scholarly journals Mitigating the Effects of Sea-Level Rise on Estuaries of the Mississippi Delta Plain Using River Diversions

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2028 ◽  
Author(s):  
Eric D. White ◽  
Ehab Meselhe ◽  
Denise Reed ◽  
Alisha Renfro ◽  
Natalie Peyronnin Snider ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Mississippi River ◽  
Large Scale ◽  
Mississippi Delta ◽  
Coastal System ◽  
Restoration Planning ◽  
Delta Plain ◽  
Salinity Gradients ◽  
River Diversions

Using the Mississippi River as a tool for restoration has been a key element of restoration planning in Louisiana for decades. The results of allowing river water and sediment back into the coastal system are manifested in a number of places in present day Louisiana, with additional plans for large scale sediment and water diversions from the Mississippi River. Many previous numerical modeling studies have focused on sediment delivery to Louisiana estuaries. This study examines the effects of river diversions on salinity gradients in receiving estuarine basins. The Integrated Compartment Model, a planning-level model that simulates multi-decadal change in estuarine hydrodynamics and wetland systems under assumed sea-level rise scenarios, was used to assess the estuarine salinity gradient under potential management regimes. The simulations for current conditions are compared to a future 50-year simulation with additional diversions, as well as cases with a variety of diversion options. This modeling analysis shows that without additional action, 50-years of sea-level rise could result in substantial increases in salinity throughout the Mississippi Delta Plain estuaries. This can be largely offset with additional large river diversions which can maintain variable salinity gradients throughout the estuary basins.

scholarly journals An Examination of Compound Flood Hazard Zones for Past, Present, and Future Low-Gradient Coastal Land-Margins

2021 ◽  
Vol 3 ◽  
Author(s):  
Félix L. Santiago-Collazo ◽  
Matthew V. Bilskie ◽  
Peter Bacopoulos ◽  
Scott C. Hagen
Keyword(s):  
Tropical Cyclone ◽  
Sea Level Rise ◽  
Sea Level ◽  
Mississippi River ◽  
Flood Hazard ◽  
Rainfall Runoff ◽  
Coverage Area ◽  
Future Projections ◽  
Delta Plain ◽  
Coastal Land

Recent events worldwide demonstrate how coastal communities of integrated natural and human systems are exposed to hydrological and coastal flooding processes. Standard flood hazard assessment practices account independently for rainfall-runoff, tides, storm surge flooding and not the non-linear combination commonly defined as compound flooding. This research evaluates compound flood hazard zones for past, present, and future (c. 1890–2090) conditions of the Mississippi River Delta Plain (MRDP). The MRDP provides a low-gradient coastal land-margin representing similar landscapes around the world that are experiencing relative sea-level rise and serves as a warning beacon for our coastal settlements. A set of plausible synthetic storms and rainfall events, which account for antecedent rainfall-runoff, tropical cyclone-driven rainfall, and tropical cyclone-driven surge, are employed in a tide and surge hydrodynamic model that integrates rain over the mesh. This study demonstrates the evolution of the compound flood hazard zones from the 1890s, before major western settlement and alterations to the Mississippi River and deltaic system, to the present day and out to 2090. Furthermore, near-future projections of the compound flood hazard zones suggest that the coastal flood zone will suffer the most significant changes in coverage area due to a combination of increasing eustatic sea-level rise and alterations to the coastal land-margin during low flood events. Our results emphasize the need to establish evolution trends of compound flood hazard zones to enable more descriptive future projections under a changing climate. Such projections will aid policy-makers, stakeholders, and authorities as they pursue enhanced coastal resilience to compound flooding.

