2016 Volume 22 Pages 457-462
In recent years, overgrowth of Egeria densa in the river mainstream have been reported from many rivers. Identifying the environmental conditions that affect washout of E. densa are important problems for its management in rivers. In this study, unmanned aerial vehicle (UAV) was used to establish a method to quantify the cover degree of E. densa. In addition, we tried to identify the washout factors of E. densa by using hydraulic models. Washout rate of each mesh (10m×10m) was calculated by comparing the cover degree of E. densa before and after flood in the two site. Velocity, dimensionless tractive force, elevation change, and bed load flux were calculated. Then, we analyzed the relationship between these parameters and the washout rate of E. densa. There were clear relationship between the washout rate and velocity and dimensionless tractive force. More than 20% washout were observed at areas whose velocity exceed 1.5m/s and dimensionless tractive force exceed 0.05.
