Subsidence and Sea-Level Rise in Southeastern Louisiana: Implications for Coastal Management and Restoration

Geologic Processes and Controls

Figure 2: Holocene sediment thickness view larger version

• Structure: The delta plain is traversed by hundreds of coast-parallel normal growth faults. Fault traces and rates of movement can be estimated from existing databases to identify the areas where fault activation contributes to subsidence.

• Mississippi River Deposits: Much of the delta plain is located over a paleo-valley cut by the Mississippi River when sea level was lower. This incised valley was filled with deltaic deposits that range in thickness from 20 to 120 m (figure 2). Deltaic deposits comprise a complex network of depositional environments including sandy channel fills, silty natural levees, and muddy interdistributary bays. The physical property thick-ness, and lateral extent, of each environment influence the rate of sediment compaction and subsidence.

• Fluid Withdrawal: At a local scale the effect of fluid withdrawal can affect subsidence. It is well documented that forced drainage areas experience enhanced subsidence (figure 3).