Deposition: Building New Landforms

Students learn best when they can see forces at work in real time, especially when those forces involve movement and change over time. Hands-on models let Year 3 learners observe how slowing water or wind drops sediments to build new landforms, making abstract ideas visible and memorable.

• Year 3
• Science
• 4 activities
• 30 min–50 min

Learning Objectives

1. Explain the process of deposition and identify three landforms created by it.
2. Compare and contrast the formation of a river delta and a sand dune.
3. Predict where deposition will occur in a river based on changes in water speed.
4. Classify sediments based on their size and the energy required to transport them.

Concept Mapping

⏱ 45 min·Small Groups

Model Building: River Delta Formation

Fill a long tray with sand and soil, add water from a height to simulate a fast river, then slow it at the end with a shallow pool. Students add coloured sediments and observe where they deposit. Discuss how the slowdown at the mouth forms a fan-shaped delta.

Prepare & details

Explain how a river delta is formed.

Facilitation Tip: During Model Building: River Delta Formation, place the tray on a slight incline so students see how the river slows as it meets still water, clearly showing sediment drop-off.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Concept Mapping

⏱ 30 min·Pairs

Wind Simulation: Sand Dune Creation

Use a fan and tray of dry sand to blow particles into piles. Vary fan speed and direction to form different dune shapes. Students measure pile heights and sketch changes over multiple trials.

Prepare & details

Compare the formation of a sand dune to the formation of a beach.

Facilitation Tip: During Wind Simulation: Sand Dune Creation, run the fan at different heights to show how dune shape changes with wind speed and direction.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Concept Mapping

⏱ 50 min·Small Groups

Stream Table: Speed vs Deposition

Set up stream tables with adjustable flow rates using pumps. Pour sediment-laden water at fast and slow speeds, mark deposition zones, and compare results. Groups predict and verify outcomes.

Prepare & details

Predict where sediment would be deposited in a slow-moving river versus a fast-moving river.

Facilitation Tip: During Stream Table: Speed vs Deposition, mark two flow rates on the table with tape so students can compare deposition at 5 cm/s and 20 cm/s.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Concept Mapping

⏱ 35 min·Whole Class

Beach Wave Tank: Coastal Build-Up

In a wave tank, students generate waves with paddles over sand, observing how they sort and deposit finer particles on the shore. Record changes after 10 wave cycles.

Prepare & details

Explain how a river delta is formed.

Facilitation Tip: During Beach Wave Tank: Coastal Build-Up, add a small paddle to create consistent waves and have students note how wave height affects sediment movement and build-up.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Teaching This Topic

Experienced teachers know that misconceptions about “faster equals more deposition” persist until students test their own predictions with real data. Use quick trial-and-repeat cycles so students see how heavier particles settle first, then lighter ones as speed drops. Keep talk time short and model time long, focusing on evidence students gather from their own setups rather than explanations from the teacher.

What to Expect

By the end of the activities, students will be able to explain why slower speeds deposit sediment first, describe how wind and water shape dunes and beaches differently, and predict where deposition happens in slow versus fast rivers using evidence from their models.

Watch Out for These Misconceptions

Common Misconception

During Stream Table: Speed vs Deposition, watch for students who predict the fastest flow will drop the most sediment.

What to Teach Instead

Have students predict deposition patterns at two marked flow rates, then run the table for 60 seconds at each speed. Ask them to compare where sediments settled and why heavier pieces drop first in slower water.

Common Misconception

During Wind Simulation: Sand Dune Creation, listen for comments that wind only moves sand in rivers.

What to Teach Instead

Run the fan first over a flat tray, then add a small mound of sand to show how wind slows and deposits sand into dunes. Ask students to trace the wind’s path with their fingers to see where air speed changes.

Common Misconception

During Model Building: River Delta Formation, expect claims that deltas form in one rainstorm.

What to Teach Instead

After the first pour, ask students to sketch the delta, then add three more slow pours over the same tray. Have them label how the delta grows gradually, reinforcing the idea of repeated deposition over time.

Assessment Ideas

Exit Ticket

After Model Building: River Delta Formation, give each student an index card to draw a simple delta with the river, ocean, and deposited sediment, and write one sentence explaining why sediment is dropped when the river meets the ocean.

Discussion Prompt

After Stream Table: Speed vs Deposition, ask small groups to discuss: 'Where in a real river would you find the most deposited sediment, near fast rapids or in a slow pool downstream? Use your table results to explain your answer, focusing on how water speed affects sediment transport.'

Quick Check

During Beach Wave Tank: Coastal Build-Up, show students images of a sand dune and a beach. Ask them to write two similarities and two differences in how wind versus waves shape these landforms.

Extensions & Scaffolding

• Challenge: Ask students to design a landform that stops deposition in a specific spot and explain their solution using the stream table.
• Scaffolding: Provide pre-cut sediment layers so students focus on flow rate rather than material prep during the delta activity.
• Deeper exploration: Have students research a real delta or dune system, then present how their model matches the natural landform, including scale and timescale.

Key Vocabulary

deposition	The process where eroded materials, like sand and silt, are dropped or settled in a new location.
sediment	Small particles of rock, sand, and silt that have been eroded and are being carried by wind, water, or ice.
delta	A landform, often fan-shaped, created when a river slows down and deposits sediment as it enters a larger body of water like an ocean or lake.
sand dune	A hill or ridge of sand built up by the wind, typically found in deserts or along coastlines.
beach	A landform along the coast of an ocean, sea, lake, or river, made up of loose particles like sand, pebbles, or shells, formed by wave action.