Distributed water balance with river dynamic-diffusive flow routing model

This article focuses on the application of coupling both river dynamic and river diffusive modeling techniques that can be used with distributed water balance model. In an upstream watershed, both overland and river diffusive flows are routed by diffusive wave approximation of the free surface flow equations. In river downstream reaches, the river dynamic flow is routed by one-dimensional dynamic wave equations (full dynamic St. Venant equations with lateral flow). The developed model is applied in a part of Arakawa River basin, Kanto area, Japan. The geographic data of river cross sections could be accurately represented by an 11-point cross-section approximation. The effects of both the grid size and lateral flow on the simulated results of the river dynamic flow model were studied. The grid size should be greater than the average width of the river cross-sections. The lateral flow from small drainage systems has significant effects on the simulated results using the river dynamic flow model. The simulated results show good and acceptable agreements with the observed flow discharges and water depths. Both the river discharge and water depth at any location of river network of compound channels with one/two complex floodplains could be correctly estimated.