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Selection of appropriate topographic data for 1D hydraulic models based on impact of morphometric variables on hydrologic process

Qi, M.J, Zhang, X.F
Journal of hydrology 2019 v.571 pp. 585-592
case studies, hydrology, models, morphometry, rivers, stream channels, topography
With the development and utilization of mountain rivers, modelers of rivers using one-dimensional (1D) hydraulic models face the challenge of selecting appropriate cross-section data for mountain rivers since previous studies have focused on alluvial rivers. Mountain rivers usually have larger bed slopes and smaller widths in comparison with alluvial rivers, which results in differences in their hydrologic processes. Our case study analyzes these differences using 1D models through the utilization of prismatic reaches with different gradient and width sizes and the provision of various boundary conditions. The influence of the size of these morphometric variables on the selection of optimal topographic data is related to the hydraulic problem at hand. In addition, mountain rivers tend to have more irregular cross sections and gradients than alluvial rivers because of their relatively erosion-resistant riverbeds. The effects of gradient deviation, width deviation and channel storage volume deviation on hydrologic process due to insufficient topographic data are compared. It is found that the influence of channel storage volume deviation, which is negligible in alluvial rivers, could be significant in mountain rivers. And the impact of width deviation is minimal in mountain rivers and alluvial rivers. Thus, in reservoir areas, measured width could be adjusted based on published stage-storage data to reduce channel storage volume deviation and improve flow simulation accuracy. This method is verified on a 605.71-km long reach in the Three Gorges Reservoir area.