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Problems of Lesser Himalaya and Terai

Short answer

Lesser Himalaya problems include landslides, weak rocks, and seismic activity, mitigated by slope stabilization and drainage. Terai problems are floods, low bearing capacity, liquefaction, and arsenic contamination, addressed by embankments, deep foundations, ground improvement, and safe water wells.

What are the engineering geological problems of the Lesser Himalaya and the Terai (Indo-Gangetic plain) zones? Mention mitigating measures.

Lesser Himalaya

The zone has weak, folded and sheared rocks (phyllite, schist, slate) and steep terrain.

  • Problems: landslides, rock fall, weak foundation rock, tunnel squeezing, karst in limestone, erosion, MBT/MCT earthquakes.
  • Mitigation: gentle slopes and retaining structures, surface drainage, rock bolts and shotcrete, bio-engineering, careful alignment, grouting in karst areas.

Terai (Indo-Gangetic plain)

The Terai consists of thick, unconsolidated Quaternary alluvium (gravel, sand, silt, clay) with a gentle slope.

  • Problems:
    1. Frequent floods and river bank cutting; shifting of river channels.
    2. Sediment deposition and aggradation of river beds.
    3. High water table and waterlogging.
    4. Low bearing capacity and large settlement of soft clay and silt.
    5. Liquefaction of loose saturated sand during earthquakes.
    6. Scarcity of rock aggregate (only boulders and gravel from rivers).
    7. Arsenic contamination of shallow groundwater.
  • Mitigation: embankments and spurs, river training, raised foundations or pile/raft foundations, soil compaction and ground improvement, drainage, deep tube wells for safe water, use of river gravel with proper testing.

✓ Answer checked by Claude Opus 5.5 (high effort)

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