3. Drainage Basin & Floodplains Flashcards
What is a Drainage Basin
An area that has been dried by a river and its tributaries
What is the Source
The area in which a river begins (usually in the mountains/at a high altitude)
What is the Mouth
Where a river ends it’s journey flowing into the sea or a lake
What is a tributary
A smaller river that joins a larger river
What is a Confluence
The point at which 2 rivers join
What is a Watershed
The boundary between 2 drainage basin marked by a ridge of high land
What happens mostly in the Upper Course of a river
Erosion
What Landforms are present in the upper course
Waterfalls and Plunge Pools
V-Shaped Valleys
Interlocking Spurs
What happens at the Middle Course of a river
Transportation
What Landforms occur at the Middle Course of a river
Meanders
What happens mostly in the Lower Course of a river
Deposition
What Landforms occur in the Lower Course
Ox-Bow Lakes
Flood plains
Levees
Hydraulic Action
This process involves the force of water against the river bed & banks
Abrasion
This is the process by which the bed & banks are worn down by the rivers load
Attrition
The load carried by the river bump into each other & are smoothed & broken down into smaller particles
Corrosion
This is the chemical action of a river water. The acids in the water slowly dissolve the bed & banks
Traction
Boulders & pebbles are rolled along the river bed at times of high discharge
Saltation
Sand sized particles are bounced along the river bed by the flow of water
Suspension
Fine clay & sand particles are carried along within the water even at low discharges
Solution
Some minerals dissolve in water such as calcium carbonate. This requires very little energy
Where does erosion occur in a river (inside or outside the bend)
Outer bend
Where does deposition occur in a river (inside or outside the bend)
Inner bend
What are some Physical causes of flooding
Heavy rainfall
Prolonged rainfall e.g monsoon
Melting of snow/glacier
What are some Human causes of flooding
Deforestation
Urbanisation
Narrowing a river channel e.g bridge
Building of leveés/embankments
What are some Positive impacts of flooding for People
Replenishes drinking water supplies especially wells
Provides sediment/silt/alluvium that fertilises the soil
Can encourage innovative solutions to flooding e.g houses on stilts
What are some Negative impacts of flooding for People
Spreads waterborne diseases e.g cholera
People & animals can drown or become homeless
Crops grown on fertile flood plains can be washed away
What are some Positive impacts of flooding for the Environment
Fish can breed in standing water
In dry areas, flooding can relieve an area from drought
What are some Negative impacts of flooding for the Environment
Flooding can wash chemical or sewage into local rivers & pollute them
Wild animals may drown or lose their habitat
What are some Hard Engineering methods
Widen/Deepen Channel
Straighten/Concrete Channel
What are some Soft Engineering methods
Afforestation- planting trees
Washlands- waste land that does not matter if flooded
Land use zoning
What is Hard Engineering
Artificial features to control the river, these methods are not sustainable in the long term
What is Soft Engineering
They are more sustainable than Hard Engineering methods
