GEOMORPHOLOGICAL EVIDENCE AND NUMERICAL MODELLING OF A LATE-GLACIAL MEGAFLOOD, SOUTH-CENTRAL BRITISH COLUMBIA
These lines of evidence are consistent with megaflood drainage of the Hamilton 2 stage of glacial Lake Nicola through Campbell Creek. Coarse gravel bars record dynamics of a high-magnitude flow within the canyonized reach. The delta records rapid sedimentation under fast, shallow flow as the flood entered the lower lake basin. The incised southern portion of Campbell Creek formed by head cutting towards the lake basin during drainage.
A range of empirical and semi-empirical paleohydraulic formulae using transported boulders and spillway cross-sections, and high resolution (25 m) three-dimensional flood modelling, estimate shear stress of 1-2 x 103 Pa, stream power of 5-15 x 103 W m-2, velocities of around 10-45 ms-1, and peak discharge of between 105 and 5 x 106 m3s-1. These estimates and the geomorphic record show excellent consilience. This study highlights the potential that megafloods may be evident in the geologic record at the local scale, and informs risk and hazard assessment of ice dammed lake drainage in deglaciating regions today.