We demonstrated an assessment of the sediments caused by a catastrophic avalanche, induced by the main shock of the 2015 Gorkha Earthquake in Nepal. Calculation of decreasing coherence and visual interpretation of amplitude images by means of the Phased Array-type L-band Synthetic Aperture Radar-2 (PALSAR-2) have a high potential for delineating the hazardous zone. These delineated outlines area highly consistent with that from a high-resolution optical image of WorldView-3 (WV-3). The delineated sediment collapse areas were estimated as 0.63 km<sup>2</sup> (PALSAR-2 coherence calculation), 0.73 km<sup>2</sup> (PALSAR-2 visual interpretation), and 1.09 km<sup>2</sup> (WV-3), respectively. In the WV-3 image, surface features were classified into 15 segments, with the flowing, scattering, and other characteristics implying different physical properties; the different features suggest sequential collapse from multiple sources. By means of satellite-derived pre- and post-event digital surface models, differences in the surface altitudes of the collapse events estimated the total volume of the sediments as 6229.1 x 10<sup>3</sup> m<sup>3</sup>, with an error possibility between 5363.3 x 10<sup>3</sup> to 7314.8 x 10<sup>3</sup> m<sup>3</sup>, most of which are distributed along the river bed and the water stream. Further altitude measurements after ice/snow melting would reveal a contained volume of melting ice and snow, which will contribute to numerical avalanche simulation and source considerations.