Gully erosion is a highly obvious form of soil erosion that affects on soil productivity, restricts land use and can endanger roads, fences and buildings. Gullying is a complex process controlled by a variety of closely related factors such as lithology, soils, climate, topography, land use and vegetation cover. Gully erosion is often the main source of sediment on a catchment scale and may also act as a sensitive indicator of environmental change. the rate of gully growth is one of the most important indicators used for assessing the area destroyed by gully erosion and evaluating the many kinds of damage it causes. Thitudy investigatedthe causeof gullyerosioin the Shurabad watershed located in Kuhdasht city, Lorestan province. We studied effectof physiographical andoilfactorothe rateofgullyerosion. Twelvegullies randomly selected andclassifiedin twoform “single-heads” and “multiple-heads”. The physiographical characteristics (length, width,and upstreamlope,floor slope)and gully characteristics (slope, elevation, landuseandgeology) were measured for each gully. Threeartofgullies including upstream,middleanddownstream were selected and theircross section was drawn. For each gully, we drilled a soil profile with 1.5 m in depth andtookoilamplefrom fourrofile layer0-25,25-50,50-100and100-150cm. Soil characteristics such as: texture, electrical conductivity (EC), saturated moisturecontent (SP), pH, amounts of calcium and magnesium ions, the rate of lime, gypsum,organic matter, bulk density, sodium and percentage of soil texture components were measured. Therelationshietween gullylengthanderosion volume were investigated using regression analysis and erosion thresholds determined. The results showed that gully erosion mostly occur in Quaternary and Bakhtiary geology formation and under road, rangeland and agricultural land use. Although number of gullies were same in different landuse but they produced different sediment rate. Average sediment rates in road, rangeland and agricultural landuses were 4, 4.2 and 1.1 m3 respectively. Erosioratewere significantly different iagriculturalunitin relation toroadandrangelands. Most gullies occur ilopeless than 5 percent. Sediment rate
