ASTRONOMY IN INDIA:

When water cannot stay contained anymore!!
By
Bhaskar Karnick & V.Krishna Moorthy
Contents

01. Introduction
02.
What is Flood
03.
Flood in Ancient times
04.
Flash Flood
05.
Most flood affected Regions
06.
History of Himalayas
07.
Floods in waiting
08.
Effect of Global warming
09.
Effect of Earthquakes
10.
Need to plan
11.
The other side of the story
12.
Water management
13.
Reference Links

Introduction

Flood does not mean much to the people who have not experienced it. In India Flood is experienced by many Indian states. There are states which see draught and Flood in the same region in different years, and in different seasons of the same year. There are states which witness flood as a routine phenomena every year. The regions which are Flood prone, like Assam and Orissa, see increase in the intensity of floods from year to year. Once after a gap of  few years a mega-flood appears, killing many people, destroying homes, cattle and agriculture lands. Even after many development programmes of building Dams, ridges etc "Flood prediction and control" remains elusive.

What is flood?

A high water flow or an overflow of rivers or streams from their natural or artificial banks, inundating adjacent low lying areas is called Flood. 

Flood in Ancient times

Flood in Sanskrit pluti,  Latvian Word, pludi,  German Flut,   Dutch vloed,  Old English flod and flood in modern English.

Call it myth or religious belief, from around the world, there are stories of  great civilizations and vast expanses of land destroyed  by cataclysmic floods. Great epics of India and the biblical stories talk of big floods. In the last fifty years, with the invention of scuba diving, systematic marine archeology been possible.  Research since the 1970s in this field, suggests that there were three global super-floods: 15,000 to 14,000 years ago; 12,000 to 11,000 years ago; and 8,000 to 7,000 years ago. The second period ties in with the date Plato ascribed in the Timaeus and Critias to the destruction by earthquakes and flooding of Atlantis, and with the Tamil myth of the submerging of the fabled land of Kumari Kandam. The first Tamil sangam was supposed to have met about 10,000 BC, convened by the rishi Agastya, the mythical Apostle of the Decccan, and even the gods participated in its deliberations. It was held on Mount mahendra in the Kumari Nadu and lasted for four thousand four hundred and forty years. But a great flood swept over the country and nearly all the writings perished, although fragments of a work known as the Agattiyam were saved.

Flash Flood

A flash flood is the fastest-moving type of flood.

In many arid regions of the world, the soil has very poor water retention characteristics, or the amount of rainfall exceeds the ground's ability to absorb water. Flash flooding occurs when the ground under a storm becomes saturated with water. Many things can cause a flash flood. Generally they are the result of heavy rainfall concentrated over one area. Most flash flooding is caused by slow-moving thunder storms, thunder storms that repeatedly move over the same area, or heavy rains from hurricanes and tropical storms.

Flash flood flows through  low-lying areas, rivers and creeks. The runoff collection in low lying areas flows rapidly downhill. As a result, anything in its path is swept off, suddenly in rising water. These most often occur in dry areas that have recently received precipitation, but the flash flood can flow for a long distance as long as there is a path downhill.

Flash floods can also be caused by other influences. Ice jams can block the normal course of a river, leading to flooding. In addition, dam breaks have been known to cause flash flood conditions. The Johnstown, Pennsylvania dam break of 1889 is an example of a devastating flash flood. Flash floods are extremely dangerous because of their sudden nature; more than half of the fatalities attributed to flash floods are of people swept away in vehicles when trying to cross flooded area.

The quick change from calm to raging river is what catches people off guard, making flash floods very dangerous. A Flash flood is a specific type of flood that appears and moves quickly across the land, with little warning that it's coming. Dam failures can create the worst flash flood events. When a dam or leeks or breaks, a gigantic quantity of water is suddenly let loose downstream, destroying anything in its path.

Many a times land slide on the hills, blocks a valley creating a artificial dam, this creates a lake. The lake fills due to rain and melting snow, grows bigger and bigger and finally the dam created by land slide gives way, releasing un controlled water in the rivers. The flood created gives only few hours of warning and can engulf large areas of habitat. There are many lakes formed regularly in Himalayas due to land slide.

