Let's understand flood, in Indian context

A flooded area in Bihar. (Photo credit: Facebook/WHO Bihar Region)

According to the Indian Meteorological Department (IMD), flood is a meteorological situation when water of a river begins to flow above the danger mark. The danger mark is fixed on the basis of average flow of the river over 25 to 50 years during monsoon period.

Drought is the situation, according to the IMD, having less than 5 cm rainfall for four continuous week any time between mid-May and mid-October. If the rainfall is less than 5 cm for any month (four continuous weeks), it is meteorological drought situation.

Flood prone areas are located practically in all parts of the country excluding the internal plateau regions. However, there has been varying tenure of flood and from that point of view, eastern India, northeastern India and eastern coastal plains are the worst affected areas as far as flood is concerned.

The IMD has divided flood into four tenures of flood and affected geographical regions:

Six-week flood region: Assam valley

4-6-week flood region: Eastern Uttar Pradesh, Bihar plain, West Bengal and isolated plain areas of the Northeast – Loktak basin and Tripura basin.

1-4-week flood region: Eastern coastal plain, Punjab, western Uttar Pradesh, Delhi Union Territory, South Gujarat especially Narmada and Tapi basins, and Kashmir Valley.

Less than one-week flood region: Central and northern Gujarat, Rajasthan, Haryana and peripheral parts of peninsular plateau.

There are some rivers, which are highly flood prone. Brahmaputra and Ganga cover about 60 per cent of flood prone areas of the country. Some flood prone rivers are Teesta, Kapoli (a tributary of Brahmaputra), Dihang and Burhi Dihang (known for flash floods).

In the Ganga system of the Himalayan rivers, the main flood causing rivers are, Mahananda, Kosi, Gandak, Burhi Gandak, Kamla Balan, Saryu, Ghaghra, Gomati, Ramganga and Yamuna. Kosi was once called the sorrow of Bihar.

In the peninsular India, the main flood causing rivers are, Son, Punpun, Ajay and Damodar, which was known as the sorrow of West Bengal once. At present, both Kosi and Damodar rivers have been managed and controlled to some extent but others continue to play the same role.

Among the East Coast river, Mahanadi, Godawari, Krishna, Cauvery and Brahmi are highly flood prone. Among west flowing peninsular rivers, Tapi and Sabarmati are highly flood prone.

In the Punjab plains, Sutlej and Beas are highly flood prone while in Haryana Ghaggar and Yamuna bring floods. The Jhelum is flood prone in the Kashmir Valley.

Besides these rivers, there are several short-distance rives, which flow on high slope and create flash flood during monsoon season.

Total area under flood-prone category, according to the Seventh Five-Year Plan papers is 320 lakh hectares where flood happens every year. Total flood-affected area is 2.42 crore hectares where flood occurs but not every year.

Causes of flood:

Flood is the manifestation of many geographical factors and, to many geographers and geologists it has become an ecological factor. This does mean that flood is bound to come in this part of the world every year. It is a flood-ecology region.

Factors:

1. Erratic behaviour of monsoon -- Sometimes the catchment area receives very high rainfall and then flood arrives. In the western India – Rajasthan, Gujarat and Haryana –torrential rain brings sudden outburst of rain which leads to flashfloods. In contrast, in the North-East, even the regular rainfall brings heavy rainfall and that is responsible for flood situation in the region.

2. Geomorphology -- Flood occurs due to geomorphological profile of central plain of India. Brahmaputra Valley is a narrow ramp valley. Similarly, the Ganga basin is sandwiched between the Himalayas and the peninsular plateaus. Both river valleys are bordered by steep rising slopes while the plains are among the flattest ones in the world.

This topographical feature brings rapid run-off from the catchment areas while the run-off in the plain moves at a slow speed. Consequently, these river basins overflow bringing flood over large areas during monsoon season.

3. Deforestation -- Deforestation in the Siwalik Himalaya has increased the volume of the run-off and therefore frequency and tenure of floods in many of Himalayan rivers.

Several peninsular rivers including small ones have become flood prone in recent years due to loss of trees in the past few decades, e.g. Ajay river has become flood-prone due to deforestation in the catchment area. Jhelum was not flood-prone earlier.

