GEOGRAPHY - Coastal Environments

Wave Action & Erosion

• Coasts are the meeting point of land and sea and are an open system with inputs (sediment), transfers (longshore drift), stores (beach) and outputs (water). 

• Coastal processes are divided into two parts:

  • Marine processes: offshore (water-based)

  • Terrestrial processes: onshore (land-based)

• These processes are then sub-divided into:

  • Wave action

  • Erosion

  • Transportation

  • Weathering

  • Mass movement

• It is these activities that are responsible for producing distinctive landforms found on the coast

Wave Action

• Waves are marine processes. They erode, transport and deposit material

• Waves are formed by winds blowing over the surface of the sea 

• The height and strength of a wave is dependent on 3 factors:

  • The fetch 

  • The amount of time the wind blows

  • The strength of the wind

• The greater the strength, time and fetch of the wind, the larger the wave

• As a wave approaches the coast and enters shallower water, friction from the sea bed causes the wave to lean forward and eventually crest and break onto the beach 

• The movement of water up the beach is called the swash, and the return movement is the backwash

Types of Waves

• There are two types of waves:

  • Destructive waves erode the beach

  • Constructive waves are beach builders

Comparison of Wave Type

Erosion

• Destructive waves erode the coastline in four ways:

  • Hydraulic Action 

  • Attrition

  • Corrosion 

  • Abrasion 

Transportation

• Material arrives from:

  • Eroded cliffs

  • Longshore drift 

  • Constructive waves

  • River discharge

• In the water, material is moved through:

  • Traction 

  • Saltation

  • Suspension

  • Solution 

Longshore Drift

• It is the main process of deposition and transportation along the coast 

• The prevailing wind pushes the waves at angle to the beach

• As the waves break, the swash carries material up the beach at the same angle

• As the swash retreats, the backwash carries the material down the beach at right angles (90°) 

• The process repeats, transporting material along the beach in a zig-zag movement

Weathering

• This is the breakdown of rock in-situ. Weathering does not involve the movement of material, making it different from erosion

• Sub-aerial weathering describes coastal processes that are not linked to the action of the sea

• It includes:

  • Freeze-thaw weathering (mechanical)

  • Salt weathering

• Weathering weakens cliffs and makes them more vulnerable to erosion

• Mechanical weathering physically breaks up rock:

  • One example is freeze-thaw or frost shattering

    •  Water gets into cracks and joints in the rock

    •  When the water freezes it expands and the cracks open a little wider

    •  Over time, pieces of rock split off the rock face, whilst big boulders are broken into smaller rocks and gravel

• Chemical weathering occurs when rocks are broken down by a chemical process:

  • Rainwater is slightly acidic through absorbing carbon dioxide from the atmosphere

  • This reacts with minerals in the rock, creating new material

  • Rock-type affects the rate of weathering; e.g. limestone chemically weathers faster than granite

  • The warmer the temperature, the faster the chemical reaction

• Biological weathering takes place when rocks are worn away by living organisms:

  • Trees and other plants can grow within the cracks in a rock formation

    • As the roots grow bigger, they push open cracks in the rocks, making them wider and deeper

    • Over time, the growing tree eventually forces the rock apart

  • Tiny organisms like bacteria, algae and moss can grow on rocks

    • These produce chemicals that break down the surface layer of the rock

  • Burrowing animals, such as rabbits, disturb the ground 

    • This destabilises the rock above the burrow

    • Increasing pressure on any cracks

    • Eventually, pieces fall off the rock

Mass Movement

Mass Movement

• The downhill movement of material under the influence of gravity

• Throughflow and runoff caused by heavy rain can also make cliffs more unstable and increase the likelihood of mass movement

• It includes landslides, slumping and rockfalls

What influences the type of movement?

