A Dam Breach Model of Epic Proportions — Simulating the Glacial Lake Missoula Floods

The Columbia River Gorge and the Scablands of Eastern Washington are just two of the incredibly stunning geologic features carved out by the great Missoula Floods approximately 10 to 40 thousand years ago. These floods of epic proportions were triggered by the "failure" of a massive glacial ice dam that impounded a lake about the same size as the Great Slave Lake in Canada. With the improvements of available GIS data and dam breach modeling capabilities in HEC-RAS, a hydrodynamic model was constructed of this enormous flood stretching from Eastern Montana to the Pacific Ocean. The results of this model shed light on some of the enormities of this flood event, specifically the magnitude of discharge, flow velocities, and inundation extents. In addition, the progression of the flood wave through Eastern Washington, the Columbia River Gorge, up the Willamette River Valley and out to the Pacific Ocean is demonstrated through GIS.