Flash flood waters move at very fast speeds. They have the power to move boulders, tear out trees, destroy buildings, and obliterate bridges. Walls of water can reach heights of 10 to 20 feet and generally carry a huge amount of debris with them.

Coastal Flood - Hurricanes and tropical storms can produce heavy rains, or drive ocean water onto land. Beaches and coastal houses can be swept away by the water. Coastal flooding can also be produced by sea waves called tsunamis, giant tidal waves that are created by volcanoes or earthquakes in the ocean.

Flash Floods in Arroyos - An arroyo is a water-carved gully or a normally dry creek found in arid or desert regions. When storms appear in these areas, the rain water cuts into the dry, dusty soil creating a small, fast-moving river. Flash flooding in an arroyo can occur in less than a minute, with enough power to wash away sections of pavement.

River Flood - Flooding along rivers is a natural event. Some floods occur seasonally when winter snows melt and combine with spring rains. Water fills river basins too quickly, and the river will overflow its banks. Often the land around a river will be covered by water for miles around.

Urban Flood - As undeveloped land is paved for parking lots, it loses its ability to absorb rainfall. Rain water can not be absorbed into the ground and becomes runoff, filling parking lots, making roads into rivers, and flooding basements etc.

Most flood affected Regions

The most affected regions in India are Assam, Bihar, and Uttar Pradesh The rivers Brahamputra, Ganges and their tributaries carry ton of debris and water through out the year, in monsoon the rain in the catchments area provides more water to the river, eventually the water flowing exceed the capacity of river and the high flow of water breaks the man made ridges, flooding the whole area with enough water to cause havoc.

To understand the mechanics of flood it is necessary to know the history of Himalayas from the ancient times.

State-wise Areas liable to Floods:

State Area liable to Floods 
(million Ha.)
1. Andhra Pradesh 1.39
2. Assam 3.15
3. Bihar 4.26
4. Gujarat 1.39
5. Haryana 2.35
6. Himachal Pradesh 0.23
7. Jammu & Kashmir 0.08
8. Karnataka 0.02
9.Kerala 0.87
10. Madhya Pradesh 0.26
11. Maharashtra 0.23
12. Manipur 0.08
13. Meghalaya 0.02
14. Orissa 1.40
15. Punjab 3.70
16. Rajasthan 3.26
17. Tamil Nadu 0.45
18. Tripura 0.33
19. Uttar Pradesh 7.336
20. West Bengal 2.65
21. Delhi 0.05
22. Pondichery 0.01
Total 33.516

Source: NIC

History of Himalayas

According to the most accepted geological theories, India once belonged to an Island continent called Gondwanaland and was separated from the Eurasian continent by the primordial Tethyan ocean. One billion years ago, the Aravallis, whose eroded remnants are visible around Delhi, formed a chain higher than the Himalayas today. Over millions of years these mountains suffered the forces of erosion and their sediments were deposited in the Tethyan ocean. Then 140 million years ago, India began it's northward movement, on a collision course with the Eurasian continent. The generally accepted proposed codification date of 1200 BC, first established by Max Muller in 1890, does not signify either the Vedas' date or era of origin. Many researchers now accept that their composition lies long before in India's oral tradition and that they could be the creation of the Indus-Sarasvati civilization, inferring that there was a movement of language from India to Europe rather than from Europe to India.

The Vedas themselves, however, contain an account of their creation: the story of Manu, India's Noah. Graham Hancock in his book on Under World - The mysterious origin of civilization, draws close ties between the story of Manu, that of the Sumerian flood survivor Ziusudra, the ancient yuga theory of the cyclical destruction and rebirth of worlds, and the Seven Sages, a group of "wise men" whose duties include the preservation of the knowledge contained within the Vedas - the ancient traditions of India itself . . . "Manu and the Seven Sages retreated to the Himalayas from a place that was not the Himalayas at the time of a terrible oceanic flood, and that they brought with them from their antediluvian homeland not only the Vedas but also all the 'seeds' that would be necessary to re-establish permanent food-producing settlements".

There is also strong evidence that nearly half the total melted water released at the end of the last Ice Age was concentrated into these three relatively short periods. Such events would have had a momentous impact on the human inhabitants at that time, leaving a marked impression on oral tradition, the original transmitter of all ancient myths.

