GEOLOGIC HAZARDS AND CRITICAL AREAS ORDINANCE UPDATE, LEWIS COUNTY, WA

A review of geologic hazards in Lewis County, WA was prepared for updating the critical area ordinance. Geologic hazards in Lewis County include volcanic, seismic, landslides, alluvial fans, channel migration, flooding, erosion, and abandoned mines.

Historic development patterns in Lewis County resulted in settlement primarily along the valley bottoms. Volcanic hazard areas where Mt Rainier and Mt Adams will produce pyroclastic flows, lahars, and outburst floods are also along the main valley bottoms. The transition from a natural resource largely timber based economy to a recreation based economy has resulted in increasing development in those valley's subject to volcanic hazards. The conflict between current economic benefits of development and long term risks of catastrophic loss has raised a number of issues that local residents are not well equipped to evaluate. The local community is primarily dependent on studies by the USGS Cascades Volcano Observatory for mapping volcanic hazard areas, monitoring for volcanic activity, and information about risk. A key factor is the reliability of forecasts of future volcanic activity and whether evacuations can be implemented in a way that allows current use and minimizes potential for catastrophe. A volcanic hazard plan is under development by cooperating groups. It can identify at-risk facilities, educate the public, and setup warning and evacuation planning; but cannot fully resolve the fundamental risks.

Past response to natural hazards provides limited assurance that the local community is equipped to address such issues. Historic encroachments onto the river floodplains, channel migration zones, and alluvial fans has left residents with the classic flooding problems. The community response generally has also been classic, control the behavior of the rivers rather than human behavior. There has been limited public recognition that the fundamental problem is our view of rivers as static features, when in fact they are very dynamic features that make structural solutions expensive, failure prone, and in direct conflict with aquatic habitat conditions.

This community provides a classic case of the transition in thinking and approach faced by many small rural communities with a mandate to change the way they look at natural hazards in relation to their own behavior.