Belalp: Avalanche radar monitors ridge avalanche
On 22 February 1999 at 5 PM a gigantic powder avalanche descended near Blatten, Switzerland. The width of the so-called “ridge avalanche” was 3.5 km with a slab thickness of 3 to 8 m (P. Schwitter & L. Stoffel, ISSW 2009 in German). The avalanche destroyed or damaged over 30 buildings and covered the main road more than 10 meters high. No people were injured thanks to timely evacuations. Twenty years have passed and much has been achieved in avalanche protection since.
Various measures have been taken at Belalp to manage the ridge avalanche. The construction of avalanche barriers in the starting zone to prevent large-scale avalanches did not bring the desired success. As a result, local avalanche control focused primarily on artificial triggering of avalanches. Blasting from a helicopter worked well, but was limited to good weather days. This is why at Belalp fixed Gasex systems have been in use for several years now. These systems allow to trigger avalanches regardless of weather conditions. Just on time for this winter season, another important instrument was added to assist the local security service: the avalanche and people radar system for permanent monitoring of the ridge avalanche.
Always ready
The avalanche radar permanently monitors the entire starting zone of the ridge avalanche at a distance of up to 3.5 km. It automatically detects avalanches in real time in all visibility conditions, be it in the dark, in snow or fog. Verification of triggered avalanches is now possible at any time and safety operations can be carried out regardless of the weather or time of day. The local security service can thus work at off-peak times (e.g. early in the morning), when any short, preventive road closures hardly affect morning traffic. The permanently running avalanche radar also detects spontaneous avalanches and provides valuable information on avalanche activity in the area.
Prior to a scheduled safety operation, it must be ensured that no people ( e.g. ski tourers) are present in the danger area. For this purpose, we additionally equipped the avalanche monitoring system with a people radar. This type of radar is able to automatically detect people moving in the monitored area and record their movements on a map. This enables the local security service to always keep track of people within the potentially dangerous area and to plan their operations accordingly.
Avalanche radar in the media
The avalanche radar Belalper already made several TV appearances: The documentary “Avalanches – fate or guilt? – A Long-Term Observation” on Swiss television reviews the 1999 avalanche winter and illustrates how avalanche protection has developed since (in German). The avalanche radar (from minute 47) is described as the latest cry in avalanche protection. In addition, Kanal 9/Canal 9 reported in more detail about the new system at Belalp (in German with English subtitles below, in French here from minute 14 onwards).