ENNS-STYRIA
Description of the project area
The project area comprises the Styrian Enns on a length of 128 km. It extends from the Styrian-Salzburg border to the entrance of the gorge “Gesäuse” and drains a catchment area of 4 200 km².
The largest tributaries in the project area are the rivers Sölkbach, Salza, Grimmingbach, Donnersbach, Döllachbach and Phyrnbach.
At the entrance of the gorge “Gesäuse”, in the municipality of Admont, the peak of a 100-year flood event (HQ100) is indicated with 730 m³/s. The medium flow (MQ), on the other hand, is only 80 m³/s.
The shape of the Enns Valley in its present form was created by the eroding power of the glaciers of the Ice Age. In the flat valley floor, the Enns formed a meandering river course that oscillated from one side of the valley to the other. In the course of the river regulation measures of the 19th and 20th centuries, most of the meanders were cut off. Numerous water-filled oxbow lakes occurred and were abandoned to sedimentation.
A total of 40 cut-offs shortened the course of the river by 19 km. This corresponds to about 13 percent of the former river length of 147 km! At the same time, the active floodplain lost around 55 percent of its area and shrank from 600 to 270 hectares. Around 1,500 hectares of wet meadows were drained. All these measures primarily aimed for land reclamation to increase agricultural production.
To protect the villages from flood disasters, the northern tributaries of the Enns, which transport large amounts of bedload, were regulated in order to retain the bedload. Together with the shortening of the river course of the Enns, this led to a deepening of the riverbed. As a result, the water level in the river’s floodplain dropped by up to three metres. A progressive decoupling of the river from the surrounding floodplain is the result, wetland habitats are becoming increasingly dry and many valuable habitats are being lost.
ENNS-STYRIA
Description of the project area
The project area comprises the Styrian Enns on a length of 128 km. It extends from the Styrian-Salzburg border to the entrance of the gorge “Gesäuse” and drains a catchment area of 4 200 km².
The largest tributaries in the project area are the rivers Sölkbach, Salza, Grimmingbach, Donnersbach, Döllachbach and Phyrnbach.
At the entrance of the gorge “Gesäuse”, in the municipality of Admont, the peak of a 100-year flood event (HQ100) is indicated with 730 m³/s. The medium flow (MQ), on the other hand, is only 80 m³/s.
The shape of the Enns Valley in its present form was created by the eroding power of the glaciers of the Ice Age. In the flat valley floor, the Enns formed a meandering river course that oscillated from one side of the valley to the other. In the course of the river regulation measures of the 19th and 20th centuries, most of the meanders were cut off. Numerous water-filled oxbow lakes occurred and were abandoned to sedimentation.
A total of 40 cut-offs shortened the course of the river by 19 km. This corresponds to about 13 percent of the former river length of 147 km! At the same time, the active floodplain lost around 55 percent of its area and shrank from 600 to 270 hectares. Around 1,500 hectares of wet meadows were drained. All these measures primarily aimed for land reclamation to increase agricultural production.
To protect the villages from flood disasters, the northern tributaries of the Enns, which transport large amounts of bedload, were regulated in order to retain the bedload. Together with the shortening of the river course of the Enns, this led to a deepening of the riverbed. As a result, the water level in the river’s floodplain dropped by up to three metres. A progressive decoupling of the river from the surrounding floodplain is the result, wetland habitats are becoming increasingly dry and many valuable habitats are being lost.
Hot Spots & Highlights
The river basin of the Styrian Enns is home to numerous habitats for endangered and rare animal and plant species. These include alluvial forests, the remains of the Enns side arms, litter meadows formed in the old river beds, endangered species such as otter, kingfisher and sandpiper, which depend on river-typical structures, as well as fish species such as the European Bullhead, the Ukrainian river lamprey and the grayling. Large parts of the Enns Valley are designated as NATURA 2000 European protected areas.
The 4 187 ha NATURA-2000 protected areas “Ennstal between Liezen and Niederstuttern”, “Gersdorfer Altarm” as well as “Pürgschachen-Moos and close areas between Selzthal and the Gesäuseeingang” in the district of Liezen formed the spatial framework of the LIFE+ project “River Landscape Development Enns”.
The Enns valley with its widely ramified side valleys and almost untouched landscape is intensively used for tourism throughout the year.
Need for action
The pressure of use on the landscape in the Ennstal is particularly high. Not only residential and industrial areas require more space, also infrastructure projects generate demands.
The importance of preserving the existing flood plains was demonstrated by the flood event of 2002. In the Schladming area, the flood runoff corresponded to a 100-year event, and the existing retention areas reduced the flood peak downstream in the Liezen area to a 30-year event.
Flood risk management and river ecology face the challenge of developing flood protection concepts for existing settlement and industrial areas. These concepts should not only focus on technical flood protection, but should also take into account the ecological potential of the river basin and the ecological status. In the catchment area of the Styrian Enns there are river sections that do not yet reach the good ecological status required by the EU Water Framework Directive.
In addition, cross-border coordination with the measures on the Salzburger Enns in Salzburg is necessary.
Goals
The project LIFE IRIS offers an ideal framework to further secure and improve the natural habitat of the Ennstal. For this purpose, a “River Development and Risk Management Concept” (GE-RM) will be developed, which on the one hand comprises flood protection concepts for the existing settlement and industrial areas as well as infrastructure facilities, and on the other hand also takes into account the ecological status of the river as well as the Natura 2000 areas and their protected resources. Public participation is intended to achieve broad acceptance of the GE-RM-results and the initial pilot measures derived from it.
Outlook and time plan
By the end of 2021, the “Enns River Development and Risk Management Concept” will be finalised, and will also include a hazard zone plan. The involvement of stakeholders and the population is planned in order to achieve the best possible acceptance of the proposed measures. Once the GE-RM concept is in place, detailed projects will be developed for selected pilot measures, which will then be implemented by mid-2026.
