Project part-financed by the European Union (European Regional Development Fund)

The Interreg IVB North Sea Region Programme

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Compensation channel Hahnöfer Nebenelbe

Crux of the matter

All options of the preliminary investigation showed that the measure had only a small positive effect on the current situation of the channel. Long periods of slack water and related increased sedimentation rates are the dominant phenomenon and will possibly lead to the siltation of the area. The analysis of the current velocities showed that the maximum velocity of the flood current in the eastern part of the channel decreased by 10 cm/s. Velocities of the ebb current remained unaltered, as well as the currents of the rest of the ’Hahnöfer Nebenelbe‘. Analysis of the gauge data showed an increase of sedimentation of more than 2 m and no flow through during ebb tide in parts of the eastern channel 2-3 years after completion. Taking all insecurities into account it can be assumed, based on the modeling study that a partial aggregation will occur after 2-3 years within the channel after its rebuilding. Effects of single events like storm surges or high discharges have not been considered.

Concerning the morphological stability of the eastern part of the “Hahnöfer Nebenelbe” under today´s conditions it can be concluded that there is no indication of a change of the system that could lead to a sustainable state without maintenance. The competent authorities have to consider whether to dredge every 3 years or to leave the area untouched and accept a habitat change from shallow water area to a mudflat.

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Reports / Measures / Tools

Report: Management measures analysis and comparison