MODELING BEACH GROUNDWATER SUPERELEVATION DUE TO WAVE RUNUP AND OVERTOPPING AT A REFLECTIVE BEACH

Coastal aquifers are highly dynamic groundwater systems. Sea level rise will raise coastal water tables resulting in increased risk of shallow or emergent groundwater (Befus et al., 2020). Marine water level fluctuations cause the beach groundwater table to oscillate over a relatively large range. Wave action further elevates beach groundwater through wave setup (Li and Barry, 2000), and infiltration from runup (Kang, 1994). Groundwater models that incorporate waves typically only consider setup, assuming infiltration from wave runup is negligible. This may be incorrect at steeper beaches with large runup excursions. Wave runup may also cause overtopping of beach crowns or dunes, resulting in ponded water in the back beach causing extended periods of elevated groundwater and flooding (e.g., Ludka et al., 2018). This work aims to quantify the magnitude and duration of wave runup and overtopping impacts on beach groundwater by modeling water table oscillations at Imperial Beach, a reflective beach in southern California.