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Isar-Plan – Water management plan and restoration of the Isar River, Munich (Germany)

Isar-Plan – Water management plan and restoration of the Isar River, Munich (Germany) (2015)

This case study describes the flood risk management plan and the related restoration of a formerly canalized eight kilometer stretch of the Isar river in the city of Munich (the so called “Isar Plan”). Still in the beginning of the 19th century, the Isar river was a typical wild alpine river with wide gravel islands and sandbanks and a constantly changing river bed. In the middle of the 19th century after repeated flooding suffered by the Lehel, Au and Thal districts in Munich, hydraulic regulation began and the riverbed was canalized. Main aims of the Isar Plan were to improve flood control, biodiversity and recreational quality.

Case Study Description

Challenges

One challenge related to climate change for the city of Munich is the expected change of rain patterns. Especially an increase in local heavy rain events is expected. Heavy rain events in the Alps in the years of 1999, 2005 and 2013 led to major floods and substantial financial damage in the South of Germany.

Objectives

Main aims of the Isar-Plan are:

  • Improvement of flood control by increasing the water retention capacity of the river stretch in Munich;
  • Improvement of the habitats for wild species, considering issues related to: ecological upgrading of the river Isar, morphological processes, longitudinal and lateral continuity, natural habits for animals and plants, biodiversity and water quality.
  • Improvement of recreational quality due to the growing need for recreational space within a dense urban area, i.e. access to waterline, attractive landscape and views.
Solutions

More space and new banks for the river

The formerly fixed, canal-like river bed has been transformed to a river bed of varying width with gravel banks and gravel stone islands which develop dynamically in a system of coming and going. Through the widening of the main channel from 50 m up to 90 m, incorporating the forelands along the river and the floodplains, average discharge and flood runoff has been improved and has given more space to the river. The steep embankments secured with concrete slabs and paving have been replaced with flat sloping banks and naturally developing banks. Technically designed cross-river sills with linear cross-section that are spaced at 200 meters with drops of maximum one meter cannot be passed by fish in most cases. These have been replaced by flat ramps with stone rock steps in a honeycomb design with intermediate pools. These measures not only restore a near-natural appearance of the River Isar, but also improve the living conditions and types of habitat for flora and fauna characteristic of the River Isar.

Flood control: more essential today than ever before

After restoration, flood runoff has been improved. Now, flood water can run off without causing damage at a rate of 1,100 cubic meters per second. In order to better protect lower-lying city districts from extraordinary high flood waters and the associated damage, an additional safety distance of one meter between the flood water level and the crest of the dyke had to be ensured.
In areas with reduced dyke safety, new dykes were filled in front of the old ones in order to maintain the air-side tree population. The water-side sealed embankment with its thin layer of top soil is an ideal site for species of dry grassland. By sowing indigenous wild herbs , spreading cut hay and transplanting sods with endangered plant species on the new dyke embankments and in the foreland, the scars left by the construction work in the first development sections quickly healed.

Relevance

Case mainly developed and implemented because of other policy objectives, but with significant consideration of CCA aspects

Additional Details

Stakeholder Participation

In 1995, an interdisciplinary working group “Isar-Plan” was initiated. Members were the State Office of Water Management Munich, the City of Munich (Department of Public Construction, Department of Urban Planning and Building Regulation and Department of Health and Environment) and the “Isar-Allianz” (an alliance of NGOs) The working group examined the flood-water situation, the need for recreational areas at the riverside and the area’s animal and plant worlds and their habitat. Based on their findings, the development goals were defined. The City Council and the District Councils were involved during the progress of the project. Public participation was ensured through: internet platform, info-brochures, excursions, workshops, TV and press, round tables, info-points, service telephone.

Success and Limiting Factors

The level of cooperation achieved between all stakeholders involved within the Isar-Plan was excellent and one key success factor for the project.

Costs and Benefits

Approximately 35 million euros were spent in total for the project: 28 million euros in construction costs, 7 million euros for the remediation of contaminated sites and the removal and disposal of weapons from the Second World War. The costs are being split between the Bavarian State Government (55%) and the City of Munich (45%). Main Benefits of the project include:

  • Flood protection. The big flood of 2005 had a major impact in the whole catchment area of the Isar river. The restoration measures had a significant effect on the extent of the damages caused by the flood. Compared to other parts in the South of Germany, the flooding did not cause substantial damages in Munich due to the restoration of the Isar river.
  • Water quality. Also the Isar-Plan contributed to the improvement of water quality in the Isar River in order to achieve bathing water quality. The degree of effort that went in achieving bathing-water quality for the Isar was unmatched in Europe. All communities situated on the Isar have completed the process of upgrading their waste-water treatment plants to include UV germicidal irradiation systems. These measures have considerably improved the quality of water. Today, swimming is possible within the Isar River.
  • Water and land habitats. The widening of the riverbed not only led to an improved flow of flood water, but also created room for development and design measures on the banks. The Isar River now has more room to move and reshape itself along this entire stretch.
  • Recreational quality. The recreational quality has greatly improved, the restored Isar is, especially in summer, one of the favorite places of Munich citizens.
Legal Aspects

Various City Council resolutions (starting in 1980 with the first ideas, so far more than 30 resolutions).

Implementation Time

The project was launched in 1995 by the State Office of Water Management Munich and the City of Munich. Restoration work began in February 2000 and was finished In 2011.

Life Time

There is not a defined lifetime for this measure. Banks, riversides and islands are designed to trigger a development process: they assign the most important task to the Isar River itself, allowing it to evolve into a river within set limitations.

Reference Information

Contact

Daniela Schaufuß
Department of Public Construction, City of Munich
Tel.: +49 89 233 61400
E-mail: daniela.schaufuss@muenchen.de

Source
ISAR-Plan, involving: State Office of Water Management Munich, City of Munich - Department of Public Building, City of Munich - Department of Health and Environment

Keywords

Isar river, Munich, blue-green infrastructure, flood protection, river restoration

Sectors

Urban, Water management

Climate impacts

Flooding

Governance level

Local (e.g. city or municipal level)

Geographic characterization

Europe

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