topic 4 river processes and pressures Flashcards
What is traction?
Movement of larger rocks rolling along the river bed.
What is saltation?
Hopping motion of particles to heavy to be suspended.
What is solution?
Particles dissolves in water
What is suspension?
Particles carried within water
(Physical)freeze thaw:
Fluctuating tempratures-water expands when frozen.
(Chemical)-acid rain
High pH(acidic) water touches rock
What is a confuence?
Where 2 rivers meet
What is the river land form found in the upper couse?
Waterfalls(gorges
And interlocking spurs
What river land form is found in the middle course?
Meanders and Ox-Bow-Lakes
Discharge
The volume of water flowing in a river at one particular point and time
Measured in cubic meters/second
What is long profile?
The long profile shows how a river’s gradient changes as it flows from its source to its mouth
What is the long profile of a river?
Shows the steepness of a river changes over the course of a river.
The gradient ________ (the slope becomes more gentle)
as the river moves from its upper course towards its lower course.
Decreases
What are the sections of a river’s course?
- upper course
- middle course
- lower course
Whaere in the river is the gradient steepest?
Upper course
What is the cross-profile of a river?
It shows you the cross section of the river
(you can see the shape of the river bed.)
(As rivers flow downhill, they form valleys and channels. The shape of these features changes along the course of the river.)
Corss profile Upper course landmarks:
Erosion>deposition
This means there is the valley is a steep sided( v shaped valley)
-the channel the water flows through is shallow and not very deep.
Corss profile middle course landmarks:
the middle course, neither erosion nor deposition is particularly dominant.
This means that
- the valley has a gentle slope
- the channel is wider and deeper than the upper course
Cross profile-lower course landmarks:
Deposition>erosion
This menas that
- The valley is wide and flat
- The channel is wide and deep
A river’s long profile shows how the _______ changes over its course.
Steepness
What are the characteristics of valleys and channels in the upper courses of rivers?
- shallow channel
- steep valley
- v-shaped valley
- narrow channel
Lateral erosion dominates in the ______course and ______course.
- lower
- middle
Vertical erosion dominates the ______course
Upper
Why is vertical erosion dominant in the upper course?
because high levels of turbulence make rough and angular particles drag along the river bed.
What affects the river’s cross profile?
- vertical erosion
- lateral erosion
How do the processes of erosion work in rivers?
Solution
Solution is where soluble rocks are dissolved by the water in the river or sea (limestone and chalk in particular). They are carried along with the river or sea.
How do the processes of erosion work in rivers?
Attrition
Attrition is where pieces of bedload (material carried by a river or seawater)
are hit against one another.
This causes them to break apart and become smaller and more rounded.
How do the processes of erosion work in rivers?
Hyraulic action:
When the force of water hits against the sea bed or river banks causing rock to break of
How do the processes of erosion work in rivers?
Abrasion:
Where peices of rocks are picked up by the river and hit against the banks, this wears them away.
Which method of transporting sediment involves the sediment dissolving in water?
Solition
Saltation is where small sand and gravel _______ bounce along the river bed or ______bed.
- particles
- sea
What is deposition?
when the sediment that a river is transporting is dropped
This happens in the lower and middle course and in low energy conditions
What are the reasons a river loses velocity and drops material (deposition)
- reduced volume of water in the channel
- increased amount of sediment in the channel
- water becomes shallower
- the river’s mouth is reached
Why does deposition of sediment happen?
A river slows down
What are the 4 processes of erosion?
- abrasion
- attrition
- solution
- hydraulic action
_______ is when the sediment that a river is transporting is dropped.
Deposition
What are the four processes of transportation?
- suspension
- traction
- solution
- saltation
When are gorges formed?
When waterfalls retreat over time
How can a waterfall form?
When a river flows over hard rock that overlays softer rock
Simple explination:(When there is hard rock and soft rock right after, the soft rock gets eroded and it forms a waterfall)
Stage 1 of a waterfall:
The less resistant (softer) rock begins to erode because of ____ and ____.
A step or ____forms in the softer rock, creating a river ____
- Abrasion
- hydraulic action
- notch
- rapid
What is a river rapid?
Rapids are areas along a river where the water flows faster and more turbulent.
