Date of Award

Spring 2019

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geosciences

Committee Chair

Glenn Shaw

First Advisor

Larry Smith

Second Advisor

Raja Nagisetty

Third Advisor

Robert Pal

Fourth Advisor

Liping Jiang

Abstract

Historic placer mining operations along the Middle Fork John Day River (MFJD) north of Galena, Oregon have left the MFJD channel straightened, incised and lacking in riverbed structure. This lack of riverbed structure makes this stretch of the MFJD poor habitat for trout and migrating salmon. In order to restore this stretch of the MFJD to better serve aquatic species, Inter-Fluve Inc. (IF), United States Forest Service (USFS) and The Freshwater Trust (TFT) will be performing restoration to both the MFJD channel as well as Bear Creek, a tributary of the MFJD. The proposed restoration work will consist of re-routing of the MFJD and Bear Creek, re-meandering of the MFJD and construction of riverbed structure throughout the MFJD.

In preparation for this proposed restoration, the connectivity of groundwater and surface water throughout the reach must be assessed. The main focus of this groundwater and surface water connectivity assessment will be to characterize how wetlands located along the reach interact with surface water features via groundwater. Characterizing the connection between groundwater and surface water will aid in determining the potential risk of proposed restoration having negative impacts on wetlands located along the reach. In order to fully characterize the groundwater and surface water connectivity at the site, a monitoring plan focused on geologic, hydrogeologic and hydrologic characteristics was implemented. Data obtained from site monitoring was used to support a groundwater model for the site. This groundwater model was used to make predictions of how proposed restoration would impact the site wetlands.

Steady state and transient groundwater models of observed conditions calibrated relatively well producing low error values. Groundwater models revealed that initial restoration performed on Bear Creek has had a negative impact on the site wetlands. When all proposed restoration work is modeled, an overall increase in wetland water elevations is predicted throughout most the wetland area. Water elevations near the abandoned Bear Creek channel however, show a decrease in water elevation when all restoration work is implemented. This decrease in water elevation only occurs between May and July; modeling of July through October in this area show an increase in water elevation levels. Overall when all proposed restoration is completed, the site wetlands and entire site in general will benefit in terms of higher water elevations, especially during base flow conditions.

Comments

A thesis submitted in partial fulfillment of the requirements for the degree of Masters of Geoscience in Hydrogeological Engineering

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