Changing coastal environments

Cambridge IGCSE Geography 0460 Current syllabus: 2027, 2028 and 2029 Official syllabus points: 2.1.1 to 2.3.8 Assessed on: Paper 1, Physical Geography

Exam Essentials

1. What this topic asks of you

Topic 2 has three parts, and the exam moves through them in order.

Two things run through the whole topic and decide your grade.

Place-specific detail. The mark schemes cap a 7 mark extended answer at 5 marks if there is no named example, and reserve the top level for answers that give real places, real figures and real dates.

Sustainability. The syllabus attaches the phrase "including sustainable" to almost every management point. Examiners want you to judge whether a strategy still works in fifty years, not only whether it works now.

2. Waves

Where wave energy comes from

Fetch is the distance of open water over which the wind blows towards a coast.

The energy in a wave comes from three things: wind speed, how long the wind has blown, and fetch. A long fetch gives the wind more distance to transfer energy to the water, so coasts facing thousands of kilometres of open ocean receive the most powerful waves.

Swash is the movement of water up the beach after a wave breaks. Backwash is the movement of water back down the beach under gravity.

The balance between swash and backwash decides whether a beach grows or shrinks. This single idea explains wave type, beach profile and longshore drift, so learn it first.

Constructive and destructive waves

That frequency figure of 10 waves a minute is the exact dividing line used in the mark schemes, so quote it.

1. Constructive wave breaks with a long low form
2. strong swash carries sand and shingle up the beach
3. weak backwash sinks into the beach and cannot return it all
4. sediment is left behind and the beach builds up.

1. Storm generates a steep high wave
2. the wave plunges rather than spills, so swash is weak
3. backwash runs strongly back down the steep face
4. material is combed offshore and the beach is lowered.

Exam trap: questions comparing the two wave types are marked as comparative. Writing three facts about destructive waves with nothing about constructive waves will lose marks, because the mark scheme states that answers must be comparative.

Wave refraction

Wave refraction is the bending of waves as they enter shallow water, so that the wave crest becomes more nearly parallel to the shape of the coastline.

1. Wave approaches an irregular coast
2. the part of the crest over the shallow water off a headland slows down first while the part over the deeper water of the bay keeps its speed
3. the crest bends round the headland
4. wave energy is concentrated on the headland and spread out in the bay.

This is the rule that explains why a headland keeps being attacked and worn back while the bay behind it quietly fills with sand. Refraction is the reason the coastline tends, over long periods, to straighten itself out.

3. Coastal erosion

The syllabus names four processes. Learn all four with a definition you can write in one line.

Hydraulic action: waves force air into cracks and joints in the cliff, the arriving wave compresses that trapped air, and as the wave falls back the air expands explosively, widening the crack until blocks of rock break away.

Corrasion (also called abrasion): waves pick up sand, shingle and boulders and hurl them at the cliff face, grinding the rock away like sandpaper.

Corrosion (also called solution): weak acids and salts dissolved in seawater dissolve the rock. It matters only where the rock is calcium carbonate, so chalk and limestone coasts, and it is very slow.

Attrition: the fragments already in the water collide with each other and with the sea bed, breaking down into smaller, smoother and rounder pieces.

Exam trap: attrition wears down the sediment, it does not wear back the coast. A question asking why a cliff is retreating should be answered with hydraulic action and corrasion, not attrition.

Note on names: the 2027 to 2029 syllabus uses corrasion and corrosion. The mark schemes accept abrasion and solution as alternatives, so either word earns the mark, but use the syllabus word and put the alternative in brackets.

Why some coasts erode faster than others

The mark schemes credit all of the following as reasons for a fast rate of retreat.

• Rock type and structure. Unconsolidated boulder clay or sand erodes far faster than granite or chalk. Joints, faults and bedding planes give the waves lines of weakness to exploit.
• Fetch and wave energy. A long fetch and a high proportion of destructive waves.
• Beach width. A wide beach absorbs wave energy before it reaches the cliff, so a coast with no beach erodes fastest.
• Sub-aerial processes. Weathering breaks up the cliff face from above, and rainwater soaking into clay lubricates it so that it slumps. This is why so many management techniques involve draining water out of cliffs and planting vegetation on them.
• Human activity. Defences further along the coast can starve a stretch of the sediment that would otherwise protect it.

