Streams & Running WaterQuestions to contemplatePowerPoint PresentationSlide 4Slide 5Meandering StreamsSlide 7Slide 8Meandering streams Spoon shaped Channels developSlide 10Slide 11Slide 12Meanders grow and migrate over timeSlide 14Meanders can be cut off from the stream and form Oxbow LakesSlide 16How do we explain this?Entrenched meandersSlide 19The Formation of DeltasSlide 21Slide 22When river reaches Lake or Ocean, velocity of the stream drops to almost zeroSlide 24Stream usually branches at DELTA to form DISTRIBUTARIESSlide 26Deltas migrate over time – sediment blocks a distributary and reroutes stream BUT, a Delta depends on sedimentSlide 28Slide 29Slide 30Other notable stream typesSlide 32Slide 33Slide 34FloodsP = E + I + RSlide 37Slide 38Slide 39Stream HydrographSlide 41Slide 42GroundwaterQuestions to ponderSlide 45Hydrologic Cycle Precipitation = Evaporation + Infiltration + RunoffInfiltration = GW RECHARGEAt some point in depth, all rocks and/or soil become completely saturated with waterSlide 49Slide 50Slide 51Streams & Running WaterStreams & Running WaterLecture 30Lecture 30Questions to contemplate•What are characteristics of low gradient streams?•How do meanders form and migrate over time? How does this influence channel shape?•How do deltas form?•How does the hydrologic cycle relate to floods?Stream characteristics – longitudinal profileV-shaped valleyNumerous rapids and waterfallsExtensive downcutting (erosion)Minimal deposition of sedimentStream course is more-or-less straightNo FloodplainsStream characteristics – longitudinal profileU-shaped valleyFew if any rapids and waterfallsSide Cutting is dominant erosionSediments deposited on floodplainStreams meander (width of meander belt = width of floodplain)Stream characteristics – longitudinal profileBroadly U-shaped valleyNo rapids and waterfallsSide cutting is extensiveExtensive floodplain depositsWidth of floodplain is many times the width of the meander beltMeandering Streams•Very low gradient•Sidecutting produces “bends” in stream path•The sinuous curves of stream are called MEANDERS•Meanders form from lateral erosion, which creates differentials in stream velocityCut BankHigh velocityPoint BarLow velocityErosionDepositionMeandering streamsSpoon shaped Channels develop•Higher energy = more erosion on Cut Bank side–Cut Bank side is deeper•Lower Energy = deposition on Point Bar Side–Point bar side is shallowerSpoon shaped channelMeanders grow and migrate over timeErosion of Cut bank will cut off the meanderMeanders can be cut off from the stream and form Oxbow LakesRiver channel migrates across Floodplain over timeOXBOW LAKEOXBOW LAKEHow do we explain this?Entrenched meanders•Obviously some changes in stream dynamics•From slow, low gradient (side cutting), to high gradient (Down cutting)•Change in Base Level?•Uplift of rocks?The Formation of DeltasWhen river reaches Lake or Ocean, velocity of the stream drops to almost zeroSediment is Sediment is released near the released near the Mouth of the Mouth of the streamstreamLarger particles like sandFiner Particles like silt and claysStream usually branches at DELTA to formDISTRIBUTARIESDeltas migrate over time – sediment blocks a distributary and reroutes streamBUT, a Delta depends on sedimentOther notable stream types•Braided Streams•High sediment loads cause stream channels to become choked•Many channels develop•Associated with glacial melts; and dry regionsDevelopment of a Braided StreamDevelopment of a Braided StreamDevelopment of a Braided StreamFloodsP = E + I + R•P = PrecipitationE = Evaporation + TranspirationI = InfiltrationR = RunoffStream Flow - Discharge•DISCHARGE – the volume of water a stream moves at a given point•Measured as Volume/time•Volume = Cubic length•Stream Discharge (Q) is measured by:Q = A x VA = Cross sectional area of stream (length2)V = Stream velocity (Length/time)Stream Discharge:Q = A x VStream HydrographFlood stageDischargeQGroundwaterGroundwaterLecture 32Lecture 32Questions to ponder•How does geologic material hold and move water? What characteristics of the rocks makes this possible?•Why is groundwater so important yet so fragile of a resource?•What are groundwater issues and problems?•How does Karst topography form, what are the features and how does this relate to erosion?Hydrologic CyclePrecipitation = Evaporation + Infiltration + RunoffInfiltration = GW RECHARGE–Gravity is primary driving force•Pulls water down into soil/rock–Water enters the system at the ground surface through recharge•Recharge from infiltration–Precipitation, Wetlands, lakes and streams–Leaves the system through discharge•Springs, seeps,•Wetlands, lakes and streamsAt some point in depth, all rocks and/or soil become completely saturated with waterWater TableUnsaturatedzoneSaturatedzoneThe Water Table•Water is found at some depth everywhere beneath the Earth’s surface•The water table defines the boundary below which all pore spaces are filled with water•The volume of pore spaces decreases as you go deeper into the crust•Usable water is restricted to a few hundred meters below the