Tsunami risk at Ucluelet Harbour, British Columbia / Alexander Rabinovich, Denny Sinnott, and Richard Thomson.: Fs97-18/373E-PDF

"Ucluelet Harbour is part of a 7 km long inlet on the west coast of Vancouver Island, British Columbia. Although the region is well sheltered from major weather systems and associated storm waves, the narrow harbour entrance increases the quality ("Q") factor and, consequently, the amplification of long oceanic waves such as tsunamis arriving from open Pacific. On 15 January 2022, an eruption of the underwater volcano Hunga-Tonga in the Tonga-Kermadec volcanic arc generated tsunami waves that spread throughout the entire Pacific Ocean. The tsunami was recorded along the entire coast of British Columbia by more than 30 Canadian Hydrographic Service (CHS) tide gauges, reaching maximum trough-to-crest wave heights at Ucluelet Harbour in excess of 50 cm. Strong tsunami-induced currents in Ucluelet Inlet affected coastal infrastructure and severely damaged the community water line of the Ucluelet First Nations. In this study, we examine the tsunami waves that impacted Ucluelet and several nearby sites. The goal is to provide estimates of the maximum tsunami wave heights and tsunami-induced current speeds that can be expected from tsunamis in Ucluelet and vicinity, and to define the steps needed to mitigate future tsunami-related hazards for the region. These estimates are compared to the numerical modelling results of Cherniawsky et al. [2007] for a Cascadia Subduction Zone (CSZ) event. According to our estimates, the current speed in Ucluelet Inlet associated with the 2022 Tonga tsunami was only about 0.5 m/s (1 knot), whereas a major CSZ earthquake could produce tsunami-induced currents of up to 5 m/s (10 knots) in the inlet"--Abstract, page iv.

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