The viewpoint of a river is changing as people regard the river as water-friendly space where they can enjoy and share the space beyond the simple purpose of flood control alongside the improving social level. The floating islands installation was planned featuring three islands. The river’s flow and channel stability could be changed when new structures are built in a river. Hence an analysis of the hydraulic characteristic changes should need. The hydraulic model experiment in this study sought to review the impacts of the floating islands installation on the safety of flood control and stability of river channel. This study analyzed the hydraulic features affecting the surrounding stability when installing floating islands and proposed stable floating islands layout in terms of hydraulics based on the experiment results

The field formed by groyne has the function of aquatic habitats for the underwater biology. The characteristic of groyne field occurring around downstream of groyne depends on groyne type and shape. Thus to maximize the function of groyne, it needs to understand the flow characteristic around groyne. In this study, experiment model test was conducted in recirculation zone located in downstream of groyne. Groyne types for experiment are three: permeable, impermeable and inclined crest groyne. LSPIV (Large Scale Particle Image Velocimetry) is used to measure flow field around the groyne and it revealed flow characteristic in recirculation zone at each case. In order to estimate the aquatic habitats of groyne fields, critical swimming speed of major fleshwater fish in Korea was compared with the variation of velocity distribution in groyne fields. From the results, the rate of velocity decreases in groyne fields, V/V app were measured to be 0 to 0.5 and the results can be fundamental data which are used to estimate the aquatic habitable function of groyne.

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This study presents a physical habitat modeling of adult Zacco platypus in a reach of the Dalcheon Stream located downstream of the Goesaan Dam. CASiMiR model is used to estimate habitat suitability index based on the fuzzy logic. Results are compared with those from River2D model, which uses habitat preference curve for habitat suitability index. Hydraulic data simulated by River2D are used as input data for CASiMiR model after verification against field measurements. The result shows that the habitat suitability of the adult Zacco platypus is maximum around the riffle area located upstream of the bend.CASiMiR and River2D estimate the maximum weighted usable areas at the discharge rates of 7.23 m 3 /s and 9.0 m 3 /s, respectively. Overall comparison of the two models employed in this study indicates that CASiMiR model overestimates the weighted usable area by 0.3～25.3% compared with River2D model in condition of drought flow (Q355), low flow (Q275), normal flow (Q185), and average-wet flow (Q95).

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.