Friction factors for coniferous trees along rivers

A physically based model for estimating the resistance coefficient for coniferous trees in open-channel flow is modified to account for variations in the flexibility between species. The new model is based on the assumption of a linear increase in foliage area with height and a dimensional analysis. It is supported by experiments in air and water. The advantage of the new model over existing methods for estimating resistance factors is its ability to account for the interaction between the vegetation and the flow, taking into account velocity, depth of flow, and vegetative conditions (including type, size, stage of maturity, and density of vegetation). Based on the mathematical model, a table is provided to estimate Manning's n value for flow through vegetation.