Chehalis River
Chehalis River Valley (left), Grays Harbor (middle distance) and Satsop River Valley (along bottom)
Map of the Chehalis River watershed
Mouth of the Chehalis River in Washington Show map of Washington (state) Chehalis River (Washington) (the United States) Show map of the United States
Location
Country	United States
State	Washington
Counties	Grays Harbor, Thurston, Lewis
Cities	Aberdeen, Centralia, Chehalis
Physical characteristics
Source
• location	Lewis County
• coordinates	46°27′6″N 123°17′30″W / 46.45167°N 123.29167°W / 46.45167; -123.29167 [1]
• elevation	1,000 ft (300 m) [2]
Mouth	Pacific Ocean
• location	Grays Harbor, Aberdeen
• coordinates	46°57′29″N 123°50′5″W / 46.95806°N 123.83472°W / 46.95806; -123.83472 [1]
• elevation	0 ft (0 m) [2]
Length	115 mi (185 km) [3]
Basin size	2,660 sq mi (6,900 km2) [4]
Discharge
• location	near Satsop, WA [5]
• average	6,425 cu ft/s (181.9 m3/s) [5]
• minimum	440 cu ft/s (12 m3/s)
• maximum	47,000 cu ft/s (1,300 m3/s)
Discharge
• location	mouth (Grays Harbor) [4]
• average	11,208 cu ft/s (317.4 m3/s) [4]
Basin features
Tributaries
• right	South Fork Chehalis River, Newaukum River, Skookumchuck River, Satsop River, Wynoochee River, Wishkah River

The Chehalis River ( /ʃəˈheɪlɪs/ shə-HAY-lis) ^[6] is a river in Washington in the United States. It originates in several forks in southwestern Washington, flows east, then north, then west, in a large curve, before emptying into Grays Harbor, an estuary of the Pacific Ocean. The river is the largest solely contained drainage basin in the state.

History

Last Glacial Period

The river was once much larger during the Ice Age when the tongue of the glacial ice sheet covering the Puget Sound terminated near Olympia and glacial runoff formed a large torrent of meltwater. This carved a large oversized valley that is much larger than the current river could have produced. The river's mouth was out near current Westport until rising sea levels at the end of the ice age flooded the broad Chehalis Valley to form a ria, known today as Grays Harbor.

The glacial sheet tongue is known as the Puget Lobe which, when it began to melt, formed Glacial Lake Russell. The lake drained through the Chehalis River Valley and the slow deposits of glacial sediment raised the depressed valley. ^[7]

Native American

The Quinault Indian Nation and the Confederated Tribes of the Chehalis Reservation are stakeholders of the river. Though the people ceded the lands surrounding the Chehalis River upon the signing of the 1856 Treaty of Olympia, the tribes have retained fishing and hatchery rights. ^[8]

Flooding

December 3, 2007, floods

During the Great Coastal Gale of 2007, a 20-mile (32 km) stretch of Interstate 5 was closed between exits 68 and 88 because of flooding from the Chehalis River, causing the roadway to be under about 10 feet (3.0 m) of water. The recommended detour added about four hours and 280 miles (450 km). ^[9] It was not expected to reopen for several days. ^[10] However, upon breaching a dike on Dec. 5, 2007, ^[11] the water receded more quickly than anticipated. Amtrak train service between Portland, Oregon, and Vancouver, British Columbia, was also disrupted. ^[12] Washington governor Christine Gregoire declared a state of emergency on December 3. ^{[13] [14]}

January 7, 2009, floods

During the January 7, 2009, Pacific Northwest storms, a 20-mile (32 km) stretch of Interstate 5 was closed between exits 68 and 88 because of flooding from the Chehalis River, causing the roadway to be under several feet of water. Since the main east–west mountain passes were also closed during this event, the flooding from the Chehalis River essentially cut off interstate traffic to the Puget Sound area from the south, and no detour was available.

Water rights

The Chehalis River, along with the Dungeness River, is part of only two river basins in Washington state that are granted protections and rights under "in-stream flow regulation". Passed in 1976, the law allows the river the right to maintain its own water levels. Unfettered access to the river is granted to grandfathered "senior" rights holders as they existed before the 1976 rule went into effect; the senior holders mostly consist of tribal communities and farmers. As of 2023 ^[update], there are 93 recorded junior water rights holders, mostly homeowners, in the Chehalis basin. ^{[15] [16]}

Course

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The Chehalis River is the largest drainage basin completely within the state. ^[8] It begins at the confluence of the West Fork Chehalis River and East Fork Chehalis River, in southwestern Lewis County. From there the Chehalis flows north and east, collecting tributary streams that drain the Willapa Hills and other low mountains of southwestern Washington. The South Fork Chehalis River joins the main river a few miles west of the city of Chehalis. The Newaukum River joins the Chehalis River at Chehalis, after which the river turns north, flowing by the city of Centralia, where the Skookumchuck River joins. After Centralia, the Chehalis River flows north and west, collecting tributaries such as the Black River, which drains the Black Hills to the north, then in the Chehalis Gap collects the Satsop River and Wynoochee River, which drain the southern part of the Olympic Mountains.

The Wynoochee River joins the Chehalis near Montesano, after which the Chehalis River becomes increasingly affected by tides and widens into Grays Harbor estuary. The city of Aberdeen lies at the mouth of the Chehalis River. Just east of Aberdeen, the Wishkah River joins the Chehalis, and just west, between Aberdeen and Hoquiam, the Hoquiam River joins. At this point the river has become Grays Harbor. Before the estuary of Grays Harbor empties into the Pacific Ocean, the Humptulips River joins.

