Floods trail would trace route of natural disaster

By WALT WILLIAMS, Chronicle Staff Writer

Picture the waves of a great lake lapping against the eastern flanks of the Bitterroot Mountains.

The lake's southern tip stretches past Hamilton, while its northern shore reaches over Thompson Falls into Idaho.

This lake holds as much water as Lake Erie and Lake Ontario combined. It is so deep that Missoula is drowned under 950 feet of water. At its deepest point, 2,000 feet of water covers the lake bottom.

Now imagine the waters of the lake catastrophically draining in a matter of two or three days, spilling out the equivalent of 10 times the combined flow of the world's rivers into northern Idaho.

The flood scours valleys and carries boulders over three states until finally pouring into the Pacific Ocean.

Such an event really did happen more than 13,000 years ago during the last ice age. There may or may not have been people around to witness it -- that much is debatable -- but regardless, the massive flood has its own fan club.

"It's a Hollywood disaster movie that really happened," said Jim Shelden, regional geologist for the U.S. Forest Service in Missoula.

The Glacial Lake Missoula floods were a little-known catastrophe until recently. Articles about the disaster have started cropping up in newspapers and popular magazines in the past few years, and crews from the PBS science show "NOVA" are filming a future show about the floods.

Some people see the disaster's dawning popularity as an economic opportunity for Montana and other northwestern states. A bill now before Congress would appropriate up to $500,000 a year for the creation of an Ice Ages Floods Trail that would allow tourists to follow the course of the catastrophe, from Missoula to the Washington shoreline.

Not that it's been easy. Both bad timing and opposition from at least one group seeing the trail as a government land grab have held up the bill. But it looks closer to passage now than it ever has.

"It's just a great story and it's something we can tell the world about us," said Larry Lambert of the Missoula chapter of the Ice Age Floods Institute. "It's who we are."

BIG FLOODS

Montana was very different place when Glacial Lake Missoula first formed around 18,000 years ago. The northern part of the state was more like Antarctica, with a great ice cap stretching down from Canada.

An ice dam blocked the Clark Fork River's drainage in the Idaho panhandle, allowing the lake to form. The dam itself must have been enormous -- at its height, it held back 2,000 feet of water. Hoover Dam, by comparison, is 726 feet tall.

Still, the ice dam couldn't hold back that much water forever. It gave way spectacularly, dumping the entire lake into Idaho's valleys. The resulting flood swept down into the Columbia River and out to sea.

Along the way, the flood carved out Washington's Channeled Scablands and steepened the walls of the Columbia River Gorge. It picked up boulders in Montana and deposited them in Oregon.

Anyone standing in the course of the flood would've been in for a terrifying sight, according to Shelden. The first thing the person would've noticed was a gust of wind, like a sandstorm, as the great mass of water displaced the air before it.

Soon an enormous sloping wall of water would have come thundering toward the person, its base a boiling broth of mud from all the topsoil the waters had picked up.

"Once you were where the water was on the move, things would have probably gotten pretty ugly," Shelden said.

Such a flood didn't happen once, but dozens of times as the ice dam broke and was rebuilt by the advancing glaciers, creating a new glacial lake. The exact number of floods is unknown, but the phenomenon ended around 13,000 years ago as the ice sheets retreated.

The event was so spectacular that the geologist who first proposed it in 1923, J. Harlen Bretz, was ridiculed by his colleagues, according to author David Alt in his book, "Glacial Lake Missoula and its Humongous Floods."

Geologists usually seek out slow, gradual processes to explain natural formations, and what Bretz suggested was hardly that.

It wasn't until roughly 20 years later than Bretz was proven right. Geologist J.T. Pardee showed in a paper that Glacial Lake Missoula had suddenly emptied, giving Bretz the source of water for his floods.

TRAIL PROPOSAL

Few people other than geologists knew about the floods until a few years ago. At the that time, a group of government employees came together to pitch an idea of using the story of the floods as a way to draw tourists to Montana and the other northwestern states, Shelden said.

Government employees are not allowed to lobby, so they appealed to private citizens. In 1995, a volunteer group called the Ice Age Floods Institute was formed to promote awareness of the floods.

It's true not many people know now about about the floods, said Dale Middleton of Seattle, a retired librarian who is now president of the institute.

"When the facts are presented to them, or they slowly pick up on this or that aspect of the story, I think they're overwhelmed with the scale and the volume of the floods and what the floods did in shaping the landscape," he said.

The institute's big project is establishing an Ice Age Floods Trail, which would start in Missoula, run through western and northwest Montana, and cross Idaho, Oregon and Washington before ending at the ocean.

The idea is similar to that of the Lewis and Clark Trail, but where that is based in history, "the trail we are proposing is from natural history," Middleton said.

"Trail" actually is a bit misleading. The route would follow existing roads and highways, with a series of interpretive signs and centers telling the story along the way.

Still, the term drew the ire of one Montana group -- Middleton wouldn't say which one -- that saw the proposal as a federal land grab.

Lambert, a hotel owner from Missoula, said the group has nothing to worry about. He wouldn't be involved if it meant increased powers for government.

"That has been my stance from the first minute I got involved in it," he said.

The U.S. House bill that would fund the proposal does allow for the government to acquire 25 acres of land, but only from willing sellers or by donation or trade.

The bill was first introduced in the House two weeks before the Sept. 11 terrorist attacks, but the institute decided not to push it further because of events of the time. It was recently reintroduced and gained the support from lawmakers in every state along the trail except Montana, but no vote has been taken on it yet.

Lambert is confident the trail will bring tourists to Montana. They may not come exclusively for it, but he compares it to the Museum of the Rockies in Bozeman: Few tourists probably travel to the city only for its museum, but knowing it's there makes the city that much more attractive.

"That is just one more exciting thing they have, and one more reason to enjoy their trip to Bozeman," he said.

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