GEOL 102 1st Edition Lecture 10 Outline of Last Lecture I. Residence TimeOutline of Current Lecture I. ReviewII. Stream Erosion and Sediment TransportIII. FloodsIV. SalmonCurrent LectureI. ReviewResidence time can be applied to watersheds, glaciers, and oceansThe larger the volume, the longer the residence timeAmount going in per year is roughly the same to what is going outRT = volume / Q Q=fluxFast flux makes for a shorter residence timeLinking glacier deformation with glacier morphology Stress at the base of a glacier tends to increase when slopes are steep and ice is thickAs stress builds up, glaciers flow and thin outII. Stream Erosion and Sediment TransportErosion of rock: 3% of stream’s energy goes into erosionRivers erode rock via abrasion and pluckingThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Transport capacity: sediment flux able to be carried by the river channelSediment load: sediment flux delivered to the streamWhat happens if TC > SL? There is erosion down to the bedrockWhat happens if SL > TC? So much sediment in the streamDissolved load: river carries mass in solution (ions)Bedload: particles in contact with the riverbedMove about by rolling, sliding, and saltation (decreased pressure above the particle causes lift)Suspended load: particles suspended in the load90% of sediment delivered to oceans is in the suspended loadChannel TypesBraided streams: high sediment supply, multiple channels, lack of bank stabilizationMeandering: migration via erosion on outer banks and deposition on inner banks, oxbow lakesHypotheses for maintaining a meandering channel1) bank strength (through cohesive vegetation, sediment, or ice)2) fine sediment to fill the downstream end of bars and chutes between banksIII. FloodsFlood Frequency AnalysisRank peak discharge event for each yearCalculate recurrence intervalRecurrence interval = n + 1 / rank (n = number of years in the record)Probability (%) = 1 / recurrence interval x 100A 50-year flood will have 2% probability, a 25-year flood 4% probability, and so onIV. Salmon4 H’s of salmon decline: harvest, habitat, hydro, hatcheriesDams disrupt fish migration routesThe salmon life cycle involves residence in freshwater as juveniles, followed by migration to oceans, and back to freshwater to swimHabitat: spawning- appropriately-sized gravels and proximity to pools, summer rearing- pools with shade, winter rearing- off-channel wetlands and floodplain side