Grand Coulee the Ice Age Floods. Archeological records date human presence back to nearly the end of the Ice Age, but the raging torrents erased the land of clear evidence, leaving us to question who, if anyone, may have survived. With the end of the last glacial advance, the Columbia settled into its present course. The river bed is about below the Grand Coulee. Walls of the coulee reach in height. Grand Coulee is the longest and deepest of eastern Washington canyons. Its unique characteristics include a lower floor at the head of the channel than at its outlet and the widest
Foster Coulee Foster Coulee Foster Coulee is a coulee in Douglas County, Washington. 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. Washington State Route 17 between Bridgeport, Washington and Coulee City, Washington follows East Foster Creek along much of the coulee's valley floor. East Foster Creek now flows east to west through Foster Coulee to Grand Coulee. The United States Geological Survey quadrangle map "Foster Coulee" is named for this prominent feature. Foster Coulee was formed during the Missoula Floods. The Okanogan lobe of the