Why in News?

There has been an increased incidence of high intensity Rainfall in short duration, causing Urban Flooding which is further compounded by unplanned growth, encroachment of natural water bodies, and Poor Drainage System.

What is urban flooding?

Urban flooding describes the flooding of land or property within a constructed environment, especially in locations that are more densely inhabited (like cities), as a result of excessive rainfall that exceeds the capacity of drainage systems.

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, urban flooding occurs very quickly due to faster flow times which is 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.

Steps taken to Mitigate Urban Flooding

• 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.
• Special feature in India
  • Heavy rainfall during monsoons
  • Storm surge affect coastal cities/ towns
  • Urban heat island due to global warming
  • Sea surge increase the level of sea in coastal cities

Causes:

• Encroachments on Drainage Channels: Due to increased land prices and less availability of land new developments have come up in low-lying areas of cities, such as encroachments over lakes, Wetlands and riverbeds.
  • Ideally, the natural drains should have been widened to accommodate the higher flows of stormwater.
  • But on the contrary, there have been large scale encroachments without widening the natural drains, leading to decrease in the capacity of the natural drains resulting in flooding.
• Climate Change: Climate Change has caused an increase in the frequency of short duration heavy rainfall leading to higher water run-off.
  • Whenever the rain bearing clouds pass over the urban heat island, the hot air pushes the clouds up, resulting in highly localised rainfall which may sometimes be of high intensity.
• Uninformed Release of Water from Dams: Unplanned and sudden release of water from dams and lakes lead to floods in an urban area, without giving the public enough time to respond.
  • Example: Chennai Floods 2015 due to release of water from Chembarambakkam Lake.
  • The July 2023 flood in Delhi was magnified by 2 lakh cusecs of water discharged from the Hathnikund Barrage into the Yamuna river.
• Illegal Mining: Illegal mining of river sand and quartzite for use in building construction deplete the natural bed of the rivers and lakes.
  • It causes soil erosion and reduces the water retention capacity of the waterbody increasing the speed and scale of water flow.
  • Example: Jaisamand Lake- Jodhpur, Cauvery river- Tamil Nadu.

What lies ahead?

• Legal Enforcement- India should enforce laws to check on encroachment of lands in the urban areas.
• Climate resilient structures- It should be in line with SDG 11-Sustainable cities and communities.
• Proper drainage infrastructure- Conduct monsoon audits regularly to mitigate the flood effects.
  • Tamil Nadu has appointed Tirupugazh Committee to recommend on flood mitigation.
• Greening cities –East Kolkata’s wetlands have been an effective flood defence mechanism that help treat a large share of the city’s sewage, produce half of the city’s fresh vegetables.
• Flood plain mapping- It improves flood management response and helps the community to understand their flood risk.
• Rain Water Harvesting (RWH) – Adopt RWH in all infrastructure constructions to ensure better water management.
• Bioswales- It must be constructed for percolation of rainwater into the ground.
• Blue-Green Infrastructure- It uses infrastructure, ecological restoration, and urban design to connect people with nature to solve urban and climate problems.

FAQs about Urban Flooding in India

Read also:- Water Bodies Census