Stream restoration

For centuries, flowing waters have been used by humans. In the beginning, mainly for energy generation, irrigation and the transport of goods. Even then, structures were built along the watercourses to direct the water into the desired channels. Over time, flood protection has become increasingly important. As a result, practically all of Germany's watercourses are now straightened and constructed.

This has many negative consequences for biodiversity. Naturally, flowing waters have a mosaic of diverse habitats for a variety of organisms. Shallow and deep, shaded and sunny, slow and fast flowing areas alternate. Due to development and maintenance, almost all habitats in the watercourses have been lost. The floodplains have also suffered greatly from the development of watercourses. Not only in the nowadays built-up areas has there been a sharp decline in species diversity, but also in unused areas. This is because these areas are now rarely flooded. In many places, river dikes prevent water bodies from overflowing. In addition, the straightening of watercourses has increased the flow velocity, which has led to erosion and thus to the deepening of the watercourses. This lowers both the water level in the watercourse and the groundwater level in the floodplain, causing the area to dry out. The diverse and often rare species of the floodplains are therefore replaced by a few "commonplace species". This has led to a sharp decline in biodiversity.

It was not until the second half of the 20th century that the negative consequences of the expansion were recognised and a rethink took place. Especially since the entry into force of the Water Framework Directive, efforts have been made in many places to renaturalise flowing waters. In order to develop water bodies in an ecologically meaningful way, diversity and dynamics must be restored. Therefore, measures should primarily contribute to restoring the natural dynamics so that the watercourse can develop on its own. This is not only much cheaper than constructing structures, but also leads to more natural and diverse habitats that are also preserved in the long term.

Such processes result from temporally and spatially changing flow conditions, which lead to erosion and sedimentation, i.e. the bed of the watercourse is constantly rearranged and changed. To make this possible, structures such as weirs must be dismantled to allow for natural changes in water levels. On the other hand, "disturbance stones" must be allowed in the watercourse, which lead to a local change in flow velocity. Naturally, this task is carried out by deadwood that originates from the vegetation along the watercourse. It is therefore important to introduce this into watercourses in a targeted manner and to enable a long-term supply by planting woody plants.

The problem is that in order to allow dynamic processes to take place, space must always be available in which the water body can develop. Often these areas are not available or must first be acquired. The necessary funds are often lacking, which is why only 8.2 % of surface waters were in good status in 2015.

The MuP Group also makes a significant contribution to making our environment more natural again within the framework of such renaturation measures.