City to use updated geological data to amend zoning process

The data was collected by a University of Washington research team after a year-long field study.

The City of Kirkland began a city-wide zoning amendment process this week that will review updated geological data and maps that outline landslide and earthquake hazard areas within its limits.

The public presentation Monday evening at City Hall was led by Kathy Troost, a University of Washington earth and space science professor who presented her research team’s findings after a year-long field study. City staff used the presentation to mark the beginning of their amendment process that will use this study to improve zoning codes in upcoming months.

The UW GeoMapNW Center team used light detection and ranging (LiDAR) to collect field data and create a 3-D map. LiDAR is similar to radar, but instead of radio waves, it uses quick light bursts to collect precise distance measurements.

LiDAR has been used in Kirkland since 2001 but the team’s new tools helped them create maps with nearly eight times the previous resolution.

The maps highlight different danger areas that are vulnerable to earthquake impacts with the main hazards being landslides and liquefaction.

Landslides are most dangerous around hillsides, while liquefaction is particularly dangerous around valley bottoms where water-saturated sandy deposits can behave like a liquid when an earthquake strikes.

The project was peer reviewed by Associated Earth Sciences Incorporated, a local geotechnical engineering consulting firm.

“We feel confident about what’s in our map,” Troost said, “but there’s definitely some data gaps out there. So there’s room for improvement down the line.”

According to Troost, the project didn’t provide new or unexpected information, but further refined the previous data, which will help homeowners prepare their property for a disaster.

Troost recommended residents prepare an earthquake kit, look for cracks and other signs of movement in and around their homes, monitor national landslide forecast models and retrofit their homes.

“These things will happen, but we can’t tell you when and where,” she said. “These new products are significant improvements over what was previously available.”

The presentation was recorded and will eventually be available on the City of Kirkland website along with all the maps and geological hazard information.

City staff will consult the research as they amend zoning codes to better align with the updated geologic hazard zones.

The city doesn’t have any projections for what exactly the amendments will be, but staff aims to use the maps and reports to update development codes on a site-by-site basis, according to David Barnes, a senior planner in Kirkland’s planning and building department.

“Information is a vital tool for emergency preparedness,” said council member and public safety committee chair Penny Sweet, in a press release. “The council invested in this geo-hazard mapping project to help residents, developers, engineers, architects and first responders understand where the risks are in our city so we can plan and prepare for any scenario.”

Kirkland is one of the first cities in the area to use this geo-hazard mapping project, according to the press release.

AESI is also working closely with the city to provide expert knowledge and help city staff interpret the geotechnical reports.

“I’m not a technical expert on geotechnical matters,” Barnes said with a laugh. “They’ll be helping the decision makers understand what we need to do and what gaps we may have in our code to make it better.”

The city will host two study sessions with AESI on Jan. 11 and sometime in February. The sessions are open to everyone but won’t have a public comment period.

The city will then host a joint-hearing in March with the Planning Commission and Houghton Community Council where residents can ask questions and comment on the new amendments.

Barnes said they hope to make their amendment recommendations to council by May next year.

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