Total water level driving processes influence the potential for coastal change along United States coastlines.

Abstract

Effectively managing coastal impacts requires understanding how hydrodynamic processes interact with beach morphology and alter sandy beaches. Sallenger's Storm Impact Regime classification provides proxies for identifying these interactions by classifying potential coastal changes into impact regimes based on the elevation of total water levels (TWLs), the combination of waves, tides and nontidal residuals, compared to the elevation of beach morphology features. Here, we evaluate spatiotemporal variations in TWL drivers during storm impact regimes across sandy beaches along the continental U.S. coastlines. TWL magnitude and composition vary across impact regimes and regions. Although impacts are identified using consistent definitions, the processes contributing to regimes are location-specific, influencing where and how often impacts occur. Wave runup is the dominant contributor to TWLs in all regimes, but its contribution is gradually offset by increases in the nontidal residual as storm impacts intensify, despite waves becoming more energetic during storms. The Pacific and Atlantic coasts show the highest susceptibility to coastal impacts due to high average TWLs relative to morphological thresholds. Our findings identify regional differences in TWLs with potential for coastal impacts, offering critical insights into how large-scale changes in individual processes may influence local coastal hazards along open sandy coastlines.