Unit 1A - Our Dynamic Landscape Flashcards
Drainage Basin definition
A Drainage Basin is described as the area of land that is drained by a river and its tributaries.
Why is the drainage basin system often described as an ‘open system’?
The drainage basin is an open system because energy and matter can be transferred across its boundaries.
Water may be evaporated forming clouds in drainage basin A. Wind blows the clouds to drainage basin B. It rains in drainage basin B.
What is hydrology?
Hydrology is the study of water.
What is a flood hydrograph?
A flood hydrograph is a graph which displays discharge (in cumecs) and precipitation (in mm) on the Y-axis and time (usually in days or hours) on the X-axis.
Flood hydrograph
What is a rising limb?
The increase in discharge as rainwater reaches the river.
Flood hydrograph
What is a falling limb?
Some rainwater is still reaching the river but in decreasing amounts.
Flood hydrograph
What is peak discharge?
Highest volume of water in the river at a certain point and at a certain time.
Flood hydrograph
What is peak rainfall?
The highest intensity of rainfall in millimetres.
Flood hydrograph
What is lag time?
Lag time is the difference between the time of the heaviest rainfall and the maximum level and/or discharge of the river.
‘The Water Cycle’ definition
The Water or Hydrological Cycle is a natural system where water is in constant movement above, on or below the surface of the earth, and is changing state from water vapour (gas), to liquid and into ice (solid).
Definition of water table
The level at which saturation occurs in the ground or soil.
Name the processes of the Water Cycle in chronological order and visualise the layout of the drainage basin.
1 - Evaporation 2 - Transpiration 3 - Precipitation 4 - Infiltration 5 - Throughflow 6 - Percolation 7 - Groundwater flow 8 - Surface runoff or Overland flow
Describe each process within the Water Cycle
Evaporation - Water is transformed from seawater into water vapour in the atmosphere.
Transpiration - Water vapour is lost from vegetation into the atmosphere.
Precipitation - Water vapour condenses into drizzle, rain, sleet, snow and hail, and this falls towards the surface of the land.
Infiltration - Water soaks (filters) into the soil.
Throughflow - Water moves downhill through the soil.
Percolation - Water moves from the soil and into the rock.
Groundwater flow - Water moves slowly through the soil and rocks back into the sea.
Surface runoff or Overland flow - Water moves across the surface of the earth, becoming a stream, tributary or river.
Ass 2
Describe the features of a destructive wave
Size - High and close together
Frequent - Up to 15 per minute
Season - Common in winter (storm waves)
Effects - Stronger backwash than swash, erodes beach
Ass 2
Describe the features of a constructive wave
Size - Low and far apart
Less frequent - 6 to 9 per minute
Common in summer
Strong swash, weak backwash - Deposition
Ass 2
What processes cause coastal erosion?
Hydraulic pressure - Force of the waves alone
Abrasion (Corrasion) - Sand papering action of sand and pebbles bashing and smoothing rocks at base of cliff
Solution (corrosion) - Chemical action of seawater dissolving rocks
Attrition - Rocks and pebbles hit each other, breaking up
Ass 2
Describe some processes responsible for coastal transportation
Swash - Wave breaks, carrying water and sediment up the beach
Backwash - Water/sediment returns back down beach due to gravity
Longshore drift - Zigzag movement along beach, etc
Ass 2
How does coastal deposition occur?
The water slows down and has less energy to carry the sediment, it is therefore dropped.
Ass 2
Describe some of the erosional features caused by erosional processes
Wave cut notch - Where waves attack bottom of cliff
Cliff - Forms when unsupported rock falls into the sea
Wave cut platforms - Almost level area as cliff retreats
What is an input in the drainage basin system, and give an example of one.
An input is when water is introduced or put into the system.
Precipitation
What is a store in the drainage basin system, and give examples of some.
A store occurs when water is kept within the system and not moved through it.
Interception (from vegetation)
Soil moisture
Groundwater
Surface storage
What is a transfer in the drainage basin system, and give examples of some.
Transfers are processes or flows within the system, where water is moved from one place to another.
Surface runoff/ overland flow Infiltration Throughflow Percolation Groundwater flow
What is an output in the drainage basin system, and give an example of one.
Outputs occur in the river system when the water is carried through the river and back into the sea.
River discharge
Definition of watershed
The dividing line between one drainage basin and another.
Definition of source
The starting point of a river channel, where drops of water join to start a river.
Definition of confluence
Where two rivers meet and join.
Definition of tributary
A small river or stream which contributes to the main river channel.
Definition of river mouth
The place where the river flows into the sea.
Definition of river channel
The main body of water, flowing downhill.
Definition of discharge
The amount of water that passes a particular point in a river at a particular time.
