sediment transport. This associates MRD's asymmetric evolution with an increased wave influence during the Neoglaciation. Coastal currents formed by the geostrophically

  17. Geochemical flows of heavy metals in the Don and Kuban Rivers deltas

    NASA Astrophysics Data System (ADS)

    Tkachenko, Oleg; Tkachenko, Anna; Lychagin, Mikhael

    2015-04-01

    Don and Kuban are the two biggest rivers of the Azov sea basin. Deltaic areas of Don and Kuban Rivers have been influenced by agricultural and industry for a long time. A significant amount of heavy metals and biogenic elements comes into the rivers downstream annually. However, in the deltaic areas these geochemical flows are transformed due to changing of the environment conditions, some pollutions are excluded from the flows and accumulated in the deltaic landscapes. In this way Don and Kuban Rivers deltas can be considered as the biogeochemical filters on the way of the heavy metals and biogenic elements flows in to the Azov Sea. The paper presents the results of the heavy metals flows investigation in the Don and Kuban Rivers deltas. This investigation is based on the field studies of the water flow and sediment load distributions and heavy metals (Fe, Mn, Zn, Cu, Cd, Ni, Cr, Co, Pb) content in the water and suspended matter of the deltas. Quantities arriving of heavy metals in the delta apex in the low water period are calculated; seasonal patterns of flows are considered. Is shown that greater number of heavy metals flow into the delta during the flood period, especially with respect to the dissolved forms of zinc and copper; it is also shown a significant increase of the heavy metals flows downstream of the large cities (Rostov-on-Don, Azov, Temryuk). All these facts indicate anthropogenic impact on the heavy metals inflow. In comparing the heavy metals flow in the Don and Kuban Rivers deltas investigated that Don River flows is an order of magnitude greater than the Kuban River flows. When it comes about the structure of the flows, shown that Don River characterized increased content of dissolved form of heavy metals; Kuban River originates in the Caucasus Mountains so the proportion of suspended forms is higher.

  18. Variability Matters: New Insights into Mechanics of River Avulsions on Deltas and Their Deposits

    NASA Astrophysics Data System (ADS)

    Ganti, V.

    2015-12-01

    River deltas are highly dynamic, often fan-shaped depositional systems that form when rivers drain into a standing body of water. They host over a half billion people and are currently under threat of drowning and destruction by relative sea-level rise, subsidence, and anthropogenic interference. Deltas often develop planform fan shapes through avulsions, whereby major river channel shifts occur via "channel jumping" about a spatial node, thus determining their fundamental length scale. Emerging theories suggest that the size of delta lobes is set by backwater hydrodynamics; however, these ideas are difficult to test on natural deltas, which evolve on centennial to millennial timescales. In this presentation, I will show results from the first laboratory delta built through successive deposition of lobes that maintain a constant size that scales with backwater hydrodynamics. The characteristic size of deltas emerges because of a preferential avulsion node that remains fixed spatially relative to the prograding shoreline, and is a consequence of multiple river floods that produce persistent morphodynamic river-bed adjustment within the backwater zone. Moreover, river floods cause erosion in the lowermost reaches of the alluvial river near their coastline, which may leave erosional boundaries in the sedimentary record that may appear similar to those previously interpreted to be a result of relative sea-level fall. I will discuss the implications of these findings in the context of sustainability management of deltas, decoding their stratigraphic record, and identifying ancient standing bodies of water on other planets such as Mars. Finally, I will place this delta study in a broader context of recent work that highlights the importance of understanding and quantifying variability in sedimentology and geomorphology.

  19. Modelling suspended sediment distribution in the Selenga River Delta using LandSat data

    NASA Astrophysics Data System (ADS)

    Chalov, Sergey R.; Bazilova, Varvara O.; Tarasov, Mikhail K.

    2017-03-01

    The Selenga River is the largest tributary of Baikal Lake and it's delta covers around 600 km2. Suspended sediment concentrations (SSC) in the Selenga river delta were modelled based on LandSat images data. The seasonal variability in suspended sediment retention during the period 1989 to 2015 was calculated. The results suggest that sediment storage in the Selenga delta is observed during high discharges (> 1500 m3 s-1), whereas sediment export increases under lower flow conditions (< 1500 m3 s-1). The changes in seasonal SSC patterns are explained by wetland inundation during floods and channel erosion or Baikal wind surge during low flow periods.

  20. Establishing river basin organisations inVietnam: Red River, Dong Nai River and Lower Mekong Delta.

    PubMed

    Taylor, P; Wright, G

    2001-01-01

    River basin management is receiving considerable attention at present. Part of the debate, now occurring worldwide, concerns the nature of the organisations that are required to manage river basins successfully, and whether special-purpose river basin organisations (RBOs) are always necessary and in what circumstance they are likely to (i) add to the management of the water resources and (ii) be successful. The development of river basin management requires a number of important elements to be developed to a point where the river basin can be managed successfully. These include the relevant laws, the public and non-government institutions, the technical capabilities of the people, the understanding and motivation of people, and the technical capacity and systems, including information. A river basin organisation (or RBO) is taken to mean a special-purpose organisation charged with some part of the management of the water resources of a particular river basin. Generally speaking, such organisations are responsible for various functions related to the supply, distribution, protection and allocation of water, and their boundaries follow the watershed of the river in question. However, the same functions can be carried out by various organisations, which are not configured on the geographical boundaries of a river basin. This paper outlines recent work on river basin organisation in Vietnam, and makes some comparisons with the situation in Australia.

  1. Morphology and Sediment Transport Dynamics of the Selenga River Delta, Lake Baikal, Russia

    NASA Astrophysics Data System (ADS)

    Dong, T. Y.; Il'icheva, L.; Nittrouer, J. A.; Pavolv, M.

    2013-12-01

    The Selenga River fan delta is a lacustrine system located in southeastern Siberia, Russia, where Selenga River flows into Lake Baikal. The Selenga River is the largest source of sediment and water entering Lake Baikal. Covering ~550 km2, the Selenga delta is one of the largest freshwater deltas in the world. Evaluating the Selenga delta and its morphology is very important for local residents who rely upon the delta for both ecological and agricultural welfare. However, a sediment budget remains poorly constrained, as do estimates for the partitioning of water and sediment amongst the numerous bifurcating delta channels. This information is critical for addressing how the delta morphology evolves and influences the stratigraphic composition of the delta. To investigate the morphological characteristics of the delta, a field expedition was undertaken during July 2013 in collaboration with Russian scientists. The overall goal of the field work was to constrain delta dynamics through data collection. Field measurements included single-beam bathymetry data and sidescan sonar data to characterize: 1) channel geometries of the delta; 2) bedform sizes and distribution; and 3) grain-size composition of the channel bed. Flow velocity measurements were collected within the bifurcating channels to measure water discharge. Bedload samples were obtained within the active distributary channels to measure downstream sediment fining. Additionally, channel island cores were collected in order to analyze the internal architecture of the delta. The data reveal a systematic downstream sediment fining, from a predominantly gravel bed near the delta apex, to a fine-sand bed at the delta-lake interface (~40 km total distance). Bathymetry data document how width-to-depth ratios systematically decrease downstream in association with increasing channel bifurcations and decreasing channel-bed grain size. Furthermore, the investigations reveal that the delta is actively terraced, with the

  2. Network topology, Transport dynamics, and Vulnerability Analysis in River Deltas: A Graph-Theoretic Approach

    NASA Astrophysics Data System (ADS)

    Tejedor, A.; Foufoula-Georgiou, E.; Longjas, A.; Zaliapin, I. V.

    2014-12-01

    River deltas are intricate landscapes with complex channel networks that self-organize to deliver water, sediment, and nutrients from the apex to the delta top and eventually to the coastal zone. The natural balance of material and energy fluxes which maintains a stable hydrologic, geomorphologic, and ecological state of a river delta, is often disrupted by external factors causing topological and dynamical changes in the delta structure and function. A formal quantitative framework for studying river delta topology and transport dynamics and their response to change is lacking. Here we present such a framework based on spectral graph theory and demonstrate its value in quantifying the complexity of the delta network topology, computing its steady state fluxes, and identifying upstream (contributing) and downstream (nourishment) areas from any point in the network. We use this framework to construct vulnerability maps that quantify the relative change of sediment and water delivery to the shoreline outlets in response to possible perturbations in hundreds of upstream links. This enables us to evaluate which links (hotspots) and what management scenarios would most influence flux delivery to the outlets, paving the way of systematically examining how local or spatially distributed delta interventions can be studied within a systems approach for delta sustainability.

  3. Community-based restoration of desert wetlands: the case of the Colorado River delta

    Treesearch

    Osvel Hinojosa-Huerta; Mark Briggs; Yamilett Carrillo-Guerroro; Edward P. Glenn; Miriam Lara-Flores; Martha Roman-Rodriguez

    2005-01-01

    Wetland areas have been drastically reduced through the Pacific Flyway and the Sonoran Desert, with severe consequences for avian populations. In the Colorado River delta, wetlands have been reduced by 80 percent due to water management practices in the Colorado River basin. However, excess flows and agricultural drainage water has restored some areas, providing...

  4. Sand as a stable and sustainable resource for nourishing the Mississippi River delta

    NASA Astrophysics Data System (ADS)

    Nittrouer, Jeffrey A.; Viparelli, Enrica

    2014-05-01

    The Mississippi River delta is undergoing a catastrophic drowning, whereby 5,000 km2 of low-lying wetlands have converted to open water over at least the past eight decades, as a result of many anthropogenic and natural factors. Continued net land loss has been thought inevitable due to a decline in the load of total suspended sediment--both sand and mud--carried by the river. However, sand--which accounts for ~50-70% of modern and ancient Mississippi delta deposits but comprises only ~20% of the sampled portion of the total load--could be more important than mud for subaerial delta growth. Historically, half of the Mississippi River sediment load is supplied by the Missouri River. Here we analyse suspended sediment load data from two locations downstream from the lowest Missouri River dam to show that the measured sand load in the lower 1,100 km of the Mississippi River has not significantly diminished since dam construction. A one-dimensional numerical model of river morphodynamics predicts that the sand load feeding the delta will decrease only gradually over the next several centuries, with an estimated decline from current values of no more than about 17% within the coming six centuries. We conclude that the lower Mississippi River channel holds a significant reservoir of sand that is available to replenish diminished loads via bed scour and substantially mitigate land loss.

  5. [Community structure of planktonic rotifers in the Pearl River Delta].

    PubMed

    Gao, Yuan; Li, Xin-Hui; Lai, Zi-Ni; Yu, Jing; Wang, Chao; Zeng, Yan-Yi; Liu, Qian-Fu; Yang, Wan-Ling

    2014-07-01

    Four ecological investigations were carried out on planktonic rotifers in Pearl River Delta in 2012. The community structure, including spatial and temporal patterns of species composition, dominant species, biomass and biodiversity, was investigated. The correlation between the community structure of rotifers and the environmental factors was discussed. Moreover, the aggregation structures of rotifers were analyzed. A total of 53 rotifer species were found. Dominant species changed markedly with season and space. Polyarthra trigla had higher dominance. In terms of seasonal changes, the density and biomass were higher in dry season than in wet season, while the biodiversity and evenness indices were vice versa. The biomass and biodiversity of rotifers showed highly significant differences among seasons. In terms of spatial distribution, the average density and the average biomass showed an increase from the southwest to the northeast. The highest density and biomass were recorded in Shiqiao. The biodiversity and evenness indices had an opposite spatial distribution, with the highest values being recorded in Qingqi. The rotifer density was significantly different among the investigated sites, while the biomass and biodiversity were not significantly different. Correlation analysis demonstrated a highly significant positive correlation between rotifer density and biomass, as well as between biodiversity and evenness indices, and a highly negative correlation between biodiversity and biomass. The biodiversity and evenness indices both decreased markedly with the increase of biomass. Principal component analysis indicated that the rotifer density was closely correlated with environment factors, such as water temperature, pH, dissolved oxy- gen, chlorophyll a content, total phosphorus, and total nitrogen, in different seasons. Aggregation analysis based on rotifer density revealed five aggregation structures in the investigated sites, indicating significant differences

  6. Sediment transport and morphodynamic changes in Ziarat Estuary and Mond River Delta, the Persian Gulf

    NASA Astrophysics Data System (ADS)

    Razavi Arab, Azadeh; Haghshenas, S. Abbas; Samsami, Farzin

    2014-05-01

    The Mond River, which is considered as one of the Major Iranian rivers discharging in to the Persian Gulf, is bounded within the region from 51°10' to 54°28' E and 27°20' to 29°51' N, flowing in two provinces of Fars and Boushehr. The latest part of the river is completely meandered and the river mouth has been migrating twice during the past 50 years. Total sediment discharge of the river is estimated as 12 million cubic meter per year. Analysis of meandering river phenomenon and river mouth migration as well as evolution of the down-stream sand spits has long been one of the challenges in hydrodynamic discussions. This natural process usually takes place in rivers to provide energy equilibrium and its integration with human desires has posed as a management issue. The sediment discharging to the Persian Gulf plays an essential role in formation of Mond River Delta as well as a set of sand spits formed in downstream of the river mouth. The morpho-dynamic of entire environment of the Mond River - Mond Delta highly affects marine environment in the surrounding area. The present study offers the results of a numerical and field investigation of various features of river-delta interaction on Ziarat Estuary and the Mond Delta area. A numerical model has been utilized to investigate cases of flow and sediment transport behaviour in the coastal Mond area and future migration patterns of the River Mouth is estimated. Sediment sources and relevant contributions in morphodynamic changes of the sand spits are widely investigated through sediment constituent analysis. The results of the numerical model are compared with field observations and comprehensive GIS based analysis of historic shoreline changes from aerial photos and satellite imagery. It is concluded that the model achievements are capable to predict the observed phenomena. Management guidelines and suggestions are deducted and drawn from the calibration and verification of the results with field observations

  7. The population health and income nexus in the Mississippi River Delta Region and beyond.

    PubMed

    Bloom, David E; Bowser, Diana M

    2008-01-01

    The association between health and income has been well established using cross-country panel data. This paper explores this association further using data for corresponding cross sections of counties in the United States in 1970 and 2000. Special attention is paid to the stability of the associations over time and to differences between counties in the Mississippi River Delta Region and those in the rest of the United States. Regression results show that income is positively correlated with improvements in life expectancy over the period 1970 to 2000. This relationship strengthens from 1970 to 2000 for the U.S. and the non-Delta region and weakens slightly for the Delta region. Decomposition analysis shows that income explains more of the improvements in life expectancy from 1970 to 2000 for the Delta region (49%) than for the U.S. (35%) or the non-Delta region (32%). Factors other than income are less important in the Delta region during this time period. In 1970, income (64%) explains more of the difference in health between the Delta and non-Delta counties than non-income factors (36%). By the year 2000, non-income factors (77%) explain more of the disparities in health between the Delta and non-Delta countries than income factors (23%). For the year 2000, if the Delta region were to count on increased income to improve life expectancy to the average of the non-Delta region, it would need to increase its income level by 135%. The analysis indicates that population health in the Mississippi River Delta Region lags behind the rest of the United States not only because of lower income levels, but more importantly because of lower contributions to health of non-income factors.

  8. Connectivity in river deltas: Field measurements and development of a conceptual framework

    NASA Astrophysics Data System (ADS)

    Passalacqua, P.; Hiatt, M. R.

    2014-12-01

    River deltas are dynamic systems composed of a network of channels and interchannel islands that are subject to forces such as river discharge, tides, wind, and anthropogenic activities. The delivery of water, sediment, and nutrients from the channel to the delta floodplain is important for maintaining and evolving delta systems. This delivery depends on the connectivity between channels and delta floodplains. Connectivity is a concept that has been investigated extensively in tributary systems but remains relatively unexplored in delta distributary networks. This may be due to the structure of delta networks, often more complex than the one of tributary networks, and forces such as wind and tides acting on delta systems. In this study, we present a framework for analyzing connectivity in river delta networks and present field evidence of surface water connectivity mechanisms from Wax Lake Delta (WLD) in coastal Louisiana, USA through measurements of water discharge and hydraulic tracer propagation. Calculated discharges from velocity measurements reveal that 46-77% of the flow exits the system via the distributary channels, while the remaining volume is routed to the islands, highlighting the importance of channel-island connectivity and the role of islands in the hydrological network at WLD. Tides and wind also play an important role in the channel-island connectivity by modulating flow into and out of the islands, as well as influencing the hydraulic residence time of the inundated island interiors, which has implication for nutrient cycling. A framework for analyzing connectivity in river deltas is presented, in which we characterize the importance of dynamic island inundation, environmental forces, and network structure.

  9. Recent morphodynamic evolution of coastline of Mekong river Delta, towards an increased vulnerability

    NASA Astrophysics Data System (ADS)

    Besset, Manon; Brunier, Guillaume; Anthony, Edward

    2015-04-01

    Key words: Mekong river delta - Coastal deltaic morphodynamic - Deltaic vulnerability The complexity of coastal river deltas lies in part in aspects of sediment supply and redistribution, trapping and readjustment. The sediment supply and involved processes are governed by river-marine forcing, weather and climate, increasingly affected by humans, all within a frame of interactivity and morphodynamic equilibrium/disequilibrium that determine the evolution of the delta. The Mekong river delta is the third largest delta in the world. It is subject to important tidal influence, alluvial contribution from the fourth largest Asian river, seasonal monsoons and associated swell and other high-energy events. After a strong advance of over 200 km from 6.0 ka to near present (Tamura et al., 2012), the delta shoreline is rapidly and irregularly retreating, constraining the 20 million people living off the delta to suffer or adapt. This study documents changes over the last 50 years affecting the 700 km-long shoreline of the delta based on analysis of USGS topographic maps (1965), low-resolution Landsat (1973-2014) and very high-resolution SPOT 5 (2003-2011) satellite imagery. The results show widespread erosion of nearly 10 m/year over the period corresponding to the Second Indochinese conflict (1962-1972). Then followed a multi-decadal phase of accretion of about 8 m/yr, with spatial fluctuations of up to nearly -20 m/yr. This variability could reflect alternation of periods of resilience and self-organization in coastal sediment cells. A deceleration of accretion in the 2000s (+0.63 m/yr) and even a shift to erosion since 2011 (-1 m/s) are observed in parallel with the intensification of land-use changes, exploitation of the river-bed by sand mining, and hydropower dams (Brunier et al., 2014), and deforestation of deltaic wetlands for agriculture and fisheries(Thu et al., 2007). These erosion trends and their spatiotemporal disparities exacerbate the vulnerability of the

  10. Numerical investigation of surface water-groundwater interactions in a river-dominated delta

    NASA Astrophysics Data System (ADS)

    Sawyer, Audrey; Edmonds, Douglas; Knights, Deon

    2015-04-01

    Deltas are fragile coastal wetland systems that are rapidly vanishing due to subsidence and sea level rise. In most wetland environments, groundwater plays a central role in carbon and nutrient cycles, vegetation community structure, and contaminant transport, yet little is known about groundwater in vanishing delta wetlands. Here, we characterize the basic patterns, rates, and residence times of groundwater flow in a model delta wetland. Delta topography was simulated by growing the delta in Delft3D, a morphodynamic flow and sediment transport model. Water surface elevations under mean annual discharge conditions were used to drive a steady groundwater flow model. Under these average hydrologic conditions, surface water-groundwater exchange represents a small fraction (<1%) of river discharge to the coast, but storm surge, waves, and tides likely increase exchange rates periodically. Groundwater residence times range widely from hours to years. The residence time distribution exhibits power-law tailing that is characteristic of surface water-groundwater exchange in single-threaded river channels. The patterns of groundwater residence times within delta networks are likely to control redox chemistry and may therefore influence the community structure of microbes, benthic invertebrates, and plants. This study illustrates the tremendous potential for numerical approaches to characterizing groundwater flow in delta wetlands. Continued efforts are needed to understand the role of groundwater in delta wetlands, particularly in light of growing initiatives to restore deltas and their ecosystems.

  11. Morphologic and stratigraphic evolution of muddy ebb-tidal deltas along a subsiding coast: Barataria Bay, Mississippi River delta

    USGS Publications Warehouse

    FitzGerald, D.M.; Kulp, M.; Penland, S.; Flocks, J.; Kindinger, J.

    2004-01-01

    The Barataria barrier coast formed between two major distributaries of the Mississippi River delta: the Plaquemines deltaic headland to the east and the Lafourche deltaic headland to the west. Rapid relative sea-level rise (1??03 cm year-1) and other erosional processes within Barataria Bay have led to substantial increases in the area of open water (> 775 km2 since 1956) and the attendant bay tidal prism. Historically, the increase in tidal discharge at inlets has produced larger channel cross-sections and prograding ebb-tidal deltas. For example, the ebb delta at Barataria Pass has built seaward > 2??2 km since the 1880s. Shoreline erosion and an increasing bay tidal prism also facilitated the formation of new inlets. Four major lithofacies characterize the Barataria coast ebb-tidal deltas and associated sedimentary environments. These include a proximal delta facies composed of massive to laminated, fine grey-brown to pale yellow sand and a distal delta facies consisting of thinly laminated, grey to pale yellow sand and silty sand with mud layers. The higher energy proximal delta deposits contain a greater percentage of sand (75-100%) compared with the distal delta sediments (60-80%). Associated sedimentary units include a nearshore facies consisting of horizontally laminated, fine to very fine grey sand with mud layers and an offshore facies that is composed of grey to dark grey, laminated sandy silt to silty clay. All facies coarsen upwards except the offshore facies, which fines upwards. An evolutionary model is presented for the stratigraphic development of the ebb-tidal deltas in a regime of increasing tidal energy resulting from coastal land loss and tidal prism growth. Ebb-tidal delta facies prograde over nearshore sediments, which interfinger with offshore facies. The seaward decrease in tidal current velocity of the ebb discharge produces a gradational contact between proximal and distal tidal delta facies. As the tidal discharge increases and the inlet

  12. Grain size controls on the morphology and stratigraphy of river-dominated deltas

    NASA Astrophysics Data System (ADS)

    Burpee, Alex; Parsons, Daniel; Slingerland, Rudy; Edmonds, Doug; Best, Jim; Cederberg, James; McGuffin, Andrew; Caldwell, Rebecca; Nijhuis, Austin

    2015-04-01

    The proportions of sand and mud that make up a river-dominated delta strongly determine its topset morphology, which in turn controls its internal facies and clinoform geometry. These relationships allow prediction of the stratigraphy of a delta using the character of its topset and reconstruction of deltaic planform from measures of clinoform geometry. This paper presents results from the Delft3D modeling system which was used to simulate nine self-formed deltas that possess different sediment loads and critical shear stresses that are required for re-entrainment of mud. The simulated deltas were set to prograde into a shallow basin without waves, tides, Coriolis forcing, and buoyancy. Model results indicate that sand-dominated deltas are more fan-shaped whilst mud-dominated deltas are more birdsfoot in planform, because the sand-dominated deltas have more active distributaries, a smaller variance of topset elevations, and thereby experience a more equitable distribution of sediment to their perimeters. This results in a larger proportion of channel facies in sand-dominated deltas, and more uniformly-distributed clinoform dip directions, steeper dips, and greater clinoform concavity. These conclusions are consistent with data collected from the Goose River Delta, a coarse-grained fan delta prograding into Goose Bay, Labrador, Canada and also allow us to undertake a re-interpretation of the Kf-1 parasequence set of the Cretaceous Last Chance Delta, a unit of the Ferron Sandstone near Emery, Utah, USA. We argue that the Last Chance delta likely possessed numerous distributaries with at least five orders of bifurcation.

  13. Linking rapid erosion of the Mekong River delta to human activities.

    PubMed

    Anthony, Edward J; Brunier, Guillaume; Besset, Manon; Goichot, Marc; Dussouillez, Philippe; Nguyen, Van Lap

    2015-10-08

    As international concern for the survival of deltas grows, the Mekong River delta, the world's third largest delta, densely populated, considered as Southeast Asia's most important food basket, and rich in biodiversity at the world scale, is also increasingly affected by human activities and exposed to subsidence and coastal erosion. Several dams have been constructed upstream of the delta and many more are now planned. We quantify from high-resolution SPOT 5 satellite images large-scale shoreline erosion and land loss between 2003 and 2012 that now affect over 50% of the once strongly advancing >600 km-long delta shoreline. Erosion, with no identified change in the river's discharge and in wave and wind conditions over this recent period, is consistent with: (1) a reported significant decrease in coastal surface suspended sediment from the Mekong that may be linked to dam retention of its sediment, (2) large-scale commercial sand mining in the river and delta channels, and (3) subsidence due to groundwater extraction. Shoreline erosion is already responsible for displacement of coastal populations. It is an additional hazard to the integrity of this Asian mega delta now considered particularly vulnerable to accelerated subsidence and sea-level rise, and will be exacerbated by future hydropower dams.

  14. Tidal hydrodynamics and erosional power in the Fly River delta, Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Canestrelli, A.; Fagherazzi, S.; Defina, A.; Lanzoni, S.

    2010-12-01

    A two-dimensional numerical model is used to study tidal hydrodynamics and distribution of bed shear stresses in the Fly River delta, Papua New Guinea. The model describes the propagation of the tidal wave within the delta and along the river. Model results indicate that tidal discharge at the mouths of the distributary channels is between 10 and 30 times larger than the river discharge, and that the upstream part of the delta is flood-dominated, whereas near the mouth, the delta is ebb-dominated. Numerical simulations allow us to investigate the sensitivity of fluxes and bottom stresses with respect to the variations of sea level and the area of delta islands. The results suggest that a decrease in the total area of the delta occupied by islands increases the tidal prism and, therefore, the bed shear stresses. Similarly, an increase in sea level reduces the dissipation of the tidal signal and speeds up the propagation of the tidal wave within the delta, thus yielding higher discharges and increased bed shear stresses.

  15. Food web implications of delta13C and delta15N variability over 370 km of the regulated Colorado River USA.

    PubMed

    Shannon, J P; Blinn, D W; Haden, G A; Benenati, E P; Wilson, K P

    2001-01-01

    Dual stable isotope analysis in the regulated Colorado River through Grand Canyon National Park, USA, revealed a food web that varied spatially through this arid biome. Down-river enrichment of delta13C data was detected across three trophic levels resulting in shifted food webs. Humpack chub delta13C and delta15N values from muscle plugs and fin clips did not differ significantly. Humpback chub and rainbow trout trophic position is positively correlated with standard length indicating an increase in piscivory by larger fishes. Recovery of the aquatic community from impoundment by Glen Canyon Dam and collecting refinements for stable isotope analysis within large rivers are discussed.

  16. Sediment transport dynamics linked to morphological evolution of the Selenga River delta, Lake Baikal, Russia

    NASA Astrophysics Data System (ADS)

    Dong, T. Y.; Nittrouer, J.; McElroy, B. J.; Czapiga, M. J.; Il'icheva, E.; Pavolv, M.; Parker, G.

    2014-12-01

    The Selenga River delta, Lake Baikal, Russia, is approximately 700 km2 in size and contains three active lobes that receive varying amounts of water and sediment discharge. This delta represents a unique end-member in so far that the system is positioned along the deep-water (~1500 m) margin of Lake Baikal and therefore exists as a shelf-edge delta. In order to evaluate the morphological dynamics of the Selenga delta, field expeditions were undertaken during July 2013 and 2014, to investigate the morphologic, sedimentologic, and hydraulic nature of this delta system. Single-beam bathymetry data, sidescan sonar data, sediment samples, and aerial survey data were collected and analyzed to constrain: 1) channel geometries within the delta, 2) bedform sizes and spatial distributions, 3) grain size composition of channel bed sediment as well as bank sediment, collected from both major and minor distributary channels, and 4) elevation range of the subaerial portion of the delta. Our data indicate that the delta possesses downstream sediment fining, ranging from predominantly gravel and sand near the delta apex to silt and sand at the delta-lake interface. Field surveys also indicate that the Selenga delta has both eroding and aggrading banks, and that the delta is actively incising into some banks that consist of terraces, which are defined as regions that are not inundated by typical 2- to 4-year flood discharge events. Therefore the terraces are distinct from the actively accreting regions of the delta that receive sedimentation via water inundation during regular river floods. We spatially constrain the regions of the Selenga delta that are inundated during floods versus terraced using a 1-D water-surface hydrodynamic model that produces estimates of stage for flood water discharges, whereby local water surface elevations produced with the model are compared to the measured terrestrial elevations. Our analyses show that terrace elevations steadily decrease downstream

  17. Cyclone Nargis survey in Myanmar's Ayeyarwady River delta

    NASA Astrophysics Data System (ADS)

    Fritz, H. M.; Blount, C.; Thwin, S.; Thu, M. K.; Chan, N.

    2008-12-01

    Tropical cyclone Nargis (Cat. 4) made landfall on May 2, 2008, causing the worst natural disaster in Myanmar's recorded history. Official death toll estimates exceed 130,000 fatalities making it the 7th deadliest cyclone ever recorded worldwide. Nargis took a rare nearly eastern track over the Bay of Bengal while developing sustained winds over 210 km/h with gusts up to 260 km/h hours prior to landfall in Myanmar at untypically low latitude near 16°N. It then proceeded northeast and approximately 12 hours later weakened to a Category 1 storm with sustained wind speeds of 130 km/h as it passed over Yangon. The first independent storm surge reconnaissance team was deployed to Myanmar from 9 to 23 August 2008. Cyclone Nargis struck low-lying coastal plains particularly vulnerable to storm surge flooding due to the lack of effective barriers. The team surveyed coastal and inland villages from Pyapon to Purian Point, encompassing the Bogale and Ayeyarwady River mouths. The survey by boat spanned more than 150 km parallel to the cyclone track between Pyapon and Pyinkhayan encompassing 20 hardest hit settlements such as Pyinsalu. More than 1m vertical erosion and 150 m land loss were measured at various coastal locations such as Aya. Massive deforestation of mangroves and land use were documented. Maximum storm surge elevations and overland flow depths were measured based on water marks on buildings, scars on trees, and rafted debris. The storm surge peaked in the landfall area south of Pyinkhayan and eastwards in Pyinsalu exceeding 5m. Storm waves more than 2m high were superimposed on the storm surge level in most areas according to eyewitnesses. Inundation distances reached beyond 50 km inland. Catastrophic peak fatality rates exceeded 80% in hardest hit villages with the majority being children and women. The high water marks and fatality rates significantly exceeded corresponding 2004 Indian Ocean tsunami values at every location. Eyewitnesses were interviewed to

  18. EAARL Coastal Topography-Pearl River Delta 2008: First Surface

    USGS Publications Warehouse

    Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Miner, Michael D.; Michael, D.; Yates, Xan; Bonisteel, Jamie M.

    2009-01-01

    These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the University of New Orleans (UNO), Pontchartrain Institute for Environmental Sciences (PIES), New Orleans, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Pearl River Delta in Louisiana and Mississippi, acquired March 9-11, 2008. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the

  19. EAARL Coastal Topography-Pearl River Delta 2008: Bare Earth

    USGS Publications Warehouse

    Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Miner, Michael D.; Yates, Xan; Bonisteel, Jamie M.

    2009-01-01

    These remotely sensed, geographically referenced elevation measurements of Lidar-derived bare earth (BE) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the University of New Orleans (UNO), Pontchartrain Institute for Environmental Sciences (PIES), New Orleans, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Pearl River Delta in Louisiana and Mississippi, acquired March 9-11, 2008. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the

  20. Subaquatic soils in the Volga, Don and Kuban Rivers deltas.

    NASA Astrophysics Data System (ADS)

    Tkachenko, Anna; Gerasimova, Maria; Lychagin, Mikhail

    2015-04-01

    River deltas occupy a special interface position in the environment and are characterized by contrasting hydrological and landscape-geochemical regimes. Small depth of water and weak currents contribute to suspended matter deposition. Significant spread of aquatic plants provides the enrichment of subaquatic soils in organic matter. All these factors contribute to the formation of different subaquatic soils. Possibility of including them in the classification systems is discussed by many authors (Demas and Rabenhorst, 2001; Stolt et al., 2011); there is also a special subaquatic qualifier for submerged soils in WRB; however, they are still absent in many national classification systems, as well as in the recent Russian one (2008). The purpose of this research is to reveal the properties of the subaquatic soils in the Volga, Don and Kuban Rivers deltaic areas and to propose pedogenetic approaches to categorize AQUAZEMS. Investigations of deltaic areas were performed in 2010-2012 in deltaic lagoons, fresh-water bays, small channels, oxbow lakes, and also in the part of deltaic near-shore zone. Morphological descriptions of distinguishable layers (colour, texture, thickness, boundaries, consistence, plant residues and shell debris) were made in columns obtained by augering as it is done by other researchers (Stolt et al., 2011), and supplemented with analytical data (pH, Eh, TDS, particle-size composition, and Corg). It is suggested to name the horizons in aquazems in the same way as in terrestrial soils in the recent Russian soil classification system, and apply symbols starting with the combination of caps - AQ. Most typical for aquazems is their aquagley AQG horizon that has features similar to terrestrial gleys - homogeneity in color and consistence, permeation by clay, predominance of dove grey colour. The AQG horizon gradually merges into parent material - stratified bottom sediments. The "topsoil" is usually enriched in organic matter and may be different in

  1. Polycyclic aromatic hydrocarbons increase in Athabasca River Delta sediment: temporal trends and environmental correlates.

    PubMed

    Timoney, Kevin P; Lee, Peter

    2011-05-15

    The Athabasca River in Alberta, Canada, flows north through an area undergoing extensive bitumen resource extraction and processing before discharging its water and sediments into the Athabasca Delta and Lake Athabasca. Polycyclic aromatic hydrocarbons (PAHs) have been identified as an environmental concern in the region. We analyzed environmental data collected by the Regional Aquatics Monitoring Program and government agencies to determine whether temporal trends exist in the concentration of sediment PAHs in the Athabasca River Delta. We then determined what environmental factors related to the trends in sediment PAH concentrations. Total PAH concentrations in the sediment of the Athabasca River Delta increased between 1999 and 2009 at a rate of 0.05 mg/kg/yr ± 0.02 s.e. Annual bitumen production and mined sand volume, extent of landscape disturbance, and particulate emissions were correlated with sediment PAH concentrations as were total organic carbon in sediment and discharge of the Clearwater River, a major tributary of the Athabasca River. Within four tributaries of the Athabasca River, only the Clearwater River showed a significant correlation between discharge and sediment PAH concentration at their river mouths. Carefully designed studies are required to further investigate which factors best explain variability in sediment PAH concentrations.

  2. Geomorphology of the Chippewa River delta of Glacial Lake Saginaw, central Lower Michigan, USA

    NASA Astrophysics Data System (ADS)

    Connallon, Christopher B.; Schaetzl, Randall J.

    2017-08-01

    We introduce, characterize, and interpret the geomorphic history of a relict, Pleistocene-aged delta of the Chippewa River in central Lower Michigan. The broad, sandy Chippewa delta developed into various stages of Glacial Lake Saginaw, between ca. ≈ 17 and 15 ka·BP (calibrated ages). Although the delta was first identified in 1955 on a statewide glacial geology map, neither its extent nor its Pleistocene history had been previously determined. The delta is typically forested, owing to its wet, sandy soils, which stand out against the agricultural fields of the surrounding, loamy lake plain sediments. The delta heads near the city of Mt Pleasant and extends eastward onto the Saginaw Lowlands, i.e., the plain of Glacial Lake Saginaw. Data from 3285 water well logs, 180 hand augered sites, and 185 points randomly located in a GIS on two-storied (sand over loam) soils were used to determine the extent, textural properties, and thickness of the delta. The delta is ≈ 18 km wide and ≈ 38 km long and is sandy throughout. Deltaic sediments from neighboring rivers that also drained into Glacial Lake Saginaw merge with the lower Chippewa delta, obscuring its boundary there. The delta is thickest near the delta's head and in the center, but thins to 1-2 m or less on its eastern margins. Mean thicknesses are 2.3-2.9 m, suggestive of a thin sediment body, frequently impacted by the waves and fluctuating waters of the lakes. Although beach ridges are only weakly expressed across the delta because of the sandy sediment, the coarsest parts of the delta are generally coincident with some of these inferred former shorezones and have a broad, incised channel that formed while lake levels were low. The thick upper delta generally lies above the relict shorelines of Glacial Lakes Saginaw and Arkona (≈ 17.1 to ≈ 16 ka·BP), whereas most of the thin, distal delta is associated with Glacial Lake Warren (≈ 15 ka·BP). Together, these data suggest that the Chippewa delta formed

  3. The Atchafalaya River Delta: Report 2, Field Data; Section 4: Terrebonne Marshes Program Description and Data

    DTIC Science & Technology

    1990-08-01

    Delta, LA Prototype data acquisition Avoca Island Levee Terrebonne Marsh, LA Numeric mdel ,redictions 19. ABSTRACT (Continue on reverse if necessary and...the data collected fo use in development and verification of numerical models to predict the effects of the Avoca Island Extension and delta evolution...These sediment-laden waters of the Atchafa- laya River can reach Terrebonne marsh by going around the southern tip of the existing Avoca Island

  4. Impacts of Declining Mississippi River Sediment Load on Subaqueous Delta Front Sedimentation and Geomorphology

    NASA Astrophysics Data System (ADS)

    Maloney, J. M.; Bentley, S. J.; Xu, K.; Georgiou, I. Y.; Miner, M. D.

    2016-02-01

    The Mississippi River delta system is undergoing unprecedented changes due to the effects of climate change and anthropogenic alterations to the river and its delta. Since the 1950s, the suspended sediment load of the Mississippi River has decreased by approximately 50% due to the construction of >50,000 dams in the Mississippi basin. The impact of this decreased sediment load has been observed in subaerial environments, but the impact on sedimentation and geomorphology of the subaqueous delta front has yet to be examined. To identify historic trends in sedimentation patterns, we compiled bathymetric datasets, including historical charts, industry and academic surveys, and NOAA data, collected between 1764 and 2009. Sedimentation rates are variable across the delta front, but are highest near the mouth of Southwest Pass, which carries the largest percentage of Mississippi River flow and sediment into the Gulf of Mexico. The progradation rate of Southwest Pass (measured at the 10 m depth contour) has slowed from 67 m/yr between 1764 and 1940 to 26 m/yr between 1940 and 1979, with evidence of further deceleration from 1979-2009. Decreased rates of progradation are also observed at South Pass and Pass A Loutre, with the 10 m contour retreating at rates >20 m/yr at both passes. Advancement of the delta front also decelerated in deeper water (15-90 m) offshore from Southwest Pass. In this area, from 1940-1979, depth contours advanced seaward 30 m/yr, but rates declined from 1979-2005. Furthermore, over the same area, the sediment accumulation rate decreased by 81% for the same period. The Mississippi River delta front appears to be entering a phase of decline, which will likely be accelerated by future upstream management practices. This decline has implications for offshore ecosystems, biogeochemical cycling, pollutant dispersal, mudflow hazard, and the continued use of the delta as an economic and population center.

  5. River delta network hydraulic residence time distributions and their role in coastal nutrient biogeochemistry

    NASA Astrophysics Data System (ADS)

    Hiatt, M. R.; Castaneda, E.; Twilley, R.; Hodges, B. R.; Passalacqua, P.

    2015-12-01

    River deltas have the potential to mitigate increased nutrient loading to coastal waters by acting as biofilters that reduce the impact of nutrient enrichment on downstream ecosystems. Hydraulic residence time (HRT) is known to be a major control on biogeochemical processes and deltaic floodplains are hypothesized to have relatively long HRTs. Hydrological connectivity and delta floodplain inundation induced by riverine forces, tides, and winds likely alter surface water flow patterns and HRTs. Since deltaic floodplains are important elements of delta networks and receive significant fluxes of water, sediment, and nutrients from distributary channels, biogeochemical transformations occurring within these zones could significantly reduce nutrient loading to coastal receiving waters. However, network-scale estimates of HRT in river deltas are lacking and little is known about the effects of tides, wind, and the riverine input on the HRT distribution. Subsequently, there lacks a benchmark for evaluating the impact of engineered river diversions on coastal nutrient ecology. In this study, we estimate the HRT of a coastal river delta by using hydrodynamic modeling supported by field data and relate the HRT to spatial and temporal patterns in nitrate levels measured at discrete stations inside a delta island at Wax Lake Delta. We highlight the control of the degree of hydrological connectivity between distributary channels and interdistributary islands on the network HRT distribution and address the roles of tides and wind on altering the shape of the distribution. We compare the observed nitrate concentrations to patterns of channel-floodplain hydrological connectivity and find this connectivity to play a significant role in the nutrient removal. Our results provide insight into the potential role of deltaic wetlands in reducing the nutrient loading to near-shore waters in response to large-scale river diversions.

  6. Sedimentary facies of distributary channels of the whole Mekong River delta

    NASA Astrophysics Data System (ADS)

    Saito, Y.; Nguyen, V. L.; Ta, T. K. O.; Tamura, T.; Kanai, Y.; Nakashima, R.; Uehara, K.

    2016-02-01

    The Mekong River delta, one of the world's largest deltas, has extended from Phnom Penh in Cambodia (apex) to the Vietnam coast from the Saigon River mouth in its eastern end to Cape Camau in its western end, and has the delta plain area of > 50,000 km2. The delta has prograded more than 200 km for the last 6-7 ka. The river-mouth area of the delta is meso-tidal with the mean tidal range of 2.5 ± 0.1 m and the maximum tidal range is 3.2-3.8 m. Sea level in winter (dry season) is higher than summer by 30-40 cm due to setup in the South China Sea basin by northerly. Mean wave height is 0.9 m. The water discharge of the Mekong is 470 km3/y and its sediment discharge is 160 million t/y, or tenth and ninth largest in the world, respectively. The water discharge varies by season, controlled by a monsoonal tropical-subtropical regime. The flow at Phnom Penh, Cambodia, reaches a maximum in October and a minimum in May. SSC has also a seasonal change from more than 300 mg/L in a wet season to less than 50 mg/L in a dry season at the Cambodia-Vietnam border. 1m tidal water-level changes are observed at the border in a dry season. To understand the combined influences of rivers and tides on river-bottom sediments, we have collected 210 surface samples from distributary channels of the whole Mekong River delta in Vietnam from the Cambodia border to five river mouths during a dry season from January to May 2015. Additional sampling expedition in a wet season will be conducted in October 2015 for one distributary channel from the border to its river mouth. The characteristics of channel bottom sediments in a dry season show clearly river- and tide-dominated areas spatially, based on sedimentary facies (grain size and sedimentary structures). Tidal rhythmites are well recognized within 100km from the river mouths and mud balls are well found in the middle reach of the survey area. The spatial distribution of river- and tide-dominated areas is closely linked with the morphology

  7. A graph-theoretic approach to River Deltas: Studying complexity, universality, and vulnerability to change.

    NASA Astrophysics Data System (ADS)

    Tejedor, Alejandro; Longjas, Anthony; Zaliapin, Ilya; Foufoula-Georgiou, Efi

    2015-04-01

    River deltas are landforms with complex channel networks that deliver water, sediment and nutrient fluxes from rivers to oceans or inland water bodies via multiple pathways. Most of the deltas are subject to anthropogenic and natural perturbations causing topological and dynamical changes in the delta structure and function. We present a quantitative framework based on spectral graph theory within which a systematic study of the topology, transport dynamics and response to change of river deltas can be performed, as well as computation of sub-networks (from apex to shoreline outlets), and contributing/nourishing areas. We introduce metrics of topologic and dynamic complexity and define a multidimensional complexity space where each delta projects. By analysis of seven deltas of different morphodynamic and environmental settings, we report a surprising power law relationship between sub-network size and its dynamic exchange with surrounding sub-networks within the deltaic system. The exponent of the relationship is universal (predicting that a sub-network twice as large leaks out to other sub-networks only 1.3 times its total flux) and the pre-exponent depends on the topologic complexity of the delta network as a whole, i.e., the ensemble of the interacting sub-sub-networks. We also use the developed framework to construct vulnerability maps that quantify the relative change of sediment and water delivery to the shoreline outlets in response to possible perturbations in hundreds of upstream links. This enables us to evaluate which links (hotspots) and what management scenarios would most influence flux delivery to the outlets, paving the way for systematically examining how local or spatially distributed delta interventions can be studied within a systems approach for delta sustainability.

  8. Estimating sediment budgets at the interface between rivers and estuaries with application to the Sacramento-San Joaquin River Delta

    NASA Astrophysics Data System (ADS)

    Wright, Scott A.; Schoellhamer, David H.

    2005-09-01

    Where rivers encounter estuaries, a transition zone develops where riverine and tidal processes both affect sediment transport processes. One such transition zone is the Sacramento-San Joaquin River Delta, a large, complex system where several rivers meet to form an estuary (San Francisco Bay). Herein we present the results of a detailed sediment budget for this river/estuary transitional system. The primary regional goal of the study was to measure sediment transport rates and pathways in the delta in support of ecosystem restoration efforts. In addition to achieving this regional goal, the study has produced general methods to collect, edit, and analyze (including error analysis) sediment transport data at the interface of rivers and estuaries. Estimating sediment budgets for these systems is difficult because of the mixed nature of riverine versus tidal transport processes, the different timescales of transport in fluvial and tidal environments, and the sheer complexity and size of systems such as the Sacramento-San Joaquin River Delta. Sediment budgets also require error estimates in order to assess whether differences in inflows and outflows, which could be small compared to overall fluxes, are indeed distinguishable from zero. Over the 4 year period of this study, water years 1999-2002, 6.6 ± 0.9 Mt of sediment entered the delta and 2.2 ± 0.7 Mt exited, resulting in 4.4 ± 1.1 Mt (67 ± 17%) of deposition. The estimated deposition rate corresponding to this mass of sediment compares favorably with measured inorganic sediment accumulation on vegetated wetlands in the delta.

  9. Estimating sediment budgets at the interface between rivers and estuaries with application to the Sacramento-San Joaquin River Delta

    NASA Astrophysics Data System (ADS)

    Wright, Scott A.; Schoellhamer, David H.

    2005-09-01

    Where rivers encounter estuaries, a transition zone develops where riverine and tidal processes both affect sediment transport processes. One such transition zone is the Sacramento-San Joaquin River Delta, a large, complex system where several rivers meet to form an estuary (San Francisco Bay). Herein we present the results of a detailed sediment budget for this river/estuary transitional system. The primary regional goal of the study was to measure sediment transport rates and pathways in the delta in support of ecosystem restoration efforts. In addition to achieving this regional goal, the study has produced general methods to collect, edit, and analyze (including error analysis) sediment transport data at the interface of rivers and estuaries. Estimating sediment budgets for these systems is difficult because of the mixed nature of riverine versus tidal transport processes, the different timescales of transport in fluvial and tidal environments, and the sheer complexity and size of systems such as the Sacramento-San Joaquin River Delta. Sediment budgets also require error estimates in order to assess whether differences in inflows and outflows, which could be small compared to overall fluxes, are indeed distinguishable from zero. Over the 4 year period of this study, water years 1999-2002, 6.6 +/- 0.9 Mt of sediment entered the delta and 2.2 +/- 0.7 Mt exited, resulting in 4.4 +/- 1.1 Mt (67 +/- 17%) of deposition. The estimated deposition rate corresponding to this mass of sediment compares favorably with measured inorganic sediment accumulation on vegetated wetlands in the delta.

  10. Estimating sediment budgets at the interface between rivers and estuaries with application to the Sacramento-San Joaquin River Delta

    USGS Publications Warehouse

    Wright, S.A.; Schoellhamer, D.H.

    2005-01-01

    [1] Where rivers encounter estuaries, a transition zone develops where riverine and tidal processes both affect sediment transport processes. One such transition zone is the Sacramento-San Joaquin River Delta, a large, complex system where several rivers meet to form an estuary (San Francisco Bay). Herein we present the results of a detailed sediment budget for this river/estuary transitional system. The primary regional goal of the study was to measure sediment transport rates and pathways in the delta in support of ecosystem restoration efforts. In addition to achieving this regional goal, the study has produced general methods to collect, edit, and analyze (including error analysis) sediment transport data at the interface of rivers and estuaries. Estimating sediment budgets for these systems is difficult because of the mixed nature of riverine versus tidal transport processes, the different timescales of transport in fluvial and tidal environments, and the sheer complexity and size of systems such as the Sacramento-San Joaquin River Delta. Sediment budgets also require error estimates in order to assess whether differences in inflows and outflows, which could be small compared to overall fluxes, are indeed distinguishable from zero. Over the 4 year period of this study, water years 1999-2002, 6.6 ?? 0.9 Mt of sediment entered the delta and 2.2 ?? 0.7 Mt exited, resulting in 4.4 ?? 1.1 Mt (67 ?? 17%) of deposition. The estimated deposition rate corresponding to this mass of sediment compares favorably with measured inorganic sediment accumulation on vegetated wetlands in the delta.

  11. What Role do Hurricanes Play in Sediment Delivery to Subsiding River Deltas?

    NASA Astrophysics Data System (ADS)

    Smith, J. E., IV

    2016-02-01

    James E. Smith IV1, Samuel J. Bentley, Sr.1, Gregg A. Snedden2, Crawford White1 Department of Geology and Geophysics and Coastal Studies Institute, Louisiana State University, Baton Rouge, LA 70803 USA United States Geological Survey, National Wetlands Research Center, Baton Rouge LA 70803 USA The Mississippi River Delta has undergone tremendous land loss over the past century due to natural and anthropogenic influences, a fate shared by many river deltas globally. A globally unprecedented effort to restore and sustain the remaining subaerial portions of the delta is now underway, an endeavor that is expected to cost $50-100B over the next 50 yr. Success of this effort requires a thorough understanding of natural and anthropogenic controls on sediment supply, accumulation, and delta geomorphology. In the Mississippi River Delta, hurricanes have been paradoxically identified as both agents of widespread land loss, and positive influences for marsh vertical sediment accretion. We present the first multi-decadal chronostratigraphic assessment of sediment supply for a major coastal basin of the Mississippi River Delta that assesses both fluvial and hurricane-induced contributions to sediment accumulation in deltaic wetlands. Twenty seven cores have been analyzed for radioisotope geochronology and organic content to establish the chronology of mineral sediment supply to the wetlands over the past 70 years. Our findings indicate that over multidecadal timescales, hurricane-induced sediment delivery may be an important contributor for deltaic wetland vertical accretion, but the contribution from hurricanes to long-term sediment accumulation is substantially less than sediment delivery supplied by existing and planned river-sediment diversions at present-day river-sediment loads.

  12. Birds of the Indigirka River Delta, Russia: Historical and biogeographic comparisons

    USGS Publications Warehouse

    Pearce, John M.; Esler, Daniel; Degtyarev, Andrei G.

    1998-01-01

    We documented the breeding status and relative abundance of all avian species on the coastal portion of the Indigirka River Delta during spring and summer 1993-95. Data on avifaunal composition were then compared to data from adjacent areas from Eastern Siberia to the Chukotka Peninsula to evaluate how species composition changes longitudinally within the arctic and typical tundra zones of northern Russia. We recorded 63 species on the Indigirka River Delta, 37 (58.7 %) of which were confirmed breeders during at least one of the three years. Five new species were recorded breeding (Arenaria interpres, Calidris acuminata, Limnodromus scolopaceus, Stercorarius parasiticus, and Asio flammeus), and 13 previously unrecorded species were observed during this study. We also identified several species of rare or threatened status in Russia and North America, including Branta bernicla, Somateria fischeri, Polysticta stelleri, and Rhodostethia rosea. We used parsimony and distance matrix methods to compare the breeding species richness on the Indigirka River Delta to that of six other Russian Arctic areas. Biogeographic comparisons revealed the presence of two clades in the Russian Arctic: the Lena River Delta east to Chaun Delta and the Chukotka Peninsula.

  13. Linking rapid erosion of the Mekong River delta to human activities

    PubMed Central

    Anthony, Edward J.; Brunier, Guillaume; Besset, Manon; Goichot, Marc; Dussouillez, Philippe; Nguyen, Van Lap

    2015-01-01

    As international concern for the survival of deltas grows, the Mekong River delta, the world’s third largest delta, densely populated, considered as Southeast Asia’s most important food basket, and rich in biodiversity at the world scale, is also increasingly affected by human activities and exposed to subsidence and coastal erosion. Several dams have been constructed upstream of the delta and many more are now planned. We quantify from high-resolution SPOT 5 satellite images large-scale shoreline erosion and land loss between 2003 and 2012 that now affect over 50% of the once strongly advancing >600 km-long delta shoreline. Erosion, with no identified change in the river’s discharge and in wave and wind conditions over this recent period, is consistent with: (1) a reported significant decrease in coastal surface suspended sediment from the Mekong that may be linked to dam retention of its sediment, (2) large-scale commercial sand mining in the river and delta channels, and (3) subsidence due to groundwater extraction. Shoreline erosion is already responsible for displacement of coastal populations. It is an additional hazard to the integrity of this Asian mega delta now considered particularly vulnerable to accelerated subsidence and sea-level rise, and will be exacerbated by future hydropower dams. PMID:26446752

  14. Deltaic Morphology and Sedimentology, with Special Reference to the Indus River Delta.

    DTIC Science & Technology

    1985-01-01

    424 DELTAIC MORPHOLOGY AND SEDIMENTOLOGY WITH SPECIAL REFERENCE TO THE INDUS RIVER DELTA J. T. Wells and J. M. Coleman 1985 Marine Geology...Reinhold ~~3thUWIOE s’?A’nT .4 Alived &6 6 c 2 25 86 2 02 771 Deltaic Morphology and Sedimentology , with special reference to the Indus River Delta J. T...and Previous research has shown that deltaic configurations as a result of the complex morphology and sedimentology are a function of interactions

  15. Tidal impacts on the subtidal flow division at the main bifurcation in the Yangtze River Delta

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Feng, Haochuan; Hoitink, A. J. F.; Zhu, Yuliang; Gong, Fei; Zheng, Jinhai

    2017-09-01

    Flow division at bifurcations in the Yangtze Estuary has received ample attention, since it may control the pathways of terrestrial sediments over downstream river branches including the 12.5 m Deepwater Navigation channel. While some efforts have been made to interpret flow division at the bifurcations of the Yangtze Estuary, little attention has been paid to the role of tides. Flow division at estuarine bifurcations is made complicated by tides that propagate from the outlet of the tidal channels into the delta. To quantify the tidal influence on the distribution of river discharge, and more generally, to understand the mechanisms governing the subtidal flow division at the tidally affected bifurcation in the Yangtze River Delta, a two-dimensional hydrodynamic model is employed. In this model, the landward boundary is chosen beyond the tidal limit, where the tidal motion has faded out entirely. The seaward boundary is chosen such that the river discharge does not influence the water level. Subtidal discharges are decomposed using the method of factor separation, to distinguish between the effects of tides, river discharge and river-tide interactions on the subtidal flow division. Results indicate that tides modify the river discharge distribution over distributary channels in the Yangtze River Delta, particularly in the dry season. A significant difference in the subtidal flow division during spring tide and neap tide shows that the tidally averaged flow division over the distributaries in the delta greatly depends on tidal amplitude. By varying the river discharge at the landward boundary and amplitudes and phases of the principal tidal constituents at the seaward boundary of the established model, the sensitivities of the subtidal flow division to the river discharge and tidal amplitude variation were investigated in detail. Generally, the tidal impacts on the subtidal flow division are around 12% to 22%, with river discharge varying from 30,000 m3s-1 to 20

  16. River Delta Subsidence Measured with Interferometric Synthetic Aperture Radar (InSAR)

    NASA Astrophysics Data System (ADS)

    Higgins, Stephanie

    This thesis addresses the need for high-resolution subsidence maps of major world river deltas. Driven by a combination of rising water, sediment compaction, and reduced sediment supply due to damming and flood control, many deltas are sinking relative to sea level. A lack of data constraining rates and patterns of subsidence has made it difficult to determine the relative contributions of each factor in any given delta, however, or to assess whether the primary drivers of land subsidence are natural or anthropogenic. In recent years, Interferometric Synthetic Aperture Radar (InSAR) has emerged as a satellite-based technique that can map ground deformation with mm-scale accuracy over thousands of square kilometers. These maps could provide critical insight into the drivers of subsidence in deltas, but InSAR is not typically applied to non-urban delta areas due to the difficulties of performing the technique in wet, vegetated settings. This thesis addresses those difficulties and achieves high-resolution measurements of ground deformation in rural deltaic areas. Chapter 1 introduces the processes that drive relative sea level rise in river deltas and investigates open questions in delta subsidence research. Chapter 2 assesses the performance of InSAR in delta settings and reviews interferogram generation in the context of delta analysis, presenting delta-specific processing details and guiding interpretation in these challenging areas. Chapter 3 applies Differential (D-) InSAR to the coast of the Yellow River Delta in China. Results show that subsidence rates are as high as 250 mm/y due to groundwater extraction at aquaculture facilities, a rate that exceeds local and global average sea level rise by nearly two orders of magnitude and suggests a significant hazard for Asian megadeltas. Chapter 4 applies interferometric stacking and Small Baseline Subset (SBAS)-InSAR to the Ganges-Brahmaputra Delta, Bangladesh. Results show that stratigraphy controls subsidence in

  17. Effect of tides, river flow, and gate operations on entrainment of juvenile salmon into the interior Sacramento–San Joaquin River Delta

    USGS Publications Warehouse

    Perry, Russell W.; Brandes, Patricia L.; Burau, Jon R.; Sandstrom, Philip T.; Skalski, John R.

