Mapping large- scale river flow hydraulics in the Amazon Basin

Research on actual requirements for a numerically consistent representation of flow dynamics in large-scale river-flood models are needed to improve both modeling performance and computational efficiency. Still, regional- and global-scale characterizations of river hydrodynamics are absent. A first attempt to map river hydrodynamics in the Amazon Basin is presented. Flood wave type maps at 0.25 degrees spatial resolution are derived from a classification method based on the analysis of Saint-Venant equation terms. Global river geometry data sets derived from both digital elevation models and empirical equations supported by stream gauge observations are used as input variables. Errors of input variables are estimated, and a sensitivity analysis is performed. Results show that 64.5% of rivers (headwaters and high-slope rivers) can be represented by the kinematic wave (KI), 34.5% (main Amazon tributaries, low slope, and wetland regions) by the diffusive wave (DF), and 1% (lower Amazon) by the full Saint-Venant equations (SV). In a rigorous scenario, i.e., a case where the most restricted classification of each grid cell is considered, approximate to 33% is classified as KI, approximate to 62% as DF, and approximate to 5% as SV. Most of the basin presents subcritical flow with very low Froude number (Fr), while the Andean region is dominated by larger Fr values and supercritical flow can be found. According to our evaluation mostly based on in situ data, the map has a percentage of detection of 83.4%.