Magnitudes and implications of

New field evidence and discharge calcula-tion procedures provide new estimates of maximum late Pleistocene glacial Lake Mis-soula flood discharges for two important reaches along the flood route. Within the Spokane Valley, near the point of release, the peak discharge probably exceeded 17 ± 3 mil-lion m3-sec-1. Downstream at Wallula Gap, a major point of flow convergence, peak dis-charge was about 10 ± 2.5 million m^*sec-'. Flow duration was on the order of several days. These are the largest known terrestrial fresh-water flows. Consideration of these discharge values constrains models for the failure of glacial Lake Missoula. The maximum discharges es-timated here are larger than theoretical and empirical predictions of maximum subglacial jdkulhlaup-style releases for Lake Missoula. We postulate, consistent with geological rela-tions in the glacial Lake Missoula basin and in the Channeled Scabland, that the largest late Wisconsinan Missoula Flood resulted from a cataclysmic failure of the impounding ice dam of glacial Lake Missoula. This large release may have been the result of a complete rup-ture of the ice dam. Subsequent multiple flows of lesser magnitude may have resulted from repeated subglacial releases from the lake