Urban Floods: Why Chennai Went Under Water Again

Context:  This article is based on an Editorial “Why Chennai went under water again” which was published in the Hindu. Recently, Cyclone Michaung delayed about 100 km off the coast of Chennai for about 16 hours. 

• It has caused torrential rains and extensive floods, causing severe damage to infrastructure and disruptions of livelihoods. 

About Urban Floods

• It is the submergence of usually dry areas by a large amount of water that comes from sudden excessive rainfall, an overflowing river or lake, melting snow, or an exceptionally high tide. 

What are the causes of urban floods in India?

• Meteorological Factors: Such as heavy rainfall, cyclonic storms, and thunderstorms.
• Hydrological Factors: Urban flood risk arises when the surface runoff is greater than the infiltration rate. Lower infiltration leads to higher run-off and flooding.
  • Factors impacting the Infiltration Rates: Type of soil, their respective water retention capacities, vegetation cover (reduces the speed of water and increases infiltration), etc.
    • Urbanization reduces the rate of infiltration due to paved roads and lack of vegetation cover.
• Anthropogenic/Human Factors: Urbanization has led to encroachments on water bodies and construction on beds of rivulets/rivers and lakes. 
  • This obstructs the natural flow of water and consequently, such areas are inundated with water during events of heavy rainfall.
  • Example: In Bengaluru, the Dakshina Pinakini River had been dry for three decades and was considered extinct. With heavy rainfall, it was flooded and damaged buildings in its path.
• Inadequate Infrastructure: Most Indian cities have undergone haphazard urbanization and infrastructure has not been commensurately upgraded with rising population e.g., stormwater drainage lacks capacity to adjust for loss of natural run-off due to construction.
  • The Karnataka State Action Plan on Climate Change (2013) noted that the drain infrastructure of Bengaluru is not enough to handle even moderate rainfall events.
• Lack of Regular Cleaning and Upkeep of Drains: It leads to clogging and flooding.

What are the impacts of urban floods?

• Economic Loss: Damage to critical infrastructure in major urban centers has an impact at both the State and National level.
  • Example: The 2005 flood in Mumbai led to disruption of operations of Stock Exchanges (BSE and NSE) and shut down financial services, resulting in losses exceeding US$ 100 million.
• Impact on Daily Life Activities: Disruptions in power and transportation impact the day-to-day life of residents. 
• Impact on Livelihood: For lower-income groups, the major challenge is the ability to earn a livelihood, which is directly affected by urban floods. 
  • The urban poor are at more risk because in most cases the slums in which they live are most vulnerable to urban floods.
• Loss of Life and Property: Extreme events cause such great losses of life and property.
• Serious Health Risks: Flood waters from industrial facilities or storage locations may disperse dangerous chemicals and fuels into water. 
  • Toxic chemicals and untreated sewage can both pose serious risks to the general public’s health and the water supply.
  • Spread of infection post-flood event can cause the spread of epidemics.

Way Forward

• Water-sensitive urban design and planning techniques are most critical. 
• Vulnerability analyses and risk assessments should be mandatory in city master plans.
• A comprehensive database of all wetlands and water bodies in urban areas should be established. 
  • Protected areas for river, lake, and other water channel catchments must be identified and freed from encroachments. 
  • Flood plains and natural water bodies must be restored.
• Use of the concept of Sponge Cities. 
  • Sponge cities can solve the problem of urban flooding as well as scarcity of water during the summer season.

Conclusion:

As per a Climate Change Assessment Report (2020), increased frequencies of heavy rainfall have enhanced flood risk all over India, particularly in the urban areas which requires an urgent fix.

• Collaborative Approach: Addressing the challenge of urban floods requires a concerted effort of Union, State, and Local Governments along with the citizens.