The point where the two continents were joined is known, appropriately, as the Indus- Yarlung Suture zone, marked by the courses of these two greatest rivers of the Kailash. After 60 million years, the Indian and Asian plates became closely welded along this suture zone. The northward movement of India continued but at a slower rate - 2-3 centimeters per year.

And what birth pangs.... as a result of the collision itself, and the related contraction of the Tethyan ocean, all the rocks of this area, from the mountains of then northern India to the oceanic crust, and the deep sea sediments of the Jurassic and Cretaceous ages, joined in the formation of the Himalayas.

This then is the result of those ancient events ..... each layer tells the story of the play of millions of years of brute force by nature.

The Himalayas as we see them today went through some distinct epochs of uplift. First came the Trans. Himalaya. South of this is the high Himalayan region, where the range reaches it's highest points. Here we find old crystalline rock, the oldest core material in the entire Himalayas, almost 2 billion years old, the bottom layers of the compacted Tethyan sediments. This is known as the main central thrust.

As the Himalayas rose the forces of erosion kept pace, leading to the formation of a contiguous lower range of hills known as the Shivaliks. Made of erosion material

from the still rising Himalayas, their sediments reflect the history of the up thrust of the emergent Himalayas. Numerous fossil finds allow the Shivaliks to be dated with accuracy and provide evidence of the comparative youth of the Himalayas.

In the second phase of upheaval, further uplift of the central axis took place. It was now that the great peaks of the Garhwal himalaya..Nanda devi etc achieved their present eminences. In this period, intrusions of young granites, known as leucogranites because of their whitish colour, took place in the highest peaks.. such as the Bhagirathi sisters and Shivling.

The last up thrust affected not only the Himalayas, Transhimalaya and the Karakorum, but also the whole of the Tibetan region. With an area of 2.5 million square kilometers, this region is the highest land mass on earth and in the last 1 million years it has risen by nearly 5,000 meters, an average of 4-5 millimeters per year.

The uplift continues even today at a measurable 10 meters every hundred years. Mount Everest has itself risen 8.2 meters in the last 100 years.

Very little is known about the start, duration and extent of the Ice ages in the Himalayas. Geologists have however determined that the second last was the most severe. The period after this major ice age saw a marked retreat of the glaciers and this was also the period that most Himalayan lakes came into being, amidst the ice polished rock landscape. The Pangong and the Chandratal are classic examples of such glacial remnants.

Large lakes were also formed as rising rivers were blocked by the emergent ranges. As the rising Pir panjal blocked the Jhelum it turned, what we know as The Vale of Kashmir, into a lake. This primeaval lake, called the Karewa, drained, and from it's sediments, pieces of primitive tools have been recovered - our only evidence of a pre ice- age culture in the Himalayas.

All the major rivers of the Himalayas have their source in the holy Kailash region. The Indus to the north, the Yarlung -Brahmaputra in the east, the Sutluj in the west and the Ganga, Karnali streams to the south and southwest. This amazing situation, making Mt. Kailash the literal lynchpin of the Himalaya, is the result of a 30 million year old upthrust of the Kailash range at a time when the Himalayas were in the slow, initial phase of their formation.

Two of these great rivers, the Indus and the Yarlung-Brahmaputra, were forced to flow along the lines of the suture zone in an east west direction, only penetrating the range at it's eastern and western extremities.

To further confound matters, this penetration takes place at points of highest uplift, Nanga Parbat in the west and Namche Barwa in the east. The cutting action of the other rivers kept pace with the rising Himalaya and they come right through the range at some of the highest points.

In the East, the Yarlung Tsangpo parallels the Himalaya till it comes to the great axial bend at Namche Barwa. Then, cutting one of the deepest gorges on earth, three times as deep as the Grand canyon, it enters the plains of Assam.

The sources of all major Himalayan rivers lie, therefore, on the north side of the great range and besides the Kailash group, include most larger Himalayan rivers.

