Urban Floods

How does a strong El-nino affect Chennai? Are you curious? Read the Explainer as well!

Urban Floods

Why Assam gets flooded every year


From UPSC perspective, the following things are important :

Prelims level : Brahmaputra River

Mains level : Flood management

The pre-monsoon has brought destruction to the most-populated northeastern state of Assam.

Why in news?

  • Rains has brought chaos, displacing thousands of people and animals, and damaging crops and properties worth billions.
  • We also get to read about Kaziranga NP being completely submerged due to floods.

Floods in Assam

  • Assam is one of the most flood-prone states in India and it has almost become an annual calamity.
  • In terms of impact on human lives, the floods of 1988, 1998 and 2004 were the worst – the 2004 floods alone affected 12.4 million people and claimed 251 lives.
  • According to the Assam government, the flood-prone area of the state is 31.05 lakh hectares, against a total area of 78.523 lakh hectares – this means nearly 40% of the state’s area is flood-prone.
  • Overall, Assam accounts for nearly 10% of the total flood-prone area of the country.

Why are floods an annual occurrence in the state of Assam?

Apart from the natural topography and annual excessive rainfall in Assam, there are various reasons – both man-made and natural – behind the destructive floods that hit Assam every year.

  • Assam is home to a vast network of rivers, including the Brahmaputra and Barak River, and more than 50 tributaries feeding them.
  • Assam also receives river water from neighboring states like Arunachal Pradesh and Meghalaya.
  • In 2004 and 2014, the south bank tributaries of the Brahmaputra in lower Assam experienced flash floods of high magnitude due to cloud bursts in the catchment areas in Meghalaya.
  • Bank erosion caused by the river Brahmaputra is one of the major reasons why Assam gets flooded every year.
  • It means the removal of soil, sediment, or rock fragments along the banks, which results from high water flow.
  • Due to erosion, the width of the river increases and it changes its course.
  • The width of the river Brahmaputra has increased up to 15 kilometres at some places due to bank erosion, making it the widest river in India.

Man-made causes

  • Floods are also caused by human intervention – like encroachment of river banks and wetlands, lack of drainage, unplanned urban growth, hill cutting and deforestation.
  • The dams that are being built are further aggravating these disasters.
  • People in Arunachal Pradesh and Assam allege that flood has aggravated in the region as China has constructed several big dams in the upper reaches of Brahmaputra.

Government measures so far

  • In 1982, the Brahmaputra Board suggested that dams and reservoirs be built to mitigate floods in Assam.
  • While dams are meant to regulate the flow of water, they can also be beyond the capacity of the channels downstream, proving to be a double-edged sword.
  • The Water Resources Department of Assam has constructed embankments and flood walls across the state.
  • River training, bank protection, anti-erosion and town protection are also in the works. Here’s how their plan has progressed thus far:


[Prelims Spotlight] Major Rivers in India

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Urban Floods

Devastation in Dima Hasao and its after-effects


From UPSC perspective, the following things are important :

Prelims level : NA

Mains level : Flash floods

Disaster struck Dima Hasao, central Assam’s hill district, in mid-May after incessant heavy rainfall.

Impacts of the disaster

  • The 170 km railway line connecting Lumding in the Brahmaputra Valley’s Hojai district and Badarpur in the Barak Valley’s Karimganj district was severely affected.
  • The Assam government and Railway Ministry’s assessments said the district suffered a loss of more than ₹1,000 crore, but ecologists say the damage could be irreversibly higher.

How severe has the rain been in Assam?

  • Assam is used to floods, sometimes even four times a year, resultant landslides and erosion.
  • But the pre-monsoon showers this year have been particularly severe on Dima Hasao, one of three hill districts in the State.
  • Landslips have claimed four lives and damaged roads.
  • The impact has been most severe on the arterial railway, which was breached at 58 locations leaving the track hanging in several places.
  • The disruption of train services, unlikely to be restored soon, has cut off the flood-hit Barak Valley, parts of Manipur, Mizoram and Tripura.

Why is the railway in focus post-disaster?

  • Dima Hasao straddles the Barail, a tertiary mountain range between the Brahmaputra and Barak River basins.
  • The district is on the Dauki fault (the prone-to-earthquakes geological fractures between two blocks of rocks) straddling Bangladesh and parts of the northeast.
  • British engineers were said to have factored in the fragility of the hills to build the railway line over 16 years by 1899.
  • The end result was an engineering marvel 221 km long over several bridges and through 37 tunnels, laid along the safer sections of the hills.

A faulty experiment

  • A project to convert the metre gauge track to broad gauge was undertaken in 1996 but the work was completed only by March 2015 because of geotechnical constraints and extremist groups.
  • The broad-gauge track was realigned to be straighter, but a 2009-10 audit report revealed that the project had been undertaken without proper planning and visualisation of the soil strata behaviour.
  • The report gave the example of the disaster-prone Tunnel 10 on the realigned track that was pegged 8 meters below the bed of a nearby stream.

Is only the railway at fault?

  • There is a general consensus that other factors have contributed to the situation Dima Hasao is in today.
  • Roads in the district, specifically the four-lane Saurashtra-Silchar (largest Barak Valley town) East-West Corridor, have been realigned or deviated from the old ones that were planned around rivers and largely weathered the conditions.
  • The arterial roads build over the past 20 years often cave in and get washed away by floods or blocked by landslides.
  • Shortened cycles of jhum or shifting cultivation on the hill slopes and unregulated mining have accentuated the “man-made disaster”.
  • Massive extraction of river stone, illegal mining of coal and smuggling of forest timbe has led to the disaster.
  • These activities have increased water current besides weakening either side of riverbanks.

