Topic : Urban Floods in India
Topic in Syllabus: General Studies Paper 3: Ecology & Environment
After the Incessant rainfall strikes in states like of Bihar, Madhya Pradesh has badly hit normal life, with almost all areas of city. These Cities are facing are multipronged problems in terms of Health crisis, education jeopardizing and choke block transportation system.
- 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 & Sendai Framework:
- The Government of India is a signatory to the Sendai Framework for Disaster Risk Reduction, which was adopted at the Third World DRR Conference held in Sendai in Japan in the year 2015.
- India is thus committed to mainstream disaster risk reduction by investing in resilient infrastructure, urban planning, land use, etc. so as to not only reduce the risk of flooding but reduce the losses of lives and livelihoods in case it occurs.
- Sendai Framework convention focuses on the reduction of disaster risk as an expected outcome, a goal focused on preventing new risk, reducing existing risk and strengthening resilience, as well as a set of guiding principles, including primary responsibility of states to prevent and reduce disaster risk, all-of-society and all-of State institutions engagement.
- In addition, the scope of disaster risk reduction has been broadened significantly to focus on both natural and man-made hazards and related environmental, technological and biological hazards and risks. Health resilience is strongly promoted throughout.
- The Sendai Framework also articulates the need for improved understanding of disaster risk in all its dimensions of exposure, vulnerability and hazard characteristics; the strengthening of disaster risk governance, including national platforms; accountability for disaster risk management; preparedness to Build Back Better; recognition of stakeholders and their roles; mobilization of risk-sensitive investment to avoid the creation of new risk and resilience of health infrastructure.
Factors Responsible for Urban Flooding:
- Increased rainfall due to changing climatic patterns; Meteorological factors include heavy rainfall, cyclonic storms and thunderstorms.
- Unplanned construction in low-lying areas; Hydrological factors include presence or absence of overbank flow channel networks and occurrence of high tides impeding the drainage in coastal cities.
- Human factors:
- Solid waste in urban drainage channels; the indiscriminate disposal of solid waste into urban water drains and channels is a major impediment to water flow during the monsoon season.
- Human factors include land use changes, surface sealing due to urbanization (which increases run-off), occupation of flood plains and obstruction of flood flows, urban heat island effect (which has increased the rainfall in and around urban areas), sudden release of water from dams located upstream of citizen towns and the failure to release water from dams resulting in backwater effect.
Effects of urban flooding
- Damage to vital infrastructure, loss of life and property.
- Disruption in transport and power and incidence of epidemics, loss of livelihood.
- Urban flooding cause localized incidents to major incidents, resulting in cities being inundated from hours to several days.
- Deterioration of water quality and risk of epidemics.
- Temporary relocation of people, damage to civic amenities.
- Firstly, the existing drainage path should be well demarcated. There should be no encroachments on the natural drainage channels of the city.
- A large number of bridges, flyovers and metro projects are being constructed with their supporting columns located in the existing drainage channels. This can be avoided using proper engineering designs, such as cantilever construction. Storage of rainwater in tanks at the rooftop, intermediate, ground or underground levels can reduce the overflows and help in reducing urban flood volumes.
- Storage or holding ponds should also be provided at judiciously selected locations to store water during heavy rainfall so that it does not cause downstream flooding. Once the rain subsides, the water can be released gradually.
- Whenever a road is resurfaced, the existing layer is scraped first and then the new layer be laid. This shall ensure that the plinth level and the road level remain where they were prior to the resurfacing. Also, various cities, across the world, have constructed porous pavements. These allow the water to gradually infiltrate into the underlying soil thereby maintaining the pre-development sub-soil water conditions.
- At the community level, people should spread awareness and be ready to respond to a flood as a community. Schools have a greater role to play – as children need to be sensitized not only about floods but other disasters as well.
- At the city level, the authorities should ensure that the building by-laws are followed both in spirit and practice at the ground level. People should also cooperate with municipal authorities.
- Urban flood, being a natural disaster, cannot be avoided; however, the losses occurring due to flooding can be prevented by proper flood mitigation planning.
- It is necessary to have a proper estimation of flood extent and flood hazard for the different flow conditions so that proper flood evacuation and disaster management plan can be prepared in advance.
- If we take appropriate measures, we can ensure that the flood incidences remain within tolerable limits. The Intergovernmental Panel on Climate Change (IPCC) has indicated that in future, there could be increase in instances of heavy rainfall in shorter spans of time. This means that our existing drainage systems have to be redesigned to accommodate the increased flow-levels. This can be done either by resizing the drains or by judiciously integrating the best management practices into the drainage infrastructure.