Institute of Geoecology An analysis of hydraulic, environmental and economic impacts of flood polder management at the Elbe River A dissertation submitted to the Faculty of Mathematics and Natural Sciences at the University of Potsdam, Germany for the degree of Doctor of Natural Sciences (Dr. rer. nat.) in Geoecology by Saskia Förster Potsdam, August 2008 Online published at the Institutional Repository of the Potsdam University: http://opus.kobv.de/ubp/volltexte/2008/2726/ urn:nbn:de:kobv:517-opus-27260 [http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27260] Contents Summary........................................................................................................................................ 7 Zusammenfassung ........................................................................................................................ 9 Chapter I Introduction........................................................................................................... 11 1 Background ......................................................................................................................................................11 2 Objective and Research questions ................................................................................................................12 3 Study areas........................................................................................................................................................12 4 Outline of the thesis........................................................................................................................................14 Chapter II Flood risk reduction by the use of retention areas at the Elbe River....................15 1 Introduction .....................................................................................................................................................16 2 Description of the study area.........................................................................................................................16 3 Research approach ..........................................................................................................................................17 4 Modelling the inundation of the polder system..........................................................................................17 4.1 Outline of the CR Model .......................................................................................................................17 4.2 Application of the CR Model to the Lower Havel River ..................................................................18 4.3 Aggregation of simulation results .........................................................................................................20 5 Damage assessment in the polder system....................................................................................................20 6 Assessment of potential damage reduction in Wittenberge......................................................................21 6.1 Determination of flooded areas ............................................................................................................21 6.2 Assessment of potential damage in Wittenberge................................................................................23 7 Cost-benefit analysis .......................................................................................................................................23 8 Discussion and conclusions...........................................................................................................................24 Chapter III Hydrodynamic simulation of the operational management of a proposed flood emergency storage area at the Middle Elbe River.......................................27 1 Introduction .....................................................................................................................................................28 2 Study area..........................................................................................................................................................28 3 Hydrodynamic model setup...........................................................................................................................31 4 Considered flood scenarios and control strategies.....................................................................................32 4.1 Flood frequency analysis ........................................................................................................................32 4.2 Definition of flood scenarios.................................................................................................................33 4 4.3 Definition of control strategies .............................................................................................................33 5 Results...............................................................................................................................................................35 6 Conclusions and discussion ...........................................................................................................................37 Chapter IV Comparison of hydrodynamic models of different complexities to model floods with emergency storage areas.....................................................................39 1 Introduction .....................................................................................................................................................40 2 Study Area and Data Used.............................................................................................................................41 3 Methodology ....................................................................................................................................................42 3.1 One-dimensional model setup ..............................................................................................................42 3.1.1 Calibration and validation of model ..........................................................................................43 3.2 One-/ two-dimensional model setup...................................................................................................43 3.3 Sensitivity analysis ...................................................................................................................................44 3.3.1 Manning’s n...................................................................................................................................44 3.3.2 DEM’s of different resolutions ..................................................................................................44 3.3.3 Number of cross-sections used..................................................................................................44 3.3.4 Gate opening time and opening/closing duration...................................................................45 4 Results and Discussions .................................................................................................................................45 4.1 Calibration and validation of the one-dimensional model ................................................................45 4.2 One-dimensional model results for flooding and emptying processes in the polder....................46 4.3 Comparison of one- and one-/ two-dimensional model results......................................................48 4.4 Computation time, storage space requirements and modelling effort ............................................48 4.5 Sensitivity analysis ...................................................................................................................................50 4.5.1 Manning’s n...................................................................................................................................50 4.5.2 DEM’s of different resolutions ..................................................................................................51 4.5.3 Number of cross-sections used..................................................................................................53 4.5.4 Gate opening time and opening/closing duration...................................................................53 5 Conclusions......................................................................................................................................................54 Chapter V Simulation of water quality in a flood detention area using models of different spatial discretisation ...............................................................................57 1 Introduction .....................................................................................................................................................58 2 Study site...........................................................................................................................................................58 3 Methods and data ............................................................................................................................................59 3.1 Comparison of the 0D and the 2D approach.....................................................................................59 3.2 Water quality processes ..........................................................................................................................60 3.3 Computational procedures.....................................................................................................................63