1. RUNNING WATER

2. RUNNING WATER River Systems Streamflow Stream Channels
Depositional Landforms
Floods

3. GEOL 131: Running Water
River Systems

4. Drainage Basin Area drained by a river and its tributaries
GEOL 131:Running Water: River Systems
Drainage Basin
Area drained by a river and its tributaries
Divide: separates adjacent basins

5. GEOL 131:Running Water: River Systems

6. Drainage Patterns Arrangement of streams in a drainage basin
GEOL 131:Running Water: Drainage Patterns
Drainage Patterns
Arrangement of streams in a drainage basin
Depends on
Topography
Underlying geology (rock types, folding, faulting)

7. GEOL 131:Running Water: Drainage Patterns
Chapter 9, Figure 9.26

8. Dendritic GEOL 131:Running Water: Drainage Patterns
Chapter 9, Figure 9.26a

9. Radial GEOL 131:Running Water: Drainage Patterns
Chapter 9, Figure 9.26b

10. Rectangular GEOL 131:Running Water: Drainage Patterns
Chapter 9, Figure 9.26c

11. Trellis GEOL 131:Running Water: Drainage Patterns
Chapter 9, Figure 9.26d

12. GEOL 131: Running Water
Streamflow

13. How Does Water Get Into Rivers?
GEOL 131:Running Water: Streamflow
How Does Water Get Into Rivers?
Precipitation
Melting snow/ice

14. Precipitation and snowmelt can:
GEOL 131:Running Water: Streamflow
Precipitation and snowmelt can:
Infiltrate
absorbed into ground
becomes part of groundwater
Run off (flow over surface)

15. Streamflow Characteristics
GEOL 131:Running Water
Streamflow Characteristics
Flow velocity
Channel steepness (gradient)
Channel roughness
Channel size and shape
Discharge

16. Flow Velocity Speed of water movement
GEOL 131:Running Water: Streamflow
Flow Velocity
Speed of water movement
Affects how much and what kind of sediment can be carried

17. Gradient and Roughness
GEOL 131:Running Water: Streamflow: Factors affecting velocity
Gradient and Roughness
Gradient: Elevation change per unit distance
E.g. feet per mile
10 feet per mile means river drops 10 feet for every mile
Gradient tends to decrease away from source
Roughness
Steeper not always faster
Water can be slowed by
a rough channel

18. GEOL 131:Running Water: Streamflow: Factors affecting velocity
Channel Size and Shape
Wide, shallow channel slower than narrower, deeper one with same cross-sectional area

19. Discharge Volume of water moving through channel
GEOL 131:Running Water: Streamflow: Factors affecting velocity
Discharge
Volume of water moving through channel
Discharge = width x depth x velocity
Volume units per sec

20. GEOL 131: Running Water
Stream Channels

21. Two Basic Stream Channel Types
GEOL 131:Running Water: Stream Channels
Two Basic Stream Channel Types
Bedrock
Cut into rock
Alluvial
Cut into sediment or soil
Two types:
Meandering
Braided

22. Bedrock Channels Steep-sided V-shaped Prone to flash floods
GEOL 131:Running Water: Stream Channels
Bedrock Channels
Steep-sided
V-shaped
Prone to flash floods
Yellowstone River, Yellowstone NP

23. Alluvium Channels: Meandering
GEOL 131:Running Water: Stream Channels
Alluvium Channels: Meandering
Fine to medium-grained sediment
Consistent discharge

24. GEOL 131:Running Water: Stream Channels: Meandering
Meander Migration

25. Bend migrates in direction of erosion, and also slightly downstream
GEOL 131:Running Water: Stream Channels: Meandering
Meander Migration
Bend migrates in direction of erosion, and also slightly downstream

26. Meander Cutoff & Oxbow Lakes
GEOL 131:Running Water: Stream Channels
Meander Cutoff & Oxbow Lakes 1 2 3 4
Oxbow lake

27. GEOL 131:Running Water: Stream Channels
Oxbow Lakes

28. Alluvium Channels: Braided
GEOL 131:Running Water: Stream Channels
Alluvium Channels: Braided
Coarse-grained sediment
Highly variable discharge

29. Alluvium Channels: Braided
GEOL 131:Running Water: Stream Channels
Alluvium Channels: Braided
Coarse sediment moves only when discharge is high
Forms bars when discharge is low
Water forced to split around bars

30. Alluvium Channels: Braided
GEOL 131:Running Water: Stream Channels
Alluvium Channels: Braided
Sand and gravel bars

31. Depositional Landforms
GEOL 131: Running Water
Depositional Landforms

32. Depositional Landforms
GEOL 131:Running Water: Depositional Landforms
Depositional Landforms
Features created by deposition of sediment by rivers
Deltas, alluvial fans

33. GEOL 131:Running Water: Depositional Landforms
Deltas
At river mouths
Fine-grained sed deposited when river enters standing water
Mississippi River Delta, Louisiana

34. GEOL 131:Running Water: Depositional Landforms
Deltas
Delta grows as distributary channels deposit sediment along a wide arc

35. The Mississippi Delta GEOL 131:Running Water: Depositional Landforms
Distributary channel switching: channel becomes plugged with sediment, and water switches to a new channel

36. Alluvial Fans Similar to a delta, but on land
GEOL 131:Running Water: Depositional Landforms
Alluvial Fans
Similar to a delta, but on land
Base of steep mountain range
Fed by rainfall and snowmelt

37. GEOL 131: Running Water
Floods

38. Regional Floods Heavy rains saturate soil
GEOL 131:Running Water: Floods
Regional Floods
Heavy rains saturate soil
Additional rain runs off into rivers
Rivers overtop banks and enter floodplains

39. GEOL 131:Running Water: Floods
Flash Floods
Rain or snowmelt funneled down a narrow steep-walled channel
Short duration
Antelope Canyon
flash flood video
Antelope Canyon, Arizona before and during a flash flood.

40. Ice-Jam Floods During spring breakup of river ice
GEOL 131:Running Water: Floods
Ice-Jam Floods
During spring breakup of river ice
Ice floes can clog river and cause flooding

41. Dam Failure Floods Johnstown, PA, 1889 GEOL 131:Running Water: Floods
South Fork dam failed
2,209 deaths

42. End of Chapter