Chehalis River Surge Plain Natural Area Preserve

Chehalis River Surge Plain
This large wetland area is spread out at the lower end of the Chehalis River, just upstream from where it empties into Grays Harbor. Sitka spruce and western redcedar thrive in the wet soils where fresh and salt water mingle on this 4,494-acre site. This preserve contains the largest and best quality tidal surge plain wetland in the state, including sloughs that shelter young salmon and other fish. The surge plain also supports osprey, bald eagles, and state-listed sensitive Olympic mudminnows. Vegetation communities represented in the Chehalis River Surge Plain preserve are Sitka spruce/red-osier dogwood/skunk cabbage vegetation, lady fern coastal herbaceous vegetation, softstem bulrush herbaceous vegetation, red-osier dogwood–willow species shrubland, Lyngby’s sedge herbaceous vegetation, and cattail surge plain herbaceous vegetation. 
Features Protected: Freshwater tidal surge plain wetland and vegetation communities, bald eagle, and Olympic mudminnow  
Ecoregion:  Northwest Coast (Grays Harbor County) 

Science, Research and Monitoring

Public and private universities, other research institutions and individual researchers may contact DNR to propose a research project at the site. If you are interested in pursuing research at Chehalis River Surge Plan NAP, please contact David Wilderman, natural areas ecologist, at

Environmental Education and Public Access 

hikers on trail at view areaChehalis River Surge Plain NAP is a place for discovery and respite. A three-and-a-half mile trail follows an old railroad bed and offers a glimpse of the wild Chehalis River to walking enthusiasts, families, and school classes. Views into the winding waterways reveal plants and animals that like their habitat wet, wetter, wettest! Along the trail, colorful interpretive signs tell stories about the natural systems at work in the surge plain, and the plants, bugs, fish, and animals that depend on this place where the seawater meets the river. 
The first half mile of trail is barrier-free yet rustic compacted gravel, leading to an observation platform at Preacher’s Slough. A rougher-surfaced interpretive trail continues for 3 miles along Blue Slough. In addition to the trail and signs, the site offers toilet facilities and a parking lot at the Preachers’ Slough access. The preserve includes two water-access sights for small hand-launched watercraft, one at Preacher’s Slough (past the first parking area) and the other off of Blue Slough Road. 
“Navigating the Chehalis River Surge Plain” Teacher’s Guide
This interdisciplinary educational guide is designed to help teachers and their students explore one of our state’s outstanding natural areas, the Chehalis River’s unique tidal surge plain wetland. Activities provided in this guide help students explore the estuary environment where fresh and salt water systems come together, and understand the importance of wetland functions. The guide offers in-classroom preparatory exercises, onsite activities, and post-visit follow-up.
For more information, contact the DNR Pacific Cascade Region natural areas manager. 

Directions to the Site

The preserve boundary includes much of the flood plain area between river miles 2.9 and 10.3 of the Chehalis River. From Montesano, at the junction of U.S. 12 and Highway 107, travel south and west on Hwy 107 for 3.9 miles. Turn right at Preacher’s Slough Road. Trail parking and toilet facilities are on the left, and water access is further down the road. 
A Washington State Discover Pass is required for parking at this site. This funding helps DNR manage these important natural areas across the state.