4. Transportation and deposition

Sediment is carried along the coast in four ways, the same four used in rivers:

• traction: the largest boulders are rolled along the sea bed
• saltation: pebbles bounce along the bed in a series of small hops
• suspension: fine sand, silt and clay are carried within the body of the water
• solution: dissolved minerals are carried invisibly in the water

Deposition happens when the water no longer has enough energy to carry its load. It occurs where waves are constructive, where the coast is sheltered by a headland or a spit, where the water is shallow, and where a river brings in more sediment than the sea can remove.

5. Longshore drift

Longshore drift is the zigzag movement of sediment along a beach, caused by waves approaching the shore at an angle.

1. Prevailing wind drives waves onto the beach at an angle
2. swash carries sediment up the beach at that same angle
3. gravity pulls the backwash straight back down the steepest line, at right angles to the shore
4. each wave shifts the sediment a short distance along the coast, and the repeated zigzag moves it many kilometres.

Longshore drift is the single most examined process in this topic, because it explains spits, bars, the build-up of sediment on one side of a groyne, and the starving of coasts downdrift of defences.

Field evidence you can quote: where groynes have been built, the beach is measurably higher on the updrift side. In one Cambridge fieldwork paper, candidates measured an average drop of about 0.4 m from the top of the groyne to the beach on the west side and about 0.8 m on the east side, which shows drift running west to east.

6. Erosional landforms

Headlands and bays

1. Alternating bands of resistant and less resistant rock meet the coast at right angles
2. the less resistant rock is eroded faster and retreats inland to form a bay
3. the resistant rock is left projecting into the sea as a headland
4. wave refraction then concentrates energy on the headland and a beach builds up in the sheltered bay.

Cliffs and wave-cut platforms

1. Destructive waves attack the cliff base between high and low tide
2. hydraulic action and corrasion cut a wave-cut notch
3. the overhanging rock above the notch loses support and collapses
4. the cliff retreats inland and leaves behind a gently sloping wave-cut platform, exposed at low tide.

A wave-cut platform slopes gently seawards and is usually widest where the cliff has retreated furthest. It also limits its own growth: once the platform is wide enough, waves break on it and lose energy before reaching the cliff.

Caves, arches, stacks and stumps

1. Waves exploit a joint or fault in a headland
2. hydraulic action and corrasion widen it into a cave
3. erosion cuts the cave right through to the other side of the headland, forming an arch
4. weathering above and undercutting below weaken the arch roof until it collapses
5. an isolated pillar of rock, a stack, is left
6. the stack is undercut at its base and eroded down to a stump, often visible only at low tide.

Named examples: Old Harry Rocks on the Isle of Purbeck, Dorset, show a chalk stack with its stump beside it. Durdle Door on the same coast is a limestone arch. Flamborough Head in Yorkshire has chalk caves, arches and a broad wave-cut platform.

Exam trap: on a "describe the features shown in the photograph" question, the mark scheme states that details of processes earn nothing, and that you cannot describe a landform as a stage in the formation of another one. Writing "a cave which will become an arch" scores zero. Describe what it looks like: size, shape, colour, height, rock layers, vegetation, position.

7. Depositional landforms

Beaches

1. Constructive waves carry sediment towards the shore
2. strong swash pushes it up the beach and the weak backwash cannot carry it all away
3. sediment accumulates between the high and low water marks
4. a gently sloping beach forms, with the coarsest material at the back where only the strongest storm waves reach and the finest sand near the water.

The ridge of coarser material at the back of the beach is a berm, and it marks the highest recent tide.

Spits

A spit is a long, narrow ridge of sand or shingle joined to the land at one end and projecting into the sea or across an estuary at the other.

1. Longshore drift moves sediment along the coast
2. the coastline turns sharply or a river mouth interrupts it, and the water deepens
3. the drift carries on in its old direction into open water and loses energy
4. deposition builds a ridge outwards from the land
5. a secondary wind direction curves the far end landwards into a recurved hook, and the sheltered water behind fills with mud and salt marsh.

Named example: Spurn Head at the mouth of the Humber estuary in England is about 5 km long and is built entirely from material eroded off the Holderness coast to the north.

Bars

1. A spit grows right across the mouth of a bay
2. the ridge seals the bay off from the open sea
3. the water trapped behind it becomes a lagoon.

Named example: Slapton Sands in Devon is a shingle bar about 4 km long which encloses Slapton Ley, a freshwater lagoon.

