Geology1 MT2 Hydrology

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Geology1 MT2 Hydrology
2011-05-24 15:54:13
Geology1 MT2 Hydrology

Geology1 MT2 Hydrology
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  1. Hydrologic cycle
    • ocean water evaporates; (liquid) --> (gas)
    • condensation; (gas) --> (liquid) or (solid)
    • precipitation
    • infiltration (groundwater) and runoff (rivers)
  2. potential energy
    energy of position
  3. adiabatic heating/cooling
    • temperature change due to volume change
    • ↑volume = ↓temperature
    • ↓volume = ↑temperature
    • -- no heat exchanged
  4. aquifer
    groundwater reservoir
  5. permeability
    ability to allow the passage of fluids; interconnectedness of pores
  6. porosity
    • the amount of our rocks/sediments that are void space
    • expressed as a percentage of total volume
    • primary: porosity that forms with rocks/seds deposition
    • secondary: forms due to weathering/erosion
  7. recharge
    • the refilling of our groundwater reservoir
    • largely due to infiltration
  8. infiltration
    • movement of water through soils and rocks
    • manner of transport of precipitation into groundwater system
  9. anatomy of an aquifer, top to bottom
    • surface
    • -----------------------------
    • zone of aeration (vadose zone)
    • -----------------------------
    • capillary fringe
    • ------------------------water table
    • zone of saturation
    • __________________
    • bedrock or impermeable layer
  10. three types of aquifers
    • unconfined; the upper surface is the water table
    • confined; impermeable layers above (aquiclude/aquitard) and below (bedrock)
    • perched; a lens of water that gets trapped above an impermeable bit of sed or rock
  11. potentiometric surface
    height to which pressurized water can pump itself using its potential energy
  12. recharge basin
    • collects water in a depression which creates pressure
    • uses that pressure to pump water into ground
  13. anatomy of a river/stream
    • headwaters; place water originates
    • tributaries; small channels that combine to form larger streams
    • trunk, main channel; larger streams
    • distributaries; smaller channels form when river chokes itself with sediment
    • delta
  14. gradient
    • change in elevation ÷ horizontal distance
    • slope
  15. thalweg
    • deepest and highest velocity portion of a channel
    • highly erosive part of a river
  16. bedload
    sediment that is rolled or dragged along the bed of a river
  17. suspended load
    seds that are carried in the flow of a river
  18. dissolved load
    ions that are carried in the river water
  19. discharge (Q)
    • the volume of water that flows past a point in a given time
    • Q = velocity x area
    • or, cubic feet per second
  20. two types of channels
    • linear
    • sinuous
  21. describe a meandering stream
    • the thalweg migrates to the outside of bends in a sinuous channel, creating...
    • cutbank; a region of increased erosion on the outside of a bend
    • point bar; a region of increased deposition on the inside of a bend
  22. oxbow lake
    an abandoned bend that is cut off from the main channel due to sediment deposition
  23. characteristics of an urban stream
    • infiltration is slowed/stopped due to pavement
    • all precipitation will directly enter the channel
    • large discharge (tall peak on hydrograph)
    • velocity will be high due to rapid input of water
  24. characteristics of a rural stream
    • infiltration forms a lag in the hydrograph
    • runoffs begin when the soils become saturated
    • runoff is slower due to soils, plants, etc. so the maximum discharge slowly builds and falls
  25. types of floods
    • flash floods
    • regional floods
  26. flash floods
    • intense rain over a small area over a short amount of time
    • fast moving runoff
  27. regional floods
    • sustained rain over large drainage
    • slow rise and fall
  28. recurrence interval
    • amount of time expected to pass between floods of the same size
    • RI = (n+1) ÷ m
    • n: number of years of data
    • m: numerical rank of the flood
  29. probability that a flood will occur in any given year
    p = 1 ÷ RI
  30. channelization
    • if you decrease the roughness in bed, you increase the velocity of flow
    • allows for the movement of more water in less time
  31. anatomy of a beach, top to bottom
    • marine terrace
    • cliff
    • berm
    • beach face
    • wave-cut platform
  32. wave-cut platform
    flat ledge cut into bedrock due to wave activity
  33. beach face
    portion of beach where sand is transported due to wave activity
  34. berm
    portion of beach above high-tide line where the sand does not move
  35. marine terrace
    elevated wave-cut platform
  36. wave frequency =
    • 1/wavelength
    • shorter wavelengths have higher frequency = more energy
    • longer wavelengths have lower frequency = less energy
  37. longshore transport
    the transport of sediments along a coast at an angle to the shoreline, which is dependent on prevailing wind direction, swash and backwash
  38. swash
    onshore movement of water in a wave
  39. backwash
    the offshore movement of water in a wave
  40. 4 man-made structures that interfere with sand drift:
    • jetties; closely spaced groins designed to keep longshore transport from closing off a waterway
    • groins; beach ⊥ structure; designed to slow down the longshore current
    • breakwater; beach || structure; built offshore to prevent waves from reaching the shore, forms calm area
    • seawall; beach || structure; built on beach, prevents waves from striking the beach