Chapter 2 0 conceptual framework

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The theoretical considerations which appear as relevant to the objectives of the present work include the very broad concepts of land as an amalgam of resources and as an ecosystem as well as the concept of environmental balance in general and also the relatively fragmented but locally very important question of agriculture and water bodies including rivers and paleo-channels as resource processes, as natural and cultural ecosystems and bases of human ecosystem.


The broadest concept which engulfs the relatively minor question of agricultural land, land and water-based commodities, flood and riverbank erosion etc. is that concerning the stability of the world civilization and that ultimate survival of mankind on this planet. Scientists and social thinkers of the present time almost equivocally claimed that only a stationary state economy can ensure permanent tenure of man on this planet (Daly, 1971: 71-76), a view which had been advocated long back in 1857 by John Stuart Mill, the great synthesizer of classical economics, in his Principles of Political Economy. The principles on which the ‘spaceship earth’(Simmons, 1974:163-172) should continue to revolve round the sun forever are based on the assumption of an equilibrium between an ever renewable supply of resources, principally energy, on one side of the scale and a stationary population feeding on the renewed energy on the other side. Ecologists have very successfully demonstrated that such stability in nature is guaranteed only by biodiversity and certainly not by selective extermination of species which do not come to the immediate benefit of man. One of the chief responsibilities of the scientific community of the world today, therefore is to find out a mechanism to control the population growth to a limit which is sustainable by essentially the biological process of conversion of solar energy into food and other materials supported by the use of other forms of flow energy like wind, ocean current, solar power etc. The other responsibility is to curb the rate of consumption through such measures as standardization and miniaturization of products, energy saving techniques, waste- recycling and finally to device a zero-waste technology.

It has been said that the initial success of man in creating a surplus from land through sedentary agriculture depended heavily upon his choice of immature ecosystem with a surplus energy stock or on retarding the process of maturity by selective de-speciation (Bourne,1976: 43-48), at the same time it has been rightly claimed that the present crisis also follows from the same logic of depending upon an additional source of energy from outside the ecosystem boundary over the amount which can be fixed by the local ecosystem. On the other hand, the communities which chose to live in mature ecosystem along with their full range of specietal diversity achieved a lesser degree of success but have survived better against internal stress by a spontaneous mechanism of population control. That they have not been able to survive successfully against external threats on their habitat and culture is a different question which should not undermine the validity of their world view. To understand the rationality behind this kind of world view and its relevance to the contemporary global ecological crisis, it is necessary to review the concepts of land as a resource process, as natural ecosystem and as human ecosystems.


A land can be regarded as an object of trade or exchange or even as a responsibility which has been given to the holder of the land by his forefathers. In the first case, land is perceived as a private property and its possessor has got every right to retain it or sell it out in exchange of money. Here the holder is interested in his own economic benefits. But in the second case, the property holder has to retain the property, maintain it and improve its productivity with care not for his benefit alone but also for the benefits of his family, his friends and all those who belong to his community. When land is taken as a private exchangeable economic resource then its possessors may not be interested in the alternative environmental possibilities associated with the land. But when land is perceived as resource for the community then only its proper qualities are judged by the community and it is given to a particular mode of use of different alternatives (Bhar, 1989: 7-10).

Land is not necessarily a resource by itself. The usefulness of land depends on the methods and techniques of land utilization. To avail the long run potential of a land, it is required to utilize the land with a clear perception and with the proper selection of the mode of use. So, a land is rarely a resource by itself from the wider communal view point; but it is a container of different resources which are used by proper management (Biswas, 1989:11-12).


It is generally thought that the concept of ecosystem is monistic and thus it brings together man, plant and animal worlds within a single framework within which their mutual interactions can be understood and analyzed. The concept of ecosystem is also functional in its design, which offers a sound working principle for geographical analysis of man- environment interaction of any specific area or region. Therefore in its real sense ecosystem is a kind of general-system or open-system tending towards a steady state under the laws of thermodynamics (Odum, 1959: 5-28).

