1. Classroom presentations to accompany Understanding Earth, 3rd edition
prepared by
Peter Copeland and William Dupré
University of Houston
Chapter 13
Streams: Transport to the Ocean

2. Streams: Transport to the Ocean
Gary D. McMichael/Photo Researecher

3. Rivers and streams Stream : body of water flowing in a channel
The floor of the channel is called the bed.
When rainfall is very heavy or snow melts rapidly, bodies of water overflow their banks and water covers the adjacent land called the floodplain.

4. Rivers and streams Carry away runoff to lakes and seas
Erode land (degradation)
Transport and deposit sedimentary debris

5. Stream behavior Mostly determined by velocity and shape of channel.
These factors combine to allow either laminar or turbulent flow.
Turbulent flow is much more erosive.
Stream velocities may vary from 0.25 to 7 m/s.

6. Laminar flow Smooth sheet-like flow at a low velocity
Usually confined to edges and top of stream

7. Turbulent flow Irregular swirling flow
Occurs at most rates of stream flow
Keeps particles in suspension

8. Laminar flow
Fig. 13.1a

9. Turbulent flow
Fig. 13.1b

10. Laminar to turbulent transition
Laminar flow
Turbulent flow
ONERA
Fig. 13.1c

11. Streams move material in three forms
Dissolved load
Suspended load
Bed load (traction and saltation)

12. Sediment Transport
Fig. 13.2

13. Saltation
Fig. 13.3

14. Grain Size and Flow Velocity
Fig. 13.1

15. Stream terms
competence: measure of the largest particles a stream can transport proportional to v2
capacity: maximum quantity of sediment carried by stream proportional to Q and v

16. Lower Velocities Form Ripples
Fig. 13.5a

17. Higher Velocities Form Dunes
ripples
dune
dune
Fig. 13.5b

18. Pebbles Caught in Eddies Form Potholes
Fig. 13.6
Carr Clifton/Minden Pictures

19. Waterfall Retreating Upriver
Fig. 13.7
Donald Nausbaum

20. Parts of a River System
Fig. 13.8

21. Two important stream types
1. Meandering Streams
Gentle gradients, fine-grained alluvium
Minimizes resistance to flow and dissipates energy as uniformly as possible (equilibrium)
Examples: point bars,oxbow lake, migrating meanders

22. Two important stream types
2. Braided Streams
Sediment supply greater than amount stream can support.
At any one moment the active channels may account for only a small proportion of the area of the channel system, but essentially all is used over one season.
Common in glacial, deserts, and mountain regions.

23. Incised Meanders, Utah
Fig. 13.9
Tom Bean

24. Meandering River Over Time
Fig

25. Lateral migration by erosion at the outside. &
Lateral migration by erosion at the outside & deposition on the inside of the river
Fig a

26. Meandering River
Point Bar
Fig
Peter Kresan

27. Braided River
Fig
Tom Bean

28. Formation of Natural Levees
Fig. 13.1

29. Discharge Total amount of water that passes a
given point in a stream per unit time
Q = w d v

30. Discharge
Discharge (m3/s) = width (m)  depth (m)  average velocity (m/s)
In the U.S., this is expressed as cubic feet per second (cfs):
1 m3/s = 35.9 ft3/s

31. River at Low Discharge
Fig a

32. River at High Discharge
Fig b

33. Flooding
Water in the stream is greater than the volume of the channel.
Interval between floods depends on the climate of the region and the size of the channel/

34. City Built on a Floodplain
Xie Jiahua/China Features/Sygma

35. Recurrence interval Average time between the
occurrences of a given event
The recurrence interval of a flood of
a given size at a given place
depends on:
• climate of the region
• width of the floodplain
• size of the channel

36. Annual Flood Frequency Curve
Fig. 13.1

37. Longitudinal Stream Profile of the Platt and South Platt Rivers
Fig

38. Elevation at which a stream enters a large body of water such
Base level
Elevation at which a stream
enters a large body of water such
as a lake or ocean

39. Role of Base Level in Controlling Longitudinal Profile of Rivers
Fig

40. Effects of Building a Dam Original Profile Graded to Regional Base Level
Fig a

41. Effects of Building a Dam Dam Forms New Local Base Level
Fig b

42. Effects of Building a Dam Deposition Upstream and Erosion Downstream
Fig c

43. Graded stream Stream in which neither erosion nor
deposition is occurring, due to an
equilibrium of slope, velocity, and
discharge.

44. Geologic evidence of changes in stream equilibrium
Alluvial fans
Terraces: erosional remnants of former floodplains

45. Alluvial Fans
Fig
Michael Collier

46. Formation of River Terraces
Fig

47. Drainage divides separate adjacent drainage basins
Fig

48. Drainage basin Area of land surrounded by
topographic divides in which all the
water is directed to a single point

49. Drainage Basin of the Colorado River
Fig

50. Typical Drainage Networks
Fig

51. Stream was present before deformation
Antecedant Stream
Deformation causes gorge to form
Stream was present before deformation
Fig &b

52. A Superimposed Stream Downcutting causes gorge to form
Deformation occurred before stream was present
Fig

53. Delaware Water Gap A Superimposed Stream
Fig c
Michael P. Godomski/Photo Researchers

54. Location of significant sedimentation where a river meet
Delta
Location of significant
sedimentation where a river meet
the sea.

55. Mississippi Delta
Fig
Landsat 2 image annotated by Moore, 1979

56. Typical Large Marine Delta
Fig

57. Shifting Mississippi River Delta Over the Past 6000 Years
Fig