Illgraben
| Illgraben | |
|---|---|
 Illgraben, seen from the Illhorn | |
| Floor elevation | 830 m (2,720 ft) |
| Length | 4 km (2.5 mi) |
| Area | 9 km2 (3.5 sq mi) |
| Geography | |
| Country | Switzerland |
| State | Valais |
| Coordinates | 46°16′54″N 7°36′51″E / 46.28159°N 7.61419°E |
| River | Illbach |
The small Illgraben valley is one of the most geologically unstable regions of Switzerland, and is located south of Leuk in the Canton of Valais.
Geology and Geography
The valley consists of triassic dolomite, porous limestone and quartzite,[1] and due to intense weathering, the valley is well-known among geologists as a place to study processes like erosion, rockfall, debris and mud flows. Likewise, the Illgraben serves as a laboratory to test mudflow warning systems. The Swiss Federal Institute for Forest, Snow and Landscape Research uses radars, microphones and cameras to register mudflow events, and to warn the population of Leuk.[2] Due to the unique geology, mudflows occur two to three times a year, while places threatened by mudflows usually experience only one every 30 to 40 years.[1]
Several times a year, the Illgraben's mud flows cause the Rhône river to turn murky until it reaches Lake Geneva, which is 90 kilometers (56 miles) downriver. The Pfynwald (French: bois de Finges or forêt de Finges), a natural reserve and one of the largest continuous Scots pine forests of Europe, is located on the alluvial cone of Illgraben's stream, the Illbach.[3] The Pfynwald itself is an important center for ecological studies.
Tourism
A spectacular, north-easterly view into the Illgraben is possible from the hiking path Chandolin - Plaine Madeleine.[4] From Susten (650 m,part of Leuk), hikers will first encounter the Bhutan bridge, a 134 meter suspension bridge, before seeing the valley's interior. From there, there is an unmarked trail to the aptly called Steinschlaghütte (English: rock fall hut), or to the alpine lake Illsee and the Illhorn.[5]
Image gallery
-
Bhutan bridge at the entrance to the valley -
View of the lower riverbed, with the Onyx SIGINT site visible -
A scene inside the valley's river bed -
Pfynwald forest, with the Illgraben and the Illhorn mountain in the background
Literature and further information
- Fritz, Angela (2017-06-05). "Each year this 'terrifying' mudslide careens down Switzerland's Illhorn mountain". Washington Post. Retrieved 2022-06-07.
- Bennett, G. L.; Molnar, P.; Eisenbeiss, H.; McArdell, B. W. (2012). "Erosional power in the Swiss Alps: characterization of slope failure in the Illgraben". Earth Surface Processes and Landforms. doi:10.1002/esp.3263.
Video documents by the Swiss Federal Institute for Forest, Snow and Landscape Research:
- "Spectacular mudslide research site in Valais, Switzerland". 2022-04-05. Retrieved 2022-06-07. French, with selectable English subtitles.
- "2nd Field trip: Debris Flow monitoring. Illgraben, Valais". 2013-10-31. Retrieved 2022-06-07. Geologists visiting the Illgraben; explanations spoken in English.
- "Murgang im Illgraben, 28. Juni 2000" [Mud slide in Illgraben, 28th June 2000]. 2016-03-21. Retrieved 2022-06-07.
References
- ^ a b WSL video "Spectacular mudslide research site in Valais", April 2022, see Literature section
- ^ Fritz (2017)
- ^ Bellwald, Werner (2010-09-28). "Pfynwald". Historical Dictionary of Switzerland (in German). Retrieved 2022-06-09.
- ^ "Illgraben". Val d'Anniviers (in German). Val d'Anniviers tourism office. Retrieved 2022-06-09.
- ^ According to the Swiss map, accessible at http://map.geo.admin.ch