Preserving Washington’s biggest and best tidal surge plain

Tucked between Montesano and Cosmopolis near the mouth of the Chehalis River rests Washington’s largest and highest-quality coastal surge plain wetland.

The Chehalis River Surge Plain Natural Area Preserve is a 4,493-acre site that protects rare plant communities and species that thrive in the estuary environment where fresh and salt water systems meet. It is one of the 94 Natural Areas conserved by the Washington Department of Natural Resources for their high-quality native ecosystems and rare species or communities of species. Visitors to this minimally impacted, rural surge plain can learn about wetland function, use of the area by a variety of species, and the cultural significance of the site.

DNR wants to continue to enhance these opportunities for visitors. That’s why the agency has submitted a $1.5 million Environmental Resilience budget request for the 2019-2021 Biennium to the State Legislature.

A portion of that request for management of DNR Natural Areas will cover invasive weed control and facilities maintenance at the Chehalis River Surge Plain. DNR is also requesting a $55,000 investment from the state capital budget for future trail improvements and bridge and sign installation in the area.


“The Chehalis River Surge Plain gives families and children an incredible opportunity to get outside and enjoy our state’s Natural Areas together,” Commissioner of Public Lands Hilary Franz said. “In a time when we are so often looking at screens, it’s critical for our kids to have opportunities to learn, explore, and play in nature.”

People of all ages and abilities can experience the Chehalis River Surge Plain from the trail and boardwalk that follows an old railroad bed alongside portions Preachers Slough and Blue Slough, two significant side channels along the Chehalis River. They can also launch hand-carry watercraft at one of the small parking areas on the main stem of the Chehalis River and at the smaller Blue Slough parking area.

DNR has poured significant effort into the Chehalis River Surge Plain to make it a fun, safe, and engaging place for visitors, as envisioned during the community planning process that shaped the development of access features. The agency has recently completed several projects to increase accessibility, including the installation of new ADA handrails on Preachers Trailhead Bridge, new signage, new bollards at the Preachers Slough boat launch, and re-grading of Preachers Slough Road with new vehicle pullouts.

“The Chehalis River Surge Plain has come a long way in terms of providing a place for the public to come to enjoy the outdoors and learn about the ecological and historical features of the preserve,” Renee Mitchell, DNR Natural Areas Manager, said. “Although the site has been available for public access for 30 years, it was in definite need of some significant site improvements. In all of its transformation, however, the greatest success I feel is seeing people bring their kids out there.”

This summer, visitors can expect to see fresh gravel on the ADA Shoreline Access Trail and new fiberglass bridges this summer. The agency is also working on new interpretive signs for the three-and-a-half mile interpretive hiking loop.


DNR designated the Chehalis River Surge Plain as a Natural Area Preserve in 1989 to protect rare and high-quality native ecosystems and native species. The area is home to a remarkable variety of wildlife, including the rare Olympia mudminnow, pileated woodpeckers, bald eagles, reticulate sculpins, wood ducks, osprey, and mink. Now is an especially great time of year to visit the surge plains because several species are more visible during the spring mating season.

Throughout the year, families visit the area to walk along the interpretive trail, paddlers launch canoes and kayaks from the Blue Slough Access and Preachers Slough Road, and birders watch for wildlife.

About DNR’s Natural Areas Program
Under the oversight of Commissioner of Public Lands Hilary Franz, DNR conserves nearly 164,000 acres of lands and ecological features in designated natural area preserves and natural resources conservation areas, protecting the highest-quality examples of natural Washington and providing opportunities for research, environmental education, and low-impact recreation. In addition, the Commissioner manages 2.5 million acres of trust lands for public benefit to ensure forested watersheds for clean water, wildlife habitat, recreation access, and wildfire protections. Commissioner Franz also oversees the state’s 3 million acres of aquatic lands, as well as industrial activities within forested areas, statewide geologic information, and forest health efforts.