Chennai’s Flood Crisis: Urban Hydrology and Climate Change

Context:

Frequent heavy rainfall in recent years has led to an upswing in climate change-induced floods in India. Notably in Chennai, the extreme El Nino conditions and warming in the Bay of Bengal have also contributed to the flood episode.

  • The city has faced devastating floods in 2005, 2015, and 2023, with the recent inundation being the worst in almost five decades.

Relevance:

GS-01, GS-03 (Physical Geography, Disaster Management)

Mains Question:

To what extent are historical human errors responsible for floods, and how can a nation like India transform disaster into an opportunity by becoming flood-resilient and water-abundant, Explain. (250 words)

Dimensions of the Article:

  • Flood Severity in Chennai
  • Proposed Solutions
  • El Nino and Its Impact on Indian Monsoon

Flood Severity in Chennai:

  • Chennai has experienced a surge in floods, labeled as climate change-induced disasters. The 2023 flood is identified as the most severe in the last 47 years.
  • The region possesses 3,588 irrigation tanks forming crucial watersheds. Unfortunately, neglect, silt accumulation, and encroachments have diminished their capacity, leading to excessive run-off during heavy rainfall.
  • Chennai faces not only inland floods but also the challenges of coastal floods and rising seawater due to climate change. The unique geography, with three rivers—Kosasthalaiyar, Cooum, and Adyar—provides an opportunity for effective drainage.
  • Rapid urban expansion in Chennai has led to the irreversible loss of ecological hotspots, including water bodies, marshlands, and wetlands.

Proposed Solutions:

  • It proposes a comprehensive study of urban and peri-urban water dynamics, protection of around 4,000 water bodies, restoration of their original capacity, and mapping of upstream-downstream watersheds.
  • The crux lies in decoding Chennai’s urban and peri-urban hydrology comprehensively. By mapping water bodies, safeguarding catchment areas, and restoring the missing links between tanks, Chennai can enhance its flood resilience.

El Nino and Its Impact on Indian Monsoon:

  • Overview of El Nino and La Nina: El Nino and La Nina events are inherent components of the global climate system, influencing weather patterns worldwide.
    • El Nino is characterized by warming in the central and eastern tropical Pacific, whereas La Nina entails sustained cooling in the same regions.
    • These phenomena operate within the El Nino–Southern Oscillation (ENSO) cycle.
  • El Nino’s Mechanism and Consequences: El Nino transpires when trade winds weaken or reverse, allowing warm water from the western Pacific to flow eastward, displacing cooler water in the eastern Pacific.
    • This disrupts atmospheric conditions, leading to varied global weather impacts. Effects include heightened rainfall in the southern US and Peru, alongside droughts and bushfires in the West Pacific and Australia.
  • El Nino’s Influence on Indian Monsoon: El Nino significantly influences the Indian monsoon through atmospheric circulation.
    • The weakened southwest monsoon results in below-normal rainfall, while the northeast monsoon experiences above-normal rainfall during El Nino.
    • The extreme 2015 El Nino, for instance, played a crucial role in Chennai’s heavy rainfall.
  • Correlation with Bay of Bengal Warming: A correlation emerges with the consistent warming of the Bay of Bengal off the Tamil Nadu and Andhra Pradesh coasts.
    • Researchers highlight a positive and significant correlation between Bay of Bengal sea surface temperature and northeast monsoon rainfall.
    • The magnitudes of correlations with El Nino conditions and Bay of Bengal warming are remarkably similar, emphasizing their collective impact on weather patterns.

Way Forward:

  • Study and Mapping: Conduct a detailed study of urban and peri-urban water dynamics, mapping water bodies, and understanding interconnected hydrological conditions.
  • Restoration of Water Bodies: Restore neglected water bodies to their original or increased capacity to minimize run-off, thus preventing floods and ensuring water conservation.
  • Protection of Ecological Hotspots: In the Master Plan III, identify and designate ecological hotspots and “no development zones” to safeguard lakes, floodplains, forests, major drains, and wetlands.
  • Continuous Maintenance: Prioritize year-long attention and maintenance of waterways, including major rivers and drains, to prevent sludge and silt deposits, ensuring their continuous functionality.
  • Regulate Urban Expansion: Acknowledge the irreversible nature of urban expansion and regulate it effectively to protect ecological features, preventing further loss of water bodies and wetlands.