Urban flooding

What is Urban Flooding?

Urban flooding refers to submerging of urban lands, which usually remains dry. This overflow of water can be attributed to varied reasons, including precipitation, lack of drainage system and accumulation of wastages. As compared to the rural flooding, the urban flooding is significantly different. Because urbanization leads to developed catchments which increases the flood peaks from 1.8 to 8 times and flood volumes by up to 6 times. As a consequence of faster flow times, the flooding occurs very quickly, sometimes in a matter of minutes.

Overview of Urban Flood

Nowadays the increasing trend of urban flooding is a universal phenomenon and poses a great challenge to urban planners the world over. Over the past several years there has been an increasing trend of urban flood disasters in India whereby major cities in India have been severely affected.

Some of 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, Jamshedpur in 2008, Delhi in 2009 and Guwahati and Delhi in 2010.

Causes of Urban flooding are:

• Faster flow: Flood happens in a matter of minutes, due to faster flow of water on paved surfaces

• Defective Drainage System: Unauthorized construction, lack of proper drainage system or below capacity sewage system lead to Urban Flooding

• Global Warming: Melting of Snow, change of Climate and Heavy Precipitation can cause Urban Floods

• Lack of Waste Management System: An ineffective waste management system leads to clogged drainage and consequently aids Urban Flooding

Issues in Urban Flooding:

• In India, the average annual rainfall dramatically varies among the important cities. On the higher side varies from 2932 mm in Goa and 2401 mm in Mumbai, to 669 mm in Jaipur on the lower side
• Due to ongoing climate change and global warming, urban flooding is becoming more and more common
• India receives the maximum rainfall from the south-west monsoons. So, the pattern and temporal duration of rainfall is almost similar in all these cities
• The capacity of storm water drainage systems were designed for rainfall intensity of 12 – 20 mm in the past. But whenever rainfall of higher intensity has been experienced these capacities have been getting very easily overwhelmed
• Ideally, the natural drains should have been widened (similar to road widening for increased traffic) to accommodate the higher flows of storm water. But on the contrary, there have been large scale encroachments on the natural drains and the river floodplains
• Improper disposal of solid waste (commercial, domestic, and industrial waste) and dumping of construction debris into the drains also contributes significantly to reducing their capacities
• Overburdened drainage, no regard to the natural topography and hydro- geomorphology all make urban floods a man-made disaster. This increasing trend of urban flooding is a universal phenomenon and poses a great challenge to urban planners in India and all over the world
• Being the centers of economic activities, the Urban areas are also with vital infrastructure which needs to be protected 24×7. In some cities, damage to vital infrastructure has a bearing not only for the state and the country but it could even have global implications. Ex: Mumbai, the financial capital of the country
• According to the report published by the World Bank, there has been a 217 percent increase in the incidence of malaria during the last decade. It identified unhygienic living conditions in slums and water accumulation during and after monsoons as the leading factors

Steps taken to Mitigate Urban Flooding

Under Atal Mission of Rejuvenation and Urban Transformation (AMRUT), steps are taken to define clearly established Standard Operating Procedures, which are to be implemented at district level to mitigate the risk associated with Urban Flooding. 

Three Phases for efficient Management of Urban Floods are:

Pre- Monsoon Phase – Preparation for reduction of Urban Flooding.

Monsoon Phase –

• Early Warning
• Response and Management
• Relief Planning and Execution

Post Monsoon Phase – Restoration and Rehabilitation

NDMA provides guidelines for effective management of Urban Flood. These guidelines provide a plan to the State’s Nodal Department and ULB’s Urban Flood Cell to act.

NDMA Guidelines on Urban Flooding:

• CWC should maximize the real-time hydro-meteorological network to cover all the urban centers in support of the emerging priorities in dealing with urban flooding
• It is essential to design and strengthen local hydro-meteorological data networks to cater for the needs of urban flooding holistically
• State-of-the-art automatic water level recorders must be installed throughout the drainage network of the watershed, which may sometimes extend beyond the administrative boundary of the ULB
• Efforts shall be made to restore water bodies by de-silting and taking other measures. Efforts shall also be made to revive 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 disposal of bodies and carcasses, public health issues including trauma and control of epidemics
• Encourage local residents to constitute Community Level First Responder Support consisting of ex-servicemen, retired police personnel, paramilitary forces and Resident Welfare Association (RWA)
• Suitable hedging mechanisms, like insurance of life and property, need to be evolved to reduce urban flood vulnerability
• Public awareness will be created about the need to keep safety kits containing medicines, torch, identity cards, ration cards, important documents and non-perishable edibles ready before commencement of monsoon so that they can carry the same with them, in case they have to be evacuated
• Media companies shall be motivated to launch/expand awareness generation programmes as a part of their CSR

Conclusion:

The trend of Urban Floods is increasing, it possesses many threats attributing to possibilities of damages associated with it. With Proper Planning and implementation of SOPs, India can manage the threat associated with them. There are flood mitigation plans in place at different levels with specific guidelines from precautionary steps to restoration steps.