Application of 2D morphological model to assess the response of Karnafuli River due to capital dredging

Abstract

The major sea port of Bangladesh is the Chittagong port located on the right bank of Karnafuli river of Bangladesh. This river port is considered as the lifeline of the economic activities of the country due to its increasing trade demand. Many port facilities have been planned to be implemented in future to meet this increasing demand. Due to manmade interventions the river flow becomes interrupted and thereby may cause the change in river morphology. Recently Chittagong Port Authority (CPA) has undertaken 3.5 Mm3 Capital Dredging and 2.5 km long bank protection initiative from 3rd Karnafuli bridge to Sadarghat jetty. This study focuses mainly on the application of 2D mathematical model to assess the response of the river due to such development works on Karnafuli River. Necessary data have been collected from CPA and the model was set using the bathymetry of 2009. The river reach between Kalurghat and Khal no-18 has been selected for the study purpose. Time series discharge and water level data were used as boundary condition at upstream and downstream consecutively. Calibration and validation have been carried out with the recent water level data at Sadarghat and Khal no-10. After hydrodynamic calibration and validation the model was adjusted to match the change in bed level with the observed data. Different hydrodynamic and morphological assessments like variation of velocity, sediment transport and bed level changes have also been studied. It was further used to assess the effect of Capital dredging and Bank Protection near Sadarghat area. Model result shows slight increase in velocity and sediment transport due to project implementation. It also changes the rate of erosion/ deposition at some location of the selected reach. It is hoped that the results of the model simulation will be helpful to suggest the effect of possible future development work to be implemented on this river.