Study on roughness coefficient for unsubmerged reed in the Changjiang Estuary

The influence of density, foliage and stem flexibility on the roughness coefficients under unsubmerged conditions, such as Manning's n, is investigated experimentally. An instrumentation system has been developed for measuring the flow rate ranging from 0.1 to 0.3 L/s under the condition of different artificial foliated reeds. Based on the experimental results, the influence on the relationship between n with different density, foliage, flexibility and flow depth is discussed. It is found that the foliage and the density are the important factors affecting Manning's n. At a range of relatively low velocity and relatively large bending stiffness of stem, Manning's n is not influenced significanthy by the flexibility of stem.