These rivers are the principal architects of the Himalayan landscape and each river system has created it's own unique geomorphology. The Indus and it's tributaries like the Zanskar and the Suru in the transhimalaya. It's major Himalayan tributaries which are river systems in their own right ... the Chenab, Ravi, Beas and the Sutlej. Further east the Garwhal

 

himalaya is the domain of the Ganga and it's feeder streams while the Teesta drains the Sikkimese himalaya. Beyond, in Arunachal is the true lower catchement of the great Brahmaputra river system.

The gradual rise of the Himalaya took place in a series of long, curvilinear, parallel folds, and in this stupendous upthrust of the earth's crust, was created a mountain range that contains all the worlds mountains over 7,000 meters in height, and constitutes the line of demarcation between two of the world's great faunal realms - the Oriental to the south and the Palearctic to the north. Here we find compressed into a few tens of kilometers, the most abrupt environmental changes in the terrestrial world.

Floods in waiting

More than 40 lakes in the Himalayas could burst their banks at any time and flood communities up to 100 kilometres downstream, according to a new UN study. Very few of the people at risk would get any advance warning.

The analysis of more than 5000 Himalayan glaciers and lakes revealed 20 in Nepal and 24 in Bhutan that are at bursting point. Hundreds more lakes elsewhere in the Himalayas remain un surveyed.

The lakes are formed as mountain glaciers melt, a process much accelerated by global warming. The water is kept in place by ice or piles of sediment, known as moraines, that were deposited when the glacier was at its longest. But as the lakes grow, the moraines are starting to collapse and every monsoon season, the risk of a disaster grows.

"Unless urgent action is taken, any one of these lakes could burst its banks with potentially catastrophic results," says Surendra Shrestha of the UN Environment Programme. He warns that just two of the identified lakes have early warning systems that would alert those that live in the path of the threatened flood.

There have been 12 glacial lake bursts in Tibet since 1935, says Pardeep Mool of the International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu, who carried out the new survey. There have been three major bursts in Bhutan since 1950 and a similar number in Nepal, he says.

When the Sangwang Cho glacial lake in Tibet burst in 1954, the flood damaged a city 120 kilometres away. A 15-metre wall of water burst from the Dig Tsho lake in Nepal in 1985, destroying 14 bridges and drowning dozens of people.

Two years ago, engineers in Nepal lowered one lake, Tsho Rolpa, by three metres to ward off imminent collapse. They installed sensors in the river bed below the lake that will set off sirens in villages below, giving about 15 minutes warning and potentially saving 6000 lives.

But this arrangement remains unique in Nepal because there is no money to help other threatened communities, says Mool.

Effect of Global Warming

The global climatic change during the first half of the twentieth century has brought a tremendous impact on the high mountainous glacial environment. Many of the big glaciers melted rapidly and gave birth to the origin of a large number of glacier lakes. Due to the faster rate of ice and snow melting, possibly caused by the global warming, the accumulation of water in these lakes has been increasing rapidly and resulting sudden discharge of large volumes of water and debris and causing flooding in the downstream. Glacial lake outburst flood (GLOF) causes disasters to life and property along the downstream, results serious death tolls and destruction of valuable forests, farms and costly mountain infrastructure.

In the Himalayan region, it has been observed that the frequency of the occurrence of GLOF events has been increasing in the second half of the twentieth century. The recent catastrophic GLOF event in the Nepal Himalaya known as the Dig Tsho GLOF in 1985, has destroyed the Namche small hydel project that was built at the cost of US$ 1.5 million approximately. Accurate and timely information on the spatial locations and regular monitoring of the glacier lakes' behavior is needed, to prevent and monitor the GLOF hazards and assess the damages to be occurred in the near future. Modern information tools such as Remote Sensing and GIS could play a lead role in identifying potential risk lakes and monitoring the GLOF events in near real time.

UNEP through its facilities at Environment Assessment Program for Asia-Pacific (EAP.AP), Asian Institute of Technology, Bangkok, is trying to establish an operational early warning system to monitor GLOF hazards in the Hindu Kush Himalayan region. The expected outputs of the proposed study are (i) an inventory of existing glacier lakes along the Hindu Kush Himalaya; (ii) monitoring of potential risk lakes for draining; and (iii) an operational early warning mechanism for GLOF hazards.

