Dynamic analysis of the 2012 Johnsons Landing landslide at Kootenay Lake, British Columbia: the importance of undrained flow potential
The Johnsons Landing landslide occurred on 12 July 2012 on the shores of Kootenay Lake, British Columbia. The landslide consisted of poorly sorted, low-plasticity debris that initially descended a steep channel, before avulsing onto a glaciofluvial terrace. This event destroyed three homes and killed four people who lived on this terrace. This paper presents a back-analysis of this event using numerical runout modelling. It is shown that undrained flow can explain the observed channel avulsion with fewer model parameters than needed by previous analyses. This mechanism should be considered in similar settings, as ignoring it can lead to underestimation of runup and overtopping of natural and anthropogenic flow obstacles, such as landslide protection structures.