1. Earth Science- Chapter 13 Mr. Hendricks and Mr. McMahon
Surface Water
Earth Science- Chapter 13
Mr. Hendricks and Mr. McMahon

2. Chapter Outline Streams and River Erosion and Deposition River Valleys
Floodplains and Floods

3. Streams and Rivers River Systems Vocabulary - Continental Divide:
- Water Shed aka Drainage Basin:
- River system
- Tributary

4. River System

5. River System
Definition- A river and all of its tributaries (feeder river or connecting rivers)
Example: Mississippi River System

6. Drainage Basin or Watershed
Drainage Basin or Watershedall is all the land that drains into the river directly or through it’s tributaries.
Example: green area is
Mississippi R. Basin

7. Continental Divide
Defined as the highland that separates one drainage basin from another.
Usually a mountain range
Sub-Continental divide in Men. Falls

8. Tributary
A tributary is a feeder river/ creek/ stream that flows into a large parent river.
There are some 250 tributaries of the Mississippi which drain a total area of more than 1,247,000 square miles--one third of the nation's landmass!

9. River Characteristics
Channelized flow- water flows in a chanel
Velocity- how fast a river is flowing
Gradient- how steep a river is
Discharge- how much water is flowing

10. Velocity How fast something is moving High velocity = high speed
Low velocity = low speed

11. Channelized Flow Cross section of river displaying channelized flow
Rivers are “Confined” by their channel
Affects Velocity of water

12. Gradient Slope of a stream Rise over Run
A river may drop 10 feet over a distance of 100 feet
Gradient is 1/10 or 10%

13. Discharge Cross Sectional Area = Width * Depth
5 ft * 100 ft = 500 ft2
Velocity = 1 foot / second
Discharge = 500 ft2 * 1 ft/sec
= 500 ft3 / second

14. Discharge Volume of water that passes a point over an amount of time
How much water is flowing in a river
Cross sectional area * Velocity

15. Stream Discharge

16. How to determine discharge
Discharge = Cross sectional area * Velocity
Determine the discharge of a stream with the following characteristics:
Confined by two vertical walls.
The average depth of water is 5 feet.
The channel is 100 feet wide
Average velocity = 1 foot per second

17. Discharge Discharge is not constant. Depends on conditions
Increased down river
Increased during times of high precipitation or melt
Spring = High Discharge

18. Yearly Discharge

19. Erosion and Deposition
How does it happen?
Mechanical Weathering- Abrasion
Running water
What does it produce?
Sediment
Rounded rocks
Potholes

20. Erosion, Transport, and Deposition
Whether sediment is being eroded, transported, or deposited depends on the size of the particle and velocity of water
Hjulstrom Curve

21. Color Hjulstrom

22. Transportation of Sediment
Load: material transported by river
Bedload: moved along bottom, rocks, gravel, pebbles
Suspension: clay- silt muddy water
Solution: material dissolved in water
Capacity:
total amount of sediment a stream can carry
Competence:
Maximize size particles a steram can carry

23. Stream Load

24. Stream Load

25. Deposition
Sediment is deposited when the velocity of the current can no longer transport material
Examples:
A boulder will not be transported by a trickling crick
A rapid river will move particles of all sizes because of the high V
Silt and Clay is deposited in the deep ocean because there is barely a current (low V)

26. Color Hjulstrom

27. Depositional Feautres
Delta
Sandbars
Deposit Bank

28. Delta
A fan-shaped deposit that forms when a river flows into a quiet or large body of water
Where do you think clay particles are deposited on the diagram?

29. Sand Bars
Wisconsin River-
How do they form?
-Discuss for 2 mins

30. Sand Bar Formation Current carries sediment
Sediment is deposited when current is slowed down
Sediment begins to pile up and catch more sediment
Bars constantly move to change in current and water depth

31. River Deposit

32. River Valleys
Toad River, Canada

33. Why do some rivers grow so big?
All rivers start on a small scale
Rainstorm forms a valley in loose soils called a gullie
Rainstorm ends, water evaporates, but depression remains
Next rainstorm, erosion continues
As time goes on, a gullie increases length, width, and depth
Continuous erosion of land

34. Headward Erosion
The process by which land is worn away at the head of a stream or gully
Head: An abrupt drop in elevation
Waterfall
Erosion opposite the direction of waterflow

35. Canyons Canyon- river valley with steep vertical sides
Form in areas with low rainfall
Factors in formation: Type of rock, amount of water, climate
Colorado R. -Grand Canyon)

36. V-Shaped Valleys
Rain erodes the sides of a valley which forms a V shape
Deeper channel = greater width
Ex: Yellowstone River

37. Base Level
Streams can’t cut any deeper than the body of water they flow into
Ultimately, all rivers only can cut to sea level

38. Rapids and Waterfalls
Water flowing over a cliff or steep, jagged slope forms rapids and waterfalls
High rate of erosion at Rapids and WF
Undermining
Temporary features

39. Undermining
1) Waterfall creates pool 2) Undercuts the waterfall 3) Creates overhang 4) Overhang collapses 5) Recession upstream

40. Niagara Falls

41. Dry Niagrara Falls?

42. Floodsplains and Floods
Features of a Floodplain:
Meanders
Oxbow Lake
Natural Levees

43. Floodplain Features
Meander-River winding back and forth with broad curves

44. Features
Oxbow Lake- A curved body of water that separates a meander from its river
Formed due to erosion of river banks

45. Oxbow Lake

46. Floodplain Feature
Natural Levee- thick deposits alongside stream banks
Elevated ridges

47. Floods Naturally occurring event after heavy or long-lasting rains
Positive and Negative Effects
Recent Flooding?

48. Flood Effects Positive Negative
Relieve water and sediment overload of the channel
Floods deposit minerals on floodplains making these areas fertile for agriculture
Destructive for people near rivers
Cause damage to buildings, farmland, and other properties
Dangerous water levels/velocity

49. Flood Causes
For large rivers, like the Mississippi, floods occur after many days of heavy, steady rainfall- No flash floods
Spring melt
Dam failures- Ex: Lake Delton

50. Lake Delton

51. Flood Control and Prevention
People rely on controlling and preventing floods
Communities built on flood plains are of special concern
Any time a flood occurs their property and their life is at risk

52. Flood Prevention/Control
Means:
Restore natural flood protections
Replanting removed vegetation
Urbanization = problem
Dams
Creates reservoir
Risk of failure – Lake Delton
Eventually fill up with sediment

53. Flood Prevention Continued
3. Artificial Levees- sandbags
Deeper river holds more water
May create erosion downstream
4. Spillways
Channels parallel to river to collect water

54. Floodgates

55. Artificial Levee

56. Stream Stages Youthful Old ________: _______: Rapids Waterfalls
Fast-moving water
Steep slope
_______:
Broad floodplain
Meanders
Oxbow lakes
Meander Scars

57. ________ – the bends and curves of a stream
Meanders

58. Oxbo w lake
depositi on
erosio n

59. ____________ – deposit formed when a stream spreads out onto a less steep area

60. _____ – where a stream empties into a larger body of water
Delta

61. ____________ – when an old age stream downcuts to “make it new again”
Rejuvenation