Nearly 50 lakes, high in the Himalayas, could burst their banks sending millions of gallons of deadly floodwaters swirling down valleys, putting at risk tens of thousands of lives scientists are warning.

The lakes are rapidly filling with icy water as rising temperatures in the region accelerate the melting of glaciers and snowfields that feed them.

In Nepal, for example, data from 49 monitoring stations reveals a clear increase in temperature since the mid-1970s with highest temperatures found at higher altitudes.

Scientists with the United Nations Environment Programme (UNEP) and the International Centre for Integrated Mountain Development (ICIMOD) have found at least 44 glacial lakes that are filling so rapidly they could burst their banks in as little as five years' time.

Surendra Shrestha, Regional Coordinator in Asia for UNEP's Division of Early Warning and Assessment, said: "Our findings indicate that 20 glacial lakes in Nepal and 24 in Bhutan have become potentially dangerous as a result of climate change. We have evidence that anyone of these could, unless urgent action is taken, burst its banks in five to 10 years time with potentially catastrophic results for people and property hundreds of kilometres downstream. These are the ones we know about. Who knows how many others, elsewhere in the Himalayas and across the world, are in a similar critical state?"

Klaus Toepfer, Executive Director of UNEP, said: "Mountains were once considered indomitable, unchanging and impregnable. But we are learning that they are as vulnerable as the world's oceans, grasslands and forests to environmental threats and insensitive, unfettered, development".

Mountains are the world's water towers feeding the rivers and lakes upon which all life depends. If the glaciers continue to retreat at the rates being seen in places like the Himalayas, then many rivers and freshwater systems could run dry, threatening drinking water supplies as well as fisheries and wildlife. We now have another compelling reason to act to reduce emissions of carbon dioxide and other greenhouse gases," said Mr Toepfer.

In August 1985, a sudden out burst flood from the Dig Tsho glacial lake in Nepal destroyed 14 bridges and $1.5 million worth of damage was caused to the nearly completed Namche Small Hydropower Plant.

Bhutan's Raphstreng Tsho glacial lake in the Pho Chu River sub-basin measured 1.6 km long, 0.96 km wide and was 80 metres deep in 1986. The figures (1995) show the lake has swollen to be1.94 km long, 1.13 km wide and has a depth of 107 metres. Its neighboring glacier could generate a GLOF up to two-and-a-half-times that which caused major devastation in October 1994. The 43 other glacial lakes, pin pointed in the survey and deemed to be in a dangerous state, show similar patterns

The filling of the lakes, and the threat of their mud and debris walls being breached, is as a result of rising temperatures melting the glaciers.

Satellite, mapping and other surveys indicate that, for example, the glaciers in Bhutan are retreating at a rate of 30 to 40 metres a year.

In some areas the retreat is even faster. The Tradkarding glacier, which feeds the Tsho Rolpa glacial lake in Nepal's Rolwaling Valley, is retreating at a rate of over 20 metres a year and, in some years within the last decade, reached 100 metres per year.

The UNEP Regional Resource Centre-Asia and the Pacific, the ICIMOD's Division of Mountain Environment and Natural Resources' Information System, the Department of Geology and Mines of the Royal Government of Bhutan and the Department of Hydrology and Meteorology of His Majesty's Government of Nepal carried out the research.

Effect of Earthquakes

The major Himalayan rivers are older than the mountains and have their headwaters in the Tibetan plateau, behind the main chain. The rivers rose as the mountains were formed, cutting deep gorges and they store great amounts of potential energy. As the mountains rose, they formed a monsoon trap giving the southern slopes one of the highest precipitation rates on the planet. The annual rains turn this steep and seismically unstable mountain range into a crumbling, shattering mass that erodes faster and washes down more sediment than any other mountain system.

It is the debris from the erosion of the young Himalaya that filled up the Tethys Sea and turned it into what is now the Gangetic plains. This process of mass wasting that deposits debris in the plains continues, so the notion that floods in northern India and Bangladesh can be controlled is wishful thinking. The rainfall volume, sedimentation levels, and the size and frequency of earthquakes in the Himalaya far outstrip parameters laid out in engineering textbooks prepared for comparatively docile climes. Many of our specialists have been trained for technological solutions based on case studies that greatly underestimate the Himalayan dimensions of cloudburst, glacial lake outburst floods, and earthquakes in this part of the world.

