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The inundation of land and human settlements by the rise of water in the channels and its spill-over presents the condition of flooding.

• Out of the total geographical area of 329 million hectares (MHA), more than 40 MHA are flood-prone.
• Floods affect an average area of around 7.5 million hectares per year.
• On average, 75 lakh hectares of land are affected every year, 1600 lives are lost, and the damage caused to crops, houses, and public utilities is Rs.1805 crores.

Regions Prone to Flooding in India:

1. The Brahmaputra River Region: This region consists of the rivers Brahmaputra and Barak and their tributaries, and covers the states of Assam, Arunachal Pradesh, Meghalaya, Mizoram, Manipur, Tripura, Nagaland, Sikkim and the northern parts of West Bengal.
2. The Ganga River Region: It covers the states of Uttarakhand, Uttar Pradesh, Jharkhand, Bihar, south and central parts of West Bengal, Punjab, parts of Haryana, Himachal Pradesh, Rajasthan, Madhya Pradesh and Delhi.
3. The North-West River Region: The main rivers in this region are the Indus, Sutlej, Beas, Ravi, Chenab and Jhelum. This region covers the states of Jammu and Kashmir, Punjab and parts of Himachal Pradesh, Haryana and Rajasthan.
4. The Central and Deccan India: Important rivers in this region are the Narmada, Tapi, Mahanadi, Godavari, Krishna and Cauvery.

Nodal Ministry: Min. of Jal Shakti (MOJS)

Types of Floods:

1. Riverine Floods: Result from overflowing rivers or streams. Example: Ganga-Brahmaputra Delta in East India experiences annual riverine flooding during the monsoon.
2. Flash Floods: Rapid-onset floods often caused by heavy rainfall or dam breaks. Example: Uttarakhand Flash Floods in 2013, triggered by heavy rains and glacial lake outburst.
3. Coastal Floods: Occur along coastlines due to storms, cyclones, or high tides. Example: Coastal areas of West Bengal and Bangladesh faced flooding during Cyclone Amphan in 2020.
4. Pluvial Floods: Caused by excessive rainfall, leading to localized flooding. Example: Urban areas like Chennai and Bangalore face pluvial flooding during heavy rains.
5. Dam or Levee Break Floods: Result from the failure of dams or levees. Example: The Machu Dam failure in Gujarat in 1979 led to significant flooding.

Criteria to Declare:

The Indian government typically declares a flood based on specific criteria that may vary slightly from state to state. However, some common criteria for declaring a flood in India include:

1. Rainfall Thresholds: When heavy and sustained rainfall exceeds certain predefined thresholds for a particular region or river basin.
2. River Water Levels: water levels in rivers or reservoirs rise significantly and pose a threat to communities downstream,
3. Dam Releases: The release of water to maintain their structural integrity can lead to downstream flooding.
4. Weather Warnings: Based on weather warnings from meteorological agencies, such as the India Meteorological Department (IMD), which predict heavy rainfall.
5. Impact Assessment: Assessment of rising water levels on communities, infrastructure, and agriculture done by authorities.

Causes: Floods can also be caused due to a storm surge (in the coastal areas), high intensity rainfall for a considerably longer time period, melting of ice and snow, reduction in the infiltration rate and presence of eroded material in the water due to higher rate of soil erosion.

Mitigation:

1. Early Warning Systems: India has an extensive network of meteorological and hydrological stations to monitor rainfall and river levels.
2. River Basin Planning: Regulate water flow, reduce siltation, and control flooding which includes the construction of dams, reservoirs, and embankments.
3. Floodplain Zoning: Identify and demarcate flood-prone areas, and restrict or regulate construction and development in these zones.
4. Flood Forecasting and Modeling: Utilize advanced technologies and modeling techniques to predict and analyze floods, enabling more effective response planning.
5. Embankments and Flood Control Structures: Construct and maintain flood control structures such as embankments, levees, and flood walls to protect vulnerable areas.
6. Climate Change Adaptation: Consider the potential impacts of climate change on flooding patterns and incorporate adaptive strategies into flood mitigation plans.
7. International Collaboration: Collaborate with neighboring countries, especially in the case of transboundary rivers, to share data and coordinate flood management efforts.
8. River Training and Dredging: Undertake River training and dredging projects to improve the flow of rivers and reduce the risk of flooding.

NDMA Guideline:

• Battery operated torch
• Extra batteries
• Battery operated radio
• First aid kit and essential medicines
• Emergency food (dry items) and water (packed and sealed)
• Candles and matches in a waterproof container
• Knife
• Chlorine tablets or powdered water
• Thick ropes and cords

Way Forward:

• The entire suite of measures structural and non-structural, an appropriate mix of grey, blue, and green infrastructure needs to be considered for flood management.
• Mindsets needing changing flood flows should be seen as a resource to be conserved for subsequent use and water security.
• A river basin approach should be adopted for flood management while taking care of the environment.
• It is prudent we upgrade the hydro infrastructure in the country now so that the tools to manage increased variabilities are available in time.

