Urban Flooding in Delhi

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Urban Flooding in Delhi

  • The term urban flood consists of two parts – ‘urban’ and ‘flood’. Flood is defined as “an overflow of a large body of water over areas not usually inundated”.
  • Thus, flooding in urban areas is caused by intense and/or prolonged rainfall, which overwhelms the capacity of the drainage system.
  • Urban flooding is significantly different from rural flooding- urbanization increases flood risk by up to 3 times, increased peak flow result in flooding very quickly.
  • Further, it affects a large number of people due to the high population density in urban areas.

Causes of Urban Flooding :

  • Meteorological Factors:
  • Heavy rainfall, cyclonic storms and thunderstorms
  • Hydrological Factors:
  • Overbank flow channel networks, occurrence of high tides impeding the drainage in coastal cities.
  • Anthropogenic Factors:
  • Unplanned Urbanization:
  • Unplanned Urbanization is the key cause of urban flooding.
  • A major concern is blocking of natural drainage pathways through construction activity and encroachment on catchment areas, riverbeds and lakebeds.
  • Some of the major hydrological effects of urbanization are:
  • Increased water demand, often exceeding the available natural resources;
  • Increased wastewater, polluting rivers and lakes and endangering the ecology-
  • Destruction of lakes is a major issue in Indian cities. Lakes can store the excess water and regulate the flow of water.
  • However, pollution of natural urban water bodies and converting them for development purposes has increased risk of floods
  • Reduced infiltration due to paving of surfaces which decreases ground absorption and increases the speed and amount of surface flow
  • Reduced groundwater recharge, increased use of groundwater, and diminishing base flow of streams
  • Increased peak flow
  • Climate Change:
  • Climate change due to various anthropogenic events has led to extreme weather events
  • Poor Solid Waste Management System:
  • Improper waste management system
  • Clogging of storm-water drains because of silting, accumulation of non-biodegradable wastes and construction debris.
  • Drainage System:
  • Old and ill maintained drainage system is another factor making cities in India vulnerable to flooding.

Impact of Urban Flooding:

  • Impact on Human:
  • Loss of life & physical injury
  • Increased stress; psychological trauma
  • Disease outbreak:
  • Contamination of water supplies leading to diseases
  • Rise in mosquito borne diseases
  • Impact on Economy:
  • Damage to buildings, roads and other infrastructures
  • Disruptions to industrial production
  • Disruptions to utility supplies
  • Impact on heritage or archaeological site
  • Post-disaster rescue and rehabilitation adds to financial burden of the government
  • Impact on Transport and Communication:
  • Increased traffic congestion, disruption in rail services
  • Disruption in communication- on telephone, internet cables
  • Impact on environment:
  • Loss of tree cover, loss of habitat
  • Impact on animals in zoo, stray animals