River training structures: a natural approach to river bank protection and flood defence
In 2007, a flood devastated the village of Flamatt (Canton of Fribourg), which is located on the river Taverna in the foothills of the Alps. On that occasion, the flood caused damage costing CHF 3.5 million. Basler & Hofmann was contracted to improve the flood defences along the Taverna. The team recommended an innovative but highly efficient method in which so-called river training structures are used to achieve stabilisation and renaturation.
Working with nature, not against her
In 2011, river training structures consisting of blocks of stone left in their natural condition were installed on a 550-meter stretch of the Taverna in the populated area. These inconspicuous installations cause spiral flows which consistently divert the water's flow force away from the banks, even in case of flooding, so as to protect the banks against erosion. This approach largely eliminates the need for costly solid embankment structures, thereby yielding distinct economic and ecological benefits. The chosen solution also increases flow diversity, variability of water depth and substrate sorting, leading to the creation of a structure-rich waterway bed with valuable habitats. As the training structures support the river's naturally induced movement, they achieve a major effect in return for intervention on a minor scale.
An innovation that offers great potential for Switzerland
Because training structures achieve major results in return for low expenditure on materials, they have the potential to become firmly established as a method for riverbank protection and renaturation. The stretch of the river Taverna where they have been installed will serve as an example to supply important empirical values when the next major flood occurs, thus providing a reference for further applications in Switzerland.
Commune of Wünnewil-Flamatt and Public Works Department of the Canton of Fribourg