• The angle of slope (steeper is faster)

• Nature of regolith

• Amount and type of vegetation

• Water

• Type and structure of rock

• Human activity

• Climate

Types of movement

• Soil Creep:

  • Speed is below 1cm per year

  • Common in humid climates 

  • When soil expands, individual particles are lifted up at right angles to the slope

  • Soil also expands when it freezes, gets wet or is heated up in the sun

  • When the soil shrinks again, the particles fall straight back down

  • Soil creep takes a long time because the soil moves only a millimetre to a few centimetres at a time

• Flow:

  • It occurs on slopes between 5° and 15°

  • Usually, after the soil has become saturated with a flow of water across the surface

  • Vegetation can be flattened and carried away with the soil

  • Speeds range from 1 to 15km per year

• Slide:

  • A movement of material 'en masse' which remains together until hitting the bottom of a slope

• Fall:

  • Slopes are steep and movement is rapid

  • Caused by a number of reasons:

    • Extreme weathering—freeze-thaw action—can loosen rocks that become unstable and collapse

    • Rainfall: too much rain will soften the surface, leading to the collapse of the slope

    • Earthquakes can dislodge unstable rocks 

    • Hot weather can dry out soil, causing it to shrink and allowing rocks to fall

• Slump:

  • Usually found on weaker rock types (i.e. clay) that become saturated and heavy

  • This is common at the coast and is also known as rotational slip

  • It involves a large area of land moving down the slope in one piece

  • Due to the nature of the slip, it leaves behind a curved surface

Erosional Landforms

Headland and bay 

• Found in areas of alternating bands of resistant (hard) and less resistant (soft) rocks running perpendicular to oncoming waves (discordant coastline)

• Initially, less resistant rock (e.g. clay) is eroded back, forming a bay

• A bay is an inlet of the sea where the land curves inwards, usually with a beach

• The more resistant rock (e.g. limestone) is left protruding out to sea as a headland

Headland and bay formation

Cove

• A cove forms where the coastline has bands of resistant and less resistant rock running parallel to the oncoming waves (concordant coastline)

• There is usually a band of resistant rock facing the oncoming waves, with a band of softer rock behind

• Wave processes of abrasion, corrosion and hydraulic action will exploit faults in the resistant rock and erode through to the softer rock 

• Further wave action will erode the softer rock quickly, which will leave behind a circular cove with a narrow entrance to the sea

• Wave refraction within the cove spreads out the erosion in all directions, creating the typical horseshoe shape

• Lulworth Cove in Dorset, UK, is a good example of a cove

The formation of coves

Cliff and wave-cut platform

• Cliffs are shaped through erosion and weathering processes

• Less resistant rock erodes quickly and will form sloping cliff faces

• Steep cliffs are formed where there is harder rock facing the sea

• A wave-cut platform is a wide gently sloped surface found at the foot of a cliff:

  • As the sea attacks the base of a cliff between the high and low water mark, a wave-cut notch is formed

  • Abrasion, corrosion and hydraulic action further extend the notch back into the cliff

  • The undercutting of the cliff leads to instability and collapse of the cliff

  • The backwash of the waves, carries away the eroded material, leaving behind a wave-cut platform

  • The process repeats and the cliff continues to retreat, leading to a coastal retreat

The formation of cliffs and wave-cut platforms

Cave, arch, stack and stump

• Found on a headland due to wave action and sub-aerial weathering

• Any weaknesses in the headland are exploited by erosional processes of hydraulic action, abrasion and corrosion

• As the crack begins to widen, abrasion will begin to wear away at the forming cave

• The cave will become larger and eventually break through the headland to form an arch

• The base of the arch continually becomes wider and thinner through erosion below and weathering from above

• Eventually, the roof of the arch collapses, leaving behind an isolated column of rock called a stack

• The stack is undercut at the base by wave action and sub-aerial weathering above until it collapses to form a stump

Stack formation

Depositional Landforms

Beach

• Form in sheltered areas such as bays

• Deposition occurs through constructive wave movement, where the swash is stronger than the backwash

• Beach formation usually occurs in the summer months when the weather is calmer

• Sometimes sand from offshore bars can blow onto the shore by strong winds

• Blown sand can create sand dunes at the backshore of a beach

Spit

• An extended stretch of sand or shingle that extends out to sea from the shore

• Spits occur when there is a change in the shape of the coastline

• Or the mouth of a river, which prevents a spit from forming across the estuary

• A spit may or may not have a 'hooked' end, depending on opposing winds and currents

• A good example is Spurn Point, which stretches for three and a half miles across the Humber Estuary in the northeast of England

Stages of Formation:

• Sediment is transported by longshore drift

• Where the coastline changes direction, a shallow, sheltered area allows for deposition of sediment

• Due to increased friction, more deposition occurs 

• Eventually, a spit slowly builds up to sea level and extends in length

• If the wind changes direction, then the wave pattern alters and results in a hooked end