The rock strata bent by the enormous forces beneath the Himalaya trigger thousands of small tremors every year. But every once in a while there is a major crack as the pressures are too much for the elasticity of the rocks, and the strata snap. When that happens, there is a magnitude Richter 8+ earthquake. Geologists now agree that there occurs a high intensity earthquake once every 100 years along any section of the Himalayan chain.

The catastrophic impact of the failure of a dam like Tehri or Pancheswar with 20 cubic kilo-metres of impounded water on the downstream plains is unthinkable. But there are failures of natural dams caused by landslide blockage of rivers in the past that give us an indication of the scale of such a disaster. In 1893, a rockslide on a river in the Garhwal Himalaya burst, causing a huge flashflood and great loss of life all the way down to the plains. In 1970, debris flow on the Alkananda River created a 60-metre high dam on this tributary of the Ganga. When this burst, it caused a flashflood that thundered down all the way to the plains of Uttar Pradesh, destroying settlements, bridges and highways.

Some scientists believe that as long as the dangers are known, there are engineering measures that can be taken to make the catastrophic failure of a high dam less likely. But the question is how much is it going to cost and if the risk, however minimal, is acceptable. Thirty years after they happened, reports are filtering out now of dam bursts in south-central China that killed tens of thousands of people.

Dam failures then become like nuclear war, you dont want to think about them. Designing earthquake-proof storage dams is a question of how much risk countries are prepared to take. The Great Bihar-Nepal Earthquake of 1934 registered 8.4 on the Richter scale and virtually destroyed Kathmandu killing about 4,000 people-about one in every ten inhabitants. Kathmandus population was a lot less then, and there were fewer lethally unstable concrete structures. If an earthquake of similar intensity were to occur today, the National Society for Earthquake Technology-Nepal estimates that as many as 40,000 people could be killed in Kathmandu Valley alone. And any dams in the vicinity could be severely damaged.

Earthquake prediction is still an imperfect science, but there are ways to reduce risks from earthquakes and their aftermath by preparedness. Provided basic data are correctly accumulated, earthquake zonation maps could be drawn up to show more vulnerable areas. Li Tianchi, a geologist and natural disaster expert with the Kathmandu-based International Centre for Integrated Mountain Development (ICIMOD), is working on zonation. He says: "We can identify which areas are more sensitive to earthquakes and take measures accordingly. But so far in Nepal, Bhutan, India and Pakistan-nations south of the Himalaya-no such map exists."

Earthquake predication is more like trying to speak out the next member of a pure random sequence.

In a candid report, Nepals Department of Mines and Geology assesses the risks to high dams from earthquakes: "A high dam can cause colossal downstream consequences in case of failure by an earthquake. Assessment of the seismic risk should be carried out for such structures."

Need to Plan

This years devastating monsoon floods in Bangladesh, Assam and northern Uttar Pradesh reminded the inhabitants of these regions, yet again, about how bad things can get. The disasters were also a warning to others in the Himalayan watershed that even bigger disasters will surely come. To estimate the extent of the casualties and the inadequacy of relief and rescue efforts one only needs to look at some of the great Himalayan events in recent geological time and imagine what would happen if they were to take place today.

A gigantic avalanche and flood came off the Annapurna Range in Nepal about 1,000 years ago and swept down the Seti River depositing debris several hundred feet deep in a valley where the town of Pokhara is now located. A similar avalanche now would kill as many as 100,000 people.

The Tista River that flows down from the Darjeeling hills into Bangladesh to meet up with the Brahmaputra used to flow into the Mahananda and the Ganges in Bihar till 200 years ago. Had that sudden river capture happened today, it would have swept away thousands of villages in a gigantic flash flood.

The nearby Kosi River has "migrated" some 150 km westwards in the past 200 years, and in the next great flood it could easily revert to its earlier riverbed with catastrophic consequences for northern Bihar.