Note: where a bar links an offshore island to the mainland it is called a tombolo, as at Chesil Beach and the Isle of Portland. Tombolo is not on the 2027 to 2029 list of named landforms, but mark schemes have credited it, so it is worth knowing.

Sand dunes

1. At low tide the wide beach dries out
2. onshore winds pick up the dry sand and move it inland by saltation
3. an obstacle such as driftwood or a clump of marram grass slows the wind, so the sand is dropped and piles up
4. marram grass grows through the sand and its roots bind it together
5. successive ridges build inland, from low mobile embryo and yellow dunes at the front to taller fixed grey dunes behind.

Marram grass is the key to the whole system, which is why "plant marram grass" and "boardwalks to keep visitors off the dunes" are standard management answers.

8. Discordant and concordant coastlines

This is new content in the 2027 to 2029 syllabus, and it is the point most candidates will be weakest on.

How a cove forms on a concordant coast. This is the classic exam application.

1. Waves break through a weak point in the resistant band of Portland limestone that fronts the coast
2. the much softer clays behind are exposed and erode rapidly
3. wave refraction spreads the energy sideways inside the gap
4. a near circular bay about 400 m across develops behind a narrow entrance, stopped at the back by a further resistant band of chalk.

Named example: Lulworth Cove, Dorset.

9. Opportunities of living near the coast

10. Hazards of living near the coast

• Coastal erosion: loss of farmland, homes, roads and businesses as cliffs retreat and collapse.
• Cliff collapse and slumping: sudden, and often triggered by heavy rain rather than by a storm.
• Coastal flooding: low-lying land inundated by high tides and by storm surges, which also contaminates soil and fresh groundwater with salt.
• Tropical storms: high winds, torrential rain and storm surge, covered in section 11.
• Salt-water intrusion: over-pumping of coastal groundwater lets seawater seep in and ruin the water supply.

Note: the mark schemes also credit tsunamis as a coastal hazard. In the 2027 to 2029 syllabus tsunamis belong to Topic 4, Tectonic hazards, so use one as an example of a hazard only, and do not spend an answer explaining how it forms.

11. Managing coastal erosion and flooding

The syllabus requires an evaluation of hard and soft engineering. That means every technique needs an advantage and a disadvantage, not just a description.

▶

Hard engineering

Hard engineering builds a structure to resist or absorb the sea's energy.

Soft engineering

Soft engineering works with natural processes rather than against them.

Named soft engineering example: at Medmerry in West Sussex, England, the Environment Agency deliberately breached the shingle bank in 2013 and moved the flood defence about 2 km inland, at a cost of about £28 million. The scheme created around 180 hectares of new intertidal habitat and protects roughly 350 properties and a wastewater treatment works that had flooded repeatedly.

Making the judgement

Examiners reward answers that reach a reasoned conclusion rather than listing techniques. Use these tests.

• Does it treat the cause or the symptom? A sea wall does nothing about the destructive waves, it just stands in their way.
• What happens next door? Almost every hard structure that traps sediment starves the coast downdrift of it.
• Who pays, and forever? Hard engineering has a high capital cost and an endless maintenance bill. Cost benefit analysis is why a shoreline management plan protects a town but leaves farmland to erode.
• Will it survive sea level rise? A defence designed for today's tides may be overtopped within its own design life.

12. Tropical storms: distribution and impacts

One storm, three names

A tropical storm is the same phenomenon everywhere. The name depends only on where it forms.

Distribution and why it looks like that

Tropical storms form between roughly 5° and 20° north and south of the equator, and track polewards and westwards, sometimes reaching 30°. Four conditions explain the map:

• Sea surface temperature of at least about 26.5 °C, to a depth of roughly 50 m to 60 m. Warm water evaporating supplies the moisture and the latent heat that power the storm. This restricts them to the tropics and to the late summer and autumn of each hemisphere.
• Enough Coriolis effect to make the air spin. The Coriolis effect is zero at the equator, which is why storms almost never form within about 5° of it.
• Low wind shear, so the rising column of air is not torn apart at height.
• Deep, unstable, converging air.

A storm dies once it moves over land or over cooler water, because its supply of warm moist air is cut off.

Impacts

Separate them the way the syllabus asks: social, economic and environmental, positive and negative, and at different scales.

Named example, Cyclone Amphan, May 2020. Amphan crossed the Bay of Bengal and made landfall in West Bengal, India, and southern Bangladesh with sustained winds near 155 km/h and a storm surge of up to 5 m. It killed about 128 people, damaged or destroyed more than a million homes, and caused around US$13 billion of damage, making it the costliest cyclone recorded in the North Indian Ocean. Around 3 million people were moved into shelters before landfall.

