In most such bars, there are many layers, suggesting that the floods recurred at fairly regular intervals up to as many as seventy times. This evidence strengthened Bretz' case, but left many unconvinced. What was missing was evidence for the large body of water and its sudden drainage. These lines can be followed for miles and allow outlining a lake which extended over much of western Montana. A glacial dam can be located at the east end of Lake Pend Oreille in the Clark Fork River valley.
Further evidence comes from giant ripple marks.
Fast flowing water leaves ripples in the terrain it flows over. These are larger and farther apart as the more water flows faster. In fact, they are large enough to be difficult to recognize from ground level, but become obvious in aerial photographs. With the source of the water identified and supporting evidence for its volume and flow, Bretz' idea was accepted. Like many of those who disputed Bretz, he had never before visited the Channeled Scablands, so the disparity between the small stream and the big canyon and plunge pool at Palouse Falls had not hit him.