Redistribution of Sediment and Particulate Mercury Within Upstream Reaches of Galveston Bay in Response to Hurricane Harvey

Abstract Extreme storms and flooding can remobilize legacy contaminants stored in the sediment bed; however, event‐scale models that resolve the transport of these materials remain underdeveloped. This study developed a numerical model of contaminated sediment transport during Hurricane Harvey (August 2017), which struck the upstream reaches of Galveston Bay (URGB) and caused severe flooding in response to storm surges, record breaking precipitation, river floods, and prolonged reservoir releases. Previous observations indicate significant sediment and particulate mercury (HgP) redistribution within URGB, but they had limited spatial and temporal coverage, leaving the redistribution timing and patterns uncertain. To address these gaps, a three‐dimensional coupled hydrodynamic and sediment transport model was developed. The model encompassed oceanic surge, peak discharge, and post‐peak flood stages and used river inputs derived from a calibrated hydrological model. The results reveal two distinct sediment transport peaks, linked to asynchronous flood pulses from Buffalo Bayou and the San Jacinto River. In contrast, because the initial sediment bed of Buffalo Bayou had high concentrations of HgP, the peak erosion and transport of HgP coincided with Buffalo Bayou flooding. The post‐peak prolonged reservoir release from Buffalo Bayou caused minimal redistribution of sediment and HgP. Spatially, the model estimates indicate that Buffalo and Patrick Bayous accounted for more than half of the remobilized HgP, while the San Jacinto Estuary may have been the source of one‐third. The methods and findings offer a transferable framework for investigating sediment and contaminant redistribution in other coastal systems impacted by extreme storms or flood‐control operations.