Program Name Mt. Rainier Lahar Warning System and
Lahar Travel Time Mapping Project
Administering Agency Pierce County Department of Emergency
Management
Contact Steven C. Bailey, Director
Address 901 Tacoma Avenue South, Room 300, Tacoma, WA 98402
Telephone Number 253-798-6595
Fax Number 253-798-3307
E-mail sbailey@co.pierce.wa.us
At 14,411 feet, Mt. Rainier dominates the Pierce County skyline. This
glacier-clad mountain is capable of generating large lahars which have
historically reached the shores of Puget Sound. Any Case I or II lahar
that travels through the Puyallup and Carbon River Valleys will be a
calamitous disaster. The largest lahars are triggered by massive collapse
of the steep flank of a volcano. A large earthquake unrelated to rising
magma could trigger a flank collapse on Mt. Rainier. At least one flank
collapse on Mt. Rainier could have been caused by a great prehistoric
earthquake that occurred at about the same time. As many as 30 earthquakes
occur under Mt. Rainier annually, making it the most seismically active
volcano in the Cascade Range after Mt. St. Helens.
Geologists surmise that a lahar or debris flow traveling down the
populated river valleys would be catastrophic and result in a tremendous
loss of life and property. Over 50,000 inhabitants of the urbanizing river
valleys work and reside on the deposits of prehistoric and historic debris
flows of different types including lahars. A Case I lahar would reach the
town of Orting within 30 minutes and could reach other Valley towns within
an hour.
Two separate programs address the lahar hazard: Lahar Warning System and
Lahar Travel Time Mapping Project, each described separately.
Lahar Warning System:
Reduction of casualties from such an unexpected disaster requires an
automatic detection system combined with procedures for clear warning,
public understanding of the hazard, and practiced response by the
citizenry. To this end, Pierce County Department of Emergency Management
(PC DEM) led the effort in implementing and testing the Mt. Rainier Lahar
Warning System. Through the use of detection devices, warning sirens, and
evacuation signs and routes, the Lahar Warning System helps the public to
prepare for, and respond to, the lahar hazard.
The Lahar Warning System uses Acoustic Flow Monitors (AFMs) to detect a
lahar as it occurs. The warning signal is relayed to both the WA State
Emergency Management Division and Pierce County Law Enforcement Support
Agency (PC LESA). If the signal is confirmed as a lahar, an array of
sirens sounds a lahar alert throughout the Puyallup and Carbon River
Valleys. Residents may then follow predetermined, marked evacuation routes
to higher ground and out of the lahar path. This system is the first of
its kind in the world to be fully automated, an innovation that has
decreased to less than two minutes the time between a lahar's occurrence
and the sounding of the warning siren. Further, both the AFM technology
and the detection relay organization greatly reduce possibility of false
alarms.
PC DEM has spearheaded 10 tests (including four System-wide tests) of the
Lahar Warning System in order to evaluate the technology and the response
practices. Testing the Lahar Warning System allows for improved
coordination among participating agencies and for review of the evacuation
and response plans. The tests also help to increase public awareness of
the lahar threat and give the public an opportunity to practice their
response.
As the lead agency, PC DEM has worked with great dedication and
persistence over the past several years to coordinate and implement the
Mt. Rainier Lahar Detection System. Only through extensive collaboration
with the WA State Emergency Management Division, Tacoma-PC LESA, the
cities and political jurisdictions/special purpose districts in the lahar
hazard area, the Puyallup Tribe of Indians, DNR, USGS, CVO, the Mt.
Rainier Working Group, the Valley Evacuation Planning Group, and Champion
Timber (now Rainier Timber Co.), has this extensive undertaking been
possible.
Lahar Travel Time Mapping Project:
Land use planners are challenged by the need to keep the public out of
harm's way and discourage building in hazardous areas. For the first time,
Pierce County has employed scientifically estimated lahar travel times to
support land use policies to support evacuation of the public and guide
the size and location of the built environment in the lahar hazard zone.
This innovation is due to the efforts of USGS scientists Tom Pierson, PhD,
and Kevin Scott, PhD, in collaboration with Pierce County Departments of
Planning & Land Services and Emergency Management. Combining their
efforts, these two scientists created the first ever Lahar Travel Time (LTT)
estimates for Case I cohesive lahars originating from Mt. Rainier. Working
with Pierson and Scott, County emergency and land use planners were able
to produce LTT maps which clearly delineate four time travel zones. The
zones are based upon the amount of time each area would have to evacuate,
from the time the Acoustic Flow Monitor (AFM) alarm sounds until the lahar
reaches that zone.
These zones are particularly critical for volcanic hazard mitigation
efforts. Previous to this Project there was no data correlating distance
from the volcano to evacuation time. The new land use policies in these
critical areas require that potential developers indicate in which travel
time zone they wish to build, and then extrapolate a more site-specific
estimate of the lahar travel time. The development must adhere to the
requirements of the zone within which it falls. This not only encourages
progressive development trends, it also forces each new development to
consider evacuation routes, secondary hazards, traffic, disabled
populations, post-lahar activities, and so on.
The project also provides a visual tool for the public so that they may
better plan their evacuation procedures. The maps are available on the
County's Emergency Management website,
www.co.pierce.wa.us. The LTT
map, the first of its kind, is a simple and easily understandable tool,
helping to expand the public's awareness of the lahar hazard and protect
people and property from harm.
