Questioning the Rules in Coastal Erosion

Douglas, Leatherman, and Zhang reply: Our paper investigated how increasing sea level will-exacerbate the long-term sandy beach erosion that affects nearly 90% of the US coastline. ¹ Storms are commonly blamed for the erosion, but 150 years of US shoreline position data do not support that cause. ² US sea level is rising at varying rates, so we investigated the regional sensitivity of beach erosion to sea-level rise.

The Bruun model, which relates sea-level rise to erosion rate, works well in wave tanks and lakes. With its assumption of a depth of closure, the model is also reasonably consistent with regional (not local) East Coast erosion trends. We discovered an erosion sensitivity of about two orders of magnitude greater than the rate of sea-level rise, which indicates that a small amount of sea-level rise has a big effect on sandy beaches. Loss of beach width increasingly exposes fixed structures to flooding and the destructive energy of storm waves.