COASTAL SYSTEMS AND LANDSCAPES
The coast as an open system
The coast has inputs that originate from outside the system (such as sediment carried into the coastal zone by rivers) and
outputs to other natural systems (such as eroded rock material transported offshore to the ocean). As an open system, the coast
has important links with other natural systems such as the atmosphere (the importance of the wind generating waves),
tectonics, ecosystems and oceanic systems. These natural systems are linked together by flows of energy and by the transfer of
material.
Sources of energy in the coastal environment
The sun- The primary source of energy for all-natural systems is the sun. Heat and light from the sun is converted by natural
processes (such as photosynthesis) to form energy. At the coast, the main form of energy is derived from the sea in the form of
waves. Although waves can be generated by tectonic activity or underwater landslides creating tsunami, they are mostly formed
by the wind.
The wind – Wind moves from high pressure to low pressure. Variations in atmospheric pressure primarily reflect differences
between two places – called the pressure gradient – the faster (stronger) the wind.
A number of factors affect wave energy:-
- The strength of the wind (pressure gradient)
- The duration of the wind (the longer the wind blows, the more powerful the waves will become)
- The fetch (the distance of open water over which the wind blows) The longer the fetch, the more powerful the waves.
How are waves formed?
As air moves across the water, frictional drag disturbs the surface and forms ripples or waves. In the open sea, there is little
horizontal movement of water. Instead there is an orbital motion of the water particles. Close to the coast, horizontal
movement of water does occur as waves are driven onshore to break on the beach.
1. The water becomes shallower
and the circular orbit of the water
particles changes to an elliptical
shape.
2. The wavelength and velocity both
decrease, and the wave height
increases – causing water to back
up from behind and rise to a point
where it starts to topple (break).
3. The water rushes up the beach as
swash and retreats as backwash.
Currents
A high tidal range creates relatively powerful tidal currents (important sources of energy) as tides rise and fall, which can be
particularly strong in estuaries and narrow channels. These currents are important transfer mechanisms in transporting
sediment either within the coastal system or beyond through an output.
RIP CURRENTS – strong localised underwater currents that occur on some beaches. Rip currents are commonly formed when a
series of plunging waves cause a temporary build-up of water at the top of the beach. Met with resistance from the breaking
waves, water returning down the beach (backwash) is forced just below the surface following troughs and small undulations in
the beach profile.
Low energy coastlines
In contrast, sandy and estuarine coasts are generally indicative of low-energy environments. In the UK these tend to be :
o Stretches of the coast where the waves are less powerful or where the coast is sheltered from large waves (such as the
estuaries and the bays of Lincolnshire)
o Where the rate of deposition exceeds erosion
Landforms such as beaches, spits and coastal plains tend to be found in these environments.
High energy coastlines
Rocky coasts are generally found here. In the UK these tend to be:
o Stretches of the Atlantic-facing coast, where the waves are powerful for much of the year (such as Cornwall)
o Where the rate of erosion exceeds the rate of deposition
,Erosional landforms such as headlands, cliffs and wave-cut platforms (abrasion platforms) tend to be found here
Sources of Sediment
The main sediment sources are as follows:
o Rivers: vast majority of coastal sediment, especially in high rainfall environments where active river erosion occurs.
Sediment will be reworked by waves, tides and currents
o Cliff Erosion: important locally in areas of relatively soft or unconsolidated rocks.
o Longshore drift: sediment is transported from one stretch of the coastline (output) to another stretch of coastline (as
an input).
o Wind: in glacial or hot arid environments, wind-blown sand can be deposited in coastal regions.
o Glaciers: Ice shelves calve into the sea, depositing sediment trapped within the ice.
o Offshore: sediment from offshore can be transferred into the coastal (littoral) zone by waves, tides and currents. Storm
surges associated with tropical cyclones and tsunamis waves can also be responsible for inputs of sediment into the
coastal system.
