Integrated modelling for flood risk mitigation in Romania: case study of the Timis-Bega river basin

An integrated flood modelling approach has been applied in a demonstrator of a flood management system, which was developed within the framework of a collaborative project between Romania and the Netherlands. The developed demonstrator system had two objectives: (a) operational water management under extreme conditions when actions have to be taken quickly; (b) off-line analysis and design of flood mitigation measures and alternatives. This article presents the applied approach and the achieved results for meeting the second objective. The pilot basin for the development of the system was the Timis-Bega river basin, in which the rivers Timis and Bega were considered jointly. The system is based on modelling the flood generation and routing processes by combined development and application of hydrological and hydrodynamic models. The modelling system HEC-HMS was used for the hydrological model, HEC-RAS for the one-dimensional hydrodynamic model and SOBEK for the two-dimensional (2D) model used for downstream flood analysis and design of mitigation measures and alternatives. The 2D model includes alternatives of deliberate dike breaching as part of the analysis of the system response. The analysis presented is concentrated on a specific flood event that occurred in April 2005, which occurred due to dike breaches along the Timis river. The combination of models is first used for reconstruction of inundation patterns resulting during this flood event. Subsequently the models were used for testing flood mitigation alternatives of deliberate (planned) breaches of flood protection dikes located in the downstream part of the Timis river at the same location where they had occurred during the 2005 flood event, but at different times with respect to the arrival of the flood hydrograph. The demonstrated approach can enable decision-makers to analyse the behaviour of the physical system and design possible preventive and/or mitigation measures.