Stage 2 of a waterfall:
Over time, the softer rock gets more eroded.
This leaves the hard rock sticking out above the soft rock.
The height of the drop ________ as the water pounds the less resistant rock at the base.
Eventually a waterfall forms.
-increases
What forms at the base of a waterfall over time?
A plunge pool
Stage 3 ofnthe formation of a waterfall:
The less resistant rock starts to be eroded underneath the hard rock.
This process is called_________.
The _________ harder rock collapses because there is nothing underneath it to support it.
The hard rock crumbles into the base and the abrasion between the hard rock and soft rock base creates a __________
Hydraulic action keeps undercutting behind the waterfall.
If the process repeats over a long time, a _____may form.
- Undercutting
- overhanging
- Plunge ppol
- Gorge
Why do interlocking spurs form?
- In the upper course, valleys are steep and V-shaped because most erosion happens vertically
- the rivers do not have a lot of energy because there is not a lot of fast miving water.
This lack of energy means they do not erode latterally, instead they followma winding path because they go around resistant rock
Hillsides on either side of a river that interlock are called interlocking______
Spurs
Name 3 examples of waterfalls:
Niagra falls
Angel falls
Iguazu falls
What erosional process is predominantly responsible for the formation of plunge pools?
Abrasion
Name two Characteristics of valleys in the upper courses of rivers:
- v-shaped
- steep
What are formed when waterfalls retreat over time?
Gorges
What creates a meander?
When a river bends, the current is fastest (carrying the most energy) at the outside of the bend. This high energy water erodes the side of the river, creating a river cliff.
The current is weakest where the water is shallowest, opposite the river cliff. More sediment is deposited here because the current has less energy to carry it along the river. This creates slip-off slopes.
More erosion happens on the _______of river bends, leading to the formation of a _______
- Outside
2. River cliff
Why is more sediment deposited at slip-off slopes than river cliffs?
The water is shallower and the current has less energy
What happens at slip of slopes?
current is weakest where the water is shallowest,
More sediment is deposited here because the current has less energy to carry it along the river. This creates slip-off slopes.
Over time, meanders get bigger until eventually an ox-bow lake forms.
As erosion continues, the river’s bends get nearer to each other and create a ______ neck meander (a small piece of land between bends).
During a flood, high energy water will breach the meander neck.
This makes the river flow in a straighter and faster course.
Over time, deposits will fill in the meander bends.
The meander becomes cut off from the river, forming an ox-bow lake.
Swan’s
What do we call a meander that only has a small bit of land between the bends?
Swan’s neck meander
What is created opposite a river cliff in shallow waters because of deposition?
A slip-off slope
What two processes lead to the formation of meanders?
- erosion
- deposition
What are floodplains?
the wide area of flat land that surrounds rivers in their lower courses at the bottom of a valley. As the name suggests, these areas can flood.
What are floodplains created by?
Meander migration close to the river mouth
They makes valley’s flatter by migrating downstream
What happens to flood plains during floods?
the water loses speed and deposits the sediment that it’s transporting.
This increases the height of the flood plain.
Deposition on meander slip-off slopes also increases the height of flood plains.
Flood plains are created by meander ________close to the mouth.
Migration
What is meander migration?
consists of bank erosion on the outside bank of curved channels and point bar and floodplain building on the inside bank.
Flood _____are the wide valley floors that surround rivers in their ______courses.
- plains
- lower
What is a levee?
is an elongated naturally occurring ridge or artificially constructed fill or wall that regulates water levels. It is usually earthen and often parallel to the course of a river in its floodplain or along low-lying coastlines.
How are levees created?
Levees are created naturally during floods.
When a flood happens, water overflows over the banks of a river.
The larger sediments that were being transported by the river will be deposited first.
After lots of floods, levees (which are natural piles of sediment) are created at the side of the river.
Which of the following describes levees?
Piles of sediment
____ are piles of sediment that form at the side of river channels after repeated_____
Levees
-flooding
What are deltas?
Deltas (e.g. the Nile Delta or the Mississippi Delta) are low-lying bits of land where rivers meet the ocean (or lake).
What is deposited first when a river overflows?
