Date of Award:

12-2018

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Advisor/Chair:

John C. Schmidt

Abstract

In 1899, Robert T. Hill led the first scientific exploration of the remote segment of the Rio Grande known as the Big Bend. Hill’s observations from this expedition were published in an article titled “Running the Cañons of the Rio Grande.” At the time of Hill’s expedition, the stream flow of the Rio Grande was largely depleted by water development in the upstream portions of the basin. The continued overallocation of the Rio Grande has led to the degradation of aquatic ecosystems in the Big Bend, one of North America’s largest transboundary protected areas, such that management of natural resources in this region is a high priority. Many of the native species in this region are listed as threatened or endangered due to habitat loss, which is driven by channel narrowing. Thus, excess fine sediment, along with invasive riparian species, has been identified as negatively impacting ecological resources in the Big Bend and studies recommend increased stream flow as the most effective tool for managing excess fine sediment. Aside from historical accounts, there was previously no estimate of the Rio Grande’s natural flow regime nor an adequate understanding of how the role of characteristic floods in the Big Bend shaped the pre-disturbance channel. In the following two studies, we fill in these crucial knowledge gaps by estimating the pre-disturbance flow regime of the Rio Grande, describing how channel narrowing is not spatially uniform in the Big Bend, and analyzing past floods to determine the role of past flood regimes in shaping alluvial deposits that contribute to channel narrowing.

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