Flood

Floods in India pose significant challenges, with over 40 million hectares of the country being flood-prone. Causes include heavy rainfall, siltation, drain blockages, landslides, and dam constructions. These floods result in loss of life, damage to infrastructure, and environmental degradation. Strategies like inter-basin water transfer and river interlinking are proposed for sustainable flood management. The NDMA guidelines advocate for both structural (e.g., embankments, dams) and non-structural measures (e.g., flood plain zoning, forecasting). Government efforts include the National Flood Risk Mitigation Project and Flood Risk Mitigation Scheme, aiming to enhance readiness and awareness. These initiatives focus on minimizing flood impacts on communities and infrastructure.

The surging occurrences of floods, encompassing urban flooding and Glacial Lake Outburst Floods (GLOFs), have given rise to numerous challenges. Additionally, the impacts of rising global temperatures and climate change exacerbate these challenges, necessitating authorities to formulate a comprehensive strategy. Authorities must develop a holistic approach that integrates various strategies to effectively manage flood-related challenges and safeguard communities and infrastructure from their adverse effects

Floods are characterised by the sudden and temporary inundation of a large area due to the overflowing of rivers or reservoirs. India, with a total geographical area of 329 million hectares (mha), faces high vulnerability to floods. More than 40 mha of the country is flood-prone, making floods a recurring and concerning phenomenon. The impact of floods includes significant loss of lives, damage to livelihood systems, destruction of property, infrastructure, and public utilities. The increasing trend in flood-related damages is attributed to factors such as a steep rise in population, rapid urbanization, extensive developmental and economic activities in floodplains, and the influence of global warming.

The causes of floods include:

• Heavy rainfall: Approximately eighty percent of the precipitation occurs during the monsoon months from June to September.
• Heavy siltation: The accumulation of silt in riverbeds reduces the water-carrying capacity of rivers and streams.
• Blockage in drains: Obstructions in drainage systems result in the flooding of surrounding areas.
• Landslides: The occurrence of landslides can obstruct the flow of streams, contributing to flooding.
• Construction of dams and reservoirs: Alterations to natural water flow due to the construction of dams and reservoirs can lead to flooding.
• Cyclones: Areas prone to cyclones experience strong winds, heavy rainfall, and storm surges, all of which can cause flooding.

The impacts of floods include:

• Loss of human life, damage to crops, and loss of livestock, leading to a decrease in soil fertility.
• Public health issues, such as the outbreak of diseases like leptospirosis (rat fever), as seen after the 2018 Kerala floods.
• Infrastructure damage, including closure of schools and hospitals, disruption of electricity and telephone services, and damage to buildings and roads.
• Destruction of natural landscapes, including uprooting of trees, landslides, and soil erosion, exacerbating environmental degradation.

Floods in India can be harnessed as a sustainable source of irrigation and all-weather inland navigation through various strategies:

• Inter-Basin Water Transfer: Implementing projects like the Ken-Betwa link and Periyar Vagai project, which aim to transfer surplus water from one river basin to another, can effectively manage floods while providing water for irrigation in drought-prone areas.
• Interlinking of Rivers: By interlinking rivers through dams and locks, sufficient water levels can be maintained for inland navigation. Similar to the Three Gorges Dam on the Yangtze River, interlinking projects in rivers like the Ganga and Narmada have the potential to create waterways for transportation.

Structural Measures:

• Embankments/Banks, Flood Walls, Flood Levees: Detailed hydrological and morphological studies are required before constructing these structures to understand their favorable and adverse effects.
• Dams & Reservoirs: Construction of dams and reservoirs helps in reducing floodwater through storage.
• Channel Improvement: State governments must identify locations and undertake appropriate channel improvement works.
• Desilting/Dredging of Rivers: Desilting, deepening, and increasing embankment capacity enhance the river/channel/drain's capacity.
• Diversion of Flood Water: Feasibility studies must be conducted by state governments/SDMAs (State Disaster Management Authorities) to divert excess water to existing or new channels to prevent flooding.
• Catchment Area Treatment/Afforestation: Watershed management measures like afforestation, check dams, and detention basins should be implemented in river catchment areas.
• Sea Walls/Coastal Protection Works: Coastal states/port authorities should plan and execute seawalls/coastal protection works considering sea behavior and environmental aspects.

Non-Structural Measures:

• Flood Plain Zoning: Regulate land use in floodplains to reduce damage by preventing habitation in low-lying and frequently flooding areas. Demarcate evacuation areas and highlands for shifting people during floods.
• Flood Proofing: Construct flood shelters on highlands, ensure food and fodder availability, and safeguard communication channels and health services during floods.
• Flood Forecasting and Warning: Intensity measurement of rainfall in catchment areas helps hydrology engineers calculate potential submergence areas in advance. A nationwide flood forecasting and warning system, covering major inter-state rivers, has been established by the Central Water Commission (CWC).

