Context
Cyclone Dikweh, which formed over the Bay of Bengal in late November, moved slowly over Sri Lanka before re-entering the Bay and triggering heavy rains across Tamil Nadu, South Andhra Pradesh, and Chennai. The event exposed severe infrastructure weaknesses, especially in Chennai’s storm-water drainage network, flood preparedness, and urban governance.
Key Highlights
Impact of Cyclone Dikweh
- Sri Lanka witnessed widespread flooding, with 14 lakh people affected and 174 deaths reported.
- On entering India, the system brought heavy rains, creating Chennai’s deep depression phase.
- In Chennai, 18 cm of rain in 24 hours led to:
- Severe waterlogging, flooding of streets.
- Breakdown of drainage systems.
- Intensified public frustration over recurring urban flooding.
Inadequate Urban Infrastructure
- Though Chennai experienced similar disasters in 2015, 2020, and 2023, conditions remain unchanged.
- Despite spending ₹2,500 crore on storm-water drains, critical gaps persist:
- Only half of the required 1,600 km of drains are functional.
- Key areas lack interlinked drainage networks, causing backflow and stagnation.
- Large water bodies such as Kovalam, Thuraipakkam, Tiruvallur, and Kancheepuram face encroachments and reduced holding capacity.
Institutional Shortcomings
- The GCC (Greater Chennai Corporation) has not fully implemented recommendations from the Thiruppugazh Committee, constituted after the 2020 floods.
- Persistent issues:
- Encroachment on waterways.
- Lack of real-time flood modelling.
- No unified urban flood management plan.
- Delays in upgrading canals and micro-drainage systems.
Environmental Concerns
- Impervious urban surfaces hinder water percolation.
- Ad-hoc pumps and stopgap arrangements cannot cope with climate-intensified rainfall.
- Rising sea levels further threaten coastal drainage, worsening water backflow.
Relevant Prelims Points
- Cyclone Formation (Bay of Bengal):
- Warm ocean waters + low pressure + Coriolis effect → formation of tropical cyclones.
- Bay of Bengal cyclones often intensify due to warmer waters and lack of land barriers.
- Urban Flooding Causes:
- Poor drainage, encroachment on wetlands, inadequate storm-water networks, rapid urbanisation.
- Loss of marshlands such as Pallikaranai Marsh in Chennai reduces natural absorption.
- Disaster Management Framework:
- NDMA Guidelines on urban flooding (2010).
- Role of IMD, INCOIS, CWC in forecasting & early warning.
- Thiruppugazh Committee:
- Formed after the 2020 Chennai floods.
- Suggested hydrological mapping, integrated drainage design, early flood modelling, coordinated command systems.
Relevant Mains Points
Cyclone Impact & Climate Change
- Increasing cyclone frequency and rainfall intensity highlight climate vulnerability of South India.
- Urban centres must adapt through resilient infrastructure planning.
Governance & Infrastructure Deficit
- Chronic failures emerge from lack of:
- Integrative urban planning across departments.
- Continuous updates to storm-water drainage aligned with changing rainfall patterns.
- Enforcement against encroachments.
Urban Resilience Challenges
- Chennai’s challenges reflect broader issues across Indian cities:
- Reactive flood management instead of proactive planning.
- Overreliance on pumps and temporary fixes.
- Absence of blue–green infrastructure (wetlands, open drains, floodplains).
Way Forward
- Develop Integrated Urban Flood Management Plans with real-time modelling.
- Enforce removal of encroachments on water bodies and restore wetlands.
- Complete storm-water drain upgrades with scientific hydrological mapping.
- Strengthen coordination between GCC, PWD, TN Govt, NDRF/SDRF.
- Publish annual flood risk assessments and ensure transparency in infrastructure audits.
- Adopt Nature-Based Solutions (NBS): restoring marshlands, widening canals, upgrading holding tanks.