بررسي عوامل موثر در تعيين آستانه شروع رواناب در مناطق خشك و نيمه خشك كشور به كمك استفاده از شبيه سازي و داده هاي بارش - رواناب

An Investigation of Factors Affecting Runoff Generation In Arid and Semi-Arid Area Using Simulation and Rainfall Runoff Data

One of the most important problems in watershed basins is flash runoff which causes sever damages to industrial, urban, and rural areas. Therefore, use of methods, which can utilize short-term data and estimate the runoff threshold as well as water yield of a catchment, is of paramount importance. In this study, in order to ascertain the runofft hreshold in Latian watershed, a portable rainfall simulator was employed. With use of the rainfall simulator, different rainfall intensities with different durations were simulated and the runoff threshold in each experiment measured. Analysis of rainfall simulator data indicated that the effective variables in ascertaining runoff threshold, in order of importance are: rainfall depth, rainfall intensity, vegetation cover, clay and sand percentae as well as slope. A non-linear model was developed for calculating runoff threshold using obtained data. The coefficient of relation between measured runoff threshold and the one estimated by developed model is 0.98. In the next stage of the study, a comparison between rainfall simulator data and data obtained from rainfall-runoff simulation models was made. AWBM model was employed using obtained data from Kasilian, Kardeh, Amameh, Lighvan, Kan and Kameh. Results of runoff as well as estimated parameters with model showed that AWBM could satisfactorily be used to calculate runoff threshold as well as output runoff in each basin. Results also showed that runoff threshold obtained through the model and that through rainfall simulators are comparable and depend on: rainfall depth, rainfall intensity, vegetation cover, clay and sand percentage and slope respectivley.