Numerical simulation of the landslide‐generated tsunami in Kitimat Arm, British Columbia, Canada, 27 April 1975

It remains challenging to predict and estimate potential damage from tsunamis using computer models. One of the approaches to validate models is to compare their results with site observations. We carried out numerical modeling for both the underwater landslide and the associated tsunami that occurred near Kitimat, British Columbia, Canada on 27 April 1975. A few observations of high water marks along the coastline indicated 8.2 m tsunami waves. Previous survey results of the seafloor showed that a landslide traveled about 5 km down the axis of the fjord from its source areas on the sidewall of the fjord, near the head of the inlet, and on the lower Kitimat River delta. We modeled the subaqueous slope failure as a Bingham visco‐plastic fluid (debris flow) based on previous geotechnical investigations at the site, and numerically solved the landslide‐generated tsunami wave and debris flow equations using a finite‐volume Godunov‐type scheme. This method resolves abrupt wave and landslide front interactions and remains oscillation‐free. The computed motion of the debris flow is generally consistent with observations; simulations indicate that the failure propagated approximately 4.5 km down the fjord axis from its inception point. We have found that computed amplitudes for the tsunami wave crest at the coast of Kitimat Arm were between 6 and 11 m; these values are somewhat higher than previous simplistic solitary wave theory estimates of 6.3 m and observations of 8.2 m.