Evaluation of the role of Biological practices on flood Control (Case study: Yengajeh Watershed)

Assessment of flood control projects in order to improve decision making is an efficient way to reduce the consequences of floods. Watershed projects are performed by the purpose of soil erosion control، flood control and reducing their effects. Every year in Iran so much exchequer are allocated for watershed projects. An important point in these projects is their benefit، so evaluating of watershed projects is necessary. For this purpose، this study was done for evaluating of watershed management practices in Yengajeh Watershed using HEC-HMS. So based on the observed rainfall-runoff events، HEC-HMS model was optimized and then calibrated For determining effect of biological practices، the change of CN was calculated. Next peak discharge and flood volume which were changed by practices، estimated by HEC-HMS. The results showed that the practices had effects on CN parameter. The most effects were on L1 & L2 sub basins، it is because of less region and concentration of projects، although the change of curve number in L4 sub basin was less. On the average curve numbers were reduced as 12. 45%in sub basins.