Landsat Based Analysis of Anthropogenic Land Cover Change and Implied Hydrologic Impacts in Bharatpur Metropolitan City, Nepal
Abstract
Since past several thousand years, human's deepest yearning towards owning their needs and modernizing the ways to fulfill them has led to industrial civilization and in turn the dramatic alteration of our terrestrial globe. Human practices to attain food, shelter, clothes, tools, means of transportation, and other higher-level needs trace footprints on natural cycles, e.g., hydrological, and biogeochemical, at the scale ranging from local to global. Advent of freely available satellite products and data analysis platforms have accelerated the research pace of quantifying the sprawl of built environment, agricultural lands, and population density and their impacts on hydrology. It is critical to examine the unevenness of human footprint across climatic, topographic, and physiographic regions and to assess whether the impacts to the residents are locally induced. Yet, there is a notable disparity in analysis between medium-sized cities in resource-limited regions versus larger cities from developed areas. This study aimed to elucidate the changes taking place in a medium-sized fastest-growing city, Bharatpur Metropolitan City of Central Terai, Nepal, by analyzing the growth of human-altered land cover areas during the past 30-years. We used surface reflectance products (L2) of optical and thermal bands of Landsat-5 TM and Landsat-8 OLI/TIRS selecting from the month of November 1991, 2005, and 2021 and ground-reference points to derive spatiotemporal variation of Modified Normalized Difference Impervious Surface Index (MNDISI). Later, we used Otsu's binary thresholding function on MNDISI to categorize landcover into altered and natural types. Mean value of MNDISI was found to be 0.07± 0.14 in 1991, 0.08±0.14 in 2005, and 0.30 ± 0.15 in 2021. The land area covered by current Bharatpur Metro city was found to be transformed from dominantly natural (54% natural,46% anthropogenic) in 1991 to dominantly anthropogenic (60% anthropogenic, 40% natural) in 2021 by gaining about 62.5 km2 of anthropogenic land. The annual rate of growth of anthropogenic land was found significantly higher during 2005-2021 (0.77%/year) compared to 1991-2005 (0.16%/year) implying the effect of large influx of internal migration followed by land modification starting around 2006, and suggesting a potential hydrologic alteration.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H25R1322K