Restoring river ecology- A complex challenge

摘要

All over Europe, rivers have been regulated during this century in order to drain and free agricultural land and to provide flood protection. In the process, 95% of the natural wetlands along European rivers have been detached from the rivers and unique ecological systems have been destroyed. The river regulations have many places been far from successful, leading to increased risk of embankment breaching and environmental deterioration. The present trend is that an increasing number of these rivers are restored by moving the embankments and turning them back into a meandering course. The development of such 'ecological' rivers is a highly interdisciplinary task, which requires complex tools describing the interaction between hydraulics, sediment transport and morphology, water quality, habitat and ecology and the interaction between surface water and ground water. The paper describes the necessary elements of such study and the implementation of 2 ambitious river restoration projects in Denmark. The restoration of Skjern River is the largest project of its kind in Northern Europe. The restoration project is unique is its size, in the public awareness around it and in the technical difficulties it has to deal with.