Rivers and Streams Self-paced lesson

River/stream weathering, erosion, and deposition

​River systems are the result of weathering, erosion, and deposition done by water

The landforms and patterns that emerge from them are the result of varying amounts of energy in the river itself.
The energy is determined by how steep the river is (gravitational
potential energy)
Steeper=Faster water=more energy= More Weathering and erosion
Less steep=Slower water=less energy=more deposition

Mountain Stream-
steeper
Faster water
Erodes downwards

Meandering Stream-
less steep
slower water (but more of it)
Erodes horizontally.



REVIEW THE LANDFORMS FOUND IN BOTH

Two parts of a river system:

​MOUNTAIN

​Meandering

​Source- where a river starts (usually in a mountain)
Confluence- Where two or more rivers join
Tributary- smaller river that connects to a larger river.




Meander- A curve in a river.
Oxbow lake- curved lake created from a cut off meander
Floodplain- flattened area near a meandering river. Created by horizontal erosion. Holds water that floods the banks of a river.
Delta- Area of deposited sediments at the end of a river, usually in a large body of water.
Estuary- area where river meets sea.
Mouth- area where a river ends, and opens into another larger body of slow-moving water.

Categorize

Options (13)

Slower water

Faster water

horizontal erosion

downward erosion

Meanders

Oxbow lakes

Deposition

Floodplain

Estuary

Delta

Waterfall

Source

Steep gradient

Categorize the different characteristics and landforms of each stream type

River Stream

Mountain Stream

Labelling

Label the different parts of a river system with the correct label.

Drag labels to their correct position on the image

Meander

Source

Confluence

Mouth

Multiple Choice

This diagram shows a _____________ .

• Delta

• Confluence

• Source

• mountain stream

​Meandering streams change shape back and forth due to the energy differences in them.

They curve and erode different areas over time.

The outer curve of a river is called the cutbank.
The inside curve of a river is called a point bar.

Labelling

Label the part of the meandering stream.

Drag labels to their correct position on the image

Cutbank

Point Bar

But why do these rivers curve?

Multiple Select

Faster-moving water leads to (select all that apply)

• Deposition

• weathering

• erosion

Multiple Select

Slower-moving water leads to (select all that apply)

• Deposition

• weathering

• erosion

Multiple Choice

Weathering and erosion happen at the _______ curve(s).

• inside

• outside

• both

• left

• right

Multiple Choice

Deposition happens at the _______ curve(s).

• inside

• outside

• both

• left

• right

Many rivers end in a delta around the world. How do they form?

Dropdown

Deltas are created by​

Select answer

of sediments at the end of a river. ​ Rivers that carry enough sediments will drop them if the ocean is ​

Select answer

Awesome. Sediments can erode (move) or deposit (stop and lay down). But when do they deposit and when do they erode?


There are two main factors that affect this: Sediment size and water speed (velocity).


Larger sediments need more water speed to move them.
Smaller sediments will only deposit in calmer waters.



The graph that helps us predict what they will do is called the Hjulstrom Curve.

​River Speed

Sediment Size

If something has a smaller size and/or more river speed, it will usually erode (except for clays, because they stick together)

If something has a larger size and/or less river speed, it will usually deposit

Multiple Choice

If a particle of gravel has size 10, and the river velocity is only 1 cm/sec, the gravel particle will

• be transported

• be deposited

• be eroded

Multiple Choice

If a particle of sand has size 1.0, and the river velocity is 100 cm/sec, the gravel particle will

• be transported

• be deposited

• be eroded

Multiple Choice

If a particle of silt has size 0.01, and the river velocity is 10 cm/sec, the gravel particle will

• be transported

• be deposited

• be eroded

Multiple Select

Based on the graph, if the stream speed is 1 cm/sec, which particle sizes would be deposited?

• clay

• sand

• gravel

• boulders

The speed of a river is partially due to its slope. However, it can also change depending on friction. In a flood stage, rivers can have less in their way, and move faster.


One tool to track river levels (drought, normal, flooding) is a hydrograph.

​A Hydrograph shows the volume of water passing a point in a river over time. As the amount of water increases (such as during a flood), the hydrograph line begins to peak.

A horizontal line usually indicates where the "flood stage" for a particular river is. This isn't the same as height of the water. VOLUME does not equal HEIGHT of the water.


The peak height of a hydrograph happens AFTER a rainfall event. It takes time for the rain to fill the river, and so the peak discharge (most water passing the point) is always after the peak rainfall.

Multiple Choice

According to the hydrograph, when was the peak volume of the river?

• August 20

• August 22

• August 24

• August 26

Multiple Choice

According to the hydrograph, when did the river reach flood stage?

• August 21

• August 28

• August 24

• August 26

Multiple Choice

What term likely describes the August 19 level of the river

• flood

• normal

• drought

​Time to review what we learned.....

Hotspot

Pick the area(s) of erosion in the river

Hotspot

Which areas of the stream show a point bar? (Select 2)

Labelling

Drag the labels for the fastest part of the river and the slowest part of the river

Drag labels to their correct position on the image

Slower water speed

Faster water speed

Labelling

Drag the correct water speed to the correct part of the diagram. (For example, if you think the upper course has medium speed water, drag medium speed water below upper course).

Drag labels to their correct position on the image

Fastest Water

Slowest Water

Medium speed water

Labelling

Label the features of the river.

Drag labels to their correct position on the image

Meanders

sediment

Delta

Tributary

Source

Multiple Choice

Deltas are created when

• Rivers deposit mud and sand at their end

• Rivers erode mud and sand

• Crystallization of minerals occurs in a river

• Weathering occurs at the end of a river

Multiple Choice

If a particle of gravel has size 10, and the river velocity is only 500 cm/sec, the gravel particle will

• be transported

• be deposited

• be eroded

Multiple Choice

How many days was the river at or above flood stage?

• 2

• 4

• 6

• 8