Sediment Cells
A sediment cell is a stretch of coastline where the movement of sediment is mostly contained. It is technically a closed system;
however, the boundaries aren’t 100% closed off and therefore dissolved minerals or load transported during heavy storms or
human impact can overflow into other sediment cells and therefore defy the term “closed”. Here, there are very clear inputs of
sediment (rivers or cliffs), transfers (longshore drift), stores (beaches and spits) and outputs (into the deeper ocean).
There are 11 sediment cells in England and Wales, an example being Flamborough Head to the Wash.
Sediment Budgets
Material in a sediment cell can be considered in the form of a “sediment budget”, with losses and gains. Losses are often things
such as deposition into sediment sinks while gains are more coastal erosion or sediment brought into the system through rivers
or from offshore sources. In principle, the sediment budget seeks to achieve a state of dynamic equilibrium where erosion and
deposition are balanced.
Weathering
Weathering is the breakdown or disintegration of rock in situ (its original place) at or close to the ground surface. Energy flows can be clearly
demonstrated as most processes involve (directly or indirectly) energy transfer from the sun, in the form of radiation or rain.
If the rate of debris removal exceeds the rate of weathering or mass movement then a positive feedback may operate.
If debris removal is slow and ineffective, this will lead to a build-up of an apron of debris (scree) that reduces the exposure of the cliff
face as it extends up the cliff face. Weathering and mass movement rates will decrease (Negative feedback)
Mechanical (Physical) Weathering- The break-up of rocks without any chemical changes taking place.
Frost-Shattering (Freeze Thaw)
Salt Crystallisation
Wetting and Drying
Raindrop Impact
Hydration
Thermal Expansion
Pressure Release
Biological Weathering – breakdown of rocks by organic activity.
Humic Acid
Biological
Chemical Weathering – chemical reaction where salts may be dissolved.
Carbonation, Oxidation, Hydrolysis, Solution
Mass Movement
The downhill movement of material under the influence of gravity is known as mass movement. It can range from being
extremely slow (soil creep) to horrifyingly fast (rockfall and landslide). Mass movement as the coat is very common – the sheer
weight of rainwater, combined with weak geology is the major cause of cliff collapse.
Mass movement forms an important group of processes and flows within the coastal system, transferring both energy (in
response to gravity) and sediment. The sediment forms an input to shoreline processes, forming the “tools” for erosion and
providing material to be transported and deposited elsewhere along the coastline. Mass movement, along with cliff erosion
provides an important input to sediment cells.
Coastal Erosion
,Coastal erosion plays a vital role in the coastal system, removing debris from the foot of cliffs and providing an input into coastal
sediment cells. Coastal erosion is a manifestation of the energy of the Sun, converted by the power of the wind into waves
capable of sculpting landforms and eroding sediment.
Factors affecting coastal erosion:
Waves- The rate and type of erosion experienced on a particular stretch of coast is primarily influenced by the size and type of
waves that reach the coast. At winter destructive waves are at their largest and most powerful state.
Rock type (lithology) – physical strength and chemistry of rock is important. Hard rock and soft rock erode at different rates
(DIFFERENTIAL EROSION).
Geological structure – cracks, joints, bedding planes and faults create weaknesses in a cliff that can be exploited by erosive
processes.
Presence/absence of a beach – Beaches absorb wave energy.
Subaerial processes- weathering and mass movement will weaken cliffs and creates piles of debris that are easily eroded.
Coastal Management – The presence of structures will decrease erosion.
Longshore (Littoral) Drift
Longshore drift is an important transfer (flow) mechanism as it is responsible for moving vast amounts of sediment along the
coastline and eventually out to sea (for example on the tip of a spit). It is a very important component in a sediment cell and, if
interrupted by management strategies, can lead to distortions of natural patterns, depriving beaches of material and
exacerbating erosion.
Swash comes in at an angle but
backwash returns at a right angle.
Landforms of coastal deposition
Barrier Beaches (bars)
Where a beach or spit extends across a bay to join two headlands, it forms a BARRIER BEACH or BAR. Barrier beaches and bars
can also trap water behind them to form lagoons, such as SLAPTON LEY.
