Tsunami Articles

WSSPC TSUNAMI ARTICLES

TSUNAMI LEGISLATION AND RISK REDUCTION EFFORTS IN OREGON

Information for this article was provided by
John D. Beaulieu Ph.D., Deputy State Geologist,
Oregon Department of Geology and Mineral Industries

The rapidly growing awareness of locally generated tsunamis in Oregon led to the passage of SB 378 and SB 379 by the 1995 Session of the Oregon Legislature. The reality of Cascadia subduction zone earthquakes came to the attention of the state from a variety of sources including local geology, local archeology, historic tsunami records in Japan, tree ring data, marsh data, and plate tectonic theory. Fast on the heels of Cascadia earthquake awareness came concern for tsunamis and their potential damage.

From the standpoint of life safety, tsunamis are viewed as the greatest risk to Oregonians. With proper public education tens of thousands of deaths on and near Oregon's beaches may be averted.
In Oregon the preferred strategy is that of a rapid and effective evacuation in the event of a tsunami. Senate Bill 378 requires tsunami drills in coastal schools. To avoid reducing class time, the tsunami drills were scheduled to replace some of the current fire drills.

SB 379 places strict limits in state statute on the construction of certain high occupancy structures in the actual tsunami zone. If "Plan A" is to evacuate, then "Plan B" is to avoid high occupancy if evacuation is not feasible. In a sense SB 379 goes to "Plan B" for buildings that cannot be evacuated in the event of a tsunami.

In both bills, Oregon experienced the confusion and crossfire that can occur where science meets policy. Science identifies the problem (large tsunami every 300-600 years or so, with the last one occurring on January 26, 1700 and locally generated tsunamis hitting the Oregon coast in 5-30 minutes after a subduction earthquake depending on location), and the policy tells people what to do about it. With regard to SB 378 the conflicts were trivial since the investment required for school evacuation is quite low, and the resource being protected, school children, is a quite high.

With regard to SB 379, however, the conflicts were greater. Some buildings were not going to be built on locations of choice because scientists had a notion about tsunami risk. To avoid confusion, the building classification scheme that is imbedded in the state building code was used. This system was also used because State Building Codes were going to be part of the implementation of the bill. To ameliorate the conflicts, political support was developed with the Oregon School Boards Association, League of Women Voters, Oregon Ports Association, Oregon Fire Fighters Association, Oregon Coastal Zone Management Association and the Seismic Safety Policy Advisory Commission.

The discussions were directed away from land use legislation, because past experience showed that land use regulations are blunter tools than were called for in this effort to reduce risk. The focus was on targeting certain kinds of buildings for which evacuation was not a viable option in the event of a tsunami. Attention was directed at building codes and not a land use zonation. This was an early tactical decision that required a clear understanding of both the purpose and the options.

As it turned out the buildings that could not be built were public to semi-public buildings with high and immobile occupancy such as schools an jails, or critical post-event structures which need to be functional, like fire stations. The public aspect of this set of buildings also avoided the issues of "takings". At the local level exemptions from the law are possible if there are overriding issues, such as a community which lies totally in the tsunami zone needing a fire station.

On technical grounds the Oregon Department of Geology and Mineral Industries (DOGAMI) can grant exceptions to the prohibitions, but it must do so based on modeling and science.

A most remarkable aspect of this legislation was that the law was passed BEFORE the actual tsunami inundation lines were placed on maps. DOGAMI was assigned the responsibility of making the maps for the entire coastline. The desire for uniformity, timeliness, and science underpinned this decision. Plotting of the lines was preceded by field visits from Oregon Emergency Management staff to tsunami sites in Nicaragua and Japan plus the development of partnerships with computer modelers with whom DOGAMI could blend its geologic data and the geology of others to yield lines guided by models as well as outcrops.