A type of geological event near an opening/vent in the Earth’s surface including volcanic eruptions of lava, ash, hot vapour, gas, and pyroclastic material.

• Ash fall 
• Lahar – Hot or cold mixture of earthen material flowing on the slope of a volcano either during or between volcanic eruptions
• Lava Flow
• Pyroclastic Flow – Extremely hot gases, ash, and
• other materials of more than 1,000 degrees Celsius that rapidly flow down the flank of a volcano (more than 700 km/h) during an eruption. 

• There are about 1500 potentially active volcanoes worldwide. 
• Volcanic activities and wildfires affected 6.2 million people and caused nearly 2400 deaths between 1998-2017.

Regions Prone to Volcanic eruptions: Barren island (A&N), Narcondam (Andaman Sea), Deccan trap in Deccan plateau, Baratang (Andaman Island), Dhinodhar hills (Gujarat), Dhosi hills (Aravali mountains), Tosham hills (Haryana).Nodal Ministry: Min. of Earth Sciences (MOES)

Types of Volcanic Eruptions:

1. Stratovolcanoes: Steep-sided with explosive eruptions. Example: Mount St. Helens.
2. Shield Volcanoes: Broad and gently sloping with non-explosive eruptions. Example: Mauna Loa.
3. Cinder Cone Volcanoes: Small, steep-sided with ash and cinder eruptions. Example: Paricutin.
4. Caldera Volcanoes: Large, basin-like depressions from explosive eruptions. Example: Yellowstone Caldera.
5. Lava Domes: Bulbous mounds from slow-moving lava. Example: Novarupta Dome.
6. Submarine Volcanoes: Form underwater. Example: Lo’ihi (Hawaii).
7. Fissure Volcanoes: Erupt along cracks. Example: Laki (Iceland).
8. Super-volcanoes: Erupt cataclysmically. Example: Yellowstone (potential supervolcano).

Criteria to Declare:

Central or State authorities declare the area as volcanically active based on these parameters:

1. Volcanic Activity: This includes volcanic eruptions, lava flows, ash emissions, and any other signs of volcanic unrest.
2. Geological Evidence: The presence of volcanic rocks, craters, calderas, lava domes, or volcanic vents features strong evidence of volcanic origin.
3. Seismic Activity: Monitoring seismic activity, including volcanic earthquakes and tremors, is crucial.
4. Gas Emissions: Measuring the composition and quantity of (SO2) or carbon dioxide (CO2), can provide insights into volcanic activity and potential hazards.
5. Ground Deformation: Detected through techniques like GPS and satellite-based interferometry, can indicate magma movement.
6. Historical Records: Historical records of past eruptions, including eyewitness accounts, written records, and geological studies, are important for assessing a volcano’s history and potential future behavior.
7. Remote Sensing: Used to monitor changes in surface temperature, volcanic ash plumes, and ground deformation.

Causes:

1. Underwater Earthquakes: When tectonic plates at subduction zones converge, they suddenly displace a massive amount of water, generating a tsunami.
2. Volcanic Eruptions: The expulsion of magma and gas from a volcano can create a sudden and forceful displacement.
3. Landslides: Landslides from coastal cliffs or mountains, can displace a significant amount of water upon impact, generating a tsunami.
4. Meteorite Impacts: Although rare, The energy released from such an impact can create powerful waves.
5. Glacial Calving: When large pieces of ice break off from glaciers and fall into the ocean, they can displace water and generate small tsunamis, known as “glacial tsunamis.”
6. Fault Zones: Faults that lie beneath the ocean can slip suddenly, displacing seawater and causing a tsunami.

Mitigation:

India had a set of official guidelines primarily related to the Barren Island volcano in the Andaman Sea. These guidelines were primarily managed by the Geological Survey of India (GSI) and the Indian Meteorological Department (IMD).

1. Monitoring and Early Warning: Continuous monitoring of volcanic activity using seismic instruments, gas analyzers, and satellite technology to detect signs of volcanic unrest.
2. Hazard Zonation: Establishment of hazard zones based on the type and potential impact.
3. Evacuation Plans: Development of evacuation plans and routes for nearby communities. Regular drills and training exercises to ensure preparedness.
4. Public Awareness and Education: Educate local communities about volcanic hazards and safety measures.
5. Coordination: Coordination between the GSI, IMD, local administration, and disaster management authorities to ensure minimal harm caused.
6. Emergency Response: Prepositioning of emergency supplies, medical teams, stockpiling food, water, medicines, and setting up emergency shelters.

Tsunamis (Japanese for “harbour wave”), also known as a seismic sea wave, are a series of very large waves with extremely long wavelengths, in the deep ocean, the length from crest to crest may be 100 km and more. When the seafloor abruptly deforms the sudden vertical displacements over large areas disturb the ocean’s surface, displace water, and generate tsunami waves.

