Study Of Effective Factors On Sediment Yield of Loess Deposits Using Rainfall Simulator

Loess Deposit is one of the most important Quaternary Deposits of northeastern parts of Iran which have high erosion rate. This study was performed with field- Rainfall- Simulator which has a plot area of 1 m2 in Gorganrood Drainage Basin to determine the effective factors on sediment yield. Landuse، slope and erosion feature maps were overlaid in GIS to obtain land unit map. Then on work units، rainfall simulator analyses were performed. The produced runoff and sediment in 69 points on work units were collected and were measured. Adjacent to each rainfall simulator plot، samples of surface material were collected in the field to analyze for physical and chemical characteristics. In the field، descriptive tables were prepared for different work units in which locality، slope percentage، elevation، depth of A horizon of the soil and other necessary informations were recorded. In order to determine logical relationship between different variables، regression and correlation analyses were performed. In statistical analyses، it was found that slope percentage has the highest correlation coefficient and has the highest direct relationship with sediment yield and sediment production and silt amount is the second factor. The investigation of multiple regression analyses generated a model which shows %80 of sediment production variations. In this model slope percentage، cation exchange capacity and silt have possitive relationship and Calcium cation has negetive relationship with sediment yield.