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