Publication Date

Summer 2016

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

Advisor

Dr. Emmanuel J. Gabet

Keywords

Debris Flow Fans, Debris Flows, Yosemite Valley National Park

Subject Areas

Geology; Geomorphology

Abstract

Formation of debris flow fans poses a potential hazard to the infrastructure and inhabitants of Yosemite Valley. Research was conducted on debris flow fans at three field sites in Yosemite Valley: Indian Creek, Eagle Creek, and Sentinel Creek. The study utilized a Trimble Pro XR Differential Global Positioning System (DGPS), Cosmogenic Berellium-10 (10Be) dating, and debris flow volume measurements to better understand the spatial distribution, age, and magnitude of prehistoric debris flow deposits at each field site. It is hypothesized that all three fans were constructed quickly after the last glacial maximum (LGM), which is dated at 19.8 ka. It is also proposed that increased rainfall and sediment production during the LGM provided the necessary conditions for debris flow initiation in each catchment. Future debris flow initiation is contingent on channels being pre-loaded with sediment and above average rainfall. At the present time, the channels are loaded with debris, but future debris flow initiation seems unlikely to occur because the fans have been inactive for thousands of years. Debris flows only pose a significant hazard to Yosemite Valley, if and when, the optimum conditions are met.

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