How vital are the rail and highway through Dima Hasao?

  • Meghalaya aside, Dima Hasao is the geographical link to a vast region comprising southern Assam’s Barak Valley, parts of Manipur, Mizoram and Tripura.
  • Moreover, this track is vital for India’s Look East policy that envisages shipping goods to and from Bangladesh’s Chittagong port via Tripura’s border points at Akhaura and Sabroom.
  • These are the last railway station near the Feni River that serves as the India-Bangladesh border.


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Urban Floods

Recurring urban floods point to need for moving away from land-centric urbanism


From UPSC perspective, the following things are important :

Prelims level : Not much

Mains level : Paper 3- Urban floods


Flood in Chennai has revived memories of the devastating Chennai floods of 2015, a collective trauma that its residents are yet to outlive.

Role of climate change

  • In August this year, as monsoon floods raged across the subcontinent, IPCC’s 6th Assessment Report (AR6) was published.
  • The report noted the increasing frequency of heavy precipitation events since the 1950s and inferred that they were being driven by human-induced climate change.
  • The climate crisis, is here.
  • It has made extreme rainfall events more severe and unpredictable than ever before.

Role of poor planning and encroachment

  • In 2015, the National Green Tribunal in India formed a committee to report on the status of natural stormwater drains in Delhi.
  • On inspection, out of the 201 “drains” recorded in 1976, 44 were found to be “missing.
  • Geospatial imaging established that 376 km of natural storm drains — encroached on and paved over — had disappeared from Bengaluru.
  • In both cases, these “missing” waterways were either encroached and built over or connected to sewage drains.
  • Poor design and corruption significantly contribute to urban floods.
  • By violating environmental laws and municipal bye-laws, open spaces, wetlands and floodplains have been mercilessly built over, making cities impermeable and hostile to rainwater.

Way forward

  • We need to move away from land-centric urbanisation and recognise cities as waterscapes.
  • We need to let urban rivers breathe by returning them to their floodplains.
  • The entire urban watershed needs to heal, and for that to happen, we need less concrete and more democracy and science at the grassroots.


Ever since concretisation became shorthand for urbanisation, rainfall in a changing climate no longer finds its way towards subterranean capillaries or surface water bodies.

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Urban Floods

Why cloudbursts could become more frequent?


From UPSC perspective, the following things are important :

Prelims level : Cloudburst

Mains level : Flash floods

Recently, cloudbursts have been reported from several places in J&K, Ladakh, Uttarakhand and Himachal Pradesh. A

What is a Cloudburst?

  • Cloudbursts are short-duration, intense rainfall events over a small area.
  • According to the IMD, it is a weather phenomenon with unexpected precipitation exceeding 100mm/h over a geographical region of approximately 20-30 square km.

What causes Cloudburst?

  • A study published last year studied the meteorological factors behind the cloudburst over the Kedarnath region.
  • They analyzed atmospheric pressure, temperature, rainfall, cloud water content, cloud fraction, cloud particle radius, cloud mixing ratio, total cloud cover, wind speed, wind direction, and relative humidity during the cloudburst, before as well as after the cloudburst.
  • The results showed that during the cloudburst, the relative humidity and cloud cover was at the maximum level with low temperature and slow winds.
  • It is expected that because of this situation a high amount of clouds may get condensed at a very rapid rate and result in a cloudburst.

Impact of climate change

  • Several studies have shown that climate change will increase the frequency and intensity of cloudbursts in many cities across the globe.
  • As temperatures increase the atmosphere can hold more and more moisture and this moisture comes down as a short very intense rainfall for a short duration.
  • This results in flash floods in the mountainous areas and urban floods in the cities.
  • Also, there is evidence suggesting that globally short duration rainfall extremes are going to become more intense and frequent.

Answer this PYQ in the comment box:

Q.During a thunderstorm, the thunder in the skies is produced by the:

  1. meeting of cumulonimbus clouds in the sky
  2. lightning that separates the nimbus clouds
  3. violent upward movement of air and water particles

Select the correct option using the codes given below:

(a) 1 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) None of the above

Urban Floods

Tide–Rainfall Flood Quotient


From UPSC perspective, the following things are important :

Prelims level : Tide–Rainfall Flood Quotient

Mains level : Flood management

To understand if a coastal city is more prone to floods caused by tidal events or extreme rainfall, a team from the IIT Bombay devised a new metric or measure called the Tide–Rainfall Flood Quotient.

Try this PYQ:

The 2004 Tsunami made people realize that mangroves can serve as a reliable safety hedge against coastal calamities. How do mangroves function as a safety hedge?

