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
East Coulee, Alberta East Coulee, Alberta East Coulee is a community within the Town of Drumheller, Alberta, Canada. It was previously a hamlet within the former Municipal District (MD) of Badlands No. 7 prior to the MD's amalgamation with the former City of Drumheller on January 1, 1998. It is also recognized as a designated place by Statistics Canada. East Coulee is located on Highway 10, approximately southeast of Drumheller's main townsite and northeast of Calgary. It lies in the Red Deer River valley and has an elevation of . The community is within Census Division No. 5 and in the federal riding