Ecosystems are structured in an orderly, rational and comprehensible way, so that once the framework of any spatial system is clearly defined, then it becomes possible to analyze the same systematically. Moreover, ecosystems are functioning systems, involving continuous throughput of matter and energy. Therefore, ecosystems are conceptualized at different levels of complexity from a single farm unit to the extensive system of agriculture in any region or country. Similarly, an ecosystem possesses structural properties of theoretical models. With the adoption of the concept of ecosystem, geographical systems may also be examined at a series of levels. As stated by Odum (1959:7-32): “an ecosystem is a functioning introductory system composed of one or more living organism and their effective environment- both physical and biological”. Thus description of an ecosystem may include spatial relations, inventories of its physical feature, its abilities and ecological niches, its organisms and its basic reserve of matter and energy, the nature of its income or input of matter and energy and behavior or trend of entropy level (Odum, 1959: 6-28).

Within any areal frame work, the concept of ecosystem ensures us points to enquire and thus highlights both form and function within a spatial setting wherein simplistic ideas of causations and development of geographic dualism are then irrelevant. Ecosystem analysis gives geographer a tool with which he or she works (Stoddart, 1965:95-102).

The present work of analysis of the hazards and its impact, as it already has been stated, is a conviction to the ecological studies and the space frame of the study include two types of principal ecosystems, of which the dominant one is the land ecosystem the most part of which is occupied by cultural ecosystem that is agriculture and the second important ecosystem is the aquatic or more likely the wetland ecosystem with its several units scattered throughout the area under study. Thus the concepts of both the ecosystems may briefly be stated under the heads of land as ecosystem and wetland ecosystems.


From inherent implications of the wider communal viewpoint of land we understand that land is a natural resource system or “natural ecosystem linked either way hierarchically and taxonomically with super-systems and sub-systems” (Biswas, 1989; 15). All these systems have throughput of energy which is converted successively by the food chain and this converted energy is ultimately received by man, the topmost class of a trophic pyramid. So, man is responsible for the use of land ecosystem skillfully for long term survival of humanity.

With the domestication of the plant kingdom, man turns the natural ecosystems into agricultural ecosystems in various ways such as by choosing the suitable species, through removal of unwanted life forms, by providing external energy supply, by making open the closed bio-geochemical cycles of natural system and thereby reducing the net primary production of plant material over time.

In biomass production, human technology can’t effectively replace the natural system. The Alpine and Tundra vegetation regions are exception. The natural systems of most regions are capable of producing larger quantities of dry matter per unit area than are produced by the crops of human choice.

Human intervention in natural ecosystem by agricultural ecosystem produces a number of variations in productivity of energy and biomass. A lot of example may be cited in this context – in Britain, the cereal systems produce 2000 million calories from a hector of land, while the sereal fed livestock systems produce only 180-340 million calories annually. The energy content of lamb meat is only about one percent of the total input of solar energy required to produce it while that of serials is about 16 percent (Duckham and Masefield, 1970:133-138).

In the farming systems of the Western countries, there is a great inefficiency, when measured by the ecological yardstick, due to enormous expenditure of energy and wastage involved. In our country, through a research work on the cropping systems of the seven districts of West Bengal, it “is observed that these districts are capable of capitalizing on not more than 52-66 per cent of the temperature resources, 63-71 percent of the rainfall resources, 43-59 per cent of the total hours of bright sunshine and 54-69 per cent of the cropping-time available. More interestingly, much of the well-known prosperity of the district of Bardhaman appears to be ‘bought’ or ‘subsidized’ from external sources as the efficiency of its cropping system in utilizing the free atmospheric resources of temperature , rainfall and sunshine is not above mediocrity compared to other districts” (Biswas,1989: 17).


The flat riverine plain areas or deltaic plain lands generally possess a mosaic of land ecosystems and wetland ecosystems; the coexistence of these two systems is unique in character. Both of them are open-systems in function, receive matter and energy from one another, change the form of energy, distribute the energy to their consumers existing in different trophic levels and there is a regular exchange of energy and matter between these two ecosystems. For example, the nutrients and sediments released from the domain of land or agricultural ecosystem are first deposited into the wetlands and the consumers both within and outside the boundary of the wetland ecosystem are shared by the vegetation, the microbes, the hydrophytes, the swimming animals and all the life forms existing within the boundary. The hydrophytes and the shallow water grasses are able to convert solar energy as they are directly open to the solar radiation. It should be noted down that most of this wetlands continue their function for a substantial part of the year. The nutrients from the lands located around its boundary are deposited into the beds of the wetlands and help to sustain both shrubs, hydrophytes, small and big fishes even the water birds and the flying birds also. At a certain period, particularly in the dry summer, the layer of humus deposited in the beds are collected and distributed to the agricultural fields as a very nonpolluting replenishment of fertility as a natural fertilizer. There are more than 20 large and more than 30 medium sized natural wetlands which impart profound effect upon the ecology and economy of a different group of communities inhabiting in the area. The following definition may do justice to the types, characters and functions of the wetlands located in the study area.

