Physical landscapes in the UK - Rivers Flashcards
how has the UK landscape been formed
water, wind and ice over millions of years through erosion, transportation and deposition
what is a source of a river
where a river starts, usually in the mountains
what is a mouth of a river
where a river ends, usually at a lake or ocean
what is a tributary
a small river that joins a larger one
what is a confluence
where two or more rivers meet
what is a watershed
the area of land between two drainage basins
what is a drainage basin
an area of land that is drained by a river and its tributaries
what is an input in a river
the addition of water into a river
what is a flow / transfer in a river
a process where water moves from one point to another
what is a storage in a river
where water is held for a period of time
what is an output in a river
the loss of water from a drainage basin
what is interception
when vegetation catches water and stores it for a period of time
what is infiltration
the flow of water from the surface to the soil
what is percolation
the flow of water from the soil to the rocks
what is surface run off
flow of water along the surface
what is through flow
the flow of water through the soil
what is groundwater flow
the flow of water through the rocks
what is a fluvial process
a process in a river that usually erodes or picks up things in the upper course
what is a solution (f)
soluble particles of rock dissolved in a river
what is hydraulic action
force of the river against its banks and causes air to be trapped in cracks that weakens the banks and wears it away
what is abrasion
rocks carried along the river wear down the banks and bed
what is vertical erosion
downward erosion of a river bed that usually occurs in the upper and middle course of a river - making it deeper
what is lateral erosion
sideways erosion of a river bed that usually occurs in the middle and lower course of a river - making it wider
what is attrition
when rocks carried by the channel crash into each other and break into smaller, smoother and rounder particles so the load gets smaller, smoother and rounder
what is transportation in a river
when rivers carry and transport its load - usually through the middle course
what is traction
when pebbles and boulders roll along the river bed in the upper course - this requires the river to have high energy levels
what is saltation
smaller pebbles bouncing along the river bed in the middle course as when one pebble lands, it causing others to bounce and this usually requires high energy levels
what is suspension
when very small, fine particles are carried in the water flow in the lower course
what is solution (t)
when dissolved particles of rock are carried by the river
when does deposition happen
the river moves slowly as the speed decreases causing the river to lose energy
commonly happens when the gradient of the river decreases in the lower course
what is the order of deposition
heavier and larger rocks
so on and so forth
until only the small, fine particles are left
how does a waterfall / gorge form
soft rock gets eroded by the river while the hard rocks remains, causing a waterfall
the continuation of soft rock getting eroded faster
this leads to an overhang as the soft rock gets under-cut and retreats
this leaves the overhang
unsupported to it collapses into the plunge pool where hydraulic action occurs
the repetition of this causes the waterfall to repeat and a steep sided gorge is left behind
how does a meander / oxbow lake form
water travels at different speeds - slower in shallower areas and faster in deeper areas
this causes the fastest current to move around obstacles in a winding motion
the fast water has lots of energy so begins to erode at the banks of the river causing the channel to bend
where there is a slower channel, deposition occurs
abrasion and hydraulic action continue on the outside bend creating a river cliff
deposition continues on the inside bend creating a slip off slope
as this continues - along with helicoidal flow which is when the water hits the banks in a corkscrew motion, eroding material and then flows to the inside bend where there is less energy where it deposits the material
this makes the meander larger
once the neck of the meander is small, the river erodes through it during times of high energy
this ‘shortcut’ becomes the new route and leaves the old meander route redundant
the water flowing in it will be much slower and deposition occurs
over time, marsh plants colonise it which encourages more deposition and the meander loop is cut off from the rest of the river leaving an oxbow lake
how are interlocking spurs formed
vertical erosion as the river is trying to reach sea level
the valley sides are prone to weathering such as freeze thaw, which can cause them to collapse
the deposit is carried away by the river leaving a v-shaped valley
the upper course has little energy and can’t erode the hard rock so it takes the easiest route, winding round obstacles
this leaves a zig-zag sort of pattern from above
how are floodplains and levees formed
during a flood, the river discharge is so high that the river can’t hold all the water so the banks burst
water slows down as it leaves the channel and therefore loses energy and deposits the load
deposited material is sorted, the courser, heavier material closest to the bank and the finer sediment further away
after many floods, the banks build up to form levees with layers of material and the floodwaters recede, leaving a layer of alluvium across the flood plain
what is a floodplain
