permaculture

[Keith Johnson <keithdj@mindspring.com>]

I sent the following letter to the publishers of Walter and Merritt's 
article:

   *Dammed, you say...*

   When Walter and Merritts were researching their article, it seems
   that they may have overlooked some landscape patterns which preceded
   those established by settlers, specifically the impacts of those
   supreme hydrological engineers, beavers.

   These organisms, estimated to number 100-400 million before being
   made into hats for Europeans, built as many as 15 dams per mile
   stitched together by short stretches of shallow, braided channels.
   Their impact on sediment and organics impoundment, groundwater
   recharge via infiltration, complex habitat creation, and other
   ecological impacts seems, ironically, similar (though arguably
   superior) to that of the settlers who followed with their own dams.
   Even more ironic, those same settlers never even saw, or accounted
   for, the extensive earth and waterworks since the beavers were
   mostly trapped out before their arrival.

   An article, written by Toby Hemenway, and published by us in 2002
   and available online at:
   http://www.permacultureactivist.net/articles/Beavers.htm explores
   the complex ecological transformations performed by these hardy and
   handy mammals.

   Taking beavers into account may not change Walter and Merritts
   conclusions about the natural form of streams, but their impacts
   need to be factored into the equation.

<http://www.nytimes.com/2008/01/18/science/18rivers.html?_r=2&scp=1&sq=water-flow&oref=slogin&oref=slogin>
Wesley Roe and Santa Barbara Permaculture Network wrote:
> 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."
>   
--
Keith Johnson
"Be fruitful and mulch apply."
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