Urban floods occur when heavy rainfall overwhelms the drainage systems in cities, causing water to overflow onto streets, homes, and businesses. Unlike rural areas, cities have a lot of paved surfaces like roads and buildings, which do not absorb water well. This means that when it rains heavily, the water has nowhere to go, leading to flooding. Urban floods can disrupt daily life, damage property, and pose serious risks to health and safety. With more extreme weather due to climate change and increasing urbanization, managing urban floods has become a critical challenge for city planners and residents alike.
Tags: GS – 3, Disaster Management- Urban Flooding
For Prelims: Urban Flooding, Rainfall, Rural floods, Drainage System, Wetlands, Climate Change, Sewage and solid waste, Illegal Mining, Riverbank Erosion.
For Mains: Urban Flooding, Causes and Curtailment.
Context:
- There has been a rise in intense, short-duration rainfall events, leading to urban flooding exacerbated in urban cities like Delhi by unregulated urban expansion, encroachment on natural water bodies, and inadequate drainage systems.
What is Urban Flooding?
About Urban Flooding:
- Urban flooding occurs when land or property in built environments, particularly densely populated cities, becomes inundated due to rainfall exceeding the drainage system’s capacity.
Comparison with Rural Floods:
- Unlike rural floods, which affect flat or low-lying areas, urban flooding is influenced not only by heavy precipitation but also by unplanned urbanisation. This urban development alters catchments, leading to:
- Increased flood peaks, up to 8 times higher than normal.
- Increased flood volumes, up to 6 times greater than usual.
What are the Causes of Flooding in Delhi?
Unplanned Rapid Urbanization:
- Urban growth has destroyed natural drainage systems, leading to encroachment on floodplains and wetlands, less permeable surfaces due to widespread concrete construction, and changes in natural watershed boundaries.
Lack of Effective Urban Governance:
- Despite the 74th Constitutional Amendment Act, key areas such as urban planning, land use, and economic development have not fully transferred to city governments as required.
- The structure of Urban Local Bodies (ULBs) lacks clarity, leading to an uneven distribution of power between elected representatives and executive wings, resulting in poor urban governance and mismanagement of waterlogging issues.
Inadequate and Outdated Drainage Infrastructure:
- Many Indian cities are still reliant on colonial-era drainage systems designed for rainfall intensities of 20-25mm per hour, which are inadequate for current precipitation patterns.
- This results in insufficient capacity to handle increased water volume and frequent overflow during heavy rainfall.
Climate Change and Extreme Weather Events:
- Reports from the Intergovernmental Panel on Climate Change (IPCC) indicate an increase in the frequency and intensity of extreme rainfall events in India.
- This leads to a higher volume of water than drainage systems can handle and increased runoff due to the soil’s inability to absorb water quickly.
Loss of Water Bodies and Green Spaces:
- A study by the National Institute of Urban Affairs revealed that major Indian cities have lost 70-80% of their water bodies over the last 40 years.
- This has led to reduced natural water storage capacity, increased surface runoff, and disruption of the natural water cycle.
Solid Waste Mismanagement:
- Improper solid waste management is choking drainage systems, causing clogged drains and reduced water flow capacity, leading to waterlogging of cities.
Groundwater Depletion and Land Subsidence:
- Excessive extraction of groundwater has caused land subsidence in numerous urban areas.
- As groundwater is depleted, the land sinks, creating additional low-lying areas that are vulnerable to waterlogging.
Lack of Integrated Urban Water Management:
- There is a lack of coordination between various departments handling water supply, sewage, and stormwater drainage, resulting in a fragmented approach to water management.
- For example, the administration is fragmented among at least 11 different agencies responsible for roads and drains in Delhi.
Siltation of Rivers and Water Bodies:
- The National Institute of Hydrology reports significant siltation in urban water bodies and rivers. This leads to reduced water holding capacity of lakes like surajkund, badkhal and rivers like yamuna and impaired natural drainage systems.
High Population Density:
- Rapid urbanisation(2.63%) and population(33,807,403.) growth leads to more paved surfaces like pavements, roads, and buildings.
