Regional Coastal Evolution along the Mississippi River Delta Plain Barrier Shorelines
Along the South-Central barriers, conversion of interior wetlands to open water increases tidal prism, resulting in degradation of barriers due to increasing inlet cross-sectional area and sediment sequestration in ebb tidal deltas. The dominant trends during the past 125 years include erosion of ~9x108m3 of sediment from the shoreface and an increase in combined tidal inlet cross-sectional area from ~41,400m2 to ~139,500m2. The rate at which tidal inlet cross-sectional area is increasing is directly proportional to the rate of interior wetland loss.
Along the Chandeleur Islands, long-term reduction in island area is event-driven and related to major storms. The islands do not fully recover from large magnitude hurricanes because storm waves transport sand away from the mid-barrier arc to the distal flanks of the system. Volume calculations indicate ~150x106m3 of sediment has been deposited downdrift and seaward of the northern terminal spit during the past 125 years, whereas approximately half this volume has been deposited in the backbarrier.
This study is refining coastal evolutionary models and management schemes for these regions by: 1. quantifying erosional trends in degrading delta complexes, 2. identifying linkages between interior wetland loss and barrier response, 3. documenting sediment sinks, and 4. demonstrating the importance of implementing a system-wide approach to sediment management in the Mississippi River delta plain.