Runoff simulation using geomorphological instantaneous unit hydrograph (GIUH). (case study: Bar basin-Khorasan Razavi)

Considering the most of country have no gage station, in recent year one method can be proposed with the involvement of other information, which will affect hydrology condition. It can estimate flood water level. In this study, considering relationship between geomorphology and hydrology, using little information, flood hydrograph were simulated. This method is named geomorphological instantaneous unit hydrograph (GIUH). At first, the drainage basin was ranking using Strahler method. Then, the quantitative geomorphologic parameter concluding ratio of bifurcation (RB), ratio of area (RA), ratio of length (RL) and length of last order (L;Omega) were calculated considering this ranking. Then using these parameters and the peak flow velocity in outlet, peak discharge in outlet and time to peak of instantaneous unit hydrograph were calculated. For model evaluation, five events were selected from hydrometry station in outlet of basin, compared with computational hydrograph using GIUH model. Result show that, this model is suitable for this area, and little difference between observed and computed hydrograph was due to construction of earth dams in upstream, which affect hydrology conditions.