Effect of global sea level rise over the near, intermediate and long-term on extreme longwave motions at the federal government facilities in Patricia Bay and Departure Bay, British Columbia / Richard...: Fs97-18/375E-PDF

"Coastal British Columbia is susceptible to tsunamis generated by major earthquakes within the Pacific Ocean and by local underwater earthquakes. Although the Strait of Georgia is partially sheltered from tsunami waves arriving from the open ocean, tsunamis from major events have penetrated into the region. Moreover, Vancouver Island is a seismically active region; the Mw 7.3 Vancouver Island Earthquake with its epicenter in the vicinity of Campbell River, generated local tsunamis in the Strait that created considerable damage and killed one person. In this study, we examine the risk of marine flooding for the Patricia Bay and Departure Bay regions. Trans-oceanic tsunamis present a substantial, but not a major, threat to these regions. Significant tsunami waves of up to 50-100 cm can be expected at the two sites from a 1964-type Alaska earthquake. The primary concern is a future tsunami generated by a great earthquake along the Cascadia Subduction Zone; there is low probability of major tsunamigenic earthquakes inside the Strait of Georgia. Submarine landslides can produce significant tsunamis. Two specific locations of high risk for submarine slides are: (1) Roberts Bank, Fraser River delta; and (2) Malaspina Strait separating Texada Island from the mainland coast. A Roberts Bank slide could produce marked tsunami runup on the southeastern Gulf Islands, but only small (<0.5 m) runup at Patricia and Departure bays. A failure in Malaspina Strait will have negligible effects on the two sites. The flood risk from atmospheric processes is of considerable concern to low-lying coastal areas. The highest sea levels recorded at Patricia Bay over 43.5 years of observation and at Departure Bay over 12 years were found to be 1.04 m and 0.88 m, respectively. If we allow for an engineering "safety factor" of 1.5, the maximum likely sea level rise associated with meteorological forcing for these two stations is 1.6-1.7 m"--Abstract, page iv.

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