Rivers

Revise Rivers for Geography 0460 (O Level) — revision notes and instant AI marking.

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Cambridge (CIE) IGCSE Geography

Rivers

The Big Idea: Rivers are giant conveyor belts of water and sediment — they pick material up (erosion), carry it (transportation), and drop it (deposition) — and where each of these dominates along the river's journey from source to sea decides exactly what landform you get.

📋 Summary — The Whole Chapter at a Glance

Hydrological cycle: a closed system moving water between stores (atmosphere, oceans, ice, aquifers) via flows (evaporation, precipitation, infiltration, runoff...).
Drainage basin: an open system — the whole area of land that drains into one river, with a watershed, source, tributaries, confluences and a mouth.
River processes: erosion (4 types), transportation (4 types), and deposition — these change as a river moves from source to mouth, summarised by the Bradshaw Model.
Long profile & cross profiles: the river gets deeper, wider, faster and less steep as you move downstream; vertical erosion dominates upstream, lateral erosion dominates downstream.
Upland landforms: waterfalls, gorges, V-shaped valleys, interlocking spurs, potholes — all from vertical erosion.
Lowland landforms: meanders, ox-bow lakes, floodplains, levees, deltas — all from lateral erosion and deposition.
River hazards: flooding and erosion, caused by heavy/prolonged rainfall and worsened by human activity (urbanisation, deforestation, farming).
River management: hard engineering (dams, levees, channel straightening) vs soft engineering (river restoration, floodplain zoning, afforestation) — plus the flood hydrograph as a prediction tool.
Case study: the Ganges/Brahmaputra basin — huge opportunities (farming, fishing, culture, energy) but also huge flood hazards, and a mixed-success Flood Action Plan.

🌍 1. Hydrological Characteristics

Water on Earth — it's rarer than you think

Here's a fact that surprises most students: only 2.5% of all the water on Earth is freshwater — the rest (97.5%) is salty ocean water. And of that tiny 2.5% slice, most of it isn't even sitting in rivers where you could drink it — 68.7% is locked up in glaciers and ice sheets, and another 30% is groundwater hidden underground. That leaves just 1.3% of all freshwater in rivers, lakes, soil moisture and the atmosphere — the water actually available and moving around the surface of the planet.

Think of it like a giant bank account: Earth's total water is your total savings, but 97.5% is locked in an account you can't touch (the sea). Of what's left, most is frozen in a long-term deposit (glaciers) or buried underground. What's actually "in your wallet" — usable, visible, everyday water — is a tiny sliver.

The Hydrological Cycle — a closed system

The hydrological cycle is called a closed system because no water enters or leaves Earth — it just gets recycled endlessly between different stores (places water sits for a while) and flows/transfers (ways water moves between stores).

Practice Question 1

Explain, in your own words, the difference between "interception" and "infiltration." Why might a densely forested hillside have less overland flow than a bare, ploughed field during the same rainstorm?

🗺️ 2. Drainage Basin

drainage basin open system

Every drainage basin has the following key features — these come up constantly in labelling questions:

Watershed

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Rivers

Rivers

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