Evaluation of causes and effects of environmental shifts in the Lower Digaru River Basin, Assam, India

Abstract

Environmental issues like deforestation, biodiversity loss, soil erosion, siltation, wetland shrinkage, river bank erosion, etc. in drainage basin perspectives today are in a rapid flux triggered by population growth and developmental activities. Focusing on the Lower Digaru River basin of North-East India,the present study investigates the changes in theLand Use / Land Cover (LULC)trend using geospatial techniques and the cause-effect relationship by identifying the various environmental issues operating within the study area. The study area has been classified into nine LULC classes: dense forest, openforest, scrub forest, fallow land, barren land, cropland, dense scrub, mixed built-up land, and water body. The results revealed that the area under dense forest has drastically declined from 60.25 % to 16.63 % during 1999-2020. In contrast, the other important categories like Mix built-up land (8.11 % to 14.05 %), scrub forest (2.1 % to 25.11 %), barren land (0.2 % to 6.63 %) and open forest (11.9 % to 18.34 %) show an increasing trend of change during the said period. Post-classification comparison of the classified images based on the transition matrix indicated that approximately 40 % of the total area under forest had been converted to scrub forest, followed by 25.09 % to open forest and, most significantly, 5.22 % to mix built-up land during 1999 -2020. Increasing population pressure and growth of economic activities like the establishment of brick industries, coke industries, and sand mining were the major driving forces for such LULC changes. Environmental implications like wetland shrinkage, river bank erosion, alteration of human occupation and economy, etc., were the study area’s prime concern. The findings suggest that integrated watershed management and land use planning should be implemented in the Lower Digaru River Basin.