    2015-01-01

    Juvenile Chinook Salmon Oncorhynchus tshawytscha emigrating from natal tributaries of the Sacramento River, California, must negotiate the Sacramento-San Joaquin River Delta (hereafter, the Delta), a complex network of natural and man-made channels linking the Sacramento River with San Francisco Bay. Fish that enter the interior and southern Delta—the region to the south of the Sacramento River where water pumping stations are located—survive at a lower rate than fish that use alternative migration routes. Consequently, total survival decreases as the fraction of the population entering the interior Delta increases, thus spurring management actions to reduce the proportion of fish that are entrained into the interior Delta. To better inform management actions, we modeled entrainment probability as a function of hydrodynamic variables. We fitted alternative entrainment models to telemetry data that identified when tagged fish in the Sacramento River entered two river channels leading to the interior Delta (Georgiana Slough and the gated Delta Cross Channel). We found that the probability of entrainment into the interior Delta through both channels depended strongly on the river flow and tidal stage at the time of fish arrival at the river junction. Fish that arrived during ebb tides had a low entrainment probability, whereas fish that arrived during flood tides (i.e., when the river's flow was reversed) had a high probability of entering the interior Delta. We coupled our entrainment model with a flow simulation model to evaluate the effect of nighttime closures of the Delta Cross Channel gates on the daily probability of fish entrainment into the interior Delta. Relative to 24-h gate closures, nighttime closures increased daily entrainment probability by 3 percentage points on average if fish arrived at the river junction uniformly throughout the day and by only 1.3 percentage points if 85% of fish arrived at night. We illustrate how our model can be used to

  18. Nile Delta

    Atmospheric Science Data Center

    2013-04-15

    article title:  The Nile River Delta     View Larger Image ... of eastern Africa. At the apex of the fertile Nile River Delta is the Egyptian capital city of Cairo. To the west are the Great Pyramids ...

  19. Characterizing Seismic Properties of the Sacramento-San Joaquin River Delta, California

    NASA Astrophysics Data System (ADS)

    Eberhart-Phillips, D. M.; Thurber, C. H.; Teel, A.

    2010-12-01

    The Sacramento-San Joaquin River Delta is a component of the major basins east of the California Coast Ranges, and it contains levees that may fail in major earthquakes. The largest magnitude earthquake sources may occur on Bay Area faults, over 50-km away from the Delta, and thus regional attenuation is important to consider. Regionally, long-term seismic networks record numerous earthquakes and this data has been used for several regional-scale 3-D velocity studies. However there is little knowledge of 3-D Q structure. A small number (7-10) of broadband instruments have been deployed in the Delta since 2007, by the USGS (Fletcher and Sell, 2009) for site response studies. The Delta itself is relatively aseismic, yet the Delta array has provided useful records of regional earthquakes. We are using the permanent and temporary data to improve the velocity structure and to obtain the 3-D Q structure. For P-arrival windows, t* (t-star) is obtained, including site response, and then 3-D Q is computed. Stations across the Delta array indicate varied attenuation with apparent low Q in the central Delta. Velocity results are being used to refine the basin shape. Ref: Fletcher, J. B., R. Sell, Site response and slow basin waves in the Sacramento/San Joaquin Delta, Am. Geophys. U., Fall Meeting 2009, abstract #S42B-01, 2009.

  20. An Observed Step Change in River Delta Turbidity Following 1982-1983 El Nino Floods

    NASA Astrophysics Data System (ADS)

    Hestir, E. L.; Schoellhamer, D. H.; Morgan-King, T.; Ustin, S.

    2010-12-01

    Sediment transport influences the geomorphology, biogeochemical cycling, pollutant load, and ecology of river deltas and estuaries. In the Sacramento-San Joaquin Delta, turbidity is largely considered a surrogate of suspended sediment concentration, and has been declining over the past 30 years. This has contributed to dramatic changes in the ecology of the Delta and to the decline of the endemic and endangered delta smelt. The declining turbidity trend in the Delta has been attributed to reduced sediment inputs and expansion of invasive submerged aquatic vegetation. In this study, we analyzed historic monthly turbidity records collected by the California Department of Water Resources Environmental Monitoring Program from 1975-2008. We investigated structural changes in the turbidity trend, and identified a significant step decrease in turbidity after the beginning of the 1984 water year at nine different sites within the Delta. This significant decrease in Delta turbidity appears to have been caused by the combination of large El-Nino driven winter floods from both the San Joaquin and Sacramento Rivers in 1982-1983 and the high inflows throughout the summer. We suggest that these extended high flow events flushed the erodible sediment pool from the Delta into the San Francisco Bay. This event has left the Delta in its current, low-turbidity state. Another study found that a step decrease in suspended sediment concentration in San Francisco Bay in 1999 may have been caused by depletion of erodible sediment. This indicates that depletion of erodible sediment may have progressed downstream and, if the erodible sediment pools were created by hydraulic mining in the late 1800s, sedimentation in the estuary has largely recovered from hydraulic mining.

  1. An advanced method for flood risk analysis in river deltas, applied to societal flood fatality risks in the Netherlands

    NASA Astrophysics Data System (ADS)

    de Bruijn, K. M.; Diermanse, F. L. M.; Beckers, J. V. L.

    2014-02-01

    This paper discusses the new method developed to analyse flood risks in river deltas. Risk analysis of river deltas is complex, because both storm surges and river discharges may cause flooding and since the effect of upstream breaches on downstream water levels and flood risks must be taken into account. A Monte Carlo based flood risk analysis framework for policy making was developed, which considers both storm surges and river flood waves and includes hydrodynamic interaction effects on flood risks. It was applied to analyse societal flood fatality risks (the probability of events with more than N fatalities) in the Rhine-Meuse delta.

  2. An advanced method for flood risk analysis in river deltas, applied to societal flood fatality risk in the Netherlands

    NASA Astrophysics Data System (ADS)

    de Bruijn, K. M.; Diermanse, F. L. M.; Beckers, J. V. L.

    2014-10-01

    This paper discusses a new method for flood risk assessment in river deltas. Flood risk analysis of river deltas is complex, because both storm surges and river discharges may cause flooding and the effect of upstream breaches on downstream water levels and flood risk must be taken into account. This paper presents a Monte Carlo-based flood risk analysis framework for policy making, which considers both storm surges and river flood waves and includes effects from hydrodynamic interaction on flood risk. It was applied to analyse societal flood fatality risk in the Rhine-Meuse delta.

  3. Methane ebullition and fate in the Rhone River delta (Lake Geneva) and its subaquatic canyons

    NASA Astrophysics Data System (ADS)

    DelSontro, T.; Sollberger, S.; Corella, J. P.; Wehrli, B.; Girardclos, S.; Anselmetti, F. S.; Senn, D. B.

    2012-04-01

    There is increasing knowledge of the importance of inland waters as sources of atmospheric methane, but widespread variability of total and individual emission pathway estimates remain in the literature. Ebullition (bubbling) is potentially the most efficient transport mechanism from water bodies, particularly shallow water bodies or regions thereof where bubbles have the greatest chance of reaching the atmosphere. However, ebullition is one of the least monitored of the pathways, mostly due to its stochastic nature making it difficult to constrain spatially and temporally. Recent studies on a large tropical reservoir and a large European lake have shown that river deltas (i.e., localized regions of high allochthonous organic matter sedimentation) can be methane ebullition hot spots emitting disproportionate amounts of methane. Therefore, in this study the Rhone River delta (one Europe's most important rivers) of the Alp's largest lake, Lake Geneva, was surveyed for methane ebullition using a bubble size-calibrated 120 kHz split-beam echosounder (Simrad EK60, Kongsberg Maritime). Extensive ebullition was found in the current river delta complex in proximity to the river inflow, which is the major source of atmospheric methane emission in the entire 100 km2 deltaic region. As water depths approach 100 m, ebullition is constrained to only the top levees of the 10 - 40 m high walls of the subaquatic canyon formed by the plunging Rhone River. Ebullition occurs to depths over 200 m on the levee of the active canyon, where CTD profiles suggest that Rhone River water does extend that far along the canyon. As bubble dissolution depends on release depth and bubble size, which was estimated from the rise velocity of deep bubbles, it was discovered that bubbles emitted from 100 m or deeper would not reach the surface; thus the proximal delta remains the prominent methane source. Eight other canyons exist in the delta complex, of which two non-active canyons formed by previous

  4. STS-65 Earth observation of Omo River Delta, Lake Turkana in Ethiopia / Kenya

    NASA Technical Reports Server (NTRS)

    1994-01-01

    STS-65 Earth observation taken aboard Columbia, Orbiter Vehicle (OV) 102, is of Omo River Delta and Lake Turkana in Ethiopia / Kenya. The Omo Delta at the north end of Lake Turkana (Rudolph) is one of the long-term environmental study sites of the Space Shuttle program. The environmental interest in this instance is the documentation of the delta's extension into the lake. This delta extension, or aggradation, is felt to be the result of large-scale soil erosion in the recently deforested areas of Ethiopia in the watershed of the Omo River. Using digitized, rectified, machine-classified, and mensurated NASA photography, it has been determined that the Omo Delta has increased in area by approximately 400% to about 1,800 square kilometers since it was first photographed during the Gemini program in 1965. This photograph documents the long-term and increasing turbidity of Lake Turkana and the continuing delta extension southward by both the northwest and northeast distributaries of the Om

  5. Detection of Area Changes in River Mouthbars at the Mekong River Delta using ALOS/PALSAR data

    NASA Astrophysics Data System (ADS)

    Tanaka, A.; Uehara, K.; Tamura, T.; Saito, Y.

    2011-12-01

    Projected sea-level rise by the year 2100 would be ~1m recently and its negative impact on the coastal zone has been pointed out, particularly for mega-deltas in Asia by the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2007). The relative sea-level rise varies with specific conditions and processes over broad spatial and temporal scales. Therefore, long-term monitoring of geomorphological changes in coastal areas over wide areas is of highly interest and importance for coastal management. However, due to limited data availability and accessibility in developing countries, there is not enough systematic coastal monitoring. The Mekong River Delta is one of typical mega-deltas in Asia, which has a low-lying wide delta-plain located in Cambodia to South Vietnam. Sediment and water discharges of the Mekong River are controlled by the monsoon with high and low discharge in summer (wet season) and winter (dry season), respectively. Therefore, technologies such as SAR (Synthetic Aperture Radar) not affected by the cloud conditions offer potential for monitoring in the monsoon Asia region. In this study, ALOS (Advanced Land Observing Satellite) PALSAR (Phased Array type L-band SAR) data acquired over a period from December 2006 to January 2011 are analyzed to investigate the relation between the sea level and the shape of mouthbars in the Mekong River. Level-1.0 PALSAR data were processed, coregistered, and geocoded to make SAR backscatter intensity images. River mouthbars with strong backscatter, which is surrounded by the water with weak backscatter, are successfully extracted using a histogram thresholding algorithm. Estimated areas of river mouthbars, which are located at the central part of the delta and openly faced to the South China Sea, gradually increase on an annual time scale. These river mouthbars are growing to the seaward. Besides this overall increasing trend, seasonal variations of areas are observed; these correlate with

  6. Sources of excess urban carbonaceous aerosol in the Pearl River delta region, China

    EPA Science Inventory

    Carbonaceous aerosol is one of the important constituents of fine particulate matter (PM2.5) in Southern China, including the Pearl River Delta (PRD) region and Hong Kong (HK). During the study period (October and December of 2002, and March and June of 2003), the monthly average...

  7. Spawning and movement behavior of migratory coastal cutthroat trout on the western Copper River delta, Alaska.

    Treesearch

    D.A. Saiget; M.R. Sloat; Reeves. G.H.

    2007-01-01

    We studied the movement patterns of migratory coastal cutthroat trout Oncorhynchus clarkii clarkii in the western Copper River delta, Alaska, near the northern extent of the subspecies' distribution. Life history information for coastal cutthroat trout is scarce within this region. Movement of coastal cutthroat trout was monitored from 1994 to...

  8. Composition, biomass and structure of mangroves within the Zambezi River Delta

    Treesearch

    Carl C. Trettin; Christina E. Stringer; Stan Zarnoch

    2015-01-01

    We used a stratified random sampling design to inventory the mangrove vegetation within the Zambezi River Delta, Mozambique, to provide a basis for estimating biomass pools. We used canopy height, derived from remote sensing data, to stratify the inventory area, and then applied a spatial decision support system to objectively allocate sample plots among five...

  9. The impact of rice pesticides on the aquatic ecosystems of the Sacramento River and Delta (California).

    PubMed

    Byard, J L

    1999-01-01

    Since the early 1980s, when molinate was demonstrated to have killed carp in agricultural drains, an intensive research effort has been undertaken to assess the impact of rice pesticides on aquatic ecosystems in the Sacramento River and Delta. No impact has been found that can be clearly attributed to rice pesticides. However, the rice insecticides methyl parathion and carbofuran, and probably also bufencarb, reached levels in the River and Delta that, based on laboratory bioassays, would have been toxic to aquatic microinvertebrates and, in the case of bufencarb, to early life stages of striped bass. Reductions in microinvertebrate populations could have impacted higher organisms in the aquatic food chain such as striped bass and chinook salmon. Bufencarb was not used after 1981. Since then, changes in the management of the remaining rice pesticides have resulted in dramatic decreases in the levels of these chemicals in the River and Delta. Levels achieved today have no known toxicity to aquatic organisms. As releases of rice pesticides were reduced to achieve nontoxic levels in the River and Delta, however, commensurate recoveries of striped bass and chinook salmon did not occur, suggesting that rice pesticides may have had little or no role in the decline of these species.

  10. What role do hurricanes play in sediment delivery to subsiding river deltas?

    USGS Publications Warehouse

    Smith, James E.; Bentley, Samuel J.; Snedden, Gregg; White, Crawford

    2015-01-01

    The Mississippi River Delta (MRD) has undergone tremendous land loss over the past century due to natural and anthropogenic influences, a fate shared by many river deltas globally. A globally unprecedented effort to restore and sustain the remaining subaerial portions of the delta is now underway, an endeavor that is expected to cost $50–100B over the next 50 yr. Success of this effort requires a thorough understanding of natural and anthropogenic controls on sediment supply and delta geomorphology. In the MRD, hurricanes have been paradoxically identified as both substantial agents of widespread land loss, and vertical marsh sediment accretion. We present the first multi-decadal chronostratigraphic assessment of sediment supply for a major coastal basin of the MRD that assesses both fluvial and hurricane-induced contributions to sediment accumulation in deltaic wetlands. Our findings indicate that over multidecadal timescales, hurricane-induced sediment delivery may be an important contributor for deltaic wetland vertical accretion, but the contribution from hurricanes to long-term sediment accumulation is substantially less than sediment delivery supplied by existing and planned river-sediment diversions at present-day river-sediment loads.

  11. Classification of community types, successional sequences, and landscapes of the Copper River Delta, Alaska.

    Treesearch

    Keith. Boggs

    2000-01-01

    A classification of community types, successional sequences, and landscapes is presented for the piedmont of the Copper River Delta. The classification was based on a sampling of 471 sites. A total of 75 community types, 42 successional sequences, and 6 landscapes are described. The classification of community types reflects the existing vegetation communities on the...

  12. The Copper River Delta pulse study: an interdisciplinary survey of aquatic habitats.

    Treesearch

    M.D. Bryant

    1991-01-01

    In July 1987, a 2-week synoptic survey was conducted on the wetlands of the Copper River Delta by an interdisciplinary team of scientists. Disciplines included geomorphology, limnology—water chemistry and nutrients, plankton and macroinvertebrates, anadromous fish populations, and wetland plant ecology. The purpose of this report is to present a summary of the findings...

  13. Sediment consolidation settlement of Chengbei Sea area in the northern Huanghe River subaqueous delta, China

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Feng, Xiuli; Liu, Xiao

    2016-06-01

    One of the most important factors controlling the morphology of the modern Huanghe (Yellow) River delta is consolidation settlement, which is impacted by fast deposition, high water content, and low density of seafloor sediment. Consolidation settlement of the Huanghe River subaqueous delta was studied based on field data, laboratory experiments on 12 drill holes, and the one-dimensional consolidation theory. Results show that vertical sediment characteristics varied greatly in the rapidly forming sedimentary bodies of the modern Huanghe River subaqueous delta. Sediments in the upper parts of drill holes were coarser than those in the deeper parts, and other physical and mechanical properties changed accordingly. On the basis of the one-dimensional consolidation theory and drilling depth, the final consolidation settlement of drill holes was between 0.6 m and 2.8 m, and the mean settlement of unit depth was at 1.5-3.5 cm/m. It takes about 15-20 years for the consolidation degree to reach 90% and the average sedimentation rate within the overlying 50 m strata was at 5 cm/a to 12 cm/a. This study helps to forecast the final consolidation settlement and settlement rate of the modern Huanghe River subaqueous delta, which provides key geotechnical information for marine engineers.

  14. Sources of excess urban carbonaceous aerosol in the Pearl River delta region, China

    EPA Science Inventory

    Carbonaceous aerosol is one of the important constituents of fine particulate matter (PM2.5) in Southern China, including the Pearl River Delta (PRD) region and Hong Kong (HK). During the study period (October and December of 2002, and March and June of 2003), the monthly average...

  15. Soil properties of mangroves in contrasting geomorphic settings within the Zambezi River Delta, Mozambique

    Treesearch

    Christina E. Stringer; Carl C. Trettin; Stan Zarnoch

    2016-01-01

    Mangroves are well-known for their numerous ecosystem services, including sequestering a significant carbon stock, with soils accounting for the largest pool. The soil carbon pool is dependent on the carbon content and bulk density. Our objective was to assess the spatial variability of mangrove soil physical and chemical properties within the Zambezi River Delta and...

  16. HABITAT ASSESSMENT USING A RANDOM PROBABILITY BASED SAMPLING DESIGN: ESCAMBIA RIVER DELTA, FLORIDA

    EPA Science Inventory

    Smith, Lisa M., Darrin D. Dantin and Steve Jordan. In press. Habitat Assessment Using a Random Probability Based Sampling Design: Escambia River Delta, Florida (Abstract). To be presented at the SWS/GERS Fall Joint Society Meeting: Communication and Collaboration: Coastal Systems...

  17. What Role do Hurricanes Play in Sediment Delivery to Subsiding River Deltas?

    PubMed Central

    Smith, James E.; Bentley, Samuel J.; Snedden, Gregg A.; White, Crawford

    2015-01-01

    The Mississippi River Delta (MRD) has undergone tremendous land loss over the past century due to natural and anthropogenic influences, a fate shared by many river deltas globally. A globally unprecedented effort to restore and sustain the remaining subaerial portions of the delta is now underway, an endeavor that is expected to cost $50–100B over the next 50 yr. Success of this effort requires a thorough understanding of natural and anthropogenic controls on sediment supply and delta geomorphology. In the MRD, hurricanes have been paradoxically identified as both substantial agents of widespread land loss, and vertical marsh sediment accretion. We present the first multi-decadal chronostratigraphic assessment of sediment supply for a major coastal basin of the MRD that assesses both fluvial and hurricane-induced contributions to sediment accumulation in deltaic wetlands. Our findings indicate that over multidecadal timescales, hurricane-induced sediment delivery may be an important contributor for deltaic wetland vertical accretion, but the contribution from hurricanes to long-term sediment accumulation is substantially less than sediment delivery supplied by existing and planned river-sediment diversions at present-day river-sediment loads. PMID:26628104

  18. The Persian Gulf and the Delta of the Tigris and Euphrates Rivers, Kuwait, Iraq, and Iran

    NASA Image and Video Library

    2008-09-04

    This image from NASA EarthKAM is of the northern end of the Persian Gulf and the broad delta complex of the Tigris, Euphrates, Shatt al Arab, and Karun rivers has captured the arid-looking wetlands of northeast Kuwait Bubiyan Island,

  19. HABITAT ASSESSMENT USING A RANDOM PROBABILITY BASED SAMPLING DESIGN: ESCAMBIA RIVER DELTA, FLORIDA

    EPA Science Inventory

    Smith, Lisa M., Darrin D. Dantin and Steve Jordan. In press. Habitat Assessment Using a Random Probability Based Sampling Design: Escambia River Delta, Florida (Abstract). To be presented at the SWS/GERS Fall Joint Society Meeting: Communication and Collaboration: Coastal Systems...

  20. Goose mass and vegetation data, Colville River Delta, Alaska, 2012-2014

    USGS Publications Warehouse

    Hupp, Jerry

    2017-01-01

    This data release contains three tables of information from the Colville River Delta, Alaska, 2012-2014: offtake of Carex subspathacea, standing crop of C. subspathacea, and snow goose and black brant gosling mass data. Data were collected as part of the USGS Changing Arctic Ecosystems Initiative to understand the response of wildlife to rapid physical changes taking place in the Arctic.

  1. What Role do Hurricanes Play in Sediment Delivery to Subsiding River Deltas?

    PubMed

    Smith, James E; Bentley, Samuel J; Snedden, Gregg A; White, Crawford

    2015-12-02

    The Mississippi River Delta (MRD) has undergone tremendous land loss over the past century due to natural and anthropogenic influences, a fate shared by many river deltas globally. A globally unprecedented effort to restore and sustain the remaining subaerial portions of the delta is now underway, an endeavor that is expected to cost $50-100B over the next 50 yr. Success of this effort requires a thorough understanding of natural and anthropogenic controls on sediment supply and delta geomorphology. In the MRD, hurricanes have been paradoxically identified as both substantial agents of widespread land loss, and vertical marsh sediment accretion. We present the first multi-decadal chronostratigraphic assessment of sediment supply for a major coastal basin of the MRD that assesses both fluvial and hurricane-induced contributions to sediment accumulation in deltaic wetlands. Our findings indicate that over multidecadal timescales, hurricane-induced sediment delivery may be an important contributor for deltaic wetland vertical accretion, but the contribution from hurricanes to long-term sediment accumulation is substantially less than sediment delivery supplied by existing and planned river-sediment diversions at present-day river-sediment loads.

  2. Biological assessment: water hyacinth control program for the Sacramento/ San Joaquin River Delta of California

    USDA-ARS?s Scientific Manuscript database

    A detailed Biological Assessment was developed for the proposed Areawide Water Hyacinth Control Program to outline the procedures that will be used to control this invasive aquatic plant in the Sacramento/ San Joaquin River Delta, and to help determine if this action is expected to threaten endanger...

  3. Sediment consolidation settlement of Chengbei Sea area in the northern Huanghe River subaqueous delta, China

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Feng, Xiuli; Liu, Xiao

    2017-05-01

    One of the most important factors controlling the morphology of the modern Huanghe (Yellow) River delta is consolidation settlement, which is impacted by fast deposition, high water content, and low density of seafloor sediment. Consolidation settlement of the Huanghe River subaqueous delta was studied based on field data, laboratory experiments on 12 drill holes, and the one-dimensional consolidation theory. Results show that vertical sediment characteristics varied greatly in the rapidly forming sedimentary bodies of the modern Huanghe River subaqueous delta. Sediments in the upper parts of drill holes were coarser than those in the deeper parts, and other physical and mechanical properties changed accordingly. On the basis of the one-dimensional consolidation theory and drilling depth, the final consolidation settlement of drill holes was between 0.6 m and 2.8 m, and the mean settlement of unit depth was at 1.5-3.5 cm/m. It takes about 15-20 years for the consolidation degree to reach 90% and the average sedimentation rate within the overlying 50 m strata was at 5 cm/a to 12 cm/a. This study helps to forecast the final consolidation settlement and settlement rate of the modern Huanghe River subaqueous delta, which provides key geotechnical information for marine engineers.

  4. A survey of sport fish use on the Copper River Delta, Alaska.

    Treesearch

    Dirk W. Lang

    2010-01-01

    Aerial counts, in-person interviews, and mail-in questionnaires were used to survey sport fish use during the coho salmon (Oncorhynchus kisutch Walbaum) season on the Copper River Delta, Alaska from 2002 through 2006. Angler counts provided an index of use on individual streams and were used to develop a spatial database exhibiting patterns of use...

  5. What Role do Hurricanes Play in Sediment Delivery to Subsiding River Deltas?

    NASA Astrophysics Data System (ADS)

    Smith, James E.; Bentley, Samuel J.; Snedden, Gregg A.; White, Crawford

    2015-12-01

    The Mississippi River Delta (MRD) has undergone tremendous land loss over the past century due to natural and anthropogenic influences, a fate shared by many river deltas globally. A globally unprecedented effort to restore and sustain the remaining subaerial portions of the delta is now underway, an endeavor that is expected to cost $50-100B over the next 50 yr. Success of this effort requires a thorough understanding of natural and anthropogenic controls on sediment supply and delta geomorphology. In the MRD, hurricanes have been paradoxically identified as both substantial agents of widespread land loss, and vertical marsh sediment accretion. We present the first multi-decadal chronostratigraphic assessment of sediment supply for a major coastal basin of the MRD that assesses both fluvial and hurricane-induced contributions to sediment accumulation in deltaic wetlands. Our findings indicate that over multidecadal timescales, hurricane-induced sediment delivery may be an important contributor for deltaic wetland vertical accretion, but the contribution from hurricanes to long-term sediment accumulation is substantially less than sediment delivery supplied by existing and planned river-sediment diversions at present-day river-sediment loads.

  6. Land loss by pond expansion on the Mississippi River Delta Plain

    NASA Astrophysics Data System (ADS)

    Ortiz, Alejandra C.; Roy, Samapriya; Edmonds, Douglas A.

    2017-04-01

    The world's river deltas may collapse under the combined effects of rising sea levels, subsidence, and reduced sediment supply. Saving these deltaic environments requires quantifying processes driving collapse. In the Mississippi River Delta, rapid land loss offers an important opportunity to test existing theories for marsh collapse. We use Landsat images to examine how pond expansion by edge retreat contributes to land loss over 34 years in the Atchafalaya-Vermillion, Terrebonne, and Barataria basins of the Mississippi Delta. Tracking the area changes in ponds on the marsh surface, we find a striking consistency between pond expansion direction and the dominant wind direction and show that wind-generated waves are capable of causing edge erosion. Expansion rate increases rapidly for ponds wider than 300 m in Terrebonne and Barataria basins. From this, we suggest that ponds in Atchafalaya-Vermillion basin are stable, whereas ponds in Terrebonne and Barataria are unstable.

  7. Recent morphological changes in the Mekong and Bassac river channels, Mekong delta: The marked impact of river-bed mining and implications for delta destabilisation

    NASA Astrophysics Data System (ADS)

    Brunier, Guillaume; Anthony, Edward J.; Goichot, Marc; Provansal, Mireille; Dussouillez, Philippe

    2014-11-01

    The Mekong delta, in Vietnam, is the world's third largest delta. Densely populated, the delta has been significantly armoured with engineering works and dykes to protect populations and infrastructure from storms, and shrimp farms from saltwater intrusion. Considerable development pressures in Vietnam and in the upstream countries have resulted in the construction of several dams in China and in important channel-bed aggregate extractions especially in Cambodia. The effects of these developments impact the delta dynamics in various ways. In this study, changes in the channel morphology of the Mekong proper and the Bassac, the two main distributaries in the 250 km-long deltaic reach from the Cambodian border to the coast, were analysed using channel depth data for 1998 and 2008. The channels display important and irregular bed changes over the 10-year comparison period, including significant incision and expansion and deepening of numerous pools. The mean depth of both channels increased by more than 1.3 m. Both channels also showed correlative significant bed material losses: respectively 90 million m3 in the Mekong and 110 million m3 in the Bassac over the 10-year period. These important losses over a relatively short period, and weak correlations between bed incision and hydraulic parameters suggest that the marked morphological changes are not in equilibrium with flow and sediment entrainment conditions, and are therefore not related to changes in river hydrology. We claim that aggregate extraction, currently practised on a very large scale in the Mekong delta channels and upstream of the delta, is the main cause of these recent morphological changes. These changes are deemed to contribute actively to rampant bank erosion in the delta as well as to erosion of the Mekong delta shoreline. Other contributory activities include the numerous dykes and embankments. The role of existing dams in bed losses remains unclear in the absence of reliable data on the Mekong

  8. Mapping the change of Phragmites australis live biomass in the lower Mississippi River Delta marshes

    USGS Publications Warehouse

    Ramsey, Elijah W.; Rangoonwala, Amina

    2017-07-28

    Multiyear remote sensing mapping of the normalized difference vegetation index (NDVI) was carried out as an indicator of live biomass composition of the Phragmites australis (hereafter Phragmites) marsh in the lower Mississippi River Delta (hereafter delta) from 2014 to 2017. Maps of NDVI change showed that the Phragmites condition was fairly stable between May 2014 and July 2015. From July 2015 to April 2016 NDVI change indicated Phragmites suffered a widespread decline in the live biomass proportion.  Between April and September 2016, most marsh remained unchanged from the earlier period or showed improvement; although there were pockets of continued decline scattered throughout the lower delta. From September 2016 to May 2017 a pronounced and widely exhibited decline in the condition of Phragmites marsh again occurred throughout the lower delta. This final NDVI change mapping supported field observations of Phragmites decline during the same period.

  9. Insights into the formation of wave-dominated deltas from ground-penetrating radar profiles of the Oxnard Plain, California and the Elwha River Delta, Washington

    NASA Astrophysics Data System (ADS)

    Zurbuchen, J.; Simms, A.; Warrick, J. A.; Miller, I. M.

    2016-12-01

    Distinguishing wave-dominated deltas from prograding clastic shorelines in ancient rock settings is a difficult task due to the lithologic similarities of the two depositional environments. Nevertheless, it is an important distinction in reconstructing the paleogeography essential in interpreting the rock record. Ground-penetrating radar (GPR) surveys were collected at the shoreline of the Oxnard Plain, Southern California and at the Elwha River Delta, Washington to determine if a stratigraphic signature for wave-dominated deltas could be identified. GPR profiles from the shoreline of the Oxnard Plain, CA show landward-dipping reflections near the mouth of the Holocene wave-dominated delta of the Santa Clara River. The landward-dipping reflections do not appear in GPR profiles away from the river mouth and may be one way to distinguish wave-dominated deltas from prograding clastic shorelines in outcrops with limited exposure. The landward-dipping reflections are likely formed by the amalgamation of offshore bars onto the shoreline. Inland storms often cause flooding along rivers, increasing the sediment supplied to the delta mouth. This leads to the formation of offshore bars and back-bar lagoons, which slowly fill with overwash deposits as the bars weld to the shoreline. We propose that the overwash deposits form landward-dipping sediment packages, imaged in GPR profiles as landward-dipping reflections and are unique to wave-dominated deltas. The Elwha River Delta provides a test ground for our model of offshore bar-amalgamation and its geometries within the wave-dominated delta deposits. The geomorphic response of the delta to increased sediment supply due to two dam removals on the Elwha River, initiated in September 2011, has been well documented with aerial photography, topographic surveys, and bathymetric surveys by the USGS. The dam removal greatly increased the sediment supply to the delta and led to delta growth and the formation and subsequent welding of

  10. Mississippi River Delta front loading mechanisms using non-linear wave modeling

    NASA Astrophysics Data System (ADS)

    Georgiou, I. Y.; Bentley, S. J.; Xu, K.; Maloney, J. M.; Miner, M. D.; Keller, G. P.; Obelcz, J.

    2016-02-01

    River deltas often exhibit submarine slides caused by the nature of weak unconsolidated clays deposited through rapid fine grained sedimentation. The role of waves as trigger mechanisms has been suggested and studied by many previous efforts, highlighting among others; the effect of cyclic loading from large hurricane waves shoaling on the delta front seafloor, high near-bed orbital velocities resulting from these waves that can exceed 2m/s, and the development of a pressure gradient across a wave crest that can differentially load the seabed. With declines in suspended sediment load over recent time (1700-present) delta front degradation is inevitable, and recent works suggest that the MRDF is nearing that phase. The impacts of delta front degradation and the potential increase in submarine failures pose an important economic and societal risk to delta populations and infrastructure. Here, we revisit the pressure gradient as a possible loading mechanism for triggering submarine slides and failures. We extend previous studies by hindcasting waves from known hurricanes that influenced the delta using a fully non-linear fluid dynamics model. By controlling the wave properties at the seaward boundary (wave height, length, period) and the type of waves that are forced (linear-sinusoidal, and non-linear-cnoidal, higher order stokes) we examine the pressure gradients along a wave crest and compare with measured shear strength of delta front soils. We further our analysis by evaluating the potential increase in pressure gradients near the bed resulting from shoaling waves on the delta front, in combination with variations in delta-front slopes. Results suggest that the presence of non-linear waves creates larger pressure gradients over shorter wave lengths (or periods), which produce differential loading of the seabed due to transient pressures. Furthermore, our results suggest that the resulting transient pressures may be higher than previously reported, due to the rapid

  11. Dispersal of larval suckers at the Williamson River Delta, Upper Klamath Lake, Oregon, 2006-09

    USGS Publications Warehouse

    Wood, Tamara M.; Hendrixson, Heather A.; Markle, Douglas F.; Erdman, Charles S.; Burdick, Summer M.; Ellsworth, Craig M.; Buccola, Norman L.

    2012-01-01

    An advection/diffusion modeling approach was used to simulate the transport of larval suckers from spawning areas in the Williamson River, through the newly restored Williamson River Delta, to Upper Klamath Lake. The density simulations spanned the years of phased restoration, from 2006/2007 prior to any levee breaching, to 2008 when the northern part of the delta was reconnected to the lake, and 2009 when levees on both sides of the delta had been breached. Model simulation results from all four years were compared to field data using rank correlation. Spearman ρ correlation coefficients were usually significant and in the range 0.30 to 0.60, providing moderately strong validation of the model. The correlation coefficients varied with fish size class in a way that suggested that the model best described the distribution of smaller fish near the Williamson River channel, and larger fish away from the channel. When Lost River and shortnose/Klamath largescale suckers were simulated independently, the correlation results suggested that the model better described the transport and dispersal of the latter species. The incorporation of night-time-only drift behavior in the Williamson River channel neither improved nor degraded correlations with field data. The model showed that advection by currents is an important factor in larval dispersal.

  12. Chlorinated and polycyclic aromatic hydrocarbons in riverine and estuarine sediments from Pearl River Delta, China.

    PubMed

    Mai, Bi-Xian; Fu, Jia-Mo; Sheng, Guo-Ying; Kang, Yue-Hui; Lin, Zheng; Zhang, Gan; Min, Yu-Shuan; Zeng, Eddy Y

    2002-01-01

    Spatial distribution of chlorinated hydrocarbons [chlorinated pesticides (CPs) and polychlorinated biphenyls (PCBs)] and polycyclic aromatic hydrocarbons (PAHs) was measured in riverine and estuarine sediment samples from Pearl River Delta, China, collected in 1997. Concentrations of CPs of the riverine sediment samples range from 12 to 158 ng/g, dry weight, while those of PCBs range from 11 to 486 ng/g. The CPs concentrations of the estuarine sediment samples are in the range 6-1658 ng/g, while concentrations of PCBs are in the range 10-339 ng/g. Total PAH concentration ranges from 1168 to 21,329 ng/g in the riverine sediment samples, whereas the PAH concentration ranges from 323 to 14,812 ng/g in the sediment samples of the Estuary. Sediment samples of the Zhujiang River and Macao harbor around the Estuary show the highest concentrations of CPs, PCBs, and PAHs. Possible factors affecting the distribution patterns are also discussed based on the usage history of the chemicals, hydrologic condition, and land erosion due to urbanization processes. The composition of PAHs is investigated and used to assess petrogenic, combustion and naturally derived PAHs of the sediment samples of the Pearl River Delta. In addition, the concentrations of a number of organic compounds of the Pearl River Delta samples indicate that sediments of the Zhujiang river and Macao harbor are most likely to pose biological impairment.

  13. A large-scale environmental flow experiment for riparian restoration in the Colorado River delta

    USGS Publications Warehouse

    Shafroth, Patrick B.; Schlatter, Karen; Gomez-Sapiens, Martha; Lundgren, Erick; Grabau, Matthew R.; Ramirez-Hernandez, Jorge; Rodriguez-Burgeueno, J. Eliana; Flessa, Karl W.

    2017-01-01

    Managing streamflow is a widely-advocated approach to provide conditions necessary for seed germination and seedling establishment of trees in the willow family (Salicaceae). Experimental flow releases to the Colorado River delta in 2014 had a primary objective of promoting seedling establishment of Fremont cottonwood (Populus fremontii) and Goodding's willow (Salix gooddingii). We assessed seed germination and seedling establishment of these taxa as well as the non-native tamarisk (Tamarix spp.) and native seepwillow shrubs (Baccharis spp.) in the context of seedling requirements and active land management (land grading, vegetation removal) at 23 study sites along 87 river km. In the absence of associated active land management, experimental flows to the Colorado River delta were minimally successful at promoting establishment of new woody riparian seedlings, except for non-native Tamarix. Our results suggest that the primary factors contributing to low seedling establishment varied across space, but included low or no seed availability in some locations for some taxa, insufficient soil moisture availability during the growing season indicated by deep groundwater tables, and competition from adjacent vegetation (and, conversely, availability of bare ground). Active land management to create bare ground and favorable land grades contributed to significantly higher rates of Salicaceae seedling establishment in a river reach with high groundwater tables. Our results provide insights that can inform future environmental flow deliveries to the Colorado River delta and its ecosystems and other similar efforts to restore Salicaceae taxa around the world.

  14. Permafrost Mobilization from the Watershed to the Colville River Delta: Evidence from Biomarkers and 14C Ramped Pyrolysis

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Bianchi, T. S.; Cui, X.; Rosenheim, B. E.; Ping, C. L.; Kanevskiy, M. Z.; Hanna, A. M.; Allison, M. A.

    2016-12-01

    As temperatures in the Arctic rise abnormally fast, permafrost in the region is vulnerable to extensive thawing. This could release previously frozen organic carbon (OC) into the contemporary carbon cycle, giving a positive feedback on global warming. Recent research has found the presence of particulate permafrost in rivers, deltas, and continental shelves in the Arctic, but little direct evidence exists on the mechanism of transportation of previously frozen soils from watershed to the coast. The Colville River in northern Alaska is the largest North American Arctic River with a continuous permafrost within its watershed. Previous work has found evidence for the deposition of previously frozen soils in the Colville River delta (Schreiner et al., 2014). Here, we compared the bulk organic carbon thermal properties, ages of soils and river and delta sediments from the Colville River drainage system using 14C Ramped Pyrolysis and chemical biomarkers. Our data show that deep permafrost soils as well as river and delta sediments had similar pyrograms and biomarker signatures, reflecting transport of soils from watershed to the delta. Surface soil had pyrograms indicative of less stable (more biodegradable) OC than deeper soil horizons. Similarity in pyrograms of deep soils and river sediment indicated the limited contribution of surface soils to riverine particulate OC inputs. Sediments in the delta showed inputs of yedoma (ice-rich syngenetic permafrost with large ice wedges) from the watershed sources (e.g., river bank erosion) in addition to peat inputs, that were largely from coastal erosion.

  15. A brief history and summary of the effects of river engineering and dams on the Mississippi River system and delta

    USGS Publications Warehouse

    Alexander, Jason S.; Wilson, Richard C.; Green, W. Reed

    2012-01-01

    The U.S. Geological Survey Forecast Mekong project is providing technical assistance and information to aid management decisions and build science capacity of institutions in the Mekong River Basin. A component of this effort is to produce a synthesis of the effects of dams and other engineering structures on large-river hydrology, sediment transport, geomorphology, ecology, water quality, and deltaic systems. The Mississippi River Basin (MRB) of the United States was used as the backdrop and context for this synthesis because it is a continental scale river system with a total annual water discharge proportional to the Mekong River, has been highly engineered over the past two centuries, and the effects of engineering have been widely studied and documented by scientists and engineers. The MRB is controlled and regulated by dams and river-engineering structures. These modifications have resulted in multiple benefits including navigation, flood control, hydropower, bank stabilization, and recreation. Dams and other river-engineering structures in the MRB have afforded the United States substantial socioeconomic benefits; however, these benefits also have transformed the hydrologic, sediment transport, geomorphic, water-quality, and ecologic characteristics of the river and its delta. Large dams on the middle Missouri River have substantially reduced the magnitude of peak floods, increased base discharges, and reduced the overall variability of intraannual discharges. The extensive system of levees and wing dikes throughout the MRB, although providing protection from intermediate magnitude floods, have reduced overall channel capacity and increased flood stage by up to 4 meters for higher magnitude floods. Prior to major river engineering, the estimated average annual sediment yield of the Mississippi River Basin was approximately 400 million metric tons. The construction of large main-channel reservoirs on the Missouri and Arkansas Rivers, sedimentation in dike

  16. Sediment- and hydro-dynamics of the Mekong Delta: From tidal river to continental shelf

    NASA Astrophysics Data System (ADS)

    Ogston, A. S.; Allison, M. A.; Mullarney, J. C.; Nittrouer, C. A.

    2017-09-01

    This introduction to the special issue entitled, "Sediment- and hydro-dynamics of the Mekong Delta: from tidal river to continental shelf", describes the setting and program design of collaborative studies with integrated field and modeling experiments in 2014-2015, along with associated research in the region. The Mekong River is among the largest on Earth in terms of water discharge, and much of the sediment delivered from the Tibetan Plateau has accumulated in the subaerial and subaqueous components of the Mekong Delta. As a group, the papers in this special issue describe the portion of the system where the sediment source signal is altered along the tidally influenced river and is delivered to the shorelines and continental shelf. The linked studies provide a holistic view of the system, and emphasize the interactions between hydrodynamics and sediment transport processes in sub-environments as sediment makes its way along the path from source to sink.

  17. Geomorphic evolution of the Lilas River fan delta (Central Evia, Greece), during the Quaternary

    NASA Astrophysics Data System (ADS)

    Karymbalis, Efthimios; Valkanou, Kanella; Tsironis, Giorgos; Tsodoulos, Ioannis; Iliopoulos, George; Tsanakas, Konstantinos; Batzakis, Vasilis

    2015-04-01

    This study deals with the geomorphic evolution of the Lilas river fan delta, which is a late Holocene fan delta with an area of about 25 km2, extended mainly towards the south Evoikos Gulf and a secondary extension of approximately 5 km2 towards the north Evoikos Gulf (Central Evia Isl., Greece). This work has combined field geomorphological mapping with the study of the stratigraphy of late Pleistocene - Holocene deltaic sediments. A detailed geomorphic map at the scale of 1:5,000 has been prepared showing both the deltaic plain and the coastal zone features using GIS techniques. Comparative interpretation of aerial photographs taken in different dates and reliable maps of the last two centuries along with field observations depict recent changes of the delta morphology. Profiles of seven drill cores up to the depth of 70 m, provided by the municipality authorities, were considered in order to study the late Pleistocene - Holocene stratigraphy of the broader fan delta plain. Additionally, two boreholes reaching the depth of 4.75 m were drilled with a portable drilling set. The stratigraphy of the late Holocene sediments was studied in detail and 41 sediment samples, collected from selected sedimentary layers, were analyzed using micropaleontological and grain size analysis methods, while samples were dated using OSL. The study of the stratigraphy of the late Holocene deltaic sediments showed that during this period the sea invaded the area of the northwestern delta and created a shallow open marine environment which at times was disturbed by multiple quiet lagoonal phases of fine sediment deposition. Geomorphological mapping showed that among the most important factor for the recent development of the delta is fluvial sedimentation. The dominant landforms in the deltaic plain are the numerous abandoned palaeochannels. The main channel of the river changed its course several times leading to the building and subsequent abandonment of at least four fan delta lobes

  18. Heavy Metals and Biogenic Elements in Aquatic Systems of the Don River Delta

    NASA Astrophysics Data System (ADS)

    Tkachenko, Anna; Tkachenko, Oleg

    2014-05-01

    River deltas are located in the lower parts of the cascade landscape-geochemical systems of the river basins, so their geochemical conditions often characterize the anthropogenic impact on whole river system. The Don River runs through the one of the most agriculturally developed and densely populated area of Russia, and flows into the Azov Sea - the smallest and shallowest sea in the world. These factors determine the geochemical features of aquatic systems of the Don River mouth area and the specificity of the "river-sea" geochemical barrier zone. The paper presents results of the field studies of the geochemical structure of the Don River mouth area, which were conducted in frames of the RFBR project in 2012-2013. Major types of the deltaic water streams and bodies were studied in different hydrological seasons: spring floods, summer, autumn and winter low water periods. About 50 samples of water, suspended matter and 60 samples of bottom sediments have been collected and analyzed for heavy metals (Fe, Mn, Zn, Cu, Ni, Co, Pb, Cr, Cd etc.) and biogenic elements (nitrate, nitrite, ammonium, phosphates, silica, total nitrogen and phosphorus, dissolved oxygen and chlorophyll) content. To assess the toxicity degree and nutrient potential of water, bioassay test conducted by growing daphnia in water samples were held. The study shows that the Don River delta water is characterized by the relatively low values of dissolved heavy metal content. Significantly higher values of heavy metals were determined in the vicinity of settlements only. Metal accumulation in bottom sediments can be associated mainly with the rate of water flow. Higher values were found in sediments of small channels with weak flow velocity and prevailing processes of the suspended matter deposition. The data on the seasonal dynamics of nutrients and spatial variability of their forms have been obtained. The maximum concentration of nitrogen, phosphorus, silicon, and other biogenic elements are

  19. Holocene evolution in weathering and erosion patterns in the Pearl River delta

    NASA Astrophysics Data System (ADS)

    Hu, Dengke; Clift, Peter D.; BöNing, Philipp; Hannigan, Robyn; Hillier, Stephen; Blusztajn, Jerzy; Wan, Shiming; Fuller, Dorian Q.

    2013-07-01

    Sediments in the Pearl River delta have the potential to record the weathering response of this river basin to climate change since 9.5 ka, most notably weakening of the Asian monsoon since the Early Holocene (˜8 ka). Cores from the Pearl River delta show a clear temporal evolution of weathering intensity, as measured by K/Al, K/Rb, and clay mineralogy, that shows deposition of less weathered sediment at a time of weakening monsoon rainfall in the Early-Mid Holocene (6.0-2.5 ka). This may reflect an immediate response to a less humid climate, or more likely reduced reworking of older deposits from river terraces as the monsoon weakened. Human settlement of the Pearl River basin may have had a major impact on landscape and erosion as a result of the establishment of widespread agriculture. After around 2.5 ka weathering intensity sharply increased, despite limited change in the monsoon, but at a time when anthropogenic pollutants (e.g., Cu, Zn, and Pb) increased and when the flora of the basin changed. 87Sr/86Sr covaries with these other proxies but is also partly influenced by the presence of carbonate. The sediments in the modern Pearl River are even more weathered than the youngest material from the delta cores. We infer that the spread of farming into the Pearl River basin around 2.7 ka was followed by a widespread reworking of old, weathered soils after 2.5 ka, and large-scale disruption of the river system that was advanced by 2.0 ka.

  20. Flooding the Colorado River Delta: A Landscape-Scale Experiment

    NASA Astrophysics Data System (ADS)

    Flessa, Karl W.; Glenn, Edward P.; Hinojosa-Huerta, Osvel; Parra-Rentería, Carlos A.; Ramírez-Hernández, Jorge; Schmidt, John C.; Zamora-Arroyo, Francisco A.

    2013-12-01

    A large pulse of water is planned to be released into the dry Colorado River channel in Mexico. This engineered experimental spring flood, which will flow from Lake Mead and pass through downstream reservoirs, is the culmination of decades of applied research. The pulse flow is a rare opportunity for research at the landscape scale [Glenn et al., 2013].

  1. Insecticide susceptibilities of the two rice planthoppers Nilaparvata lugens and Sogatella furcifera in East Asia, the Red River Delta, and the Mekong Delta.

    PubMed

    Matsumura, Masaya; Sanada-Morimura, Sachiyo; Otuka, Akira; Sonoda, Shoji; Van Thanh, Dinh; Van Chien, Ho; Van Tuong, Phan; Loc, Phung Minh; Liu, Ze-Wen; Zhu, Zeng-Rong; Li, Jian-Hong; Wu, Gang; Huang, Shou-Horng

    2017-09-12

    The two rice planthoppers Nilaparvata lugens and Sogatella furcifera, have different life cycles in the regions of East Asia, the Red River Delta, and the Mekong Delta. The susceptibilities of these species to a range of insecticides have not previously been compared among the three regions over multiple years. Here we describe the differences and similarities in insecticide susceptibilities of the two species among the three regions from 2006-2011. In all three regions during 2006 to 2011, N. lugens developed high and moderate levels of resistance to imidacloprid and thiamethoxam, respectively, but this species did not develop resistance to fipronil. In contrast, S. furcifera developed a high level of resistance to fipronil. The ranges in LD50 values for N. lugens treated with both imidacloprid and thiamethoxam were similar over time between East Asia and the Red River Delta, and were different in the Mekong Delta. The results support the idea that resistant populations migrate from the Red River Delta region to East Asia. Therefore, continuous monitoring of the susceptibility of N. lugens to insecticides in the Red River Delta is very important for insecticide resistance management in East Asia. This article is protected by copyright. All rights reserved.

  2. Conceptual model of sedimentation in the Sacramento-San Joaquin River Delta

    USGS Publications Warehouse

    Schoellhamer, David H.; Wright, Scott A.; Drexler, Judith Z.

    2012-01-01

    Sedimentation in the Sacramento–San Joaquin River Delta builds the Delta landscape, creates benthic and pelagic habitat, and transports sediment-associated contaminants. Here we present a conceptual model of sedimentation that includes submodels for river supply from the watershed to the Delta, regional transport within the Delta and seaward exchange, and local sedimentation in open water and marsh habitats. The model demonstrates feedback loops that affect the Delta ecosystem. Submerged and emergent marsh vegetation act as ecosystem engineers that can create a positive feedback loop by decreasing suspended sediment, increasing water column light, which in turn enables more vegetation. Sea-level rise in open water is partially countered by a negative feedback loop that increases deposition if there is a net decrease in hydrodynamic energy. Manipulation of regional sediment transport is probably the most feasible method to control suspended sediment and thus turbidity. The conceptual model is used to identify information gaps that need to be filled to develop an accurate sediment transport model.

  3. SAR Interferometry as a Tool for Monitoring Coastal Changes in the Nile River Delta of Egypt

    NASA Technical Reports Server (NTRS)

    Aly, Mohamed H.; Klein, Andrew G.; Giardino, John R.

    2005-01-01

    The Nile River Delta is experiencing rapid rates of coastal change. The rate of both coastal retreat and accretion in the Eastern Nile Delta requires regular, accurate detection and measurement. Current techniques used to monitor coastal changes in the delta are point measurements and, thus, they provide a spatially limited view of the ongoing coastal changes. SAR interferometry can provide measurements of subtle coastal change at a significantly improved spatial resolution and over large areas (100 sq km). Using data provided by the ERS-1&2 satellites, monitoring can be accomplished as frequently as every 35 days when needed. Radar interferometry is employed in this study to detect segments of erosion and accretion during the 1993-2000 period. The average rates of erosion and accretion in the Eastern Nile Delta are measured to be -11.64 m/yr and +5.12 m/yr, respectively. The results of this interferometric study can be used effectively for coastal zone management and integrated sustainable development for the Nile River Delta.

  4. SAR Interferometry as a Tool for Monitoring Coastal Changes in the Nile River Delta of Egypt

    NASA Technical Reports Server (NTRS)

    Aly, Mohamed H.; Klein, Andrew G.; Giardino, John R.

    2005-01-01

    The Nile River Delta is experiencing rapid rates of coastal change. The rate of both coastal retreat and accretion in the Eastern Nile Delta requires regular, accurate detection and measurement. Current techniques used to monitor coastal changes in the delta are point measurements and, thus, they provide a spatially limited view of the ongoing coastal changes. SAR interferometry can provide measurements of subtle coastal change at a significantly improved spatial resolution and over large areas (100 sq km). Using data provided by the ERS-1&2 satellites, monitoring can be accomplished as frequently as every 35 days when needed. Radar interferometry is employed in this study to detect segments of erosion and accretion during the 1993-2000 period. The average rates of erosion and accretion in the Eastern Nile Delta are measured to be -11.64 m/yr and +5.12 m/yr, respectively. The results of this interferometric study can be used effectively for coastal zone management and integrated sustainable development for the Nile River Delta.

  5. Sources, bioavailability, and photoreactivity of dissolved organic carbon in the Sacramento-San Joaquin River Delta

    USGS Publications Warehouse

    Stepanauskas, R.; Moran, M.A.; Bergamaschi, B.A.; Hollibaugh, J.T.

    2005-01-01

    We analyzed bioavailability, photoreactivity, fluorescence, and isotopic composition of dissolved organic carbon (DOC) collected at 13 stations in the Sacramento-San Joaquin River Delta during various seasons to estimate the persistence of DOC from diverse shallow water habitat sources. Prospective large-scale wetland restorations in the Delta may change the amount of DOC available to the food web as well as change the quality of Delta water exported for municipal use. Our study indicates that DOC contributed by Delta sources is relatively refractory and likely mostly the dissolved remnants of vascular plant material from degrading soils and tidal marshes rather than phytoplankton production. Therefore, the prospective conversion of agricultural land into submerged, phytoplankton-dominated habitats may reduce the undesired export of DOC from the Delta to municipal users. A median of 10% of Delta DOC was rapidly utilizable by bacterioplankton. A moderate dose of simulated solar radiation (286 W m-2 for 4 h) decreased the DOC bioavailability by an average of 40%, with a larger relative decrease in samples with higher initial DOC bioavailability. Potentially, a DOC-based microbial food web could support ???0.6 ?? 109 g C of protist production in the Delta annually, compared to ???17 ?? 109 g C phytoplankton primary production. Thus, DOC utilization via the microbial food web is unlikely to play an important role in the nutrition of Delta zooplankton and fish, and the possible decrease in DOC concentration due to wetland restoration is unlikely to have a direct effect on Delta fish productivity. ?? Springer 2005.

