Calibrating 1D hydrodynamic river models in the absence of cross-sectional geometry: A new parameterization scheme

Abstract

Abstract. Hydrodynamic modeling has been increasingly used to simulate water surface elevation which is important for flood prediction and risk assessment. Scarcity/inaccessibility of in-situ bathymetric information has hindered hydrodynamic model development at continental-global scales. Therefore, river cross-section geometry has commonly been approximated using highly simplified generic shapes. However, strong correlations appear between cross-section shape parameters and hydraulic roughness in a hydraulic inversion approach. This study introduces a novel parameterization of 1D hydrodynamic models that reduces ambiguity by combining cross-section geometry and roughness into a conveyance parameter. Flow area and conveyance are expressed as power-law functions of flow depth, and thus are assumed to be linearly related in log-log space at reach scale. Data from a wide range of river systems show that the linearity approximation is globally applicable. Because the two are expressed as power-law functions of flow depth, no further assumptions about channel geometry are needed. Therefore, the hydraulic inversion approach allows for calibrating flow area and conveyance curves in the absence of bathymetry and hydraulic roughness. Its feasibility and performance are illustrated using satellite observations of river width and water surface elevation.