(a) The mangrove swamps separate the human settlements from the sea by a wide zone in which people neither live nor venture out

(b) The mangroves provide both food and medicines which people are in need of after any natural disaster

(c) The mangrove trees are tall with dense canopies and serve as art excellent shelter during a cyclone or tsunami

(d) The mangrove trees do not get uprooted by storms and tides because of their extensive roots

Tide–Rainfall Flood Quotient

  • Using the past rainfall data, tidal data, and topography of the region one can apply this framework to pinpoint the major factor at play.
  • This quotient helps understand the main driver of the flooding events for effective disaster management.
  • It considers three geographically diverse flood-prone coastal regions – Mithi Catchment in Mumbai, , Jagatsinghpur District in Odisha, and Greater Chennai to test their new metric.
  • The new method helped classify these regions into ‘storm-tide dominated’ or ‘pluvial (rainfall) dominated’ regions.
  • In Mithi, they found a devastating impact of storm-tide reaching even up to a distance of 7 km from the coastal boundary.
  • It concluded that Mithi catchment was ‘storm-tide dominated’, while Jagatsinghpur and Chennai were ‘pluvial dominated’

A tool for flood management

  • This metric can help disaster management experts in framing better flood risk management systems directed towards long term planning.
  • For storm-tide dominated regions, severe flood hazard can be alleviated by building coastal defence structures such as closure dams, tide breakers, and storm-surge barriers at appropriate locations.
  • The tide and surge forecasting systems in these regions should be equipped with state-of-the-art ocean circulation models.
  • On the other hand, for pluvial dominated regions, structural measures such as rainwater storage structures, lakes, and detention basins should be prioritized in the flood management plans.

Urban Floods

Bihar to change Kosi’s course to save the ancient site


From UPSC perspective, the following things are important :

Prelims level : Kosi River

Mains level : Floods in India

The Bihar government will try to divert the course of the mighty Kosi River in Bhagalpur district to save an archaeological site discovered recently.

Tap to read more about the Himalayan Drainage System:

Drainage System | Part 3

Kosi River: The Sorrow of Bihar

  • The Kosi is a trans-boundary river which flows through Tibet, Nepal and India.
  • The river crosses into northern Bihar, India where it branches into distributaries before joining the Ganges near Kursela in Katihar district.
  • Its unstable nature has been attributed course changes and the heavy silt it carries during the monsoon season, and flooding in India has extreme effects.
  • It is also known as the “Sorrow of Bihar” as the annual floods affect about 21,000 km2 of fertile agricultural lands thereby disturbing the rural economy.

Why change its course?

  • Several priceless artefacts have been found at the Guwaradih village in Naugachhia sub-division of Bhagalpur district during the excavation of a mound.
  • These items could be 2,500-years-old and could be of interest for historians if conserved.
  • The historical sites are facing threats from the Kosi floods.
  • The Kosi currently flows around 300-400 metres from the site, while its old course is about two kilometres from the village.

Threats posed by the move

  • Environmentalists have warned that changing the Kosi’s course could be disastrous for Bihar as seen in 2008.
  • At that time, the river had breached its mud embankments at Kushaha in Nepal.
  • The Kosi frequently changes its course naturally. If its course is artificially changed, it will cause floods and erosion in new areas, leading to massive displacement of people.
  • It then caused extensive damage to life and property downstream in five densely populated districts of northeast Bihar.
  • Some 500 people were killed and four million rendered homeless.

Urban Floods

Need for Sponge cities Mission in India


From UPSC perspective, the following things are important :

Prelims level : Not much

Mains level : urban floods

Issue of flood in the cities

  • Over 50 peple died in the wake of torrential rains in the third week of October in Hyderabad.
  • This experience is not unique to the city of Hyderabad, five years ago Chennai saw a massive flood costing much damage and lives.
  • Gurugram over the past few years comes to a complete standstill during the monsoon months.
  • And for Mumbai, the monsoon has become synonymous with flooding and enormous damages.

Causes of frequent urban floods:


  • Meteorological Factors: Heavy rainfall, cyclonic storms and thunderstorms causes water to flow quickly through paved urban areas and impound in low lying areas.
  • Hydrological Factors: Overbank flow channel networks, occurrence of high tides impeding the drainage in coastal cities.
  • Climate Change: Climate change due to various anthropogenic events has led to extreme weather events.


  • Unplanned Urbanization: Unplanned Urbanization is the key cause of urban flooding. A major concern is blocking of natural drainage pathways through construction activity and encroachment on catchment areas, riverbeds and lakebeds.
  • Destruction of lakes: A major issue in India cities. Lakes can store the excess water and regulate the flow of water. However, pollution of natural urban water bodies and converting them for development purposes has increased risk of floods.
  • Unauthorised colonies and excess construction: Reduced infiltration due paving of surfaces which decreases ground absorption and increases the speed and amount of surface flow
  • Poor Solid Waste Management System: Improper waste management system and clogging of storm-water drains because of silting, accumulation of non-biodegradable wastes and construction debris.
  • Drainage System: Old and ill maintained drainage system is another factor making cities in India vulnerable to flooding.
  • Irresponsible steps: Lack of attention to natural hydrological system and lack of flood control measures.

Impact of the devastation due to floods:

  • On economy: Damage to infrastructure, roads and settlements, industrial production, basic supplies, post disaster rehabilitation difficulties etc.
  • On human population and wildlife: Trauma, loss of life, injuries and disease outbreak, contamination of water etc.
  • On environment: Loss of habitat, tree and forest cover, biodiversity loss and large scale greenery recovery failure.
  • On transport and communication: Increased traffic congestion, disruption in rail services, disruption in communication- on telephone, internet cables causing massive public inconvenience.

What is to be done

1) Management of wetlands

  • We neglect the issues of incremental land use change, particularly of those commons which provide us with necessary ecological support — wetlands.
  •  We need to start paying attention to the management of our wetlands by involving local communities.
  • The risk is going to increase year after year with changing rainfall patterns and a problem of urban terrain which is incapable of absorbing, holding and discharging water.

2) Implementing the idea of 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.
  • This water can be treated easily and used for city water supply.
  • In built form, this implies contiguous open green spaces, interconnected waterways, and channels and ponds across neighbourhoods that can naturally detain and filter water.
  • It implies support for urban ecosystems, bio-diversity and newer cultural and recreational opportunities,
  • 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.

