Rivers Flashcards
Mostly definitions
Define Percolation
(Hydrological Cycle)
The ability for rocks to allow water to flow through them
Define Drainage Basin
An area which is drained by a river and its tributaries.
Define Bedload
The river’s load which is dragged along the bed.
Describe the cross-profile and features of a river’s upper course.
Profile: V-Shaped (v. narrow)
Features: e.g. Waterfalls (+ gorges), Water rapids, steep gradient.
Describe the cross-profile and features of a river’s middle course.
Profile: U-Shaped (wide + deep)
Features: e.g. Ox-bow lakes, Meanders, Tributaries
Describe the cross-profile and features of a river’s lower course.
Profile: u-Shaped (wide but shallower)
Features: e.g. Deltas, sand-banks, flood plains, v. gentle gradient
Define Solution
(erosion)
The dissolving of certain types of rocks (chalk + limestone) by rainwater
Define Attrition
When the river’s load collides with each other and break up.
Define Abrasion
When the load scrapes against the bed (most common form of erosion)
Define Hydraulic Action
Erosion caused by the sheer force hitting the bed and banks
Define Solution
(transportation)
Transportation of minerals dissolved in the water (chemical change)
Define Saltation
When small stones bounce along the bed
(they are light enough to be lifted, but too heavy to be held.)
Define Suspension
When finer sediment (e.g. sand) is carried within the water
(this often makes the water look muddier)
Define Traction
When larger stones and boulders are rolled along the river bed
(too heavy to be lifted by the water)
What causes deposition to occur?
When the river’s velocity decreases and it no longer has the power to carry the sediment.
For example, this can be due to a reduced gradient, increased load, or the river reaching the sea.
What happens if there is increased sediment in the river?
The river loses velocity and so more sediment is deposited or transported by traction and saltation.
How are waterfalls formed?
Soft rock under a band of hard rock is eroded faster, which creates a step. This grows over time until the hard rock is undercut and collapses under its own weight.
(This also causes the waterfall to retreat over time.)
What is left as a waterfall retreats?
A steep-sided gorge
What are interlocking hills called when a river zig-zags between them?
(Taken from cgp book as bonus)
Interlocking Spurs
How do meanders form?
Bends form through the erosion on the outside (river-cliff) and deposition on the inside (slip-off slope).
Define Meander Scar
An ox-bow lake (formed by a conjoined meander) that has dried up.
What form of erosion occurs mainly in the upper course?
Vertical erosion (deepening the river)
How long is the River Tees?
137km
Where is the River Tees’ source?
Cross Fell in the Pennines
What can cause flooding?
Long, prolonged rainfall.
Steep relief + rainfall.
Melted snow.
Urbanisation (bad drainage).
What is a hydrograph?
Hydrographs show the relationship between rainfall and river discharge over time.
What is steep relief?
A landscape characterized by significant and abrupt changes in elevation or height.
What is hard engineering?
Using artificial structures to try to control river processes (dams, embankments, locks, river straightening, flood relief channels).
What are some erosional landforms found along the River Tees?
High Force waterfall.
V-Shaped valleys.
Interlocking spurs.
Gorges.
How are interlocking spurs formed?
As the river erodes downwards, the spurs of land between the valley sides are left standing.
What is soft engineering?
Working with natural processes to reduce the risk of flooding (afforestation, flood warnings, land use zoning, flood storage areas).
What caused the Boscastle flood?
Saturated ground due to above average rainfall.
At confluence of three rivers.
Very steep drainage basin.
Mostly impermeable geography.
What happened in the Boscastle flood?
Extremely high discharge in the river in a short amount of time flooded the village.
What were some impacts of the Boscastle flood?
Many homes and businesses were damaged.
Cars were swept away.
What were some responses to the Boscastle flood?
£10 million was spent on a new flood defense scheme, completed in 2008, to reduce the risk of this happening again.
Low bridges were replaced with wider and taller bridges.
What hard management techniques were employed in response to the Boscastle flood?
The river was deepened and widened to increase it’s capacity.
What soft management techniques were employed in response to the Boscastle flood?
Land owners were encouraged to plant more trees.
When did the Boscastle flood occur?
16th August 2004
What are the pros of soft management techniques?
Cheaper than hard management techniques.
Won’t affect fluvial processes.
Sustainable and environmentally friendly.
Low maintenance solutions.
What are the cons of soft management techniques?
Not always reliable or effective.
Often doesn’t reduce the level of flooding.
May not be suitable in all areas.
Limited use in urban areas.
Can impact agricultural land.
What are the pros of hard management techniques?
Controls the level of flooding.
Dams can produce hydroelectric power.
Can help improve navigation for boats.
Can be used to store water.
Protects properties from flooding.
What are the cons of hard management techniques?
More expensive than soft management.
Can harm fluvial processes downstream (increased erosion, deposition, and flood risk).
Can cause habitat loss.
What does river straightening do?
By removing bends and meanders, and widening and deepening the channel, water flow and channel capacity can be increased, reducing flood risk.
What do embankments do?
By artificially raising the river banks, it reduces the risk of the river breaking its banks, lowering flood risk.
What do flood relief channels do?
By building artificial channels parallel to the river, excess water can be diverted during high flow periods, reducing flood risk.
What does afforestation do?
By planting trees along riverbanks, the riverbanks can be stabilised, reducing flood risk.
What does flood plain zoning do?
By regulating development in areas prone to flooding, potential damage from flooding can be reduced.
