1. Running Water & Groundwater
Chapter 6 (sec. 1 & 2 only)
200

2. The Role of Streams & Rivers
What role do streams & rivers play on Earth?
~½ of the water that falls to Earth’s surface eventually ends up in a stream or river
& most drain to oceans
essential part of the water cycle
Most important agent of surface erosion

3. River Systems What is a river system?
a river and all of its tributaries
What is a tributary?
a stream that runs into another stream or river

4. Drainage Basins/Watersheds
What is a drainage basin (or watershed)?
all the land that drains into the river either directly or through its tributaries
Lgst drainage system in U. S. = Mississippi River system
Continental Divide
Appalachian Mountains
Largest drainage system in U. S. is Mississippi River system
Boundaries:
East = Appalachian Mts
West = Continental Divide

5. Divides What is a divide?
high land that separates one drainage basin from another
Continental Divide (Rocky Mountains) is the major divide in the U. S.
rain falling to east flows to (Gulf of Mexico &) Atlantic
by way of Mississippi River system
rain falling to west flows to the Pacific
Continental Divide
Largest drainage system in U. S. is Mississippi River system
Boundaries:
East = Appalachian Mts
West = Continental Divide

6. Streamflow: Velocity What is “velocity”? How is velocity measured?
distance water travels in a given amount of time
How is velocity measured?
float method
flow meter
Measuring Stream Velocity Video

7. Streamflow: Velocity What affects a stream’s velocity?
amount of energy a stream has
What affects a stream’s energy?
1. gradient (slope or steepness)
2. discharge (amount of water)
3. channel (stream path)
size (width & depth)
shape of the path (straight/curved)
velocity- distance water travels in a given amount of time
1. Gradient (slope or steepness)
2. Discharge (amount of water)
3. Channel
Size (width & depth)
Shape of the path (straight/curved)

8. Streamflow: Velocity
How is stream velocity related to the size of the particles it can transport?
faster = larger particles
velocity- distance water travels in a given amount of time
1. Gradient (slope or steepness)
2. Discharge (amount of water)
3. Channel
Size (width & depth)
Shape of the path (straight/curved)

9. Streamflow: Gradient What is “gradient” steepness of the slope
gradient = change in elevation
change in distance

10. Streamflow: Gradient What affects a stream’s gradient?
closer to head (source)
steeper
closer to mouth
gentler
gradient- steepness of the slope
Steeper (larger) slope  closer to vertical  faster velocity
Gentler (smaller) slope  closer to horizontal (flat)  slower velocity
To figure out gradient:
gradient = change in elevation (rise)
change in distance (run)

11. Streamflow: Gradient How is gradient related to velocity? steeper
faster
gentler
slower
gradient- steepness of the slope
Steeper (larger) slope  closer to vertical  faster velocity
Gentler (smaller) slope  closer to horizontal (flat)  slower velocity
To figure out gradient:
gradient = change in elevation (rise)
change in distance (run)

12. Streamflow: Discharge
What is “discharge”?
volume of water that passes a certain point in a given amount of time (related to velocity)

13. Streamflow: Discharge
What affects a stream’s discharge?
# (& volume) of tributaries
discharge- amount (volume) of water that passes a certain point in a given amount of time
Often increases downstream (tributaries add water)
Not constant year-round
As discharge increases, velocity increases becomes wider, deeper, and may flood banks

14. Streamflow: Discharge
What affects a stream’s discharge?
age of stream
older
more discharge
younger
less discharge
Youthful
Mature
Old Age
discharge- amount (volume) of water that passes a certain point in a given amount of time
Often increases downstream (tributaries add water)
Not constant year-round
As discharge increases, velocity increases becomes wider, deeper, and may flood banks

15. Streamflow: Discharge
What affects a stream’s discharge?
time of year
late winter to mid-summer
greatest discharge
late summer to mid-winter
lowest discharge
Mean of monthly stream flow at Peachtree Creek for each month (for the years 1958 to 2002) The January value of 174 cubic feet per second (ft3/s) was computed by averaging the 44 mean January stream flows ( ).
discharge- amount (volume) of water that passes a certain point in a given amount of time
Often increases downstream (tributaries add water)
Not constant year-round
As discharge increases, velocity increases becomes wider, deeper, and may flood banks

