Evaluation of flood mitigation alternatives using hydrological modeling

Flood damage is one of the most important natural hazards in arid and semi-arid regions. Hydrological modeling is needed for integrated watershed assessment, determining the effects of upstream watershed disturbances and flood control measures on flooding. Historical flash floods threatening Kan watershed have shown that flood control measures are urgently needed to protect natural resources, tourist sites and metropolitans area. Kan watershed has two sub-basins with common outlet, which is caused accelerated impacts on peak flows and flood volumes in mainstream. This watershed is a very interesting case for study of synchronized flood hydrographs analysis and possible challenges for reducing the intensity of floods. In this paper, an event based hydrological model, HEC-HMS, was used to modeling the watershed response to any changes by structural and non-structural flood control measures and synchronized hydrograph analysis. A multiple decision-making method was used to find optimal flood mitigation alternative based on 25 and 100 years peak flood discharges and time lag between peak flood discharges at outlet of two sub basins. Synchronized hydrograph analyses have shown that flood control measures should not implement in Kiga sub-basin. For local flood mitigation at the Kiga sub-basin some methods for facilitating the flood flows were proposed. The analyses showed that magnitudes of the peak discharges downstream could be reduced if upstream peak flows are desynchronized. In these cases hydrograph analyses play the key role in rational flood mitigation planning.