Of Gravel and the River

Stringing ropes across a river on a March day sounded like pleasant work, especially on the Jacks Fork, which may be the most dazzling place in the world.

A few butterflies are out. Pileated woodpecker and kingfisher challenge jets for sound effects. By evening, bats try their wings as peepers sing. Only bare trees say spring hasn’t arrived, which makes Robb Jacobson happy.

Jacobson is a United States Geological Survey researcher. His job is surveying the river and tree leaves get in his way. His laser theodolite, a surveying instrument with an electronic data logger, doesn’t see through leaves, although they can “look around them a little,” Jacobson says.

My job for the day is setting up survey cross-sections. I had thought it would be purely educational, but I’d forgotten about chest waders. Even on a cool day they make you sweat like a kid on a hay crew.

Jacobson has spent several years gathering data on Ozark rivers. He has updated our knowledge of Ozarks rivers and the critters that live in and near them.

“People see rivers and think they have always looked like this, but we know that’s not so. With our equipment we can describe accurately what’s changing and why,” Jacobson says.

“Jacobson’s work is just solid science,” says Bob Cunningham, Conservation Department assistant district forester in West Plains. Cunningham has a personal and professional interest in Ozark forest history. “We’ve needed something like this report. I’ve always thought it was simplistic to blame early timber cutting for all the gravel in the rivers.”

The report in question, Historical Land-Use Changes and Potential Effects on Stream Disturbance in the Ozark Plateaus, Missouri, published by the U.S. Geological Survey in cooperation with the Missouri Department of Conservation in 1994, deals with issues debated for decades. It uses many geological and historical methods to reach a main conclusion: livestock grazing on open range in the Ozarks until the 1950s was primarily responsible for destabilizing the streams Jacobson examined. Recovery seems to be underway, but returning rivers to optimum conditions will take time and patient management.

That kind of care has gone into Jacobson’s research.

He crafts methods to determine what Ozark rivers were like before settlement, 200 or so years ago, as well as more recent changes.

Ropes and his theodolite are some of his more fascinating tools. Old photographs and memories can be valuable, too.

Surveying’s difficulties come from the need to examine exactly the same portions of the same rivers year after year. Jacobson and his apprentice, Rose McKenney, a graduate student who also works for the USGS, have become experts on the Little Piney and Jacks Fork rivers and the Buffalo River in Arkansas.

To support this detailed research, the Conservation Department has cooperated with the USGS, the National Park Service, which administers three rivers as parks in the Ozarks, and the National Biological Service, a new federal agency. In the Ozarks the NBS has focused its Global Change Research Project on rivers, because our streams may be impacted by changing weather and other variations in the future. The NBS is also helping fund a closely related study of fish and changing Ozark rivers.

“These different sites we’re studying have a variety of river habitats,” McKenney points out as we work. “Riffles, runs and pools are affected by floods and other factors. We’re surveying how and why river channels change over time.”

A native of the Pacific Northwest, McKenney says she particularly enjoys how Ozark rivers vary with each season. “By the end of August in places they’re like little bitty caves under all the green limbs. We don’t have that so much out West.”

Her dissertation will focus on how and why river habitats change. Her special interest is bluffs, which tend to form deep pools, a favorite habitat for bass.

We worked near Alley Spring to measure some 20 cross-sections. Once rope and survey line are run across, the surveyor sets up the theodolite on shore at one end of the line. The other person holds a stake topped with a special target and stops at about each meter marked along the line.

This allows the instrument to record the depth of the river channel at intervals along the line. By comparing data from all 20 cross sections, Jacobson and McKenney can see how this half mile of the Jacks Fork has changed over time and in relation to many variables, such as floods, river bed materials and surrounding vegetation.

Stringing heavy nylon rope from one bank to the other side, I tried to stay ahead of Robb and Rose. A three person crew can do about seven or eight cross-sections a day, fewer if deep water makes a boat necessary.

As a survey-rope runner I learned its difficulties: stakes get covered by flood-borne sediments; a line of sycamores at the edge of a gravel bar makes it nearly impossible to run rope straight across; some wide stretches of river and gravel bar require extra rope and survey lines; the river can top your waders.

