COMPARATIVE ANALYSIS OF UNSUPERVISED LAND COVER AND LAND USE (LCLU) CLASSIFICATION AND THE NORMALIZED DIFFERENCE VEGETATION INDEX (NDVI) METHODS FOR ASSESSING AREAS AROUND TONGI KHAL, DHAKA, BANGLADESH

The Tongi Khal in Bangladesh, connecting the Turag and Balu Rivers, suffers from severe pollution due to the increased industrial activity around it. This study employs a multi-approach investigation including GIS, Remote Sensing, utilizing Landsat imagery from 1990 to 2023, and employing unsupervised classification NDVI and NDWI techniques to analyze Land Use and Land Cover (LULC) changes in Tongi Khal.

LULC analysis documents the presence of relatively stable waterbody areas from 1990 to 2023, with a slight decrease but a significant drop from 697 to 517 hectares between 2010 and 2020. Built-up areas exhibit steady growth, reflecting continuous urbanization, with significant expansion between 2000 and 2010 and further increases by 2023. Vegetation areas declined from 1990 to 2010 due to deforestation and urban development, but recovered notably by 2023, nearly reaching 1990 levels. Bare land increased until 2010, peaking and then slightly decreasing by 2023. NDVI assessment indicates a substantial decline in waterbody areas from 1990 to 2023, particularly pronounced from 1990 to 2000. Built-up areas experienced rapid expansion from 1990 to 2010, although a decrease is noticeable from 2010 to 2023. Vegetation areas decreased until 2010, mostly due to urbanization, but substantially recovered by 2023.

The consistent increase in built-up areas suggests significant urban expansion largely driven by population growth and economic development. The rise in vegetation from 2010 to 2023 may indicate reforestation efforts or improved land management. The increase in bare land until 2010 implies land degradation and subsequent stabilization by 2023. The decline in waterbody area from 2010 to 2023 could result from climatic shifts or anthropogenic activities ensuing progressive alteration of land use. Land Cover and Land Use (LCLU) analysis demonstrates a reduction in waterbody areas, rapid built-up zones reflecting urban growth, and varying vegetation trends, with significant recovery by 2023 due to reforestation or improved land management.

Keywords: GIS, Land use and Land cover, NDVI, NDWI, Urbanization, and Anthropogenic activities.