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2 Lower River and Deltaic Systems: Common Problems and Challenges
Pages 27-54

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From page 27...
... A PERSPECTIVE ON THE MISSISSIPPI RIVER DELTA Water, Land, and Ecosystem Dynamics Deltas form where rivers intersect the sea, disperse laterally, and deposit sediment, often in a classic triangular delta (∆) pattern.
From page 28...
... can accelerate landscape subsidence, making delta habitats susceptible to erosive forces from sea level rise, storm surge, and wave action. Tectonic processes provide a background forcing on the Mississippi Delta; fault-driven slumping over geologic time scales combined with the severe reduction in the historic sediment loading from the Missouri River contributes to loss of land and habitat (Dokka et al., 2006)
From page 29...
... Clear examples include the Danube and Mississippi River deltas, where shifts in nutrient dynamics (N vs.
From page 30...
... Physical agents of change can generate problems for societies, which are amplified or dampened by infrastructural development and resource use, which in turn give rise to management and institutional responses to promote or regulate them. However, these agents of change often are coupled with one another, such as in the joint impacts of flood hazards, accelerated subsidence, and sea level rise.
From page 31...
... Over the twentieth century, the sediment supply to the Mississippi River delta has decreased from about 400 million metric tons per year to about 145 million metric tons per year because of upstream dams, erosion control, and channel engineering works (Meade and Moody, 2010)
From page 32...
... 0 50 100 150 200 250 300 350 Ganges-Brahmaputra Mekong Lena Huang He (Yellow) Indus Mississippi Volga Orinoco Irrawaddy Amu Darya Niger Shatt el Arab Godavari Dneiper Po Nile Red Chao Phraya MacKenzie Krishna Parana Danube Senegal Ord Tana Burdekin Klang Sao Francisco Magdalena Colville Ebro FIGURE 2-2  Some major river deltas ranked by delta area.
From page 33...
... (2009) estimate a 48 percent reduction in sediment delivery for the Mississippi River delta over the twentieth century, which is comparable with loss of sediment supply to deltas in Europe and South Asia (Table 2-1)
From page 34...
... TABLE 2-1  Delta Database with Key Environmental Data 34
From page 35...
... Rates of relative sea-level rise are time-variable and the ranges provided cover either different times or different areas of a delta. 35 SOURCE: Syvitski et al., 2009.
From page 36...
... 36 DELTA WATERS TABLE 2-2  Comparison of Subsidence in the Delta Alliance Comparative Study SOURCE: Bucks et al., 2010. FIGURE 2-3  Map of projected subsidence ranges for south Louisiana generated by the Subsidence Advisory Panel for the Louisiana CPRA Master Plan 2012 Update, following a meeting on October 14, 2010.
From page 37...
... components. In the Mississippi River delta, the concentration and flux of inorganic nitrogen are often key drivers of coastal water quality as high nitrogen fluxes lead to increased plant productivity and biomass, stimulation of noxious algal species, increased rates of organic matter deposition, and, ultimately, hypoxia.
From page 38...
... . Sea level rise coupled with land subsidence represents a stressor of coastal ecosystems through changes in salinity dynamics that cascade from physical alterations in the range and distribution of water depths.
From page 39...
... Thus, changes in water depths in the Mississippi River delta and along the Louisiana coast are likely to alter existing relationships between salinity gradients, mixing, and oxygen replenishment. Water withdrawals, as well as reduced flood peaks (e.g., due to upstream dams and flood control operations)
From page 40...
... The project, via the Old River Control Structure located near Simmesport, Louisiana, diverts 30 percent of Mississippi River discharge into the Atchafalaya River and valley. The project's flood control levees inhibit distribution of sediments in high water into extensive floodplain areas.
From page 41...
