The spatiotemporal shore morphological changes at east Bhola Island in Meghna Estuary of Bangladesh’s central coast

This article focuses on the spatiotemporal shore erosion–accretion progression of east Bhola Island, located in the Ganges-Brahmaputra-Meghna (GBM) basin at the mouth of Meghna Estuary on the central coast of Bangladesh. The erosion–accretion in this dynamic coastal region has caused significant morphological changes and frequent shoreline displacement over the last 40 years. This research analyzed 13 LANDSAT satellite images spanning from 1989 to 2018 to evaluate the shoreline change rates for the east face of Bhola Island over the four selected periods, i.e., 1989–2000, 2000–2005, 2005–2010, and 2010–2018. In general, the upstream portion of the east Bhola Island experienced a higher shore erosion rate up to −139 m/year at the northeast face, close to the confluence of the GBM Rivers. At this portion, the Island’s geometric shape caused the stability of the shore vulnerable against the ebb tide-dominated high monsoon GBM River flows. In the interim, the southeast portion of the Island near the Bay of Bengal faced a slower rate of shore erosion up to −40 m/year because the upper part of the Island provided shelter to the downstream portion that diverts and minimizes the downward GBM River outfall flow intensities towards the sea. Construction of barrages on the major upstream rivers resulted in the widening of the Bhola’s adjoining rivers through lean dry periods and increased wet season flows may be liable for a severe shoreline erosion of −171 m/year in 1989–2000. Further, higher annual rainfall and prolonged floods in 1998 and 2004 increased the shoreline erosion rate to −249 m/year from 2000 to 2005. Nevertheless, after considerable erosion from 1989 to 2005, recently implemented and ongoing shore protection works along the east face of the Island declined the erosion rate drastically to −41 m/year, while some sections achieved shore stability in the latest period of 2005–2018. •Satellite images were analyzed to delineate the shorelines and assess the spatiotemporal shoreline erosion–accretion rate at Bhola Island’s east face in the Meghna Estuary.•Upstream segments are experiencing higher shoreline erosion than downstream segments of the Island.•The overall decline rate of shoreline erosion was observed in the recent period.•The interaction of upstream river discharge, tides, government-sponsored protective measures with dynamic shoreline changes are thoroughly discussed in this manuscript.•Understanding specific location-based erosion patterns will