Protect Our Streams


Our floodplains and riparian areas are not just a location for flood problems. They also perform some very valuable natural functions.

Probably the most important natural function of the area’s floodplains is to provide habitat for aquatic species. Unfortunately, aquatic species in the Chehalis River Basin are significantly diminished from their historic level. Salmon habitat in the Basin already is degraded by 44%–78%, depending on the species. Other species, like the Oregon Spotted Frog, could soon be listed under the Endangered Species Act.

Don’t damage habitat or any of the valuable natural floodplain functions. Check with the Community Development Department at 360.740.2696 before you build, alter, or improve your structure, or alter the regrade, or fill on your property. We can tell you if you’re in a floodplain, buffer zone, or other critical area and what rules are in effect.

Help clean up our streams. Don’t dump garbage, oil, grease, pesticides, or other pollutants into storm drains, ditches, or streams.

To see what species live in your immediate area, checkout the Washington Department of Fish and Wildlife Priority Habitats and Species (PHS) click here.


Other areas important to many species’ habitat are wetlands. They also help attenuate flooding by storing floodwaters. What can be done in wetlands is regulated in Chapter 17.38, Article III. Click here to see a map of our wetlands.

Lewis County enforces several regulatory approaches to protect floodplain habitats, in addition to floodplain regulations that discourage development. Habitat protection rules are found in the Critical Areas Regulations in Chapter 17.38, Articles IV(B) - Fisheries Habitat and IV(C) - Wildlife Habitat.

Chapter 17.38 and the Shoreline Master Program set requirements for building in stream buffers – areas within a certain distance of a channel. A map of these areas can be found here.