EVALUATION OF IMPACTS OF LAND USE CHANGES ON ZAYANDEHROUD RIVER FLOOD HYDROGRAPH IN ISFAHAN REGION

Land use is one of the most important that effect on the natural cycle of water. The present study evaluates land use changes effect on Zayandehroud river flood hydrograph in Isfahan region. The land used map of the studied basin was obtained from ETM(+) 1990 Landsat and IRS 2008 satellite images using ENVI software. Runoffrainfall events were also simulated using SCS model and the model was calibrated based on the measured hydrographs. The results showed that the coefficient of the SCS model should be considered by 0.21 for the basin. Also the hydrograph obtained from the coupled HEC-HMS model and GIS tools showed that effect of the land use change in the flood peak flow may be decreased with increasing the return period of the floods. For example for 5 year flood, the peak discharge from year 1990 to 2008 to be increased by 39.9 % but for the 200 year flood, the value was obtained at 10.3 %.