1.1 River Health

Traditionally the term ‘river health’ (Richard et al. 1999) depends solely on the measurement of physical, chemical and some biological characteristics of the river (Gore 1985; Boon et al. 1992; Brookes and Shields 1996). It is usually applied to the assessment of river condition and often found as analogous to human health.

Physical characteristics of river include the fluvial geomorphology and surface hydrology of a river basin, which control the structure and dynamics of river channel. Changes in flow and sediment regimes following catchment modification can markedly alter the physical nature of the channel. River channel can function in unnatural ways (Schumm 1988; Gurnell and Petts 1995). Moreover the chemical indicators (mostly of water quality) are the most commonly used for detecting the ‘river health’ (Hart et al. 1999; Maher et al. 1999).

Hynes (1975) argued that ‘in every respect the valley rules the stream’, where catchment character influences a river by large-scale controls on hydrology, sediment delivery and chemistry (Allan and Johnson 1997). Rivers are among the most intensively human-influenced ecosystems on the earth. They serve for transportation, water supply, power generation and also as a source of food as well as sinks for waste products. As a result, in highly industrialised countries and in some developing countries, many rivers are now severely unhealthy. Most common impacts are channel and bank modifications (i.e. canalisation for agricultural purposes, bank protection, development of slums), flow regulation and fragmentation (i.e. reservoirs for water supply, diversion for irrigation and industrial purposes), unscientific collection of soil and sediments (e.g. sand quarrying from the riverbed and bank for industrial as well as domestic purpose) and chemical pollution (e.g. heavy metals, pesticides, fertilisers) and organic pollution (e.g. domestic and cattle-raising waste water). All these alterations have led to an extensive ecological degradation of these rivers, making them no longer sustainable in providing goods and services (e.g. decline in water quality and availability, intense flooding) (Poff et al. 1997). Norris and Thoms (1999) defined the term river from biological point of view. According to them the term ‘river health’, applied to the assessment of river condition, is often seen as being analogous with human health, giving many a sense of understanding. Unfortunately, the meaning of ‘river health’ remains obscure. It is not clear what aspects of river health sets of ecosystem-level indicators actually identify, nor how physical, chemical and biological characteristics may be integrated into measures rather than just observations of cause and effect.

Certainly it is argued that if the river side habitat was in poor condition, the health of the stream would be affected adversely (Plafkin et al. 1989; Brookes and Shields 1996). It shows that if we have an unhealthy catchment or valley, we would have an unhealthy stream. Similarly, this assessment can also do in reverse: a stream may be assessed as being unhealthy and then it is concluded that the catchment is unhealthy (Sweeney 1992; Osborne and Kovacic 1993).

In a nutshell, river health may be defined as the condition of the anatomy and physiology of any river. Anatomy of any river mainly includes the physical condition of the river, whereas the physiology of any river includes the chemical and biological condition of the river. Physical condition of the river further includes the changing hydrological behaviour of the river, channel shifting and migration, river course change, flood and river bank erosion and related phenomena. On the other hand, physiological condition of the river includes the chemical and biological properties of the river water. Thus, river health is a subject, which combines fluvial geomorphology, river hydrology and environmental pollution. It is worth mentioning that all of the aforesaid conditions of the river health may be changed due to human intervention.

1.2 The Problem

The river is treated as the lifeline of Agartala, the Capital City of Tripura. Originating from the Baramura Hill, the river debouches onto the rolling plain at Chandrasadhubari near the NH 44. Thousands of people between Chandrasadhubari and the boundary of Bangladesh have been settled along the river bank and directly dependent on the river. Moreover, about 60 % of population of Agartala City is directly or indirectly dependent on the river for drinking water and other domestic purposes.

Previous records show that the river bank was almost uninhabited and the population of the whole basin was also less. During that period, most part of the upper catchment of the river was densely covered with vegetation without any human intervention. Since the partition of India and East Pakistan (presently Bangladesh), and particularly from 1950, huge number of people immigrated to the state from East Pakistan (Bangladesh) as refugee. Most of those immigrants were spread over the whole basin, and the weaker section (below poverty line) of such population settled along the river and thereby increased the pressure on the river enormously. Moreover, with the increasing population, medium- and small-scale industries have also emerged within the Haora River basin. The workers of such industries started to commit nuisances and throw all types of solid wastes along the river bank. All of these activities affected the quality of river water and the pollution level of water also started to increase.