The largest sediment
What are deltas?
Low-lying bits of land where rivers meet the ocean or lake
Why do deltas form?
Rivers lose momentum in the flatter lower course as they reach the ocean causing them to deposit their sediment load
- the rivers channel can be blocked by this build up of material- it splits the river into small rivers called distributaries
- if this material builds up enough a Delta is created
What are the effects of meander migration?
- eanders widen flood plains by migrating across them
- meanders flatten valley floors by migrating down stream
______ are piles of sediment that form at the side of river channel after repeated______
- levees
- flooding
What do we call low-lying areas where rivers meet the sea or a lake?
-deltas
Flood____ are wide valley floors that surround rivers in their____ courses
- plains
- lower
Deltas form because rivers lose momentum in the flatter ______ course as they reach the ocean, causing them to _______their sediment load.
- lower
- deposit
What are the physical factors that help shape a river landscape and determin a river’s sediment load.
- geology
- climate
- slope processes
How does geology help shape river landscapes and determine a river’s sediment load?
Soft rock erodes faster than hard rock. Therefore, a river will have a lower sediment load if it flows over hard rock.
In areas of harder more resistant rocks, valleys are usually steeper.
Waterfalls are created where soft and hard rock meet.
Interlocking spurs are created when soft rock erodes more quickly than hard rock (a bit like bays and headlands on coastlines)
How does slope proccesses help shape river landscapes and determine a river’s sediment load?
In steeper valleys, more debris is likely to be pulled by gravity down the valley to the river bed.
Mass movement can add a lot to a river’s load. Mass movements are more likely during cold weather or during intense periods of precipitation.
Soil creep is when gravity causes soil to fall down a valley or slope. This can add large amounts of fine material to a river’s sediment load.
How does climate help shape river landscapes and determine a river’s sediment load?
Heavy rainfall causes high runoff because the water arrives so quickly that there isn’t enough time for it to infiltrate the soil.
Prolonged rainfall makes the soil become saturated, and so any more rainfall will run off instead of infiltrating.
Erosion happens faster when there is higher river discharge.
More material (or sediment) is transported when a river has more energy.
Mass movements add large amounts of material to a river’s sediment load. This process is more likely during _______weather or intense rainfall.
-cold
What is river discharge?
The volume of water flowing through the river each second
What is river discharge measured in?
Cubic metres per second
What does a hydrograph show?
Rainfall and river discharge over time
What physical factors affect the shaownof a hydrograph ?
A steeper valley will funnel more rainfall into a river faster, increasing river discharge.
Impermeable rocks will absorb less water and channel more rain into a river, increasing discharge (infiltration is lower).
Impermeable soils will have higher runoff and channel more water into a river.
Circle-shaped drainage basins will channel more water into a river, reducing the lag time.
If the weather has been cold and the ground is frozen, the runoff will be higher, decreasing the lag time on the hydrograph.
What are the human factos that can affectthr shape of a hydrograph
Deforestation means that less water will be intercepted by trees, reducing the lag time from rainfall to peak discharge.
Impermeable building materials are used for housing and buildings in urban areas. This will reduce infiltration and reduce the lag time.
Deforestation means that less water will be intercepted by trees, increasing runoff, and reducing the lag time from rainfall to peak ______
Discharge
What is the lag time on a hydrograph?
the time taken between peak rainfall and peak discharge
What does the rising limb on a hydrograph show?
the increase in discharge
What does the falling limb show on a hydrograph?
Return of discharge to normal
What are the physical factors affecting storm hydrographs?
- geology
- soil type
- slope
- drainage basin type
- if the ground has been frozen
Which term describes the volume of water flowing in a river each second?
River discharge
Erosion happens slower when rivers flow through areas of _______rock, and so the river will have a reduced ______ load.
- hard
- sediment
WhT are flood walls?
Artificial barriers built on the banks of rivers
Don’t represent a constant eyesore.
But, they are expensive to build and they might not be put in place quickly enough.
What is an eyesore?
something that is largely considered to look unpleasant or ugly.
What are flood gates?
built on estuaries to prevent flooding caused by extreme high tides or storm surges.
Shutting them if a storm surge is forecast can save a lot of land.
