Assessment of Shoreline and Agricultural Land Use Changes in the Onshore Coastal Region of Bangladesh Delta Using Satellite Remote Sensing and GIS

Bangladesh is a global south hotspot due to climate change and sea level rise concerns. It is a highly disaster-prone country in the world with active deltaic shorelines. The shorelines are quickly changing to coastal accretion and erosion. Erosion is one of the water hazards to landmass sinking, and accretion related to land level rises due to sediment load deposition on the Bay of Bengal continental shelf. Therefore, this study aimed to explore shoreline status with change assessment for the three study years 1991, 2006, and 2021 using satellite remote sensing and geographical information system (GIS) approaches. Landsat 5, 7 (enhanced thematic mapper plus, ETM+), and 8 (operational land imager, OLI) satellite imageries were employed for onshore tasseled cap transformation (TCT) and land and sea classification calculations to create shore boundaries, baseline assessment, land accretion, erosion, point distance, and near-feature analysis. We converted 16,550 baseline vertices to points as the study ground reference points (GRPs) and validated those points using the country data sheet collected from the Survey of Bangladesh (SoB). We observed that the delta’s shorelines were changed, and the overall lands were accredited for the land-increasing characteristics analysis. The total accredited lands in the coastal areas observed during the time periods from 1991 to 2006 were 825.15 km2, from 2006 to 2021 were 756.69 km2, and from 1991 to 2021 were 1223.94 km2 for the 30-year period. Similarly, coastal erosion assessment analysis indicated that the results gained for the period 1991 to 2006 and 2006 to 2021 were 475.87 km2 and 682.75 km2, respectively. Therefore, the total coastal erosion was 800.72 km2 from 1991 to 2021. Neat accretion was 73.94 km2 for the 30-year period from 1991 to 2021. This research indicates the changes in shorelines, referring to the evidence for the delta’s active formation through accretion and erosion processes of “climate change” and “sea level rise.” This research projects the erosion process and threatens land use changes toward agriculture and settlements in the coastal regions of Bangladesh. The agricultural land use class was ranked one among other major land use and land cover (LULC) classes. In the study area, 34.03%, 34.47%, and 33.52% were occupied by agricultural land use for the study years 1991, 2006, and 2021, respectively, within the studied area of interest (AoI). Among all LULC patterns in the study, the agricultural lands increased in 2006 from the year 1991. On the other hand, the cultivated agricultural land had decreased in the year 2021 from the study year 2006. Hence, the agricultural lands were under great threat of loss of lands due to the coastal erosional processes in the Bangladesh delta. Therefore, it is urgent to develop new croplands area in the accredited new mud, soil, and intertidal (MSI) land-covered area for mitigating the loss of agricultural lands in onshore coastal areas of Bangladesh to strengthen the food security of the coastal region in Bangladesh.