Abstract
A new simplified horizontal coordinate for computations of river flow, named a horizontal sigma coordinate, is presented to employ boundary-fitted grids along river channels like a generalized coordinate without losing the simplicity of numerical models such as Cartesian and orthogonal curvilinear coordinates. For this purpose, we introduce the sigma coordinate system normally used as vertical coordinates for ocean current and meteorological simulations into the horizontal coordinates in river-flow simulations. The fundamental performance of the horizontal sigma coordinates is confirmed through its application to river-flow simulations. The computational results demonstrate that the horizontal sigma coordinates may be one of promising tools for the numerical approximation in the horizontal direction with computational efficiency as well as higher numerical accuracy.
