19 Oct

Floods

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Contents

• Introduction
• What caused heavy torrential rain in Himachal, Punjab, J&K and Delhi
• Dealing with Flood Disasters/ Flood Management in India
• Assam Case Study

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Introduction

• Inundation of land and human settlements by the rise of water in the channels and its spill-over presents the condition of flooding. Flood is a natural disasters which affects some or the other part of the country for almost every year now. (Kerala, Chennai, Assam, Bihar, UP etc. ).
• According to ADB, floods are the most devastating among climate related disasters in India. They account for more than 50% of all climate related disasters in the country.

Situation in India

• In India, around 40 million hectares area is flood prone, which is 1/8th of the total area.

Causes of Floods

• Natural Causes: Flood is generally seen as a natural phenomenon. It is associated with:
  • Heavy Rainfall
    • Cyclones etc.
    • Monsoon Climate – all rainfall confined to a period

What caused heavy torrential rain in Himachal, Punjab, J&K and Delhi in the first week of July 2023

• Interaction of Western Disturbance with the Monsoon Low Pressure System.
  • A western disturbance (WD) is an extra tropical storm in the upper layers of the atmosphere that is carried towards India by the subtropical jet stream, a band of fast flowing winds that circulates the Earth.
  • A Low Pressure System (LPS), is an area of low pressure that generally forms over seas and oceans and cause rainfall.
  • This is rare phenomenon as the WD generally don’t occur during Monsoon season. But, global warming have brought variability and have increased the instances of WD during monsoon.
• A Heat wave in northern Bay of Bengal:
  • The Bay of Bengal, especially its northwestern part, is usually warm. This enables it to play an important role in NW Monsoon trajectory.
• Deep Convection triggered by orographic uplift combined with the steep terrain of Himalayas.
• Sediment Deposition
  • Causes rivers to overflow or change paths

Manmade causes: Experts believe that the recent increase in intensity of floods have to do a lot with human activities:

i. Climate Change has led to extreme variability in the intensity of rainfall which has increased the chances of floods.

• For e.g., global warming has caused rainfall due to western disturbances even in Monsoon season in July 2023 causing huge rainfalls in NW India.

ii. Unplanned development along the natural drainage system has led to rivers losing its buffer areas and thus any increase in the water levels is causing floods. This include colonization of flood plains and river beds.

• The number of people living in floodplains across the world increased by 58-86 million during 2000-2015

iii. Indiscriminate Deforestation has led to increased devastation due to floods. Trees generally acted as a breaker in the intensity of floods.

• For e.g. According to Madhav Gadgil, if we would have protected Western Ghats, the loss and devastation by the Kerala floods of 2018 would have been less severe.

iv. Unsustainable agri-practices can also be considered an important factor behind the recent rise in floods.
v. Inefficient Dam Management sometimes lead to large scale release of water in small time period leading to flood conditions.

• E.g. Kerala floods pf 2018

vi. Urban Floods are also mostly a result of human made factors

• Blocking the natural flow of rivers
• Destroying the natural sinks like ponds, lakes etc.
• Concretization – Reduces the seepage of water – all water flows and cause floods
• Improper Urban Planning -> siltation of drainage system, Insufficient drainage system

Consequence of floods – Life, Property, Infrastructure, Agriculture, Water Borne diseases etc.

• According to Central Water Commission, the total flood related losses in the country were estimated to be over 37 lakh crore from 1953 to 2017.
• As per the the State of the Climate in Asia 2021 report, loss and damages from floods, storm cost India $7.6 billion in 2021 alone.

Some positive impact

• It deposits fertile alluvial soil and thus perpetuates the fertility of the area.

Dealing with Flood Disasters/ Flood Management in India

a. Risk Reduction, Preparedness

• Flood Plane Zonation (FPZ) to mitigate damages caused by floods and to allow rivers
  their ‘Right to Way’. As a policy flood plain zonation has two major components:
  Removing Encroachment and Regulating Land Use.