the relatively flat area of land on either side of a river channel forming the valley floor
what marks the edges of the floodplain
bluffs
what is an estuary
where a river meets an ocean and is affected by the tide so saltwater mixes with freshwater
how are estuaries formed
the land is at sea level and uses its energy for lateral erosion so estuaries are very wide
freshwater mixes with the saltwater from the sea
at high tide, the water level rises and the river slows down as the water trying to get out competes with the water trying to get in
this causes a reduction in the river’s velocity and the energy levels drop, causing deposition
the material being transported is mostly very fine
the alluvium mixes with the sand and silt and muddy sediment is deposited
over time, these build up so that at low tide, mudflats are visible
at high tide these may be covered or partially visible, and may develop small creeks between the higher patches of mud
how are estuaries formed
the land is at sea level and uses its energy for lateral erosion so estuaries are very wide
freshwater mixes with the saltwater from the sea
at high tide, the water level rises and the river slows down as the water trying to get out competes with the water trying to get in
this causes a reduction in the river’s velocity and the energy levels drop, causing deposition
the material being transported is mostly very fine
the alluvium mixes with the sand and silt and muddy sediment is deposited
over time, these build up so that at low tide, mudflats are visible
at high tide these may be covered or partially visible, and may develop small creeks between the higher patches of mud
what is river flooding
when there’s too much river to be contained so it overflows onto the floodplain
what are physical features that lead to flooding
precipitation
geology
relief
what are the human factors that lead to flooding
deforestation
urbanistation
what is discharge
the amount of water flowing through a river at any one time
what is CUMECs and how is it calculated
the amount of discharge and it calculated by the cross sectional area x velocity
what is the lag time
the time between peak rainfall and peak discharge
what is the discharge line
the amount of water in a river
what is a flashy hydrograph
a hydrograph that peaks earlier on and curves upwards and has a high peak discharge and short lag time
when might you have a flashy hydrograph
where there’s deforestation
steep-sided valleys
lots of surface streams
urban areas
rain for prolonged periods of time
prolonged, heavy rainfall
temperatures above freezing causing snow to melt
concrete and artificial channels
what is a subdued hydrograph
a hydrograph that remains fairly steady and has a low peak discharge and long lag time
when might you have a subdued hydrograph
in forested areas
gently sloping land
few surface streams
rural areas
dry and hot (unless too hot and land can’t absorb water)
gentle showers
snow and below 0 degrees
dams and reservoirs
what is hard engineering
artificial, man made structures to prevent flooding
what is soft engineering
using natural environments to prevent flooding
what are the benefits in river management
financial savings made by preventing flooding along with any environmental improvements
what are the costs in river management
the financial cost of the scheme, and any negative impacts on the environments and people’s lives
what are hard engineering methods to prevent flooding
dams and resevoirs
channel straightening
embankments
flood relief channels
what are soft engineering methods to prevent flooding
flood warnings and preparation
flood plain zoning
planting trees
river restoration
does the River Tees need managing
high relief land
high levels of precipitation (2,000mm/yr)
impermeable rocks
flashy hydrographs
400 year history of flooding
lots of properties at risk including 12 schools, 8500 homes and 1200 commercial properties
687,000 residents nearby
how is flooding on the River Tees managed
Cow Green reservoir
Tees Barrage
Flood defence scheme in Yarm
Dredging
Cutting of meanders
Cow Green reservoir
built in 1970 to protect against flooding - regulating reservoir
s - bronze age farming discovered and studied
ec - less cost effective than it used to be and still needs other flood relief measures
en - increased population of brown trout but concerns over protection of rare plant species
Tees Barrage
man made barrier across the river with aims to improve water quality and recreational value and was completed in 1995
s - £500m towards leisure activities and housing
en - reduces flood risk but doesn’t mix with tidal salt water
ec - cost £54m but was a catalyst for £500m of investments
dredging
sediment is removed in lower parts of the Tees estuary periodically to improve navigation
s - increased capacity protects schools and businesses from flooding
en - sediment removed reduces flood risk
ec - can be expensive
cutting of meanders
in 1810, Tees Navigation Company cut across the neck of the Mandale Loop, shortening the river by 4km
s - faster channel protects schools and businesses from flooding
en - reduced flood risk due to faster channel
ec - allows more trade as ships can navigate around the river
flood defence schemes in Yarm
after the 1995 flood, a new defence scheme was put in place costing £2.1mil including things such as putting in concerete with metal flood gates, earth embankments and gabions
s - land is used for leisure areas such as playing fields and parks
en - gabions helped reduce erosion
ec - made the area look nicer and more attractive, making more people want to go there