Influences of Relative Sea-Level Rise and Mississippi River Delta Plain Evolution on the Holocene Middle Amite River, Southeastern Louisiana

1993 ◽  
Vol 39 (1) ◽  
pp. 68-74 ◽  
Author(s):  
Whitney J. Autin
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Mississippi River ◽  
Drainage Basin ◽  
River Delta ◽  
Mississippi River Delta ◽  
Relative Sea Level ◽  
The Holocene ◽  
Delta Plain ◽  
Relative Sea Level Rise

AbstractThe 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.

scholarly journals The large-scale impact of climate change to Mississippi flood hazard in New Orleans

2012 ◽  
Vol 5 (1) ◽  
pp. 333-349
Author(s):  
T. L. A. Driessen ◽  
M. van Ledden
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
New Orleans ◽  
Sea Level ◽  
Mississippi River ◽  
Large Scale ◽  
Flood Hazard ◽  
Impact Of Climate Change ◽  
High Flows ◽  
The Impact

Abstract. The objective of this paper is to describe the impact of climate change on the Mississippi River flood hazard in the New Orleans area. This city has a unique flood risk management challenge, heavily influenced by climate change, since it faces flood hazards from multiple geographical locations (e.g. Lake Pontchartrain and Mississippi River) and multiple sources (hurricane, river, rainfall). Also the low elevation and significant subsidence rate of the Greater New Orleans area poses a high risk and challenges the water management of this urban area. Its vulnerability to flooding became dramatically apparent during Hurricane Katrina in 2005 with huge economic losses and a large number of casualties. A SOBEK Rural 1DFLOW model was set up to simulate the general hydrodynamics. This improved model includes two important spillways that are operated during high flow conditions. Subsequently, a weighted multi-criteria calibration procedure was performed to calibrate the model for high flows. Validation for floods in 2011 indicates a very reasonable performance for high flows and clearly demonstrates the necessity of the spillways. 32 different scenarios are defined which includes the relatively large sea level rise and the changing discharge regime that is expected due to climate change. The impact of these scenarios is analysed by the hydrodynamic model. Results show that during high flows New Orleans will not be affected by varying discharge regimes, since the presence of the spillways ensures a constant discharge through the city. In contrary, sea level rise is expected to push water levels upwards. The effect of sea level rise will be noticeable even more than 470 km upstream. Climate change impacts necessitate a more frequent use of the spillways and opening strategies that are based on stages. Potential alternatives on how to cope with the flood hazard of this river in the long term, such as river widening and large-scale redistribution of the flow through diversions, are proposed.

scholarly journals Adapting to sea level rise: Emerging governance issues in the San Francisco Bay Region

2018 ◽  
Author(s):  
Pedro J. Pinto ◽  
G. Mathias Kondolf ◽  
Pun Lok Raymond Wong
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
San Francisco ◽  
Urban Areas ◽  
Path Dependence ◽  
Large Scale ◽  
San Francisco Bay ◽  
Metropolitan Region ◽  
Environmental Benefit ◽  
Formidable Challenge

San Francisco Bay, the largest estuary on the Pacific Coast of North America, is heavily encroached by a metropolitan region with over 7 million inhabitants. Urban development and infrastructure, much of which built over landfill and at the cost of former baylands, were placed at very low elevations. Sea-level rise (SLR) poses a formidable challenge to these highly exposed urban areas and already stressed natural systems. “Green”, or ecosystem-based, adaptation is already on the way around the Bay. Large scale wetland restoration projects have already been concluded, and further action now often requires articulation with the reinforcement of flood defense structures, given the level of urban encroachment. While levee setback, or removal, would provide greater environmental benefit, the need to protect urban areas and infrastructure has led to the trial of ingenious solutions for promoting wetland resilience while upgrading the level of protection granted by levees.We analyzed the Bay’s environmental governance and planning structure, through direct observation, interviews with stakeholders, and study of planning documents and projects. We present two cases where actual implementation of SLR adaptation has led, or may lead to, the need to revise standards & practices or to make uneasy choices between conflicting public interests.Among the region’s stakeholders, there is an increasing awareness of the risks related to SLR, but the institutional arrangements are complex, and communication between the different public agencies/departments is not always as streamlined as it could be. Some agencies and departments need to adapt their procedures in order to remove institutional barriers to adaptation, but path dependence is an obstacle. There is evidence that more frank and regular communication between public actors is needed. It also emphasizes the benefits of a coordination of efforts and strategies, something that was eroded in the transition from government-led policies to a new paradigm of local-based adaptive governance.

