Channeled Scablands

The Channeled Scablands at one time were a relatively barren and soil-free region of interconnected relict and dry flood channels, coulees and cataracts eroded into Palouse loess and the typically flat-lying basalt flows that remain after cataclysmic floods within the southeastern part of the U.S. state of Washington. The channeled scablands were scoured by more than 40 cataclysmic floods during the Last Glacial Maximum and innumerable older cataclysmic floods over the last two million years. These cataclysmic floods were repeatedly unleashed when a large glacial lake repeatedly drained and swept across eastern Washington and down the Columbia River Plateau during the Pleistocene epoch. The last of the cataclysmic floods occurred between 18,200 and 14,000 years ago.
Geologist J Harlen Bretz defined "scablands" in a series of papers written in the 1920s as lowlands diversified by a multiplicity of irregular channels and rock basins eroded into basalt. Flood waters eroded the loess cover, creating large anastomizing channels that exposed bare basalt and creating butte-and-basin topography. The buttes range in height from 30 to 100 m , while the rock basins range from 10 m in width up to the 11 km long and 30 m deep Rock Lake. Bretz further stated, "The channels run uphill and downhill, they unite and they divide, they head on the back-slopes and cut through the summit; they could not be more erratically and impossibly designed."

Wikipedia