What is the unit of measurement for discharge?
Cubic metres of water per second (Cumecs)
How is discharge calculated?
The discharge of a river is the product of the cross-sectional area (depth and width, m*2) and the velocity (speed, m/sec).
What are some of the characteristics of the upper course of the river? (Give six points)
- Steep gradient
- Shallow, thin river channel
- Fast flowing
- Low discharge
- Lots of erosion
- Load is mostly angular
What are some of the characteristics of the middle course of the river? (Give six points)
- Less steep gradient
- River channel deepens and widens
- Water slows down
- Discharge increases
- Erosion, transportation and some deposition
- Load is mostly sub-angular
What are some of the characteristics of the lower course of the river? (Give six points)
- Gentle gradient
- River is both deep and wide
- Water can be very slow
- High discharge
- Some erosion and transportation but mostly deposition
- Load is mostly rounded
What is the load of a river?
The load of a river is the material that the river is carrying.
What is a river process?
A river process is simply a description of something that happens in the river.
What is river erosion?
Erosion happens in a river when parts of the river bed and/or river bank get eroded and are removed from the landscape.
What are the four types of river erosion?
Attrition
Abrasion/corrasion
Hydraulic action
Solution/corrosion
Definition of river attrition
Attrition takes place when stones that are being carried downstream knock against each other and start to wear each other down. This knocks the edges of the stones and results in smaller, rounder sized stones further downstream.
Definition of river abrasion/corrasion
The force of the moving water in the river throws the stones and other eroded particles that it is carrying against the bed and banks of the river, and this dislodges more material. It works like a piece of sandpaper grinding and eroding the rocks.
Definition of river hydraulic action
This is when the force of the water pounds into the river bed and banks and dislodges more material. It works a bit like a power hose.
Definition of river solution/corrosion
This is when weak acid (chemicals) in the water react with the Rock and dissolves soluble minerals. It happens often in limestone areas.
What is river transportation?
Transportation is when the eroded material in the river is carried from one place to another through the river system.
What are the four types of river transportation?
Traction
Saltation
Suspension
Solution
Definition of river traction
This is when the heaviest particles of eroded material are rolled along the river bed. Usually these stones and boulders can only be moved when the river has a large volume of water in it.
Definition of river saltation
This is when some of the heavier particles are not held up in the flow of the river all of the time. Instead they may be bounced along the river bed.
Definition of river suspension
As the speed of the water increases, the river is able to pick up larger particles and stones in its flow. When particles are carried along in the flow of the water and do not make contact with the river bed, they are suspended within the water.
Definition of river solution
This happens when some minerals (like limestone) dissolve easily in water and the microscopic particles are held up in the solution of the water.
What is river deposition?
Deposition is where the river load becomes too heavy for the river to carry and is dumped or deposited along the course of the river.
What river landform is often found in the upper course of the river channel?
Waterfall
Where does the majority of river deposition occur along the course of the river, and why?
Lower course, river mouth
Velocity of water decreases, less transportation
Large areas of deposition near the river mouth are known as …
Deltas
Describe the formation of a waterfall
- River moves from and area of hard rock (igneous) to an area of softer rock (sedimentary)
- The softer rock is eroded, creating a drop in height
- Erosional processes (Hydraulic action, abrasion/corrasion and attrition) erode the rock further (undercutting the hard rock), creating an overhang and plunge pool.
- The overhang continues to extend and the hard rock is exposed forming a ledge
- Finally, the hard rock cannot support its own weight, forms cracks and is eroded (collapses). This process repeats itself causing the waterfall to recede, forming a gorge.
What river landform is often found in the middle course of the river channel?
Meanders
In relation to meanders, what are deeper areas of water known as?
Pools
In relation to meanders, what are shallower areas of water known as?
Riffles
In a meandering river, what evidence suggests that the process of lateral/sideways erosion is occurring?
The presence of the river cliff or erosion cliff.
On what bend of a meandering river does erosion take place and what structure does it form?
The outer bend
Erosion cliff or river cliff
On what bend of a meandering river does deposition take place and what structure does it form?
The inner bend
Deposition beach
On what bend of a meandering river does the fastest flow of water take place?
Outer bend
On what bend of a meandering river does the slowest flow of water take place?
Inner bend
On what bend of a meandering river does transportation take place and why?
Outer bend
Increased velocity
On a meandering river, what material(s) is the deposition beach comprised of?
Sand
Shingle
On what bend of a meandering river is the deepest depth of water found and why?
Outer bend
Increased velocity —> Increased erosional processes —> River bed deepened
On what bend of a meandering river is the shallowest depth of water found and why?
