Rivers Flashcards
What are Dams and reservoirs?
A barrier built across the valley to interrupt river flow and create a man-made lake (reservoir)
Cross profile
Side to side cross-section of a river channel and or valley
What is Discharge?
The quantity of water that passes a given point on a stream or river bank within a given period of time
Embankments
Raise banks constructed along the river they effectively make the river deep so It can hold more water
Estuary
The title mouth of the river where it meets the sea wide banks of deposited mud are exposed at low tide
What is a Flood?
when a river discharge exceeds river channel capacity
Floodplain
The relatively flat area forming the valley floor on either side of the river channel
Floodplain zoning
This attempts to organise the flood defences in such a way that land near the river and often floods is not built on
Flood relief channels
Building new artificial channels which are used when a river is close to maximum discharge
Flood risk
The predicted frequency of floods in an area
Flood warning
Providing reliable advance information about possible flooding
Fluvial processes
Processes relating to erosion transport and deposition by river
What is a Gorge?
A narrow steep sided valley often formed as a waterfall retreats upstream
Attrition
When stones carried by the river knock against each other making a stone smaller and more rounded
Hydraulic action
The force of the water hitting the river bed and banks
Abrasion
When the load carried by the river repeatedly hits the bed and banks dislodging particles into the flow of the river
Solution
When the river flows over limestone or chalk the rock is slowly dissolved
Suspension
Fine, light material is held up and carried within the river flow
Traction
Large boulders and rocks are rolled along the river bed
Saltation
Small pebbles and stones are bounced along the river bed
Upper course valley characteristics
-vertical erosion with hydraulic action, abrasion and attrition dominant processes
-traction and saltation at high flow
-load size is large and Angular
-V shaped valleys
Middle course valley characteristics
-Channel is deeper and wider
-vertical erosion decreasing in importance, more lateral erosion and deposition
-suspension is the main transportation type
-load become smaller and less Angular
Lower course Valley characteristics
-Channel is at its widest and deepest, and maybe tidal
-Deposition more important than erosion
-fine material deposited
-large amount of load but the size is very small and very rounded
River Deposition
Deposition occurs when the velocity of a river decreases.
Formation of an oxbow lake
Deposition on inside Bends, erosion on outside Bends
Examples of hard engineering:
-Dams and reservoirs
-Channel straightening
-embankment
-flood relief channels
Soft engineering
-wetlands and flood storage areas
-floodplain zoning
-River restoration
-preparing for floods
causes of flooding: physical factors
precipitation:
-heavy rain
-prolonged rain
-snowmelt
Geology (rock type):
-impermeable
-Steep Slopes
-Low-lying land
Causes of flooding: Human factors
Farming:
-removal of hedges
-intensive arable farming leaves soil bear
-disappearing fields
-urbanisation
-deforestation