Mahananda was not so acute in bring floods. But at present all these rivers bring flood almost every year and that is related to deforestation. Several plateau districts of Jharkhand and Madhya Pradesh have fallen under flood due to deforestation and rapid run-off in these areas.

4. Soil Erosion and Siltation -- These are responsible for increased flood-frequency mainly in the central plain of the country. According to the UNEP, River Kosi is the second-most affected siltation affected river in the world, only after Hwang-ho of China.

Bed siltation occurs due to soil erosion in the catchment area and the deposition of silt in the plains owing to rivers’ inability to carry the load any further. It makes the valley shallow and whenever there is voluminous flow of water, it brings flood and water spreads in the surrounding areas.

5. Drainage Pattern -- It is responsible for the flood in the central plain. Most of the rivers make meandering courses. So, overflow brings waters of different rivers close and vast areas, thus, get inundated.

Punjab does not witness spread of water because of parallel, man-made, drainage of rivers. Although, the rivers often flow over danger mark during flood season but water does not spread. In Punjab, the doab line is always free from flood due to parallel pattern of drainage but the meandering courses of rivers in Bihar and Uttar Pradesh, and braided courses in all delta regions create floods.

Most of the rivers have wide V-shaped valleys. So, the depth of the valley is not great and any increase in the volume of water leads to overflowing and inundation of the neighbouring areas.

Again some of the rivers have created natural levee which protects one side of the valley from flooding but the other bank is flooded and cause flood over low lying areas adjacent to that bank. Bihar plain is noted for this type of flood. Western banks of rivers in Darbhanga have natural levee.

In the central Bihar, there is also flood due to overflow of the main consequent river. Its overflow prevents the inflow of tributary water channels. In fact, the water of the main river, Ganga, begins to enter the course of the tributaries and the tributaries’ water is pushed back and water spreads over vast areas, e.g. Tal area flood in South Bihar and Jharkhand, Chaur area flood in West Bihar and West Bengal. Chaurs are the floodplains situated in the abandoned courses of rivers. They form ox-bow lakes during floods.

6. Shifting Course of Rivers -- Such flooding is mainly important in regions where river have a history of shifting their course. Rivers like Kosi, Teesta, Gomati and Mahananda are facing this problem.

Kosi is now believed to have settled in its course but others are still active. All these rivers have westward shifting courses. These rivers have a tendency to migrate to west. Hence, the west banks of these rivers are constantly being eroded and the east bank extends to a huge low lying floodplain. These rivers cause phenomenal spread of water beyond eastern banks onto the vast plain.

Rotation of the earth is held indirectly responsible for the westward shifting of these rivers and the associated floodplains. Rotational impact brings westward shift of rivers. The eastern banks become low lying and vulnerable to floods.

Eastern coastal plains receive floods not simply due to deforestation and rapid run-off but also because of cyclonic rainfall and greater havoc is caused by the combination of these factors. If there is high tide situation along with cyclone, rainfall causes great damage.

Cyclone brings rainfall and high tide water on the coastal plains as well as increases the velocity of the sea waves. Tidal water enters the mouth of the rivers pushing back the river water. The water level of the river increases. The river goes in a spate. The flow of the river is reversed and low lying floodplain is taken over by the floodwater. Such tidal flooding is seen in the Mahanadi and the Godawari.

Western coastal rivers generally receive flash floods. The duration of such floods is about one week. The situation mainly occurs due to deforestation along the Western Ghats. Loss of vegetation means less obstruction to run-off.

Rapid run-off leads to greater water volume in the river valleys than the channel is capable of carrying off to the sea. This pushes the water level up in the river valleys leading overflow and inundation in the neighbouring areas.

7. Human Factors -- Floods are also caused by human factors. Ironically, flood control programmes and some other developmental programmes have indirectly contributed in greater spreading of flood. Although, multi-purpose vally projects and other power generation projects have controlled floods in the basins of some of the rivers and regions. But the problem has emerged in a different way.

Due to siltation on the beds, the reservoirs’ capacity has reduced and whenever excess water is released from that reservoir through canals and other outlets, flood is caused. Flood water even enters the areas where flood had never come previously.