... . Centers with information that compare international flood events, losses, and trends include the maps and records of the University of Colorado's Dartmouth Flood Observatory2 (Figure 2-6; NASA's near real-time flood mapping imagery,3 and the Center for Research on the Epidemiology of Disasters EMDAT database.4 Deltas that experience large numbers of tropical cyclones provide comparisons with the Mississippi River delta (e.g., as mapped by the Joint Typhoon Warning Center; NASA; NOAA; and others)
From page 42...
... . Regarding the implications of sea level rise, changes in climate may affect sea level rise globally; but there may be regional differences in sea level rise, as well, because of differences in geologic factors such as subsidence and tectonics, which raise or lower coastal land masses and landforms.
From page 43...
... . An assessment from the Intergovernmental Panel on Climate Change of global coastal vulnerability to sea level rise put the Mississippi delta in the "high" but not "extreme" category of population displacement related to an estimated eustatic (worldwide, uniform change)
From page 44...
... Commercial Navigation and Dredging Commercial navigation on the lower Mississippi River is one of the region's important and vital economic sectors, which also has great national economic significance. Some 6,000 vessels and 300 million tons of cargo
From page 45...
... . Commercial navigation interests also have concerns about the potential effects of proposed diversions along the lower Mississippi River to enhance wetlands creation (as proposed in the Louisiana 2012 Coastal Master Plan)
From page 46...
... However, the Corps of Engineers showed that only 25 percent of the dredging is a result of the diversion; therefore, dredging costs attributable to the diversion were lower than expected, and the diversion continues to create land. Land Development -- Rural, Industrial, Residential, and Urban Although not as densely populated as some large river deltas around the world, the Mississippi River Delta is home to an impressive concentration of industrial and navigational infrastructure, the maintenance of which largely motivates efforts to preserve the status quo of the current birds' foot delta mouth and petroleum industry logistics centers, such as Port Fouchon.
From page 47...
... LOWER RIVER AND DELTAIC SYSTEMS 47 FIGURE 2-11  Oil and gas fields in southern Louisiana in 1941, 1964, and 1981. SOURCE: Turner, 1987.
From page 48...
... The Sundarbans mangrove forest of Bangladesh and India is another major international deltaic region listed as a UNESCO World Heritage Site.5 UNESCO has raised concerns about the infrastructure for ecological monitoring and protection, which may be 5  For more information, see: http://whc.unesco.org/en/list/798/; and: http://whc.unesco.org/ en/list/452.
From page 49...
... Although institutional and governance research have expanded recently in the fields of water and environmental management, they may be less mainstreamed in Mississippi River delta research than in the Rhine-Meuse delta and other regions (Table 2-3)
From page 50...
... (2006) estimates future land losses to sea level rise in the Mississippi delta between 2000 and 2050 at almost 20 percent.
From page 51...
... . A SYSTEMS APPROACH TO INTEGRATED WATER AND ENVIRONMENTAL MANAGEMENT The foregoing overview of environmental agents of change in the Mississippi River delta region and selected international delta analogues indicate that agents of change have cumulative effects.
From page 52...
... 52 DELTA WATERS TABLE 2-4  Deltaic Population and Areas NOTE: Distribution of the total population potentially impacted, percentage of delta population influenced, and the delta area impacted for each delta under base line ESLR conditions extended from 2000 through 2050. SOURCE: Ericson, Vörösmarty et al.
From page 53...
... • It therefore is important to articulate a "human-environmental sys tems approach," grounded in the Mississippi delta base case -- and to use that systems approach to seek partial analogues with other large deltas in ways that inform, inspire, and challenge integrated water and environmental management in the lower Mississippi River delta. Promising International Analogues This report's statement of task calls for it to address commonalities between the Mississippi River and other deltas of the world.
From page 54...
... • Large deltas of the world vary so greatly that international compari son focused solely on one or a few agents of change are not likely to provide comparisons robust enough to advance the theory and practice of integrated water and environmental resources manage ment in the Mississippi River delta. • Research on deltaic "analogues" focuses first on a base case, which in this study is the Mississippi River delta.


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