1. Of the nearly 7,500 km long coastline, close to 5,700 km is prone to cyclones and tsunamis.
2. States Prone to Tsunami:
   1. Kerala- Alleppey and Earnakulam
   2. Tamil Nadu- Cuddalore, Kancheepuram, Chennai, Kanyakumari, Tirunelveli, Thoothukudi, Villupuram, Thiruvarur, Ramanathapuram, Thanjavur
   3. Andhra Pradesh- Nellore, Prakasam, Guntur. Visakhapatnam, East and West Godavari
   4. Pondicherry
   5. Orissa
3. Between 1998-2017, tsunamis caused more than 2,50,000 deaths globally, including more than 2,27,000 deaths due to the Indian Ocean tsunami in 2004.
4. More than 700 million people live in low-lying coastal areas and Small Island Developing States exposed to extreme sea-level events including tsunamis.

Nodal Ministry: Min. of Earth Sciences (MOES).

Types of Tsunamis:

1. Tectonic Tsunamis: Caused by underwater earthquakes, volcanic eruptions, or fault movements along tectonic plate boundaries.
2. Landslide Tsunamis: Triggered by underwater landslides, which can displace a large volume of water.
3. Meteorological Tsunamis (Metetsunamis): Generated by atmospheric disturbances such as severe storms, rapid pressure changes, or weather fronts.

Criteria to Declare:

The Indian government, like many other governments around the world, relies on various criteria and systems to detect and declare tsunamis. Key components of the criteria include:

1. Seismic Activity: A significant earthquake with a magnitude above a certain threshold (usually around 6.5 or higher) can trigger tsunami alerts.
2. Ocean Buoy Data: Buoy systems are equipped with sensors that can detect changes in sea level. A sudden, abnormal rise in sea level can be indicative of a tsunami wave.
3. Tide Gauge Readings: Provide real-time data on sea level changes. Unusual, rapid and significant increase in fluctuations in sea level, can be a sign of an approaching tsunami.
4. Earthquake Location and Depth: Shallow, undersea earthquakes are more likely to cause tsunamis.
5. Historical Data: Areas with a history of tsunamis are often given higher priority for monitoring and early warning systems.
6. International Coordination: India is part of the Indian Ocean Tsunami Warning and Mitigation System (IOTWMS), which collaborates with other countries in the region.

Mitigation:

The Ministry of Earth Sciences primarily managed these guidelines through agencies like the Indian National Centre for Ocean Information Services (INCOIS) and the National Disaster Management Authority (NDMA).

1. Early Warning System: Network of seismometers, tide gauges, and buoy systems helps for the detection of undersea earthquakes and the issuance of timely warnings.
2. Public Awareness: Educate coastal communities and residents by signage, community drills, and educational materials.
3. Evacuation Plans: Identify safe evacuation routes and locations for residents in case of a tsunami warning.
4. Coordination: Ensure coordination amoung NDMA, INCOIS, Indian Meteorological Department (IMD), and local administrations, to ensure a coordinated response in the event of a tsunami.
5. Building Codes: Enforce building codes and construction standards for more reselience.
6. Community Preparedness: Encourage community-based disaster management and preparedness initiatives. Local communities should be actively involved in planning and response efforts.
7. Research and Monitoring: Invest in research to better understand the tsunami hazard in Indian waters.
8. International Collaboration: Collaborate with neighboring countries and international organizations to share data and expertise related to tsunami warning and response.

NDMA Guidelines:

1. It would be best if you continued using a Weather Radio or staying tuned to a Coast Guard emergency frequency station or a local radio or television station for updated emergency information.
2. Check yourself for injuries and get first aid, if necessary, before helping injured or trapped persons.
3. Help people who require special assistance—Infants, elderly people,
4. Use the telephone only for emergency calls. Telephone lines are frequently overwhelmed in disaster situations. They need to be clear for emergency calls to get through.
5. Wear long pants, a long-sleeved shirt, and sturdy shoes. The most common injury following a disaster is cut feet.
6. Use battery-powered lanterns or flashlights when examining buildings.
7. Battery-powered lighting is the safest and easiest to use, and it does not present a fire hazard for the user, occupants, or building. DO NOT USE CANDLES.
8. Check for gas leaks.
9. Look for electrical system damage.
10. Watch for loose plaster, drywall, and ceilings that could fall.
11. Take pictures of the damage, both of the building and its contents, for insurance claims. Open the windows and doors to help dry the building.

Way Forward

The Indian National Centre for Ocean Information Services (INCOIS) has now developed a system that will be able to predict risk to coastal areas, the height of waves that can hit them, and even pinpoint vulnerable buildings, all in “real-time,” represents a significant improvement in India’s capacity to assess dangers following a tsunami event.