The Role of Coral Reefs in Coastal Protection: Analysis of Beach Morphology.

Abstract

This paper evaluates the effect of a fringing reef on the morphodynamic behaviour of adjacent beaches in terms of profile stability and cross-shore sediment exchange. Variations in subaerial beach morphology along 39 cross-shore profiles at Pontal do Cupe beach (Northeastern Brazil) were analysed, using modelled wave data and monthly beach topography acquired from November 2014 to September 2016. Pontal do Cupe has a reef to the south but is exposed to waves in the north, making this an ideal location to assess the sheltering effect of the reef. Beach volume and beach width data were used to compare the reef-fronted profiles with those of the exposed adjacent beach. Seven groups of profiles were identified by applying Principal Component Analys is to the topography dataset. A simple numerical model was used to quantify the role of the reef in dissipating wave energy, showing a reduction of approximately 50% in incoming wave energy to the shore. The reef-fronted beach is significantly more stable than the exposed beach. Total beach volume is similar for both the exposed and the reef-fronted beach. The results of this survey can be used as a proxy for the ecosystem service of coastal protection provided by reefs.