Coastal flood impacts on the built environment in Wells, Maine: Assessing the effectiveness of pool-to-marsh restoration in reducing exposure

In January 2024, the state of Maine's, USA, coastline experienced multiple storms that caused extensive damage to public infrastructure and private property. The town of Wells, which encompasses the Webhannet and Ogunquit estuaries, suffered damage to “grey” coastal defenses, such as seawalls, bulkheads, and riprap, which were breached and therefore not able to protect roads and buildings. Failure of traditional defenses has partly motivated a growing interest in nature-based solutions, in addition to the range of ecosystem services these natural systems can provide, for enhancing protection along Maine’s coastline in areas where the adoption of such “green” solutions is  feasible. Saltmarsh restoration, for example,  is an approach that aims to bring back degraded ecological function of a tidal marsh, while simultaneously providing increased flood protection. In this study, we develop a LISFLOOD-FP model for the town of Wells using high-resolution (~1m) DEM and land cover datasets. We validate the model through satellite imagery such as Sentinel-2 data. We use the model to map the inundation extent in Wells during the January 10^th coastal storm and to estimate flood exposure of the built environment. Next, we simulate the restoration of the tidal marsh within the two estuaries and assess its ability to reduce the flood footprint of the January 10^th storm. To this end, we identify megapools suitable for drainage, thin layer placement, and revegetation, and therefore modify the model’s elevation and roughness coefficient in these targeted areas. Our study evaluates the effectiveness of pool-to-marsh restoration as a nature-based approach in decreasing flood depth and velocity near adjacent buildings and roads.