The canals also face siltation problems, which get compounded by the seepage of river water from the sides of the canals into neighbouring agricultural lands. These agricultural fields become unproductive due to excess of water and behave like marshy land and are waterlogged at times even if water is not pulled from these canals. The excessive wet lands are not conducive for agriculture.

This type of flood brings greater loss as this is relatively new phenomenon and people dependent on such lands are neither prepared nor equipped to deal with such a situation. In 1995, Banka district of Bihar turned into a wasteland due to opening of two reservoirs – Chandan and Orhni.

Governmental approach to construct embankments for the protection of settlement and agricultural lands has also deteriorated the situation in many parts of the country. Now, the approach is being modified. Such programmes are now being called flood protection programmes instead of flood control programme.

Thus, several new regions, e.g. in northeastern towns of Bihar, many new settlements have fallen in the trap of flood. Flood control measures have brought new dimensions in floods in India.

Factors of Deforestation in India

Fig Tree. (Photo: MOEF GOI)

India has about 19 per cent of its area under forest while ecologically it should have had not less than 33 per cent of land under forest cover.

Although India is characterised by various types of forests but it is dwindling over a couple of centuries. Recent efforts at afforestation are but an aberration in the general trend of decades.

On an average 1.5 lakh hectare forest was lost every year between 1951 and 1980. The rate of deforestation between 1980 and 1990 was at 55,000 hectare a year while between 1990 and 1995, it stood at 4,500 hectare of 450 sq km.

Recently the rate of deforestation has declined due to two factors –

Some strong punitive measures have been taken to check deforestation.

Due to afforestation programmes, the scale of deforestation has been compensated a bit. In 1996, newly afforested area was equal in expanse to deforested area. Even the afforestation is taking place but the real acreage has been decreasing.

Deforestation is the result of a number of factors:

1   

      Agricultural progress – Two types of agricultural practices have been prevalent in India for long. These are shifting agriculture and plantation agriculture. A substantial portion of Indian population has lived in and near forests for centuries. They largely depended on gathering of forest produce to sustain their livelihood.

Now those who had gathering economy have shifted to a more settled economy. The shift in their economic practices necessitated cutting of forests. These people practiced shifting agriculture, which requires fresh and virgin land every few years.

Shifting agriculture proved to be a major factor causing wide-scale deforestation. Finally, this practice was declared illegal with laws like Jhoom Farming Prevention Act, 1976. Though, the practice continued for few more decades as it took lots of persuasion and in sensitizing people living in those areas about the legal and environmental consequences of shifting agriculture.

The effectiveness of the laws is not surmised but it has definitely contributed in slowing down the rate of deforestation. Tribal population growth rate has been very high. Nagaland has showed highest population growth rate for long. Swelling tribal population and need for more dwelling units in their homeland put more and more pressure on forest land which saw vanishing trees.

In the areas where plantation form of agriculture is practiced, deforestation has not much increased in last few decades. Sustained efforts by various governments have ensured that after 1980, plantation area is not increased by cutting down the forests.

After the World War I, tea and other crops brought more areas under plantation acreage in India. In Himachal Pradesh, open forest areas were given to tea plantation even till 1985-86. But, this practice has almost stopped completely.

2.       Fuel wood pressure – A 2015 report by Indiaspend.com said that more than 67 per cent rural households in India depended on firewood or wood chips. It also stated that over 95 per cent rural households in six states – Bihar, Jharkhand, Madhya Pradesh, Odisha, Uttar Pradesh and West Bengal still used traditional fuel such as firewood, dung cakes and agricultural waste for cooking.

According to the Access to Clean Cooking Energy and Electricity Survey of States (ACCESS), only 14 per cent households in rural areas across six states surveyed used biogas, liquefied petroleum gas (LPG), electricity or natural gas as their primary source for cooking.

Another IndiaSpend report said that the use of LPG increased 7.5 times between 1993-94 and 2011-12 in rural areas across India. About 2 per cent rural households used LPG in 1993-94 while about 15 per cent households used LPG in 2011-12.

This overdependence of vast majority of rural India has caused massive cutting of trees from forests – big and small. Many state governments have passed laws to declare cutting of trees for fuel illegal e.g. in Kerala, Garhwal area of Uttarakhand, most of northeastern states and states along Western Ghats.