  1. In a simple sense, here we use the term ‘wetlands’ to mean the areas of land that remained water logged for a substantial period of the year. In general, the wetlands are those areas inundated or saturated by surface water, in this case freshwater, at a frequency and duration sufficient to support a prevalence of vegetation and different species of swimming and benthic animals, particularly large verities of fishes and cat fishes, typically adopted for life in saturated soil condition. In the concerned area these wetlands are known as ‘bils’, many of which are the abandoned courses of rivers, or stagnation of spilled-over water in a shallow saucer-shaped basin area having a natural capacity to accommodate and store floodwater. These are mainly the riverine perennial fresh water wetlands including permanent rivers and streams and inland deltas, temporary wetlands like seasonal and irregular rivers and streams, riverine flood plain including river floods, flooded river basin, and seasonally flooded grass land. These also includes some man-made wetlands like aquaculture ponds including fish ponds, agriculture ponds including farm pond, stock ponds, small tanks, irrigated lands and irrigation channels including rice fields, canals and ditches and seasonally flooded arable lands. But this conceptual part is principally concern with the large fresh water permanent wetlands. Like land as an ecosystem, wetland also displays its functional characters may be stated in brief. Flood control is considered as most important among the vital function of wetlands. They function like sponge, storing, and gradually releasing the rainfall and runoff-water that reduces the severity of flood. With the proper management, wetland can reduce the need for expensive dams and other engineering structures generally prescribed for flood control.

  2. Another important aspect of wetland is the binding effect of their vegetation which helps in the stabilization of banks and shores. Thus it functions as a control of erosion.

  3. Recharge of ground water and its discharge is one of the important roles played by the wetlands.

  4. Regular deposition of nutrient-rich silt and sediment has a great contribution to the success of agriculture of a large tract around the boundary of the wetland.

  5. Biological, chemical and physical process in wetland is often able to immobilize and transform a wide range of environmental contaminants and nutrients, the excess deposition of which could cause severe eutrophication and pollution.

  6. Wetlands can act as a sink, preventing nitrate build up. Nitrate runoff from fertilized agricultural areas can be recycled to harmless nitrogen gas by this mechanism.

  7. Wetland flora in particular is able to sink nutrient and contaminant.


Resources used by the human community can be logically subdivided into three categories:

  1. Resources used in the human metabolic process and alter after use;

  2. Resources used outside the body ; these resources may be taken in their raw form or biologically or chemically processed from both renewable and non renewable resource and are altered after use;

  3. Resources used outside the body and their appropriation leaves them unaltered; (Simmons, 1974:165-167).

Simmons defines resources process after Firey (1960:85-87) as “the total flow of material from its state in nature through its period of contact with man to its disposal”. He specifically identified several resource processes like unused land of the world, specially protected landscape and ecosystems, forestry, food and agriculture, recreation and tourism, water, sea, mineral energy, wastes, and pollution.

Interrelations between resource process and ecosystem are definite. Odum (1959:45-52) defines ecosystems as “that part of nature where living organisms and non-living substances exist and interact to produce an exchange of materials between living and non-living parts”. Therefore agricultural fields and wetlands should be considered as ecosystems dominated by autotrops or producers. In both of these ecosystems the green vegetation are the fundamental elements in the systems, because they are the principal organs of photosynthesis which produces energy and constitute the productivity of ecosystem. Since the biological productivity of these ecosystems has been manipulated by man for various purposes, they can also be conceived as resource processes.

