Streamline-Based Method for Reconstruction of Complex Braided River Bathymetry

Abstract

Reconstruction of complex braided river bathymetry is important for supporting hydrodynamic simulation and understanding river morphological processes. To our knowledge, existing methods generate and interpolate channel-fitted coordinate lines using the measured cross-sectional data to reconstruct river bathymetry. Nevertheless, in these methods, the generation of channel-fitted lines obeys the law of splines or a set of equations without considering the laws of river dynamics. Moreover, it is difficult to interpolate bathymetry using the channel-fitted lines when dealing with complex braided rivers. This paper introduced a novel method to fill the gap. Briefly, in the introduced method, an initial bathymetry is interpolated and a velocity field is calculated using a set of simplified two-dimensional (2D) shallow-water equations. Then, streamlines are generated using the velocity field data, and the elevations of the nodes on the streamlines are interpolated using the measured cross-sectional data. Finally, the bathymetry of the domain is interpolated using the streamlines and the measured elevation points or contour lines at the sandbars and floodplains. For demonstration purpose, the introduced method was applied to a 20-km section in the middle reaches of the Yellow River (China) with many branches and sandbars. The reconstructed bathymetry of the domain was investigated in terms of their geometrical shape and hydrodynamic performance (including inundation area and water level). When compared with the measured water level, the hydrodynamic results of the reconstructed bathymetry showed acceptable accuracy. In addition, because the channel-fitted method is widely applied to interpolate the river bathymetry, we compare the channel-fitted method with the introduced method in discussion section.