Urban Floods

The heavy rainfall and the crazy Banglore flood: A case to study


From UPSC perspective, the following things are important :

Prelims level: NA

Mains level: urban floods mitigation


  • The recent events of heavy downpours in short period of time and the recent example of Banglore flood, highlights how cities in India and elsewhere need to adapt to climate change as it brings more extreme rainfall in the future.

What is heavy downpour?

  • A downpour or cloudburst is a sudden and unexpected heavy fall of rain.
  • It is usually local in nature and of brief duration. Most so-called cloudbursts occur in connection with thunderstorms.
  • Heavy downpour in short period causes flood, damage to buildings and infrastructure can disrupt transport, communications and connectivity, loss of crops and livestock.

The heavy rainfall and the Banglore flood causes

  • Rise in built up area: Lakes and natural depressions may not always fill up during many monsoons so the people who are unaware of hydrology tempts to build and buy in the catchment areas of water-bodies, which will be disastrous when it rains heavily as there is rise in the quantity.
  • Water-logging: rainwater and sewage water are forced to build up, which results in water-logging. The highway acts as a dam for the water ,Garbage frequently clogs drains, which limits the flow of sewage, and they are too small to support the weight of the expanding population.
  • Physical shrinkage of water-bodies: Destruction of lakes is a major issue .lakes can store the excess water and regulate the flow of water however the pollution of natural water bodies and converting them for development purposes has increased the risks of floods. Unplanned growth, Rise in population, rise in the built up areas along streams, canals, around the lakes, leaving no storage capacity.
  • Compromised runoff potential and health hazards: Choked and encroached drains and lakes, ill designed infrastructure and missing pipes compromising run off potential. Not only the physical quantity of the runoff that poses a hazard. When polluted drains and lakes overflow, the flood can pose a health hazard especially to vulnerable and exposed marginal communities living in informal settlements.
  • Zero or limited ability to allow infiltration of water: Encroachments in and around wetlands and green lands harming the natural way of water infiltration and ground water recharge.
  • Lack of vision in rain water harvesting: Ignorance towards the tradition rain water harvesting techniques and no or limited vision for creating new systems of rain water harvesting. Exceptionally heavy monsoon rains have been exacerbated by poor urban planning in the Indian tech hub, showing the need for improved water systems.

floodWhat are the reasons behind the frequent floods in urban areas?

  • Meteorological factors: change in the weather patterns, increase in the temperature leading to heavy rainfall, sudden downpour, cloudburst, thunderstorms, hailstorms etc.
  • Hydrological factors: Natural surface infiltration rate, soil moisture level, presence or absence of Overbank flows, Presence of impervious cover, the occurrence of high tides impeding the drainage in coastal cities.
  • Man-Made factors:
    • Unplanned urbanization: Unplanned settlement is one of the main cause of urban flooding. Blocking of natural drainage pathways through construction activity and encroachment on catchment areas, streams, rivers, lakebeds. Reduced infiltration and ground water recharge of water, destruction of lakes, Land-use changes (e.g. surface sealing due to urbanization, deforestation) increase runoff and sedimentation. Inefficiency or non-maintenance of infrastructure etc.
    • Outdated Drainage systems: The old and ill-maintained drainage system is one of the main factor making cities in India vulnerable to flooding
    • Encroachments on and around water-bodies: Illegal Habitations started growing into towns and cities alongside rivers and watercourses. As a result of this, the capacity of the natural drains has decreased, resulting in flooding.
    • Climate Change: Climate change due to various anthropogenic events has led to extreme weather events, increasing temperature which resulting in heavy rainfall in one part while drought and dry spells in other.
    • Poor Solid Waste Management System: Indiscriminate disposal of solid waste, poor waste management system, clogging drains because of accumulation of non-biodegradable wastes are major concerns. Domestic, commercial and industrial waste and dumping of it into the drains also contribute significantly to reducing their capacities.
    • Reduced Seepage: use of hard and non-porous construction material making the soil impervious, reducing the seepage capability in no of cities in India.
    • Weak Implementation and lack of awareness:Even with provisions of rainwater harvesting, sustainable urban drainage systems, etc, in regulatory mechanisms like the Environmental Impact Assessment (EIA), adoption at user end as well as enforcement agencies remains weak.
    • No Community Participation:Flood control measures planned without participation of the affected community are unsustainable as they do not meet the needs of relevant stakeholders.

What can be done to prevent the urban floods and prevent losses?

  • Developing climate Resilient Infrastructure: using permeable material for roads and pavement, green roofs and harvesting systems in buildings. To reduce the burden of road infrastructure in cities Outer Ring Road should be explored. Innovative approaches like Sponge Cities wetland restoration, flushing systems using collected rooftop water, public spaces as flexible water retention facilities can be applied to Indian urban areas.
  • Use of technology in Early Warning Systems and Communication: Early-warning systems using sensors across waterbodies and drains, and a network of communication for hotspots of emerging flood risk in the wet-season should be put in place. Providing real-time data where traditional systems fail. Tools such as predictive precipitation modelingcan help do that and are also able to link it with the adaptive capacity of urban land use.
  • Proper management and regular upgrade of Urban Drainage System: drains need to be cleaned on a regular basis to permit the free flow of water .Proper management of the drainage system is necessary to ensure that the water does not get stored in one place. Watershed management and emergency drainage plan should be clearly enunciated in policy.
  • Rainwater Harvesting: It will serve the twin purposes of lowering the peak runoff and raising the groundwater table. Many municipal corporations in India have already made rainwater harvesting compulsory
  • Conservation of Water Bodies: Urban water bodies like lakes, tanks, and ponds also play a very important role in the management of urban flooding by reducing the flood water run-off by capturing it.
  • Holistic approach: Improved monitoring, forecasting, and decision-support systems. Find out the different method for improving the preparedness for urban flooding.
  • Responsibility on every stakeholder: Locally, citizens, local ward officials and staff will need to work together to minimize dumping of solid waste and garbage in storm-water drains. As this is a socio –political problem, public participation awareness and responsibility of citizen is the need of the hour. To develop a long-lasting solution, all parties must acknowledge the issues and adopt a thorough strategy.

What we as citizens can do on a personal level to prevent the urban environment?

  • Raising voice at all available forums and platforms
  • Making politicians and bureaucrats accountable
  • Refuse to buy a house in the encroached lands.
  • Applying methods of rain water harvesting on individual level.

Way ahead

  • Exceptionally heavy monsoon rains have been exacerbated by poor urban planning in the Indian tech hub, showing the need for improved water systems.
  • Urbanization is a global and inevitable process, and with cities as engines of the economy, built-up areas will continue to grow. But we need to draw upon these experiences and the growing perils of climate change and extreme rain events and change course.
  • According to UN projections, by 2050 more than 68% of the world’s population could be concentrated in urban areas.
  • In this context, resilience-based strategies should be adopted to improve the capacity to handle the crisis arising out of climate change.
  • Wetlands are the kidneys of the earth, let’s keep it healthy.


Mains Question

Q. What are the factors causing flood in the urban cities? What are the measures to prevent the urban flooding keeping in mind the sustainable development? Discuss.


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