LAUSR

ABSTRACT Pedreros, R.; Idier, D.; Muller, H.; Lecacheux, S.; Paris, F.; Yates-Michelin, M.; Dumas, F.; Pineau-Guillou, L., and Sénéchal, N., 2018. Relative contribution of wave setup to the storm surge: observations and modeling based analysis in open and protected environments (Truc Vert beach and Tubuai island). In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1046–1050. Coconut Creek (Florida), ISSN 0749-0208. Recent events like the Xynthia (2010, France) storm illustrate the potentially devastating effect that storm surges can have on the coasts. Nearshore storm surges at the result mainly from two processes: atmospheric surges and wave setup. This paper investigate the relative wave setup contribution in the storm surge signal for energetic events and focusing on two cases: an open beach (Truc Vert beach, France) and a high island protected by a reef lagoon (Tubuai, French Polynesia). The two selected events are the Johanna storm (March'08), for the Truc Vert site, and the Oli cyclone (February'10), for Tubuai. The data analysis shows that the maximum total storm surge reaches 1.2 m on the Truc Vert site and 1.1 m in the Tubuai lagoon. On the Truc Vert beach, the ECORS'08 in-situ measurements allow estimating a wave setup contribution of 80% of the total storm surge, at the time of maximum storm surge. The relative contribution of the wave setup is investigated a bit further, using the modeling approach. The modeling relies on the joint use of a shallow-water (MARS 2DH) and wave (SWAN) models. It shows an heterogeneous distribution of the wave setup in the Tubuai lagoon and a longshore variability close to the waterline for Truc Vert (~ 30%). In both cases, the wave setup contribution to the whole storm surge is predominant, with relative values ranging from 71 to 120% of the total maximal storm surge. Values larger than 100% occur on the Tubuai site when the atmospheric storm surge is negative.