Exam trap: one 2024 mark scheme warns that the same stem and the same development cannot be credited twice. "Houses destroyed" and "buildings damaged" is one mark, not two. Spread your points across social, economic and environmental.

13. Managing tropical storms

The syllabus names four approaches. Use these four as your paragraph headings and the structure of the answer writes itself.

Prediction. Geostationary satellites track storms from formation, aircraft fly through them to measure central pressure, and computer models forecast the likely track. Warnings are issued days ahead and the storm is graded, for example on the Saffir-Simpson scale. Prediction saves lives but cannot reduce damage to property, and track forecasts still carry hundreds of kilometres of uncertainty several days out.

Preparation. Education and drills, evacuation routes, stockpiles of food, water and fuel, emergency services rehearsals, and insurance. Bangladesh runs a Cyclone Preparedness Programme staffed by tens of thousands of trained local volunteers who carry warnings to villages that have no radio or phone.

Planning. Land use zoning that keeps housing and hospitals off the most exposed low-lying land, building codes requiring reinforced roofs and shutters, and siting shelters so that every household is within walking distance.

Protection. Raised cyclone shelters on concrete stilts, embankments and sea walls, and deliberately preserved mangrove greenbelts along the shore. Bangladesh now has several thousand purpose-built cyclone shelters along its coast.

The evaluation examiners want. Compare Cyclone Bhola, which struck the same Bangladeshi coastline in November 1970 and killed an estimated 300,000 people, with Cyclone Amphan in 2020, which killed about 128 across two countries. The storms were of broadly similar strength. The difference is warning, shelters and evacuation. Management cannot reduce a storm's physical power, but it can cut the death toll by orders of magnitude. It is far less effective at reducing economic loss, because buildings and crops cannot be evacuated.

14. Coral reefs

Global distribution

Coral reefs are found in shallow tropical seas, broadly between 30° north and 30° south. They cluster on the eastern sides of continents and around tropical islands, where warm ocean currents flow, and they are largely absent from the western coasts of continents where cold upwelling currents run, and from the mouths of large rivers.

The distribution follows directly from the conditions coral polyps need:

• water between about 18 °C and 27 °C, warm enough for growth all year
• water no more than about 60 m deep, so that sunlight reaches the zooxanthellae, the algae living inside the coral that supply most of its food
• clear water free of sediment, because silt blocks light and smothers the polyps
• salt water with an alkaline pH of about 8
• plenty of oxygen and plankton
• moving but not violent water, to deliver nutrients without destroying the structure

Note: the 2027 to 2029 syllabus asks for the distribution rather than the conditions, but the conditions are the explanation for the distribution and past mark schemes have set a full 7 mark question on them. Learn them with the figures.

Why coral reefs matter

• They cover well under 1 per cent of the ocean floor but support around 25 per cent of all marine species.
• They provide food and income for hundreds of millions of coastal people through fishing.
• They are a major tourism asset, generating foreign currency and employment.
• They act as a natural breakwater, absorbing the great majority of the wave energy that would otherwise hit the coast, which protects beaches and settlements.
• They are a nursery for fish species that are caught elsewhere, and a source of compounds used in medicine.

Threats

Management

Marine protected areas with no-take zones, mooring buoys so that boats do not drop anchors, catchment controls on farm run-off, culling of crown of thorns starfish, coral gardening and reef restoration, tourist codes of conduct and visitor limits, and licensing of fishing.

The sustainability judgement: local management works well against local threats, and fish stocks recover measurably inside no-take zones. None of it touches bleaching, which is driven by global sea temperature. Cutting greenhouse gas emissions is the only measure that treats the cause, and it lies far outside the control of any reef authority.

15. Mangroves

Mangroves are salt-tolerant trees and shrubs growing in the intertidal zone of sheltered tropical and subtropical coasts, in estuaries, deltas and lagoons, broadly between 30° north and 30° south. The largest single block is the Sundarbans, spanning the Ganges delta in India and Bangladesh at around 10,000 km².

They survive conditions no other tree tolerates through stilt roots that hold the trunk above the tide and pneumatophores, vertical roots that break the surface of the waterlogged mud to take in oxygen, along with the ability to filter or excrete salt.

