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The importance and impact of gravel-bed rivers

“A river isn’t just a river. It is water and power,” Dr. Ric Hauer said.

Dr. Ric Hauer.

Dr. Hauer is the director of the University of Montana’s Center for Integrated Research on the Environment. He was in town last week to share his ground-breaking research on gravel-bed rivers like the Big Wood.

Before presenting his study to a standing room-only crowd at The Community Library last Wednesday night, Dr. Hauer gave a presentation to a group of local political and governmental agency leaders over lunch.

“The most important feature, the one that plays the largest role and has the biggest impact on the landscape, from species as small as microbes to as large as ungulates, is the river,” said Dr, Hauer, who joked he’s been in academia since kindergarten.

Dr. Hauer explained that gravel-bed rivers like the Big Wood can be found all over the West and throughout the world. Up until recently, however, our understanding of these rivers, their impacts and how best to manage them was inaccurate. That is why most of our attempts to heal gravel-bed rivers, or control them in “natural” ways, as well meaning as they’ve been, have failed.

“We try to take these highly complex, non-linear systems and make them linear and predictable and low risk and they are anything but,” Dr. Hauer clarified.

Dr. Hauer explained that we have long viewed such rivers as vital, but relatively limited features of the landscape that simply run from bank to bank—and occasionally flow over those banks. But thanks to the work of Dr. Hauer and his interdisciplinary team (which you can read more about online in ScienceMag.com or the New York Times), we now realize our view was askew and far too small.

“The river is way more expansive than just the water running within the banks. It is much, much larger than its channel,” Dr. Hauer said, explaining that the surface water and the ground water (aquifer) of gravel-bed rivers aren’t separate systems, but are all part of one, ever-changing river.

“There’s a high rate of ground water and surface water exchange. It’s all one system, from valley wall to valley wall,” he said, showing pictures of aquatic insects normally associated with the river being found in wells miles away from the main channel.

During seasonal surges and flooding episodes, gravel-bed rivers use cut-and-fill alluviation to move material like rocks, trees and soil around to create new habitat. This natural action of gravel-bed rivers rebirthing themselves in sections is especially important to the health of floodplains.

Species that rely on floodplains. Courtesy of Dr. Hauer.

“The magic happens in floodplains,” Dr. Hauer said, justifying his statement with the fact that approximately 80% of the bird populations in the West use floodplains as part of their survival—and they’re far from alone. Floodplains are the focal point for a high diversity of species, from insects, amphibians and trout, to moose, deer and bears.

“Rivers flood. That’s what they do. You can put up a levy but the water is just going to rise up through the surface and flood anyway,” Dr, Hauer told the crowd at The Community Library as many members of the audience shook their head in agreement after witnessing so much ground-water flooding last spring.

“The idea that there are 500 year floods or 100 year floods is a fantasy. They happen much more frequently than that,” Dr. Hauer bluntly stated.

“On the individual level, it’s heartbreaking,” he said to the lunch assembly, but he warned the consequences of not letting the river flood are even more dire to every species relying on the river, including humans. The more channelized a river is and the less room it has to expand, the less it is able to support wildlife of every kind.

“As you reduce the complexity of the river it reduces the complexity of the biological community. When we lose that habitat, we lose way beyond just some bird species,” Dr, Hauer said. “If we don’t do something about it, we’re going to lose nature as we know it.”

When asked what we could do for our troubled Big Wood River, the entertaining college professor said it all begins with education. “Knowledge is the answer,” he explained, imploring us to make ecologically-based management decisions.

The story as it appeared in The Weekly Sun.

“This is not so complicated that it can’t be done,” he said, strongly stating that if we can find places to let the river act naturally, it can heal itself. “Let the river do the work.”

After the question and answer session at the library, Scott Boettger, the executive director of the Land Trust reminded the audience that one of the best things we can do now to help the Big Wood is to save the places we still can, places that still have functioning floodplains, like Colorado Gulch in Hailey.

“The Land Trust is looking at what we can do to actually prioritize our protection efforts. Obviously, we’re not going to able to afford to buy up all the development in the floodplain, “Boettger said. “First and foremost, we need to protect those places that are not developed yet, and make sure they’re here for not just today, but for tomorrow also.”

Dr. Hauer’s timely and important presentation was sponsored by the Wood River Land Trust, The Community Library, the cities of Hailey and Ketchum, The Nature Conservancy, Trout Unlimited and Flood Control District  No. 9.  The lecture can be seen in its entirety at www.livestream.com/comlib/mountainrivers.

By Mike McKenna

*This story originally appeared in the February 14, 2018 edition of The Weekly Sun.