“Natural” rivers are actually man-made

This is fascinating: Apparently geologists have spent decades assuming that the shapes of Mid-Atlantic-state rivers were natural — when they’re actually man-made.

Basically, one of the problems with studying rivers in the US is that so many have been warped by commercial and residential development that it’s hard for us to know what the stream ought to look like, naturally. The closest to “natural” that the geologists could identify were rivers of the mid-Atlantic states — which move in ribbon-like channels through silty banks. They assumed, for decades, that this ribbon-like shape was the Platonic solid.

But it turns out that those ribbon-straight rivers were in fact affected by human development, as two scientists — Robert C. Walter and Dorothy J. Merritts — report in Science today. As the New York Times reports:

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.”

(Image above by Fhantazm, via his Creative Commons Attribution-NonCommercial-ShareAlike license!)


blog comments powered by Disqus

Search This Site


Bio:

I'm Clive Thompson, a writer on science, technology, and culture. This blog collects bits of offbeat research I'm running into, and musings thereon.

Currently, I'm a contributing writer for the New York Times Magazine and a columnist for Wired magazine. I also write for Fast Company and Wired magazine's web site, among other places. Email or AOL IM me (pomeranian99) to say hi or send in something strange!

More of Me

Twitter
Tumblr
Flickr


Recent Entries

New technique renders objects at sea “invisible” to waves of water

Poll: Young people who use landlines are more conservative than those who use mobile phones

At Amherst college, 1% of first-year students have landlines, 99% have Facebook accounts

North Dakota the most outgoing state, according to study of “the geography of personality”

Why the next wave of high-tech CEOs will be as old as your parents: My latest column in Wired magazine

» visit the Collision Detection archives

Clive Thompson's Tumblr
a bunch of stuff

September 26, 2008 » 01:57 PM

From an interview with ethnobotanist and anthropologist Wade Davis:

One of the cultures you celebrate in Light at the Edge of the World is the Inuit. What do you most admire about them?

Davis: The Inuit didn’t fear the cold; they took advantage of it. During the 1950s the Canadian government forced the Inuit into settlements. A family from Arctic Bay told me this fantastic story of their grandfather who refused to go. The family, fearful for his life, took away all of his tools and all of his implements, thinking that would force him into the settlement. But instead, he just slipped out of an igloo on a cold Arctic night, pulled down his caribou and sealskin trousers, and defecated into his hand. As the feces began to freeze, he shaped it into the form of an implement. And when the blade started to take shape, he put a spray of saliva along the leading edge to sharpen it. That’s when what they call the “shit knife” took form. He used it to butcher a dog. Skinned the dog with it. Improvised a sled with the dog’s rib cage, and then, using the skin, he harnessed up an adjacent living dog. He put the shit knife in his belt and disappeared into the night.

September 25, 2008 » 11:21 AM
“Video from a camp north of Toronto in December 2005 shows a car spinning around in a nearby, snow-covered parking lot. Prosecutors characterized that as special driver training but the defense, and many outsiders, said it was nothing more than “cutting doughnuts,” a favorite winter pastime of young Canadian motorists.” - A key piece of evidence submitted in the trial of a gang of alleged young Canadian terrorists.

September 24, 2008 » 11:21 PM
“Life imitates art imitating life: just thought a gnat crawling across my monitor was part of a Flash-based ad. I clicked it.” - A Tweet from Bill Braine.

September 24, 2008 » 02:37 PM
“Funniest FB friend request ever: “Twitter friend hoping to get to second base (Facebook!) ;-).”” - A recent Tweet by Pistachio

September 24, 2008 » 12:28 PM
Chinese powdered-milk crisis creates a new market: The return of the wet nurse

» visit my Tumblr

Recent Comments

Photos

» see all of my photos on Flickr

Collision Detection: A Blog by Clive Thompson