Hydrosphere Flashcards
What is Hydraulic Action?
hydraulic action (1 mark) which is when air is compressed into the river bank causing materials to be dislodged (1 mark)
What is Abrasion?
abrasion (1 mark) when the force of the water throws bedload against the banks causing erosion (1 mark)
What is Attrition?
Attrition (1 mark) when the river load rubs and impact against each other, breaking and rounding the river load.
What is Corrosion?
Corrosion (1 mark) is the chemical erosion of rocks surfaces by the flowing water. (1 mark)
Describe the formation of a V-shaped Valley
Valleys in the upper course are narrow and steep sided (1).
Vertical erosion is dominant due to the speed of river flow (1),
Physical weatheringincreases the bed‑load which enhances erosion (1).
Swirling water during floods may create potholes (1).
The valley bottom is usually narrow and filled mainly by the channel (1).
The valley sides of a river are steep and in a cross section V shaped. (1 mark)
How is a waterfall formed
Remember to refer to processes which are not included here.
Differential erosion takes place (1 mark) over bands of more and less resistant rock/where harder rock is overlaying softer rock/bands of hard/soft rock (1 mark)
Softer rock is more easily eroded (1 mark)
Undercutting causes an overhang of the hard rock (1 mark)
Over time the hard rock is unsupported (1 mark) and collapses due to gravity into the plunge pool (1 mark)
Attrition can occur here (1 mark) where the rocks in the plunge pool hit off each other, eroding further (1 mark)
The waterfall retreats upstream. (1 mark)
Describe a Meander
River flow aids movement of sediment from the outside, undercut edge of the meander to the inside, point bar on the meander where it is deposited.
The processes of erosion involved in the enlarging of the outside bend are hydraulic action, corrosion and corrasion. These are enhanced by an effect known as helicoidal flow.
A meander begins to form where small bends are found in a river channel.
Over time these processes repeat themselves,so enlarging the river bend into a curved, swooping meander.
A meander is formed in a rivers lower/middle course where the processes of erosion, transportation and deposition are active.
During flow down a river channel, pools and riffles are encountered creating a corkscrew like helicoidal flow in the water.
The outside bend is undercut, being eroded vertically and laterally as river energy is greatest here.
Lateral erosion takes place in the middle/ lower course of a river as the land is flatter (1).
Development of pools and riffles due to changes in river speed (1)
erosion on the outside (concave) bank of the bends due to faster flow (1), helicoidal (corkscrew) flow moves material to other river bank (1)
deposition on the inside (convex) bank of bends due to slower flow (1), creation of point bars (1), migration of meanders downstream (1).
Describe how an Oxybow Lake
An ox-bow lake is formed in a river lower/middle course where the processes of erosion, transportation and deposition are active.
This flow aids movement of sediment from the outside, undercut edge of the meander to the inside, point bar on the meander where it is deposited.
As meanders migrate downstream there bends get closer together producing pronounced loops.
The processes of erosion involved in the enlarging of the outside bend are hydraulic action, corrosion and corrasion. These are enhanced by a corkscrew like flow effect known as helicoidal flow.
The outside bend is undercut, being eroded vertically and laterally as river energy is greatest here.
During spate, or flood conditions, the narrow neck of land between the meander loop can be cut through by the river, forming a new straight channel.
The old meander loop is blocked by deposition of sediment forming an isolated ox-bow lake.
What are the inputs of a drainage basin?
The main input to the drainage basin is through precipitation
What are the storage of the drainage basin?
Storage:
- Stored water is held within the drainage basin system in lakes/lochs this is known as surface
storage.
- Water can also be stored by being absorbed by soils and stored by trees this is known as
interception.
-The amount of water that can be stored as groundwater depends on the rock type underlying
the soil. If the rock is porous (like a sponge) the water may be held .
-Human activity can also interrupt the flow of water as water can be dammed by HEP to create
reservoirs to produce electricity or fresh water; furthermore increased forestry plantations
in a catchment will store more water.
What are the transfers and flows of a drainage basin
Transfers/Flows:
-Water transfers through tributary and river courses known as surface runoff.
-Water can transfer by infiltrating through soil and transfer through the soil known as
through-flow
-Water can then percolate through rock this is known as infiltration. The water transfers
through the rock this is known as groundwater flow.
-During periods of heavy rainfall the soil and sub-soil may become saturated resulting in an
increase in surface run-off.
-Sub rock may be impermeable (can’t hold water) meaning it contribute to the groundwater flow
Describe the outputs of the drainage basin
Output:
- Evapotranspiration is the combined return of water into the atmosphere by evaporation and
transpiration. Evaporation is the water loss from the ground or water surfaces due to the heat
from the sun. Transpiration is water loss from vegetation.
-River courses eventually return water through the drainage system through surface runoff
and condensation
Describe the human impacts on a drainage basin
For deforestation:
-The cutting down of trees increases run-off and the potential for soil erosion.
-Decreases in evapo-transpiration and therefore cloud formation impacts on local rainfall
patterns.
- Changes to vegetation cover can lead to more extreme river flows as water is not intercepted
and stored by the trees.
For irrigation:
- Taking water from a river or ground water storage can reduce river flow.
-Lowering water tables and increasing evaporation/evapo-transpiration by placing water in
surface stores, eg ditches/canals.
-Increased farming opportunities provided by irrigating crops removes water.
For urbanisation: - The removal of natural vegetation and replacement with impermeable concrete/hard surfaces
and drains can speed up overland flow and can lead to higher river levels.
-As more urban land is concreted over the rate of evaporation from these surfaces increases
as the rate of percolation through the land surface decreases. It also decreases the amount
of water which returns to groundwater storage, possibly reducing the water table.
For mining:
- The silting up of lakes, rivers and reservoirs leads to reduced storage capacity in these areas.
-Mining may also lead to reduced vegetation cover leading to increased run-off higher
evaporation and cloud formation altering the rainfall pattern.
For Dams, Reservoirs and HEP
-Due to increasing demand for fresh clean water and in renewable energy sections of the
drainage basin are dammed to store water within a catchment. The water is stored and used
for drinking water and HEP. As a result the water is intercepted and cannot complete the
hydrological cycle. This then reduces the flow of water through the drainage system.
What is a hydrograph used to show?
A hydrograph may be used to show how the water flow in a drainage basin (particularly river
runoff) responds to a period of rain. This type of hydrograph is known as a storm or flood
hydrograph and it is generally drawn with two vertical axes. One is used to plot a line graph
showing the discharge of a river in cumecs (cubic metres per second) at a given point over a period
of time. The second is used to plot a bar graph of the rainfall event which precedes the changes in
discharge.
What are the main characteristics of a hydrograph?
Precipitation – shown as a bar graph but sometimes not always shown
Base Flow – flow supplied by groundwater. This is the normal flow of the river
Rising Limb – represents the rapid increase in the height of the river due to precipitation.
Various factors can affect how quickly the rising limb rises
Peak discharge shows the highest point of the river flow
The falling limb shows the river level returning to normal