On a top priority, such a mission should address the following.

  • 1) 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.
  • Regardless of ownership, land use on even this small scale needs to be regulated by development control.
  • 2) Watershed management and emergency drainage plan is next.
  • This should be clearly enunciated in policy and law.
  • 3) Ban against terrain alteration is third.
  • Lasting irreversible damage has been done to the city by builders, property owners, and public agencies by flattening terrain and altering drainage routes.
  • 4) Use of porus material: Our cities are becoming increasingly impervious to water, not just because of increasing built up but also because of the nature of materials used.
  • 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.


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.

Urban Floods

National Flood Commission


From UPSC perspective, the following things are important :

Prelims level : NFC

Mains level : Paper 3- Urban floods and related issues

At least 43 years after India’s first and last commission on floods was constituted, there is no national-level flood control authority in the country so far.

Try this question for mains:
Q. What are the various causes of urban floods in India?

National Flood Commission

  • Rashtriya Barh Ayog or the National Flood Commission (NFC) was set up by the Ministry of Agriculture and Irrigation in 1976.
  • It aimed to study India’s flood-control measures after the projects launched under the National Flood Control Programme of 1954 failed to achieve much success.

NFCs recommendation

  • In 1980, the NFC made 207 recommendations and four broad observations:
  • First, it said there was no increase in rainfall in India and, thus, the increase in floods was due to anthropogenic factors such as deforestation, drainage congestion and badly planned development works.
  • Second, it questioned the effectiveness of the methods adopted to control floods, such as embankments and reservoirs, and suggested that the construction of these structures be halted until their efficacy was assessed.
  • Third, it said there have to be consolidated efforts among the states and the Centre to take up research and policy initiatives to control floods.
  • Fourth, it recommended a dynamic strategy to cope with the changing nature of floods. An analysis of the report suggested that the problem began with the methods of estimating flood-prone areas of the country.

Why revive NFC?

  • An accurate estimate is crucial for framing flood management programmes.
  • The NFC estimated that the total area vulnerable to floods in 1980 was around 40 million hectares.
  • There is another problem. The very definition of the flood-prone area does not reflect the effectiveness of the flood management works undertaken.

Urban Floods

I-FLOWS: Mumbai Flood Management System


From UPSC perspective, the following things are important :

Prelims level : IFLOWS

Mains level : Urban floods in India

Integrated Flood Warning System for Mumbai (I-FLOWS Mumbai), a state-of-the-art flood warning system has been developed for the city.

Practice question for mains:

Q. Urban floods in India are consequences of unplanned urbanization in India. Discuss with references to the frequent annual floods in Mumbai.

What is IFLOWS-Mumbai?

  • IFLOWS is a monitoring and flood warning system that will be able to relay alerts of possible flood-prone areas anywhere between six to 72 hours in advance.
  • The Ministry of Earth Sciences (MoES) has developed the system with in-house expertise and coordination with the Brihanmumbai Municipal Corporation (BMC).
  • The system can provide all information regarding possible flood-prone areas, likely height the floodwater could attain location-wise problem areas across all 24 wards and calculate the vulnerability and risk of elements exposed to flood.
  • Mumbai is only the second city in the country after Chennai to get this system. Similar systems are being developed for Bengaluru and Kolkata.

How will it work?

  • The primary source for the system is the amount of rainfall, but with Mumbai being a coastal city, the system also factors in tidal waves and storm tides for its flood assessments.
  • The system has provisions to capture the urban drainage within the city and predict the areas of flooding.
  • The system comprises seven modules- Data Assimilation, Flood, Inundation, Vulnerability, Risk, Dissemination Module and Decision Support System.

Why was this system needed in Mumbai?

  • Mumbai, the financial capital of India, has been experiencing floods with increased periodicity.
  • Floods, especially the ones in 2005 and 2017, are etched in everyone’s memory.
  • Last year, post-monsoon and unseasonal rainfall as late as October, two tropical cyclones in the Arabian Sea had caught authorities off guard and left a trail of destruction.
  • The flood during 26th July 2005, when the city received a rainfall of 94 cm, a 100 year high in a span of 24 hours had paralyzed the city completely.
  • Urban flooding is common in the city from June to September, resulting in the crippling of traffic, railways and airlines.
  • As preparedness for floods before they occur, the system will help in warning the citizens so that they can be prepared in advance for flooding conditions.


  • IFLOWS-Mumbai will enhance the resilience of the city by providing early warning for flooding, especially during high rainfall events and cyclones.
  • Using this, it will be possible to have an estimate of the flood inundation three days in advance, along with immediate weather updates.
  • The Union Minister said the system was “one of the most advanced” ones and will help the city, which has been experiencing floods with increasing periodicity.
  • The hi-tech system will predict floods before they occur, therefore enabling Mumbaikars to take due precautions in advance.

Urban Floods

Private: Urban Flood Management


From UPSC perspective, the following things are important :

Prelims level : Not Much

Mains level : Urban flood management


  • Urban flooding is a common experience in most of the cities around the world. 
  • In India, it becomes more pronounced on the onset of monsoons and hampers the daily activities of the huge urban population. 
  • To prevent flooding there is a need for efficient urban water management systems, especially in cities, which are largely based on traditional engineering approaches till date.

Urban Flooding:

What is urban flooding?

