Natural calamities are the extreme forms of such punishments. Many view them also as a kind of apocalypse for a new beginning. The great Noachian flood, the preamble of which we have quoted from the book of Genesis, was such an apocalypse. Such myths and legends involving floods find a place not only in Hebraic but also in many other literatures. Some are fictions fabricated to point a moral and to justify the ways of God to man, but many have their basis in facts. All of them today read as fables because they have come down to us through oral traditions and were reduced to written records much later. 

Since the time man learnt how to keep records of all happenings he has also kept the records of natural disasters that have visited him. This he has done to understand their causes so that he can devise suitable means to save himself from their destructions. Today he knows better than his primitive forefathers and does not believe that they are sent by a supernatural being or God to teach him a lesson or as punishments for his moral aberrations. They are natural calamities and have natural causes. If God has His ways Nature also has her ways. If man wants to avoid divine punishments he has to understand the ways of God and abide by them. Similarly, if he wants to escape the furies of Nature he has to understand her ways and pattern his own ways of life accordingly. Floods are one of the most cataclysmic of natural calamities. In occurrence they are universal and in causing death and destructions they do not discriminate between saints and sinners. They are not something unusual but are fundamental to the scheme of things. The inherent property of water is to wet and inundate, as is the power to burn the property of fire, and by virtue of such properties water is life-giving. If by any unearthly reason it ceases to have those properties life as we know it will be extinct. But unfortunately the same water when in flood causes death and destruction. Without water we cannot survive but when we have too much of it our survival is endangered. 

What causes are responsible for flood? Which are the areas most vulnerable to it? How one is to avoid its devastations? The total quantity of water that exists on this planet is so vast that it can permanently flood it totally. Fortunately the surface of the earth is not flat. Had it been so and if all the water were spread over that surface in its liquid form it would be under water to the depth of one and a quarter of a mile. But thanks to what the geologists call tectonic processes or the primordial building activities of the earth, one quarter of the surface of the globe is high and elevated ground called continents where man can live. The remaining three quarters is so low that it is permanently flooded. According to the law of gravitation water flows from higher to lower grounds and thus most of the liquid water of the earth was collected in its low lying areas and this is how the oceans came to be formed. These broad features of the earth's surface are not fixed or permanent because the earth is living and dynamic. It is in the process of continuous change both gradual or gentle and abrupt or violent. Through the operation of these tectonic processes whole landmass of an existing continent may suddenly subside, sink into the oceans or get uplifted, or a new landmass may rise from their unfathomable depths.

The disappearance of Atlantis in ancient times and the birth of new islands now and then confirm these geological processes. The surface of the earth again consists of a number of plates continuously moving. At times they collide or drift apart or fall asunder. According to the geologists about 200 million years ago the world probably contained a single super continent which in course of time got split up along faults and its various parts drifted apart and the continents as we know them were formed. In the remote past India was located near where now the Antarctica is. It got torn away from that landmass, raced north and ultimately thrust itself against the southern sea face of Asia. The result has been the birth of the highest mountain range of the world, the Himalayas, which once formed the bed of a sea and this is evident from the marine fossils that have been found on its peaks thousands of feet above the sea level. This also gave birth to many water bodies which were previously nonexistent. An obvious example is the creation of the Red Sea and the Gulf of Aden as the continents moved apart and the Arabian peninsula split away from Africa. That the same process is still in operation is evident from what is happening in the west coast of North America. Embedded in the Pacific plate a small segment of southwestern California is moving away from the continental landmass and the land along the San Andreas fault is subsiding giving birth to a lake and causing destruction to adjacent settlements. Fortunately such things now do not happen every now and then and on a very large scale, because after millions of years of violent upheavals and changes the planet has geologically become comparatively stable. But nobody can vouch for this stability for long, so inscrutable are the ways of nature. Thus viewed in a geological perspective and its unimaginably vast timescale no place on earth is totally safe from flooding.

Another fortunate fact is that all the water of the earth does not exist in liquid form, considerable portions of it are either frozen or are in a gaseous state. If these proportions vary the proportions of the dry and permanently flooded lands will also vary. For example, according to the geologists the Pleistocene-epoch glaciers used up enough ocean water to make the sea level 300 feet lower than it is now and much of the land now under the sea was dry at that time. If the temperature of the earth's atmosphere increases the opposite will happen. There is enough evidence that the planet is getting increasingly warmer, the polar icecaps are melting and the sea level is rising. If this goes on coastal regions and many low lying areas of the world will gradually get permanently submerged. Since the Ijsselmeer barrier dam was closed in 1932, converting this large body of water into a freshwater lake, the Dutch have been continually enclosing and reclaiming smaller bodies known as 'polders'. After dykes are built around a polder, it is drained by pumping out the water. If the sea level keeps on rising not only such reclamation of land will be more difficult, if not totally impossible, but also the land already reclaimed by the Dutch from the seas will be lost. Similarly a few more feet of water level rising in its Bay, the entire deltaic Bengal will be permanently flooded and become totally unfit for human habitation. And much before such a catastrophe happens vast areas in coastal regions now supporting large populations will become saline and unfit for agriculture. According to the UNEP report Climate Change ' 2001, in case of some selected Asian countries alone the potential land loss and the percentage of population likely to be affected as a result of coastal flooding due to rise in sea level would be as follows'