Vulnerable geological structure, unconsolidated soil layers and heavy and concentrated rainfall along with deforestation, cutting of uplands (locally called tilla) and unscientific and unplanned usage of land have led to the establishment of a vicious cycle of denudation. All these eroded materials are carried down the lower reach of the Haora River during monsoon period and created a fluctuating nature of river physiology through the enhancement of scouring and filling. In addition to that, artificial deposit of solid waste along the river bank supplies some extra amount of sediment load to the river. The river sometimes fails to carry these excess sediment loads and deposits them in different sections of its lower reach. As a result, the depth as well as the cross-sectional area of the river valley decreases that fails to carry excess amount of unusual monsoonal discharge and allows water to spill causing floods ruining the lives and properties of the local inhabitants.

Moreover, in some places, people hinder the natural flow of the river by constructing causeways, putting cement bags across the river for water storage and also cultivating the dry riverbed during lean season, through which the natural dynamics of the river is being changed. If immediate necessary measures are not taken, the whole area will suffer from the scarcity of drinking water and flood hazard during monsoon period. Therefore, the present study has been undertaken to find out the problems related to the overall health of the Haora River and to bring out some possible suggestions for restoring ecological balance and geopolitical stability of this strategically important part of the country.

For an in-depth study of the river health, the Haora River from the state of Tripura (NE India) has been taken into consideration under the following points:

  • To identify the nature and extent of population change within the basin along the river up to the floodplain boundaries

  • To detect the nature of changing course of the Haora River and probable causes behind it

  • To assess anthropogenic impact on the river in terms of agricultural growth, industrialisation and expansion of slums

  • To analyse the pollution status of river water

  • To estimate the amount of soil loss contributing to augmented sediment load within the channel with the help of RUSLE method

  • To analyse the nature and extent of bank erosion along the Haora River

1.3 Past Works

1.3.1 Earlier Published Works on Different Issues Related to the Haora River

Many research works have been carried out on several topics like population and urban growth, sedimentation and pollution on the Haora River both nationally and internationally.

Different government and non-government agencies have prepared reports on the inventory about the present status of the water quality of Haora River near Agartala town by analysing the impact of slum dwellers and urban growth on the river near Agartala; urban infrastructure and service improvement including the rehabilitation, improvement and expansion of (i) water supplies, (ii) sewerage and sanitation and (iii) solid waste management for the Agartala city. Most of the reports are kept for departmental use only and not available for public use. Tripura State Pollution Control Board (2004) prepared a detailed study on pollution status of the Haora River.

Datta et al. (2008) used distributed hydrological modelling to quantify the future water availability as well as the importance of Haora River basin and to formulate the water quality management. The Tripura State Pollution Control Board has published the detailed monograph of De (2012) on the ‘Geoenvironmental status of Haora River’. The monograph was prepared on the basis of an intensive study on the Haora River in order to save the river from its deterioration and was the premier report of its kind on the river. Bhattacharyya et al. (2007) prepared a model for estimating the soil loss and its impact on crop productivity for the entire Tripura.

1.3.2 Human Population Growth and Its Impact on the River Basin

Anthropogenic activity plays an important role in the modification of environment. With the rapid development of technology, man is reforming landforms for fulfilling their need and greed. This reformation of topography has both positive and negative impacts on the environment. Several anthropogenic activities are responsible for changing the physical, chemical and biological characteristics of any river, but most of the earlier works are mainly concentrated on the human impacts on the chemical and biological properties of the river. Very few works have been done on the physical health of the river.

Keith et al. (2013) prepared a survey on the demand of water resource of the growing population within the Nile Valley. Some other works of Swain (1997, 2002) and Tadesse (2004) have also emphasised on the demand of population on the same area. On the same issue, but on other rivers have been conducted by Pitchammal et al. (2009). Yeasmin and Khan (2012) published a detailed report on the impact brick industries within a river basin.

Impact of anthropogenic activity on river is an important issue, but there is hardly any generalised work on it. Most of the works have been carried out on the basis of one or two individual parameters, e.g. Nawa and Frissell (1993), Langer (2003) and Salahuddin (2009) have published papers on the impact of sand mining in the river and also recommend best possible alternative ways for scientific sand quarrying. Michael and Layher (1998) and Kori and Mathada (2012) have worked on the impact of sand mining in altering land use and habitat degradation of the riparian environment.

Similarly very few works have been published internationally on the impact of causeways on river (e.g. Percy 2008). The effect on bridges on the river system is an important issue worldwide (Hencock 2002). Heidarnejad et al. (2010) accounted for a detailed engineering report on the flow pattern and mechanisms of unnatural riverbed scouring around the bridge piers. Coleman and Melville (2001) also provide a detailed work on the mechanism of scouring and bridge failure. The works on related field, such as the nature of gravel scouring around the bridge on different rivers, and the works of Laursen (1960), Ettema (1980), Klaassen and Vermeer (1988a) and Watson (1990) are notable.