National Flood Risk Mitigation Project(NFRMP)

• The National Flood Risk Mitigation Project (NFRMP) aims to ensure readiness for relief, rehabilitation, rebuilding, and recovery from flood-related tragedies, while also raising awareness among vulnerable communities.
• The project is overseen by the National Disaster Management Authority (NDMA), which is responsible for preparing a Detailed Project Report (DPR).

Flood Risk Mitigation Scheme (FRMS)

• The Scheme encompasses various activities, including:
  • Pilot Projects for developing model Multi-Purpose Flood Shelters.
  • Development of River Basin specific Flood Early Warning Systems and Digital Elevation Maps to prepare Inundation Models for timely evacuation alerts in flood-prone areas.
• Financial support is allocated to flood-prone states for implementing pilot schemes related to these activities.
• The scheme is currently in the preparation phase, with the aim of enhancing flood risk management and minimizing the impact of floods on communities and infrastructure.

Urban floods occur when a city experiences a significant influx of water, often due to heavy precipitation, rapid snowmelt, or storm surges from cyclones or tsunamis. This influx leads to the submersion of parts or the entirety of the city. Additionally, the city's infrastructure may be unable to drain the water rapidly or manage it effectively, resulting in inundation In recent years, the threat of urban floods has significantly increased globally, particularly in India. Major flood incidents have occurred in various cities across the country:

• Hyderabad experienced significant floods in both 2020 and 2021.
• Chennai faced flooding in November 2021.
• Bengaluru and Ahmedabad witnessed flood incidents in 2022.
• Parts of Delhi were affected by floods in July 2023.
• Nagpur saw flooding in September 2023

• Meteorological Factors:
  • Heavy rainfall: Intense and prolonged rainfall events can overwhelm drainage systems, leading to flooding.
  • Cyclonic storms: Cyclones can bring heavy rainfall and storm surges, exacerbating flooding in coastal areas.
  • Thunderstorms: Sudden and intense thunderstorms can result in flash flooding, especially in urban areas with inadequate drainage systems.
• Hydrological Factors:
  • Overbank flow channel networks: The presence or absence of effective drainage networks can influence the severity of urban flooding.
  • High tides: Coastal cities may experience flooding due to high tides impeding drainage during heavy rainfall events.
• Human Factors:
  • Land-use changes: Urbanization and surface sealing reduce natural absorption areas, increasing runoff and exacerbating flooding.
  • Occupation of floodplains: Construction in flood-prone areas obstructs natural flood flows and increases flood risk.
  • Urban heat island effect: Urban areas experience higher temperatures, which can lead to increased rainfall and intensity of storms, contributing to flooding.
  • Dam operations: Sudden release or failure to release water from upstream dams can cause downstream flooding, known as the backwater effect.

These factors interact to create complex and multifaceted urban flood risks, highlighting the importance of comprehensive flood management strategies

• Early Warning System
  • National Hydro-Meteorological Network: CWC ( Central Water Commission) should maximise the network to cover all urban centres
  • Local Network Cell at IMD Headquarters:
    • The Indian Meteorological Department (IMD) will establish local network cells at its headquarters to collect real-time rainfall data.
  • Doppler weather radars: The IMD and Ministry of Urban Affairs will collaborate to strategically expand the Doppler Weather Radar (DWR) network across the country, improving weather monitoring and forecasting capabilities.
• Design & Management of Urban Drainage System
  • An inventory of the existing stormwater drainage system should be prepared on a Geographic Information System (GIS) platform to facilitate effective management and maintenance.
  • Rainwater harvesting: Urban Local Bodies (ULBs) are responsible for ensuring that every building in urban areas has rainwater harvesting systems installed.
  • Regular desilting of all major drains should be conducted annually before the monsoon season
  • Efforts should be made to protect, restore, and revive urban water bodies to enhance natural drainage systems
  • Any encroachment on drains must be strictly prohibited, and penal action should be taken against violators
• Urban Flood Disaster Risk Management
  • Multi-Hazard Risk Assessment for Land Use Planning:
    • Risk assessment will adopt a multi-hazard approach to ensure comprehensive land use planning, mitigating various potential hazards effectively.
  • Ward-Level Risk Reduction and Vulnerability Assessment:
    • Vulnerability assessments will be conducted at the ward level using community-based strategies, enabling targeted risk reduction measures and enhancing community resilience.
  • Expansion of National Urban Information System (NUIS):
    • The NUIS database will be expanded to include infrastructure facilities at the community level, integrated with socio-economic data, facilitating informed decision-making and risk management.
  • De-Linking Urban Flooding from Riverine Floods:
    • Urban flooding will be treated as a distinct disaster, separate from riverine floods, allowing for focused attention and tailored mitigation strategies.
  • Establishment of Urban Flooding Cells:
    • States/UTs will establish Urban Flooding Cells within the Department of Urban Development, tasked with:
      • Preparation and implementation of Disaster Management Plans.
      • Conducting regular mock drills and preparedness exercises.
      • Promoting Community Based Disaster Preparedness (CBDP) efforts.
      • Launching awareness generation campaigns to enhance public preparedness and response to urban flooding events.

