Urban flooding is the inundation of property in a built environment, particularly in densely populated urban areas, caused by intense rainfall (on impermeable surfaces) which overwhelms the capacity of drainage systems. There has been an increasing trend of urban flood disasters in India over the past several years. The most notable amongst them are Hyderabad in 2000, Ahmedabad in 2001, Delhi in 2002 and 2003, Chennai in 2004, Mumbai in 2005, Surat in 2006, Kolkata in 2007. The most recent devastating ones were Srinagar in 2014 and Chennai in 2015. Causes of increased urban flooding include poor urban planning:

• Land use changes without any regard for proper drainage; for example:
  • surface sealing due to urbanization,
  • deforestation and increased runoff.
  • Indian cities are becoming impervious to water seepage due to hard, non-porous construction material used in built up areas.
• Indiscriminate disposal of solid waste leading to blocked drainage systems.
• Encroachment of the flood plain and thereby obstructing flows.
• Inefficiency or non-maintenance of flood management infrastructure.
• Unmindful construction and encroachment on wetlands. The number of wetlands has reduced to 123 in 2018 from 644 in 1956.

In this context, NDMA issued guidelines on urban flooding which contains following major points

• It designates the Ministry of Urban Development as the Nodal Ministry for Urban Flooding.
• Early Warning System and Communication
  • Create a National Hydro-meteorological Network- for providing early warning in all urban centres.
  • Developing local networks for real-time rainfall data collection with a ‘Local Network Cell’
  • Subdivide Cities/ towns on the basis of watersheds in the IMD headquarters. and develop a protocol for forecasting rainfall for urban areas on the basis of watershed.
• Design and Management of Urban Drainage System
  • A watershed based and ward-based inventory of the existing storm water drainage system to be prepared.
  • Integrated planning and interactions between Water and Solid Waste Management.
  • Other steps like pre-monsoon de-silting of all major drains, rainwater harvesting, Rain Gardens etc. are to be promoted.
• Urban Flood Disaster Risk Management
  • Risk assessment will be carried out with a multi-hazard concept leading to fool proof land use planning.
  • The research should focus on three key areas: risk identification, risk pooling and risk transfer. The risk should focus on both property and people.
  • Identification of potential damage areas, according to the physical characteristics of the area such as land use, topography, drainage area, outfall system and the capacity of the existing storm water drainage system.
  • National Database for Mapping Attributes- The database required for mapping different ward/community level attributes will be made accessible to all ULBs and concerned departments/ agencies/ stakeholders.
• Techno-Legal Regime
  • Storm water drainage concerns will be made a part of all EIA norms.
  • Growth of urban sprawls can be made a part of urban flood management.
• Capacity Development, Awareness Generation and Documentation
  • Urban Flood Education, Institutional & Community Capacity Development, enhanced Role of Civil Society, Awareness on Insurance etc.
  • Role of Public Representatives, Role of Media is also discussed.

Increasing instances of urban flooding calls for better urban planning in accordance with NDMA guidelines to develop sustainable cities.