This is the longest beaver dam I have found so far with a systematic Google Earth search and interpretation of beaver habitat across Canada. Beaver lodges are visible and the dam must be the result of at least two beaver families. Dams of about 500 meters are quite common in Canada, but 850 meters (2790 ft) is exceptional. Long dams like this tend to develop mainly in large wetlands. Many more beaver dams can be observed in the surrounding area. This dam is located near the southern edge of Wood Buffalo National Park , in Northern Alberta, Canada and about 190 km North of Fort McMurray and the Alberta Tar Sands.

Wikipedia provides a reference for a beaver dam near Three Forks, Montana, with a length of 652 meters (2,140 feet), 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.

The challenge: "Find the largest beaver dam in your area"


For more information:
http://www.geostrategis.com/p_beavers-longestdam.htm



The direction of waterflow is indicated by the blue arrow. Waterflows subsurface through a wetland, treed muskeg, with stunted tamarack and black spruce. Just to the left of the big dam two small new dams are being build. They are much better visible with Google Earth tahn on this image. The big dam itself is a combination of the work of at least two beaver families.



The NASA LandSat 7 Pseudo Color Image (2000) 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. That is where the longest beaver dam was found. (See black arrow).

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).

This situation is similar to Canada's Beaver Capital located on the slopes of the Pasquia Hills in Saskatchewan.

See also:
http://www.geostrategis.com/p_beavers-pasquia.htm

www.geostrategis.com

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..

.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. The red dotted line shows the location of the beaver dam in 2007 (or rather the date of the Digital Globe image)


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 Image [+]



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)

EXPLORING BEAVER HABITAT WITH GOOGLE EARTH:

BEAVER ENGINEERED LANDSACPES- THE HIGHEST DENSITIES OF BEAVERS IN CANADA, THE WORLD?

Beavers played a key role in the settlement and development of Canada. Beaver pelts drove the economy and formed the "currency" for the trade between the Hudson Bay Company and the aboriginal nations in Canada.

The beaver population steeply declined under the pressures of over trapping and reached a threatened species status. Presently beavers are reclaiming much of their original habitat, at least what is left of it. In many areas this recovery is rather spectacular. This recovery is captured by comparison of old Aerial Photography with recent high resolution Google Earth imagery

The north american beaver, with its beaver dams, beaver lodges and ponds is unique in the sense that it provides a clearly visible footprint on satellite images, particularly the high resolution imagery accessible through Google Earth.

Figure 1 Pakwaw Lake Beaver Community, Saskatchewan , Canada . This high resolution Google Earth (Digital Globe) shows an unusually high concentration of the beaver dams. The highest I have observed in Canada (in the world?). Over 20 dams and lodges per Km2. The beaver lodges are clearly visible as light dots (actual size on the ground is 7-8 meters in size) in the inundated areas. It is typical to find high densities of dams in streams (10 - 25 dams per linear Km) but is is rather unusual to find them evenly spread out over a wetland like this. This image shows a portion of a large beaver community near Pakwaw Lake (see below)


Figure 2
This NASA World Wind Pseudo Colour Landsat Image (2000) shows the broader landscape setting of this high density beaver area. The near infrared enhances the beaver ponds (small dark blue spots creating a loosely knitted landscape impression. The white square represents the approximate location of the Google Earth image above. The thin red lines outline the concentrations of beaver dams in the landscape. The Pakwaw Lake first nation's community is to the left of the square.




Figure 3 There is a dramatic difference between the 1945 air photo (right) of the same area as the Google Earth image (left). There is certainly no larges scale presence of beaver in 1945. Tree cover at that time was probably birch and aspen with alder and willow shrubs and some open wetlands. In the surrounding area some signs of beaver activity were seen.


