Flood hazard assessment based on geomorphological analysis with GIS tools - the case of Laconia (Peloponnesus, Greece)

Abstract

The aim of the study was the development of a GIS tool, to be exploited eventually in the form of a WebGIS, as a decision support tool for flood hazard (and risk) assessment. The research was conducted in Laconia Prefecture in Peloponnesus. In this work, flood hazard assessment was implemented using hydrological models into a GIS environment (Arc Hydro model) taking into account the geomorphologic characteristics of the study area. More specifically, a DEM was used as input data of the Arc hydro model in order to produce the hydrographic network and the hydrological basins layer. For each basin, the morphologic characteristics such us area, mean slope, mean elevation and total relief, were calculated. These factors, all enhancing flood hazard, were combined in a product (by simple multiplication) in order to produce the inherent flood hazard map for each water basin and enhance the spatial differentiation of the phenomena. The final flood hazard map was produced by the combination of the aforementioned map and the slope map of the study area. The results of the followed methodology were evaluated using recorded flood incidents of the study area and shown that 60% of the incidents were related with the predicted high flood risk areas, which can be considered very high, once many of the flood phenomena in the non-predicted areas were largely due to previous human activity at the sites. Ultimately, the flood hazard map was published into a web GIS environment providing a friendly GUI to the end users. Except of analyzing the static flood hazard map, the end user have also the potential to interact dynamically with the map, adding to model calculation the meteorological factor (e.g. rain intensity, mean precipitation) in order to reassess the flood hazard of the study area.