Moses Coulee the southern portion of the plateau. These streams had combined into a canyon that drained to the Columbia near the current mouth of Moses Coulee. These side drainages are still visible today along the coulee walls as truncated streambeds, interspersed with gable-like highlands. The Okanogan lobe of the Cordilleran Glacier moved down the Okanogan River valley, covering 500 mi² of the Waterville Plateau and blocked the ancient route of the Columbia River, backing up water to create Glacial Lake Columbia and Lake Spokane. Initially water discharged from Lake Columbia by running up through the head of Grand Coulee and down
Grand Coulee Dam Coulee Dam flooded over 21,000 acres (85 km) of prime bottom land where Native Americans had been living and hunting for thousands of years, forcing the relocation of settlements and graveyards. The Office of Indian Affairs negotiated with the United States Bureau of Reclamation on behalf of tribes who were concerned about the flooding of their grave sites. The Acquisition of Indian Lands for Grand Coulee Dam, 54 Stat.703 Act of June 20, 1940 allowed the Secretary of the Interior to remove human remains to new Native American grave sites. The burial relocation project started in September 1939. Human remains