The general Bottom Velocity Computation method (BVC method) has been proposed to calculate vertical velocity and pressure distributions within the frame work of two-dimensional computation method to evaluate multi-scale phenomena of flood flows. This paper derived the dynamic rough wall law (DWL) composed of continuity and momentum equations for vortex and roughness layers and developed BVC-DWL method to take into account non-equilibrium fluid motions and flow exchanges near the bed in the BVC method. The applicability of the BVC-DWL method was discussed for flows with relative roughness scales and shallowness parameters based on the momentum equations for DWL. The adequacy of the BVC-DWL method was indicated through the applications to three dimensional flows around structures in the laboratory and field experiments.

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 The synthesis probability method, which estimates T-year annual maximum flood peak discharge considering spatio-temporal distribution of rainfall, has the assumption of independency between total precipitation and its spatio-temporal distribution. This research improved the method to consider a relation between the two by using conditional probability distributions of total precipitation given rainfall duration. The improved method was applied to the Yura-gawa river basin and performed more reasonable estimation of T-year annual maximum flood peak discharge than the original method.

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