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Baba’s Explainer – Urban Flooding

  • IASbaba
  • September 17, 2022
  • 0
Environment & Ecology, Governance
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Syllabus

  • GS-1: Urbanization, their problems and their remedies
  • GS-3: Government policies and interventions for development in various sectors and issues arising out of their design and implementation

Context: Parts of Bengaluru, India’s IT and startup capital, have been facing unprecedented floods in the recent days. This is not the first instance of urban flooding in India. In fact, urban flooding is becoming increasingly common in many parts of the country with this monsoon season itself seeing many such instances in the states of Rajasthan, Gujarat, and Madhya Pradesh.

  • The fact that such instances are spreading to more cities and happening with greater frequency, suggests that something is broken in our response to such events.
  • The repeated and growing problems of urban floods is a systemic problem and the root cause of this is prioritising economic gains over everything else.
What are the reasons for Urban Flooding?
  • Urban Flooding is an inundation of land in a constructed setting, particularly in densely populated areas, caused by rainfall overwhelming the capacity of drainage systems.

Natural Reasons

  • Higher rainfall: As per the IMD, monsoon has become frequent and unpredictable.
  • Storm surges (for coastal cities): Cyclone Amphan in 2020 flooded the streets of Kolkata. Within eastern India, the storm killed 98 people and caused $13.8 billion (2020 USD).
  • Climate Change: Exacerbated by changing climate, resulting in extreme events. The climate change has caused an increase in the frequency of short duration heavy rainfall leading to higher water run-off.

Anthropological Reasons:

