Modeling the Effect of Hill Slope Length on Features of Rill Erosion Based on Incomplete Gamma Function in Ahmad-Abad, Mashhad

Rill erosion due to run off on hill slopes is a kind of water erosion which causes the highest soil loss in world-wide scale. Since the length of hill slope is one of the most effective factors in erosion، in this research، the variation of width، depth، cross-section، and frequency of rills were evaluated on the length of hill slops. In addition، soil components were evaluated due to the variation of hill slope length. Some hill slopes with pronounced rills were chosen in Ahmad-Abad location and on each slope، fifty-meter –transect was selected with the distances of 10، 20، 30، 40 and 50 meters and the features of rills were measured. As the routine models of linear regression have not been fitted to the observed data، the incomplete gamma function was used to obtain logical relation between hill slope length and mentioned parameters. Therefore، this model were fitted well to all parameters، except to the frequency of rills and the mean amounts of clay (p)