REMOTE SENSING, GIS AND HEC-RAS TECHNIQUES, APPLIED FOR FLOOD EXTENT VALIDATION, BASED ON LANDSAT IMAGERY, LIDAR AND HYDROLOGICAL DATA. CASE STUDY: BASEU RIVER, ROMANIA

Floods have always posed great threat to human settlements, and their monitoring has always been a very important step in the understanding, managing and predicting similar, future events, in order to mitigate flood risk and the concrete impact it has on communities and the environment. Modern techniques of analysing flood extent include remote sensing, by extracting flood limits from satellite imagery, and Geographical Information Systems (GIS), which are used in tandem, to generate cartographic material, depicting areas suffering from flood damage. Unfortunately, the results are not always precise, and can induce significant errors, due to which, the results are questionable and cannot be efficiently included in management plans, by authorities. The current study addresses the validation process of digitally generated GIS layers, based on statistical data derived from hydrological field recordings, with satellite images that reveal the proper flood extents, from the same time period, as the case study flash flood. The emphasis was put on comparing absolute and relative accuracy values, in order to validate several results, such as digital, HEC-RAS generated water levels (based on statistical analysis) with recorded water levels; 5% recurrence interval flood extents of HEC-RAS model, correlated withreal-world flood extent, and through satellite imagery.