Side Weir Flow on a Movable Bed

Abstract

Side weirs are hydraulic structures widely used for flow control in rivers and canals. Whenever the water level rises above the side weir crest elevation, a fraction of the main flow is diverted so that the water discharge flowing downstream in the main channel is reduced. In movable bed channels, the lateral outflow may have significant interactions with the sediment transport processes affecting the side weir flow. The spilled discharge creates a reduction of the downstream sediment transport capacity with a consequent deposition in the side weir proximity. In addition, sediment in the main channel can be diverted into the lateral branch. To investigate these interactions, experimental data at the laboratory scale have been collected and analyzed. The increase of the spilled discharge induced by the local sediment deposition is described according to the classical De Marchi hypothesis. Furthermore, the sediment transport leaving the main channel through the lateral structure is modeled in terms of the stream power associated with the bed-shear stress. Results allow for prediction of the bed dynamics and for the development of new design criteria.

Flow and Suspended Sediment Division at Two Highly Asymmetric Bifurcations in a River Delta: Implications for Channel Stability

“…The amount of sediment that enters the Kapuas side branches is thus not influenced by an inlet step. Even in the presence of a step, the secondary circulation diverts near‐bed flow and thus sediment into the side branch (Dutta et al., ; Michelazzo et al., ).…”

Diversion of Flow and Sediment Toward a Side Channel Separated From a River by a Longitudinal Training Dam

“…Often, a side weir is present at the entrance of such a lateral outflow channel. Side weirs have been extensively studied regarding their effect on the water level profile and discharge regulation (El‐Khashab & Smith, 1976; Hager & Volkart, 1986; Hager, 1987; Michelazzo et al, 2016; Paris et al, 2012), and their discharge distribution is well described by empirical formulas (Bos, 1976; Lee & Holley, 2002; Paris et al, 2012). However, the obtained results are strictly valid for the experimental conditions under study, which are mostly free flow conditions for short, high, sharp‐crested weirs.…”

Effect of Lateral Outflow on Three‐Dimensional Flow Structure in a River Delta

“…difference in bed elevation between the main and lateral channel) flow system is a side weir where channel bedform morphology has been observed to be impacted by the lateral outflow through the weir (Michelazzo et al, 2016;Paris et al, 2012;Rosier et al, 2011). 3-D eddies forming at the side weirs divert sediment into the weirs and the efficiency of the transport process is dependent on turbulent intensity in the main channel, local bed morphology, and weir geometry (Michelazzo et al, 2016). The side weirs resemble many natural systems that often exhibit bed discordance, especially in the transition from main channels to floodplains and small crevasses.…”

“…Side weirs generally resemble the flow in such discordant environment. Main channel bedform morphology has been observed to be influenced by the lateral outflow through side weirs (Michelazzo et al, 2016;Paris et al, 2012;Rosier et al, 2011). According to Michelazzo et al (2016), 3-D eddies form at the mouth of side weirs and act to divert sediment into the weirs.…”

“…Main channel bedform morphology has been observed to be influenced by the lateral outflow through side weirs (Michelazzo et al, 2016;Paris et al, 2012;Rosier et al, 2011). According to Michelazzo et al (2016), 3-D eddies form at the mouth of side weirs and act to divert sediment into the weirs. Despite these efforts in open channel hydraulics, there remains a gap between the understanding of flow and transport mechanism from the hydrodynamic models (Dutta et al, 2017) and the more morphology focused studies (Szewczyk et al, 2020) for channelized systems.…”