The Lower Damodar River, India

The Damodar River, a subsystem of the Ganga River in India, exhibits most of the characteristics of a seasonal tropical river with a fluctuating regime. In this chapter, the author examines the Damodar valley region, focusing on the various factors that led her to select the applied geomorphological perspective as the most appropriate perspective for the study. In the absence of an a priori model to examine applied geomorphological and human environmental issues in a controlled riverbed, several concepts from inter-connected disciplines will be utilized to verify empirical facts. One of the objectives of this study is to explain land use characteristics and human perception, adaptability and resource evaluation on the riverbed in relation to human adjustment to floods and dams of the Lower Damodar. Therefore, a brief discussion of the concept of land, land resources and land use has been provided. Some concepts such as social space, perception, culture, refugee, human ecology, hazard, and empiricism, borrowed from sociology, anthropology, ecology, philosophy and similar disciplines, have been considered in explaining a human-modified fluvial environment.

The Damodar River, a subsystem of the mighty Ganga system, has always been notorious as a calamitous river like the Hwang Ho of China and the Kosi of India. People as well as governments throughout the centuries have dealt with the caprices of these vital water resources using different strategies. In the case of the Damodar, heavy embankments were used in its lower sector to reduce flood hazard in the Rarh plain. When the Damodar Valley Corporation (DVC) was first conceived and modeled after the Tennessee Valley Authority (TVA) of USA in 1948, the river was again controlled, this time through the construction of sophisticated engineering structures. This chapter focuses on the hydrogeomorphic consequences of lateral control structures. The riverbed has been raised, soil composition in the adjacent riparian tract has been changed, cross sections have been increased, and a number of spill channels have been opened on the right bank. In addition, shifting of banklines and bank erosion are observed on the left bank.

Rivers respond to anthropogenic activities through morphological and hydrological adjustments in the channel. This chapter addresses the hydromorphological consequences of the control structures on the Damodar River. Dams have altered the flow regime, channel characteristics and the sediment supply of the river. Under natural flow conditions, on an average, 12 days per year experienced a flow above 2,265.6 m³/s. This has decreased to 4 days under artificial conditions. Monsoon streamflow has been reduced, but non-monsoon flow has increased albeit with a very high variability in the post-dam period. The R.I. of the bankfull stage, a flow of 7,080 m³/s in the pre-dam period, increased from 2 to 14 years in the post-dam period. The magnitude of the design flood from Maithon and Panchet reservoirs has been reduced by about 56%. During the non-monsoon period canal discharge in most cases exceeds the river discharge. The low volume of water released downstream during dry months virtually transforms this section into a sandy waste whereas the high discharge released during monsoon months converts the section to a vigorous flowing channel. Although some sediment is trapped in the reservoirs, a million tons of sediment nevertheless pours into the river from the uncontrolled stretch. Capacity of the river to transport this sediment has been reduced due to the reduction of flood peaks. A chain of sandbars has emerged within the riverbed below the control structures. The channel deposits in the study area support agriculture and most of the channel bars have been settled and are now used as a resource base, mostly by Bangladeshi refugees.

The Damodar riverbed has been colonized in different phases since 1947, mostly by Bangladeshi refugees. They are self-alienated refugees who have rejected the dole-sustained existence in government-sponsored refugee camps and opted, instead, for life on the controlled riverbed. After India achieved independence in 1947, fuller utilization of the river resources was needed to solve socio-economic problems. At the same time, the partition of India initiated large scale migration, particularly of Hindus from both West and East Pakistan (Present Bangladesh). Of all the refugee-receiving states in India, West Bengal had the maximum number of refugees, a problem that was aggravated after the Bangladesh War of 1970 when there was a fresh influx of refugees from independent Bangladesh. In both phases, a significant number of Bangladeshi refugees selected the riverbeds of West Bengal as their second home. The Lower Damodar bed is one such riverbed. It has been permanently occupied by these Bangladeshi refugees and has become a major resource base for them. The flood of September 1978 also initiated a desperate migration of locals from the flood-affected areas of Medinipur and Hooghly districts to the adjacent riverine sandbars. Control structures on the river have brought many changes to the riverbed environment and the refugees are constantly struggling with this changed environment for their survival.

The Damodar riverbed consists of a series of alluvial bars that are now used as a resource base mostly by refugees. The stretch between Panchet Maithon reservoirs and Barsul-Chanchai is not atypical in terms of contemporary riverbed morphology and bed materials particularly below the Durgapur barrage. But the riverbed landscape, formed by interactions between the riverbed and its occupiers, shows diversity at a micro level. Using their knowledge of river stages, settlers have matched land use at fine scales to flood incidence, applying a concept of flood zoning to the riverbed and effectively utilizing every available inch of space. Functional relations between the riverine environment and riparian community have been influenced by culture, social space, perceived environment, land ownership rights and political forces. As there is no a priori model for human-environment relations, assessment of short-term risks and long-term benefits of water release from the reservoirs and decisions on specific land use are made on the basis of personal experience. The stretch between Maithon/Panchet reservoirs and Barsul Chanchai has become less hazardous and more resource-rich with the mitigation of the annual flood discharge. Here risk is capitalized as resource and long term benefits have overshadowed the short term risk. Paikpara is an example of changing location of the resource base subsequent to a geomorphic threshold. The opening of the Muchi-Begua Hana has transformed an over-bank settlement to a mid-channel settlement. The thalweg of the Amta Channel is extremely narrow compared to the culturally defined riverbed and is not so significant in comparison to the other two sectors of the Lower Damodar.

The Lower Damodar should be culturally defined. Forms, processes and materials in the controlled section are generically quasi-natural in character. Social space of Bengali refugees has played a significant role in riverbed colonization and in subsequent land use practices. There is a strong linkage between changing geomorphic space and perceived environment. Land ownership rights are crucial factors in riverbed land utilization. The modified concept of human ecology helps in explaining land uses. There can be no a priori model for human-environment interactions. Human interaction with the environment depends on personal experience. The controlled Lower Damodar is a product of twin processes; quasi-natural hydro-geomorphic processes on the one hand and anthropogenic land-utilization processes on the other.

The Damodar riverbed has provided a home for marginalized communities, but the riverine environment itself has deteriorated; presenting us with a challenge to develop a more holistic and sustainable water management system. There should be a mix of structural and non-structural measures that acknowledge and incorporate local cultural attitudes, experience and knowledge. For effective water resource management, river communities must be part of the effort so their interests are aligned with the aims of the project and they feel committed to the success of the endeavor. River regimes should be treated as economic assets since ongoing economic and human development depend on an ecologically sound riverine environment.