Rockfall-Talus Process-Response Systems in the Canadian Rockies, Canada

Abstract:

Rockfalls are an important hillslope process operating at bedrock locations on mountain landscapes. Rockfall erosion and deposition may: (i) contribute to geomorphic modification and weathering (ii) dominate low-order catchments and affect connectivity between hillslopes and stream channels (iii) affect mountain hydrology. Prior studies have shown that rockfall occurrence in alpine environments is controlled by factors such as joint frequency/width, frost cracking, glacial history and seismic activity. Further work is required to better understand regional controls on rockfall events in the Canadian Rockies. Extensive glaciation in these landscapes resulted in oversteepened hillslopes that were susceptible to rockfall activity, particularly during the paraglacial period, but with activity continuing until present day. Herein, we investigate large-scale controls in rockfall-talus process-response systems in the Front Ranges and Main Ranges of the Canadian Rockies. Structural geology and climate differ between these two regions. Our study area includes drainage basins covering a total of ~1,000 km² in Kananaskis Country (Front Ranges) and Kootenay National Park (Main Ranges). Talus inventories are collected from aerial photographs to analyze rockfall-talus process-response systems in the Front and Main Ranges. Talus deposits represent accumulation over millennial temporal scales and are used to evaluate long-term rockfall erosion rates. Preliminary results suggest differences in rockfall-talus processes between the two study areas. The Main Ranges are less deformed and have horizontal bedding relative to the Front Ranges which have a combination of gently and steeply dipping slopes. These differences in bedding planes may produce distinct distributions of rockfall-talus systems in each region. Other factors will be investigated, such as glacial sculpting, jointing patterns and amount of time that rock is in the frost cracking temperature window (-3 to -8 ⁰C).