Publication Date

5-2023

Advisor(s) - Committee Chair

Nahid Gani, M. Royhan Gani, Christopher Groves

Degree Program

Department of Earth, Environmental, and Atmospheric Sciences

Degree Type

Master of Science

Abstract

Bangladesh's Bengal Delta faces multiple challenges, such as rising sea levels, coastal flooding, and high population density, leading to land subsidence, saltwater intrusion, and biodiversity loss. The region's groundwater security, essential for the country's survival, is at risk due to climate change and saltwater intrusion. Groundwater security is dependent on the Bengal Water Machine (BWM), which is at risk due to saltwater intrusion and monsoon rainfall distribution from climate change. Groundwater exhaustion leads to natural hazards such as subsidence, landslides, and flooding. A large portion of the population is at risk from groundwater insecurity, which requires mitigating worldwide greenhouse gas emissions and more sustainable groundwater consumption practices in Bangladesh. This study utilized Differential Interferometric Synthetic Aperture Radar (DInSAR) and Persistent Scatter Interferometric Synthetic Aperture Radar (PInSAR or PSI) to quantify ground subsidence in urban and agricultural areas from Sentinel-1 data. A total of 55 pairs of Sentinel-1 scenes covering five target locations within the period from March 2017 to October 2022 were analyzed using DInSAR to derive ground displacement. In addition, displacement information for the metropolitan capital city, Dhaka was analyzed from 142 pairs from 52 ascending pass images over the same time period using PSI. This new study found consistent subsidence in urban Dhaka and semi-seasonal variability-related subsidence in five agricultural locations throughout Bangladesh. Urban Dhaka's average subsidence is estimated to be 16 mm/yr while the agricultural locations of Dhaka show subsidence trends of 7 mm/yr. Agricultural areas of Mymensingh are subsiding at 8 mm/yr, Rajshahi at 8 mm/yr, and Rangpur at 9 mm/year. The study highlights the vulnerability of Bangladesh's agricultural system and the impact of climate change on the world's largest mangrove forest, which

provides vital defense against cyclones. In addition, the research enhances our understanding of natural and anthropogenic hazard observance over significant periods, with BWM also playing a significant role in subsidence and groundwater consumption. The new subsidence results are instrumental in understanding the effect of sea-level rise driven by climate change that the region is experiencing today, but further work may be needed to better understand the relationship between subsidence, geologic controls, and geomorphological changes.

Disciplines

Earth Sciences | Environmental Studies | Geographic Information Sciences | Geography | Geology | Geomorphology | Physical Sciences and Mathematics | Remote Sensing

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