The effect of vegetation is often an important consideration in hydraulic engineering.
The design flowrate for hydraulic structures reflects the amount of overland flow and
storage, both of which are affected by vegetal resistance. In open channels, the energy
loss from the flow through and above vegetation affects the water surface profile,
which could result in flooding. The velocity distribution, pressure distribution, and
boundary shear stress distribution are also affected by the hydraulic resistance of the
vegetation. Knowledge of these flow parameters is typically needed for the design of
The density, extent, and type of vegetation present affect the capacity of water supply
and flood diversion canals. Canals designed with earth linings can be susceptible to
weed infestation, which can increase flow depth and lead to overbank flow or
increased seepage, or which can create flow concentrations leading to increased
erosion. The Research Institute for Weed Control and Channel Maintenance in Cairo,
Egypt estimated that 10% of the earth-lined canal length in Egypt is infested with
emergent weeds, and 50% is infested with submerged weeds (Balay, Gates and
Khattab, 1992). Grass lining is frequently used in irrigation canals, spillways, terraces.
and roadside ditches. The condition and type of the grass directly influence channel
capacity and stability. As with earth-lined channels, weed maintenance plays a
significant role in channel performance (Temple, Robinson, Ahring, and Davis, 1987).
Ginsberg, Abigail; Stefan, Heinz G..
Hydrodynamics of Flow Through Vegetation in Open Channels: A Review.
St. Anthony Falls Hydraulic Laboratory.
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