The Union Government has undertaken various initiatives to promote groundwater recharge and implement nature-based solutions for addressing urban flooding in flood-prone areas. Some of these initiatives include

• Master Plan for Artificial Recharge of Groundwater
  • The CGWB (Central Ground Water Board) has formulated the 2020 Master Plan for Artificial Recharge to Groundwater.
  • This plan aims to construct approximately 1.42 crore rainwater harvesting and artificial recharge structures across the country.
• Jal Shakti Abhiyan (JSA): This initiative focuses on rainwater harvesting and groundwater recharge to enhance water availability and sustainability.
• Amrit Sarovar Mission: Launched with the objective of developing and rejuvenating 75 water bodies in each district across the country, aiming to improve water resources management.
• Atal Bhujal Yojana: It emphasizes demand-side management of groundwater by promoting water-saving interventions like micro-irrigation, crop pattern shifts, and mulching to conserve water resources.
• Atal Mission for Rejuvenation and Urban Transformation (AMRUT) 2.0 Scheme: Includes provisions for rainwater harvesting through stormwater drains into water bodies, along with the creation and strengthening of stormwater drains around these water bodies.
• National Water Policy (2012): It advocates for the conservation of rivers, river corridors, water bodies, and infrastructure in a scientifically planned manner, with community participation being integral to the process.
Integrated Flood Warning System for Mumbai (iFLOWS-MUMBAI): Launched by the Ministry of Earth Sciences, this system captures urban drainage within the city and predicts flood-prone areas, helping in proactive flood management and mitigation efforts.

A GLOF is a type of flood occurring when water dammed by a glacier or a moraine is released suddenly.

Factors contributing to the hazards include:

1. large lake volume;
2. narrow and high moraine dam;
3. stagnant glacier ice within the dam; and
4. limited freeboard between the lake level and the crest of the moraine ridge.

Potential outburst flood triggers include avalanche displacement waves from (i) calving glaciers; (ii) hanging glaciers; (iii) rock falls; (iv) settlement and/or piping within the dam; (v) melting ice-core; and (vi) catastrophic glacial drainage into the lake from sub-glacial or englacial channels or supraglacial lakes.

Understanding Risks

• Conduct hazard and risk assessments to identify vulnerable areas and develop appropriate mitigation strategies
• Utilise Doppler radar systems and satellite imagery for accurate monitoring and assessment of hazards.

Structural Measures:

• Implement strategies like lowering lake levels, constructing deflection dams, and enhancing river cross sections to reduce the risk of GLOFs.
• Utilise artificial drainage systems, including pumps, to manage water levels effectively and mitigate flood risks.

Non-Structural Measures:

• Incorporate hazard maps into spatial planning to guide land-use decisions and infrastructure development in safer areas.

Preparedness Measures:

• Establish early warning systems and toll-free helplines for timely alerts and evacuation.
• Set up a national data centre dedicated to GLOFs for centralized information management and analysis.
• Conduct Information, Education, and Communication (IEC) activities to raise awareness and promote preparedness among communities.

As India tackles the ongoing challenge of floods, it is important to adopt forward-looking and comprehensive strategies. Recognizing floods not only as a threat but also as a potential resource for sustainable irrigation and inland navigation is important. We should leverage inter-basin water transfers and river interlinking projects. Adhering to the NDMA guidelines, both structural and non-structural measures must be employed, encompassing embankments, dams, floodplain zoning, and early warning systems.

In the urban context, proactive measures such as robust drainage systems, rainwater harvesting, and risk reduction strategies outlined in the NDMA guidelines for urban floods are crucial. Government initiatives, including the National Flood Risk Mitigation Project and the Flood Risk Mitigation Scheme, demonstrate the commitment to comprehensive flood management. Additionally, initiatives like the Master Plan for Artificial Recharge of Groundwater and Integrated Flood Warning System for Mumbai showcase a multi-pronged approach towards tackling diverse flood-related challenges. Similarly, other cities with a flooding problem must adopt and successfully implement water management plans. Constant assessment and re-direction of the plans is also important. By integrating technological advancements, community engagement, and sustainable practices, India can forge a resilient path forward in managing and mitigating the impact of floods across different landscapes and contexts.