Though the origin of Grand Canyon is of great interest to sedimentologists and structural geologists, the problem more properly rests within the field of geomorphology. That is because in spite of its imposing size, it is a water gap—one of over a thousand catalogued across the Earth. Like many other geomorphological features, most water gaps are best explained as formed during the retreating stage of the Flood. Clues to the formation of Grand Canyon are provided by the processes that occurred when the glacial Lake Missoula flood overtopped a ridge between Washtucna Coulee and the Snake River in the southeast Channeled Scabland. There are other water gaps present on the Colorado Plateau, and all are readily explained by the distinct processes of the retreating stage of the Flood. None of these features are easily explained by any dam-breach hypothesis.