| Insight
stoplog units, which were in a dogged condition at the top of the dam, were washed away during the overtopping event. The intake gates, which regulate water flow into the power generation system, could not be closed, and intake tunnels were blocked by debris and sediment carried by the flood. The mechanical systems controlling the gates were damaged, preventing proper operation and leading to further complications in managing the water flow.
Impact on the dam structure The dam’s foundation and embankments were eroded
by the intense floodwaters. The downstream face of the dam suffered significant scouring. The concrete structures of the dam, including the spillway and retaining walls, experienced cracking and spalling (breaking into smaller pieces) due to the impact force of the water and debris. Additionally, access roads, bridges, and other auxiliary structures supporting the dam and its operations were washed away, hindering rescue and repair efforts. To provide a precise account of the damage and outline a timeline for restoration, below is a detailed assessment based on the Teesta Dam failure incident in 2023 due to a Glacial Lake Outburst Flood (GLOF):
Tentative damage assessment: Hydromechanical equipment: The spillway gates, including all five radial gates, two sets of stoplogs, hydraulic hoists, gantry crane, embedded parts, glacis liners, and other associated equipment, were completely washed away or damaged beyond repair. The silt flushing gates had all hydraulic cylinders, power packs, and control panels submerged and now require replacement or extensive repairs. The intake gates suffered blockages from debris, damage to the mechanical system, and structural damage to the hoist.
Dam structure: The foundation and embankments experienced erosion, scouring, and compromised structural integrity. Concrete structures of the dam, including cracking, spalling, and sections being washed away. Auxiliary structures, such as access roads, bridges, support structures, electric installations, vehicles, equipment, and inventories, were completely destroyed or washed away.
Restoration and timeline: Phase 1: Immediate response (0-3 months):
Activities include evacuation and rescue operations, initial damage assessment, temporary stabilization of the dam structure to prevent further collapse, clearing debris, and securing the site. The timeline for this phase is three months. Phase 2: Detailedassessment and planning (3-6 months): This phase involves a comprehensive structural assessment, planning and design of repair and restoration works, and procurement of necessary materials and equipment. The timeline for this phase is three months. Phase 3: Structural repairs (6-18 months): Activities during this phase include repairing and reinforcing the dam foundation and embankments,
reconstructing damaged concrete structures, and restoring auxiliary structures such as access roads and bridges. The timeline for this phase is twelve months.
Phase 4: Hydro-mechanical equipment and gates repair (18-30 months): This phase focuses on the restoration of spillway and intake gates. Phase 5: Testing and commissioning (30-36 months): Activities include comprehensive testing of all systems, commissioning of hydroelectric power generation, and final safety inspections and certifications.
The total expected timeline for full restoration is thirty- six months (three years).
Lessons learned Importance of timely gate operation: Gates must
be operated proactively based on real-time data and predictive models, rather than relying solely on reactive measures. Automated gate systems should be reliable, regularly tested, and equipped with manual override capabilities.
Enhanced forecasting, advance warning system, and communication: Weather forecasting models need improvement to better predict extreme weather events. Developing integrated systems for real-time data sharing between weather agencies, dam operators, and emergency services is crucial. Regular drills and training: Conducting regular drills and training for dam operators is essential for effective emergency response. Increasing public awareness and preparedness for dam-related emergencies is also necessary. Infrastructure resilience: Investing in infrastructure upgrades is important to enhance the resilience of dams against extreme weather events. Regular safety audits and maintenance of dam structures and operating systems should be conducted.
Conclusion The catastrophic damage to the Teesta Dam and
its infrastructure following the 2023 GLOF incident demands an urgent and robust response. Restoration efforts must not only focus on the immediate repair and reconstruction but also on enhancing the overall resilience of the dam against future disasters. The recovery plan should be bold, aiming for rapid stabilization and protection of the dam within the first year, followed by phased reconstruction over the next two to three years. Key actions include immediate emergency
measures to prevent further damage, comprehensive structural assessments to identify vulnerabilities, and extensive repairs to both civil and hydro-mechanical systems. The installation of advanced weather forecasting and monitoring systems is essential. These systems must be integrated with real-time data-sharing networks linking meteorological agencies, dam operators, and emergency response teams to prevent such disasters in the future. By taking these decisive steps, the Teesta Dam can
be restored not just to its original capacity but can be transformed into a model of resilience and safety, safeguarding against the growing threat of climate- induced disasters.
www.waterpowermagazine.com | October 2024 | 11
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