City assessing landslide-hazardous areas of Kirkland

This slide in 2010 threatened multiple homes and an access road on Goat Hill in north Kirkland.  - Reporter file photo
This slide in 2010 threatened multiple homes and an access road on Goat Hill in north Kirkland.
— image credit: Reporter file photo

The city of Kirkland is currently assessing the risk of landslide hazardous areas.

City Manager Kurt Triplett said although they are examining neighborhoods designated as landslide hazardous, the risk is “nothing of the same magnitude” as the Oso landslide.

“What we’re trying to assess is whether there is more to be done,” he said.

After they are done they will present the city council with a set of recommendations for them to consider, he said, which is expected to occur during the fall.

Right now, Kirkland residents who want to find out if they live in a landslide-hazardous area can check with a city map. If they want to find out how high the risk is for an actual landslide on their property, they will have to do their own homework.

As the risk assessment is being made by the city, King County recently announced it is seeking federal funding to update its 24-year-old map of unincorporated areas considered landslide hazardous. Part of the update will include a risk assessment of those areas. Numerous Kirkland neighborhoods were a part of unincorporated King County during the 1990s when the old map was drawn but those areas will now be left out.

One of those neighborhoods is Goat Hill near Juanita Beach Park, which suffered a landslide in 2010, forcing nine people to evacuate their homes. The Department of Transportation determined the landslide was caused by drainage issues and soil erosion.

The city is also reaching out to residents to discuss ways in which they can reduce soil erosion and landslide risk on their property. The Finn Hill Neighborhood Alliance will have landslide experts attend its regularly scheduled meeting for June 25 at Finn Hill Middle School in order to address those concerns.

Goat Hill was included by the city of Kirkland in a proposed annexation area map in 2004. At the time, it was considered landslide hazardous. The larger neighborhood, and more specifically the steep slopes on west side of Finn Hill, were also included on both the county and city hazardous maps. The majority of the area is located in and around Big Finn Hill Park, O.O. Denny Park and Saint Edward State Park in Kenmore. But many of the houses in the Holmes Point area of Finn Hill are also included.

In 2004, the city of Kirkland also came out with a map of landslide-hazardous areas located within the old city boundaries as part of their comprehensive plan. It includes areas like Crestwood in what was considered the North Juanita neighborhood, though much of the land is either open space or public land.

Kirkland and King County used the same criteria for their maps when designating an area to be landslide hazardous. One of the criterion is a history of landslides, which is determined either by records or the topography, according to John Bethel, a geologist with the King County Department of Natural Resources and Parks. The other criteria included were geologic factors that make the area predisposed to landslides, such as clay soil, exposed hillsides or hillsides with drainage.

Triplett said the city’s code requires developers to demonstrate it is safe for them to build, usually done by hiring environmental engineers. They also have to sign a waiver acknowledging that they are building on a landslide hazardous property.

After the Oso landslide the city received calls from concerned residents worried about their own homes, according to Patty Hooper, the emergency manager for the city of Kirkland. While properties have to conform to city building codes and the hazard map can act as a reference, Hooper said residents need to take steps to maintain their property in order to mitigate potential landslides.

“Like all places there are inherent risk when people intersect with nature,” Hooper said. “Whether you’re going to buy a home or rent a property, you have to be aware of that risk.”

She said residents should look for signs of landslide conditions like eroding slopes, sagging utility lines or significant cracking in the pavement.

Finn Hill is a neighborhood where landslides are a concern.

Although some areas in the state are monitored by the U.S. Geological Survey and the Washington State Department of Transportation, the majority are not. Additionally, hazard maps designate areas where landslides can occur, but they don’t account for how likely they are to happen.

There is a fundamental difference between a landslide-hazardous area and an area with a high-risk for landslides, according to David Montgomery, a geologist at the University of Washington.

“I would view the spirit of the mapping as basically saying, ‘Hey, here’s a place you might want to have a closer look to see how big the risk is,’” Montgomery said. “A hazard, one would think, may potentially subject the land to that kind of a thing [landslide] happening. It’s the kind of thing to me, as a geologist, that is a yellow flag, not a red flag, something you’d want to get more knowledge of and get a geologist’s opinion of.”

For example, Montgomery said that a property can be designated as landslide hazardous because it is located on a steep slope, but if it is built on very stable rock or lacks drainage, the risk would be low. On the other hand, he said, if it is on a weak slope and has evidence of ancient landslides, the risk is much higher.

Montgomery added that the risks can be mitigated by how the property is developed, such as building a retaining wall, shoring up the slope or controlling the drainage to prevent erosion.

If insurance is a measure of risk, then the risk of a landslide on Finn Hill is not a concern for some Kirkland residents like Ken Kehle, who has lived in the same house since 1959. The area where Kehle lives is included in the county map from the 1990s. He is a retired insurance agent and has never considered insuring the house for landslides, which is not included in homeowner’s insurance. Although major insurance carriers like Liberty Mutual do not offer landslide insurance coverage in Washington, Kehle said a homeowner can get a Difference in Conditions policy through an insurance broker.

Kehle told the Reporter in May his property suffered a small landslide in the late 1960s after he installed a tennis court on the lot he owns next to his home. During the process, he removed dirt from a hillside at the edge of his property and it caused seven feet of dirt to collapse from the hill after heavy rainfall. Afterwards, he took precautions to prevent further problems by carving out a terrace on the hill, planting more trees and removing bad soil or clay on the rest of his property.

“You get smarter,” he said.

At the same time, he’s never worried about a major landslide due to mutual cooperation between property owners. He said this lessens the worries, since all neighbors have incentive to ensure the surrounding properties are stable.

“Neighbors just work it out,” he said.

In dark grey are the areas that are landslide hazardous on Finn Hill and Goat Hill in Kirkland.

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