3.       Resource utilisation pressure – Various industries and economic activities depend on utilisation of forest resources. Forest products are used and trees cut for paper and pulp industry, woodcraft, chemical and drug industries.

The pressure from woodcraft industry is particularly huge in Karnataka, Himachal Pradesh and Jammu and Kashmir. Wooden packing of fruits worked like an industry in itself till 1996 in the country. It was particularly taking toll on forests in the northeast and Himalayan states. The practice has become less intensive in recent years.

Tribal subsistence economy also promotes destruction of forests for resource purposes but they have not been able to make economically competitive use of forests.

The loss is much more in comparison to economic gain. The economic gains from forest dependent industries are short-term while the loss is permanent.

4.       Livestock pressure – Himachal Pradesh and Jammu and Kashmir are among the states which have witnessed serious deforestation on account of livestock pressure. It has caused indirect deforestation.

Trans-Himalayan tribes, as part of their traditional practice, take their livestock towards higher altitudes for grazing purposes during spring. Tall grasses could hardly emerge in the region.

Lack of tall grasses results in an ecological situation where horizon A of the soil is not properly developed. In that situation, the vegetation growth becomes scanty.

Continuous grazing on newly emerged grassy surface causes uprooting of grass which leads to soil erosion reducing the capacity of the soil surface to hold running or rainy water. This leads to deterioration of ground water table which ultimately causes decay of tree vegetation in the region.

5.       Development pressure – River valley projects have caused massive deforestation in India. About 4,97,000 hectare or 4,970 sq km forest was lost to river valley projects in the Himalayan region between 1952 and 1977.

Besides, about 1,27,000 hectare of forest was lost in the Himalayan region for large scale industries and another 57,000 hectare was lost to road construction in the same zone. Deforestation has continued for mining, railways, roadways, airports and helipads in the hilly regions.

Chhotanagpur region of Jharkhand has witnessed massive deforestation due to developmental pressure.

6.       Wild fires – Among other factors for deforestation, wild fires are major contributor. High inflammability of trees – especially the old ones - is one big reason for loss of forest. Collision of trees, branches due to high wind speed during hot summers causes huge wild fires in forests. Western Ghats have witnessed several such fires.

Human errors – forced and unforced, both – are also responsible for forest fires. This is a major cause for destruction of forests in tribal dominated areas. Throwing of untrashed beedis by tribals or cigarettes by tourists and other visitors has led to many wild fires.

It is suspected that such fires were deliberately caused by some people with vested interests. In some cases, terrorists and insurgents have created fires in forests to escape security forces or to serve their own purposes.

1993-94 was a bad year for forests. According to the Forest and Environment Ministry’s data 1,428 incidents of wild fires were reported from Maharashtra in 1993, 644 forest fires in Gujarat, 600 in Himachal Pradesh, 461 in Madhya Pradesh, 418 in Jammu and Kashmir, 258 in Uttar Pradesh, 112 in Kerala and 90 in Tamil Nadu.

 In April-May, 2016 forests of Uttarakhand and Himachal Pradesh kept burning for several weeks. Some 1,600 incidents of fires were reported during the period. Air Force helicopters were pressed into use but did not help much to contain the fire. Finally, heavy rain on May 3 slowed down the fire, which went off after raging for few more days. About 4,048 hectare forest was lost to these fires.

7.        Illegal cutting of trees –Kerala is facing big problem due to cutting of trees on large scale. Problem is not less alarming in Tamil Nadu, Karnataka, Himachal Pradesh, Jammu and Kashmir and the northeastern states. Those who get the contracts for cutting of some trees, are suspecting to be the ones who have ended up damaging the forest the most by overcutting.

8.      Tree cutting by tribals – People living in the forest areas are generally those belonging to tribal groups of the Indian population. They have been cutting trees for various kinds of usage. Though, traditionally, such groups have been very forest-friendly but their age practices have become corrupt. Many have shed the old practice of planting more trees in their neighbourhood while continue to believe that cutting trees from forest is their inherited right.

9.       Population growth – Population growth rate in the hilly regions has been high. So, population pressure has caused damage to forests. Immigration in hilly regions is another reason contributing to population pressure on forests of such areas.