Semester of Graduation

Fall 2018

Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Thesis

Abstract

In mountainous regions, extreme floods occur every year, placing societies and infrastructures at risk. Communities rely on local, state, and federal agencies to emplace flood structures, perform flood risk assessments, and simulate catastrophic events. While, our ability to quantify and predict the movement of sediment in streams with low gradients is well developed (Bathurst, 1987), our ability to quantify and predict the movement of sediment along steep mountain streams (SMS) has not been developed to a similar degree (Yager, 2012; Schneider, 2016). To most effectively manage mountainous watersheds and understand the risk associated with flood events, scientists must better understand the hydraulics, morphometric controls, and processes that drive sediment transport in SMS systems.

In September 2013, a large low-pressure system brought torrential rainfalls to the state of Colorado, producing hazardous floods and amassing $3 billion in damages (Kimbrough, 2015). Louisiana State University owns a 1400 - acre property southwest of Colorado Springs, Colorado within the 35-km2, Upper Little Fountain Creek (ULFC) watershed. The stream is classified as a SMS, and exhibits cascade and step-pool morphologies. Extensive flooding was observed throughout the entire Little Fountain Creek watershed during the 2013 flood event. Within ULFC, the simulated peak streamflow discharge was 40 m3/s. Keeton Reservoir, a structure downstream of the studied mountainous reach, was compromised during the 2013 food event infilling 60% full with 12,615 m3 of sediment. The 2013 flood and resultant sediment transport event combined with the documented infilling of the Keeton Reservoir provided an ideal experiment for testing our understanding and ability to predict sediment movement during extreme floods in ungauged watersheds. Thus, the objectives are to (1) apply two methods used to quantify event-driven sediment transport in SMS, (2) determine the range and magnitude of event-driven sediment transport in LFC for the 2013 flood event, and (3) compare the results to the known volume of sediment that was deposited in Keeton Reservoir. We hypothesize that the integration of simulated hydraulic parameters with high-resolution measurements of channel morphology and grain-size distribution will increase the accuracy of sediment transport quantifications for the 2013 flood event in ULFC.

Date

10-30-2018

Committee Chair

Wicks, Carol

DOI

10.31390/gradschool_theses.4814

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