But, they are expensive to build and require frequent maintenance.
What is an estuary?
Where the river means the sea
What are embankments?
Embankments are walls built either side of the river channel to raise the height of the banks.
Embankments reduce flooding risk by increasing the capacity of the river.
But, embankments are expensive to build and if the banks do burst, then flooding can still happen.
What are the 3 hard engineering stratergies for flood managment?
- flood walls
- embankments
- flood barriers(flood gates)
Floodgates are built on estuaries to stop flooding from storm ______or extreme high ______
- surges
- tides
What are the 2 soft engineering flood defences?
- river restoration
- floodplain retention
What is river restoration?
River restoration returns a river to its natural state.
This allows a river to swell its banks and flood the flood plain naturally.
This does not do much to stop flooding.
It feels a bit like a passive approach, a bit similar to managed retreat.
What is floodplain retention?
Flood plain retention involves not building on flood plains.
Building usually stops in zones that are at high risk of flooding.
If there are fewer impermeable surfaces, surface runoff will be lower and flooding should be less common.
However, this involves having smaller towns and cities. This can increase house prices and create housing shortages
_________ reduce flooding risk by increasing the capacity of the river.
-embankments
Which process is river restoration a bit similar to?
Managed retreat
What afrects the risk of flooding?
- land use
- geology
- steep relief
- precipitation and storms
How can land use increase the risk of flooding?
Roads and buildings are made from impermeable materals, caused greater surface runofff and more discharge.
-trees intercept water and store water that they take up from the ground, removing trees will increase flood risk as more water will be able to get into the river channel
How can Geology increase the risk of flooding?
Runoff is higher in areas that are mainly made up of impermeable soil (e.g. clay) or impermeable rock (e.g. granite).
Hiw can relief increase the risk of flooding?
Rainfall will reach the channel quicker in a steep sided valley
What does relief refer to?
The way the landscape changes in height
How can precipitation and storms increase the risk of flooding?
Heavy rainfall causes high runoff because the water arrives so quickly that there isn’t enough time for it to infiltrate the soil.
Prolonged rainfall makes the soil become saturated, and so any more rainfall will run off instead of infiltrating.
If storms are more frequent have more rainfall, then the risk of flooding will rise.
What are 4 things that would increase the risk of flooding?
- laying down tarmac roads
- impermeabke rock type
- steep relief
- removing trees
How does floods thereaten people
-floods can wash people away and kill them( Four people were killed by Storm Dennis in 2020)
Floodwater can easily get contaminated with sewage, leaving water unsafe to drink.
Possessions can be destroyed or lost. In the Boscastle flood, 150 cars were swept away.
Businesses and homes can be damaged. People think that the Boscastle flood cost the town £50 million in damage and lost income.
How does flooding threaten the enviroment?
Habitats can be polluted by floodwater. In the Boscastle flood, 1,850 tonnes of flood debris were recovered from the surrounding area.
Deposited silt can damage agricultural land.
Erosion of river banks can significantly change a river’s course and nature.
Vegetation can be uprooted and killed by forceful floodwater.
Floodwater can easily get contaminated with sewage, leaving water unsafe to drink and river ________polluted.
Habitats
What are 3 threats posed to people by river flooding?
- homelessness
- death or injury
- damaged possessions
Where is the river Eden located?
north-west England at the boundary between Yorkshire and Cumbria
What are 4 features of the river Eden?
- floodplains
- waterfalls
- meanders
- v-shaped valleys
What are flood plains created by?
Meander migration
What is emaner migration?
bank erosion on the outside bank of curved channels
_____ Gill Force is an 8-metre waterfall. It is the tallest waterfall on the River Eden. Gorges are formed when waterfalls retreat over time.
Hell
Floodplains in the river Eden basin?
The Eden’s floodplain is home to the town of Carlisle.
A flood plain is the wide area of flat land that surrounds rivers in their lower courses at the bottom of a valley.
As the name suggests, these areas can flood.
Flood plains are created by meander migration close to the mouth of the river.
During floods, the water loses speed and deposits the sediment that it’s transporting. This increases the height of the flood plain.
Wateraflls in the river Eden basin:
Hell Gill Force is an 8-metre waterfall. It is the tallest waterfall on the River Eden.
