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Abstract:

In the paper usefulness of one dimensional model for restoration purposes was investigated. The sediment model of downstream part of the Flinta River (Western Poland) was prepared using HEC-RAS 5.0.0. The set of deflectors, which was implemented as constrained cross-sections, was analyzed. Computations were carried out for three formulas for intensity of sediment transport: Yang, Ackers-White and MPM-Toffaleti. Two geometry variants were tested: without modifications of the channel and with deflectors. Moreover, within geometry with structures, two variants of markers for mobile beds were distinguished, where at the location of structures erosion was allowed (variant A) or blocked (variant B). The obtained results showed different responses of each formula in relation to inflow hydrographs, and impact of deflectors on sediment transport processes. At the bank opposite to structures obtained erosion while, in the location of structures, there was erosion (variant A) or deposition (variant B) of sediment. Additionally, analysis of maximum values of shear stresses indicated high peak values for variant B. Basically, results were consistent with other studies with deflectors however, the size and length of the scour, which are crucial during designing these structures, were not obtained. For this reason, one dimensional model was considered as insufficient to planning restoration measures, as simplistic information about impact of structures was not enough. The main practical output of our research is showing the limits in application 1D models to analyze simple river management hydraulic structures.