Modeling hurricane-induced wetland-bay and bay-shelf sediment fluxes

Hurricanes have long been recognized as a strong forcing in shaping the coastal morphology, especially by redistributing sediments among coastal wetlands, bays and inner continental shelves. However, the contribution of hurricane-induced sediment transport to the sediment budget of a shelf - bay - wetland system has not been evaluated using a physics-based numerical model. There is a particular confusion on how sediment transport to coastal wetlands contributes to sediment accretion in wetlands and thus wetland adaptation to sea level rise. In this paper, we present a coupled modeling system for hurricane winds, storm surge, waves and sediment transport on the Louisiana coast, and use it to investigate two fundamental questions: (1) How much sediment is transported and deposited on coastal wetlands during a major hurricane event like Hurricane Gustav (2008), and (2) where is the source of the deposited sediment on the wetland soil surface. Our model successfully reproduced the measured basin-averaged sediment accretion in the Terrebonne and Barataria Basins after Gustav, and estimated that Hurricane Gustav imported approximately 27 million metric tons of sediment on wetlands in that area. The estimated deposition was mainly made up of mud suspended from the coastal bays, and the contribution of this sediment to wetland deposition was 88.7% in Terrebonne Bay and 98.2% in Barataria Bay within the tested range of sediment properties. This paper demonstrates a useful tool to help understand how sediment dynamics in the coastal zone during hurricane events play a significant role in the sediment budget of a deltaic coast.