Application of decadal modeling approach to forecast barrier island evolution, Dauphin Island, Alabama

Abstract

Forecasting barrier island evolution provides coastal managers and stakeholders the ability to assess the resiliency of these important coastal environments that are home to both established communities and existing natural habitats. This study uses an established coupled model framework to assess how Dauphin Island, Alabama, responds to various storm and sea-level change scenarios, along with a suite of restoration measures, over the course of a decade. The coupled model framework uses validated models for long-term alongshore sediment transport (Delft 3D; Deltares, 2019), short-term storm induced impacts (XBeach; Roelvink and others, 2009), as well as dune building and recovery (empirical dune growth model; Mickey and others, 2019). This model framework was simulated with the various storm and sea-level change scenarios on a non-restored Dauphin Island, then a subset of the storm and sea-level change scenarios were applied to a suite of seven different restoration measures to determine how they would influence the morphologic evolution over a decadal period. Topographic and bathymetric changes captured in post-simulation digital elevation models were then passed on to partners for various simulations to determine the effects on habitat evolution and water quality as it relates to oyster reef and submerged aquatic vegetation. Introduction The forecasting of long-term evolution of barrier island systems is an emerging necessity for coastal managers aimed at increasing the resiliency of the system for future generations. The work of Mickey and others (2019) to develop a modeling technique to forecast evolution of barrier islands has provided coastal managers a way to inform decisions related to proposed island modifications and varying climatic changes. As part of the Alabama Barrier Island Restoration Assessment (https://coastal.er.usgs.gov/alabama-barrier-island-restoration-study), the coupled model framework methodology was used to forecast a range of potential outcomes for Dauphin Island, Alabama, over a decadal period under varying climatic changes related to sea level change (SLC) and storminess with varying proposed restoration scenarios. The modeling scheme 1U.S. Geological Survey. 2U.S. Army Corp of Engineers. 3The Water Institute of the Gulf. 4University of North Carolina at Wilmington.