January 18th issue of Science had an interesting article on stream dynamics. The author states that most of the stream studies that developed our sense of how a “natural” stream works were done in the Piedmont area of eastern Pennsylvania and Maryland. The author compiles an impressive variety of data to show that the streams in this area are far from “natural.” Instead, throughout the 1700’s and up to around the Civil War era, many eastern streams were dammed all along their lengths to create water power for mills. Over time, these millponds filled in. After these water-powered mills were abandoned, the unmaintained dams were breached and since then, the creeks have been cutting down through the pond sediments. A single channel with cutbanks on its outside bends has been viewed as “natural.” The author presents geological evidence that what preceded the millpond era were streams flowing within many branching channels through a wooded swampland across a broad, level valley. The author raises the intriguing question as to how much our practices of stream restoration are based on erroneous assumptions of how streams “naturally” function.
[This is significant to me because I’ve come to think a single channel with cutbanks indicates erosion. It’s nice to get confirmation.]
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