Transport and Sedimentation Processes - A Comparison between Physical and Mathematical Models

Several Austrian and Slovenian rivers have modified their morphology by hydraulic works for one century or more. River floodplains have often been transformed in a succession of reservoirs and of canalised reaches (e.g. River Drau and the River Mur that are a common concern of both neighbouring countries). The management of such rivers requires permanent action on discharges, sediments, etc. and thus detailed modelling of what will occur after the various works. From that point of view, free surface flow and pollutant transport simulations are a very important task in hydraulic engineering. Recently, two- and three-dimensional codes become more and more popular. To rely on these modern tools, the codes should be tested, calibrated and verified well. In the first two years of the common Slovene-Austrian project SLO-A/31, we focused on the use of hydrodynamic modules of such codes. The main question was how far the models can be trusted in the river flow situations. The result of three codes (PCFLOW2D, PCFLOW3D and SMS) were tested and compared with measurements on three laboratory experiments. The model PCFLOW2D was applied first on the flow around an obstacle in a laboratory channel built at INSA (Lyon, France). The objective was to test the capacity of a 2D code to represent the recirculating flow downstream of an obstacle and the change in water levels. The second case was the hydraulic model of the river Mur in Graz where the SMS code was tested.