Coastal Management (Cambridge International IGCSE Geography)

Managing the Impacts of Coastal Erosion

Spec point — 2.3.5 · Explain what can be done to manage the impacts of coastal erosion

• There are conflicting views about what type of engineering to use 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's needs

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 a more sustainable approach to coastal protection
• However, they are not as effective as hard engineering methods

Soft-engineered defences

Beach replenishment

• This is the pumping or dumping of sand and shingle back onto a beach to replace eroded material

• Advantages

  • Beaches absorb wave energy
  • Widens beachfront

• Disadvantages

  • Has to be repeated regularly, which is expensive
  • Can impact sediment transportation down the coast

Fencing, hedging, and replacing vegetation

• Helps to stabilise sand dunes or beaches

• Reduces wind erosion

• Advantages

  • Cheap method to protect against flooding and erosion

• Disadvantages

  • Hard to protect larger areas of coastal cliffs

Cliff re-grading

• This is when the angle of a cliff is softened to reduce mass movement

• Advantages

  • Prevents the sudden loss of large sections of cliff
  • As wave energy is slowed, wave-cut notching is reduced at the base of the cliff

• Disadvantages

  • It does not stop cliff erosion; it only slows it down

Beach re-profiling

• Beach reprofiling is the artificial re-shaping of a beach using existing beach material

• Advantages

  • Replaces shingle after winter storms
  • Increasing the profile reduces wave energy before the base of the cliffs

• Disadvantages

  • Reprofiling may have a negative effect on beach habitats

Managed retreat

• The existing coastal defences are abandoned, allowing the sea to flood inland until it reaches higher land or a new line of defences

• Advantages

  • There are no expensive construction costs
  • Creates new habitats such as salt marshes

• Disadvantages

  • Disruptive to people where land and homes are lost
  • The cost of relocation can be expensive
  • Full compensation to people and businesses may not be paid

Hard engineering methods

• Hard engineering involves building concrete, wood, or rock sea defences
• Building and maintaining structures is costly
• Defences work against the power of the waves
• Each defence has pros and cons
• Protection in one place can increase erosion and flooding along the coast
• When settlements and expensive installations (power stations, etc) are under risk, hard engineering is used because the economic gain outweighs the costs

Hard-engineered defences

Sea wall

• A sea wall is usually concrete and curved outwards to deflect the power of the waves

• Advantages

  • Most effective at preventing both erosion and flooding (if the wall is high enough)

• Disadvantages

  • Very expensive to build and maintain
  • It can be damaged if the material in front of the wall is not maintained
  • Restricts access to the beach
  • Unsightly to look at

Groynes

• These are wood, rock or steel pilings that are built at right angles to the shore

• Longshore drift moves beach material into groynes

• Advantages

  • Most effective at preventing both erosion and flooding (if the wall is high enough)

• Disadvantages

  • Keeps material from moving down the coast and protects cliff bases elsewhere
  • Starves other beaches of sand
  • Wooden groynes need maintenance to prevent wood rot
  • Makes walking along the shoreline difficult

Rip-rap or rock armour

• Large boulders are piled up to protect a stretch of coast

• Works to absorb wave energy from the base of cliffs and sea walls

• Advantages

  • Cheaper method of construction

• Disadvantages

  • Boulders can be eroded or dislodged during heavy storms

Gabions

• Wire cages are filled with stone, concrete, sand, etc.

• Cages absorb wave energy

• Advantages

  • Cheapest form of coastal defence
  • Can be stacked at the base of a sea wall or cliffs

• Disadvantages

  • Wire cages can break, and they need to be securely tied down
  • Not as efficient as other coastal defences

Revetments

• Sloping wooden or concrete fence with an open plank structure

• Revetments work to break the force of the waves

• Advantages

  • Traps beach material behind them
  • Set at the base of cliffs or in front of the sea wall
  • Cheaper than sea walls but not as effective

• Disadvantages

  • Not effective in stormy conditions
  • Can make beach inaccessible for people
  • Regular maintenance is necessary
  • Visually unattractive

Off-shore barriers

• Large concrete blocks, rocks and boulders are sunk offshore to alter wave direction and weaken wave energy

• Advantages

  • Beach material is built up
  • Low maintenance
  • Maintains natural beach appearance

• Disadvantages

  • Expensive to build
  • Can be removed in heavy storms
  • Can be unattractive
  • Prevents surfing and sailing

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 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 forecast and track potential hazardous events such as:

