The 2018 earthquake-triggered landslides of Palu, Indonesia, attained very large displacements on sub-horizontal slopes directly below a major irrigation canal. New research reveals a causal link between irrigation and landslide development, and highlights the risks to other irrigated areas.
The appalling devastation caused by landslides in suburban parts of Palu, Indonesia, after the magnitude 7.5 earthquake last September took the region and the scientific community by surprise and demanded careful study to understand what happened. New research from Royal Holloway University of London has revealed an unmistakable connection between the landslides and a large-scale communal irrigation system and the canals that fed it. Their research, published in Nature Geoscience, analyses the structures and displacement distribution of the landslides. It shows that water introduced into soils and deeper sandy layers below agricultural fields and adjacent suburban areas facilitated widespread liquefaction, creating perfect conditions for enormous landslides when coupled with the strong earthquake shaking. Seismically active countries that rely on major irrigation projects for agriculture, such as India, Myanmar, the Philippines and other parts of Indonesia, may be vulnerable to similar hazards in the future.
Structural map of the Petobo landslide, just east of Palu city. Irrigation canals are marked blue, landslide crown scarp and exhumed basal detachment are shown in green, the toe thrust system is shown in pink, and fluidised debris flows in brown. Light blue grid squares are 1 km wide.