Author(s): J. Jalonen; J. Jarvela; J. -P. Virtanen; M. Vaaja; And H. Hyyppa
Linked Author(s): Juha Järvelä
Keywords: Drag force; Flow resistance; Woody vegetation; Floodplains; Terrestrial laser scanning
Abstract: Correct estimation of flow resistance caused by trees is required in hydraulic engineering applications such as river restoration and modeling floodplain sediment processes. The purpose of this paper is to evaluate the impact of reconfiguration on the plant characterization and estimation of drag forces for woody riparian vegetation. Our research focused on 1) the investigation of the drag forces and reconfiguration of leafy and leafless trees of different scales and 2) the characterization of trees by utilizing terrestrial laser scanning (TLS) in addition to conventional methods. Hydraulic experiments were conducted with four tree species in a towing tank. The trees exhibited significant reconfiguration up to the highest measured velocities (1. 5-2. 5 m/s) though most of the streamlining of the foliated specimens occurred by0. 5 m/s. As the contribution of foliage drag to the total drag was large at low velocities (<0. 5m/s), the leaf mass caused the foliated specimens to bend more rapidly than the defoliated specimens. The TLS investigations provided detailed information about characteristic plant areas and their vertical distributions, which is useful for subsequent hydraulic model development.
Year: 2014