    • Tropical storms: track the storm's path and associated storm surge
    • Earthquakes: the size and position of underwater tremors and possible tsunami outcome

• Both forecasting methods help officials determine when and where the event will occur

• They shows the risk of damage and fatalities as well as the potential intensity and scope of the flooding

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

• Any new development should be planned away from high-risk-areas

• Design buildings to deal with low levels of flooding

  • Raise buildings to allow floodwaters to flow underneath
  • Strengthen barriers
  • Sealing a property to prevent floodwater intrusion is known as dry floodproofing
  • Wet floodproofing allows some flooding of the building

Buffer zones

• Areas of land are allowed to flood before reaching settlements

  • This slows down the floodwater's journey by allowing the surge's energy to dissipate
  • 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

• Identifying risks allows resources to be used efficiently to limit their impacts

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

Shoreline management plans

• Shoreline management plans (SMPs) outline strategies to prevent flooding and erosion along a coastline
• The strategies try to limit the risk to people, settlements, agricultural land, and natural habitats (such as salt marshes)
• There are four ways to manage coastal areas, each with different costs and consequences

Hold the line

• This is a long-term approach and the most costly
• It involves building and maintaining coastal defences to keep the current position of the shoreline
• Dominated with hard engineering with soft engineering supporting it

Advance the line

• New defences are built to extend the existing shoreline
• Involves reclaiming land
• Hard and soft engineering is used

Managed realignment

• The coastline is allowed to move naturally
• Processes are monitored and directed when and where necessary
• The most natural approach to coastal defence
• Mostly soft engineering with some hard engineering to support

Do nothing

• The cheapest method, but also the most controversial of the options

• The coast is allowed to erode and retreat inland

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

• Decisions about which approach to use 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: are there any local campaigns to protect the region?
  • The social value of communities: long-standing, historic communities

Worked Example Explain how gabions protect the coast

[2 marks]

Solution

Gabions absorb/dissipate/reduce the wave's energy/power [1 mark]. This reduces the impact of the waves at the foot of cliffs and seawalls, which reduces/prevents coastal erosion [1 mark].

Marking guidance

The command word here is 'explain,' and answers need to be developed for full marks.

• 1 mark for identifying the purpose
• 1 mark for development

Case Study - Super Typhoon Haiyan

Spec point — 2.3.5 · The opportunities presented by an area, or areas of coastline, the associated hazards and their management

Case Study: Super Typhoon Haiyan

• Managing tropical storms is difficult due to the unpredictability of their paths
• The distribution of the population along a coast increases the risk associated with tropical storms
• The strength of the storm does not always cause the most damage; developing countries are usually the worst affected
• Preparedness is an effective way of managing tropical storms
• Hazard mitigation relies on effective response to natural events

Background

• Typhoon Haiyan (Yolanda) was one of the strongest tropical storms to hit the Philippines
• It made landfall on November 8, 2013, as a Category 5 with sustained winds above 195 mph
• The Philippines are a group of South China Sea islands located east of Vietnam and north of Indonesia
• Southwest typhoons regularly sweep in every tropical storm season
• Even though the islands sit in warm ocean water, the storm's sea temperature at the time was 30 °C
• Since 1900, sea levels have risen 20 cm around the world. Higher seas are known to contribute to stronger storm surges
• Over-abstraction of groundwater has caused parts of the country to sink
• Tacloban stands at the end of a bay that is funnel-shaped and this squeezes water into destructive storm surges

Formation of tropical storms

• All tropical storms need:

  • warm, deep water (>27°C and >70 m depth)
  • sufficient spin from the earth’s rotation (Coriolis force)

• This is why they form between 5-20° N and S of the equator

• Warm water encourages sea surface evaporation, while rising air cools, condenses, releases latent heat, and produces large thunderclouds

• The heat from below produces vertical growth and intense low-pressure

• Tropical storms form when several storms merge at the eastern side of an ocean

• A major low-pressure cell develops and as winds are drawn in, the whole system begins to spin anticlockwise and westward

• Winds rotate around a central eye, where cold air descends, creating an area of calm

