@article{fdi:010091934,
  title = {{F}actors controlling mud floc settling velocity in a highly turbid macrotidal fluvial-estuarine system},
  author = {{D}efontaine, {S}. and {J}alón-{R}ojas, {I}. and {S}ottolichio, {A}. and {G}ratiot, {N}icolas and {L}egout, {C}. and {L}ienart, {C}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}his study assesses the settling dynamics of suspended sediments along the hyper-turbid {G}ironde {G}aronne fluvial-estuarine system, with an innovative optical {SCAF} instrument ({S}ystem of {C}haracterization of {A}ggregates and {F}locs). {T}wo fields campaigns were carried out to determine the settling velocity and properties of suspended sediments during a semi-diurnal tidal cycle, as well as hydrodynamic conditions and water properties. {T}he two sampling stations were representative of two regions: a tidal river dominated by fresh water and an estuary affected by salty or brackish waters. {A} high spatial variability of the settling velocity was observed along the fluvial-estuarine system and vertically along the water column. {S}ettling velocities ranged from 0.02 to 0.4 mm/s. {T}his study confirms that in hyper-turbid systems, the suspended sediment concentration ({SSC}) is predominantly driving the settling dynamics of suspended sediment. {T}hreshold concentrations have been defined for the flocculation and hindered regimes where the settling velocity may vary by one order of magnitude. {A}lthough in natural environments it is difficult to distinguish between the effects of {SSC} and turbulence (as they are correlated), in the {G}ironde-{G}aronne system the turbulent shear {G} seems to affect the settling of suspended sediment to a lower extent. {S}ettling velocity variations cannot be directly correlated to salinity or organic matter content. {D}espite differences in hydrodynamic and environmental conditions in fluvial and estuarine regions, a common prediction law has been found to estimate settling velocity of suspended sediment as a function of suspended sediment concentration. {E}stuaries and rivers are biotically rich environments strongly impacted by human activities. {M}ud trapping capacity of such systems has a major influence on water quality by reducing light availability, promoting oxygen depletion and by trapping adsorbed contaminants, bacteria and nutrients. {A} key dynamical parameter impacting the trapping of mud is the sediment settling velocity. {S}ediment settling is influenced by a wide range of environmental factors such as salinity, sediment concentration, turbulence of the flow and organic matter. {T}his manuscript presents sediment settling data from field surveys carried out along the {G}aronne {R}iver-{G}ironde {E}stuary system ({F}rance), where large quantities of mud are trapped during the dry season. {I}t highlights the driving role of sediment concentration on the settling dynamics along the entire system, despite the hydrodynamics and water properties of riverine waters differing from the estuarine waters. {T}he turbulence of the flow appeared to be of secondary importance. {A}n unique empirical prediction law has been established for the whole system contrary to other systems around the world. {A}n improved understanding of sediment fluxes contributes to effective waterways management and the preservation of essential ecological environments. {I}n such hyper-turbid system, the suspended sediment concentration predominantly drives the settling dynamics of suspended sediment {T}he turbulent shear appeared to be a control parameter of secondary importance {A} common prediction law can be found for the whole system},
  keywords = {settling velocity ; estuary ; tidal river ; {SCAF} ; hyper-turbid system ; {FRANCE} ; {ATLANTIQUE} ; {GIRONDE} ; {GARONNE}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {O}ceans},
  volume = {129},
  numero = {10},
  pages = {e2024{JC}021558 [17 ]},
  ISSN = {2169-9275},
  year = {2024},
  DOI = {10.1029/2024jc021558},
  URL = {https://www.documentation.ird.fr/hor/fdi:010091934},
}