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
Birch Coulee Battlefield edge is a steep wooded ravine, a landform known locally by the French term "coulee," also spelled "coulie" or "cooley." Birch Coulee, known to the Dakota as "Tanpa Yukan" (Place of the White Birch), is deep and runs for a total of down to the Minnesota River. A few hundred yards to the west of the coulee, the prairie rises slightly onto a gentle knoll. On September 1, 1862, a burial detail of about 170 Union Army volunteers and civilians under Major Joseph R. Brown camped on the prairie west of Birch Coulee. The site was selected by Captain Hiram