Coastal Mississippi experienced unprecedented flooding and storm damage resulting from Hurricane Katrina. Barrier island beaches of the NPS Gulf Islands National Seashore and associated backbarrier environments fronting Mississippi Sound help protect mainland beaches from storm water inundation and destructive wave forces. The exchange of sediment between the barrier island littoral drift system, navigation channels, inlet shoals between the islands, and Mississippi Sound controls the sand budget throughout the system. Historical shoreline surveys recorded rapid lateral island migration in response to dominant east to west directed longshore sediment transport, and changes in island area relative to historical shoreline movement. These data, in addition to recorded bathymetry changes, were used by Applied Coastal to quantify regional sediment dynamics and evaluate historical sediment budgets for use in planning and design of restoration efforts for the Mississippi Sound barrier islands.
After completing detailed analyses of historical shoreline and bathymetry survey data sets, documenting channel dredging and placement quantities, and developing a sediment budget, Applied Coastal personnel provided technical assistance regarding plan implementation, particularly related to sand sources, restoration design, sand placement procedures, and potential impacts on littoral transport processes. Specific tasks included: 1) detailed QA/QC analyses of modern bathymetry surveys for sediment transport and design analyses; 2) establishing template designs for restoration of the Camille Cut area, East Ship Island foreshore, and nearshore placement of sand seaward of East Ship Island for supplying sand to the littoral zone; 3) evaluating nearshore profile shape on the north side of West Ship Island for establishing “equilibrium” shape for estimating sand fill adjustments to be placed near Fort Massachusetts; 4) evaluating shoreline change and breach infilling at Katrina Cut using 2010 lidar and bathymetry data sets; 5) integrating all applicable survey and dredging information into the final modern sediment budget.
Because the final sediment budget is a critical component of restoration design and implementation, analysis results are subject to technical review. CDM Smith personnel provided an independent technical review of analysis procedures and results associated with sediment budget development.