Urban flooding is significantly different from rural flooding as urbanization leads to developed catchments, which increases the flood peaks from 1.8 to 8 times and flood volumes by up to 6 times. Consequently, flooding occurs very quickly due to faster flow times (in a matter of minutes). Urban areas are densely populated and people living in vulnerable areas suffer due to flooding, sometimes resulting in loss of life. It is not only the event of flooding but the secondary effect of exposure to infection also has its toll in terms of human suffering, loss of livelihood and, in extreme cases, loss of life.

Urban Flood Risk in India

There has been an increasing trend of urban flood disasters in India over the past several years whereby major cities in India have been severely affected. 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.

Reasons for frequent flooding

• A special feature in India is that we have heavy rainfall during monsoons. There are other weather systems also that bring in a lot of rain. Storm surges can also affect coastal cities/ towns.
• Sudden release or failure to release water from dams can also have severe impact.
• Indian cities are getting increasingly water resistant, not only as the population grows, but also due to the nature of the materials utilised (hard, non-porous construction material that makes the soil impervious).
• In addition, the urban heat island effect has resulted in an increase in rainfall over urban areas. Global climate change is resulting in changed weather patterns and increased episodes of high intensity rainfall events occurring in shorter periods of time.
• Property builders, property owners, and government organisations have flattened the ground and altered natural drainage routes, causing lasting damage to the city.
• Then the threat of sea-level rise is also looming large, threatening all the coastal cities. Cities/towns located on the coast, on river banks, upstream/ downstream of dams, inland cities and in hilly areas can all be affected.

How land centric urbanisations is an issue

• Urban drainage would turn cities into sieves that allowed water to soak and pass through. This required safeguarding the numerous natural watercourses threading the city as they drain water away and sustain fragile groundwater aquifers.
• These waterways — belittled as natural storm drains or nullahs — have been sacrificed at the altar of land-centric urban growth.
• Missing” waterways were either encroached and built over or connected to sewage drains.
• Poor design and corruption — inseparable bedfellows in South Asian urban planning — significantly contribute to urban floods.
• By violating environmental laws and municipal bye-laws, open spaces, wetlands and floodplains have been mercilessly built over, making cities impermeable and hostile to rainwater.

Way forward

• Move away from land-centric urbanisation and recognise cities as waterscapes.
• This scale of urban flooding cannot be controlled by municipal authorities alone. Floods cannot be controlled without concentrated and focused energy and resource inputs.
• Water Sensitive Urban Design: This strategy takes into account topography, surface types (permeable or impermeable), natural drainage, and has a low environmental impact.
• Metropolitan Development Authorities, the National Disaster Management Authority, state revenue and irrigation departments, as well as municipal corporations, should all be involved. Only a mission mode organisation with active participation of civil society organisations at the metropolitan scale can make such investments.
• Let urban rivers breathe by returning them to their floodplains.
• It is critical to begin paying attention to wetlands management by incorporating local communities. Without a doubt, terrain modification must be rigorously restricted, and any future terrain modification must be prohibited.
• Sponge Cities are being developed to collect rainwater, which is then organically filtered by the soil and allowed to reach metropolitan aquifers.
• New porous materials and technologies must be encouraged or mandated at all sizes to improve the city’s ability to absorb water. Bioswales and retention systems, permeable road and pavement material, drainage systems, green roofs, and building harvesting systems are all examples.
• All of these can be efficiently implemented through an urban mission, such as the Atal Mission for Rejuvenation and Urban Transformation (AMRUT), the National Heritage City Development and Augmentation Yojana (HRIDAY), or the Smart Cities Mission.

Reference:

https://indianexpress.com/article/opinion/columns/chennai-floods-climate-crisis-
7618776

How to structure:
1) Give an intro flooding in major cities. Use maps and statistics
2) Identify the reason for frequent flooding
3) Explain how land centric urbanisation is a cause for this and how recognising cities as
waterscapes is the need of the hour.
4) Suggest way forward and government schemes.