Seasonal and Episodic Runup Variability on a Caribbean Reef‐Lined Beach

Abstract

AbstractMany low‐lying coastlines are exposed to overwash and marine flooding during large storm events, and the role of coastal ecosystems in reducing these hazards has been increasingly investigated and reported. This paper deals with the assessment of processes involved in coastal flooding over 2 years and 10 months at Anse Maurice, a reef‐fringed pocket beach located in Guadeloupe Island, in the Caribbean region. Daily maximum marine inundation was assessed using a fixed video system, and a hydrodynamic measurement campaign was organized to monitor local wave transformation through the reef system. The results show that daily highest runups (dHRs) are not linearly correlated with storm events since storm runup intensity is highly modulated by (a) the steric‐induced annual periodicity of sea level which showed minima in April and maxima in September and (b) the tidal level which influenced shortwave propagation on the reef flat (RF). These variables determined the reef submergence, an important parameter involved in wave transformation over reefs. Consequently, different runup responses existed for similar incident wave conditions, but generally wave attenuation ranged between 50% and 80%. Low‐frequency waves were found to dominate the hydrodynamics on the RF for the most intense wave conditions. The upper beach vegetation also reduces the maximum swash excursion at the beach between 1.7% and 42.8% for the observed storms, and thus reduces the potential for back beach flooding. This study demonstrates new comprehensive elements on runup behavior and nearshore processes, at different time scales, on reef‐lined beaches.