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.