Why in the news?

  • The Brahmaputra, Teesta, and Dharla rivers have become unpredictable, eroding land faster than ever before.

Riverbank Erosion

  • Definition: Riverbank erosion refers to the removal of soil and sediment from riverbanks due to the flowing water’s hydraulic action, leading to bank failure, channel migration, and loss of land. It is a fluvial geomorphic process.
  • Causes of Riverbank Erosion
    • Natural Factors
      • Hydraulic Action & River Velocity: High discharge, meandering rivers, and steep gradients.
      • Sediment Load Fluctuations: Excess or deficit of sediment alters erosive capacity.
      • Bank Material: Loose alluvium, sand, silt, peat, or unconsolidated deposits.
      • Floods & Flash Floods: Sudden rise in water volume accelerates bank collapse.
      • Meandering & Channel Migration: Erosion on concave banks; deposition on convex banks.
      • Seasonality: Monsoon-driven rivers (e.g., Brahmaputra, Ganga) show peak erosion during rainy seasons.
    • Anthropogenic Factors
      • Deforestation & removal of riparian vegetation.
      • Sand mining, often illegal.
      • Unplanned embankments altering river flow.
      • Construction near riverbanks (roads, settlements, infrastructure).
      • Dams & barrages modifying downstream sediment flow.
      • Climate Change: Increased frequency of extreme rainfall, glacial melt, altered discharge patterns.
  • Regions of Severe Riverbank Erosion in India
    • Brahmaputra River Basin (Assam): Majuli island shrinking; severe bank line retreat.
    • Ganga River Basin: Bihar, West Bengal, Uttar Pradesh.
    • Padma–Ganga confluence in West Bengal.
    • Kosi River (“Sorrow of Bihar”) — notorious for frequent avulsions.
    • Mahanadi Delta (Odisha) and Godavari–Krishna deltas (Andhra Pradesh).
    • Yamuna riverfront near Delhi–Agra region.
  • Impacts of Riverbank Erosion
    • Social Impacts
      • Displacement of populations: e.g., erosion-induced migrants in Assam and Bihar.
      • Loss of homes, livelihoods, agricultural land.
      • Migration, poverty, and social vulnerability.
    • Economic Impacts
      • Loss of fertile alluvial land and crops.
      • Damage to infrastructure: roads, bridges, embankments, schools.
      • Increased disaster-management costs.
    • Environmental Impacts
      • Alteration of river morphology, delta shrinkage.
      • Loss of riparian ecosystems and biodiversity.
      • Increased sedimentation downstream, affecting wetlands and deltas.
    • Strategic Dimension
      • Triggering border instability (e.g., India-Bangladesh enclaves invited issues earlier).
  • Measures to Control and Mitigate Riverbank Erosion
    • Engineering Measures
      • Embankments, spurs, revetments, gabions.
      • Geotextile tubes and geo-bags for bank protection.
      • Channel training works to control meandering.
      • Dredging (selective and micro-managed).
    • Ecological / Bio-engineering Measures
      • Riparian vegetation restoration (willow, vetiver grass).
      • Riverfront buffer zones.
      • Afforestation in catchments to reduce silt load.
    • Policy & Management Measures
      • Regulated sand mining (based on scientific assessments).
      • River Basin Management approach – holistic, multi-state coordination.
      • Early warning systems, satellite-based erosion monitoring (NRSC, Bhuvan).
      • Relocation and compensation policies for erosion-affected communities.
      • Ban on construction within floodplains (as per NGT guidelines).