• The strongest winds are within the eyewall

Typhoon Haiyan's timeline

Path of Typhoon Haiyan November 2013

Nov 2013

• 2nd: an area of low pressure develops several hundred kilometres east of Micronesia
• 3rd: Haiyan begins to track westward, deepening into a tropical depression
• 5th: The Philippines Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) classified it as a typhoon and issued a low-level public storm warning
• 6th: declared a Category 5 super typhoon by the Joint Typhoon Warning Centre. PAGASA raises storm warning to highest level, indicating expected wind speeds in excess of 115 mph
• 7th: Haiyan's winds continue to intensify up to 195 mph. Haiyan makes first landfall at Guiuan, Eastern Samar, without losing any intensity
• 8th: Haiyan makes five more landfalls within the Philippines before passing into the South China Seas
• 10th: Haiyan turns to the NW and makes landfall in Northern Vietnam as a Category 1 typhoon
• 11th: Haiyan finally weakens into a tropical depression

Typhoon Haiyan's characteristics

• Lowest pressure: 895 mb
• Peak strength: category 5
• Strength at landfall: Category 5 with 195 mph winds
• Highest sustained wind speed: 196 mph
• Radius of typhoon strength winds: 53 miles
• Rainfall: 400 mm
• Storm surge height: 15 m

Preparation for Typhoon Haiyan

• Despite being an LEDC, the Philippines take disaster preparedness seriously, as they are usually the first Pacific landmass to experience a typhoon
• For decades, the Philippines have practiced risk reduction and resilience, publishing risk maps and providing evacuation shelters
• The International Charter on Space and Major Disasters was triggered when Haiyan made landfall, allowing relief agencies to get satellite data from space agencies to aid recovery
• The military deployed planes and helicopters in advance to areas expected to be worst hit
• Community structures like conference centres were designated storm shelters, but there were concerns they would not withstand the wind
• After years of community preparation and education, entire islands like Tulang Diyot were evacuated, with all 1000 residents evacuating before Haiyan
• The local mayor won an award in 2011 for community work based on the 'Purok system', in which community members agree to deposit their own money into a community fund regularly for post-disaster help rather than waiting for government relief

Impacts of Haiyan

Short- and long-term impacts

Social

• Short-term

  • 6201 people died
  • 1.1 million homes lost
  • more than 4 million displaced
  • Casualties: 28,626 from lack of aid
  • 16 million people affected
  • UN admitted its response was too slow amid reports of hunger/thirst among survivors

• Long-term

  • UN feared the possibility of the spread of disease, lack of food, water, shelter and medication
  • Areas less affected; an influx of refugees into the area
  • 21,000 families were still in 380 evacuation centres two months later, waiting for the government to build bunkhouses to house them in

Economic

• Short-term

  • Estimated at $13 billion
  • Major sugar/rice-producing areas were destroyed
  • Between 50,000 and 120,000 tonnes of sugar were lost
  • Over 130,000 tonnes of rice were lost
  • government estimated that 175,000 acres of farmland was damaged (worth $85 million)

• Long-term

  • The Philippines declared 'a state of national calamity.’
  • Asked for international help the next day
  • President Aquino was under growing pressure to speed up the distribution of food, water, and medicine
  • Tacloban city was destroyed
  • Debt is a major obstacle for the Philippines; the country is locked in a debt cycle, with more than 20% of government revenue spent on foreign debt repayments

Environmental

• Short-term

  • Loss of forests and trees, and widespread flooding
  • Oil and sewage leak into local ecosystems
  • Lack of sanitation in the days following led to a higher level of pollution
  • Coconut plantations were said to be 'completely flattened' (coconut equated to nearly half of the Philippine's agricultural exports and is the world's biggest producer of coconut oil)
  • Fishing communities were severely affected

• Long-term

  • Small-scale farmers make up 90% of typhoon-affected rural populations
  • After 33 million coconut trees were cut, international help was sought to mill the 15 million tonnes of rotting lumber that attracted pests that threatened healthy trees
  • Families lack funding for local marketplaces without crops

Immediate relief

• The survivors immediately searched flattened buildings for bodies
• People began looting to find food supplies when the government was slow to respond
• Roads were undamaged, but debris slowed rescue vehicles
• Emergency teams were slowed as airports and harbours were closed, which hampered aid distribution
• Diggers, land rovers, and heavy lifting gear from the UK and USA were sent to Tacloban airport by international charities
• The European Commission released $4m in emergency funds and the UK Rapid Response Facility provided $8m in aid
• Twelve IFRC (International Federation of the Red Cross) Emergency Response Units worldwide were deployed
• The Philippines had already experienced a 7.3-magnitude earthquake in October 2013 and Typhoon Bopha in 2012. These tragedies left the Philippines short on financial, material, and human resources