"Most geologists now believe that for slightly more than 2000 years .... at least 40 tremendous cataclysms of almost inconceivable force and dimensions swept across part parts of the Columbia River drainage basin. These occurred between 15,000 and 12,800 years ago, at the end of the Ice Age. More than 16,000 square miles were repeatedly inundated to depths of hundreds of feet, ..... These floods on the Columbia contained up to ten times the flow of all the rivers in the world, 60 times the flow of the Amazon River."
These floods shaped the Columbia Gorge and made all its waterfalls. They also gave the Willamette Valley 100 feet of topsoil because that is where there was enough room for the water to spread out and stop moving. Thanks Eastern Washington for all the topsoil!
Old Man Travels calls them the Bretz floods because he was the geologist who first figured out that the floods happened. Of course he was ridiculed at the time. This link will take you to his photo essay on the Bretz Floods.
This is a photo of a back road on his journey. I wish I was driving on this road. I need a road trip...