Inner bed
Decreased velocity —> Increase deposition —> Shallow river bed
How is an ox bow lake formed?
- The river is meandering as usual, with deposition taking place on the inside of the bend and erosion occurring on the outside of the bend to create river cliffs.
- Erosion continues on the outside of the bend. During a river flood, when the velocity and discharge of the river are much higher, there is more erosion and the river cuts through the neck.
- Deposition takes place and starts to block up the neck of the river. The meaner is permanently cut off from the new, straight river channel.
- The former river channel now forms an ‘ox bow lake’, where the water will gradually infiltrate into the soil and evaporate, leaving the river bed exposed and likely to be populated by surrounding plant species over time.
What will eventually happen to the small river cliff or erosion cliff?
The river bank will collapse.
What river landform is often found in the lower course of the river channel?
Floodplain
What is a floodplain?
The floodplain is the area of land that has been covered with the silt deposited by the changing course of the river. It is essentially the area of land over which the river is likely and able to flood.
What is the bluff line?
Boundary of the flood plain where higher land is.
When the river channel floods, what material(s) is deposited close to the river bank?
Sand
Silt
Alluvium
When the river channel floods, what material(s) is deposited farthest from the river banks?
Sand
Gravel
How are levees formed?
As the river floods and continues to deposit materials across the valley floor, the largest, coarsest material will be dumped first, close to the river bank. This forms a raised bed called a levee. The levees are formed by the repeated flooding of the river. These can build up over a long period of time.
How is land used near rivers? (Give seven points)
Defensive position Drinking water Source of power (watermills) Water for irrigation Silt to add nutrients to the soil (agriculture) Easy transport (trade) Recreation and tourism
What are the two different types of causes of flooding in a river?
Physical causes
Human causes
Name four physical causes of flooding in a river
- Precipitation
- Soil and underlying rock
- Land use/vegetation
- Steepness and size of drainage basin
Name four human causes of flooding in a river
- Deforestation
- Urban growth
- River management
- Global warming
Explain why precipitation is a physical cause of river flooding
Flooding occurs more often when there are periods of heavy rainfall over a few days. The general rule is that the more water that falls onto a drainage over a short period of time, the more rapidly the water will fill up the air spaces in the soil, and the quicker the water will be forced to run off the surface and into the river. Sometimes the worst flooding is associated with short but intensive thunderstorms. Heavy snowfalls can also cause flooding, as water is melted by a rise in temperature. If this rise in temperature is accompanied by rainfall, there can be serious flooding.
However, flooding can also happen following periods of dry weather and drought. In the summer, the soil can become baked by the sun, making it hard and the rainwater can struggle to infiltrate into the soil. The water runs across the surface and creates a flash flood, which is when the water levels in the river rise very quickly following a rain event.
Explain why the soil and underlying rock are a physical cause of river flooding
Different types of soil will influence how quickly or how slowly any rainwater will infiltrate through the soil. Sandy soils are permeable and allow water to pass through quickly. Clay soils are less permeable and will stop the water from passing through, which can cause flooding at the surface and increased surface runoff at a much faster rate.
Rock type also influences the passage of water through. Some rocks are permeable (porous) and allow the water to pass through with relative ease (for example, limestone, chalk and sandstone). However, some rocks have very small pores (non-porous) and are said to be impermeable, as water does not pass through them (for example, basalt, slate and granite).
Explain why land use/vegetation are a physical cause of river flooding
Another important factor that can influence flooding is how the land is used within the drainage basin. Any drainage basin that has very little vegetation will be more likely to experience flooding than areas where there is much vegetation and forests. This is because trees intercept water through their leaves and root system, and any water stored in this way will reduce the amount of water reaching the river system.
Flood levels can be affected by the levels of vegetation in an area as they increase interception, transpiration, water absorption and their roots intercept water in the through flow. These factors reduce the amount of water reaching the river system.
Explain why the steepness and size of a drainage basin are a physical cause of river flooding
The size and shape of the drainage basin can also dictate if a river is more or less likely to flood. A large drainage basin means that the water will take a long time to reach the river and is less likely to flood quickly. A small drainage basin means that the water will get to the river channel quicker and has a higher chance of flooding. Sometimes drainage basins can be small and the slopes within the area are quite steep. This means that gravity will move the water more quickly towards the river channel and again, this is more likely to cause a flash flood.
Explain why deforestation is a human cause of river flooding
If the presence of vegetation helps to slow down the return of water to the river channel, then the removal of this vegetation is going to cause an increase in the surface run-off, and therefore the chances for flooding. Removal of trees also means that the roots that would have helped to hold the soil structure together will not be able to do this anymore. This causes an increase in soil erosion, which can also lead to a rapid increase in flooding.
