streams geo 2

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streams geo 2
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2010-06-21 03:35:26
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streams geo 2
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  1. Streams
    • A. GENERAL TERM FOR RIVERS, CREEKS,ETC
    • B.STREAMS ARE VERY IMPORTANT EROSIONAL AGENTS
    • C. STREAMS ERODE, TRANSPORT, AND DEPOSIT MATERIAL
    • D. STREAMS DO MOST OF THEIR WORK DURING FLOODING
    • E. LONGITUDINAL PROFILE OF A STREAM
  2. STREAM CHARACTERISITCS
    • A.VELOCITY
    • 1.Distance water travels in given unit of time
    • 2. Velocity determines how much a material a stream can erode and transport
    • 3. Velocity is influenced by
    • a. Gradient
    • i. Slope of stream channel
    • ii. Vertical drop over horizontal distance ft/mi, m /km
    • b.Discharge
    • i. Volume of water flowing past certain point-ft3/sec, m3/sec
    • c. Size and shape of the channel and size of material in channel
    • i. Large boulders impede the velocity of the stream
  3. Work Streams
    • A.EROSION
    • 1. Lifting and removal material
    • 2.. Hydraulic action
    • a. Force of running water loosens and lifts material
    • 3. Abrasion- material transported along channel has an abrasive effect
    • B. TRANSPORTATION
    • 1. Dissolved load
    • a. Ions transported in solution
    • b. Derived primarily from chemical weathering
    • 2. Suspended load
    • a. Sediment transported in the water column
    • b. Usually clay, silt and fine sand
    • 3. Bedload
    • a. Material transported along channel bottm
    • b. Sand and larger sized sediment
    • C. DEPOSITION
    • 1.Alluvium
    • a. Sediment deposited by streams
    • b. Critcical settling velocity
    • i. Largest particles settle first
    • ii. Clay sized particles wont settle until there is little turbelence to keep sediment suspended
    • 2. Deltas
    • a. Depostional features formed when strams enter lake or ocean
    • b. Have an overall triangular shape
    • c. Delta Deposits
    • i. Topset beds
    • ii. Forest beds
    • iii. Bottomset beds
  4. Base Level
    • A. LOWEST LEVEL TO WHICH A STREAM CAN ERODE ITS CHANNEL
    • B. ULTIMATE BASE LEVEL
    • 1. Sea level
    • a. Streams cannot erode their channels below sea level bc they need gradient to flow
    • C.TEMPORARY BASE LEVEL
    • 1. May formed by lakes or resistant layers of rock along course of stream
    • 2. Limits the amount of downcutting may occur upstream from a dam or resistant rock layer
  5. STREAM VALLEYS
    • A. NARROW STREAM VALLEYS (youthful stage)
    • 1. Form where streams are high above base level
    • 2. Characteristics
    • a. V-shaped valley
    • b. Downcuttin is dominant
    • i. Stream is cuttin its valley deeper
    • c.Rapids and waterfalls
    • d. Lacks a floodplain
    • B. WIDE STREAM VALLEYS (mature to old stage)
    • 1. Form where streams are close to base level
    • 2. Features of meandering streams
    • a. Wide stream valley
    • b. Dominant work is lateral erosion
    • c. Floodplain-flat valley floor between valley walls
    • d. Meanders-looping bends in streams
    • e. Points bars-deposits of sand on the inside of the meander (slowest velocity)
    • f. Cut banks-highest velocity is on the outside of the meander-erosion occurs
    • g. Oxbow lakes- form when a river cuts off a meander
    • h. Natural Levee
    • i. Deposit of fine sand along stream change
    • ii. Form during successive floods
    • i. Braided Streams
    • i. Bedload streams
    • ii. Network of channels
    • C. REJUVENATION
    • 1. Stream terraces- Older, higher, abandoned floodplain
    • 2. Entrenched stream meanders- streams that meander but have no floodplain
  6. DRAINAGE BASINS AND DIVIDES
    • A. DRAINAGE BASIN- Arrea that contributes water to a stream
    • B DIVIDE-SEPEATES DRAINAGE BASINS
    • C. TYPES OF DRAINAGE PATTERNS IN DRAINAGE BASINS
    • 1. Dendritic pattern
    • a. Tributaries join in a treelike branching pattern
    • b. Forms in areas underlain by fairly unifrom rock types
    • 2. Rectangular pattern
    • a. Streams join at right angles
    • b. Pattern is controlled by joints in the underlying bedrock
    • 3. Radical pattern
    • a. Streams diverge in all direction from high area such as volcano
    • b. Pattern controlled by topography
    • 4. Trellis pattern
    • a. Tributary streams are parralel
    • b. Forms where the underlying beds are folded
  7. Floods and Flood Control
    • A. FLOODING IS CAUSED BY WEATHER-low pressure systems or heavy spring snow melts
    • B. STRUCTURES CREATED TO CONTROL FLOODING
    • 1.Artificial levees
    • a. Built on top of natural levees or where no levees exist
    • b. Keeps water channelized
    • c. Increases flooding downstream
    • 2.Flood-control dams
    • a. Built to trap floodwaters and slowly release them
    • b. After streams in various ways
    • 1. Effect ecology of streams
    • 2. Reservoirs cover large areas of unsable land
    • 3. Artificial cutoffs
    • a. Meanders are cutoff by humans
    • b. Increases gradient of stream

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