Streams And Sediment Transport Notes

Sediment transport Sediment Rating Curve slope that compares sediment discharge and quanity of sediment carried Discharge increases = more erosion material added to flow from erosion Low discharge = little sediment movement Fluid Drag friction on surface Bed Load pebbles and sand not permanently suspended Dissolved Load  Dissolved in water Suspended load silts and clays in suspension Note: Human activity adds dissolved and solid material to streams ie. Fertilizers, animal waste, soluble compounds (agriculture by products). Deforestation causes increased amounts of water due to lack of vegetation Channels narrow with high velocity flow at top end of many streams Bars Coarse sediments that deposit in streams to form land in the middle. Point Bar stream flow is reduced b/c of friction and shallow depth Thalweg Deepest area of stream with most velocity in most cases *bars form away from thalweg. Riffle coarse deposit which develop under thalweg when it moves upwards Dunes mainly made of sand and silt Ripples few cm in height and spacing – slow moving streams with fine beds Lee Side Stoss Side Delta sediment that contains horizontal and vertical layers. Caused by sudden reduction of velocity Foreset beds deposits in main body of delta. Steep angles finer sediments. Topset on top of foreset bed – nearly horizontal Bottomsetin front and beneath foreset beds Alluvial Fan fan shaped deposit that braided stream flows over. Trellised: strong structural control on streams. Channels align parallel to bedrock structures Parallel: steep relief / non cohelsive materials Dendritic: Adjusted systems on erodible sediments and dipping bedrock Deranged: recently disturbed by events eg. Glacial activity/ volcanic deposition.