Bangladesh'15,668 to 29,846 sq. km (5 to 13%), 
India'5,763 sq. km (0.8%), 
Indonesia'24,000 sq. km (1.1%), 
Japan ' 1,412 sq. km (2.3%), 
Malaysia ' 7,000 sq. km (0.3%),
Pakistan ' 1,700 sq. km (NA), 
Vietnam ' 40,000 sq. km (23.1%).

The places nearest to the seas, particularly the coastal regions, -- and deltaic Bengal is one of them -- are vulnerable to flooding also as a result of tsunamis, typhoons, hurricanes or cyclonic storms, unusually high tides and mountainous sea waves caused by earthquakes. According to the same UNEP report their frequency and intensity will increase as a result of climate change due to global warming. 

All these do not however mean that the places situated at higher altitudes or away from the seas are safe from floods. The surface of the continents is not smooth but rugged, and contains mountains, plateaus, valleys and plains. There are areas that lie hundreds of feet below the sea level where large bodies of water have collected to form large lakes and flood them permanently. As their water level also periodically falls and rises, their shorelines may also at times experience flood. Another very important property of water is that it is not static and stagnant and found only in the oceans and lakes but is ubiquitous and dynamic. It is omnipresent and always in motion in a cycle, called the hydrological cycle, constantly changing from liquid to solid or gaseous states in which it exists. It is in a process of continuous circulation all around the globe from the oceans to the atmosphere, thence to the land and back to the oceans through evaporation, condensation and precipitation as rain or snow. Through this cycle however much she may try to be just to all, in the matter of distribution of water through precipitation nature does not follow any Marxist principle nor is she egalitarian. Neither the sacrifice of human beings by the primitive barbarians could, nor the revolutionary exhortation of a modern day poet can*, redirect a single piece of rain cloud from Cherapunji to the deserts of Gobi or Sahara.

Some regions of the earth are specially favored by nature with more precipitation than others, but this pattern is subject to changes over time. The places where there will be rains or snowfall, and when and how much, are determined by climatic cycles and weather patterns which are not always amenable to the weatherman's exact predictions. This is the reason why that hapless person is very often the favorite butt of our ridicule. The climatologists have found out broad patterns of climates and divided the earth into regions and zones no doubt but such patterns are not fixed but dynamic. Climates or weather patterns of two consecutive years are never exactly the same. At intervals violent shifts and deviations from the normal take place and extremes like floods, droughts, storms etc. occur, the causes of which cannot always and easily be explained. Here again global warming is playing havoc with the familiar climatic patterns, and according to the UNEP report cited earlier the frequency and intensity of catastrophic extreme events like droughts, floods, cyclones etc. are on the rise along with the rise in atmospheric temperature. 

Considerable parts of the water that falls on the earth as precipitation get evaporated by heat, transpired by plants and absorbed by the ground. Its remaining part travels as surface flow, following the law of gravitation, from higher to lower grounds along natural depressions and ultimately gives birth to rivers and streams whose most important function is to drain their basins. Low lying areas that have no natural outlets for the water falling within their boundaries form lakes, marshes or swamps. They remain permanently under water unless drained or filled up by artificial means. So long as rivers and streams are able to discharge their draining function efficiently the other areas of their basins remain free from the danger of flood. For various reasons rivers often fail to do so and cause inundations. All rivers undergo a natural process of degeneration because of progressive silting of their channels due to seasonal variation in their flow as a result of variation in meteorological conditions and precipitation. Usually this takes a very long time.

