The people of Pierce County, just south of Seattle, who live at the foot of the almost magical Mt Rainier (4393m) are preparing for the day the magic turns to a nightmare, when their beautiful playground turns nasty.
There are many lessons from the planning and activities at Pierce County for what would be a catastrophic disaster which might usefully inform judgements about warnings, sirens, evacuations and preparations in other areas.
Mt Rainier is classed as an active volcano, in an earthquake zone, subject to throwing off catastrophic mudslides, known as “lahars.” (pro: la-hars). It is usually referred to as America’s most dangerous volcano although it last erupted in 1894, and there’s no evidence of present volcanic activity. It’s earthquakes generating lahars which are of more concern.
“Eruptions usually have some sort of lead time as they can be forecast,” says Tom Sharp of Pierce County, which is planning to support its community of a catastrophic event occurs.. “If our system detects a lahar, the people have to go. They don’t have a choice. And they have to be out of the area in 30 minutes,” says Tom, who’s responsible for the lahar detection and warning system.
Lahars comes from the Indonesian word “berlahar.” Imagine the recent Japanese tsunami. Wikipedia says Lahars have the consistency, viscosity and approximate density of concrete: fluid when moving, solid at rest. Lahars can be huge. A lahar of sufficient size and intensity can raze virtually any structure in its path, and is capable of carving its own pathway, making the prediction of its course difficult. Conversely, a Lahar quickly loses force when it leaves the channel of its flow: even frail huts may remain standing, while at the same time being buried to the roof line in mud. A lahar’s viscosity decreases with time, and can be further thinned by rain, but it nevertheless solidifies quickly when coming to a stop. With the potential to flow at speeds up to 100 kilometres per hour, and distances of more than 300 kilometres, a lahar can cause catastrophic destruction in its path. Lahars from the 1985 Nevado del Ruiz eruption in Colombia caused the Armero tragedy, which killed an estimated 23,000 people, when the city of Armero was buried under 5 metres of mud and debris. A lahar caused New Zealand’s Tangiwai disaster, where 151 people died after a Christmas Eve express train fell into the Whangaehu River.
Geological evidence reveals Mt Rainier has thrown off previous lahars on extraordinary in scale. Wikipedia says the Osceola lahar produced by Mount Rainier 5,600 years ago resulted in a wall of mud 140 metres deep in the White River canyon, and which covered an area of over 330 square kilometres. The mountain blew off 500 metres of its top, which flowed down to the sea at Tacoma, 60 km away.
Tom Sharp studied the del Ruiz event. “An unheralded lahar could be generated by a volcanic eruption, but it doesn’t have to be a big one, it could be a minor eruption which loosens the mountain edge. The side of the mountain might give way in a weak area, particularly after heavy rain. They can also be caused by an earthquake.”
“They start small and get bigger as they gather up debris.” There are 40,000 people at risk of lahar in Pierce Country, about 7,000 of whom live in the town of Orting. The Washington State fair occurs in the region each year, and attracts 50,000-100,000 people more people.
The warning systems rely on technology, and is based on the premise it will remain intact (say, after an earthquake). The lahar warning system was installed in 2000 is simple. Pierce Country has a five monitors on each of two rivers on the mountain which detect vibration. “I can read an animal walking past them, or a human jumping up and down” says Tom. “They don’t have false alarms.”
When the detection is made Tom has 30-40 minutes to clear the region of people. The plan is to have a warning to the public within five minutes. “In practice we can do it in two minutes from time of detection,” he says. A series of sirens scattered through the community will sound, triggered at the Pierce County Warning Centre. But they are outdoor sirens, and might not be heard over the car radio or inside.
The sirens are always accompanied by a voiced message. These messages are kept short, with just the most basic information and a warning to leave the area immediately. “The messages cant go for more than a minute. If they go for two minutes, that’s one less minute people will have to evacuate. We’ve been practicing these recorded messages for about ten years and the feedback from the public has given us a good understanding of what the people want.”
The Pierce County Warning Centre will alert all emergency agencies and utilities via phone/email/cell/pager. Police will immediately stop all traffic from entering the region, allowing all vehicles to travel on all lanes out. The public will follow well sign posted evacuation routes. A automated warning will be posted on the US emergency alert system (EAS) , which will be picked up by people with National Weather Radios. That will also trigger a series of warnings which go to radio and TV stations, who are expected to broadcast the information immediately, or in some cases, that will occur automatically.
The Country has its own phone alert system and will rely heavily on phone messaging. “Pierce County Alert is an opt-in system for residents, but we also subscribe to the Sheriffs reverse 911 phone subscriber list. We think we can get a phone message to about 85 percent of our community,” says Pierce County Emergency Co-ordinator Ken Parrish.
“The county can deliver thousands of simultaneous calls a minute. “We issued 26,000 in five minutes for a winter storm a few years ago.” The County is a big supporter of the private warning and alert developer, Everbridge, which developed their phone system and which is now creating feedback loops. “They are without doubt the world leaders in mass notification” says Ken.
“No alert system is perfect so we cover as many bases as we can. EAS is a powerful tool, but only for those watching TV or listening to the radio.” By ensuring that the messages are distributed multiple ways, the natural human reticence to avoid acting until the threat has been validated, means there are multiple channels for the warnings that will confront people very quickly.
Evacuation routes are permanently signposted. There was some debate about having signage that can be opened when needed, and closed for the rest of the time. “But we wont have time to open them when needed, and anyway, it puts the issue right in the faces of people who live here, so they know constantly they are at risk,” says Tom.
“At first real estate agents were concerned about property values, but we dont hear from them any more.”
The public have to get to higher ground, so those who live along the edge of the valley don’t have to travel very far. “The school kids, aged seven or eight, practice their evacuation each year, and although they’ve got small legs, they can get to safer high ground in 30 minutes, but they have to walk fast or run to do that.”
The schools use all available means to evacuate – their own buses, staff cars, but many of the kids will have to walk out. “It’s important the kids practice this system, as they take home the messages to their parents. Ideally people should be practicing their evacuation monthly, as roads might change due to maintenance work, or be impassable for any other reason.”
“They wont have time to go and retrieve anything. They will get what they have and just go.”
Ken Parrish describes the appraoch as:” multi layered defence with back up.”
“Our preparations are better than most counties,” Ken says, but he isn’t boasting. “We are energetic and robust and we’ve won awards for our education and planning.”
The warning system is focussed on the chance of a lahar caused by an earthquake, which are common in the region. But the system, including the sirens, is designated “all hazards.” Floods, fires, all weather related emergencies, chemical spills, nuclear accidents, snow emergencies, and that most modern and unfortunate human hazard known by emergency managers as “the active shooter.”
So, what happens if the technology fails? The public must be prepared for that too. They should know from their training, practicing and available literature, that if the ground shakes it is possible a lahar was generated and they should leave the region, without waiting for a warning.
The “Big Shakeout” that was practiced by 750,000 people in Washington State on October 18 (and millions more in a dozen US states, Canada, Italy and New Zealand) warns that if the vibrations occur for more than about two minutes, then the public should assume the worst, and not wait for a warning about a lahar, or other emergency. They are very real issues in this part of the world.