T147 Dynamics of Huge Floods

Tuesday, 12 October 2021
8:00 AM - 12:00 PM
Portland Ballroom 254 (Hybrid Room)

GEOLOGICAL IMPLICATIONS FROM HYDRAULIC MODELING OF THE LARGEST MEGAFLOODING ON EARTH

Paper number: T147-13
Program: Technical Sessions
Time: 11:10 AM – 11:25 AM

Authors

  • Tao Liu Presenting Author
    The University of Arizona, Tucson, AZ
  • Victor Baker
    Univ of Arizona Dept Hydrology & Atmospheric Sciences, Tucson, AZ

Abstract

The Channeled Scabland and various Columbia River pathways of the northwestern U.S., as impacted by the Late Pleistocene “Missoula Floods,” provide the best-studied examples of megaflood-generated landscapes. Combining a 1/3 arc-second DEM with the GeoClaw and HEC-RAS 2D hydraulic models, we analyzed the effects on megaflood routings of various boundary conditions dictated by current understanding of the region’s geological history. Our modeling results confirm the long-recognized issue of a mismatch between the regional high-water marks and the megaflooding discharge peaks associated with current understanding of the boundary conditions. We find that the minimum megaflood-generating water volumes required to match the geological evidence is about two times the maximum that can be achieved through cataclysmic outflow from Glacial Lake Missoula (GLM). Among the factors that might explain this discrepancy, we consider the addition of non-GLM megaflooding sources to be a reasonable working hypothesis. Nevertheless, regardless of the source issue, we find that simulated local flow strengths are basically comparable with previous work about Channeled Scabland megaflooding and with results obtained for many other megaflood landscape on Earth and Mars. These results are inconsistent with recent proposals that the causative megaflooding responsible such morphologies needs to be “downsized.” Our study also indicates that an iterative simulation modeling approach needs to be employed, involving both geological and hydraulic analyses, to properly understand the role of late Pleistocene megaflooding in creating the Channeled Scabland and similar megaflood landscapes.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-368487

© Copyright 2021 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.