Where a beach becomes separated from the mainland. It is referred to as a BARRIER ISLAND. Barrier islands vary in scale and
form – are usually sand or shingle features – and are common in areas with low tidal ranges, where the offshore coastline is
gently sloping. Large-scale barrier islands can be found along the coast of the Netherlands and in the North America along the
South Texas coast. Barrier islands are offshore bars that are built up above high tide level, to create a platform that is eventually
that of an island and therefore gaining the name as a “Barrier Island”.
Offshore bar/sandbars
Offshore bars are submerged (or partly exposed) ridges of sand or coarse sediment created by waves offshore from the coast.
Destructive waves erode sand from the beach with their strong backwash and deposit it offshore. Offshore bars act as sediment
sinks and, potentially, sediment input stores. They can absorb wave energy thereby reducing the impacts of waves on the
coastline.
Tombolo
A tombolo is a beach (or ridge of sand and shingle) that has formed between a small island and the mainland. Deposition occurs
where waves lose their energy, and the tombolo begins to build up. Tombolos may be covered at high tide (for example the
Shetland Islands and Chesil Beach). This is due to wave refraction around a headland that creates that curved spit that the
tombolo forms from and also the wave refraction from either side of the island that it is connecting to, causing deposition to
allow that spit to rather turn into that tombolo and connecting piece of land.
Spits
A spit is a long, narrow feature, made of sand or shingle that extends from the land into the sea (or part of the way across an
estuary). Spits form on drift-aligned beaches. Sand or shingle is moved along the coast by longshore drift but if the coastline
suddenly changes direction (eg because of a river estuary), sediment begins to build up across the estuary mouth and a spit will
form. The outward flow of the river will prevent the spit from extending right across the estuary mouth. The end of the spit will
also begin to curve round (recurved lateral) as wave refraction carries material round into the more sheltered water behind the
spit. This can also be known as a recurved tip.
Estuarine mudflats and saltmarshes
River estuaries are important sediment stores (sinks) where huge quantities of river sediment are deposited in water close to
the edges of the river, away from the faster tidal currents that scour the channels. Rising tides create a buffer to the river flow,
slowing velocity and leading to considerable deposition. Most of the sediment that accumulates here is mud, due to the low
velocities and, over time, expansive MUDFLATS can form that then develop into SALTMARSHES.
Saltmarshes are areas of flat, silty sediments that accumulate around estuaries or lagoons. They develop in 3 types of
environment:
, 1. In sheltered areas where deposition occurs (lee of a spit)
2. Where salt and freshwater meet (estuaries)
3. Where there are no strong tides or currents to prevent sediment deposition and accumulation
Saltmarshes are covered at high tide and are exposed at low tide. They are common around the coast of Britain and, as with
sand dunes, develop over time exhibiting a clear vegetation succession.
Mud is deposited close to the high-tide line, dropping out of the water by a process known as FLOCCULATION. This
involves the tiny individual particles of clay (mud) sticking together such that their combined mass enables them to sink
to the seabed.
Pioneer plants such as EELGRASS and CORDGRASS start to colonise the transition zone between high and low tide.
These plants can tolerate inundation by salty water and they also help to trap further deposits of mud.
Gradually, the mud level rises above high tide and a lower saltmarsh develops with a wider range of plants that no
longer need to be so well adapted to salty conditions.
Soil conditions improve and the vegetation succession continues to form a meadow.
Eventually, shrubs and trees will colonise the area as the succession reaches its climatic climax.
As mud flats develop, salt-tolerant plants such as EEL GRASS begin to colonise and stabilise these flats.
HALOPHYLETS (salt tolerant species) such as GLASSWORT and CORDGRASS help to slow tidal flow and trap more mud
and silt.
As sediment accumulates, the surface becomes drier. Different plants begin to colonise (such as SEA ASTERS and
MEADOW GRASS).