  6. Mississippi River delta plain, Louisiana coast, and inner shelf Holocene geologic framework, processes, and resources

    USGS Publications Warehouse

    Williams, S. Jeffress; Kulp, Mark; Penland, Shea; Kindinger, Jack L.; Flocks, James G.; Buster, Noreen A.; Holmes, Charles W.

    2009-01-01

    Extending nearly 400 km from Sabine Pass on the Texas-Louisiana border east to the Chandeleur Islands, the Louisiana coastal zone (Fig. 11.1) along the north-central Gulf of Mexico is the southern terminus of the largest drainage basin in North America (>3.3 million km2), which includes the Mississippi River delta plain where approximately 6.2 million kilograms per year of sediment is delivered to the Gulf of Mexico (Coleman 1988). The Mississippi River, active since at least Late Jurassic time (Mann and Thomas 1968), is the main distributary channel of this drainage system and during the Holocene has constructed one of the largest delta plains in the world, larger than 30,000 km2 (Coleman and Prior 1980; Coleman 1981; Coleman et al. 1998). The subsurface geology and geomorphology of the Louisiana coastal zone reffects a complex history of regional tectonic events and fluvial, deltaic, and marine sedimentary processes affected by large sea-level fluctuations. Despite the complex geology of the north-central Gulf basin, a long history of engineering studies and Scientific research investigations (see table 11.1) has led to substantial knowledge of the geologic framework and evolution of the delta plain region (see also Bird et al., chapter 1 in this volume). Mississippi River delta plain, Louisiana coast, and inner shelf Holocene geologic framework, processes, and resources. Available from: https://www.researchgate.net/publication/262802561_Mississippi_River_delta_plain_Louisiana_coast_and_inner_shelf_Holocene_geologic_framework_processes_and_resources [accessed Sep 13, 2017].

  7. Shallow stratigraphy of the Skagit River Delta, Washington, derived from sediment cores

    USGS Publications Warehouse

    Grossman, Eric E.; George, Douglas A.; Lam, Angela

    2011-01-01

    Sedimentologic analyses of 21 sediment cores, ranging from 0.4 to 9.6 m in length, reveal that the shallow geologic framework of the Skagit River Delta, western Washington, United States, has changed significantly since 1850. The cores collected from elevations of 3.94 to -2.41 m (relative to mean lower low water) along four cross-shore transects between the emergent marsh and delta front show relatively similar environmental changes across an area spanning ~75 km2. Offshore of the present North Fork Skagit River and South Fork Skagit River mouths where river discharge is focused by diked channels through the delta, the entire 5–7-km-wide tidal flats are covered with 1–2 m of cross-bedded medium-to-coarse sands. The bottoms of cores, collected in these areas are composed of mud. A sharp transition from mud to a cross-bedded sand unit indicates that the tidal flats changed abruptly from a calm environment to an energetic one. This is in stark contrast to the Martha's Bay tidal flats north of the Skagit Bay jetty that was completed in the 1940s to protect the newly constructed Swinomish Channel from flooding and sedimentation. North of the jetty, mud ranging from 1 to 2 m thick drapes a previously silt- and sand-rich tidal flat. The silty sand is a sediment facies that would be expected there where North Fork Skagit River sedimentation occurred prior to jetty emplacement. This report describes the compositional and textural properties of the sediment cores by using geophysical, photographic, x-radiography, and standard sediment grain-size and carbon-analytical methods. The findings help to characterize benthic habitat structure and sediment transport processes and the environmental changes that have occurred across the nearshore of the Skagit River Delta. The findings will be useful for quantifying changes to nearshore marine resources, including impacts resulting from diking, river-delta channelization, shoreline development, and natural variations in fluvial

  8. Land subsidence at aquaculture facilities in the Yellow River delta, China

    NASA Astrophysics Data System (ADS)

    Higgins, Stephanie; Overeem, Irina; Tanaka, Akiko; Syvitski, James P. M.

    2013-08-01

    Differential Interferometric Synthetic Aperture Radar is applied to the coast of the Yellow River delta (YRD) in China. Like many deltas, the coastline of the YRD is dominated by aquaculture. Advanced Land Observation Satellite Phased Array L-Band Synthetic Aperture Radar (SAR) and Envisat Advanced SAR data acquired between 2007 and 2011 show that subsidence rates are as high as 250 mm/y at aquaculture facilities, likely due to groundwater pumping. These rates exceed local and global average sea level rise by nearly 2 orders of magnitude and suggest that subsidence and associated relative sea level rise may present a significant hazard for Asian megadeltas.

  9. Geotechnical properties of Mississippi River delta sediments utilizing in situ pressure sampling techniques

    SciTech Connect

    Johns, M.W.

    1985-01-01

    Rapid accumulation of organic-rich sediments and the subsequent anaerobic, biogenic decomposition of the organic material on the Mississippi River delta have led to sediment regions with high methane concentrations. The presence of the very soft, underconsolidated, gassy sediments creates a variety of problems for the acquisition of seismic data and samples for geotechnical analyses. A pressure core barrel has been developed by Texas AandM University, in conjunction with the US Geological Survey Mississippi Delta Project, to investigate these shallow gas-charged sediments.

  10. 2500 years of changing shoreline accretion rates at the mouths of the Mekong River delta

    NASA Astrophysics Data System (ADS)

    Besset, Manon; Tamura, Toru; Anthony, Edward; Brunier, Guillaume; Saito, Yoshiki; Dussouillez, Philippe; Lap Nguyen, Van; Ta, Oahn

    2016-04-01

    The Mekong River delta prograded rapidly in a relatively sheltered bight in the South China Sea under the influence of high fluvial sediment supply 5300 to 3500 years ago, developing from an estuary into a delta. This >200 km seaward growth resulted in increasing exposure of the delta to ocean waves that led to a more wave-influenced mode of progradation characterized by the construction of numerous sets of beach ridges in the eastern sector of the delta, which shows a system of multiple distributary mouths. The growth pattern of this river-mouth sector over the last 2500 years has been determined from OSL dating of these beach-ridge deposits, while the most up-to-date trends (1950-2014) have been highlighted from the analysis of maps and satellite images. The OSL ages show that the area of the delta in the mouths sector remained nearly constant till about 500 yr BP, following which significant accretion occurred, possibly in response to changes in catchment land-use and monsoon rainfall and attendant river water and sediment discharge. A fine-tuned analysis of changes since 1950 shows dominant but fluctuating accretion, with two periods of erosion. The first (1965-1973) occurred in the course of the second Indochina war, and the second more recently from 2003 to 2011, followed by mild recovery between 2011 and 2014. These fluctuations most likely reflect changes in sediment supply caused by the vicissitudes of war and its effect on vegetation cover, as well as variations in monsoon rainfall and discharge, and, for the most recent period, massive sand mining in the river and deltaic channels. Accretion of the mouths sector has gone apace, over the same recent multi-decadal period, with large-scale erosion of the muddy shores of the delta in the western South China Sea and the Gulf of Thailand, thus suggesting that the mouths sector may be increasingly sequestering sediment to the detriment of the rest of the delta shoreline. The accretion in the mouths sector is

  11. Analysis of relationships between land surface temperature and land use changes in the Yellow River Delta

    NASA Astrophysics Data System (ADS)

    Ning, Jicai; Gao, Zhiqiang; Meng, Ran; Xu, Fuxiang; Gao, Meng

    2017-06-01

    This study analyzed land use and land cover changes and their impact on land surface temperature using Landsat 5 Thematic Mapper and Landsat 8 Operational Land Imager and Thermal Infrared Sensor imagery of the Yellow River Delta. Six Landsat images comprising two time series were used to calculate the land surface temperature and correlated vegetation indices. The Yellow River Delta area has expanded substantially because of the deposited sediment carried from upstream reaches of the river. Between 1986 and 2015, approximately 35% of the land use area of the Yellow River Delta has been transformed into salterns and aquaculture ponds. Overall, land use conversion has occurred primarily from poorly utilized land into highly utilized land. To analyze the variation of land surface temperature, a mono-window algorithm was applied to retrieve the regional land surface temperature. The results showed bilinear correlation between land surface temperature and the vegetation indices (i.e., Normalized Difference Vegetation Index, Adjusted-Normalized Vegetation Index, Soil-Adjusted Vegetation Index, and Modified Soil-Adjusted Vegetation Index). Generally, values of the vegetation indices greater than the inflection point mean the land surface temperature and the vegetation indices are correlated negatively, and vice versa. Land surface temperature in coastal areas is affected considerably by local seawater temperature and weather conditions.

  12. The diversity of permafrost-affected soils in the Lena River Delta and its hinterland

    NASA Astrophysics Data System (ADS)

    Zubrzycki, Sebastian; Kutzbach, Lars; Yakshina, Irina; Pfeiffer, Eva-Maria

    2013-04-01

    The North-Siberian Lena River Delta is the largest Arctic delta and an important interface between the Arctic Ocean in the North and the large Siberian land masses in the South. This delta consists not only of Holocene deltaic sediment deposits as a river terrace and the modern active floodplains but also of remnants of the former Pleistocene mainland including large islands of ice-complex sediments and the Arga-Muora-Sise Island, which is composed of pure sand sediments of still debated origin. The highly diverse landscape structure of the Lena River Delta is reflected by a great variety of permafrost-affected soils (gelisols). This study aims at describing this great gelisol diversity and at analysing the dominant soil-forming processes in this comparatively scarcely studied soil region. The soil development in the investigated continuous permafrost region is limited by the short thawing period of around three months (June to September) and takes place in the shallow (< 1 m) seasonally thawed active layer. The geological parent material plays an important role for the development of soils in the Lena River Delta region. The distribution of the various soil types closely follows the pattern of the geomorphic units characterised by differing sedimentation conditions. The properties and genesis of the soils on the Holocene river terrace and the modern floodplains are strongly affected by the enormous amounts of fluvial sediments (about 12 x 106 tons per year) brought by the Lena River into its delta. The fluvial sedimentation together with the also pronounced aeolian sedimentation results in a fast vertical growth of soils. The upward rise of the soil surface leads to an upward movement of the permafrost table resulting in fast incorporation of soil material formed in the supra-permafrost zone into the permafrost. Due to the morphodynamics of ice-wedge polygons and resulting formation of patterned ground with elevated rims and depressed and water-saturated centres

  13. Evolution of an Anthropocene Delta: Understanding the Interplay of Natural and Anthropogenic Forces That Shaped the Brazos River Subaqueous Delta, USA

    NASA Astrophysics Data System (ADS)

    Carlin, J. A.; Dellapenna, T. M.

    2014-12-01

    Deltas are unique environments that are rich in natural resources and human populations. As a result, human activities directly to the delta and indirectly to the watershed in the Anthropocene have led to changes within the deltaic system as a response to these natural and anthropogenic forces. Understanding the response of deltas to these new forcings will be critical to assess the vulnerability of deltas to global climate change and expanding human populations. The Brazos River Delta, located in the northwestern Gulf of Mexico, served as an ideal study area to investigate the effect of human activities on a delta. Historical alterations to the system include agricultural activity, jetty construction, an engineered mouth diversion, and reservoir construction throughout the early and mid 20th Century. Three subaerial deltaic growth phases were identified based on historic shoreline configurations, and combined with high-resolution geophysical data (swath bathymetry, side scan sonar, CHIRP subbottom profiling) from the subaqueous delta to investigate the subaqueous delta changes over time. Evidence from these alternating progradational and retrogradational periods are preserved within the subaqueous delta. The data showed that as the growth of the subaerial delta changed over time, the subaqueous clinoform was subjected to regions of progradation or abandonment. The abandoned clinoform sections were characterized by a thinning modern clinoform sequence downslope from an erosional scarp. High side scan sonar backscatter features are believed to distinguish exposed erosional surfaces throughout the subaqueous delta demarcating the abandoned sections at the seabed. Prograding clinoform areas lack these high backscatter features. In these areas the modern clinoform was relatively thicker and does not exhibit the upslope erosional scarps. This noticeable asymmetry across the subaqueous delta shows that the Brazos Delta has migrated southwestward resulting from shifts in

  14. Basin-Scale Exports vs. Coastal Delivery of Carbon, Nutrients and Particulates Above and Below Arctic River Deltas

    NASA Astrophysics Data System (ADS)

    Striegl, R. G.; Tank, S. E.; Weeks, G.; Holmes, R. M.; McClelland, J. W.

    2014-12-01

    Recent studies have substantially improved our understanding of water, sediment and materials exports by arctic rivers. Seasonality of exports, particularly during the spring freshet, is better quantified, as are the inland sources of water and sediment discharge and the source and chemical character of other material exports, including carbon and nutrients. Measurements on small rivers discharging directly to the Arctic Ocean and lacking complex deltas can accurately quantify local inputs to coastal regions. However, the majority of hydrologic inputs to the Arctic Ocean derive from 6 major Eurasian and North American rivers. Water, sediment, and chemical exports from these rivers are typically measured above head of tide, far inland, and commonly above large river deltas. These deltas settle particles and provide favorable environments for deposition, storage, and biogeochemical consumption, production, and transformation of aquatic carbon and nutrients. Consequently, basin exports measured above river deltas likely misrepresent actual delivery to coastal regions. In addition to accumulating sediment, observed and modeled arctic delta effects include enrichment of the organic content of suspended solids, increased dissolved organic carbon and nitrogen (DOC; DON) concentration, decreased inorganic nutrient concentration, and settling and likely increased bioavailability of particle associated contaminants, such as mercury. Increased DOC concentration in the Mackenzie River delta has also been associated with a change in DOC quality, with increased potential for biodegradation of DOC and decreased potential for photodegradation of DOC from head of tide to within the delta. For the most part, assessments of differences between head of tide basin exports and coastal delivery tend to be qualitative rather than quantitative, largely because of difficulties quantifying tidally affected flow. This points to the need to resolve data gaps, improve quantitative assessments

  15. Greenhouse Gas Emissions within Seasonally Flooded Tropical River Deltas

    NASA Astrophysics Data System (ADS)

    Salvador, A. K.; Schaefer, M.; Roberts, K. A.; Fendorf, S. E.; Benner, S. G.

    2015-12-01

    Soils contain the largest terrestrial carbon pool on Earth, and approximately one-third of soil carbon is stored in the tropics. Gas exchange between soil and the atmosphere occurs largely as a result of microbial degradation (mineralization) of organic carbon. The rate of soil organic matter (SOM) mineralization is determined by a combination of climatic factors and soil ecosystem properties, which dictate the dominant metabolic pathway(s) within soil at a given time; major changes in metabolic rate are particularly pronounced between aerobic and anaerobic mineralization. Here we assessed the impact of soil moisture, a major factor determining soil anaerobiosis, on greenhouse gas fluxes in a tropical, seasonally flooded wetland in the Mekong Delta. We monitored CO2, CH4, and N2O gas fluxes, porewater chemistry, and soil moisture content in a seasonal wetland. Additionally, we collected wetland soil cores (10 cm diameter) and manipulated them in the laboratory, allowing us to control soil moisture and drying rates, and to simulate multiple periods of wetting and drying. During drying, CH4 fluxes within the wetland initially increase to a maximum before decreasing as soil moisture decreases and oxygen diffusion into the soil increases. Maximum CH4 fluxes vary with moisture content, but the wettest sites produced fluxes >1000 mg C m-2 d-1 for short periods of time. As drying continues, CH4 fluxes decrease to nearly zero, and N2O fluxes begin to increase to ~3 mg N m-2 d-1 but do not appear to have reached a maximum before sampling ceased. Gas flux from soil core incubations (n=5) exhibit trends and values similar to field measurements. CH4 fluxes initially increase and reach >1000 mg C m-2 d-1 in cores while N2O fluxes reach up to 10 mg N m-2 d-1 and decrease with continued drying. CO2 fluxes in both field and laboratory are sustained until near desiccated conditions. Seasonal wetlands are characteristic of large tropical deltas. Our findings provide a means to

  16. Assessing Subaqueous Mudflow Hazard on the Mississippi River Delta Front, Part 1: A Historical Perspective on Mississippi River Delta Front Sedimentation

    NASA Astrophysics Data System (ADS)

    Maloney, J. M.; Bentley, S. J.; Obelcz, J.; Xu, K.; Miner, M. D.; Georgiou, I. Y.; Hanegan, K.; Keller, G.

    2014-12-01

    Subaqueous mudflows are known to be ubiquitous across the Mississippi River delta front (MRDF) and have been identified as a hazard to offshore infrastructure. Among other factors, sediment accumulation rates and patterns play an important role in governing the stability of delta front sediment. High sedimentation rates result in underconsolidation, slope steepening, and increased biogenic gas production, which are all known to decrease stability. Sedimentation rates are highly variable across the MRDF, but are highest near the mouth of Southwest Pass, which carries the largest percentage of Mississippi River sediment into the Gulf of Mexico. Since the 1950s, the sediment load of the Mississippi River has decreased by ~50% due to dam construction upstream. The impact of this decreased sediment load on MRDF mudflow dynamics has yet to be examined. We compiled MRDF bathymetric datasets, including historical charts, industry and academic surveys, and NOAA data, collected between 1764 and 2009, in order to identify historic trends in sedimentation patterns. The progradation of Southwest Pass (measured at 10 m depth contour) has slowed from ~66 m/yr between 1764 and 1940 to ~25 m/yr between 1940 and 1979, with evidence of further deceleration from 1979-2009. Decreased rates of progradation are also observed at South Pass and Pass A Loutre. Advancement of the delta also decelerated in deeper water (15-90 m) offshore from Southwest Pass. In this area, from 1940-1979, depth contours advanced seaward ~25 m/yr, but did not advance from 1979-2005. Furthermore, over the same area and time ranges, the sediment accumulation rate decreased by ~82%. We expect these sedimentation trends are occurring across the delta front, with potential impacts on spatial and temporal patterns of subaqueous mudflows. The MRDF appears to be entering a phase of decline, which will likely be accelerated by future upstream sediment diversion projects. New geophysical data will be required to assess

  17. Decades of Change on the Ganges-Brahmaputra Delta; Rivers, Coastlines, Agriculture and Development

    NASA Astrophysics Data System (ADS)

    Small, C.; Sousa, D.; Chiu, S.; Mondal, D. R.; Steckler, M. S.; Akhter, S. H.; Mia, B.; Goodbred, S. L., Jr.; Wilson, C.; Seeber, L.

    2014-12-01

    The Ganges-Brahmaputra delta (GBD) is formed by the convergence of two great rivers, superlative in both size and geologic activity. The GBD is home to > 150 million people with a mean population density of more than 1000 people/km2. The fertile soils, abundant water and favorable climate also make the delta one of the most agriculturally diverse and productive areas on Earth. We seek to better understand the coupled natural and anthropogenic dynamics of the delta through a number of cross-disciplinary field studies of the contributing geophysical, biophysical and anthropogenic processes. To provide a synoptic multitemporal perspective for these studies, we use a variety of remotely sensed observations collected over the delta since 1988. In this overview we provide a synthesis of recent results from studies of 4 interrelated processes; river channel migration, coastal erosion and deposition, co-evolution of agriculture and aquaculture, and economic development. In each study we use multi-sensor spatiotemporal analysis of remotely sensed imagery spanning more than 2 decades to observe and quantify a variety of processes at multiple spatial and temporal scales. MODIS Enhanced Vegetation Index (EVI) composites provide 16 day temporal and 250m spatial resolution of the entire delta from 2000 to present. This image time series captures not only agricultural phenology over the entire delta but also the development of aquaculture on the lower delta and interannual fluvial dynamics on both the Ganges and Brahmaputra rivers. Landsat TM, ETM+ and OLI allow us to represent land cover as continuous fields of soil and sediment substrate, vegetation and dark surfaces (water and shadow) throughout the delta since 1988. Despite its irregular temporal sampling, Landsat's 30 m pixels better resolve both natural and anthropogenic land cover units and its longer time series extends retrospective analyses back to 1988. More recent sensors like Ikonos, Quickbird, GeoEye and World

  18. Geogenic Sources Strongly Contribute to the Mackenzie River Delta's Methane Emissions Derived From Airborne Flux Data

    NASA Astrophysics Data System (ADS)

    Kohnert, K.; Serafimovich, A.; Metzger, S.; Hartmann, J.; Sachs, T.

    2015-12-01

    Arctic permafrost-associated wetlands and thawing permafrost emit the greenhouse gas methane (CH4), either as a product of recent microbial activity in the active layer or taliks, or from deeper geogenic sources where pathways through the permafrost exist. Current emission estimates vary strongly between different models and there is still disagreement between bottom-up estimates from local field studies and top-down estimates from atmospheric measurements. We use airborne flux data from two campaigns in the Mackenzie River Delta, Canada, in July 2012 and 2013 to directly quantify permafrost CH4 emissions on the regional scale, to analyse the regional pattern of CH4 fluxes and to estimate the contribution of geogenic emissions to the overall CH4 budget of the delta. CH4 fluxes were calculated with a time-frequency resolved version of the eddy covariance technique, resulting in a gridded 100 m x 100 m resolution flux map within the footprints of the flight tracks. We distinguish geogenic gas seeps from biogenic sources by their strength and show that they contribute strongly to the annual CH4 budget of the delta. Our study provides the first estimate of annual CH4 release from the Mackenzie River Delta and the adjacent coastal plain. We show that one percent of the covered area contains the strongest geogenic seeps which contribute disproportionately to the annual emission estimate. Our results show that geogenic CH4 emissions might need more attention, especially in areas where permafrost is vulnerable to thawing sufficiently to create pathways for geogenic gas migration. The presented map can be used as a baseline for future CH4 flux studies in the Mackenzie River Delta.

  19. Environmental and eelgrass response to dike removal: Nisqually River Delta (2010–14)

    USGS Publications Warehouse

    Takesue, Renee K.

    2016-10-03

    Restoration of tidal flows to formerly diked marshland can alter land-to-sea fluxes and patterns of accumulation of terrestrial sediment and organic matter, and these tidal flows can also affect existing nearshore habitats. Dikes were removed from 308 hectares (ha) of the Nisqually National Wildlife Refuge on the Nisqually River Delta in south Puget Sound, Washington, in fall 2009 to improve habitat for wildlife, such as juvenile salmon. Ecologically important intertidal and subtidal eelgrass (Zostera marina) beds grow on the north and west margins of the delta. The goal of this study was to understand long-term changes in eelgrass habitat and their relation to dike removal. Sediment and eelgrass properties were monitored annually in May from 2010 to 2014 at two sites on the west side of the Nisqually River Delta along McAllister Creek, a spring-fed creek near two restored tidal channels. In May 2014, the mean canopy height of eelgrass was the same as in previous years in an 8-ha bed extending to the Nisqually River Delta front, but mean canopy height was 20 percent lower in a 0.3-ha eelgrass bed closer to the restored marsh when compared to mean canopy height of eelgrass in May 2010, 6 months after dike removal was completed. Over 5 years, the amount of eelgrass leaf area per square meter (m2) in the 8-ha bed increased slightly, and surface-sediment grain size became finer. In contrast, in the 0.3-ha bed, eelgrass leaf area per m2 decreased by 45 percent, and surface sediment coarsened. Other potential stressors, including sediment pore water reduction-oxidation potential (redox) and hydrogen sulfide (H2S) concentration in the eelgrass rhizosphere, or root zone, were below levels that negatively affect eelgrass growth and therefore did not appear to be environmental stressors on plants. Eelgrass biomass partitioning, though less favorable in the 8-ha eelgrass bed compared to the 0.3-ha one, was well above the critical above-ground to below-ground biomass ratio of

  20. Transient modeling of the ground thermal conditions using satellite data in the Lena River delta, Siberia

    NASA Astrophysics Data System (ADS)

    Westermann, Sebastian; Peter, Maria; Langer, Moritz; Schwamborn, Georg; Schirrmeister, Lutz; Etzelmüller, Bernd; Boike, Julia

    2017-06-01

    Permafrost is a sensitive element of the cryosphere, but operational monitoring of the ground thermal conditions on large spatial scales is still lacking. Here, we demonstrate a remote-sensing-based scheme that is capable of estimating the transient evolution of ground temperatures and active layer thickness by means of the ground thermal model CryoGrid 2. The scheme is applied to an area of approximately 16 000 km2 in the Lena River delta (LRD) in NE Siberia for a period of 14 years. The forcing data sets at 1 km spatial and weekly temporal resolution are synthesized from satellite products and fields of meteorological variables from the ERA-Interim reanalysis. To assign spatially distributed ground thermal properties, a stratigraphic classification based on geomorphological observations and mapping is constructed, which accounts for the large-scale patterns of sediment types, ground ice and surface properties in the Lena River delta. A comparison of the model forcing to in situ measurements on Samoylov Island in the southern part of the study area yields an acceptable agreement for the purpose of ground thermal modeling, for surface temperature, snow depth, and timing of the onset and termination of the winter snow cover. The model results are compared to observations of ground temperatures and thaw depths at nine sites in the Lena River delta, suggesting that thaw depths are in most cases reproduced to within 0.1 m or less and multi-year averages of ground temperatures within 1-2 °C. Comparison of monthly average temperatures at depths of 2-3 m in five boreholes yielded an RMSE of 1.1 °C and a bias of -0.9 °C for the model results. The highest ground temperatures are calculated for grid cells close to the main river channels in the south as well as areas with sandy sediments and low organic and ice contents in the central delta, where also the largest thaw depths occur. On the other hand, the lowest temperatures are modeled for the eastern part, which is an

  1. Factors regulating benthic food chains in tropical river deltas and adjacent shelf areas

    NASA Astrophysics Data System (ADS)

    Alongi, D. M.; Robertson, A. I.

    1995-09-01

    Benthic food chains of the Amazon (Brazil) and Fly (Papua New Guinea) river deltas and adjacent shelves are compared. Abundance patterns of the major trophic groups (bacteria, meiofauna, and macroinfauna) are similar between regions, with very low densities, or the absence of benthos, within and near the deltas. For muds in the more quiescent areas, benthic abundance and productivity are highest, commonly coinciding with maximum pelagic primary production. Episodes of physical disturbance, erratic food supply, and dilution of river-derived, particulate organic matter foster the development of opportunistic benthic communities of variable diversity and low biomass, dominated by bacteria. These pioneering assemblages are the main food of penaeid shrimp, which dominate the demersal trawl fisheries of both fluvial-dominated regions.

  2. Remote Sensing of Bidecadal Urbanization and its impact on Ecosystem Service in the Yangtze River Delta

    NASA Astrophysics Data System (ADS)

    Haas, Jan; Ban, Yifang

    2013-01-01

    The degree of urbanization and resulting effects on Ecosystem Services is investigated in the Yangtze River Delta in China within a 20 year time frame from 1990 to 2010. A Random forest classifier is used to classify the Landsat mosaic from 1990 and the HJ-1A/B mosaic dating from 2010. Urban Land Index (UI) and Urban Expansion Index (UX) are used to represent the intensity and rapidity of urbanization. Post-Classification Change Detection is then performed and Ecosystem Service value losses for the land-cover classes water, wetland, forest and cropland that transitioned to urban areas are calculated according to a valuation scheme adapted to the Chinese market. The results showed that Yangtze River Delta experienced significant urbanization during 1990 to 2010. Urban areas increased alongside a major decrease in cropland resulting in a substantial loss of 4.2 billion CNY in Ecosystem Services.

  3. beta (+)-Thalassaemia in the Po river delta region (northern Italy): genotype and beta globin synthesis.

    PubMed Central

    Del Senno, L; Pirastu, M; Barbieri, R; Bernardi, F; Buzzoni, D; Marchetti, G; Perrotta, C; Vullo, C; Kan, Y W; Conconi, F

    1985-01-01

    Six beta(+)-thalassaemic patients from the Po river delta region have been studied. Using synthetic oligonucleotides as specific hybridisation probes, the beta(+) IVS I mutation (G----A at position 108) was demonstrated. This lesion and the enzyme polymorphism pattern in the subjects examined are the same as have been described for other Mediterranean beta(+)-thalassaemias. Antenatal diagnosis through DNA analysis of beta(+)-thalassaemia is therefore possible. The production of beta globin in a beta(+), homozygote and in a beta (+), beta(0) 39 (nonsense mutation at codon 39) double heterozygote is approximately 20% and 10% respectively of total non-alpha globin synthesis. Despite some overlapping of the results, similar beta globin synthesis levels have been obtained in 43 beta(+)-thalassaemia patients. This suggests that in the Po river delta region the most common thalassaemic genes are beta(0) 39 and beta(+) IVS I. Images PMID:2580095

  4. Arsenic in benthic bivalves of San Francisco Bay and the Sacramento/San Joaquin River Delta.

    PubMed

    Johns, C; Luoma, S N

    1990-11-01

    Arsenic concentrations were determined in fine-grained, oxidized, surface sediments and in two benthic bivalves, Corbicula sp. and Macoma balthica, within San Francisco Bay, the Sacramento/San Joaquin River Delta, and selected rivers not influenced by urban or industrial activity. Arsenic concentrations in all samples were characteristic of values reported for uncontaminated estuaries. Small temporal fluctuations and low arsenic concentrations in bivalves and sediments suggest that most inputs of arsenic are likely to be minor and arsenic contamination is not widespread in the Bay.

  5. Cryostratigraphy, sedimentology, and the late Quaternary evolution of the Zackenberg River delta, northeast Greenland

    NASA Astrophysics Data System (ADS)

    Gilbert, Graham L.; Cable, Stefanie; Thiel, Christine; Christiansen, Hanne H.; Elberling, Bo

    2017-05-01

    The Zackenberg River delta is located in northeast Greenland (74°30' N, 20°30' E) at the outlet of the Zackenberg fjord valley. The fjord-valley fill consists of a series of terraced deltaic deposits (ca. 2 km2) formed during relative sea-level (RSL) fall. We investigated the deposits using sedimentological and cryostratigraphic techniques together with optically stimulated luminescence (OSL) dating. We identify four facies associations in sections (4 to 22 m in height) exposed along the modern Zackenberg River and coast. Facies associations relate to (I) overriding glaciers, (II) retreating glaciers and quiescent glaciomarine conditions, (III) delta progradation in a fjord valley, and (IV) fluvial activity and niveo-aeolian processes. Pore, layered, and suspended cryofacies are identified in two 20 m deep ice-bonded sediment cores. The cryofacies distribution, together with low overall ground-ice content, indicates that permafrost is predominately epigenetic in these deposits. Fourteen OSL ages constrain the deposition of the cored deposits to between approximately 13 and 11 ka, immediately following deglaciation. The timing of permafrost aggradation was closely related to delta progradation and began following the subaerial exposure of the delta plain (ca. 11 ka). Our results reveal information concerning the interplay between deglaciation, RSL change, sedimentation, permafrost aggradation, and the timing of these events. These findings have implications for the timing and mode of permafrost aggradation in other fjord valleys in northeast Greenland.

  6. Dispersion mechanisms of a tidal river junction in the Sacramento–San Joaquin Delta, California

    SciTech Connect

    Gleichauf, Karla T.; Wolfram, Philip J.; Monsen, Nancy E.; Fringer, Oliver B.; Monismith, Stephen G.

    2014-12-17

    In branching channel networks, such as in the Sacramento–San Joaquin River Delta, junction flow dynamics contribute to dispersion of ecologically important entities such as fish, pollutants, nutrients, salt, sediment, and phytoplankton. Flow transport through a junction largely arises from velocity phasing in the form of divergent flow between junction channels for a portion of the tidal cycle. Field observations in the Georgiana Slough junction, which is composed of the North and South Mokelumne rivers, Georgiana Slough, and the Mokelumne River, show that flow phasing differences between these rivers arise from operational, riverine, and tidal forcing. A combination of Acoustic Doppler Current Profile (ADCP) boat transecting and moored ADCPs over a spring–neap tidal cycle (May to June 2012) monitored the variability of spatial and temporal velocity, respectively. Two complementary drifter studies enabled assessment of local transport through the junction to identify small-scale intrajunction dynamics. We supplemented field results with numerical simulations using the SUNTANS model to demonstrate the importance of phasing offsets for junction transport and dispersion. Different phasing of inflows to the junction resulted in scalar patchiness that is characteristic of MacVean and Stacey’s (2011) advective tidal trapping. Furthermore, we observed small-scale junction flow features including a recirculation zone and shear layer, which play an important role in intra-junction mixing over time scales shorter than the tidal cycle (i.e., super-tidal time scales). Thus, the study period spanned open- and closed-gate operations at the Delta Cross Channel. Synthesis of field observations and modeling efforts suggest that management operations related to the Delta Cross Channel can strongly affect transport in the Delta by modifying the relative contributions of tidal and riverine flows, thereby changing the junction flow phasing.

  7. Dispersion mechanisms of a tidal river junction in the Sacramento–San Joaquin Delta, California

    DOE PAGES

    Gleichauf, Karla T.; Wolfram, Philip J.; Monsen, Nancy E.; ...

    2014-12-17

    In branching channel networks, such as in the Sacramento–San Joaquin River Delta, junction flow dynamics contribute to dispersion of ecologically important entities such as fish, pollutants, nutrients, salt, sediment, and phytoplankton. Flow transport through a junction largely arises from velocity phasing in the form of divergent flow between junction channels for a portion of the tidal cycle. Field observations in the Georgiana Slough junction, which is composed of the North and South Mokelumne rivers, Georgiana Slough, and the Mokelumne River, show that flow phasing differences between these rivers arise from operational, riverine, and tidal forcing. A combination of Acoustic Dopplermore » Current Profile (ADCP) boat transecting and moored ADCPs over a spring–neap tidal cycle (May to June 2012) monitored the variability of spatial and temporal velocity, respectively. Two complementary drifter studies enabled assessment of local transport through the junction to identify small-scale intrajunction dynamics. We supplemented field results with numerical simulations using the SUNTANS model to demonstrate the importance of phasing offsets for junction transport and dispersion. Different phasing of inflows to the junction resulted in scalar patchiness that is characteristic of MacVean and Stacey’s (2011) advective tidal trapping. Furthermore, we observed small-scale junction flow features including a recirculation zone and shear layer, which play an important role in intra-junction mixing over time scales shorter than the tidal cycle (i.e., super-tidal time scales). Thus, the study period spanned open- and closed-gate operations at the Delta Cross Channel. Synthesis of field observations and modeling efforts suggest that management operations related to the Delta Cross Channel can strongly affect transport in the Delta by modifying the relative contributions of tidal and riverine flows, thereby changing the junction flow phasing.« less

  8. Modelling suspended sediment dynamics on the subaqueous delta of the Mekong River

    NASA Astrophysics Data System (ADS)

    Thanh, Vo Quoc; Reyns, Johan; Wackerman, Chris; Eidam, Emily F.; Roelvink, Dano

    2017-09-01

    Fluvial sediment is the major source for the formation and development of the Mekong Delta. This paper aims to analyse the dynamics of suspended sediment and to investigate the roles of different processes in order to explore flux pattern changes. We applied modelling on two scales, comprising a large-scale model (the whole delta) to consider the upstream characteristics, particularly the Tonle Sap Lake's flood regulation, and a smaller-scale model (tidal rivers and shelf) to understand the sediment processes on the subaqueous delta. A comprehensive comparison to in-situ measurements and remote sensing data demonstrated that the model is capable of qualitatively simulating sediment dynamics on the subaqueous delta. It estimates that the Mekong River supplied an amount of 41.5 mil tons from April 2014 to April 2015. A substantial amount of sediment delivered by the Mekong River is deposited in front of the river mouths in the high flow season and resuspended in the low flow season. A sensitivity analysis shows that waves, baroclinic effects and bed composition strongly influence suspended sediment distribution and transport on the shelf. Waves in particular play an essential role in sediment resuspension. The development of this model is an important step towards an operational model for scientific and engineering applications, since the model is capable of predicting tidal propagation and discharge distribution through the main branches, and in predicting the seasonal SSC and erosion/deposition patterns on the shelf, while it is forced by readily available inputs: discharge at Kratie (Cambodia), GFS winds, ERA40 reanalysis waves, and TPXO 8v1 HR tidal forcing.

  9. Validation of a Parcel-Based Reduced-Complexity Model for River Delta Formation (Invited)

    NASA Astrophysics Data System (ADS)

    Liang, M.; Geleynse, N.; Passalacqua, P.; Edmonds, D. A.; Kim, W.; Voller, V. R.; Paola, C.

    2013-12-01

    Reduced-Complexity Models (RCMs) take an intuitive yet quantitative approach to represent processes with the goal of getting maximum return in emergent system-scale behavior with minimum investment in computational complexity. This approach is in contrast to reductionist models that aim at rigorously solving the governing equations of fluid flow and sediment transport. RCMs have had encouraging successes in modeling a variety of geomorphic systems, such as braided rivers, alluvial fans, and river deltas. Despite the fact that these models are not intended to resolve detailed flow structures, questions remain on how to interpret and validate the output of RCMs beyond qualitative behavior-based descriptions. Here we present a validation of the newly developed RCM for river delta formation with channel dynamics (Liang, 2013). The model uses a parcel-based 'weighted-random-walk' method that resolves the formation of river deltas at the scale of channel dynamics (e.g., avulsions and bifurcations). The main focus of this validation work is the flow routing model component. A set of synthetic test cases were designed to compare hydrodynamic results from the RCM and Delft3D, including flow in a straight channel, around a bump, and flow partitioning at a single bifurcation. Output results, such as water surface slope and flow field, are also compared to field observations collected at Wax Lake Delta. Additionally, we investigate channel avulsion cycles and flow path selection in an alluvial fan with differential styles of subsidence and compare model results to laboratory experiments, as a preliminary effort in pairing up numerical and experimental models to understand channel organization at process scale. Strengths and weaknesses of the RCM are discussed and potential candidates for model application identified.

  10. Sediment suspension and the dynamic mechanism during storms in the Yellow River Delta.

    PubMed

    Bian, Shuhua; Hu, Zjian; Liu, Jianqiang; Zhu, Zichen

    2016-12-01

    The suspension and hydrodynamic characteristics of the Yellow River Delta during storms were analyzed based on suspended samples obtained using automatic samplers during a storm event in the Yellow River Delta. Synchronous data for winds, waves, and tides were also collected from a nearby station. The results show that under wind speeds of 5-15 m/s and wave heights of 50-150 cm, the suspended content reached 5.7-49.6 kg/m(3), which is 10-100 times higher than that under normal weather conditions. The medium diameter of suspended particles was 1.2-2.1 μm (8.9-9.7 Φ), which was approximately 1-2 Φ finer than that under normal weather conditions. During the early stages of the measurements, the sea level had risen by 50 cm owing to the storm, which was in addition to the tidal sea level change. We suggest that during the storms, the waves strengthened and the storm-induced sea level change, which was combined with tidal currents moving in the same direction, produced high-speed currents. This overcame the cohesive forces among the fine sediment particles and suspended a large amount of sediment. As a result, the suspended content increased markedly and the suspended particle size became finer. This explains the intense siltation and erosion of the Yellow River Delta during storms.

  11. Measurement comparison of gas phase pollutants during field campaign in Pearl River Delta, China

    NASA Astrophysics Data System (ADS)

    Shao, M.; Zeng, L.; Hu, M.; Zhang, Y.

    2005-12-01

    Pearl River delta, an economically developed region in Guangdong province China, has been suffering from serious ground-level ozone pollution. To understand the formation mechanisms of the photochemical smog in this area, a field measurement campaign involving 12 separate institutes, was performed from Oct. 1 to Nov. 4, 2004. Measurements of gas phase pollutants, performed by the different research groups using several different methods, were inter-compared. Ambient SO2, O3 and NO were measured by Peking University and Hong Kong Polytechnic University using the same methods: chemiluminescence for NOx, pulsed fluorescence for SO2, and UV photometric method for O3. VOC speciation was accomplished using canister sampling followed by GC-MS measurement by Peking University and on-line GC-FID technology by National Central University in Taiwan. Ambient concentrations of HONO, the photolysis of which is the most important source of OH radical in Pearl River delta, was measured by two wet chemical methods: one from Energy Research Foundation of the Netherlands and one developed in Peking University. Based on these inter-comparisons, the co-variation of O3, NO and VOCs at an urban site and one rural site in Pearl River delta and estimates of the relative contributions to OH production from photolysis of O3, HONO and HCHO will be presented.

  12. Modern Pearl River Delta and Permian Huainan coalfield, China: A comparative sedimentary facies study

    USGS Publications Warehouse

    Suping, P.; Flores, R.M.

    1996-01-01

    Sedimentary facies types of the Pleistocene deposits of the Modern Pearl River Delta in Guangdong Province, China and Permian Member D deposits in Huainan coalfield in Anhui Province are exemplified by depositional facies of anastomosing fluvial systems. In both study areas, sand/sandstone and mud/mudstone-dominated facies types formed in diverging and converging, coeval fluvial channels laterally juxtaposed with floodplains containing ponds, lakes, and topogenous mires. The mires accumulated thin to thick peat/coal deposits that vary in vertical and lateral distribution between the two study areas. This difference is probably due to attendant sedimentary processes that affected the floodplain environments. The ancestral floodplains of the Modern Pearl River Delta were reworked by combined fluvial and tidal and estuarine processes. In contrast, the floodplains of the Permian Member D were mainly influenced by freshwater fluvial processes. In addition, the thick, laterally extensive coal zones of the Permian Member D may have formed in topogenous mires that developed on abandoned courses of anastomosing fluvial systems. This is typified by Seam 13-1, which is a blanket-like body that thickens to as much as 8 in but also splits into thinner beds. This seam overlies deposits of diverging and converging, coeval fluvial channels of the Sandstone D, and associated overbank-floodplain deposits. The limited areal extent of lenticular Pleistocene peat deposits of the Modern Pearl River Delta is due to their primary accumulation in topogenous mires in the central floodplains that were restricted by contemporaneous anastomosing channels.

  13. Potential Activity of Subglacial Microbiota Transported to Anoxic River Delta Sediments.

    PubMed

    Cameron, Karen A; Stibal, Marek; Olsen, Nikoline S; Mikkelsen, Andreas B; Elberling, Bo; Jacobsen, Carsten S

    2017-01-09

    The Watson River drains a portion of the SW Greenland ice sheet, transporting microbial communities from subglacial environments to a delta at the head of Søndre Strømfjord. This study investigates the potential activity and community shifts of glacial microbiota deposited and buried under layers of sediments within the river delta. A long-term (12-month) incubation experiment was established using Watson River delta sediment under anaerobic conditions, with and without CO2/H2 enrichment. Within CO2/H2-amended incubations, sulphate depletion and a shift in the microbial community to a 52% predominance of Desulfosporosinus meridiei by day 371 provides evidence for sulphate reduction. We found evidence of methanogenesis in CO2/H2-amended incubations within the first 5 months, with production rates of ~4 pmol g(-1) d(-1), which was likely performed by methanogenic Methanomicrobiales- and Methanosarcinales-related organisms. Later, a reduction in methane was observed to be paired with the depletion of sulphate, and we hypothesise that sulphate reduction out competed hydrogenotrophic methanogenesis. The structure and diversity of the original CO2/H2-amended incubation communities changed dramatically with a major shift in predominant community members and a decline in diversity and cell abundance. These results highlight the need for further investigations into the fate of subglacial microbiota within downstream environments.

  14. River-plume sedimentation and 210Pb/7Be seabed delivery on the Mississippi River delta front

    NASA Astrophysics Data System (ADS)

    Keller, Gregory; Bentley, Samuel J.; Georgiou, Ioannis Y.; Maloney, Jillian; Miner, Michael D.; Xu, Kehui

    2017-06-01

    To constrain the timing and processes of sediment delivery and submarine mass-wasting events spanning the last few decades on the Mississippi River delta front, multi-cores and gravity cores (0.5 and <3 m length respectively) were collected seaward of the Mississippi River Southwest Pass in 25-75 m water depth in 2014. The cores were analyzed for radionuclide activity (7Be, 210Pb, 137Cs), grain size, bulk density, and fabric (X-radiography). Core sediments are faintly bedded, sparsely bioturbated, and composed mostly of clay and fine silt. Short-term sedimentation rates (from 7Be) are 0.25-1.5 mm/day during river flooding, while longer-term accumulation rates (from 210Pb) are 1.3-7.9 cm/year. In most cores, 210Pb activity displays undulatory profiles with overall declining activity versus depth. Undulations are not associated with grain size variations, and are interpreted to represent variations in oceanic 210Pb scavenging by river-plume sediments. The 210Pb profile of one gravity core from a mudflow gully displays uniform basal excess activity over a zone of low and uniform bulk density, interpreted to be a mass-failure event that occurred 9-18 years before core collection. Spatial trends in sediment deposition (from 7Be) and accumulation (from 210Pb) indicate that proximity to the river mouth has stronger influence than local facies (mudflow gully, depositional lobe, prodelta) over the timeframe and seabed depth represented by the cores (<40 years, <3 m length). This may be explained by rapid proximal sediment deposition from river plumes coupled with infrequent tropical cyclone activity near the delta in the last 7 years (2006-2013), and by the location of most sediment failure surfaces (from mass flows indicated by parallel geophysical studies) deeper than the core-sampling depths of the present study.

  15. River-plume sedimentation and 210Pb/7Be seabed delivery on the Mississippi River delta front

    NASA Astrophysics Data System (ADS)

    Keller, Gregory; Bentley, Samuel J.; Georgiou, Ioannis Y.; Maloney, Jillian; Miner, Michael D.; Xu, Kehui

    2016-10-01

    To constrain the timing and processes of sediment delivery and submarine mass-wasting events spanning the last few decades on the Mississippi River delta front, multi-cores and gravity cores (0.5 and <3 m length respectively) were collected seaward of the Mississippi River Southwest Pass in 25-75 m water depth in 2014. The cores were analyzed for radionuclide activity (7Be, 210Pb, 137Cs), grain size, bulk density, and fabric (X-radiography). Core sediments are faintly bedded, sparsely bioturbated, and composed mostly of clay and fine silt. Short-term sedimentation rates (from 7Be) are 0.25-1.5 mm/day during river flooding, while longer-term accumulation rates (from 210Pb) are 1.3-7.9 cm/year. In most cores, 210Pb activity displays undulatory profiles with overall declining activity versus depth. Undulations are not associated with grain size variations, and are interpreted to represent variations in oceanic 210Pb scavenging by river-plume sediments. The 210Pb profile of one gravity core from a mudflow gully displays uniform basal excess activity over a zone of low and uniform bulk density, interpreted to be a mass-failure event that occurred 9-18 years before core collection. Spatial trends in sediment deposition (from 7Be) and accumulation (from 210Pb) indicate that proximity to the river mouth has stronger influence than local facies (mudflow gully, depositional lobe, prodelta) over the timeframe and seabed depth represented by the cores (<40 years, <3 m length). This may be explained by rapid proximal sediment deposition from river plumes coupled with infrequent tropical cyclone activity near the delta in the last 7 years (2006-2013), and by the location of most sediment failure surfaces (from mass flows indicated by parallel geophysical studies) deeper than the core-sampling depths of the present study.

  16. Contamination profiles of perfluoroalkyl substances in five typical rivers of the Pearl River Delta region, South China.

    PubMed

    Pan, Chang-Gui; Ying, Guang-Guo; Liu, You-Sheng; Zhang, Qian-Qian; Chen, Zhi-Feng; Peng, Feng-Jiao; Huang, Guo-Yong

    2014-11-01

    A survey on contamination profiles of eighteen perfluoroalkyl substances (PFASs) was performed via high performance liquid chromatography-tandem mass spectrometry for surface water and sediments from five typical rivers of the Pearl River Delta region, South China in summer and winter in 2012. The total concentrations of the PFASs in the water phase of the five rivers ranged from 0.14 to 346.72 ng L(-1). The PFAS concentrations in the water phase were correlated positively to some selected water quality parameters such as chemical oxygen demand (COD) (0.7913) and conductivity (0.5642). The monitoring results for the water samples showed significant seasonal variations, while those for the sediment samples showed no obvious seasonal variations. Among the selected 18 PFASs, perfluorooctane sulfonic acid (PFOS) was the dominant PFAS compound both in water and sediment for two seasons with its maximum concentration of 320.5 ng L(-1) in water and 11.4 ng g(-1) dry weight (dw) in sediment, followed by perfluorooctanoic acid (PFOA) with its maximum concentration of 26.48 ng L(-1) in water and 0.99 ng g(-1) dw in sediment. PFOS and PFOA were found at relatively higher concentrations in the Shima River and Danshui River than in the other three rivers (Xizhijiang River, Dongjiang River and Shahe River). The principal component analysis for the PFASs concentrations in water and sediment separated the sampling sites into two groups: rural and agricultural area, and urban and industrial area, suggesting the PFASs in the riverine environment were mainly originated from industrial and urban activities in the region. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Chiral profiling of azole antifungals in municipal wastewater and recipient rivers of the Pearl River Delta, China.

    PubMed

    Huang, Qiuxin; Wang, Zhifang; Wang, Chunwei; Peng, Xianzhi

    2013-12-01

    Enantiomeric compositions and fractions (EFs) of three chiral imidazole (econazole, ketoconazole, and miconazole) and one chiral triazole (tebuconazole) antifungals were investigated in wastewater, river water, and bed sediment of the Pearl River Delta, South China. The imidazole pharmaceuticals in the untreated wastewater were racemic to weakly nonracemic (EFs of 0.450-0.530) and showed weak enantioselectivity during treatment in the sewage treatment plant. The EFs of the dissolved azole antifungals were usually different from those of the sorbed azoles in the suspended particulate matter, suggesting different behaviors for the enantiomers of the chiral azole antifungals in the dissolved and particulate phases of the wastewater. The azole antifungals were widely present in the rivers. The bed sediment was a sink for the imidazole antifungals. The imidazoles were prevalently racemic, whereas tebuconazole was widely nonracemic in the rivers. Seasonal effects were observed on distribution and chirality of the azole antifungals. Concentrations of the azole antifungals in the river water were relatively higher in winter than in spring and summer while the EF of miconazole in the river water was higher in summer. The mechanism of enantiomeric behavior of the chiral azole antifungals in the environment warrants further research.

  18. Influence of changes in hydrodynamic conditions on cadmium transport in tidal river network of the Pearl River Delta, China.

    PubMed

    Dou, Ming; Zuo, Qiting; Zhang, Jinping; Li, Congying; Li, Guiqiu

    2013-09-01

    With rapid economic development, the Pearl River Delta (PRD) of China has experienced a series of serious heavy metal pollution events. Considering complex hydrodynamic and pollutants transport process, one-dimensional hydrodynamic model and heavy metal transport model were developed for tidal river network of the PRD. Then, several pollution emergency scenarios were designed by combining with the upper inflow, water quality and the lower tide level boundary conditions. Using this set of models, the temporal and spatial change process of cadmium (Cd) concentration was simulated. The influence of change in hydrodynamic conditions on Cd transport in tidal river network was assessed, and its transport laws were summarized. The result showed the following: Flow changes in the tidal river network were influenced remarkably by tidal backwater action, which further influenced the transport process of heavy metals; Cd concentrations in most sections while encountering high tide were far greater than those while encountering middle or low tides; and increased inflows from upper reaches could intensify water pollution in the West River (while encountering high tide) or the North River (while encountering middle or low tides).

  19. The influence of delta formation mechanism on geotechnical property sequence of the late Pleistocene-Holocene sediments in the Mekong River Delta.

    PubMed

    Hoang, Truong Minh; van Lap, Nguyen; Oanh, Ta Thi Kim; Jiro, Takemura

    2016-11-01

    The aim of the study was to characterize a variety of microstructure development-levels and geotechnical property sequences of the late Pleistocene-Holocene deposits in the Mekong River delta (MRD), and the paper furthermore discusses the influences of delta formation mechanisms on them. The survey associated the geotechnical engineering and the sedimentary geology of the late Pleistocene-Holocene deposits at five sites and also undifferentiated Pleistocene sediments. A cross-section which was rebuilt in the delta progradation-direction and between the Mekong and Bassac rivers represents the stratigraphy. Each sedimentary unit was formed under a different delta formation mechanism and revealed a typical geotechnical property sequence. The mechanical behaviors of the sediment succession in the tide-dominated delta with significant fluvial-activity and material source tend to be more cohesionless soils and strengths than those in the tide- and wave-dominated delta and even the coast. The particular tendency of the mechanical behavior of the deposit succession can be reasonably estimated from the delta formation mechanism. The characteristics of the clay minerals from the Mekong River produced the argillaceous soil which does not have extremely high plasticity. The microstructure development-levels are low to very high indicating how to choose hydraulic conductivity value, k, for estimating overconsolidation ratio, OCR, by the piezocone penetration tests (CPTU). The OCR of sediments in the delta types strangely change with depth but none less than 1. The post-depositional processes significantly influenced the microstructure development, particularly the dehydrating and oxidizing processes.

  20. Connecting the historic 2011 Mississippi River flood to marsh sedimentation on the Delta

    NASA Astrophysics Data System (ADS)

    Lutken, C.; D'Emidio, M.; Falcini, F.; Horton, B. P.; Jerolmack, D. J.; Khan, N. S.; Li, C.; Macelloni, L.; McKee, K. L.

    2011-12-01

    The 2011 Mississippi River flood was arguably the largest in history. Although the massive inundation resulting from the flood was devastating for residents on the Delta, sediment carried to sea by the swollen river had the potential to combat wetland loss in some areas. There is currently much debate regarding how, and to what degree, sediment from the Mississippi and Atchafalaya Rivers contributes to maintaining and building fragile coastal marshes. This historic flood presented a rare and time-sensitive opportunity to determine the impact of a geologically-significant flood event on coastal sedimentation patterns and rates. We present a multi-disciplinary and multi-institutional effort to use the 2011 Mississippi flood to connect the dots between river dynamics, coastal dynamics, and marsh maintenance. We performed a coupled satellite analysis, boat survey and surface sediment sampling approach to characterize if and how sediments from this historic flood contributed to deposition and maintenance of Mississippi Delta coastal marshes. Sea surface temperature, height and color from satellite data have been used to track mixing and transport of river plume sediments; the boat survey measured the currents and sediment concentrations of the Mississippi plume in-situ during the peak of the flood; and a helicopter survey sampled marsh sediments after the flood subsided, allowing determination of flood-induced deposition rates and also sediment provenance. Preliminary results show that the Mississippi River injected sediment into the Gulf and did not contribute greatly to wetland development because of its narrow, focused jet. The Atchafalaya River plume spread diffusely across the landscape, and sediments reaching the sea were trapped within the coastal zone because the weak jet was incapable of penetrating the coastal current. Significant sedimentation occurred around the Atchafalaya, demonstrating that the flood contributed to wetland maintenance.

