Why Nepal Himalaya is landslide-prone

The Nepal Himalaya is very prone to landslides due to a combination of geological, topographic, climatic and human factors.

1. Young, active tectonics: the Himalaya is still rising due to the Indo-Eurasian collision (about 4-5 cm/year), producing steep, unstable slopes and frequent earthquakes that trigger slides.
2. Steep topography: very high relief and steep slopes; rivers cut deep gorges and undercut the toe.
3. Weak and fractured rocks: phyllite, schist, slate, shale and Siwalik mudstone; the rocks are folded, faulted and highly jointed, especially near the MBT and MCT.
4. Adverse structure: foliation and joints dipping out of the slope.
5. Intense monsoon rainfall: about 80% of the annual rainfall falls in June-September, with cloudbursts, increasing pore water pressure and erosion.
6. Weathering: deep weathering and thick colluvium and residual soil.
7. Glaciers and snow melt in high areas.
8. Human activity: unplanned road construction by bulldozer, deforestation, agriculture on steep slopes, quarrying and settlements.
9. Earthquakes: the 2015 earthquake triggered thousands of landslides.