Impact of bridge piers in the river system is an emerging issue in the current research. The works of Breusers et al. (1977), Heidarnejad et al. (2010) and Shen and Schneider (1969) are mainly based on the mechanism of scouring of river around the bridge piers and the impact of this on the river. Biswas (2010) and Seiyaboh et al. (2013) have given more emphasis on the environmental impact of bridge piers on the river.

Saviour (2012) has prepared a detailed report on the impact of sand mining on the environment. A field analysis on the impact of sand mining on the natural dynamics of the Padma River has been done by Singh et al. (2007). Suvendu (2013) has prepared a report on the impact of four causeways on the temporal change in the cross section, course and depositional pattern of the Kunur River, West Bengal. Impact of bridge piers has also been an important issue in India (Dey 1999; Kumar et al. 1999).

Large river systems throughout the planet have been dramatically transformed due to river control projects such as large dams and embankments. Unlike other major human impacts like anthropogenic climate change, the alteration of river systems has been deliberate and planned by a small, powerful set of experts (Baghel 2014). The concept of large-scale transformation of fluvial environments into technological hydroscapes originated in the West, widespread construction of large dams started in the countries of the Global South in the period after decolonisation. Construction and operation of large dams are amongst the most prestigious but also most sensitive development issues, often accompanied by massive resistance of adversely affected people and civil society organisations that affect the river health to a greater extent (Nüsser 1995).

1.3.3 Course Change of the River

The course of any river is very dynamic in nature. Since its origin, a river changes its course in response to topography, tectonic settings, sediment flow and human activity. Ebro River, Spain (Ollero 2010); Beatton River, Canada (Nanson 1981); and Po River, Italy (Braga and Gervasoni 1989) changed their course for several times due to any of the aforesaid reasons.

Several papers on channel shifting or course change on numbers of rivers like the Ganga River (Harijan et al. 2003; Pati et al. 2008; Swamee et al. 2003), the Kosi River, (Gole and Chitale 1966; Wells and Dorr 1987), the Gandaki River (Mohindra et al. 1992), the Brahmaputra River (Kotoky et al. 2005), the Meghna River (Rahman and Khan 2001; Rahman et al. 2004) and the Indus River (Harbor et al. 1994) have been published in which the trend and causes of such changes have been discussed.

1.3.4 Bank Erosion of the River

Bank erosion is a severe problem to any fluvial system, and several attempts have been made to demarcate, quantify and control bank erosion. The following are different methods of estimating bank erosion:

  1. (a)

    Graft method (Graft 1984) proposed that bank erosion probability for any given cell could be determined by taking its lateral distance towards the upstream side of the active river channel and a value representing flood magnitudes for the given period.

  2. (b)

    Bank shifting method (Sandra and David 2000) estimates bank erosion by superimposing temporal river banks and measuring the gap between them.

  3. (c)

    Photoelectronic erosion pin (PEEP) method (Lawler 1991) provides quasi-continuous data of the frequency, magnitude and timing of the individual erosion and deposition on the river banks.

  4. (d)

    Experiment method (Imanshoar et al. 2012) estimated subsurface bank erosion of vertical river banks, composed of alternate layers of sand and clay under uniformly distributed constant overhead pressure

  5. (e)

    Method of measuring bank material strength (Thorne 1981) by using erosion pins to large-scale studies using aerial photos and maps.

  6. (f)

    Numerical analysis of river channel processes with bank erosion (Nagata et al. 2000) used for investigating both bed deformation and bank line shifting in 2D platform in a moving boundary-fitted coordinate system.

  7. (g)

    Bank Erosion Hazard Index (BEHI) and near-bank stress (NBS) method (Rosgen 1996). BEHI and NBS are used together as independent variables in a series of regression equations that predict annual lateral bank retreat. Some other GIS-based methods have also been introduced to estimate bank erosion (Bhakal et al. 2005; Kummu et al. 2008; Thakur et al. 2012).

