Isar River Basin, Germany

The Isar river is one of the main affluents of the Danube, sources in the Alps, and crosses the Bavarian capital Munich. Heavy rain events in the Alps in the years of 1999, 2005 and 2013 led to major floods.

For example, in June 2013 flood damage costs amounted to € 1.3 billion in Bavaria, Germany (BSUV, 2014). To limit the flood risk to housing areas, hydraulic regulation began and the riverbed was canalized. However, grey infrastructure caused accelerated river incision, which resulted in major risks for biodiversity and cultural buildings such as bridges.

Therefore, during the last two decades, the state of Bavaria in cooperation with city governments and other relevant stakeholders implemented a wide range of local NBSs, e.g. restoration measures. These succeeded to decrease flood risks and the river incision rate, ameliorate recreational quality and improve the ecological status of the river course and its floodplains according to the Water Framework Directive (Directive 2000/60/EC) as well as Natura 2000 (Ballon et al., 2005), achieving the first German award for river development (‘Gewässerentwicklungspreis’) in 2007.

The post-analysis of this concept case will provide a good practice framework of a successfully implemented flood risk management plan and related river restoration, enabling to identify the key factors relevant to the PHUSICOS case study sites. Efforts to reduce hydro-meteorological risks by NBSs continue, as for example there is an increasing awareness for the necessity of measures on a broader landscape scale such as improved forest management practices in the upstream mountain catchment areas.

The Isar river during (left) and after (right) the hydro-morphological restoration. Today’s near-natural landscape raises awareness on the usefulness of NBSs both for DRR and recreational purposes (Pictures: Zingraff-Hamed 2011 and 2015)