It happens in the provinces

Wangen has always been a picturesque town. 27,000 inhabitants live and work there, surrounded by the wonderfully green hills of the Allgäu. The Argen, a 1st order river, and thus under the jurisdiction of the state, flows along the edge of the old town. Originally the lifeline and the founding spark for Wangen, it has been dammed, built-up, straightened over the course of many decades and thus relieved of any dynamism and liveliness.

More than 10 years ago, the city set out to change this negation process. The Argen was to become an accessible and lively part of the city again. A first preliminary study showed the potentials and it became clear that the renaturalisation and reintegration of the Argen should not only become the central focus of the garden show, but also has the potential to bring about a long-term improvement in the quality of life for the entire city.

A lifeline with many functions

The preliminary study had examined the river over a length of almost six kilometer. About half of it led along the city centre and the State Garden Show grounds, the rest was in the western and eastern outskirts. The most important water ecological functions were examined and an overall concept was developed, which, with an eye to the future, was to integrate and improve many aspects:

Flooding

A look at the flood map showed that the critical areas in the city can be significantly relieved by more retention volume in the upper reaches, i.e. in front of the old town in the “Hinteres Ebnet/Südring” area. But even in the further course of the Argen, the narrowed river needed space and volume. The increase in retention volume in this area was combined with allowing more flow dynamics. For this purpose, land was acquired from the city and “sleeping bank protection” was installed at the maximum spread area of the river. More flood protection leads to more biodiversity – synergies sought and found!

Biodiversity

The essential aspect of the success of high-quality biodiversity in river projects is the allowance of dynamics. An aspect that is usually contrary to our use of the landscape. Nevertheless, this was precisely the goal: a sustainably lively, active floodplain landscape with a large number of continuously changing habitats and thus high ecological productivity and great biodiversity. How can this be achieved:

Terrestrial biodiversity

It was interesting that the map of the protected biotopes traced the course of the river. This clearly showed how important the river is for the networking of flora and fauna. The expansion of the protected and dynamic shore areas created an important improvement here. To support this expanded habitat, further riparian edge areas have been developed as habitats. Among other things, the black poplar that was once native to this area was reintroduced. To ensure that only genetically regional plants are used, young plants from natural propagation from the mouth of the Argen were obtained two years before construction and planted throughout the new section of the river.

Aquatic Biodiversity

The basic precondition was the liberation of the Argen from their technically developed corset. Dynamism, dynamism, dynamism was the mantra to revitalise the floodplain landscape and enable a whole new type of biodiversity. For example, the flooding frequency for larger floodplain areas was increased by foreland subsidence and profile widening. This initiates dynamic erosion processes, supported by a variety of structures such as pile and stone buh, but also horseshoes (horseshoe-shaped rock formations in the riverbed), shallow water zones, oxbow lakes or engineering biological bank protection. Habitats are constantly being created or changed again on a small scale and temporarily. In the river itself, the focus was on fish and macrozoobenthos. The lake trout acted as the leading species here, as it migrates from Lake Constance to the spawning grounds in the Argen and its tributaries to reproduce.

The human being

Accessibility to the river was achieved through a variety of measures. In particular, the ‘Garden Show’ vehicle firstly generated additional financial resources, secondly additional areas could be secured and developed and thirdly there was a completion date. This created new uses, paths, insights and nature experiences along the Argen. But also in the outer, now very natural areas, shallow banks and gravel banks help to make the river experience possible.

Overall, a new lifeline for many generations was created in a dynamic community for people, flora and fauna.

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