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EXPLORING BEAVER HABITAT AND DISTRIBUTION WITH GOOGLE EARTH:

THE LONGEST BEAVER DAM IN THE WORLD

The longest beaver dam observed with Google Earth to date (October 2 2007) is located in Northern Alberta. The dam has a length of about 850 meters (2790 ft). It has at least existed at this spot for over 15 years as it can be observed on the 1990 LandSat 7 Pseudo Color Imagery Provided by NASA World Wind. However 1975 aerial photo's show that this dam did not exist in 1975.

The actual location of the world longest beaver dam (that is until someone find a longer one) is just south of Lake Claire, and about 190 km to the NNE of Fort McMurray, just inside Wood Buffalo National Park.

Wikipedia lists the largest dam reported: near Three Forks, Montana, with 652 meters (2,140 feet) long, 4.3 meters (14 feet) high at the highest point, and seven meters (23 feet) thick at the base. I have not been able to find this dam on Google Earth.

Longest beaver dam in the world found with Google Earth (Digital Globe): October 2, 2007

This dam was measured with the Google Earth Measuring tool to be about 850 meters in length. It has clearly two or more lodges and is a combination of two original dams. No surface water drainage can be seen. Water moves down the very slight sloping wetland. The ( relative thin layer) of organic material of the wetland works as a sponge . The flow is slow and over a wide area of wetland which requires the building of very long dams. Many dams can be found in areas like this with lengths of 500 meters. Any dam over 600 meter remains exceptional.

1975 Aerial photo of the dam area: Some minor beaver activity can be observed (green arrows) but most of the area is covered by trees and shrubs. I expect this area was burned about 20-30 years before the date photos. A evenaged stand of stand of poplar (Po) is visible on the 1970 photo, has been replaced by a wetland in 2005. Melting peat plateaus and palsas are present in the surrounding wetlands, and I suspect that permafrost melting may have played a role in this as well.

This image is part of flight line A24215 ( photo number 253). Date: 9 August, 1975; original scale: 1:50'000.

Aerial photos of Canada can be obtained from the National Air Photo Library (NAPL)
   
Comparison of the two images shows interesting elements. The dams 1 and 2 existed in 1970 but have changed very little. The beaver lodge near Dam 1, has not changed much. Dams 3 and 4 have been build since 1975. The beaver offspring of dam 4 are building two smaller dams just to the side (green arrow). Larger images [+]
 

Identifying the best potential beaver habitat with Google Earth

This slight sloping area around the Birch Mountains was identified as a potential excellent beaver habitat after the study of a similar environment and beaver community near the Pasquia Hills in Saskatchewan. The NASA LandSat 7 Pseudo Color Image (2005) was taken from World Wind. Relief is exaggerated 5x to enhance the relief significance for beaver habitat and occurrence. The alluvial fans and associated drainage systems provide exceptional habitat.

Some of the high run off areas (purple) appear less suitable for or preferred by beavers.

This pseudo image with a near infra red band shows clearly the small open surface water areas representing (not always) beaver ponds. (Some of the black spots on the slopes are caused by cloud shadows).
   

The Longest Beaver Dam as Part of a Beaver system. The alluvial fans are fed by a series of stream and creeks from the Birch Mountains (blue arrows). Because of the very low slope of the alluvial fans, drainage flows have shifted and no clear drainage channels have developed. Beaver dams and ponds identified with light yellow arrows seem to be inactive. The light blue arrows indicate active ponds and dams with lodges.

Wave modified strand lines can be seen near B. Just to the east peat plateaus with collapse scars show the presence of permafrost in the wetlands. The longest dam is marked with the red sign.

 

The History of the Longest Beaver Dam

The NASA LandSat 7 images of 1990 and 2000 accesible as part of its magnificent World Wind System, give a simple overview of the beaver ponds and dams since 1990. It is clear that the this dam (Red Arrow) did exist in 1990 and had a similar size as in 2000 and 2007 (Digital Globe- Google Earth)

 

 

 
The Surficial Geology Map of Canada provides a thumbnail sketch of the parent materials which are present in this area. The white asterix shows the approximate location. The parent material in the alluvial fan areas where the dams occur is silty and sandy alluvial material washed down from the hills and slopes of Birch Mountain and modified by glacial lake action.
The Largest Beaver Dam in the World is actually just inside the boundary of Wood Buffalo National Park. See the red circle.
 
The Topographic map below shows the location of the largest beaverdam. It is interesting to see that the contor line near the dam reflect the topography of the alluvial fans at the bottom of the Birch Mountain slopes