Dynamics of human presence and flood-exposure risk in close proximity to Bangladesh's river network: an evaluation with multitemporal satellite imagery

Assessing human presence in close proximity to river network is crucial for frequently flood-affected populous countries, like Bangladesh, to reliably estimate flood-exposure risk. Using multitemporal satellite nighttime light (NTL) as a proxy for human presence, we examined the spatial distribution and change in NTL luminosity (+11,225.69 km(2) areas) across Bangladesh during 2000-2018 at national and river network scales. Results showed a rising trend and emerging hotspots of nightlights and increased near-river population (+1.5 million) under flood-exposure risk. These patterns were coincident with the dwindling of forests (-91.89%), grasslands (-6.02%) and barren lands (-27.92%) and increased built-up (11.06%) areas. Positive correlations were found between annual NTL luminosity and LandScan population (r = 0.48) and annual population (%) access to electricity (r = 0.82), revealing the effect of rural electrification. Our analytical approach and results provide a basis for timely monitoring of floodplain occupancy and flood-exposure risk at scale in the rapidly developing regions globally.