Reading MaterialPuget Sound MorphologySlide 3Bathymetry (water depth)Slide 5Slide 6Slide 7Slide 8Hydrography (water properties)Slide 10Slide 11Types of river-mouth environmentsPuget Sound SedimentationSlide 14Mechanisms associated with SedimentationSlide 16Slide 17Slide 18Slide 19Slide 20Slide 21Reading Material“River Deltas”from “The Coast of Puget Sound”J.P. Downing, Puget Sound BooksPuget Sound MorphologyGlacial Originscour – flow under ice sheetformed depressionse.g., Main Basin, Hood Canal, Lake Washingtonsedimentary deposits – also raised land surfaceglacial tills, outwash deposits, lake depositsold glacial sediment now provides new input to PScliff erosionlandslidesland surface erosionBathymetry (water depth)Shallow entranceglacial origin – moraineoceanographic name – sillprimary sill is Admiralty InletSeveral others divide PS into separate basins (>200 m)Main Basin has 46% of water volumeSinuous shape – result of originSouthern Basin has 29% of shorelinesFluvial (river) sediment supplyfills PS from shorelineWhidbey Basin has 43% of tidelandsHydrography (water properties)Salinity (amount of salt dissolved in water)river water has 0 ppt (parts per thousand)ocean water has ~35 ppt – differs around worldbrackish water at depth in PS – 20-30 pptDensity (low salinity = low density)river plume flows over more dense brackish waterInput of river water - varies with space and timenorthern PS rivers supply the most watersmall input during late summerlarge input during late autumn and winter rainslarge input during spring snowmeltTypes of river-mouth environmentsestuary – semi-enclosed setting river and salt water meet and mixfjord – estuary with glacial origin deep, with shallow sill near mouthdelta – river mouth receiving much sediment estuary filled with sediment shoreline growing seawardPuget Sound SedimentationSources of sedimentshallow – shoreline erosion, landslidesdeep – biological productivity, algal debris much carbon decomposes, forming methane gasall depths – river discharge deltas form near river mouths river plume carries sediment deepernear sill – inflow with deep ocean waterMechanisms associated with Sedimentationplume transport – turbid surface waterriver momentum, tides, windflocculation – silt and clay particles form larger aggregates, which sink quicklylandward bottom flow – traps sediment near riverdelta formation – thick deposits near river mouth topset = tidelands foreset = steep surface, rapid accumulation bottomset = deep deposits, escape seawardDuwamish deltaIntensely impacted by humansWetlands hardened (landfill, roads, parking lots, buildings)Distributary channels altered and stabilizeddepth in mDuwamish delta4-m resolution, 5x VENisqually deltanearly natural conditionSeveral distributary channels bring water and sediment across delta to Puget SoundNisqually Delta, 5x VE3-m resolution, looking SWdepth inmeterspitchyawrollheave&squatpositiontidewater-column sound
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