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Several parts in Chennai and its suburban areas reported waterlogging on after heavy rains lashed the city. The showers have now been marked as the heaviest downpour since 2015. In fact there has been an increasing trend of urban flood disasters in India over the past several years whereby major cities in India have been severely affected. Some of the most notable amongst them are Hyderabad in 2000 & 2020, Ahmedabad in 2001 & 2020, Delhi in 2002, 2003, 2009 & 2010, Chennai in 2004 & 2015, Mumbai in 2005, Surat in 2006, Kolkata in 2007 and Srinagar in 2014. Urban flooding is significantly different from rural flooding as urbanization leads to developed catchments, which increases the flood peaks from 1.8 to 8 times and flood volumes by up to 6 times. Consequently, flooding occurs very quickly due to faster flow times. Urban areas are densely populated and people living in vulnerable areas suffer due to flooding and the secondary effect of exposure to infection also has its toll in terms of human suffering, loss of livelihood and in extreme cases, loss of life. Increasing trend of urban flooding is a universal phenomenon and poses a great challenge to urban planners the world over. According to a recent report on Urban planning capacity in India by NITI Aayog Urban planning has not received adequate attention and 65% of the 7933 urban settlements do not have any master plan.

Urban flooding is the inundation of land or property in a built environment, particularly in more densely populated areas, caused by rainfall overwhelming the capacity of drainage systems, such as storm sewers. Due to rapid, unscientific, unplanned urbanization across the globe, the carrying capacity of urban areas is often breached leading to impending disasters. Floods and water-logging show that urban planners have paid scant respect to hydrology.

Causes for the rise in urban floods

  • Inadequate Drainage Infrastructure:Cities like Hyderabad, Mumbai rely on a century-old drainage system, covering only a small part of the core city.
    • In the last 20 years, the Indian cities have grown manifold with its original built-up area.
    • As the city grew beyond its original limits, not much was done to address the absence of adequate drainage systems.
  • Terrain Alteration:Lasting irreversible damage has been done to the city by property builders, property owners, and public agencies by flattening terrain and altering natural drainage routes.
  • Reducing Seepage:Indian cities are becoming increasingly impervious to water, not just because of increasing built up but also because of the nature of materials used (hard, non-porous construction material that makes the soil impervious).
  • Lax Implementation: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.
  • Encroaching Natural Spaces:The number of wetlands has reduced to 123 in 2018 from 644 in 1956.
    • Green cover is only 9 per cent, which ideally should have been at least 33 per cent.

Way forward

    • Need for Holistic Engagement:Urban floods of this scale cannot be contained by the municipal authorities alone. Floods cannot be managed without concerted and focused investments of energy and resources.
      • The Metropolitan Development Authorities, National Disaster Management Authority, State revenue and irrigation departments along with municipal corporations should be involved in such work together.
      • Such investments can only be done in a mission mode organisation with active participation of civil society organisations at the metropolitan scale.
    • Developing Sponge Cities:The idea of a sponge city is to make cities more permeable so as to hold and use the water which falls upon it.
      • Sponge cities absorb the rain water, which is then naturally filtered by the soil and allowed to reach urban aquifers.
      • This allows for the extraction of water from the ground through urban or peri-urban wells.
      • This water can be treated easily and used for city water supply.
  • Wetland Policy: There is a need to start paying attention to the management of wetlands by involving local communities.
    • Without doubt, terrain alteration needs to be strictly regulated and a ban on any further alteration of terrain needs to be introduced.
    • To improve the city’s capacity to absorb water, new porous materials and technologies must be encouraged or mandated across scales.
    • Examples of these technologies are bioswales and retention systems, permeable material for roads and pavement, drainage systems which allow storm water to trickle into the ground, green roofs and harvesting systems in buildings.
  • Drainage Planning: Watershed management and emergency drainage plan should be clearly enunciated in policy and law.
    • Urban watersheds are micro ecological drainage systems, shaped by contours of terrain.
    • Detailed documentation of these must be held by agencies which are not bound by municipal jurisdictions; instead, there is a need to consider natural boundaries such as watersheds instead of governance boundaries like electoral wards for shaping a drainage plan.
  • Water Sensitive Urban Design: These methods take into consideration the topography, types of surfaces (permeable or impervious), natural drainage and leave very less impact on the environment.
    • Vulnerability analyses and risk assessments should form part and parcel of city master plans.
    • In a changing climate, the drainage infrastructure (especially storm water drainage) has to be built considering the new ‘normal’.
    • Tools such as predictive precipitation modelling can help do that and are also able to link it with the adaptive capacity of urban land use.


  • These can all be delivered effectively through an urban mission along the lines of the Atal Mission for Rejuvenation and Urban Transformation (AMRUT), National Heritage City Development and Augmentation Yojana (HRIDAY)and Smart Cities Mission.
  • Urban Flood management will not just help control recurring floods but also respond to other fault lines, provide for water security, more green spaces, and will make the city resilient and sustainable.
  • Disabling spawning of squatter settlements in sensitive zones by providing adequate affordable housing will reduce number of persons vulnerable to changing climate.
  • All this means urban local bodies will continue to have a central role to play in cities’ battle with extreme weather events such as flooding and their overall resilience.