A rapid method for settling velocity and flocculation measurement within high suspended sediment concentration rivers.
Résumé
In headwater catchments, fine sediment transport is a main issue with regard to monitoring
erosion, pollutant fluxes, and reservoir siltation. In these environments, suspended sediment
concentrations exhibit high temporal variations during runoff events and commonly exceed
10 g/l. The settling velocity of suspended sediment is a key variable to understand and model
sediment transport. For such concentrated events, hindered settling and flocculation processes
increase the difficulty to model sediment transport. Currently, no automated method for the
measurement of settling velocity and propensity to flocculate within high concentration
sediment environments exists. Methods used to measure individual particle settling velocity
(e.g., LISST, video) are limited to low concentrations (<1g.l). They can be adapted to higher
concentration after dilution in particle-free water, however, measured settling velocities may
not be representative of the initial sample as hindered and flocculation effects are eliminated
or reduced.
In order to measure quasi in situ sediments settling velocity spectrum and propensity to
flocculate in high concentrated environment, we assessed a processing method based on light
transmission measurement within a quiescent settling column condition.
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