Flood Directive implementation in Greece: Experiences and future improvements

The implementation of the European Directive 2007/60 is a crucial step towards the development of a sophisticated flood management plan for the main River Basin Districts by including any necessary structural measures. For this reason, extensive hydrological and hydraulic analysis is needed under the ubiquitous uncertainty which cannot be eliminated by numerical models. In this study, we present our experience from the directive implementation and we discuss structural components of uncertainty in the flood modelling practice mostly related to the river network. We propose and review some of the most efficient engineering practices by examining issues like: (a) the consistency and accuracy of the required input data of the topography such as the Digital Elevation Model, cross-sectional measurements of the river and maps of land use; (b) the uncertainty components related to the hydrological SCS-CN framework and other hydrological methods for the determination of the input hydrograph; (c) the theoretical framework of each hydraulic model such as the scheme dimension (1d, 2d or coupled 1d/2d), the type of solution of the numerical scheme (explicit or implicit), the boundary conditions and the type of discretization (grid or sectionbased); (d) the uncertainty components related to the flood inundation modelling, such as the roughness coefficient at the river and floodplain; (e) the necessity of validation data such as the flow discharge, the flood inundation area, and the velocity measurements.