Overbank sediment deposition patterns for straight and meandering flume channels

Abstract

Experiments with the 10 m Flood Channel Facility at HR Wallingford, UK, indicate a fundamental dependency of the overbank deposition pattern of channel suspended sediments on channel planform. Two experiments (100 and 140 l s 1 ) in a 1Ð95 m wide straight channel showed deposition concentrated in a berm along the channel bank. Little sediment was transferred further onto the floodplain. For the larger flow, the berm formed further from the channel. A single experiment (103 l s 1 ) with a 1Ð31 m wide meandering channel showed deposition across the entire floodplain tongue between successive meanders. Maximum deposition occurred on the downstream side of the meander, just past the bend apex. These generalized flume results complement the real-world but site-specific data of field studies.

Sedimentary records of 2010 and 2011 Warta River seasonal floods in the region of Poznań, Poland

“…These field in ves ti ga tions of floodplain sed imen ta tion are ac com pa nied by nu mer ous lab o ra tory ex per iments (e.g., Bathurst et al, 2002;Fraselle et al, 2010) and numer i cal mod el ling (e.g., Marriott, 1992). These stud ies show that river flood sed i men ta tion is sig nif i cantly con di tioned by local fac tors and re mains poorly un der stood.…”

“…Al though the ex tent of river flood ing was rel a tively sig nif i cant -in ex cess of 1 km -the wa ter flow and sed i ment trans port in the di rec tion per pen dic u lar to the river chan nel banks is con sid ered to be small for rivers with a rel atively straight course (James, 1985;Bathurst et al, 2002). Conse quently, the dis per sion of sed i ments is small and the sands pre dom i nantly pro duce lev ees.…”

“…The lim ited sus pen sion load in the trans port and the hydrau lic char ac ter of the flood wa ters in the straight course of the river are pos si ble causes (Bathurst et al, 2002). The Warta River is a typ i cal low land river with a small slope and rel a tively flat catch ment area.…”

Environmental impact of flooding: studies of ‘self‐cleaning’ of river ecosystem during consecutive flood events

“…Although the interaction between the channel and flood plain is intensive during flood, its perpendicular flow to the riverbanks on the straight-line section is of minor significance (James, 1985;Bathurst et al, 2002).…”

Three-dimensional numerical modelling of levee depositions in a Scandinavian freshwater delta

“…Turbulent diffusion involves the transport of suspended sediment by eddies from concentration differences between main channel and floodplain, whereas advection is the transport by currents flowing away from the channel onto the floodplain. For straight channels, the channel-floodplain interface has strong mixing but no significant flow perpendicular to the channel, and depositions occur in the form of a narrow stripe or berm along the channel bank (Bathurst et al, 2002). Advective sediment transfer out of the channel and into the floodplain or interlevee basin may occur where there is a flow component perpendicular to the channel, as it is typical for overbank flows in meandering rivers (Baryshnikov, 1984;Shiono and Muto, 1998;Wormleaton et al, 2005).…”