• The area behind the spit becomes sheltered

• Silts are deposited here to form salt marshes or mud flats

Spit formation

Bar

• When a spit grows across a bay, and joins two headlands together

• A bar of sand is formed (sandbar)

• Sandbars can also form offshore due to the action of breaking waves from a beach

Bar formation

Lagoon

• A lagoon is where a small body of water is cut off from the sea 

• A lagoon may form behind a bar or tombolo

• Lagoons do not last forever and may fill with sediment and form new land

Tombolo  

• A tombolo is formed when a spit joins the mainland to an island

• Chesil Beach in Dorset is a tombolo, as the mainland is joined to the Isle of Portland 

Barrier Island

• Barrier islands form parallel to the coast 

• The main difference between a bar and barrier island is that a bar joins two headlands, whereas a barrier island is open at one or both ends

Deposition landforms

Influence of Geology

• Geology shapes the coastline over time, place and space

• A coastline made up of softer rocks such as sands and clays will be easily eroded by destructive waves to form low, flat landscapes such as bays and beaches

• Coastlines of more resistant, harder rock will take longer to erode and produce rugged landscapes such as headlands

• The differences between hard and soft rocks will also impact the shape and characteristics of cliffs

• Geology, therefore, shapes the coastline vertically through the height and profile of a cliff and horizontally with bays and headlands

Influence of Vegetation

• The longer a coastal landform has existed, the more likely it will be colonised by vegetation

• Over time, vegetation will 'fix' a feature (e.g. a sand dune)

• Vegetation adaptation is important in order to survive coastal conditions

• Vegetation has to cope with high levels of salt in both air and soil

• The largest influence of vegetation is to assist in protecting and preserving coastal landforms such as sand dunes, salt marshes and mangroves 

Influence of Sea-level Changes & People

• Rising sea levels produce submergent coastlines, with rias and fjords

• Falling sea levels produce emergent coastlines, with relic features such as raised beaches, cliffs with caves, arches etc.

• Sea levels have risen and fallen many times in the past

• During the last Ice Age, sea levels fell as the water was locked up in glaciers and ice sheets, rising again as the ice melted

• Sea levels are linked to global warming and will have a significant effect on many low-lying coasts and islands

• Many Pacific Ocean islands, such as Kiribati and Tuvalu are at risk of being completely submerged by rising sea levels

• This issue is made worse as many of the world's densely populated areas are located on coastal lowlands

• New York and Miami in the US are major cities vulnerable to sea-level rise as the cities are built at sea level

Influence of People

Human Activity

• Human activities, either intentionally or not, transform the features and landscape of a coastline:

  • Settlement - coasts have always been a place of attraction and residence for people 

  • Economic Development -  exploitation through fishing, farming, trade, tourism and energy production 

  • Coastal Management - controlling the coastline to protect human interests

• Through any or all of the above, the natural landscapes and features of the coast can be changed, thereby changing the coastline over time, space and place

Distribution & Features of Coral Reefs

Distribution of Coral Reefs

• Coral reefs are large deposits of calcium carbonate built entirely of living organisms called coral polyps

• Corals are scattered throughout the tropical and subtropical Western Atlantic and Indo-Pacific oceans, generally within 30°N and 30°S latitudes

• Western Atlantic reefs include these areas: Bermuda, the Bahamas, the Caribbean Islands, Belize, Florida, and the Gulf of Mexico

• The Indo-Pacific ocean region extends from the Red Sea and the Persian Gulf through the Indian and Pacific Oceans to the western coast of Panama

• Corals grow on rocky outcrops in some areas of the Gulf of California

• The Great Barrier Reef in northern Australia is renowned for its great biodiversity and size and can be seen from space

• Their distribution is controlled by four factors: 

  • Temperature

  • Light

  • Water depth

  • Salinity

What are the features of Coral Reefs?

Main Features of Coral Reefs

• At a local level, other factors will affect development:

  • Wave action - corals need well-oxygenated, clean water and wave action provides this

  • Exposure to air - although corals need oxygenated water, they cannot be exposed to air for too long or they will die

  • Sediment - all corals need clear, clean water. Any sediment in the water will block normal feeding patterns by reducing the availability of light affecting the photosynthesis of the microscopic algae 'zooxanthellae' living in polyp tissue. The corals provide algae with a home and compounds for photosynthesis. In return, the algae produce food, and oxygen and help remove wastes

Types of Coral Reefs

• Fringing Reefs - these are reefs that form around a land mass

• Barrier Reefs - these are found parallel to the shore but are separated by a channel of water:

  • The Great Barrier Reef in the Coral Sea, off the coast of Queensland, Australia is a good example of a barrier reef.

