Landslide dam breach during 2015 earthquake in Nepal: Computational modelling of hydraulic and morphological effects

Landslides are rather common in Himalayan country Nepal. Almost every monsoon the country suffers significant losses and fatalities due to floods and landslides. A landslide,which occurred onMay 24, 2015, had some specific characteristics and aftermath.The landslide occurred during dry period, and in effect, there was no trigger other than the fact that it occurred a month after the ‘great’ earthquake,whichwas very destructive. Furthermore, the landslide formed a natural dam in Kali Gandaki River (the length was approximately 700mand the height was about 30 m), and formed a lake of about 2 km length and more than 30m deep. Particularly, downstream towns Galeshwor Bazar and Beni Bazar were in threat of inundation in case the breach occurred. The town is located in alluvial deposits, and very vulnerable to extreme flows, propagating from upstream. The landslide dam breached relatively quickly (about 15 hours later), so fortunately there was no fatality due to the propagating flood flow.