Urban Flooding

• 04 Aug 2023

For Prelims: Urban Flooding, Rainfall, Rural floods, Drainage System, Wetlands, Climate Change, Sewage and solid waste, Illegal Mining, Riverbank Erosion.

For Mains: Urban Flooding, Causes and Curtailment.

Source: PIB

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?

• About:
  • Urban flooding is the inundation of land or property in a built environment, particularly in more densely populated areas (like cities), caused by rainfall overwhelming the capacity of drainage systems.
  • Unlike Rural floods (Heavy rain over a flat or low-lying area), urban flooding is not only caused by just higher precipitation but also unplanned urbanisation (catchments) that:
    • Increases the flood peaks from 1.8 to 8 times
    • Increases the flood volumes by up to 6 times.
• 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 are the Implications of Urban Flooding?

• Loss of Life and Property:
  • Urban floods are often associated with loss of life and physical injury either directly due to the effect of floods or indirectly due to infections by water-borne diseases spreading during the inundated period.
• Ecological and Environmental:
  • Trees and plants are washed away during extreme flood events and riverbank erosion is caused by high-speed flood water.
• Impact on Animal and Human Health:
  • Stagnation of stormwater in the localities, and Contamination of consumable water leads to various health problems resulting in plagues/epidemics.
  • The sewage and solid waste washing into houses and neighborhoods also causes a variety of diseases to spread.
• Psychological Impacts:
  • Loss of shelter and relatives creates emotional turmoil in the mental health of the stranded. The recovery process in case of such incidents is a tiresome process and time consuming that often leads to long lasting psychological trauma.

What are the Government Initiatives to Curtail Urban Flooding?

• Jal Shakti Abhiyan (JSA)
• Amrit Sarovar Mission
• Atal Bhujal Yojana
• Atal Mission for Rejuvenation and Urban Transformation (AMRUT) 2.0
• Model Building Bye Laws (MBBL), 2016
• Standard Operating Procedures (SoPs) on Urban Flooding by MInistry of Housing and Urban Affairs.

Way Forward

• Implement sustainable urban planning practices that prioritize green spaces, retention ponds, and permeable surfaces to absorb and manage stormwater. Avoid construction in flood-prone areas and preserve natural drainage systems.
• Invest in upgrading and expanding drainage infrastructure, including natural drains, stormwater channels, and flood-control systems. Regular maintenance and cleaning of drains are essential to ensure effective water flow.
• Identify and map flood-prone areas and develop appropriate floodplain management strategies. Restrict construction and development in these vulnerable zones to reduce the risk of flooding.
• Establish and improve Early Warning Systems to alert residents about impending floods. Timely warnings can help people evacuate and take necessary precautions.