Geomorphologic processes associated with cataclysmic flows defy direct measurement. As such, very little is understood regarding flow conditions, sediment transport, erosional and depositional threshold, and patterns of energy expenditure associated with these extreme hydrologic events. Recent develop- ments in paleohydraulic and paleohydrologic techniques provide an avenue for quantitative exploration of these phenomena. Late Pleistocene cataclysmic flooding along the Snake and Big Lost Rivers of southern Idaho and in the Channeled Scabland of eastern Washington has provided an excellent field laboratory for application of these methodologies. Utilizing field evidence of maximum flow stages in conjunction with step-backwater and hydraulic flow routing models, we propose to reconstruct the hydraulics (discharge, velocity, shear stress, and unit-area stream power) of these flows. It is hypothesized that these variables, and their spatial variations, can be directly related to the abundant field evidence of depositional and erosional thresholds. We will test these relationships at several different scales and within different flow environments to determine their general applicability for cataclysmically flooded terrains.
