Evaluation of coastal flood risk areas and adaptation strategies for a sustainable planning

This work illustrates the methodology developed to evaluate the risk of coastal flooding and its application to Vale do Lobo beach, located in the Loulé Municipality, a Portuguese coastal area under significant touristic pressure. The methodology is based on six main steps: 1) division of the study area into sub-areas with similar characteristics in terms of coastal defense; 2) determining the probability of exceeding the pre-set thresholds of flood levels for each study area; 3) establishment of qualitative factors related to the consequences of such excess of the flood levels; 4) the combination of the above steps for expeditious assessment of flood risks; 5) identification of the risk areas; 6) proposal for risk adaptation. The determination of the flood levels is based on the local wave regime at the Faro wave-buoy over 9 years, on its propagation to the study area using the SWAN model integrated in the geographic information system (GIS), GUIOMAR, together with the calculation of runup and flooding levels based on empirical formulae. Special emphasis is placed on the automation of this process in GUIOMAR to make it an efficient tool for risk assessment. To determine the risk of coastal flooding, a methodology has been developed using the geographic information system and a multi-criteria analysis to assess the vulnerability of the territory in several episodes of flooding and to determine the different risk areas.