Date of Award

Spring 2022

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

Committee Chair

Glenn Shaw

First Advisor

Robert Pal

Second Advisor

Andrew Bobst

Abstract

Beaver dam analogs (BDAs) are a low cost, low disturbance stream restoration technique that may improve surface-water/groundwater interactions and wetland connectivity. BDAs are intended to imitate the effects of natural beaver dams by slowing stream velocity, promoting infiltration, increasing dry-season streamflow, aggrading the streambed, and capturing organic matter and other nutrients. This study was conducted to evaluate the degree to which these objectives were being met at a study site on Perkins Gulch, southwest Montana, USA. The Perkins Gulch study area can be summarized by four gauging sites that separate three reaches along the creek. By detailing background processes and separating the field site into reaches with distinct properties, we can understand the temporal and spatial similarities and differences between intact BDAs, blown out BDAs, and abandoned beaver dams. This approach also allows for evaluation of how riparian conditions in these restored reaches compare to historical conditions. BDAs resulted in increased stream sinuosity and wetland connectivity. Despite recent restoration and observations of continuous annual flow in 2019, several sections of Perkins Gulch ran dry in the 2021 field season. This was caused by anomalously dry conditions, geologic features, and blowout of several BDA structures. An abandoned beaver complex at the site served as a proxy to gauge how BDAs might impact surface groundwater conditions. If BDA structures are repaired and replaced as needed, they may increase local surface/groundwater interactions, provide for continuous streamflow, and alter stream corridor geomorphology.

Comments

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology with an Emphasis in Hydro-geology and a Certificate in Ecological Restoration.

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