Characterization of landform evolution and slope response to the 2015 earthquake sequence and annual monsoon in Central Nepal

The April 25th, 2015 Mw 7.8 Gorkha earthquake triggered thousands of co-seismic landslides across Central Nepal. This thesis investigates the evolution and controls on co- and post-seismic mass movements at two case study slopes, Tushare and The Last Resort using a range of remote sensing techniques collected prior to and following the 2015 earthquakes over the five-year period from 2012 to 2017. A range of remote sensing techniques including terrestrial laser scanning, digital photography, photogrammetry, and satellite imagery were used to characterize the landslides at these slopes. Engineering geological and geomorphological mapping and three-dimensional rockfall modelling were employed to analyze structural controls on mass movements. Analysis of surface change using change detection techniques was used to evaluate landform evolution at the slopes in response to the earthquakes and 2015 to 2017 annual monsoons. Observed post-seismic instability is dominated by reactivation of colluvium from the co-seismic failures as opposed to initiation of new failures. Elevated landslide hazard associated with loose debris on the slopes is anticipated to continue in future monsoons.