Explain why urban growth is a human cause of river flooding
The world is urbanising at a fast rate, and more and more farmland is being converted into concrete jungle instead. This change of land-use means that less water is held in storage within the drainage basin system. It also means that any water that falls onto buildings and roads gets channelled into drainage pipes very quickly (less infiltration and throughflow), which rapidly returns the excess water to rivers (increased surface run-off). Urban growth can cause a big increase in flooding along a river.
As land is urbanised, the artificial structures will increase discharge due to: roofs, gutters. The impermeable tarmac will stop water storage increasing surface run-off making it more likely to flood.
Explain why river management is a human cause of river flooding
Sometimes the actions that local governments take to try to change the shape of a river channel can actually make a flood more likely. For example, the 1953 flood of the River Lynn in Lynmouth was amplified by the decision to try to move the river channel, to allow a hotel to be built in a particular position. Changing the river channel, by making it more narrow or building a bridge at an inappropriate position, can cause the river capacity to be reduced and make flooding more likely.
Explain why global warming is a human cause of river flooding
As more water is being melted from ice stores (glaciers and polar ice caps) due to the increase in temperatures, water levels in drainage basins and in the hydrological cycle will increase water levels in rivers.
Case Study: Sustainable Management of Rivers
Give the name, date and location of a river flood event within the British Isles
Boscastle
North Cornwall
16th August 2004
River Valency, River Jordan and River Paradise
Case Study: Sustainable Management of Rivers
Give the physical causes for a river flood event within the British Isles. (Include seven points and at least two facts and figures)
- Prolonged rainfall - The whole month of August was wet. Rained 12 of 14 days —> Soil saturation
- Heavy rainfall - 200mm in 24hrs —> Infiltration restriction
- Steep valley sides - Rises 300m in only 6km —> Water flows quickly
- Underlying rock - Slate —> Difficult to percolate into groundwater
- Thin, I permeable soils - Peat soils —> Couldn’t infiltrate
- Relatively small drainage basin - 20km*2 —> Water flows quicker to river
- Little interception - Deforestation
Case Study: Sustainable Management of Rivers
Give the human causes for a river flood event within the British Isles. (Include three points and at least two facts and figures)
- Deforestation - Many trees had been cut down (for farming) —> Rate of interception decreases —> Water travels faster to river.
- Urbanisation - Many buildings and concrete —> Little infiltration due to impermeable surfaces —> Surface run-off directed at river.
- Bridges - Bridges built over the river were too small, got blocked by debris (such as trees, etc) —> Small blockage breaks, surge of water down the river.
Case Study: Sustainable Management of Rivers
Give the impact(s) on the people for a river flood event within the British Isles. (Include three points and include at least two facts and figures)
- Death, Injury and homelessness
No one died
Injury - Broken thumb
1,000 people were affected
7 RAF helicopters airlifted people to safety
People had to stay in town halls, caravans and friend’s houses while their homes were being repaired - Impact on property
98 properties flooded and damaged
4 properties were demolished by the force of the water
4 footbridges were washed away
115 cars washed away, only 84 were recovered in the harbour, the remainder are unaccounted for - Impact on economy
Cost of rebuilding the town and ensuring a flood like this could never happen again was an estimated £50 million
Lost business in the aftermath of flood, tourists are afraid of being trapped in the event of a flood. This has affected jobs and incomes in the town.
Case Study: Sustainable Management of Rivers
Give the impact(s) on the environment for a river flood event within the British Isles. (Include one point and include at least two facts and figures)
- Pollution
31 cars unaccounted for (115-84=31), present in the river and harbours, release oil and petrol.
Increased amount of water flooded the sewage system so that dirty water floated through the town.
Sustainable River Management Strategy
What is a hard engineering strategy?
These require major alternations and changes to the river to try and stop the river from flooding. Generally these involve big building projects, where machinery is used to change the river and new walls or banks are built. These measures are not sustainable in the long term.
Sustainable River Management Strategy
What is a soft engineering strategy?
This is where limited alterations take place and flooding is more managed than prevented. These are generally more sustainable, as they use more natural processes and do not damage the environment to the same extent as hard engineering strategies would.
List all of the hard engineering strategies. (Give six points)
Note: Use mnemonic
- Channel enlargement
- Bridge widening
- River straightening
- Levees and embankments (flood walls)
- Dams/Reservoirs
- Storage areas/Diversionary Spillways
Conor Brolly Really Likes Darth Sidious
List all of the soft engineering strategies. (Give three points)
- Land use zoning
- Afforestation
- Washlands
Sustainable River Management Strategy
What is Channel Enlargement (Deepening and Widening)?
