Grand Coulee Columbia Rivers pathway and onto the southern plateau creating an ice dam. This dam backed up the waters of the Columbia into Glacial Lake Columbia and later during the Missoula Floods forced those waters into eastern Washington, creating the Scablands. The river at Grand Coulee found no existing valley and thus forged its own pathway across the divide, creating the Upper Coulee. The plateau is not level, but is marked with wrinkles and upfolds of the basalt. The diverted waters of the Columbia, encountered the monoclinal flexure, a steep warping up of toward the northwest. Lake Columbia topped the ridge
East Coulee, Alberta a land area of , it had a population density of in 2011. 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 .