Washington Geological Survey shows Thurston County landslide inventory as residents press for stronger CAO protections
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Summary
At a Jan. 7 Planning Commission meeting, Washington Geological Survey staff demonstrated new high-resolution landslide mapping and a public portal intended as a screening tool for site investigations. Multiple residents urged the county to use the data to strengthen the Critical Areas Ordinance and to limit harms from upslope forestry and land-disturbing activities.
Washington Geological Survey staff presented a new, county-scale landslide inventory and public-facing mapping portal to the Thurston County Planning Commission on Jan. 7, emphasizing the product is a screening tool that identifies past landslide deposits and other hazard features for further site-specific review.
"We are tasked with using the best available science to identify and map landslide hazards," said Mitch Allen of the Washington Geological Survey during the presentation, describing mapping methods that rely on high-resolution LiDAR, field checks, and a review process involving licensed engineering geologists. Allen said the inventory draws polygons for landslide deposits, fans and rockfall and assigns confidence ratings that are visible to portal users.
The presentation followed several public comments urging tighter local protections tied to the Critical Areas Ordinance (CAO). "I ask that the updated CAO adopt performance-based protections to ensure upslope activities in geologically hazardous areas do not harm downslope homes, infrastructure, watersheds, and fish habitat," said Christy White, a resident who described a past state-logging-related landslide that nearly destroyed a neighbor's bridge. White asked the commission to require county monitoring of logging and major land-disturbing activities, mandatory geotechnical analyses where slope failures could affect people or infrastructure, and a standard that prevents any net increase in landslide or erosion risk.
Other public commenters described mapping and permitting challenges. Kyle Willoughby, who said his family has spent "tens of thousands of dollars" and county fees of about "$12,000" pursuing approvals on rural property, called the current CAO-driven permitting process "regulatory paralysis" and argued reasonable use of private property should not routinely require exceptions.
Commissioners and staff asked WGS technical questions about scope and limitations. Allen repeatedly stressed that the inventory documents where landslides have occurred in the past and is intended to flag sites for further study, not to predict future failures. "Our landslide inventories are intended to be a screening tool to identify areas where someone with a trained eye saw something that someone might want to take a closer look at," he said. He also described a separate "recently reported landslides" point layer that documents events not visible in LiDAR (for example, rapid failures captured in news reports or field observations).
County staff and commissioners discussed how the WGS mapping will be integrated into local systems. A staff member said the county is working on a phased GeoData update and that the CAO will be revised to align with the new data so that WGS maps become a primary resource rather than a secondary screening tool. Commissioners asked about mapping of shoreline bluffs and post-fire debris-flow fans; WGS staff said the group maps fans after fires and conducts rapid assessments along with modeling to estimate probabilities for debris-flow occurrence.
Why it matters: Thurston County is updating its CAO and comprehensive plan, and residents and commissioners flagged landslide and related ecological risks as immediate inputs to regulatory updates. Presenters and commentors tied the technical mapping to policy choices — for example, whether the county should require pre-approval monitoring of logging activity, site-specific geotechnical studies, or stronger code provisions to avoid downstream harm.
The meeting record shows the commission accepted the WGS briefing and proceeded to later discuss docket prioritization and code updates where CAO integration will be addressed. The commission did not take a final action to adopt regulatory changes at the Jan. 7 meeting; staff indicated CAO revisions and phased GeoData integration will proceed as part of the docket process.