When a river flows over hard rock that overlays softer rock, a waterfall can form.
There is a gorge behind. Gorges are formed when waterfalls retreat over time.
Meanders in the river Eden basin
Meanders form because of lateral erosion.
There are lots of meanders in the lower course (e.g. the meanders by Salkeld).
Some of these meanders have become ox-bow lakes.
What is the river Eden’s course?
Its sources js the pennines in Cumbria ans ots mouth us at the English-Scottish border
The middle course of the Eden flows through an area of soft rock. In the middle course, neither erosion nor deposition is particularly dominant. This means that the valley is more gentle and the channel is wider.
In the lower course, deposition dominates over erosion. This means that the valley is wide and flat, and the channel is wide and deep.
(Rocks and sediment are more eroded in the lower courseand are smaller and more round
V-shped valley’s in the river Eten:
The edge of the River Eden’s basin is dominated by hills at about 500-700m above sea level.
These steep slopes have streams that carve V-shaped valleys into the side of the Lake District’s hills.
4 river landforms in the Eden basin:
- meanders
- floodplains
- v-shaped valleys
- waterfalls
What are the Influences of Climate on Geomorphic Processes:
- temperature
- rainfall
Influences of Climate on Geomorphic Processes: temperature?
Temperatures can get very low on the high ground near the Eden’s source. In winter, this high ground freezes, leading to freeze-thaw weathering (particularly in the upper course).
Weathering weakens the rock in the valley, increasing the likelihood of mass movement.
Material from mass movement events increases the amount of material or sediment being carried by the river, leading to increased erosion by abrasion.
Influences of Climate on Geomorphic Processes: rainfall
Intense precipitation can cause the ground and soil by the River Eden to get saturated. The reduced stability of saturated ground makes landslides more likely.
Heavy rain can rapidly enter water channels in the basin from V-shaped valleys. Rapid surface runoff can lead to rapid increases in channel volume.
More material is transported when the channel is more full. Increased transportation means increased erosion by abrasion.
In winter, this high ground freezes, leading to freeze-thaw weathering (particularly in the upper course). Weathering weakens the rock in the valley, increasing the likelihood of mass _________
Movement
What is Cumbria’s climate like?
Mild and wet
What kind of weathering happens in the upper course in winter by the River Eden?
Freeze-thaw weathering
What were the influences of Geology on the River Eden)s Geomorphic processes?
- edges of the Eden basin
- west of the Basin
- middle and lower courses of the Eden
How does the edges of the Eden basin influence the river’s geomorphic processes?
- at the edges of the Eden’s basin are hard rocks that have resisted erosion over time and so remain as elevated ground
- carbonation weathering is wearing away the limestone that is exposed
How does west if the Eden basin influence the river’s geomorphic processes?
- to the west of the Eden’s basin are impermeabke igneous rocks that are covered in streams
- heavy rain can repeatedly enter the channels in the basin from streams in v-shaped valleys,
Radid surface runoff can lead to rapid increases in channel volume
How does the middle and lower courses of the Eden influence the river’s geomorphic processes?
Sandstone dominates in the Eden’s middle and lower courses.
This soft sandstone is easily eroded by the river, which has considerable energy to erode laterally.
Lateral erosion leads to the formation of meanders and river cliffs
What dominates in the Eden’s middle and lower courses?
Sand stone
What is the name of the tallest waterfall on the River Eden?
Hell Gill force
Impacts of Management Strategies on the River Eden: reservoirs
A dam is a large earth, stone or concrete wall built across a river in the upper course. Behind the dam, a reservoir (man-made lake) forms.
Downstream of reservoirs, water flow is limited and there is not much material left to be deposited. This can lead to increased erosion and decreased build-up of the floodplain.
South-east of Carlisle, a reservoir has been created by damming Castle Carrock beck.
Impacts of Management Strategies on the River Eden:
Planting trees
Planting trees in river valleys increases interception of rain water and the lag time between rain falling and it making its way into the river channel.
As a result, the energy of the river will decrease and so meanders will form more slowly.
£500,000 was spent planting 1,000 trees near the River Eden, trying to reduce flooding and soil erosion.
