ABSTRACT
We present an explorative hydraulic and morphological analysis of a major bifurcation of the Lower Jamuna in Bangladesh based on satellite images, ground data and morphological modelling. We used Aqua Monitor to process multispectral satellite images to estimate the spatiotemporal extent of morphological processes and alterations. The tool is found to be quite effective for on-the-fly analysis of large-scale changes of such a dynamic river bifurcation. Furthermore, we analyzed the dynamics of the deep channels at the bifurcation based on bathymetry measurements. We also simulated the morphological changes using numerical modelling. Our study reveals the importance of deep-channel dynamics at the bifurcation. This regards branches with highly erodible bed and banks under large variations in upstream flow and morphological conditions including human interventions. The focus on deep channels is a key change of perspective as numerical modelling of large rivers usually focuses on sandbar dynamics. Understanding and predicting the deep-channel dynamics is important to identify present and future vulnerable areas and prioritize measures and adaptation. The analysis highlights the complexity of the system which can be quantified but is difficult to replicate and predict due to the large natural and human-induced uncertainties involved. It appears that the morphological behavior of such a large bifurcation does not fully comply with assumptions and guidelines that are mainly applicable to idealized and smaller bifurcations under relatively milder flow and morphological conditions. We present partial results as a preview of a more complete paper currently under preparation.
