Disaster Management: Floods | UPSC Mains: Internal Security & Disaster Management PDF Download

Floods

• A high water level that overflows the natural banks along any portion of a stream is called a flood. Thus, Floods are commonly associated with a stream or river.
• A stream floods when its discharge is greater than the capacity of its river channel. Excess water flows over the river banks and submerges the adjacent land which is usually dry. When it happens, the channel and the flood plain together allow passage of water.

• Floods and Droughts on one hand are cumulative hazards. On the other hand, due to the peculiar nature of the Indian monsoon floods and droughts may affect different pockets of the country at the same time of a year. Thus, floods can be seasonal, and sometimes flash floods also occur.

Causes of Floods

Unlike other natural disasters, the causes of floods are well established. They are relatively slow in occurrences and often occur in well-identified regions and within expected time in a year. There are many causes of floods. Some of the Important causes of floods are:

Natural Causes

• Heavy rainfall and cloud bursts – Heavy concentrated rainfall reduces the capacity of rivers to accept any more surface run–offs due to rainfall and as result water spills over to adjoining areas. Clod bursts are basically thunderstorms which yield very heavy rains (>50 – 100 cm within few hours). All of these can cause extensive damage within short span of time.
• Heavy melting of ice and snow,
• Changes in river systems and large catchment areas,
• Sediment deposition/Silting of river beds,
• The collapse of dams,
• Transgression of sea at the occasion of tropical cyclone, and
• Tsunami in coastal areas and landslides in course of rivers

Man-made/Anthropogenic causes

Unlike other natural disasters, human beings play an important role in the genesis as well as spread of floods.

• Deforestation – It leads to soil erosion and Landslides. It is responsible for the loss of vegetation and soils which holds down the soil that acts as a sponge and absorbs most of the water when it rains. It also leads to silting of river beds.
• Unscientific use of land utilization and bad farming practices – Some farmers have caused soil and water to flush into the rivers by leaving fields bare. Even choosing the wrong direction to plough in can cause floods.
• Increased Urbanisation – It has reduced the ability of the land to absorb rainfall through the introduction of hard impermeable surfaces. This results in an increase in the volume and rate of surface run-off as less water infiltrates into the ground.

Consequences of Floods

Though floods are temporary inundation, they cause extensive damage as the frequency, intensity, and magnitude of floods are increasing day by day. Floods cause more damage than any other single disaster now a day.

• Floods are taking thousands of lives and loss of property every year.
• The crops get adversely affected by the temporary loss of the agricultural season and fertile soil cover.
• It leads to changes in habitats, destruction of habitats, and loss of animals due to drowning.
• Disruption of the lines of rail, road communication, and essential services creating great problems for the movements of people and goods.
• Spread of water-borne and infectious diseases like cholera, gastro-enteritis, etc. immediately after floods.
• Positive consequences – Floods also make a few positive contributions. Every year floods to deposit fertile silt over agricultural fields which are good for the crops. It also recharges the groundwater table.

Flood distribution in India

• Floods have been a recurrent phenomenon in India and cause huge losses to lives, properties, livelihood systems, infrastructure, and public utilities. India’s high-risk vulnerability is highlighted by the fact that 40 million hectares out of the geographical area of 3290 lakh hectares are prone to floods, which is 12%.
• State-wise study shows that about 27% of the flood damage in the country is in Bihar, 33% in Uttar Pradesh and Uttarakhand, and 15% by Punjab and Haryana.
• The major flood areas in India are in the Ganges – Brahmaputra – Meghna Basin which accounts for nearly 60% of the total river flow of the country.
• Distribution of flood plains –
  • Brahmaputra River Region
  • Ganga River Region
  • North – West River Region
  • Central and Deccan India
• The middle and lower courses of North Indian rivers such as Ganga, Brahmaputra, Kosi, Damodar, Mahanadi, etc. Are prone to floods due to very low gradient. The flat plains do not have enough gradients for the outlet of drainage.
• Peninsular rivers are mature and have hard rock beds, so they have shallow basins. This makes them prone to flooding.
• Parts of the Eastern coasts of India are particularly prone to cyclones during October – November. These cyclones are accompanied by strong winds, storm surges, tidal waves, and torrential rains.

Flood Control Management

The central and State Government have taken the following steps to reduce the menace of floods:-

Flood Forecasting-

• It involves giving prior information regarding the occurrence of floods. It is of immense help in taking timely action to reduce the loss of human lives, livestock, and movable properties. The central water commission started flood forecasting in November 1985, when the first flood forecasting station was established near the old railway bridge of Delhi.
• At present, there are 175 flood forecasting stations on various rivers in the country. The flood forecasting network covers the flood-prone states and UTs where the station issues daily flood warnings throughout the flood season from May to October.

Reduction in Run-Off-

• It is one of the very effective methods of flood control. Runoff can be reduced by inducing and increasing infiltration of the surface water into the ground in the catchment areas. This can be done by large scale afforestation, especially in the upper catchment areas.

Construction of Dams-

• Dams and multi-purpose projects are being constructed across the rivers to store the surplus water in the reservoirs. A number of such reservoirs were constructed during the 1st Five-year plan. In the subsequent plans also, many dams have been constructed to reduce the run-off and to store and release water under controlled conditions.

Channel Improvements and Construction of Embankments-

• The channels of the rivers more prone to flood are improved by deepening and widening. The water of those rivers is also diverted into canals.
• The central and state governments have constructed a number of embankments along the rivers to reduce the menace of floods. Such embankments have been constructed along the Brahmaputra, Krishna, Godavari, Gandak, Kosi, and Narmada, Tapi, son, satluj, and their tributaries.

Flood Plain Zoning –

• It is also an important step to control floods which are based on information regarding flood plains, particularly the identification of floodways in relation to land use.

NDMA Guidelines for Flood Management

Government Programmes for Flood management

• In addition to the steps given above, legislative measures are taken to restrict the construction of industrial and residential units in flood-prone areas. The construction of buildings, factories, houses in the zones adjacent to river channels should be prohibited. The areas occasionally flooded should be under green belts and social forestry should be encouraged in the flood plain.
• National Flood Control Management Programme, 1954
  • At the national level, the first policy statement on flood control in India was established on 3 September 1954. This policy statement envisaged 3 types of flood control measures, namely, Intermediate, short and long term.
• National Hydrology Project, 2016
  • It is a central sector scheme with 50% of the outlay amount received from the World Bank loan. This project gathers hydro-meteorological data which will be stored and analyzed on a real-time basis and can be seamlessly accessed by any user at the State/District/Village level.

Mitigation (Post – Flood Management)

• Rescue Operations
• Speedy restoration of the transport system
• Supply of safe drinking water
• Repair of power, telephone, and sewerage lines
• Supply of food, shelter, and clothing
• Survey to assess the loss and compensation
• Rehabilitation of properties
• Desilting and dewatering of inundated areas
• Contingency Plan for the agriculture sector