This is the region of the world that combines areas with the highest rainfall in the world, the highest, youngest and most unstable mountain chain, the greatest population density and one of the most extensive levels of poverty. But the science to study this watershed, and the engineering solutions to build rivers, bridges and dams in them are based on inappropriate parameters, false premises and wrong priorities. Rules made for the gentle brooks and placid rivers of more temperate climes are just not applicable for the stupendous sediment loads, precipitation levels, and looming dangers like glacial lake outbursts and seismic damming of rivers.

Take the Kulekhani Dam built in the early 1970s near Kathmandu at a cost of 180 million dollars to generate 90 megawatts of power and have an economic life of 100 years. On the night of 20 July 1993, a severe cloudbuurst in its catchment area unleashed 540 mm of rain in a 24 hour period bringing down an estimated five million cubic metres of silt and boulders into the reservoir. The rain dumped in one night a sediment load several times larger than the estimate made by Kulekhanis designers for the entire lifespan of the dam. It blocked the penstock intake and required another 40 million dollars to design a bypass to extending the dams life by another 30 years-provided there are no more rainfall events like 1993.

Cloudburst like the one that hit Kulekhani happen several times during every monsoon season in different parts of the Himalaya. This year, 406 mm of rain fell in one day in the Butwal area of central Nepal on the same week that another cloudburst triggered landslides in Garhwal that buried several hundred pilgrims bound for Mansarovar. Both caused severe floods in northern Uttar Pradesh.

Although those floods and the ones in Assam were bad, the mother of all floods was the one that hit Bangladesh this year. The Ganges-Brahmaputra delta is at the tailend of the discharge funnel for the basins of two major rivers stretching from the borders of Himachal Pradesh to southern Tibet, the whole of Nepal, Bhutan, Assams eastern rimlands and Meghalaya. It would be surprising if there were no floods in Bangladesh. In fact, floods have been happening there ever since the Himalayas rose and became a raintrap, and the reason Bangladesh exists is because of the silt deposition over millenia during annual floods.

Questions are again being asked: can Bangladesh ever be free of floods? Does it even make sense to try to control them?

In trying to prevent floods, we first need to separate the myths from the truth, and pinpoint the real causes. Complete flood control in the Himalayan watershed is impossible. Even partial control is an exercise that may be geopolitically, financially and (more important) technically problematic at present.

The other side of the story

And the question arises: should we be trying to prevent floods at all? Or should we be looking at what it is we do to when we try to control them that makes floods worse. Is it better to try to live with them, and to minimise the danger to infrastructure while maximising the advantages that annual floods bring to farmers? Plans for long-term flood mitigation efforts need a paradigm shift in the way we think about them, about what is possible and what isnt.

After the 1993 floods on the Bagmati River in Bihar, farmers were interviewed. They said: "Our houses are all gone, but thats all right. We have a bumper crop." Every major flood in Bangladesh has been followed by good winter and spring harvests the following year because of the silt replenishment of farmlands. People of Tangail in Bangladesh looked at the oxbow lake that used to flow by their village as the artery that fertilised the fields every year and brought fish when the flood waters receded. The villagers make a distinction between the beneficial barsha floods and the destructive bona flooding. Traditionally villagers are well prepared for the three months of high water. But ever since levees were built to "protect" Tangail from floods under Bangladeshs ambitious Flood Action Plan, the oxbow is dry, harvests have fallen. "Floods never killed us," they say. "It is flood control that is killing us."

But there are some serious questions being asked about whether we are not putting all our hopes on regional cooperation when there is little proof that even if flood control reservoirs were built in the Himalaya they would be adequate to stop the annual submergence. There are also doubts about the presumption that deforestation in the Himalaya is making the floods worse because of increased soil erosion and siltation. Recent studies show that human activity in the upper catchment of the Himalaya did not have a major effect on floods in Bangladesh and India. In fact, there seemed to be little correlation even between high rainfall in the Himalaya and floods in Bangladesh. It is the rainfall pattern in the Meghalaya Hills directly north of Bangladesh was the main cause of flooding in the delta.

The call to build high dams in the Himalaya is not new, neither is the controversy surrounding it. But the tide of expert opinion is running against dams. First, their cost. The proposed Kosi High Dam at the point where the Kosi breaks into the plains in Nepal will cost anything up to 15 billion dollars, and if it is ever built will be the largest infrastructure project ever conceived in South Asia. Even if the money is found, the kind of negotiations needed for cost-benefit sharing between the governments of Nepal, India and Bangladesh will be extremely convoluted given the political instability and sensitivity to water issues in all three countries.

