Spatio-temporal Dynamics of Riverbank Erosion and Accretion and Their Socio-economic Impacts: A Case Study from Bhola Island of Bangladesh

Riverbank erosion and accretion are natural and ongoing geomorphological processes in the huge delta of Bangladesh, driven by the mighty Ganges-Brahmaputra-Meghna river systems. The turbulent rivers of Meghna and Tetulia are posing serious threat to two high-risk erosion unions of Hasanagar and Pakshia in Burhanuddin Upazila of Bhola district. In these coastal tracts, high tidal surges and faster monsoon floods are continuously eating up homesteads and farmlands. The long-term fluctuations of seven reference years (from 1995 to 2025) were chosen with only images captured during the month November to February were used. The most significant erosion occurred between 1995 and 2000, with a loss of 3,055 ha of land. Erosional activity decreased afterward to its minimum of 973 hectares between 2015 and 2020. In 1995 it was 16,852 hectares and increased to maximum of 20,305 hectares in 2005 due to significant widening of the channels as a consequence of erosion. The water area reached its peak in 2005 and then decreased until 2020, which shows a stage of erosion–accretion and channel occupation, after which there was a minor increase in 2025. Over 70 per cent of the people surveyed stated that riverbank erosion had caused them to change their farming methods. Erosion has affected half of the respondents from low-income sectors. River bank erosion is responsible for almost 70% of the total displaced population. A vast majority of traditional social institutions and organizations like family and relative community of vulnerable regions like the river Meghna, are living with a threat of how long will their lives continue being survived in slums; hence there should be an appropriate understanding of the process that can build up effective management policies for the rivers under investigation. It is suggested that further investigations should concentrate on the efficient usage of newly added land by accretion and possibilities to diminish the negative impact of river erosion.

Keywords: Riverbank erosion; Accretion; Displacement; Population; Income.