Harry Truman died for his belief.
Warnings that Mount St. Helens could erupt at any time did not faze the owner of a mountain lodge. He believed that the miles of forest standing between his home and the summit would block any geologic hazard that came his way. The power that might be unleashed by a volcanic eruption was beyond his comprehension. When the 1980 eruption came, he perished.
“Solid as the ground we stand on,” goes the old saying. We regard the ground we walk on – and build our homes and infrastructure on -- as solid, firm, stable and immovable. That perception ignores the geologic reality. The scale of geologic movements can defy our comprehension.
A year ago, on the morning of March 22, an incomprehensibly powerful geologic event took the lives of 43 people in the community of Steelhead Heaven at Oso. The Hazel landslide, as geologists refer to it, unleashed a wave of mud, soil and chunks of sediments nearly 70 feet high.
The existence of the hazard now commonly known as the Oso mudslide had been known for more than 50 years. Yet warnings of the risks posed by this mountain of unstable debris never reached the level of importance and significance given to the rumblings of Mount St. Helens, which failed to cause Harry Truman to leave.
Something has gone terribly awry.
There are numerous landslides in the state, especially west of the Cascade Mountains. While geologic maps identify and delineate some of them, there is no complete inventory of landslides in urban and rural areas. Compiling such an inventory, using latest technology, would be a first step in facing up to the risk posed by landslide hazards.
While the Oso tragedy struck in rural area, cities have huge reasons to worry. The high population density of urban areas makes it imperative for decision-makers to address the landslide risk. Rural areas, for the most part, escape such scrutiny. But even in those urban areas where the danger has been acknowledged, there are daunting challenges.
What should the state and local governments do with existing developments within or near landslide hazard areas?
Current regulations require scrutiny of development plans in urban landslide hazard areas, but the demand for more living space in urban areas tends to dilute the evaluation process. That’s because we see in concrete and steel the power to counter the force of geologic hazards of landslides. To a certain degree, and at a vastly smaller scale than would have been required at Oso, skillful use of concrete and steel has, in fact, tamed the potent power of some landslides.
However, the high cost of concrete and steel limits such applications. In a residential setting, elaborate bulwarks generally are not feasible for the average homeowner. Homeowners insurance typically does not cover damage to the property from earth movements. So when a major landslide does occur in a developed area, litigation ensues and for the most part, we as taxpayers end up footing the bill.
There’s an example in the Santa Monica area of Los Angeles County of what can happen. A development boom there came to a screeching halt following one particularly heavy rainy period that spawned landslides. The ensuing litigation ended up costing taxpayers several tens of millions of dollars. As a result, political will of the community led the county to institute comprehensive regulations. Now, the landowner of a proposed development has to commission a study by an engineering geologist and a soils engineer to show that the development will be safe and will not harm adjoining properties. The county reviews the application and then decides on the merit of the proposal.
How should local regulators deal with neighborhoods like Perkins Lane in Seattle? This neighborhood, and similarly situated neighborhoods in the Puget Sound area, could be wiped out in catastrophic landslide. Worst, if the triggering event is an earthquake in rainy season, landslides will occur simultaneously all over. It’s a frightening scenario.
Not all events follow the example of Oso. A slow-moving, massive landslide in Kelso, Cowlitz County, left 137 homes either destroyed or condemned. But at Rolling Bay in Bainbridge Island, a sudden slide destroyed one home and took four lives in 1997. The scenarios that have played out in many other landslides underscore the diversity and unpredictability of landslides.
There are continuing efforts to unravel the mystery of triggering mechanism of landslides that could help in predicting a landslide. But until the required resources are allocated and research results become available, many communities remain at risk.
Sooner rather than later, we as a community must decide the fate of the neighborhoods at risk. To aid such decision, we must identify neighborhoods situated in landslide hazard areas, categorize the landslide risks and take action.
It would be a most suitable tribute to the 43 who perished in the Oso landslide, and the heroic efforts of the emergency responders, for all of us to make a concerted effort to do whatever we can to prevent such tragedies.