Creeks (created by water flowing across the estuary at low tide) divide up the salt marsh.
Submergent coastal landforms:
Fjords are formed when deep glacial troughs are flooded by a rise in sea level. They are long and steep-sided with a U shaped
cross section and hanging valleys. Unlike rias, fjords are much deeper inland than they are at the coast. The shallower entrance
marks where the glacier left the valley. Fjords can be found in Norway.
Recent and predicted climatic change and potential impact on coasts:
Evidence of past sea levels:
1. Shoreline deposits such as shells, wood and peat are found in marine cores.
2. Exposed outcrops of rock containing marine fossils.
3. Vegetated tidal flats above the high water mark.
4. Exposed coral reefs
5. Marine rocks displaying evidence of wind-borne erosion
Consequences of rising sea levels:
- Accelerated erosion of cliffs and beaches
- Flooding of urban areas through inundation and storm surges
- Salinisation of agricultural land
- Widespread destruction of habitats especially coastal marshes
Responses to the threat of a rise in sea levels:
- Boulder ramparts to reduce cliff erosion
- Sea walls
- Artificial raising of land behind walls
- Groynes
- Construction of under cliff promenades
- Soft engineering such as artificial beaches
- River barriers (Thames Barrier)
- Retreat (abandon land to sea to take stresses off of other areas)
- Increased investment into coastal defences
- Introduction of multi-cropping, maximising the use of available land which can also be very useful to reducing
greenhouse gas emissions due to biodiversity and increased plant coverage which could altogether also be a buffer to
surges, waves and other erosion.
- Upstream draining of dammed lakes to allow increased sediment supply to the deltas
- Artificially raising the land by pumping in sand dredged from the sea floor.
- Land reclamation projects/artificial beach emplacement such as the Essex March Realignment
Hard Engineering
1. Sea wall (£6000/m) A recurved concrete wall which reflects the energy of the waves.
2. Revetments (£4500/m) A sloped wall of wood that absorbs the wave energy. Need regular replacing.
The coast as an open system
The coast has inputs that originate from outside the system (such as sediment carried into the coastal zone by rivers) and
outputs to other natural systems (such as eroded rock material transported offshore to the ocean). As an open system, the coast
has important links with other natural systems such as the atmosphere (the importance of the wind generating waves),
tectonics, ecosystems and oceanic systems. These natural systems are linked together by flows of energy and by the transfer of
material.
Sources of energy in the coastal environment
The sun- The primary source of energy for all-natural systems is the sun. Heat and light from the sun is converted by natural
processes (such as photosynthesis) to form energy. At the coast, the main form of energy is derived from the sea in the form of
waves. Although waves can be generated by tectonic activity or underwater landslides creating tsunami, they are mostly formed
by the wind.
The wind – Wind moves from high pressure to low pressure. Variations in atmospheric pressure primarily reflect differences
between two places – called the pressure gradient – the faster (stronger) the wind.
A number of factors affect wave energy:-
- The strength of the wind (pressure gradient)
- The duration of the wind (the longer the wind blows, the more powerful the waves will become)
- The fetch (the distance of open water over which the wind blows) The longer the fetch, the more powerful the waves.
How are waves formed?
As air moves across the water, frictional drag disturbs the surface and forms ripples or waves. In the open sea, there is little
horizontal movement of water. Instead there is an orbital motion of the water particles. Close to the coast, horizontal
movement of water does occur as waves are driven onshore to break on the beach.
1. The water becomes shallower
and the circular orbit of the water
particles changes to an elliptical
shape.
2. The wavelength and velocity both
decrease, and the wave height
increases – causing water to back
up from behind and rise to a point
where it starts to topple (break).
3. The water rushes up the beach as
swash and retreats as backwash.
Currents
A high tidal range creates relatively powerful tidal currents (important sources of energy) as tides rise and fall, which can be
particularly strong in estuaries and narrow channels. These currents are important transfer mechanisms in transporting
sediment either within the coastal system or beyond through an output.
