Critical Areas

Silver Lake

Cowlitz County is mandated by the Washington State Growth Management Act to designate critical areas and adopt development regulations to assure their conservation.

Designated Critical Areas of Cowlitz County are wetlands, fish and wildlife habitat, frequently flooded areas, geologically hazardous areas and critical aquifer recharge areas.

Development activity within critical areas or their buffers is required to comply with the Cowlitz County Critical Areas Ordinance.


undefined Opens in new windowWetlands provide numerous valuable functions, including but not limited to providing wildlife and fish habitat, water quality enhancement, flood and erosion control, aquifer recharge and discharge, shoreline stabilization, research and education opportunities and recreation.

Wetlands must be delineated using the Washington State Wetland Rating System for Western Washington: 2014 Update. More information on the rating system can be found on the Department of Ecology's website:

Map Sources

National Wetlands Inventory Maps, US Department of Interior, Fish and Wildlife Service

Fish and Wildlife Habitat 

Fish and wildlife habitat conservation areas perform many important physical and biological functions that benefit the County and it's residents. These functions include but are not limited to providing opportunities for food, cover, nesting, breeding, and movement for fish and wildlife; maintaining and promoting diversity of species and habitat; helping to maintain air and water quality; controlling erosion, serving as areas for recreation, education and scientific study and aesthetic appreciation; providing neighborhood separation and visual diversity within urban areas, sustaining ESA-listed species, and supporting recreational and commercial fisheries.

Map Sources

Priority Habitat and Species Maps, Washington Department of Fish and Wildlife

Forest Practices Application Mapping Tool (FPAMT) (

Natural Heritage Program | WA - DNR

Anadromous and resident salmonid distribution maps, Washington State Department of Fish and Wildlife

Natural Resources Conservation Areas | WA - DNR

Frequently Flooded Areas Home in Floodplain  Opens in new window

Frequently flooded areas - also known as Special Flood Hazard areas and Floodplains/Floodways - pose a risk to public and private property and public health. Regulation of these lands protects human life. It also minimizes loss and the need for rescue and relief when flooding occurs.

2023 Floodplain Management Ordinance Update

The Board of County Commissioners adopted an updated Floodplain Management Ordinance effective November 21, 2023.  The updated ordinance can be found at this link: Floodplain Management Ordinance CCC 16.25 -2023 Update

Am I in a floodplain? Where are flood risks?

Building in the Floodplain

Elevation Certificates - to be prepared by Washington State Licensed Surveyors

Flood Insurance - It usually takes 30 days for a policy to go into effect.

Emergency Management

Are you Flood Ready? 

Cowlitz County Flood Hazard Management Plan

Natural and Beneficial Functions of Floodplains

Drainage and Stormwater Resources

Geologically Hazardous Areas 

Pacific Way LandslideGeologic hazards pose a risk to public health and private property and to the natural systems that make up the county's environment. These lands are susceptible to landslides, erosion, seismic, volcanic and mining hazards. Building and development practices should consider topographical and geological features. Future development should be directed to more geologically stable areas and restricted on unsuitable ground. Regulating these lands, and avoiding or minimizing alteration of geologic hazards, is necessary to protect the health, safety and general welfare.

Seismic Hazard Areas:

Seismic hazard areas are any area subject to:

  • Underlying deposits indicative of risk of liquefaction during a seismic event;
  • Areas subject to slope failure, including lateral spreading, during a seismic event;
  • Areas subject to surface faulting during a seismic event;
  • Areas that are at risk of mass wasting due to seismic forces.

All development within seismic hazard areas must comply with the adopted International Building Code or International Residential Code.

Map Sources

Liquefaction Susceptibility and Site Class Maps of Cowlitz County, Open File Report 2004-20, Washington State Department of Natural Resources

Mine Hazard Areas:

The earliest recorded coal discovery in the State of Washington was made in 1833 near the junction of the Cowlitz and Toutle rivers (1).

Coal mining primarily occurred within the north-central part of Cowlitz County. Mine hazard areas are those areas underlain by or affected by mine workings such as adits, gangways, tunnels, drifts, or airshafts, and those areas of probably sink holes, gas releases, or subsidence due to mine workings. Locations of mine hazard areas may be known or unknown, based on best available information.

(1) Culver, Harold E., The coal fields of southwestern Washington: Washington Geol. Survey Bull. 19, p. 16, 1919.

Volcanic Hazard Areas:

The eruption of Mt. St. Helens on May 18, 1980, was the most destructive eruption in the history of the United States with respect to economic impact and loss of life and property. Portions of the Mt. St. Helens National Monument are within Cowlitz County, and the mountain is the source of four major river drainages that pass through the County to the Columbia River.

Scientists cannot precisely predict when Mt. St. Helens will erupt, the force of future eruptions, nor the area of land that will be affected. However, research does provide a record of areas that have been affected by volcanic activity throughout the volcano's history and the types of hazards that have occurred.

Cowlitz County has identified Volcanic Hazard Areas based on the Mount St. Helens Flowage-Hazard Zones Map prepared in 1995 by the United States Geological Society. These hazard areas can be subject to pyroclastic flows, lava flows, debris avalanche, and inundation by debris flows, lahars, mudflows, or related flooding resulting from volcanic activity.

Map Sources

Mount St. Helens Flowage-Hazard Zones Map, 1995 USGS

Erosion Hazard Areas:

Erosion hazard areas are those areas identified by the U.S. Department of Agriculture's Natural Resource Conservation Service as having a "severe" or "very severe" erosion hazard. Erosion hazard areas are also those areas impacted by shore land and/or stream bank erosion and those areas within a stream's channel migration zone.

Map Sources

NRCS Cowlitz County Soil Survey

Landslide Hazard Areas:

Landslide hazard areas are areas potentially subject to landslides based on a combination of geologic, topographic, and hydrologic factorrs. They include areas susceptible because of any combination of bedrock, soil, slope (gradient), slope aspect, structure, hydrology, or other factors. Modification of topography and vegetation in landslide hazard areas is carefully regulated in order to preserve long-term stability of sensitive slopes, reduce erosion potential and stormwater runoff, and preserve related ecological values.

Map Sources 

Department of Natural Resources Landslide Study 2006 - Digital Landslide Inventory, Cowlitz County, WA. Wegman, 2006 (I-5 Corridor Study)

WGS Geologic Information Portal

Critical Aquifer Recharge Areas

Aquifer recharge areas perform many important biological and physical functions that benefit the county and its residents, including but not limited to: storing and conveying groundwater. Protection of aquifer recharge areas is, therefore, necessary to protect the public health, safety and general welfare.

Map Sources

NRCS Soil Survey Cowlitz County

Historic Preservation

Historic Preservation County Code

Department of Archeology and Historic Preservation Wisaard Maps