“We’ve found one section of a stream that has moved about 300 meters across the flood plain in the last 50 years,” Jacobson said as we broke for lunch. “That’s roughly the channel moving the length of a car every year.

“Few cross-sections show that much instability. We’re trying to find factors causing such disturbance. One of the biggest problems in the last 200 years seems to be that fine sediments are not being replaced on banks. Instead, mud is washing downstream leaving wider and shallower channels.

Part of Jacobson’s enthusiasm for research comes from working as a geomorphologist, a geologist who specializes in the dynamics which shape landforms. Years of experience as a geomorphologist help him see shapes of past river channels in the slight rise and fall of bottomland fields.

“Many complex factors affect rivers, that’s what makes this project so fascinating,” he explains. “We’ve gathered valuable data on these streams. Nothing like this has been done before in Missouri. We’re getting a holistic view of rivers and the processes that form them.”

In addition to measuring channels, the stream geomorphology project has drilled into riverbottoms to see how channels have changed by examining sediment layers. Comparing channel changes and human use of the land shown on aerial photos each decade or so also has helped explain forces affecting rivers. Three reports on geomorphology studies have been published recently and more are planned.

Jacobson says Ozark rivers have gone through three phases. First was a pre-settlement period lasting roughly until 1800, when channels were fairly narrow and deep. Then, until about 1950, we had the period of greatest disturbance when many channels became wider, shallower and more unstable. This is when many gravel bars developed. We’re in a recovery period now with more vegetation returning along streams.

The project’s 1994 publication examines historic records to present an environmental chronology of Ozark rivers. Some of the most fascinating records used are comparisons of historic and contemporary photos. Accounts by early Ozark explorers also suggest extensive gravel bars on rivers are relatively recent features.

Jacobson uses cattle and hog population figures from the last 150 years, statistics on land cultivated and early government land surveys. From my point of view, the most engaging data involves oral history accounts of farming, logging and life along the Jacks Fork and Little Piney.

For parts of three years I was hired to find long-time residents of these watersheds who had good memories of changing use of the land. Such oral insights into recent history were important because no written records exist to document many farming methods. Rapid change in the 20th Century has made oral history methods useful to many disciplines.

As might be expected, each person interviewed had a slightly different point of view and different memories of his or her farm, river or neck of the woods:

We used to always burn every spring. You had to burn every spring because, you see, there wasn’t no stock law. People just turned their stock out on what they call the free range. Over there at the old home place where this house is, well we’d milk the old cows and just kick them out of the gate … You could go back out north out there and there’d be as high as 50 bells. You could just hear cow bells, horses and cows … and they all had bells on them.

That’s the late Ab Detwiler speaking, a Mennonite farmer who lived south of the Jacks Fork near Birch Tree. He and his wife, Lottie, and others spoke about how common spring or fall burning was 50 or 60 years ago. Burning promoted grass to support livestock roaming the countryside, which was mostly open range. It may have also contributed to erosion and streambed instability in the long run.

These and related observations, when joined with data about livestock numbers, suggested to Jacobson patterns of land use that may have changed rivers. By using different kinds of data, a picture of the changing Ozarks and its rivers emerges.

“This report is valuable in managing the Current, Jacks Fork and other streams,” observes Dave Foster, a biologist recently retired from the National Park Service. “We have limited resources so this helps us know what sections of river may be unstable and why. We’ve had to move campgrounds in the past and must avoid such expense in the future.”

Can study of stream geomorphology be any help in the related issue of gravel mining? Regulations in recent years have affected how gravel can be taken from streams.

“Many believe rivers were so damaged by timber cutting a hundred years ago it doesn’t make any difference where gravel comes from,” Jacobson says about the question. “Rivers are recovering according to our research. If we study them we can find what areas have been disturbed the most. These places might be better for mining than more stable zones.”

Any spring day along a river makes questions of stability and past uses of rivers seem irrelevant, but geomorphology may make it possible to sustain and improve our rivers so we can enjoy them all the more.

From the Missouri Conservationist Magazine
AUGUST 1996 ISSUE
Publish Date: Aug 02, 1996
Revised Date: Oct 25, 2010