  • It is the world's largest coral reef system with over 2,900 individual reefs and 600 islands that stretch for over 2,300 kilometres and can be seen from space

• Atolls - horseshoe-shaped rings, consisting of a coral rim that encircles a lagoon

Distribution & Features of Mangroves

Distribution of Mangroves

• Both mangroves and coral reefs are found in warm tropical waters, however, unlike the sensitive coral reefs, mangroves are highly adapted to changing conditions

• This has made them the most successful ecosystems on Earth

Global Distribution of Mangroves

• Originate from Southeast Asia and spread across the globe

• Mainly found in warm tropical waters and coastal swamps within 30° N and S of the equator

• Some have adapted to more temperate conditions and have colonized as far south as New Zealand's North Island

• They grow in the intertidal zone of the coast

• South-East Asia has mangroves with the highest biodiversity in the world

Characteristics of Mangroves

• Mangroves are trees that live on the coastline

• They sit in water between 0.5 to 2.5 metres high 

• They range in size from small shrubs to trees over 60m high

• They have numerous tangled roots that grow above ground and form dense thickets

• They need high levels of humidity (75 - 80%) and rainfall per annum (1500 - 3000 mm)

• The ideal temperature is around 27° C but are adapting to more temperate climates

• The mangrove root system is complex, with a filtration system to keep salt out

• Some have snorkel-like roots that stick out of the mud to help them take in air

• Others use 'prop' roots or 'buttresses' to keep their trunks upright in the soft sediment at the tidal edge

 Prop Roots        Mangrove Root Systems              Snorkel Roots

• It is the roots that trap mud, sand and silt which eventually builds up the intertidal zone into the new land

• At the same time, the mangrove is colonizing new intertidal areas

• The fruits and seedlings of mangroves can float and can travel many kilometres on ocean currents 

• As they drift with the incoming tide, they become lodged in the mud and begin to grow, colonizing new areas

Distribution & Features of Sand Dunes

Distribution of Sand Dunes

• Coastal sand dunes are found all over the world

• They are the accumulation of sand, shaped into mounds and ridges by the wind

• Found at the back of a beach, above the maximum reach of the tide

Global Distribution of Coastal Sand Dune Systems

• Coastal sand dunes develop best when:

  • There is a wide beach and large quantities of sand

  • The prevailing wind is onshore

  • There is a large tidal range to allow time for the sand to dry

  • There are suitable locations for the sand to accumulate

Characteristics of Sand Dunes

• Sand dunes can be small ridges or large hills usually found at the back of a beach

• They can extend backwards for many miles as well as along the beach

• They are an important ecosystem supporting unique flora and fauna that have adapted to live within the dune system

• Dunes are vulnerable to erosion by natural processes and human activity:

  • It is common to see vulnerable sections of dunes fenced off to prevent public access, or for paths to be laid to prevent people from eroding the dunes further

Formation of a Sand Dune

• Wind-blown sand is deposited against an obstruction - pebble or driftwood

• As more sand particles are caught, the dunes grow in size, forming rows at right angles to the prevailing wind

• Over time, the ridges of the dunes will be colonized and fixed by vegetation in a process called succession

• The first plants (pioneer species) have to deal with:

  • Salinity

  • Lack of moisture as sand drains quickly (highly permeable)

  • Wind

  • Temporary submergence by wind-blown sand

  • Rising sea levels

Coastal Sand Dune Succession

• Embryo Dunes

  • Wind-blown dried sand is trapped by debris and deposition begins

  • Pioneer species such as Lyme Grass and Sea Couch Grass begin to colonise

  • There is little soil content and high pH levels (alkaline)

  • Embryo dunes  are very fragile and reach a maximum height of 1 metre

• Fore Dunes

  • The embryo dunes bring some protection against the prevailing wind

  • This allows other species of plant to grow such as Marram Grass

  • Marram grass begins to stabilise the dune with its root system

  • These plants add organic matter to the dunes making the dunes more hospitable for plants that later grow