The energy and nutrient flow of these two ecosystems are cyclic and there is a balance between loss and gain. These features ensure these ecosystems as long term stability. An ecologically sound resource process is, therefore, to be ensured in order to perpetuate the cyclic energy and nutrient flow, if their products are to be used as yields.


In ecological perspective, the physical elements like land, water, soil, climate etc. are considered as the ‘ecological infrastructure’ (Guha, 1994:5) of human society. Humans are unique amongst the earth’s creatures in their elaborately developed cultures; they do not stand above or apart from nature. These ecological infrastructure are understood with the reference to the natural environment and are the basic resources within which humans, like any other species live, survive and reproduce. The ecological infrastructure powerfully conditions the evolution and direction of human economic life, political relations, social structure and ideology. On contrary, human intervention reshapes the natural environment in its own image (Guha, 2004:6). In the present context the land and water bodies are not mare the natural systems , but to the people of the area, these are the resource containers from which they not only receive the energy for their metabolic needs but also the materials needed for the survival and development of their economy and culture. The land shaped into different plots of agricultural fields , establishing a subsidized ecosystem with renewal of nutrients through addition of natural and chemical fertilizers for growing crops which are periodically managed in which water supply and management have intricate role behind the continuation of the ecosystem as well as harvest different crops. The residues of crop plants are used as fodder for the herbivores which has a definite role both in the economy and food system of the local people. Thus land and soil in combination with the supply of water are important resource bases. Simultaneously, the water bodies including the rivers, paleo-channels or the bils, tanks and ponds are also used as resource containers for fishing, duckery, collection of the hydrophytes and grasses growing in stagnant water bodies as fodder. In addition, these water bodies play most important role as sources of irrigation and hence, considered as resource base. Considerable depth of water is necessary for processing of jutes which is valuable economic crop of the study area. Therefore, lands and water have integrated values as resource bases.


The concept of ‘hydraulic society’ has best been illustrated by Wittfogel (1957:33-38) drawing upon the ideas of ‘Asiatic mode of production’ of Karl Marx. Wittfogel emphasised upon the control over water by certain elite class exercising the state power and made artificial irrigation by canals and water-works, the very basis of Oriental agriculture. The most important necessity of an economical and common use of water drove private enterprises to voluntary association necessitated in the Orient in the interference of the centralizing power of Government.

Wittfogel substituted "hydraulic civilization” for “Oriental society” and believed that the new nomenclature that emphasised institutions rather than geography, facilitated comparison with ‘industrial society’ and ‘feudal society’ and the term ‘hydraulic’ draws attention to the agro-managerial and agro-bureaucratic character of these civilizations. Accepting this sense, the society depending on water for its survival, subsistence and development following “specific hydraulic order of life” (Wittfogel, 1957:49-52) is termed as ‘hydraulic society’. In such society, the hydraulic order of life has its own type of division of labour and necessitates cooperation on a large scale to carry on the activities like irrigation, flood control, fishing, agro-based industries, trade and commerce etc.

According to Wittfogel, hydraulic societies are those societies where the ever-increasing drive to control water through the development of knowledge and technology lead to an ever-increasing concentration of power to control water. The group of people who hold such power are tasked with the providing of the expert knowledge on hydrological conditions and devising the organizational procedures required to mobilize the labour necessary to build irrigation channels, locks and weirs even dams for the control of water. Wittfogel clearly states that the ruling class of hydraulic societies is those who control the ‘hydraulic means of production’ and the driving force for change in increasing technological control of power (Wittfogel, 1957:53).

Kirstain Henderson (2010: 1), pointed out that, in the activities of a hydraulic society, there must be three requirements: a) the development and building of water controlling technology, b) the social organization of labour to carry out the water works, and c) the development of what Wittfogel caused the time keeping ability or the development of a calendar to became able to predict the availability of water. According to Henderson, these are Wittfogel’s principal points to understand hydraulic societies. Henderson farther stated that Wittfogel’s analysis on hydraulic society is a starting point for a way to think about nature and society together. His question on the role of water in the process of the development of a society based on utilization and management of water is very important concept. Wittfogel included the examples of hydraulic society from ancient China, Egypt, Asia etc. Even the modern hydraulic engineers in China has incorporated the knowledge of hydraulic society and in their modern plants they also given importance to the managerial part of water for agriculture and water-based production systems with the challenge in their mind : a number of regions are extremely short of water resources, the water pollution still serious, the ground water is overly exploited , most of the rivers on riverine plains are gradually going dry, rainfall and water resources are unevenly distributed in space and time and, the social and economic development and the improvement of people’s life bringing forth higher demand for water resources (Hebei Provincial Hydraulic Engineering Society).

