The global landslide distribution in the 2015-16 El Nino event

It is commonly perceived that the global landslide distribution is heavily influenced by the El Nino / La Nina cycle, and that strong El Nino events are associated with a higher than average occurrence of landslides in many areas. Thus, for example, the very intense 1997-98 El Nino event coincided with high incidence of landslides in parts of North America and South America, and elsewhere. However, there is comparatively little systematic analysis on a global basis. The 2015-16 El Nino event was the most intense since 1997-98, and had been anticipated to generate significant landslide impacts. The occurrence of landslides worldwide through the 2015-16 El Nino has been examined using the author's landslide fatality database, which has been compiled since 2002. The data indicates that 2015 was a year with an unusually small number of rainfall-induced landslides, significantly below the long term average and with unusually low consequences. This is primarily because of two key factors: first, the South Asian monsoon was anomalously weak, resulting in low landslide impacts in the Himalayas. Second, the occurrence of intense landfalling tropical cyclones across East Asia was also unusually low. The combined effect of these two sets of meteorological conditions was low landslide occurrence across Asia. Landslide occurrence across the Americas was also low. On the other hand, 2016 is proving to be an unusually intense landslide year. In particular, intense rainfall associated with early part of the South Asian monsoon has resulted in very widespread landsliding across South Asia. This paper examines the lessons that can be learnt from an improved understanding the relationship between El Nino events and global landslide impacts, and reflects upon the capability to anticipate the impacts of future large El Nino events.