- This reduces natural water absorption and increases surface runoff, worsening waterlogging during heavy rains because water can’t soak into impermeable surfaces.
What is the impact of urban flooding in Delhi?
Loss of Lives and Injuries:
- During urban flooding in Delhi, people often become trapped or swept away in submerged areas, resulting in fatalities and injuries.
- In 2023 alone, several incidents of drowning and injuries were reported due to severe flooding.
Damage to Infrastructure:
- Urban flooding in Delhi leads to widespread damage to buildings, roads, bridges, and other infrastructure.
- Homes, businesses, and public facilities suffer flooding and destruction, causing substantial financial losses.
- For instance, recent floods in Delhi caused an estimated Rs. 500 crore in infrastructure damage.
Displacement of Vulnerable Population:
- Poor individuals in low-lying areas of Delhi are forced to vacate their homes and seek temporary shelter during floods.
- They face challenges in finding appropriate accommodation and endure the loss of personal belongings.
- In 2023, over 10,000 vulnerable residents were displaced due to flooding in Delhi.
Disruption of Vital Services:
- Urban flooding disrupts essential services like electricity, water supply, and communication networks in Delhi.
- This aggravates hardships for affected communities and impedes rescue and relief efforts.
- During the last major flood event, over 30% of Delhi faced power outages and water supply disruptions.
Waterborne Diseases:
- Flooding in Delhi increases the risk of waterborne diseases such as cholera, typhoid, and diarrhoea.
- Contaminated flood waters pose health hazards to residents, necessitating urgent public health interventions to prevent disease outbreaks.
Economic Consequences:
- Businesses in Delhi suffer substantial financial losses from property damage and operational interruptions during floods.
- Additionally, the government incurs expenses for rescue operations, infrastructure repairs, and rehabilitation efforts, amounting to approximately Rs. 800 crore annually.
Mental and Psychological Stress:
- The experience of trauma, anxiety, and stress during urban flooding in Delhi significantly impacts the mental health of affected individuals.
- Loss of personal belongings and disruption of normal life routines exacerbate psychological distress, highlighting the need for comprehensive mental health support services
What steps have been taken by the Indian government and various state governments to address the issue of urban flooding?
National Level Initiatives:
- National Urban Flooding Programme: This initiative aims to establish a holistic approach to urban flood management. It includes guidelines for flood risk assessment and strategies for mitigation.
- Smart Cities Mission: Integrated urban flood management is a pivotal component of this mission. It advocates for the adoption of technology in real-time flood monitoring and early warning systems.
- Atal Mission for Rejuvenation and Urban Transformation (AMRUT): Focuses on enhancing urban infrastructure, particularly stormwater drainage systems. It allocates funds for upgrading and expanding drainage networks in selected cities.
- National Disaster Management Authority (NDMA): Provides comprehensive guidelines on urban flooding, offering a framework for flood risk assessment and management.
State and City-level Initiatives:
- Mumbai (BRIMSTOWAD): This project involves upgrading existing pumping stations, installing new ones, and desilting major drains (nullahs) before the monsoon season to prevent flooding.
- Chennai (C-FLOWS): A flood warning system customised for Chennai, capable of predicting flooding due to heavy rainfall, sea-level rise, and increased water levels in rivers like Cooum, Adyar, and Kosasthalaiyar.
- Kolkata (KEIP): The Kolkata Environmental Improvement Project focuses on upgrading sewerage and drainage systems, installing new pumping stations, and dredging and renovating canals to mitigate flooding.
- Bengaluru: Initiatives include lake rejuvenation, rain gardens, bioswales in specific areas, and efforts to remove encroachments on stormwater drains to improve water management during heavy rains.
- Ahmedabad (Sabarmati Riverfront): The Sabarmati Riverfront development includes flood management measures aimed at reducing the impact of urban flooding in the city.
What should be the way forward?
- Capacity Development of ULBs:
- Encouraging staff to acquire new skills through incentives is crucial. State governments and ULBs should prioritise rebuilding the foundational structure of local government institutions, ensuring adequate staffing and establishing training facilities.
