# Model Sediment Movement

Part of the Oceanography Merit Badge Digital Resource Guide: [Introduction & Overview](https://merit-badge.university/merit-badges/oceanography/guide/index.md)

*7. Hands-On Investigation*

> **7d.** Make a model showing the inshore sediment movement by littoral currents, tidal movement, and wave action. Include such formations as high and low waterlines, low-tide terrace, berm, and coastal cliffs. Show how offshore bars are built up and torn down.

Coastlines are always moving, even when they look still. This option helps you model how sand and sediment shift because of waves, tides, and currents.

## What Your Model Should Demonstrate

Your model should show that sediment is not fixed in one place. Waves move it up and down the shore. Littoral currents move it along the shore. Tides change where water reaches. Stormy conditions can tear down sandbars that calm conditions later rebuild.

### Key features to include

- **high waterline**
- **low waterline**
- **low-tide terrace**
- **berm**
- **coastal cliffs**
- **offshore bars**

Video: [Longshore Drift Model Demo (video)](https://youtu.be/bfzAeQXhSGk)

## Useful Terms

A **littoral current** moves parallel to the shore and can carry sand along the beach.

A **berm** is the raised ridge of sand or gravel built by wave action above the normal waterline.

A **low-tide terrace** is the flatter exposed area you may see at low tide.

An **offshore bar** is a ridge of sand built underwater or just offshore by waves and sediment transport.

## Building the Model

A tray or shallow box works well. Use sand, clay, or damp soil for land and beach forms, and water to show how movement happens.

Try to build:

- a sloping beach
- one higher edge to represent a coastal cliff
- a low offshore sand ridge
- markers for high and low tide lines

Then use small waves or repeated pours to show how sediment can move.

> **Tip**
>
> Colored sand or small flags can make movement easier to see. If you place one stripe of darker sand on the beach, you can watch it shift as you test your model.

## What to Explain to Your Counselor

Do not only show the finished model. Explain the processes:

- how waves push and pull sediment
- how an angled wave approach can move sand downshore
- how tides change where erosion and deposition happen
- how offshore bars can build up during some conditions and be torn down during others

![Tray model coastline showing longshore sediment movement, berm, low-tide terrace, offshore bar, and cliff](https://ik.imagekit.io/doulacoop/tr:w-800/mbu-assets/merit-badges/oceanography/guide/littoral-current-model?v=08da76a3)

The next option keeps the water-motion theme but switches to a focused wave experiment.

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- Previous: [Track Water Conditions](https://merit-badge.university/merit-badges/oceanography/guide/req7c/index.md)
- Next: [Build a Wave Tank](https://merit-badge.university/merit-badges/oceanography/guide/req7e/index.md)