Hydrographic and suspended sediment measurements of the Mississippi River plume during the historic 2011 flood: a coupled satellite analysis and boat survey approach to determine an efficiency factor for sediment trapping in the nearshore zone
Abstract
During the 2011 Mississippi River (MR) flood, sediment carried to sea by the River had the potential to combat wetland loss in some areas. The movement and fate of river sediments is determined by a combination of river plume momentum, and coastal and offshore currents [Walker, 1996; Walker et al., 2005; Rego et al., 2010]. We therefore used a coupled satellite analysis and boat survey approach in order to track mixing and transport of MR plume sediments during one of the largest recorded floods in history. During the flood crest in June of 2010, MR discharge was held at a constant and large value for several weeks, providing a unique experiment that allowed us to study plume structure under steady flow conditions. Sea surface temperature, height, and color data from satellites were employed in order to quantify river plume dispersion, surface sediment concentration [Peckham, 2008; Shi and Wang, 2009] and sediment migration pathways in the nearshore zone for the Mississippi and Atchafalaya Rivers, for the duration of the flood. The boat survey measured current velocity, salinity, temperature and sediment concentration of the MR plume, during the peak of the flood. Although plumes emanating from the MR Delta should contribute significant sediment to the coastal zone [cf. Wright and Nittrouer, 1995; D'Sa and Ho, 2008], our investigation shows that the focused jet of the MR during the flood penetrated the coastal current and contributed little to the coastal sediment budget. Collected data allowed calculation of the hydrodynamic structure of the plume and thus its Potential Vorticity. We show that a novel PV, recently described by Falcini and Jerolmack [2010], works as an efficiency factor: the fraction of sediment emitted from each river plume that is trapped in the nearshore zone (and on marshes) is directly related to the PV of each river effluent. This relation may help to better understand and predict how future floods, or human-constructed river diversions, will contribute to land building on the Delta. Theoretical results and data we collected can also be useful for testing and verification of numerical models in the future.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMEP44A..07F
- Keywords:
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- 1821 HYDROLOGY / Floods;
- 1862 HYDROLOGY / Sediment transport;
- 4217 OCEANOGRAPHY: GENERAL / Coastal processes