Numeral simulation of longitudinal river profile considering fluvial sediment transportation

Tanikawa, Shinichi; Sanga, Tomoji*; Yasue, Kenichi

Existing simulation methods of long-term fluvial processes, represented as conventional difference scheme of diffusion equation, cannot control about the expression of sediment transportation satisfactorily, particularly around confluences in middle and lower reach of the river. To address this, we newly developed a numeral model and simulation program of fluvial processes, in which sediment outflux is distributed to multiple grids with the formula that enlarges the fluvial transport efficiency downstream as a function of grain-size and drainage area (named "transport distance increment curve"). This formula can control the concavity of longitudinal profile. With this model, analyses about expressions of geomorphic development in longitudinal river profile were carried out. As a result, it was confirmed that, with accurate settings of parameters, this model can yield features of river profiles, considering sediment transportation around confluences. It is believed from the above that this model enables the expression of fluvial topography as seen in nature, by translating the concept of long-term fluvial process into parameters.