Evolution and Reclamation of the Bhasan Char Island, Meghna Estuary, Bangladesh
摘要
The Bhasan Char is a 30-km2 island (2021) off the Meghna Estuary, eastern Ganga–Brahmaputra–Meghna Delta, Bangladesh. The island has gained prominence after its selection as a major relocation centre for the Rohingya refugees. We used 25 satellite images representing 11 different years between 2001 and 2022 from the IRS/Resourcesat (Sensors: Pan, LISS-3, LISS-4-mono, LISS-4-fmx), Landsat (TM, ETM + , OLI), Sentinel (MSI, SAR-C), and Google Earth repositories to trace the evolution and reclamation stages of the island. We also considered 1970–2021 tracks and intensities of tropical cyclones landfalling within 100 km of the Bhasan Char, regional sedimentation, and its tectonic setting to assess its suitability for the relocation project. The results showed that the Bhasan Char first emerged in 2002 above high tide water and took a coherent form in 2004 (14.96 km2). It then migrated towards the southeast at 0.55 km/yr till 2007 when it attained relative stability. Subsequently, the island recorded rapid overall accretion of its supratidal and intertidal areas. Since 2017, 8.18 km2 of the island was reclaimed by placing an 11.5-km marginal dyke for the relocation settlement. At cyclone periodicity of 3.5 yr within 100 km of the island, five storms passed within 25 km of the current position of the Bhasan Char during 1970–2021 (52 yr). It is situated on a vast 850-km2 tidal sand ridge that is accreting from the Meghna sediments and also uplifting as a part of an anticlinal axis of the Chittagong–Tripura Fold Belt. There seems to be no imminent threat to the resettlement project over the short-term. However, the dyke is susceptible to the post-2012 trend of coastal erosion that may undercut it from the southwest despite the presence of wave breakers.