Water On The Land Flashcards
What is the hydrologicak cycle?
The constant movement of water between land, sea and the atmosphere
What type of cycle is the hydrological cycle?
A continuous cycle, no beginning or end
What is river erosion?
The wearing away of the Earth’s surface by rivers
Where does river erosion occur?
The upper course because the land is steeper
What are the two erosional directions?
Lateral and vertical
What is hydraulic action?
The sheer force of the water against the bed and banks of the river
What is abrasion?
When the load that the river is carrying repeatedly hits the bed and banks of the river causing sime of the material to break off
What is attrition?
When stones and boulders that are carried in the river hit and knoch into eachother are weakened over time. Bits fall off and they reduce in size
What is solution?
The chemical action of rivers. Only occurs when the water flows over certain rocks like limestone because its soluble and dissolves in water
What are the four methods of transportation?
Traction, saltation, suspension, solution
What is traction?
Large boulders rolling along the river bed - this is the method with the most amount of energy required
What is saltation?
Smaller pepples that are bounced along the river bed, picked up then dropped as the flow in the river changes
What is suspension?
The finer salt and silt sized particles are carried in the flow of the river giving the river a brown appearance
What is solution? Transportation
Minerals dissolved in the water of the river which can’t be seen
Why is the rivers load often deposited?
Because the amount of energy in the river drops
Where does verticle erosion occur?
Upper course of the river
Where does lateral erosion occur?
Lower and middle course of the river
How is a waterfall formed?
Water falls over a ledge.
Water in the plunge pool flicks rocks up into soft rock (hydraulic action) to erode it
Forms and undercut and the hard rock becomes an over hang
Over time it becomes so weak it breaks off
Eventually the waterfall retreats
Why is a meander formed?
Lateral erosion
The river uses surplus energy by swinging one way and the other
Where are meanders usually found?
Middle and lower course of a river
Where is there more energy in a meander? And what does it cause?
Outside bend, erosion
Where does deposition occur in a meander?
On the inside of the bend
How is an oxbow lake formed?
The neck of the meander narrows and eventually joins together to cut off the bend because the river finds the shortest course where there can be a strong current
What is a levée?
A natural embankment
How is a levée formed?
Increased deposition on the river bed when the river is low gradually raises the river bed upwards and after many floods the deposits on the bank build
Why does river flooding occur?
When the volume of water discharge is so great that all the water cannot be contained in the river channel
What does a flood hydrograph show?
How a river responds to a rainstorm
What is lag time?
The difference in time between the peak of the rainstorm and the peak of river discharge
Hat does the line on a hydrograph show?
The river discharge
What is river discharge measured in?
M^3 /s
What factors affect discharge?
Previous weather conditions, precipitation, land use, deforestation, builing construction, temperature, rock type (if it is permeable or not)
What are some hard engineering strategies to control flooding?
Dams Channel straightening Dredging Levees or foood walls Dredging
Where is a dam usually built?
Upper course
What does a dam do?
Controls discharge downstream so can reduce the chance of flooding
What can be created by a dam and why is it good?
Resevoir
Recreation and HEP
What are some problems of dams?
Expensive to build and maintain
Loss of farmland and villages by flooding of land for resevoir
If it breaks it will be a disaster
What is good about channel straightening?
Water moves quickly from the area
What is bad about channel starightening?
Increases flood rick downstream because the water travels so quickly
What is good about building levees?
Relatively cheap and only need building once
What is bad about the building of levees?
They block views of the river, dredging needs to be done every year
What is soft engineering?
Adapting to floods and using natural processe to help deal with heavy rainfall
What are some soft engineering strategies?
Flood plain zoning
Afforestation
Flood warning system
What is Kielder Water?
A man made lake in northumbria
How much did kielder water cost to create
£185million
Why was kielder water created?
More fresh water
HEP
stop flooding in newcasle
Supplying water to Tyneside and Teeside
How much does kielder water store?
200billion litres
What are rivers and pipelines used for?
To transfer water from major resevoirs in wet areas to big cities where there is a high demand for water