Simulation and Evaluation of Perennial Rivers Flows with HEC-RAS and RubarBE Models

The application of mathematical models in river engineering schemes is inevitable. The one-dimensional model of HEC-RAS is widely used in river studies in Iran, since it demands less field data with low computational capacities. The main aim of the present study was to test the simulation of steady and unsteady flows by HEC-RAS model in a large perennial river (the Danube River), and to compare the corresponding results with another well-known European model (RubarBE), under similar geometric and hydraulic conditions. A reach of 42 km of the Danube River in Slovakia was selected. The two models were run for seven different flows (ranging from 890 to 9100 m3/s), and flow principal parameters were compared. The adaptation of simulated and observed water surface profiles along the river reach was satisfactory for the two models, particularly at flows within the main channel. The bankfull discharge was about 2000 m3/s, and was considered as a threshold of flooding in most part of the river reach. This flood flow rate was consistent with the results from both the HEC-RAS and RubarBE models. Sensitivity of the HEC-RAS model was also tested for five geo-hydraulic parameters. The bed slope was the most sensitive for the normal flow boundary conditions. Among different hydraulic characteristics, the water surface levels were less affected by the variations of the five parameters. The results were compared with a similar study on an Iranian perennial river (Nazloo River, Urmia Lake Basin), and good agreement was achieved.