The water depth, flow velocity, salinity, and suspended sediment concentration on an intertidal mudflat in the vicinity of a river mouth were measured for 564 wet cycles from July 2004 to October 2005. The measured time series were analyzed using time averaging to extract the wave components as well as tidal phase averaging to obtain typical variations and variability during the wet cycles. The wave component varied little during the wet cycle and was significant in the measured velocities. The variability of the time-averaged quantities for the 564 wet cycles was considerable, but the deviations from the phase-averaged values were correlated very little. As a result, the phase-averaged water fluxes and suspended sediment fluxes were approximately the same as those estimated using the phase-averaged water depth, velocities, and concentration. The phase-averaged quantities were used to understand the temporal variations of the flow and sediment transport during one typical wet cycle, which appeared to be influenced by the local bathymetry and the river discharge.