Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 11 4 2007 10.5194/hess-11-1391-2007 http://www.hydrol-earth-syst-sci.net/11/1391/2007/ http://www.hydrol-earth-syst-sci.net/11/1391/2007/hess-11-1391-2007.html http://www.hydrol-earth-syst-sci.net/11/1391/2007/hess-11-1391-2007.pdf 1391 1401 2007-07-03 The effectiveness of polder systems on peak discharge capping of floods along the middle reaches of the Elbe River in Germany S. Huang J. Rauberg H. Apel M. Disse K.-E. Lindenschmidt GFZ GeoForschungsZentrum Potsdam, Section 5.4 – Engineering Hydrology, Telegrafenberg, 14473 Potsdam, Germany GFZ GeoForschungsZentrum Potsdam, Section 2.3 – Earth's Magnetic Field, Telegrafenberg, 14473 Potsdam, Germany Institute of Hydroscience, University of German Armed Forces, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Germany In flood modelling, many one-dimensional (1-D) hydrodynamic models are too restricted in capturing the spatial differentiation of processes within a polder or system of polders and two-dimensional (2-D) models are very demanding in data requirements and computational resources. The latter is an important consideration when uncertainty analyses using the Monte Carlo techniques are to complement the modelling exercises. This paper describes the development of a quasi-2-D modeling approach, which still calculates the dynamic wave in 1-D but the discretisation of the computational units are in 2-D, allowing a better spatial representation of the flow in polders and avoiding large additional expenditure on data pre-processing and computational time. The model DYNHYD (1-D hydrodynamics) from the WASP5 modeling package was used as a basis for the simulations and extended to incorporate the quasi-2-D approach. A local sensitivity analysis shows the sensitivity of parameters and boundary conditions on the filling volume of polders and capping of the peak discharge in the main river system. Two flood events on the Elbe River, Germany were used to calibrate and test the model. The results show a good capping effect on the flood peak by the proposed systems. 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