Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Deforestation in snowy regions causes more floods

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:

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


Neither the paper nor this press release are under embargo.

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

snow environments”

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:

Sean Treacy | American Geophysical Union
Further information:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

New method increases energy density in lithium batteries

24.10.2016 | Power and Electrical Engineering

International team discovers novel Alzheimer's disease risk gene among Icelanders

24.10.2016 | Life Sciences

New bacteria groups, and stunning diversity, discovered underground

24.10.2016 | Life Sciences

More VideoLinks >>>