Abstract

The low elevation of barrier islands places them at the forefront of coastal landforms threatened by rising sea levels. As projections of sea level rise rates continue to increase these island systems will be stressed to maintain their morphology in the coming decades. Facies formation on barrier islands is partially a function of elevation, however it has yet to be shown how significant the influence of elevation might be on barrier island landcover. Here we identify and describe the elevation controls on facies distribution on a siliciclastic barrier island. To do this we analyze three digital elevation models for Padre Island, Texas, collected over a multi-year period along with accompanying 4-band satellite imagery to map facies and extract corresponding elevations. We find strong elevation limits exist for the facies mapped, which are then linked to formation processes. We then describe a new model for island accretion where back-barrier accretion is controlled by the redistribution of sediment out of dunes into the surrounding tidal flat. The model is then used to simulate future morphological changes to the study area under varying sea level rise scenarios. The results presented highlight that elevation exerts a strong control on facies coverage and that many barrier islands may experience an equilibrium state change going from a stable wide island state to a narrow island state as they respond to increasing pressure from sea level rise.