Variable Shoreline Responses to Sea-Level Rise and Climate Change

Researchers and coastal managers are addressing how climate change will affect shorelines. Important questions include: How far will a sandy shoreline retreat as sea level rise accelerates? And, how far landward will the effects of possibly intensified storms reach? These questions are most often investigated in a cross-shore profile framework, fostering the implicit assumption that coastline responses will be approximately uniform in the alongshore direction. However, we describe here experiments with a recently developed numerical model of coastline change involving shoreface geology and sediment-transport processes which suggest that the responses to sea-level rise are likely to be alongshore-heterogeneous. The interactions between accelerating sea-level rise, alongshore sediment transport, and spatially variable underlying material will tend to cause spatially variable retreat rates. We compare these sea-level-rise effects to other climate-change related shoreline impacts suggested by recent modeling work. Slott et al. have suggested that as storm behaviors and wave climates change, shifts in complex large-scale coastline shapes will cause alongshore variation in shoreline-change rates that could be an order of magnitude greater than sea-level-rise-related shoreline changes.