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 Coulee </div> Coulee, or coulée ( or ) is a term applied rather loosely to different landforms, all of which refer to a kind of valley or drainage zone. The word "coulee" comes from the Canadian French "coulée", from the French word "couler" meaning "to flow". The term is often used interchangeably in the Great Plains for any number of water features, from ponds to creeks. In southern Louisiana the word "coulée" (also spelled "coolie") originally meant a gully or ravine usually dry or intermittent but becoming sizable during rainy weather. As stream channels were dredged or canalized, the term