ABSTRACT: Rockfall catchment fences and avalanche protection systems: Flexible structures for flexible solutions.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Rockfall and avalanche processes are common place in mountainous regions, impacting structures of all kinds, but most notably linear infrastructure such as roads, railways and utility corridors. Authorities responsible for these infrastructure spend large amounts of resources and money every year to mitigate their effects. In this respect, it is only relatively recently that new technology in the form of high-strength fences, stemming from Europe, is being applied in Canada to mitigate small to medium sized rockfall and debris flow events, as well as for preventing snow avalanches. Rockfall catchment fences are steel beam structures that utilize a flexible net and steel cables to capture falling debris/rocks in the runout or deposition zones, thereby stopping damage to an element at risk. Energy from the event is absorbed and transferred from the structure to the ground through rock or soil anchors. Currently, events with energies up to more than 5000 kJ can be mitigated (e.g. 13 000 kg traveling at approximately 100 km/h). These fences are manufactured under strict regulations and will soon be required to carry a CE marking. There are only a handful of examples of such fences in Canada, mostly in British Columbia. Avalanche protection systems are similar in appearance to rockfall catchment fences but differ largely in function. Where a rockfall fence is designed to accommodate a dynamic load, avalanche systems are purely static structures that are installed in the initiation zones of avalanches. The steel fences support the unstable snow mass and thus stop an avalanche from ever forming. These structures are custom designed for every installation site and are generally applicable for snow depths less than 5 m when measured normal to slope. Because no avalanche ever forms, they offer protection all season long, even during poor weather conditions when helicopter bombing and other methods that require line of sight are unavailable. As well, they eliminate large maintenance budgets associated with explosive methods and allow reforestation of the avalanche tracks themselves. There is only one site in Canada where such a system has been implemented, installed in the fall of 2008 in the Kicking Horse Canyon located near Golden, British Columbia. The poster and models presented outline the basic technology used and show examples of testing procedures, installation and implementation.

Bibliography of Canadian Geomorphology