Impacts of Management Strategies on the River Eden:
Channel management
Channel straightening involves removing bends and meanders by adding artificial straight channels.
Channel straightening was common in the River Eden basin in the past.
Artificial meanders increase deposition by decreasing a river’s velocity.
Recently, artificial meanders have been installed to try to restore the Eden basin to its natural state.
Impacts of Management Strategies on the River Eden:
Flood walls and embankments:
Flood walls and embankments are artificial barriers built on river banks.
They effectively increase the height of the river banks.
Carlisle is currently protected by 10 kilometres of flood walls and embankments.
In 2019, a new £25 million flood defence programme was being developed.
How many trees have been planted near Dalston with the aim of reducing flooding and soil erosion?
1000
What are the Impacts of Human Activity on the River Eden?
Farming
Deforestation
Impacts of Human Activity on the River Eden:
Draining land for farming
Draining land decreases soil stability which can increase the amount of soil that is washed away when it rains.
Soil that is washed away finds its way into river channels, adding to the river’s load. -A higher load means that there is more deposition downstream.
mpacts of Human Activity on the River Eden: deforestation
increased surface runoff, which means that rainfall enters the river faster.
This gives the river more energy and more power to erode, potentially leading to mass movements.
________has caused increased ___________, which means water finds its way into the river more quickly.
Deforestation
Surface run off
Where has a reservoir been created by damming Castle Carrock beck?
South east of Carlsile
Many upland areas of the basin of the River Eden have been cleared of what?
Forests
What do we call the wide valley floors that surround rivers in their lower courses?
Floodplain
What is undercutting of a waterfall?
Rocks coming down from the waterfall; these then cut back into the soft rock at the base of the waterfall eroding it away
What is the process of undercutting?
The less resistant rock starts to be eroded underneath the hard rock. This process is called undercutting.
How does a plunge pool form?
Overhanging rick collapses because ther eis nothing underneath it to support it.
Hard rock crumbles into the base and the abrasion between the hard rock and soft rock base creates a plunge pool
What keeps indercutting behind the waterfall
Hydarulic action
What is respinsible for the formation of plunge pools
Abrasion
What are the Main ways that tectonic activity shaped the UK landscape?
- active volcanos
- plate movement
- plate collisions
How did plate collisoons shape the landscape?
These collisions also generated intense heat and pressure which led to the formation of hard metamorphic rocks in northern Scotland and Northern Ireland.
-they also creared mountain ranges
How did active volcanos shape the lanscpae?
Active volcanoes at this boundary erupted magma onto the UK landscape, which then cooled to form igneous rocks, such as granite.
How did plate movements shape the UK landscape?
345-280 million years ago, the UK was in the tropics. At this time, sea levels were also higher, and so carboniferous limestone ended up forming in the warm and shallow seas.
(These areas are now found in the uplands of the Peak District, South Wales and south-west England.
The lowland chalk and clay landscapes of southern England are the youngest rocks in the UK, and these also formed in the shallow seas and swamps all those years ago.)
How is a river cliff formed?
force of the water erodes and undercuts the river bank on the outside of the bend where water flow has most energy due to decreased friction.
This will form a river cliff.
What do contour lines on a map show?
Contour lines are added to a map to show height and gradient.
What is hard engineering?
involves the construction of physical structures to protect coasts from erosion
What is soft engineering?
a shoreline management practice that uses sustainable ecological principles to restore shoreline stabilizatio
Why is the holderness coast so vulnerable to erosion?
- strong prevaling winds
- clay cliffs
How far does the Holderness coast retreat every year?
1-2 meters
Which town on the Holderness Coast saw a £2m coastal defence scheme in 1991?
Mappleton
how can human activities affect storm hydrographs?
- Drainage systems that have been created by humans lead to a short lag time and high peak discharge as water cannot evaporate or infiltrate into the soil.
- Area that have been urbanised result in an increase in the use of impermeable building materials.
why is there an increased risk of coastal flooding in the uk?
- increased storm frequency
- rise in se level
Why do rivers deposit material?
- volume of water in river falls
- amount of eroded material in water increases
- water is shallowe(inside of a bend)
- river reaches mouth