  1. DELTAE

    SciTech Connect

    Ward, W.C.; Swift, G.W. )

    1993-11-01

    In thermoacoustic engines and refrigerators, and in many simple acoustic systems, a one dimensional wave equation determines the spatial dependence of the acoustic pressure and velocity. DELTAE numerically integrates such wave equations in the acoustic approximation, in gases or liquids, in user-defined geometries. Boundary conditions can include conventional acoustic boundary conditions of geometry and impedance, as well as temperature and thermal power in thermoacoustic systems. DELTAE can be used easily for apparatus ranging from simple duct networks and resonators to thermoacoustic engines refrigerators and combinations thereof. It can predict how a given apparatus will perform, or can allow the user to design an apparatus to achieve desired performance. DELTAE views systems as a series of segments; twenty segment types are supported. The purely acoustic segments include ducts and cones, and lumped impedances including compliances, series impedances, and endcaps. Electroacoustics tranducer segments can be defined using either frequency-independent coefficients or the conventional parameters of loudspeaker-style drivers: mass, spring constant, magnetic field strength, etc. Tranducers can be current driven, voltage driven, or connected to an electrical load impedance. Thermoacoustic segment geometries include parallel plates, circular and rectangular pores, and pin arrays. Side branches can be defined with fixed impedances, frequency-dependent radiation impedances, or as an auxiliary series of segments of any types. The user can select working fluids from among air, helium, neon, argon, hydrogen, deuterium, carbon dioxide, nitrogen, helium-argon mixtures, helium-xenon mixtures, liquid sodium, and eutectic sodium-potassium. Additional fluids and solids can be defined by the user.

  2. DELTAE

    SciTech Connect

    Ward, W.C. ); Swift, G.W. )

    1993-11-01

    In thermoacoustic engines and refrigerators, and in many simple acoustic systems, a one dimensional wave equation determines the spatial dependence of the acoustic pressure and velocity. DELTAE numerically integrates such wave equations in the acoustic approximation, in gases or liquids, in user-defined geometries. Boundary conditions can include conventional acoustic boundary conditions of geometry and impedance, as well as temperature and thermal power in thermoacoustic systems. DELTAE can be used easily for apparatus ranging from simple duct networks and resonators to thermoacoustic engines refrigerators and combinations thereof. It can predict how a given apparatus will perform, or can allow the user to design an apparatus to achieve desired performance. DELTAE views systems as a series of segments; twenty segment types are supported. The purely acoustic segments include ducts and cones, and lumped impedances including compliances, series impedances, and endcaps. Electroacoustics tranducer segments can be defined using either frequency-independent coefficients or the conventional parameters of loudspeaker-style drivers: mass, spring constant, magnetic field strength, etc. Tranducers can be current driven, voltage driven, or connected to an electrical load impedance. Thermoacoustic segment geometries include parallel plates, circular and rectangular pores, and pin arrays. Side branches can be defined with fixed impedances, frequency-dependent radiation impedances, or as an auxiliary series of segments of any types. The user can select working fluids from among air, helium, neon, argon, hydrogen, deuterium, carbon dioxide, nitrogen, helium-argon mixtures, helium-xenon mixtures, liquid sodium, and eutectic sodium-potassium. Additional fluids and solids can be defined by the user.

  3. Analysis of the Sediment Hydrograph of the alluvial deltas in the Apalachicola River, Florida

    NASA Astrophysics Data System (ADS)

    Daranpob, A.; Hagen, S.; Passeri, D.; Smar, D. E.

    2011-12-01

    Channel and alluvial characteristics in lowlands are the products of boundary conditions and driving forces. The boundary conditions normally include materials and land cover types, such as soil type and vegetation cover. General driving forces include discharge rate, sediment loadings, tides and waves. Deltas built up of river-transported sediment occur in depositional zones of the river mouth in flat terrains and slow currents. Total sediment load depends on two major abilities of the river, the river shear stress and capacity. The shear stress determines transport of a given sediment grain size, normally expressed as tractive force. The river capacity determines the total load or quantity of total sediments transported across a section of the river, generally expressed as the sediment loading rate. The shear stress and sediment loading rate are relatively easy to measure in the headwater and transfer zones where streams form a v-shape valley and the river begins to form defined banks compared to the deposition zone where rivers broaden across lower elevation landscapes creating alluvial forms such as deltas. Determinations of deposition and re-suspension of sediment in fluvial systems are complicated due to exerting tidal, wind, and wave forces. Cyclic forces of tides and waves repeatedly change the sediment transport and deposition rate spatially and temporally in alluvial fans. However, the influence decreases with water depth. Understanding the transport, deposition, and re-suspension of sediments in the fluvial zone would provide a better understanding of the morphology of landscape in lowland estuaries such as the Apalachicola Bay and its estuary systems. The Apalachicola River system is located in the Florida Panhandle. Shelf sedimentation process is not a strong influence in this region because it is protected by barrier islands from direct ocean forces of the Gulf of Mexico. This research explores the characteristic of suspended sediment loadings in

  4. Glacial lake McConnell: Paleogeography, age, duration, and associated river deltas, mackenzie river basin, western Canada

    NASA Astrophysics Data System (ADS)

    Smith, Derald G.

    Glacial Lake McConnell lasted from 11.8 to 8.3 ka BP while occupying parts of the Great Bear, Great Slave and Athabasca Lake basin. The retreating Laurentide ice-front formed the eastern margin, whereas low rolling hills formed the north, west and south shorelines. Three major deltas were deposited at the mouths of the Laird, Peace and Athabasca rivers. The total extent of all phases of the lake was 240,000 km2, while the largest extent was 210,000 km2 at 10.5 ka BP. Downwarping of the basin by glacial ice was the main cause of the lake, whereas sediment blockage between Jean Marie River and Fort Simpson was secondary. Initially, glacial Lake McConnell occupied the northwestern corner (Smith Arm) of the Great Bear Lake basin and discharged through the Hare Indian River outlet. By 11.5 ka BP the enlarged water body flowed out the Great Bear River, but only for a short period of time. The Mackenzie River formed the third outlet near Jean Marie River at 11 ka BP and flow in the Great Bear River ceased until 9 ka BP. At 9.9 ka BP glacial Lake McConnell was impacted by a major flood from glacial Lake Agassiz with a peak discharge of 2-7 × 106 m3/sec. Flood water discharged from glacial Lake McConnell, peaking at 0.35-0.57 × 106 m3/sec and receding flow continued for 30 months. The massive influx of floodwater into glacial Lake McConnell caused an abrupt increase of discharge, which enlarged the outlet channel to between 6 and 13 km wide between Fort Simpson and Jean Marie River. At 8.3 ka BP, isostatic rebound ended the 3500-year-old extensive lake by dividing it into the Great Slave Lake and Lake Athabasca.

  5. Discontinuities in braided patterns: The River Rhône from Geneva to the Camargue delta before river training

    NASA Astrophysics Data System (ADS)

    Bravard, Jean-Paul

    2010-05-01

    This study presents the upstream-downstream complexity of the Rhone, which earlier was a braided river. The fluvial patterns of the Rhône ca. 1860-70 are discussed, i.e. at the end of the Little Ice Age, which was also the beginning of the period of river dredging for improving navigation in the channel (1840-1930) and before the development of a chain of hydroelectric dams (1892-1986) on the river. Flowing across Switzerland and France to the Camargue delta on the Mediterranean, the Rhône drains the western part of the Alps in Europe. Befitting a large river flowing from the mountains, the Rhône was braided along most of its course, due to large quantities of coarse sediments formerly contributed by tributaries from the Alps, Jura Mountains, and Massif Central. The paper begins with a summary of palaeo-environmental studies on the Rhône, which show that the river experienced several events of fluvial metamorphosis during the Holocene. The reaches, which were braided during the late 19th century, alternated between meandering and braided patterns during this period due to the high sensitivity of the channel pattern to external variables such as changing water and sediment discharges. A discussion on the methods used to describe different aspects of the braided pattern of the Rhône from 1860 to 1870, using large-scale maps follows. Discrete reaches on the river are identified using slope, downstream variations of discharge, and stream power. These can be attributed to three factors: the tributaries (large supplies of bed load are brought by the Arve, the Ain, the Drôme, the Ardèche and the Durance rivers), Quaternary tectonics, and the along-channel distance from tributary confluences. Finally, the study assesses the pre-modern conditions of the Rhône for restoring selected reaches on the modern river.

  6. Sediment infilling and wetland formation dynamics in an active crevasse splay of the Mississippi River delta

    USGS Publications Warehouse

    Cahoon, Donald R.; White, David A.; Lynch, James C.

    2011-01-01

    Crevasse splay environments provide a mesocosm for evaluating wetland formation and maintenance processes on a decadal time scale. Site elevation, water levels, vertical accretion, elevation change, shallow subsidence, and plant biomass were measured at five habitats along an elevation gradient to evaluate wetland formation and development in Brant Pass Splay; an active crevasse splay of the Balize delta of the Mississippi River. The processes of vertical development (vertical accretion, elevation change, and shallow subsidence) were measured with the surface elevation table–marker horizon method. There were three distinct stages to the accrual of elevation capital and wetland formation in the splay: sediment infilling, vegetative colonization, and development of a mature wetland community. Accretion, elevation gain, and shallow subsidence all decreased by an order of magnitude from the open water (lowest elevation) to the forest (highest elevation) habitats. Vegetative colonization occurred within the first growing season following emergence of the mud surface. An explosively high rate of below-ground production quickly stabilized the loosely consolidated sub-aerial sediments. After emergent vegetation colonization, vertical development slowed and maintenance of marsh elevation was driven both by sediment trapping by the vegetation and accumulation of plant organic matter in the soil. Continued vertical development and survival of the marsh then depended on the health and productivity of the plant community. The process of delta wetland formation is both complex and nonlinear. Determining the dynamics of wetland formation will help in understanding the processes driving the past building of the delta and in developing models for restoring degraded wetlands in the Mississippi River delta and other deltas around the world.

  7. Wetland loss due to land use change in the Lower Paraná River Delta, Argentina.

    PubMed

    Sica, Y V; Quintana, R D; Radeloff, V C; Gavier-Pizarro, G I

    2016-10-15

    Wetland loss is a global concern because wetlands are highly diverse ecosystems that provide important goods and services, thus threatening both biodiversity and human well-being. The Paraná River Delta is one of the largest and most important wetland ecosystems of South America, undergoing expanding cattle and forestry activities with widespread water control practices. To understand the patterns and drivers of land cover change in the Lower Paraná River Delta, we quantified land cover changes and modeled associated factors. We developed land cover maps using Landsat images from 1999 and 2013 and identified main land cover changes. We quantified the influence of different socioeconomic (distance to roads, population centers and human activity centers), land management (area within polders, cattle density and years since last fire), biophysical variables (landscape unit, elevation, soil productivity, distance to rivers) and variables related to extreme system dynamics (flooding and fires) on freshwater marsh conversion with Boosted Regression Trees. We found that one third of the freshwater marshes of the Lower Delta (163,000ha) were replaced by pastures (70%) and forestry (18%) in only 14years. Ranching practices (represented by cattle density, area within polders and distance to roads) were the most important factors responsible for freshwater marsh conversion to pasture. These rapid and widespread losses of freshwater marshes have potentially large negative consequences for biodiversity and ecosystem services. A strategy for sustainable wetland management will benefit from careful analysis of dominant land uses and related management practices, to develop an urgently needed land use policy for the Lower Delta. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Influences of Hurricanes, Floods, and Organic Production on River-Delta Evolution

    NASA Astrophysics Data System (ADS)

    White, C.; Bentley, S. J.

    2016-02-01

    The modern Mississippi River Delta plain has been largely disconnected from the main distributary by a highly engineered system of levees and floodways. This vast and fragile landscape is experiencing land-loss and is increasingly susceptible to inundation. Intense debate exists in the scientific community as to whether direct fluvial or hurricane-driven re-suspension and sedimentation are the present dominant sources of mineral sediment to the wetland surfaces of the modern delta complex. The relative importance of these sources remains a matter of public discussion and scientific debate, and this lack of clarity strongly influences development of tools, strategies, and policies to conserve coastal Mississippi River Delta lands. Research fueling this debate has been restricted both spatially and temporally thus far. Furthermore, the contribution of organic production is unknown at these scales. A comprehensive study of the Lafourche and Plaquemine-Balize Mississippi River Delta complexes at a temporal scale similar to that of natural deltaic cycles (102 - 103years) is being completed to address the deficiencies in our current understanding. A suite of 38 5m vibracores and 33 co-located 1m piston cores are being analyzed at moderate- to high- resolution for bulk density, grain-size, organic matter, magnetic susceptibility, and X-ray fluorescence to create the recognition criteria necessary to distinguish sedimentary sources for this time period. 210Pb and 137Cs data show that despite rapid subsidence and sea-level rise, many studied wetlands are still able to maintain their elevations. Sedimentary accumulation rates in the subaerial components of the Lafourche complex would seem to indicate that following distributary abandonment/cutoff and the elimination of pre-levee and overbank flooding and crevasse sediments, resuspension by cold fronts and hurricanes has become the primary sediment source for affected wetlands.

  9. Mechanism of formation of the heaviest pollution episode ever recorded in the Yangtze River Delta, China

    NASA Astrophysics Data System (ADS)

    Fu, Qingyan; Zhuang, Guoshun; Wang, Jing; Xu, Chang; Huang, Kan; Li, Juan; Hou, Bing; Lu, Tao; Streets, David G.

    The heaviest aerosol pollution day in the historical record of the Yangtze River Delta occurred on 19 January 2007, in which the daily concentration of PM 10 reached 512 μg m -3 in Shanghai, 463 μg m -3 in Suzhou, 354 μg m -3 in Hangzhou, and 282 μg m -3 in Nanjing. The hourly concentrations of PM 2.5 and PM 10 reached peak values of 466 and 744 μg m -3, respectively, in Shanghai. With visibility <0.6 km, the regional haze covered nearly the entire Yangtze River Delta. High ratios of PM 2.5/PM 10 (61%), SO 2/PM 10 (0.38) and NO 2/PM 10 (0.24) were observed. The unusual stagnant dispersion conditions before a cold front played the predominant role in this high pollution episode, with relative humidity (RH) of 88%, both surface and upper-level inversions, as well as low wind speed (<1 m s -1). The sulfur oxidation rate (SOR) reached 0.67 and the nitrogen oxidation rate (NOR) reached 0.61, signifying that formation of sulfate and nitrate contributed significantly to the high secondary aerosol concentration of PM 2.5. The enrichment factors of As, Cd, and Pb reached 4058, 6971, and 3972, which were 4.45-6.68 times higher than those on good/moderate days. It was demonstrated that emissions from anthropogenic sources, especially stationary sources such as power plants, industrial boilers, and furnaces, were the major contributors to the heaviest aerosol pollution in the delta. More attention should be paid to the increases in emissions and the higher occurrence of haze days that have accompanied the rapid development of the economy in the Yangtze River Delta.

  10. Sea-Floor Mapping and Benthic Habitat GIS for the Elwha River Delta Nearshore, Washington

    USGS Publications Warehouse

    Cochrane, Guy R.; Warrick, Jonathan A.; Sagy, Yael; Finlayson, David; Harney, Jodi

    2008-01-01

    From March 1531, 2005, more than 252 km (19.5 km2) of seafloor offshore of the Elwha River Delta in the central Strait of Juan de Fuca was mapped by the USGS Coastal and Marine Geology Program. The purpose of this nearshore mapping was to (1) obtain high resolution bathymetry and acoustic reflectance properties of the seabed, (2) examine and record geologic characteristics of the seafloor, and (3) construct maps of sea-floor geomorphology and habitat. Substrate distribution was characterized with video-supervised statistical classification of the sonar data. Substrate of the survey was dominated by mixed sand-gravel and sand. Numerous boulder reefs were observed west of the river mouth within Freshwater Bay, whereas the sea-floor immediately adjacent to the river mouth was dominated by sand.

  11. Temporal and spatial variability of annual extreme water level in the Pearl River Delta region, China

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Yan, Yixin; Zheng, Jinhai; Li, Ling; Dong, Xue; Cai, Huijuan

    2009-10-01

    This paper is concerned with identifying the spatial and temporal patterns in the annual maximum and minimum water level in the Pearl River Delta (PRD) region. The Mann-Kendall test and Pettitt test are used to detect trends and abrupt change points, and the Trend Free Pre-Whitening (TFPW) approach then eliminates the effect of serial correlation in data series with significant autocorrelation. Approximately fifty years of the annual hydrological variables from 18 stations in the three major rivers (the West River, the North River, and the East River) are examined. The changing trends of the extremes in water level show different features in different parts of the PRD region. Generally speaking, in the upper part of the delta, the water levels show a decreasing trend while in the middle and lower part there is an increasing trend. This spatial pattern of the extreme water level variation is unlikely to be due to a long-term change in stream flow in the PRD region because the water level changes do not always coincide with the extreme stream flow variations. Sand excavation initiated in the 1980s and continuing for more than 20 years in almost all tributaries around the PRD region is one of the most serious intensive human activities affecting water levels. The result of the Pettitt test indicates that most abrupt change points occurred in 1980s-1990s, which reveals that sand excavation and channel regulation are likely to have been the most significant factors contributing to the change over this period. These anthropogenic activities modify the annual extreme water level dramatically in a way that affects the morphology of river channels and estuaries of the PRD and also the redistribution of discharge. However, there are differences in the geographic locations of significant trends for the water level investigated, which implies that these impacts are not spatially uniform.

  12. Bioanalytical and instrumental analysis of estrogenic activities in drinking water sources from Yangtze River Delta.

    PubMed

    Hu, Xinxin; Shi, Wei; Cao, Fu; Hu, Guanjiu; Hao, Yingqun; Wei, Si; Wang, Xinru; Yu, Hongxia

    2013-02-01

    The estrogenic activities of source water from Yangtze River, Huaihe River, Taihu Lake and groundwater in Yangtze River Delta in the dry and wet season were determined by use of reporter gene assays based on African green monkey kidney (CV-1) cell lines. Higher estrogenic activities were observed in the dry season, and the estrogenic potentials in water samples from Taihu Lake were greater than other river basins. None of the samples from groundwater showed estrogen receptor (ER) agonist activity. The 17β-Estradiol (E2) equivalents (EEQs) of water samples in the dry season ranged from 9.41×10(-1) to 1.20×10(1) ng E2 L(-1). In the wet season, EEQs of all the water samples were below the detection limit as 9.00×10(-1) ng E2 L(-1) except for one sample from Huaihe River. The highest contribution of E2 was detected in Yangtze River as 99% of estrogenic activity. Nonylphenol (NP, 100% detection rate) and octylphenol (OP, 100% detection rate) might also be responsible for the estrogenic activities in water sources. Potential health risk induced by the estrogenic chemicals in source water may be posed to the residents through water drinking.

  13. Soil Organic Carbon Stocks in Arctic Deltaic Sediments: Investigations in the Lena River Delta.

    NASA Astrophysics Data System (ADS)

    Zubrzycki, S.; Kutzbach, L.; Desyatkin, A.; Pfeiffer, E.-M.

    2012-04-01

    The soil organic carbon stock (SSOC) of deltaic sediments in arctic permafrost regions is known to be significant but is insufficiently investigated so far. Previous SSOC studies were conducted mainly in the comparatively well studied Mackenzie River Delta (area: 13,000 km2) in Canada. The few studies from other arctic delta regions report only the gravimetric carbon (C) contents and are limited to the active layer depth at the time of sampling. Since C deposits in permafrost regions are likely to become a future C source, more detailed investigations of the presently frozen likely carbon-rich sediment and soil layers in other arctic delta regions are of importance. Our investigations were performed on Samoylov Island in the southern-central part of the Lena River Delta (32,000 km2) which is the largest arctic delta and the fifth largest delta worldwide. Samoylov Island is representative for the Lena River Delta's first terrace and the active floodplains. Within this study a new portable Snow-Ice-Permafrost-Research-Establishment (SIPRE) auger was used during a spring field session to obtain 1 m deep frozen soil cores (n = 37) distributed over all known soil and vegetation units. These cores are analyzed for bulk contents of nitrogen (N) and C, ice content and bulk density (BD) and to determine the SSOC including the rarely investigated currently permanently frozen layers up to 1 m depth on Samoylov Island. Our study provides evidence for high SSOC for a depth of 1 m for the investigated area ranging between 6 kg m2 and 54 kg m2. Considering the spatial extent of different soil units on the two geomorphological units of Samoylov Island, the area-weighted average SSOC were 31 kg m2 (n = 31) for the first terrace and 15 kg m2 (n = 6) for the active floodplain. For the correspondent soil units of Turbels and Orthels in circumpolar permafrost regions, Tarnocai et al. 2009 reported a mean SSOC of 27 kg m2 (min: 0.1 kg m2, max: 126 kg m2) for a depth of 1 m. For up

  14. Geomorphic change and sediment transport during a small artificial flood in a transformed post-dam delta: The Colorado River delta, United States and Mexico

    USGS Publications Warehouse

    Mueller, Erich R.; Schmidt, John C.; Topping, David J.; Shafroth, Patrick B.; Rodríguez-Burgueño, Jesús Eliana; Ramírez-Hernández, Jorge; Grams, Paul E.

    2017-01-01

    The Colorado River delta is a dramatically transformed landscape. Major changes to river hydrology and morpho-dynamics began following completion of Hoover Dam in 1936. Today, the Colorado River has an intermittent and/or ephemeral channel in much of its former delta. Initial incision of the river channel in the upstream ∼50 km of the delta occurred in the early 1940s in response to spillway releases from Hoover Dam under conditions of drastically reduced sediment supply. A period of relative quiescence followed, until the filling of upstream reservoirs precipitated a resurgence of flows to the delta in the 1980s and 1990s. Flow releases during extreme upper basin snowmelt in the 1980s, flood flows from the Gila River basin in 1993, and a series of ever-decreasing peak flows in the late 1990s and early 2000s further incised the upstream channel and caused considerable channel migration throughout the river corridor. These variable magnitude post-dam floods shaped the modern river geomorphology. In 2014, an experimental pulse-flow release aimed at rejuvenating the riparian ecosystem and understanding hydrologic dynamics flowed more than 100 km through the length of the delta’s river corridor. This small artificial flood caused localized meter-scale scour and fill of the streambed, but did not cause further incision or significant bank erosion because of its small magnitude. Suspended-sand-transport rates were initially relatively high immediately downstream from the Morelos Dam release point, but decreasing discharge from infiltration losses combined with channel widening downstream caused a rapid downstream reduction in suspended-sand-transport rates. A zone of enhanced transport occurred downstream from the southern U.S.-Mexico border where gradient increased, but effectively no geomorphic change occurred beyond a point 65 km downstream from Morelos Dam. Thus, while the pulse flow connected with the modern estuary, deltaic sedimentary processes were not

  15. High Resolution Partitioning of Soil Properties and Soil Organic Carbon Storage in the Lena River Delta

    NASA Astrophysics Data System (ADS)

    Hugelius, G.; Siewert, M. B.; Heim, B.

    2015-12-01

    High-resolution vertical and spatial information on SOC storage and other key properties of permafrost-affected soils is key for the assessment and modeling of the vulnerability of permafrost carbon. We present findings of soil investigations from the high Arctic Lena river delta. In total 50 soil pedons have been sampled from different geomorphological units (delta terraces) in the delta in late summer 2013. All pedons have been classified according to the U.S. soil taxonomy. We described and sampled 19 Turbels, 27 Orthels and 4 Histels. On average 7.9±2.7 samples have been analyzed from each profile, including samples of the upper permafrost down to one meter depth. Soil horizons are described from open soil pits and their respective thicknesses are calculated from perspective-corrected photographs. Soil samples were analyzed for bulk density, as well as content of water/ice soil organic carbon (SOC) and nitrogen (N). The data is aggregated for the different geomorphological units and partitioned at centimeter level. High resolution vertical depth plots of different soil properties, including C%, N%, water and ice content and soil horizon distribution, are generated to demonstrate the information density of the dataset. A high-resolution land cover classification is generated for a subregion of the delta using advanced remote sensing classification methods. The soil pedon data and the land cover classification are combined for thematic upscaling of SOC and N stocks. We identify major geomorphological units of the Lena delta to control SOC storage in the subregion. We can show that SOC storage is highly variable with depth. Strong cryoturbation contributes to much deep SOC storages on the relatively stable first and third delta terraces, while fluvial deposition controls SOC storage in the recent alluvial floodplain. Soils sampled on thermokarst-affected rims of the third terrace show lower SOC storages indicating considerable reworking of the SOC.

  16. Geochemical Flows of Heavy Metals in Aquatic Systems of the Volga River Delta

    NASA Astrophysics Data System (ADS)

    Lychagin, Mikhail; Tkachenko, Anna; Kasimov, Nikolay

    2014-05-01

    The paper presents the results of the long-term environmental-geochemical studies of aquatic systems of the Volga River mouth area. It occupies a special place among the world's largest river deltas. The strong interest of researchers from different fields of science in the problems of the Volga River delta is associated with the high rate of periodic fluctuations of the Caspian Sea level, and also many factors of the technogenic geochemical impact on the aquatic systems. They range from the local impact of pollution sources in the delta to the regional impact of pollution sources located upstream. Aquatic systems of the Volga delta are highly diverse in morphology, hydrodynamic regime, lithology, sediments, and biota. This diversity determines the considerable spatial and temporal variability of the conditions of migration of heavy metals (HM) and other chemical elements. The study showed that the present contamination of the aquatic systems is manifested mainly in excess of heavy metals (Cu, Pb, Cd) in suspended matter over the global background values, most notably, in the flood period. In general the content of HM in the water and sediments during the last decades remains low; pollution of the bottom sediments is largely insignificant and of local character. We have identified the significant role of the water plants due to migration and accumulation of heavy metals in the shallow near-shore zones. Higher aquatic plants may serve as biogeochemical indicators of aquatic systems pollution. The metal content in macrophytes varies substantially depending on the ecological and morphological characteristics of species, as well as on conditions of their habitat. The difference between the minimal and maximal HM content may reach two to three orders of magnitude. Thickets of hornweed (Ceratophyllum demersum) and of other macrophytes in the mouths of the watercourses at the near-shore mouth area play the role of the biofilters precipitating a significant part of the

  17. Long-term change in tidal dynamics and its cause in the Pearl River Delta, China

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Ruan, Xiaohong; Zheng, Jinhai; Zhu, Yuliang; Wu, Hongxu

    2010-08-01

    This paper focuses on identifying changes in the tidal range and the duration of the flood tide in the Pearl River Delta region, China. Mann-Kendall test and regression methods are employed to verify the existence of trends in the annual tidal range and duration series (from the 1950s to 2005) at 17 stations in the 3 major tributaries of the delta. The research results indicate that generally there is an increasing trend in the tidal range and flood tide duration at most of the stations in the channel network. Moreover, the more upstream the location of the station, the more obvious the change in trend is, and these increasing trends are all significant at the stations in the upper part of the delta. Specifically, the tidal range at Shilong station in the East River has increased abruptly since the middle of the 1980s such that the mean level of post-1990 data is approximately three times that for pre-1985. Most stations near the mouth of the estuary show significant downward trends in the tidal range and flood tide duration. Results of the intersection point of the Mann-Kendall test curves for these Pearl River Delta stations appear mostly in 1980s-1990s, indicating that a noticeable change point occurs during this period. Human activities in the Pearl River Delta reached their peak during the 1980s. Among these, large-scale and long-term sand excavation modified the hydrodynamic regime dramatically in a way that increased the water depth and lowered the level of the riverbed, leading to an increased tidal prism and upstream movement of the tidal limit. Land reclamation is also likely to have had a relatively large effect on the tidal range and flood tide duration at stations near to the estuary mouth. Changes in other factors, such as freshwater flow and sea-level rise, seem to be of relatively minor importance. It is noteworthy that in a dry season the tidal dynamics are greatly enhanced and has resulted in strong saltwater intrusion into the estuary in recent

  18. Carbon Stocks in Permafrost-Affected Soils of the Lena River Delta

    NASA Astrophysics Data System (ADS)

    Zubrzycki, S.; Kutzbach, L.; Grosse, G.; Desyatkin, A.; Pfeiffer, E.

    2012-12-01

    The soil organic carbon stock (SSOC) of soils in arctic permafrost regions is known to be significant but is insufficiently investigated so far. Previous SSOC studies report mainly the gravimetric carbon (C) contents and are limited to the active layer depth at the time of sampling. Since C deposits in permafrost regions are likely to become a future C source, more detailed investigations of the presently frozen likely carbon-rich sediment and soil layers are of importance. Our investigations were performed on Samoylov Island in the southern-central part of the Lena River Delta (32,000 km2) which is the largest arctic delta and the fifth largest delta worldwide. Samoylov Island is representative for the Lena River Delta's first terrace and the active floodplains. Within this study a new portable Snow-Ice-Permafrost-Research-Establishment (SIPRE) auger was used during a spring field session to obtain 1 m deep frozen soil cores (n = 29) distributed over all known soil and vegetation units. These cores are analyzed for bulk contents of nitrogen (N) and C, ice content and bulk density (BD) and to determine the SSOC including the rarely investigated currently permanently frozen layers up to 1 m depth on Samoylov Island. Our study provides evidence for high SSOC for a depth of 1 m for the investigated area ranging between 7 kg m-2 and 48 kg m-2. Considering the spatial extent of different soil units on the two geomorphological units of Samoylov Island, the area-weighted average SSOC were 29 kg m-2 (n = 22) for the first terrace and 14 kg m-2 (n = 7) for the active floodplain. For the correspondent soil units of Turbels and Orthels in circumpolar permafrost regions a mean SSOC of 27 kg m-2 (min: 0.1 kg m-2, max: 126 kg m-2) for a depth of 1 m was reported [1]. For up-scaling solely over the soil-covered areas of the Lena River Delta, we excluded all water bodies >3,600 m2 from the geomorphological units studied (first river terrace and the active floodplains) and

  19. Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, February 2016

    USGS Publications Warehouse

    Stevens, Andrew; Gelfenbaum, Guy R.; Warrick, Jonathan; Miller, Ian M.; Weiner, Heather M.

    2016-01-01

    Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography, and surface sediment grain size from the Elwha River delta, Washington. Survey operations were conducted between February 15 and February 19, 2016 (USGS Field Activity Number 2016-608-FA) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), Washington Sea Grant, and National Park Service (table 1). Nearshore bathymetry data were collected using two personal watercraft (PWCs) and a kayak, each equipped with single-beam echosounders and survey-grade global navigation satellite systems (GNSS). Topography data were collected on foot with GNSS mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound velocity profiles measured with a conductivity-temperature-depth (CTD) sensor during the survey. A total of 126 km of

  20. Low-energy Beach ridge sedimentation in the Mississippi River delta plain

    SciTech Connect

    Gerdes, R.G.; Penland, S.

    1985-01-01

    Regressive beach ridge plains, such as Cheniere Caminada, Cheniere Caillou, and Cheniere Ronquille, are common depositional features within the Mississippi River delta plain in southeastern Louisiana. Vibracored sequences indicate beach ridge formation is a 3 stage process: Stage 1: Distributary Progradation, followed by Stage 2: Longshore Transport Interception, and completed by Stage 3: Beach Ridge Progradation. Cheniere Caminada is the largest beach ridge plain and is associated with the Late Lafourche delta. Radiocarbon dates indicate beach ridge building began approximately 720 years BP, when the Bayou Lafourche distributaries built seaward of the older, retreating Bayou Blue shoreline and intercepted westward longshore sediment transport, resulting in the progradation of Cheniere Caminada. Near the fan apex, beach ridges are 7-8 m thick and thin westward 2-3 m thick against the levees of Bayou Moreau. A typical beach ridge vertical sequence coarsens upward, with shoreface silty sands overlain by a thin cap of beach, washover, and aeolian sands. Beach ridge progradation in this area ceased approximately 300 years BP with the abandonment of Bayou Lafourche. The documentation of multiple regressive beach ridge plains suggest these deposits are stratigraphically more significant in the Mississippi River delta plain than recognized previously. The regressive beach ridge sequence documented in this study both stratigraphically and genetically contrasts with the classic transgressive chenier ridges of southwestern Louisiana.

  1. Late Quaternary strata and carbon burial records in the Yellow River delta, China

    NASA Astrophysics Data System (ADS)

    Zhao, Guangming; Ye, Siyuan; Li, Guangxue; Ding, Xigui; Yuan, Hongming

    2015-06-01

    Sediment carbon sequestration plays an essential role in mitigating atmospheric CO2 increases and the subsequently global greenhouse effect. To clarify the late Quaternary strata and carbon burial records in Yellow River delta (YRD), detailed analysis of benthic foraminifera, total carbon (TC), organic carbon (Corg), sedimentary characteristics and moisture contents of sediments, was performed on core ZK3, 30.3 m in length and obtained from YRD in 2007. Eight depositional units (designated U1-U8 in ascending order) were identified. A comprehensive analysis method of historical geography and sedimentary geology was used to determine the precise depositional ages of the modern Yellow River delta (MYRD), from which pre-MYRD ages were deduced. The results indicates that the maximum burial rates of TC, inorganic carbon (IC) and Corg occurred in the delta front (U5), and the minimum in the shallow sea (U3). Remarkable high sedimentation rates in the MYRD are responsible for burial efficiency of carbon, with an average rate of Corg burial reaching 2087±251 g (m2 yr)-1, and that of IC reaching 13741±808 g (m2 yr)-1, which are much higher than those of other regions with high contents of Corg. Therefore, YRD has a significant burial efficiency for carbon sequestration.

  2. Spatial and temporal variation in erosion and accumulation of the subaqueous Yellow River delta (1976-2004)

    NASA Astrophysics Data System (ADS)

    Bi, N.; Xing, G.; Wang, H.; Yang, Z.

    2016-02-01

    Yellow River Delta (YRD), one of the most heavily human-influenced delta systems, had dramatic changes since 1976. The erosion and accretion pattern of the subaqueous YRD was delineated by 1) the northern abandoned delta lobe, consisted of the heavily eroded Diaokou and Shenxiangou lobes; 2) the active delta lobe, comprised of Qingshuigou (QSG) and Q8 lobes and featured with fast progradation; 3) the Laizhou Bay (LZB) with slight accumulation. Three stages were summarized based on the evolution of the northern abandoned delta lobe. During 1976-1980, the northern abandoned delta was severely eroded due to the cutoff of sediment supply. As the subaqueous slope became gentler during 1980-1996, the deeper part of the subaqueous delta turned into slight accretion state while the shallow part continued to be eroded. However, the erosion rate of the northern delta slowed down during 1996-2004. Meanwhile, the development of the active delta lobe was a product of riverine sediment supply, channel geometry and estuarine hydrodynamics. Multi-depocenter was formed along the coastal area of the active subaqueous delta during 1976-1980, when multiple channels were active for sediment transportation. As the main river channel developed, the depocenter progradated eastward with an exceptional high accumulation rate during 1980-1985. The progradation direction turned southeastward with a lower accumulation rate during 1985-1996. Then, the depocenter shifted to the newly formed Q8 river mouth after a channel diversion in 1996, leaving the QSG river mouth in severe erosion. The channel diversion also caused erosion at the offshore area in LZB, where slight accumulation dominated before 1996. The erosion and accumulation pattern of the subaqueous YRD showed significant spatial and temporal variability during 1976-2004. A comprehensive understanding of their driven mechanisms would be critical for the prediction of the evolution of the YRD in the context of global change.

  3. Modern sediment characteristics and accumulation rates from the delta front to prodelta of the Yellow River (Huanghe)

    NASA Astrophysics Data System (ADS)

    Zhou, Liangyong; Liu, Jian; Saito, Yoshiki; Gao, Maosheng; Diao, Shaobo; Qiu, Jiandong; Pei, Shaofeng

    2016-08-01

    Since 1976, the main channel of the Yellow River (Huanghe) has been on the east side of the delta complex, and the river has prograded a broad new delta lobe in Laizhou Bay of the Bohai Sea. In 2012, extensive bathymetric and high-resolution seismic profiles were conducted and sediment cores were collected off the new delta lobe. This study examined delta sedimentation and morphology along a profile across the modern subaqueous Yellow River delta and into Laizhou Bay, by analyzing sediment radionuclides (137Cs, 210Pb and 7Be), sedimentary structure, grain-size composition, organic carbon content, and morphological changes between 1976 and 2012. The change in the bathymetric profile, longitudinal to the river's course, reveals subaqueous delta progradation during this period. The subbottom boundary between the new delta lobe sediment and the older seafloor sediment (before the 1976 course shift) was identified in terms of lithology and radionuclide distributions, and recognized as a downlap surface in the seismic record. The accumulation rate of the new delta lobe sediment is estimated to be 5-18.6 cm year-1 on the delta front slope, 2 cm year-1 at the toe of the slope, and 1-2 cm year-1 in the shelf areas of Laizhou Bay. Sediment facies also change offshore, from alternations of gray and brown sediment in the proximal area to gray bioturbated fine sediment in the distal area. Based on 7Be distribution, the shorter-term deposition rate was at least 20 cm year-1 in the delta front.

  4. Morphodynamics and Sedimentology of a Falling Stage Sandy Fjord Delta, Goose River, Labrador

    NASA Astrophysics Data System (ADS)

    Slingerland, R.; Edmonds, D. A.; Parsons, D. R.; Best, J. L.; Royce, J.; Burpee, A.; Cederberg, J.; Caldwell, R.; Nijhuis, A.; McGuffin, A.

    2012-12-01

    Sediment size and degree of cohesion are thought to exert a strong control on the morphodynamic processes, planform shape and clinoform stratigraphy of deltas. To test model predictions concerning these two parameters, we present a morphometric and stratigraphic analysis of a sandy delta formed where the Goose River flows into Goose Bay at the western end of Lake Melville, Labrador. Goose River delta sediments consist of arkosic, heavy-mineral-rich sand (D50 = 225 to 600 microns) with very little silt and clay, placing this delta at the coarser-grained, non-cohesive end of the spectrum. The delta started to form approx. 7000 years ago as the Laurentide ice sheet retreated and post-glacial rebound created a relative base level fall of approximately 4 mm/yr. The current tidal range in Goose Bay averages 0.5 m, and the average wave height is negligible. Results from our 2012 field season show that the delta planform consists of two moribund lobes at elevations of ~ 5 m and ~ 2 m and a presently active delta at sea level. Aerial photography from 1951 to 2012 show there has been surprisingly little progradation despite active channel change at the six-month timescale and an assumed base level fall of 244 mm during that period. A topographic section along a dipline consists of three treads and two clinoform risers. The bottomset tread is a virtually featureless fjord bottom at ~35 m from which a first clinoform rises to a second tread at ~-15 m. The second tread is a sandy platform onto which an upper clinoform downlaps. This upper sandy clinoform ranges in dip from 9 to 17 dg. and passes into the topset at an elevation of ~ -1 m. The topset consists of braid-like trapezoidal unit bars that in GPR show little evidence of wave, alongshore current, or ice reworking, even though they are submerged at higher high tides. The planform, bar geometries and facies, and clinoform dips and dip-directions are remarkably consistent with model predictions from Delft3d.

  5. Variation in Ground Shaking on the Fraser River Delta (Greater Vancouver, Canada)

    NASA Astrophysics Data System (ADS)

    Cassidy, J. F.; Rogers, G. R.

    2003-04-01

    The thick, soft soils of the Fraser River delta, just south of Vancouver, Canada, are home to critical infrastructure such as one of North America's busiest port facilities, Canada's second busiest airport, and key transportation and power-transmission facilities for 2-3 million people. This area is also one of the most seismically active regions in Canada. We have utilised recent three-component, digital records of recent moderate (1996 M=5.1 at 200 km distance, 1997 M=4.3 at 40 km distance) and large (2001 M=6.8 at 300 km distance) earthquakes to examine the response to seismic shaking in the greater Vancouver, region, with an emphasis on the site response of the Fraser River delta. These suites of accelerograms have relatively low amplitudes (maximums of 0.015g for the 1996 records, 0.024g for the 1997 records, and 0.035g for the 2001 records). The 1997 data set is significant as it contains the first three-component recordings made on bedrock in greater Vancouver, and the 2001 data set is significant as it contains long-period signal (1-10 second energy). Using the method of spectral ratios, we estimate the site response for each of the strong motion instrument soil sites. Our results show frequency-dependent amplification, with factors of up to 12 times (relative to competent bedrock) near the edge of the delta. Here, the amplification is observed over a relatively narrow frequency range of 1.5-4 Hz (0.25-0.67 s period). Near the centre of the delta(where the soft soils are thickest) peak amplification of 4-10 times(relative to competent bedrock) is measured. Relative to firm soil, the peak amplification ranges from 2-5 for the thick soil delta centre sites, and 2-6 for the delta edge sites. At higher frequencies, little or no amplification, and in many cases slight attenuation is observed. The more distant earthquakes (200-300 km) present a simpler and more predictable picture of ground motion variation than that of the 1997 earthquake (40 km distant). The

  6. Beach morphodynamics of the mixed grain-size delta of the dammed Elwha River, Washington

    NASA Astrophysics Data System (ADS)

    Warrick, J. A.; Gelfenbaum, G. R.; George, D. A.; Ruggiero, P.; Kaminsky, G. M.; Beirne, M.; Miller, I. M.

    2009-12-01

    Sediment supply provides a fundamental control on the morphology of river deltas, and humans have significantly modified these supplies for centuries. Here we examine the effects of almost a century of sediment supply reduction from the damming of the Elwha River in Washington on shoreline position and beach morphology of its wave-dominated delta. The mean rate of shoreline erosion during 1939-2006 is ~0.6 m/yr. Shoreline change and morphology differ spatially, however. Negligible shoreline change has occurred updrift (west) of the river mouth, where the beach is mixed sand to cobble, cuspate, and reflective. The beach downdrift (east) of the river mouth has had significant and persistent erosion, but this beach differs in that it has a reflective foreshore with a dissipative low-tide terrace. Erosion of the downdrift beach results from foreshore retreat, which broadens the low-tide terrace with time, and the rate of this kind of erosion has increased significantly from ~0.8 m/yr during 1939-1990 to ~1.4 m/yr during 1990-2006. Erosion rates for the downdrift beach derived from 2004-2007 topographic surveys vary between 0 and 13 m/yr, with an average of 3.8 m/yr. The 2004-2007 surveys also show that most erosion occurs during the winter with lower rates of change in the summer. We note that the low-tide terrace is significantly coarser (mean grain size ~100 mm) than the foreshore (mean grain size ~30 mm), a pattern contrary to the typical observation of fining low-tide terraces in the region and worldwide. Because this cobble low-tide terrace is created by foreshore erosion, has been steady over intervals of at least years, is predicted to have negligible longshore transport compared to the foreshore portion of the beach, and is inconsistent with oral history of abundant shellfish collections from the low-tide beach, we suggest that it is an armored layer of cobble clasts that are not generally competent in the physical setting of the delta. Thus, the cobble low

  7. Groundwater salinity influenced by Holocene seawater trapped in incised valleys in the Red River delta plain

    NASA Astrophysics Data System (ADS)

    Larsen, Flemming; Tran, Long Vu; van Hoang, Hoan; Tran, Luu Thi; Christiansen, Anders Vest; Pham, Nhan Quy

    2017-04-01

    Salty and brackish groundwater has been observed at least 100 km inland in some aquifers contained within Quaternary delta plains. This phenomenon limits access to fresh groundwater resources, particularly in the densely populated deltas of Southeast Asia. However, the causes of inland salinity are unclear. Here we present borehole and geophysical data that show that in the Red River delta plain of Vietnam, salty and brackish groundwater primarily occurs in incised valleys that were formed during sea-level lowstands during the Pleistocene. During the mid-Holocene, these valleys were filled with fine-grained marine deposits containing trapped seawater. We conduct groundwater flow simulations that show that the age, thickness, and permeability of the marine sediments are the primary controls on the leaching of salty porewater into the freshwater aquifer. We find that salty groundwater originating from this trapped seawater is still present in Holocene-aged sediments with low permeability, and affects groundwater salinity in adjacent aquifers. In contrast, trapped seawater from all Pleistocene-aged sediments has been leached. We identify a number of brackish to saline delta aquifers elsewhere in Asia and throughout the world that have a similar sedimentary history, and thus are likely to be influenced by this leaching process.

  8. LANDSCAPE ECOLOGY ASSESSMENT OF THE TENSAS RIVER BASIN, MISSISSIPPI RIVER DELTA REGION, AND GULF OF MEXICO

    EPA Science Inventory

    A group of landscape ecological indicators were applied to biophysical data masked to the Tensas River Basin. The indicators were use to identify and prioritize sources of nutrients in a
    Mississippi River System sub-basin. Remotely sensed data were used for change detection a...

  9. Hydraulic Survey and Scour Assessment of Bridge 524, Tanana River at Big Delta, Alaska

    USGS Publications Warehouse

    Heinrichs, Thomas A.; Langley, Dustin E.; Burrows, Robert L.; Conaway, Jeffrey S.

    2007-01-01

    Bathymetric and hydraulic data were collected August 26-28, 1996, on the Tanana River at Big Delta, Alaska, at the Richardson Highway bridge and Trans-Alaska Pipeline crossing. Erosion along the right (north) bank of the river between the bridge and the pipeline crossing prompted the data collection. A water-surface profile hydraulic model for the 100- and 500-year recurrence-interval floods was developed using surveyed information. The Delta River enters the Tanana immediately downstream of the highway bridge, causing backwater that extends upstream of the bridge. Four scenarios were considered to simulate the influence of the backwater on flow through the bridge. Contraction and pier scour were computed from model results. Computed values of pier scour were large, but the scour during a flood may actually be less because of mitigating factors. No bank erosion was observed at the time of the survey, a low-flow period. Erosion is likely to occur during intermediate or high flows, but the actual erosion processes are unknown at this time.

  10. Environmental Assessments in the Riparian Corridor of the Colorado River Delta

    NASA Technical Reports Server (NTRS)

    2001-01-01

    We will develop remote sensing methods to conduct environmental assessments in the riparian corridor of the Colorado River delta, shared by the United States and Mexico. This important regional ecosystem is dependent upon US water flows, yet the most important wildlife habitats are in Mexico. The delta region is poorly known and difficult to monitor on the ground. We will use ground-validated, aerial and satellite methods to develop accurate vegetation and habitat maps and predictive hydrological and vegetation models of this ecosystem in response to US flood releases. The work products will advance our understanding of water resource issues in dryland climates and provide a specific application tool for a critical binational natural resource area.

  11. A potential vorticity theory for the formation of elongate channels in river deltas and lakes

    NASA Astrophysics Data System (ADS)

    Falcini, Federico; Jerolmack, Douglas J.

    2010-12-01

    Rivers empty into oceans and lakes as turbulent sediment-laden jets, which can be characterized by a Gaussian horizontal velocity profile that spreads and decays downstream because of shearing and lateral mixing at the jet margins. Recent experiments demonstrate that this velocity field controls river-mouth sedimentation patterns. In nature, diffuse jets are associated with mouth bar deposition forming bifurcating distributary networks, while focused jets are associated with levee deposition and the growth of elongate channels that do not bifurcate. River outflows from elongate channels are similar in structure to cold filaments observed in ocean currents, where high potential vorticity helps to preserve coherent structure over large distances. Motivated by these observations, we propose a hydrodynamic theory that seeks to predict the conditions under which elongate channels form. Our approach models jet velocity patterns using the flow vorticity. Both shearing and lateral spreading are directly related to the vertical component of vorticity. We introduce a new kind of potential vorticity that incorporates sediment concentration and thus allows study of jet sedimentation patterns. The potential vorticity equation reduces the number of fluid momentum equations to one without losing generality. This results in a compact analytical solution capable of describing the streamwise evolution of the potential vorticity of a sediment-laden jet from initial conditions at the river mouth. Our theory predicts that high potential vorticity is a necessary condition for focused levee deposition and the creation of elongate channels. Comparison to numerical, laboratory, and field studies indicates that potential vorticity is a primary control on channel morphology. Our results may be useful for designing river delta restoration schemes such as the proposed Mississippi Delta diversion.

  12. Geochemical Dataset of the Rhone River Delta (Lake Geneva) Sediments - Disentangling Human Impacts from Climate Change

    NASA Astrophysics Data System (ADS)

    Silva, T. A.; Girardclos, S.; Loizeau, J. L.

    2016-12-01

    Lake sediment records are often the most complete continental archives. In the last 200 years, in addition to climatic variability, humans have strongly impacted lake watersheds around the world. During the 20th century the Rhone River and its watershed upstream Lake Geneva (Switzerland/France) have been subject to river channelization, dam construction, water flow regulation, water and sediment abstraction as well as various land use changes. Under the scope of the SEDFATE project (Swiss National Science Foundation nº147689) we address human and climatic impact on the sediment transfer from the Rhone River watershed to Lake Geneva. Nineteen short sediment cores were collected in the Rhone River delta area in May 2014. Cores have been scanned with MSCL and XRF, sub-sampled every 1cm and 8 cores were dated by radiometric methods (137Cs and 210Pb). Photographs taken right after core opening were used for lithological description and in addition to MSCL data were used to correlate cores. Core dating shows that mass accumulation rates decreased in the 1964-1986 interval and then increased again in the interval between 1986-2014. XRF elements and ratios, known to indicate detrital sources (Al, Al/Si, Fe, K, Mn, Rb, Si, Ti, Ti/Ca), show that clastic input diminished from 1964 to 1986 and re-increased to the present. Other elemental (Zr/Rb, Zr/K, Si/Ti) and geophysical data (magnetic susceptibility) combined with lithology identify density flow deposits vs hemipelagic sedimentation. Changes in frequency of these event deposits indicate changes in the sedimentation patterns in the Rhone River sublacustrine delta during the last century. From these results we hypothesize that a significant sediment amount was abstracted from the system after the major dam constructions in the 1950's and that, since the 1990's, a contrary signal is due to increased sediment loads that follows glacial melting due to global warming.

  13. On the control of climate- and human-modulated fluvial sediment delivery on river delta development: The Indus

    NASA Astrophysics Data System (ADS)

    Giosan, L.; Clift, P. D.; Blusztajn, J.; Tabrez, A.; Constantinescu, S.; Filip, F.

    2006-12-01

    Deltas are particularly vulnerable coasts, affected by changes in both continental and coastal ocean processes. The currently accelerated loss of deltaic lands across the world is primarily due to fluvial sediment starvation following the pandemic construction of river dams and water diversions. However, the influence on deltas of human- or even climate-modulated changes in fluvial sediment discharge has been studied less comprehensively than other controls e.g., the sea-level rise. We examined the Indus delta to understand how the sediment source (i.e., available fluvial sediment) has affected the development of the sediment sink (i.e., the subaerial and subaqueous delta evolution). With an elevated topography and generally arid climate in the watershed, the Indus has been, in natural conditions (i.e., before dams reduced its flow and sediment discharge by over 80%), one of the most important sediment-producing rivers in the world. Bathymetric data show that the Indus shelf morphology exhibits a compound clinoform morphology. Whereas the inner shoreface-connected clinoform has clearly developed as the subaqueous part of the modern Indus delta, the offshore clinoform is either a relict or a contemporaneous prodelta clinoform. Following the reduction in sediment discharge after the late 1950's, the deltaic shoreline in the central part of the delta coast started to recede providing sediment for the southeastern and northwestern coast sectors that remained largely progradational. This differential behavior of the delta shoreline indicates that even a drastic loss of fluvial sediment is initially buffered by an erosional smoothing of the delta coast. New data from onland drilling shows that unlike most Holocene deltas, the Indus delta prograded through the later part of the deglacial sea level rise, starting no later than 12,000 cal. years BP. Neodymium isotope data indicate that sediments comprising the entire Holocene delta originated predominantly in the monsoon

  14. [Integrated assessment of eco-environmental vulnerability in Pearl River Delta based on RS and GIS].

    PubMed

    Xu, Qing-Yong; Huang, Mei; Liu, Hong-Sheng; Yan, Hui-Min

    2011-11-01

    Based on the remote sensing data and with the help of geographic information system, an integrated assessment was conducted on the eco-environmental vulnerability of Pearl River Delta in 2004-2008. Spatial principal component analysis was used to generate the evaluation indicators, and analytic hierarchy process (AHP) was applied to determine the weights of the evaluation factors. The reasons causing the vulnerability of the eco- environment in Pearl River Delta were discussed. In the study area, its middle part was the most vulnerable region, occupying 34.0% of the total, eastern part was the moderately vulnerable region, accounting for 25.5%, and western part was the lightly and slightly vulnerable areas, accounting for 28.7 and 11.8%, respectively. Totally, the moderately and lightly vulnerable areas occupied 54.2%, indicating that a majority of the Delta was under moderate and light vulnerability. The natural factors affecting the eco-environmental vulnerability of the Delta were altitude, heavy rain days, water and soil erosion rate, flooded infield rate, normalized difference vegetation index (ND VI) and landscape diversity index, whereas the human factors were population density, waste discharge per unit area, exhaust emission per unit area, land use change, chemical fertilization intensity, pesticide application intensity, amount of motor vehicles possessed by ten thousands people, and index of environmental protection investment. The main characteristics of the extremely and heavily vulnerable regions were low altitude, high frequency of flood disaster, large flooded infield, serious vegetation degradation, high pollution level and low environment protection investment index.

  15. Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, July 2016

    USGS Publications Warehouse

    Stevens, Andrew; Gelfenbaum, Guy R.; Warrick, Jonathan; Miller, Ian M.; Weiner, Heather M.

    2016-01-01

    Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography and surface sediment grain size from the Elwha River delta, Washington.  Survey operations were conducted between July 17 and July 20, 2016 (USGS Field Activity Number 2016-653-FA) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), Washington Sea Grant, and National Park Service (table 1). Nearshore bathymetry data were collected using two personal watercraft (PWCs) and a kayak, each equipped with single-beam echosounders and survey-grade global navigation satellite systems (GNSS). Topography data were collected on foot with GNSS mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound velocity profiles measured with a conductivity-temperature-depth (CTD) sensor during the survey. A total of 182 km of

  16. Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, July 2015

    USGS Publications Warehouse

    Stevens, Andrew; Gelfenbaum, Guy R.; Warrick, Jonathan; Miller, Ian M.; Weiner, Heather M.

    2016-01-01

    Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography and surface sediment grain size from the Elwha River delta, Washington.  The majority of survey operations were conducted between July 29 and July 31, 2015 (USGS Field Activity Number 2015-648-FA) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), Washington Sea Grant, and National Park Service (table 1). Grain-size data from sediment samples collected during USGS Field Activity 2015-652-FA are also included in this dataset.Nearshore bathymetry data were collected using two personal watercraft (PWCs), each equipped with single-beam echosounders and survey-grade global navigation satellite systems (GNSS). Topography data were collected on foot with GNSS mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound

  17. Spatial distribution and partition of perfluoroalkyl acids (PFAAs) in rivers of the Pearl River Delta, southern China.