  • 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 is significantly different from rural flooding- urbanization increases flood risk by up to 3 times, increased peak flow results in flooding very quickly. Further, it affects large number of people due to high population density in urban areas

Causes of urban flooding

Meteorological Factors:

  • Heavy rainfall, cyclonic storms and thunderstorms

Hydrological Factors:

  • Overbank flow channel networks, occurrence of high tides impeding the drainage in coastal cities.

Anthropogenic Factors:

1.Unplanned Urbanization:

Unplanned Urbanization is the key cause of urban flooding. A major concern is blocking of natural drainage pathways through construction activity and encroachment on catchment areas, riverbeds and lake beds.

Some of the major hydrological effects of urbanization are:

  • Increased water demand, often exceeding the available natural resources;
  • Increased wastewater, polluting rivers and lakes and endangering the ecology-
  • Destruction of lakes is a major issue in India cities. Lakes can store the excess water and regulate the flow of water. However, pollution of natural urban water bodies and converting them for development purposes has increased risk of floods
  • Reduced infiltration due paving of surfaces which decreases ground absorption and increases the speed and amount of surface flow
  • Reduced groundwater recharge, increased use of groundwater, and diminishing base flow of streams
  • Increased peak flow

2.Climate Change:

  • Climate change due to various anthropogenic events has led to extreme weather events

3.Poor Solid Waste Management System:

  • Improper waste management system
  • Clogging of storm-water drains because of silting, accumulation of non-biodegradable wastes and construction debris.

4.Drainage System:

  • Old and ill maintained drainage system is another factor making cities in India vulnerable to flooding.

Impact of Urban Flooding:

1.Impact on Human:

  • Loss of life & physical injury
  • Increased stress; psychological trauma

2.Disease outbreak:

  • Contamination of water supplies leading to diseases
  • Rise in mosquito borne diseases

3.Impact on Economy:

  • Damage to buildings, roads and other infrastructures
  • Disruptions to industrial production
  • Disruptions to utility supplies
  • Impact on heritage or archaeological site
  • Post-disaster rescue and rehabilitation adds to financial burden of the government

4.Impact on Transport and Communication:

  • Increased traffic congestion, disruption in rail services
  • Disruption in communication- on telephone, internet cables

5.Impact on environment:

  • Loss of tree cover, loss of habitat
  • Impact on animals in zoo, stray animals

Notable Urban Flooding Events in India since 2000:

  • Hyderabad in 2000
  • Ahmadabad in 2001
  • Delhi in 2002 and 2003, 2009, 2010
  • Chennai in 2004, 2015
  • Mumbai in 2005, 2017
  • Surat in 2006
  • Kolkata in 2007
  • Jamshedpur in 2008
  • Guwahati in 2010
  • Bengaluru in 2017

National Disaster Management (NDMA) Guidelines on Urban Flood Management:

  • In 2010, NDMA had issued guidelines on Urban Flood Management in India to create a National Hydro-meteorological Network.
  • The guidelines say that for providing early warning, the Central Water Commission (CWC) CWC should maximize the real-time hydro-meteorological network to cover all urban centres to effectively deal with the problem of urban flooding
  • Use of Doppler Weather Radarsto be expanded to cover all urban areas in the country
  • An inventory of the existing storm water drainage system to be prepared. The inventory will be both watershed based and ward based.
  • Catchment to be the basis for planning and designing the storm water drainage systems in all ULBs
  • All future road and rail bridges in cities crossing drains to be designed such that they do not block the flows resulting in backwater effect
  • Every building in an urban area must have rainwater harvesting as an integral component of the building utility.
  • Low-lying areas in cities have to be reserved for parks and other low-impact human activities.
  • Encroachments on the drain should attract penal action.
  • Pre-monsoon desilting of all major drains to be completed by March 31 each year.
  • Urban Flooding has to be dealt as a separate disaster, de-linking it from riverine floods which affect the rural areas.
  • Suitable interventions in the drainage system like traps, trash racks can be provided to reduce the amount of solid waste going into the storm sewers.
  • Inlets to be provided on the roads to drain water to the roadside drains and these has to be designed based on current national and international practices.
  • Every building in an urban area must have rainwater harvesting as an integral component of the building utility.
  • Concept of Rain Gardens to be incorporated in planning for public parks and on-site storm water management for larger colonies and sites those are to be developed.
  • Flood hazard assessments should be done on the basis of projected future scenarios of intensities and duration of rainfall and land use changes.

Way Forward:

  • Better forecasting of rainfall events; timely dissemination of information to the mass- ‘Nowcasting’ alerts or real-time weather updates

Example: The Municipal Corporation of Greater Mumbai has installed 60 automatic weather stations for recording the rainfall every 15 minutes. This information is disseminated through the GMDMA (Greater Mumbai Disaster Management Authority) web portal in real-time during the monsoon.

  • Installation of proper, functional drainage system. Maintenance of existing drainage channels, providing alternative drainage path
  • Develop ‘sponge’ cities in line with cities in China
  • Proper solid waste management system- control of solid waste entering the drainage systems
  • Restrict encroachments in natural drainage areas; clearance of river beds, proper implementation of Coastal Regulation Zone rules.
  • Each city should have their Flood mitigation plans strongly embedded within the master plan of the city.
  • There should be prompt, well-coordinated and effective response in case of urban floods to minimize casualties and loss of property and also facilitate early recovery.

