In Seattle, city officials have a couple initiatives of their own to update local landslide maps, along with the DNR’s help through the new LIDAR technology. The city has been keeping landslide records since the late 1800s, said Susan Chang, Seattle’s geotechnical engineering group supervisor.

“By having a more accurate map, when people come in for permitting, we’re able to say with more accuracy whether or not they’re likely to have a landslide hazard area on their site or not,” Chang said. “And that determines the permitting path and how much scrutiny it gets.”

Municipal planners and builders say that if a piece of land is at risk for landslides, it doesn’t necessarily mean that it can’t be built on. Rather, it triggers more intensive review for building permits and geological assessments to ensure that whatever is built there is safe and doesn’t pose a risk to neighboring properties on a hillside.

“It’s pretty uncommon to find you can’t build there at all,” Pierce County’s Brells said. “Sometimes they have to do mitigation to eliminate the risk.”

That can simply mean removing water from a hillside by funneling it through a trench or pipe. But the requirements can be much more complex. “In some cases, a special foundation design is necessary — like putting a house on soldier piles or needle piles,” Brells said. “That’s a common thing we see.”

Landerholm said building his home on Perkins Lane “was the most difficult project I’ve ever done in my life” because of the engineering involved. To build into the hillside, he said, he had to drill 17-foot piles and also use I-beams for stability.

Today, there’s at least one new home under construction on Perkins Lane, and a handful of properties are listed for sale on the street.

“We call it the Malibu of Washington,” John Wellman, a broker who owns four of Windermere’s local real estate offices, said in reference to the waterfront city in Southern California known for its relaxed, upscale lifestyle. “It’s quiet. It’s the most tranquil place in the city, and as we grow and expand, people are really taking a second look.”

A “for sale” sign on Perkins Lane in 1938 incorrectly states there’s no landslide risk in the hillside neighborhood, which sits along steep bluffs on the edge of Seattle’s Magnolia neighborhood. (Photo courtesy of Seattle Municipal Archives)

The landslide risk at Perkins Lane has been known since the 1930s, DNR’s Slaughter said, and yet developers built a slew of homes on the bluffs anyway, drawn by the spectacular views. A photo from 1938, kept by the Seattle Municipal Archives, boasts of a “best buy, best view” deal on Perkins Lane and falsely warned prospective buyers of “no slides. Civil Engineer says ‘good condition to build on.’ ”

“People are willing to live on steep slopes, like the Puget Sound bluffs, where they trade beautiful views for their personal safety,” Slaughter said. “Living on these bluffs — these bluffs are steep and they calve material regularly, and people are willing to take that risk to have those beautiful views in the [expectation] that ‘well, hopefully it won’t happen in my lifetime.’ ”

Landerholm acknowledges the risk but he comes at it from a different perspective, given his builder’s experience. “You can engineer around most of the critical areas issues,” he said.

Landslide hazard areas and steep slopes “are way, way, way safer after construction than they were previously because [the city is] asking for more stringent engineering and construction practices to pin those buildings down better and reduce the risk, by either strengthening the building or reducing the amount of water that gets into the hillside.”

“From a practicality standpoint, the best thing we could do is pave over every one of those steep slopes — but politically you can’t do that,” Landerholm said. “With paving, you could take all the water that would be a trigger and stick it into a pipe. If you got a gun with no bullets, it's not going to go boom.”

Geologists and city planners have looked to past landslide disasters to learn lessons for the future. After the deadly Oso slide in Snohomish County four years ago, local leaders adopted new regulations for their critical areas with greater setbacks and buffers near landslide hazard areas.

The winter of the Perkins Lane slide, Seattle saw more than 300 landslides, which prompted a task force and an extensive study to assess the city’s risk. Since then, the city has seen a decrease in slides, from roughly 10 to 20 per year about five years ago, to just about five a year in the last few years, said Bryan Stevens, customer service manager for the Seattle Department of Construction and Inspections.

“I really think that with the small number of slides we see each year, even in years where we see heavy rains, it means the regulations and the way we carry them out are effective,” Chang said.

Meanwhile, Bainbridge just updated its critical areas ordinance, and Carr, the city planner, says the trend is toward buffers “getting bigger or staying the same.”

“The bar really is safety — not only safety for you and your family and your structure, but it can’t create slope instability for neighbors,” she said. “It’s somewhat controversial ... there’s a perspective that they shouldn’t be able to get that close to the top of the steep slope and why would the city allow that? I hear that from people. But people who want to buy these properties want to do with them what they want to do and optimize the view. It is a tricky topic. It is a reasonable use of someone’s property and ‘reasonable’ is subjective.

“Obviously, it’s a risk,” Carr added, “and some people are more OK with that risk.”