Several attempts have also been made for demarcation and mitigation of bank erosion in different rivers in India. Das and Saraf (2007), Goswami (2001) and Singh et al. (2004) tried to estimate the bank erosion of the Brahmaputra River, one of the major bank erosion-prone rivers of India. Some other individuals worked on the demarcation and mitigation processes of Ganga River bank erosion, like Banerjee (1999), Mukhopadhyay (2003), Pati et al. (2008) and Roy (2004). The nature and extent of bank erosion have been studied for a part of Majuli Island using remote sensing data (Mani et al. 2000, 2003) and the Brahmaputra River channel, Assam, India (Kotoky et al. 2005).

1.3.5 Soil Erosion and Sedimentation Problem of the River Basin

The Universal Soil Loss Equation (USLE), the Revised Universal Soil Loss Equation (RUSLE) and the Modified Universal Soil Loss Equation (MUSLE) methods of FAO/UNEP are widely used methods of estimating soil erosion. Using USLE with the help of GIS technology, Gupta et al. (2005) estimated soil loss for the Luni River basin, Allahabad, and found that this method is useful for better soil conservation practice in the basin. Similar method has been used for estimating soil loss for different areas of the world by Beach (1992), Sadeghi (2004), Nontananandh and Changnoi (2012), etc., and got positive results. Shrestha (1997) and Ande et al. (2009) have used Morgan and Morgan Finney (MMF) model on highly dissected terrain land in their respective areas of study. Ferro and Minacapilli (1995) argued that a particular model revealed more accurate result than other versions of RUSLE, because of the predominance of higher relative relief in their study areas.

Changes in agricultural techniques reduce the amount of erosion and subsequent sediment transport throughout a basin (Julien and Vensel 2005). Adams and Roberts (1993) proposed an inventory on erosion and sedimentation (both natural and artificial) of Mississippi Delta through the analysis of hydrological parameters and the factors that lead to soil erosion in the upper catchment of the river. Sedimentation problem in some of the large rivers of Asia have been studied by Bali and Karale (1977), Sadeghi (2011), Walling (2011) and Khan et al. (2007), and some case studies have been done to investigate their nature and extent of sedimentation by Chappell et al. (2011), Furuichi and Wasson (2011), Sarker et al. (2011) and Ziegler et al. (2011).

Chandramohon and Durbude (2001) used ILWIS software for estimating soil loss of the Hire Nadi Catchment, Karnataka, and analysed the terrain condition through the RUSLE method. Some other works on estimating soil erosion applying RUSLE have got real result with the field (Singh et al. 1985; Gupta et al. 2005; Javed et al. 2009; Ahmad and Verma 2013). MMF model of soil erosion has also been successfully used by Behera et al. (2005), Kumar and Sharma (2005), Ghosh and Guchhait (2012) and Kale and Vadsola (2012).

Kothyari (1997, 2011) and Kothyari and Jain (1997) have prepared an inventory on the sedimentation problem and its management for the sub-Himalayan regions (Jain and Jain 2011; Mishra and Sen 2011).

1.3.6 Water Pollution

Increasing growth of population along with the development in the agricultural and industrial sectors is considered as a major threat to river health. Unscientific releases of toxic chemicals from the industries into the river make the water polluted and become the source of several waterborne diseases. Environmentalists have enacted several laws for regulating the pollution level, but still it is a great threat to the society as well as environment.

Most of the papers related to pollution are focused on the concentration of several metallic, nonmetallic and biological pollutants on the river water that are coming from the industrial and agricultural sectors (Bolawa and Gbenle 2012; Graft et al. 1991; Ladd et al. 1998). The Surface Water Quality Bureau (1999) conducted a series of multiple-day intensive water quality surveys of the Red River watershed and selected tributary streams. Solid waste disposal from the city or other overpopulated areas along the river bank or inside the river is another source of water pollution (APHA 1996; Aramini et al. 2009; Coleman 1976; Radha Krishnan et al. 2007 and Sallae 1974). BIS (1992) analysed the impact of solid waste disposal in the Yamuna River.

Effluents from tannery industries along the Ganga River at Kanpur City pollute the river water as well as the sediment (Beg and Ali 2008). Changes in water quality of the Jhelum River and other springs due to urban waste disposal have brought great threat to the health of the people living downstream to Srinagar and Jammu valley (Rather et al. 2010, 2014). Heavy metal concentration and sediment quality in the Indian rivers have been studied by Reddy and Baghel (2010) and Rengalakshmi et al. (2007).

Spatiotemporal analysis of pollution and sedimentation of any river system is very difficult because of the shortage of available data. Selection of proper technique is also a difficult task. The magnitude of anthropogenic impact also varies from one river to another. Thus, we need to select proper technique of analysing such problems considering all such facets. The statistical methods or approaches based on GIS seem to be more reasonable as it provides high accuracy.