Henderson viewed and explained the hydraulic society and also stated that in the processing or harnessing nature in the form of water, to raise cities and farm land where local condition would not allow them to be, there are some type of alienations from the rules of hydrological cycles where the societies may face scarcity of water.

The area selected for present study is an ideal example of hydraulic society being a part of the flat riverine plain of Bengal, having maximum dependence upon the management and utilization of water resources. Agriculture had been the principal occupation of the people from ancient times and the people developed the knowledge of growing different crops in different situation of water availability. The area, being a small part of Oriental or Asiatic mode of production has passed from the feudal to the present government system including a considerable time under the foreign (British) rulers. In the feudal period, the local ‘elites’ being directed by the feudal lords ruled the area, formed the system of protecting the agricultural economy from flood hazards with construction of embankments through a number of flood prone rivers . On contrary, during the period of rainfall shortage the same ruler constructed a number of irrigation channels and excavated larger tank to save the crops in the types of needs. Excluding the farmers and agricultural labourers, a number of labours were employed to manage and maintain the irrigation network. On the other hand a number of tax collectors were engaged by the rulers to collect rents for irrigation and a share of their crops for royal tax. This system was continued and developed by the British rulers from 1857 to 1947, up to the time of Independence and tax for irrigation and embankment protection for flood control was marked higher than that of the feudal period. The system came into the hand of the government of India, some new irrigation cannels and weirs were built and for which the people still have to pay tax to the local government system. Therefore the political and economic power to control water resources remained in the hands of the rulers and the group of communities, following different occupation like farming, agricultural labourers, fisher man, agro-based trades etc consciously followed the character of a hydraulic society.


It has already been mentioned that the area under review bears a unique characteristic resembling the mosaic of land, water bodies and settlements except some old urban and semi-urban centers. While the area is interspersed with rural settlements, the duelling places of the people who followed the occupations directly or indirectly linked with the production from land – agriculture, agriculture labourer, fishing and allied occupations. As an ideal tropical area, it has a seasonal rhythm of alternative humid and dry period which is instrumental to store, supply, manage and utilize water in different time for different crops which demand variable amount of water for their growth. Therefore, it may be considered as a precondition to be settled in the area where there is source of water for irrigation and domestic utilisation. The cropping fields are also needed to be located near the habitation for taking care of the crops which are mainly related with labour intensive agricultural system to reach the field in a shortest time for transplantation, weeding, nurturing, watering, harvesting and bring to the home steps for threshing which need a minimum distance from the farmers and labourers. During the crucial time of growing of plants, irrigated water needs to reach quickly with minimum seepage to the crop filed, thus it is necessary to locate the irrigation sources near the agricultural fields which are mainly the larger tanks and ponds, but in other cases a larger canals and sub-canals operated far from the area, sometimes extraction of ground water for the crops demanding large amount of water , and in some cases lifting pumps installed on the banks of rivers and paleo- channels are not also far from the agricultural fields. Therefore, it has given a unique characteristic that there is a close proximity of the agricultural fields, the sources of water and the settlement of the communities linked to agriculture and water works. Fishing from rivers and paleo-channels is one of the most important sources of employment for the fishing community and beyond. Slow flowing water is vital in the life and economy of the fishing community; similarly the bils or the paleo channels which are annually renewed with water and nutrition are the sources of a verity of small fishes, precious cat fishes, and a number of other life forms like snails, crabs, etc. Therefore the whole area disposes the unique association of land, water and people association.


