Rivers - Geography Flashcards
What is the definition of a river?
A river is a large, flowing body of water that usually empties into a sea or ocean.
What is through flow?
Water flows downhill within the soil
What is groundwater
water underground in saturated zones beneath land surface
Ways of reducing floods?
Afforestation
River restoration
Dams
Levees + Embankments
Straightening + Dredging
Flood relief channels
What are the three main sections of a river?
Upper course, middle course, lower course.
Which course of a river typically has the steepest gradient?
Upper course
What is a tributary?
A tributary is a smaller river or stream that flows into a larger river.
Mekong River Delta
Vietnam is worlds 2nd largest producer of rice - irrigation
80& of 17 million who live on Mekong produce rice
Use of hydro-electric power through 11 dams
Fish farming especially for prawns - extra $7000 a year
Use domestically for cooking/cleaning
What term describes the land area that drains into a river?
Watershed
Opportunities of living near a river?
Agriculture
Trade
Leisure
Energy
Homes
Formation of a delta?
- Lot of sediment been brought downstream
- River approaches mouth so velocity decreases = deposition
- heaviest material dropped first, eventually blocks water flow so river divides up into distributaries
- lack of current means this material grows towards sea, so distributaries eventually re-join to form bradded pattern
- Deposition continues and delta forms with vegetation colonising islands which continue to grow
What is erosion in the context of rivers?
Erosion is the process by which soil and rock are removed from one location and transported to another by a river.
How does an oxbow lake form?
- Continued erosion on outside of meander bend
- Deposition continues form larger slip-off slope
- Outside bends of meander grow closer together, meander neck narrows
- Swans neck meander as 2 meanders move closer together
- During period of high discharge, river cuts through neck and shortens its course
- Fastest current now flowing in centre of channel, deposition more likely next to bank, deposition causes original meander to be blocked off
- Oxbow lakes forms
What is deposition in river geography?
Deposition is the process where the river drops the sediment it has been carrying.
What does the term ‘meander’ refer to?
A meander is a winding curve or bend in a river.
How does a meander form?
Water erodes outer bank of river bend, creating curve.
On the inner bank, slower water causes sediment to build up, forming a point bar.
Erosion on outside and deposition on inside exaggerate the bend over time.
The meander becomes more pronounced as process repeats, forming a winding river path.
What is a river basin?
A river basin is the area of land drained by a river and its tributaries.
Features of a meander:
(bend in rivers channel)
Thalweg - fastest flow of water
Outside of bend - erosion = river cliff
Inside of bend - deposition = slip-off slope/river beach
How does a pothole form:
If river bed is uneven, pebbles are trapped.
Swirling currents causes pebbles to rotate.
Erode circular holes in riverbed
Formation of a waterfall?
- Hard rock over soft rock, water is eroding soft rock creating steep gradient
- Hard rock is under-cut, HA and ABR create a plunge pool at foot of waterfall
- Ledge which overhangs plunge-pool collapses, transported by HA and ABR, material then eroded downstream
- Waterfall retreat back
Characteristics of lower course:
Flattest gradient
Highest total load
Smallest particle size
Fastest average velocity
Flood plains/deltas
Characteristics of middle course:
Less steep
Increasing total load
Increasing average velocity
Increasing discharge
Decreasing particle size
Meanders/oxbow lakes
Lateral erosion
Characteristics of upper course :
Waterfalls
Rapids
Steep gradient
Low load
Slowest average velocity
Vertical erosion
Big particles
What is the term for the speed at which a river flows?
Velocity
