Date of Award:

8-2017

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

Joseph M. Wheaton

Committee

Joseph M. Wheaton

Committee

Daniel Buscombe

Committee

Peter Wilcock

Abstract

The Colorado River in Glen, Marble, and Grand Canyons is subject to a complex regulatory framework, including the Colorado River Compact, the Endangered Species Act, and the Grand Canyon Protection Act of 1992. Physical, biological, and cultural resources are extensively monitored by the Glen Canyon Dam Adaptive Management Program (GCDAMP) to assess the effect of Glen Canyon Dam (GCD) operations on the downstream environment. The GCDAMP consists of a diverse group of stakeholders who identify priority resources and agree upon water releases at GCD. Large expenditures of money have been devoted to monitoring physical and biological resources in Grand Canyon.

A major management goal for physical resources in Glen, Marble, and Grand Canyons are to maintain or attain levels of fine sediments storage within the main channel and along shorelines. Sandbars are used as campsites for recreational boaters, and in-channel sediment can provide suitable habitat for native fishes. Since the closure of GCD in 1963, sediment is in limited supply and is primarily limited to the seasonal (mostly summer monsoon season) inputs from the Paria and Little Colorado Rivers. Currently, fine sediment is actively managed using experimental High Flow Experiment (HFE) releases from GCD. In 2012, the HFE protocol was passed and provided with the framework to determine the magnitude and duration of a HFE based on seasonal inputs of sediment from tributaries. The protocol is designed to provide a better understanding of how to incorporate high releases into future dam operations with the goal of effectively conserving sand in the long term. HFEs have been proven to effectively build sandbars along the channel shorelines.

Although HFEs have proven effective at increasing the amount of find sediment throughout the system, the effects of increased storage of fine sediment on native and non-native fish are somewhat inconclusive. The central objectives of the GCD Adaptive Management program, as they pertain to fish, are to increase the abundance of native fishes of the Colorado River while providing a high quality rainbow trout fishery immediately downstream of GCD. The perceived success of there goals is largely determined by quantifying the percentage of critical habitat lost or gained, condition of species variability (native population, abundance, distribution), carrying capacity thresholds, and population estimates. This thesis directly contributes to physical habitat assessment. However, measuring the amount of critical habitat lost or gained is difficult because there currently is no protocol to concurrently monitor bed sediment during fish sampling and other activities. This thesis was funded by GCDAMP and was designed to develop a protocol that a fish biologist can use to incorporate fine sediment dynamics into their studies. Specifically, the goal of this thesis was to establish objective ways to map physical habitat characteristics with a low cost, recreational-grade side scan sonar system. The primary findings were:

  • Riverbed sediment create distinct textures on side scan sonar imagery that correspond with broad changes in bed sediment grain size
  • Statistical texture analyses provided objective measures of textures associated with distinct sediment types
  • Data collected from a recreational-grade system often has sufficient quality to identify groupings of sand, gravel, and boulders when collected under suitable conditions and protocols
  • An automated method was developed to identify groupings of similar sized sediment at the scale of ⩾ 9 m2 patches

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