  • A microclimate forms in the dune slack

  • Maximum height is 5 metres

• Yellow Dunes

  • These are initially yellow but darken as organic material adds humus to the soil

  • Marram grass still dominates the vegetation, but more delicate flowering plants and insects are found in the dune slacks

  • 20% of the dune is exposed, down from 80% 

  • Height does not exceed 8 metres

• Grey Dunes 

  • Grey dunes are more stable, with less than 10% of exposed sand and have a good range of biodiversity

  • Soil acidity and water content increase as more humus is added

  • Shrubs and bushes begin to appear

  • Height is between 8 - 10 metres

• Mature Dunes

  • As the name suggests, these are the oldest and most stable of the dunes

  • They are found several hundred metres or more from the shoreline

  • The soil can support a variety of flora and fauna such as oak trees and alders (climax vegetation)

  • This is the final stage in succession which is known as the climax community stage

Distribution & Features of Salt Marshes

Distribution of Salt Marshes

• Salt marshes are found all over the world and are not temperature dependant

• Like mangroves, they are an ecosystem of the intertidal zone 

• They are typically very flat, with numerous channels running through them

• They form in:

  • Coastal areas that are well sheltered, such as inlets and estuaries where fine sediments can be deposited 

  • Areas behind spits and artificial sea defences where tidal waters can flow gently and deposit fine sediments

  • They form in brackish water

Global Distribution of Salt Marshes

Features of Salt Marshes

• Salt marshes are communities of nonwoody, salt-tolerant plants

• They begin as tidal mud flats, gaining height as more sediment is deposited

• This builds up to and above the level, and frequency of tidal flooding ensuring that the soil never dries out and remains muddy and sticky

• Pioneer species of halophyte plants begin to colonise

• As these plants die and add nutrients to the soil, sediment builds up. This makes the conditions more favourable and other species start to develop.

• The process of the development of vegetation, over time is known as succession. In a salt marsh, this is known as a halosere

• The lower marshes are flooded daily by the rising tide.

• They are good coastal defences in some areas, acting as a natural buffer against coastal erosion and flooding

• However, in many areas they have been reclaimed for agriculture or development, and are threatened by human activities

Characteristics of Coral Reef Ecosystems

• An ecosystem is a community of interacting biotic and abiotic organisms

• All ecosystems, whether on land or in water function in the same way

• All survive by nutrient cycling around three stores:

  • Biomass

  • Litter

  • Sea Water

Nutrient Cycle of a Coastal Ecosystem 

Nutrient Cycle of Coastal Ecosystems

Overview of Coastal Nutrient Cycling

THREATS:

Industrialisation

The Value of Coastal Ecosystems

• All ecosystems offer people a range of opportunities – goods and services

  • Goods – a material resource that can be extracted and used

  • Services – general benefits and advantages

• Coastal ecosystems can provide the following:

Industrial Threats

• Threats to Coral Reefs

  • Coral reefs are easily stressed by human action, if the stress persists, then the death of the reef soon follows

  • Pollution, overfishing and quarrying of coral for building stone

  • Industrialisation is responsible for rising sea temperatures and sea-level rise, putting coral reefs under threat

  • Rising sea temperatures increase levels of coral bleaching

• Threats to Mangroves

  • Pollution, overfishing and deforestation for aquaculture

  • Clearance for land development particularly in developing countries

• Threats to Sand Dunes

  • Least threatened at a global level due to value being mainly tourism and leisure

  • Local level the biggest threat is sand mining

• Threats to Salt Marsh

  • Industrial pollution

  • Ideal sites for nuclear power stations 

  • Clearance for development - commercial and private

  • Development can lead to increased noise and light pollution which may affect wildlife behaviour and nesting 

Agricultural Practices

• Threats to Coral Reefs

  • Overfishing reduces the number of grazing fish that keep coral clear of algae

  • Fishing using explosives damage coral reefs

  • Commercial farming 

  • Fertiliser runoff

  • Pesticide overspray 

• Threats to Mangroves

  • Aquaculture - intense fish and shrimp farms

  • Pesticide use

  • Antibiotics used in aquaculture practices

  • Clearance for farm development particularly in developing countries

• Threats to Sand Dunes

  • Destabilisation due to grazing animals on dunes

• Threats to Salt Marsh

  • Drained and cleared for farming 

  • Eutrophication through heavy use of fertilisers 

  • Pollution from pesticides and herbicides 

  • Slurry run-off from cattle

Tourism

• Threats to Coral Reefs

  • Tourism is the biggest threat globally and locally to coral reefs

  • 58% of all coral reefs are at threat from human activity

  • Any contact with the human body is likely to kill coral immediately around the point of contact

