Reading MaterialPuget Sound MorphologySlide Number 3Bathymetry (water depth)Slide Number 5Slide Number 6Slide Number 7Slide Number 8Hydrography (water properties)Slide Number 10Slide Number 11 Types of river-mouth environments Puget Sound SedimentationSlide Number 14Mechanisms associated with SedimentationSlide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 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 settingriver and salt water meet and mixfjord – estuary with glacial origindeep, with shallow sill near mouthdelta – river mouth receiving much sedimentestuary filled with sedimentshoreline growing seawardPuget Sound SedimentationSources of sedimentshallow – shoreline erosion, landslidesdeep – biological productivity, algal debrismuch carbon decomposes,forming methane gasall depths – river dischargedeltas form near river mouthsriver 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 mouthtopset = tidal flatsforeset = steep surface, rapid accumulationbottomset = 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-columnsound
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