RIP CURRENTS – strong localised underwater currents that occur on some beaches. Rip currents are commonly formed when a
series of plunging waves cause a temporary build-up of water at the top of the beach. Met with resistance from the breaking
waves, water returning down the beach (backwash) is forced just below the surface following troughs and small undulations in
the beach profile.
Low energy coastlines
In contrast, sandy and estuarine coasts are generally indicative of low-energy environments. In the UK these tend to be :
o Stretches of the coast where the waves are less powerful or where the coast is sheltered from large waves (such as the
estuaries and the bays of Lincolnshire)
o Where the rate of deposition exceeds erosion
Landforms such as beaches, spits and coastal plains tend to be found in these environments.
High energy coastlines
Rocky coasts are generally found here. In the UK these tend to be:
o Stretches of the Atlantic-facing coast, where the waves are powerful for much of the year (such as Cornwall)
o Where the rate of erosion exceeds the rate of deposition
,Erosional landforms such as headlands, cliffs and wave-cut platforms (abrasion platforms) tend to be found here
Sources of Sediment
The main sediment sources are as follows:
o Rivers: vast majority of coastal sediment, especially in high rainfall environments where active river erosion occurs.
Sediment will be reworked by waves, tides and currents
o Cliff Erosion: important locally in areas of relatively soft or unconsolidated rocks.
o Longshore drift: sediment is transported from one stretch of the coastline (output) to another stretch of coastline (as
an input).
o Wind: in glacial or hot arid environments, wind-blown sand can be deposited in coastal regions.
o Glaciers: Ice shelves calve into the sea, depositing sediment trapped within the ice.
o Offshore: sediment from offshore can be transferred into the coastal (littoral) zone by waves, tides and currents. Storm
surges associated with tropical cyclones and tsunamis waves can also be responsible for inputs of sediment into the
coastal system.
Sediment Cells
A sediment cell is a stretch of coastline where the movement of sediment is mostly contained. It is technically a closed system;
however, the boundaries aren’t 100% closed off and therefore dissolved minerals or load transported during heavy storms or
human impact can overflow into other sediment cells and therefore defy the term “closed”. Here, there are very clear inputs of
sediment (rivers or cliffs), transfers (longshore drift), stores (beaches and spits) and outputs (into the deeper ocean).
There are 11 sediment cells in England and Wales, an example being Flamborough Head to the Wash.
Sediment Budgets
Material in a sediment cell can be considered in the form of a “sediment budget”, with losses and gains. Losses are often things
such as deposition into sediment sinks while gains are more coastal erosion or sediment brought into the system through rivers
or from offshore sources. In principle, the sediment budget seeks to achieve a state of dynamic equilibrium where erosion and
deposition are balanced.
Weathering
Weathering is the breakdown or disintegration of rock in situ (its original place) at or close to the ground surface. Energy flows can be clearly
demonstrated as most processes involve (directly or indirectly) energy transfer from the sun, in the form of radiation or rain.
If the rate of debris removal exceeds the rate of weathering or mass movement then a positive feedback may operate.
If debris removal is slow and ineffective, this will lead to a build-up of an apron of debris (scree) that reduces the exposure of the cliff
face as it extends up the cliff face. Weathering and mass movement rates will decrease (Negative feedback)
Mechanical (Physical) Weathering- The break-up of rocks without any chemical changes taking place.
Frost-Shattering (Freeze Thaw)
Salt Crystallisation
Wetting and Drying
Raindrop Impact
Hydration
Thermal Expansion
Pressure Release
Biological Weathering – breakdown of rocks by organic activity.
Humic Acid
Biological
Chemical Weathering – chemical reaction where salts may be dissolved.
Carbonation, Oxidation, Hydrolysis, Solution
Mass Movement
The downhill movement of material under the influence of gravity is known as mass movement. It can range from being
extremely slow (soil creep) to horrifyingly fast (rockfall and landslide). Mass movement as the coat is very common – the sheer
weight of rainwater, combined with weak geology is the major cause of cliff collapse.
