Spatial and numerical methodologies on coastal erosion and flooding risk assessment

Abstract

In the last decades the combination of an increasing human occupation along the coast combined with an anticipated intensification in the frequency of meteorological extreme events stimulated the development of different methodological alternatives to assess and predict coastal risk. Conceptually, a global risk analysis may involve susceptibility and vulnerability, in both temporal and spatial scales, with the goal of identifying critical hazard areas. In this work, two different analytical approaches are presented within the perspective of their future integration: spatial analysis based on Geographic Information Systems and numerical modeling. In the first approach, individual information layers associated with various themes (e.g. backshore landforms, backshore altitude, shoreline displacement, shoreline exposure to wave incidence and man-made structures at risk) were integrated and allowed the development of a numerical index of coastal vulnerability. In order to define inundation levels, a wave run-up study integrated numerical modeling and in situ measurements, allowing the recognition of sensible variations along an embayed beach. Finally, an erosional hot spot area was investigated by calculating longshore sediment transport rates. For this, a numerical model of wave propagation defined the coastal wave climate and the average sediment budget was determined in the surf zone. The three case studies of beaches with historical sensibility to erosion and storm surge flooding presented a very good correlation with reality.