ABSTRACT
Gutierrez, S.M.; Wang, P.; Royer, E.L.; Bishop, J.E., and Dabees, M.A., 0000. Long-term performance of cyclic beach nourishment and roles of erosional hotspots.
This study examined the long-term performance of repeated beach nourishments over an ∼35 year period at two barrier islands, Sand Key and Treasure Island, along the west-central Florida coast, based on extensive field data and numerical modeling. Five cycles of beach nourishment on Sand Key and six cycles on Treasure Island were conducted during the study period. The 14 km nourished stretch was divided into six segments based on beach dynamics, including three erosional hotspots and one gap in the nourishment. The processes that cause erosional hotspots were examined through numerical modeling of nearshore wave and current fields. The repeated nourishment maintained a minimum 10-m-wide dry beach at all the studied beaches. The current nourishment design at the Sunset Beach erosional hotspot on Treasure Island is insufficient because the dry beach becomes progressively narrower after each renourishment. The gap in the nourishment on Sand Key did not gain any significant dry beach width due to the lack of a mechanism to retain sand. The nourishments successfully compensated for the existing sand deficit but did not fundamentally eliminate the processes that created the deficit. Therefore, the repeated nourishment served as a maintenance strategy. The three erosional hotspots are caused by a gradient in nearshore sediment transport depicted based on computed wave and current fields, although the causes and magnitude of the transport gradient are different. Generally, transport gradients are influenced by alterations in wave and current fields by existing coastal structures and local morphologic features such as headlands and inlet ebb shoals.