16. Streamflow: Discharge
How is discharge related to velocity?
greater discharge
greater velocity
lower discharge
lower velocity
discharge- amount (volume) of water that passes a certain point in a given amount of time
Often increases downstream (tributaries add water)
Not constant year-round
As discharge increases, velocity increases becomes wider, deeper, and may flood banks

17. Streamflow: Discharge
discharge- amount (volume) of water that passes a certain point in a given amount of time
Often increases downstream (tributaries add water)
Not constant year-round
As discharge increases, velocity increases becomes wider, deeper, and may flood banks

18. Streamflow: Channel What is a stream’s “channel”?
path through which the water flows

19. Streamflow: Channel What affects a stream’s channel? age of stream
older
wider & deeper
younger
narrower & shallower
Youthful
Mature
Old Age
material’s resistance to erosion also plays a role

20. Streamflow: Channel How is a stream’s channel related to its velocity?
straight, wide, & deep
small surface area in contact with the water
less friction
faster (especially at center near surface)
channel- the path through which the water flows in a stream or river

21. Streamflow: Channel How is a stream’s channel related to its velocity?
shallow & winding
large surface area in contact with water
greater friction
slower
fastest on outside of curve
channel- the path through which the water flows in a stream or river

22. How Streams Weather & Erode Material
mostly mechanical weathering
split rocks due to pounding
abrasion
by “cutting tools”  sand, pebbles, boulders, etc.
rounded & smoothed

23. How Streams Weather & Erode Material
What is a “pothole”?
Deep, rounded basin
formed when sand, pebbles, & small boulders swirl around in whirlpools & grind into the rocks
What is a “plunge pool”?
basin worn away at the base of a waterfall
formed by the action of falling water and abrasion of churning particles
In potholes the “cutting tools” are often found at the bottom

24. Erosion/Transport Streams are effective agents of erosion.
gravity pulls water downhill
soil & rock carried with it
Weathering = break up of materials
Erosion = transport of material
Deposition = dropping of materials
Running water breaks up bedrock (weathering) and removes the rock and soil materials (erosion).
Mostly mechanical weathering… Split and move rocks… Abrasion (by “cutting tools” = sand, pebbles, boulders, etc.)… Produces the rounded and smoothed rocks and sand grains that are commonly found in streams/rivers.
The level of the largest body of water into which a stream flows = base level… Lowest level a stream can erode to
Lakes and rivers  local base level (temporary)
Ocean (sea level)  ultimate base level (final)

25. Erosion/Transport What is a stream’s “load”?
eroded rock & soil materials that are transported downstream
transported 3 ways:
1. solution (dissolved)
2. suspension (floating)
3. bed load
How Streams Transport Materials
Solution… minerals are dissolved from the bedrock & carried in the water; commonly include calcium, magnesium, & bicarbonate; most comes from groundwater seeping into river
Suspension… particles are swept up and carried in the water as it swirls around (turbulence); particles do not touch the bottom; includes clay, silt, and fine sand; often looks muddy
Bed load… larger particles rolled along the bottom of a stream; includes sand, pebbles, & boulders that are too heavy to be carried by suspension; move by rolling, sliding, jumping, or bouncing

26. Erosion/Transport
What are two measures used to describe the ability of a stream to erode materials?
competence
maximum size of particles stream can carry
capacity
total amount of sediment stream can carry

27. • velocity (speed of stream)
The size and amount of sediment carried by a stream depends on:
• velocity (speed of stream)
• discharge (volume of water)
choice A
choice B
Which stream carries larger/more sediment?