Mass movement forms an important group of processes and flows within the coastal system, transferring both energy (in
response to gravity) and sediment. The sediment forms an input to shoreline processes, forming the “tools” for erosion and
providing material to be transported and deposited elsewhere along the coastline. Mass movement, along with cliff erosion
provides an important input to sediment cells.
Coastal Erosion
,Coastal erosion plays a vital role in the coastal system, removing debris from the foot of cliffs and providing an input into coastal
sediment cells. Coastal erosion is a manifestation of the energy of the Sun, converted by the power of the wind into waves
capable of sculpting landforms and eroding sediment.
Factors affecting coastal erosion:
Waves- The rate and type of erosion experienced on a particular stretch of coast is primarily influenced by the size and type of
waves that reach the coast. At winter destructive waves are at their largest and most powerful state.
Rock type (lithology) – physical strength and chemistry of rock is important. Hard rock and soft rock erode at different rates
(DIFFERENTIAL EROSION).
Geological structure – cracks, joints, bedding planes and faults create weaknesses in a cliff that can be exploited by erosive
processes.
Presence/absence of a beach – Beaches absorb wave energy.
Subaerial processes- weathering and mass movement will weaken cliffs and creates piles of debris that are easily eroded.
Coastal Management – The presence of structures will decrease erosion.
Longshore (Littoral) Drift
Longshore drift is an important transfer (flow) mechanism as it is responsible for moving vast amounts of sediment along the
coastline and eventually out to sea (for example on the tip of a spit). It is a very important component in a sediment cell and, if
interrupted by management strategies, can lead to distortions of natural patterns, depriving beaches of material and
exacerbating erosion.
Swash comes in at an angle but
backwash returns at a right angle.
Landforms of coastal deposition
Barrier Beaches (bars)
Where a beach or spit extends across a bay to join two headlands, it forms a BARRIER BEACH or BAR. Barrier beaches and bars
can also trap water behind them to form lagoons, such as SLAPTON LEY.
Where a beach becomes separated from the mainland. It is referred to as a BARRIER ISLAND. Barrier islands vary in scale and
form – are usually sand or shingle features – and are common in areas with low tidal ranges, where the offshore coastline is
gently sloping. Large-scale barrier islands can be found along the coast of the Netherlands and in the North America along the
South Texas coast. Barrier islands are offshore bars that are built up above high tide level, to create a platform that is eventually
that of an island and therefore gaining the name as a “Barrier Island”.
Offshore bar/sandbars
Offshore bars are submerged (or partly exposed) ridges of sand or coarse sediment created by waves offshore from the coast.
Destructive waves erode sand from the beach with their strong backwash and deposit it offshore. Offshore bars act as sediment
sinks and, potentially, sediment input stores. They can absorb wave energy thereby reducing the impacts of waves on the
coastline.
Tombolo
A tombolo is a beach (or ridge of sand and shingle) that has formed between a small island and the mainland. Deposition occurs
where waves lose their energy, and the tombolo begins to build up. Tombolos may be covered at high tide (for example the
Shetland Islands and Chesil Beach). This is due to wave refraction around a headland that creates that curved spit that the
tombolo forms from and also the wave refraction from either side of the island that it is connecting to, causing deposition to
allow that spit to rather turn into that tombolo and connecting piece of land.
Spits
A spit is a long, narrow feature, made of sand or shingle that extends from the land into the sea (or part of the way across an
estuary). Spits form on drift-aligned beaches. Sand or shingle is moved along the coast by longshore drift but if the coastline
suddenly changes direction (eg because of a river estuary), sediment begins to build up across the estuary mouth and a spit will
form. The outward flow of the river will prevent the spit from extending right across the estuary mouth. The end of the spit will
also begin to curve round (recurved lateral) as wave refraction carries material round into the more sheltered water behind the
spit. This can also be known as a recurved tip.
