Monitoring of Storm Surges on Cassino Beach, RS, Brazil

Abstract

■■■■■■■■■^■^^^^■■■■■■■^■■■■l SARAIVA, J. M. B.; BEDRAN, C. and CARNEIRO, C, 2003. Monitoring of Storm Surges on Cassino Beach, RS, Brazil. Journal of Coastal Research, SI 35 (Proceedings of the Brazilian Symposium on Sandy Beaches: Morphodynamics, Ecology, Uses, Hazards and Management), 323-331 Itajai, SC Brazil, ISSN 0749-0208. The monitoring of Storm Surges events over a period of three years (1997-1999) on Cassino Beach, coupled with sea condition observations and analysis of atmospheric conditions, shows that the simultaneous action of cyclones in the ocean and anticyclones in the South American continent result in the creation of a large fetch in the study area, with exchange of momentum from the atmosphere to the sea. This phenomenon may be associated with frontal systems. It was observed that the speed of the winds in these events is 20 m/s. Another important characteristic in some of the events observed is the formation of a second cyclone along the Northern Coast of Argentina, Uruguay and Southern Brazil. These cyclones generate waves in a sea area agitated due to the fetch which had been previously formed. It was also noted that when the cyclone is formed in the area of study or close to it, the coastal zone is damaged by the action of waves and not by the meteorological tide. The analysis of the global model on the surface (1000 hPa) and of higher levels (500 hPa) shows that these cyclones are very intense, with strong wind convergence on the surface and cyclonic relative vorticity at higher levels. ADDITIONAL INDEX WORDS: Cassino Beach, Storm Surge, wind fetch, extratropical cyclones and anticyclones.