Flood control

Flood control and concerns for the Chehalis River and its watershed is managed by the Chehalis River Basin Flood Authority, which is overseen and funded by the Washington Department of Ecology Office of Chehalis Basin (OCB). ^[17]

In 2010, the flood authority implemented the installation of an online flood warning system available to residents in the Chehalis basin. Known as the Chehalis Basin Flood Warning System, it expanded a sensor network already in place, providing information on rainfall and temperature, as well as additional gauges. Alert warnings are sent via email and provide information on 13 rivers in the area. The system won the 2023 National Hydrologic Warning Council (NHWC) Operational Excellence Award ^[17]

Chehalis Basin Strategy

Counties within the Chehalis River basin, various other regional governments, and the Washington Department of Fish and Wildlife (WDFW), in association with Native American tribes, environmental groups, scientists, and local citizens, organized a partnership in 2014 named the "Chehalis Basin Strategy" to propose and research a combination of plans along the Chehalis River to mitigate flooding and to restore aquatic habitat, particularly for local Chinook salmon. ^[18] The initial proposal outlined several flood control reduction measures, with downstream levee improvements particularly at the Centralia-Chehalis Airport, and a flood retention dam in Pe Ell which is planned to limit catastrophic damage from 100-year floods within the Chehalis River Basin. ^{[19] [20]} The projects are to be carried out in three phases.

First phase

The first phases of the strategy began in 2012 and declared achieved in the early 2020s with a combined 140 flood and habitat projects completed at a cost of $152 million. ^[21] One of the first projects, planned in 2011, included the construction of evacuation routes and a raised fenced, dirt pen, on farmlands that were susceptible to floods. A combined 23 pads were built in Lewis and Gray counties by 2017 and there was no loss of farm animals or equipment recorded after a large January 2022 flood event. ^[22]

The city of Hoquiam received a new pump house to replace an ineffective, aging pump. Completed in 2018 at a cost of $1.3 million, the modernized station protects the community's northern residential area, including an elementary school, and is considered a vital infrastructure project for future levee builds. Pipelines that direct the flow of floodwaters were also replaced. During a January 2022 flood, the rebuilt station pumped a combined 51,000,000 US gallons (190,000,000 L; 42,000,000 imp gal) of water without fail over 30 consecutive hours. ^[23]

The installation of log jacks in Montesano during 2018-2019 helped increase the riverbank of the migrating Wynoochee River, which was threatening the local wastewater plant that during flooding would have inundated the community with sewage runoff. The $2 million cost of the project was estimated to have saved over $40 million in future cleanup and containment efforts. The fortification increased the habitat of aquatic species and extended the operating life of the plant by several decades. ^[21]

Stillman Creek, which courses west of Boistfort as a tributary to the South Fork, underwent an erosion and habitat restoration plan known as the Stillman Creek Restoration Project. The creek had lost salmon and plant habitats due to a combination of warming waters and erosion brought on by consequences of flooding, particularly the 2007 floods, and human activities which had shifted the outflow and floodplain of the creek. At a cost of $8.5 million, the four-year project began in 2018 with the help of local landowners and the work culminated in slowing down the flow of the creek to prevent additional erosion and will help to restore the floodplain and course of the waters. The plan also renewed 2.0 miles (3.2 km) of the creek habitat for a total of 38 acres (15 ha), and included the planting of native vegetation over several dozen acres. ^[24]

Second and third stages

The second stage of the program was implemented soon thereafter and is focused on long-term solutions and strategy for flood control and financial backing of future tasks. The final phase is planned to begin in the mid-2020s and will target construction, additional financing, and devising long-term structural government oversight. ^[25]

Long-term projects

Part of the basin strategy is to remove artificial barriers and to restore forests and woodlands near the Chehalis River and its tributaries, to promote the habitats of aquatic species such as salmon, steelhead, and trout. As of 2023 ^[update], the project, called the Aquatic Species Restoration Plan, has worked with an ongoing WDFW program begun in 2005 that has removed or reengineered 81 man-made impediments in the Chehalis basin at a cost of $27.6 million. ^[26]

Connected projects

Chehalis Basin Strategy partnerships helped create the Blooms Preserve around a tributary of Black River in Thurston County. Meant to restore the habitat of the Oregon spotted frog, thought extinct, 5.0 acres (2.0 ha) of land was purchased via a partnership of a landowner and the non-profit Capitol Land Trust. New ponds were built and invasive plants were removed and the riparian habitat replanted with native vegetation. ^[27]

Wildlife

The river is home to several salmon species, specifically Chinook salmon. A petition was filed by conservation groups in 2023 to list the Chinook salmon as endangered under the Endangered Species Act. ^[8]

See also

• List of Washington rivers

References

External links

• Chehalis Basin Flood Warning System (FWS)
• USGS Chehalis River Basin map
• USGS Chehalis River Basin schematic diagram
• U.S. Geological Survey Geographic Names Information System: East Fork Chehalis River, USGS, GNIS
• U.S. Geological Survey Geographic Names Information System: West Fork Chehalis River, USGS, GNIS
• U.S. Geological Survey Geographic Names Information System: South Fork Chehalis River, USGS, GNIS