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River Systems - Runoff

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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River Systems - Runoff

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  1. River Systems - Runoff

  2. Running Water • Integral part of sculpting the Earth’s surface • MOST IMPORTANT AGENT OF EROSION • Indirectly results in the formation of sedimentary rocks

  3. 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

  4. 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

  5. Fig. 11.13

  6. 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

  7. Stream Terminology • Stream System • Drainage Basin • Drainage Divide • Function of size/scale Fig. 11.7

  8. Fig. 11.6

  9. 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

  10. Drainage Patterns Fig. 11.8

  11. Streamflow Dynamics • Examine the physical and hydraulic properties of the stream • Discharge • Velocity • Gradient • Channel Properties • Wetted Perimeter • Shape • Size • Roughness • Sediment Load

  12. 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

  13. 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)

  14. 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

  15. 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

  16. 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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