Vibhash C Jha.Cdr

NGJI, An International Peer-Reviewed Journal NGSI-BHU, ISSN: 0027-9374/2020/1733 Vol. 66, No. 2, June 2020 Environmental Risk Assessment: A Geomorphic Investigation over the Bolpur-Santiniketan-Illambazar Lateritic Patch of Birbhum District, West Bengal, India Vibhash C. Jha1 and Subhasis Ghosh2 1Professor of Geography, Former Vice-Chancellor, TMBU, Former Director NATMO, DST, Government of India, Visva-Bharati University, Santiniketan, West Bengal, 2Research Scholar, Department of Geography, Visva-Bharati University, Santiniketan, West Bengal, (Corresponding author's e-mail: [email protected]) Abstract A proper geomorphic study of a region can be useful in understanding past and present environmental circumstances and analyzing potential environmental risks. Careful analysis of morphodynamic processes and existing diagnostic landforms reveal several aspects about the origin, characteristics and possible pattern of morpho-climatic interactions on the landscape over temporal scale, which helps significantly in proper terrain evaluation from societal welfare and integrated management point of view, including environmental risk assessment and disaster management. This paper has made a thorough geomorphic investigation based on intensive fieldwork and multi-sourced remote sensing data to characterize the lateritic soil profile and landforms of the study area in respect to their morphology and Physico-chemical properties at the different sites of land degradation to understand the outcome of morphoclimatic interactions on the landscape over time, and to evaluate the severity of operation with pedo-geomorphic constraints in the lateritic environment for sustainable management purposes. It is found that the region is highly sensitive to weathering, mass movement and denudational activities, mainly caused by rainwater erosion which has resulted into varied landforms including well-developed rills and gullies, lateritic ridges, isolated residual hills etc and generated a unique identity to this part of the lateritic region. The study also suggested a model for the development of geomorphic landforms in a lateritic terrain based on past and present morphoclimatic interactions, nature of physiography, lithology, soil characteristics and other biotic and abiotic elements. The region is also found to be a subject to moderate to severe land degradation due to the active geomorphic processes in operation in tropical regions and inherently poor physical and chemical formation of the existing soil profile and radical conversion of land uses as observed at cadastral level leading towards irresistible desertification. Annual topsoil loss amount has been calculated using the Universal Soil Loss Equation method. Three sample Mouzas namely Ballavpur, Shyambati and Chawpahari jungle have been assessed to be having 36.98%, 71.42% and 61.73% of degraded land in respect to their total village area. Various conservative measures like stabilization of gully heads and beds through reforestation and afforestation with cutting earth plug, brush fills and check dams; improvement of the irrigation network, suitable dryland farming etc. have been recommended to arrest the desertification process. Environmental Risk Assessment: A Geomorphic Investigation ... 95 Keywords: Land degradation, desertification, environmental management, lateritic terrain, morphoclimatic interaction, environmental risk Introduction The rapidly evolving discipline of limited to the planet earth, but it also takes a geomorphology has undergone a sea change in close look at the images of Moon, Mars and methodology and approaches to the study of other planets provided by spacecraft has landforms and related processes since 1945 created an extraterrestrial aspect to when R. E Horton introduced a quantitative geomorphology. The main aspects i.e. Static method for the analysis of morphometric Geomorphology, Dynamic Geomorphology, characteristics of a fluvial eroded landscape. Genetic Geomorphology and Environmental Although the subject matter of geomorphology Geomorphology can be studied in terms of is often commonly restricted to those Spatio-temporal concepts to understand the landforms that have developed at or above sea factors and independent variables responsible level, in reality, it includes all the aspects of the for landscape modifications and the cycle of interface between the solid earth, the process-form mechanisms existing in a region hydrosphere and the atmosphere, therefore not (Verstappen,1983). With alteration in scale only are the landforms of the continents and different problems can be identified, different their margins are of concern, but also the types of explanations become relevant and morphology of the seafloor. Today though, the dominant variables can be identified for proper