28. horizontal sorting in a stream animation
Deposition
deposition patterns
settling rate by size, shape, density animation
vertical sorting animation
When a stream flows to base level (lake/ocean), what happens to its energy?
It decreases.
What happens…?
graded (sorted) deposition occurs
largest closest to mouth & smallest farthest out
largest on bottom & smallest on top
Weathering = break up of materials
Erosion = transport of material
Deposition = dropping of materials
Running water breaks up bedrock (weathering) and removes the rock and soil materials (erosion).
Mostly mechanical weathering… Split and move rocks… Abrasion (by “cutting tools” = sand, pebbles, boulders, etc.)… Produces the rounded and smoothed rocks and sand grains that are commonly found in streams/rivers.
The level of the largest body of water into which a stream flows = base level… Lowest level a stream can erode to
Lakes and rivers  local base level (temporary)
Ocean (sea level)  ultimate base level (final)

29. Depositional Features
What is a delta?
fan-shaped deposit of silt & clay at mouth of river
forms when river flows into quiet or large body of water & energy decreases
How do the rates of erosion & deposition affect the size of the delta?
If deposition > erosion  delta grows.
If erosion > deposition  delta shrinks.
A river flowing into a delta splits into distributaries.
smaller channels that bring sediment to front of delta

30. Stream Valleys: Youthful Streams
What is the gradient of youthful stream like?
steep
How does the river flow?
in a straight line
In which direction does the river erode?
downward
What is the shape of the resulting valley?
V-shaped (a.k.a. canyon, gorge, chasm)
steep, almost vertical sides and narrow bottom
Is the discharge large or small?
small
Form:
in areas of less rainfall
when river cuts into bed rapidly
when rock is resistant to erosion

31. Stream Valleys: Mature Streams
What happens to the gradient as a stream matures?
gradient decreases
How does the river flow?
slight curves b/c velocity decreases
In which direction does the river erode?
outward b/c less erosion of bed & more erosion of sides
The level of the largest body of water into which a stream flows
Lowest level a stream can erode to
Lakes and rivers  local base level (temporary)
Ocean (sea level)  ultimate base level (final)

32. Stream Valleys: Mature Streams
What is the shape of the resulting valley?
wider, broad floor, gently sloping walls
Is the discharge large or small?
medium
The level of the largest body of water into which a stream flows
Lowest level a stream can erode to
Lakes and rivers  local base level (temporary)
Ocean (sea level)  ultimate base level (final)

33. Stream Valleys: Old Age Streams
What happens to the gradient in an old age stream?
gradient decreases to almost horizontal (stream approaches base level)
How does the river flow?
wide meanders across floodplain
can form oxbow lakes
In which direction does the river erode?
outward b/c less erosion of bed (bottom) & more erosion of sides
Flood: when a river overflows its banks
Floodplain: the area of the valley floor that is covered when a river floods its banks
Sometimes forms oxbow lakes The river becomes so s-shaped, that the next time the river floods… it is easier for the water to "take a short cut" and go straight across the flood plain.
More sediment deposited on sides

34. Stream Valleys: Old Age Streams
What is the shape of the resulting valley?
valley floor widens into a floodplain
Is the discharge large or small?
large
Flood: when a river overflows its banks
Floodplain: the area of the valley floor that is covered when a river floods its banks
Sometimes forms oxbow lakes The river becomes so s-shaped, that the next time the river floods… it is easier for the water to "take a short cut" and go straight across the flood plain.
More sediment deposited on sides

35. Youthful
Mature
Old Age
Life of a Stream

36. Stream Flow, Erosion, & Deposition
Why does water move faster in center?
less friction
What does the profile of a straight section of a stream look like?
Slow
Fast
Slow
Fast

37. Stream Flow, Erosion, & Deposition
What happens when a stream meanders?
erosion in some areas
cut banks
deposition in other areas
point bars
Cut banks curve outward from stream
Point bars point inward toward stream

38. Stream Flow, Erosion, & Deposition
What does sediment size tell us?
large  water moving fastest (only lg sediments left behind)
small  water slowed down (& dropped small sediments)
Cross-section on next slide
point bar
deposition of small sediments
shallow
cut bank
erosion of small sediments, large sediments left behind
deep

39. Stream Flow, Erosion, & Deposition
In a meander where does water move fastest?
outside of bend
In a meander where does water move slowest?
inside of bend
What does the profile of a meandering stream look like?
slow
cut bank
erosion
deep
fast
point bar
deposition
shallow