Geology of the Pacific Northwest along their course. The larger cataract was that of the upper Grand Coulee, where the river roared over an waterfall. The eroding power of the water plucked pieces of basalt from the precipice, causing the falls to retreat and self-destruct by cutting through to the Columbia River valley near what is now the Grand Coulee Dam. The other major cataract is now known as Dry Falls. It started near Soap Lake in Washington State, where less resistant basalt layers gave way before the great erosive power of this tremendous torrent and waterfalls developed. As in the upper Grand Coulee, the
Coulee City, Washington Coulee City, Washington Coulee City is a town in Grant County, Washington. The population was 562 at the 2010 census. The town was named after nearby Grand Coulee. Coulee City was officially incorporated on May 10, 1907. Coulee City is located at (47.611942, -119.290904). According to the United States Census Bureau, the town has a total area of , all of it land. As of the census of 2010, there were 562 people, 265 households, and 150 families residing in the town. The population density was . There were 331 housing units at an average density of . The racial