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Rebirth of a River

The Big Wood River Better the Second Time Around

(page 3 of 3)

The value of the floodplain.

Floodplain areas are critical for water quality, providing overhanging vegetation that keeps water cool for fish during the summer months, and crucial areas for water to spread out during flood events. The river needs these areas and so do the fish. Doug Megargle explains that in floodplain areas sediment can settle out as water slows down. “If [the river] can’t expand into side channels first and it can’t expand into the floodplain successfully, the river will scour and recruit an abnormally high sediment load,” he says. Increased sediment harms fish populations when it is disturbed or deposited in areas that fish need for spawning; trout need clean gravel on which to lay their eggs. Too much sediment in the channel can also impact the river’s interaction with the groundwater below the channel.

When the river is cut off from the floodplain, it cannot settle sediment outside of the main channel. This leads to unnaturally high amounts of sediment settling in the floodway which contributes to increased flood volume and velocity. Allowing the river as much room to move as possible and allowing the river to sheet flood and settle out sediment is critical to spreading out its energy and keeping flood volumes—and damage from flooding—at lower levels. Rather than constricting the river’s tendency to meander, the river should be allowed to move and spread out, particularly during flood events.

Lessons learned for future flood fighting.

Property owners living in the floodplain are understandably concerned with flooding. This year starkly revealed the risks of living in the floodplain. Historically, individuals have applied for stream alteration permits that allow them to riprap or otherwise alter the river to protect their property from flooding. Yet, there are limits to this individual approach. Riprap often transfers flooding to a neighbor downstream, across the river, or both.

Dr. Lium says that the wood deposited into the Big Wood this year is good not just for the river and its fish, but for landowners as well. “We should leave it in the system,” says Lium. Lium not only thinks it should remain in the system, but he hopes to use cottonwood logs in bank stabilization projects. To further stabilize the banks, landowners should add plantings along banks on top of the log work. In some cases, simply restoring native plants along river banks will help preserve banks during flooding and slow the flows.

What does the future hold?

This year, the Big Wood River lived up to its name. River anglers and other enthusiasts will experience a river that harkens back to a by-gone era of pools and logjams too numerous to count. As Fish and Game’s Megargle notes, this year it is “time to learn a new river. What was a run may not have water in it anymore; pools will be where they have never been before with large thanks to woody debris.” Heading out to a favorite fishing hole and finding it gone is one way to learn. But if we are to fully embrace the lessons of the new river, then we must learn how to live with the new river, as well as the process by which it was re-born. A natural force that plays an important role in the health of the communities in the Wood River Valley, the river can be tricky to contain. The wisest approach is to yield to it as much as we can, because the power of the river only increases as we try to confine it.

Carrie Norton, Code Compliance Specialist with Blaine County, sees a limit to the property-by-property approach to flood response. “If everybody works together on it, better solutions for more people can be reached.” Norton believes floodplain residents need to “come together and craft a vision for the river, beginning at the neighborhood level. First and foremost, we have to allow the floodplain to function.” While this doesn’t mean letting bridges wash out or endangering homes, it does mean allowing sheet flooding to enter the floodplain, using more natural techniques to stabilize banks and protecting homes over landscaping.

Approaches include re-vegetating areas along the river that have been covered in grassy lawn with native shrubs with good root systems, such as red osier dogwood and willows and re-thinking when and how to construct more intensive bank stabilization projects. Norton also raises an important point for local communities to consider when planning for future flooding: costs to the public. Planning for restoration at the neighborhood level can eliminate costly, last-minute dikes and riprap. These types of projects constructed amidst flooding keep the river from sheet flooding and transfer damages from flooding downstream.

Private landowners, local governments, non-profit organizations, and state and federal agencies will all play a role in protecting the health of the river. A coordinated vision that brings all the players together and allows the most natural functions of the floodplain to continue will benefit all—and potentially cost communities less in flood-fighting dollars over time. Leaving wood in the river is one vital step. Local ordinances setting development away from the river’s edge will play a key role, as will future restoration projects designed to improve the function of the floodplain. Private landowners can have a major impact on the health of the river by taking a cooperative and multi-faceted approach to protecting their property. And when waters rise, homeowners should protect their structures, while allowing the sheet flooding to occur.

Working together, residents of the Valley’s communities can ensure the health of the river while safeguarding private property. Letting the river change, grow, and reach its greatest potential will be the measure by which we can judge our success as neighbors who live on and love the Big Wood River.

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