---
title: "From Source to Sea"
description: "Follow one river the whole way and the changes are systematic: steeper and rockier near the source, wider and slower near the mouth. That pattern is why upland and lowland landscapes look so different"
canonical: https://lightmysky.com/learn/geography/from-source-to-sea-mt_VuUB9PiYan
source: https://lightmysky.com/learn/geography/from-source-to-sea-mt_VuUB9PiYan.md
retrieved: 2026-09-12
---

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# From Source to Sea

Follow one river the whole way and the changes are systematic: steeper and rockier near the source, wider and slower near the mouth. That pattern is why upland and lowland landscapes look so different.

Subject: Geography · Area: Physical Geography · Ages 11 to 13
Page: https://lightmysky.com/learn/geography/from-source-to-sea-mt_VuUB9PiYan

## Ready when they can

- Describe how width, depth, gradient and load change between source and mouth
- Match three landforms to the part of the course where each is usually found
- Explain why a river usually gets faster downstream even though the slope gets gentler

## Lesson: From Source to Sea

Every river starts at a source, often high in the hills, and ends at a mouth where it meets the sea, a lake, or a larger river.

Upstream the channel runs narrow, shallow and steep over stones where fast water wears rock away. Downstream it grows wide, deep and gentle, carrying fine mud. Deeper water passing more each second usually runs faster despite a gentle slope, but flat lower reaches can slow.

**Example.** Small streams called tributaries join along the way and add their water. When two channels match in size, shape, slope, and bed with equal water-filled space, the one passing more water each second usually flows faster. A dam stores and releases water on its own schedule, so the timing and size of flow below can shift.

Where a river meets still water it slows, and dropped mud can build a fan called a delta.

**Recap.** From source to sea the channel often widens and deepens. Deeper flow with more water each second usually runs faster despite a gentle slope, but flat lower reaches can slow. With matching size, shape, slope, and bed, the flow passing more water each second usually runs faster.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [How a River Shapes Its Valley](https://lightmysky.com/learn/geography/how-a-river-shapes-its-valley-mt_v6D9mgcf0P)

## Opens up

- [Coasts on the Move](https://lightmysky.com/learn/geography/coasts-on-the-move-mt_IVnXDRpfqE)
- [Drainage Basins and Why Rivers Flood](https://lightmysky.com/learn/geography/drainage-basins-and-why-rivers-flood-mt_Vu4fTs7goJ)