Lahar Hazard Mapping of Mount Shasta, California: A GIS-based Delineation of Potential Inundation Zones in Mud and Whitney Creek Basins

Master of Science, Geography, Oregon State University, Spring 2005
Emphasis in Geographic Information Science, Minor in Physical Geography

Graduate committee: D. Wright, A.J. Kimerling, K. Scott (USGS Cascades Volcano Observatory), R. Keller

Steve McClung
Dept of Geosciences, Oregon State Univ
Corvallis, OR 97331-5506
steve-at-mynextadventure.com
www.mynextadventure.com

Abstract.
Mount Shasta, the southernmost stratovolcano in the Cascade Range (41.4°N) has frequently produced lahars of various magnitudes during the last 10,000 yr. These include large flows of eruptive origin, reaching more than 40km from the summit, and studies have shown that at least 70 debris flows of noneruptive origin have occurred during the last 1,000 yr in various stream channels. The Mud and Whitney Creek drainages have historically produced more debris flows than any other glacier-headed channel on the volcano. Periods of accelerated glacial melt have produced lahars in Whitney Creek with a volume of 4 x 106 m3 and a runout distance of about 27 km from the summit. Mud Creek flows from 1924 – 1931 covered an area of more than 6 km2 near the community of McCloud with an estimated 23 million m3 of mud. A much older lahar in Big Canyon Creek may have deposited a volume of 70 x 107 m3 over present day Mount Shasta City and beyond. A lahar inundation modeling tool developed by USGS analysts is used to objectively delineate lahar inundation zones on Mount Shasta by embedding predictive equations in a geographic information system (GIS) that uses a digital elevation model, hypothetical lahar volumes, and geometric relationships as input. Volumes derived from these lahar deposits are extrapolated to the selected drainages to generate probable lahar inundation hazard zones with a focus on mapping and hazards implications.

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