Effects of storm surge exceedance value on overwash and inundation forecasts

This study analyzed the skill of probabilistic forecasts of overwash and inundation along the Louisiana coastline from back-to-back Hurricanes Laura and Delta in 2020. To test skill, forecasts were compared with observations of mean water level relative to beach elevations and evidence of overwash and inundation identified in post-storm aerial imagery. 

Authors found that probabilistic forecasts accurately identified areas where overwash and inundation were likely to occur. In some cases, forecasts also produced a conservative estimation of overwash and inundation. For the first time, they explored the role of exceedance value in probabilistic forecasts of overwash and inundation and found that choice of exceedance value can influence forecasts. Additionally, they found that waves contributed up to 27 per cent of the mean water level and up to 63 per cent of the extreme water level during Hurricanes Laura and Delta. The findings provide insights for improving operational coastal hazard forecasting and support more informed emergency response decisions before landfall.