Forschungsprojekt ::

LIFE+ - Isobel - Isobel - Integrated SOlutions for BEd Load management

Projektbeschreibung

Background

River segments with hydropower facilities are usually considered as ‘heavily modified water bodies’ under the Water Framework Directive. A natural river continuously carries bed load material downstream, forming gravel and shallow water areas. These structures are important spawning grounds and nursery areas for many species. Barrages disrupt this process by keeping the bed load in the retaining area, which eventually silts up. This is the case for the river Iller (Germany), which is heavily influenced by water power facilities. Between Altusriedz and Lautrach, five power plants with barrages stop the natural bed load transport of the river.

The riverbanks are steep and mounted with large rocks. Many of the barrages already have bypasses to enable fish to pass the barrier. However, key habitats are still missing for several species that lived in this part of the river before the barriers were present. Therefore, despite the existing fish bypass structures, no natural development of the river banks and the alluvial zones is possible. Current bed load management techniques play a key role in the process of establishing these key habitats. However, they are not 100% effective and still disrupt the environment as they imply aggressive excavation and transfer of sediments.


Objectives

The LIFE+ ISOBEL project will demonstrate an innovative and environmentally-friendly approach to revitalise the free flowing parts of the river Iller, and to reach the good ecological status of all water bodies requested by the Water Framework Directive. The project’s integrated bed load management system will be accompanied by guidelines for its implementation in rivers throughout Europe. The main added value of the proposed system will be its reduced environmental impact, being much less disruptive to the river and river banks than current techniques, and also less noise-generating, transport- and energy-demanding.

The project aims to:

• Define the ‘good ecological status’ for the targeted water body;
• Develop and implement target-orientated, minimally invasive, bed load management that generates the desired water structures;
• Establish suitable near-natural habitats for the flora and fauna (e.g. spawning and nursery grounds, protection against drifting at high water levels), by replacing existing rock mountings by flat riverside structures;
• Through varied structure and habitat-creation make the ecosystem more robust and climate resilient;
• Connect river, river banks and alluvial zones;
• Evaluate the water structure development, the effects on biodiversity and socio-economic impacts; and
• Develop guidelines to boost replication and transferability of project results.

Expected results: The project expects to achieve ‘good ecological potential’ at three river Iller segments (one km each) by integrated bed load management with better ecological results and much less translocation of material. In particular it will show the following results:

• Diverse river and riverbank structures will provide key habitats for the target species;
• Reduced overall demand for bed load material compared to conventional measures, namely, some 1 500 tonnes of bed load material for river structures plus about 500 t/year for maintenance of the structures, 1 800 t/year to widen each of four river sections, and up to 1 600 t of large rocks for additional water structures in each section;
• The quality and quantity of habitats in the river, the river banks, the riparian zones and the bypasses will be improved significantly, especially for rheophilic fish species;
• Biodiversity will improve and self-sustaining populations of many endangered species (e.g. Hucho hucho, Cottus gobio, Triturus cristatus) will develop;
• The impact of the activities will be monitored continuously (before, directly after, and one year and two years after), including the ways fish use the bypasses;
• The new, more natural habitats will have a better ability to adapt to climate change, and will improve the landscape for recreational activities;
• Based on the monitoring results, guidelines for effective bed load management will be developed that are transferable to all European rivers; and
• The results of the project will be disseminated to all relevant target groups at regional and EU-level.