Revise what students have learned about erosion so far, with a focus on wind erosion as explored last lesson.

Revise the ways that water can contribute to weathering, including facilitating the movement of rock down a river, or in freeze-thaw weathering.

Noting the difference between weathering and erosion—as students have already discussed over the course of the sequence—pose the question: How does water cause erosion?

This step provides three different models for simulating soil erosion on different landscapes (also outlined on the Modelling water erosion Resource sheet). You might test all models across the classroom, select and test one model that is most appropriate for your location and students' experiences, or modify the models to suit your context more closely.

Students should work in collaborative teams to build one of the landscapes, test how water moves through it, and observe any erosion that occurs.

Provide students with a variety of materials that they may use to build their landscapes within a defined container in order to hold the water. An aluminium or plastic tray is ideal. The other materials you provide for students to use can be varied, but should include soil and/or sand so that students see how it specifically moves through the landscape. See the List of materials above for suggested materials.

You might model this process of building a landscape as a class beforehand, discussing the materials that can be used to mimic the features of that landscape. For example you might use rocks or plaster to build elevated embankments, twigs/sticks and string to mimic trees and tree roots, pop-sticks to build fences or barriers, or uprooted weeds as grasses/plants.

Optional: Allow teams time to search for and look at images of examples of their chosen landscape so their models are more accurate.

Modelling water erosion caused by rainfall on a sloping landscape

Students build a sloping landscape in an aluminium or plastic tray, then pour water over the landscape.

1. Build a sloping/hillside landscape in the aluminium or plastic tray.
   • Build an elevated section at one end of the tray, making sure that the ‘land’ at the other end is lower.
   • Cover the landscape in things you might find on a hillside. Leave parts of the soil exposed.
2. Cut a small notch at the end of the tray where the land is lower.
3. Draw an annotated diagram of the landscape in your science journal.
4. Prop up the end of the tray opposite the notch to ensure the water flows downwards.
5. Hold the bucket/tub under the notch to catch overflow of water and sand.
6. Using the bottle, pour the water on a specific area of the landscape, at a consistent rate. Alternatively, use a spray bottle or cup with holes in the bottom to simulate rainfall.
7. Observe how the water flowing interacts with features of the landscape.
8. On the annotated diagram mark the areas where water was poured.
9. On the annotated diagram draw how the water has affected the landscape, using a different coloured pen.

Optional: Students could collect numerical data by adding coloured aquarium stones to the sloping landscape, then counting the number of stones that end up at the base of the tray after the water has been poured on it. This data could be graphed. This could be built on in the following lesson, if students test erosion control strategies, by calculating the difference between the number of stones that end up at the base of the tray when there are no erosion control strategies in place compared to when there are.

Modelling water erosion caused by waves

1. Build a beach landscape in an aluminium or plastic tray.
   • Cover the whole tray with sand to simulate a beach.
   • One section of the ‘land’ should be very low, to simulate the seabed where the water will sit. One section should be higher to simulate the beach, and one section should be higher again to simulate sand dunes.
   • Include other natural features you might find at a beach.
2. Fill the shallow side of the tray with water, making sure you leave some flat area exposed to represent the shoreline.
3. Draw an annotated diagram of the landscape in your science journal.
4. Use a wide piece of hard plastic to push large amounts of water towards the ‘shore’, simulating waves.
5. Observe how the waves interact with features of the landscape, particularly the sand dunes.
6. On the annotated diagram draw how the water has affected the landscape, using a different coloured pen.

Modelling water erosion of riverbanks caused by heavy rainfall

1. Build a river landscape in an aluminium or plastic tray.
   • Each side of the landscape should be elevated (but not necessarily completely flat) with a gully/channel running through it.
   • Include bends in your ‘river’ and other features you might see in the landscape.
2. Pour a small amount of water into the river, as would appear in nature.
3. Draw an annotated diagram of the landscape in your science journal.
4. Use a large water bottle or bucket to pour a large amount of water into one end of the ‘river’ all at once.
5. Observe how the sudden increase in water level interacts with features of the landscape, particularly the riverbanks and any bends in the river.
6. On the annotated diagram draw how the water has affected the landscape, using a different coloured pen.

Invite teams to share their observations, encouraging the use of the terms ‘transportation’ and ‘deposition’.

Discuss the people and animals that will be most affected by erosion in the scenario/s students modelled, and how they would be affected.

Optional: Further consolidate understanding of how water erosion causes changes to the landscape and can re-shape rivers by viewing River Erosion: The Wrath of Nature Unveiled (3:09).

In their science journal, and in reference to their observations of their model, students write a response to answer the question How does water cause erosion?

Reflect on the lesson

You might:

• add new words and images to the word wall or glossary.
• add to the W and H sections of the TWLH chart.
• create a table to compare the positive and negative effects of water erosion.
• discuss how students were thinking and working like scientists during the lesson. Focus on the use of modelling to represent changes that occur over long time scales and/or in large environments.