Tuning into rivers 

Audio research aims to aid restoration

When Mark Lorang listens to rivers, he hears answers. The scientist from the University of Montana Flathead Biological Station has spent the last five years studying the sounds of rivers for clues about their physical and biological characteristics. A new phase of his research, made possible with the help of a local technology company, could provide a breakthrough on better understanding river restoration and potentially foretell problems with underwater oil pipelines.

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  • An earlier stage of the Sound of Rivers project used hydrophones, as shown above. New fiber optic cables buried beneath the Nyack Floodplain of the Flathead River will improve his data collection.

Lorang was first approached about the Sound of Rivers project by his colleague, German scientist Klement Tockner. Though Tockner already had the funding for the project and a graduate student for Lorang to work with, Lorang was skeptical. He worried they would only hear white noise, but Tockner assured him there was more to it.

"I said, 'Klement, you are nuts, but I'll try and see if your student is any good,'" Lorang says. Swiss graduate student Diego Tonolla turned out to be great, and Lorang was in.

That was five years ago. Since then, Lorang, Tonolla, and Tockner have developed ways to record and listen to river sounds using hydrophones. What they've found is that not all moving water sounds the same, and the different sounds reveal important details about how the river works.

"The water is trapping air and creating sound that way," Lorang says. "It is moving sediment in different areas and creating sound, and hence each little environment has its own little soundscape."

Among other things, Lorang is attempting to use these different soundscapes to quantify and monitor how sediment moves through the water. At any given time, a river takes sediment from one bank and deposits it on another. Depending on the season, the amount of sediment moving in the river changes. For example, think of the difference between the Clark Fork now and when it turns muddy in the spring. Lorang monitors the sediment transport because of its effects on aquatic and riparian habitat.

One new technology may change how Lorang collects his data. He's buried highly sensitive fiber optic audio cables beneath the Nyack Floodplain of the Flathead River to record its sounds.

"From a remote location then, we can bury the cable, listen to the river and know where in the river the sediment transport is occurring, and the different intensities that are occurring out there, and how they change with flow," Lorang says.

Lorang hopes to apply the information in a couple different ways, beginning with the restoration of stream banks after dam removal. When a dam is in place, it traps all the natural sediment a river carries. Downstream of a dam, all the natural eroding is still taking place but, because the water is now devoid of sediment, none of the rebuilding occurs. As a result, riparian habitat and stream banks downstream from dams are disappearing.

If Lorang can create a standard for what healthy rivers sound like, he can use that to help restore riverbanks after a dam has been removed.

Another way Lorang can use the data from the fiber optic audio cables is in preventing oil spills like that of the Yellowstone River in 2011.

"In Montana, there are 1,800 oil pipelines going underneath rivers. Some of them are deep, some of them aren't," Lorang says. "If you had this fiber optic cable in there, you could actually listen to the river and know where and hopefully how severe the scour is occurring as a warning sign."

In other words, the cables can potentially detect when and where rock, logs and sediment are dragging along the river bottom most intensely. Lorang can then use that information to predict where oil pipelines are in danger of being uncovered and punctured.

Lorang acquired the audio cables from Alex Philp, a scientist for Adelos, Inc., which is partially owned by Flathead Reservation-based S&K Technologies. Philp says the cables have been primarily used for security purposes until now.

"I can't go into too much detail on this, but our customers include various levels of the U.S. government interested in using this as a warning system for security," Philp says.

He explains that the cables are buried underground and, once connected to a sophisticated electronic system, emit an array, or light. The array is sensitive enough to pick up on sound waves both underwater and above ground.

Philp says the cables have been a success in the security industry because of their ability to sense intruders. He now hopes to expand their use with environmental monitoring.

"Hell, you can listen to the wind blow with this thing," he says.

In fact, that sensitivity is creating a challenge. Though the cables are successfully recording sounds in the river, they are also recording much more.

"The cable we have buried is just 18 inches below the surface, so there's a lot of other sounds that are in there," Lorang says. "We can hear the wind blowing, we can hear the rain, we can hear trees creaking."

With time, Lorang and Philp are confident that they can filter out any extraneous sounds. Once Lorang hears only the river, the answers should follow.

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