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The Drainage Basin “your friend, and all of its secrets”

The Drainage Basin “your friend, and all of its secrets”. Introduction --two general relationships realized concerning drainage basins. Introduction --two general relationships realized concerning drainage basins * streams form their valleys in which they flow. Introduction

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The Drainage Basin “your friend, and all of its secrets”

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  1. The Drainage Basin “your friend, and all of its secrets”

  2. Introduction --two general relationships realized concerning drainage basins

  3. Introduction --two general relationships realized concerning drainage basins * streams form their valleys in which they flow

  4. Introduction --two general relationships realized concerning drainage basins * streams form their valleys in which they flow * every river consists of a major stream that is fed by a number of mutually adjusted branches that diminish in size away from the main stem.

  5. Introduction II. Slope Hydrology and Runoff Generation

  6. Introduction II. Slope Hydrology and Runoff Generation A. Basin Hydro. Cycle and Budget Input = Output + change in storage

  7. Introduction II. Slope Hydrology and Runoff Generation A. Basin Hydro. Cycle and Budget Overland flow Interflow Baseflow Input = Output + change in storage

  8. Introduction II. Slope Hydrology and Runoff Generation • Basin Hydro. Cycle and Budget • The Storm Hydrograph

  9. B. The Storm Hydrograph Unit hydrograph: ‘where the runoff volume is adjusted to the same unit value (e.g., one inch of rainfall spread evenly over a basin in one day”

  10. Overland flow Baseflow Direct ppt Interflow

  11. Discharge Basin Area

  12. III. Initiation of Channels and the Drainage Network A. The concept

  13. III. Initiation of Channels and the Drainage Network • The concept Shear stress…….

  14. III. Initiation of Channels and the Drainage Network • The concept Shear stress……. τ = ρgds Effects of Vegetation….

  15. III. Initiation of Channels and the Drainage Network • The concept Rills develop, and they begin to “bifurcate” “repeated divisions of single channel segments”

  16. Rills develop, and they begin to “bifurcate” “repeated divisions of single channel segments”

  17. III. Initiation of Channels and the Drainage Network B. Basin Morphometry refers to the geometry of the basin

  18. B. Basin Morphometry refers to the geometry of the basin Drainage Composition refers to the distinct fabric of the drainage basin

  19. Drainage Composition refers to the distinct fabric of the drainage basin Strahler (1952) Shreve (1967)

  20. 2. Linear Morphometric Relationships Certain linear parameters of a basin are proportionally related to stream order. • Bifurcation ratio (Rb) streams of one order streams of the next highest order

  21. 2. Linear Morphometric Relationships Certain linear parameters of a basin are proportionally related to stream order. • Bifurcation ratio (Rb) streams of one order streams of the next highest order Ex: 1 6th order stream 3 5th order 9 4th order 27 = 3 27 3rd order 9 81 2nd order Ratio value is nearly constant between adjacent orders AND….where geology is homogeneous, Rb = 3.0 – 5.0

  22. 2. Linear Morphometric Relationships Certain linear parameters of a basin are proportionally related to stream order. b. Length ratio ave length of streams of one order ave length streams of the next highest order Can be used to determine the average length of streams in an unmeasured order.

  23. 3. Aerial Morphometric Relationships • Drainage density (Dd) total length of streams in basin basin area Reflects the interaction between geology and climate In general….

  24. IV. Basin Morphology and Flood Hydrograph

  25. IV. Basin Morphology and Flood Hydrograph

  26. V. Basin Evolution and Denudation

  27. V. Basin Evolution and Denudation A. Factors affecting sediment yield * climate

  28. V. Basin Evolution and Denudation A. Factors affecting sediment yield * climate

  29. V. Basin Evolution and Denudation A. Factors affecting sediment yield • Basin size • Elevation • Relief

  30. V. Basin Evolution and Denudation A. Factors affecting sediment yield * rock type

  31. V. Basin Evolution and Denudation A. Factors affecting sediment yield * Human Factor

  32. V. Basin Evolution and Denudation A. Factors affecting sediment yield * Human Factor

  33. V. Basin Evolution and Denudation A. Factors affecting sediment yield B. How do basins erode (denute?)

  34. Sediment Transport and Denudation

  35. 0.398km2

  36. Before After ? ? ?

  37. 0.398 km2 13, 364 m3

  38. Volume = 13, 364 m3 = 0.034 m Area 0.398 km2 or 398,000 m2 = 3.4 cm

  39. Event Basin Basin Area (km2) Volume of Sediment Eroded (m3) Mean Basin Denuda-tion (cm) Hurricane Camille Willis Cove 4.08 173,488 4.25 Hurricane Camille Ginseng Hollow 1.75 88,727 5.07 Hurricane Camille Polly Wright Cove 2.47 87,707 3.55 Rapidan Flood Jenkins Hollow 0.398 13,364 3.36 Rapidan Flood Teal Hollow 0.123 2,492 2.03 Summary of Basin Denudation of Blue Ridge Systems

  40. Hurricane Camille Rapidan Storm

  41. B. How do basins erode (denute?) High Magnitude Low Frequency Low Magnitude High Frequency

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