I have traversed the scablands from the Wallula Gap to the Grand Coulee Dam, and everything I have seen fits the basic narrative of megafloods. The details of the theory will no doubt be refined over time, but the basic thesis appears undeniable. Anyone who doubts the possibility of a Great Flood of Biblical proportion, just pay a visit to eastern Washington state.
Me too, I did some of the same hikes.
The channeled scablands were formed by the failure of an ice dam that released a huge meltwater glacial lake. It wasn’t a worldwide event.