This theory states that a natural dam formed above the present canyon which would have filled the Colorado Plateau with water creating several large lakes.
The alleged lakes would have covered an estimated 30,000 square miles, or roughly three times the size of present day Lake Michigan (Austin 19-94).
This fits into the larger field of Creation Science, in which people try to prove with scientific evidence that the world is only 6,000 years old. Austin's claims and delve into the evidence he uses to support them by examining his book. Austin supports his claim with theories of rapid erosion and Flood deposition of fossils.
He also addresses issues like radiometric dating, in which he attempts to cast doubt on established scientific methods of dating Earth's features.
His most noted example is that of the Missoula Flood in western Montana, Idaho, and eastern Washington.