You've found the home of your dreams in the forests of Oregon. You've bought a few acres, built a home, planted a garden. Chickens scratch in the wild lupine at the edges of your yard. Hummingbirds scuffle at the feeders outside your window, which overlooks a creek edged with red alder. Chickadees call their dee-dee-dee in the Douglas-firs on the slope above your house.
Life is good.
But one night you awaken with a sense that something is dreadfully wrong. There's a roar and rumble in the distance, and the windows in your bedroom are rattling. It's not an earthquake.
It's a landslide.
This is the nightmare that ruined the homes and ended the lives of five Oregonians last year.
Record rainfall and storms lashed the Pacific Northwest in 1996. Parts of Oregon received seven inches of rain in a 10-hour period. Some areas were drenched with as much as 30 inches. The storms caused extensive flooding and triggered thousands of landslides.
Highways caved in and hillsides slumped. Rivers overflowed. Disasters were declared, and emergency crews spanned half the state.
When the floodwaters receded, though, the fight was on. Environmental groups demanded a ban on clearcutting. Lawyers filed lawsuits. The controversy launched a debate about the connections between logging and landslides, and heated up a conflict about public safety, traditional land use, and private property rights.
The debate was exacerbated by environmentalists who flew over forested areas and reported that nearly all the landslides they found were in clearcut areas. Media reports and editorials fueled the fire by concluding that the environmentalists' claims were correct.
Frightened homeowners accused state agencies, particularly the Oregon Department of Forestry (ODF), which regulates logging on non-federal lands, of hedging the issue and hiding the facts. Researchers who were most familiar with the causes and effects of landslides were under the gun and over the barrel, with reporters, activists and citizens demanding simple answers to complex questions.
No one in Oregon wants another tragedy like the one on Hubbard Creek that left two children without parents. But landslides are more than just mud coming down a hill, and they're not caused only by logging.
"Landslides are natural and can't be stopped," says Stone.
Though they can't be prevented, we have come a long way toward understanding landslides and what causes them. Scientists have studied a vast array of debris flows -- a generic term describing the rapid downhill movement of rocks, soil, water, and vegetation -- from landslides to debris torrents to mudslides. Debris flows vary in speed and water content. Rock avalanches, for example, can travel at speeds greater than 60 mph. Mudslide speed ranges up to 22 mph. The heaviest materials, such as boulders, are carried along at the front of the flow where they do the most damage.
Debris flows are nature's way of and moving soils and rock from one place to another. Though they can do damage, they can also create or even improve fish habitat in streams.
"Periodic disturbance is necessary," explains Gordon Reed, a fish biologist with the U.S. Forest Service research lab in Corvallis. At first, slide material may choke a stream -- but as it recovers, the boulders, gravel, and woody material create new salmon spawning areas, wintering pools, and micro-habitats for other organisms.
But, what about the human factor? While recent deaths in Oregon focused the connection between clearcuts and landslides, many other factors contribute to debris flows. Water, soil composition and bedrock, slope, vegetation, and previous land use -- including road building, clearcuts, and housing development -- all play a role in creating a landslide risk.
Some of the risk can be reduced. Poor management practices, such as clearcutting and road building on steep slopes, can be avoided. However, slides will still happen. As Marvin Pyles, a geo-engineer with the Oregon State University forestry school puts it, "A steep slope will fail with or without human impact."
At this point we know something about how slides work. We know how to assess landslide risk based on slide-triggering factors such as soil type and slope. But is it possible to predict when and where a slide will occur? Though landslides have only recently become a hot topic, scientists have been working on pieces of the puzzle for years.
As the public argument over logging's role in landslides gained momentum, each side began trotting out their scientific weapons: research studies. Meant to inform and enlighten society about the way the world works, science has been reduced to a supporting role in a much larger play.
What are these studies which have gained near-mythical significance? Why can they be used to support either side of a volatile argument? Do researchers disagree about whether logging causes landslides?
Science generally seems rather straightforward: Come up with an idea. Design and conduct an experiment to test the idea. Learn from the results.
Scientific inquiry, though, is not always so simple.
Most studies testing the idea that logging contributes to landsliding do find a higher incidence of slides in clearcuts than in uncut forest. However, some scientists question the methods used in the studies -- it's difficult to see a landslide from an airplane when you're looking down at a slope covered with 200-year-old trees. Others question the core assumptions involving slope stability. Consensus, if it ever existed, is coming unraveled.
While scientists often can describe in great detail how the world works, they still haven't cracked the most complex cases. Predicting landslides is one of these.
"The earth doesn't cooperate in our statistical studies," says Pyles. "It's just not a clear picture. We are forever thwarted in our attempts to get clear answers."
"Landslides for Dummies" just doesn't exist.
The differing results of landslide studies, and the general lack of clarity about how and why landslides occur, leads to a quandary. How can policymakers protect human lives and property without clear guidance from scientists?
When Oregon Board of Forestry members debated that recently in Salem, they asked for guidance from the state's most knowledgeable scientists. Those who restrict activity on a slide-prone slope need to know exactly which slopes are slide-prone.
"You need to recognize that we'll never identify all of them," said Charlie Stone, ODF geotechnical engineer. Classing a parcel of land as slide-prone can be done quickly and inexpensively -- with less accuracy -- or it can be done very precisely, which takes more time and more money.
How much public risk are we willing to accept?
Writing regulations is not as simple as telling landowners that if their ground is steep they can't log there, or telling people they can't build a house on a hill because of the risk of landslides. Regulating one activity to protect another is a calculated risk.
If logging and road building in steep areas can trigger landslides, the dilemma then is the government responsibility to protect public safety weighed against citizens' rights to build homes on land they own, and companies' rights to profit from their land. Protecting one group of people from another becomes a dance, with regulations that step on others' toes.
Buried somewhere deep in the discussion is the question of individual responsibility. If you build your house in a stupid place, you assume the risk of the site. If you recklessly strip the trees and shrubs from a steep slope on your land, you assume liability for people who might drive by or live downhill of your property.
Because government does not legislate against stupidity, though, policy makers must choose among conflicting studies. They must decide which researchers have the best information. And they must weigh the value of public safety against the rights of those who want to live in, work in, and play in the forests of Oregon.
. . . Jen Shaffer, David Hockman-Wert, and Kelly Andersson.