Foster Coulee

Like the larger Moses Coulee nearby, it was formed during the Missoula Floods at the end of the last ice age, some 14,000 years ago.

The United States Geological Survey quadrangle map "Foster Coulee" is named for this prominent feature.

The Okanogan lobe of the Cordilleran Glacier moved down the Okanogan River valley and blocked the ancient route of the Columbia River, backing up water to create Glacial Lake Columbia.

[5] The coulee would be dammed and approximately 500 MW generation capacity installed, exploiting the c. 500-foot (150 m) difference in elevation between the new reservoir and the existing Banks Lake.

[6] Banks Lake is in turn created by pumping water 280 feet (85 m) uphill from the Columbia River at the Grand Coulee Dam.