Comparison of Derived Instantaneous Unit Hydrograph fromH2U, Laplaceand H2U-Nash, Case Study:North Karoon River Basin, Iran

ABSTRACT: Floodingisa kind of natural disasteraffects life, livelihoods and human assertsat an unexpected scale. Recently there is heightened research interest in simulation of flood hydrograph as watershed response to rainfall. Hence, studying floodsis counted as significantportionof hydrology and reservoir managementprojects;one of the most popular methods in volumetricevaluation of output water from ungauged catchments is applying synthetic unit hydrograph, particularly the instantaneous type. Due to the lack of good knowledge about the performance of Laplace transformation, H2U, and H2U-Nash models in the study area the present workis an attempt to explore derived values on threecatchments located in western part of Iran, which are named Bazoft, Juneghan, and Khanmirza. For each catchment 10 individual rainfall-runoff events were collectedas observation to compare to transformed Laplace hydrograph (simulated based on effective rainfall and lag time), H2U(characterized by ranking parameters of catchments and average travel time) and H2U-Nash (by applyingmomentum of effective rainfall and direct runoff). Statistical comparison between simulated hydrographs and observationsranked H2U-Nash, Laplace transformation, and H2U model with RMSE 0.3, 0.37, and 0.51 in their agreement with measurements respectively. The Nash–Sutcliffe model efficiency coefficientapproved this ranking as well. Moreover, Bazoft, Khanmirza, and Juneghan catchments, withmean absolute of relative errors 0.31, 0.41, and 0.46 respectively, stand in the aforesaid hierarchy based on the precision of hydrograph properties estimation in all three models. This study also covers a comparison among different properties of simulated hydrograph, on the whole models showed comprising results for the base time of hydrographs.