  • Encroachments on Drainage Channels: In Indian cities and towns, due to increased land prices and less availability of land in the city centre settlements are coming up in low-lying areas, usually as encroachments over lakes, wetlands and riverbeds. On the contrary, there have been large scale encroachments without widening the natural drains. Consequently, the capacity of the natural drains has decreased, resulting in flooding.
  • Inability to manage the city’s drainage systems: The Hyderabad floods of October 2020 occurred because discharge of water did not take place on time. And when water was discharged it was in a sudden, uncontrolled manner.
    • 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.
  • Antiquated drainage infrastructure: In majority of the cities, there exists century-old drainage system (developed during colonial time period) which covered only a small part of the core city. In the last 20 years, these cities have grown at least four times its original built-up area and not much was done to address the absence of adequate drainage systems.
  • Destruction of Wetlands: Neglecting issues of incremental land use change, particularly of those commons which provide us with necessary ecological support — wetlands. This has led to creation of urban terrain which is incapable of absorbing, holding and discharging water.
  • Urban heat island effect also results in increased rainfall over urban areas that in turn leads to flooding.
    • 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
  • Unsustainable Development: A lot of urban flooding such as the recent one in Bengaluru is a result of unregulated construction in regions such as wetlands and floodplains.
  • Poor Governance: Urban expansion, which is often carried on in collusion with urban authorities, at the expense of natural drainage of water. CAG report (last year) pulled up Bengaluru municipality for this poor management. It also also found that the Bengaluru municipality did not maintain proper records of the stormwater management funds allotted to it under the JNNURM.
    • In 2019, Patna faced massive urban floods in late September. One of the reasons the municipal authorities were unable to deal with the problem was that they could not even locate the drainage map of the city, which has a population of 5.8 million according to the 2011 Census.
    • According to a 2010-11 report by the ministry of urban development, storm water drain coverage – they are essential for draining away large discharge in a short time such as heavy rainfall – was below 50% in 56 of the 104 cities which sent responses. Bengaluru, the city which is facing floods at the
      moment, had just 10% of its roads covered by storm water drains.
    • Municipal authorities do not have an idea about drainage requirements and they also lack funds to build such capacity.
  • Ethical Dilemma between Development vs Environment: Any policy which prioritises environmental concerns over construction will have to deny permission for a lot of construction activity in India, especially in cities. This is bound to lead to economic losses for the those engaged in this sector, as well as increase the cost of housing for those who want to buy such houses. This is not an easy decision to make, given the growing importance of the real estate sector in India.
  • Illegal Mining Activities: 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 Impacts 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.
  • Disruption to Civic Amenities: Urban flooding has localised impacts like structural damage to buildings, property, crops. Besides, it causes disruptions of water supply, sewerage, power and transmission lines, communication, traffic- road and railways and other infrastructure.
  • 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.
  • Ecological Impacts: Trees and plants are washed away during extreme flood events and riverbank erosion is caused by high-speed flood water.
What are the steps to be taken to mitigate Urban Flooding?
  • Sponge Cities Mission: The idea of a sponge city is to make cities more permeable so as to hold and use the water which falls upon them.
  • Planned Development: Implementation of Atal Mission for Rejuvenation and Urban Transformation (AMRUT) in a planned manner.
    • The Brihanmumbai Storm Water Disposal System or BRIMSTOWAD, the project to overhaul Mumbai city’s old stormwater drainage system was started after the 2005 deluge.
  • Change in Policy mindset: Water-sensitive urban design (WSUD in Australia) regards urban stormwater runoff, and waste water as a resource rather than a nuisance or liability.
  • Ecological Solutions: Bioswales or ‘Rain Garden’ (New York) are landscape features that collect polluted stormwater runoff, soak it into the ground, and filter out pollution.
  • Rainwater harvesting:
    • People must invest heavily in rainwater harvesting.
    • Need to make sure that collection of the rainwater as much as possible, use that to recharge our aquifers and try to design our plots and apartments and gated communities as zero rainfall discharge areas.
  • Design on a watershed basis:
    • Every lake is a micro or mini watershed. Authorities must understand that a watershed is a hydrological unit, understand how water flows and ensure that it is drained into channels and flows into the lake.
    • When the lake overflows, it connects to the next downstream lake, for which they will need sluice gates that they can operate.
What is Sponge Cities?
  • The idea of a sponge city is to make cities more permeable so as to hold and use the water which falls upon it.
  • Sponge cities absorb the rain water, which is then naturally filtered by the soil and allowed to reach urban aquifers. This allows for the extraction of water from the ground through urban or peri-urban wells.
  • In built form, this implies contiguous open green spaces, interconnected waterways, and channels and ponds across neighbourhoods that can naturally detain and filter water
  • These can all be delivered effectively through an urban mission along the lines of the Atal Mission for Rejuvenation and Urban Transformation (AMRUT), National Heritage City Development and Augmentation Yojana (HRIDAY) and Smart Cities Mission
What steps need to be taken to take forward the idea of Sponge Cities Mission?
  • Wetland policy: 
    • In most of our lakes, the shallow ends, which often lie beyond the full tank level, have disappeared.
    • These shallow ends are best characterised as wetlands; sometimes owned by private individuals, other times existing as ecological commons.
    • Regardless of ownership, land use on even this small scale needs to be regulated by development control.
  • Watershed management and emergency drainage plan
    • This should be clearly enunciated in policy and law.
    • Urban watersheds are micro ecological drainage systems, shaped by contours of terrain.
    • Detailed documentation of these Urban watersheds must be held by agencies where natural boundaries instead of governance boundaries (like wards) are used to come up with drainage plan.
    • The Metropolitan Development Authorities, National Disaster Management Authority, State revenue and irrigation departments along with municipal corporations should be involved in such work together.
  • Ban against terrain alteration
    • Lasting irreversible damage has been done to the city by builders, property owners, and public agencies by flattening terrain and altering drainage routes.
    • Terrain alteration needs to be strictly regulated and a ban on any further alteration of terrain needs to be introduced.
  • Change in material usage
    • Our cities are becoming increasingly impervious to water, not just because of increasing built up but also because of the nature of materials used (hard, non-porous construction material that makes the soil impervious).
    • To improve the city’s capacity to absorb water, new porous materials and technologies must be encouraged or mandated across scales.
    • Examples of these technologies are bioswales and retention systems, permeable material for roads and pavement, drainage systems which allow storm water to trickle into the ground, green roofs and harvesting systems in buildings.
    • These not only reduce run-off and the load on infrastructure, but also help keep water in the city for later use.
  • Involvement of other stakeholders
    • Urban floods of this scale cannot be contained by the municipal authorities alone. Nor can they be dealt with by the State government.
    • It can be managed with concerted and focused investments of energy and resources.
    • Such investments can only be done in a mission mode organisation with active participation of civil society organisations at the metropolitan scale.

Main Practice Question: Inability to upgrade drainage infrastructure has led to Urban Flooding. Critically Comment.

Note: Write answers to this question in the comment section.


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