The term hazard is best viewed as a naturally occurring or human induced process, or event, with the potential to create loss which is a general source of future danger (Smith, 2001:11-27) and thus in real sense, hazard is an inescapable part of life. Every one perceives hazards in different ways, and views generally vary from place to place and over time. As stated by Whittow (2002: 620-646), so long water is under control in a reservoir, it will be seen as an important resource, but once its volume deviates beyond the band of tolerance, it will be surely recognized as a flood hazard. Due to these fluctuating degrees of human perception, there have been difficulties in arriving at a precise definition of environmental hazard, but the most explicit states that they are ‘extreme geo-physical events and major technological accidents, characterized by concentrated release of energy or material, which pose an unexpected threat to human life and can cause significant damage to goods and the environment’ (Smith, 2001:259-288). The term ‘risk’ is sometimes taken as synonymous with ‘hazard’, but risk has the additional implication of the chance of a particular hazard actually occurring. Thus risk is the actual exposure of something of human value to a hazard and is often regarded as the product of probability and loss. As stated by Smith, one can define hazard (or cause) as ‘a potential threat to humans and their welfare’ and risk (or consequence) as ‘the probability of a hazard occurring and creating loss’. This distinction was illustrated by Okrent (1980:372-75) who explained two people crossing an ocean, one in a liner and the other in a rowing boat. The main hazard (deep water and large waves) is the same in both cases but the risk (probability of capsizing and drowning) is very much greater for the person in the rowing boat. Therefore, as in our case, flood hazard can occur in an uninhabited region but a flood risk can occur only in an area where people and their position exist. Linked with this concepts is that, both hazards and risk can be increased and reduced by human actions, but when large number of people are killed, injured or affected in some way, the event is termed as ‘disaster’. Unlike hazards and risk, a disaster is an actual happening, rather than a potential threat. Therefore disaster is simply defined as ‘the realization of hazard’. But disaster is essentially social phenomenon that occurs when a community suffers an exceptional, non- routine level of stress and disruption. The term disaster is defined as an event, concentrated on time and space, in which a community experiences severe danger and disruption of its essential functions, accompanied by wide spread human, material or environmental losses, which often exceed the ability of the community to cope without external assistance. In our case, particularly flood hazard, for a number of times it was proved disastrous causing a huge loss of life and property. Natural hazards are sometimes known as ‘environmental hazards’ and the term generally refers to ‘geo-physical events such as earthquakes, volcanoes, drought, flooding, lightening, bush- fire, and high winds that can potentially cause large scale economic damage and physical injury or death.’ (Johnstone et. al, 2001: 216-17). Such events have different impacts depending upon both in their magnitude and the character of the receiving environment. Sometimes, the effects may be beneficial, as with the renewal of mineral nutrients to soil of a flood plain during flooding. But it is agreed that a precise definition of environmental hazard is still difficult. Burton and Kates (1964: 412-41) defined natural hazards as ‘those elements of the physical environment harmful to man and caused by forces extraneous to him’. Sometimes, natural hazards have also been seen as ‘Acts of God’. These perspectives, in most cases, have not been helpful. They actually over- emphasize the ‘surprise’ factors in disaster when, in reality, it is now possible to delineate an hazard -prone areas and to recognize that common disasters, such as floods, are recurrent events at certain locations, of which the present study area is an ideal example. In addition, because the ‘Act of God’ approaches suggest quite strongly that human have no part to play on creating disasters, it also implies that they have little hope to mitigate them (Smith, 2001: 259-288).

But in reality, most environmental hazards have both natural and human component. For example, flood problems may be exacerbated by fluctuation in climate, such as increased storm frequency and abnormally heavy rainfall, and also by human activities, such as land drainage and unwise and frequent diversion of stream channels or deforestation in the catchment basin. The loss of life caused by tropical cyclone depends on storm severity but it can be greatly reduced by means of a warning massage. Another example, the effects of a man made nuclear accident may be influenced by the prevailing weather condition. These interactions have lead to the increasing recognition of hazards as hybrid events resulting from an overlap of environmental, technological and social processes (Jones, 1993: 121-40). Other compound term includes ‘Quasi natural’ and ‘Na-tech’ hazards, and despite the convenience the term ‘truly natural hazards do not exist’ (Smith, 2001: 259-288).

The human ecological perspective on natural hazard distinguishes between natural events and their interpretation as natural hazards (or resource), can be illustrated in the following figure (Fig.-1). The concepts implicit behind this is that most natural events show a wide range of variation through time in the use of energy and material for environmental processes because the Earth is a highly dynamic planet. The conflict of geophysical process with people gives human a central role in hazards and it is only by retaining a balance between resources and hazards that sustainable economic development may be made (Smith, 2001: 11-288).