    PubMed

    Liu, Baolin; Zhang, Hong; Xie, Liuwei; Li, Juying; Wang, Xinxuan; Zhao, Liang; Wang, Yanping; Yang, Bo

    2015-08-15

    This study investigated the occurrence of perfluoroalkyl acids (PFAAs) in surface water from 67 sampling sites along rivers of the Pearl River Delta in southern China. Sixteen PFAAs, including perfluoroalkyl carboxylic acids (PFCAs, C5-14, C16 and C18) and perfluoroalkyl sulfonic acids (PFSAs, C4, C6, C8 and C10) were determined by high performance liquid chromatography-negative electrospray ionization-tandem mass spectrometry (HPLC/ESI-MS/MS). Total PFAA concentrations (∑ PFAAs) in the surface water ranged from 1.53 to 33.5 ng·L(-1) with an average of 7.58 ng·L(-1). Perfluorobutane sulfonic acid (PFBS), perfluorooctanoic acid (PFOA), and perfluorooctane sulfonic acid (PFOS) were the three most abundant PFAAs and on average accounted for 28%, 16% and 10% of ∑ PFAAs, respectively. Higher concentrations of ∑ PFAAs were found in the samples collected from Jiangmen section of Xijiang River, Dongguan section of Dongjiang River and the Pearl River flowing the cities which had very well-developed manufacturing industries. PCA model was employed to quantitatively calculate the contributions of extracted sources. Factor 1 (72.48% of the total variance) had high loading for perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), PFBS and PFOS. For factor 2 (10.93% of the total variance), perfluorononanoic acid (PFNA) and perfluoroundecanoic acid (PFUdA) got high loading. The sorption of PFCAs on suspended particulate matter (SPM) increased by approximately 0.1 log units for each additional CF2 moiety and that on sediment was approximately 0.8 log units lower than the SPM logKd values. In addition, the differences in the partition coefficients were influenced by the structure discrepancy of absorbents and influx of fresh river water. These data are essential for modeling the transport and environmental fate of PFAAs. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. More than 100 Years of Background-Level Sedimentary Metals, Nisqually River Delta, South Puget Sound, Washington

    USGS Publications Warehouse

    Takesue, Renee K.; Swarzenski, Peter W.

    2011-01-01

    The Nisqually River Delta is located about 25 km south of the Tacoma Narrows in the southern reach of Puget Sound. Delta evolution is controlled by sedimentation from the Nisqually River and erosion by strong tidal currents that may reach 0.95 m/s in the Nisqually Reach. The Nisqually River flows 116 km from the Cascade Range, including the slopes of Mount Rainier, through glacially carved valleys to Puget Sound. Extensive tidal flats on the delta consist of late-Holocene silty and sandy strata from normal river streamflow and seasonal floods and possibly from distal sediment-rich debris flows associated with volcanic and seismic events. In the early 1900s, dikes and levees were constructed around Nisqually Delta salt marshes, and the reclaimed land was used for agriculture and pasture. In 1974, U.S. Fish and Wildlife Service established the Nisqually National Wildlife Refuge on the reclaimed land to protect migratory birds; its creation has prevented further human alteration of the Delta and estuary. In October 2009, original dikes and levees were removed to restore tidal exchange to almost 3 km2 of man-made freshwater marsh on the Nisqually Delta.

  19. Dependence of flow and transport through the Williamson River Delta, Upper Klamath Lake, Oregon, on wind, river inflow, and lake elevation

    USGS Publications Warehouse

    Wood, Tamara M.

    2012-01-01

    The hydrodynamic model of Upper Klamath and Agency Lakes, Oregon, was used to run 384 realizations of a numerical tracer experiment in order to understand the relative effects of wind, lake elevation, and Williamson River inflow on flow and transport (the movement of water and passively transported constituents) through the Williamson River Delta. Significant findings from this study include: * The replacement rate of water increased in Tulana and Goose Bay with increasing lake elevation, Williamson River inflow, and wind speed. * The fraction of Williamson River inflow passing through either side of the Delta increased with lake elevation and Williamson River inflow. * The partial replacement rate of water in Goose Bay with water from the Williamson River increased with wind speed. * The partial replacement rate of water in Tulana with water from the Williamson River decreased with wind speed. * Strong wind forcing at the water surface caused more of the Williamson River inflow to pass through Goose Bay than through Tulana. * Westerly to northwesterly winds result in more of the Williamson River inflow passing through the Goose Bay side of the Delta than through the Tulana side. * Regression models developed from the tracer experiments can be used to quantify the dependencies between transport and the independent variables to obtain rough estimates of useful quantities such as residence time and steady-state solute concentrations.

  20. Nesting ecology of Spectacled Eiders Somateria fischeri on the Indigirka River Delta, Russia

    USGS Publications Warehouse

    Pearce, John M.; Esler, Daniel; Degtyarev, Andrei G.

    1998-01-01

    In 1994 and 1995 we investigated breeding biology and nest site habitat of Spectacled Eiders on two study areas within the coastal fringe of the Indigirka River Delta, Russia (71°20' N, 150°20' E). Spectacled Eiders were first observed on 6 June in both years and nesting commenced by mid-June. Average clutch size declined with later nest initiation dates by 0.10 eggs per day; clutches were larger in 1994 than 1995 and were slightly larger on a coastal island study area compared to an interior area. Nesting success varied substantially between years, with estimates of 1.6% in 1994 and 27.6% in 1995. Total egg loss, through avian or mammalian predation, occurred more frequently than partial egg loss. Partial egg loss was detected in 16 nests and appeared unrelated to nest initiation date or clutch size. We found no difference among survival rates of nests visited weekly, biweekly, and those at which the hen was never flushed, suggesting that researcher presence did not adversely affect nesting success. A comparison of nine habitat variables within each study area revealed little difference between nest sites and a comparable number of randomly located sites, leading us to conclude that Spectacled Eiders nest randomly with respect to most small scale habitat features. We propose that large scale landscape features are more important indicators of nesting habitat as they may afford greater protection from land-based predators, such as the Arctic Fox. Demographic data collected during this study, along with recent conservation measures implemented by the Republic of Sakha (Yakutia), lead us to conclude that there are few threats to the Indigirka River Delta Spectacled Eider population. Presently, the Indigirka River Delta contains the largest concentration of nesting Spectacled Eiders and deserves continued monitoring and conservation.

  1. Seismic stratigraphy of the quaternary Yellow River delta, Bohai Sea, eastern China

    NASA Astrophysics Data System (ADS)

    Cui, Shuguo; Liu, Huaishan; Tong, Siyou; Zhang, Jin; Wu, Zhiqiang; Wu, Jinlong

    2008-01-01

    The upper 40 m of stratigraphy of the Yellow River (Huang He) subaqueous delta has been well documented, but the nature of the underlying strata is currently unknown at high-resolution. To address this deficiency we used a Geopulse seismic system to image shallow sedimentary deposits up to 120 m deep on the Yellow River delta. High-resolution seismic reflection images were processed with a series of specific techniques (e.g. swelling attenuation, dynamic s/n filter; f-x deconvolution, predictive deconvolution dipscan stack), and used with borehole data to investigate the Quaternary offshore sequences in the Yellow River (Huang He) delta. Repetitive sequences were observed and interpreted as containing layers of transgressive and regressive deposits. Six seismic transgressive and regressive cycles are identified. Unit M6F-C6F correlates with a relative sea-level rise (173-157 ka) and fall (231-173 ka), while Unit M5F-C5F is associated with a relative sea-level rise (124-100 ka) and fall (157-124 ka). Unit M4F-C4F spans a period of sea-level fall at 100-87 ka, followed by a rise at 87-76 ka. Unit M3F-C3F is a transgressive-regressive cycle dated as 76-58 ka. Unit M2F-C2F correlates with relative sea level fall at 58.2-36 ka and subsequent rise at 36-22 ka. Unit M1F-C1F was deposited during relative sea level fall (22-18 ka), followed by a rise, especially since 8.5 ka.

  2. Epidemiological investigation of Clonorchis sinensis infection in freshwater fishes in the Pearl River Delta.

    PubMed

    Chen, Daixiong; Chen, Jieyun; Huang, Ji; Chen, Xueying; Feng, Dana; Liang, Baofang; Che, Yuchuan; Liu, Xiaodan; Zhu, Cuihua; Li, Xiaomin; Shen, Haoxian

    2010-09-01

    Pearl River Delta region is a high clonorchiasis-endemic area in China. However, no complete epidemiological data exist regarding its infection in freshwater fishes, an important epidemic factor for Clonorchis sinensis. The present study collected freshwater fishes and shrimps from 32 sites of nine cities in the Pearl River Delta, and the encysted metacercariae of C. sinensis were detected by digesting these specimens with artificial gastric juice. The mean infection rate of freshwater fishes was 37.09% (2,160/5,824) with a mean number of 14.269 encysted metacercariae in every infected fish and 0.460 encysted metacercariae in every gram of fish meat. Of these freshwater fishes, 5,219 were domesticated, and the infection rate was 36.69% with a mean number of 10.743 encysted metacercariae in every infected fish and 0.312 encysted metacercariae in every gram of fish meat; the other 605 were wild, and the infection rate was 40.50% with a mean number of 41.829 encysted metacercariae in every infected fish and 8.812 encysted metacercariae in every gram of fish meat. A total of 228 shrimps were examined, and 3.07% of them were infected with a mean number of 1.00 encysted metacercariae in every infected shrimp. Pseudorasbora parva and Ctenopharyngodon idellus had the highest infection rate and degree of infection in the fishes studied. The results demonstrated a high incidence of C. sinensis infection in freshwater fishes and shrimps within Pearl River Delta region and a great difference in the infection rate among different collection sites and different fish species.

  3. [Recent Distribution and Sources of Polycyclic Aromatic Hydrocarbons in Surface Soils from Yangtze River Delta].

    PubMed

    Li, Jing-ya; Wu, Di; Xu, Yun-song; Li, Xiang-dong; Wang, Xi-long; Zeng, Chao-hua; Fu, Xiao-fang; Liu, Wen-xin

    2016-01-15

    A total of 243 surface soil samples collected from 11 cities in the Yangtze River Delta region were analyzed for the concentrations, spatial distribution, component profiles and emission sources of 29 PAH species. The analytical results indicated the total concentrations of PAHs in Yangtze River Delta fell in the range from 21. 0 ng x g(-1) to 3 578.5 ng x g(-1) with an arithmetic mean and standard deviation of 310.6 ng x g(-1) and 459.1 ng x g(-1), respectively. Our data showed spatial distribution of PAHs concentrations varied greatly in the region. In addition, the contents of PAHs were positively correlated with the total organic carbon fractions in topsoil. The sites with the highest levels of PAHs in the 11 cities studied were located in Suzhou with 759.0 ng x g(-1) +/- 132.9 ng x g(-1) ollowed by the areas of Wuxi and Shanghai, with the total PAHs concentrations of 565. 3 ng x g(-1) +/- 705.5 ng x g(-1) and 349.4 ng g(-1) 220. 1 ng-g(-1) respectively. The profiles of different components pointed to a predominant role of the species with 2-4 rings, and especially for the low molecular weight components with 2-3 rings. A preliminary identification on emission sources of local PAHs was performed by the specific ratios of isomeric species and principal component analysis (PCA). The results designated industrial coal and biomass combustion as the main mixed emission sources of PAHs in surface soils from Yangtze River Delta, and tail gas from transport as another major source in some areas.

  4. [Regional distribution and ecological risk evaluation of heavy metals in surface sediments from coastal wetlands of the Yellow River Delta].

    PubMed

    Liu, Zhi-Jie; Li, Pei-Ying; Zhang, Xiao-Long; Li, Ping; Zhu, Long-Hai

    2012-04-01

    Characteristics of heavy metal distributions in surface sediments of different areas in the Yellow River Delta coastal wetland are analyzed, and the influences of sediment environment on heavy metal distributions are discussed. Heavy metal pollution and potential ecological risk in surface sediments of the Yellow River Delta coastal wetland are estimated by using Hakanson potential ecological risk (PER) factors method. The analyzed results indicate that the average contents of Hg, Cu, Pb, Zn, Cd and Cr are 0.034, 18.733, 19.393, 65.317, 0.235 and 62.940 microg x g(-1), respectively. The heavy metal distributions vary with regional environment changes. The accumulating index of heavy metals in the current outfall area is the highest of the three regions assigned by author,the second is that of the ancient Yellow River Delta in the north of Shandong province, and the lowest is that of the abandoned delta. Heavy metal distributions in the Yellow River Delta coastal wetland are affected significantly by hydrodynamic system. In addition, the content of clay in surface sediments plays an important role in the distribution and accumulation of heavy metals. The results also suggest that the heavy metal pollution in the Yellow River Delta coastal wetland is in a low pollution level, with a comprehensive pollution index varying from 0.10 to 4.14. And element Cr is the major pollution factor and its average of single pollution index is 0.63. The order of pollution extents of six typical pollutants is Cr > Cu > Zn > Cd > Pb > Hg. The comprehensive potential ecological risk index is between 0.46 and 51.88, indicating a low potential ecological risk. The order of potential ecological risk parameter is Cd > Hg > Cu > Cr > Pb > Zn. Element Cd is also the major factor of potential ecological risks in the Yellow River Delta coastal wetland.

  5. Refining the link between the Holocene development of the Mississippi River Delta and the geologic evolution of Cat Island, MS: implications for delta-associated barrier islands

    USGS Publications Warehouse

    Miselis, Jennifer L.; Buster, Noreen A.; Kindinger, Jack G.

    2014-01-01

    The geologic evolution of barrier islands is profoundly influenced by the nature of the deposits underlying them. Many researchers have speculated on the origin and evolution of Cat Island in Mississippi, but uncertainty remains about whether or not the island is underlain completely or in part by deposits associated with the past growth of the Mississippi River delta. In part, this is due to a lack of comprehensive geological information offshore of the island that could augment previous stratigraphic interpretations based on terrestrial borings. An extensive survey of Cat Island and its surrounding waters was conducted, including shallow-water geophysics (e.g., high-resolution chirp seismic, side-scan sonar, and swath and single-beam bathymetry) and both terrestrial and marine vibracoring. High-resolution seismic data and vibracores from south and east of the island show two horizontally laminated silt units; marine radiocarbon dates indicate that they are St. Bernard delta complex (SBDC) deposits. Furthermore, seismic data reveal that the SBDC deposits taper off toward the southern shoreline of Cat Island and to the west, morphology consistent with the distal edge of a delta complex. The sedimentology and extent of each unit suggest that the lower unit may have been deposited during an earlier period of continuous river flow while the upper unit may represent reduced or sporadic river flow. OSL dates from the island platform (beneath beach ridge complexes) indicate three stages of terrestrial evolution: island emergence resulting from relative sea-level rise (~ 5400 ybp) island aggradation via littoral transport (~ 2500–4000 ybp) and island degradation due to delta-mediated changes in wave direction (present– ~ 3600 ybp). Finally, the combination of terrestrial and marine data shows that portions of Cat Island that are lower in elevation than the central part of the island are younger and are likely underlain by a thin layer of deltaic sediments. This

  6. Mississippi River delta mudslides: techniques allow for continued development with reduced risk

    NASA Astrophysics Data System (ADS)

    Handley, Lawrence R.

    1982-09-01

    The Mississippi River delta environment provides all the necessary ingredients to make sediment instability a critical geohazard to be dealt with in a productive oil and gas region. Some of the early development has encountered problems with the unstable sediments as pipelines have been ruptured and platform foundations have been damaged. From experience and surveys, the government agencies and industry involved on the continental shelf are aware of the nature of instability, mechanism of movement, rate of movement and structural failure that can result, and are applying that knowledge to oil and gas exploration, development and to leasing and permitting.

  7. Sediment-hosted contaminants and distribution patterns in the Mississippi and Atchafalaya River Deltas

    USGS Publications Warehouse

    Flocks, James G.; Kindinger, Jack G.; Ferina, Nicholas; Dreher, Chandra

    2002-01-01

    The Mississippi and Atchafalaya Rivers transport very large amounts of bedload and suspended sediments to the deltaic and coastal environments of the northern Gulf of Mexico. Absorbed onto these sediments are contaminants that may be detrimental to the environment. To adequately assess the impact of these contaminants it is first necessary to develop an understanding of sediment distribution patterns in these deltaic systems. The distribution patterns are defined by deltaic progradational cycles. Once these patterns are identified, the natural and industrial contaminant inventories and their depositional histories can be reconstructed. Delta progradation is a function of sediment discharge, as well as channel and receiving-basin dimensions. Fluvial energy controls the sediment distribution pattern, resulting in a coarse grained or sandy framework, infilled with finer grained material occupying the overbank, interdistributary bays, wetlands and abandoned channels. It has been shown that these fine-grained sediments can carry contaminants through absorption and intern them in the sediment column or redistribute them depending on progradation or degradation of the delta deposit. Sediment distribution patterns in delta complexes can be determined through high-resolution geophysical surveys and groundtruthed with direct sampling. In the Atchafalaya and Mississippi deltas, remote sensing using High-Resolution Single-Channel Seismic Profiling (HRSP) and Sidescan Sonar was correlated to 20-ft vibracores to develop a near-surface geologic framework that identifies variability in recent sediment distribution patterns. The surveys identified bedload sand waves, abandoned-channel back-fill, prodelta and distributary mouth bars within the most recently active portions of the deltas. These depositional features respond to changes in deltaic processes and through their response may intern or transport absorbed contaminants. Characterizing these features provides insight into the

  8. Sediment facies, depositional environments, and distribution of phytoclasts in the recent Mahakam River delta, Kalimantan, Indonesia

    SciTech Connect

    Gastaldo, R.A. ); Huc, A.Y. )

    1992-12-01

    The Mahakam River delta is a tide- and wave-dominated delta located on the edge of the Kutei basin, eastern Kalimantan, Borneo. It is a coastal deltaic sequence, Neogene to Holocene in age, from which all recoverable hydrocarbons (crude oil and natural gas) are considered to be derived from kerogen III predecessors. However, a complete understanding of the types of sediments sourcing the hydrocarbons has not yet been achieved. A vibracoring program sampled the principal fine-grained depositional environments in two transects; one within the fluvially-dominated regime, one within the tidally-dominated regime. Ten sedimentary facies are distinguished and phytoclasts have been recovered from all environments of deposition. Canopy parts from the mixed tropical forest community are preserved throughout the delta, whereas dicotyledonous angiosperm mangroves are restricted to the subtidal zone and delta front. Nypa parts are preserved in most depositional environments. In sites where there appears to be an absence of macrodetritus, dispersed cuticle is recoverable. Identifiable plant parts include wood and fibrous tissues, Nypa petioles and leaf laminae, dicotyledonous angiosperm leaves and isolated cuticles, fruits and seeds, roots and rootlets, and moss. Dammar is found either as dispersed resin ducts or amorphous clasts. Additional biotic components found in bedded plant litters include insects, gastropods, bivalves, sand dollars, ostracods, and crabs. Fluvial channels and depositional sites associated with these systems in the delta front can be differentiated from Nypa swamps and mixed tropical hardwood-palm swamps based on their phytological components and accessory biotic elements. 39 refs., 10 figs., 3 tabs.

  9. Origins of the SHEBA freshwater anomaly in the Mackenzie River delta

    NASA Astrophysics Data System (ADS)

    Steele, M.; Porcelli, A.; Zhang, J.

    2006-05-01

    The formation of a low salinity anomaly observed in the southern Beaufort Gyre in fall 1997 is examined, using output from a numerical sea ice - ocean climate model. The anomaly forms from locally reduced fall ice growth and from advection of river water. With regard to the latter, we find anomalous northwestward advection of water from the Mackenzie River delta (MRD) during 1997-1999, which fed a low salinity anomaly that circulated and deepened in the Beaufort Gyre until summer 2002, when it dissipated. The MRD salinity anomaly was especially fresh in 1997 because unusually convergent sea ice the previous summer and fall 1996 suppressed fall ice growth. The model shows a high correlation between advection from the MRD and salinity anomalies in the southern Beaufort Gyre until about 2002, when the correlation weakens as local sea ice melt/growth becomes the dominant forcing.

  10. Water quality in select regions of Cauvery Delta River basin, southern India, with emphasis on monsoonal variation.

    PubMed

    Solaraj, Govindaraj; Dhanakumar, Selvaraj; Murthy, Kuppuraj Rutharvel; Mohanraj, Rangaswamy

    2010-07-01

    Delta regions of the Cauvery River basin are one of the significant areas of rice production in India. In spite of large-scale utilization of the river basin for irrigation and drinking purposes, the lack of appropriate water management has seemingly deteriorated the water quality due to increasing anthropogenic activities. To assess the extent of deterioration, physicochemical characteristics of surface water were analyzed monthly in select regions of Cauvery Delta River basin, India, during July 2007 to December 2007. Total dissolved solids, chemical oxygen demand, and phosphate recorded maximum levels of 1,638, 96, and 0.43 mg/l, respectively, exceeding the permissible levels at certain sampling stations. Monsoonal rains in Cauvery River basin and the subsequent increase in river flow rate influences certain parameters like dissolved solids, phosphate, and dissolved oxygen. Agricultural runoff from watershed, sewage, and industrial effluents are suspected as probable factors of water pollution.

  11. [Hydrochemical characteristics and formation mechanism of shallow groundwater in the Yellow River Delta].

    PubMed

    An, Le-Sheng; Zhao, Quan-Sheng; Ye, Si-Yuan; Liu, Guan-Qun; Ding, Xi-Gui

    2012-02-01

    Understanding the chemical characteristics of groundwater in the Yellow River Delta is very important. It can provide a useful reference for the development and construction of the Yellow River Delta High-efficiency Ecological Economic Zone and ecological regulation in the lower Yellow River. Based on partitioning the sediment environment and the recharge-runoff-discharge system, we studied the hydrochemical features and causes of shallow groundwater in the Yellow River Delta by mathematical statistics and geostatistics, Piper diagram, ion ratios and so on. Following results are obtained: 1) Major cations and anions such as Na+, Mg2+, Ca2+, Cl(-), SO4(2-), HCO3(-) and TDS concentrations range from 0.1-25.0 g x L(-1), 3.6-3 815.0 mg x L(-1), 5.6-3 377.0 mg x L(-1), 0.1-45.1 g x L(-1), 24.2-4 947.0 mg x L(-1), 62.6-850.0 mg x L(-1) and 0.4-80.7 g x L(-1). Average ion concentrations further indicate that Cl(-), Na+ and TDS concentrations are high while HCO3(-), CO3(2-) and K+ concentrations are very low in the study area. 2) The Cl(-) and TDS concentrations of shallow groundwater possess conspicuous directional spatial variability and gradually increase along the groundwater flow direction, showing that Cl(-) is the most critical ion of shallow groundwater. 3) From the recharge area to the discharge area, shallow groundwater changes from the Na+ -Mg2+ -Ca2+ -Cl(-) -SO4(2-) facies to the Na -Mg2 + -Ca2+ -Cl(-), Mg2+ -Na+ -Ca2+ -Cl(-) and Na+ -Mg2+ -Cl(-) facies, finally evolves into Na+ -Cl(-) facies in the coast. 4) Ion ratios indicate that the following main hydrochemical processes are inferred to control the shallow groundwater chemical composition: mixing, evaporation concentrating, mineral dissolution, cation exchange and adsorption and human activities. These findings strongly suggest that changes of the Yellow River water course and seawater intrusion are key drivers to form the chemical characteristics of shallow groundwater in the region.

  12. Geoarchaeological research for Roman waterworks in the Rhine-Meuse river delta, the Netherlands

    NASA Astrophysics Data System (ADS)

    Verhagen, Jan; Kluiving, Sjoerd; van Leeuwen, Liz; Anker, Emiel

    2015-04-01

    It is known that Romans in the Low Countries at the northern margin of their empire were practicing diverse systems of water state management to maintain economic and above all strategic stability. In early Roman period Romans created a shipping route from the Rhine towards the north by digging canals and constructing dams. This was done in order to submit the northern part of Germania through the Waddenzee and the German rivers Eems, Weser and Elbe. During the middle Roman period the Romans had canceled their efforts to submit Germania. In that period we know the River Rhine as the limes, which not only was a borderline of the Roman empire, but can also be seen as a guarded transport route. The research area is situated in the eastern part of the Rhine-Meuse river valley/delta system. The area represents a highly dynamic geological history of erosion and deposition close to the river system's equilibrium point. In order to reconstruct the former landscape and investigate whether traces of Roman waterworks could be indicated or disproved geoarchaeological coring campaigns have been carried out with lithological, textural and palaeoecological analyses. The results of the research presented in this poster will be: 1) Assessment of the condition of the covered Pleistocene sediments in the area, 2) Identification of the buried gullies and levees in the vicinity of the remains of the Roman castellum 'Carvium ad molem', which should have been built at the bifurcation of the delta branches of Rhine and Waal, 3) Chronological control of gullies and levees, 4) Landscape reconstruction in different time periods. Finally based on the geoarchaeological results a comment will be made on the location of the Drusus dam in the study area, the landscape context of the castellum and its position on the apex of the Insula Batavorum.

  13. Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, September 2014

    USGS Publications Warehouse

    Stevens, Andrew; Gelfenbaum, Guy R.; Warrick, Jonathan; Miller, Ian M.; Weiner, Heather M.

    2016-01-01

    Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography, and surface sediment grain size from the Elwha River delta, Washington.  Survey operations were conducted between September 5 and September 8, 2014 (USGS Field Activity Number 2014-649-FA) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), and Washington Sea Grant (table 1). Nearshore bathymetry data were collected using two personal watercraft (PWCs), each equipped with single-beam echosounders and survey-grade global navigation satellite system (GNSS) receivers. Topography data were collected on foot with GNSS receivers mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound velocity profiles measured with a conductivity-temperature-depth (CTD) sensor during the survey. A total of 143 km of nearshore

  14. Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, January 2015

    USGS Publications Warehouse

    Stevens, Andrew; Gelfenbaum, Guy R.; Warrick, Jonathan; Miller, Ian M.; Weiner, Heather M.

    2016-01-01

    Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography, and surface sediment grain size from the Elwha River delta, Washington. Survey operations were conducted between January 27 and January 30, 2015 (USGS Field Activity Number 2015-605-FA) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), Washington Sea Grant, National Park Service, and Olympic Raft and Kayak (table 1). Nearshore bathymetry data were collected using two personal watercraft (PWCs) and a kayak, each equipped with single-beam echosounders and survey-grade global navigation satellite system (GNSS) receivers. Topography data were collected on foot with GNSS receivers mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound velocity profiles measured with a conductivity-temperature-depth (CTD) sensor

  15. In situ Detection and Habitat Characteristics Analysis of Anammox Bacteria in Sediments from River-network Area, Yangtze River Delta

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Ruan, X.; Ao, J.; Ma, T.

    2010-12-01

    Anammox (anaerobic ammonium oxidation) is the conversation of NO2-and NH4+ to N2 in anaerobic condition processed by anammox bacteria. Recently, anammox bacteria has been identified in many different freshwater systems around the world. However, Many reports have only focused on the distribution and diversity of anammox bacteria in freshwater systems, little is known about the habitat characteristics of sediments suitable for anammox bacteria. Yangtze River Delta, located in the east of China, has many shallow lakes and river networks. In this study, 41 sediment samples were collected from three typical study areas (shallow lake, regional river and urban rivers) for in situ detection of anammox bacteria and physical-chemical analysis of deposital environment of sediments. Anammox specified sequences were analyzed by PCR amplification of the 16S rRNA from the sediments. Phylogentic analysis revealed that sequences from shallow lakes and regional rivers were related to 'Candidatus Brocadia fulgida', 'Candidatus Brocadia anammoxidans' and 'Candidatus Scalindua', and most of the sequences were affiliated to'Candidatus Brocadia'. No sequence was amplified from urban river's sediments. Principal Components and Classification Analysis (PCCA) of all samples shows that, 13 sites from shallow lake fell in the same set, and 28 samples from the rivers differed from each other. The nitrogen concentration of porewater from the sediments where anammox bacteria were detected in situ are: NH4+-N 6.5~33.71mg/L, NO2--N 0~0.22 mg/L, NO3--N 0.08~3.27mg/L, and the ammonium is the main form of inorganic nitrogen. The total organic carbon (TOC) in porewater varied from 15.07 mg/L to 500.49 mg/L, and the loss on ignition (LOI) in sediments is 3.9%~10.0%. The physical-chemical parameters of deposital environment of urban rivers fell in the former range, but no anammox bacteria was detected from the samples. Further study of the biological characteristics of the bacteria is needed.

  16. Coastal processes of the Elwha River delta: Chapter 5 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

    USGS Publications Warehouse

    Warrick, Jonathan A.; Stevens, Andrew W.; Miller, Ian M.; Gelfenbaum, Guy; Duda, Jeffrey J.; Warrick, Jonathan A.; Magirl, Christopher S.

    2011-01-01

    To understand the effects of increased sediment supply from dam removal on marine habitats around the Elwha River delta, a basic understanding of the region’s coastal processes is necessary. This chapter provides a summary of the physical setting of the coast near the Elwha River delta, for the purpose of synthesizing the processes that move and disperse sediment discharged by the river. One fundamental property of this coastal setting is the difference between currents in the surfzone with those in the coastal waters offshore of the surfzone. Surfzone currents are largely dictated by the direction and size of waves, and the waves that attack the Elwha River delta predominantly come from Pacific Ocean swell from the west. This establishes surfzone currents and littoral sediment transport that are eastward along much of the delta. Offshore of the surfzone the currents are largely influenced by tidal circulation and the physical constraint to flow provided by the delta’s headland. During both ebbing and flooding tides, the flow separates from the coast at the tip of the delta’s headland, and this produces eddies on the downstream side of the headland. Immediately offshore of the Elwha River mouth, this creates a situation in which the coastal currents are directed toward the east much more frequently than toward the west. This suggests that Elwha River sediment will be more likely to move toward the east in the coastal system.

  17. Examining Spatio-Temporal Change Detection in the Indus River Delta with the Help of Satellite Data

    NASA Astrophysics Data System (ADS)

    Mahar, G. A.; Zaigham, N. A.

    2016-12-01

    The morphology of a river thalweg in a deltaic environmentiscontinuouslyreshapedbytheinteractivebalancing of the fluvial and marine hydrodynamic processes. Fluvial flow parameters such as volume and flow velocity are favorable to increase the width of thalweg and develop a braided pattern in river course within a delta region. The present study utilized historical satellite images to show that asresultofthedevelopmentoftheworldlargestwaterdivergentnetworks,theIndusRiverdischargeandsedimentsload dischargeintotheIndusdeltahavebeenenormouslydepleted inthelast150years.Satelliteimagesrevealedsignificantand successive narrowing of the thalweg and distinct widening of the course of the Indus River near the delta. Based on the model results, we show that the style of the rapid morphological changes demonstrates seaward widening and the landwardnarrowingoftheIndusrivercourseanditsthalweg. Ourresultsindicatethatanthropogenicdiversionsoftheflow intheupstreamregionoftheIndusRiverhaveresultedinthe devastating domination of marine hydrodynamic processes over theweakened and destabilized natural fluvial processes in the delta region.

  18. A review of environmental and human exposure to persistent organic pollutants in the Pearl River Delta, South China.

    PubMed

    Zhang, Kai; Wei, Yan-Li; Zeng, Eddy Y

    2013-10-01

    Rapid economic growth in South China (including Guangdong Province, Hong Kong, and Macau), particularly within the Pearl River Delta region, has resulted in severe pollution of the natural eco-environment in the last three decades. Large amounts of monitoring data on organic pollution in the Pearl River Delta have been accumulated, which allows us to conduct a fairly comprehensive assessment of the state of the Pearl River Delta and elucidate spatial and temporal patterns of pollution on a regional scale. Of various causes for environmental deterioration, negative impact from persistent organic pollutants (POPs) is a global concern. This review examines the current levels and distribution patterns of several POPs, namely DDT (and its metabolites DDD and DDE), hexachlorocyclohexanes, and polybrominated diphenyl ethers, in various environmental compartments of South China. The general information on environmental occurrence, regional behaviors, ecological effects, and human exposure of these POPs in this region are reviewed. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Morphodynamics of an eroding beach and foredune in the Mekong River delta: Implications for deltaic shoreline change

    NASA Astrophysics Data System (ADS)

    Anthony, E. J.; Dussouillez, P.; Dolique, F.; Besset, M.; Brunier, G.; Nguyen, V. L.; Goichot, M.

    2017-09-01

    River delta shorelines composed of sand may be characterized by complex spatial and temporal patterns of erosion and accretion even when sand supply is readily available. This is especially the case for deltas with multiple mouths subject to significant wave and tide influence. High-resolution topographical and wave and current measurements were conducted from 2010 to 2012 at Ba Dông beach, a popular resort located on the largest of the multiple inter-distributary plains of the Mekong River delta. Ba Dông beach is a mesotidal, multiple bar-trough system. The upper beach corresponds to the current active beach ridge in the sequence of ridges that have marked the progradation of the inter-distributary delta plains, and is capped by a low foredune that protects villages and agricultural land from marine flooding. During the low river-flow season, the beach is characterized by Northeast monsoon waves and strong longshore currents that transport sediment towards the southwest. Weaker longshore currents towards the northeast are generated by Southwest monsoon waves during the high river-flow season. Ba Dông beach underwent strong erosion between 2010 and 2012, following a phase of massive accretion. In 2012, this erosion resulted in breaching of the foredune, contributing to concerns that the Mekong delta had become vulnerable to retreat. The local erosion at Ba Dông needs to be considered, however, in the broader context of delta shoreline morphodynamics, which involves space- and time-varying patterns of beach accretion and erosion. These patterns are the present expressions of plan-view beach-ridge morphology in the delta, which is characterized by flaring and truncations that reflect changing beach morphodynamics in the course of deltaic progradation. We surmise that these patterns are related to complex interactions involving river water and sediment discharge, waves and wave-generated longshore currents, tidal currents, and shoreline orientation.

  20. Paleoenvironments and sea level changes of Holocene from Nakdong River Delta sediments, Korea

    NASA Astrophysics Data System (ADS)

    Cheong, Daekyo

    2015-04-01

    The Holocene delta sediments(ND-01) which was acquired from the Nakdong River Delta as a rotary-style sediment core in southern Korea is divided into four sedimentary units based on sedimentary structure, texture, and occurrence of microfossils. Unit A(18.8˜33.54 m) is mostly homogeneous mud and shell fragments are well observed. Marine microfossils such as ostracods, diatoms, and sponge spicules decrease towards the top of the core sediments. Unit B(16.6˜18.8 m) is generally laminated mud and laminated sand. Marine microfossils disappear at the top of Unit B, but wood fragments contents increase towards the top. At Unit C(14.2˜16.6 m), mud content is lower than Unit B and laminated sand is well developed. Unit D(8˜14.2 m) is mostly homogeneous sand and shows better sorting than lower unit.. The sedimentary environments of the sequence are supposed to be a progradational delta system.

  1. Constraining rates and trends of historical wetland loss, Mississippi River Delta Plain, south-central Louisiana

    USGS Publications Warehouse

    Bernier, Julie C.; Morton, Robert A.; Barras, John A.

    2006-01-01

    The timing, magnitude, and rate of wetland loss were described for five wetland-loss hotspots in the Terrebonne Basin of the Mississippi River delta plain. Land and water areas were mapped for 34 dates between 1956 and 2004 from historical National Wetlands Inventory (NWI) datasets, aerial photographs, and Landsat Thematic Mapper (TM) satellite images. Since 1956, the emergent land area at the five study areas in south-central Louisiana has decreased by about 50%. Comparison of the water-area curve derived from the 29 TM images with water-level records from the nearby Grand Isle, Louisiana tide gauge (NOS #8761724) clearly shows that changes in land and water areas fluctuate in response to variations in regional water levels. The magnitude of water-area fluctuations decreased from the 1980s to the 1990s as former areas of wet marsh within and immediately adjacent to the wetland-loss hotspots became permanently submerged. The most rapid wetland loss occurred during the late 1960s and 1970s. Peak wetland-loss rates during this period were two to four times greater than both the pre-1970s background rates and the most recent wetland-loss rates. These results provide constraints on predicting future delta-plain wetland losses and identify Landsat TM imagery as an important source for analyzing land- and water-area changes across the entire delta plain.

  2. [Relationships between typical vegetations, soil salinity, and groundwater depth in the Yellow River Delta of China].

    PubMed

    Ma, Yu-Lei; Wang, De; Liu, Jun-Min; Wen, Xiao-Hu; Gao, Meng; Shao, Hong-Bo

    2013-09-01

    Soil salinity and groundwater depth are the two important factors affecting the vegetation growth and distribution in the Yellow River Delta. Through field investigation and statistical analysis, this paper studied the relationships between the typical vegetations (Suaeda heteroptera-Tamarix chinensis, Robinia pseudoacacia, Phragmites australis, and cotton) , soil salinity, and groundwater depth in the Delta. In the study area, groundwater depth had significant effects on soil salinity, with the average influence coefficient being 0.327. When the groundwater depth was 0.5-1.5 m, soil salinization was most severe. The vegetation growth in the Delta was poorer, with the NDVI in 78% of the total area being less than 0.4. Groundwater depth and soil salinity had significant effects on the vegetation distribution. Soil salinity had significant effects on the NDVI of R. pseudoacacia, S. heteroptera-T. chinensis, P. australis, and cotton, while groundwater depth had significant effects on the NDVI of S. heteroptera - T. chinensis, but lesser effects on the NDVI of P. australis, cotton and R. pseudoacacia.

  3. Detection of the Three Gorges Dam influence on the Changjiang (Yangtze River) submerged delta.

    PubMed

    Dai, Zhijun; Liu, James T; Wei, Wen; Chen, Jiyu

    2014-10-16

    While most large river-deltas in the world are facing the risk of subsidence and erosion in the Anthropocene, it is suspected that the Changjiang submerged delta (CSD) could be subjected to the impacts of the world's largest dam, the Three Gorges Dam (TGD). Here we firstly indicate that the CSD went through high accumulation (1958-1978); slight accumulation (1978-1997), slight erosion (1997-2002); and high accumulation (2002-2009), despite the 70% reduction of the sediment load from upstream since the operation of the TGD in 2003. Meanwhile, at the depocenter of the submerged delta, the accumulation maintained a high rate of 10 cm/yr during 1958-2009. This suggests on a longer term, the distal sediment source from the upstream had little effect on the CSD. Within this time frame the changes in the partition of sediment load among the branching channels of the Changjiang Estuary could likely control the shifting of the depocenter of the CSD on a decadal time scale. Episodic extreme floods and storm surges also increased the magnitude of deposition and erosion of the CSD on short-term scales. A re-evaluation of the impacts of TGD on the CSD is urgently needed.

  4. Detection of the Three Gorges Dam influence on the Changjiang (Yangtze River) submerged delta

    PubMed Central

    Dai, Zhijun; Liu, James T.; Wei, Wen; Chen, Jiyu

    2014-01-01

    While most large river-deltas in the world are facing the risk of subsidence and erosion in the Anthropocene, it is suspected that the Changjiang submerged delta (CSD) could be subjected to the impacts of the world's largest dam, the Three Gorges Dam (TGD). Here we firstly indicate that the CSD went through high accumulation (1958–1978); slight accumulation (1978–1997), slight erosion (1997–2002); and high accumulation (2002–2009), despite the 70% reduction of the sediment load from upstream since the operation of the TGD in 2003. Meanwhile, at the depocenter of the submerged delta, the accumulation maintained a high rate of 10 cm/yr during 1958–2009. This suggests on a longer term, the distal sediment source from the upstream had little effect on the CSD. Within this time frame the changes in the partition of sediment load among the branching channels of the Changjiang Estuary could likely control the shifting of the depocenter of the CSD on a decadal time scale. Episodic extreme floods and storm surges also increased the magnitude of deposition and erosion of the CSD on short-term scales. A re-evaluation of the impacts of TGD on the CSD is urgently needed. PMID:25321660

  5. River avulsions in the presence of tectonic tilting, and the Ganges-Brahmaputra Delta

    NASA Astrophysics Data System (ADS)

    Reitz, M. D.; Steckler, M. S.; Paola, C.; Goodbred, S. L.; Petter, A. L.; Pickering, J.; Williams, L. A.

    2013-12-01

    In Bangladesh, the set of active rivers of the Ganges-Brahmaputra Delta overlie a landscape that is being continually modified by tectonics. The response of rivers to a surface being altered by tectonic tilting or other causes of spatially variable subsidence is generally understood to be a preferred path direction toward regions of higher subsidence. Quantifying the magnitude of the effect of variable subsidence on the timescale and path direction of channel avulsion remains, however, an open question. Recent experimental work has suggested an equilibrium-slope explanation for the timescale and conditions for avulsion, which provides a way forward on understanding how varied subsidence conditions would affect the avulsion process. Here we adapt this model for avulsion to the context of variable subsidence, developing a new framework to quantify its effect on channel avulsions. We find that variable subsidence results in two effects: differing timescales between avulsions on different parts of the delta, and differing frequencies of avulsion to these locations. Regions of higher subsidence both draw avulsions more frequently, and result in longer channel residence times in these locations. We also describe the effect of incision or aggradation due to sea level changes within this framework: incisional events lengthen avulsion timescales everywhere on the delta, while periods of sea-level rise drive the timescales back toward their minimum values. Finally, we apply this theory to the Ganges-Brahmaputra Delta, where we use a map of regional variable subsidence that we derived from GPS and published stratigraphic data, to predict the variation in avulsion timescale and frequency for the Brahmaputra River due to this variable subsidence. We make estimates for two different tectonic history interpretations, and for the cases with or without the estimated incision from the most recent sea-level fall. Comparison between our predictions and our stratigraphy

  6. Urban Household Carbon Emission and Contributing Factors in the Yangtze River Delta, China

    PubMed Central

    Xu, Xibao; Tan, Yan; Chen, Shuang; Yang, Guishan; Su, Weizhong

    2015-01-01

    Carbon reduction at the household level is an integral part of carbon mitigation. This study analyses the characteristics, effects, contributing factors and policies for urban household carbon emissions in the Yangtze River Delta of China. Primary data was collected through structured questionnaire surveys in three cities in the region – Nanjing, Ningbo, and Changzhou in 2011. The survey data was first used to estimate the magnitude of household carbon emissions in different urban contexts. It then examined how, and to what extent, each set of demographic, economic, behavioral/cognitive and spatial factors influence carbon emissions at the household level. The average of urban household carbon emissions in the region was estimated to be 5.96 tonnes CO2 in 2010. Energy consumption, daily commuting, garbage disposal and long-distance travel accounted for 51.2%, 21.3%, 16.0% and 11.5% of the total emission, respectively. Regulating rapidly growing car-holdings of urban households, stabilizing population growth, and transiting residents’ low-carbon awareness to household behavior in energy saving and other spheres of consumption in the context of rapid population aging and the growing middle income class are suggested as critical measures for carbon mitigation among urban households in the Yangtze River Delta. PMID:25884853

  7. Quantitative analysis and simulation of land use changes in the Pearl River Delta, China

    NASA Astrophysics Data System (ADS)

    Zhang, Honghui; Zeng, Yongnian; Zou, Bin; Xiao, Pengfeng; Hu, Deyong; Peng, Jianchao

    2007-06-01

    This paper analyzes and simulates the land use changes in the Pearl River Delta, China, using Longgang City as a case study. The region has pioneered the nation in economic development and urbanization process. Tremendous land use changes have been witnessed since the economic reform in 1978. Land use changes are analyzed and simulated by using stochastic cellular automata model, land use trajectories analysis, spatial indices and multi-temporal TM images of Longgang City (TM1987, TM1991, TM1995, TM1999, TM2003, TM2005) in order to understand how urbanization has transformed the non-urban land to urban land and estimate the consequent environment and ecological impacts in this region. The analysis and simulation results show that urban land continues to sprawl along road and fringe of towns, and concomitant to this development is the loss of agricultural land, orchards and fish ponds. This study provides new evidence with spatial details about the uneven land development in the Pearl River Delta.

  8. Risks posed by trace organic contaminants in coastal sediments in the Pearl River Delta, China.

    PubMed

    Fung, C N; Zheng, G J; Connell, D W; Zhang, X; Wong, H L; Giesy, J P; Fang, Z; Lam, P K S

    2005-10-01

    Local marine environments in China's Pearl River Delta (PRD), the most rapidly developing region in one of the world's fastest growing economies, have been experiencing significant environmental stress during the past decades. This investigation was conducted to determine the status and trends of persistence organic pollutants (POPs) such as polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHCs), polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides and dioxin-related compounds in marine sediments collected from sixteen coastal stations in the Pearl River Delta (PRD) in March 2003. Elevated concentrations of PAHs (94-4300 ng/g), PCBs (6.0-290 ng/g), PHCs (14-150 microg/g), and DDTs (1.4-600 ng/g) were detected in sediment samples. In addition, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-like activities in the sediment samples were estimated to range from 0.3 to 440 pg TCDD-EQ/g. Sediments collected from Xiashan contained the greatest concentrations of trace organic contaminations amongst all the sampling stations in the present study. The degree of trace organic contamination was, in general, more severe at stations situated along the west shores of the PRD than their counterparts in the east. A preliminary assessment was performed to examine the probable risks to the marine ecosystem due to POPs. The results showed that OC pesticide contamination in the PRD was particularly serious and might pose a threat to the health of the marine inhabitants.

  9. Regional Integrated Experiments on Air Quality over Pearl River Delta 2004 (PRIDE-PRD2004): Overview

    NASA Astrophysics Data System (ADS)

    Zhang, Y. H.; Hu, M.; Zhong, L. J.; Wiedensohler, A.; Liu, S. C.; Andreae, M. O.; Wang, W.; Fan, S. J.

    The aims of the Program of Regional Integrated Experiments on Air Quality over Pearl River Delta of China 2004 (PRIDE-PRD2004) were to characterize in depth the pollution, and to improve the understanding of the chemical and radiative processes in the atmosphere of Pearl River Delta (PRD) in South-Eastern China. This comprehensive program integrated ground-base in situ measurements, vertical observations (including aircraft) and model simulations. The intensive field campaign was conducted from 4 October to 5 November 2004 at two super-sites: an urban site in Guangzhou city (23.13°N, 113.26°E) and a non-urban site at Xinken (22.61°N, 113.59°E). They were coordinated with concurrent meteorological observations as well as measurements at stations of a regional monitoring network. Quality control and quality assurances, application of closure studies and observation-based modeling were the key elements of the research strategies for the PRIDE-PRD2004 campaign. Knowledge and understanding of the important issues, including 3-D distribution of air pollution, ozone formation process and its control strategies, sources of volatile organic compounds, chemical and physical characteristics and radiative properties of aerosols, and the important role of nitrous acid atmospheric chemistry, have been improved substantially by this study.

  10. Transfer of Cadmium from Soil to Vegetable in the Pearl River Delta area, South China

    PubMed Central

    Zhang, Huihua; Chen, Junjian; Zhu, Li; Yang, Guoyi; Li, Dingqiang

    2014-01-01

    The purpose of this study was to investigate the regional Cadmium (Cd) concentration levels in soils and in leaf vegetables across the Pearl River Delta (PRD) area; and reveal the transfer characteristics of Cadmium (Cd) from soils to leaf vegetable species on a regional scale. 170 paired vegetables and corresponding surface soil samples in the study area were collected for calculating the transfer factors of Cadmium (Cd) from soils to vegetables. This investigation revealed that in the study area Cd concentration in soils was lower (mean value 0.158 mg kg−1) compared with other countries or regions. The Cd-contaminated areas are mainly located in west areas of the Pearl River Delta. Cd concentrations in all vegetables were lower than the national standard of Safe vegetables (0.2 mg kg−1). 88% of vegetable samples met the standard of No-Polluted vegetables (0.05 mg kg−1). The Cd concentration in vegetables was mainly influenced by the interactions of total Cd concentration in soils, soil pH and vegetable species. The fit lines of soil-to-plant transfer factors and total Cd concentration in soils for various vegetable species were best described by the exponential equation (), and these fit lines can be divided into two parts, including the sharply decrease part with a large error range, and the slowly decrease part with a low error range, according to the gradual increasing of total Cd concentrations in soils. PMID:25247431

  11. PAHs in soils and estimated air-soil exchange in the Pearl River Delta, South China.

    PubMed

    Liu, Guoqing; Yu, Lili; Li, Jun; Liu, Xiang; Zhang, Gan

    2011-02-01

    In this study, 74 soil samples collected from the Pearl River Delta were analyzed for polycyclic aromatic hydrocarbons (PAHs). The PAH mixture in the soils is mainly of low molecular weight compounds, with naphthalene (21.4%) and phenanthrene (21.8%) being dominant. Soil PAH levels from the Pearl River Delta are relatively low (28-711 ng/g, averaged 192 ng/g) compared to those from urban soils in temperate regions. The mean concentration of ΣPAHs generally decrease with increasing distance from the city center, with ΣPAHs of paddy soils>crop soil>natural soil. PAHs in the air were measured during a year-round sampling campaign using semipermeable membrane devices, and the transfer of chemicals between the soil and air compartments were estimated. Soil-air fugacity quotient calculations showed a highly uncertain equilibrium position of PAHs, with net volatilization of naphthalene and fluorene, whereas net deposition of phenanthrene, fluoranthene, and pyrene, indicating a capacity for the air to supply the soil with more substances.

  12. [Microbial community in nitrogen cycle of aquaculture water of the Pearl River Delta].

    PubMed

    Cai, Xiaolong; Luo, Jianfei; Lin, Weitie; Tian, Guoliang

    2012-05-04

    In order to study the characteristic of nitrogen transport, the community structure and diversity of related microorganisms in aquaculture water of the Pearl River Delta. We established an artificial aquaculture ecosystem to study the microbial community of 15N-stable isotope probing (15N-SIP) labeled nitrogen transport microorganisms. The 15N-labeled DNA was separated by CsCl-ethidium bromide density gradient centrifugation, and was used to construct 16S rRNA gene clone libraries of bacteria and archaea. Phylogenetic analysis shows that 19 Operational Taxonomic Units (OTUs) from bacterial library were clustered in Proteobacteria and Planctomycetes. Proteobacteria (99.2%) was the dominant group, mainly consisted of Comamonas (15.7%), Nitrosomonas (12.4%), Enterobacteriaceae (11.5%) and Nitrobacter (11.5%). From archaeal library 9 OTUs were divided into 3 phyla: Thaumarchaeota, Crenarchaeota and Euryarchaeota. We successfully elucidated the microbial community of nitrogen transport microorganisms in aquaculture water of Pearl River Delta by using 15N-SIP. The data of the community will provide essential information for isolating nitrogen degrading microorganism, and provide scientific basis for creating a healthy aquaculture environment.

  13. Influence of different geographical factors on carbon sink functions in the Pearl River Delta.

    PubMed

    Xu, Qian; Dong, Yuxiang; Yang, Ren

    2017-03-08

    This study analyzed carbon fixation across different land use types in the Pearl River Delta to identify the influence of different geographical factors on carbon fixation ability. The methodology was based on interpreting land use data from TM imagery, MODIS13Q1 data, and climate data, using the improved CASA and GeogDetector models. The results show that: (1) From 2000 to 2013, the total carbon sink increased slightly, from 15.58 × 10(6) t to 17.52 × 10(6) t, being spatially low at the center and increasing outwards; (2) Proxy variables (topography and landform characteristics), influencing urbanization, significantly affect the carbon sink function of the Pearl River Delta region. The proportion of urban and other construction land showed increasing effect on the regional carbon sink each year. However, the spatial structure of land in the study area changed from complex to simple, with enhanced stability; consequently, the influence of landscape characteristics (landscape dominance and landscape perimeter area fractal dimension) on the regional carbon sink gradually decreased; (3) The influence of the same factors differed with different land use types. Slope and altitude were found to have the greatest influence on the carbon sink of cultivated land, while landscape perimeter area fractal dimension more significantly affected the forest carbon sink.

  14. Transfer of cadmium from soil to vegetable in the Pearl River Delta area, South China.

    PubMed

    Zhang, Huihua; Chen, Junjian; Zhu, Li; Yang, Guoyi; Li, Dingqiang

    2014-01-01

    The purpose of this study was to investigate the regional Cadmium (Cd) concentration levels in soils and in leaf vegetables across the Pearl River Delta (PRD) area; and reveal the transfer characteristics of Cadmium (Cd) from soils to leaf vegetable species on a regional scale. 170 paired vegetables and corresponding surface soil samples in the study area were collected for calculating the transfer factors of Cadmium (Cd) from soils to vegetables. This investigation revealed that in the study area Cd concentration in soils was lower (mean value 0.158 mg kg(-1)) compared with other countries or regions. The Cd-contaminated areas are mainly located in west areas of the Pearl River Delta. Cd concentrations in all vegetables were lower than the national standard of Safe vegetables (0.2 mg kg(-1)). 88% of vegetable samples met the standard of No-Polluted vegetables (0.05 mg kg(-1)). The Cd concentration in vegetables was mainly influenced by the interactions of total Cd concentration in soils, soil pH and vegetable species. The fit lines of soil-to-plant transfer factors and total Cd concentration in soils for various vegetable species were best described by the exponential equation (y = ax(b)), and these fit lines can be divided into two parts, including the sharply decrease part with a large error range, and the slowly decrease part with a low error range, according to the gradual increasing of total Cd concentrations in soils.

  15. Natural Selection in a Bangladeshi Population from the Cholera-Endemic Ganges River Delta

    PubMed Central

    Karlsson, Elinor K.; Harris, Jason B.; Tabrizi, Shervin; Rahman, Atiqur; Shlyakhter, Ilya; Patterson, Nick; O'Dushlaine, Colm; Schaffner, Stephen F.; Gupta, Sameer; Chowdhury, Fahima; Sheikh, Alaullah; Shin, Ok Sarah; Ellis, Crystal; Becker, Christine E.; Stuart, Lynda M.; Calderwood, Stephen B.; Ryan, Edward T.; Qadri, Firdausi; Sabeti, Pardis C.; LaRocque, Regina C.

    2015-01-01

    As an ancient disease with high fatality, cholera has likely exerted strong selective pressure on affected human populations. We performed a genome-wide study of natural selection in a population from the Ganges River Delta, the historic geographic epicenter of cholera. We identified 305 candidate selected regions using the Composite of Multiple Signals (CMS) method. The regions were enriched for potassium channel genes involved in cyclic AMP-mediated chloride secretion and for components of the innate immune system involved in NF-κB signaling. We demonstrate that a number of these strongly selected genes are associated with cholera susceptibility in two separate cohorts. We further identify repeated examples of selection and association in an NF-kB / inflammasome-dependent pathway that is activated in vitro by Vibrio cholerae. Our findings shed light on the genetic basis of cholera resistance in a population from the Ganges River Delta and present a promising approach for identifying genetic factors influencing susceptibility to infectious diseases. PMID:23825302

  16. A methodological approach to rapid assessment of a river flood in coastal waters. First test in the Po River delta

    NASA Astrophysics Data System (ADS)

    Campanelli, Alessandra; Bellafiore, Debora; Bensi, Manuel; Bignami, Francesco; Caccamo, Giuseppe; Celussi, Mauro; Del Negro, Paola; Ferrarin, Christian; Marini, Mauro; Paschini, Elio; Zaggia, Luca

    2014-05-01

    As part of the actions of the flagship project RITMARE (Ricerca ITaliana per il MARE) a daily oceanographic survey was performed on 29th November 2013 in front of the Po River delta (Northern Adriatic Sea). The Po river affects a large part of the Northern Adriatic Sea with strong implications on the circulation and functionality of the basin. Physical-chemical and biological properties of coastal waters were investigated after a moderate flood occurred around 25th-27th November. The cruise activities, carried out using a small research boat, were mainly focused on the test of a methodological approach to investigate the environment variability after a flood event in the framework of rapid assessment. The effects of the flood on the coastal waters, have been evaluated in the field using operational forecasts and real-time satellite imagery to assist field measurements and samplings. Surface satellite chlorophyll maps and surface salinity and current maps obtained from a numerical model forced by meteorological forecast and river data were analyzed to better identify the Po plume dispersion during and after the event in order to better locate offshore monitoring stations at the sea. Profiles of Temperature, Salinity, Turbidity, Fluorescence and Colored Dissolved Organic Matter (CDOM) throughout the water column were collected at 7 stations in front of the Po River delta. Sea surface water samples were also collected for the analysis of nutrients, Dissolved Organic Carbon (DOC) and CDOM (surface and bottom). The CDOM regulates the penetration of UV light throughout the water column and mediates photochemical reactions, playing an important role in many marine biogeochemical processes. Satellite images showed a strong color front that separates the higher-chlorophyll coastal water from the more oligotrophic mid-basin and eastern boundary Adriatic waters. In front of the river mouth, the surface layer was characterized by low salinity (14-15), high turbidity (8-11 NTU

  17. [Shifting path of industrial pollution gravity centers and its driving mechanism in Pan-Yangtze River Delta].

