Cyclone Ditwah Causes Major Flooding

Key Notes on Cyclone Ditwah Impact and Infrastructure Challenges in Chennai

1. Natural Disaster Overview:

   • Cyclone Ditwah affected Sri Lanka in November, leading to a national disaster with widespread flooding.
   • Approximately 1.4 million people were affected; at least 474 fatalities reported.
   • After impacting Sri Lanka, the cyclone re-entered the Bay of Bengal, causing heavy rains in North Tamil Nadu and South Andhra Pradesh.

2. Rainfall Statistics:

   • Chennai recorded 18 cm of rain within 24 hours following the cyclone's passage, which led to severe flooding and waterlogging.

3. Infrastructure and Urban Planning:

   • The Greater Chennai Corporation (GCC) has invested ₹5,200 crore over four years to enhance stormwater drainage with approximately 1,100 km of new drains.
   • Three-fourths of drainage infrastructure upgrades have been completed, but isolated issues remain from incomplete repair of smaller drainage links, leading to persistent waterlogging.

4. Historical Context & Challenges:

   • Chennai’s stormwater management has faced significant challenges since the devastating floods of 2015 and additional infrastructure improvements made since 2023.
   • Urban layout (flat terrain and increased paved surfaces) and rivers (Kosasthalaiyar and others) exacerbate flooding during heavy rains.

5. Judicial and Legislative Oversight:

   • The Thiruppugazh Committee was established post-2021 floods, producing a 600-page report with basin-wise flood management recommendations.
   • The State government references this report for urban flood project funding but it remains largely unavailable to the public.
   • No consolidated implementation plan or timeline is currently accessible for monitoring progress.

6. Essential Recommendations:

   • State must publish the Thiruppugazh Committee report to enhance public transparency.
   • Establishment of hazard maps and comprehensive coordinated efforts across the basin for effective flood management is crucial.
   • Delivery of temporary solutions to manage immediate flooding needs, such as portable pumps, should coincide with ongoing infrastructure upgrades.

7. Summary of Infrastructure Gaps:

   • There are notable inadequacies in the existing stormwater network capabilities to handle extreme weather patterns, which have prompted public frustration.
   • Flood maps and elevation models for Chennai, while existing, lack integration into enforcement and relief measures.

8. Conclusion:

   • The rain events highlight ongoing infrastructure and planning challenges in Chennai, indicating the need for transparency, better management strategies, and quicker response systems to prepare for future storms.