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Coastal vulnerability assessment of Cape Cod National Seashore to sea-level rise

March 30, 2021

A coastal vulnerability index (CVI) was used to map the relative vulnerability of the coast to future sea-level rise within the Cape Cod National Seashore (CACO). The CVI ranks the following in terms of their physical contribution to sea-level rise-related coastal change: geomorphology, regional coastal slope, rate of relative sea-level rise, shoreline change rates, mean tidal range and mean wave height. The rankings for each variable were combined and an index value calculated for 1-minute grid cells covering the park. The CVI highlights those regions where the physical effects of sea-level rise might be the greatest. This approach combines the coastal system's susceptibility to change with its natural ability to adapt to changing environmental conditions, yielding a quantitative, although relative, measure of the park's natural vulnerability to the effects of sea-level rise. CACO consists of high glacial cliffs, beaches, sand spits, and salt marsh wetlands. The areas most vulnerable to sea-level rise are those with the lowest regional coastal slopes, geomorphologic types that are susceptible to inundation, and the highest rates of shoreline change. Most of CACO's infrastructure lies on high elevation uplands away from the shore; most high use areas are accessible by foot only. The CVI provides an objective technique for evaluation and long-term planning by scientists and park managers.