USING DRONE AND NEARSHORE BUOY DATA TO PREDICT EROSION AND OVERWASH AT A LAKE MICHIGAN BEACH: APPLICATION OF THE USGS STORM-IMPACT SCALE MODEL TO THE GREAT LAKES

The USGS Storm-Impact Scale model accurately predicts hurricane and other storm-induced coastal erosion and overwash along the U.S. East and Gulf Coasts; however, there exists no similar predictive model for large lacustrine coasts, such as those in the Great Lakes Region. In this study, we refine the USGS Storm-Impact Scale model for use in the Great Lakes Region and then test the model with field data from Illinois Beach State Park along western Lake Michigan. In this model four regimes of coastal erosion (swash, collision, overwash, and inundation) are predicted by comparing total water elevation during a storm (wave setup + runup + still water level) to the maximum elevation of beach and dune morphology. We parameterize the model with wave data from a nearshore buoy, water level data from a NOAA station, and beach and dune morphology generated from repeated drone surveys. Beach elevation profiles are extracted from the drone digital elevation models, which were constructed using structure-from-motion algorithms implemented in Agisoft Metashape Professional. These profiles were used to determine the maximum elevation of berm and dune features and to generate beach slopes, which were used to calculate wave runup. Wave and water level data were extracted for specific storm events that align with beach surveys and were used to compute wave setup and runup. The total elevation of water level generated from these computations were compared to the maximum elevation of morphology along each profile to predict what coastal change regime would result from that storm. These predictions were validated using post-storm survey data and we evaluated the factors resulting in over-or under-prediction of coastal response. Results from this study will yield an operational coastal change prediction model that can be used to predict coastal response in advance of a storm and can be expanded to sites throughout the Great Lakes Region.