Of Gravel and The River
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