Analysis of the impact of land use change on the amount surface runoff in the Rigan watershed of Kerman province

The development of residential and urban areas on the banks of rivers and flood plains, regardless of the hydraulic and hydrological conditions govering the upstream basin and the river, increases the risk of flooding. Therefore, the study of floods for the purposes of planning, optimal exploitation and management of this natural phenomenon is one of the important issues in water resources management. The current research aims to investigate the rate of land use change using the HEC-HMS hydrological model and geographic information system (GIS) and Landsat satellite images during the years 1991, 2001 and 2011 in the Rigan watershed of Kerman province with an area of 7091 square kilometers. It was investigated on the increase of flooding of surface runoff in the area. For this purpose, in the first step, satellite images were interpreted and processed, and changes in land use was determined and soil CN values were calculated. Then, with the help of HEC-HMS model, the rainfall-runoff process in this basin was simulated and the peak flood discharge values were obtained in each period, and finally the flood hydrograph of the watershed was estimated. The results showed that with the increase of urban impervious surfaces and destruction of agricultural lands and pastures in the study area, the rate of soil CN from 1991 to 2011 increased from 65.28 to 70.25, following which the peak flood discharge from 29 m3 / sec in 1991 to 29.3 m3 / sec In 2011 and also the volume of runoff has increased from 3.4 to 6 mm during this period. The obtained results can be of great help to the implementation of watershed projects.