1. What happens to rainfall when it hits earth????
Some evaporates
Some is absorbed and becomes ground water
Some is run off

2. Running Water Running water is the most powerful agent of erosion.
Running water is abrasive – it wears down rocks and makes them smaller, smoother, and rounder. (USSR = U see Small, Smooth, Round).

4. How Does Running Water Carry Sediment?
Running water carries sediment in three ways:
1. In solution – things that are dissolved in the water.
2. In suspension – very small sediment like silt and clay that hang or dangle in the water but never settle and won’t dissolve.
3. As bedload – sand, pebbles, boulders that are rather large and heavy and travel along the stream bed (bottom of the stream/river).

6. Carrying Power of Running Water
Carrying power of running water depends on its velocity (speed) and discharge (amount of water).
The top of page 6 in your ESRT? It shows how larger sediment can only be transported by fast moving water.

7. PARTICLE SIZE vs. VELOCITY
Different sized materials require different water velocities to be carried via suspension, solution, or bedload. This is illustrated by the size/velocity curve…

10. Running Water Gradient
Running water has gradient (slope).
The steeper the gradient of the stream/river, the faster the water will flow.

11. Calculate the gradient Calculate the gradient of the following stream: A stream’s source (where it begins) is found at 100 ft., 25 miles away is its mouth (where it ends) at 50 ft.
Gradient = change in field value
distance
2. G = 100 ft. – 50 ft.
25 mi.
3. G = 2 ft/mi.

12. The River Valley
River valleys are V-shaped!!!!! (Just remember “V” for valley).

13. V shape valley is evidence of running water.

14. The River Valley
In the late maturity stage and old age stage of a river, the valley will become flattened and wide.
The older rivers become the more they meander (bend) and thus the wider the valley becomes.

15. Stages of Stream Development
Youth (very young river
Early Maturity
Old Age
Late Maturity

16. Divides and Drainage Basins
A high piece of land that separates one river valley from another is called a divide.
A river and all the tributaries that flow into a river is a river system.
Drainage basins or watersheds include all the land that drains into the river system.

17. WATERSHED Land from which water runs off into a stream.
Tributary – feeder stream that flows into a main stream.

21. Meanders and Oxbow Lakes
Water in a river or stream does not move at the same speed at every point.
As a river swings around a bend, the fastest moving water is on the OUTSIDE of the bend.
The slowest moving water is on the INSIDE of the bend.

22. Meanders and Oxbow Lakes
Because of this difference in speed, EROSION occurs on the OUTSIDE of a river bend.
DEPOSITION occurs on the INSIDE of river bends.
This will eventually create meanders or loops in the river.

24. deposition

25. Meandering Channels

28. Meanders and Oxbow Lakes
As this erosion and deposition process continues and the meander swings wider, the curve becomes a loop.
The river eventually breaks through and becomes a cutoff.
The river begins to deposit more sediment at the site of the cutoff and the meander completely separates from the river forming an oxbow lake.

29. Oxbow Animations

31. Oxbow Lake

32. Depositional Features
Since moving water can be very powerful, it has the power to sort sediment.
Sediment gets sorted by size, shape, and density.
Once the water slows down, it deposits or drops sediment it can no longer carry.
The largest, most dense sediment gets deposited first, then medium, then small and less dense gets deposited last.

33. Depositional Features
The greatest loss of speed that can occur is when a river empties into an ocean.
It is literally like it hits a brick wall.
It “throws-up” all the sediment it’s been carrying.
One example of this is a river delta.

34. Deltas
Deltas are triangle shape.

35. Nile River Delta

36. Nile River Delta at Night

37. How’s it going to sort itself.

38. Drops the biggest sediment first
Last ?

40. Depositional Features
If it were not for the Mississippi River depositing all the sediment into the Gulf of Mexico, the city of New Orleans would not be.
This is why New Orleans is considered to be below sea level, it lies on a delta.

41. Is this triangle shape?

42. Depositional Features
In mountainous regions, often a river or stream will just empty into the bottom of the mountain where it is dry.
When this happens, the sediment spreads out and creates an alluvial fan.

44. The Flood Plain
A flood occurs when water spills over the sides of a river or stream’s banks.
During floods, thick deposits build-up alongside the stream banks, this forms levees.
Beyond levees, the flood plain is lower and swamps form.
Flood plains are very fertile (vegetation grows well) because they get so much minerals and nutrients deposited there during floods.

46. RAPIDS AND WATERFALLS
Rapids - Different resistance among rocks cause FAST-FLOWING WATER
Waterfalls – Rapids develop into waterfalls as softer rock erodes

47. Typical Erosion of Waterfalls