Author(s): Jos S. L. J. Van Alphen
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Keywords: Flood protection measures; Hydrodynamics; Hydraulic bottleneck; Bypass; Backward dike relocation
Abstract: After the near floods along the rivers Rhine and Meuse in 1993 and 1995 there has been a major shift in Dutch policy regarding flood protection; from raising the dikes to giving the rivers more space for their expected increased discharge. Measures under this policy include backward dike relocation, making bypasses, channel deepening, removing hydraulic obstacles and floodplain lowering. In view of the rapid economic and urban development, urgent choices have to be made to reserve the space needed for these measures. Near the city of Nijmegen, the cross section of the river Waal, the major branch of the Rhine in the Netherlands, decreases by 50% within 2 km. At this point, an urban development project of12,000 houses, to be built right up to the present dikes, started in 2000. The Ministry of Transport, Public Works and Water Management, the Nijmegen municipal authorities, the water board and the provincial authorities started a joint study to investigate how this hydraulic bottleneck could be removed by taking measures that would be effective in the long term and would take account of the higher design discharges expected and the new urban development scheme. Channel deepening, flood plain lowering, bypasses and dike relocation were compared for their hydraulic and spatial effects. The dike relocation appeared to be the most promising option and is discussed in more detail here. Nijmegen thus became the first example in the Netherlands of how hydraulic bottlenecks in an urban environment can be eliminated.
Year: 2002