Global case studies

  • Heavy rainfall in July 2011 prompted the city of Copenhagen to develop a Cloudburst Management Plan in 2012 to prepare the city for one of the biggest climate change challenges — extreme rainfall and pluvial flooding.
  • The plan contains site identification, developing stormwater roads and pipes that transport water towards lakes and harbour, detention areas to store large volumes of water, green roads to detain and hold back water in smaller side streets.
  • The Netherlands is dotted with ponds, lakes, seaside parking garages and city plazas that double up as water storage ponds during flooding events.
  • To address the urban flooding issue, China’s sponge city initiative set an ambitious goal — by 2020, 80 percent of urban areas should absorb and re-use at least 70 percent of rainwater.
  • The initiative seeks to reduce the intensity of rainwater runoff by enhancing and distributing absorption capacities more evenly across targeted areas.
  • The resulting groundwater replenishment increases availability of water for various uses.

URDPFI guidelines:

  • According to guidelines from the Urban and Regional Development Plans Formulation & Implementation (URDPFI), 2016, the maximum percentage of land is allotted to residential areas in different sizes of urban centres — metropolises to small towns.
  • Residential clusters, which occupy the largest share (35 to 45 per cent, apart from recreational areas of 18 to 20 per cent) of land use in cities and towns, comprise building rooftops, sidewalks, paved parking spaces and previous areas that could be gardens or just open land and accessible roads.
  • According to the guidelines, the average built-up area for an urban area is 24 per cent, while for an open space, it is 76 per cent.
  • The standards and guidelines provide enough open areas to design such stormwater management projects.
  • The 2019 manual on storm water drainage systems, prepared by Central Public Health and Environmental Engineering Organisation, included a chapter on innovative stormwater management practices.
  • It talked about integrating smart practices such as water sensitive urban design.
  • However, it is a herculean task to be incorporated at city level.


  • There is a need to include public open spaces within urban fabric in the form of storm management infrastructure, which could help our cities transform into water-sensitive cities.
  • It requires effective policy implementation, addressing technical integration problems, legislative constraints, social equity, and community acceptance for Urban management of flooding.  


Urban Floods

[op-ed snap] Mumbai marooned


From UPSC perspective, the following things are important :

Prelims level : Nothing Much

Mains level : Urban Floods in Mumbai


Mumbai once again struggled to stay afloat after the first heavy spell of rain this year, bringing back memories of the July 2005 flood. Each massive rainfall event is making it evident that the city is putting on a brave front and projecting resilience, but the failure of the Maharashtra government to upgrade its tattered infrastructure is taking a heavy toll and weighing down on the financial capital.

Impact of monsoon

  • A single day of rain has killed 22 people in a wall collapse in north Mumbai, while many more died in Pune and elsewhere.
  • In Ratnagiri, a dam gave way creating a catastrophe; flights have been cancelled and normal life is affected.
  • Clearly, the State government should have regarded the 94 cm of rain that paralysed Mumbai in one day 14 years ago as the baseline disaster to prepare for.

Ineffective Administration

  • That it could not manage 37 cm in 24 hours, that too after incurring a massive expenditure on management projects, shows a lack of resolve among political leaders, rampant inefficiency and lack of integrity in the administrative machinery.
  • As one of the wettest metropolises in India getting about 210 cm of rain annually, it should have been a top order priority to restore rivers and canals to manage floods.
  • The government s needs to explain why Mumbai is yet unprepared to cope, especially when rainfall is projected to become erratic in coming years, and when scientific insights point to intense rainfall in a short span of time, driven by warmer oceans and hotter cities.

CAG’s Report on ineffectiveness

  • In a recent report, the Comptroller and Auditor General identified prolonged delays in the upgrading of storm water drain infrastructure in Mumbai.
  • On the other hand, after the deluge of 2005, the consensus was for the flood-carrying capacity of the Mithi river in the city to be increased.
  • But the choked and polluted river was again overflowing this year.

Change in monsoon rainfall pattern

  • Beyond the sclerotic management of flood waters that relies on storm drains in Mumbai, and several other Indian cities, there is a need for a new urban paradigm.
  • For one thing, Mumbai, Thane, Ratnagiri and Raigad have, during the last century, displayed a high seasonality index, indicating a relatively small monsoon window bringing a lot of rain.
  • This is in contrast to steady, prolonged rain in the central districts in Maharashtra.
  • So a new climate change-influenced normal could mean fewer days of torrential rain and erratic monsoons.

Way Forward

  • Managing them calls for a new approach that is ecological, and makes restoration of existing urban wetlands and creation of reservoirs and water channels a high priority.
  • The water question is the biggest challenge for Indian cities today, as both drought and flood are common.
  • State governments should give it priority and address it by making urban planning people-centric. A strong framework is needed to manage water, starting with Mumbai.

Urban Floods

[pib] Flood Management and Border Areas Programme (FMBAP)


Mains Paper 3: Environment| Disaster and Disaster Management

From UPSC perspective, the following things are important:

Prelims level: FBMAP

Mains level: Flood management


  • The Union Cabinet has approved the “Flood Management and Border Areas Programme (FMBAP)” for Flood Management Works in entire country and River Management Activities and works related to Border Areas.


  • The Scheme “FMBAP” has been framed by merging the components of two continuing XII Plan schemes titled “Flood Management Programme (FMP)” and “River Management Activities and Works related to Border Areas (RMBA)”.
  • The aim of the scheme is to assist the State Governments to provide reasonable degree of protection against floods in critical areas.
  • The works under the scheme will protect valuable land from erosion and flooding and help in maintaining peace along the border.
  • The Scheme aims at completion of the on-going projects already approved under FMP.
  • Further, the scheme also caters to Hydro-meteorological observations and Flood Forecasting on common rivers with the neighbouring countries.

