Abstract
Runoff is excess rainfall or a portion of rainfall that flows over the watershed. In un-gauged streams, due to lack of data, many methods are used for runoff estimation. In this paper annual runoff and peak flow of Nazanin watershed were estimated at Nazanin Dam location using different methods. Soil Conservation Service (SCS) method, basin relation, (Hydrologic Engineering Center – Hydrologic Modeling System) HEC-HMS and Hydrologic engineering center (HEC-1) models were provided. The Watershed Modeling System (WMS) package was used for watershed delineation and computation of curve number. The area of Nazanin catchment is 72.14 km2, and the composite curve number is 81.3. The results of average annual rainfall estimated using the basin relationship method are more than that obtained from SCS method. The results of peak flood discharge for different return periods using different approaches such as SCS method, HEC-HMS and HEC-1 models are very close. But the results of basin relation are lower than SCS method. From the results of comparison, it was observed that HEC-HMS and HEC-1 models can be used for generation flood hydrograph at ungagged watershed.
Highlights
Runoff is usually generated from rainfall after infiltration a part of rainfall and the area become saturated
Because the characteristics of the catchment area of AL-Khazer River are almost similar to characteristics of most catchment area of local rivers, so this similarity is used for estimating annual runoff for Nazanin stream
Four approaches were provided for calculation peak flood discharge and mean annual runoff for Nazanin catchment area which is an ungagged catchment and concluded as follows
Summary
Runoff is usually generated from rainfall after infiltration a part of rainfall and the area become saturated. Estimation of peak discharge and runoff hydrographs in any catchment area are used for a variety of purposes in hydraulic structures such as spillways and flood control structures. In ungagged catchment area due to lack of data; empirical formulae are used for estimation runoff. Steenhuis et al (1995) revised SCS approach for predicting runoff over a catchment area good agreement was found by comparing its results with observed runoff. It was concluded that GSSHA is better to predict peak flood discharge and runoff volume for changes of land. Younis et al, (2014) HEC-1 model based on SCS method could accurately predict peak discharge when compared with the observed data. Hoseini et al (2017) compared different models in WMS such as TR-20, TR55 and HEC-1 for predicting flood discharge; it was observed that TR-55 yields better results than others Younis et al, (2014) HEC-1 model based on SCS method could accurately predict peak discharge when compared with the observed data. Hoseini et al (2017) compared different models in WMS such as TR-20, TR55 and HEC-1 for predicting flood discharge; it was observed that TR-55 yields better results than others
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