Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Deforestation in snowy regions causes more floods

04.10.2012
New research suggests that cutting down swaths of forest in snowy regions at least doubles – and potentially quadruples – the number of large floods that occur along the rivers and streams passing through those forests.

For decades, the common perception in hydrology has been that deforestation in such areas made seasonal floods bigger on average, but had little effect on the number of large floods over time, said geoscientist Kim Green of the University of British Columbia.

But a new study by Green and her co-author Younes Alila published today in Water Resources Research, a journal of the American Geophysical Union, suggests that deforestation consistently causes more floods – both big and small. In the interior regions of North America, many creeks and rivers get most of their flow from melting snow accumulated during winter storms in mountainous areas.

How much water flows down these streams depends not only on how much snow falls upstream, but how fast the snow melts. But deforestation shines a new – and glaring – light on this water source. While ordinarily the trees keep the melting under control by shielding snow from the sunlight, “as soon as you get rid of the trees, the snow melts faster,” said Green. “It’s that simple.”

The difference between Green and Alila’s study and what hydrologists have historically done is how they crunched the data. In the past, hydrologists used a technique called chronological pairing – they compared each year’s flood data from a stream in a deforested area to that year’s data from a nearby, fully forested stream. This allowed the scientists to describe how floods become larger on average in deforested areas. But chronological pairing doesn’t deduce how much more frequent these floods might be. For this, scientists need a method called frequency pairing.

In frequency pairing, researchers review a decade or more of data all at once to determine a flood’s return period – how often a flood of a given size recurs. Green’s study is the first to use frequency pairing to explore how deforestation affects flood frequencies in streams in mountainous regions where at least half the annual precipitation falls as snow. She analyzed data from four creeks – Camp Creek, Redfish Creek and 240 Creek in British Columbia and Fool Creek in Colorado. With two creeks, Fool and Camp, she studied data from the past few decades in comparison to nearby, similar creeks where the terrain had not been deforested. With the other two, Redfish and 240, she used flood data generated by a computer model to study the simulated effect of deforestation of the terrain over more than 90 years.

The analysis showed that, in all four waterways, deforestation turned 10-year floods into three-to- five-year floods. Twenty-year floods recurred every 10 to 12 years. Most dramatically, in 240 Creek, 50 year floods happened every 13 years, almost four times as often. “Once you look at how the frequency has changed,” Green said, “you start to realize that deforestation has had a pretty dramatic effect on floods.”

Green’s model for how deforestation affects the flow of water is “something that’s going to be tested in other places many times, to see if their theory actually holds,” said Sandy Verry, a retired U.S. Forest Service hydrologist in Grand Rapids, Minn., who was not involved in the study but has studied streams using chronological pairing in the past. Verry said he believes Green’s conclusions about flood rates to be reasonable.

Until recently, the decades of data needed for frequency pairing data was scarce, Verry said, because hydrologists only started recording stream measurements in the North American West about 50 years ago. He expects there will be a “plethora” of further studies that study the frequency of floods over a broad array of deforested landscapes, including streams that flow into farmlands and cities. “There’s a whole realm of application to forest landscapes at lower elevations and flatland that this can be applied to,” Verry said.

Notes for Journalists

Journalists and public information officers (PIOs) of educational and scientific institutions who have registered with AGU can download a PDF copy of this paper by clicking on this link:

http://dx.doi.org/10.1029/2012WR012449

Or, you may order a copy of the paper by emailing your request to Sean Treacy at
streacy@agu.org. Please provide your name, the name of your publication, and your phone

number.

Neither the paper nor this press release are under embargo.

Title:
“A paradigm shift in understanding and quantifying the effects of forest harvesting on floods in

snow environments”

Authors:
Kim Green and Younes Alila: Department of Forest Resources Management, University of British Columbia, Vancouver, BC, Canada.
Contact information for the authors:
Kim Green, (250) 352-6725, Email: apexgeo.kg@telus.net

Sean Treacy | American Geophysical Union
Further information:
http://www.agu.org

More articles from Earth Sciences:

nachricht How much biomass grows in the savannah?
16.02.2017 | Friedrich-Schiller-Universität Jena

nachricht Canadian glaciers now major contributor to sea level change, UCI study shows
15.02.2017 | University of California - Irvine

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Switched-on DNA

20.02.2017 | Materials Sciences

Second cause of hidden hearing loss identified

20.02.2017 | Health and Medicine

Prospect for more effective treatment of nerve pain

20.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>