Rivers Flashcards
Stages of a river
Upper course/youthful stage
Middle course/mature stage
Lower course/old stage
Course
Rout a river takes as it flows into the sea
Tributary
River which joins a larger one
Confluence
Place where rivers join
Mouth
Place where a river enters a sea or lake
Estuary
Part of a river’s course which is tidal
Basin
Entire area drained by a river and it’s tributaries
Watershed
High ground which separates one river basin from another
Youthful/upper stage
River has steep gradient
Mature/middle stage
River has a gentler gradient
Old/lower stage
River has an almost flat gradient
Youthful stage explanation
As river moves through upper/youthful stage, cuts downwards
Gradient is steep, river narrow
Vertical erosion in this highland part helps to creat steep sided v-shaped valleys, interlocking spurs, rapids, waterfalls, gorges
Erosion
Hydraulic action, abrasion, attrition
Hydraulic action
Force of moving water breaks off material from banks + bed of river
Abrasion
Load of material carried along by river hits banks * bed of river, wearing them away
Attrition
Load is itself worn down smoothed, rounded
Solution
Some rocks dissolved by acids in water
Landforms of youthful stage
V-shaped valley
Interlocking spurs
Waterfalls & gorges
Transportation in a river
Traction/rolling
Bouncing
Suspension
Solution
Traction/rolling
When large objects (pebbles, stones) are rolled along bed of river
Bouncing
Smaller objects, eg. small pebles, bounced along bed of river
Suspension
Lightest objects, eg. slit + clay, carried along suspended in water
Solution (transportation)
Dissolved material (eg. limestone) is carried in solution
Mature river
River has a greater volume, now that many tributaries joined it
Flows over gentler gradient (slope)
River has large load of material to transport
Flows slower
Landforms of mature river
Wider valley
Meander
Flood plains
Meander
Feature of erosion + deposition
River’s volume increased but slope is gentler in middle course.
River slows down on inside of bend - deposition
River speeds up on outside of bend - erosion
Flood plains
Area at either side of river is called flood plain
When river floods it deposits fine fertile clay called alluvium
Old river
River starts to slow down bc gradient is flat
Has large load (sand, rock, etc.) & starts to deposit it
Landforms of old river
Oxbow lakes
Leeves
Deltas
Oxbow lake
- Formed by erosion + deposition
- Begins life as meander
- Outer curve - river moves fast + erodes.
- Load of river increases
- At inner curve - river moves slowly as load is deposited
- Dloely, open end of curve closes
- River now flows straight through instead of following meander
- Sediment is deposited, seals ends and creates oxbow lake
Leeves
Raised banks of alluvium found along banks of some rivers in old age
When river floods, deposits load
After many periods of flooding, deposits build up to form leeves
Deltas
Triangular areas of land formed by deposition
When mouth of river becomes clogged become of deposition of load, river splits into smaller channels called distributaries
Deposits build up above sea level, form delta
Examples - river Nile, Missisipi, Amazon
Advantages of dams
Can be used to hold back water
Used for production of hydroelectric power
Can be used for water based activities
Disadvantages of dams
Farm land may be flooded
destruction of people’s proprty
People’s homes destroyed, had to be relocated
Large build up of alluvium behind dams
Source
Where river begins