Impact CHURCHILL-NELSON Water Diversion- Manitoba

MONITORING ECOSYSTEMS WITH SATELLITES:   THE CHURCHILL-NELSON RIVERS DIVERSION IN MANITOBA

In September of 1969 I was doing fieldwork in Northern Manitoba as part of the Canada Land Inventory Project and the in preparation of the Manitoba Remote Sensing Test Projects. Our fieldwork was concentrated that year in the Wekusko (63J), Grand Rapids(63G), Norway House (63H) and Cross Lake (63I) topographic map sheet areas. During the fieldwork using helicopters, fixed wing aircraft, and boats we collected a wide range of vegetation, soil, and photographic data. 

Since I seem to have some time at hand, I am reviewing now, almost 50 years later to see if our predictions then, are now visible on satellite images. As can be seen from some of my other posts, my special interest is the study of the melting of permafrost in palsas and peat plateaus so common in these area. My original slides taken during the fieldwork show some interesting aspects of flooding. For example the slide/photos in this post show the impact of the start of the flooding caused by the Churchill-Nelson River Diversion Project in Northern Manitoba:

1969 Photo of Flooding impact




Google Earth does not provide a  great resolution image for this area, but Apple Maps program provides very high resolution images for part of this area. In spite of the clouds the image shows that the floating wetlands are still floating. Dead trees have been removed along the shoreline. The logging road is visible on both the Google Earth and Apple Maps image. It did not exist at the time of the helicopter photo.

2012/13? Image taken from Apple Maps



The amount of tree kill is very high because wetlands with permafrost were flooded. The original floating peat wetlands adjusted to the new water level (green arrow right)l, but the mainly Black Spruce forest on peat plateaus were flooded and killed (red arrow). It is interesting to see that the former collapse scars of the peat plateaus also float and adjusted to the new water level (green arrow left). Both satellite images show the very murky colour of the lake water. Much of the original shoreline was composed of lacustrine clay and silt deposits from Glacial Lake Agassiz. Since the flooding the erosion of this silt and clay have changed the lake.


Also the slide below provides a good visualization of the extent of the flooding damage. The the tree kill along the shorelines is quite obvious. Also the tree kill in wetland is extensive(light blue arrow)

1969 Photo of Flooding Impact




Attached is also the KMZ file with the locations on Google Earth. More information on www.geostrategis.com/p_churchill-nelson.htm

Churchill-Nelson-Rivers-diversion.kmz (1006 B)

Significant shoreline erosion: Playgreen Lake, Manitoba

It has actually been more than a few decades that I have looked at this area again, that is looking at more than the melting of permafrost. I am systematically going through my slide collection taken during my field work in 1969 and 1970. It is an interesting puzzle to locate the images on Google Earth. Sometimes it proves too much of a challenge. The helicopter photo below shows the shoreline of Playgreen Lake, on a flight line bringing us back to Norway House. We were flying a Bell 47 helicopter which has such a marvellous view to take pictures.

Figure 1: 1969 photo taken from helicopter



Strangely enough I could not find the actual and precise location where the photo was taken, not on Google Earth, Apple maps or Bing. Fortunately, I still had a 1954 1:70'000 scale aerial photos for this area. The red dotted lines on the 1953 aerial photo below show the area covered by the colour photo taken from helicopter. (In fact these were the type of aerial photos we used for mapping soils, vegetation and ecosystems).

Figure 2: 1953 panchromatic aerial photo taken at an altitude of 35'000 ft on October 18.


Actually the land area had disappeared !. The Google Earth image below is dated 1984!!!. The aerial photo date is 1953. The amount of shoreline erosion is quite dramatic.

The longest red line represents about 450 meters in erosion; the shorter line on the right is about 175 meters in shoreline erosion. This means-for this stretch of shoreline an annual erosion rate of 5-15 meters. How much of this can be contributed to the Churchill- Nelson Diversion, in particular the Eight Mile Channel which was constructed in the early to mid-seventies?

Figure 3: Overlay of 1953 aerial photo on 1984 Google Earth image


The Google Earth overview and 'transparent overlay of the 1953 aerial photo gives a good overview of the situation. The red arrow shows the start of the Eight-Mile Channel constructed by Manitoba Hydro in the mid-seventies. The water flow in Playgreen lake can easily be determined by the surface water tones reflecting suspended sediments: the erosion from this area appears to flow directly in the Eight-Mile Channel.

Figure 4: Oblique overview of the shoreline erosion and the relationship to the inlet of the 8-mile Channel.


The important question is actually: "How much of this erosion is 'natural' or the result of the 8 mile channel?" 
It will be interesting to see if satellite images can provide this answer as well. Perhaps the topic of a next post.

more information at www.geostrategis.com/p_churchill-nelson.htm

Attachments:

playgreen shoreline overlay.kmz (457.64 KB)