Your tray begins with a route you made. Water may carry some sand away and leave it somewhere else. Erosion means material is removed. Deposition means carried material is put down.

A meander is a bend in a river. In a simple explanation, faster water near the outer bank helps wear it away. Slower water toward the inner bend can deposit material. A point bar is a deposit on the inside of a bend.

As banks change, the bend can change too. Real rivers have different slopes, flow patterns and bank materials. A small tray may make a straight channel, splits or little bends. None of those results is a failed observation. Describe what happened instead of announcing that you built a real meander.

A river loop can grow until its two sides come close. Water may then find a shorter channel across the narrow neck, the strip of land between those sides.

When the old loop is cut off from the main route, water can remain in it. The curved lake is called an oxbow lake. It is a clue that a river’s route has changed.

Drawing a shortcut across a paper loop helps you see which part is still connected. It does not show how a particular real river changed. For that, you would need evidence such as maps or observations from different times. A river is not simply following a plan to take the shortest route. Water and the material around it affect how its channel develops.

together · About 10 minutes; untested estimate.

You need

• Tray inside a larger catch tray
• Damp sand
• Cup of water
• Paper and pencil

Try it

1. Ask an adult to put damp sand in a tray held at a gentle slope over a catch tray.
2. Make a shallow curved starting channel.
3. Draw the channel before water enters.
4. Pour a slow small trickle at its high end.
5. Stop and sketch where material moved or collected.