Caractéristiques spatiales de la formation des surcotes marines dans le Golfe du Lion. Spatial charcateristics of sea-surges formation in the Gulf of Lions

Abstract

This paper is based on the analysis of hourly tide measurements at four tide gauges stations around the Gulf of Lions: Marseille, Grau-de-la-Dent, Sète and Port-Vendres. For each tidal value, surge heights have been determined to keep only the atmospheric forcing on the level of the Sea. The aim is to improve our understanding of surge related-coastal-risks by analyzing the relationship between strong surges and their atmospheric forcing factors at different spatial scale. Sea-surges variations around the Gulf of Lions are spatially consistent at different time scales. Hourly and daily maximum surges are strongly correlated between the four stations. Around the Gulf of Lions, sea surges are regionally associated with a southerly wind tending to drag the water towards the coasts. Although regional surges results from a combination of air pressure pattern and its regional associated wind over an extended area, local surges peaks are often reached when the local wind direction favors water accumulation on that particular coastal area. That’s why each station has its sea-surge preferential southerly wind directions. But according to the local coastal orientation, strong surges at Port-Vendres and Marseille can be even forced by a local northerly wind enable to favor the water accumulation too. Taking into account the various spatial scales is crucial here in order to improve our understanding of coastal risks associated with sea surges around the Gulf of Lions.

Keywords

• sea level
• sea surge
• meteorology
• risk
• Golfe du Lion