    PubMed

    Zhao, Hai-Xia; Jiang, Xiao-Wei; Cui, Jian-Xin

    2014-11-01

    Shifting path of industrial pollution gravity centers is the response of environmental special formation during the industry transfer process, in order to prove the responding of industrial pollution gravity centers to industry transfer in economically developed areas, this paper calculates the gravity centers of industrial wastewater, gas and solid patterns and reveals the shifting path and its driving mechanism, using the data of industrial pollution in the Pan-Yangtze River Delta from 2000 to 2010. The results show that the gravity center of the industrial waste in Pan-Yangtze River Delta shifts for sure in the last 10 years, and gravity center of solid waste shifts the maximum distance within the three wastes, which was 180.18 km, and shifting distances for waste gas and waste water were 109.51 km and 85.92 km respectively. Moreover, the gravity center of the industrial waste in Pan-Yangtze River Delta shifts westwards, and gravity centers of waste water, gas and solid shift for 0.40 degrees, 0.17 degrees and 0.03 degrees respectively. The shifting of industrial pollution gravity centers is driven by many factors. The rapid development of the heavy industry in Anhui and Jiangxi provinces results in the westward shifting of the pollutions. The optimization and adjustment of industrial structures in Yangtze River Delta region benefit to alleviating industrial pollution, and high-polluting industries shifted to Anhui and Jiangxi provinces promotes pollution gravity center shifting to west. While the development of massive clean enterprise, strong environmental management efforts and better environmental monitoring system slow the shifting trend of industrial pollution to the east in Yangtze River Delta. The study of industrial pollution gravity shift and its driving mechanism provides a new angle of view to analyze the relationship between economic development and environmental pollution, and also provides academic basis for synthetical management and control of

  18. REE systematics in modern bottom sediments of the Caspian Sea and river deltas worldwide: Experience of comparison

    NASA Astrophysics Data System (ADS)

    Maslov, A. V.; Kozina, N. V.; Shevchenko, V. P.; Klyuvitkin, A. A.; Sapozhnikov, Ph. V.; Zavialov, P. O.

    2017-07-01

    The results of comparison of a number of main parameters of the chondrite-normalized REE distribution spectra in modern bottom, mainly pelitic, sediments of various sedimentary subsystems of the Caspian Sea and marginal filters of the Volga and Ural rivers with those characteristic of the pelitic fraction of modern bottom sediments of different river deltas worldwide are discussed. According to the features of the REE distribution spectra, as well as the ɛNd(0) values, it has been established that most samples of the Caspian bottom sediments are similar to those of large rivers and rivers, draining watersheds composed of sedimentary formations.

  19. Genesis and Diversity of Cryosols of the Northeast Siberian Lena River Delta

    NASA Astrophysics Data System (ADS)

    Zubrzycki, Sebastian; Pfeiffer, Eva-Maria; Kutzbach, Lars

    2017-04-01

    The North-Siberian Lena River Delta (LRD) is the largest Arctic delta and an important interface between the Arctic Ocean in the North and the large Siberian land masses in the South. LRD consists not only of Holocene deltaic sediment deposits as a river terrace and the modern active floodplains but also of remnants of the former Pleistocene mainland including large islands of ice-complex sediments and the Arga-Muora-Sise Island, which is composed of pure sand sediments of still debated origin. The highly diverse landscape structure of LRD is reflected by a great variety of permafrost-affected soils (cryosols). This study aims at describing this great cryosol diversity and at analysing the dominant soil-forming processes in this comparatively scarcely studied soil region. The soil development in the investigated continuous permafrost region is limited by the short thawing period of around three months (June to September) and takes place in the shallow (below 1 m) seasonally thawed active layer. The geological parent material plays an important role for the development of soils in the LRD region. The distribution of the various soil types closely follows the pattern of the geomorphic units characterised by differing sedimentation conditions. The properties and genesis of the soils on the Holocene river terrace and the modern floodplains are strongly affected by the enormous amounts of fluvial sediments (about 12 x 106 tons per year) brought by the Lena River into its delta. The fluvial sedimentation together with the also pronounced aeolian sedimentation results in a fast vertical growth of soils. The upward rise of the soil surface leads to an upward movement of the permafrost table resulting in fast incorporation of soil material formed in the supra-permafrost zone into the permafrost. Due to the morphodynamics of ice-wedge polygons and resulting formation of patterned ground with elevated rims and depressed and water-saturated centres, the Holocene river terrace

  20. Cryosols of the Northeast Siberian Lena River Delta and its hinterland - genesis and diversity

    NASA Astrophysics Data System (ADS)

    Zubrzycki, Sebastian; Kutzbach, Lars; Pfeiffer, Eva-Maria

    2016-04-01

    The North-Siberian Lena River Delta (LRD) is the largest Arctic delta and an important interface between the Arctic Ocean in the North and the large Siberian land masses in the South. LRD consists not only of Holocene deltaic sediment deposits as a river terrace and the modern active floodplains but also of remnants of the former Pleistocene mainland including large islands of ice-complex sediments and the Arga-Muora-Sise Island, which is composed of pure sand sediments of still debated origin. The highly diverse landscape structure of LRD is reflected by a great variety of permafrost-affected soils (cryosols). This study aims at describing this great cryosol diversity and at analysing the dominant soil-forming processes in this comparatively scarcely studied soil region. The soil development in the investigated continuous permafrost region is limited by the short thawing period of around three months (June to September) and takes place in the shallow (below 1 m) seasonally thawed active layer. The geological parent material plays an important role for the development of soils in the LRD region. The distribution of the various soil types closely follows the pattern of the geomorphic units characterised by differing sedimentation conditions. The properties and genesis of the soils on the Holocene river terrace and the modern floodplains are strongly affected by the enormous amounts of fluvial sediments (about 12 x 106 tons per year) brought by the Lena River into its delta. The fluvial sedimentation together with the also pronounced aeolian sedimentation results in a fast vertical growth of soils. The upward rise of the soil surface leads to an upward movement of the permafrost table resulting in fast incorporation of soil material formed in the supra-permafrost zone into the permafrost. Due to the morphodynamics of ice-wedge polygons and resulting formation of patterned ground with elevated rims and depressed and water-saturated centres, the Holocene river terrace

  1. The Lena River Delta Observatory, Arctic Siberia: a Contribution to the ESA DUE Permafrost Project

    NASA Astrophysics Data System (ADS)

    Heim, Birgit; Boike, Julia; Moritz, Langer; Annett, Bartsch; Sina, Muster; Jennifer, Sobiech; Konstanze, Piel; Günter, Stoof; Anne, Morgenstern; Mathias, Ulrich

    2010-05-01

    The major task of the ESA Data User Element DUE PERMAFROST is to develop and use Earth Observation services specifically for monitoring and modelling of permafrost. In order to setup the required information services, a target area approach with specified case study regions is used. Long-term ground data series and multidisciplinary ongoing projects make the Lena River delta (Arctic Siberia) a prime study region for evaluation and validation of the DUE PERMAFROST remote sensing products. The Lena River Delta located in the zone of continuous permafrost is a key region for Arctic system science. Since 1998, the Alfred Wegener Institute for Polar and Marine Research AWI in collaboration with the Lena Delta Reserve in Tiksi has operated the German-Russian research station Samoylov. Relevant ground-based data (air temperature, radiation, snow, albedo, soil temperature and moisture) are collected continuously. The high landscape heterogeneity (wet polygonal centres, dry polygonal rims, ponds and lakes) challenges all ground data observations. Match-up data sets of ground data and remote sensing products coincident in time and location are being built up. Exclusion and selection criteria will be based on experience, especially the knowledge on parameter variability in time and space. The main focus are the remote sensing products ‘surface temperature', ‘surface moisture', ‘albedo', ‘vegetation' and ‘water'. Statistical and contextural methods will be used for the upscaling from the plot to the meso-scale. Problems will have to be identified such as process-dependent scales and the water body ratio within the pixel.

  2. Geochronology of Mudflow Deposits on the Mississippi River Delta Front, Louisiana, USA

    NASA Astrophysics Data System (ADS)

    Keller, G. P.; Bentley, S. J.; Xu, K.; Georgiou, I. Y.; Miner, M. D.; Obelcz, J.; Maloney, J. M.

    2016-02-01

    Short multicores (<50cm) and longer gravity cores (up to 3m) were collected seaward of the Southwest Pass of the Mississippi River Delta (Gulf of Mexico) and were analyzed to assess the frequency, extent, and potential causes of submarine mass wasting events. Cores were analyzed for radionuclide activity, grain size, and density at 2cm resolution, with x-radiography for the whole core. Short-term sedimentation rates calculated from 7Be are 2-12cm/y, while longer-term accumulation from 210Pb are only 1.3-5.5cm/y. In most cores, 210Pb activity steadily decreases downcore without displaying a "stairstep" nature. However, six cores have layers of low 210Pb activity stratigraphically above layers with higher activity. In one long core from a mudflow gully, 210Pb steadily decreases for the upper 90cm before stabilizing for the remaining 130cm. Clay content generally ranges between 25-40% and sand ranges between 5-15% with silt making up the rest of each sample. Sedimentation rates derived from 210Pb in the short cores indicate that proximity to the river mouth has stronger influence than depositional environment (mudflow gully, depositional lobe, prodelta). This finding may be explained by rapid sedimentation rates coupled with a reduced tropical cyclone activity over the delta in the last seven years (2006-2013). The regions of decreased 210Pb activity may be evidence of scavenging effects of plume sedimentation because they do not correspond with decreases in clay fraction. The zone of homogenized activity below 90cm in the gully core occurs at a depth equivalent to 18 years, indicating mixing on a decadal scale, potentially from mudflows. These results may be explained by a lack of recent mass failures corresponding with lulls in tropical cyclone activity over the delta, preceded by a period of more active hurricane-driven mudflow activity.

  3. [The lower Neretva basin as a pathological topos: press reports and politicization of the memories of the age of cholera in 1886].

    PubMed

    Fatović-Ferencić, Stella; Wokaunn, Mario

    2012-01-01

    The lower Neretva basin as a space that has undergone historical transformation into a myth of a pathological topos has been analyzed. Starting from the fact that temporality is essential for understanding of the elements that partake in conceptualization of a myth, we have analyzed the state of this area as it was during its exposure to an epidemic of cholera in 1886. There is evidence that at this time exactly a step forward was made in comprehension of the etiology of the disease, which resulted in the change of centuries-long concepts of the Neretva basin as an unhealthy area. In this paper the Neretva basin was understood and presented as a field of unfolding of all kinds of transformations, a habitat exposed to manifold social arrangements, lushly documented in newspapers and other printed material. The arguments about the natural disaster in these texts are ethically and politically coloured, which to a large extent corresponds to the vocabulary of current print media on similar occasions. Thus, the area of the Neretva basin imposes itself as a multilayered anthropological concept, a multi-semantic ecologically and socially constituted reality, within which history functions as a valuable source of knowledge pliable to contemporary usage.

  4. Observational and numerical particle tracking to examine sediment dynamics in a Mississippi River delta diversion

    NASA Astrophysics Data System (ADS)

    Allison, Mead A.; Yuill, Brendan T.; Meselhe, Ehab A.; Marsh, Jonathan K.; Kolker, Alexander S.; Ameen, Alexander D.

    2017-07-01

    River diversions may serve as useful restoration tools along coastal deltas experiencing land loss due to high rates of relative sea-level rise and the disruption of natural sediment supply. Diversions mitigate land loss by serving as new sediment sources for land building areas in basins proximal to river channels. However, because of the paucity of active diversions, little is known about how diversion receiving-basins evacuate or retain the sediment required to build new land. This study uses observational and numerical particle tracking to investigate the behavior of riverine sand and silt as it enters and passes through the West Bay diversion receiving-basin located on the lowermost Mississippi River delta, USA. Fluorescent sediment tracer was deployed and tracked within the bed sediment over a five-month period to identify locations of sediment deposition in the receiving-basin and nearby river channel. A computational fluid dynamics model with a Lagrangian sediment transport module was employed to predict selective pathways for riverine flow and sand and silt particles through the receiving-basin. Observations of the fluorescent tracer provides snapshots of the integrated sediment response to the full range of drivers in the natural system; the numerical model results offer a continuous map of sediment advection vectors through the receiving basin in response to river-generated currents. Together, these methods provide insight into local and basin-wide values of sediment retention as influenced by grain size, transport time, and basin morphology. Results show that after two weeks of low Mississippi River discharge, basin silt retention was approximately 60% but was reduced to 4% at the conclusion of the study. Riverine sand retention was approximately near 100% at two weeks and 40% over the study period. Modeled sediment storage was predicted to be greatest at the margins of the primary basin transport pathway; this matched the observed dynamics of the silt

  5. Estimating suspended sediment loads in the Pearl River Delta region using sediment rating curves

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Wei, Xiaoyan; Jinhai, Zheng; Yuliang, Zhu; Zhang, Yanjing

    2012-04-01

    In this study, sediment rating curves are employed to study the variations in relationships between water discharge and suspended sediment concentration based on the recent 50 years of monthly data set in the three major rivers of the Pearl River Delta. Results show that sediment rating parameters vary with time. The lowest rating coefficient, ln(a), and the highest rating exponent, b, mostly occur in the 1980s, indicating that sediment transport reached its peak in this decade at the same level as water discharge. This upward shift of sediment load is probably caused by exacerbated karst rocky desertification in the upper reaches of the Pearl River. However, since the beginning of the 1990s sediment loads from the Pearl River to its estuary began to show a dramatically decreasing trend, which is attributed mainly to deposition in the reservoirs, leading to an increase of ln(a) and a decrease of b. Furthermore, the sediment rating curve in 1957 to1970 is applied to estimate potential sediment load (1971 to 2006) in the absence of human influences. It is also estimated quantitatively by the sediment rating curves that in the 1980s, the annual sediment load decreased by 7.59×106 t/yr because of natural factors, while sediment increase induced by human activities was 20.07×106 t/yr, which resulted in an actual increased sediment load of 12.47×106 t/yr compared with the reference level in 1957 to 1970. In the last two decades, the difference between measured and estimated sediment loads became considerable, and the annual deficit sharply increased to 26.80×106 t/yr in the 1990s, and 50.46×106 t/yr in the 2000s, indicating that human activities, mainly referring to dam and reservoir construction, play a dominant role in the decrease of sediment load. The decrease in sediment supply from the Pearl River should be paid special attention because it may cause serious impacts on the river delta and the coastal ocean.

  6. Decoupled Changes in Western Niger Delta Primary Productivity and Niger River Discharge Across the Last Deglacial

    NASA Astrophysics Data System (ADS)

    Parker, A. O.; Schmidt, M. W.; Slowey, N. C.; Jobe, Z. R.; Marcantonio, F.

    2014-12-01

    Abrupt droughts in West Africa impart significant socio-economic impacts on the developing countries of this region, and yet a comprehensive understanding of the causes and duration of such droughts remains elusive. Much of the summertime rainfall associated with the West African Monsoon (WAM) falls within the Niger River basin and eventually drains into the eastern Gulf of Guinea, contributing to the low sea-surface salinity of this region. Of the limited number of studies that reconstruct Gulf of Guinea salinity through the deglacial, the most comprehensive of those is located ~ 400 km east of the Niger delta and may not be solely influenced by WAM runoff. Here, we present XRF and foraminiferal trace metal data from two new cores located less than 100 km from the Western Niger Delta. Radiocarbon dating of cores Grand 21 (4.72oN, 4.48oE) and Fan 17 (4.81oN, 4.41oE) produced near linear sedimentation rates of 20 cm/kyr and 15 cm/kyr respectively. Elemental sediment compositions from XRF core scanning reveal an abrupt 50% increase in SiO2 between 17-15 ka during Heinrich Event 1. This increase, coeval with increases of CaCO3 (+12%) content and Ba/Ti ratios suggests a large increase in primary productivity during H1. Values then decrease at the onset of the Bolling-Allerod (~14.6 kyr) until a similar, albeit smaller increase is recorded during the Younger Dryas beginning at 12.7 kyr. In contrast, FeO2 and TiO2 are thought to be a proxies of Niger River discharge strength and suggest a more gradual change in riverine discharge across the deglacial that is most likely driven by precession. These proxies suggest Niger River runoff was low from the LGM through Heinrich 1, gradually increasing around 13 ka. FeO2 and TiO2 values then peak between 11.5-7.5 kyr, consistent with the African Humid Period, before gradually decreasing through the mid-late Holocene. This deglacial pattern of riverine input is markedly different from previous reconstructions of WAM variability and

  7. Analyzing Economic Spatial-Temporal Disparities at County Level in Yangtze River Delta Based on ESDA-GIS

    NASA Astrophysics Data System (ADS)

    Yang, He; Liu, Jin-Ping; Wang, Tao

    Regional economic disparities have been a hot topic in recent academic world. This paper explores the feasibility of coefficient of variance (CV) and exploratory spatial data analysis (ESDA) in investigating the spatial dynamics of regional disparities at county level in Yangtze River Delta by analyzing per capita GDP data from 1999 to 2008. Empirical results show that the overall spatial disparities of regional economy in Yangtze River Delta have been increasing throughout the study period. The polarization effect is beyond its spread effect, which indicates the spatial heterogeneity of the whole regional economy into two different clubs through the process of cumulative causation.

  8. Enhancing mud supply from the Lower Missouri River to the Mississippi River Delta USA: Dam bypassing and coastal restoration

    NASA Astrophysics Data System (ADS)

    Kemp, G. Paul; Day, John W.; Rogers, J. David; Giosan, Liviu; Peyronnin, Natalie

    2016-12-01

    Sand transport to the Mississippi River Delta (MRD) remains sufficient to build wetlands in shallow, sheltered coastal bays fed by engineered diversions on the Mississippi River (MR) and its Atchafalaya River (AR) distributary. But suspended mud (silt & clay) flux to the coast has dropped from a mean of 390 Mt y-1 in the early 1950s, to 100 Mt y-1 since 1970. This fine-grained sediment travels deeper into receiving estuarine basins and plays a critical role in sustaining existing marshes. Virtually all of the 300 Mt y-1 of missing mud once flowed from the Missouri River (MOR) Basin before nearly 100 dams were built as part of the Pick-Sloan water development project. About 100 Mt y-1 is now intercepted by main-stem Upper MOR dams closed in 1953. But the remaining 200 Mt y-1 is trapped by impoundments built on tributaries to the Lower MOR in the 1950s and 1960s. Sediment flux during the post-dam high MOR discharge years of 1973, 1993 and 2011 approached pre-dam levels when tributaries to the Lower MOR, including the Platte and Kansas Rivers, contributed to flood flows. West bank tributaries drain a vast, arid part of the Great Plains, while those entering from the east bank traverse the lowlands of the MOR floodplain. Both provinces are dominated by highly erodible loess soils. Staunching the continued decline in MR fine-grained sediment flux has assumed greater importance now that engineered diversions are being built to reconnect the Lowermost MR to the MRD. Tributary dam bypassing in the Lower MOR basin could increase mud supply to the MRD by 100-200 Mt y-1 within 1-2 decades. Such emergency measures to save the MRD are compatible with objectives of the Missouri River Restoration and Platte River Recovery Programs to restore MOR riparian habitat for endangered species. Rapid mobilization to shunt fine-grained sediments past as many as 50 Lower MOR tributary dams in several U.S. states will undoubtedly require as much regional coordination and funding in the 21st

  9. Hydro-environmental status and soil management of the River Nile Delta, Egypt

    NASA Astrophysics Data System (ADS)

    Elewa, H. H.; El Nahry, A. H.

    2009-04-01

    The sea level rise has its own-bearing on the coastal recession and hydro-environmental degradation of the River Nile Delta. Attempts are made here to use remote sensing to detect the coastal recession in some selected parts and delineating the chemistry of groundwater aquifers and surface water, which lie along south-mid-northern and coastal zone of the Nile Delta. Eight water samples from groundwater monitoring wells and 13 water samples from surface water were collected and analyzed for various hydrochemical parameters. The groundwater samples are classified into five hydrochemical facies on Hill-Piper trilinear diagram based on the dominance of different cations and anions: facies 1: Ca-Mg-Na-HCO3-Cl-SO4 type I; facies 2: Na-Cl-HCO3 type II; facies 3: Na-Ca-Mg-Cl type III, facies 4: Ca-Na-Mg-Cl-HCO3 type IV and facies 5: Na-Mg-Cl type V. The hydrochemical facies showed that the majority of samples were enriched in sodium, bicarbonate and chloride types and, which reflected that the sea water and tidal channel play a major role in controlling the groundwater chemical composition in the Quaternary shallow aquifers, with a severe degradation going north of Nile Delta. Also, the relationship between the dissolved chloride (Cl, mmol/l), as a variable, and other major ion combinations (in mmol/l) were considered as another criterion for chemical classification system. The low and medium chloride groundwater occurs in southern and mid Nile Delta (Classes A and B), whereas the high and very high chloride (classes D and C) almost covers the northern parts of the Nile Delta indicating the severe effect of sea water intrusion. Other facets of hydro-environmental degradation are reflected through monitoring the soil degradation process within the last two decades in the northern part of Nile Delta. Land degradation was assessed by adopting new approach through the integration of GLASOD/FAO approach and Remote Sensing/GIS techniques. The main types of human induced soil

  10. Outbreaks of the Brown Planthopper Nilaparvata lugens (Stål) in the Yangtze River Delta: Immigration or Local Reproduction?

    PubMed Central

    Zhai, Bao-Ping; Lu, Ming-Hong; Liu, Wan-Cai; Zhu, Feng; Wu, Xiang-Wen; Chen, Gui-Hua; Zhang, Xiao-Xi

    2014-01-01

    An effective control strategy for migratory pests is difficult to implement because the cause of infestation (i.e., immigration or local reproduction) is often not established. In particular, the outbreak mechanisms of the brown planthopper, Nilaparvata lugens (Stål), an insect causing massive losses in rice fields in the Yangtze River Delta in China, are frequently unclear. Field surveys of N. lugens were performed in Jiangsu and Zhejiang Provinces in 2008 to 2010 and related historical data from 2003 onwards were collected and analyzed to clarify the cause of these infestations. Results showed that outbreaks of N. lugens in the Yangtze River Delta were mostly associated with an extremely high increase in population. Thus, reproduction rather than immigration from distant sources were the cause of the infestations. Although mass migration occurred late in the season (late August and early September), the source areas of N. lugens catches in the Yangtze River Delta were mainly located in nearby areas, including the Yangtze River Delta itself, Anhui and northern Jiangxi Provinces. These regions collectively form the lower-middle reaches of the Yangtze River, and the late migration can thus be considered as an internal bioflow within one population. PMID:24558459

  11. Quantitative tolerance values for common stream benthic macroinvertebrates in the Yangtze River Delta, Eastern China.

    PubMed

    Qin, Chun-Yan; Zhou, Jin; Cao, Yong; Zhang, Yong; Hughes, Robert M; Wang, Bei-Xin

    2014-09-01

    Aquatic organisms' tolerance to water pollution is widely used to monitor and assess freshwater ecosystem health. Tolerance values (TVs) estimated based on statistical analyses of species-environment relationships are more objective than those assigned by expert opinion. Region-specific TVs are the basis for developing accurate bioassessment metrics particularly in developing countries, where both aquatic biota and their responses to human disturbances have been poorly documented. We used principal component analysis to derive a synthetic gradient for four stressor variables (total nitrogen, total phosphorus, dissolved oxygen, and % silt) based on 286 sampling sites in the Taihu Lake and Qiantang River basins (Yangtze River Delta), China. We used the scores of taxa on the first principal component (PC1), which explained 49.8% of the variance, to estimate the tolerance values (TV(r)) of 163 macroinvertebrates taxa that were collected from at least 20 sites, 81 of which were not included in the Hilsenhoff TV lists (TV(h)) of 1987. All estimates were scaled into the range of 1-10 as in TV(h). Of all the taxa with different TVs, 46.3% of TV(r) were lower and 52.4% were higher than TV(h). TV(r) were significantly (p < 0.01, Fig. 2), but weakly (r(2) = 0.34), correlated with TVh. Seven biotic metrics based on TVr were more strongly correlated with the main stressors and were more effective at discriminating references sites from impacted sites than those based on TV(h). Our results highlight the importance of developing region-specific TVs for macroinvertebrate-based bioassessment and to facilitate assessment of streams in China, particularly in the Yangtze River Delta.

  12. Evolution and structure of a coastal squirt off the Mississippi River delta: Northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Walker, Nan D.; Huh, Oscar K.; Rouse, Lawrence J.; Murray, Stephen P.

    1996-09-01

    In early October 1992, satellite-derived sea surface temperature data revealed a 200 km long and 10- to 30-km-wide stream of cool water flowing toward the southwest from the Mississippi River delta region. Satellite imagery and in situ measurements have enabled a detailed study of the squirt's kinematics and subsurface characteristics over a 2-week period. In its early stages, the squirt appeared as a narrow, high-speed (>75 cm/s) jet of water which flowed westward over the Mississippi Canyon, forcing a semi-submersible drilling rig to suspend operations from October 2 to 4. After crossing back onto the shelf, the squirt spread laterally, yielding a mushroom-shaped feature, 75 km wide, which consisted of counter-rotating vortices. Northeasterly wind forcing (averaging 10-15 m/s) and water level setup east of the delta appear to have been the primary mechanisms for evolution of the high-velocity currents. Satellite and in situ measurements demonstrate that the dipole eddy was comprised of a cool, low-salinity, low-density water mass at least 26 m deep in the center and 16 m deep along its margins. This event demonstrates that strong northeasterly winds over the northern Gulf of Mexico can initiate along-shelf and off-shelf flows of cooler coastal waters, contributing significantly to seasonal cooling and freshening of the continental shelf and to shelf/slope exchanges of water. During this event, approximately 100 km3 of inner shelf and river water was transported off the continental shelf, a volume equivalent to 17% of the average annual discharge of the Mississippi and Atchafalaya Rivers.

  13. Methane concentrations and oxidation in nearshore waters of the Lena River Delta

    NASA Astrophysics Data System (ADS)

    Joye, S. B.; Samarkin, V.; Shakhova, N. E.; Semiletov, I. P.

    2014-12-01

    The Arctic is warming dramatically, with potentially catastrophic impacts on climate change through rapid mobilization of labile carbon reservoirs sequestered presently in permafrost. Increasingly, Arctic feedbacks are recognized as key contributors to climate change, including cycles associated with the powerful greenhouse gas methane, whose atmospheric concentration has more than doubled since the pre-industrial epoch. Sustained methane release to the atmosphere from thawing Arctic permafrost and delivery to the coastal ocean through groundwater or riverine discharge or expulsion from the seabed is a positive and likely highly significant feedback to climate warming. Microbially-mediated methane oxidation provides a key sink and effective biofilter that can limit methane fluxes from coastal environments to the atmosphere. We examined methane dynamics on the East Siberian Arctic Shelf by determining concentrations and oxidation rates at a series of stations near the Lena River Delta and moving offshore. Methane concentrations and oxidation rates were highly elevated in and near the river mouth compared to offshore waters, except when the offshore waters were impacted by seabed methane seepage. The regulation of methane oxidation in Arctic waters appears two-fold: first, rates are strongly related to methane availability and second, in the presence of methane, nutrient availability strongly regulates methane consumption. Along the Lena river delta, elevated concentrations of both nutrients and methane create ideal conditions to support high rates of pelagic methanotrophy. Offshore, where nutrient concentrations are lower and more limiting, methane oxidation rates are considerably lower. These data suggest that, at present, nearshore waters are fairly efficient methane sinks while in offshore waters, pelagic methanotrophy is inefficient, allowing methane to escape to the atmosphere.

  14. Characterization of elements in the irrigated water in the Changjiang River Delta Region

    NASA Astrophysics Data System (ADS)

    Yuan, X.

    2009-12-01

    Introduction The river networks are dominated in the Changjiang River Delta Region. Most agricultural areas are irrigated with these small rivers. Rivers also receive the effluence from point and nonpoint sources. It is significative to recognize the distribution and potential hazard of irrigated water in this populated area. Study area and sampling The study area covers about 1.1×106 km2, including 16 cities from the northside of Changjiang River in Jiangsu to the middle Zhejiang. Ninety samples were collected in rural irrigated rivers. And the major cations, anions and trace elements of water were determined. Results We observe that Ca2+ is obviously higher in cations, and Cl-, SO42- higher in anions. The southern Jiangsu and coast of middle Zhejiang show high Na+, the hill area of southern Jiangsu and northern Zhejiang show high Ca2+. HCO3- is relatively uniform distributed in these areas. The high SO42- in a few samples occour in industrial spots of Jiangsu and Zhejiang. Cl- increases in waters along the coast. NO3- fluctuates and disperses in samples. Trace elements in waters are unevenly distributed. The two sides of Changjiang River have high As and Cr. Mercury is higher in southern Jiangsu than in other areas. Iron shows an enrichment in the middle Zhejiang. Compared with the background concentrations of trace elements in the lower Changjiang River, Pb, Cu and Cd are much higher in middle Zhejiang than in other areas. But Zn of most samples are lower than the background value.Cu is associated with organic matter in water. Dicussion The research area consists of hill, plain and coast, where farms, industries and houses distribute. In the hilly area of carbonate-dominated, the waters show high Ca2+ and HCO3-, rivers have high Cl- in vicinity of sea. NO3- and SO42- are strongly influenced by anthopogenic input. NO3- shows a high concentration in areas of fertilizer usage. SO42- increases in areas with a lot of industrial discharge. The distribution of trace

  15. Financial Impacts of Priority Swine Diseases to Pig Farmers in Red River and Mekong River Delta, Vietnam.

    PubMed

    Pham, H T T; Antoine-Moussiaux, N; Grosbois, V; Moula, N; Truong, B D; Phan, T D; Vu, T D; Trinh, T Q; Vu, C C; Rukkwamsuk, T; Peyre, M

    2017-08-01

    A study was conducted between May 2013 and August 2014 in three provinces of Vietnam to investigate financial impacts of swine diseases in pig holdings in 2010-2013. The aim of the study was to quantify the costs of swine diseases at producer level in order to understand swine disease priority for monitoring at local level. Financial impacts of porcine reproductive and respiratory syndrome (PRRS), foot and mouth disease (FMD), and epidemic diarrhoea were assessed for 162 pig holders in two Red River Delta provinces and in one Mekong River Delta province, using data on pig production and swine disease outbreaks at farms. Losses incurred by swine diseases were estimated, including direct losses due to mortality (100% market value of pig before disease onset) and morbidity (abortion, delay of finishing stage), and indirect losses due to control costs (treatment, improving biosecurity and emergency vaccination) and revenue foregone (lower price in case of emergency selling). Financial impacts of swine diseases were expressed as percentage of gross margin of pig holding. The gross margin varied between pig farming groups (P < 0.0001) in the following order: large farm (USD 18 846), fattening farm (USD 7014) and smallholder (USD 2350). The losses per pig holding due to PRRS were the highest: 41% of gross margin for large farm, 38% for fattening farm and 63% for smallholder. Cost incurred by FMD was lower with 19%, 25% and 32% of gross margin of pig holding in large farm, fattening farm and smallholder, respectively. The cost of epidemic diarrhoea was the lowest compared to losses due to PRRS and FMD and accounted for around 10% of gross margin of pig holding in the three pig farming groups. These estimates provided critical elements on swine disease priorities to better inform surveillance and control at both national and local level. © 2016 Blackwell Verlag GmbH.

  16. Evolution of the Yellow River Delta and its relationship with runoff and sediment load from 1983 to 2011

    NASA Astrophysics Data System (ADS)

    Kong, Dongxian; Miao, Chiyuan; Borthwick, Alistair G. L.; Duan, Qingyun; Liu, Hao; Sun, Qiaohong; Ye, Aizhong; Di, Zhenhua; Gong, Wei

    2015-01-01

    Long-term data from a hydrological monitoring station and remotely-sensed satellite images were used to explore the effects of runoff and suspended sediment load on evolution of the Yellow River Delta (YRD) from 1983 to 2011. During this period, an average runoff of 18 × 109 m3 yr-1 and an average sediment load of 341 × 106 t yr-1 flowed through the delta lobes into the sea. The runoff and sediment load exhibited downward trends with time, along with large inter-annual fluctuations. Three stages were evident in the data. From 1983 to the late 1990s, the Yellow River experienced progressively severe droughts which reduced both runoff and sediment load to its delta lobe. The delta nevertheless grew to a peak area of about 3950 km2 in 2000. From 2000 to 2003, the YRD area decreased. Meanwhile, the operation of the dam at Xiaolangdi and changes in water consumption driven by a new regulatory framework helped stabilize the runoff. Although the sediment load continued to decline, partly due to sediment check dams along the middle Yellow River and the reduced sediment carrying capacity of the river, the YRD area nevertheless increased between 2003 and 2011. The variations in runoff and sediment load directly influenced changes to the plan-form area, shoreline migration, and morphology of the YRD. From 1983 to 2011, the net land area of the delta increased by 248 km2, its coastline extended by 36.45 km, and its shape became increasingly irregular due to the emergence of its delta lobes. In 1996, an artificial diversion altered the position of the main delta lobe from Qingshuigou to Qing 8. A stepwise multiple regression analysis indicated that the YRD would have required average sediment loads of about 441 × 106 t yr-1 before 1996 and 159 × 106 t yr-1 after 1996 to maintain equilibrium.

  17. Heavy metals in oysters, mussels and clams collected from coastal sites along the Pearl River Delta, South China.

    PubMed

    Fang, Zhan-Qiang; Cheung, R Y H; Wong, M H

    2003-01-01

    Concentrations of 8 heavy metals: cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), chromium (Cr), antimony (Sb) and tin (Sn) were examined in 3 species of bivalves ( Perna viridis, Crassostrea rivularis and Ruditapes philippinarum) collected from 25 sites along the Pearl River Delta coastal waters in the South China Sea from July to August 1996. In general, Cd, Cu, Zn and Sn concentrations in the three bivalve species collected from the Estuarine Zone were significantly higher than those collected from the Western and Eastern Zones of the Pearl River Delta, which are related to the existence of various anthropogenic activities in the catchment of the Pearl River Delta. The Western Estuarine Zone is mainly impacted hy Cr, Ni and Cu contamination. In Victoria Harbor, heavy metal contamination is mainly due to Cu and Pb, Cd, Cu and Zn concentrations in oysters were significantly higher than those in mussels and clams. This could be explained by the fact that oysters live mainly in the Estuarine Zone of the Pearl River Delta which receives most of the polluting discharges from the catchment of the Delta. During turbid condition, heavy metals( soluble or adsorbed on suspended particulates) discharged from the Delta are filtered from the water column and subsequently accumulated into the soft body tissues of oysters. Heavy metal concentrations in the three bivalve species were compared with the maximum permissible levels of heavy metals in seafood regulated by the Public Health and Municipal Services Ordinance, Laws of Hong Kong, and it was revealed that Cd and Cr concentrations in the three bivalve species exceeded the upper limits. At certain hotspots in the Delta, the maximum acceptable daily load for Cd was also exceeded.

  18. The Science and Policy of the First Environmental Flows to the Colorado River Delta

    NASA Astrophysics Data System (ADS)

    Flessa, K. W.; Kendy, E.; Schlatter, K.

    2014-12-01

    The first transboundary flow of water for the environment was delivered to the Colorado River Delta in spring of 2014. This engineered mini-spring flood of 130 million cubic meters (105,000 acre-feet) was implemented as part of Minute 319, an addition to the 1944 U.S.-Mexico Water Treaty. Minute 319 is a temporary agreement, expiring in 2017. Teams of scientists from government agencies, universities, and environmental NGOs from both the U.S. and Mexico are measuring the surface flow rates, inundation, ground water recharge, ground water levels and subsurface flows, geomorphic change, recruitment, survival and health of vegetation, and avian response to the environmental flow. Monitoring includes on-the-ground observations and measurements and remote sensing. Surface water from the pulse flow reached restoration sites, prompted germination of both native and non-native vegetation, recharged groundwater and reached the Gulf of California - the first reconnection of the Colorado River and the sea in 16 years. People in local communities joyously welcomed the return of the river; extensive media coverage was overwhelmingly positive - despite widespread drought in the West. After about ten weeks, most of the pulse flow had infiltrated the subsurface, ponded in a few cut-off meanders, or run to the sea. The river no longer flows. Monitoring of seedling survival, groundwater, vegetation and wildlife will continue through 2017. Results of this landscape-scale experiment will play a role in negotiations to renew the agreement, help model and design future flows and guide the efficient use of water for restoration in semi-arid river systems.

  19. Seasonal changes in particulate and dissolved organic matter composition and quality in the Lena River Delta

    NASA Astrophysics Data System (ADS)

    Mollenhauer, G.; Winterfeld, M.; Hefter, J.; Bodenstab, L.; Morgenstern, A.; Eulenburg, A.; Heim, B.; Koch, B.; Schefuss, E.; Moerth, C. M.; Rethemeyer, J.

    2016-12-01

    Arctic rivers are known to export large quantities of carbon by discharge of dissolved and particulate organic carbon (DOC, POC), and in a warming and progressively moister Arctic, these exports may increase resulting in a reduction of arctic continental carbon stocks. These rivers have highly variable discharge rates with a pronounced maximum during the spring freshet associated with highest concentrations of DOC and POC. Most studies investigating the isotopic composition and quality of carbon exported by Arctic rivers rely on samples taken in summer during base flow, which is due to the logistical challenges associated with sampling in the remote Arctic permafrost regions. Here we present a record of δ13C and ∆14C of DOC and POC collected between late May during the freshet and late August 2014 in the Lena River Delta. POC ∆14C shows an initial trend towards older values in the spring samples, which is reversed in summer, associated with a shift towards more depleted δ13C values. We interpret this aging trend as reflecting progressive thawing throughout the ice-free season, resulting in mobilization of progressively older carbon from deeper thawed layers. The summer reversal indicates admixture of aquatic organic matter. DOC ∆14C, in contrast, remains at relatively modern levels with rather constant δ13C values throughout the sampling period. We furthermore analysed the biomarker composition of Lena Delta particulate OM collected in spring and summer. From spring to summer, we observe trends in abundance of individual leaf-wax derived biomarkers indicating higher abundance of algal biomass in the summer particles. Trends in soil microbial biomarkers and compound-specific δD of leaf-wax lipids suggest a shift in sources towards higher contributions from the southern catchment in summer. DOC composition investigated with FT-ICR-MS changes from spring with higher abundances of compounds with high H/C and low O/C ratios to late summer, when fewer compounds

  20. 2010-2015 Juvenile fish ecology in the Nisqually River Delta and Nisqually Reach Aquatic Reserve

    USGS Publications Warehouse

    Hodgson, Sayre; Ellings, Christopher S.; Rubin, Steve P.; Hayes, Michael C.; Duval, Walker; Grossman, Eric E.

    2017-01-01

    The return of tidal inundation to over 750 acres of the U. S. Fish and Wildlife Service Billy Frank Jr. Nisqually National Wildlife Refuge (NNWR) in fall of 2009 was the crowning moment in the effort to protect and restore the Nisqually Delta. The Nisqually NWR project complemented three earlier restoration projects completed by the Nisqually Indian Tribe (Tribe) on tribal property to restore over 900 acres of the estuary, representing the largest estuary restoration project in the Pacific Northwest and one of the most significant advances to date towards the recovery of Puget Sound (USFWS 2005). In 2011 the Washington Department of Natural Resources (WADNR established the over 14000 acre Nisqually Reach Aquatic Reserve (Reserve), complementing the protection and restoration successes in the Nisqually Delta. The Reserve includes all state-owned aquatic lands around Anderson, Ketron and Eagle islands and part of McNeil Island (Figure 1, WDNR 2011). The Reserve also includes a diverse assemblage of nearshore and offshore habitats important to resident and migratory fish including federal endangered species act listed fish like Chinook salmon (Oncorynchus tshawytscha) and steelhead (O. mykiss). Studies in the Nisqually Estuary (Ellings and Hodgson 2007, David et al. 2014, Ellings et al. 2016) and South Puget Sound (Duffy 2003) have summarized fish use of the area. However, the fish ecology of the reserve had not been systematically surveyed. The Tribe, U.S. Geological Survey (USGS), NNWR, Nisqually River Foundation (NRF), and others are currently conducting a multi-year, interdisciplinary, hypothesis-based research and monitoring study investigating the impact of delta restoration on estuarine processes, habitat structures, and functions. Our interdisciplinary monitoring framework enables us to link key estuarine processes with habitat development and biological response at multiple scales across the restored footprint, reference marshes, and throughout the Nisqually

  1. Greenhouse gas emissions of different land uses in the delta region of Red River, Vietnam

    NASA Astrophysics Data System (ADS)

    Zhou, Minghua; Ha, Thu; An, Ngo The; Brüggemann, Nicolas

    2017-04-01

    Agricultural activities are responsible for up to a third of total anthropogenic GHG emissions. The subtropical/tropical delta areas of the large rivers in Southeast Asia are long-term history agricultural regions in the world. However, due to lack of field measurements, the estimation of the contribution of agro-ecosystems in the subtropical/tropical delta areas to global greenhouse gas emissions remains largely uncertain. Here, we conducted field experiments since January 2016 to quantify greenhouse gases (CO2, CH4 and N2O) emissions from four agricultural land uses of annual rice-rice, rice-vegetable, continuous vegetable system and fish pond in Red River delta region of Vietnam by using the transparent static chamber-gas chromatography technique. Higher N2O emissions were observed in the rice-vegetable and continuous vegetable systems, while lower N2O emissions were observed in the rice-rice and find pond systems. Compared to rice-rice system the cumulative N2O fluxes were on average twenty-fold higher in the rice-vegetable and continuous vegetable systems but significantly lower (75%) in the fish pond. Overall the net CO2 sinks were observed in the rice-rice system while other three land uses of rice-vegetable, continuous vegetable and fish pond acted as the net CO2 sources. The rice-rice and fish pond showed net CH4 emissions while variations of CH4 emissions (i.e. shifting between sources and sinks) along variations of soil moisture and temperature were observed in rice-vegetable and continuous vegetable systems. Compared to rice-rice system, the cumulative CH4 fluxes were significantly decreased by 100% for continuous vegetable system, 94% for rice-vegetable system and 89% for fish pond. Overall, the data suggest that conversion of traditional rice-rice paddy system to rice-vegetable, continuous vegetable system and find pond, which are currently undergoing driven by the economical requests and environmental changes (e.g., salinity intrusion) in this delta

  2. Large-river delta-front estuaries as natural "recorders" of global environmental change.

    PubMed

    Bianchi, Thomas S; Allison, Mead A

    2009-05-19

    Large-river delta-front estuaries (LDE) are important interfaces between continents and the oceans for material fluxes that have a global impact on marine biogeochemistry. In this article, we propose that more emphasis should be placed on LDE in future global climate change research. We will use some of the most anthropogenically altered LDE systems in the world, the Mississippi/Atchafalaya River and the Chinese rivers that enter the Yellow Sea (e.g., Huanghe and Changjiang) as case-studies, to posit that these systems are both "drivers" and "recorders" of natural and anthropogenic environmental change. Specifically, the processes in the LDE can influence ("drive") the flux of particulate and dissolved materials from the continents to the global ocean that can have profound impact on issues such as coastal eutrophication and the development of hypoxic zones. LDE also record in their rapidly accumulating subaerial and subaqueous deltaic sediment deposits environmental changes such as continental-scale trends in climate and land-use in watersheds, frequency and magnitude of cyclonic storms, and sea-level change. The processes that control the transport and transformation of carbon in the active LDE and in the deltaic sediment deposit are also essential to our understanding of carbon sequestration and exchange with the world ocean--an important objective in global change research. U.S. efforts in global change science including the vital role of deltaic systems are emphasized in the North American Carbon Plan (www.carboncyclescience.gov).

  3. A magnetic record of heavy metal pollution in the Yangtze River subaqueous delta.

    PubMed

    Dong, Chenyin; Zhang, Weiguo; Ma, Honglei; Feng, Huan; Lu, Honghua; Dong, Yan; Yu, Lizhong

    2014-04-01

    The rapid industrial development in the Yangtze River watershed over the last several decades has drawn great attention with respect to heavy metal pollution to the Yangtze River estuary and nearby coastal areas. In this study, a 236 cm long sediment core was retrieved from the Yangtze River subaqueous delta (122°36' E, 31°00' N) in 2008 and analyzed for magnetic properties and geochemical compositions to investigate heavy metal pollution history. The activity of (137)Cs peaked at depth 140 cm, with a broad plateau between 120 cm and 140 cm, suggesting an average sedimentation rate of 3.11 cm yr(-1) for the upper 140 cm layer. Magnetic susceptibility (χ), saturation isothermal remanent magnetization (SIRM), anhysteretic remanent magnetization (χARM) and heavy metal enrichment factors (EF) all showed an upward increase trend above depth 140 cm, suggesting that increased ferrimagnetic mineral concentration was accompanied by heavy metal enrichment in the sediment. Geochemical and granolumetric analyses showed that sediment sources and particle sizes played minor roles in the variations of magnetic properties. The effect of diagenesis, which can lead to the selective removal of magnetic minerals, was noticeable in the lower part of the core (140-236 cm). Co-variation between magnetic properties (χ, SIRM and χARM) and EF of Cu and Pb suggests that the elevated ferrimagnetic mineral concentration can be used as an indicator of heavy metal pollution in the reconstruction of environmental changes in estuarine and coastal settings.

  4. PCB contamination in soils of the Pearl River Delta, South China: levels, sources, and potential risks.

    PubMed

    Zhang, Haibo; Luo, Yongming; Teng, Ying; Wan, Hongfu

    2013-08-01

    Polychlorinated biphenyls (PCBs) contamination in tropical and sub-tropical areas and the associated risks have attracted great concern. A total of 69 samples representing five distinct land types were collected to assess PCB concentrations in the Pearl River Delta (PRD), South China, including spatial distributions in soils of the area, the probable anthropogenic sources, and related potential risks. PCBs concentrations in soils of the PRD ranged from 0.3 to 202 ng g(-1). More severe PCBs contamination was presented in the western part than in the eastern part of the PRD region. The PCBs were dominated by low-chlorinated biphenyls; however, the proportion of higher-chlorinated biphenyls was elevated with the influence of industrial activities. Principal component analysis indicated that PCBs contamination in soils of the PRD region was mainly associated with 1#PCBs, while 2#PCB and e-waste emission in South China also accounted for it partly, especially to the industrial activity severely impacted areas. Toxic equivalent (TEQ) of the dioxin-like PCBs in the soils indicated that higher risk of PCB contamination was presented in the Dongjiang River Valley (55 ng TEQ kg(-1), on average) than in the Xijiang River Valley, and were mostly contributed by the congener of PCB126.

  5. Distribution of organophosphorus flame retardants in sediments from the Pearl River Delta in South China.

    PubMed

    Tan, Xiao-Xin; Luo, Xiao-Jun; Zheng, Xiao-Bo; Li, Zong-Rui; Sun, Run-Xia; Mai, Bi-Xian

    2016-02-15

    Twelve organophosphorus flame retardants (PFRs) were identified in the sediments and the sediment core collected from the rivers and the estuary in the Pearl River Delta, with the aim of investigating their spatial and vertical distributions. The concentrations of PFRs ranged from 8.3 to 470 ng/g dry weight with high levels of PFRs in the urban area and the e-waste recycling region. Generally, TPhP, TCPP, TEHP, TCEP, and TBEP were the dominant compounds of the PFRs, the composition of which varied across the different regions, reflecting the different sources of PFRs. In the estuary, the PFRs mainly derived from the Xijiang River and the Shunde sections. Increased concentrations of halogen-containing PFRs have been observed in the upper layers of the sediment core. Conversely, relatively high concentrations of halogen-free PFRs were observed in the lower layers of the sediment core, indicating different usage patterns or environmental behaviors between the halogen and the non-halogen PFRs in the study area.

  6. A coupling simulation based on a hydrodynamics and water quality model of the Pearl River Delta, China

    NASA Astrophysics Data System (ADS)

    Zhou, Nianqing; Westrich, Bernhard; Jiang, Simin; Wang, Yan

    2011-01-01

    SummaryThe rapid economic development has caused heavy pollution in the Pearl River Delta Region (PRDR) and neighboring regions. In order to investigate the polluted characteristics, a coupled modelling approach has been deployed and the study area in the Pear River Delta is divided into two modelling systems: a river network that is simulated by a 1D hydrodynamic and water quality model, and an estuary that is modelled by a 3D model. The 1D river network model is coupled with the 3D estuary model based on the mass conservation criteria. The hydrodynamic (HD) model is based on 1D hydrostatic shallow water equations, and is solved by the Alternating Direction Implicit Approach. The water quality (WQ) model component is based on advection-diffusion equations. Some physical and bio-chemical processes are included in the WQ model to address the water pollution problems by different pollution substances, in particular, to the chemical oxygen demand (COD). The water quality data of the main rivers from 2004 to 2007 were collected, processed and evaluated. Because no detailed water quality data in the river is available, the COD source pollution intensity in the water quality model is taking the pollutant load from the confluence of the main five outlets of the Pearl River Estuary (PRE) for 1996-2007 as surrogate. The results show that the pollutants from the PRDR have a large impact on the quality of the Hong Kong seawater and much more serious in the wet season with high river discharge. An insight of the flow and transportation mechanism in the river and estuary system has been obtained through the paper, and a reliable basis to control water pollution of the Pearl River Delta is provided in this paper.

  7. Estuarine science and decision-support tools to restore Puget Sound delta and estuarine ecosystems: The Skagit River Delta

    NASA Astrophysics Data System (ADS)

    Grossman, E. E.; Rosenbauer, R. J.; Takesue, R. K.; Gelfenbaum, G.; Reisenbichler, R.; Paulson, A.; Sexton, N. R.; Labiosa, B.; Beamer, E. M.; Hood, G.; Wyllie-Echeverria, S.

    2006-12-01

    Historic land use, ongoing resource extraction, and population expansion throughout Puget Sound have scientists and managers rapidly seeking effective restoration strategies to recover salmon (a cultural icon, as well as, a host of other endangered species and threatened habitats. Of principal concern is the reduction of salmon (Oncorhynchus spp.) and diminished carrying capacity of critical habitat in deltaic regions. Delta habitats, essential to salmon survival, have lost 70 to 80 % area since ~1850 and are now adjusting to a new suite of environmental changes associated with land use practices, including wetland restoration, and regional climate change. The USGS Coastal Habitats in Puget Sound Project, in collaboration with partners from the Skagit River System Cooperative, University of Washington, and other federal, state, and local agencies, is integrating geologic, biologic, hydrologic, and socioeconomic information to quantify changes in the distribution and function of deltaic-estuarine nearshore habitats and better predict "possible futures". We are combining detailed geologic and geochemical analyses of sedimentary environments, plant biomarkers (n-alkanes, PAHs, fatty-acids, and sterols), and compound-specific isotopes to estimate historic habitat coverage, eelgrass (Zostera marina) abundance and modern characteristics of nutrient cycling. Hydrologic and sediment transport processes are being measured to characterize physical processes shaping modern habitats including sediment transport and freshwater mixing that control the temporal and spatial pattern of substrate and water column conditions available as habitat. We are using geophysical, remote sensing, and modeling techniques to determine large-scale coastal morphologic and land-use change and characterize how alteration of physical, hydrologic, and biogeochemical processes influence the dynamics of freshwater mixing, and sediment and nutrient transport in the nearshore. To assist restoration

  8. Soil phosphorus forms and profile distributions in the tidal river network region in the Yellow River Delta estuary.

    PubMed

    Yu, Junbao; Qu, Fanzhu; Wu, Huifeng; Meng, Ling; Du, Siyao; Xie, Baohua

    2014-01-01

    Modified Hedley fraction method was used to study the forms and profile distribution in the tidal river network region subjected to rapid deposition and hydrologic disturbance in the Yellow River Delta (YRD) estuary, eastern China. The results showed that the total P (Pt) ranged from 612.1 to 657.8 mg kg(-1). Dilute HCl extractable inorganic P (Pi) was the predominant form in all profiles, both as absolute values and as a percentage of total extracted Pi. The NaOH extractable organic P (Po) was the predominant form of total extracted Po, while Bicarb-Pi and C.HCl-Po were the lowest fractions of total extracted Pi and Po in all the P forms. The Resin-P concentrations were high in the top soil layer and decreased with depth. The Pearson correlation matrix indicated that Resin-P, Bicarb-Pi, NaOH-Pi, and C.HCl-Pi were strongly positively correlated with salinity, TOC, Ca, Al, and Fe but negatively correlated with pH. The significant correlation of any studied form of organic P (Bicarb-Po, NaOH-Po, and C.HCl-Po) with geochemical properties were not observed in the study. Duncan multiple-range test indicated that the P forms and distribution heterogeneity in the profiles could be attributed to the influences of vegetation cover and hydrologic disturbance.

  9. Soil Phosphorus Forms and Profile Distributions in the Tidal River Network Region in the Yellow River Delta Estuary

    PubMed Central

    Yu, Junbao; Qu, Fanzhu; Wu, Huifeng; Meng, Ling; Du, Siyao; Xie, Baohua

    2014-01-01

    Modified Hedley fraction method was used to study the forms and profile distribution in the tidal river network region subjected to rapid deposition and hydrologic disturbance in the Yellow River Delta (YRD) estuary, eastern China. The results showed that the total P (Pt) ranged from 612.1 to 657.8 mg kg−1. Dilute HCl extractable inorganic P (Pi) was the predominant form in all profiles, both as absolute values and as a percentage of total extracted Pi. The NaOH extractable organic P (Po) was the predominant form of total extracted Po, while Bicarb-Pi and C.HCl-Po were the lowest fractions of total extracted Pi and Po in all the P forms. The Resin-P concentrations were high in the top soil layer and decreased with depth. The Pearson correlation matrix indicated that Resin-P, Bicarb-Pi, NaOH-Pi, and C.HCl-Pi were strongly positively correlated with salinity, TOC, Ca, Al, and Fe but negatively correlated with pH. The significant correlation of any studied form of organic P (Bicarb-Po, NaOH-Po, and C.HCl-Po) with geochemical properties were not observed in the study. Duncan multiple-range test indicated that the P forms and distribution heterogeneity in the profiles could be attributed to the influences of vegetation cover and hydrologic disturbance. PMID:24971393

  10. Recent human impacts on the morphological evolution of the Yangtze River delta foreland: A review and new perspectives

    NASA Astrophysics Data System (ADS)

    Du, Jing-Long; Yang, Shi-Lun; Feng, Huan

    2016-11-01

    This paper reviews the morphological change in the Yangtze River delta due to increasing human impacts from three major aspects. The first is the reduction of sediment supply to the ocean due to dam construction, soil conservation, and sand mining within the Yangtze River basin. The reduced sediment supply has decreased the progradation rate of the delta and triggered erosion in the front of the delta. The second impact relates to the reclamation of intertidal wetlands by human activities. Since the 1950s, approximately 1100 km2 of intertidal land has been embanked, resulting in the disappearance of salt marshes and even the entire intertidal zone along some sections of the coastline. The third change in the delta due to human interference is the construction of deep-waterway structures at the mouth bar, which has greatly modified the local hydrodynamics and morphology. Sediment accretion has increased significantly in these areas as a result of sheltering by these deep-waterway structures. This review shows that human activities have severely altered the natural balance among the hydrodynamics and sediment supply, affecting the morphological features of the Yangtze River watershed and delta. Human impacts on the morphological evolution of deltaic coasts in general are becoming an increasingly concern, and more attention should be paid to the management and mitigation of these effects.

