The river and its drainage basin experienced some of the world's greatest known catastrophic floods toward the end of the last ice age. The periodic rupturing of ice dams at Glacial Lake Missoula resulted in the Missoula Floods, with discharges exceeding the combined flow of all the other rivers in the world, dozens of times over thousands of years. The exact number of floods is unknown, but geologists have documented at least 40; evidence suggests that they occurred between about 19,000 and 13,000 years ago.