The physical sustainability of the coastal zone of the Ganges-Brahmaputra-Meghna delta under climatic and anthropogenic stresses

2021 ◽  
Author(s):  
Stephen Darby ◽  
Md. Munsur Rahman ◽  
Anisul Haque ◽  
Robert Nicholls ◽  
Frances Dunn
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Average Rate ◽  
River Management ◽  
Tidal River ◽  
Natural Conditions ◽  
Fluvial Sediment ◽  
Average Value ◽  
Delta Plain ◽  
The Ganges

<p>The Ganges-Brahmaputra-Meghna (GBM) delta is one of the world’s largest deltas, and consists of large areas of low flat lands formed by the deposition of sediment from the GBM rivers. However, recent estimates have projected between 200~1000 mm of climate-driven sea-level rise by the end of the 21st century, at an average rate of ~6 mm/yr. Eustatic sea-level rise is further compounded by  subsidence of the delta, which in the coastal fringes varies from 0.2 to 7.5 mm/yr, at an average value of ~2.0 mm/yr. Therefore, the combined effect of sea-level rise and subsidence (termed relative sea-level rise, RSLR) is around 8.0 mm/yr. Such high values of RSLR raise the question of whether sediment deposition on the surface of the delta is sufficient to maintain the delta surface above sea level. Moreover, as the total fluvial sediment influx to the GBM delta system is known to be decreasing, the retained portion of fluvial sediment on the delta surface is also likely decreasing, reducing the potential to offset RSLR. Within this context, the potential of various interventions geared at promoting greater retention of sediment on the delta surface is explored using numerical experiments under different flow-sediment regime and anthropogenic interventions.  We find that for the existing, highly managed, conditions, the retained portion of fluvial sediment on the delta surface varies between 22% and 50% during average (when about 20% of the total floodplain in the country is inundated) and extreme (> 60% of the total floodplain in the country is inundated) flood years, respectively. However, the degree to which sediment has the potential to be deposited on the delta surface increases by up to 10% when existing anthropogenic interventions such as polders that act as barriers to delta-plain sedimentation are removed. While dismantling existing interventions is not a politically realistic proposition, more quasi-natural conditions can be reestablished through local- sediment management using tidal river management, cross dams, dredging, bandal-like structures and/or combinations of the above measures.</p>

scholarly journals Tipping points of Mississippi Delta marshes due to accelerated sea-level rise

2020 ◽  
Vol 6 (21) ◽  
pp. eaaz5512 ◽  
Author(s):  
Torbjörn E. Törnqvist ◽  
Krista L. Jankowski ◽  
Yong-Xiang Li ◽  
Juan L. González
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Mississippi Delta ◽  
Time Windows ◽  
Open Water ◽  
Tipping Points ◽  
Coastal Marshes ◽  
Short Term ◽  
Global Sea Level ◽  
Coastal Louisiana

Coastal marshes are threatened by relative sea-level (RSL) rise, yet recent studies predict marsh survival even under the high rates of RSL rise expected later in this century. However, because these studies are mostly based on short-term records, uncertainty persists about the longer-term vulnerability of coastal marshes. We present an 8500-year-long marsh record from the Mississippi Delta, showing that at rates of RSL rise exceeding 6 to 9 mm year−1, marsh conversion into open water occurs in about 50 years. At rates of RSL rise exceeding ~3 mm year−1, marsh drowning occurs within a few centuries. Because present-day rates of global sea-level rise already surpass this rate, submergence of the remaining ~15,000 km2 of marshland in coastal Louisiana is probably inevitable. RSL-driven tipping points for marsh drowning vary geographically, and those for the Mississippi Delta may be lower than elsewhere. Nevertheless, our findings highlight the need for consideration of longer time windows in determining the vulnerability of coastal marshes worldwide.

Sign in / Sign up

Export Citation Format

Share Document