Grand Coulee at the higher side of the flexure. Encountering the steep slope of the monocline, the new river would have cascaded off the rim, down onto a broad plain where Coulee City and Dry Falls State Park now stand. Upper Grand Coulee began as an cascade just north of Coulee City. As the rush of water eroded the surface, it steepened into a waterfall. The falls continued to erode backward (northward) creating the canyon. When the falls reached the divide into Lake Columbia, i.e., preglacial Columbia Valley, it disappeared, leaving the elongated notch. Today, the waters of the Lake Roosevelt are
Birch Coulee Battlefield Birch Coulee Battlefield Birch Coulee Battlefield in Renville County, Minnesota, United States, was the site of the Battle of Birch Coulee, the costliest military engagement for U.S. forces during the Dakota War of 1862. It is now a historic site with self-guided trails and markers interpreting the battle from both sides. Birch Coulee was nominated to the National Register of Historic Places for having state-level significance in military history, and was listed in 1973. Birch Coulee Battlefield lies on what, in 1862, was open prairie stretching on to the north and west, with woods to the south. Defining the east