For more informationwww.geostrategis.com

The Longest beaver dam post made the news in Canada this past week. Patti-Kay Hamilton , a reporter for the Canadian Broadcasting Corporation (CBC -North) located in Yelloknife was visiting the Wood Buffalo National Park Office where parks conservation officers where looking at the Google Earth post of this beaver dam. She wrote the short story line for this news item below which triggered a series of radio newspaper and tv (Discovery Channel) interviews

Quote:

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Big dam! Alberta beavers build 850-metre barrier

Wood Buffalo structure the world's largest dam, ecologist says

Last Updated: Monday, April 14, 2008 | 5:50 PM ET Comments 60 Recommend 186

CBC News

An Ottawa scientist has identified what he believes to be the world's largest beaver dam in Wood Buffalo National Park in northern Alberta.
Ecologist Jean Thie, who is Executive Director of the Canadian Institute of Geomatics, said he discovered the 850-metre long dam while scanning satellite images for signs of climate change.
"They are one of the few species that really leave a footprint on the Earth that is visible from satellite," Thie told CBC News in an interview.
"In addition to looking at permafrost melting, I started looking at beaver dams and just scanning all of northern Canada."
The dam is located just south of Lake Clair, north of the Birch Mountains and within the boundaries of the national park. It's about 190 kilometres northeast of Fort McMurray, Alta.
Thie said northern Alberta has the richest beaver habitat in the world, adding that he intends to continue to search for even larger dams in the area.
"These are some of the most amazing beaver landscapes in the world," he said. "I would not be surprised if we find a longer dam there than the one we have found so far."
The previously reported largest beaver dam was a 652-metre structure in Three Forks, Montana, Thie said.

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CBC link: http://www.cbc.ca/canada/north/story/2008/04/14/beaver-park.html
Beaver dam description
http://www.geostrategis.com/p_beavers-longestdam.htm

BEAVER ENGINEERED LANDSACPES- THE HIGH LEVEL ALBERTA BEAVER LANDSCAPE- AN EXCEPTIONAL EXTENSIVE BEAVER DOMAIN


Figure 1: High Level Beaver Landscape, Alberta , Canada .. This low resolution obique Google Earth image (Digital Globe) shows an unusually high concentration of beaver dams in in all the drainage channels. All the creeks (Bede, Caribou, Parma, Melto etc.) have been transformed by beaver into a long strips of beaver ponds and beaver controlled lakes. The Makenzie highway is visible as the thin grey line in the high resolution strip on the right side of the image. the town of High Level, Alberta is just to the north of the east of the red outline on the Highway.



Figure 2. High Resolution Detail of Beaver dams and Ponds. This is the Yellow circle area enlarged. Drainage is to the right. Beaver dams, ponds and lodges are clearly visible.



Figure 3 This NASA World Wind Pseudo Colour Landsat Image (2000) shows the broader landscape setting of this high density beaver area. The near infrared enhances the beaver ponds (small black spots creating a loosely knitted landscape impression).

For more informationwww.geostrategis.com

Jean -

I've enjoyed this post and checking in for your updates. Thank you for sharing this fascinating information with us! I hope there is more to come.

Regards,
Diane

EXPLORING BEAVER HABITAT WITH GOOGLE EARTH:
COLLAPSE OF BEAVER DAMS BLAMED FOR TRAIN DERAILMENT AND FUEL SPILL IN THE OTTAWA RIVER


In the early morning of June 3, 2009, a freight train derailed about 16 kilometers east of Mattawa. The derailment included two locomotives and six empty rail cars used to haul lumber. About 15,000 liters of fuel was spilled in the Ottawa river. One car was in the river. (Canadian Press CBC News)

The Ottawa Valley Railway train went off the tracks around 3.10 a.m. when it ran into 180 meters of washed out tracks on an embankment just besides the Ottawa River.
The destructions of three successive beaver dams was blamed for the wash out of the rail embankment. The collapse of the dams apparently released a wall of floodwater up to 12 feet (3.7 meters) high over part of the tracks.

more information:
www.ecoinformatics.com
CBC News Canadian Press
The North Bay Nugget