Storm Induced Sediment Transport on the Louisiana Shoreface: Implications for the Morphodynamic Trajectory of Barrier Island Coastlines

Barrier islands are long, narrow deposits of sand or sediments that parallel to the coastline. The islands are separated from the main land by a shallow sound, bay or lagoon and are fronted by the shoreface, which gradually slopes away from the barriers toward deeper water. Despite their ability to migrate, barrier islands are constantly threatened by storms, and with climate change, this threat will continue to grow as hurricane intensity and frequency is expected to rise. The onset of large waves and surge on the coast during storms, mobilize fine-grained sediments for the shoreface facilitating erosion and sediment dispersal. While there are numerous studies addressing sediment transport on the shelf, too few studies exist that directly address shoreface transport and determine where the sediment goes (offshore or inshore). In this study, we have coupled SWAN wave model with storm surge and morphology model within the Delft3D Modeling Suite, to evaluate sediment transport and exchange between barrier islands and the shoreface, assessing transport trends for short-term (event scale), near-term (~decadal scale), and longer-term (>20 year) timescales. This allows an assessment of key bypassing mechanisms of sediment along the shoreface and provides insight into regional sediment budgets along the central coast of Louisiana. Moreover, assessing event-scale sediment transport has additional implications on how sediment is exchanged between the shoreface and interior bays.