Estuarine mudflats and saltmarshes
River estuaries are important sediment stores (sinks) where huge quantities of river sediment are deposited in water close to
the edges of the river, away from the faster tidal currents that scour the channels. Rising tides create a buffer to the river flow,
slowing velocity and leading to considerable deposition. Most of the sediment that accumulates here is mud, due to the low
velocities and, over time, expansive MUDFLATS can form that then develop into SALTMARSHES.
Saltmarshes are areas of flat, silty sediments that accumulate around estuaries or lagoons. They develop in 3 types of
environment:
, 1. In sheltered areas where deposition occurs (lee of a spit)
2. Where salt and freshwater meet (estuaries)
3. Where there are no strong tides or currents to prevent sediment deposition and accumulation
Saltmarshes are covered at high tide and are exposed at low tide. They are common around the coast of Britain and, as with
sand dunes, develop over time exhibiting a clear vegetation succession.
Mud is deposited close to the high-tide line, dropping out of the water by a process known as FLOCCULATION. This
involves the tiny individual particles of clay (mud) sticking together such that their combined mass enables them to sink
to the seabed.
Pioneer plants such as EELGRASS and CORDGRASS start to colonise the transition zone between high and low tide.
These plants can tolerate inundation by salty water and they also help to trap further deposits of mud.
Gradually, the mud level rises above high tide and a lower saltmarsh develops with a wider range of plants that no
longer need to be so well adapted to salty conditions.
Soil conditions improve and the vegetation succession continues to form a meadow.
Eventually, shrubs and trees will colonise the area as the succession reaches its climatic climax.
As mud flats develop, salt-tolerant plants such as EEL GRASS begin to colonise and stabilise these flats.
HALOPHYLETS (salt tolerant species) such as GLASSWORT and CORDGRASS help to slow tidal flow and trap more mud
and silt.
As sediment accumulates, the surface becomes drier. Different plants begin to colonise (such as SEA ASTERS and
MEADOW GRASS).
Creeks (created by water flowing across the estuary at low tide) divide up the salt marsh.
Submergent coastal landforms:
Fjords are formed when deep glacial troughs are flooded by a rise in sea level. They are long and steep-sided with a U shaped
cross section and hanging valleys. Unlike rias, fjords are much deeper inland than they are at the coast. The shallower entrance
marks where the glacier left the valley. Fjords can be found in Norway.
Recent and predicted climatic change and potential impact on coasts:
Evidence of past sea levels:
1. Shoreline deposits such as shells, wood and peat are found in marine cores.
2. Exposed outcrops of rock containing marine fossils.
3. Vegetated tidal flats above the high water mark.
4. Exposed coral reefs
5. Marine rocks displaying evidence of wind-borne erosion
Consequences of rising sea levels:
- Accelerated erosion of cliffs and beaches
- Flooding of urban areas through inundation and storm surges
- Salinisation of agricultural land
- Widespread destruction of habitats especially coastal marshes
Responses to the threat of a rise in sea levels:
- Boulder ramparts to reduce cliff erosion
- Sea walls
- Artificial raising of land behind walls
- Groynes
- Construction of under cliff promenades
- Soft engineering such as artificial beaches
- River barriers (Thames Barrier)
- Retreat (abandon land to sea to take stresses off of other areas)
- Increased investment into coastal defences
- Introduction of multi-cropping, maximising the use of available land which can also be very useful to reducing
greenhouse gas emissions due to biodiversity and increased plant coverage which could altogether also be a buffer to
surges, waves and other erosion.
- Upstream draining of dammed lakes to allow increased sediment supply to the deltas
- Artificially raising the land by pumping in sand dredged from the sea floor.
- Land reclamation projects/artificial beach emplacement such as the Essex March Realignment
Hard Engineering
1. Sea wall (£6000/m) A recurved concrete wall which reflects the energy of the waves.
2. Revetments (£4500/m) A sloped wall of wood that absorbs the wave energy. Need regular replacing.
