Manning's coefficient of alternatively arranged sandbars with tree vegetation

Kohji Michioku, Keiichi Kanda, Shunichi Kometani, Yoshiyuki Irie, Chinami Sakamoto

Friday 3 july 2015

13:30 - 13:45h at North America (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology

Parallel session: 16F. Environment - Ecohydraulic

Recently, many river channels tend to be densely vegetated due to regime shifts in hydrological, fluvial and ecological processes. It is a critical engineering issue for flood control and management to evaluate the conveyance capacity of vegetated channels. In this study, an equivalent Manning’s coefficient nv of vegetation canopy drag in an open channel of compound cross section with alternatively arranged floodplain is analyzed by using a two-dimensional two-layer (2D2L) model. It is found that nv monotonically increases with increasing discharge when vegetation is emerged. On the other hand, nv gradually decreases with discharge in the case of submergent vegetation. The numerical solutions of flow structure and nv is compared with experimental data to verify the model and satisfactory agreement between the analysis and the experiment is recognized.