Context: Untimely, excessive rainfall, as in Hyderabad and Pune, is here to stay. It’s time to plan for vagaries of weather, build resilience.
GS Paper 1: Urbanization: problems and remedies
GS Paper 3: Disasters & Disaster Management (Urban Flood)
1: Major cities of India are becoming more vulnerable to flood conditions. Discuss. 15 marks
2: The idea of a sponge city is to make cities more permeable so as to hold and use the water which falls upon it. Discuss the statement in context of Urban Flood in India. 15 marks
3: The frequency of urban floods due to high intensity rainfall is increasing over the years. Discussing the reasons for urban floods, highlight the mechanisms for preparedness to reduce the risk during such events. 15 marks
Dimensions of the article:
- What is urban flood?
- What are the causes of urban flood in India?
- Consequences of Urban Flooding.
- Measures to address the Urban Flood.
- Way forward
What is urban flood?
Urban flooding is not just “flooding that happens in an urban area.” This isn’t what happens when a river overflows its banks or when a cyclones drives a storm surge across a coastal neighbourhood. Instead, it’s caused by excessive runoff in developed areas where the water doesn’t have anywhere to go e.g. Floods of Chennai (December 2015), the Kashmir Floods (2014), the Surat Floods (2006) and the Mumbai Floods (2005 & 2017), Hyderabad flood reflect the vulnerability of our Cities.
What are the causes of Urban flood in India?
Flooding in the cities and the towns is a recent phenomenon caused by
- Increasing incidence of heavy rainfall in a short period of time,
- Indiscriminate encroachment of waterways,
- Inadequate capacity of drains and lack of maintenance of the drainage infrastructure.
- Disappearing of lakes, pond and other water bodies from the cities.
- Deforestation, which causes loss of absorption of water during the rainfall.
- Poor management in drainage system in urban cities.
Consequences of Urban Flood:
Urban Flooding has localized impacts on commercial, industrial, business, residential and institutional locations. Disruption of water supply, sewerage, power supply and communications is common. Shutdown of commercial, industrial and business activity and loss to property and assets is often observed. Disruption of traffic – road, rail and air is frequent. New slums come up in areas which are not approved.
Measures to address Urban flood: In order to check the threat of urban flooding, each city should have their Flood mitigation plans (floodplain, river basin, surface water, etc.) strongly integrated with the overall land use policy and master plan of a city. The following three phases of disaster management for effective and efficient response to urban flooding include:
- Pre-Monsoon Phase (Preparedness): It involves an estimation of emergency needs, familiarization of the stakeholders, particularly the communities through training and simulation exercises, identification of Teams for maintaining the drains and roads and conducting exercises for prevention of water logging/ inundation.
- During Monsoon Phase (Early Warning & Effective Response): It includes timely, qualitative and quantitative warnings based on the intensity of rainfall to various agencies to take preventive measures. The Response phase focuses primarily on emergency relief: saving lives, providing first aid, minimizing and restoring damaged systems (communications and transportation), meeting the basic life requirements of those impacted by disaster (food, water, and shelter), and providing mental health and spiritual support and comfort care.
- Post Monsoon Phase: Restoration and Re-habilitation phase includes establishment of a programme to restore both the disaster site and the damaged materials to a stable and usable condition.
- Idea of sponge city: 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. This water can be treated easily and used for city water supply.
- 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.
- 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 therefore terrain alteration needs to be strictly regulated and a ban on any further alteration of terrain needs to be introduced.
We must not allow nature, human conduct, and urbanisation to be mystified and rendered as trans-historic villains. We can learn to live with nature, we can regulate human conduct through the state and we can strategically design where we build. We need to urgently rebuild our cities such that they have the sponginess to absorb and release water without causing so much misery and so much damage to the most vulnerable of our citizens, as we have seen.
1: NDMA Guidelines on Urban Flood:
- Early Warning System and Communication: National Hydro-meteorological Network and Doppler Weather Radars can provide and a lead time of 3 to 6 hours. Once flood warning is generated, it must be communicated to public in an effective manner.
- Design and Management of Urban Drainage: Rapid urbanisation has resulted in increased impermeable surfaces in the form of pavements, roads and built-up areas, thereby reducing the infiltration and natural storage.
- Drainage System: A proper inventory of water supply system with details of all pumping, storage etc. must be maintained, particularly of the minor drainage systems.
- Catchment as a basis of design: As run off processes are independent of states and city administrative boundaries outlines of drainage divides must be depend on watershed delineation.
- Contour Data: Accurate contours are necessary for determining the boundaries of a watershed/ catchment and for computing directions of flow.
- Design Flow: Estimation of peak flow rates for adequate sizing and quantity control facilities.
- Removal of Solid Waste: Most towns and cities have open surface drains besides the road, into which there is unauthorized public disposal of waste. Solid waste increases hydraulic roughness, causes blockage and generally reduces flow capacity.
- Drain Inlet Connectivity: It is seen that the inlets to drain the water from the roads into the roadside drains are either not properly aligned or non-existent leading to severe waterlogging on the roads.
- Rain Gardens: Rain gardens consist of a porous soil covered with a thin layer of mulch. Stormwater runoff is directed into the facility, allowed to pond and infiltrates through the plant/mulch/soil environment.
- Vulnerability Analysis and Risk Assessment: Identification of areas at risk, classification of structures according to function and estimation of risk for each structure and function using Hazard Risk Zoning.
- Urban Flooding Cells: A separate Urban Flooding Cell (UFC) will be constituted within MoUD which will coordinate all UFDM activities at the national level. ULBs will be responsible for the management of urban flooding at the local level.
- Response: Emergency Operation Centres, Incident Response System, flood shelters, search and rescue operations, emergency logistics are some key action areas of flood response mechanism.
- Sanitation: Diseases like malaria, dengue and cholera can spread if adequate sanitation and disinfection are not carried out.
- Capacity Development, Awareness Generation and Documentation: Participatory urban flood planning and management involving both local government and the community