Sonar Survey to Assess Rising Silt Levels in Sunni Region from Dec 15: DC Kashyap

Shimla, 4 Dec 2025 — Deputy Commissioner Anupam Kashyap announced that a sonar-based silt assessment survey will begin in the Sunni region on 15 December, following concerns over rising water levels and rapid silt accumulation in the Sutlej River. The survey, commissioned through the Kol Dam management, will take 15–20 days, after which a detailed report will guide future mitigation strategies.

Kashyap, who reviewed the affected areas including the ITI campus, rest house, gosadan and residential pockets, said that protecting lives and property remains the administration’s top priority. He confirmed that ₹10 crore has been approved to repair the damaged Thali Bridge, with work beginning this month. A new suspension-based structure, three metres higher than the existing bridge, will be completed before the next monsoon to restore the crucial Mandi–Shimla link.

Officials from NTPC, district administration and technical teams attended the meeting.

Sonar Technology Explained:
The DC highlighted that sonar mapping is the most reliable method to study underwater silt behaviour, especially where visibility is low. The technique uses sound waves to create detailed subsurface maps.

IIT Roorkee Findings:
A 10-year study (2014–2024) by IIT Roorkee shows that silt levels surged sharply after 2021. In Sunni alone, silt spread increased from 0.5 hectares in 2022 to 10 hectares in 2023. The report suggests that the accumulated silt is suitable for construction and may be mined to reduce water levels. NTPC has agreed to provide NOC for regulated silt mining.

Crores Lost to Damage:
As per PWD data, altered river flow since the commissioning of Kol Dam has caused repeated damage: