Title
Presentation on Tsunami Awareness. (Fire 3240)
Body
To: Honorable Mayor and Members of the City Council
EXECUTIVE SUMMARY
Though Alameda has not experienced a significant tsunami, there is a potential for such an event, especially after a major seismic event. The probability of a tsunami impacting Alameda is low, but if one should occur the risk of significant damage is high. To provide awareness about tsunamis, City of Alameda (City) staff undertook an initial outreach effort last fall and will continue on an on-going basis to reach out to the community as part of an “all-hazard” approach to emergency preparedness.
BACKGROUND
Though Alameda has not yet experienced a significant tsunami, there is a potential for such an event, especially after a major seismic event. The probability of a tsunami impacting Alameda is low, but if one should occur the risk of significant damage is high. Tsunamis can cause rapid changes in water level and unpredictable, dangerous currents that are magnified in marinas, ports and harbors, and can inundate bay communities. Damaging wave activity can continue for twenty-four (24) hours or longer following the initial tsunami impact. Although Alameda’s shorelines are considered “sheltered” waters, the impacts of a large tsunami affecting the coast could cause a devastating surge in tidal areas inside of San Francisco Bay. Furthermore, the first tsunami surge may not be the largest one.
Though Alameda has not yet experienced a significant tsunami, there have been about 100 tsunamis that have impacted California since 1800. The 2011 tsunami from Japan resulted in one death in California where the Klamath River meets the Pacific Ocean.
DISCUSSION
Worst Case Scenario
The most significant tsunamis that could impact Alameda are expected to come from the Aleutian Islands in Alaska, taking about 5 hours to arrive in Alameda. Other potential locations that could trigger a tsunami impacting Alameda include earthquakes in the Cascadia area of Oregon and Washington, which are expected to take 1.5 hours to arrive, Japan at 10 hours to arrive and Chile at 13 hours to arrive.
The maximum inundation in Alameda is expected to be as much as 18 feet (Figure 1).
What To Do If Tsunami Hits the Island?
Central Avenue is the highest point, and community members are encouraged to walk or bicycle to the center part of the main island or drive/bike beyond I-880. For Bay Farm Island, the Bay Farm School area is the highest point, and most evacuations are expected to be by car or bus with some community members being able to bicycle or walk to the main island. Contraflow travel lanes are expected to be needed on Doolittle Drive to facilitate evacuations. Vertical evacuation to multi-story stable structures is an option if it is not safe to evacuate. Evacuating by car is more likely to put the individual and others at risk. For boaters, it is not recommended to evacuate in a boat offshore. Instead, it is safer to keep the boat docked, since a boat would be difficult to navigate and would need to stay offshore in water of at least 180 feet in depth for over 24 hours.
If a tsunami is expected, the City would issue tsunami warnings to alert the public of areas that would need to be evacuated. To receive tsunami warnings as well as other emergency alerts by voice, text, and email, community members are encouraged to click on the “subscribe” button on the AC Alert web page: <https://www.acgov.org/emergencysite/>. Notifications also would come from broadcast TV, radio, wireless emergency alerts and reverse 911 calls as well as directly from the U.S. Tsunami Warning System: <https://tsunami.gov/>
Outreach To Date
To provide awareness about tsunamis, City staff launched an initial outreach effort last fall and will continue these efforts on an on-going basis as part of an “all-hazard” approach to emergency preparedness (Figure 2). City staff and tsunami experts conducted community meetings and presented tsunami information at the Transportation Awareness Advisory Group and the Transportation Commission, as well as to key stakeholders throughout the City. The first community meeting focused on boaters and the marinas, and the second meeting focused on preparing all potentially impacted Alameda community members.
Planned Outreach
Future outreach includes the installation of almost 100 tsunami warning signs at strategic locations throughout the City, as well as presenting at other speaking engagements such as to the Chamber of Commerce government relations committee (Figure 3). The City also plans to become a designated Tsunami Ready Community by the National Weather Service, as shown here: <https://www.weather.gov/tsunamiready/communities>, which will be possible with the City’s planned on-going mitigation, preparedness and response steps. For more information on disaster preparedness including information and videos from the tsunami community meetings and training with Alameda’s Community Emergency Response Team (CERT) program, please refer to the following City web page: <https://www.alamedaca.gov/Departments/Fire-Department/Disaster-Preparedness>.
Next Steps
The next phase of planning involves purchasing message and detour signs, receiving and installing tsunami evacuation and message signs, displaying earthquake/tsunami hazard decals and customized signs with maps in public places, becoming a designated Tsunami Ready Community and formalizing the evacuation process in coordination with the City of Oakland staff.
ALTERNATIVES
• Undertake the community awareness and outreach efforts described in this report.
• Modify the community outreach efforts described in this report, as directed by City Council.
• Do not provide on-going outreach to community members since the probability of a tsunami in Alameda is low, and instead, City staff would focus on awareness efforts for more probable events such as earthquakes.
FINANCIAL IMPACT
There is no financial impact from the tsunami awareness program since the California Office of Emergency Services provides the tsunami signs and the education and awareness is part of the City’s ongoing emergency preparedness efforts.
MUNICIPAL CODE/POLICY DOCUMENT CROSS REFERENCE
This action is consistent with the Alameda Municipal Code and the City’s Emergency Operations Plan (EOP). The EOP focuses on the need to enhance the City’s emergency and disaster preparedness, response, and recovery capabilities.
ENVIRONMENTAL REVIEW
This action is not a project for the purposes of the California Environmental Quality Act (CEQA) pursuant to CEQA Guidelines section 10561(b)(3) as there is no possibility that this action may have a significant effect on the environment.
CLIMATE IMPACTS
This action is consistent with the City’s Safe Climate Resolution No. 15510.
RECOMMENDATION
Discuss Tsunami Awareness
CITY MANAGER RECOMMENDATION
This is to provide City Council with an emergency management program being worked on by staff. It is a presentation, no action is necessary.
Respectfully submitted,
Rick Zombeck, Acting Fire Chief
By,
Sharon Oliver, Disaster Preparedness Coordinator
Exhibits:
1. Tsunami Evacuation Zone Map
2. Tsunami Brochure
3. Tsunami Sign Placement
4. Presentation
cc: Eric Levitt, City Manager