Local vulnerability to inundation assessment at the coastal zone of Lake Region, Rio de Janeiro

Abstract

Assessing coastal risk at local scale including both physical and socio-economic variables has been a difficult task due to the low spatial resolution of the statistical data, frequently available only for a whole District unit. In order to bypass this constrain the relation of social statistics with other environmental variables was made using “urban statistical sensing units” from the Brazilian Geographic and Statistic Institute (IBGE) database which size varies as a function of the number of individuals a sensor is able to interview. The study area is Região dos Lagos located at the East coast of  Rio de Janeiro state, an area of rapid population growth and strong tourist vocation. A classification of vulnerability and risks to coastal erosion, inundation and ground water pollution is presented, based on the integration of field observation, beach morphodynamic state and reports of inundation by the Civil Defense with demographic and social data. Domiciliary access to water and sewage treatment was used to analyze indirect impacts of inundations on ground water pollution and potable water availability. Thirteen coastal segments with high to very high vulnerability to wave overwash were identified with constructions immediately behind the beach in six of these segments. The most critical situations occur where wave overwash were associated to coastal erosion. Areas prone to flood were identified mostly in the northern margin of the lagoon system, specifically in the municipality of Saquarema, with the highest number of registered occurrences, two of them due to wave overwash. More than 75.000 inhabitants have lived in flood, overwash or coastal erosion vulnerable areas and about 3.000 of them have very bad conditions of water access and sewage treatment indicating areas with very high potential risk of ground water pollution and deficient water access.