1. Rivers and Running Water

2. What is a River System? River system contains 3 parts: River
Tributaries
Watershed

3. How does a river system develop?
Drainage Basin: area of land drained by a river and its tributaries
Feed water into the river system
Groundwater
Runoff
Drainage basins are separated by divides

5. River Profile
Water always travels from a higher elevation to a lower elevation.
Why??
GRAVITY!
The ultimate goal of nature is to erode down to sea level (base level)
As rivers travel downward, towards the ocean, they erode or deposit land creating new land features.

6. Parts of a River Head = where the river begins
Some rivers have many branches or “tributaries”
The head of the river is the FURTHEST one away from where the river meets another body of water (ocean, another river, lake, etc)
Mouth = where the river joins another larger body of water (ocean, another river, lake, etc)

7. Although the Mississippi river has many smaller tributaries, it only has one head which is located north in Minnesota

8. Rivers and Land Formations
Rivers have a significant effect on shaping Earth’s surface.
It does this in two ways:
Erosion: wearing away or destruction of land
Deposition: process in which sediments, soil, and rocks are added to a landform or land mass

9. Erosion and Deposition
Meander = bend in the river
Erosion happens on the outside of a meander
Waters are moving faster
Deposition occurs on the inside of a meander
Waters are moving slower

10. Running Water
The velocity or speed of water flow in a river depends on:
Slope (gradient) of the river
Channel dynamics (size, shape, roughness)
Volume of water
The more quickly water is running, the more erosion/deposition will occur

11. (Photo by Tom & Susan Bean)
River Erosion
Erosion happens by:
Lifting loose particles
Abrasion (water rubbing against the rock)
dissolving
Paria Canyon, AZ
(Photo by Tom & Susan Bean)
Niagara Falls, NY
(Photo by David Ball)
Big Wood River Canyon, ID

12. Transport of Sediment
Three types of gravel/sand (“load”) a river carries
1. Dissolved Load
Supplied by groundwater
Mineral salts
2. Suspension Load
Largest amount
Makes water look “muddy”
Silt and clay-size particles
3. Bed Load
Sand sized and larger
Move along bottom of river by turbulence (called saltation)

13. Deposition of Sediment
Deposition occurs when the stream velocity decreases.
Occurs on the INSIDE of a meander
As the speed of the waters slow down, particles are able to settle and deposit themselves on land.
Particles are sorted according to size
Larger particles will deposit first (heavier and take more energy to move)
Deposition Animation

14. Dominate in arid & semi-arid regions
Deposition Features
Alluvial Fan
Delta
Death Valley, CA
The mouth of a river dumps the sediment into the slower water
Dominate in arid & semi-arid regions

15. River Valley Development
Each stage of development is characterized by land features
Youth
V-shaped valleys
Waterfalls and rapids
High relief (very steep)
Erodes more

16. River Valley Development
2. Mature
Narrow flood pains
Meanders
Equilibrium (amount erosion = amount of deposition)
3. Old
Oxbow lakes
Large meanders
Wide flood plains
Low relief (less steep)
Deposits more

18. River Valleys vs. Glacial Valleys
Rivers erode in V-shaped valleys
Trying to erode DOWN to base level
Glaciers erode in U-shaped valleys
Fill up entire valley and push THROUGH

19. Oxbow Lake Formation Meander develops due to low energy of river.
Erosive action causes the river channel to move laterally.
Meander develops a cutoff from main river channel.
Oxbow lake forms as old channel is abandoned.