Impact of an emergent model vegetation patch on flow adjustment and velocity.

This study achieved three goals to clarify the impact of a vegetation patch on flow adjustment and velocity. First, a valid equation for the interior adjustment distance (Ld) inside a model patch was developed for a wide range of velocities and flow depths. Second, the minimum distance inside a patch beyond which the resuspension of fine sediment is suppressed (Lmin) was found to be related to the position at which the local velocity decreases to the threshold for generating stem-scale turbulence. Lmin primarily depends on the flow blockage (Cdab) and the stem diameter (d): a shorter Lmin is a result of a larger Cdab and a smaller d. An equation was formulated for estimating Lmin. Third, for the fully developed flow region inside a patch (L > x > Ld), an equation was developed to estimate the increase in the mean velocity in the bare channel relative to the overall mean channel velocity. For Cdab < 2, this fraction is controlled by both the patch density (ad) and the patch blockage (b/B) whereas, for Cdab > 2, this fraction is controlled by only b/B. A suggestion for choosing the patch size in future flow and sediment research projects is presented. [ABSTRACT FROM AUTHOR]