Effect of Partially Submerged Vegetation Distribution Directions on Flood Flow Resistance

The large-scale distribution of vegetation influences flood flow concentration. Natural and cultivated high plants impact the flood flow velocity field and volume distribution in a watershed. Many studies have examined flow resistance associated with plant density and stalk flexibility. Some researchers have explored the effect of vegetation distribution and suggest that the flow resistance changes with vegetation distribution. This assertion, however, was made without experimental verification. In our research, we built a hydraulic model with constant vegetation density and flexibility from beginning to end, which can simulate various distribution directions of partially submerged plant stems and reveal the flood flow resistance for different slope gradients. After more than 300 tests, we demonstrated that the change of partially submerged vegetation distribution direction leads to directional differences in flood flow resistance. We found that the flow resistance coefficient (f) increases linearly with increasing submergence depth (h), at an incremental rate α () that is influenced by the distribution directions of vegetation. In addition, we discovered that the relationship between the incremental rate (α) and the projection width of vegetation (K) on flow direction can be represented with a noteworthy power function: .