Why mangroves matter

• Coastal protection. A wide belt of mangrove absorbs wave energy and slows a storm surge, so villages behind it survive cyclones that flatten unprotected coasts.
• Nursery habitat. Juvenile fish, prawns and crabs shelter among the roots, supporting fisheries far beyond the mangrove itself.
• Sediment trapping. The roots hold mud in place, so the coast accretes rather than erodes, and the water behind stays clear enough for coral to survive.
• Carbon storage. Mangrove soils store several times more carbon per hectare than tropical rainforest.
• Direct resources. Timber, fuelwood, honey, thatch and traditional medicines.

Threats

Clearance for shrimp and prawn ponds is the single largest cause of loss, followed by conversion to rice paddy and oil palm, coastal development for ports and tourism, pollution and oil spills, upstream dams that cut the sediment supply the mangrove needs, and coastal squeeze, where rising sea level pushes the mangrove landwards into a sea wall it cannot cross.

Management

Protected area and Ramsar wetland designation, large-scale replanting, licensing and restriction of shrimp farming, community managed forests with harvest quotas so that local people gain from keeping the trees, and national greenbelt policies that require a mangrove strip along vulnerable coastlines.

16. Detailed specific example: coastal erosion on the Holderness coast, England

Syllabus point 2.3.7 requires one named country or coastal area covering the causes and impacts of coastal erosion, and the strategies used to manage erosion and protect against tropical storms.

Location. The Holderness coast runs about 61 km down the east coast of England, from Flamborough Head in the north to Spurn Head in the south, facing the North Sea.

Causes of the erosion.

• The cliffs are boulder clay, glacial till left by ice sheets. It is soft, unconsolidated and slumps readily when saturated with rainwater.
• The fetch across the North Sea from the north east is several hundred kilometres, and the narrow, shallow sea generates steep destructive waves.
• The clay erodes into fine particles carried away in suspension, so almost no beach material is left behind. Without a beach there is nothing to absorb wave energy at the cliff foot.
• Longshore drift runs from north to south, removing what little sediment there is.

Rate and impacts. Holderness retreats at an average of about 1.8 m a year, among the fastest rates in Europe, and locally much faster. Roughly 29 villages recorded since Roman times have been lost to the sea. Farmland disappears every year, homes at Skipsea have been condemned and demolished, the coast road has repeatedly had to be rerouted, and the Easington gas terminal, a major landfall for the United Kingdom's gas supply, sits close to a retreating cliff edge.

Management.

• Hornsea and Withernsea are protected by concrete sea walls, timber groynes and rip rap.
• Mappleton was defended in 1991 with two rock groynes and about 61,000 tonnes of imported granite rock armour, at a cost of roughly £2 million, to save the village and the B1242 coast road.
• Easington gas terminal is protected by a revetment.
• Most of the remaining coastline is designated for no active intervention or managed retreat, because the value of farmland does not justify the cost of defending it.

Evaluation, and this is the part that earns the top level. The Mappleton scheme succeeded on its own terms: the village is still there. But the groynes trap the sediment that longshore drift used to carry south, so the coast immediately downdrift at Great Cowden has been starved of material and now erodes at up to about 10 m in a single year, several times the natural rate. This is the classic demonstration that hard engineering can move the problem along the coast rather than solve it. The same logic threatens Spurn Head, a spit built entirely from Holderness sediment, which is being starved by every defence installed to the north of it.

17. Detailed specific example: the Great Barrier Reef, Australia

Syllabus point 2.3.8 requires one named coral reef, covering why it is important, the threats to it, and the strategies used to protect and manage it.

Location and scale. The Great Barrier Reef lies in the Coral Sea off the coast of Queensland, north east Australia. It stretches about 2,300 km, covers roughly 344,000 km², and is made up of around 3,000 individual reefs and 900 islands. It became a World Heritage Site in 1981.

Why it is important. It supports around 1,600 species of fish, 400 species of coral and six of the world's seven species of marine turtle. Reef tourism is worth roughly A$6 billion a year to the Australian economy and supports about 64,000 jobs. The reef also acts as a breakwater sheltering the Queensland coast, and as a nursery for commercial fish stocks.

Threats.

