Sunday, March 21, 2010

STH Investigation...NHPC Stage III Lo Dam at 27th Mile (20Mar2010)

At max magnification
on Google maps one could see lines resembling cracks at the ridge of a hill overlooking the National Hydroelectric Power Corporation (NHPC) Stage III Lo dam (Teesta River) at 27th Mile near Kalimpong , refer Slide 'A' (top).
STH organized a trip there on 20Mar2010 and walked the areas where the "crack" should have been with 2 local youths acting as guides ( see attachment 'B'jpg.).
We found no evidence of  "cracks/fissures" and the local village people whom we talked to verified this finding.

A possible explanation to the mysterious lines/cracks has been offered by Dr David Petley ,BSc (Hons) AKC PhD FRGS FGS ILTM CGeog (Wilson Chair in Hazard and Risk in the Department of Geography, Univ of Durham UK), whom I contacted yesterday. He writes:-

"Interpreting satellite imagery is notoriously difficult in situations like this, which is why we need either a good elevation model or (preferably) stereo coverage to do so properly. One particular problem is that when the sun angle is low (as per the Google Earth image), small features create shadows that make them look far more substantial. I suspect (though of course cannot say for certain) that this is the case in the images that you have looked at. I suspect that there is a small path or suchlike up there and the edges are casting shadows that look like cracks.I think if there really were cracks up there that one can see on Google Earth then they would have been very obvious on the ground."

That's the good news, the downside is that there are sinking areas below Deorali village (towards 28th Mile) and just above the dam site.

Praful Rao

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