Balancing trade-offs between different priorities

Published: 21 September 2017
Last edited: 21 June 2019

The interdisciplinary working group “Isar-Plan” was initiated in 1995, with membership from the Munich City and the State Office of Water Management Munich and the “Isar-Allianz”. The group examined the flooding situation, the need for recreational areas at the riverside and the area’s biodiversity. The study included a comprehensive atlas of fauna and flora, existing public uses and spatial qualities, which later were merged into a conflict and value analysis of all aspects in relation to one another.  Based on these findings, development goals were defined. Flood defense measures were chosen that mostly maintained the existing undergrowth on the dykes to conserve ecosystems and have areas for recreation. A sufficient runoff capacity was generated by broadening the main channel bed which simultaneously enables near-natural and flat river bank stabilization.

Classifications

Category
Collection of baseline and monitoring data and knowledge
Management planning
Technical interventions and infrastructure
Scale of implementation
Local
Phase of solution
Planning phase
Implementation

Enabling factors

Hydrological modelling helps to determine what is needed and what is possible for restoring the river and a suitable flow. Furthermore, while most of the river in that area had been canalized, a part near the city had maintained its character so it could serve as a model function of the river. Finally, good cooperation between stakeholders for balancing priorities between flood protection, nature and recreation was essential.

Lessons learned

The design of rough ramps enhances natural development of the river regime. With their pools, stone rock steps and the downstream gravel banks and gravel stone islands have an important ecological function and contribute towards the overall morphological development of the river bed. They also provide an attractive site for recreation. Dynamically developing banks are a special feature of the natural river, changing and retreating during high water levels and flood runoff. However, to prevent future erosion, rear-defense protection measures were implemented for safety reasons. In the inner city, the Isar Plan had to deal with several restrictions for the river development due to the existing infrastructure, and deal with the controversial public discussions over two competing restoration designs (see above). A clever compromise between the two designs was reached with reinforcements built below ground and covered with vegetation to provide a naturalized appearance.

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