BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Memento EPFL//
BEGIN:VEVENT
SUMMARY:Advances in the study of bedload sediment transport in gravel-bed 
 rivers
DTSTART:20100427T121500
DTSTAMP:20260427T200843Z
UID:0ed73757a1cb57d79b838dde2349ca2f12bf7a91bba359f1f470fa40
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. André G. Roy\, Chaire de recherche du Canada en dynamiq
 ue fluviale\, Département de géographie\, Université de Montréal\nEsti
 mating bedload sediment transport is critical for the maintenance of river
  bed morphology and channel stability. In spite of its importance\, bedloa
 d sediment transport is very difficult to measure and evaluate in situ. Se
 veral techniques provide measures at limited spatial and temporal scales\,
  thus limiting their usefulness for estimating sediment transport rates an
 d sedimentary budgets. This presentation has two objectives. Firstly\, we 
 will briefly review a set of techniques to measure bedload transport in ri
 vers and will examine their potential and efficiency as a function of the 
 objectives and spatiotemporal scales of the study. Several innovations off
 er new avenues in particular for monitoring the displacement of individual
  clasts. For example\, passive transponders (PIT tags) and accelerometres 
 are now used for an efficient tracking of pebbles in gravel-bed rivers and
  they are informative on the modes of transport. Secondly\, we will presen
 t the results from two studies illustrating the usefulness of combining te
 chniques and approaches to gain insights on the role of turbulence in the 
 movement of particles as bedload and on the dynamics of a small gravel-bed
  river. In the first study\, we have used video images taken simultaneousl
 y with measures of the flow velocity fluctuations with the objective of li
 nking turbulent flow properties and the motion of particles. Results show 
 that fluid acceleration and deceleration are critical variables to explain
  sediment transport events. The figure below shows that transport events o
 f individual particles are generally associated with combinations of strea
 mwise and vertical velocity acceleration values that are larger than those
  observed during periods without transport. In a second study\, we have ga
 thered observations in a 6 meter wide gravel-bed river from sediment traps
 \, tagged particles\, topographic measures of the river bed\, erosion chai
 ns et bed markers assessing the active area of the bed during sediment tra
 nsport events. Data show an intense and complex activity of bedload transp
 ort while the bed remained relatively stable. Our hypothesis to explain th
 ese dynamics is related to the dilatation and contraction of the sediments
  composing the river bed during floods. 
LOCATION:CO 124
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR