Flux of bedwaves was measured beside the wave-length, cross section, “reduced height” and migration rate during transition from plane bed through “upper ripples” to dunes, after decrease of flow velocity from upper-plane-bed regime. The flux has the minimum value on the way, while migration rate almost monotonously decreases, and length, cross section and “reduced height” show roughly monotonous increases even in the constant flow velocity. The reason flux has the minimum value may be explained by the abrupt decrease of migration rate in the early time and successive increase in “reduced height” in the later time, although this explanation does not include the influence of increasing bed roughness. The existence of the minimum may be related to the annexation of a few small bedwaves into a large one, which causes discontinuous bedform-transition. The possibility of explanation of this phenomenon by the change of dynamical characteristics of the fluid and/or moving sand in the whole systems can be pointed out now. This paper is showing the importance of attention to the a mounts such as flux of bedwaves which would take the lead in understanding bedform dynamically, although details wait for further researches.