Land use changes and the development of road network and residential areas have caused an increase

in runoff generation and flood hazard. The present study has been done to investigate the effects of land

use changes on runoff generation and flood hazard in Kasilian watershed. The study of land use changes

has been carried out by using aerial photos, topographic maps with scale of 1: 25000, land use maps and

satellite images. Also a rainfall- runoff model has been presented by using GIS (HEC- GeoHMS extension)

and hydrologic model (HEC- HMS). We used the SCS and CN methods (hydrograph simulation and runoff

height estimation) for presenting the hydrologic model. It is noted that the optimized model is validated by

the other four events of flood. Then, land use changes have been included in the validated hydrologic

model and their effects on intensifying runoff generation and flood hazard have been investigated quantitatively.

The results showed that land use changes caused an increase in runoff generation potential and

flood hazard.