The performance and stability of a numerical model which consist of a shallow water flow model and an equilibrium bedload transport model for calculating bed evolution in rivers is discussed. Such system equations which are generally adopted for calculating reach-scale river bed evolution have a hyperbolic feature. This fact has implied that upwind schemes to the space derivative of bedload transport in Exner equation are useful numerical methods to avoid bed instabilities in calculating the propagation of a small disturbance. Whereas, a bed diffusion effect which is essentially included in bedload dominated bed evolution has been modelled in equilibrium bedload transport models by considering the local slope effect to the bedload transport. The relation between the numerical and physical diffusion effect to the bed evolution should be investigated to understand the performance and stability of the model. A hyperbolic differential equation controlling the bed evolution was derived from the linearized system equations to understand the numerical characteristic of the propagation of the bed disturbance. We defined a Péclet number, P_e, as the ratio between the advective effect which controls the propagation of the bed disturbance and the diffusive effect associated with the bed slope effect. The effect of physical diffusion of the bed exceeds the effect of numerical diffusion by the upwind scheme to the bedload transport in the condition which P_e < 2. The series of computations which focus on the propagation of hump type bed disturbance were conducted. The numerical results show that the calculation of propagating the bed disturbance can be physically stable without the upwind scheme when the grid size which satisfies P_e < 2 is used. The grid size which is required such physically stable computation depends on how the bed slope effect is modelled in the bedload transport model.

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 We developed Buried Seeds Removal Method (BSRM) for bur cucumber population control and verified its effect. In the results, BSRM remove buried seeds from surface material in 99% accuracy. Germinations number of bur cucumber in BSRM treatment area were smaller than control area. Twenty three species were not observed in treatment area germinated and more 14 species germinated in treatment area comparing to control area. The results indicated that BSRM reduce the reproduction of bur cucumber and restored vegetation community diversity.

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 This paper investigates an influence of the modelling of secondary flows to the formation and development of free bars in rivers by comparing the results of the numerical simulation, the linear stability analysis and the experiments. Free bars which are developed by a physical instability phenomenon between turbulent flow and bed surface of rivers are one of fundamental river morphologies. Theoretical studies by the linear stability analysis have successfully shown that two dimensional morphodynamic models for calculating the river bed evolution can explain the formation of free bars. However, three dimensional flow structures, for instance, secondary flows caused by the meandering flows with increasing the bar height, have also important roles in the dynamics of free bars on a nonlinear level. Although quasi-three dimensional flow models can be a powerful tool to include the three dimensionalities of flows on the framework of two dimensional approaches, the applicability of such models to the dynamics of free bars has not been well verified yet. The results of the linear stability analysis suggested that the model of secondary flows which is assumed under the fully developed stage allows developing the bar with unrealistically high mode. This high mode bar tends to develop under the hydraulic conditions in which the effect of transverse slope for the sediment transport direction is relatively weak. Such instability can be physically suppressed by applying a model of secondary flows which includes the effect of development of secondary flows. The results of numerical simulation shows that proposed model which considers the development of the secondary flows can reasonably reproduce the incipient of free bars which is indicated from the linear stability analysis as well as the equilibrium bar waveheight in the experiments.

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