When a river is in its full vigor it is able to drain its basin well when the precipitation is normal and well distributed over time and space. At this stage of its life it may fail to do so on occasions when the precipitation is abnormally heavy and takes place within a very short period of time and over a limited area. But such failures are not usually very frequent. However with the passage of time as its channel progressively deteriorates and its draining capacity also progressively diminishes, such failures become more frequent and its basin experiences frequent floods. Frequent flooding of a basin is the sure indication that the river system that drains it is degenerating or dying or is already dead. Human agency is normally helpless in such circumstances, but by a fortunate coincidence of natural causes such a river may regenerate by leaving the old course and finding a new channel. A shoal or a bar or an island formed by silting may be removed by dredging, but for deepening the whole length of the riverbed it is unthinkable because it is prohibitively costly and technically seldom viable. The problem is compounded if the rate of natural scouring of the riverbed is far below the rate of its silting because of lack of enough gradient. This usually happens in regions known as floodplains and deltas which are most vulnerable to floods. Here the natural degeneration of the channel is more rapid because of gentle gradient of the flat country and consequent heavy silting. The natural mitigating factor is the existence of spill channels which act as safety valves to partially relieve the river of its excess flow and parts of its heavy silt burden. Otherwise rivers are compelled to change their courses very frequently in these areas. Here it is very easy for the rivers to do so because of the character of the soils which are unconsolidated sedimentary deposits left by the rivers themselves and very easy to erode. In floodplains and delta regions floods are very common no doubt but there they are not unmixed evils. There they not only destroy but also build and enrich the land by continually depositing layers of alluvium. These areas are traditionally the most fertile and prosperous places in the world. That is why people overcrowd them inspite of risks of frequent floods. In the upper reaches of the river and at higher altitudes floods are not uncommon. There they occur less as a result of degeneration of river channels but more because of their sudden obstruction by landslides and ice-jams. Large scale deforestation of high gradient mountain slopes and thoughtless 'development' of hilly areas often increase the risks of landslides. Global warming may cause mountain glaciers to melt at higher rates and cause more frequent flooding by increasing river flow in high altitude regions. 

Throughout history man has settled next to rivers and streams because they offer advantages in transportation, commerce, energy, water supply, soil fertility and waste disposal. He has derived immense benefits from them, but not without occasionally suffering devastations caused by one of the greatest natural hazards, that of flood. He has tried his best to control them but he has not been always successful. This was the case in early times when he was yet to develop his technological skill. He was helpless when floods occurred. His attitude was therefore fatalistic and bore with them as divine punishments for his immoral conduct. His policy was one of adjustment with nature. Common sense told him not to settle in low lying areas which get easily inundated. Nor did he use them for economic activities which were unsuitable in these flood prone places. In Eastern Bengal people cultivate a special type of paddy in areas subject to annual flooding. Along either banks of the Nile the ancient Egyptians sowed crops which could be raised before the return of the annual flood. Sir William Willcocks speaks of the ancient system of irrigation in Bengal which was not as elaborate and sophisticated as it is now.

During the British period on the plinths of important public buildings were recorded the elevation above the sea level of the plots of land on which they stood. As chief engineer of undivided Bengal S.C.Majumdar had initiated contour mapping to facilitate land use planning that would minimize flood damages. With the acquisition of technological power man's attitude has radically changed. His method of water management has become sophisticated. Common measures of flood control today include improvement of river channels, construction of protective levees and storage reservoirs, and indirectly, implementation of programs of soil and forest conservation to retard and absorb runoff from precipitation. But the magnitude of catastrophic floods is often so great that even with all his technological might it is beyond modern man's power to control them when they do take place. The best he can do is to calculate the magnitudes of such floods, known as 100-, 500-, and 1000-year floods, by extrapolating existing records of stream flow, and using the results in the design engineering of his water resources projects, including dams and reservoirs, and other structures that may be affected by catastrophic floods. To deal with flood disasters he has developed an elaborate early warning system, and prior arrangements for rescue and relief operations, including medical care. 

These flood control measures are undertaken nowadays generally as a part of multipurpose river valley projects planned also for irrigation and power generation which have become essential for maximum possible exploitation of river water to meet the ever growing agricultural, industrial and domestic needs of ever growing populations all over the world. The population growth showing no signs of abatement and its needs becoming varied and voluminous, rivers are being exploited more and more intensively necessitating greater human interference in their natural regimes. Enormous quantities of water are being withdrawn from their channels by building dams or impounded in large reservoirs or diverted through canals by putting up huge barrages. In many cases such interference has crossed reasonable limits. These projects were a great hope but now they have become a nightmare. They are precipitating and hastening the natural process of degeneration of rivers and consequent risks of flood.

High optimism and pressing needs of the moment made us blind to this danger but their long-term harmful and disastrous effects on rivers are today too apparent to be ignored any more. That is why movements have started against them all over the world. Not only rivers but also their entire basins, not only water but also all other physical resources of the earth, are being mercilessly exploited. As the pressure of population keeps on mounting existing arable lands are being cultivated more intensively and marginal lands earlier lying fallow are being brought under the plough by wholesale deforestation. Their soils are being exposed to the elements. They are getting eroded and impoverished and the rivers are being overloaded with enormous amount of sediments which are silting up the channels. Losing their vegetable cover the basins are becoming increasingly unable to retard or absorb the runoff from precipitation and thus contributing to the causes of flooding. This is also depriving the rivers of one of their major sources of supply by reducing the rate of recharging of the underground aquifers. Low lying lands previously not used for settlement or cultivation because they get easily inundated are also being recklessly used.

