Planform channel dynamics and bank migration hazard assessment of a highly sinuous river in the north-eastern zone of Bangladesh

Rivers or watercourses in Sylhet plain of Bangladesh are very dynamic over time. The aim of the present study is to investigate the channel planform dynamics, the prediction of future lateral migration of the bankline and assessment of the hazards associated with Manu River, Bangladesh. The name Manu River represents the river study reach from Tripura, India to Moulvibazar, Bangladesh of 41.6 km. Channel contraction and expansion are very frequent in this river. Studies had shown that the sinuosity of the river varies from 1.36 to 2.48. Also the meandering ratio of the river ranges from 0.32 to 1.67. Satellite data were collected and analyzed to determine the planform characteristics, meandering parameters and bankline migration rates between 1975 and 2013. The study is based on the Landsat satellite imagery of 1975, 1988, 1999, 2003 and 2005 and aerial photograph of 2009 and 2013 which were accumulated from United States Geological Survey. Specific critical bends have been elected where bank erosion and accretion rates were severe. The purpose of this paper is to show the erosion rate, behavior and pattern of upstream side of Manu River, Bangladesh through the study period of 38 years from 1975 to 2013 by comparing its different geomorphological parameters. This study has contributed to develop a model for bankline migration prediction of the forthcoming years and address the physical hazard to provide a risk surface. Present assessment has revealed that, there are some critical regions where erosion would be up to 29.18 hectares in 2025.