Fiducia TogetherFlooding
Why rivers flood, and the choice between hard and soft management.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
A flood occurs when a river's discharge exceeds its channel capacity. Physical causes include prolonged or intense rainfall, impermeable geology and steep relief; human causes include urbanisation and deforestation.
Where it applies
GCSE geography physical topics.
How it works
A hydrograph shows discharge against time after a storm. Lag time is the gap between peak rainfall and peak discharge — shorter lag and higher peak mean higher flood risk, and urbanisation shortens lag by adding impermeable surfaces and drains.
Management splits into hard (dams, embankments, channel straightening) and soft (afforestation, floodplain zoning, river restoration).
How to use it in your work
Read hydrographs properly: name lag time, peak discharge and rising limb, and explain what changed them.
For management, cost and knock-on effects downstream are the evaluation points. Straightening a channel moves the problem downstream.
Where to get help
Your teacher and your board's specification — options differ enormously between centres, and yours is the one that counts. Bitesize covers the skills; the subject song runs the topics.
Revise this with a song
These are ours. We write revision songs because a lot of people remember a tune when they cannot remember a page, and because revising out loud in the kitchen beats staring at a highlighter.
- The Geography Song The GCSE geography topics, set to music.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.