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.
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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.
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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on the 1970 photo, has been replaced by a wetland in 2005.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) |
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| 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 [+] |
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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). |