  • Propellers and anchors directly damaging corals from boat tours

  • Pollution through diesel spills

• Threats to Mangroves

  • Clearance of mangroves to build hotels and other tourist attractions

  • Diversion of fresh water to hotels etc

  • Disturbance of habitats

  • Collection of souvenirs by tourist

  • Tours in waterways and pollution through spills of boat fuel

• Threats to Sand Dunes

  • Largest threat to sand dunes due to trampling of delicate, unfixed dunes

  • Driving using 4x4 or quadbikes over sand dunes

  • Sporting events - sand surfing etc

  • Collecting shells and driftwood

  • Pollution from rubbish left by tourists

  • Car parks

  • Sand mining for building hotels

  • Development of seaside towns

• Threats to Salt Marshes

  • Tourism is limited to the local level and nature reserves

  • Roads have divided salt marshes cutting off parts of it

  • Trampling by visitors

  • Dog walkers letting dogs roam and disturb the wildlife

  • Noise from local tourist areas may disturb the wildlife

Deforestation

• Threats to Coral Reefs

  • Clearance of coastal forests and mangroves disturbs natural flows of water and nutrients leading to stress and coral bleaching

  • Removal of coral reef for stone building or tourist sales 

  • Any destruction of coral reef leaves the coastline open to coastal flooding and storm surges

• Threats to Mangroves

  • Removal of the trees leads to the collapse of the ecosystem

  • Leaves the coast open to storms, flooding and coastal retreat

  • Mangrove wood is used for timber and fuel

  • Cleared to reduce malaria - unsupported evidence that this works

• Threats to Sand Dunes

  • Removal of trees destroys the mature dunes and allows for dune migration

  • Leaves coast open to storms and flooding

• Threats to Salt Marshes

  • Real threat is through industrialisation and agriculture

Conflict Between Development & Conservation

• Careful management of coastal regions is necessary for sustainability

• Coastal environments have multiple uses:

  • Development such as homes, shops, roads etc.

  • Nature reserves

  • Industry such as ports, fishing and aquaculture

  • Tourism

  • Agriculture

• These different activities bring people and ecosystems together and there becomes a competition for space

• Conflict arises when coastal development is given a higher priority than coastal conservation

Conflict Between Coastal Users

• Coastal users and wildlife are referred to as stakeholders

• Each stakeholder has a different priority or need

  • Wildlife want an unpolluted, safe and quiet environment

  • Local residents want jobs, clean beaches, affordable housing and schools

  • Tourists want beaches, hotels, B&Bs, entertainment, holiday homes, and marinas

  • Employers want building space, offices, and factories

  • Developers want areas by the sea for tourists—hotels, duplexes, golf courses

  • Fishermen want harbours, unpolluted waters, and ease of access to the sea

  • Farmers want well-drained land, sheltered from prevailing winds

  • Government and Councils want to build offshore wind farms and coastal defences

  • Transport companies want good road networks, well-connected ports and terminals

• The different needs of stakeholders often conflict as they compete for the same resources

      Relationship between Stakeholders and Coastal Zone Issues

• The level of conflict varies depending on who and what the needs are

• This can be shown in a conflict matrix

Conflict Matrix 

Causes of Coastal Flooding

• Coastal flooding results from a number of factors:

  • Storm surges - a rapid rise in sea level caused by really low-pressure storms (e.g. tropical storm) 

  • Storm tides - occur when there is a combination of high tide and low-pressure storm

  • Tsunamis - large sea waves due to underwater earthquakes. The closer to the coast, the bigger the impact

  • King tides

  • Sea level rise due to global warming

  • High river discharge after a storm - when combined with a spring tide, water in the estuary cannot discharge into the sea causing a backflow of water and flooding

• The worst flooding arises from a combination of any of these

• The biggest impacts are felt by emerging countries, although the biggest economic cost is are to developed countries

Prediction & Prevention of Flooding

Prediction

• Early warning systems allow communities to prepare (evacuate or take shelter) before flooding occurs

• Two methods are used to help forecast coastal flooding:

  • Past records (diaries, newspapers, government/council records etc)

    • These will identify areas that are at high risk of flooding and their frequency

  • Modern technology - GIS, satellite and computer monitoring, weather stations (local and national) etc

    • These allow for forecasting and tracking potential hazard events i.e.

