In 1995 it will be 25 years since the estuary of the Rhine and Maas was closed off from the sea by a dam with outlet sluices. After 1970 it gradually became clear that the change of an open estuary into a semi-stagnant lake had many negative ecological effects: bank erosion, accumulation of polluted sediments and the disappearance of a natural transition zone between the estuary and the sea. As the public attention to nature conservation in The Netherlands grew over the years, this ecological degradation was more and more recognized as a problem.
To achieve a healthier ecosystem a program of remedial action has been launched. Some elements such as the protection of valuable wetlands against erosion have almost completely been realised. Others such as the removal of large quantities of polluted sediment and a change in the operating program of the outlet sluices are being prepared. The main challenge is to find a compromise between ecological values and all kinds of human use of the water system.