  11. Shallow Groundwater Movement in the Skagit River Delta Area, Skagit County, Washington

    USGS Publications Warehouse

    Savoca, Mark E.; Johnson, Kenneth H.; Fasser, Elisabeth T.

    2009-01-01

    Shallow groundwater movement in an area between the lower Skagit River and Puget Sound was characterized by the U.S. Geological Survey to assist Skagit County and the Washington State Department of Ecology with the identification of areas where water withdrawals from existing and new wells could adversely affect streamflow in the Skagit River. The shallow groundwater system consists of alluvial, lahar runout, and recessional outwash deposits composed of sand, gravel, and cobbles, with minor lenses of silt and clay. Upland areas are underlain by glacial till and outwash deposits that show evidence of terrestrial and shallow marine depositional environments. Bedrock exposures are limited to a few upland outcrops in the southwestern part of the study area, and consist of metamorphic, sedimentary, and igneous rocks. Water levels were measured in 47 wells on a quarterly basis (August 2007, November 2007, February 2008, and May 2008). Measurements from 34 wells completed in the shallow groundwater system were used to construct groundwater-level and flow-direction maps and perform a linear-regression analysis to estimate the overall, time averaged shallow groundwater-flow direction and gradient. Groundwater flow in the shallow groundwater system generally moves in a southwestward direction away from the Skagit River and toward the Swinomish Channel and Skagit Bay. Local groundwater flow towards the river was inferred during February 2008 in areas west and southwest of Mount Vernon. Water-level altitudes varied seasonally, however, and generally ranged from less than 3 feet (August 2007) in the west to about 15 feet (May 2008) in the east. The time-averaged, shallow groundwater-flow direction derived from regression analysis, 8.5 deg south of west, was similar to flow directions depicted on the quarterly water-level maps. Seasonal changes in groundwater levels in most wells in the Skagit River Delta follow a typical pattern for shallow wells in western Washington. Water

  12. Role of photoexcited nitrogen dioxide chemistry on ozone formation and emission control strategy over the Pearl River Delta, China

    EPA Science Inventory

    A new hydroxyl radical formation pathway via photo-excited nitrogen dioxide chemistry is incorporated into a chemistry-only box model as well as a 3D air quality model to examine its potential role on ozone formation and emission control strategy over the Pearl River Delta region...

  13. Role of photoexcited nitrogen dioxide chemistry on ozone formation and emission control strategy over the Pearl River Delta, China

    EPA Science Inventory

    A new hydroxyl radical formation pathway via photo-excited nitrogen dioxide chemistry is incorporated into a chemistry-only box model as well as a 3D air quality model to examine its potential role on ozone formation and emission control strategy over the Pearl River Delta region...

  14. Employee Training Needs and Perceived Value of Training in the Pearl River Delta of China: A Human Capital Development Approach

    ERIC Educational Resources Information Center

    Au, Alan Kai Ming; Altman, Yochanan; Roussel, Josse

    2008-01-01

    Purpose: This paper aims to explore Hong Kong firms' training needs in the Pearl River Delta, a booming region in the fast growing People Republic of China economy, by resorting to a human capital approach. Also, to identify the training policies selected by those firms in order to cater for those needs. Design/methodology/approach: A survey based…

  15. Biological assessment:Egeria densa control program for the Sacramento/San Joaquin River Delta of California

    USDA-ARS?s Scientific Manuscript database

    A detailed Biological Assessment was developed for the proposed Area wide Egeria densa Control Program to outline the procedures that will be used to control this submerged invasive aquatic plant in the Sacramento/ San Joaquin River Delta, and to help determine if this action is expected to threaten...

  16. Examining the Impact of Nitrous Acid Chemistry on Ozone and PM over the Pearl River Delta Region

    EPA Science Inventory

    The impact of nitrous acid (HONO) chemistry on regional ozone and particulate matter in Pearl River Delta region was investigated using the community multiscale air quality (CMAQ) modeling system and the CB05 mechanism. Model simulations were conducted for a ten-day period in Oct...

  17. Examining the Impact of Nitrous Acid Chemistry on Ozone and PM over the Pearl River Delta Region

    EPA Science Inventory

    The impact of nitrous acid (HONO) chemistry on regional ozone and particulate matter in Pearl River Delta region was investigated using the community multiscale air quality (CMAQ) modeling system and the CB05 mechanism. Model simulations were conducted for a ten-day period in Oct...

  18. Employee Training Needs and Perceived Value of Training in the Pearl River Delta of China: A Human Capital Development Approach

    ERIC Educational Resources Information Center

    Au, Alan Kai Ming; Altman, Yochanan; Roussel, Josse

    2008-01-01

    Purpose: This paper aims to explore Hong Kong firms' training needs in the Pearl River Delta, a booming region in the fast growing People Republic of China economy, by resorting to a human capital approach. Also, to identify the training policies selected by those firms in order to cater for those needs. Design/methodology/approach: A survey based…

  19. Carbon Sequestration in Mediterranean Tidal Wetlands: San Francisco Bay and the Ebro River Delta (Invited)

    NASA Astrophysics Data System (ADS)

    Callaway, J.; Fennessy, S.; Ibanez, C.

    2013-12-01

    Tidal wetlands accumulate soil carbon at relatively rapid rates, in large part because they build soil to counteract increases in sea-level rise. Because of the rapid rates of carbon sequestration, there is growing interest in evaluating carbon dynamics in tidal wetlands around the world; however, few measurements have been completed for mediterranean-type tidal wetlands, which tend to have relatively high levels of soil salinity, likely affecting both plant productivity and decomposition rates. We measured sediment accretion and carbon sequestration rates at tidal wetlands in two mediterranean regions: the San Francisco Bay Estuary (California, USA) and the Ebro River Delta (Catalonia, Spain). Sampling sites within each region represented a range of conditions in terms of soil salinity and plant communities, and these sites serve as potential analogs for long-term carbon sequestration in restored wetlands, which could receive credits under emerging policies for carbon management. Within San Francisco Bay, we collected six sediment cores per site at four salt marshes and two brackish tidal wetlands (two transects with three stations per transect at each site) in order to identify spatial variation both within and among wetlands in the Estuary. At the Ebro Delta, individual sediment cores were collected across 14 tidal wetland sites, including salt and brackish marshes from impounded areas, river mouths, coastal lagoon, and open bay settings. Cores were collected to 50 cm, and cores were dated using 137Cs and 210Pb. Most sites within San Francisco accreted 0.3-0.5 cm/yr, with slightly higher rates of accretion at low marsh stations; accretions rates based on 137Cs were slightly higher than those based on 210Pb, likely because of the shorter time frame covered by 137Cs dating. Accretion rates from the Ebro Delta sites were similar although more variable, with rates based on 137Cs ranging from 0.1 to 0.9 cm/yr and reflecting the wide range of conditions and management

  20. Ultraprecise compaction and vertical strain measured in the Mississippi River Delta using Optical Fiber Strainmeters

    NASA Astrophysics Data System (ADS)

    Hatfield, W.; Zumberge, M. A.; Allison, M. A.; Bridgeman, J.; Dixon, T. H.; Elliott, D.; Nooner, S. L.; Steckler, M. S.; Tornqvist, T. E.; Wyatt, F. K.

    2016-12-01

    We are using tensioned optical fibers for the ultraprecise measurement of Earth strain in the Mississippi River Delta, where high subsidence rates threaten a large area with flooding from the Gulf of Mexico. As part of a "superstation" near Myrtle Grove, Louisiana (established with funding from the U.S. Army Corps of Engineers), we have instrumented two boreholes, 10 m and 40 m deep, with interferometric optical fiber sensors. These continuously record the vertical displacements of surface monuments to cemented-in anchors at depth. GPS stations attached to the same surface monuments tie the local compaction measurements to an absolute reference frame. These measurements, with a planned installation at an intermediate depth, will allow us to partition the subsidence between layers at various levels above the Pleistocene basement. Correlating tidal loading and vertical strain, and comparing vertical strain from distant teleseisms, reveals variations in local properties with depth.

  1. Extreme saline water advection into the Don River delta and ice advections into Kerch Strait

    NASA Astrophysics Data System (ADS)

    Matishov, G. G.

    2015-11-01

    Analysis of such extreme natural phenomena as inflow of saline transformed waters from the Black Sea into the Don River delta, ice drift, and some others, which have been observed in the Sea of Azov in the recent years, is performed. The process and consequences of the ice movement from the Sea of Azov into Kerch Strait under the effect of hurricane-force NE winds is characterized. Data on the salinity and water level changes during the intensive westerly winds are given. The relationship between salinity and water level during episodes of the surges and downsurges is found. Recommendations for organizing the monitoring measures, intended to increase the accuracy of forecasting emergency situations in the Gulf of Taganrog, Sea of Azov, are presented.

  2. Harmful Algae Records in Venice Lagoon and in Po River Delta (Northern Adriatic Sea, Italy)

    PubMed Central

    Bilaničovà, Dagmar; Marcomini, Antonio

    2014-01-01

    A detailed review of harmful algal blooms (HAB) in northern Adriatic Sea lagoons (Po River Delta and Venice lagoon) is presented to provide “updated reference conditions” for future research and monitoring activities. In the study areas, the high mollusc production requires the necessity to identify better methods able to prevent risks for human health and socioeconomical interests. So, an integrated approach for the identification and quantification of algal toxins is presented by combining microscopy techniques with Liquid Chromatography coupled with High Resolution Time of Flight Mass Spectrometry (HPLC-HR-TOF-MS). The method efficiency was first tested on some samples from the mentioned coastal areas, where Dinophysis spp. occurred during summer in the sites directly affected by seawaters. Although cell abundance was always <200 cells/L, the presence of Pectenotoxin-2 (PTX2), detected by HPLC-HR-TOF-MS, indicated the potential release of detectable amounts of toxins even at low cell abundance. PMID:24683360

  3. Numerical experiments on the long-term morphodynamics of the Colorado River Delta

    NASA Astrophysics Data System (ADS)

    Montaño, Yovani; Carbajal, Noel

    2008-03-01

    The interaction among tidal currents, sediment transport, and long-term changes of the sea bottom in the Colorado River Delta have been investigated applying a two dimensional nonlinear hydrodynamic-numerical finite differences model. The system was forced by the dominant M 2 tidal component at the open boundary. We carried out calculations to study the morphodynamics of the actual bathymetry caused by the bedload sediment transport. To investigate the origin of actual morphological features, we performed experiments using a smoothed bathymetry, in which the islands Montague, Gore, and Pelícano were eliminated. Under the imposed tidal hydrodynamics, the results indicate that the bedload transport contributes significantly in the genesis of sandbanks and in the formation and maintaining of the Montague and Gore Islands.

  4. Vegetation, substrate and hydrology in floating marshes in the Mississippi river delta plain wetlands, USA

    USGS Publications Warehouse

    Sasser, C.E.; Gosselink, J.G.; Swenson, E.M.; Swarzenski, C.M.; Leibowitz, N.C.

    1996-01-01

    In the 1940s extensive floating marshes (locally called 'flotant') were reported and mapped in coastal wetlands of the Mississippi River Delta Plain. These floating marshes included large areas of Panicum hemitomon-dominated freshwater marshes, and Spartina patens/Scirpus olneyi brackish marshes. Today these marshes appear to be quite different in extent and type. We describe five floating habitats and one non-floating, quaking habitat based on differences in buoyancy dynamics (timing and degree of floating), substrate characteristics, and dominant vegetation. All floating marshes have low bulk density, organic substrates. Nearly all are fresh marshes. Panicum hemitomon floating marshes presently occur within the general regions that were reported in the 1940's by O'Neil, but are reduced in extent. Some of the former Panicum hemitomon marshes have been replaced by seasonally or variably floating marshes dominated, or co-dominated by Sagittaria lancifolia or Eleocharis baldwinii. ?? 1996 Kluwer Academic Publishers.

  5. Identifying hotspots and management of critical ecosystem services in rapidly urbanizing Yangtze River Delta Region, China.

    PubMed

    Cai, Wenbo; Gibbs, David; Zhang, Lang; Ferrier, Graham; Cai, Yongli

    2017-04-15

    Rapid urbanization has altered many ecosystems, causing a decline in many ecosystem services, generating serious ecological crisis. To cope with these challenges, we presented a comprehensive framework comprising five core steps for identifying and managing hotspots of critical ecosystem services in a rapid urbanizing region. This framework was applied in the case study of the Yangtze River Delta (YRD) Region. The study showed that there was large spatial heterogeneity in the hotspots of ecosystem services in the region, hotspots of supporting services and regulating services aggregately distributing in the southwest mountainous areas while hotspots of provisioning services mainly in the northeast plain, and hotspots of cultural services widespread in the waterbodies and southwest mountainous areas. The regionalization of the critical ecosystem services was made through the hotspot analysis. This study provided valuable information for environmental planning and management in a rapid urbanizing region and helped improve China's ecological redlines policy at regional scale. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. "Nile River Delta, Cairo and the Pyramids taken from Atlantis during STS-106"

    NASA Image and Video Library

    2000-09-09

    STS106-701-025 (8-20 September 2000) --- One of the STS-106 crew members on board the Space Shuttle Atlantis used a handheld 70mm camera to photograph this image of Cairo, Egypt, the largest city in Africa. Its population is nearly 16 million, a figure which translates to approximately 130,000 people per square mile. Metropolitan Cairo shows as a gray area in the green of the Nile River valley at the apex of the Delta. The shadows of the three major pyramids at Giza on the Western edge of the city are visible. They are right below the bright new road construction. This side of the metropolitan area is experiencing rapid growth. According to geologists who have been studying shuttle-to-Earth imagery for many years, this photograph documents some of the many changes in land use in the Western Desert.

  7. Induction of lipids and resultant FAME profiles of microalgae from coastal waters of Pearl River Delta.

    PubMed

    Daroch, Maurycy; Shao, Congcong; Liu, Ying; Geng, Shu; Cheng, Jay J

    2013-10-01

    This article presents a study on identification, cultivation and characterisation of microalgal strains from the coastal waters of the Pearl River Delta in Guangdong, China. Thirty-seven identified strains belong to the families: Chlorellaceae, Scotiellocystoidaceae, Scenedesmaceae,Selenastraceae,Micractiniaceae, Coccomyxaceae, Trebouxiaceae and Chlorococcaceae. Of isolated strains, Hindakia PKUAC 169 was selected for lipid induction using two methods: nitrogen starvation and salt stress. After derivatisation of algal lipids through in situ transesterification, lipid profiles of the alga under the two methods were analysed. The results have shown that both lipid yield and fatty acid profiles vary with the methods. Of the two tested methods of inducing lipid production, salt stress yielded three-fold higher lipid productivity than nitrogen starvation. The lipids are predominantly composed of C14-C18 fatty acids, which are favourable for biodiesel production. Moreover, the content of polyunsaturated fatty acids was below the limit of 12% set by EN14214 biodiesel standard.

  8. Quantifiable effectiveness of experimental scaling of river- and delta morphodynamics and stratigraphy

    NASA Astrophysics Data System (ADS)

    Kleinhans, Maarten G.; van Dijk, Wout M.; van de Lageweg, Wietse I.; Hoyal, David C. J. D.; Markies, Henk; van Maarseveen, Marcel; Roosendaal, Chris; van Weesep, Wendell; van Breemen, Dimitri; Hoendervoogt, Remko; Cheshier, Nathan

    2014-06-01

    Laboratory experiments to simulate landscapes and stratigraphy often suffer from scale effects, because reducing length- and time scales leads to different behaviour of water and sediment. Classically, scaling proceeded from dimensional analysis of the equations of motion and sediment transport, and minor concessions, such as vertical length scale distortion, led to acceptable results. In the past decade many experiments were done that seriously violated these scaling rules, but nevertheless produced significant and insightful results that resemble the real world in quantifiable ways. Here we focus on self-formed fluvial channels and channel patterns in experiments. The objectives of this paper are 1) to identify what aspects of scaling considerations are most important for experiments that simulate morphodynamics and stratigraphy of rivers and deltas, 2) to establish a design strategy for experiments based on a combination of relaxed classical scale rules, theory of bars and meanders, and small-scale experiments focussed at specific processes. We present a number of small laboratory setups and protocols that we use to rapidly quantify erosional and depositional types of forms and dynamics that develop in the landscape experiments as a function of detailed properties, such as effective material strength, and to assess potential scale effects. Most importantly, the width-to-depth ratio of channels determines the bar pattern and meandering tendency. The strength of floodplain material determines these channel dimensions, and theory predicts that laboratory rivers should have 1.5 times larger width-to-depth ratios for the same bar pattern. We show how floodplain formation can be controlled by adding silt-sized silicaflour, bentonite, Medicago sativa (alfalfa) or Partially Hydrolyzed PolyAcrylamide (a synthetic polymer) to poorly sorted sediment. The experiments demonstrate that there is a narrow range of conditions between no mobility of bed or banks, and too much

  9. Historical trace element distribution in sediments from the Mississippi River delta

    USGS Publications Warehouse

    Swarzenski, P.W.; Baskaran, M.; Rosenbauer, R.J.; Orem, W.H.

    2006-01-01

    Five sediment cores were collected on the shelf of the inner Mississippi Bight in June 2003 for a suite of radionuclides to establish geochronologies and trace elements to examine patterns of contaminant deposition and accumulation. Core sites were chosen to reflect a matrix of variable water depths, proximity to the Mississippi River mouth as the primary source for terrigenous particles, and extent and duration of summertime water column hypoxia. The vertical distribution of 239,240Pu and 210Pbxs (= 210Pbtotal - 226Ra) provided reliable geochronological age constraints to develop models for mass accumulation rates and historic trace element inputs and variations. Mass accumulation rates ranged from 0.27 to 0.87 g cm-2 yr-1 and were internally consistent using either 210Pbxs or 239,240Pu. Measured inventories of 137Cs, 239,240Pu, and 210Pbxs were compared to atmospheric deposition rates to quantify potential sediment focusing or winnowing. Observed variability in calculated mass accumulation rates may be attributed foremost to site-specific proximity to the river mouth (i.e., sediment source), variability in water depth, and enhanced sediment focusing at the Mississippi River canyon site. Trace element concentrations were first normalized to Al, and then Al-normalized enrichment factors (ANEF) were calculated based on preanthropogenic and crustal trace element abundances. These ANEFs were typically > 1 for V and Ba, while for most other elements studied, either no enrichment or depletion was observed. The enrichment of Ba may be related, in part, to the seasonal occurrence of oxygen-depleted subsurface waters off the Mississippi River delta, as well as being an ubiquitous by-product of the petroleum industry. ?? 2006 Estuarine Research Federation.

  10. Mapping locust habitats in the Amudarya River Delta, Uzbekistan with multi-temporal MODIS imagery.

    PubMed

    Sivanpillai, Ramesh; Latchininsky, Alexandre V

    2007-06-01

    Reed beds of Phragmites australis in the River Amudarya delta near the Aral Sea constitute permanent breeding areas of the Asian Migratory locust, Locusta migratoria migratoria. Every year, thousands of hectares are treated with broad-spectrum insecticides to prevent locust swarms from damaging crops in adjacent areas. To devise efficient locust monitoring and management plans, accurate and updated information about the spatial distribution of reeds is necessary. Given the vast geographic extent of the delta, traditional, ground survey methods are inadequate. Remotely sensed data collected by the MODIS sensor aboard the TERRA satellite provide a useful tool to characterize the spatial distribution of reeds. Multi-temporal MODIS data, collected at different times of the growing season, were used to generate spectral-temporal signatures for reeds and other land cover classes. These spectral-temporal signatures were matched with reed phenology. MODIS information was digitally classified to generate a land cover map with an overall accuracy of 74%. MODIS data captured 87% of the ground-verified reed locations. Estimates derived from MODIS data indicate that 18% of the study area was covered by reeds. However, high commission error resulted from misclassification of reeds mixed with shrubs class and shrubs class as reeds. This could have resulted in overprediction of the area covered by reeds. Additional research is needed to minimize the overlap between reeds and other vegetation classes (shrubs, and reed and shrub mix). Nevertheless, despite its relatively low spatial resolution (250 m), multi-temporal MODIS data were able to adequately capture the distribution of reeds. Instead of blanketing the fragile wetland ecosystem of the Amudarya delta with chemical anti-locust treatments, plant protection specialists can use this information to devise ecologically sound pest management plans aimed at reducing the adverse environmental impact in the zone of the Aral Sea

  11. Concentration of contaminants in breeding bird eggs from the Colorado River Delta, Mexico.

    PubMed

    García-Hernández, Jaqueline; Sapozhnikova, Yelena V; Schlenk, Daniel; Mason, Andrew Z; Hinojosa-Huerta, Osvel; Rivera-Díaz, Juan José; Ramos-Delgado, Norma Alicia; Sánchez-Bon, Gerardo

    2006-06-01

    Organic contaminants (organochlorine [OC], organophosphorus [OP] pesticides and polychlorinated biphenyls [PCBs]), and metals (As, Cd, Hg, Pb, and Se) are a concern to avian health in the Colorado River delta, Mexico. We determined concentrations of contaminants in eggs of three breeding species of birds from the delta (mourning doves [Zenaida macroura], burrowing owls [Athene cunicularia], and marsh wrens [Cistothorus palustris]). We collected 27 eggs of mourning doves, eight eggs of burrowing owls, and 18 eggs of marsh wrens for analyses. Polychlorinated biphenyls, OC, and OP pesticides were analyzed by gas chromatography equipped with an electron capture detector, and metals were analyzed by inductively coupled plasma mass spectrometry. The non-ortho PCB congeners (PCB 77 and 126) were found in mourning dove and burrowing owl eggs at concentrations in which hatchability can be affected. Mean selenium concentration found in marsh wren eggs (5.6 microg/g dry wt) exceeded the level of concern. Arsenic and Cd were found at higher than normal concentrations, Hg concentrations did not exceed the level of concern in any of the species, and Pb concentrations were higher in eggs of species subject to hunting. With the exception of lead, marsh wren eggs contained the highest metal concentrations.

  12. Sequence stratigraphy of the subaqueous Changjiang (Yangtze River) delta since the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Xu, Taoyu; Wang, Guoqing; Shi, Xuefa; Wang, Xin; Yao, Zhengquan; Yang, Gang; Fang, Xisheng; Qiao, Shuqing; Liu, Shengfa; Wang, Xuchen; Zhao, Quanhong

    2016-01-01

    This study focuses on sedimentary research at the subaqueous Changjiang (Yangtze River) delta, based on five high-resolution seismic profiles and seven borehole cores with accurate AMS 14C datings. Three distinct seismic units were identified from the seismic profiles according to seismic reflection characteristics, and five sedimentary facies were recognized from borehole cores. These facies constituted a fining upward sedimentary sequence in relation to postglacial sea-level transgression. Three sequence surfaces (sequence boundary (SB), transgressive surface (TS), and maximum flooding surface (MFS)) demarcate the boundaries between early transgressive system tract (E-TST), late transgressive system tract (L-TST), early highstand system tract (E-HST) and late highstand system tract (L-HST), which constitute the sixth order sequence. These system tracts were developed coevally with postglacial sea-level rise. E-TST (~ 19-12 ka BP) corresponds to an incised-valley infilling in the early stages of postglacial transgression whereas L-TST (~ 12-7.5 ka BP) was formed during the last stage of postglacial transgression. The progradational structure of L-TST reflected in seismic profiles is possibly related to the intensification of the East Asian summer monsoon. E-HST (~ 7.5-2 ka BP) was deposited in response to the highstand after maximum postglacial transgression was reached, while L-HST (~ 2 ka BP-present) was initiated by accelerated progradation of the Changjiang delta.

  13. Biology of Amur sleeper (Perccottus glehni) in the Delta of the Selenga River, Buryatia, Russia

    USGS Publications Warehouse

    Litvinov, Alexander G.; O'Gorman, Robert

    1996-01-01

    We determined the fecundity, growth, diet, and density of the Amur sleeper (Perccottus glehni) in the Selenga River Delta on Lake Baikal during 1986-1991 to better understand how this invading exotic will affect Baikal's endemic fishes. We also compared the Amur sleeper's diet with that of other fishes living in the delta. The largest Amur sleepers were about 200 mm long and weighed 200 g; the oldest were age 7. All females were mature at age 2. Fecundity ranged from 884 eggs at age 1 to 37,056 eggs at age 7. Highest densities of Amur sleepers were found in oxbow lakes where densities sometimes exceeded 4,000 fish per ha. The bulk of the diet of Amur sleeper age 2 and older was chironomids, fish, and fish eggs. Chironomids were also important in the diet of the commercially valuable Siberian roach (Rutilus rutilus lacustris) and Siberian dace (Leuciscus leuciscus baicalensis). Thus the Amur sleeper may cause population declines of these important endemic fishes through resource competition and predation on their juvenile life stages. However, Amur sleepers were the species of fish most frequently eaten by Eurasian perch (Perca fluviatilis) and northern pike (Esox lucius). So, maintaining vigorous populations of these two predators may well be an effective strategy for limiting the size of Amur sleeper populations.

  14. Spatio-temporal analysis of recent groundwater-level trends in the Red River Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Bui, Duong Du; Kawamura, Akira; Tong, Thanh Ngoc; Amaguchi, Hideo; Nakagawa, Naoko

    2012-12-01

    A groundwater-monitoring network has been in operation in the Red River Delta, Vietnam, since 1995. Trends in groundwater level (1995-2009) in 57 wells in the Holocene unconfined aquifer and 63 wells in the Pleistocene confined aquifer were determined by applying the non-parametric Mann-Kendall trend test and Sen's slope estimator. At each well, 17 time series (e.g. annual, seasonal, monthly), computed from the original data, were analyzed. Analysis of the annual groundwater-level means revealed that 35 % of the wells in the unconfined aquifer showed downward trends, while about 21 % showed upward trends. On the other hand, confined-aquifer groundwater levels experienced downward trends in almost all locations. Spatial distributions of trends indicated that the strongly declining trends (>0.3 m/year) were mainly found in urban areas around Hanoi where there is intensive abstraction of groundwater. Although the trend results for most of the 17 time series at a given well were quite similar, different trend patterns were detected in several. The findings reflect unsustainable groundwater development and the importance of maintaining groundwater monitoring and a database in the Delta, particularly in urban areas.

  15. Trace Gas Emissions from Extensive Aquaculture Systems in the Red River Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Beman, J.; Seto, K. C.

    2002-12-01

    The Red River Delta of Vietnam is an area undergoing rapid land use change. Aquaculture development is among the most significant of these transformations, with important economic, social and environmental effects. We explored the potential for managed mangrove' and `converted paddy' aquaculture systems in the Delta to produce and/or consume greenhouse gasses. We measured dissolved concentrations of the radiatively-important trace gasses methane (CH4) and nitrous oxide (N2O), as well as associated parameters. All ponds were super-saturated with CH4, with concentrations ranging from 132-1203 nM, (mean 561 nM) in managed mangrove, and 28-521 nM (mean 110 nM) in converted paddy. Surprisingly, none of the ponds was measurably supersaturated with N2O. Methane fluxes were calculated for all ponds using five well-accepted models of gas flux based on wind speed. Mean flux values ranged from 1.04 to 17.09 mg CH4 m-2 d-1 for managed mangrove, falling somewhere between fluxes reported for natural systems and those receiving sewage inputs. Further measurements should be made in more intensive systems to better understand the potential for trace gas production-particularly N2O-in aquaculture systems.

  16. Subsidence of River Delta Systems and Enclosed Basins Caused by Multi-decadal to Millennial Scale Sediment and Ocean Loading

    NASA Astrophysics Data System (ADS)

    Blom, Ronald G.; Ivins, Erik R.; Klemann, Volker; Dokka, Roy K.; Lohman, Rowena; Fielding, Eric J.

    2010-05-01

    The causes of multi-decadal coastal subsidence that exceed the rate of 20th-21st Century mean sea-level rise are numerous. A host of causal relationships between anthropogenic activity and coastal erosion and subsidence are both compelling and well understood. A short list of these processes should include: fluid extraction, reservoir compaction; fluid-induced motion of shallow growth-faults; decomposition of organic sediments (left in the wake of major water diversion projects) and sediment empoundment and/or diversion. Non-anthropogenic post-glacial sediment loading-induced subsidence has also been demonstrated to be a candidate mechanism that could dominate the GPS-mapped subsidence in the Mississippi-Atchafalaya Rive Delta system (Ivins, Dokka and Blum, GRL, 34, L16303, 2007). More recent changes in sediment load can also have a substantial impact on the active subsidence of the crust and mantle. These can be of both anthropogenic and natural origins. Here we examine, in varying degrees of detail, the world's major delta systems wherein the necessary and sufficient conditions are met that allow sediment plus water load to drive gravitationally-layered, hydrostatically pre-stressed viscoelastic Earth model simulations far enough away from gravitational equilibrium that a detectable geodetic signal in tide-gauges and GPS vertical position would be predicted. Sediment-load-induced subsidence occurs over horizontal length scales, λ, comparable to thickness of the lithosphere: λ ≥ 40-60 km and has amplitudes ranging from of 0.5 to 8 mm/yr (Ivins et al. GRL34, 2007; Syvitski Sustain. Sci., 3, 2008). The cases of the pan-Arctic deltas, the Atchafalya -Mississippi River Delta system, the Yangzte River and Yellow River Deltas of China, the Danube River Delta Plain, and the generally complex postglacial water-sediment loading of the Black Sea and Caspian Sea.

  17. Vegetative ecological characteristics of restored reed (Phragmites australis) wetlands in the Yellow River Delta, China.

    PubMed

    Wang, Xuehong; Yu, Junbao; Zhou, Di; Dong, Hongfang; Li, Yunzhao; Lin, Qianxin; Guan, Bo; Wang, Yongli

    2012-02-01

    In this study, we compared ecological characteristics of wetland vegetation in a series of restoration projects that were carried out in the wetlands of Yellow River Delta. The investigated characteristics include plant composition structure, species diversity and community similarity in three kinds of Phragmites australis wetlands, i.e. restored P. australis wetlands (R1, R2, R3 and R4: restored in 2002, 2005, 2007 and 2009, respectively), natural P. australis wetland (N) and degraded P. australis wetland (D) to assess the process of wetlands restoration. The coverage of the R1 was 99%, which was similar to natural wetland. Among all studied wetlands, the highest and lowest stem density was observed in R1 and R2, respectively, Plant height and stem diameter show the same trend as N > R2 > R1 > R3 > D > R4. Species diversity of restored P. australis wetlands became closed to natural wetland. Both species richness and Shannon-Wiener index had similar tendency: increased first and then decreased with restored time. The highest species richness and species diversity were observed in R2, while the lowest values of those parameters were found in natural P. australis wetland. Similarity indexes between restored wetlands and natural wetland increased with the restoration time, but they were still less than 50%. The results indicate that the vegetation of P. australis wetlands has experienced a great improvement after several years' restoration, and it is feasible to restored degraded P. australis wetlands by pouring fresh water into those wetlands in the Yellow River Delta. However, it is notable that costal degraded P. australis wetland in this region may take years to decades to reach the status of natural wetland.

  18. Sediment-vegetation interactions on the subaqueous Susquehanna River delta, upper Chesapeake Bay (USA)

    NASA Astrophysics Data System (ADS)

    Russ, E.; Palinkas, C. M.; Sanford, L. P.; Gurbisz, C.; Hinkle, D.

    2016-12-01

    Submersed aquatic vegetation (SAV) historically were abundant on the shallow, subaqueous delta of the Susquehanna River (SR), the largest tributary delivering water and sediment to Chesapeake Bay, USA. SAV began to decline in the 1960s on the delta (referred to as the Susquehanna Flats) due to poor water quality and disappeared completely following Tropical Storm Agnes (1972), which resulted in the highest recorded discharge of the SR and delivery of enormous fine-sediment loads to the upper Bay. In response to improved water quality, SAV have returned to the Flats in the last decade and once again are a prominent feature of the upper Bay. While it is well established that SAV promote sediment and nutrient retention, the timing and magnitude of trapping on the Flats is unclear but has important implications for water quality in the Bay. This study evaluates sediment trapping over seasonal to decadal time scales, using naturally occurring radioisotopes (7Be, 210Pb), within the context of fluvial sediment supply and plant biomass, as well as sediment erodibility experiments. Results show that, while average river discharge and suspended-sediment concentration (SSC) were lowest during the summer (plants present), sedimentation rates and mud content were highest, especially in the middle of the plant bed. In contrast, while average discharge and SSC were highest in the spring (plants absent), recent sedimentation was observed only at sites farthest downstream of the SR mouth. Thus, seasonal fluvial sediment supply is out of phase with the maximum deposition on the Flats, suggesting that sediment delivered during the spring freshet bypasses the Flats and enters the upper Bay, while fluvial sediment loads delivered during the SAV growing season can be retained on the Flats. This retention is aided by lower sediment erodibility during summer, relative to spring. This pulsing of seasonal sedimentation is also preserved in the sedimentary record over decadal time scales.

  19. Numerical study of urbanization influence on local and regional climate of Yangtze River Delta, China

    NASA Astrophysics Data System (ADS)

    Zhang, N.

    2016-12-01

    Yangtze River Delta is one of the most urbanized area in China, which has been experienced a very quick urbanization processes in the recent decades. Weather Research and Forecasting model (WRF) coupled with a single-layer urban canopy model is used to investigated the influence of urbanization in different scales, from a single city to regional area. The results show that the near-surface temperature increases in both near urbanized area and old city core. Urban heat island (UHI) circulation enhances the local lake breeze circulation in the daytime and weakens it at night. Horizontal convection rolls may occur in the downwind area of cities. The background south-east wind in summer may cause an `upwind UHI impact' in this area. The downwind city experienced a stronger UHI than the windward city, because the warm air is transported from the windward city to the downwind one. This may increases the downwind UHI intensity by 20% at night, while it increases the atmospheric boundary layer stability over the downwind city in the daytime. Two numerical simulation experiment sets of a five-January simulations and a five-July simulations are designed and the results show that the urbanization processes in this area not only impact local urban climate but also have influence on regional climate in Yangtze River Delta. The urbanization process increases the near-surface temperature, UHI intensity, decreases the diurnal temperature variation range, near-surface wind speed and humidity. The influences on UHI and near-surface temperature are greater in summer than in winter due to the background climate characteristics.

  20. Dissolved and colloidal trace elements in the Mississippi River Delta outflow after Hurricanes Katrina and Rita

    USGS Publications Warehouse

    Shim, Moo-Joon; Swarzenski, Peter W.; Shiller, Alan M.

    2012-01-01

    The Mississippi River delta outflow region is periodically disturbed by tropical weather systems including major hurricanes, which can terminate seasonal bottom water hypoxia and cause the resuspension of shelf bottom sediments which could result in the injection of trace elements into the water column. In the summer of 2005, Hurricanes Katrina and Rita passed over the Louisiana Shelf within a month of each other. Three weeks after Rita, we collected water samples in the Mississippi River delta outflow, examining the distributions of trace elements to study the effect of Hurricanes Katrina and Rita. We observed limited stratification on the shelf and bottom waters that were no longer hypoxic. This resulted, for instance, in bottom water dissolved Mn being lower than is typically observed during hypoxia, but with concentrations still compatible with Mn–O2 trends previously reported. Interestingly, for no element were we able to identify an obvious effect of sediment resuspension on its distribution. In general, elemental distributions were compatible with previous observations in the Mississippi outflow system. Co and Re, which have not been reported for this system previously, showed behavior consistent with other systems: input for Co likely from desorption and conservative mixing for Re. For Cs, an element for which there is little information regarding its estuarine behavior, conservative mixing was also observed. Our filtration method, which allowed us to distinguish the dissolved (<0.02 μm) from colloidal (0.02–0.45 μm) phase, revealed significant colloidal fractions for Fe and Zn, only. For Fe, the colloidal phase was the dominant fraction and was rapidly removed at low salinity. Dissolved Fe, in contrast, persisted out to mid-salinities, being removed in a similar fashion to nitrate. This ability to distinguish the smaller Fe (likely dominantly organically complexed) from larger colloidal suspensates may be useful in better interpreting the

  1. Presence of pyrethroid pesticides in water and sediments of Ebro River Delta

    NASA Astrophysics Data System (ADS)

    Feo, M. L.; Ginebreda, A.; Eljarrat, E.; Barceló, D.

    2010-11-01

    SummaryThe distribution of pyrethroid insecticides of the Ebro River Delta (NE Spain) was assessed by measuring concentrations in surface water and sediment samples. Pyrethroid extraction from water was carried out by ultrasound-assisted emulsification-extraction (UAEE), while the sediment was sonicated and cleaned up using Florisil cartridge. Method detection of limits (MLODs) for the 12 pyrethroids analyzed by gas chromatography-mass spectrometer in negative chemical ionization (GC-NCI-MS) ranged from 0.03 to 35.8 ng L -1 for water and 2.6 to 62.4 pg g -1 for sediment. Recoveries values were in the range of 47-105% for water and 51-105% for sediments, showing satisfactory robustness of the method for analyzing pyrethroids in water and sediment samples. Cypermethrin was detected in 22 water samples collected from Ebro River Delta, while deltamethrin was present only in three water samples at concentrations ranging from 0.73 ng L -1 to 57.2 ng L -1 and 2 ng L -1 to 58.8 ng L -1 for cypermethrin and deltamethrin, respectively. These concentration levels were higher than median lethal concentration (LC50) values found for deltamethrin and lower than LC50 values found for cypermethrin when short time toxic effects are considered. In sediment samples only cypermethrin was detected at concentration levels ranged from 8.27 ng g -1 to 71.9 ng g -1. These levels were higher than its LC50 values. Environmental dynamic behaviour and fate were also evaluated for cypermethrin measuring the sediment/water partition coefficient (ranging from 5.0 to 6.3) and kinetic data (half-life ranging between 13 and 50 days). Results were in good agreement to those reported in literature

  2. Source apportionment of surface ozone in the Yangtze River Delta, China in the summer of 2013

    NASA Astrophysics Data System (ADS)

    Li, L.; An, J. Y.; Shi, Y. Y.; Zhou, M.; Yan, R. S.; Huang, C.; Wang, H. L.; Lou, S. R.; Wang, Q.; Lu, Q.; Wu, J.

    2016-11-01

    We applied ozone source apportionment technology (OSAT) with tagged tracers coupled within the Comprehensive Air Quality Model with Extensions (CAMx) to study the region and source category contribution to surface ozone in the Yangtze River Delta area in summer of 2013. Results indicate that the daytime ozone concentrations in the YRD region are influenced by emissions both locally, regionally and super-regionally. At urban Shanghai, Hangzhou and Suzhou receptors, the ozone formation is mainly VOC-limited, precursor emissions form Zhejiang province dominate their O3 concentrations. At the junction area among two provinces and Shanghai city, the ozone is usually influenced by all the three areas. The daily max O3 at the Dianshan Lake in July are contributed by Zhejiang (48.5%), Jiangsu (11.7%), Anhui (11.6%) and Shanghai (7.4%), long-range transport constitutes around 20.9%. At Chongming site, the BVOC emissions rate is higher than urban region. Regional contribution results show that Shanghai constitutes 15.6%, Jiangsu contributes 16.2% and Zhejiang accounts for 25.5% of the daily max O3. The analysis of the source category contribution to high ozone in the Yangtze River Delta region indicates that the most significant anthropogenic emission source sectors contributing to O3 pollution include industry, vehicle exhaust, although the effects vary with source sector and selected pollution episodes. Emissions of NOx and VOCs emitted from the fuel combustion of industrial boilers and kilns, together with VOCs emissions from industrial process contribute a lot to the high concentrations in urban Hangzhou, Suzhou and Shanghai. The contribution from regional elevated power plants cannot be neglected, especially to Dianshan Lake. Fugitive emissions of volatile pollution sources also have certain contribution to regional O3. These results indicate that the regional collaboration is of most importance to reduce ambient ozone pollution, particularly during high ozone episodes.

  3. Aerosol profiles determined with lidar and sun-photometer over the Pearl River Delta, China.

    NASA Astrophysics Data System (ADS)

    Heese, B.; Althausen, D.; Bauditz, M.; Deng, R.; Bao, R.; Li, Z.

    2012-04-01

    The priority program "Megacities-Megachallenge - Informal Dynamics of Global Change" is a large interdisciplinary project funded by the German Research Foundation (DFG). One of the subproject deals with mega-urbanisation in the Pearl River Delta, South-China, with special respect to particulate air pollution and public health. In the frame of this subproject the vertical distribution of aerosol optical properties are investigated by measurements with the multiwavelength-Raman-polarization lidar PollyXT of the IfT. The instrument can measure the particle backscatter coefficient at 355 nm, 532 nm, and 1064 nm, the particle extinction coefficients at 355 nm and 532 nm, and the particle linear depolarization ratio at 532 nm. These measurements are supported by a dual-polar sun photometer that provides height integrated data as the aerosol optical depth and the degree of linear depolarization. These instruments are placed at the East campus of the Sun Yat-sen University in Guangzhou, China. Guangzhou and the Pearl River Delta is a developing area with currently around 11 Million inhabitants. The measurements started in November 2011 and are supposed to continue for at least half a year covering the late autumn and winter season and parts of the spring season. Extensions of the measurements towards a whole seasonal cycle are planned. Thus, different meteorological conditions will lead to particle transport from several source regions. Different aerosol types are expected to be observed during the measurement period: urban particles from local and regional sources as well as dust from the deserts in Central Asia. The observed particles can be distinguished by analyzing their optical properties at several wavelengths. In particular, the depolarization measurements from both instruments promise a better determination of the particle shape.

  4. Effects of drought on birds and riparian vegetation in the Colorado River Delta, Mexico

    USGS Publications Warehouse

    Hinojosa-Huerta, Osvel; Nagler, Pamela L.; Carrillo-Guererro, Yamilett K.; Glenn, Edward P.

    2013-01-01

    The riparian corridor in the delta of the Colorado River in Mexico supports internationally important bird habitat. The vegetation is maintained by surface flows from the U.S. and Mexico and by a high, non-saline aquifer into which the dominant phreatophytic shrubs and trees are rooted. We studied the effects of a regional drought on riparian vegetation and avian abundance and diversity from 2002 to 2007, during which time surface flows were markedly reduced compared to the period from 1995 to 2002. Reduced surface flows led to a reduction in native tree cover but an increase in shrub cover, mostly due to an increase in Tamarix spp., an introduced halophytic shrub, and a reduction in Populus fremontii and Salix gooddingii trees. However, overall vegetation cover was unchanged at about 70%. Overall bird density and diversity were also unchanged, but riparian-obligate species tended to decrease in abundance, and generalist species increased. Although reduction in surface flows reduced habitat value and negatively impacted riparian-obligate bird species, portions of the riparian zone exhibited resilience. Surface flows are required to reduce soil salt levels and germinate new cohorts of native trees, but the main source of water supporting this ecosystem is the aquifer, derived from underflows from irrigated fields in the U.S. and Mexico. The long-term prospects for delta riparian habitats are uncertain due to expected reduced flows of river water from climate change, and land use practices that will reduce underflows to the riparian aquifer and increase salinity levels. Active restoration programs would be needed if these habitats are to be preserved for the future.

  5. Dissolved and colloidal trace elements in the Mississippi River delta outflow after Hurricanes Katrina and Rita

    NASA Astrophysics Data System (ADS)

    Shim, Moo-Joon; Swarzenski, Peter W.; Shiller, Alan M.

    2012-07-01

    The Mississippi River delta outflow region is periodically disturbed by tropical weather systems including major hurricanes, which can terminate seasonal bottom water hypoxia and cause the resuspension of shelf bottom sediments which could result in the injection of trace elements into the water column. In the summer of 2005, Hurricanes Katrina and Rita passed over the Louisiana Shelf within a month of each other. Three weeks after Rita, we collected water samples in the Mississippi River delta outflow, examining the distributions of trace elements to study the effect of Hurricanes Katrina and Rita. We observed limited stratification on the shelf and bottom waters that were no longer hypoxic. This resulted, for instance, in bottom water dissolved Mn being lower than is typically observed during hypoxia, but with concentrations still compatible with Mn-O2 trends previously reported. Interestingly, for no element were we able to identify an obvious effect of sediment resuspension on its distribution. In general, elemental distributions were compatible with previous observations in the Mississippi outflow system. Co and Re, which have not been reported for this system previously, showed behavior consistent with other systems: input for Co likely from desorption and conservative mixing for Re. For Cs, an element for which there is little information regarding its estuarine behavior, conservative mixing was also observed. Our filtration method, which allowed us to distinguish the dissolved (<0.02 μm) from colloidal (0.02-0.45 μm) phase, revealed significant colloidal fractions for Fe and Zn, only. For Fe, the colloidal phase was the dominant fraction and was rapidly removed at low salinity. Dissolved Fe, in contrast, persisted out to mid-salinities, being removed in a similar fashion to nitrate. This ability to distinguish the smaller Fe (likely dominantly organically complexed) from larger colloidal suspensates may be useful in better interpreting the bioavailablity

  6. Soil organic carbon of degraded wetlands treated with freshwater in the Yellow River Delta, China.

    PubMed

    Wang, Hui; Wang, Renqing; Yu, Yue; Mitchell, Myron J; Zhang, Lianjun

    2011-10-01

    Supplying freshwater is one of the important methods to help restore degraded wetlands. Changes in soil properties and plant community biomass were evaluated by comparing sites with freshwater treatment versus reference sites following freshwater addition to wetlands of the Yellow River Delta for 7 years. The results indicated that soil organic carbon (SOC) was significantly increased in all wetland sites that were treated with freshwater compared to the reference sites. The treatment wetlands had greater total nitrogen (TN), lower pH and electrical conductivity and higher water content in the soil compared to the reference wetlands. In general, the upper soil layer (0-20 cm) had greater SOC than the lower soil layer (20-40 cm). The increase of SOC in the freshwater reintroduction wetlands was higher in the Suaeda salsa plant community (mean ± standard error) (6.89 ± 0.63 g/kg) and Phragmites communis plant community (4.11 ± 0.12 g/kg) than in the Tamarix chinensis plant community (1.40 ± 0.31 g/kg) in the upper soil layer. The differences were especially marked between the treated and reference wetlands for SOC and TN in the P. communis plant communities. The C:N ratio of the soil was significantly greater in the treated compared to the reference wetlands for the S. salsa plant community. Although the C: N ratios increased after treatment, they were all <25 suggesting that N availability was not limiting soil organic matter decomposition. Our results indicate that freshwater addition and the concomitant increase in soil moisture content enhances the accumulation of SOC in the Yellow River Delta. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Occurrence, sources, and risk assessment of OCPs in surface sediments from urban, rural, and reclamation-affected rivers of the Pearl River Delta, China.

    PubMed

    Wang, Wei; Bai, Junhong; Xi, Min; Zhao, Qingqing; Zhang, Guangliang; Wen, Xiaojun; Xiao, Rong

    2017-01-01

    Sediments were collected to a depth of 20 cm from urban, rural, and reclamation-affected rivers in the Pearl River Delta of China. In total, 16 organochlorine pesticides (OCPs) were analyzed in all sediment samples, and the occurrence, possible sources, toxicity, and health risks of OCPs were evaluated to compare the contamination characteristics of OCPs in sediments among the three types of rivers. The results showed that concentrations of Σ16OCPs in sediments from the three rivers followed the order urban river > reclamation-affected river > rural river, with a mean value of 247.21, 232.91, and 114.92 μg/kg, respectively, and the predominant OCPs were hexachlorobenzene (HCB), dieldrin, aldrin, endrin, and hexachlorocyclohexanes (HCHs). Source diagnostics illustrated that there might be recent input of HCHs, dichlorodiphenyltrichloroethanes (DDTs), and endosulfan in some sampling sites. Based on the soil quality thresholds of China, both HCHs and DDTs fell within the range of class II criteria except for some sediment samples in urban rivers with lower levels (below class I criteria). According to sediment quality guidelines, 92.86 % of samples were predicted to be toxic. The health risk assessment showed that OCPs would not pose a threat to people via dermal contact, ingestion, and inhalation, and the followed order of incremental lifetime cancer risks for OCPs in sediment samples was reclamation-affected river > urban river > rural river.

  8. How did the delta respond? An analysis of greenup and evapotranspiration (ET) of the Colorado River Delta following the Minute 319 pulse flows to Mexico

    NASA Astrophysics Data System (ADS)

    Jarchow, C.; Nagler, P. L.; Glenn, E. P.

    2016-12-01

    During the spring of 2014, 130 million cubic meters of water was released to the lower Colorado River Delta in Mexico, allowing water to reach the Gulf of California for the first time in nearly 13 years. We continue to track the effect of this pulse flow, the result of a historic agreement between the United State and Mexico. To assess the response of vegetation to the pulse, we used remote sensing techniques to measure greenup and evapotranspiration (ET) of vegetation within the delta's riparian corridor. We applied two different algorithms to estimate ET using both MODIS Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI) data and assessed greenup using a modified form of Landsat 8-based NDVI data. We found a small, but significant increase (3%) in ET and a significant increase (17%) in NDVI from 2013 (pre-pulse) to 2014 (post-pulse) within the delta's riparian corridor (P < 0.05). While NDVI declined in 2015, it was still significantly higher than in 2013 (P < 0.05). This reverses an overall decline in NDVI and ET since the last major flood in 2000. Using our ET findings coupled with salinity data collected during the pulse flows, we developed and present a conceptual model explaining the role of groundwater and surface flows in maintaining the riparian corridor in Mexico. Based on preliminary findings, pulse flows could be an effective tool for restoring the lower Colorado River's riparian zone.

  9. Historical Reconstruction of Organic Carbon Inputs to Sediments in the Colville River Delta, Alaska: The Application of Biomarker Proxies

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Bianchi, T. S.; Allison, M. A.

    2014-12-01

    Arctic permafrost represents about 50% of the total belowground global carbon pool, and thus the fate of this pool, as it thaws in the wake of global warming, warrants close attention. Large-river delta-front estuaries (LDEs) have been shown to be important recorders of natural and human-induced changes in watersheds, as they are critical zones for the exchange of organic carbon between the continents and the ocean. The Colville River is the largest North American Arctic River with a continuous permafrost watershed. Simpson's Lagoon, an eastward distal component of the Colville River Delta is an excellent location for historical reconstruction work since it is an area well protected from intense ice grounding and has minimal bioturbation. Sediment cores were collected from the mouth of the river and the lagoon in August of 2010, and analyzed for bulk organic carbon and nitrogen proxies, biomarkers (including lignin phenols, fatty acids), and compound-specific 13C isotope analysis (CSIA) of fatty acids. Downcore sediment data from CSIA of short-chain fatty acids (C14-C18) to the delta over the past ca. 50 years were found to be more depleted and had a wider isotopic range (-17.0~-33.2‰) than long-chain fatty acids (C22-C30, -30.3~-36.8‰). This possibly reflects alterations of inputs of freshwater flow to the delta which could have resulted in isotopic changes that caused corresponding changes in marine versus freshwater phytoplankton inputs. Downcore short-chain saturated and monounsaturated fatty acid profiles reflected differences in the abundance of bacteria and post-depositional decay of algal inputs across different regions of the delta. Ongoing analyses will also focus on compound-specific radiocarbon analyses (CSRA) of fatty acids and lignin phenols to better understand the changes of organic inputs from terrestrially-derived organic-rich horizons in surface soils vs. old deep permafrost-derived organic horizons.

  10. Recent morphological changes of the Yellow River (Huanghe) submerged delta: Causes and environmental implications

    NASA Astrophysics Data System (ADS)

    Jiang, Chao; Pan, Shunqi; Chen, Shenliang

    2017-09-01

    The Yellow River (Huanghe) submerged delta (YRSD) has been under the threat of erosion and retreat during the Anthropocene due to dramatic climatic and anthropogenic changes in the Yellow River basin. The analysis of field data shows that over the period of 1977-2005, the changes in climate (decrease in precipitation and increase in air temperature) and human interventions (increase in water diversion projects) throughout the watershed have resulted in the sharp reductions of river flow and sediment discharges into the Bohai Sea. Consequently, over the decadal timescale, morphological evolution of the YRSD has gone through three stages: i.e. rapid accumulation (5.77 × 108 m3/year) in 1977-1985, moderate accumulation (3.80 × 108 m3/year) in 1986-1995 and slow accumulation (0.91 × 108 m3/year) in 1996-2005. Climatic change within the catchment characterized by the rapid increase of air temperature contributed significantly to the transitions from the rapid accumulation to the moderate accumulation, and to the subsequent slow accumulation. The decadal morphological changes of the YRSD also show peculiar deposition/erosion characteristics over the medium timescale under river input reduction. Within the three decades, the patterns of the main sedimentary body exhibit irregular ellipses with the long axis parallel to the - 5 or - 10 m isobaths and short axis perpendicular to the isobaths. The depocentres of the YRSD are located between the - 10 and - 15 m isobaths close to the respective river mouths, with a high vertical accretion rate of 1.20 m/year. The time series data of annual volumetric change of the YRSD and river sediment load from 1977 to 2005 further demonstrate significant linear positive relationships between deltaic geomorphic change and fluvial input over shorter timescales (annual and 3-year). The critical sediment discharges for maintaining the deposition/erosion equilibrium state of the YRSD over the annual and 3-year timescales are found to be 1

  11. Distribution, source apportionment, and transport of PAHs in sediments from the Pearl River Delta and the northern South China Sea

    SciTech Connect

    Luo, X.J.; Chen, S.J.; Mai, B.X.; Sheng, G.Y.; Fu, J.M.; Zeng, E.Y.

    2008-07-15

    Polycyclic aromatic hydrocarbons (PAHs) were measured in 59 surface sediments from rivers in the Pearl River Delta and the northern continental shelf of the South China Sea. Total PAH concentrations varied from 138 to 6,793 ng/g dry weight. The sources of PAH inputs to sediments in the Pearl River Delta were qualitatively and quantitatively determined by diagnostic ratios and principal components analysis with multiple linear regression. The results showed that on average coal and wood combustion, petroleum spills, vehicle emissions, and nature sources contributed 36%, 27%, 25%, and 12% of total PAHs, respectively. Coal and biomass combustion was the main source of PAHs in sediments of the South China Sea, whereas petroleum combustion was the main source of pyrolytic PAHs in riverine and estuarine sediments of the Pearl River Delta. Perylene was formed in situ in river sediments and then transported to coastal areas along with other PAHs. The relative abundance of perylene from five-ring PAHs can be used to estimate the contribution of riverine-discharged PAHs to coastal sediments.

