Withrow Moraine overlies a flood bar in Upper Moses Coulee. Stop 7 in Baker et al.

 "At this location, a portion of the Withrow Moraine overlies an elongate pendant bar that was emplaced by cataclysmic megaflooding prior to the advance of the Okanogan lobe to its late Pleistocene terminal position (Fig. 28). A 36Cl cosmogenic nuclide date on a basalt boulder from the flood bar yielded an age of 15.5 ka (sample MF-5, Table 2). As on the plateau upland surface, the summit of the moraine has the large “haystack” blocks of basalt. There are also smaller erratic boulders of granitic composition and other basement rocks that probably derive from the Okanogan highlands to the north of the Columbia River. After its terminal phase, the moraine was breached, resulting in a sequence of outwash terraces along the western side of the coulee that reflects the history of the ice lobe at its terminus and subsequent retreat up the coulee." 

Missoula Floods

The Missoula Floods (also known as the Spokane Floods or the Bretz Floods) refer to the cataclysmic floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age. The glacial flood events have been researched since the 1920s. These glacial lake outburst floods were the result of periodic sudden ruptures of the ice dam on the Clark Fork River that created Glacial Lake Missoula. After each ice dam rupture, the waters of the lake would rush down the Clark Fork and the Columbia River, flooding much of eastern Washington and the Willamette Valley in western Oregon. After the rupture, the ice would reform, creating Glacial Lake Missoula again.

• http://en.wikipedia.org/wiki/Missoula Floods
• Page 38 - Baker, V. R., 2016, Pleistocene megaflood landscapes of the Channeled Scabland: The Geological Society of America Field Guide 41