Investigate the relationship between runoff coefficient and rainfall intensity on pasture land (Case study: Sanganeh Kalaat)

Runoff coefficient is a function of various parameters and geometric characteristics of the basin such as soil، vegetation، geology، sediment load and human factors which each of these factors can affect the amount of runoff at outlet of basin. However، rainfall is the main factor that affects the runoff. Runoff coefficient in large basin using rainfall data and flow data recorded by hydrometric stations is determined. In small basin because of lack of station، rainfall runoff coefficient and volume flow estimation is difficult. In this study، rainfall and runoff events in the Sanganeh Kalaat (the basin were small، with an area of about one hectare and a total area of approximately seven hectares) have been measured. Rainfall and runoff using a rain gauge and five runoff gauges has been recorded. Rainfall intensity is one of the factors that are effective in generating runoff. Hence، in this study، runoff coefficient with different intensities of rainfall has been examined. The results show that with increasing rainfall intensity، runoff volume has increased. Correlation curves between runoff volume and the area for different intensities of rainfall are presented that can be used to estimate runoff volume.