Presenter: Davina Passeri (USGS)

Description:
Barrier islands protect mainland coastal communities during storms. In the future, the combined effects of storms and sea level rise (SLR) threaten barrier islands with increased inundation, and loss of land and habitats for critical species. The Alabama Barrier Island Restoration Assessment (ABIRA) was a science-based, collaborative effort between the State of Alabama, the U.S. Geological Survey (USGS), and the U.S. Army Corps of Engineers (USACE) to investigate viable options for the restoration of Dauphin Island, Alabama in order to increase island sustainability and restore vital habitats for species affected by the 2010 Deepwater Horizon oil spill. This talk is focused on the predictive morphological modeling that was developed to assess decadal barrier island evolution. Models of alongshore sediment transport during quiescent conditions, storm-driven morphology and post-storm dune recovery were integrated to simulate island evolution under scenarios of increased sea level and increased storminess (intensity and frequency). Model results confirm the barrier island responses of keeping pace, width drowning, height drowning and aggradation as found in previous studies, and introduce deflation drowning as a new regime that is vulnerable to breaching. Under high SLR and storminess, the island was unable to keep pace or recover elevation after storms and drowned in just 10 years. Model output was used to inform a habitat model used to predict resulting habitat coverage and suitability for oysters and seagrass (see companion talk by N. Enwright). Together, the predictive morphological and habitat models were used to assess multiple restoration actions to assess their ability to meet multiple objectives for habitats, island sustainability, residents, and conservation values.