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River Systems - Runoff. Running Water. Integral part of sculpting the Earth’s surface MOST IMPORTANT AGENT OF EROSION Indirectly results in the formation of sedimentary rocks. Stream Formation. Sheetflow or Sheetwash – overland flow of water

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running water
Running Water
  • Integral part of sculpting the Earth’s surface
  • MOST IMPORTANT AGENT OF EROSION
  • Indirectly results in the formation of sedimentary rocks
stream formation
Stream Formation
  • Sheetflow or Sheetwash – overland flow of water
  • Repeated precipitation events cause a preferential channel to form – downcutting
  • Tributaries form & the main channel continues to grow up slope – headward erosion
stream morphology
Stream Morphology
  • Streams increase in length by headward erosion – erosion occurring at the beginning of the stream
  • Streams become wider through lateral erosion – mass wasting of the stream banks
  • Streams become deeper through downward erosion of the channel by abrasion of the sand and gravel
stream terminology
Stream Terminology
  • Stream System – main stream plus tributaries
  • Drainage Basin – area drained by main stream and tributaries
  • Drainage Divide – area of higher elevation that divides drainage basins
  • Function of size/scale

For Example:

Kickapoo Creek

Sangamon River

Illinois River

 Mississippi River

slide7
Stream Terminology
  • Stream System
  • Drainage Basin
  • Drainage Divide
  • Function of size/scale

Fig. 11.7

stream subsystems
Stream Subsystems
  • Collecting System
    • Tributaries is head water region
    • Funnel water and sediment to main channel
    • Primarily erosion and transport
  • Transporting System
    • Main tributary
    • Main process is the movement of the sediment and water
    • Erosion, transport, and deposition all occur
  • Dispersing System
    • Distributaries at mouth region
    • Primarily deposition of the sediment
    • Coarse sediment along the confluence
    • Fine particles carried further in to body of water
streamflow dynamics
Streamflow Dynamics
  • Examine the physical and hydraulic properties of the stream
  • Discharge
  • Velocity
    • Gradient
    • Channel Properties
      • Wetted Perimeter
      • Shape
      • Size
      • Roughness
  • Sediment Load
daily question
DailyQuestion

Duplicate the chart to the right.

On the chart add lines that represent how the following properties change:

Discharge

Velocity

Cross-Section Area

Gradient

Channel Roughness

Base level

The property “drainage basin area” is provided as an example

discharge q
Discharge (Q)
  • Volume of water passing a given point over a specified length of time (length3/time), generally given in ft3/s or m3/s
  • Calculated by:
  • Where A is the cross-sectional area (length2) & v is the velocity of the water (length/time)
velocity
Velocity
  • The speed of the water at a given point along a stream
  • Directly related to a stream’s ability to erode and transport material
  • High velocity water can carry heavier sediment
  • Is a function of
    • Gradient
    • Channel Properties
      • Wetted Perimeter
        • Shape
        • Size
        • Roughness
stream gradient
Stream Gradient
  • Slope or steepness of the stream channel
  • Vertical drop (relief) of a stream over a fixed distance
  • Controls the potential energy of the water
  • Steeper the gradient – the higher the velocity, the lower the gradient – the lower the velocity
  • Meanders decrease the gradient by increasing the horizontal distance of the stream
wetted perimeter
Wetted Perimeter
  • The area in which water touches the channel walls
  • Channel shape and size controls the wetted perimeter
  • Most efficient streams have small wetted perimeters
  • Roughness of the channel controls the frictional resistance to water movement
    • A smooth channel decreases frictional force
    • A rough channel increases frictional force
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