Drainage Basins and Flooding
A drainage basin collects rain; steep, impermeable land floods quickly.
About this topic
A drainage basin is the area of land drained by a river and its tributaries, bounded by a watershed, the high ground that separates one basin from the next. Key terms: source, tributary, confluence (where two rivers meet), mouth, channel and flood plain. Processes in the hydrological cycle: precipitation, interception, infiltration, surface run-off, throughflow, groundwater flow and evaporation.
Rain falling on a basin may be caught by leaves (interception), soak into the ground (infiltration) or run over the surface; surface run-off reaches the river fastest, while groundwater flow is slowest. Flooding is more likely with steep slopes, impermeable rock, saturated soil, urban surfaces and heavy rain, since water reaches the channel quickly. In a city, tarmac and drains carry rain straight to rivers, so a storm can cause a flash flood.
A storm hydrograph plots river discharge against time, showing lag time (the gap between peak rainfall and peak discharge) and peak flow; a steep rising limb and short lag time means a flashy river. Management includes dams, afforestation (planting trees to intercept rain), floodplain zoning and flood barriers, along with soft methods such as restoring wetlands. A common misconception is that flood defences remove risk; they reduce it, and can move problems downstream. Floods also bring benefits such as fertile silt.
Key ideas
- Watershed, tributary, confluence
- Hydrographs show flood risk
- Flood defences include levees and flood plains
Quick check
Use cases: where Drainage Basins and Flooding helps
- Homework: review the key idea behind Drainage Basins and Flooding before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Drainage Basins and Flooding without notes.
- Visual learning: play with the interactive lab to see how Drainage Basins and Flooding changes when you adjust its inputs.
- Teaching a friend: explain Drainage Basins and Flooding in your own words, then compare your version with the key ideas.
Geography helps with city planning, climate, trade and migration.
Frequently asked questions
What is Drainage Basins and Flooding?
A drainage basin collects rain; steep, impermeable land floods quickly.
What will I learn in Drainage Basins and Flooding?
Watershed, tributary, confluence. Hydrographs show flood risk. Flood defences include levees and flood plains.
Is Drainage Basins and Flooding part of Geography?
Yes. It is one of 40 Geography topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Drainage Basins and Flooding lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Drainage Basins and Flooding?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.