Hydrograph analysis to estimate the flood characteristics (Case study: Lishter watershed)

Unit hydrograph estimator models are considered as useful tool to predict the flood characteristics. One of the common methods in flood hydrograph forecast caused by rains in the watershed, is using instantaneous unit hydrograph. Nash and Rosso are the common forms of the instantaneous unit hydrograph (IUH) could be estimated the flood hydrograph. This study was conducted to estimate the flood hydrograph in the Lishter basin in Iran. For this subject, the hydrologic components of the study area including area, waterway length, and perimeter of the basin were evaluated using geographical information system. Then, parameters of the two methods of Nash and Rosso, k (scale parameter), n (shape parameter) and velocity (meters per second), were calculated. Instantaneous unit hydrograph obtained by the developed models were compared to the observed data for 20 selected events from 1994 to 2020 Nash Sutcliffe coefficient (NS) and Root Mean Square Error (RMSE). Results showed that Rosso method was accurately estimated the peak discharge. Furthermore, the observed data confirmed that the Rosso model could be utilized for estimating the design flood for areas of the country that are facing with a lack of observational data.