Recent Rain Tests Hallwood Restoration Project

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The storm that swept through Nevada County between the 23rd and 25th of October dropped between seven and twelve inches of much needed precipitation. This rainfall has led to, among other things, increased flows in the Yuba River. 

We sat down with one of our SYRCL scientists, Tyler Goodearly, to learn more about how this rain event interacted with the Hallwood Side Channel and Floodplain Restoration Project, a restoration effort that SYRCL has been working on and committed to for the past five years. 

Hallwood before the October rain event
Hallwood after the October rain event

Q: What did scientists learn from this big rain event?

A: One of the restoration goals was to restore a natural process called fine sediment recruitment. This rain event proved we were successful in restoring that process.

Hallwood 042021 1

In fact, fine sediment was recruited across the project footprint. As anyone who has visited the lower Yuba can attest to, the lower Yuba is covered with cobble and is fine sediment-starved. Fine sediment is important because it holds moisture, thereby providing habitat for young plants. Without fine sediment, the landscape would look more barren.

This is just one initial finding. There is much more yet to know about the impacts. SYRCL scientists and project partners will monitor what plants appear on that fine sediment in the upcoming months and years. 

Did the rain event impact spawning salmon?

We cannot know all of the impacts, but after the rain event, we can say that salmon were spotted spawning in the newly restored Hallwood side channels. 

Did the rain event impact redds?

We cannot quantify the impacts at this time. What we do know is that salmon are good at picking spots protected by scour. The other thing we know is that big rain events like this will encourage “shy spawners” to get moving. 

Existing conditions – steep cobbled embankments, little floodplain connectivity
Proposed conditions – shaded side channels and increased floodplain connectivity

How will the data collected impact future work?

We know that the river will always change and move things (like sand and debris) as it did in this rain event. The data we are collecting at Hallwood reinforces the need to respond to ever-changing rivers with dynamic plans that incorporate on-the-ground conditions with the latest science. Providing the river with space and lowered floodplains means that it can adjust to high water events naturally. 

SYRCL is involved in a number of restoration projects, which are in different phases of planning. These projects focus on restoring ecosystem services upstream at places like Lower Long Bar, Upper Long Bar, and Upper Rose Bar. The data we’re collecting at Hallwood will help us design and monitor those projects as well. 

Where does the Hallwood Restoration Project stand today?

The first phase of construction was completed in Fall 2020 with the removal of 1.2 million cubic yards of gravel, or enough gravel to fill 366,986 Olympic size pools. When complete, the project will restore 1.7 miles of perennial side channel and more than 6.1 miles of seasonal side channel, alcoves, and swales.

The project will also provide 157 acres of seasonally inundated riparian habitat. All of these improvements will help provide food and shelter for juevenile salmon. 

Hallwood Plant Crew
Planting riparian tree species at Hallwood

We also want to point out that it is not just the salmon that these projects help…it’s other fish and other wildlife like Sacramento suckers, Pacific lamprey, riffle sculpin, and  hardhead as well as mergansers, bald eagles, golden eagles, river otters, frogs, snakes, and so much more. Scientists have even spotted bears at Hallwood along with coyotes and deer, just to name a few mammals. 

Golden Eagle 2 credit Wendy Miller
Golden Eagle; photo courtesy of Wendy Miller
Mule Deer

To learn more about the Hallwood Side Channels and Floodplains Restoration Project, please click here.

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