Riparian Health - Understanding the Role of Beavers in Riparian Areas

January 26, 2012 Print Friendly and PDF

Benefits of Beaver

Well-constructed beaver dams, such as the one pictured above, will withstand the energies of high flows and spring runoff.


Beavers are key agents of riparian-wetland succession because the dams they build act as hydrologic modifiers. When a beaver dam is constructed, a flowing stream can be changed overnight to an aquatic pond. This in turn can lead to aggradation of the channel, establishment of floodplains, and raising groundwater levels. Elevated water levels also help to keep water in areas that would be otherwise dry during summer months and also during times of drought. This helps to sustain plant and animal life. The key to whether or not a beaver dam is beneficial is its stability. Beaver dams built with the correct, stabilizing woody vegetation, where there is enough additional woody vegetation to maintain the dam once built, are considered stable. Some beavers, known as “mudders,” also pack their dams with mud. The mudders' construction technique creates a better basis for vegetation to capture a dam, thus helping to stabilize it.

Disadvantages of Beaver

Although beaver dams can be a benefit, they can also be a hazard. Beaver dams that are not stable unleash tremendous energies when they fail that often results in degradation and stream adjustments, including channel widening, lowering, and lateral migration. For this reason, it is important to note when evaluating riparian health whether beaver dams that are present are being actively maintained.  A dam that isn't being maintained, or has not used mud in the construction, or is not captured by vegetation will breach at some point.

Warning Signs

Poorly constructed beaver dams, or those made from the wrong materials, such as the sagebrush dam in the above picture, will breach easily and can lead to degradation of the current channel.


Some warning signs that present beaver dams are unstable, which may lead to a breach and subsequent decline in health, or “unraveling” of riparian areas include:

  • Lack of sufficient woody vegetation. It is important to note whether there is sufficient woody vegetation present for dam construction and maintenance. If vegetation is minimal, there will be little left for maintaining the dam once built. This may cause the beaver to abandon the beaver dam.
  • Beaver dams with breaks or leaks. This may be a sign that a breach of the dam is forthcoming.
  • Beaver dams which lack captured vegetation. Captured vegetation growing within and among the beaver dam helps to stabilize it and prevent breaching.

Related Pages

Riparian Health - Evaluating the Health of Riparian Areas - An Overview

Riparian Health - Understanding the Function of Floodplains

Riparian Health - Understanding if the Channel is in Balance with the Landscape

Riparian Health - Riparian Areas and Water Storage

Riparian Health - Understanding How Uplands Contribute to Riparian Health

Riparian Health - Understanding Riparian Vegetation Age-Class and its Role in Health

Riparian Health - Understanding Species Diversity

Riparian Health - Understanding the Relationship between Vegetation and Soil Moisture Characteristics

Riparian Health - Understanding Root Masses and Bank Stability

Riparian Health - Understanding Plant Vigor

Riparian Health - Understanding if you have Adequate Vegetation

Riparian Health - Understanding the Role of Large Woody Material in Riparian Areas

Riparian Health - Understanding a Channels Ability to Dissipate Energy

Riparian Health - Point Bars

Riparian Health - Understanding Lateral Stability in Riparian Areas

Riparian Health - Understanding Vertical Stability in Riparian Areas

Riparian Health - Understanding if the Channel is in Balance with the Soil and Water Being Supplied
 

References

American Geophysical Union. "Beaver Dams Create Healthy Downstream Ecosystems." ScienceDaily 6 June 2006. 21 June 2010 <http://www.sciencedaily.com/releases/2006/06/060605120417.htm>.

University of Alberta. "Busy Beavers Can Help Ease Drought." ScienceDaily 26 February 2008. 21 June 2010 <http://www.sciencedaily.com/releases/2008/02/080220130511.htm>.

USDI Bureau of Land Management. 1998. Riparian Area Management: A User Guide to Assessing Proper Functioning Condition and the Supporting Science for Lotic Areas. Technical Reference TR 1737-15. 124 pp. More Information available at: http://www.blm.gov/or/programs/nrst/index.php

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.