Role of river bathymetry in hydraulic modeling of river channels

Accurate geometric representation of the river channel is required for accurate hydraulic modeling of rivers. These are generally obtained through remote sensing techniques such as Light Detection and Ranging (LIDAR). However, these techniques lack the ability to model the submerged channel bed effectively and need to be complemented with surveyed bathymetric data for complete representation of the channel bathymetry, which can be time and cost prohibitive. An alternative to address this issue is to develop conceptual models that can estimate bathymetry. This study aims to evaluate the potential of a conceptual model, the River Channel Morphology Model (RCMM) which estimates the channel bathymetry by relating channel planform to channel bathymetry. Channel DEMs are estimated from RCMM based algorithms and compared with those estimated from LIDAR and interpolation based algorithms to evaluate the importance and applicability of RCMM. Each of the five channel DEMs is used to develop hydraulic models for three characteristic low and high flows. They are assessed to study the propagation of errors in channel DEM to the hydraulic outputs such as inundation maps, water surface elevation (WSE), flow velocity and shear. The analysis shows that the error in hydraulic modeling due to inaccurate bathymetric representation is significantly reduced by RCMM. The error in hydraulic model outputs decreases with increasing flow. The RCMM exhibits the ability to model channel bathymetry at reaches with reliable accuracy. Results indicate that the RCMM can even outperform bathymetry estimated from interpolation of surveyed data over large distances and, hence, is an admirable prospect for channel bathymetry estimation