STREAM SYSTEMS Earth Science: Chapter 5 Reading pages 114-124 The Hydrologic Cycle Oceans not filling up Evaporation = precipitation System is balanced Earth s Water and the Hydrologic Cycle Earth s Water and the Hydrologic Cycle The Hydrologic Cycle Hydrologic Cycle File link The Hydrologic Cycle Precipitation Evaporation Infiltration Runoff Transpiration Earth s Water and the Hydrologic Cycle Comes from precipitation Transports sediment Erode channels 2
Drainage Basins Area that drains into a stream Separated by drainage divides Erosion Transportation Deposition EROSION Lifting loose particles Abrasion Dissolution EROSION Depends on velocity Gradient Channel characteristics Discharge CHANNEL CHARACTERISTICS Shape Size Roughness Gradient 3
Channel Shape GRADIENT Slope of channel Vertical drop / channel length Same cross sectional area Channel perimeter about doubled DISCHARGE Volume of water flowing past a point in a certain amount of time Cross sectional area x velocity Gaging station Discharge Calculation Willamette Discharge http://www.waterwatch.org.au/library/module-4/flow.html#10 http://waterdata.usgs.gov/or/nwis/uv?format=gif&period=31&site_no=14191000 4
Longitunal Profile Longitunal Profile Cross section of length of stream Changes from head to mouth of stream Longitunal Profile Changes from head to mouth of stream Cross section of length of stream Gradient gradually decreases downstream Discharge increases downstream Changes from head to mouth of stream Channel gradient Channel size Discharge Velocity of flow Channel shape Discharge Three modes of moving material In solution = Dissolved load Suspended load Sliding, rolling, bouncing = Bed load Dissolved load From groundwater, runoff and channel Supplies ocean with minerals in solution 5
Suspended load Most of material transported Sand, silt, clay Larger particles in flood Bed load Too large to keep suspended Grinds channel and downcuts Competence Capacity COMPETENCE Size of particles Depends on velocity V ~ (competence) 2 CAPACITY Amount of material Depends on discharge Competence vs. Capacity Ant has less competence Elephant has greater competence 6
Competence vs. Capacity Greatest competence with greatest velocity Greatest capacity with greatest discharge Maximum during floods Many ants is greater capacity Erosion Transportation Deposition DEPOSITION Slowing of velocity Largest particles deposited first ALLUVIUM Bedrock Channel Alluvial Channel High gradient Many rapids and waterfalls http://www.paul.chesterfield.btinternet.co.uk/pages/landscapes12.htm 7
High Velocity in Center Velocity displaced around meander curve Channel Pattern Natural progression to more meandering channel character Development of meanders Development of Meanders Stream Processes and Floodplain Development Meandering Stream File link 8
Channel development Channel development Channel development Formation of Oxbow Lake Oxbow Lakes Well Established Meandering Stream Oxbow Lake Formation File link 9
Channel Pattern Braided Channel High Gradient Highly variable discharge High, coarse sediment load Braided channel develops Glacial Stream Dart River South Island, New Zealand http://www.bartholmai.com/nz2/webpages%20nz2-pages/image51.html http://www-geology.ucdavis.edu/~gel109/sedstructures/lg/akriverchannel.jpg Exam Report Another extra credit opportunity Redo Part II Problems You must follow these instructions exactly to get the extra credit Do not erase or change anything on your exam paper. On a separate sheet of paper, write the problem number, show how to solve the problem, including calculations and formulas, with units. Circle the answer, reported with correct units if required. Staple your exam paper to your extra credit paper This is due at the beginning of next class: February 15. [If you are sick, send it with another student, by campus mail, or US mail (must be postmarked 2/15 if sending by US mail)] Exam Report A 63-70 points B 56-62 points C 50-55 points D 42-49 points F 28-41 points 10