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SUMMARY:Incorporating bedload transport and bed evolution in soil erosion 
 modelling
DTSTART:20100329T161500
DTSTAMP:20260408T052240Z
UID:4ed18f7d4b030f644f286b9af9a1a5c1d0daca2f01d3453488f561d3
CATEGORIES:Conferences - Seminars
DESCRIPTION:Sander\, Graham (Loughborough University\, UK)\nMost soil eros
 ion models consider only sediment transport in suspension\; bedload transp
 ort is commonly neglected and bed evolution is rarely\, if ever\, consider
 ed. Experimental data on sediment transport under both net erosion and net
  deposition conditions was recently published in the literature. The inflo
 w boundary condition cycled between net erosion (zero sediment flux) and n
 et deposition (sediment flux greater than the transport capacity) conditio
 ns\, with periods of 15 minutes per cycle.  Application of the Hairsine-Ro
 se (HR) soil erosion model to this data shows that it can reproduce the to
 tal outflowing sediment concentrations with time\, across the periodic cyc
 les in the boundary condition\, as well as the steady-state particle size 
 distribution at the end of each cycle.  The HR model also predicts the spa
 tial and temporal evolution of the mass of deposited sediment on top of th
 e original soil surface.  While physically plausible estimates of the depo
 sited layer were obtained downstream of the inflow boundary\, significant 
 overestimation occurred in a very narrow zone around the inflow boundary i
 tself during the net deposition cycle. The magnitude of the overestimation
  was such that it would have blocked the flow cross the boundary. As this 
 did not occur during the experiments\, an additional transport mechanism m
 ust have been active to move this deposited sediment downstream.  Visual o
 bservations of particles rolling along the bed suggests that bedload trans
 port could be this additional mechanism.  However changes in surface slope
  due to significant deposition can also provide an alternative mechanisms 
 for driving the sediment downstream.  An extension of the HR model to incl
 ude a both these processes allows physically consistent predictions of the
  deposited masses to be obtained for all space and time.  It is commonly t
 hought that a sufficient and demanding test of an erosion model is whether
  it can reproduce spatial and temporal experimental data on the size distr
 ibution of suspended sediment.  This is in fact not the case\, and that ac
 curate predictions of this type of data can be obtained with models that i
 gnore important transport mechanisms. Finally an application of this exten
 ded model to flumed data obtained or supercritical flow into a nail bed (r
 epresenting a filter or buffer strip) gives good agreement with both the d
 eposited mass within\, and transported mass through the nail bed.
LOCATION:GR B3 30
STATUS:CONFIRMED
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