      • Tropical storms - track the storm's path and associated storm surge

      • Earthquakes - size and position if underwater and possible tsunami outcome

• Both these methods of forecasting help officials to say when and where the event will occur

• It indicates the possible strength and scale of the flooding, and the likelihood of damage and death

Prevention

• Prevention is about taking action that reduces or removes the risk of coastal flooding

• Actions include:

  • Flood defences

    • These are built along high-risk stretches of coast 

  • Emergency centres

    • Centrally placed on higher ground where people can be safe from flooding

  • Early warning systems

    • Allows for preparation or evacuation of an area

  • Education

    • Informing local people on what to do if and when a flood occurs

  • Planning

    • Planning any new development away from high-risk-areas

    • Designing buildings to cope with low levels of flooding

      • Elevating buildings so that flood waters can pass underneath

      • Floodproof buildings with raised foundations (fixed or mechanical)

      • Reinforced barriers

      • Dry floodproofing - sealing a property so that floodwater cannot enter

      • Wet floodproofing - allows some flooding of the building

  • Buffer zones

    • Areas of land are allowed to flood before reaching settlements

      • This allows the energy in the surge to dissipate slowing down the distance the floodwater will travel

      • It can mean moving people away from the coast which could be controversial 

Coastal Strategies

• Management of coastal regions is performed by identifying coastal cells

• This breaks a long coastline into manageable sections and helps identify two related risks:

  • The risk of erosion and land retreat 

  • The risk of flooding

• Identification allows resources to be allocated effectively to reduce the impacts of these risks

• The 'cost-benefit' is easier to calculate using coastal cells

Shoreline Management Plans

• Shoreline Management Plans (SMP) set out an approach to managing a coastline from flooding and erosional risk

• The plans aim to reduce the risk to people, settlements, agricultural land and natural environments (salt marshes etc.)

• There are four approaches available for coastal management, with differing costs and consequences:

• Hold the line

  • Long term approach and the most costly

  • Build and maintain coastal defences so the current position of the shoreline remains the same

  • Hard engineering is the most dominant method used with soft engineering used to support

• Advance the line

  • Build new defences to extend the existing shoreline

  • Involves land reclamation

  • Hard and soft engineering is used

• Managed realignment

  • Coastline is allowed to move naturally

  • Processes are monitored and directed when and where necessary

  • Most natural approach to coastal defence

  • Mostly soft engineering with some hard engineering to support

• Do nothing

  • Cheapest method, but most controversial of the options

  • The coast is allowed to erode and retreat landward

  • No investment is made in protecting the coastline or defending against flooding, regardless of any previous intervention

• Decisions about which approach to apply are complex and depend on:

  • Economic value of the resources that would be protected, e.g. land, homes etc

  • Engineering solutions - it might not be possible to 'hold the line' for moving landforms such as spits, or unstable cliffs 

  • Cultural and ecological value of land - historic sites and areas of unusual diversity

  • Community pressure - local campaigns to protect the region

  • Social value of communities - long-standing, historic communities

Hard Engineering Methods

• Hard engineering involves building some form of sea defence, usually from concrete, wood or rock

• Structures are expensive to build and need to be maintained

• Defences work against the power of the waves 

• Each type of defence has its strengths and weaknesses

• Protecting one area can impact regions further along the coast, which results in faster erosion and flooding

• Hard engineering is used when settlements and expensive installations (power stations etc) are at risk - the economic benefit is greater than the costs of building structures

Hard Engineered Defences

Soft Engineering Methods

• Soft engineering works with natural processes rather than against them

• Usually cheaper and do not damage the appearance of the coast

• Considered to be a more sustainable approach to coastal protection

• However, they are not as effective as hard engineering methods

Soft Engineered Defences

• There are conflicting views about using a particular type of engineering for coastal defence

• Most coastal managers aim to use a range of methods depending on the value of what is being protected

• This method is known as Integrated Coastal Zone Management (ICZM)

• ICMZ aims to use a combination of methods to best reflect all stakeholder needs