With regard to the geology, it is noteworthy that Oregon is fairly unique in the pacific Rim in that it possesses 1) numerous estuaries, 2) sandy beach deposits fronting muddy estuarine environs, and 3) a neotectonic dynamic that acts to preserve sand washed in by tsunamis between layers of estuary mud. Without these Oregon would not have the geologic part of the recipe for making good maps.
In making the maps DOGAMI was confronted with the issue of balancing risk against gain in pursuing risk reduction. Society seems to identify with events of 100 year statistical recurrence like floods or even 500 year recurrence like earthquakes in the Building Code, but not longer recurrence intervals. Tsunamis had to be picked to match this pattern or the program may not be salable. Accordingly tsunamis were selected of average size. Thus, mitigation was keyed to an event of 300-600 years recurrence. A worst case scenario, on the other hand, would have probably been a 10,000 year event.

The effort has been very successful. Oregon DOGAMI worked constructively with several communities that sought advice on how to proceed with certain types of construction projects. DOGAMI continued to attract funds to refine their models for the higher priority estuaries and currently are cooperating with NOAA and FEMA on critical coastal work. A Tsunami Mapping and Warning Center has recently been added to the Hatfield Marine Science Center on the mid Oregon coast in Newport, Oregon with federal funding.

Outreach efforts included talks, videos, pamphlets, historic markers at key tourist points in tsunami zones along the coast, and evacuation signs. These were primarily pursued with local matching efforts. The DOGAMI Governing Board and staff have displayed a consistent willingness to work with local officials despite earlier profound differences. It has been observed that virtually nowhere do citizens now question the reality of the events. Rather they inquire about the size, frequency, and impact of the event and the balancing of risk reduction in terms of costs and benefits. The public seems happy with the answers that have been provided.

In this unique role as the definer of geologic hazards and the risk reducer for geologic hazards for Oregon the tsunami exercise reaffirms these simple lessons of risk reduction for geologic hazards.

1. Science must define the risk in terms the public will understand and will relate to.
2. Actual risk reduction will involve balancing of values and a need for administrative ease.
3. Public education is a key component of any meaningful effort of risk reduction.
4. Risk reduction in the end is a local effort if it is to be truly successful.

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TSUNAMI HAZARD SIGNS

Tsunami are devastating waves caused by great undersea earthquakes. Such earthquakes can occur along the Cascadia Subduction Zone, one of the largest active faults in North America. This fault zone lies 32 to 70 miles offshore and roughly parallels the coast.

Tsunamis are dangerous and destructive. They have struck the Oregon coast repeatedly and will again in the future. Tsunamis can follow within minutes of an earthquake. They move rapidly but quickly run out of water as they sweep inland and uphill.

In 1994, a group from the Oregon Department of Geology and Mineral Industries, Department of Transportation, Land Conservation and Development, Parks and Recreation, and Oregon State University Extension Sea Grant searched for an international warning symbol for tsunamis. When they couldn't find one, they asked Oregon State University Extension and Experiment Station Communications artist Tom Weeks for help. They gave Weeks some ideas, and he created the attached designs for the bright blue tsunami hazard zone and tsunami evacuation route signs that are currently being installed at several locations on the Oregon coast.

At its March 4, 1997, meeting in Seattle, the Tsunami Hazard Mitigation Federal/State Steering Group voted to adopt the Oregon signs as tsunami hazard zone and evacuation route signs for California, Oregon, Washington, Alaska, and Hawaii. This means that anyone visiting the beaches in any of those states will see the same signs warning them of this hazard. In addition, decals with smaller versions of the hazard zone sign will be installed on 200 all-hazard warning signs at Oregon coastal state parks.

The blue and white reflective signs are manufactured by the Oregon Department of Transportation and come in several sizes. The round evacuation route sign features a tsunami wave and is available in 12"-, 18"-, and 24"-diameter sizes. A second sign with a white arrow on a blue background is placed below the evacuation route sign to show which way to go to safely escape a tsunami. The rectangular tsunami hazard zone sign shows a person running up a hill to escape the tsunami wave and says, "In case of earthquake, go to high ground or inland." The hazard zone sign, which is to be placed in low-lying areas that are vulnerable to tsunamis, also comes in three sizes: 15" x 12", 22" x 18", and 30" x 24". Signs may be placed only in locations agreed upon by local and/or state governmental authorities and may be purchased by calling Orville Gaylor, Oregon Department of Transportation, at (503) 986-3603.

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