Socioeconomic and Environmental Predictors of Estuarine Shoreline Hard Armoring

Rising sea levels and growing coastal populations are intensifying interactions at the land-sea interface. To stabilize upland and protect human developments and infrastructure from coastal hazards, property owners commonly emplace hard armoring structures, such as bulkheads and revetments, along the estuarine shoreline. While research regarding the ecological and economic impacts that accompany hard armoring implementation has garnered significant attention, there have been limited efforts to document the extent of hard armoring or identify drivers of hard armoring patterns. This study addresses a knowledge gap in the documentation and understanding of hard armoring patterns and their drivers at the scale of individual landowners, by assessing the distribution of hard armoring along the Georgia coastline. Using a set of environmental and socioeconomic predictor variables in coordination with a novel fine-scale census of hard armoring, we present a parsimonious statistical model that predicts the probability of hard armoring emplacement at the parcel level. Our model has a high correct classification accuracy and we find that a variety of interacting environmental and socioeconomic influences contribute to patterns of shoreline armoring; in particular, the presence or absence of armoring on a neighboring parcel has a strong association with the probability of hard armoring. Our model also suggests that continued sea level rise and coastal population growth could trigger increases in armoring implementation into the future. Thus, we underscore the importance of considering both the current and potential future distributions of hard armoring when evaluating associated impacts of sea level rise on ecological systems and in socioeconomic evaluations. For example, evolving distributions of hard armoring should be considered in predictions of salt marsh sustainability through inland migration. In addition to providing the first parcel-level census analysis of hard armoring at a scope relevant to local and regional government decision-making, this study also presents a methodology adaptable to assessing patterns of hard armoring in other study areas. With improved understanding of hard armoring distributions, SLR response plans can be fully informed to design more efficient scenarios for both urban development and coastal ecosystems.