Assessing Coastal Change Forecasts on the Louisiana Coast During the
2020 Hurricane Season
Abstract
During hurricane season, the U.S. Geological Survey (USGS) forecasts the
probability of coastal change prior to named storm landfall. Forecasts
both quantify potential storm effects on the sandy coastlines and test
our understanding of the drivers of coastal change. The forecasts can
also be used to aid emergency response and management decisions in
real-time. This study analyzed the skill of three USGS forecasts of
coastal change, defined as the probability of collision, overwash, and
inundation (PCOI) along the approximately 250 km of Louisiana coast from
Hurricanes Laura, Delta, and Zeta in 2020. To test forecast skill,
forecasts were compared with coastal changes identified in post-storm
emergency response aerial imagery. Forecasts accurately identified areas
where overwash and inundation were likely (true positive forecast ratios
>0.75). Forecasts also produced an overly conservative
estimation of overwash and inundation (false positive forecast ratios
0.56). High false positive forecast ratios for overwash and inundation
may be the result of an overestimate in forecast extreme water levels.