Flooding can be reduced by increasing the size of the river channel so that it is capable of carrying more water. This means that in times of very heavy rainfall the river is less likely to flood its banks than before the enlargement, as it will be able to transport the water quickly and effectively through the river channel.
Sustainable River Management Strategy
What are the advantages and disadvantages of channel enlargement (Deepening and Widening)?
+ Visually similar
+ Protects both sides of the river
+ Protects habitats
- Heavy machinery —> Expensive, and impacts the ecosystem
- Continued maintenance, as bed silts up
- More rapid flow, areas downstream are more likely to flood
Sustainable River Management Strategy
What is bridge widening?
Bridges can be widened to stop debris such as trees and boulders from becoming trapped behind them and creating a dam, as this would cause a large wall of water to build up.
Sustainable River Management Strategy
What are the advantages and disadvantages of bridge widening?
+ Stops debris from a backlog of water
- Replacement bridge —> Expensive
- Modern bridge, unattractive for tourists
Sustainable River Management Strategy
What is river straightening?
Rivers that meander across the river flood plain can be straightened to help increase the velocity of the water. This reduces flooding as the water drains away from the flood plain more quickly. Some parties want rivers straightened for reasons other than reducing flood risk. For example, property developers find it easier to build alongside straight rivers than on bends and farmers prefer more regular field shapes and sizes, as it allows their machinery to reach the corners of fields, so there is little land wastage.
Sustainable River Management Strategy
What are the advantages and disadvantages of river straightening?
+ Increased velocity —> Water drains quicker
+ Easier to build property
+ Agricultural field sizes
- Does not always work, river can return to its natural course
- Affects wildlife, fish like to lay eggs in shallowbends (this removes the bends of the river)
Sustainable River Management Strategy
What are levees and embankments (flood walls)?
Levees and embankment walls can be built on either side of the river. The walls mean that even if the river floods above the river bank, the water cannot spread over the flood plain and cause damage.
Sustainable River Management Strategy
What are the advantages and disadvantages of levees and embankments (flood walls)?
+ Little impact on the river
+ Can be built on either side of the river
+ Even if the river does flood, the water cannot spread and cause damage
- Can be expensive
- Spoils the look of the river
- Prevents water from draining back quickly
- No silt (alluvium) deposited
- Increases speed of water —> If water does break through, it will cause more damage
Sustainable River Management Strategy
What is a dam/reservoir?
In many ways dams across the upper course of the river are an obvious way of controlling the amount of water that can travel through the river system. They ensure that the risk of flooding is almost completely reduced and can be used to generate hydro-electricity.
Sustainable River Management Strategy
What are the advantages and disadvantages of building a dam/reservoir?
+ Can be used to generate hydro-electric power, which is a cheap and renewable source of energy
+ Risk of flooding almost completely reduced
+ The dam can be used for recreational activities
- Expensive
- Major impact on environment, completely changing the natural landscape and ecosystem
Sustainable River Management Strategy
What is a storage area/ Diversionary spillway?
Water can be pumped out of the river and stored in temporary lakes. This reduces the amount of water flow in the river at peak times and the impact of flooding in more sensitive areas. When it is needed it can be pumped back into the river.
Sustainable River Management Strategy
What are the advantages and disadvantages of a storage area/ diversionary spillway?
+ Effective
+ Can be pumped back in when needed
+ Water is pumped out of river, which reduces water flow at peak times and reduces impact of flooding in some areas
- Takes up a lot of space
Sustainable River Management Strategy
What is land-use zoning?
Land-use zoning involves dividing the flood plain up into areas which experience different degrees of flood risk. Once the flood plain has been divided up into the different zones, an appropriate land-use can be chosen for each zone.
Sustainable River Management Strategy
What are the advantages and disadvantages of land-use zoning?
+ Allows the river to flood naturally
+ Minimal disruption and damage to people
+ Effective
+ Relatively cheap and easy to apply to a potential development site
- Cannot realistically be applied to an already developed and built area
Sustainable River Management Strategy
What is afforestation?
Planting trees in the upper course of the drainage basin helps to reduce flooding as trees intercept and store the water. This will help stop some of the water entering the river channel and can reduce the risk of flooding.
Sustainable River Management Strategy
What are the advantages and disadvantages of afforestation?
+ Good for environment (natural habitats)
+ Timber can be harvested for additional income
- Only reduces the likelihood of flood, doesn’t prevent it
- Takes up space
- Takes long to grow
- Land owners and users must agree
Sustainable River Management Strategy
What is a washland/ safe flood zone?
Washlands are areas of land that water can wash into during a flood. They are usually found in the lower course of a river and act a little like storage areas, with the added benefit of helping to increase friction and slow the river down.
Washlands are created by leaving a large area of land next to a river empty to receive any floodwaters.
