Surge dynamics across a complex bay coastline, Galveston Bay, TX

While tidal exchange across bay coastlines has been well studied, research to date has not provided a comprehensive analysis of the volume of surge that can flow across bay coastlines during tropical cyclone events. Such insight can particularly be useful for understanding coastal storm surge dynamics that influence regional inundation and can help guide surge mitigation strategies for semi-enclosed bay systems. In this study, a suite of 80 synthetic tropical cyclones were simulated to characterize the volume of surge that flows across Galveston Bay's complex 98 km coastline, which is made up of tidal inlets, intermittent barrier islands, and existing surge defenses along the Upper Texas Gulf Coast. Tropical cyclone characteristics analyzed in this study include the wide variety of tropical cyclone intensity (Vmax) and size (Rmax) combinations possible for the region, with the storm surge response of each tropical cyclone simulated using the ADCIRC + SWAN model. In-depth analysis of coastal and in-bay storm surge responses was performed for baseline or existing conditions as well as scenarios representing severe barrier island erosion and future conditions based on intermediate sea level projections for the year 2050 and 2 100. Findings demonstrate that while the majority of surge may flow across tidal inlets for smaller, weaker storms, a storm intensity and size threshold exists that results in greater flow across barrier islands, having important implications for surge mitigation strategies. Analysis demonstrates that while this threshold may occur for extreme tropical cyclones under baseline conditions, this transition can occur for relatively, significantly weaker and smaller storms under the erosion and sea level rise scenarios evaluated.