--- title: "Sediment on the Move: Rivers, Coasts and Where It Settles" description: "Moving water carries grains until it slows, and the size it can carry falls sharply as it does, which is why deposits are sorted. Following a grain from a hillside to a delta explains most river and c" canonical: https://lightmysky.com/learn/science/sediment-on-the-move-rivers-coasts-and-where-it-settles-mt_d1vVJBG6K7 source: https://lightmysky.com/learn/science/sediment-on-the-move-rivers-coasts-and-where-it-settles-mt_d1vVJBG6K7.md retrieved: 2026-09-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Sediment on the Move: Rivers, Coasts and Where It Settles Moving water carries grains until it slows, and the size it can carry falls sharply as it does, which is why deposits are sorted. Following a grain from a hillside to a delta explains most river and coastal landforms without needing a separate rule for each one. Subject: Science · Area: Earth's Systems · Ages 15 to 16 Page: https://lightmysky.com/learn/science/sediment-on-the-move-rivers-coasts-and-where-it-settles-mt_d1vVJBG6K7 ## Ready when they can - Explain why a slowing current deposits coarse grains before fine ones - Account for a named river or coastal landform as erosion and deposition in one system - Predict what happens downstream when sediment supply is cut off by a dam or a sea wall ## Lesson: Following a grain to the sea Fast water grips heavy grains, and slowing water lets go. Pebbles and sand roll along in a quick current, but where the flow eases, the load drops with the heaviest grains first. That sorting is why a riverbed changes on its way to the sea: gravel gives way to sand, and sand gives way to mud. Watch any slope after a storm and you will see the grades laid out by speed. Erosion and deposition are one connected system. What a river tears away upstream becomes what it builds with downstream. Where a river meets the sea it slows hard and dumps its load grain by grain, growing a delta of splitting channels and mud-trapping marshes. Wind works the same way as a river of air: it lifts sand from bare ground and drops it where it slows, so dunes march downwind gust by gust. **Example.** Cut the supply and the system bites back. A dam traps the gravel that used to rebuild land below, so the river below erodes instead and the delta stops growing and washes away. A wall shielding one bank can starve beaches further along the coast. Good river plans treat the whole basin as one budget of sediment, balancing safety, farming, and wildlife together. **Tip.** To predict any stretch, follow one grain in your head. It breaks loose on a hillside, rolls in fast water, drops as the current eases, rests in delta mud, and reaches the sea. Then ask what changed: less supply upstream means erosion wins downstream, every time. **Recap.** Slowing water sorts and drops its load, and one connected system links erosion to deltas. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Preventing Erosion](https://lightmysky.com/learn/science/preventing-erosion-mt_m6UaSmrQVG) - [Weathering, Erosion and How Soil Forms](https://lightmysky.com/learn/science/weathering-erosion-and-how-soil-forms-mt_nQOPOt1VTH) ## Opens up - [Palaeoclimate: Ice Cores, Isotopes and the Record of Past Change](https://lightmysky.com/learn/science/palaeoclimate-ice-cores-isotopes-and-the-record-of-past-change-mt_JabMZ5ZeaL)