Sustainable River Management Strategy
What are the advantages and disadvantages of a washland/safe flood zone?
+ Increases friction —> Slows down the river
+ Anticipated flooding —> Saves lives
+ May save more expensive areas downstream
- Demolishing existing structures
- Conflict between people and government
- You have to accept flooding to some extent
Case Study: Sustainable River Management Strategy
Give the name, location and date of a river flood event outside the British Isles, and include facts and figures.
Mississippi River, USA River flooded in 1993 Deaths: 43 Evacuees: 50,000 Damage: $12 billion (£8 billion) Sandbags: 26 million
Case Study: Sustainable River Management Strategy
Name the hard engineering strategies used in a river outside of the British Isles, and include facts and figures.
• Levees and embankments (flood walls)
Levees raised to 15 metres and strengthened for a stretch of 3000km
• Straightening river channel
Straightened for over 1750km, cutting off meanders
• Dams
Over 100 built, e.g. Kentucky
• Storage areas/ Diversionary spillways
Example, Bonnet Carré Floodway begins 50km north of New Orleans
Reduces flood risk at New Orleans and Baton Rouge
Case Study: Sustainable River Management Strategy
Name the soft engineering strategies used in a river outside of the British Isles, and include facts and figures.
• Afforestation
Trees planted in upper course of river, Tennessee Valley
• Washland/ Safe flood zone
Rock Island, housing demolished
How are waves formed?
Waves are created by the transfer of energy as the wind blows across the surface of the sea.
What factors affect the size of a wave?
Strength of the wind
Length of time the wind blows
Distance of sea the wave has to cross (Fetch)
What is the fetch?
The fetch is the distance that a wave travels in open water.
Why does a wave break when reaching the shoreline?
As the waves begin to approach the shore and the water becomes shallower, the amount of friction increases with the seabed and this slows the base of the wave down. However, the friction does not affect the top of the wave. It keeps its energy so the wave starts to build upwards until it eventually rolls over and breaks.
What is a constructive wave?
A constructive wave is a wave with a stronger swash than backwash, resulting in deposition which builds up the landscape.
What is a destructive wave?
A destructive wave is a wave with a stronger backwash than swash, resulting in erosion of the coastline.
What are the properties and characteristics of constructive waves? (Give eight points)
Strong swash, weak backwash Operate in calm weather Limited energy Beach increases in size Break less frequently (6-9 per minute) Build up of sediment on beach Gentle sloping beaches Low wave height (about one metre high)
What are the properties and characteristics of destructive waves? (Give eight points)
Weak swash, strong backwash Operate in storm conditions Much energy Causes erosion, beach decreases in size Breaks frequently (around 15 per minute) Removes sediment from the beach Steep beach angle High wave height (five or six metres)
List the four erosional processes which occur at the coast
- Corrasion/abrasion
- Attrition
- Solution/corrosion
- Hydraulic action/pressure
Definition of coastal corrasion/abrasion
The force of the moving water in the sea throws stones and other eroded particles that it is carrying against the coastline and cliffs, which dislodges more material.
Definition of coastal attrition
Attrition takes place when stones and boulders that are being carried by the sea knock against each other and start to wear each other down. This knocks the edges of the stones and results in smaller, rounder stones/pebbles.
Definition of coastal solution/corrosion
This is when the salts and acids in the seawater slowly dissolve coastal cliffs (particularly limestone and sandstone).
Definition of coastal hydraulic action/pressure
This is when the force of the water pounds into the cliffs and the cracks in the rocks, and dislodges more material.
List the four transportation processes which occur at the coast
Traction
Saltation
Suspension
Solution
What transportation process carries material along the coast, from one end to the other?
Longshore drift
Why and how does longshore drift occur?
Waves usually approach the coast in the same direction as the wind is coming from. As the wave breaks, the swash will carry sediment diagonally up the beach and as the swash dies away, the backwash returns the material straight back down the beach at a right angle to the sea (due to gravity). Eroded sediment is therefore slowly moved along the coastline in a zig-zag course.
What are the two different types of coastal landforms?
Erosional landforms
Depositional landforms
What is a cliff?
A steep rock face, especially at the edge of the sea, formed by erosion from the ocean and weather.
List all of the erosional landforms
Cliffs
Headlands and bays
Wave cut notches and platforms
Cracks, caves, arches, stacks and stumps
How are headlands and bays formed?
One of the most spectacular features of the coastline is the formation of bays and headlands. These are formed when outcrops of harder, more resistant rock (such as basalt) and softer, less resistant rock (such as limestone) are found in the same areas. Waves gradually erode the softer rock away, leaving the harder, more resistant rock sticking out into the sea.
