State PCS - Uttarakhand (UKPSC)

• 28 Nov 2025

National Seismic Hazard Map

Why in News? 

The Bureau of Indian Standards has released an updated National Seismic Hazard Map, placing the entire Himalayan arc into a newly created highest-risk Zone VI, reflecting its extreme tectonic vulnerability and significantly revising national earthquake-risk assessment. 

Key Points

• The new map categorises the complete Himalayan belt—from Jammu & Kashmir to Arunachal Pradesh—into Zone VI, the highest hazard classification, due to persistent tectonic stress along the Himalayan Frontal Thrust. 
• About 61% of India’s landmass is now classified as moderate to high seismic-risk zones, requiring updated building codes, stricter land-use norms, and mandatory structural safety compliance. 
• The updated zonation uses probabilistic seismic hazard modelling, incorporating new data on active faults, rupture behaviour, and strain accumulation, replacing older deterministic maps. 
• Under the revised map, any town located on a boundary between two hazard categories will be shifted to the higher-risk zone. 
• The seismic risk has increased not only in hill states but also in plains adjoining the Himalayas, including parts of Uttarakhand, Himachal Pradesh, J&K, Sikkim, Northeast, Bihar, UP, Haryana, Punjab and Delhi NCR.

Seismic Zones in India 

• India’s earlier classification had Zones II, III, IV, V — with Zone V being the highest risk. 
• The Himalayas are among the world’s most active collision zones, created by the Indian and Eurasian plate convergence (~5 cm/year). 
• Major historical earthquakes: Kangra (1905), Bihar–Nepal (1934), Assam (1950), Kashmir (2005), Sikkim (2011), Nepal (2015). 
• IS 1893, IS 4326, and National Building Code (NBC) govern seismic safety; the new map will necessitate extensive revisions. 

Silt Levels Rise in Bhagirathi River

Why in News? 

The Bhagirathi River in Uttarkashi (Uttarakhand) is witnessing dangerously high silt accumulation, with experts warning that the ban on dredging has increased flood risk and destabilised riverbanks, posing a threat to town infrastructure. 

Key Points 

• About: 
  • The National Green Tribunal (NGT) imposed a ban on dredging/excavation in the Bhagirathi in 2012, aimed at protecting the river’s ecological sensitivity as it falls under the Bhagirathi Eco-Sensitive Zone (ESZ). 
  • Officials now report that continuous silt deposition has raised the riverbed significantly, especially near the Uttarkashi district headquarters, reducing the river’s carrying capacity. 
  • The elevated riverbed increases the chances of flash floods, bank erosion, and overflow during monsoon, which may endanger homes, markets, and government buildings located close to the river. 
  • The State Government is preparing a proposal requesting the NGT to permit scientific desilting, similar to permissions granted in flood-prone rivers in other Himalayan states.
• About Bhagirathi River: 
  • The Bhagirathi is one of the two headstreams of the Ganga, originating from Gaumukh Glacier at Gangotri (Uttarakhand). 
  • It flows through Gangotri – Harsil – Uttarkashi – Tehri, meeting the Alaknanda at Devprayag, where they together form the Ganga. 
  • The stretch from Gaumukh to Uttarkashi is notified as the Bhagirathi Eco-Sensitive Zone (2012) to protect fragile Himalayan ecology and regulate hydropower, mining, and construction. 
  • Known for steep gradients, high sediment load, and vulnerability to landslides, cloudbursts and glacial melt—making riverbed elevation a significant hazard.