Effects of coupled consolidation and overwash processes on a low-lying headland system

Abstract Coastal barrier islands serve as the first line of defense against storm-induced hazards and coastal erosion. Due to sea-level rise and more frequently occurring storms, barrier island restoration and rehabilitation have become more important for coastal protection. The current-state-of-the practice for simulation of barrier island restoration design mostly overlooks consolidation as one of the governing processes. However, low-lying barrier islands, especially those built on loose deltaic or estuarine deposits, may further lose elevation due to consolidation and become more vulnerable to erosion. This study investigates the impacts of consolidation without overwash, overwash without consolidation, and coupled consolidation and overwash in Caminada-Moreau Headland in Louisiana, USA, which is built on loose deltaic deposits. Consolidation and overwash processes were simulated by using Settle3D and XBeach, respectively. The coupled consolidation and overwash simulations predicts twice the elevation loss predicted by the simulations that consider overwash or consolidation only indicating the critical role of consolidation in barrier island morphology. Based on the morphologic changes, feasible restoration strategies are developed and tested through numerical experiments. Our analyses indicate that the simultaneous restoration of the headland and back barrier marsh increases dune volume retention and project design criteria longevity when compared to the coupled simulation without a restored marsh.