Section C - River Landscapes In The UK Flashcards
what is the drainage basin
an area of land drained by a river and its tributaries
what is the source
the start of a river
what is the tributary
a small stream that joins a larger river
what is the confluence
where a tributary joins a larger river
what is the mouth
the end of a river, usually where a river joins the sea
what is the watershed
the edge of a river basin
how do the long profile of a river change from source to mouth?
> where the water is shallow and turbulent there is friction with the bed and banks, slowing the rate of flow
further downstream rhe river’s channel is much deeper. less water is in contact with the bed and banks and the velocity increases
what does the long profile of a river show you
how the gradient changes over the different courses
how does the cross profile of a river and its valley change downstream
> the river channel becomes wider and deeper with the river valley becoming wider and flatter. its sides are less steep
river management can alter the shape of a river channel and different ypes of rock or human activities
these changes downstream are due to the amout of water flowin in the river
the changes to a valleys cross profile are mainly due to?
> channel erosion broadening
>flattening
what does the cross profile show you
what a cross section of the river looke like
River erosion : what is solution
the dissolving of soluble chemicals in water
River erosion : what is hydraulic power
the power of the river water as they smash onto the river bed
River erosion : what is abrasion
the effect of pebbles grinding against the river bed
River erosion : what is attrition
pebbles carried by the river that knock against one another
River transportation : what is traction
large pebbles rolled along the riverbed
River transportation : what is suspension
particles carried within the water
River transportation : what is solution
dissolved cgemicals often derived from pebbles
River transportation : what is saltation
a bouncing motion of particles too heavy to be suspended
What is river deposition and what is an example
when the water carrying sediment loses energy. this will happenin different places along the river. an example of this is a meander where the inside of the bend reduces rivere energy, resulting in deposition
DEPOSITION : where are estuaries found
at the mouth of a river, where it meets the sea. the land is close to sea level and the river valley is at its widest
EROSION : where are interlocking spurs found
found in a rivers upper course
EROSION : how do interlocking spurs form
form because of vertical erosion wearing away the land to create a V shaped valley
EROSION : how are waterfalls formed
formed when a river flows over a relatively resistant band or hard rock
EROSION : what is a gorge
a narrow, steep sided valley that is usually found immediately downstream of a waterfall
EROSION : how are gorges formed
formed by the gradual retreat by a waterfall
DEPOSITION AND EROSION : what are meanders
wide bends of a river found mainly in lowland areas
DEPOSITION : what are pools/riffles
meandering streams carrying coarse sediment
DEPOSITION : where are pools found
pools are found on the outside bends of meanders where the faster flow erodes a deeper channel
Deposition : how are riffles found
riffles are formed from the deposition of course sediment, also of high flow
DEPOSITION AND EROSION : how is an ox bow lake formed
1) the neck of the meander is gradually eroded
2) water niw takes the shortest and steepest route
3) meander is cut off, forming an ox bow lake
DEPOSITION : what is a floodpain
a floodplain is a wide, flat area of marshy lan on either side of a river, and found in the lower courses
DEPOSITION : what is a levee
a raised river bed, found in its lower course. it is formed by flooding ober many years
DEPOSITION : why is a ridge of sediment deposited
to build up the levee
hard engineering - how do dams form a reservoir
the dam traps water, which builds up behind it, forming a reservoir
what is an advantage of dams and reservoirs
can be used to produce electricity by passing the water through a turbine within the dam
what is a disadvantage of dams and reservoirs
dams trap sediment which means the reservoir can hold less water
what does hard engineering involve
involves building artificial structures which try to control rivers
hard engineering - why straighten a river
so the water speeds up - therefore volumes of water can pass through an area quickly
hard engineering - why dredge a river
so that it is deeper and can therefore hold more water
what is an advantage of river straightening and dredging
more water can be held in the channel
what is a disadvantage of river dredging
dredging needs to be done frequently
hard engineering - what is embanking a river
raising the banks so it can hold more water
what is an advantage of emankments
cheap with a one off cost
what is a disadvantage of embankments
looks unnatural
hard engineering - what happens with flood relief channels
the flood water flows into the relief channel and is taken either to an area where it can be absorbed, or re enters the river further down its course
what is an advantage of flood relief channels
removes excess water from the river channel to reduce flooding
wht is a disadvantage of flood relief channels
expensive to build
soft engineering - what are some advantages of wetland and flood storage areas
> very efficient in storing water
>water can be stored to reduce the risk of flooding further downstream
soft engineering - what is floodplain zoning
allowing only certain land uses on the floodplain to reduce the risk of flooding to houses and important buildings
what is an advantage of floodplain zoning
more expensive buildings and land uses are further away from the river, so have reduced flood risk
what is a disadvantage of floodplain zoning
not always possible to change existing land uses
soft engineering - what does river restoration involve
using the natural processes and features of a river, such as meanders and wetlands, to slow river flow and reduce the likelihood of a major flood downstream
what is an advante of flood warnings and preperations
people have time to protect their properties e.g. with sandbags
what is a disadvantage of flood warnings and preperations
flash floods may happen too quicklyy for a warning to be effective
when do river floods usually occur
after prolonged periods of rainfall, usually in winter
when do sudden floods or flash floods usually occu
in summer
PHYSICAL - how does geology increase flood risk
impermeable rocks do not allow water to pass through them and so it flows overland into river channels
PHYSICAL - how does precipitaion increase flood risk
torrential rainstorms and/ or prolonged rainfall can lead to rapid flooding events
PHYSICAL - how does relief increase flood risk
steep slopes means water flows much quicker into river channels over a short space of time
HUMAN - how does agriculture increase flood risk
exposed soil can lead to increased runoff (especially if the field has been ploughed)
HUMAN - how does urbanisation increase flood risk
impermeable surfaces like tarmac and concrete means water flows into drains too quickly
HUMAN - how does deforestation increase flood risk
when the trees are removed, the water that would have been evaporated or stored flows into the river channel
STORM HYDROGRAPH : what is the peak
the top/highest
STORM HYDROGRAPH : what is the line
the discharge
STORM HYDROGRAPH : what is the rainfall
the bars
STORM HYDROGRAPH : what is the capacity
the rivers maximum amount of water it can hold
STORM HYDROGRAPH : what is the rising limb
the faster it rises the greather the chance of floods
how does the basin size influence hydrographs
the larger the basin, the longer the lag time and less chance of floods
how does the relief influence hydrographs
the steeper the gradient, the quicker water enters the river - greater flood chance
how does soil moisture influence hydrographs
saturated soil means increased surface run off, shorter lag time and increases flood chance
how does land use influence hydrographs
tarmac and concrete is impermeable so it increases surface run off into drains. increased flood risk