Answer: Urban floods have now become a national phenomenon, affecting many cities in India almost annually. Over the past few years, the frequency of urban floods has increased in major cities like Chennai, Mumbai, Ahmadabad, Patna and several other places.  

Floods in urban areas are largely caused by bad planning, inadequate infrastructure, uncontrolled construction, and encroachment on riverbeds, including climate change. 

Urban flooding

Urban flooding is defined as the inundation of land or property within a built environment, particularly in densely populated cities where rainfall exceeds the capacity of drainage systems. It is a manmade disaster. 

Urban flooding is significantly different from rural floods (which are caused by excessive rain over a flat or low-lying area) leads to developed catchments, which increases the flood peaks from 1.8 to 8 times and flood volumes by up to 6 times. 

Main causes of urban flooding in India

• Encroachments on Water Bodies: Urbanization has led to encroachments on water bodies which obstruct the natural flow of water and causes floods.

• For example, Bengaluru floods in Aug-Sept 2022

• Illegal Mining Activities: Illegal sand mining activities lead to soil erosion and reduce the water body's water-holding capacity.
• For example, the flood in Gandak river in East and West Champaran (Bihar). 
• Uninformed Release of Water from Dams: Unplanned and sudden releases of water from dams and lakes cause floods in urban areas, leaving the population with little time to respond.
• For example, the release of water from Chembarambakkam lake which caused Chennai floods in 2015. 
• Climate Change: Climate change has increased the frequency of short-duration heavy rainfall, leading to higher water run-off. Moreover, urban heat islands effect has increased rainfall over urban areas, causing floods. 

Ways to Mitigate urban flooding

• Effective Water-Shed Management: Rainwater harvesting into all infrastructure projects and construction of flood walls.
• For example, Tamil Nadu made rooftop rainwater harvesting compulsory across all houses in the state.
• Developing Blue Green Infrastructure: Climatic concerns can be addressed through a combination of infrastructure, ecological restoration, and urban design to reconnect people with nature.
• Flood vulnerability Mapping: Analyzing the topography and past information on floods at the city level might help identify the vulnerable locations.
• Upgradation of Urban infrastructure: The urban infrastructure must be improved, including the building of new storm water drains and the expansion of current sewerage facilities. 

The government has taken measures to tackle the problems of urban flooding through initiatives like AMRUT, Smart Cities Mission, etc., but beyond the states, community approaches are critical for disaster mitigation and management. Furthermore, capacity-building programmes for citizens across cities need to be taken up through a massive educational effort so that risk reduction behaviour becomes part of their daily lives.