Oregon Creek Placer Mine Restoration

The Oregon Creek restoration project was constructed in September 2019, on-time and under-budget. Approximately 1,400 linear feet of new stream channel and 4 acres of new floodplain were constructed in addition to the installation of 8 machine-made, off-stream beaver dams. These man-made beaver dams, or “detention ridges”, span the length of the floodplain, functioning to catch sediment, and slow and store water. These structures and other features such as dug-out pools, bank stabilizing structures, riffle crests, and willow trenches will also enhance habitat for amphibians, insects, and song birds.

The lower reach of Oregon Creek was impacted by historic gold and silver mining in the late 1800’s, leaving it pinned against large placer piles (river cobbles and sediment dug out from the channel bed and stacked next to the stream). These piles of rock confined the channel to a straight, incised, and fast-moving stream. The stream was unable to overtop its banks and spread out onto its adjacent floodplain during the spring runoff or high flow events. Due to the disconnection between the stream and its floodplain, the ability of this system to store clean, cold water was lost. This project fixed all of Oregon Creek’s alignments in the lower reach, allowing the stream to access its floodplain and naturally store water for the first time in over 150 years!  We hope that downstream beavers will take up the work from here and fully restore this area!

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Project Results

Constructed stream channel: 1,370 linear feet

Constructed “detention ridges”: 492 linear feet

Floodplain willow trenches: 1,010 linear feet (5,050 willows)

Wood habitat structures: 7

Habitat pools: 24

Constructed floodplain: 4 acres

People & Organizations Involved

Big Hole Watershed Committee (project manager)

Montana Fish, Wildlife and Parks (landowner)

Funders

Wildlife Conservation Society – Climate Adaptation Fund

Montana Department of Environmental Quality

Contractors

Morrison-Maierle, Inc.

Watershed Consulting

Basic Biological Services

Project Photos

Oregon Creek Restoration design drawings.

Oregon Creek completed construction design drawings and specifications.

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Day 1 of construction! Cutting the new channel at the downstream reach.

Cutting meanders in the new channel.

Floodplain creation. Roughening and adding hardened material to the floodplain gave added complexity and micro topography.

These constructed riffles were placed in strategic locations throughout the project area. These structures are designed to allow overbank flows and floodplain activation. They also help to create pools and instream complexity, good for fish habitat!