Dams and reservoirs primarily help irrigation and power generation but as flood control measures their effectiveness is limited. And what is worse, at times of floods their failures make them more devastating. What is happening is not only the decay and degeneration of the rivers alone but also of the whole environment of their entire basins. This has resulted in unprecedented ecological and environmental disasters, flood being only one aspect of those disasters. Many plants and animals have already become extinct whom no amount of human ingenuity can bring back into being. More are being threatened everyday and the days are not very far away when man will find himself threatened. Early man thought that God punished him with flood for his transgressions of divine laws and moral codes which he called sins. Modern man suffers the same punishment but for what sins? In unambiguous terms the answer is ' his excesses and wanton violations of the laws of nature. In Noah's time it was no sin for men to multiply on the face of the earth, for the world was wide and compared to its plentiful resources human population was sparse. In fact it was essential for him to multiply to become, among other competing creatures, the fittest to survive and it was a virtue to do so. His ability to understand the laws of nature and to use that knowledge for his survival was another virtue. His hunger for more knowledge and power for a better and civilized existence made him unique. But all these he has carried to extremes and all his virtues have today turned into vices. The sons of God are coming in too much unto the daughters of men and they have multiplied their species to such an astronomical number that it will not be possible for the earth to accommodate it for long. His hunger is no longer a virtue, he has turned it into a vice, a deadly sin ' greed. To satisfy the perverted greed of this burgeoning population man is under a compulsion to overexploit all the resources of the earth, many of which are on the point of total exhaustion. Through his knowledge and skill he has been destroying the very physical environment that has made the emergence of life and its survival possible. The decay and death of rivers is only a part of that big crisis that is facing humanity. 

What is needed most today is a greater awareness not only among a few enlightened people but also among the people at large about the sin we are committing by destroying our environment which is making certain an apocalypse that will not be a new beginning but the end of the human race, its speedy extinction. Unfortunately this awareness is very much lacking in the majority of us. Even the so-called specialists who boast that they know better than ordinary men are often very myopic. When discussing about rivers they are apt to ignore the fact that our physical environment which sustains life on earth is a totality. Its various components are inextricably linked and rivers are only one of them. It is imperiled today by the adverse impacts of the activities of technologically powerful, arrogant and greedy man. The end of the human race will not be very far if it does not mend its ways when there is yet time. But these specialists find this simple argument irrelevant which speaks of other related matters in connection with the discussion of rivers. We can do no better than repeat what Doctor Samuel Johnson once told one of his interlocutors who had admitted his inability to understand the Doctor's argument, 'Sir, I have found you an argument; but I am not obliged to find you an understanding '. 

Finally, though fundamental yet rivers are only one of the many links in the vast and complex global hydrological cycle. For a proper understanding of rivers they need to be studied in that context. They are nothing if not containers and carriers of water and that water is fresh water. They are like filters provided by nature for spontaneous renewal and supply of fresh water to make survival of life on earth possible. Any river problem is also a problem of fresh water and vice versa. Any reference to one in connection with the discussion regarding the other is therefore very much in context. Yet these specialists by some strange logic often find such references to be out of context.

The global fresh water crisis is becoming acute day by day. This free gift of nature has become so scarce in many places that it is being sold like any other commodity for a price. There exists a necessary relationship not only between rivers and fresh water but also among all the various aspects of our physical environment and a change in one produces changes in the others as well. Their steady degradation and depletion due to their overexploitation by man is a matter of deep concern today throughout the world. It is very unfortunate that still there are ill-informed people who are incapable of viewing things in their proper perspective. They masquerade as experts yet fail to appreciate this obvious fact. Unless we are careful not only in our use of our rivers, a major source of fresh water so essential for our survival, but also in our exploitation of their entire basins and all their physical resources, we are going to face a catastrophe of unprecedented magnitude in no distant future. Their overexploitation should immediately stop. That is possible only when we are able to get over our compulsions.

Unusually severe and frequent floods, droughts, cyclones and other extreme events are the outward manifestations or symptoms of serious disorders in the realm of nature. Where their causes are cosmic or geological man can do very little, but where they are due to adverse impacts of man's activities on his environment he has to be cautious and careful and mend his ways. If he fails to do so he will soon be extinct. The purpose of our harping on this theme is not to create panic, nor to frighten anybody into attention about this impending peril, but to make an impassioned appeal to everybody to wake up and try to understand that there exists a balance between human and natural activities and also a limit to our 'growth' and greed. It should be our common quest to find out that balance and that limit. We shall be happy even if only one person responds and joins that quest and try to pattern his behavior to restore that balance.