River Processes Flashcards
Why are streams called systems?
The stream system has both inpust and outputs of various types of materiaals.
Name 3 inputs and 3 outputs.
inputs: - precipitation.
- runoff
- undergroud flow.
output: - evapouration
- seepage
- flooding
- human consumption
What is a laminar flow?
Occurs when water flows smoothly in a stream. very rare.
what is turbulent flow?
it is caracterised by the horizontal eddies and small surface whirlpools that is caused by uneven shape of the bed of the stream.
name the ways in which material can be transported by a stream.
- suspention
- solution
- saltation
- traction
Describe suspention.
-suspention is when very fine particles of clay and silt are picked up by moving water and moved along without being dropped.
Describe solution.
- Solution is when salts and chemicals are dissolved into the water and carried along.
Describe saltation.
- Heavier particles like pebbles may be picked up by the stream and carried a short distance.
Describe traction.
- traction is when heavier stones and pebbles are rolled along the streembed.
Describe the meaning of the following words.
- Drainage basin.
- Watershed
- tributaries
- confluence
mouth
source
- it is the area drained by a river and its tributaries.
- high lying areas that separate drainage basins.
- Smaller streams that join the main river.
- Place where a smaller stream joins the main river.
Name the eroding processes of a river.
- hydralic action
- attrition
- abrasion/corration
Describe hydraulic action.
- sheer power of water in a turbulent stream pushes water into cracks and crevices in bed and banks of stream.
Describe abrasion.
- Stones and gravel carried by river, scour the banks and bed of river channel. like sandpaper.
Describe attrition.
- Material carried by river grinds down other materials also being carried along.
Describe headward erosion.
- occurs at the source of the river where the river extends its length upstream, caused by rainwash and soil creep.
Describe verticle erosion.
- Occurs when the river deepens its valley.
Describe lateral erosion.
- occurs when river widens its valley.
Name the characteristics of the upper course.
- verticle erosion dominates. usually in mountains.
- river develops a deep narrow v shaped channel.
- very little deposition.
- very little flood plain.
- rivers are fast flowing.
- waterfalls and rapids common.
- much erosion.
Name the characteristics of the middle course.
- Speed is lower that upper, because of more gentle slope.
- size of material carried smaller.
- valley becomes wider.
- more flood plain.
- river can braid.
Describe the caracteristics of the lower course.
- Closer to sea. gradient gradual.
- speed drops further
- main activity of deposition of sediments.
- might begin to meander.
- usually ver wide and shallow.
name the landforms associated with rivers.
- spurs and v shaped valleys.
- ## waterfalls,gorges and rapids.
Explain where and waterfalls, gorges form.
- Found in the upper course of a river, where the slopes are steep and the water is eroding vertically.
- occur where a hard rock layer crops out that is much more resistant that the soft rock below it. the layers of hard rock must lie horizontal certical or sloping upstream for a waterfall.
Explain how a waterfall is formed.
- The hard rock erodes very slowly, the soft rock faster. the force of the waterfall itself also erodes the soft rock. thus this creates a plunge pool at the bottom of the water fall.
- the hard rock get undercutted.
- the overlaying hard rock will become unsupported and eventually break of. thus the river will retreat up stream and a gorge is left behind.
