ISOBEL - Integrated SOlutions for BEd Load Management


Integrated SOlutions for BEd Load Management - ISOBEL

Start date: 01.07.2016
End date: 31.12.2019
Funded by: EU LIFE Programm
Local project leader: PD Dr. Karl-Friedrich Wetzel Prof. Dr. Arne Friedmann
External scientists / cooperations: Bayerische Elektrizitätswerke GmbH
Fischereiverband Schwaben e. V.


For over 60 years, the Iller between Altusried and Lautrach (Allgäu) has been used by Bayerische Elektrizitätswerken GmbH (BEW) to produce electrical energy through run-of-river power plants. This has led to a strong biological and water-structural impoverishment. According to the guidelines of the European Water Framework Directive (2000/60/EC) the water section has to be upgraded ecologically. The aim is to achieve the so-called good ecological potential in the heavily modified water body (HMWB).

For this purpose, the Illerstrategie 2020 was agreed by the Free State of Bavaria and the BEW. In the areas of fish protection and sediment management, the Institute of Geography of the University of Augsburg is involved in the planning of measures and leads a comprehensive impact monitoring of reactions by. The project is supported by the EU LIFE program (Integrated SOlutions for BEd Load Management – ISOBEL.


The investigation area with the five dams is located north of Kempten. The barrages Fluhmühle (no. 5) to Lautrach (no. 8) were built in the late 1930s and 1961 (Altusried No. 4) within the Iller canyons, which is caused by the deepening of the Iller into the end moraines and the upper freshwater molasses (Scholz 2015). Because of the barrages this water section is to be described as a HMWB. The Iller between barrages can be divided into a flow path (direct underwater), a transport path and a storage area. The measures of the Illerstrategie 2020 are aimed primarily at the sections where no measures have been taken to improve the situation yet.

Central research questions:

  • How can the good ecological potential in the investigation area be defined?
  • Which hydromorphological measures lead to a good ecological potential according to EC-WFD?
  • How can the function of the plant be established as habitat and spawn?
  • How can a sustainable use of sediment and bed load look like?
  • Ensure the fishways migration of diadromous or potamodromen fish species?
  • What is the importance of fish passes for water ecology?
  • Is it possible to re-initiate floodplain processes and how does the vegetation develop?
  • How can the taken actions interdisciplinary evaluated and interpreted?
  • Are the measures applicable to comparable waters?

Objective: To improve the ecological potential of flora and fauna

River morphology

The further transport of bed load has come to a standstill as a result of the construction of the dams. Without a regular introduction of bed load, this resulted in an indentation up to the upper freshwater molasses and today's stable soil conditions. Originally, the sole of the Iller consisted of a change of rock and gravel. This loose gravel sole as spawning habitat for fish and fish food organisms (benthic invertebrates) in interstitial is no longer available due to lack of gravel replenishment. By anthropogenic addition this deficiency of the lack of continuity is now to be remedied and a long-term use ensured by means of various water-building measures. How effective these measures are and how they are to be evaluated in terms of resource use and environmental effectiveness will be examined until 2020.

Natural gravel input through the inflow of Rohrach (Tsigaridas 2016)

In the absence of bed Load entry there was an indentation to the upper freshwater molasses (Drones image, König 2016)

Shore and floodplain vegetation

The shore and floodplain vegetation is in the heavily modified hybrid waters of Iller severely degraded and has been displaced by silting societies (V. A. reed bed) in the field of storage spaces. This actual state was mapped according to the plant-sociological method of Braun-Blanquet. With the help of bed load supply and bank expansions suitable locations for a bank and typical bottomland vegetation are created in the underwater barrages. The development of these areas is to be documented on the basis of permanent observation areas.

Typical landfill companies in storage rooms (Stojakowits 2016)

Development of vegetation on newly created sites (Stojakowits 2016)

Bypass channel

The consistency for the aquatic fauna is no longer possible due to the construction of the dams. For this reason, fish migration aids were installed, which are intended to enable the pilot fish species the migration upstream. Innovative fish counting tanks with raised floors are used to test their functionality. By counts can thus check whether a full migration can take place via one or more barrages. Three fish migration aids have been upgraded in terms of river diversity, spawning habitats and water structure. These can be regarded as an independent living space. The use of regular surveys (fish markings, electro-fishing, ...) should be used to assess the effectiveness of the surrounding waters as a habitat.

Innovative fish counter tank with lifting device (Tsigaridas 2016

Bypass channel power plant Maria Steinbach (Tsigaridas 2015)

Fish marking using a pain-free vaccination gun (Tsigaridas 2016)