scope of the subject has witnessed a gradual terrain evaluation purposes or to understand the change with the advancement of technology. morphodynamics of a certain region (Figure 1). Today the scope of the subject is not only The landform is a crucial part of the Figure 1 - Different Aspects of Geomorphology 96 Vibhash C. Jha and Subhasis Ghosh environment and has a direct relationship with Several studies have been carried out the environmental conditions. These are not previously by different investigators regarding created instantaneously. The smallest, such as a the concepts of the origin of Indian laterites ripple mark may develop in a few minutes, but over time as discussed by Roychowdhury et al. large landforms of continental dimensions or (1965), Bhattacharya and Banerjee (1979) who even large units of continents such as mountain discussed about the regional geology and chains or extensive plains have a history of tens geomorphology of Birbhum district; or hundreds of millions of years. Geomorphic Bandopadhyay (1987) regarding the slope processes leave their distinctive imprints upon evolution and cliff-line retreat rates of the landforms and each geomorphic process western and south-western parts of Birbhum; develops its own characteristic assemblage of Das and Bandopadhyay (1996) who strictly landforms as different erosional agencies act on analyzed the process of badland development the earth's surface, thereby producing a in the lateritic region of Santiniketan, West sequence of landforms having distinctive Bengal from the physical or geomorphic point physical and chemical characteristics at the of view; Jha (1997), Jha and Kapat (2009, successive stages of their development. It is a 2011)who extensively worked on the origin fact that different processes work in different and properties of the lateritic patches of climatic regions and with climatic variations, Birbhum district, determination of risk of rill there is also variability in the nature and mode and gully erosion hazards in terms of their kind, of influences of climatic parameters (e.g. extent and degree as manifested in morphology rainfall, temperature, humidity etc.) which and morphometric characteristic of affect denudation processes such as erosion, geomorphic features in hydrogeomorphic units weathering, mass movement, run-off etc. and land-use practices within lateritic Hence, landforms also differ significantly in confinement of the basins. Besides these, many different climatic regions. These typical other pieces of research on land degradation in diagnostic landforms are one of the main tools respect to geomorphic processes, change in of climatic geomorphologists which help them land use have been conducted as done by in determining climate-landform relationships Ghosh and Bhattacharya (2012), Ghosh and in different climatic regions. Morphoclimatic Guchhait (2015), Das (2015) and others. The mechanisms in particular significantly change present study is aimed to examine the above the landscape in terms of spatial and temporal concept by investigating and characterizing the scales. The denudational processes are very lateritic soil profile and landforms of a part of crucial in this very effective regard, Birbhum district of West Bengal State, India in particularly in the tropical and subtropical respect to their morphology and Physico- regions where the landforms characteristics are chemical properties in different sites of land the best indicator in studying the rate of degradation to understand the morphoclimatic denudation. Hence, it is considered that a effect on the landscape over the years, and to proper geomorphic study of the area of interest evaluate the severity with pedo-geomorphic (AOI) may significantly help experts in constraints at the lateritic environment for understanding the past and present better crisis management. environmental status, reasons behind the Study area evolution of present landscape and finding out The Birbhum district (23° 36'N to 24° 4' any potential environmental risk it might have. 40''N, 87° 25' 30''E to 87° 39' 26'' E) lies Environmental Risk Assessment: A Geomorphic Investigation ... 97 between the western upland and the eastern pedo-geomorphic characteristics of the alluvium plain (Jha and Kapat, 2011). This degraded lateritic region. Though the Birbhum region is a part of the Rarh region, which is also district is characterized by three types of known as 'Self of Lateritic Alluvium'. Three geomorphic processes, namely denudational, sample morphosites, i.e. Ballavpur and fluvial and anthropogenic mechanisms, Shyambati mouzas in Bolpur-Sriniketan C.D however, the sample morphosis is the result of Block, and Chowpahari Jungle situated in denudational morphoclimatic mechanisms. Illambazar

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