TY - GEN
T1 - Flow resistance of emergent vegetation
AU - Barkdoll, Brian D.
AU - Vittilam, Sandeep
AU - Bennett, Sean J.
AU - Alonso, Carlos V.
PY - 2004
Y1 - 2004
N2 - River restoration and bioengineering programs commonly use vegetation to stabilize banks. For this, it is important to know the forces that the flowing river water exerts on the vegetation. To this end, a laboratory study was performed at the USDA-ARS National Sedimentation Laboratory. Dowels were used to simulate emergent rigid vegetation. Dowels were systematically placed in the laboratory flume, beginning with a single dowel connected to a load cell to measure the drag force and then placing dowels around the single dowel to determine any shielding effect. It was found that the drag coefficient of a single dowel ranged from 4.5 to 6.5, which is higher than that published for a 2-D cylinder of infinite length. A momentum balance analysis shows that (1) for the single dowel case, the momentum balance approach determines C D>>1 contrary to the low values for a cylinder and (2) the C D for the measured dowel is about two times higher than the momentum formulation. This difference is attributed to the presence of large standing waves upstream of the dowel and the breaking of these waves. When additional vegetation elements were added to form a matrix, it was found that as vegetation elements were added, the drag forced increased initially due to the vegetation concentrating the flow towards the instrumented dowel, and then decreased due to dowels being directly upstream of the instrumented dowel and thereby blocking the flow. These results have implications for managed planting arrangements in stream corridor rehabilitation programs.
AB - River restoration and bioengineering programs commonly use vegetation to stabilize banks. For this, it is important to know the forces that the flowing river water exerts on the vegetation. To this end, a laboratory study was performed at the USDA-ARS National Sedimentation Laboratory. Dowels were used to simulate emergent rigid vegetation. Dowels were systematically placed in the laboratory flume, beginning with a single dowel connected to a load cell to measure the drag force and then placing dowels around the single dowel to determine any shielding effect. It was found that the drag coefficient of a single dowel ranged from 4.5 to 6.5, which is higher than that published for a 2-D cylinder of infinite length. A momentum balance analysis shows that (1) for the single dowel case, the momentum balance approach determines C D>>1 contrary to the low values for a cylinder and (2) the C D for the measured dowel is about two times higher than the momentum formulation. This difference is attributed to the presence of large standing waves upstream of the dowel and the breaking of these waves. When additional vegetation elements were added to form a matrix, it was found that as vegetation elements were added, the drag forced increased initially due to the vegetation concentrating the flow towards the instrumented dowel, and then decreased due to dowels being directly upstream of the instrumented dowel and thereby blocking the flow. These results have implications for managed planting arrangements in stream corridor rehabilitation programs.
UR - https://www.scopus.com/pages/publications/23844498533
M3 - Conference contribution
AN - SCOPUS:23844498533
SN - 0784407371
SN - 9780784407370
T3 - Proceedings of the 2004 World Water and Environmetal Resources Congress: Critical Transitions in Water and Environmetal Resources Management
SP - 1398
EP - 1406
BT - Proceedings of the 2004 World Water and Environmetal Resources Congress
A2 - Sehlke, G.
A2 - Hayes, D.F.
A2 - Stevens, D.K.
T2 - 2004 World Water and Environmental Resources Congress: Critical Transitions in Water and Environmental Resources Management
Y2 - 27 June 2004 through 1 July 2004
ER -