How a River Shapes Its Valley
A river carries energy, and it spends that energy cutting down, sideways, or dropping what it carries. Waterfalls, meanders and floodplains are all the same three actions in different proportions.
What a learner can do afterwards
- Name the three things a river does with the material it moves: erode, transport, deposit
- Explain why a waterfall retreats upstream over time
- Say why the outside of a meander bend is deeper and the inside is shallow
1 · Read
A river does three jobs with rock and soil: it wears it away, carries it along, and drops it somewhere new. Fast water wears more, and slow water drops its load.
On a bend the fast outside cuts deep into the bank, while the slow inside drops sand into a gentle slope. The bend keeps growing more curved.
A waterfall eats its way uphill. Soft rock below wears first, the hard lip hangs over, then it falls, and the drop steps back.
Upstream the valley runs narrow and V shaped from cutting down. Downstream it spreads into a flat floodplain from cutting sideways and dropping. People fight erosion by planting cover crops and building terraces that slow runoff and hold soil in place.
Rivers cut, carry and drop, and each bend, fall and plain shows the three at work.
2 · Watch
Take it off screen
Where it sits
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.