• Mass bleaching. Warming sea temperatures have caused repeated mass bleaching events, in 1998, 2002, 2016, 2017, 2020, 2022 and 2024. The 2016 event killed roughly 30 per cent of shallow water coral in the worst-affected northern sector.
• Water quality. Sediment, nitrogen fertiliser and pesticide wash off sugar cane and cattle land in the catchment. The nutrients also fuel outbreaks of crown of thorns starfish, a coral predator which can consume around 10 m² of coral a year each.
• Coastal development. Port expansion and dredging for coal and gas exports stir up sediment.
• Cyclones, which physically smash reef structure, and whose effects compound the damage from bleaching.
• Overfishing and tourist pressure.

Management.

• The Great Barrier Reef Marine Park Authority manages the whole area. Its 2004 Zoning Plan raised the proportion of the park in fully protected no-take green zones from around 4.5 per cent to about 33 per cent.
• The Reef 2050 Long-Term Sustainability Plan sets targets across water quality, biodiversity and coastal development.
• The Reef Water Quality Improvement Plan pays and trains farmers in the catchment to cut sediment and nitrogen run-off.
• Crown of thorns starfish control vessels cull the predator on high-value tourist reefs.
• Tourism operators need permits, use mooring buoys instead of anchors, and visitors pay a daily Environmental Management Charge that funds the park.
• Coral restoration and larval reseeding trials aim to speed up recovery on damaged reefs.

Evaluation. Zoning has worked: fish populations and coral trout numbers are measurably higher inside green zones than outside, and water quality targets have shifted farming practice across the catchment. But every one of these measures addresses a local threat. None of them lowers sea temperature, and bleaching is now the dominant cause of coral loss. The reef's long-term future therefore depends on global emissions policy rather than on anything the park authority can do inside its own boundary. That is the honest, sustainable judgement, and it is exactly the kind of conclusion an evaluation question is asking for.

18. Exam technique

How the extended answers are marked

The 7 mark extended responses in this topic are levels-marked, and the mark schemes are consistent about what separates the levels.

Never write an extended coastal answer without a named place. The 5 mark cap is applied mechanically.

Link the technique to the mechanism

One mark scheme is unusually explicit about this. Writing "groyne" on its own is Level 1. Writing "stop longshore drift" on its own scores zero. Writing "groynes stop longshore drift, so the beach builds up and absorbs wave energy" reaches Level 2. Every management technique you name must be followed by how it works.

Match your verb to the command word

• Describe means state the characteristics and main features. On a photograph question, describe what it looks like and say nothing about processes.
• Explain means say why and how, and support it with evidence. This is where the causal chains go.
• Suggest means apply your knowledge to a situation with several valid answers.
• Evaluate and assess mean reach a judgement. State it, and support it.

Shape for a process question

On a 3 or 4 mark process question, the mark scheme typically awards one mark for naming the process and the rest for explaining it. So:

1. name the process
2. state the mechanism in physical terms
3. state the effect on the landform.

Shape for an evaluation question

1. the strategy and how it works
2. its main benefit, with a figure or place
3. its main drawback, including any effect further along the coast
4. an overall judgement about whether it is sustainable.

19. Topic summary

• Fetch, wind speed and duration determine wave energy. Swash against backwash determines whether a beach grows or shrinks.
• Constructive waves break fewer than about 10 times a minute and build the beach. Destructive waves break more than about 10 times a minute and strip it.
• Wave refraction concentrates energy on headlands and disperses it in bays, which is why coasts tend to straighten over time.
• The four erosion processes are hydraulic action, corrosion, corrasion and attrition. Attrition wears down sediment, not the coast.
• Longshore drift is the zigzag of swash at an angle and backwash straight down, and it explains spits, bars and the sediment trapped behind groynes.
• Erosional landforms follow one sequence: notch, collapse, cliff retreat, wave-cut platform, and separately cave, arch, stack, stump.
• Discordant coasts have rock bands at right angles to the sea and give headlands and bays. Concordant coasts have them parallel and give straight coasts and coves.
• Hard engineering resists the sea, is expensive, and usually starves the coast downdrift. Soft engineering works with natural processes and is cheaper but slower.
• Tropical storms need sea surface temperatures of at least about 26.5 °C and enough Coriolis effect, so they form between roughly 5° and 20° of latitude and never on the equator.
• Tropical storm management is prediction, preparation, planning and protection. It cuts deaths dramatically and economic losses much less.
• Coral reefs need water of about 18 °C to 27 °C, less than about 60 m deep, clear and alkaline. Local management works, but only emissions cuts stop bleaching.
• Mangroves protect coasts from surge, nurse fisheries and store carbon, and are lost mainly to shrimp ponds.
• Every extended answer needs a named place, real figures, and a judgement.

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