Rockfall Hazard in Himalayan Region: Assessment and Review of Trajectory Analysis Parameters for Mitigation Strategies

Rockfall events are among the most common natural disasters in the Himalayan region. These high velocity and high energy events cause complete traffic interruptions, significant damages to the hilly infrastructure, and sometimes injuries and fatalities. Mitigation measures against this type of landslides require thorough rockfall trajectory analysis of the susceptible regions. However, reliability of the simulation programs modeling the rockfall trajectories depends on the correct input of rock slope characteristics, falling block characteristics, and rebound characteristics, especially coefficients of restitution. The present study reviews the reported studies on rockfall analysis of the Himalayan region and summarizes the values of the input parameters related to slope, block, and rebound characteristics, and the corresponding output parameters, especially bounce height, run-out distance, and kinetic energy of the falling block. An attempt has also been made to comparatively assess these parameters for the Himalayan region with the reported values for the European Alps. The influence of these output parameters, especially the block energy and bounce height, is then discussed with respect to the suitability of different rockfall mitigation measures.