GRAND ISLE BARRIER SHORELINE STABILIZATION STUDY
Louisiana

The purpose of this project was to develop a comprehensive long-term engineered solution that provides storm damage reduction and usable recreational beach for the Gulf shoreline of Grande Isle, from Caminada to Barataria Pass. The objectives of this study were to evaluate historical construction activities along the Grand Isle Gulf and bay shorelines and adjacent Caminada and Barataria passes in terms of their effects on the Grand Isle shoreline, determine coastal processes and forces that control long and short term shoreline stability, develop a long-term engineering solution(s) and specific recommendations that provide storm damage reduction and preserve structural integrity for the Grand Isle gulf shoreline, and to develop a preliminary design of the preferred alternative.

Existing Data and New Field Data Collection and Review
Data to assist in the analysis and design were collected. The existing data collected included historical aerial photos, bathymetric data, and engineering reports. New data collected included bathymetric and topographic data, hydrodynamic data (water levels and currents), and geophyiscal data.

Coastal Engineering Analysis
The coastal engineering analysis identified coastal processes controlling shoreline stability, short and long-term geomorphologic trends, and causes of success and failure of previously constructed coastal projects along the Grand Isle shoreline. Statistics of coastal processes were calculated including waves, water levels, tidal currents, hurricane frequency and strength, shoreline change, and sediment transport patterns. This task led to an understanding of overall processes controlling shoreline change at Grand Isle, which allowed for a comprehensive plan of feasible alternatives to increase shoreline stability to be developed.

Analytical and Numerical Modeling of Alternatives
Modeling, both analytical and numerical, was performed to validate the hypotheses on the processes controlling shoreline change and to evaluate the performance of the shoreline stabilization alternatives. Numerical modeling included wind-wave growth and transformation, tide-generated and wave-generated currents, sediment transport pathways modeling, and shoreline morphology modeling.

Prepare 30% Design and Engineering Report
A 30% level design of the engineering recommendations was completed and supported with a design report, which summarized all work completed and the methodologies of analysis and design. Results were presented to the client and public.