The name “Channeled Scablands” was first used in the early 1920's by geologist J Harlen Bretz, who proposed the idea that the erosional features were the result of a gigantic flood. The most spectacular flood features were carved into the black volcanic rock terrain in eastern Washington. This rock, the “floor” of the Scablands, is basalt—a dense crystalline lava that covers more than 100,000 square miles. [The lava field] is completely surrounded by mountains and nearly encircled by three rivers—the Columbia, the Spokane, and the Snake.
From the USGS website, "Geologic Survey of the Channeled Scablands of Eastern Washington"
At Chief Timothy Park near Clarkston, WA, at the latest Confluence Story Gathering, Thomas Morning Owl (Umatilla tribe) noted there are indigenous people’s stories of massive floods going back to 14,000 years ago.
From the Ice Age Flood Institute website