The Indian Space Agency (ISRO) activated the International Charter "Space and Major Disasters" to image the area of the disater in Uttarakhand (excellent visualisation here). Thanks to CNES and Airbus DS, Pléiades images (resolution: 70 cm in panchromatic, 2.8 m in multispectral) were acquired today 09 Feb 2021, two days after the event. These images show the detachment area with a clear rupture line of 550 m on the north face of Ronti.

This is a comparison with the latest Sentinel-2 image, before the flood.

 

Preliminary work by many scientists suggests that a rockslope failure released a mixture of rock and ice which created a potent flood in the valley of the Rishiganga River.

UPDATE 10 Feb 2021. A Pléiades stereo pair has been acquired (B/H = 0.12) which allowed us to generate a high resolution 3D model of the area.

Update 11 Feb 2021

Two elevation difference maps were computed by Etienne. A first one by differencing the above Pléiades DEM with the Copernicus 30 m resolution DEM

Then, D. Shean (Univ Washington) computed a pre-event DEM from WorldView-1 images which allowed a finer analysis. The estimated detached volume is 25 millions cubic meters.

Authors: Etienne Berthier (CNRS/LEGOS) and Simon Gascoin (CNRS/CESBIO)

2 thoughts on “Pléiades images of the Uttarakhand disaster

  1. Dear colleagues,
    Thank you for your excellent work and for the images!
    I am interested in the detachment mechanism of the Chamoli landslide. Therefore, I would like to know the orientations (dip and dip direction) of the discontinuities (faults) bordering the detached block.
    Could you please let me know the orientation of the lower cross section given in "Elevation changes in the source area"? Is the diagram W - E or E - W oriented (line of sight to N or S)?
    Thank you for your help and best regards,
    Rainer Poisel

    1. Dear Rainer, the map is oriented with the north upward. The upper panel is the ~N-S cross section.

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