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XII. Streams

XII. Streams. The Hydrologic Cycle (components and pathways) Stream Velocity (controls and results) Drainage Patterns and Landscape Features (results of erosion and deposition) Stream Valley Development (tectonic uplift and downcutting) . The Hydrologic Cycle. See Fig. 12.3.

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XII. Streams

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  1. XII. Streams The Hydrologic Cycle(components and pathways) Stream Velocity (controls and results) Drainage Patterns and Landscape Features (results of erosion and deposition) Stream Valley Development(tectonic uplift and downcutting)

  2. The Hydrologic Cycle See Fig. 12.3

  3. Drainage Basins • Systems of streams and their tributaries that collect runoff • Divide • Ground Water Great Lakes Drainage Basin

  4. Steam Profiles(Streams Shaping the Land) Flood Plain V-Shaped Valley

  5. What is this Drainage Pattern?(What does is tell of the geology?)

  6. Valley and Ridge Province of PA(Trellis Stream Patters)

  7. Stream Gradient • Slope of the land • Sinuosity of stream 10 m/km 10 m per 1¼ km = 8 m/km 10 m 10 m 1 km 1 km

  8. Higher velocities on outside of meanders causes erosion (cut bank) Lower velocities on inside of meanders causes deposition (point bar) Fig. 10.6 Meander Velocity

  9. A. Narrow and Deep Less resistance Faster flow B. Wide and Shallow More resistance Slower flow C. Rough Streambed More resistance Slower flow Channel Shape and Roughness

  10. Stream Velocity Controls: • How much and what grainsize of sediment is • Eroded and • Transported • Where and what grainsize size will be sediment

  11. Then, Erosion Solution(chemical weathering) Hydraulic Action (lifting) Abrasion(crushing and grinding) Pg. 276 . First, Weathering Fracturing (mechanical) Loosening (mechanical and chemical) Solution (chemical) Stream Erosion

  12. Stream Transport • Dissolved Load • Suspended Load • Bed Load • Saltation • Rolling, sliding Pg. 276 (ions)

  13. e.g., Alluvial Fans Fig. 12.14a Fig. 12.14b Erosion Dominated High gradients Less resistance Fast velocities Deposition Dominated Lower gradients More resistance Lower velocities Stream Deposition Braided Streams Alluvial Fan

  14. Midchannel bars Fig. 12.7b Point bars Fig 12.9 Braided streams Fig. 12.7a Stream Deposition

  15. Fig. 12.13 Reduction of velocity due to extreme widening Deposition of silt and clay Deltas

  16. Erosion and Deposition Transport E.g., Meandering streams • As meanders are migrating • Cutbanks eroding • Point bars building • Sediment is moving downstream

  17. Meander Cutoff How does the gradient change with meandering and meander cutoff?

  18. Meandering Streams D Identify • Cutbanks • Point bars • Meander neck • Oxbow lakes • Areas of Erosion • Areas of Deposition A C B E

  19. Natural Levees • Flooding • Overbank deposits • Widening of stream into flood plain • Deposition of sediment • Coarse near stream • Fine farther away Fig. 12.11

  20. Graded Streams Increased velocity and accelerated erosion. Base level: Lake or Sea Erosion acts to grade the Longitudinal stream profile to concave-upward curve Same Base level

  21. Drainage Patterns A. Dendritic Geology controls stream patterns • Uniformly Erodible (e.g., flat-lying sedimentary rocks of the Midwest) • Conical Mountains (e.g., Volcanoes) • Fractured bedrock (shallow bedrock) • Resistant ridges of tilted sedimentary rocks (e.g., Valley and Ridge Province of Pennsylvania) B. Radial C. Rectangular D. Trellis

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