The mud is falling! The mud is falling!

THREE YEARS AGO, a Pierce County Emergency Management team started setting up a system to warn communities in the Puyallup River Valley of flash floods and mudflows headed down from Mount Rainier. The system got a real-life test last Tuesday and worked perfectly—until the amateurs took over.

At about 2140 hours that night, ranger radios started crackling with reports about noisy geologic doings in the darkness on the western slopes of Rainier, among the high glacier-cut gullies drained by the Puyallup, Carbon, and Nisqually rivers. The news was quickly passed to experts at county and state emergency HQs in Tacoma and Camp Murray, who were able to assure the rangers that their monitoring equipment showed no threat to life or property in near-mountain communities like Orting and Sumner.

Unfortunately for the county's carefully laid emergency plans—and the peace of mind of thousands of Puget Sound residents—KIRO TV reporter Richard Thompson happened to be listening to the newsroom police-and-fire scanner when the word "lahar" was used. A lahar (the word is Indonesian) is a destructive high-density flow of water, mud, and rock. And the mere overheard use of the word turned the county's emergency plan into Keystone Kops comedy.

Within minutes, before even beeper-summoned emergency-management teams could assemble, TV watchers from Seattle to Olympia had been given the impression, in the words of one viewer, "that we were all about to be engulfed in a sea of mud." Passive news-consumers weren't the only ones to get a bent message. Without waiting to get the official word from the emergency chain of command, sheriffs' deputies, town constables, and volunteer fire departments from Orting to Elbe were ordering some people out of town and stopping others from getting in. (For some of the more amusing incidents, see last Thursday's coverage in the Seattle P-I. )

Elbe, on the far southwest of the mountain, actually had more to worry about than Orting. When day came and the dust cleared, it turned out that the racket of the night before had been caused by a small mudflow not on the Puyallup but the Nisqually, where such events are, if not routine, at least common enough to rate little more than passing notice, and take place far from densely populated areas.

Lahars are not a matter of concern only to small towns in the Cascade foothills. Stratovolcanoes like Mount Rainier are mostly enormous piles of loosely consolidated volcanic ash and mud, and periodically shed scabs and scales of their substance. The Duwamish lowland as far north as Kent is the result of one such event some 5,000 years ago. An earthquake, an accumulation of meltwater under a glacier, or mere internal adjustment of the mountain mass could and will lead to such catastrophes in the future.

The emergency system now in place in the Puyallup takes ingenious advantage of the physics of moving masses of material to tell monitors what's happening far upriver, often in the dark or the fogs of a Northwest winter. About 15 miles upstream of Orting, five electronic vibration sensors flank the Puyallup and its tributary Carbon rivers. The sensors are set to ignore the low-frequency vibes characteristic of earthquakes (the U.S. Geological Survey keeps track of those). Instead they're tuned to pick up shuddering in the 50 cycle-per-second neighborhood: the kind of shaking generated by water- driven rock and mud thundering down a narrow river valley.

With this system in place, even a town as close to the mountain as Orting can have at least 30 minutes' warning of the imminent arrival of a lahar—not a lot of time, but enough to grab the kids and head for high ground. Alternatively, the system can tell you when a lahar is not coming; that's what happened last Tuesday. When emergency workers checked out the automated trace from their vibration detectors, they could be virtually certain that whatever was going on out there, it wasn't a mulch of mud, water, stones, and trees moving down mountain at 20 miles an hour.

Back in the 1930s, a radio drama about invasion from Mars was enough to sow panic across a nation already edgy from rumors of war. That was fiction. Now we're faced with something trickier: "Facts" hastily assembled into fiction, which, instantly propagated, has the impact of fact. Tuesday evening's fog of confusion cleared fairly quickly; by 10:20 KING TV had Pierce County sheriff spokesman Ed Troyer on the air trying to calm things down, and the roadblocks at Orting were down by quarter to 11. But the instantaneous electronic spread of empty rumors, and the lack of any dependable source of firm information to quench the media's self-fueling sensationalism, suggests that good science and technology won't be much help in saving life and muting panic until our self-appointed purveyors of real-time information agree to get with the program.

Additional links

A terrific site about volcanoes and lahars in general and the Puyallup early-warning system in particular: http://volcanoes.usgs.gov/About/Highlights/RainierPilot/Pilot_highlight.htm l

The US Geolocal Surveys central site for scientific and hazard information for all the Cascade volcanoes: http://vulcan.wr.usgs.gov/

rdowney@seattleweekly.com

 
comments powered by Disqus