The Snoqualmie River is a 45 mile (72 km) long river in the central portion of King County, Washington. The three main tributaries are the North, Middle, and South Forks, which drain the west side of the Cascade Mountains near the town of North Bend and join near the town of Snoqualmie just above the Snoqualmie Falls. After the falls the river flows north through rich farmland and the towns of Fall City, Carnation, and Duvall before meeting the Skykomish River to form the Snohomish River near Monroe. Other tributaries include the Taylor River, the Pratt River near North Bend, the Tolt River at Carnation, and the Raging River at Fall City.
Many of the Snoqualmie River's headwaters originate as snowmelt within the Alpine Lakes Wilderness. On August 8, 2007, U.S. Representative Dave Reichert (WA-08), King County Executive Ron Sims, and others announced a proposal to expand the Alpine Lakes Wilderness to include the valley of the Pratt River, a tributary of the Snoqualmie River, near the town of North Bend. The proposal would also give the Pratt River National Wild and Scenic River status.
The Snoqualmie River has quite a few major waterfalls. By far the most famous waterfall in Washington, receiving over 1 million visitors every year is the 268 ft high Snoqualmie Falls. However, the three forks of the upper Snoqualmie River also have notable waterfalls. The north fork has Fantastic Falls (35ft) and Kanim Falls (200ft). The middle fork has Nellie Falls (150ft). And, the south fork has Twin Falls (135ft), Middle Twin Falls, Upper Twin Falls, Weeks Falls, Upper Weeks Falls, Denny Camp Falls, Franklin Falls (135ft), and Fall-into-the-Wall Falls (22ft).
The Snoqualmie River is prone to flooding and typically sees multiple flood events annually that inundate local farmland and close low-lying roads. During record level floods, all road access to the towns of Carnation and Duvall becomes closed off. The last two times this happened were during the floods of 2006 and 1990.
The river level of the Snoqualmie River is monitored by six NOAA flood gauges, one on each fork, one just above the falls, one below Carnation, and one near Duvall. The Tolt River and the Raging River are also monitored by flood gauges.
The Snoqualmie Flood Reduction Project was a controversial Army Corps of Engineers project completed in 2005 to reduce the effect of floods in the town of Snoqualmie by widening the river just above the falls.