Glacial Lake Columbia Glacial Lake Columbia Glacial Lake Columbia was the lake formed on the ice-dammed Columbia River behind the Okanogan lobe of the Cordilleran Ice Sheet when the lobe covered of the Waterville Plateau west of Grand Coulee in central Washington state during the Wisconsin glaciation. Lake Columbia was a substantially larger version of the modern-day lake behind the Grand Coulee Dam. Lake Columbia's overflow – the diverted Columbia River – drained first through Foster Coulee, and as the ice dam grew, through first Moses Coulee, and finally, the Grand Coulee. The Cordilleran ice sheet also blocked the Clark Fork River and
Battle of Birch Coulee side of the Minnesota River with a force of 350 Indians. Gray Bird's party and Brown's troops missed encountering each other during the day, but some Indian scouts discovered that Brown's troops were moving toward the campsite at Birch Coulee. The Sioux planned to ambush Brown's troops in the morning, thinking that only the cavalry was present and that they could be easily destroyed. The Birch Coulee campsite was not easily defensible, since the Indians could approach from all sides and still remain under cover. Also, since the burial detail felt themselves safe, they did not take precautions against attack