As searchers look for the last of the missing in Oso, Washington, where a massive landslide virtually wiped out the small community, it’s becoming more obvious that authorities knew about but failed to fully heed the warnings of scientists that such a disaster was a real threat.

Not only that, they even considered – but then rejected – a suggestion that they buy out home and business owners whose properties lay just across the Stillaguamish River from a steep hill that had fallen away several times before.

The Seattle Times newspaper reported this week that Snohomish County officials analyzed the situation, finding that the costs of a buyout “would be significant, but would remove the risk to human life and structures.”

Instead, they decided to build a wall intended to stabilize the slope, leaving existing structures in place and allowing more to be built. Eight people in those newer homes are dead or missing from the landslide, including four children, the newspaper reported.

Experts studying the most recent slide – and the several that preceded it over the years, particularly one in 2001 – say this was a fatal mistake.

“[T]o my mind this was [a] foreseeable event, and as such the disaster represents a failure of hazard management,” writes Dave Petley, a professor of hazard and risk at Durham University in the United Kingdom and author of The Landslide Blog, which is hosted by the American Geophysical Union.

“The 2001 landslide left material high on the hillside that was sitting above a scar that was far too steep,” Dr. Petley writes. “The LIDAR [Light Detecting and Ranging] data suggests that the runout from such a collapse could be extensive. In that context I find the decision to build new houses at the foot of the landslide to be very surprising.”

In retrospect, some residents in the area are surprised as well … some of them furious that they weren’t warned of the threat.

Davis Hargrave, a retired architect who lost dozens of neighbors and his weekend home, said knowing the county took the threat as seriously as it did would have prompted him to ask many more questions.

“We are not a bunch of stupid people ignoring warnings,” Mr. Hargrave told the Seattle newspaper. “We all make risk assessments every day of our lives. But you cannot make a risk assessment on information you do not have.”

“If I’d known it was that dangerous, I would have moved in a heartbeat,” said Dale Dunshee, who sold his property about three years ago to a couple who were not at home when the slide hit March 22.

As of Friday evening, the number of those killed had risen to 30, with 29 identified. The number of missing has dropped to 13.

The search effort – first for survivors, now for the remains of the missing – has been brutally tough. Searchers fight their way through deep boot-sucking muck, trees, crushed buildings and vehicles, and other debris. After their shifts, they must be decontaminated of the flooded waste from septic tanks, fuel tanks, and other sources.

About an inch of rain is forecast this weekend at the Oso mudslide where a few dry days this week have helped searchers looking for bodies.

The National Weather Service says steady rain could cause the Stillaguamish River to rise by about half a foot by Sunday morning.

The rain and rising river complicate recovery work in the debris field and add to the flooding caused when the landslide partially blocked the river. Melting mountain snow from rising temperatures also may cause the river to rise.

Meanwhile, the debate continues over the effect clear-cut logging in the area might have had on hillside stability.

Landslides have followed logging in that area at least four times, KUOW, the NPR affiliate at the University of Washington in Seattle, reported.

"There was cutting in the 1940s; it failed in the '50s. There was cutting in 1960, then it failed in the mid-'60s. There was cutting in '88; it failed in '91. There was cutting in 2005, and it failed in 2006 and in 2014,” said geomorphologist Paul Kennard, who worked for native American tribes in the 1980s and now works for the National Park Service at Mt. Rainier.

Whether government agencies or landowners can be held liable for damages caused by landslides in Washington state is highly dependent on the facts of each case. Generally, governments are not liable except in narrow circumstances, such as if an agency specifically tells the residents they're safe before a slide, or if an agency takes it upon itself to fix a hazard but actually makes things worse.

"This is a terrible tragedy and still very fresh. But it is nonetheless my concern that people turn to the government as the insurer of last resort," said David Bruce, a Seattle lawyer who represents governments in landslide-liability cases. "The fact of the matter is that in the Puget Sound basin and the foothills of the Cascades, there's a tremendous amount of landslide-prone areas. The government isn't here to prevent people from suffering natural catastrophes."

On Sunday, the Federal Emergency Management Agency (FEMA) Administrator Craig Fugate and Department of Homeland Security Secretary Jeh Johnson are scheduled to visit the site to survey the damage and meet with victims and emergency responders.

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Fresh search and rescue teams from FEMA arrived Friday, along with 20 highly trained search dogs.

This report includes material from the Associated Press.