Avalanches around Kedarnath : Experts rued out any threat to Kedarnath

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–by Team RPM-MF Oct 16, 2022

In September 2022 avalanche activity was observed repeatedly in the mountains to the north of Kedarnath in the Rudraprayag district of Uttarakhand. The presence of pilgrims and others in large numbers facilitated pictographic and video records of these, and stories projecting these as posing a major hazard to the township and pilgrims became viral on social media.

A multi-institutional team was thus quickly constituted by Uttarakhand SDMA to ascertain the causes of recurring avalanche activity, assess the risk, and accordingly suggest mitigation measures. After field investigations on October 3, 2022, the Committee ruled out major avalanche risk to the temple township and described the avalanches as being routine geomorphic activity.

Kedarnath

The temple township, the abode of Lord Shiva, is highly revered by Hindus. It is located at the western extremity of the Central Himalaya in a glacier-modified U-shaped valley of Mandakini river that has a catchment area of ~67 sq km (up to Rambara), of which 23% is covered with glaciers.

The township is situated on the outwash plains of Chorabari and Companion glaciers. The channels of Mandakini and Saraswati rivers encircle this outwash plain that ends to the south of the temple where the two channels meet. These streams are observed to actively erode their banks.

The temple township can be accessed by road up to Gaurikund which is at a distance of 224 km from the nearest airport at Jollygrant in Dehradun and from there one has to trek for 16 km. Helicopter service is also available for Kedarnath from Phata and Guptkashi, but one has to book the tickets well in advance to avoid inconvenience.

Avalanche

Simply speaking avalanche is nothing but downslope movement of snow and ice under the impact of gravityLaw of Inertia however precludes any movement of the material, in howsoever unstable condition, either in the form of a landslide or an avalanche, unless acted upon by an external force.

In the case of avalanches, this trigger is often provided by thermodynamic changes following variations in physical conditions such as the temperature of the air. Wind velocity, the gradient of slope on which the snow accumulates, the mass of accumulating snow, and seismogenic shaking together with mechanical or anthropogenic ground shaking could be other triggers for avalanche initiation. The avalanche probability increases with slope gradient and with increasing ice mass the magnitude of the forces acting in the downslope direction tends to increase.

The Committee consisting of officials of WIHGIIRS, and USDMA accepts avalanches as being a major threat in the high altitude regions of the state and cites previous incidences of February 7, 2021 (causing Dhauliganga floods and killing 207 persons), April 23, 2021 (killing 18 persons around Sumna in Girthiganga valley), October 2, 2021 (killing 07 mountaineers), October 1998 (killing 27 persons), and June 23,  2008 (injuring 20 persons).

Observations of the Committee

Recommendations

  • Slope modification: Benching of the slope at different elevations along the steep gradients of snow drift or channels to the north of Kedarnath temple to reduce overall slope angle and retard the velocity of downward movement of snow and debris mass.
  • Structural control: Construction of concrete wedges along the mid-slope of avalanche chutes to prevent and divert the force of descending ice mass.
  • Mounds: Construction of mounds to arrest and break the momentum of the decelerating avalanche mass and bring the moving ice mass to rest at a short distance, thereby protecting the facilities at the far end of the runout zone of avalanche slope.
  • Ban on construction: Complete ban is recommended on the construction of building or any form of shelters over the highly unstable and active debris slope that include scree fans, as the same results in the change in the angle of repose of the unconsolidated material.
  • Mass awareness: Accumulation of snow, either directly through solid precipitation or indirectly by avalanches, being common in a glacial regime, the Committee recommends of media and mass sensitisation so that they refrain from rumor mongering.
 Article borrowed from  Risk Prevention Mitigation and Management Forum  with thanks

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