Glaciomarine landslide frequency, distribution and geology in Ontario

Champlain Sea deposits are ubiquitous in the Ottawa River valley, focused on the Ottawa area but extending upstream and downstream to the marine limits of the sea. The modern Ottawa River mostly occupies the more northern side of the valley, whereas the post-Champlain Sea proto-Ottawa River channels and both its erosional and depositional landforms and deposits are found south of the modern river, in Ontario. The character of large landslides in glaciomarine soils, their engineering geology, and their spatial and temporal frequencies depend to some extent on this post-glacial history and therefore may be unique in Ontario. In this study we present the results of a thorough accounting of landslide scars evident in continuous high-resolution lidar terrain models within the Champlain Sea marine limit in Ontario. Following previous work conducted by others over parts of this study area we classify landslides by setting and surficial material. We compute both spatial and temporal frequency of landsliding for the study area. Our discussion includes an assessment of the variability in frequency through time and space, geological and engineering geology associations, and comments on methods for reliable frequency estimates to support engineering or land-use risk assessment based on our compilation.