Human sensitivity to environmental hazards represents a combination of physical exposures reflecting the range of potentially damaging events and their statistical variability at a particular location and human vulnerability reflects the breadth of social and economic tolerance to such hazard events at the same site. As explained by Smith (in the figure) the shaded zone represents an acceptable range of variation for the magnitude of physical variable, which can be any environmental element relevant to human survival, such as rainfall. When the variability exceeds some threshold beyond the normal band of tolerance, the same variable starts to impose damage and becomes a hazard. Thus, very high or very low rainfall will be deemed to create a flood or a drought respectively. The accidence of damage threshold involves two basic dimensions of hazards to be identified: the hazards magnitude is determined by the peak deviation beyond the threshold on the vertical scale and the hazards duration is determined by the length of time the threshold is exceeded on the horizontal scale.

The hazards are classified in several ways. These can take the form of a basic division between natural hazards and human induced hazards or other hazards or a tripartite subdivision of hazards, for example, in to those of endogenous origin (earthquake, volcanoes); exogenous origin (severe weather, floods and drought) and anthropogenous origin (technological accidents). Whittow (2002: 620-646) has made a comprehensive classification of hazards in which geophysical, biological, and technological and lifestyle hazards are categorized, may be presented as bellow. (Table-1)

According to the scheme of the classification presented above we are concerned with the climatic hazards as flood, the geological hazards as riverbank erosion and the technological hazard that is arsenic contamination but it is also true, these hazards in our study area, at least the flood hazards and riverbank erosion has some direct relationship with that of the exogenous origin and also anthropogenic intervention, they have quasi natural flavor also.







Climatic and meteorological

Geological and geomorphic






Blizzards and snow





Hail Storms

Heat waves


Lightning strikes and fires






Shifting sands


Volcanic eruptions

Ground surface collapse



(athlete’s foot, Dutch elm, Wheat stem rust, Blister rust, potato blight)


(weeds, phreatophytes,

Water hyacinth)

Hay fever

Poison ivy


Bacterial and viral diseases(influenza malaria, typhus, Bubonic plague, venereal disease, Rabies, foot and mouth, AIDS)


(Rabbits, termites, locusts, grasshoppers, )

Venomous animal bite





Road(automobile, motorcycle, bicycle, pedestrian)

Nuclear radiation

Fossil fuel



Surface extraction

Entire construction

Plant explosion

Structural failure(bridge, builsing , dam, tunnel)


Toxic emission,



ground water pollution(nitrates, silages, slurry)



Appliances(gas, electrical, mechanical)

Poisonous substances



Water sport

Motor sports

Aerial sports

Contract sports

Source: J. Whittow, 2002


The compound term quasi-natural hazard signifies as hybrid events resulting from an overlap of environmental, technological and social processes (Jones, 1993: 161-65). For example, flood is sometimes a natural hazard but in most cases, where technology and social processes intervene into the natural flow of water in the channels, it turns into a quasi-natural hazard. Intensive agriculture and de-vegetation make the top soil more susceptible to erosion and the sediment loads deposited within the channels decrease the channel depth and thereby decreasing the capacity of carrying water with retarding the velocity. The amount of water flowing down from the upper catchment does not find way for quick release; it spills over the bank and inundates a larger area causing flood. At the same time due to the erection of cross dams and weirs and unscientific diversion of channels and ducts, the flood water remains stagnant for long time, making the flood a quasi-natural one. Similarly, riverbank erosion is purely a natural process, where large masses of soil are suddenly slid down in to the river bed due to extensive under-cutting by river water. This process is also enhanced by anthropogenic intervention such as de-vegetation of the bank and agricultural activities which help increase the weight of the soil with additional water gradually leaching down to the soil layer and thereby loosening a considerable length of the bank. Arsenic contamination is a technological hazard related to the extraction of sub-surface water from a greater depth where the bore- holes for setting deep tube wells dissolve the arsenic elements in to water which is pumped out to the surface for agricultural and domestic purposes.


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