History of flood protection on the Arzbach - start of construction in spring

Created: 08/12/2022 18:52

By: Daniel Wegscheider

Construction site of a dewatering in the Arzbach: This is necessary in order to be able to work in the dry.

© Water Management Agency

Lenggries/Wackersberg – work on flood protection on the Arzbach is in full swing and was awarded by the Weilheim Water Management Office in autumn.

The contract work for flood protection on the Arzbach in the communities of Lenggries and Wackersberg was awarded by the Weilheim Water Management Office in September 2022 and should be completed in the coming year - so that the municipal districts of Schlegldorf and Arzbach are protected from a centennial event.

Flood protection for the Arzbach torrent has a long history: "Since the end of the 19th century, people in the village of the same name have been making local corrections to the course of the creek to protect the buildings," reports Christian Heilbock from the Weilheim Water Management Office.

From 1958 systematic expansion measures were carried out.

With the aim of stabilizing the bottom of the river and ensuring that the solids that are dissolved in the upper reaches are discharged without causing damage to the point at which they flow into the Isar.

Severe flooding as a result of accumulated driftwood

A severe storm in 1990 brought more than 100 millimeters of precipitation per hour on the mountain ridge of the Benediktenwand-Brauneck area and the foothills of the Probstenwand of the Längenberg.

"The driftwood that was transported with it moved the bridge culverts in such a way that parts of the villages of Schlegeldorf and Arzbach and important infrastructure facilities on the alluvial fan were flooded and damaged," Heilbock recalls.

Immediately after clearing up the flood, the Weilheim Water Management Office (WWA WM) concentrated on rehabilitating and expanding the torrent and its catchment area in order to control mudslides, debris and driftwood.

Erection of a debris catchment and sediment dosing barrier in the upper reaches should remedy the situation

In the years that followed, the WWA WM built a debris catchment and sediment dosing dam in the upper reaches to absorb the loosening solids.

"In the middle reaches, a combined wild wood and bed load retention structure was built in the form of a rake," explains Heilbock.

Between the debris trap and the rake, there are transverse and longitudinal structures in places that have been renovated.

Based on the experience of another flood event in 2005, the approximately 1.2-kilometer stretch of water between the wildwood rake and the existing flume had to be secured with two so-called crash structures and three bed ramps.

With these measures, it was possible to keep the debris and deadwood away from the built-up area to a large extent.

Flood protection walls protect adjacent buildings

According to the WWA WM, the "hydraulic deficits" along the flume during a hundred-year flood event are to be eliminated by the work that is still outstanding.

To protect the adjacent buildings, flood protection walls are being built in the area of ​​the tennis courts and below the swimming pool on the bank.

The preparatory work will take place this year.

Depending on the weather, the actual construction work is expected to start in March 2023 and be completed by the end of 2023.

also read

Herzogstand: Missing hiker found dead – it was probably a mountain accident

Municipal council of Kochel approves 50-meter mast near Pessenbach

Irrespective of the flood protection measures on the Arzbach, the Arzbach’s flume below State Road 2072, which was created in the 1960s, has been being renovated since this summer.

Heilbock comments: "This work is necessary in order to repair the age-related damage to the structure." This will ensure the long-term functionality of the channel.