Flood Management – Part II

Why in news?

Recently, North India including Delhi witnessed heavy rainfall resulting in flood.

To Know about Part-I - Click Here.

What is flood?

• Flooding is an overflowing of water onto land that is normally dry.
• Types of Flood
  • Flash floods - It is caused by rapid and excessive rainfall that raises water heights quickly, and rivers, streams, channels or roads may be overtaken.
  • River floods - It is caused when consistent rain or snow melt forces a river to exceed capacity.
  • Coastal floods - It is caused by storm surges associated with tropical cyclones and tsunami.

Urban flooding refers to the inundation of property in a built environment, particularly in more densely populated areas, caused by rain falling on increased amounts of impervious surfaces and overwhelming the capacity of drainage systems.

What affects the rainfall pattern?

• Extreme rainfall events are increasing both in intensity and frequency as climate change is heavily impacting the monsoon pattern in India.
• Longer rainy season - In recent times, rainfall in India is increasingly taking place in short, intense bursts.
• Persistent warmer ocean currents - Due to climate change oceans continue to remain warm even after the traditional monsoon season is over.
• Global warming -  It is the reason for extreme rainfall events as the warm atmosphere can hold more water which may result in heavy downpour of rain.
• Persistence of intense La-Nina - It is further worsened by negative Indian Ocean dipole, warming of East Indian Ocean which results in prolonged monsoon.
• Warming of Arabian Sea - Due to global warming, temperature   is 1.2–1.4 °C higher than the temperature witnessed four decades ago.
  • Example- In 2023 Gujarat witnessed heavy rainfall due to Cyclone Biparjoy which was formed in Arabian Sea.

What are the consequences?

• Human loss and property loss - Every year, millions of people become homeless and washed away due to floods.
• Spread of communicable diseases - Waterborne diseases (cholera, typhoid fever etc.,), vector-borne diseases (dengue, malaria etc.,) are caused during flood.
• Impact on agriculture - Floods destroy a large number of crops impacts the food security of the country. Livestock also gets displaced during floods.
• Disruption of communication - Flood damages transportation links such as bridges, rail, and power plants thus causing communication disruption.
• Economic and social disruption - The economy comes to a standstill as people are forced to move to another place.

What efforts were taken regarding flood management?

Government measures

• Flood management falls under the purview of State Government.
• The Union Government supplements the efforts of the States by providing technical guidance and also promote financial assistance for management of floods in critical areas.
• NDMA - National Disaster Management Authority was set up in 2005 for prevention and mitigation effects of disasters including flood disasters. 
• Central Water Commission (CWC) - It was set up in 1945 for achieving the goal of furthering and promoting measures of flood control, conservation and utilization of water resources.
• Ganga Flood Control Commission - It was set up in 1972 for preparation of comprehensive plan of flood control for Ganga Basin States

• Brahmaputra Board - The Government set up Brahmaputra Board under Brahmaputra Board Act, 1980 to survey and conduct investigations in Brahmaputra and Barak valley.
• National Water Policy (2012) - It suggested that through reservoir operation, the flood cushion can be set up to reduce the trapping of sediment during the flood season.
• National Hydrology Project (2016) - World Bank funded Central sector scheme which gathers hydro-meteorological data that will be stored and analyzed on a real-time basis.
• Flood Management and Border Areas Program (2017-20) - It is implemented for effective flood management, and soil and anti-sea erosion.

Engineering /Structural Measures

• Dams -  Example - Idukki dam across river Periyar, Gandhi sagar dam across river Chambal etc.,
• Dykes - Dikes, also called levees, are earthen embankments that are raised parallel to the river flow at some suitable distance from the deep river.
• Reservoirs - Reservoir is formed upstream when a dam or a bund is built across a river. Such a reservoir will store ample water that enters the river upstream of the dam.

Administrative / Non-structural Measures

• Early warning system - It will help in timely evacuation of people and movable property to safer grounds.
• Flood plain zoning - Flood-plain zoning measures aim at demarcating zones or areas likely to be affected by floods of different magnitudes or frequencies and probability levels.

What lies ahead?

• National Flood Commission (Rashtriya Barh Ayog 1980) had recommended solutions covering the entire gamut of the flood problem in the country like data collection, legislation enforcement, flood plain zoning etc.,
• Conducting monsoon audits regularly can mitigate the flood effects.
• Greening the cities is the need of the hour.
  • East Kolkata’s wetlands have been an effective flood defence mechanism that help treat a large share of the city’s sewage, produce half of the city’s fresh vegetables.
• Adopt best practices from state like Tamilnadu, which is successful in implementing Rain Water Harvesting (RWH) structures.

References

1. Indian Express| Prevent disruptions by flood
2. WHO| About Flood
3. NDMA| Flood Management in India
4. Indiawris| Flood Management