How are wave cut notches and platforms formed?
When the sea comes up against a solid barrier such as a cliff face, the four different types of erosion go to work trying to break down the rocks. The greatest pressure of erosion is at the base of the cliff, in what is sometimes called the ‘wave attack zone’. The waves start to undercut the foot of the cliff and this starts to create a wave cut notch. The notch continues to widen and undermines the foundation of the cliff face, which causes the cliff to collapse and retreat backwards.
A wave cut platform gets left behind as the cliff retreats further away from the original position. These are generally gently sloping or flat platforms that can be seen as low tide.
How are cracks, caves, arches, stacks and stumps formed?
- Crack is opened up by hydraulic action
- An area of weakness in the rock (such as cracks or joints) will start to come under pressure due to the relentless impact of erosion.
- The cracks in the rock will face abrasion and hydraulic action, continually being impacted by the water and will widen any weaknesses in the rock and split the crack into a cave.
- If the cave is being formed in a headland, the cave might be eroded to form an arch.
- If the waves erode the foot of the arch, it may not be able to carry the roof of the arch which will collapse leaving a stack.
- When the stack is undercut and collapses it will leave a stump.
List all of the depositional landforms found on the coastline
Beaches
Spits
How are beaches (a depositional landform) formed?
Beaches are usually described as being gently sloping areas of land that are found between the high and low water tide marks. They are built up by constructive waves moving deposited material (sand, shingle and pebbles) up the beach. They are generally fully covered by water at high tide and can be fully exposed at low tide.
What is a spit?
A spit is a long, narrow ridge of land that is made up from deposited material (sand, shingle and pebbles) along a coastline.
How are spits (a depositional landform) formed?
Spits are less common depositional features. A spit is a long, narrow ridge of land that is made up from deposited material (sand and shingle) along a coastline.
There are a few conditions in which spits can form:
- They are usually found in areas where there is an easily eroded coastline such as Boulder clay.
- They are formed when prevailing winds help to transport material down the coastline due to longshore drift (provide definition of longshore drift).
- They are formed where the coastline changes direction (usually where a river estuary meets the sea).
- The velocity of water from a river and the power of the sea meet at a certain place, causing a loss of energy and deposition.
- Many spits have a hooked or curved end as it is gradually shaped and re-shaped by the sea.
- Spits bend because of the direction of waves and wind.
- Often the area behind the spit will become a salt marsh due to deposition.
- The spit will grow in size and magnitude over time.
- The spit must have a constant supply of material, from deposition, or else it will be eroded away.
A spit is also known as a …
Spurn head
What are the four human activities that occur at the coast?
Residential
Tourism
Transport
Industry
Give a definition of residential activities at the coast and understand its conflicting nature in relation to the other activities at the coast
People like living beside the sea and there is a huge demand for houses with access to the sea and sea views. People who already live there want the area to remain attractive, they want employment opportunities and not just investment in tourist facilities. They do not want many more houses making the area overcrowded and creating empty holiday homes.
Residential - People living in towns/cities
Give a definition of tourism activities at the coast and understand its conflicting nature in relation to the other activities at the coast
Tourism is a fast growing source of employment and there is an ever-increasing demand for hotels, restaurants, accommodation, entertainment and things for tourists to do whilst on holiday. However, many residents do not want more tourists, as this can also bring increased crime, vandalism, pollution and congestion in small places.
Tourism - Holidays and days out
Give a definition of transport activities at the coast and understand its conflicting nature in relation to the other activities at the coast
The more people who live in a place, then the more transportation links are needed for that area. Ships are the most obvious way to transport people and material at the coast but this may require new facilities and infrastructure to be built at a huge cost. Boats can cause pollution which might affect the leisure users of the beaches.
Transport - Roads, railways, harbours/ports
Give a definition of industrial activities at the coast and understand its conflicting nature in relation to the other activities at the coast
Some industries use the coast.
Sand can be extracted from beaches and used in building.
Oil refineries and sewage treatment works can be built.
Sea water can be used to cool power stations.
However, most industrial land uses at the coast are unattractive, and tourists and residents are often unhappy about their development.
Industry - Oil, fishing, shipbuilding
Past Paper Question 2017 Unit 1 c) ii)
Name the process by which material is left behind on a beach due to a lack of wave energy.
Deposition
Name a stretch of coastline
Costa del Sol
Give three reasons why a stretch of coastline may need to be protected against erosion
There may be a sandy beach along the coast which needs to be maintained to attract tourists.
There may be hotels along the coast which need to be maintained to attract tourists.
The coastline may have valuable buildings such as an oil terminal which needs to be protected.
List all of the engineering strategies used for coastal management
Sea walls
Groynes
Gabions
Beach nourishment
What is the aim of sea walls?
