River Landscapes Flashcards
(33 cards)
What is a drainage basin
An area of land drained by a river and its tributaries
What is the source
Start of a river
What is a tributary
A small stream that joins a larger river
What is the confluence
Where a tributary joins a larger river
What is the watershed
The edge of a river basin
What is the mouth
The end of a river usually where a river joins the sea
How does the long profile of a river change from upper to lower course
It has a steep gradient at the start and gets gentler in the middle and very gentle in the lower coruse
How doe does the shape of a river valley change downstream
It goes from a V shaped valley which is steep sided and v shaped into more of floodplains which is wider and has a flat floor and then at the low has levees and the valley is very wide and flat
Difference between vertical erosion and lateral erosion
Vertical is downwards and lateral is sideways
What landforms mostly occur in the upper coarse
Erosion landforms such as waterfall gorges and interlocking spurs
What landforms occur most in the middle course
Mostly erosion and deposition landforms such as meanders and oxbow lakes and transportation occurs
What landforms occur in the lower course
Mostly deposition landforms such as levees and floodplains
When do larger rocks tend to be deposited
Upper Course
Where does most deposition take place
At the river mouth
What are interlocking spurs
The ‘finger’ of land that jut out in the upper coarse and since the river is near its source and is not powerful enough to cut through then it has to flow around them
Structure of a waterfall and how gorges are formed
Waterfalls are most commonly formed when a river flows over a relatively resistant band of hard rock (such as granite) with softer rock underneath (such as limestone). When the river plunges over a waterfall it forms a deep and turbulent plunge pool by lateral erosion. Here hydraulic action and abrasion are active and actively undercut the waterfall. Eventually the overhanging rock collapses and the waterfall retreats upstream. This process repeats and leaves behind a gorge.
What is the thalweg
The line of fastest flow within the river
How are meanders formed
The thalweg swings side to side. This causes lateral erosion through abrasion and hydraulic action. On the inner bend the water moves slower deposition occurs. This process repeats and the meander bend gets more exaggerated over time and they migrate across the valley floor:
How are ox-box lakes
Over time, as meanders migrate across the valley floor, they may start to erode towards each other. Gradually the neck of the meander narrows until it is completely broken through (usually during a flood) to form a straighter channel. The old meander loop is cut off by deposition to form an ox-bow lake.
What are floodplains used for and why
For farming as the soils are very fertile
Why are floodplains very wide
Because when meanders migrate across the floodplain due to lateral erosion and they reach the edge of the floodplain, they erode the valley side.
Why are floodplains flat
Because when a river flood it deposits silt
How does a levee form
When a river floods, it overflows its banks and spreads out across the floodplain. As the water spreads out is loses energy and drops the heaviest sediment first right next the river channel. Finer sediments are carried further and deposited across the wider floodplain. This process repeats until the levees are formed and they become more pronounced over repeated floods.
What are sudden floods called
Flash floods and are associated with heavy rainstorm that occur in the summer
