Multilevel fl exible debris fl ow barrier installationMilibach, Hasliberg / Switzerland

Photo documentation / September 2008Foto-Dokumentation / Mrz 2007Foto-Dokumentation / Mrz 2007

Multilevel debris fl ow barrier

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Multilevel debris fl ow barrier / Photo documentation / September 2008

Multilevel debris fl ow barrier holds back 2,000 m3 of debris fol-

lowing exceptionally heavy rain

On October 10, 2011, heavy rainfall triggered a shallow landslide containing

a total of 2,000 m3 of Alenienschiefer (schist) in the drainage area of the

Milibach river. 80 mm of rain had fallen in the space of 12 hours on top of a

70 cm layer of snow from the previous day. The Swiss Federal Offi ce for the

Environment (FOEN) rated these heavy rainfalls as a once-in-a-century occur-

rence. As recently as August 22, 2005, a storm in the Weiler Reuti and in

Meiringen caused serious debris coverage and severe damage. A cascade

comprising 13 fl exible debris fl ow barriers and with a retention volume of

up to 10,000 m3 was installed to protect the two settlements. For details,

please turn to page 4.

This multilevel debris fl ow barrier system successfully held back the latest

event of October 10, 2011, stopping an estimated 2,000 m3 of debris before

the shallow landslide had had chance to build up signifi cant erosive force,

as happened in 2005. The event fi lled barrier no. 2 completely and barrier

no. 5 partially. Barrier 1, which was situated above where the shallow lands-

lide was triggered, remained unaffected, while barriers 3 and 4 were not

fi lled up as they have a higher basal opening. Stopping the 2,000 m3 of

debris in good time helped prevent the shallow landslide further eroding

the unstable banks of the Milibach river and forestalled an even greater

shallow landslide that could have caused damage to the settlements further

downstream.

After an in-depth investigation during an on-site inspection, the customer

decided to leave barrier no. 2 fi lled to protect the riverbanks. The debris

held by barrier no. 5 is also to be left and should be carried away over time

as the water drains naturally.

10. October 2011

Satellite image of the storm that moved across the northern Swiss Alps on October 10 (source: SF Meteo website)

Multilevel fl exible debris fl ow barrierMilibach, Hasliberg, Switzerland

33

Barrier no. 2 was fi lled by a landslide triggered nearby.

Barriers no. 2 and 5 held back a total of 2,000 m3 of material.

22. August 2005

44

Multilevel debris fl ow barrier / Photo documentation / September 2008

Multilevel debris fl ow barrier Milibach, Hasliberg, Bernese Oberland / Switzerland

Floods and a debris fl ow event occurred in the Milibach torrent on August

22, 2005 which resulted in serious debris coverage and damage in the Weiler

Reuti / Hasliberg and in Meiringen. The Milibach torrent above Reuti com-

prises of two creek sections, the Lauenenbach being situated in the upper

drainage area in the Alenienschiefer (schist). Due to the large amount of

precipitation, a total of some 13 000 m3 of loose material became detached

through water saturation in ca. 1 hour which then fl owed downhill as a mud-

fl ow in two to three batches (muddy debris fl ow, rich in fi ne material).

After the devastating rainfalls a suitable barrier system for debris fl ow re-

tention had to be evaluated. On the basis of various criteria the coordinators

decided in favor of a series of high-tensile ring net barriers from Geobrugg.

As support for the design fundamentals the Federal Research Institute for

Forest, Snow and Landscape (WSL) in Birmensdorf carried out physical model

trials parallel to the project planning.

Between autumn 2007 and summer 2008, over a 500 m long axis, thirteen

ring nets with heights of up to 7 m were mounted in series down the torrent

section. The exact sites were evaluated in the fi eld. The upstream side of the

fi rst net is designed primarily for energy conversion on the occurrence of

a debris fl ow. In some cases this fi rst net is destroyed and overfl owed. The

remaining nets are activated in stages. Back-fi lled nets are overfl owed by

subsequent events and act like fi lled concrete abutments. In an emergency

this net system with thirteen barriers retains a total of 10 000 m3 derived

from the starting zone.

Position of the thirteen barriers

55

Debris fl ow starting zone

Marking off

Drilling in progress

66

Multilevel debris fl ow barrier / Photo documentation / September 2008

Ring net installation

Ringnet ready for transportation by helicopter

Anchor foundation

77

End of installation in August 2008

It is the task of our engineers and partners to analyze the problem

together with you in detail and then, together with local consul-

tants, to present solutions. Painstaking planning is not the only

thing you can expect from us, however; since we have our own

production plants on three continents, we can offer not only short

delivery paths and times, but also optimal local customer service.

With a view towards a trouble-free execution, we deliver preas-

sembled and clearly identifi ed system components right to the con-

struction site. There we provide support, if desired, including tech-

nical support from installation right on up until acceptance of the

structure.

Rockfall barriers

Rockfall drapes

Slope stabilization systems

Debris fl ow barriers

Avalanche prevention structures

Open pit rockfall barriers

Special applications

Geobrugg AGGeohazard SolutionsAachstrasse 11 CH-8590 RomanshornPhone +41 71 466 81 55 Fax +41 71 466 81 50www.geobrugg.com info@geobrugg.com

Certifi ed to ISO 9001

Geobrugg protects people and infrastructures from the

forces of nature

A company of the BRUGG Group 1.20

3.03

.EN

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