GS3 PYQs (Mains Answer Writing): Floods | UPSC Mains: Internal Security & Disaster Management PDF Download

Q1: Flooding in urban areas is an emerging climate-induced disaster. Discuss the causes of this disaster. Mention the features of two such major floods in the last two decades in India. Describe the policies and frameworks in India that aim at tackling such floods. (Answer in 250 words)
Ans: Introduction
Urban flooding, a climate-related disaster, occurs when intense rainfall exceeds drainage capacity, flooding densely populated urban areas.

Causes of Urban Flooding

• Climate Change: Increases rainfall intensity as warmer air holds more moisture, disrupting weather patterns. Urban heat islands worsen conditions, while sea-level rise threatens coastal cities with flooding and freshwater contamination.
• Urbanization: Impervious surfaces increase runoff and reduce water absorption. Encroachments on floodplains, due to lax regulations, disrupt natural water flow.
• Poor Solid Waste Management: Clogged drainage systems from improper waste disposal cause overflows during heavy rains, mixing sewage with stormwater and amplifying flood risks.

Major Flood Events

• Chennai Floods (2015): Heavy rainfall, inadequate drainage, and the loss of 300 inland water bodies due to urban expansion worsened flooding. Shrinking Pallikaranai marshlands further weakened natural flood control.
• Mumbai Floods (2005): Intense rainfall overwhelmed an outdated drainage system designed for only 25 mm of rain per hour. Urbanization reduced mangroves by 40% and diminished green spaces, hindering water absorption and exacerbating floods.

Policies and Frameworks to Address Urban Flooding in India

• NDMA Guidelines (2010): Promote a multi-disciplinary approach to urban flood management and planning.
• Smart Cities Mission (2015): Encourages sustainable urban infrastructure, including advanced drainage and flood management systems.
• AMRUT 2.0: Aims to improve stormwater drainage and urban infrastructure to reduce flood risks.
• Storm Water Drainage Manual (2019): Offers guidance on sustainable stormwater management and flood response strategies.

Conclusion
Urban flooding, intensified by climate change, threatens cities. Sustainable infrastructure and adherence to NDMA guidelines are critical for building urban resilience.

Q2: 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.
Ans: Flooding and disruption have become the new normal for the monsoon season in urban India. Recent water logging in Gurgaon, urban flood in Mumbai and Srinagar shows the increasing intensity of urban flood disasters in India. These are some of the reasons of urban floods in case of Indian cities.

• A special feature in India is heavy rainfall during monsoons. There are other weather systems also that bring in a lot of rain. Storm surges can also affect coastal cities/ towns.
• The urban heat island effect has resulted in an increase in rainfall over urban areas. Global climate change is resulting in changed weather patterns and increased episodes of high intensity rainfall events occurring in shorter periods of time.
• Stormwater drainage systems in the past were designed for rainfall intensity of 12–20 mm. These capacities get easily overwhelmed whenever rainfall of higher intensity is experienced. Further, the systems very often do not work to the designed capacities because of very poor maintenance.
• Encroachments are also a major problem in many cities and towns. The flow of water has increased in proportion to the urbanization of the watersheds. Ideally, the natural drains should have been widened (similar to road widening for increased traffic) to accommodate the higher flows of stormwater. But on the contrary, there have been large scale encroachments on the natural drains and the river flood plains. Consequently the capacity of the natural drains has decreased, resulting in flooding.
• Improper disposal of solid waste, including domestic, commercial and industrial waste and dumping of construction debris into the drains also contributes significantly to reducing drainage capacities.
• Presence of impervious cover near trees and on road pavements also reduces water runoff.

To reduce these risk following measure can be taken:

• Pre-Monsoon Desilting of drainage system.
• Solid waste disposal and its proper management has significant effect on drainage performance and reduces the chances of choking of drainage system.
• Protection and conservation of wetlands near urban habitats increase the water holding capacities and they also act as natural barriers against any surge in water level.
• Rain water harvesting reduces the load of excess rain water of rain and help in mitigating urban floods.