Floods

Introduction

• Floods occur due to encroachment of human beings and extended human settlement. This increases the level of water in the channels.
• Characteristics of floods are that they are comparatively slow in occurrences and often happen in well-identified regions mostly during the rainy season.

Cause of flood:

• Heavy rainfall for a longer period.
• Insufficient capacity of rivers to carry the high flood discharge.
• Landslides hindering streams.
• Cyclones and typhoons cause floods too.
• Flash floods happen because of high rates of water flow and also due to the poor permeability of the soil.

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Distribution of Floods in India

• 23 out of 35 states and union territories in the country are subject to floods and Rashtriya Barh Ayog (National Flood Commission) recognized 40 million hectares of the terrestrial region as flood-prone.
• Assam, West Bengal and Bihar are amongst the high flood-prone states of India. 
• Separately from these, most of the rivers in northern India like Punjab and Uttar Pradesh, are also susceptible to infrequent floods.
• It is noticed that states like Rajasthan, Gujarat, Haryana and Punjab are getting inundated in recent decades because of flash floods. This is partially because of the changing pattern of the monsoon and partially because of the blockage of most of the watercourses and river channels due to human activities.
• Sometimes, Tamil Nadu experiences flooding during November and January because of the retreating monsoon.

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Consequence and Control of Floods

• Recurrent flooding of farming land and human settlement has grave consequences on the national economy and society.
• Floods do not just destroy valuable crops every year but also damage physical infrastructure such as roads, rails, bridges and human settlements.
• Millions of people are rendered homeless and are also washed down along with their cattle in the floods. Spread of diseases like cholera, gastro- enteritis, hepatitis and other water- borne diseases spread in the flood- affected regions.
• Nevertheless, floods make a few positive contributions too:
  • Each year, floods deposit fertile silt over farming fields, which is good for crops.
  • Majuli (Assam), the biggest riverine island in the world, is the best example of good paddy crops after the annual floods in the Brahmaputra.
  • New predators and prey are introduced to the areas, balancing the aquatic population.
  • The flood offers groundwater recharge and high biological productivity.

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Mitigation of floods

• There should be a master plan for flood control and management for each flood susceptible basin area.
• Adequate flood-cushion must be provided in water storage projects, wherever possible, to ease better flood management.
• In flood-disposed areas, flood control must be given overriding consideration in reservoir regulation policy even at the cost of foregoing some irrigation or power benefits.
• While physical flood protection works like embankments and dykes will continue to be necessary, increased emphasis should be laid on non- structural measures like flood prediction  and warning, flood plain zoning and floodproofing for the minimization of losses and to reduce the repeated spending on flood relief.
• There should be strict instruction of settlements and economic activity in the flood plain regions along with floodproofing, to lessen the loss of life and property on account of floods.
• The flood estimating events should be modernised, value-added and stretched to other uncovered zones.

Flood Prevention and Mitigation

• National Flood Risk Mitigation Project (NFRMP)
  • It Aims at ensuring that preparations are in place to mobilise the resources and ability for relief, rehabilitation, rebuilding and recovery from tragedies besides creating consciousness among susceptible communities.
  • NDMA has been delegated to prepare a Detailed Project Report (DPR) on the Flood Risk Mitigation Project.

• Flood Management Programme

  • The FMP scheme was launched by the Ministry of Jal Shakti under the central plan at a total cost of 8000 crores during the 11th Plan period (2007-12).
  • The scheme delivers financial aid to the state governments for undertaking flood management works in critical areas.

NDMA Guidelines:

Structural Measures:

• By building reservoirs, checking dams etc. to store extra water in case of heavy discharge.
• Diversion of floodwater towards naturally and artificially built channels, wetlands etc. to reduce the impact.
• Flood protection structures in the form of embankments, walls to limit the overflow of floodwater towards the habitable areas.
• Activities like desilting, dredging increase the carrying capacity of the channel and reduce the spillover.
• In the catchment area, watershed management measures like tree plantation to increase the vegetation cover, reduce the erosion and run-off, increase the porosity of the soil and tackle any sudden surge.

Non-structural measures:

• Floodplain zoning to regulate land use and reduce the damage due to flood. It involves activities like preventing habitation along low- lying and frequently flooding areas, Demarcating areas to be evacuated first in case of occurrence of flood and highlands where people are to be shifted during the flood.
• Flood proofing in the form of constructing flood shelters on the highlands, ensuring availability of food and fodder, flood proofing communication channels and ensuring unhindered availability of health services in case of occurrence of flood.
• All government departments and agencies must prepare their own flood management plans depending upon the topography, frequency of flood and vulnerability of the population.
• In a step towards community participation in flood mitigation, a centrally sponsored scheme by the NDMA “Aapda Mitra” has been launched to impart training to 200 community volunteers in 30 most flood-prone districts across the country to assist in flood rescue and rehabilitation.

Conclusion 

 Flood is a natural disaster which occurs due to the rise of water in the channels by the impact of human settlements. The main causes of flood include heavy rainfall for a longer period of time and insufficient capacity of rivers to carry the high flood discharge. Floods can also occur due to landslides hindering streams and cyclones and typhoons. When the flood occurs continuously, it has grave consequences on the national economy and society. It not only damages the valuable crops every year but also damages physical infrastructure such as the roads, railways, bridges and human settlements. We can control floods by making a master plan for the control and management of each flood susceptible basin area. We can also prevent floods by building reservoirs, checking dams and artificial channels.