The Drainage Basin (Edexcel IGCSE Geography)
Revision Note
Written by: Bridgette Barrett
Reviewed by: Jenna Quinn
The Drainage Basin
A drainage basin is an open system
Every drainage basin is unique and is different in shape and size, with different rock types, relief and land use
Drainage basin features
All drainage basins have some features in common:
Watershed
Source
Confluence
Tributary
Mouth
Channel network
Every drainage basin is covered by a network of tributaries which connect to the main river channel. The number of tributaries in a drainage basin is referred to as the drainage density:
Drainage basins with lots of tributaries have a high drainage density
Drainage basins with few tributaries have a low drainage density
The drainage density is the result of the soil and rock under the surface
Where the rock or soil is impermeable this leads to high drainage density because the water cannot infiltrate
This means it flows over the surface in tributaries
Where the rock or soil is permeable water can infiltrate leading to low drainage density
Examiner Tips and Tricks
You need to ensure that you are clear about the difference between a closed system such as the hydrological cycle and an open system such as a drainage basin. Remember a closed system has no inputs or outputs whereas an open system has both inputs and outputs.
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