Community Partner

U.S. Fish and Wildlife Service and the Lower Columbia Estuary Partnership

First Advisor

Jen Morse

Date of Award

Spring 2024

Document Type

Project

Degree Name

Master of Environmental Management (MEM)

Department

Environmental Science and Management

Language

English

Subjects

Franz Lake National Wildlife Refuge (Wash.) -- Mathematical models, Wildlife refuges -- Management, American beaver, Sagittaria latifolia

DOI

10.15760/mem.85

Abstract

Located in the lower Columbia River floodplain, Franz Lake National Wildlife Refuge is a unique landscape with a complex land use history. For thousands of years, Indigenous tribes lived on this land. In the early 1990s, U.S. Fish and Wildlife Service acquired the land, after it was identified as a mitigation site following the construction of the Bonneville Lock and Dam. Franz Lake Refuge was once known for its prevalent Wapato (Sagittaria latifolia) population, an emergent plant with edible tubers and an important food source for Indigenous people. With specific growth requirements and hydrologic conditions for germination and establishment, S. latifolia is susceptible to environmental changes. American beavers (Castor canadensis) can dramatically alter a landscape to suit their needs, such as digging channels, rerouting water, and through direct consumption of vegetation. To better understand the hydrology in Franz Lake Refuge, water elevation data was collected continuously, and historical lake surface water and beaver dams were evaluated using remote sensing. Wetland vegetation transect surveys were performed and used for an image classification of the Franz Lake Refuge floodplain. The results suggest that there are many factors influencing the hydrology and wetland plant community within Franz Lake Refuge. The Columbia River has a significant influence on Franz Lake Refuge, especially during large flooding events; however, the effects from beaver dam building activity on Franz Lake hydrology were inconclusive. In addition, reed canary grass (Phalaris arundinacea) has become a dominant species and is likely encouraging on S. latifolia habitat. This project was designed to create a baseline for future monitoring and anticipated habitat restoration.

Rights

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Comments

A project report submitted in partial fulfillment of the requirements for the degree of Master of Environmental Management.

Persistent Identifier

https://archives.pdx.edu/ds/psu/42165

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