Die flächenhafte Ausbreitung der Flutwelle nach Versagen von Hochwasserschutzeinrichtungen an Fließgewässern

The collapse of a dike, a flood protection wall or a (mobile) flood protection barrier generates a flood wave into the area which the device is actually supposed to defend. This wave can cause considerable damage. Until now little is known about the propagation behaviour of this wave – in spite of the economic relevance of the problem. In a literature survey the crucial influencing factors were educed. However, they were not sufficiently quantifiable to draw on for a reliable prediction of the flooding depths and velocities.To remedy this deficiency a physical model was designed, in which detailed measurements were carried out. In a series of tests the initial water depth, the initial discharge in the inflow channel and the width of the breach were varied.For the first time semi-analytical formulas could be developed for the calculation of the hydrographs in the breach and on the propagation area. The derivation was based on the assumption that the lateral propagation can be described by the superimposition of a couple of the simpler dam break waves, which are already thoroughly investigated. The resulting formulas are applicable in the engineering practice. Additionally, an approximation for the propagation shape of the wave in plan view is proposed.The data gathered in the physical model prove the accuracy of the new calculation formulas. The remaining discrepancies are small; their reasons are discussed in detail: complex initial stage, hydrostatic pressure assumption, superimposing of subprocesses, dynamic effects and lateral deflection of the wave by the discharge in the inflow channel. During preliminary tests it turned out that a water film of even a very small depth changes the wave propagation significantly. Therefore an extra chapter is dedicated to its effects.Thus this thesis gives a good overview of the wave following the collapse of a flood protection measure, which can be efficiently used for the prediction of the flood wave's propagation. Based on this work future efforts can be devoted to the optimisation of prediction tools, which are urgently needed for accurate risk analyses