Depth-Averaged Velocity in Channels with Submerged and Unsubmerged Rigid Vegetation

A willow post system is a type of bioengineering system used to reduce streambank erosion. In essence, a willow post system is a collection of rigid cylinders placed along a streambank. Herein, an analytical model that was developed to evaluate the hydrodynamics of newly constructed willow post systems is reviewed. The model is founded on wake theory and was originally developed for predicting depth-averaged velocities in straight trapezoidal channels with unsubmerged rigid cylinders. The model was recently modified and now includes a parameter for evaluating submerged vegetation and is referred to as the submergence ratio. Observed depth-averaged velocities from a physical model study are compared to predicted depth-averaged velocities from the original and the modified version of the analytical model. A comparison of coefficient of determination (r 2 ) values shows that the submergence ratio significantly improves the accuracy of predicted velocities in channels with submerged and unsubmerged vegetation.