Gyawali says the problem stems from people who see rivers only as a source of water and devise engineering solution to use and control it. "Rivers are also drainage systems. They have a right to flow out to the sea. When you deny a river that right, it will overflow because it has nowhere else to go."

Geologists and water experts argue that the theory of Himalayan degradation worsening floods has been exaggerated. They say loss of forest cover is not the only reason for flooding, and most of the siltation is caused by natural mass-wasting of the Himalayas due to its steep and geologically young formations. However, if flood control storage is considered, watershed conservation is crucial, says ICIMOD, which looks at the specific environment and development needs of the Hindu Kush-Himalayan region.

Floods have their benefits, and a second school of thought advocates learning to live with floods so that the farmlands can take their benefit, while protecting houses, water supply and roads. Proper town planning, zoning and building design that take the annual flood events into account would be one way. Floods are good for soil, replenishing nutrients

Experts like Dr Rashid believe that if the storage dams have energy and irrigation benefits besides flood control, then they will make economic sense for countries in the region. "The first consideration must be to produce hydroelectricity. Nepal has enough potential to build dams which could produce electricity for the whole of Nepal, Bangladesh, northern India and part of Pakistan," he adds.

Water management

Prof Suresh Chalise of ICIMOD also believes in the potential of watershed management as a way of flood control: "Our experience has shown that management plans at the watershed and sub-watershed level is the most effective way to deal with the problems of floods as well as landslides at the sub-national, national and regional levels".

"It would be a great help for the flood management if a reservoirs are built in these catchments," says Prof Ainun Nishat of IUCN Bangladesh, especially citing the Kosi proposal and the Tipaimukh and the Dihang-Subanseri projects in India. Studies have identified 26 sites where such water storage could be possible by building dams in Nepal. However, seven large sites were later identified jointly which could serve all these three purposes.

The task force report also recommended that while dredging of rivers in India and Bangladesh for improving flood drainage may not be effective, it would be useful to carry out dredging of offtakes, mouths and man-made channels to improve their conveyance capability. Both Bangladesh and India also agreed that direct point to point flow of information on water level should be transmitted for effective flood management.

In the short-term, though, everyone seems to agree that the best way to avoid casualties would be to have an effective early warning system for floods based on rainfall and river flow data so that downstream inhabitants can take precautions. The Bhutan report said exchange of data and meteorological information of the catchment areas and rivers could improve flood forecasting. The real time water levels and flows of the tributaries from Bhutan namely Magdechu, Mochu, Amochu, Wagchu at their terminal stations, for instance, would be useful for early warning of floods in the Brahmaputra. The data could be transmitted electronically from Bhbutan and Nepal to India and Bangladesh. "Watershed management is a long term vision," says Dr Nishat, "Right now, we should focus on short-term solutions like proper flood forecasting. We should improve flood forecasting by continuously feeding data of major rivers. To do that, we must have cooperation from India and Nepal."

Despite the limitations of regional flood control, and its evidence that floods are more a case of drainage congestion than too much water, there is reluctance to abandon orothodox thinking and the tilt towards engineering solutions. Regional cooperation, however desirable in the long-term, has not moved beyond rhetoric. In that sense, it may be just as well that countries in the region cannot agree. This may at last force them to do their own domestic homework on water management first.

Reference Links

  • Birth of the Himalaya by Roger Bilham

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      Over two hundred fifty million years ago, India, Africa, Australia, and South America were all one continent called Pangea. Over the next several million years, this giant southern continent proceeded to break up, forming the continents we know today. Pangea essentially turned inside out, the edges of the old continent becoming the collision zones of new continents. Africa, South America, and Antarctica began to fragment............................
       
  • Himalayan Seismic Hazard
  • Early Flood monitoring  and warning systems in Bhutan
  • Early Flood monitor and warning systems in Nepal
  • Maps pin pointing those glacial lakes assessed as dangerous
  • UNEP's flood monitoring
  • Background information on UNEP's glacial lake outburst flood monitoring and early warning