During the great floods on the Oder (1997) and Elbe (2002), as the emergency services struggled to seal the dykes against the huge volumes of water, concerns were expressed over the long term efficiency of these dykes. As well as the obvious problem of overtopping the dykes could also become saturated allowing water to simply flow through them.

Many of these dykes have long histories with inhabitants having used local building materials (sand, earth and building rubble) in their construction. Even the design of new dykes must consider prevention of water permeation through the structure. Nowadays we can use modern geosynthetic materials for flood protection, such as those supplied by HUESKER

The Rotbach near Dinslaken was identified as a possible flooding problem. "There are active coal workings in this region. Were an abandoned gallery to collapse somewhere, the whole area would subside and the beck could spread out to fill the depression," explains site manager Markus Böhmer, from the river catchment water authority client, the Lippeverband.

In order to prevent flooding of the surrounding area, it is necessary that the Rotbach be kept within its existing channel. The difficulties being faced were similar, but not as extreme, as those faced on the banks of the Oder, however as the dyke was constructed from colliery waste, it required additional protection against long-term water penetration. Therefore a geosynthetic clay liner (NaBento RL-N) from HUESKER was used in the works commissioned by the Lippeverband. According to site manager Markus Böhmer: "The liner seals off the colliery waste tailings so that they can no longer become saturated."

Approximately 15,000 square metres of geosynthetic clay liner were installed along a length of almost 4 kilometres of the Rotbach, which flows around the outskirts of the town of Dinslaken and is mostly surrounded by fields and paddocks. At this site the foundation soils in the area of the embankment had to remain smooth and level, it was therefore not possible to drive or walk on the areas, prepared by local contractor, Heijmans Bau GmbH, however the liner manufactured by HUESKER made it possible to also overcome this problem."You should think of it as a carpet, which needs to be laid on a perfectly flat floor," explains Markus Böhmer. Therefore, sealing the joints in the liner with adhesive or bentonite powder or paste, after placing, would not be possible. The NaBento RL-N used here has 500 mm of bentonite pre-applied along the edges.

Markus Böhmer is confident that the works, taking place during 2003, can be completed on time. "We may even be able to finish the job slightly earlier," says the site manager. It is now established that a geosynthetic clay liner, in this case NaBento, can play its part in the protection against flooding catastrophes, whether in North Rhine-Westphalia or on the banks of the Oder and the Elbe.

Flooding protection along the Rotbach in Dinslaken, the geosynthetic clay liner (NaBento RL-N) manufactured for the project by HUESKER, ensures that the srrounding area will not be flooded. 15,000 square metres of liner seal off the colliery waste tailings and prevent them becoming saturated by water, even during floods.

A typical cross section of the construction of the dyke works on the Rotbach. The geosynthetic clay liner (NaBento RL-N), shown in yellow, protects the buried colliery waste tailings.