Abstract
Abstract. Hydrodynamic modeling has been increasingly used to simulate water surface elevation which is important for flood prediction and risk assessment. Scarcity and inaccessibility of in situ bathymetric information have hindered hydrodynamic model development at continental-to-global scales. Therefore, river cross-section geometry is commonly approximated by highly simplified generic shapes. Hydrodynamic river models require both bed geometry and roughness as input parameters. Simultaneous calibration of shape parameters and roughness is difficult, because often there are trade-offs between them. Instead of parameterizing cross-section geometry and hydraulic roughness separately, this study introduces a parameterization of 1D hydrodynamic models by combining cross-section geometry and roughness into one conveyance parameter. Flow area and conveyance are expressed as power laws of flow depth, and they are found 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 laws 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 direct observations of bathymetry and hydraulic roughness. The feasibility and performance of the hydraulic inversion workflow are illustrated using satellite observations of river width and water surface elevation in the Songhua river, China. Results show that this approach is able to reproduce water level dynamics with root-mean-square error values of 0.44 and 0.50 m at two gauging stations, which is comparable to that achieved using a standard calibration approach. In summary, this study puts forward an alternative method to parameterize and calibrate river models using satellite observations of river width and water surface elevation.
Highlights
Hydrodynamic modeling of rivers is important for quantitative assessment of river flow and water level dynamics and, critically, for risk assessment and flood prediction
We propose an alternative approach to calibrate 1D hydrodynamic river models using altimetry and imagery observations
The workflow is based on the power-law relationships between flow-area/conveyance and flow depth, which go back to Chow (1959)
Summary
Hydrodynamic modeling of rivers is important for quantitative assessment of river flow and water level dynamics and, critically, for risk assessment and flood prediction. Traditional hydrodynamic modeling approaches require a detailed river channel bathymetry, which is usually represented by a set of cross-section shapes, distributed along the river reach of interest. A common approach is to parameterize channel geometry as a simple shape, e.g., a rectangle or triangle (Garambois et al, 2017; Jiang et al, 2019; Neal et al, 2012; Schneider et al, 2017). Durand et al (2008) estimated bathymetric depth and slope by assimilating synthetic WSE data from the Surface Water and Ocean Topography (SWOT) mission into the LISFLOOD-FP hydrodynamic model. We refer the reader to Biancamaria et al (2016) and Gleason and Durand (2020) for a broader overview
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