A quasi-2D and quasi-steady hydraulic model for physical habitat simulations

This study presents a new hydraulic model for simulating the physical habitat of a river. The model is based on the quasi-steady assumption that the flow is steady, but the channel morphology changes during the computational time step. The model is also capable of simulating flow distribution in the lateral direction, making the model quasi-two-dimensional. The physical habitat simulations are carried out for a reach including a bend in the Dal River in Korea. Zacco platypus is used as the target fish. The habitat suitability index model for Zacco platypus, based on field monitoring, is used for the habitat simulation. The hydraulic model simulates morphological changes caused by a flood and the result is compared with the two-dimensional model. Simulation results obtained using the developed model compares favorably to calculations obtained using the two-dimensional model. Distributions of the habitat suitability index are provided for various flows by the present model. It is found that the morphological change by the flood increases the habitat suitability significantly by decreasing the flow depth and increasing the velocity in the study reach. In addition, the time change of the weighted usable area based on the mobile-bed computation is given, indicating that the flood decreases the habitat suitability seriously.