Accuracy Estimation of Sediment Discharge Transfer Relationships of Khondab River, Joshirvan Station using HEC-RAS Model

Due to the complexity of hydraulic and sedimentary problems in rivers, it is not possible to solve the equations analytically, so numerical methods are used. In the present study, the HEC-RAS 5.0.3 model was used to simulate the sediment flow of the Khondab River. For this purpose, using the topographic map of the route, DEM and TIN of the River route with a scale of 1: 2000, in the HEC-GeoRAS extension package in ArcMap software, 200 sections along 5 km of the river were prepared. Relevant information was inserted to introduce the river geometry to the model. The flow rate was calculated with 25-, 50- and 100-year return periods and was used for river hydraulic simulation. Quasi-volatile flow conditions, boundary conditions and granulation of riverbed materials were introduced to the model. Using sediment transport estimation relationships, river sediment transport capacity was calculated. The results showed that the Mir-Peter and Müller relationship with 26% error is closer to the observed sediment values ​​than the other relationships. Moreover, the study of erosion and sedimentation status of the river using Hjulstrom and Shields criteria showed that a part of the sections of this river is in erosion status and another part is being sedimenting.