Water and Erosion

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Chapter 13

• Water and Erosion

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• Section 13.1
• Water cycle continuous movement of water from
  the atmosphere to the earths surface and back to
  atmosphere
• Also called hydrologic cycle

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• Steps involved in water cycle
• Evaporation liquid water changes to vapor
• Transpiration plants giving off water vapor
• Evaopotranspiration evaporation and
  transpiration combined
• Condensation water vapor rising into atmosphere
• Precipitation water falls from clouds to earth
  as rain, sleet, snow, hail

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Water Cycle - Important to Ecosystem Balance
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• The continuous water cycle is what gives the
  earths its water budget
• Precipitation is the income
• Its balanced because the amount of precipitation
  the amount of evapotranspiration and runoff
• Factors that affect it are vegetation, rainfall,
  wind, amount/duration runoff

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• Section 13.2 river systems
• River system is made up of a main stream and
  feeder streams, called tributaries
• Land from which water runs off into these streams
  is called a watershed
• In Virginia there are 13 watersheds these
  watersheds drain to the Chesapeake Bay, North
  Carolina Sounds and Gulf of Mexico

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• Streams transport soil, loose rock fragments, and
  dissolved minerals stream load
• 3 forms of stream load
• Solution material that is removed from bedrock
• Suspension suspended material such as sand,
  silt, clay looks muddy
• Bed load sediment moving along stream bed or
  base pebbles/boulders

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• The discharge and velocity of a stream, as well
  as its load, affects how a stream cuts and widens
  its channel
• Discharge is the volume of water moved by a
  stream in a given time
• Faster the stream, higher discharge and larger
  load erodes faster,
• Slower streams, lower discharge and smaller load

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• Rivers develop from a youthful stage to an old
  age stage
• Youthful rivers erodes its beds more rapidly
• Produces V-shaped valleys with steep sides
• Waterfalls and rapids common
• Few tributaries

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• Mature streams
• Well-established tributaries
• Drains watershed effectively
• Erosion occurs along the valley walls
• Not many waterfalls and rapids
• Meanders and oxbow lakes water in abandoned
  meander
• Old Rivers
• Lower gradient, slower than mature river
• Deposits sediments on land instead of eroding,
  flood plain formed

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• Stream erosion
• Potholes created by sand, pebbles and small
  boulders swirling around in whirl pools, erodes
  out rock and makes hole
• Waterfalls created when rock is undermined by
  stream current

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