EXAMINING THE SENSITIVITY OF FLOOD MODELLING IN PERIURBAN AREAS IN RAINFALL INPUTS OF VARIABLE ACCURACY

摘要

Flood risk management in periurban catchments is a critical issue, mainly due to the coexistence of different land uses and their frequent interaction, which make flood risk assessment hard. For efficient flood simulations in such areas, the use of accurate and representative rainfall inputs in modelling tools is particularly important. This research focuses on the examination of the impact of rainfall inputs of variable accuracy on both the hydrological and the hydraulic response of a periurban catchment. To this end, representative and efficient models for hydrological and hydraulic simulations were selected and set up for the study area and flood simulations for different rainfall inputs were performed. More specifically, rainfall inputs included rainfall forecasts while available flow measurements from stream flow gauges were used for model calibration. The optimum number of grid points with rainfall forecasts suggested for flood modelling, as well as the impact of the number of grid points used in the hydrological and the hydraulic analysis were further investigated. The study area is the Rafina catchment, a typical Mediterranean periurban catchment located in Eastern Attica, Greece. Hydrometeorological information is retrieved from the Hydrological Observatory of Athens (HOA), operated by the Centre for Hydrology and Informatics (CHI) of the National Technical University of Athens (NTUA), while meteorological information used in the analysis includes daily rainfall forecasts provided by the National Observatory of Athens (NOA). Both organizations operate dense networks in the study area. Flow measurements from HOA are retrieved from three stream flow gauges, while forecasts from NOA are provided in 48 grid points located within the catchment boundaries. The semi-distributed hydrological model HEC-HMS and the 1D hydraulic model HEC-RAS were used for flood modelling and run for selected rainfall events. The research concludes with suggestions on the required accuracy in rainfall inputs in order to achieve reliable hydrological and hydraulic simulations in a complex periurban area.