Geomorphology Flashcards
(26 cards)
Drainage basin
The entire area drained by a river system
Stream network / river system
The main river and all its tributaries
Catchment area
The area over which rain falls and is caught by the drainage basin
Watershed / divide
High ground separating 1 drainage basin from another
Source
Where the river begins (mountains)
Mouth
Where the river ends (sea/lake)
Tributary
A river that joins another larger river
Interfluves (Spurs)
High lying ground between 2 river valleys
Confluence
The place where 2 rivers join
Permanent rivers
Flow all year
Rainfall > evaporation rates
E.g. all major rivers of the world - usually flow into oceans
South and east coasts of SA e.g. Tugela
Periodic rivers
Only flow in rainy season
Evaporation rates > rainfall
Mainly found in the interior of SA
Episodic river
Only flow after heavy rain or flush floods
Low rainfall and high evaporation rates
Rare, found in arid western parts of SA
Exotic rivers
Begin in high rainfall areas and flow into dry regions
E.g. Orange River rises in humid eastern side of SA and flows through drier western side to Atlantic Ocean
Dendritic characteristics and rock types/structured
Characteristics:
Tree branches
Tributaries join at a cute angles pointing downstream
Rocks:
Uniform rocks of similar gradient and hardness
E.g. massive igneous or horizontal sedimentary rocks
Trellis characteristics and rock types/structures
Characteristics:
Short tributaries join main stream at right angles
Streams flow parallel to each other
Rocks:
Folded sedimentary
Or
Alternating layers of hard and soft rock that are tilted
Radial/centrifugal characteristics and rock types/structures
Characteristics:
Rivers radiate from a central point
Spokes of a wheel
Rocks:
Rivers flow away from central point such as dome, volcano, Bute or meesa
Rectangular characteristics and rock types/structures
Characteristics:
90 degree bends
Rocks:
Hard rock with joints e.g. igneous
Centripetal characteristics and rock types/structures
Characteristics:
Rivers radiate in towards a low lying area
Rocks:
Rivers flow towards a central basin or low lying area such as marsh, lake
Deranged characteristics and rock types/structures
Characteristics:
Small streams no specific pattern, marshy areas with many small lakes
Rocks: flat areas that have undergone recent glaciation
Parallel characteristics and rock types/structures
Characteristics:
Steaks flow parallel to each other following the dip of land.
May join a larger river or flow into lake.
Rocks:
Common along ridge of hills
Or
Part of a trellis drainage pattern
Constant gradient
Drainage density
The average length of streams in the area of a drainage basin
= total length of in basin (km) / area of drainage basin (km2)
High density means
High rainfall
Soft rock
Little vegetation
Steep gradient
Low density means
Low rainfall
Hard rock
Much vegetation
Gentle gradient
Higher stream order
Fewer number of streams in that order.
Gentler the gradient
Longer the stream
Larger the drainage basin