Funding Pattern

  • The funding pattern for FM Component for works in general category States will continue to be 50% (Centre): 50% (State).
  • For projects of North Eastern States, Sikkim, J&K, Himachal Pradesh and Uttarakhand, the funding pattern will continue to be 70% (Centre): 30% (State).
  • RMBA component being specific to activities in border areas, the project works will continue to be funded as 100% grant-in-aid / central assistance.


  • The FMBAP Scheme will be implemented throughout the country for effective flood management, erosion control and anti-sea erosion.
  • The proposal will benefit towns, villages, industrial establishments, communication links, agricultural fields, infrastructure etc. from floods and erosion in the country.
  • The catchment area treatment works will help in reduction of sediment load into rivers.

Urban Floods

[op-ed snap] A series of unfortunate missteps


Mains Paper 2: Polity| Functions and responsibilities of the Union and the States, issues and challenges pertaining to the federal structure, devolution of powers and finances up to local levels and challenges therein.

From UPSC perspective, the following things are important:

Prelims level: Basic knowledge of the federal structure of India.

Mains level: The news-card analyses the federal fallout of the Kerala flood relief funding row, in a brief manner.


  • The differences between the Kerala and Central governments over the denial of external assistance to rebuild the State after the devastating floods of August last year surfaced again last month.


  • The Kerala Governor Justice in his policy speech in the Assembly had said that the Kerala government had requested the Centre to enhance its borrowing limit to mobilise additional resources for rebuilding the flood-hit State.
  • The state government is still awaiting a favourable response from the Central government in this regard.
  • Further, a Kerala Minister who represented Kerala at the Pravasi Bharatiya Divas in Varanasi, complained that he was not allowed to raise the issue there.
  • The bitterness over the flood money still persists.

Competitive federalism: a double-edged sword

  • Competitive federalism, in the context of interaction with foreign countries as promoted by the Prime Minister, has proved to be a double-edged sword.
  • Kerala Chief Minister now stands accused of violating rules regarding the seeking of foreign assistance.
  • He remains unclear on how to make up for the shortfall, of several crores.
  • The Central government is unable to provide the funds while Kerala has been stopped in its tracks from seeking resources from abroad, either from the Kerala diaspora or from friendly foreign governments.

Misunderstandings on both sides

  • The present situation is a result of a series of errors of judgment and misunderstandings on both sides.
  • Mutual political suspicion and a lack of appreciation of the complexities of the international situation have brought about a confrontation.
  • The Chief Minister may have even made diplomatic and tactical mis-judgements.

Diplomatic trajectory

  • India had no qualms about receiving foreign assistance for disaster management till 2004.
  • But when India’s aspiration for permanent membership of the UN Security Council met with strong resistance, New Delhi hit upon the idea of forcing a vote in the General Assembly.
  • The plan was to secure a two-thirds majority and then attempt to embarrass the permanent members into supporting the expansion of the Security Council.
  • The two false presumptions were that India would win the required number of votes and that the Security Council would wilt under pressure from the General Assembly.
  • In fact, many Assembly members were opposed to the veto even for the existing permanent members and had no interest in creating more permanent members with veto.
  • India thought that it could win over the other countries if it was seen to be helping them in emergencies rather than seeking such assistance for itself.

Rules were laid regarding foreign assistance to bring some clarity

  • The tsunami of 2004 and the threat of piracy in the Indian Ocean provided India an opportunity to test its new posture.
  • Everybody was grateful, but it made no difference to India’s claim to permanent membership.
  • However, the present government decided to lay down the rules regarding foreign assistance in order to bring some clarity to the situation.
  • The rules which were framed in 2016 clarified that India would not solicit any assistance but would receive relief assistance, even as cash, from individuals, charitable institutions and foundations.
  • If cash were to be offered bilaterally by foreign governments, the matter would be considered on a case-by-case basis.

The UAE’s offer

  • The Prime Minister was informed by the United Arab Emirates (UAE) authorities that relief assistance was being put together as a special gesture and the Prime Minister reciprocated with a warm reply of gratitude.
  • However, the Kerala Chief Minister’s announced that the UAE would provide ₹700 crore, made on the same day as the Central government’s announcement of a provision of ₹500 crore.
  • It appeared as the UAE was more generous than New Delhi was to Kerala and that the Central government was not empathetic to Kerala’s plight because of political considerations.
  • An embarrassed UAE government then asked its Ambassador in New Delhi to deny that there was any specific offer of ₹700 crore.


  • An immediate consequence was a reluctance by other governments to make any offer of bilateral assistance.
  • No one could answer the question whether any offer from other governments would be accepted.
  • When the Thai Ambassador in Delhi was stopped from being at a ceremony to hand over relief goods to an Indian official, the world was convinced that India would not accept resources.
  • The issue was also politicised.

Unwise decision by Kerala government

  • Against this backdrop, Kerala put forward an unwise proposal to despatch its Ministers abroad to collect donations.
  • This was unacceptable in the context of the policy that had crystallised after the floods in Kerala and the Central Government having refused permission for Ministers other than the Chief Minister to travel to countries.
  • Apart from the ignominy of soliciting donations, there was a clear likelihood of receiving very little by way of cash donations.
  • The possibility of loans from the International Monetary Fund and the World Bank became distant as the Centre refused to raise the limits on loans from these global organisations that a State government could take.
  • The emergence of the Sabarimala crisis further eroded the credibility of the State Government and much of the empathy over the flood damage was also lost.

