1. Abstract

The "Lausitz" region, located along the Polish border in south-eastern Germany is a landscape that is undergoing dramatic changes. During the next decades the landscape that is currently shaped by open strip mines will change to a landscape dominated by water in big lakes. About 30 larger lakes are in the making, with an estimated water surface of 13000ha (33000 acres), forming as a new habitat for nature and wildlife as well as an attractive site for tourism and recreation.

The shoreline of the new lakes will be rather monotonous, because safety considerations determine soil grading practices. Natural sukzession of vegetation is inhibited in areas where rip-rap shoreline protection with stone are being used. The water itself tends to be acid and so is the barren soil of the mine spoils, inundated by a slowly rising water level.

"Living Islands" that float are helping to create better conditions for the "greening" of shorelines, because they remain intact as the water level rises. In a pilot project, techniques were developed to build artificial islands that are similar to those found in nature. Constructed "Living Islands" were used to investigate their effects on the development of the lake, erosion control of the water edge and functional and aesthetic implications.

Islands in the pilot project were build of three different kinds of construction: the first is a "Repotexsandwich", a textile vegetation carrier, planted with Phragmites and Juncus, the second one is a fascine, build of living willow material, and the third one is a floating gabion, a wire basket filled up with reed. On the lake "Dreiweibern", ancient strip mine Lohsa, the plants and the techniques are being investigated regarding their maximum mechanical capacity. Observation occurred between 23.05.02 until end of July 2002.

While preparing and creating the pilot project, information was gained to optimise the process. How to anchor the Islands turned out to be a problem, because of the depth of the lake and its steep slopes on the ground. Fixing islands with anchors turned out to be most suitable in shallow portions of the lake. Different growth rates were observed on the islands. Examples were:
- there was a direct relationship between the density of reed is placed in gabions and a high grow rate,
- Due to anaerobic circumstances reeds were unable to grow in between the two levels of a textile carrier (Repotexsandwich).

In a future research project knowledge about plants and technique shall be used to test growing conditions in a lake with in acid water.


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