Abstract: Saltmarshes in coastal area can reduce flow velocity and stabilize sediments. In this study, we took Scirpus mariqueter in Chongming Dongtan of the Yangtze Estuary as the research object, and set up three observation transects with the pattern of “mudflat-vegetation frontier-vegetation” to measure the flow velocity, direction and water depth in different phenological periods. The results show that Scirpus mariqueter has a significant capacity to reduce flow velocity：The average velocity in saltmarsh is lower than that of the mudflat, the capacity of attenuation is stronger than that of the mudflat, and the flow attenuation rate is 1.47 to 3.48 times that of the mudflat. In different phenological periods, the flow attenuation rates in Scirpus mariqueter saltmarsh rank in the following order：Mid growing period > late growing period> withering period, which are 1.15%, 1.06%, and 0.50% m-1, respectively. The capacity of flow attenuation is positively related to the flow velocity, and the correlation coefficients of the three phenological periods are all greater than 0.80. Except for the withering period, the capacity of flow attenuation is negatively related to water depth, and the absolute value of correlation coefficient is greater than 0.90.

Key words: flow attenuation, Scirpus mariqueter, Yangtze Estuary, Chongming Dongtan, saltmarsh area