  12. Health impact assessment of marine emissions in Pearl River Delta region.

    PubMed

    Lai, H K; Tsang, H; Chau, J; Lee, C H; McGhee, S M; Hedley, A J; Wong, C M

    2013-01-15

    Global marine vessels emissions are adversely affecting human health particularly in southeast Asia. But health burdens from both ocean- and river-going vessels in Pearl River Delta (PRD) regions are not quantified. We estimated the potential health impacts using pooled relative risks of mortality and hospital admissions in China, and the model derived concentrations of sulfur dioxide (SO₂), particulate matter (PM₁₀), nitrogen dioxide (NO₂) and ozone (O₃) due to vessels emissions. SO₂ concentrations due to marine emissions in Hong Kong were 13.6 μg m⁻³ compared with 0.7 μg m⁻³ in PRD regions that were far from the marine vessels. In PRD regions, the estimated annual numbers (per million people) of excess deaths from all natural causes and hospital admissions from cardiorespiratory causes attributable to SO₂, NO₂, O₃ and PM₁₀ combined from marine emissions were 45 and 265 respectively. Marine emission control measures could contribute a large reduction in mortality and hospital admissions in PRD regions especially in Hong Kong.

  13. Remote sensing applications: Environmental assessment of the Colorado River delta in Mexico

    NASA Astrophysics Data System (ADS)

    Nagler, Pamela Lynn

    The extent of revegetation in the Colorado River delta in Mexico is described, with emphasis on the return of native cottonwood (Populus fremontii ) and willow (Salix gooddingii) trees. Low-level aerial and satellite remote sensing methods were combined with ground surveys to census the vegetation in a 100 km reach of riparian corridor in Mexico. Although the invasive plant, saltcedar (Tamarix ramosissima), still dominates the riparian zone, native trees now account for 23% of the vegetation in the delta. Multi-band digital camera images obtained by aircraft were used to calculate the Normalized Difference Vegetation Index (NDVI) and scored for percent vegetation cover (NDVI:%C has r = 0.91***). A Thematic Mapper (TM) image taken concurrently with the aerial survey was similarly classified, and by comparing scenes on the TM and aerials, it was possible to calibrate NDVI with percent vegetation on the TM image. This information was used to conduct a change analysis relating flows in the Colorado River with summer vegetation patterns on TM images for the years 1992--1999. The results support the importance of pulse floods in restoring the ecological integrity of arid-zone rivers. This dissertation also compared transpiration rates of three Sonoran Desert riparian trees using sap flow and leaf temperature methods using constructed canopies (two of each species: Populus fremontii (cottonwood), Salix gooddingii (willow) and Tamarix ramosissima (saltcedar)) in an outdoor experiment in Tucson, Arizona. Canopies were measured over 11 days for both sap flow and canopy and air temperature differential (Tc-Ta) under non stressed and stressed conditions. Objective 1: to determine the strength of the relationship between transpiration (Et) and Tc-Ta to determine if Tc-Ta can be a useful remote sensing method to measure Et for these species. Objective 2: to compare Et rates among species, to determine if the invasive species, saltcedar, has higher Et rates or ecophysiological

  14. Dynamic Emulation Modeling of irrigation water deficit in the Red-Thai Binh River Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Dinh, Q.; Cassaro, L.; Micotti, M.; Soncini-Sessa, R.

    2013-12-01

    real-world case study: the Red-Thai Binh River Delta in Vietnam. It is a large and complex river system, supplied by five unregulated rivers and four large multi-purpose reservoirs, the operating rules of which have to be designed. In order to ascertain the effects of their regulation on the WD in the Delta, a Mike11 model was calibrated and validated. It describes 320 rivers and canals for a total length of 4200 km, 11 irrigation districts and many structures, among which 88 sluice gates and 302 irrigation water intakes (simulated as controlled pumps). Its inputs are the four reservoirs releases, the non-regulated flows of the five rivers, the sea levels at the nine river mouths, the water demand at each one of the irrigation water intakes. The considered outputs are the daily WD in the 11 districts. The dimension of the state vector of the model is of the order of 16,000. From the high dimensional Mike11, a low dimensional (11 dimension) DEMo model was identified that mimics very well (R2=0.95) the WDs as computed by the Mike11 model. The DEMo model will be later on embedded within a large multi-objective optimal control problem to design the operating rules of the four reservoirs.

  15. Preliminary assessment of recent deposition related to a crevasse splay on the Mississippi River delta: Implications for coastal restoration

    USGS Publications Warehouse

    Ferina, N.F.; Flocks, J.G.; Kingdinger, Jack L.; Miner, M.D.; Motti, J. P.; Chadwick, Paul C.; Johnston, James B.

    2005-01-01

    Historically, the Mississippi River has replenished sediment across the lower deltaic plain, abating land loss. However, flood-control structures along the river now restrict this natural process and divert sediment from the modern delta offshore to the shelf break, thereby removing it from the coastal system. Localized crevasse splays, however, can deposit significant amounts of sediment in a short span of time.Satellite imagery and field investigations, including eight sediment vibracores, have identified a recent crevasse splay originating from Brant Bayou within the Delta National Wildlife Refuge on the lower Mississippi River delta. The splay deposits are estimated to be as much as 3 m thick and are located stratigraphically above shallow interdistributary-bay deposits. In addition, the deposits exhibit physical characteristics similar to those of large scale prograded deltas. The Bayou Brant crevasse splay began forming in 1978 and has built approximately 3.7 km2 of land. Coastal planners hope to utilize on this natural process of sediment dispersion to create new land within the deltaic plain.

  16. Interactions between the flooding regime and floodplain grasslands in the Tana River Delta, in Kenya

    NASA Astrophysics Data System (ADS)

    Leauthaud, Crystele; Musila, Winfred; Duvail, Stéphanie; Kergoat, Laurent; Hiernaux, Pierre; Grippa, Manuela; Albergel, Jean

    2017-04-01

    The floodplain grasslands of the Tana River Delta, located on the East African coast in Kenya, form part of an intertwined socio-ecological deltaic system of high biodiversity value that delivers numerous goods and services. Mainly composed of Echinochloa stagnina (Retz) P. Beauv., a high-value forage species, this ecosystem is the major dry-season grazing grounds of the local pastoralist communities. The construction of hydroelectric infrastructure has led to a modification of the flooding regime. The impacts of the resulting reduction of floods in the deltaic zone on ecosystem properties and services still need to be assessed. In such a perspective, this study characterizes the link between the flooding regime of the Tana River and the growth pattern of its floodplain grassland. Aboveground dry phytomass was sampled for 15 months under a wide variety of naturally flooded and non-flooded conditions and controlled irrigation and cutting frequency treatments. Annual aboveground dry phytomass attained high values between 11 T.ha-1 and 32 T.ha-1 and annual net primary production of the grasslands reached 35 T.ha-1.year-1. Growth rates clearly depended on the flooding regime, management and climate conditions and were on average more than twice as fast during, and 50% faster after the floods, relative to pre-flood conditions. A plant growth model allowed testing the effect of different flooding regimes on plant productivity, confirming very low productivity in the absence of floods. These results suggest that rangeland and water management for the Tana River deltaic wetlands are tightly linked. The projected construction of another dam could lead to a reduction of flood extent and period and a decrease of grassland productivity and growth duration. Mitigation of this type of negative impacts, which will have direct and adverse consequences for the pastoralist communities as well as on the delivery of other goods and services, needs to be undertaken.

  17. Large-river delta-front estuaries as natural “recorders” of global environmental change

    PubMed Central

    Bianchi, Thomas S.; Allison, Mead A.

    2009-01-01

    Large-river delta-front estuaries (LDE) are important interfaces between continents and the oceans for material fluxes that have a global impact on marine biogeochemistry. In this article, we propose that more emphasis should be placed on LDE in future global climate change research. We will use some of the most anthropogenically altered LDE systems in the world, the Mississippi/Atchafalaya River and the Chinese rivers that enter the Yellow Sea (e.g., Huanghe and Changjiang) as case-studies, to posit that these systems are both “drivers” and “recorders” of natural and anthropogenic environmental change. Specifically, the processes in the LDE can influence (“drive”) the flux of particulate and dissolved materials from the continents to the global ocean that can have profound impact on issues such as coastal eutrophication and the development of hypoxic zones. LDE also record in their rapidly accumulating subaerial and subaqueous deltaic sediment deposits environmental changes such as continental-scale trends in climate and land-use in watersheds, frequency and magnitude of cyclonic storms, and sea-level change. The processes that control the transport and transformation of carbon in the active LDE and in the deltaic sediment deposit are also essential to our understanding of carbon sequestration and exchange with the world ocean—an important objective in global change research. U.S. efforts in global change science including the vital role of deltaic systems are emphasized in the North American Carbon Plan (www.carboncyclescience.gov). PMID:19435849

  18. Carbon recycling in deltaic sediments: variations at different timescales in the Rhone River delta

    NASA Astrophysics Data System (ADS)

    Rabouille, C.; Rassmann, J.; Toussaint, F.; Cathalot, C.; Tisnerat-Laborde, N.; Lansard, B.

    2016-02-01

    Terrestrial aquatic environments and the land-sea connection are a major contributors to the Earth carbon cycle, as these act as a source to the atmosphere of about 1 Gt/yr for rivers and up to 0.4 Gt/yr for estuarine/detaic systems. These estimates are largely uncertain because of the large temporal variability of these systems. In estuarine and deltaic sediments, variability combines hydrological variation from the river (floods and drought) and the hydrology of the coastal seas (storms, current surge, wind induced circulation, upwelling) wich are both influencial on biogeochemistry. This hydrological variability interacts with the seasonal variation of in situ production and with thermal activation of bacterial recycling due to seasonal warming of shallow waters. The combination of these processes gives rise to a range of timescales: typically hours to days for resuspension during storms to interannual variations for particulate discharge modulations. Using in situ oxygen microprofiling devices, we have collected a new dataset on organic matter recycling in the Rhone delta and shelf sediments (Northwestern Mediterranean Sea) which covers a wide range of timescales: from hours to a decade. The hourly variation is collected using a new benthic station deployed on the sediments and specially adapted to monitor short-term variations of sediment oxygen micro-profiles during flood or storms. The seasonal to decadal timescale is constituted by a set of oxygen micro-profiles measured on an array of stations in the Rhône prodelta and shelf by an in situ microprofiler during seasonal cruises over 10 year. The results show that Diffusive Oxygen Fluxes which are related to organic matter recycling vary at all timescales, driven mostly by deposition of river material during floods. Resuspension during storms plays a role over short time scales, and its long-term effect could raise the overall oxygen demand of the sediment by 20-30%.

  19. High-resolution (spatial and temporal) Hydrodynamic Modeling in the Lower Mississippi River Delta

    NASA Astrophysics Data System (ADS)

    Karadogan, E.; Danchuk, S.; Berger, C.; Brown, G.; Willson, C.

    2007-12-01

    The lower Mississippi River is a highly engineered system existing in one of the world's largest deltas. This system is subject to a variety of spatial and temporal forcings due to its large watershed (drains about 41% of the continental U.S.) and from the Gulf of Mexico. Future perturbations on this system are anticipated due to the impacts of global climate change (e.g., rising eustatic sea level, changes in weather patterns) and from proposed modifications to the system such as diversion structures aimed at providing freshwater nutrients and sediments to the rapidly degrading coastal wetlands. Numerical modeling will play a large role in improving our understanding and management of the system and the ability to properly design future structural features. These models will need to have the necessary spatial and temporal resolution to account for the many important processes in the river, the Gulf of Mexico, and in the wetland areas where small distributary channels will form and wetting/drying must be accounted for. This paper will investigate the ability of a 2D shallow water and sediment model to reproduce the complex distributary development associated with flow diversions into quiescent bays. A reach of the Lower Mississippi River from Point a la Hache to the Gulf of Mexico was used as a test domain to evaluate the performance and capabilities of the U.S. Army Corps of Engineers ADaptive Hydraulics (ADH) model. ADH is an unstructured finite element modeling system that includes unsaturated Richards' equations for groundwater, Navier Stokes for nonhydrostatic flow calculations, and Shallow Water equations. ADH conducts automated refinement and coarsening of the mesh based upon flow characteristics. In this case the 2D shallow water model is being used. It includes coupled flow and sedimentation. An unstructured mesh was developed for the study area which includes detailed bathymetry and topography from available survey data. The mesh is fine enough to capture

  20. Sandy River Delta Habitat Restoration : Annual Report, January 2008 - March 2009.

    SciTech Connect

    Dobson, Robin

    2009-09-11

    During the period 2008-2009, there were 2 contracts with BPA. One (38539) was dealing with the restoration work for 2007 and the other (26198) was an extension on the 2006 contract including the NEPA for Dam removal on the old channel of the Sandy River. For contract 38539, the Sandy River Delta Habitat Restoration project continued its focus on riparian hardwood reforestation with less emphasis on wetlands restoration. Emphasis was placed on Sundial Island again due to the potential removal of the dike and the loss of access in the near future. AshCreek Forest Management was able to leverage additional funding from grants to help finance the restoration effort; this required a mid year revision of work funded by BPA. The revised work not only continued the maintenance of restored hardwood forests, but was aimed to commence the restoration of the Columbia River Banks, an area all along the Columbia River. This would be the final restoration for Sundial Island. The grant funding would help achieve this. Thus by 2011, all major work will have been completed on Sundial Island and the need for access with vehicles would no longer be required. The restored forests continued to show excellent growth and development towards true riparian gallery forests. Final inter-planting was commenced, and will continue through 2010 before the area is considered fully restored. No new wetland work was completed. The wetlands were filled by pumping in early summer to augment the water levels but due to better rainfall, no new fuel was required to augment existing. Monitoring results continued to show very good growth of the trees and the restoration at large was performing beyond expectations. Weed problems continue to be the most difficult issue. The $100,000 from BPA planned for forest restoration in 2008, was augmented by $25,000 from USFS, $120,000 from OR150 grant, $18,000 from LCREP, and the COE continued to add $250,000 for their portion. Summary of the use of these funds are

  1. River Bookends: Headwaters, Delta and the Volumes of Stories in Between

    NASA Astrophysics Data System (ADS)

    Waller, J. L.; Brey, J. A.

    2016-12-01

    As professors of art and earth science, we were often pleased when our students found that integrating lessons of geoscience with art rewarded them in impactful and memorable ways. Inspired by student success and our very real concern for natural and human caused threats to treasured cities and areas on the globe, we produced "Layers: Places in Peril", a gallery exhibition of paintings and scientific explanation essays. We found the combination of art and earth science was a powerful tool that touched and informed a wide and diverse population beyond classrooms. Acutely aware that current crises facing Earth are not limited to gigantic forces, we then produced "small problems, BIG TROUBLE" that addressed how seemingly small problems lead to far-reaching threats. Our conversation expanded to include twenty other scientists from geoscience, biology, physics and chemistry whose science-based essays paired with Waller's paintings. In our newest presentation in production, River Bookends: Headwaters, Delta and the Volumes of Stories in Between, we address art and geo-cultural connections associated with World rivers. Our exploration is focused on rivers as markers of time, culture and identity, yet, the importance of stressing the geoscience in this exhibition is large, indeed. An understanding of geomorphology and river ecology and of the historical changes, both natural and human-engineered which may dramatically give rise to, enrich, distress, or ultimately destroy human settlements and culture, are essential to our intended emphases in the show. In this session, we will describe these exhibitions, show images of the work and discuss some of the gallery activities that resulted from the shows, which included a discussion panel of social science and humanities faculty focused on the exhibition topics. We will describe how local high school art and science students answered our invitation to create a parallel exhibition of our show premise, concurrently exhibited in an

  2. Modeling the Impact of controlled flow and sediment releases for the restoration of the Nile River-Delta system, Egypt

    NASA Astrophysics Data System (ADS)

    Al-Zaidi, B.; Moussa, A.; Viparelli, E.

    2016-12-01

    The construction of the High Aswan Dam (HAD) and river barrages significantly modified the flow and the sediment transport regimes in the Egyptian portion of the Nile River. Field data of the Nile Research Institute reveal that flood flows are reduced more than 70% compared to pre-HAD conditions and more than 98% of the sediment load is trapped in Lake Nasser upstream of the HAD. Water diversions at the barrages further reduce the flow rate reaching the Nile delta. Consequences of the flow regulation are erosion of the channel bed and changes in channel morphology in the upstream part of the study reach, and in-channel sedimentation in the downstream part of the system. However, due to the flow reduction, the sediment load delivered to the Mediterranean Sea is negligible compared to pre-dam conditions with consequent delta wide wetland loss and shoreline retreat. Here we present the first part of a feasibility study for the restoration of the Nile River-delta system characterized by controlled flow releases and sediment augmentations downstream of the HAD. The controlled flow releases are obtained by combining the current releases form the High Aswan Dam with a 10 billion m3 annual hydrograph. Previous studies showed that this volume of water will be available if the irrigation canals are replaced by more water efficient irrigation methods. The objectives of this work are to quantify the effects of the restoration project in terms of 1) erosion in the upstream part of the study reach, 2) sedimentation in the downstream part of the study reach, and 3) flow rate and sediment load delivered to the delta apex during the restoration project. The impacts of the controlled flow and sediment releases on the Nile River delta will be quantified in the near future.

  3. Sustainability of massively anthropic deltas via dispersal of sediment to manage land building: results from two unique case studies, the Mississippi River (U.S.A.) and the Yellow River (China) deltas

    NASA Astrophysics Data System (ADS)

    Nittrouer, Jeffrey

    2016-04-01

    studies of both the Mississippi and Yellow rivers have been used to inform and validate numerical modeling efforts that seek to replicate the morphodynamics of the two diversions. The aim is to evaluate best practices for building deltaic landscape. Based on these research efforts, there are key similarities found for the delta systems: 1) coarse (sandy) sediment is the primary contributor to subaerial delta development, despite the abundance of mud for both rivers; 2) the influx of freshwater into estuarine regions of deltas has tremendous impact on vegetation development, and therefore the cohesion of the deltaic sediment deposit; and 3) it is feasible to produce efficient diversions that maximize sediment delivery and still provide for continued use of the riverine resource (for example, navigation of the channel by vessels). These findings are critical when considering future plans that seek sustainable management practices of other large, anthropic fluvial deltaic systems.

  4. Hydrogeological modeling of water exchange between a river valley aquifer and the Colorado River at a riparian corridor of the Colorado River Delta

    NASA Astrophysics Data System (ADS)

    Perez-Gonzalez, D.; Ramirez-Hernandez, J.; Zamora, F.

    2008-05-01

    The Colorado River Delta has shown a high capacity of regeneration in spite of the drastic reduction of the freshwater flows. This river has an important ecological value for the remaining ecosystems at the regional and continental level. It is not known when this river will present again surpluses of superficial water in the basin, as it happened in the decades of 1980 and 1990. The ecosystems of the Delta depend on the availability of groundwater to survive. The practices of blanket irrigation in the Valley of Mexicali have favored the vertical refill of the aquifer. Part of this water that infiltrates the ground is captured by the Colorado River (CR). As a consequence, even in years in which the CR has not received surpluses of superficial water low flow can be observed in the river, especially in the area of our study that comprises 12 km of the CR between the interception of the railroad with the river and the entrance to Carranza City. This low flow provides water to maintain the riparian vegetation of the zone. For this reason, it is important to know the hydrologic relationship between the river aquifer and the CR. The purpose of this work is to determine the volumes of water supplied by the aquifer to the riparian system and its relationship with the vegetation. Measurements of the fluctuations of the freatic level (FL) in 27 boreholes located in 8 cross sections during more than 2 years have been used for this study. The system was modelled using the program MODFLOW considering diverse water levels in the CR and flow exchange with the aquifer. The hydrogeological properties of the aquifer were found from slug tests and correlations with the textures of 100 soil samples. The modeling results allow to separate the zone of study in three sections. The first one extends 5km from the railroad to the south. In this section the CR receives water from the aquifer producing the observed water in the river bed all the year. The second section, of approximately 2 km

  5. Distribution and condition of larval and juvenile Lost River and shortnose suckers in the Williamson River Delta restoration project and Upper Klamath Lake, Oregon

    USGS Publications Warehouse

    Burdick, Summer M.; Brown, Daniel T.

    2010-01-01

    Federally endangered Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) were once abundant throughout their range but populations have declined. They were extirpated from several lakes in the 1920s and may no longer reproduce in others. Poor recruitment to the adult spawning populations is one of several reasons cited for the decline and lack of recovery of these species and may be the consequence of high mortality during juvenile life stages. High larval and juvenile sucker mortality may be exacerbated by an insufficient quantity of suitable or high quality rearing habitat. In addition, larval suckers may be swept downstream from suitable rearing areas in Upper Klamath Lake into Keno Reservoir, which is seasonally anoxic. The Nature Conservancy flooded about 3,600 acres (1,456 hectares) to the north of the Williamson River mouth (Tulana Unit) in October 2007 and about 1,400 acres (567 hectares) to the south and east of the Williamson River mouth (Goose Bay Unit) a year later to retain larval suckers in Upper Klamath Lake, create nursery habitat, and improve water quality. The U.S. Geological Survey joined a long-term research and monitoring program in collaboration with The Nature Conservancy, the Bureau of Reclamation, and Oregon State University in 2008 to assess the effects of the Williamson River Delta restoration on the early life-history stages of Lost River and shortnose suckers. The primary objectives of the research were to describe habitat colonization and use by larval and juvenile suckers and non-sucker fishes and to evaluate the effects of the restored habitat on the health and condition of juvenile suckers. This report summarizes data collected in 2009 by the U.S. Geological Survey as a part of this monitoring effort. The Williamson River Delta appeared to provide suitable rearing habitat for endangered larval Lost River and shortnose suckers in 2008 and 2009. Larval suckers captured in this delta typically were

  6. Influences of Relative Sea-Level Rise and Mississippi River Delta Plain Evolution on the Holocene Middle Amite River, Southeastern Louisiana

    USGS Publications Warehouse

    Autin, W.J.

    1993-01-01

    The Holocene geomorphic history of southeastern Louisiana's middle Amite River is recorded in the stratigraphy of three alloformations, identified in decreasing age as the Watson (WAT), Denham Springs (DS), and Magnolia Bridge (MAG). The WAT meander belt formed by at least 9000 yr B.P., when sea level was lower and the Amite River was tributary to a larger ancestral drainage basin. The DS became an active meander belt by at least 3000 yr B.P., in response to relative sea-level rise and eastward progradation of the Mississippi River delta plain. The MAG developed its meander belt, in part, during the European settlement of the drainage basin, and is now attempting to adjust to modern anthropogenic influences. Geomorphic influences on the middle Amite River floodplain have temporal and spatial components that induce regional- and local-scale effects. Regional extrinsic influences caused meander belt avulsion that produced alloformations. However, local influences produced intrinsic geomorphic thresholds that modified channel morphology within a meander belt but did not induce alloformation development. Base-level influences of the relative sea-level rise and the Mississippi River delta plain were so dominant that the effects of possible climate change were not recognized in the Holocene Amite River system.

  7. Distribution and pollution, toxicity and risk assessment of heavy metals in sediments from urban and rural rivers of the Pearl River delta in southern China.

    PubMed

    Xiao, Rong; Bai, Junhong; Huang, Laibin; Zhang, Honggang; Cui, Baoshan; Liu, Xinhui

    2013-12-01

    Sediments were collected from the upper, middle and lower reaches of both urban and rural rivers in a typical urbanization zone of the Pearl River delta. Six heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) were analyzed in all sediment samples, and their spatial distribution, pollution levels, toxicity and ecological risk levels were evaluated to compare the characteristics of heavy metal pollution between the two rivers. Our results indicated that the total contents of the six metals in all samples exceeded the soil background value in Guangdong province. Based on the soil quality thresholds of the China SEPA, Cd levels at all sites exceeded class III criteria, and other metals exhibited pollution levels exceeding class II or III criteria at both river sites. According to the sediment quality guidelines of the US EPA, all samples were moderately to heavily polluted by Cr, Cu, Ni, Pb and Zn. Compared to rural river sites, urban river sites exhibited heavier pollution. Almost all sediment samples from both rivers exhibited moderate to serious toxicity to the environment, with higher contributions from Cr and Ni. A "hot area" of heavy metal pollution being observed in the upper and middle reaches of the urban river area, whereas a "hot spot" was identified at a specific site in the middle reach of the rural river. Contrary metal distribution patterns were also observed along typical sediment profiles from urban and rural rivers. However, the potential ecological risk indices of rural river sediments in this study were equal to those of urban river sediments, implying that the ecological health issues of the rivers in the undeveloped rural area should also be addressed. Sediment organic matter and grain size might be important factors influencing the distribution profiles of these heavy metals.

  8. Groundwater response to the 2014 pulse flow in the Colorado River Delta

    USGS Publications Warehouse

    Kennedy, Jeffrey; Rodriguez-Burgueno, Eliana; Ramirez-Hernandez, Jorge

    2016-01-01

    During the March-May 2014 Colorado River Delta pulse flow, approximately 102 × 106 m3 (82,000 acre-feet) of water was released into the channel at Morelos Dam, with additional releases further downstream. The majority of pulse flow water infiltrated and recharged the regional aquifer. Using groundwater-level and microgravity data we mapped the spatial and temporal distribution of changes in aquifer storage associated with pulse flow. Surface-water losses to infiltration were greatest around the Southerly International Boundary, where a lowered groundwater level owing to nearby pumping created increased storage potential as compared to other areas with shallower groundwater. Groundwater levels were elevated for several months after the pulse flow but had largely returned to pre-pulse levels by fall 2014. Elevated groundwater levels in the limitrophe (border) reach extended about 2 km to the east around the midway point between the Northerly and Southerly International Boundaries, and about 4 km to the east at the southern end. In the southern part of the delta, although total streamflow in the channel was less due to upstream infiltration, augmented deliveries through irrigation canals and possible irrigation return flows created sustained increases in groundwater levels during summer 2014. Results show that elevated groundwater levels and increases in groundwater storage were relatively short lived (confined to calendar year 2014), and that depressed water levels associated with groundwater pumping around San Luis, Arizona and San Luis Rio Colorado, Sonora cause large, unavoidable infiltration losses of in-channel water to groundwater in the vicinity.

  9. Relevance of the Paraná River hydrology on the fluvial water quality of the Delta Biosphere Reserve.

    PubMed

    Puig, Alba; Olguín Salinas, Héctor F; Borús, Juan A

    2016-06-01

    The increasing frequency of extreme events in large rivers may affect not only their flow, but also their water quality. In the present study, spatial and temporal changes in fluvial physico-chemical variables were analyzed in a mega-river delta during two extreme hydrological years (La Niña-El Niño) and related to potential explanatory factors. Basic water variables were evaluated in situ at 13 points (distant 2-35 km from each other) in watercourses of the Delta Biosphere Reserve (890 km(2)) in the Lower Paraná River (Argentina) in nine surveys (October 2008-July 2010) without meteorological tides. Samples for laboratory analyses were collected from each main river. Multivariate tests by permutations were applied. The period studied was influenced by a drought, within a long period dominated by low flows combined with dry weather and wildfires, and a large (10 years of recurrence) and prolonged (7 months) flood. The hydrological phase, followed by the season and the hydrological year (according to the ENSO event) were the principal explanatory factors of the main water quality changes, whereas the drainage sub-basin and the fluvial environment (river or stream) were secondary explanatory factors. During the drought period, conductivity, turbidity, and associated variables (e.g., major ions, silicon, and iron concentrations) were maximal, whereas real color was minimal. In the overbanking flood phase, pH and dissolved oxygen concentration were minimal, whereas real color was maximal. Dissolved oxygen saturation was also low in the receding flood phase and total major ion load doubled after the arrival of the overbanking stage. The water quality of these watercourses may be affected by the combination of several influences, such as the Paraná River flow, the pulses with sediments and solutes from the Bermejo River, the export of the Delta floodplain properties mainly by the flood, the season, and the saline tributaries to the Lower Paraná River. The high

  10. Practicality of marine protected areas - Can there be solutions for the River Indus delta?

    NASA Astrophysics Data System (ADS)

    Kidwai, Samina; Fanning, Paul; Ahmed, Waqar; Tabrez, Mohsin; Zhang, Jing; Khan, Muhammad Wasim

    2016-12-01

    The River Indus delta is the most prominent feature on the Pakistan coast. Owing to its prominence, mangrove ecosystem, historical, ecological and economic significance it is also a proposed Marine Protected Area (MPA). Currently there are no designated MPAs in Pakistan. This paper presents findings of the Fishery Resource Appraisal Project of Pakistan (FRAPP) a fishery stock assessment carried out for the pelagic and demersal fishery resource of Pakistan from 2009 to 2015 and the Creek Survey Program (CSP) which was part of FRAPP. And discusses how the delta suffers from physical stress. The observations from FRAPP indicates deterioration in the mangrove ecosystem, that are evident in the form of loss of biodiversity and biological productivity. The 600 observations from 10 major creeks showed that trawl catches were a mix of generally small size fish and shrimp. Catches averaged less than 1 kg per tow in all the creeks sampled. Catch weights were somewhat higher in Isaro, WadiKhuddi, Paitiani, Dabbo, Richaal Creeks all of which were near mangrove areas and open sea. The most frequently occurring species of shrimps caught in the trawls belonged to 7 major taxa. The Khobar Creek and Upper Wari Creek are notable for the high rates of occurrence of every group except the Caridea. They are also the only two creeks where the freshwater family Paleomonidae is common. The size composition of the important penaeid family of shrimps in all study areas combined suggests that the smallest shrimps (0.5-1.5 cm carapace length CL) enter the creeks in February/March and adults (5-6 cm CL) move out again 6-12 months later. Four species of Penaeus (monodon, japonicus, semisulcatus, merguiensis), two species of Metapenaeus (monoceros, affinis), Parapeneoposis stylifera and Solenosera sp. were caught, all in low abundance, less than 0.5 Kg tow-1. The shrimp catches in the area off the Sindh coast, the catches averaged 4.30 ± 13.40 kg h-1 on the inner shelf (20-50 m) and 1.7 ± 6

  11. Spatiotemporal Dynamics of River Channel Migration on the Ganges-Brahmaputra Delta: 2000-2013

    NASA Astrophysics Data System (ADS)

    Small, C.; Chiu, S.; Sousa, D.; Mondal, D. R.; Steckler, M. S.; Akhter, S. H.; Mia, B.; Goodbred, S. L., Jr.; Wilson, C.; Seeber, L.

    2014-12-01

    We use multitemporal multiscale satellite remote sensing to complement field observations and subsurface measurements to better understand the relationship between recent and historic fluvial dynamics on the Ganges-Brahmaputra (GB) delta. To provide regional context for the interannual changes in river channel geometry we conduct spatiotemporal (ST) analyses of MODIS Enhanced Vegetation Index (EVI) imagery for 2000-2013 using a new method of Empirical Orthogonal Function (EOF) analysis. We use EVI because it distinguishes water from wet and dry sediment on the basis of the spectral slope at VNIR wavelengths. Water has a negative slope while dry sediment has a small positive slope and vegetation has a large positive slope. To characterize the ST patterns associated with river channel migration we use iterative EOF analysis (iEOF). In iEOF we first conduct a single year EOF analysis for each year in the time series to identify the primary spatial principal component (PC1) for each year and separate this from the spatial structure of the subannual temporal patterns associated with vegetation phenology. We then construct a decadal time series of PC 1 for each single year and conduct a second EOF analysis of the time series of 13 individual year PCs. The standard EOFs of the full (312 images x 16 day) time series only resolve a decadal trend (EOF 8), but the iEOF clearly distinguishs the progressive decadal trend (EOF 2) from the cyclic component (EOF 3) of decadal changes in sediment reflectance. The temporal feature space constructed from PC 2 and PC 3 (corresponding to temporal EOFs 2 and 3) distinguishes pixels with progressive decadal increases and decreases in reflectance from pixels with cyclic changes. Evolution of the annual structure is animated at www.youtube.com/watch?v=UM1UYvdnYXk Despite significant differences in the 2 rivers'morphologies, and the considerable magnitude of flooding every year, we observe year-to-year continuity in the progressive

  12. Distribution and condition of larval and juvenile Lost River and shortnose suckers in the Williamson River Delta restoration project and Upper Klamath Lake, Oregon

    USGS Publications Warehouse

    Burdick, Summer M.

    2012-01-01

    Federally endangered Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) were once abundant throughout their range but populations have declined. They were extirpated from several lakes in the 1920s and may no longer reproduce in other lakes. Poor recruitment to the adult spawning populations is one of several reasons cited for the decline and lack of recovery of these species and may be the consequence of high mortality during juvenile life stages. High larval and juvenile sucker mortality may be exacerbated by an insufficient quantity of suitable or high-quality rearing habitat. In addition, larval suckers may be swept downstream from suitable rearing areas in Upper Klamath Lake into Keno Reservoir, where they are assumed lost to Upper Klamath Lake populations. The Nature Conservancy flooded about 3,600 acres (1,456 hectares) to the north of the Williamson River mouth (Tulana) in October 2007, and about 1,400 acres (567 hectares) to the south and east of the Williamson River mouth (Goose Bay Farms) in October 2008, in order to retain larval suckers in Upper Klamath Lake, create nursery habitat, and improve water quality. The U.S. Geological Survey joined a long-term research and monitoring program in collaboration with The Nature Conservancy, the Bureau of Reclamation, and Oregon State University in 2008 to assess the effects of the Williamson River Delta restoration on the early life-history stages of Lost River and shortnose suckers. The primary objectives of the research were to describe habitat colonization and use by larval and juvenile suckers and non-sucker fishes and to evaluate the effects of the restored habitat on the health and condition of juvenile suckers. This report summarizes data collected in 2010 by the U.S. Geological Survey as a part of this monitoring effort and follows two annual reports on data collected in 2008 and 2009. Restoration modifications made to the Williamson River Delta appeared to provide

  13. Fire, Carbon, and Greenhouse Gas Emissions from Aquatic Ecosystems in the Yukon-Kuskokwim River Delta

    NASA Astrophysics Data System (ADS)

    Schade, J. D.; Kuhn, M. A.; Mann, P. J.; Holmes, R. M.; Natali, S.; Ludwig, S.; Wagner, S.

    2016-12-01

    Northern latitudes are experiencing rapid changes in climate that are profoundly altering permafrost-dominated ecosystems. Increased permafrost thaw and fire frequency and severity are changing the structure and function of these ecosystems in ways likely to alter greenhouse gas (GHG) emission, leading to feedbacks on climate that may accelerate warming. Our objective was to investigate changes in GHG emissions and carbon and nitrogen dynamics in aquatic ecosystems in response to recent fires in the Yukon-Kuskokwim river delta in western Alaska. In summer 2015, more area in the YK Delta burned then in the previous 74 years combined (726 km2 in 2015 vs. 477 km2 during 1940-2014). In June of 2016, we sampled water and dissolved gases from a variety of aquatic ecosystems, including small upland ponds and wetlands and streams lower in the landscape, in recently burned and control sites near the Kuka Creek 2015 burn scar in the Yukon Delta National Wildlife Refuge. We measured a range of physical parameters, including water temperature, conductivity, dissolved oxygen, and pH. We also estimated fluxes of CO2 and CH4 from surface waters using a floating chamber connected to a Los Gatos Ultraportable gas analyzer. Water samples were analyzed for dissolved organic carbon (DOC) and total dissolved nitrogen (TDN). Results show reduced DOC concentrations in small upland ponds in burned sites and evidence for loss of DOC downslope in control sites. In contrast, TDN concentration was higher in streams draining burned sites, suggesting fire mobilized N in soils, which was then transported to downslope ecosystems. Furthermore, fire generally increased pH, particularly in small ponds. Finally, we observed 3-4 fold higher CO2 and CH4 fluxes from aquatic ecosystems in burned sites as compared with control sites. We hypothesize that this is due to increased thaw depth and increased pH, which combine to increase resource availability and release methane-producing microbes from the

  14. Intercomparison study of atmospheric methane and carbon dioxide concentrations measured at the Ebre River Delta Station

    NASA Astrophysics Data System (ADS)

    Occhipinti, Paola; Morguí, Josep Anton; Àgueda, Alba; Batet, Oscar; Borràs, Sílvia; Cañas, Lídia; Curcoll, Roger; Grossi, Claudia; Nofuentes, Manel; Vazquez, Eusebi; Rodó, Xavier

    2015-04-01

    In the framework of the ClimaDat project, IC3 has established a network of eight monitoring stations across the Iberian Peninsula and the Canarian Archipelago with the aim of studying climate processes. The monitoring station at the Ebre River Delta (DEC3) is located in the Ebre River Delta Natural Park (40° 44' N; 0° 47' E) and it is characterized by the typical North-Western Mediterranean climate. Since 2013, atmospheric greenhouse gases (GHG) and 222Rn tracer gas together with the meteorological parameters are continuously measured from a 10 m a.g.l. height tower. Atmospheric GHG (CO2, CH4, CO and N2O) concentrations are determined using a Picarro analyzer G2301 (CO2 and CH4) and a modified gas chromatograph (GC) Agilent 6890N (CO2, CH4, CO and N2O). Open data access is available from the www.climadat.es website. Data collected at the DEC3 station are also submitted to the InGOS platform since this station is part of the InGOS European infrastructure project. Researchers from the Laboratory of the Atmosphere and the Oceans (LAO) at IC3 have performed an intercomparison study at the DEC3 site between three different Picarro analyzers (two Picarro G2301 and one Picarro G2301M), a Los Gatos Research (LGR) analyzer and the GC system already installed at the station. The aim of this study is to compare and assess the measuring agreement between the four optical gas analyzers and the GC. In the first part of the experiment, all instruments have been calibrated using NOAA gases as primary standards analyzing five Praxair provided targets to evaluate the precision of the measuring instruments. Max Plank Institute (MPI) gases have been used as secondary standards for the GC whereas Praxair provided tanks are used as secondary standards for the Picarro and the LGR analyzers. In the second part of the experiment, atmospheric GHG were measured from natural atmospheric air taken from a 10 m a.g.l. inlet. Daily cycles of GHG measurements were carried out using different

  15. Bottom morphology in the Song Hau distributary channel, Mekong River Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Allison, Mead A.; Dallon Weathers, H.; Meselhe, Ehab A.

    2017-09-01

    Field studies in the Song Hau distributary of the Mekong Delta in Vietnam conducted at high (Sept.-Oct 2014) and low (March 2015) Mekong River discharge are utilized to examine channel bottom morphology and links with sediment transport in the system. Multibeam bathymetric mapping surveys over the entire channel complex in the lower 80 km of the distributary channel, and over 12- to 24-h tidal periods at six transect locations in the reach are used to characterize bottom type and change on seasonal and tidal timescales, supplemented by bottom sampling. The results of this study indicate that the largest proportion of channel floor (up to 80% of the total area) is composed of substratum outcrops of relict sediment units deposited during the progradation of the delta in the last 3.5 ka. These take the form of outcrops that are either (1) steep-sided, tabular channel floor, (2) steep-sided sidewall, or (3) relatively flat channel floor. Flatter outcrops of channel floor substratum are identified by the presence of sedimentary furrows (<0.5 m deep) incised into the channel bottom that are exposed at high discharge and oriented along channel and laterally continuous for kilometers. These furrows are persistent in location and extent across tidal cycles and appear to be incised into relict units, sometimes with a thin surficial layer of modern sediment observable in bottom grabs. The extent of substratum exposure, greater than that observed previously in low tidal energy systems like the Mississippi River, may relate both to a relatively low sand supply from the catchment, and/or to an efficient transfer of both sand and mud through this tidally energetic channel. Sand bottom areas forming dunes, comprise about 19% of the channel floor over the study area and are generally less than a few meters thick except on bar extensions of mid-channel islands. Both sandy and substratum areas are mantled by soft muds 0.25-1 m thick during low discharge in the estuarine section of

  16. Temporal Fluctuation of Multidrug Resistant Salmonella Typhi Haplotypes in the Mekong River Delta Region of Vietnam

    PubMed Central

    Chau, Tran Thuy; Duy, Pham Thanh; La, Tran Thi Phi; Hoang, Nguyen Van Minh; Nga, Tran Vu Thieu; Campbell, James I.; Manh, Bui Huu; Vinh Chau, Nguyen Van; Hien, Tran Tinh; Farrar, Jeremy; Dougan, Gordon; Baker, Stephen

    2011-01-01

    Background Typhoid fever remains a public health problem in Vietnam, with a significant burden in the Mekong River delta region. Typhoid fever is caused by the bacterial pathogen Salmonella enterica serovar Typhi (S. Typhi), which is frequently multidrug resistant with reduced susceptibility to fluoroquinolone-based drugs, the first choice for the treatment of typhoid fever. We used a GoldenGate (Illumina) assay to type 1,500 single nucleotide polymorphisms (SNPs) and analyse the genetic variation of S. Typhi isolated from 267 typhoid fever patients in the Mekong delta region participating in a randomized trial conducted between 2004 and 2005. Principal Findings The population of S. Typhi circulating during the study was highly clonal, with 91% of isolates belonging to a single clonal complex of the S. Typhi H58 haplogroup. The patterns of disease were consistent with the presence of an endemic haplotype H58-C and a localised outbreak of S. Typhi haplotype H58-E2 in 2004. H58-E2-associated typhoid fever cases exhibited evidence of significant geo-spatial clustering along the Sông H u branch of the Mekong River. Multidrug resistance was common in the established clone H58-C but not in the outbreak clone H58-E2, however all H58 S. Typhi were nalidixic acid resistant and carried a Ser83Phe amino acid substitution in the gyrA gene. Significance The H58 haplogroup dominates S. Typhi populations in other endemic areas, but the population described here was more homogeneous than previously examined populations, and the dominant clonal complex (H58-C, -E1, -E2) observed in this study has not been detected outside Vietnam. IncHI1 plasmid-bearing S. Typhi H58-C was endemic during the study period whilst H58-E2, which rarely carried the plasmid, was only transient, suggesting a selective advantage for the plasmid. These data add insight into the outbreak dynamics and local molecular epidemiology of S. Typhi in southern Vietnam. PMID:21245916

  17. Distribution and abundance of the Yuma clapper rail (Rallus longirostris yumanensis) in the Colorado River delta, México

    USGS Publications Warehouse

    Hinojosa-Huerta, Osvel; DeStefano, Stephen; Shaw, William W.

    2001-01-01

    We estimated the abundance of Yuma clapper rails in the Ciénega de Santa Clara and determined the distribution of the subspecies in the Colorado River delta region in México. The maximum estimate of abundance was 6629 individuals (95% C.I. 4859–8399), assuming a response rate by rails to taped calls of 60%. Rails were widely distributed in the delta, occupying almost all marshlands dominated by cattail. As this is an endangered subspecies shared by México and the U.S., the conservation of the delta ecosystem should be the interest of both countries, especially when water management decisions upstream in the U.S. have an impact over natural areas downstream in México.

  18. [Distribution characteristics of soil organic carbon and its composition in Suaeda salsa wetland in the Yellow River delta].

    PubMed

    Dong, Hong-Fang; Yu, Jun-Bao; Guan, Bo

    2013-01-01

    Applying the method of physical fractionation, distribution characteristics of soil organic carbon and its composition in Suaeda salsa wetland in the Yellow River delta were studied. The results showed that the heavy fraction organic carbon was the dominant component of soil organic carbon in the studied region. There was a significantly positive relationship between the content of heavy fraction organic carbon, particulate organic carbon and total soil organic carbon. The ranges of soil light fraction organic carbon ratio and content were 0.008% - 0.15% and 0.10-0.40 g x kg(-1), respectively, and the range of particulate organic carbon ratio was 8.83% - 30.58%, indicating that the non-protection component of soil organic carbon was low and the carbon pool was relatively stable in Suaeda salsa wetland of the Yellow River delta.

  19. Spatial and Seasonal Variations of Total Petroleum Hydrocarbon in Surface Water and Sediment in Pearl River Delta.

    PubMed

    Zhao, Jiandi; Yin, Pinghe; Zhao, Ling; Yu, Qiming; Lu, Gang

    2015-09-01

    A field study in the Pearl River Delta of China was conducted in order to describe to the spatial and seasonal variation of occurrence and concentrations of total petroleum hydrocarbon (TPH) in surface water and sediments. Petroleum hydrocarbons and isoprenoid alkanes were quantified by UV spectroscopy and gas chromatography with a mass selective detector. The concentrations of TPH ranged from 4.3 to 68.7 µg L(-1) in surface water, and from 66.6 to 1445 µg g(-1) in surface sediments. The ratios of pristine to phytane suggested that the main sources of TPH in the sediment were petroleum importation. The highest concentrations of TPH were present in the spring season. When compared with results from previous studies, it can be concluded that the Pearl River Delta was moderately polluted by TPH. No statistically significant correlations were observed between the concentrations of TPH in surface water and sediments.

  20. Cost analysis of water and sediment diversions to optimize land building in the Mississippi River delta

    NASA Astrophysics Data System (ADS)

    Kenney, Melissa A.; Hobbs, Benjamin F.; Mohrig, David; Huang, Hongtai; Nittrouer, Jeffrey A.; Kim, Wonsuck; Parker, Gary

    2013-06-01

    Land loss in the Mississippi River delta caused by subsidence and erosion has resulted in habitat loss and increased exposure of settled areas to storm surge risks. There is debate over the most cost-efficient and geomorphologically feasible projects to build land by river diversions, namely, whether a larger number of small, or a lesser number of large, engineered diversions provide the most efficient outcomes. This study uses an optimization framework to identify portfolios of diversions that are efficient for three general restoration objectives: maximize land built, minimize cost, and minimize water diverted. The framework links the following models: (1) a hydraulic water and sediment diversion model that, for a given structural design for a diversion, estimates the volume of water and sediment diverted; (2) a geomorphological land-building model that estimates the amount of land built over a time period, given the volume of water and sediment; and (3) a statistical model of investment cost as a function of diversion depth and width. An efficient portfolio is found by optimizing one objective subject to constraints on achievement of the other two; then by permuting those constraints, we find distinct portfolios that represent trade-offs among the objectives. Although the analysis explores generic relationships among size, cost, and land building (and thus does not consider specific project proposals or locations), the results demonstrate that large-scale land building (>200 km2) programs that operate over a time span of 50 years require deep diversions because of the enhanced efficiency of sand extraction per unit water. This conclusion applies whether or not there are significant scale economies or diseconomies associated with wider and deeper diversions.

  1. Organochlorines in sediments and mussels collected from coastal sites along the Pearl River Delta, South China.

    PubMed

    Fang, Zhan-qiang

    2004-01-01

    The level and pattern of residues of organochlorine pesticide and polychlorinated biphenyls(PCBs) were analyzed in sediment and mussel (Perna viridis) samples from ten coastal sites along the Pearl River Delta, South China. The range of total HCH was < 0.01 to 0.29 ng/g freeze-dried weight in sediment, and < 0.01 to 1.35 ng/g lipid weight in mussels. Average total DDTs concentrations ranged from < 0.01 to 1.04 ng/g in sediment, and < 0.01 to 148.5 ng/g in mussels. Average total PCB concentrations ranged from 16.4 to 198.6 ng/g in sediment, and from 41 to 729.2 ng/g in mussels. Organochlorine pesticide and PCBs in mussels and sediments presented similar distribution patterns. The regression analysis indicated that PCBs concentrations in mussels were significantly correlated (p < 0.01) with concentrations in sediments. However, their concentrations in mussels were several times higher than the concentration detected in surrounding sediments. The major fraction of DDT related compounds measured in mussels and sediments was DDD. Based on average PCB concentrations, penta-, hexa-, and tetrachlorobiphenyls were preferentially accumulated by mussels as compared to the average sediment composition. According to the present results,three organochlorine polluted "hot spot" sites, including Victoria Harbour, Lingding Yang and Huangmao Sea, were found in the Pearl River estuarine zone. HCHs, DDTs and PCBs in all mussel samples were below the limits of 2, 0.2 and 5.0 microg/g wet weight recommended by the Technical Group of Guangdong Coastal Zone Resource Comprehensive Survey and U. S. Food and Drug Administration.

  2. Sectorial Water Use Trends in the Urbanizing Pearl River Delta, China

    PubMed Central

    Yao, Mingtian; Werners, Saskia E.; Hutjes, Ronald W. A.; Kabat, Pavel; Huang, Heqing

    2015-01-01

    Assessing and managing water use is crucial for supporting sustainable river basin management and regional development. The first consistent and comprehensive assessment of sectorial water use in the Pearl River Delta (PRD) is presented by analysing homogenized annual water use data from 2000 to 2010 in relation to socio economic statistics for the same period. An abstraction of water use, using the concept of water use intensity, and based on equations inspired by those used in global water resource models, is developed to explore the driving forces underlying water use changes in domestic, industrial and agricultural sectors. We do this at both the level of the region as a whole, as well as for the nine cities that constitute the PRD separately. We find that, despite strong population and economic growth, the PRD managed to stabilize its absolute water use by significant improvements in industrial water use intensities, and early stabilisation of domestic water use intensities. Results reveal large internal differentiation of sectorial water use among the cities in this region, with industrial water use intensity varying from -80 to +95% and domestic water use intensity by +/- 30% compared to the PRD average. In general, per capita water use is highest in the cities that industrialised first. Yet, all cities except Guangzhou are expected to approach a saturation value of per capita water use much below what is suggested in recent global studies. Therefore, existing global assessments probably have overestimated future domestic water use in developing countries. Although scarce and uncertain input data and model limitations lead to a high level of uncertainty, the presented conceptualization of water use is useful in exploring the underlying driving forces of water use trends. PMID:25714731

  3. Sectorial water use trends in the urbanizing Pearl River Delta, China.

    PubMed

    Yao, Mingtian; Werners, Saskia E; Hutjes, Ronald W A; Kabat, Pavel; Huang, Heqing

    2015-01-01

    Assessing and managing water use is crucial for supporting sustainable river basin management and regional development. The first consistent and comprehensive assessment of sectorial water use in the Pearl River Delta (PRD) is presented by analysing homogenized annual water use data from 2000 to 2010 in relation to socio economic statistics for the same period. An abstraction of water use, using the concept of water use intensity, and based on equations inspired by those used in global water resource models, is developed to explore the driving forces underlying water use changes in domestic, industrial and agricultural sectors. We do this at both the level of the region as a whole, as well as for the nine cities that constitute the PRD separately. We find that, despite strong population and economic growth, the PRD managed to stabilize its absolute water use by significant improvements in industrial water use intensities, and early stabilisation of domestic water use intensities. Results reveal large internal differentiation of sectorial water use among the cities in this region, with industrial water use intensity varying from -80 to +95% and domestic water use intensity by +/- 30% compared to the PRD average. In general, per capita water use is highest in the cities that industrialised first. Yet, all cities except Guangzhou are expected to approach a saturation value of per capita water use much below what is suggested in recent global studies. Therefore, existing global assessments probably have overestimated future domestic water use in developing countries. Although scarce and uncertain input data and model limitations lead to a high level of uncertainty, the presented conceptualization of water use is useful in exploring the underlying driving forces of water use trends.

  4. Sediment dispersal and accumulation off the present Huanghe (Yellow River) delta as impacted by the Water-Sediment Regulation Scheme

    NASA Astrophysics Data System (ADS)

    Wu, Xiao; Bi, Naishuang; Yuan, Ping; Li, Song; Wang, Houjie

    2015-12-01

    Surface sediment samples from 15 stations around the present Huanghe (Yellow River) river mouth were collected before, during and after the Water-Sediment Regulation Scheme (WSRS) in 2010 for grain size analysis. Hydrographic surveys conducted simultaneously at stations along three transects off the river mouth during the WSRS in 2013 were used to investigate the dispersal and accumulation of the Huanghe sediment off the present Huanghe subaqueous delta. During the WSRS period, the diluted water from the river covered all over the study area within the surface layer, whereas high-concentrated sediment was found in the bottom layers and to be limited in nearshore area shallower than 12 m, indicating that the buoyant river plume was the main sediment dispersal pattern during the WSRS. At the early stage of the WSRS when large amount of clear water was released from the Xiaolangdi Reservoir, sediment eroded from the downstream riverbed in the lower reaches increased the median grain size of surface sediment at the river mouth. During the second stage when water discharge was reduced but sediment discharge was dramatically increased, the fine-grained sediment derived from the Xiaolangdi Reservoir mixed with the previously deposited coarser surface sediment, leading to the decreasing median grain size of surface sediment that approached to be poorly sorted. After the physical sorting from winter storms, the surface sediment was redistributed and varied regularly with water depth. As the median grain size of suspended sediment discharge to the sea has been significantly increased due to the WSRS, the river-delivered sediment mostly accumulated in the nearshore area, which effectively extended the subaerial delta and steepened the subaqueous slope off the present river mouth.

  5. Assessing and classifying plant-related ecological risk under water management scenarios in China's Yellow River Delta Wetlands.

    PubMed

    Yang, Zhifeng; Qin, Yan; Yang, Wei

    2013-11-30

    The Yellow River Delta is one of the most vigorous delta areas in the world. The wetlands in this delta are ecologically important due to their hydrologic attributes and their role as ecotones between terrestrial and aquatic ecosystems. In recent years, the Yellow River Delta Wetlands have gradually shrunk and degraded due to inadequate environmental flows. Water managers have attempted to balance the needs of the environment with the need to protect water supplies for agriculture and urban needs. Despite the need for environmental protection, a broad-scale, integrated way to characterize the degree of ecological stress in the wetlands has been lacking to date. To provide a framework for evaluating various potential water regimes, we developed a model that can be used to estimate the ecological risk for wetland plants, and used the model to determine the degree of ecological risk for different soil moisture conditions based on an ecological value at risk model that we developed and the fuzzy clustering method. The results revealed the spatial distribution of areas with high, medium, or low risks associated with water stress in the study area. These results can serve as a preliminary template to guide managers in their evaluation of water stress-related risk.

  6. Natural and anthropogenic emissions of N and P to the Parnaíba River Delta in NE Brazil

    NASA Astrophysics Data System (ADS)

    de Paula Filho, Francisco José; Marins, Rozane Valente; de Lacerda, Luiz Drude

    2015-12-01

    The Parnaiba River Delta is the largest open sea delta in the Americas, having a unique ecological importance for the conservation of wildlife and fisheries resources. However, little is known about the biogeochemistry of this ecosystem. This study estimates N and P emissions to the delta using emissions factors, calibrated with field samples and N and P concentrations in different compartments of the delta. The estimated loads totaled 14.517 t N year-1 and 8.748 t P year-1, indicating that anthropogenic N and P emissions outweigh natural emissions by approximately 5 and 10 times, respectively. The activities that contribute the most to this result are livestock farming, agriculture and the release of untreated domestic sewage. The flows of N and P from the estimated loads corresponded to 339 kg N km-2 year-1 and 204 kg P km-2 year-1, so the region can be classified as "meso-active" and "eury-active" with regard to the transfer of nutrients. These results are consistent with the coastal megabasin design (COSCATs) proposed by Meyback et al. (2006). This article presents a first approach to the calculation of an estimated annual emissions inventory of N and P for the lower basin of the Parnaíba River and its coastal region, representing an approach that has been satisfactorily used in assessing the sensitivity of estuarine systems in northeastern Brazil.