Date of Award

12-2019

Degree Type

Report

Degree Name

Master of Science (MS)

Department

Watershed Sciences

First Advisor

Joseph Wheaton

Second Advisor

Peter Wilcock

Third Advisor

Edward Hammill

Abstract

This paper seeks to address a knowledge gap concerning how flood events impact beaver dams over time. To address this gap, I took four time-snapshots of beaver dams, mapping them across the Utah portion of the Logan-Little Bear watershed, from 2009 to 2016 to bookend a large flood event in 2011. I assessed dam status (intact, breached, or blown out) for each dam mapped to assess the impact of the large spring runoff on the dam status. Assessing dam status over time allowed me to assess the change in condition over time, from before to several years after, while also allowing me to visualize the change in dam locations throughout the watershed. I was curious if floods impacted dams in any statistically significant way. If floods do impact dams, are the breached and blown out dams repaired, or are they abandoned? How long until dams across the watershed returned to pre-flood conditions?

I found that, following 2011, there was a temporary decrease in the overall number of dams mapped. However, in ensuing years the total number of dams surpassed the baseline. There was a notable impact following the 2011 spring runoff, with a large percentage of 2011 dams existing in a breached or blown out state, and conditions had not returned to pre-flood levels before another flood in 2017. A large number of dams did not overlap between 2011 and 2014, possibly indicating beaver had moved into new locations. Dams and complexes that had been abandoned in 2011 were often reoccupied or rebuilt by 2016. The data gathered in the course of this study indicates that large floods act as mechanisms impacting beaver dam dynamics in the Logan-Little Bear watershed.

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