Landslide Warning System Could Save Lives
Landslides have killed 80 people in northwestern British Columbia since the mid-1800s. A heavy fall rainstorm with southerly winds, while the freezing level sits above most mountain peaks, especially raises the chances of hillsides crumbling. Analysis of the weather conditions apt to cause debris flows in the region shows that these types of storms hitting the coast after four rainy weeks pose the greatest threat of triggering landslides.
Researchers have devised a landslide susceptibility forecasting system to warn loggers in particular of high risk conditions. The highest level of risk near Terrace, for instance, occurs when the airport weather station records over 80 mm of rain in the previous four weeks and over 10 mm more rain is forecasted to fall within 24 hours. If a site has already received greater than 50 mm of rainfall during the previous 24 hours, then expect numerous landslides. Under these conditions, the advice is to shut down logging operations throughout the region and broadcast a public warning.
The accuracy in detecting landslides for this remote part of the province is severely compromised by a scarcity of rainfall data and landslide monitoring. The authors of this study note that the political will to maintain a network of rain gauges that would adequately inform landslide predictions is currently lacking.
Matthias Jakob, Kris Holm, Owen Lange and James W. Schwab. 2006. Hydrometeorological thresholds for landslide initiation and forest operation shutdowns on the north coast of British Columbia. Landslides. 3(3): 228-238.