Wabush Lake is characterized by a nearly constant sediment input, resulting from the deposition of mine tailings. Five bathymetric surveys were conducted in this lake, in order to understand the sedimentation pattern over more than 12 years. Of the morphologies studied, submarine channel and knickpoints were traced out and documented. A physical model of Wabush Lake was also constructed in order to understand specific morphologies, such as the knickpoints. As part of this study, it was observed that knickpoints migration could be explained, at least in the laboratory, by two mechanisms: landslide and erosion, and not only erosion as previously thought. This previous conclusion will be applied to some knickpoints found in Wabush Lake. Two cases are analysed: (1) a knickpoint where a tension crack is present and (2) another knickpoint that shows no sign of instability. It is found that, when an excess of pore water pressure is present due to rapid sedimentation, static liquefaction may occur at the head of a knickpoint leading to a localized slope failure.