LAUSR

Abstract Combined landslide susceptibility mapping and temporal early warning of failures can be a powerful method for mitigation and timely evacuation, but modeling must be well informed by the specific failure types and triggers unique to each climate and geomorphology. This paper describes the development of a landslide susceptibility map and threshold for riverbank erosion-triggered landslides in a northern climate with atypical landslide conditions. Located on the southern shore of Lake Superior, the Ontonagon River basin in northern Michigan receives an average of 4.8 m of snowfall annually, followed in the spring by a sharp warming trend and rain. Undercutting of the steep riverbanks causes large failures that continuously threaten bridges and a nearby hydroelectric facility. In this investigation, a landslide inventory was mapped using aerial imagery from 1992 to 2016. Landslide triggering factors were interpreted using temperature, cumulative precipitation, and river discharge data, demonstrating that river discharge is the primary predictor of landslides despite the source being either rainfall or snowmelt. A preliminary threshold was then created to determine the discharge characteristics likely to cause failures. A susceptibility map was created for the river system using a combination of Scoops3D with logistic regression, improving overall accuracy to 93%. Furthermore, Scoops3D proved valuable in constraining the model to failures of engineering significance (large volume and impact) and kinematic possibility. The threshold-susceptibility scheme is thus a powerful tool for assessing comprehensive slope stability along river channels.