[Sdpg] Researchers Challenge Water-Flow Model, New York Times Article

[Wesley Roe and Santa Barbara Permaculture Network]

hi everyone
	before 1970 researcher studying wild animals , only studied wild 
animals in cages. Except Walt Disney remember Wild Kingdom and all 
that animal porn. While guess what, the researcher that developed the 
Water-Flow Models studied degraded landscapes and stream beds for 
their research read below
                             wes


Researchers Challenge Water-Flow Model
http://www.nytimes.com/2008/01/18/science/18rivers.html?ex=1201323600&en=76c2161ce75d4eed&ei=5070&emc=eta1

By CORNELIA DEAN
Published: January 18, 2008

Decades ago, when geologists were developing ideas about how water 
typically flows across land, many of them studied the streams of the 
Mid-Atlantic States, concluding that they naturally move in 
ribbonlike channels cut through silty banks. In the years since, 
ecologists and conservationists have used this model in efforts to 
restore streams damaged by urbanization.

Now, though, researchers at Franklin and Marshall College are 
challenging it. They say the streams studied by their geological 
predecessors were not "natural archetypes" but rather the artifacts 
of 18th- and 19th-century dam building and deforestation.

The scientists, Robert C. Walter and Dorothy J. Merritts, report 
their findings on Friday in the journal Science.

In a commentary on the work, David R. Montgomery of the University of 
Washington, said it did not challenge the earlier geologists' 
"fundamental insights" into the interplay of water and sediment. But, 
Mr. Montgomery said, "in light of the new findings, what constitutes 
a natural channel form requires re-examination."

The researchers examined historical records and maps, geochemical 
data, aerial photographs and other imagery from river systems in 
Pennsylvania and Maryland. They discovered that beginning in the 
1700s, European settlers built tens of thousands of dams, with 
perhaps almost 18,000 or more in Pennsylvania alone.

In a telephone interview, Dr. Merritts described a typical scenario. 
Settlers build a dam across a valley to power a grist mill, and a 
pond forms behind the dam, inundating the original valley wetland. 
Meanwhile, the settlers clear hillsides for farming, sending vast 
quantities of eroded silt washing into the pond.

Years go by. The valley bottom fills with sediment trapped behind the 
dam. By 1900 or so the dam is long out of use and eventually fails. 
Water begins to flow freely through the valley again. But now, 
instead of reverting to branching channels moving over and through 
extensive valley wetlands, the stream cuts a sharp path through 
accumulated sediment. This is the kind of stream that earlier 
researchers thought was natural.

"This early work was excellent," Dr. Merritts said, "but it was done 
unknowingly in breached millponds."

She said she and Dr. Walters believed their work had important 
implications for stream restoration. For one thing, she said, 
evidence so far suggests that removing the overlay of sediment may 
encourage streams to return to a truly natural state. But also, she 
added, restoration "requires much more consideration of what we are 
trying to restore, and what might actually be a sustainable approach."