03/05/2005

New SAR Initiatives Fund (NIF) Final Summary Report 2004-05

TITLE: SAR response to a tsunami in Pacific Region

PROJECT NUMBER/NIFID: NIF ID 2001010

FINANCIAL SUMMARY: From NIF $220,000 From other sources $80,000

PROJECT DESCRIPTION: To develop numerical models of tsunami currents and heights to be expected following a Cascadia Subduction Zone earthquake. These models will use CHS high-resolution bathymetric data in harbours vulnerable to tsunamis to provide accurate simulations of currents in entrances to harbours, and estimates of heights in harbours. We will collaborate with Coast Guard Staff to provide guidelines for SAR staff to operate safely during such an event, and advice for mariners to avoid death.

The Cascadia Subduction Zone will generate a severe earthquake and tsunami within the next few hundred years. The earthquake will be magnitude 7 to 8 or more, and the tsunami height along the west coast of will be about 5 metres, and higher in some embayments. The last such earthquake, in A.D. 1700, set up a major tsunami that may have wiped out a native village in Pachena Bay.

PROPOSAL OBJECTIVES: Provide information to the marine and SAR community of expected tsunami heights, arrival times and currents in coastal waters. Such information will enable the marine and SAR community to develop action plans for vessels during a tsunami. To accomplish this, the following four project objectives were identified. 1) Select appropriate harbours for numerical simulations. 2) Prepare bathymetric data and grids for models and acquire incoming tsunami wave. 3) Apply relevant numerical models to problem and determine currents and estimated heights. 4) Develop SAR guidelines and information for public distribution.

IMPACT/BENEFITS: Prior to this project there was no reliable information on the effects of a Cascadia Subduction Zone tsunami on the coastal communities of southern and western Vancouver Island. The few numerical models that did exist had numerical grids too coarse to include harbours or inlets and provided no information on currents. The development of higher resolution grids will enable harbours and inlets to be modelled and will provide valuable information on estimated water levels and currents. This information will benefit SAR specialists, mariners, the Provincial Emergency Program and emergency response personnel in coastal communities. 03/05/2005

EVALUATION: Within the scope of this project four models have been completed (Victoria Harbour, , (Inlet, Harbour and Basin), and Inlet. The model results for the Victoria and Esquimalt models are available at:

http://www-sci.pac.dfo-mpo.gc.ca/osap/projects/tsunami/default_e.htm

Instructions for downloading and running the model animations are also provided.

These animations show the greater response at Esquimalt where tsunami heights from a Cascadia earthquake are up to 4.7 metres inside the harbour. Currents are up to 15 knots in both harbours, with the strongest flows in narrow channels and around headlands.

At Sooke the wave heights are much smaller, but the maximum currents in the entrance to the harbour exceed 10 knots.

The waves are extremely large on the outer coast at Ucluelet Inlet (> 10 m) and maximum modelled currents exceed 25 knots.

Model development is still in progress for Alberni and Inlets and for Port San Juan.

COMMUNICATIONS During the course of this project tsunami presentations featuring the model ACTIVITIES: animations and results were given to: • Provincial government emergency planners • and Vancouver Island emergency managers groups • DND tsunami exercise planners • Tsunami scientists at meetings in Montreal and Wellington, NZ • Institute of Ocean Sciences open house

BIBLIOGRAPHY REFERENCE: Scientific presentations: 1) Modelling large tsunami generated by Cascadia Subduction Zone earthquakes; J. Cherniawsky, F. Stephenson, K. Wang, B. de Lange Boom, and V. Titov. 2) Predicted Tsunami heights and currents in Vancouver Island Harbours caused by a future Cascadia Subduction Zone earthquake; J. Cherniawsky, K. Wang, V. Titov, F. Stephenson and A. Rabinovich

SUGGESTED FOLLOW-UP/ Excellent results have been achieved from the modelling efforts to date, ADDITIONAL ACTIVITIES: but there is additional work to do. Most notably a summary of results and recommendations suitable for use by SAR managers and responders. This work is in progress and will be contained within the final report (September 30, 2004).

The animations show the tsunami heights and currents at thousands of grid points within the model region. The data needs to be reformatted to show time series of water levels and currents at selected locations within the model areas. This has been done for a few locations, but more work is 03/05/2005

required.

As mentioned previously, models are still in progress for Alberni and Bamfield Inlets and for Port San Juan.

In March 2004 a topographic lidar survey was successfully carried out at Ucluelet Inlet. This data will be integrated into the Ucluelet model and will enhance the model by allowing the tsunami to cross the high water line into low lying areas. This integrated model will be the used to develop procedures for other integrated models where tsunami inundation could be significant (e.g. .)

Digital bathymetric data is now available for most of the west coast of Vancouver Island (as a result of a two year data conversion project funded by DND and carried out by CHS.) With this digital bathymetric data it is now possible (and recommended) to construct model grids for other locations on the west coast of Vancouver Island (e.g. , Kyoquot, .)

In areas where tsunami inundation is likely to be significant topographic lidar surveys will need to be carried out (e.g. Port Alberni, head of Port San Juan, Whiffin Spit at the entrance to Sooke Harbour) to optimize model performance.

FOR MORE INFORMATION CONTACT Coordination Sponsor/Project Manager National Search and Rescue Secretariat Fred Stephenson 275 Slater Street, 4th Floor Canadian Hydrographic Service, Pacific Region Ottawa, ON K1A 0K2 P.O. Box 6000, Sidney, BC V8L 4B2 Tel.: (613) 996-2782 Tel.: (250) 363-6350 Fax: (613) 996-3746 Fax.: (250) 363-6323 Web Site: http://www.nss.gc.ca e-mail: [email protected]