Revision as of 07:56, 11 June 2010

Klebach - Side channel

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Key features of the case study

Site description

The Drava river (also known as Drau river in German) is a 6^th order stream. At the project site, in the Upper Drava Valley, it forms the boundary between the Crystalline of the Central- and the Limestone Alps. The site of the project is located near the village of Klebach in Austria. From this point onward the Drava has a discharge basin of roughly 2500 km². The average flow of the river near the site is 76m³/s. The river at the site was historically braided with gravel banks in the channel. The Drava river has been largely regulated from the 1930 onward in the area. Banks were fixated and meanders straightened out. Lateral connection with the floodplains and side arms was removed and these areas found new use as agricultural or forestry lands. In-channel gravel banks were removed artificially or through the changes in hydrology caused by the other alterations to the river. Downstream of the side a number of hydro-power plants were constructed, these significantly disrupted longitudinal connectivity of the river. At the same time these plants do produce 'green' energy for large parts of the surrounding areas.

Measures selection

The Waterauthority of the province of Carinthia in Austria, in an effort to restore some of the natural regime and ecology of the Drava, dug a side channel near the village of Klebach. This side channel was situated on the right hand side of the river. On the left hand side groins were erected in hopes of keeping the entrance to the side channel open. Also, these groins were meant to initiate morphological variability in the river. The side channel itself was more then 300m in length and was originally build in two parts. This means that water was also able to enter/exit the channel about half way along it, creating what is best described as an artificial attempt at a braided river.

Success criteria

The aims of the project were to:

• stop degradation
• initiate a changing river morphology
• diversify the spatial variability of flow velocity and sediment grain sizes
• restore an ecologically sound environment (in the form of habitat structures)

Ecological response

Hydromorphological response

Monitoring before and after implementation of the project

Socio-economic aspects

Contact person within the organization

Wasserwirtschaft Kärnten e-mail, Tel.: 050 536-31802 _(Austria)

Extra background information

References

Related Measures

• Increase flood frequency and duration in riparian zones or floodplains
• Shorten the length of impounded reaches
• Remove bank fixation
• Recreate gravel bar and riffles
• Remove or modify in-channel hydraulic structures
• Remove bank fixation
• Reconnect backwaters and wetlands
• Construct semi-natural/articificial wetlands or aquatic habitats

Related Pressures

• Hydrological regime modification
• Hydropeaking
• Artificial barriers downstream from the site
• Impoundment
• Channelisation / cross section alteration
• Alteration of riparian vegetation
• Alteration of instream habitat
• Embankments, levees or dikes
• Sand and gravel extraction
• Loss of vertical connectivity