Is shoreline armoring a response to marsh migration? Modeling relationships between coastal marshes and private adaptation decisions

The value and vulnerability of salt marshes has led to efforts to ensure their preservation, including the preservation of marsh transgression zones (uplands onto which marshes can migrate) and restrictions on shoreline armoring. Coastal armoring involves the placement of hardened structures such as revetments and bulkheads along the shoreline. These structures can prevent coastal marshes from migrating onto adjacent uplands as sea levels rise, thereby causing marsh loss over time. Hence, efficient targeting of efforts to ensure marsh sustainability requires an understanding of where and why coastal armoring is likely to occur. This article develops a random utility model that characterizes residential landowners’ shoreline armoring decisions for beachfront and non-beachfront residential property, focusing on whether armoring is influenced by features related to marsh migration. The model is illustrated using parcel-level data from Accomack County, Virginia with armoring observations on each parcel for two time periods, 2002 and 2013. Independent models for the two time periods suggest that landowners in the case study area do not tend to construct armoring in ways that impede marsh migration—all else equal armoring is less likely to occur in areas suitable for marsh migration. Rather, armoring appears to be motivated primarily by factors associated with shoreline erosion risk such as high wave energy.