Dimensions of Debris Flow of Kedarnath Disaster 2013: A Study using Digital Elevation Models

Located in Garhwal Himalayas, Kedarnath (3,583 m) is one of the holiest sites of Hindu pilgrimage. In the morning of 17 June 2013. Kedarnath village got devastated by a debris flow resulting from bursting of a marine-dammed lake called Chorabari Tal, which is located 300 m above the settlement, in the northwest. In this study estimations are made to measure the breach parameters of the lake viz. lake volume, peak flow, peak flow velocity and momentum. They were estimated from SRTM, ASTER and CartoDEM elevation models: The 9-10 m-high lateral moraine ridge of the Chorabari Glacier was breached along a 60-m wide stretch due to high water pressure in the lake after a high intensity rainfall received in its 2.7 km² catchment The amount of water released was estimated at 0.43X10⁶ m³ (SRTM), 0.25X10⁶ m³ (ASTER), and 0.63X10⁶ m³ (CartoDEM). Using predictive equations,the peak flow was calculated for SRTM, ASTER and CartoDEM as 1352.2 m³S^-1,850.2 m³S^-1 and 2280.3 m³S^-1, respectively. Within less than one minute of the bursting of the Chorabari Tal, the flow devastated the. Kedarnath settlement. The 12.42° slope of the Mandakini along the 1.41 km Chorabari-Kedarnath stretch was steep enough for the initial flow of debris to attain the required momentum ranging between 21-25 x 10⁶ kg m³S^-1, which obliterated the northern and western parts of the settlement. Since the lake boundary and the lake watershed derived from SRTM DEM fit much better to the topographic character of the area, as noticed on the satellite images, the SRTM-derived results are considered to be the best estimate.