Evolution of flow velocity from the leading edge of 2-D and 3-D submerged canopies

Abstract

An analytical model was developed to predict the velocity evolution within a submerged canopy of finite width and used to explore the impact of plant flexibility and width on the velocity within the canopy. The analytical model was validated with laboratory experiments using canopies constructed from rigid cylinders and from individual model seagrass plants, consisting of six LDPE (low-density polyethylene) blades attached to a rigid sheath. Four canopy widths were considered, spanning 12.8 to 100 % of the channel width. As the canopy narrowed from the channel width (two-dimensional canopy) to finite width (12.8 % of the channel width), the velocity adjusted more rapidly at the leading edge and reached a lower fully developed in-canopy velocity. Predictions from the analytical model had good agreement with field and laboratory studies with real vegetation. Once validated, the model was applied to a range of field conditions to predict the within-canopy flow velocity and the adjustment length, which is the distance required for the flow to be fully developed.