Surrounded by lava and basalt flows and layers of sandstone, it flows generally southeast from near South Saddle Mountain in the Northern Oregon Coast Range and through a -wide valley to Henry Hagg Lake, an impoundment of Scoggins Dam. Just downstream from the lake, the creek empties into the Tualatin River about west of Portland, at an elevation of . The creek enters the Tualatin River upstream of the Tualatin's confluence with the Willamette River.