Urban flooding refers to the submerging of urban lands, which usually remain dry. This overflow of water can be attributed to varied reasons including precipitation, lack of drainage systems and the accumulation of waste. As a consequence of faster flow times, flooding occurs very quickly, sometimes in minutes.

Overview of Urban Flooding

Flooding is a natural calamity, and it happens when a large amount of water overflows and submerges normally dry terrain. Heavy rain, quick snowmelt, or a storm surge from a tropical cyclone or tsunami in coastal locations are all common causes of flooding.

• The most common reason for the occurrence of a flood is when the water exceeds the carrying capacity of water bodies and thus, travels to neighbouring flood-prone plains.
• Floods, similar to earthquakes, are often foreseeable because they exhibit appropriate warning signals and develop slowly enough for the authorities to make judgments. They also tend to occur at the usual time of year in well-known places or flood-prone zones.
• In coastal areas, the reasons for flooding are storm surges, melting of ice, excessive rainfall for prolonged periods, and the presence of eroded material which maximises soil erosion. 
• Floods in South Asia, Southeast Asia, and East Asia, specifically India, China, and Bangladesh, frequently experience floods.
• Nearly 40 million hectares of land in India have been recognised as flood-prone, according to the Rashtriya Barh Ayog (National Commission on Floods). 
• West Bengal, Assam, and Bihar are among India’s most flood-prone states.
• Floods are a risk in states such as Uttar Pradesh and Punjab.
• Flash floods have occurred in states like Gujarat, Rajasthan, Haryana, and Punjab in recent years.

Causes of Urban Flooding

• Faster Flow: Floods occur in a matter of minutes due to the faster flow of water on paved surfaces.

• Defective Drainage System: Unauthorised construction, a lack of proper drainage systems or below-capacity sewage systems lead to urban flooding.

• Global Warming: The melting of snow, a change in climate and heavy precipitation can cause urban floods.

• Lack of Waste Management Systems: An ineffective waste management system may cause clogged drainages and as a consequence, leads to urban flooding.

Facts about Urban Flooding

• Due to ongoing climate change and global warming, urban flooding is becoming more and more common.
• India receives its maximum rainfall from the Southwest monsoons. So, rainfall patterns and temporal duration are almost similar in all these cities.
• Urban areas are centres of economic activity and as such, they contain vital infrastructure which need to be protected. In some urban areas, any damage to vital infrastructure has consequences on not only the state or country, but has global implications as well. An example of this is Mumbai, which is the financial capital of the country.

Steps taken to Mitigate Urban Flooding

Under the Atal Mission for Rejuvenation and Urban Transformation (AMRUT), the Government of India is taking steps to define established Standard Operating Procedures, which are to be implemented at the district level to mitigate the risk associated with urban flooding. 

Three Phases for Efficient Management of Urban Floods 

Pre- Monsoon Phase

• Preparation for the reduction of urban flooding

Monsoon Phase

• Early warning
• Response and management
• Relief planning and execution

Post-Monsoon Phase

• Restoration and rehabilitation

The National Disaster Management Authority (NDMA) provides guidelines for the effective management of urban flooding. These guidelines provide a plan to establish Urban Flooding Cells at State Nodal Departments and urban local bodies (ULB). 

NDMA Guidelines on Urban Flooding

• It is essential to design and strengthen local hydro-meteorological data networks to cater to the needs of urban flooding holistically.
• Efforts shall be made to restore water bodies by de-silting and taking other measures as well as reviving water bodies that have been put to other uses.
• Local scale emergency medical response systems will be established to deal with medical preparedness, emergency treatment, mortuary facilities and the disposal of bodies and carcasses, public health issues including trauma and the control of epidemics.
• Encourage local residents to form community level first responder support groups consisting of ex-servicemen, retired police personnel, paramilitary forces and Resident Welfare Association (RWA) personnel.
• Suitable hedging mechanisms such as insurance of life and property, need to be evolved to reduce urban flood vulnerability.
• Public awareness is to be created on the need for safety kits (containing medicines, torches, identity cards, ration cards, important documents and non-perishable edibles) to be prepared before the commencement of the monsoons in case of a possible evacuation. 
• Media companies should be motivated to launch/expand awareness programmes as a part of their corporate social responsibility (CSR).

Negative Impacts of Urban Flooding

• A significant impact of floods is the frequent deterioration of agricultural land and human settlements.
• When water gets into a field, it destroys precious crops and infrastructure, including trains, roads, bridges, and transportation.
• Millions of people have died as a result of floods, and millions more have become homeless. Floods also result in the loss of livestock.

Positive Aspects of Urban Flooding

• Floods can have a significant favourable impact on agricultural areas, which is beneficial to crops. Majuli in Assam is a well-known example of good paddy crops growing in the aftermath of the Brahmaputra river’s yearly floods.

Conclusion

The trend of urban floods is increasing, and many possible damages are associated with urban flooding. There are flood mitigation plans at different levels with specific guidelines, from precautionary steps to restoration steps. With proper planning and implementation of SOPs, India can manage the threat associated with urban floods.