Seasonal runup variability at a reef-lined beach: field assessments in the Caribbean

The proposed article deals with the assessment of coral reef impact on runup-induced coastal flooding over a two years and 10 months period at Anse Maurice, a reef-fringed pocket beach located at Guadeloupe Island, in the Caribbean region. The reef is mainly constituted by complex structures of Acropora Palmata dead colonies. Daily maximum marine inundation was assessed using a fixed video system. Daily Highest Runups (DHR) remains primarily correlated to individual storm event as extreme runups are observed in correlation with storm swells. However, storm runup intensity is highly modulated by the non-astronomic annual periodicity of sea level (24% of the global runup variability) showing minima in Mars and maxima in October. Those variabilities determine the sea surface elevation and thus water depth over the reef. Yet, reef submergence is known to be an important parameter involved in wave transformation over reefs. The later itself is due to sudden bathymetric loss and high bottom roughness typical of reef environments. This leads to different runup response for similar incident wave conditions. For example, most of the winter storm events only induce moderate intensity runup (mainly due to lower water level controlled by the seasonal sea level cycle) while cyclonic events with the same swell intensity generate more extreme runups. This study brings new comprehensive elements on runup behaviour and nearshore processes at different timescales on reef-lined beach.

T. Laigre, Y. Balouin, A. Nicolae-Lerma, N. Valentini, D. Villarroel-Lamb, M. Moisan, Y. De la Torre - Paralia - XVIIèmes Journées Nationales Génie Côtier – Génie Civil, Chatou