STORMS, SEDIMENTS AND THE SUSTAINABILITY OF MARSHES IN THE MISSISSIPPI DELTA PLAIN

Plans to address the loss of over 1500 sq. miles of the Louisiana coast have addressed the need for sediment to stimulate vertical accretion and allow marshes to survive in the face of subsidence and sea-level rise. The role of storms in supplying sediment to Louisiana coastal marshes has been well documented. Hurricanes Katrina and Rita provided an opportunity to document both the sediment supplement supplied by the storms as well as the vulnerability of marshes with low sediment inputs to physical damage from storm surges and waves. Soil mineral content was a key determinant of the damage inflicted on coastal marshes with more minerogenic salt marshes, even directly in the path of the storm, suffering minimal disruption compared to more distant marshes with organic substrates. In addition, the supplement of sediment remaining after the storm surge receded increased marsh elevation by several cm in many areas. Understanding the role of sediments in maintaining current marshes in Louisiana and the role of substrate character as a factor in their resilience under storms, underscores the need for restoration efforts in Louisiana to aggressively utilize the sediment resources of the Mississippi River.