• Other River Related Steps
  • Embankments: e.g. Embankments on Yamuna in Delhi has been successful in controlling the flood to large extent.
  • Periodic desilting of river
  • Watershed based master planning and development legislated guidelines for each major river basin is needed.
    • It should demarcate ecologically sensitive zones.
      • There must be clear land use plan for these zones specifying flood plains, protected forest areas, agricultural and plantation zones.
• Continuous modernization of flood forecasting, early warning and decision support systems
  •  There is a need of more accurate rain forecast and more detailed warnings in place of the current categorization as “heavy” or “very heavy”.
  • IMD needs more Doppler weather Radars which can extend the lead time of forecast by three days.
    • E.g. IFLOWs-Mumbai was launched in June 2020 as an state of art integrated flood Early Warning system for Mumbai to enhance the resilience of Mumbai specially during high rainfall events and cyclones.
•  Reservoirs: Construction of reservoirs in the course of rivers could store extra water at the time of flood.
  • Such measures have not been much successful. Moreover it has led to increased deposition of silt in the river and reducing the water flow and further increasing the flood. (e.g. Farakka Barrage causing problems in Bihar)
  • Moreover, during huge floods, dams are double-edged sword. (e.g. Kerala floods of 2018)
• Afforestation: the furry of flood could be minimized by planting trees in catchment areas of the river
• Planned Scientific Development of Cities
  • Protect natural sinks like Ponds, lakes etc., development away from the river channel, proper drainage infrastructure, regular cleaning of this infrastructure.
  • Review and revise building by laws to focus more on environmental sustainability. They should clearly provide that natural drainage and streams shall not be obstructed by this development/ building permit.
• Improving awareness and preparedness of all stakeholders in the flood prone areas.
  • Regular Drills in Flood Prone Areas to ensure preparedness of NDRF and awareness among masses regarding steps to be taken during floods.
  • Introducing capacity development interventions for effective Flood Management (including education, training, capacity building, R&D, documentation) etc.
• International Cooperation with neighboring countries on flood controls as a number of rivers which cause flood in India originate from other neighboring countries.
  • For e.g. Dams on Rivers in Nepal can play an important role in controlling floods in the state of Bihar.

b. Response

• Improve the response system of NDRF especially for rural states like Bihar and Odisha.
•  Need to enhance capacity building for catastrophic weather events
  • Serious attention needs to be given to fast tracking the setting up of relief camps, crisis proof health infrastructure and stockpiling of dry ration and medicines.
  • Increased use of technologies like drones to identify people who are trapped in flood

c. Recovery

• Special Focus on Water borne diseases as they are the biggest killer in the post flood situation.
• Ensure that the new infrastructure created is resistant to floods.
• Bring in changes like broadening ecologically sensitive domain to protect more area from environmental degradation.

Conclusion1:

By recognizing the increasing threat of extreme precipitation and implementing proactive measures, India can improve its resilience to extreme weather events.

Conclusion2:
India being a sub-tropical country with Monsoon kind of climate will remain vulnerable to floods due to heavy rainfall and increased climate variability. An efficient disaster management mechanism will ensure that these floods remain a natural phenomenon and doesn’t become a natural disaster.

Assam Case Study

Why is Assam so vulnerable to floods?

• Incessant Monsoon Rainfall
• Nature of River Brahmaputra -> Dynamic and Unstable
  • It figures amongst the world’s top five rivers in terms of discharge as well as the sediments that it brings.
  • Because of earthquake prone nature of the region, the river has not been able to acquire a stable character.

Man-Made Factor

• Habitation, deforestation, population, growth in catchment areas also lead to higher
  sedimentation in the region.
• Destruction of wetlands: For e.g. Sylhet districts traditional wetlands called ‘haor’ used to act as sponges absorbing runoff, have been destroyed, thereby enabling the recent floods.

How has government tried to address the factors that cause flood in Assam

• In its master plan on the river in 1982, the Brahmaputra Board has suggested that dams and
  reservoirs be built to mitigate floods .
  • But, the idea has been seen as a double edged sword.
  • Further, opposition from locals, and environmentalists on the grounds of displacement and destruction to ecology, prevented the plan from moving forward.
• Building Embankments were proposed as an interim measure to deal with floods and government has recently used this as the only major approach to control floods.
  • But since, there were temporary measures, most embankments which were built in 1980s were not strong enough and thus easily give way in case of overflow of rivers.
• Dredging is another thing that government has considered, but experts have opposed it as Brahmaputra sediment yield is amongst highest in the world and next year sediments will reverse the efforts of this dredging. So, even this hasn’t been done.

Conclusion

• The above initiatives are clearly not the sustainable solution to floods. There is a need of a basin wide approach to the problem. There is a need of integrated basin management system that should ideally bring in all basin-sharing countries on board.