Direct Sediment Dispersal from Mountain to Shore, with Bypassing via Three Human-Modified Channel Systems to Lake Annecy, SE France

Abstract

. Direct sediment dispersal from mountain to shore, with bypas.sing via three human-modified channel systems to Lake Annecy, SE France. Journal of Coastal Research, 20(4),[958][959][960][961][962][963][964][965][966][967][968][969]. ISSN 0749-0208. Lake Annecy in Haute Savoie, France, receives about two-thirds of its fluvial input from three rivers that flow to its southern end-point. The channels of the Eau Morte, Ire, and Bornette rivers are almost completely channelized in their lower reaches as a result of human activity, with flow contained along parallel, but separate, paths from headlands in the proximal drainage basin directly to the lake. Pétrographie data from river samples collected in this study serve to differentiate sand-size material carried by each fluvial system. Proportions of the dominant (limestone) and five additional (dolomite, quartz, gypsum, rock fragments, and 'other') components in the 3 rivers are more closely related to source supply than to fluvial transport effects or sampling strategy. Of the 7 components, mica best records the influence of depositional mechanisms. Much of the carbonate sand and coarser material at the lake shore is derived from widespread Mesozoic outcrops. Non-carbonate sand input, partially resulting from erosion of glacial till deposits and pedogenic horizons in the southern drainage basin, provides key compositional markers to differentiate between sediment carried to the lake by each river.Until several centuries ago, deposits of the Eau Morte, Ire, and Bornette flowed to the Bou du Lac, and formed a merged, multifluvial lacustrine delta. As drainage and channel containment projects related to agricultural development intensified in lake margin lowlands, the 3 channels were separated on the delta surface, allowing bypass of river material directly onto subaqueous deltas in the lake. Specific mineral assemblages, especially quartz, mica and rock fragments, may prove useful as key tracers of human-altered sediment between the margin and deeper lake sectors.

Detecting climatic signals in an anthropogenically disturbed catchment: The late-Holocene record from the Petit Lac d’Annecy, French Alps

“…As a result the majority of the river sediment load is deposited directly into the lake (e.g. Crook et al, 2011; Dearing et al, 2001; Stanley and Jorstad, 2004; Welsh et al, 2009). Over this same time period, forest cover increased dramatically from ad 1850 onwards with the area of modern forest cover equal to the levels recorded in the ad 1730 survey (Crook et al, 2002); an example of a modern forest transition in a high-income country (Lambin and Meyfroidt, 2010).…”

Inverse Relationship of Marine Aerosol and Dust in Antarctic Ice with Fine-Grained Sediment in the South Atlantic Ocean: Implications for Sea-Ice Coverage and Wind Strength

“…For grain size analysis, four hundred samples were selected every 5-cm from 0-20 meters below the seafloor. Approximately 0.25 g of each sample was suspended in approximately 20 mL deionized water and sodium hexametaphosphate and sonicated for 5 minutes to deflocculate clay particles (Schofield and Samson, 1954;Stanley and Jorstad, 2004). Grain size analysis was then conducted on each using a Malvern laser diffraction system equipped with a sample-introduction vessel that enabled stirring and sonication to keep the sediment suspended and deflocculated throughout the analysis (Warner and Domack, 2002;Hemer et al, 2007).…”