- Water-Sensitive Urban Design and Planning:
- Incorporating water-sensitive urban design techniques is essential. These methods assess land features, surface types’ water absorption capabilities, and natural water flow patterns with minimal environmental impact. City master plans should mandate vulnerability and risk assessments.
- Adopting Scientific Management Measures:
- Mapping waterlogging-prone areas and using hydraulic and hydrological models to analyse flood patterns are critical. Results should inform urban master plans to enhance resilience against flooding.
- Decentralised Stormwater Management:
- Promoting techniques like rainwater harvesting, bioswales, and retention ponds at the local level can mitigate waterlogging effectively.
- Smart Drainage Systems:
- Implementing sensor-based drainage systems that monitor water levels and regulate flow in real-time can optimise urban drainage networks.
- Technologies like airborne laser terrain mapping (ALTM) can aid in flood risk mapping and urban planning.
- Synergistic Approach:
- Improved coordination between water resources and disaster management authorities is necessary for integrated flood management.
- Engaging Grassroots Organisations:
- Collaborating with grassroots organisations promotes awareness and facilitates coordinated flood risk management.
- For example, the Environmentalist Foundation of India (EFI) has restored lakes in Chennai, reducing waterlogging.
- Revival of Local Water Bodies:
- Prioritising protection and restoration of traditional water bodies within urban areas and integrating them into blue-green infrastructure can enhance water quality and levels.
- Biome Environmental Trust in Bengaluru has demonstrated success with initiatives like decentralised wastewater treatment.
- Green Infrastructure:
- Implementing green roofs, rain gardens, bioswales, permeable pavements, and urban green spaces helps absorb rainwater and minimise surface runoff, easing pressure on drainage systems.
- Nature-Based Solutions:
- Restoring natural wetlands, creating urban forests, and revitalising water bodies can improve water absorption capacity and reduce urban waterlogging effectively.
UPSC Civil Services Examination Previous Year’s Question (PYQs)
Prelims:
Q:1 La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino? (2011)
- La Nina is characterised by an usually cold ocean temperature in the equatorial Indian Ocean whereas El Nino is characterised by unusually warm ocean temperature in the equatorial Pacific Ocean.
- El Nino has an adverse effect on the south-west monsoon of India but La Nina has no effect on the monsoon climate.
Which of the statements given above is/are correct?
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Ans: (d)
Mains
Q:1 With reference to the National Disaster Management Authority (NDMA) guidelines, discuss the measures to be adopted to mitigate the impact of recent incidents of cloudbursts in many places of Uttarakhand. (2016)
Source: IE
FAQs
Q: What is an urban flood?
Answer: An urban flood happens when heavy rainfall overwhelms the drainage systems in a city or town, causing water to accumulate on streets, homes, and buildings. Unlike floods in rural areas, urban floods are primarily due to poor drainage and the large amount of concrete and asphalt that prevents water from soaking into the ground.
Q: Why do urban floods occur?
Answer: Urban floods occur because cities have a lot of paved surfaces like roads and buildings that don’t absorb water. When it rains heavily, the water can’t seep into the ground and instead collects on the surface. If the drainage systems are clogged or not designed to handle heavy rain, it leads to flooding.
Q: What are the impacts of urban floods?
Answer: Urban floods can cause severe damage to homes, vehicles, and infrastructure. They can disrupt transportation, leading to traffic jams and delays. Floodwaters can also contaminate drinking water supplies and lead to health issues. In worst cases, they can cause injuries or even loss of life.
Q: How can urban floods be prevented or managed?
Answer: Urban floods can be managed by improving the drainage systems, ensuring they are regularly cleaned and maintained. Cities can also create more green spaces like parks and gardens that absorb rainwater. Building permeable pavements that allow water to seep through and setting up early warning systems to alert residents of heavy rainfall can also help.
Q: What should I do during an urban flood?
Answer: During an urban flood, stay indoors and avoid walking or driving through floodwaters, as they can be dangerous and hide hazards. If water enters your home, move to higher ground or the upper floors. Keep updated with information from local authorities and follow their instructions. Prepare an emergency kit with essentials like water, food, and medications in case you need to evacuate.
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