The Chehalis River ( ) is a

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of ...

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

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 Grays Harbor is an estuarine bay located north of the mouth of the Columbia River, on the southwest Pacific coast of Washington state, in the United States of America. It is a ria, which formed at the end of the last ice age, when sea levels floo ...

, an

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

of the Pacific Ocean. It was once much larger during the

Ice Age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

when the tongue of the glacial ice sheet covering the

Puget Sound Puget Sound ( ) is a sound of the Pacific Northwest, an inlet of the Pacific Ocean, and part of the Salish Sea. It is located along the northwestern coast of the U.S. state of Washington. It is a complex estuarine system of interconnected m ...

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 Rising may refer to: * Rising, a stage in baking - see Proofing (baking technique) *Elevation * Short for Uprising, a rebellion Film and TV * "Rising" (''Stargate Atlantis''), the series premiere of the science fiction television program ''Starg ...

at the end of the ice age flooded the broad Chehalis Valley to form a ria, known today as Grays Harbor.

Course

The Chehalis River 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 The Willapa Hills is a geologic, physiographic, and geographic region in southwest Washington. When described as a physiographical province, the Willapa Hills are bounded by the Pacific Ocean to the west, the Columbia River to the south, the Ol ...

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 Olympic Mountains are a mountain range on the Olympic Peninsula of the Pacific Northwest of the United States. The mountains, part of the Pacific Coast Ranges, are not especially high – Mount Olympus is the highest at ; however, the easte ...

. 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 Aberdeen (; sco, Aiberdeen ; gd, Obar Dheathain ; la, Aberdonia) is a city in North East Scotland, and is the third most populous city in the country. Aberdeen is one of Scotland's 32 local government council areas (as Aberdeen City), a ...

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 history

December 3, 2007, floods

During the

Great Coastal Gale of 2007 The Great Coastal Storm of 2007 was a series of three powerful Pacific storms that affected the U.S. states of Oregon and Washington and the Canadian province of British Columbia between December 1, 2007 and December 4, 2007. The storms on Dece ...

, a 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 of water. The recommended detour added about four hours and 280 miles (450 km). It was not expected to reopen for several days. However, upon breaching a dike on Dec. 5, 2007, the water receded more quickly than anticipated.

Amtrak The National Railroad Passenger Corporation, doing business as Amtrak () , is the national passenger railroad company of the United States. It operates inter-city rail service in 46 of the 48 contiguous U.S. States and nine cities in Canada. ...

train service between

Portland, Oregon Portland (, ) is a port city in the Pacific Northwest and the largest city in the U.S. state of Oregon. Situated at the confluence of the Willamette and Columbia rivers, Portland is the county seat of Multnomah County, the most populous ...

, and

Vancouver, British Columbia Vancouver ( ) is a major city in western Canada, located in the Lower Mainland region of British Columbia. As the most populous city in the province, the 2021 Canadian census recorded 662,248 people in the city, up from 631,486 in 2016. The ...

, was also disrupted. Washington governor Christine Gregoire declared a state of emergency on December 3.

January 7, 2009, floods

During the January 7, 2009, Pacific Northwest storms, a 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.

References

External links

Chehalis River Council

USGS Chehalis River Basin schematic diagram
* ,

USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

, GNIS * ,

, GNIS
Interstate 5 near Chehalis shut down indefinitely
{{authority control Rivers of Washington (state) Rivers of Grays Harbor County, Washington Rivers of Thurston County, Washington Rivers of Lewis County, Washington