To keep the sea out.
What is the aim of groynes, gabions and beach nourishment?
To retain cliffs and beaches.
Provide a description of sea walls
- A solid wall that separates the land from the sea.
- This is a traditional ‘hard engineering’ method usually constructed of concrete.
- It supports the land while holding back the sea.
- The wave action can beat against the sea wall without eroding the coast.
- It can be designed to absorb and deflect wave energy.
Provide an evaluation of sea walls
- Sea walls can be expensive (over £10,000 per metre).
- They need very deep foundations so that they do not erode away.
- They can sometimes be an ugly addition to a beautiful area.
- They can reflect wave energy back into the sea, which can cause erosion further out to sea or somewhere else along the coastline.
- Sometimes sea walls can actually cause the removal of a beach.
- They might need to be replaced every 25-30 years.
Provide a description of groynes
- Groynes are wooden, concrete or rock barriers that can be built out into the sea.
- They can trap the sand carried by longshore drift and help to increase the build up of of a deposition beach.
- Usually these are seen as ‘hard engineering’ but it depends on the material being used. Some consider them to be ‘soft’ measures as they enhance the existing beach.
Provide an evaluation of groynes
- Groynes can trap sediment that is supposed to be going to another place along the coastline. This means that another area of the coastline is going to be more vulnerable to erosion.
- They are very cost effective.
- They need continual maintenance and replaced regularly.
- Some people see groynes as unattractive and an obstacle for people who like to walk along the beach.
Provide a description of gabions
- Gabions are metal cages that are filled with rocks.
- They are usually stacked together to create a wall of rock.
- As the waves crash against the gabion cages, the energy of the water is forced between the spaces in the rocks and the energy is absorbed inside the cage. This stops the cliffs from taking the brunt of the erosion.
- Water then percolates through the rocks and back into the sea.
Provide an evaluation of gabions
- Gabions can be a good short term solution. However, they rarely make an effective long term solution, as the cages can split and release the rocks inside, which can be used by the waves to erode the coast.
- They can be relatively cheap to build (as little as £11 per metre).
- The cages are often described as unattractive.
- The cages and rocks can trap debris and pollution, which can rot leaving bad smells and health concerns.
- The cages can provide an ideal habitat for rats.
Provide a description of beach nourishment
- This is when sand or pebbles are added to a beach, replenishing it or building it up.
- It is technically a ‘soft engineering’ solution but this depends on where the material is coming from. Soft engineering should not change the structure of the beach through building work. However, the size of the beach is often increased as the beach is made much wider.
- A large, wide beach naturally protects the coastline because the wave energy is absorbed through the sand.
Provide an evaluation of beach nourishment
- The sand used must be of similar quality to the existing beach material so that it can integrate with the natural processes occurring there, without causing any adverse effects.
- Sometimes beach nourishment is used alongside groyne schemes.
- Nourishment requires constant maintenance and will need constant recharging of the beach material.
- It can be expensive at between £5,000 and £20,000 per 100m.
Case Study: Sustainable Coastal Management Strategy, from within the British Isles.
Give the name of the stretch of coast you are investigating and the three engineering strategies used to protect the coastline.
Newcastle, Co. Down
Groynes
Sea wall
Gabions
Case Study: Sustainable Coastal Management Strategy
Evaluate the advantages and disadvantages of the engineering strategies used, and include at least two facts and figures.
Groynes, concrete 1980s
+ Trap sand, protect beach —> Tourists like
- Only lasted 20 years, decayed —> Need replaced (expensive)
Sea Wall, Victorian 1800s
+ Protected hotels/B&Bs
- Washed away 2002, can be eroded and is expensive to replace (£4 million)
- New one 2002, curved reflects but erodes beach, which tourists don’t like, leading to less income
Gabions, Mouth of the Shimna 2006
+ Protects recreational land, important for tourism
+ Breaks wave energy, allowing pedestrians to use footbridge
- Earlier gabions decay, replacing is expensive
Unit 1 2017
State the meaning of the term floodplain. [2]
An area of flat land on either side of the river that holds flood water.
An area of flat land either side of the river, made up of alluvium.
Unit 1 2017
b)i) Name one land use on this spit. [1]
Visitor centre Natural reserve Non-coniferous wood Track/path/other road Golf course/club house Parking/buildings Sand dunes Wind pump/wind turbine Pond
Unit 1 2017
d)iii) Explain the impact on both stores and transfers within the drainage basin if trees are cut down. [4]
If trees are to be removed, this will reduce the interception layer. Water will infiltrate into the ground more quickly leading to an increase in surface run off. This will increase the discharge of the river and the possibility of a flood occurring.
