Grand Coulee displacing local Native Americans. Grand Coulee The Grand Coulee is an ancient river bed in the U.S. state of Washington. This National Natural Landmark stretches for about 60 miles (100 km) southwest from Grand Coulee Dam to Soap Lake, being bisected by Dry Falls into the Upper and Lower Grand Coulee. The Grand Coulee is part of the Columbia River Plateau. This area has underlying granite bedrock, formed deep in the Earth's crust 40 to 60 million years ago. The land periodically uplifted and subsided over millions of years giving rise to some small mountains and, eventually, an inland sea.
Coulee ridgetops transitioning into tallgrass prairie when not turned into pasture or used for row crops. Coulees provide shelter from wind and concentrated water supplies to plants which would otherwise struggle to survive in the xeric sagebrush steppe. Trees are often found in riparian habitats along streams in coulees and at the base of their walls. 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