Runout Modelling on Turtle Mountain

John Allan's danger zone mapping.
Click on image to enlarge.

With John Allan's identification and detailed mapping of the South Peak hazard in the 1930s, the initial attempt at understanding the extent of the area at risk from a rock avalanche from South Peak was documented. This zoning was based on an assumed volume of the South Peak movement and empirical relationships, likely derived from the behaviour of the Frank Slide. Based on Allan's zoning, the Government of Alberta issued a Notice of Danger to residents in the danger zone in 1934.

In 2000, BGC Engineering revisited Allan’s assumed failure mechanism and volume calculation. Using recent advances in empirical relations for rock fall and runout, BGC Engineering revised the danger zones. All of the current early warning and emergency response planning and protocols use the BGC Empirical Upper Limit Zone.

Map showing BGC Engineering and John Allan's zones. Click on image to enlarge.

With the refined definition of the South Peak failure volume, a higher resolution digital elevation model (DEM) and improved 3D analysis, O. Hungr Geotechnical Research predicted a new runout of the South Peak failure. They used the DAN3D modelling package for the updated analyses. This model used updated theories on debris mobility and LiDAR DEM to generate an updated estimate of the zone affected by a failure of South Peak.

As Alberta Geological Survey and collaborators carry out additional structural studies, we believe these estimates will be refined and updated for the people living in the area.

Map showing runout estimates from the DAN3D model. Click on image to enlarge.