Urban flooding refers to the inundation of land or property in densely populated areas due to heavy rainfall, overflowing rivers, poor drainage systems, or other water-related incidents.The climate change is causing over 64% of Indian sub-districts witnessing more heavy rainfall days in the last decade.

Causes of Urban Flooding:

Natural Causes include:

1. Natural meteorological phenomenon like cyclones, cloud bursts, etc. is a primal factor. E.g., Cyclone Tauktae in Mumbai.
2. Monsoon bursts lead to heavy rainfall in a short period. E.g., In 2005 Mumbai witnessed 37 inches of rainfall only in 24 hours.
3. Climate change-induced sea level rise: In February 2021, McKinsey India said in a report that by 2050, Mumbai will witness a 25% increase in the intensity of flash floods accompanied by a half-meter rise in the sea level.

Anthropogenic causes include:

1. Concretization of Indian cities leading to a reduction in water absorption capacity. E.g., Mumbai saw a 99.9% increase in built-up area in the last 27 years.
2. Outdated and overwhelmed drainage systems: E.g. The last drainage master plan for Delhi was created in 1976, leading to frequent flooding.
3. Encroachment and destruction of natural water bodies: E.g., Bengaluru has lost 79% of its water bodies, reducing its flood resilience.
4. Deforestation and Loss of Green Spaces: The removal of forests and wetlands reduces the land’s ability to absorb water, causing rapid runoff into urban areas.Eg: Bengaluru’s urban flooding
5. Solid Waste and Debris: Improper waste disposal clogs drainage systems, blocking water flow and leading to waterlogging. Eg: In Mumbai, plastic waste clogging drains exacerbated the 2005 floods.
6. Unplanned Development in Ecologically Sensitive Areas: 2013 Kedarnath floods, exacerbated by unplanned development, resulted in massive destruction, highlighting the dangers of such encroachment.

Two major floods in the last two decades in India:

1. Mumbai Floods (July 2005):  

1. Mumbai experienced a record-breaking 944 mm of rainfall in 24 hours. 
2. Other Reasons – poorly maintained and antiquated stormwater drainage system, extensive encroachment on natural watercourses like the Mithi River, and blocked drainage due to improper waste management.
3. Over 1,000 people lost their lives due to flooding, landslides, and other related incidents.
4. Chennai Floods (December 2015): 

1. The city received around 494 mm of rainfall in a single day.
2. Other factors – unplanned urbanization on wetlands and floodplains, including large-scale construction on areas like Pallikaranai marshlands. Poor urban planning and blocked stormwater drains worsened the impact.
3. The release of excess water from the Chembarambakkam Reservoir further aggravated the flooding. 

Policies and frameworks in India that aim at Tackling Floods:

1. National Disaster Management Authority (NDMA) Guidelines on Urban Flooding (2010):

1. Creation of an Urban Flooding Management Plan for each city.
2. Preparation of a Rainwater Harvesting Policy to improve water absorption and reduce surface runoff.
3. Creation of capacity-building programs for urban local bodies (ULBs) to implement better flood management practices.
4. Atal Mission for Rejuvenation and Urban Transformation (AMRUT):

1. Promotion of green infrastructure, such as parks and wetlands, which act as natural buffers to absorb excess rainwater.
2. Encouragement of urban planning that integrates flood risks, ensuring that new urban developments are resilient to floods.
3. Smart Cities Mission(2015):

1. Promotion of sustainable urban development, such as the restoration of water bodies
2. Use of geospatial technologies for flood risk mapping and planning.
3. National Building Code (NBC):

1. Restricts construction in floodplains.
2. Mandates the inclusion of stormwater management systems in new developments.
3. Encourages the use of permeable materials for roads and pavements to reduce surface runoff.

Effective measures include adopting “Sponge City” concept used in China along with other non-structural measures can help realise goal of SDG-11.