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Water development Gail - An integrated model for Natura 2000 (LIFE+ Gail)
Date du début: 1 janv. 2010, Date de fin: 31 déc. 2014 PROJET  TERMINÉ 

Background Regulated rivers are now widespread in Europe, with artificial banks and flood dykes in place of their former unimpeded meandering and braided courses. This is a well-known example of the conflict between ecology and water management. From an ecological point of view, rivers should get more space to flow naturally and enable cross-links to surrounding areas. These objectives can contrast with water management practices aiming to protect people and infrastructure from flooding. This contrast of objectives is very evident in the river Gail, part of the Natura 2000 network site of Görtschacher Moos-Obermoos. Objectives The LIFE+ Gail project aimed to demonstrate possible ways to reach a balance between ecological improvement and water management guidelines. The project had three specific objectives: (i) to restore regulated parts of the Gail river and increase the space for natural river development, morphological processes, and riverine habitats, while retaining flood protection for villages by maintaining the existing dykes; (ii) to implement qualitative and quantitative improvements to floodplain habitats through cross-links and the creation of a side channel; and (iii) to create areas of floodplain forest and marsh on former arable land, to act as buffer zones separating targeted water habitats and intensively-used arable land. Results The LIFE+ Gail project selected three pilot stretches totalling 2 km of stream length, along the Gail river valley and between existing flood dykes, to demonstrate best solutions for optimal ecological improvements. Most of the riverside area was in intensive agricultural use before the project started. A total of 7.93 ha of land was purchased during the project, with a further 3.37 ha provided by ARGE Naturschutz for project actions. The restoration actions carried out by the LIFE project extended the target Natura 2000 network habitat types by 23 ha (with further extensions expected). To re-naturalise the pilot river stretches, the project created 600 m of steep and shallow banks, removed 50% of the existing berms (fortified river banks) to create shallow banks with groynes over another 600 m, and widened the river to its maximum width over an 800 m length. These changes should enable moving gravels banks to return to the riverbed. Different restoration measures were implemented in the three areas: alternating steep and shallow bank sections in pilot stretch 1; low water structures in stretch 2; and river widening and gravel banks in stretch 3. The project team created a side channel (2.55 km in length) with associated river habitats covering a total of 3.7 ha. In this area, the restoration measures initiated the development of alluvial forest (habitat type 91E0), semi-natural dry grassland (6210), and lowland and molinia meadows (6510/6410). Recurring mowing was organised by the beneficiary to further improve these habitats. Four ponds were created in riverside habitats covering 3.3 ha, with a water depth between 0.3 and 3 m. The project restored three oxbows that had become silted up along the re-naturalised river stretches, covering a total area of 0.62 ha. The project stocked one pond and the three oxbows with 5 000 bitterling (Rhodeus sericeus amarus) and 1 000 Unionacea species, swan mussel (Anodonta cygnea) and painter’s mussel (Unio pictorum), all bred at a fish farm. Through the pond creation activities, habitat type 3150 (Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation) was developed on 3.1 ha. Subsequent habitat and fish monitoring activities showed that bitterling had successfully established, with individuals in all age stages recorded. Besides bitterling, five further fish species had been detected by 2013. New floodplain areas, including areas along the newly-created side arm of the river, were replanted with native species, including around 600 trees such as white willow (Salix alba) and grey alder (Alnus incana). About 8.7 ha of habitat type 3220 (Alpine rivers and their ligneous vegetation with Salix elaeagnos) were newly created by the project. The strictly-protected (in Austria) wolf spider Arctosa cinerea was detected for the first time in this area, in two of the pilot sections. At the end of the project, hydromorphologic measurements showed that the lengths of the pilot stretches (600 and 800 m) are sufficient to initiate morphologic modifications. The widening of the river decreased flow velocity, and also changed the direction of flow velocity (horizontal and secondary flows). The biggest changes were observed in the groyne section (pilot stretch 2). Downstream of the groynes, typical back current and scours occurred, with fine sediment being deposited along the bank sections between the groynes. Monitoring showed a higher density of water depths, flow velocity and bed shear force in the pilot stretches, with alternating gravel bars developing in stretch 3. The project contributed to nature-based flood protection and retained existing flood prevention dams. The more dynamic river structure reduces depositions, hence reducing dyke maintenance costs. The main innovative aspect of the project was to provide alternatives to berms, which help protect the dykes, for example, in the form of shallow banks and groynes. These were tested in the demonstration areas. With the removal of berms, the river gained some 20 to 40 m of additional space to naturally develop new structures and river bank habitats. The project’s results will inform further river engineering work along the river Gail, and serve as an example for other rivers facing similar problems. Socio-economic benefits for the local area were achieved through the construction of an observation hill, hiking trails, and the creation of water adventure areas and three resting points with project information boards. Alongside the creation of a more diverse landscape, the project’s visitor guidance structures and awareness-raising measures contributed to the enhanced attractiveness of the region, for local visitors as well as for tourists, and an increased understanding of the link between flood protection and ecological restoration. Further information on the project can be found in the project's layman report and After-LIFE Conservation Plan (see "Read more" section).

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