Way Forward

  • Marshalling of resources is the responsibility of the Union government according to the Constitution.
  • The only option before Kerala is to demand more funding from the Centre to make up the shortfall.
  • The situation is a tragedy of errors caused by an inadequate familiarity with decision making and the complexity of international relations.
  • India is a federal state, but unitary in nature when it comes to national security and foreign policy.
  • Individual States may have some advantages in dealing with some countries in their neighbourhood, but they will do well not to transgress the thin line when it comes to managing international relations.

Chennai floods: Unfolding the real cause

Chennai witnessed its worst rainfall in 100 years. Let’s take a look at what are the main causes, it’s impact and possible ways forward to achieve [long and short term targets]


What exactly happened that wrecked a havoc in Chennai?

  • The catastrophic flooding in Chennai is the result of the heaviest rain in several decades.
  • This forced authorities to release a massive 30,000 cusecs from the Chembarambakkam reservoir into the Adyar river over two days. Causing it to flood its banks and submerge neighbourhoods on both sides.
  • It did not help that the Adyar stream is not very deep or wide, and its banks have been heavily encroached upon over the years.
  • Similar flooding triggers were in action at Poondi and Puzhal reservoirs, and the Cooum river that winds its way through the city.
  • So, unusually heavy rain has exposed the city’s broken urban planning, revealed its stolen natural waterways, and exposed its tolerance of illegal construction.

3 important Geo-climatic factors for heavy rain in 100 years – 

  • Strong el-nino
  • Upper Air divergence
  • High moisture content

How does a strong El-nino affect Chennai?

  • The summer (southwest) monsoon is adversely affected, while the northeast monsoon or the winter monsoon is favourably affected.
  • In mid-November, the sea surface temperature in the central tropical Pacific was 3 degrees Celsius warmer than normal, the largest positive deviation in recorded history.
  • To officially beat the 1997-98 El Niño as history’s worst, sea surface temperatures must stay at these levels for three months.

How does inefficient urban planning causes floods?

  • 1.5 lakh Illegal construction
  • Chocking of water exits
  • Badly planned or unimplemented projects

But, what was wrong with the Urban planning?

  • Chennai is located in a relatively flat area, hence it depends on natural water bodies, canals and rivers to drain the heavy water runoff during rains.
  • Its drainage and stormwater network, which is absent in many places, is inadequate even to convey water during moderate rains.
  • As a result, the city has a high exceedance flow (excess water that cannot be drained through the drainage system).
  • It often inundates neighbourhoods, particularly those in the suburbs, which are built in low-lying areas and poor roads. This scenario was foreseeable.


Let’s get into some details of unplanned Urban Space

  • Today, Chennai has a host of expensive infrastructure aimed at ushering in a “Make in Chennai” boom, a brand-new (though leaky) airport built on the floodplains of the River Adyar.
  • A sprawling bus terminal in flood-prone Koyambedu, a Mass Rapid Transit System constructed almost wholly over the Buckingham Canal and the Pallikaranai marshlands.
  • An IT corridor and a Knowledge Corridor consisting of engineering colleges constructed on waterbodies, and automobile and telecom SEZs and gated residential areas built on important drainage courses and catchments.
  • So, fact remains that the mindless development of Chennai over the last 2 decades, the filling up of lowlands and choking of stormwater drains and other exits for water has played a major part in the escalation of the crisis.

Way forward : Lessons from International Practices

First task : To enhance Preventive measures

  • It can learn a lesson or two from cities in Japan, Malaysia and Europe.
  • Well-prepared cities have mapped flood zones.
  • By combining field surveys, historical records, satellite imagery and infrastructure assessment, they have identified vulnerable areas.
  • Such maps and data are shared with citizens, which help them understand the status of their neighbourhoods and decide where to move or buy new homes.
  • More importantly, this data is used to regulate development.
  • The United Nations Office for Disaster Risk Reduction has collated data spanning 3 decades, starting from the 1980s, for various places in Tamil Nadu including Chennai.
  • The city corporation can quickly build on it.

Second task : To enhance Mitigation

  • Kuala Lumpur and Tokyo have built extensive water discharge tunnels to divert and store floodwater. This reduces the volume of water that washes the city.
  • Tokyo has one of the largest underground tunnels, running to a length 6.5 km, and the tank can hold 6,70,000 cubic metre of diverted water, which is later pumped into safe watercourses using turbines.
  • Canals such as the Veerangal Odai, which connected Adambakkam lake with Pallikaranai marsh in the suburbs, have almost disappeared. Reclaiming these water bodies is critical.
  • The city should also explore, as many others have done, the possibility of designing highways to conduct runoff water.
  • All this would warrant a thorough review of its urban engineering.

Third task : To enhance Response measures

  • In the first week following the heavy rains, ground reports reveal that the government response was inadequate and uncoordinated.
  • The spirited effort of citizens propelled rescue efforts, without which the damages would have been more severe.
  • As cities increasingly face natural hazards and terrorist attacks, they are investing in setting operation centres for early warning and rescue work.
  • For example, Rio de Janeiro has spent $14 million and created a real-time monitoring centre of infrastructure and traffic flows.
  • The recent experience clearly shows the need for early warning and dissemination of reliable information about floods and rescue.
  • Improved governance and non-interference of political parties in relief measures are critical.

Can you ponder on any long or short term solutions or any way ahead?

Let us know, as UPSC is fond of asking such solution based questions in Mains!


Published with inputs from Arun
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