Coastal Erosion, Sea Level Change & Flooding: A-Level Geography Review

What are the two main types of sea level change?

Eustatic and isostatic change.

What causes eustatic sea level change?

Changes in the volume of water in the ocean basins due to factors like melting ice and thermal expansion.

How does isostatic change occur?

It occurs when the height of the land changes relative to the water level.

Which type of sea level change happens more slowly?

Isostatic change.

What is thermal expansion in relation to sea level?

It occurs as water warms, causing it to expand and take up a greater volume.

What happens to sea levels when ice forms?

Sea levels may decrease as water is locked away in ice sheets and glaciers.

What is isostatic recovery?

The process where land rebounds to a higher level after the melting of heavy ice sheets.

What are raised beaches?

Beaches that are above high tide level, resulting from isostatic recovery.

What is a fossil cliff?

A steep slope at the back of a raised beach, which may show wave-cut notches, caves, and arches.

What are submergent landforms?

Landforms that exist because of a rise in sea level, often resulting in flooded coastal areas.

What is a 'ria'?

A drowned river valley that is long and funnel-shaped, created when coastal areas are flooded.

What is a fjord?

A deep, U-shaped valley that has been flooded, typically deeper than rias.

How much has global sea level risen since the start of the industrial revolution?

By about 235mm.

What is the IPCC's prediction for sea level rise by 2100?

Between 0.26 and 0.77 meters higher than current levels.

What impact does rising sea level have on coastal cities?

It can inundate cities, salinise aquifers, and increase coastal erosion.

What percentage of the world's cities are coastal?

75%.

What is the significance of understanding eustatic and isostatic changes?

They impact coastal morphology and recession rates.

What is accretion in the context of coastal geography?

The process where areas of net deposition cause land to build up within a sediment cell.

What causes subsidence in coastal areas?

Lowering of the water table or increased deposition weighing down the sediment.

What is the current state of isostatic recovery in the UK?

Land in Scotland is rebounding by approximately 1.5mm a year, while Landsend in Cornwall is sinking by 1.1mm each year.

What happens to land values in areas vulnerable to sea level rise?

Land values are likely to drop as land becomes increasingly eroded, salinised, or flooded.

What is the role of tectonics in sea level change?

Tectonic activity can lift the crust, reducing ocean capacity and causing sea levels to rise.

What is the significance of the last glacial period on current sea levels?

It caused a rise in sea levels by approximately 120 meters globally due to melting ice sheets.

What human actions contribute to rapid coastal recession?

Dredging, dam construction, and coastal management.

How does dredging affect coastal sediment?

Dredging removes sediment from rivers or the sea, reducing the amount deposited at the coast.

What is the impact of dams on coastal sediment supply?

Dams trap river sediment behind their walls, starving the coast of sediment and increasing erosion.

How much sediment is estimated to be stored behind the world's dams?

Approximately 100 billion tonnes, increasing by a billion tonnes each year.

What is terminal groyne syndrome?

It occurs when groynes reduce sediment supply to areas down the coast, leading to erosion.

What are the effects of reduced sediment supply on beaches?

Beaches decrease in size, leading to increased impact from destructive waves and greater erosion.

What is the role of coastal management in erosion?

Coastal management can either reduce erosion through defenses or affect sediment movement, impacting recession rates.

What are the sub-aerial processes that affect coastal erosion?

Weathering and mass movement.

What geological material predominates the Holderness coast?

Boulder clay.

How does wetting and drying affect boulder clay?

It causes the clay to crumble due to repeated expansion and contraction.

What is freeze-thaw weathering?

Water enters fractures in rock, freezes, expands, and causes the rock to weaken.

What is rotational slip in the context of coastal erosion?

A large area of land moves downslope in one piece due to heavy, lubricated clay.

What factors influence the rates of coastal recession?

Wind direction, tides, seasons, weather systems, and storms.

How does wind direction affect coastal erosion?

Onshore winds increase erosion rates, especially when aligned with the prevailing wind direction.

What is a spring tide?

The highest tide occurring when the Sun, Moon, and Earth are aligned, increasing gravitational pull.

When do rates of coastal recession peak?

During high tide when waves reach the backshore with more energy.

Why are erosion rates typically higher in winter?

Storm events causing destructive waves are more common in winter months.

What happens during anticyclones in coastal areas?

Gentle winds and low waves lead to lower rates of coastal recession.

What effect do storms have on coastal erosion?

Storms produce high-energy, destructive waves that significantly increase erosion rates.

What was the impact of the 2013/14 storms on Cornwall's coastline?

1,350 cubic metres of cliff face was eroded along a 300-metre stretch.

What is the estimated rate of erosion along the Holderness coast?

Approximately 1.8 metres a year.

How does the Aswan High Dam affect the Nile Delta?

It traps sediment, reducing the amount reaching the delta to almost nothing.

What is the consequence of reduced sediment supply to the Nile Delta?

Parts of the coast, like the Rosetta promontory, have eroded by over 100 m per year.

How do dams in California affect coastal beaches?

They cut sediment supply to beaches, leading to narrower beaches and increased cliff erosion.

What is the significance of coastal defenses like sea walls?

They can reduce erosion and slow the recession of the coast.

What is the impact of groynes on sediment movement?

They reduce longshore drift, affecting sediment supply to areas further down the coast.

What local factors increase flood risk on low-lying coasts?

Height of land, degree of subsidence, vegetation removal.

How does global sea level rise affect flood risk?

It further increases the risk of flooding in coastal areas.

Why are low-lying coastal areas often densely populated?

Attractive scenery, fertile deltas for agriculture, and suitability for ports and trade.

How many people live in coastal areas below 2m globally?

Almost 300 million people.

Which countries are particularly low-lying and vulnerable to flooding?

Bangladesh, Maldives, Netherlands.

What percentage of Bangladesh is 1m or less above sea level?

Over 10%.

What is the average height of the Maldives above sea level?

2m, with the highest point being 2.4m.

What percentage of the Netherlands is below sea level?

27%.

What causes storm surges?

Depressions (low pressure) and tropical cyclones.

What is the inverse barometer effect?

For every 10mb decrease in pressure, sea level rises by 10cm.

What defines a tropical cyclone?

An area of very low air pressure formed by warm rising air from the ocean.

At what wind speed is a storm categorized as a tropical cyclone?

When wind speeds reach 74 mph.

What are some short-term impacts of storm surges?

Deaths, destruction of homes, increase in waterborne diseases, loss of infrastructure.

What are the two main factors increasing flood risk due to climate change?

Global sea level rise and increased frequency/magnitude of storms.

How much have global sea levels risen since 1880 according to NOAA?

About 21-24 cm.

What is the predicted sea level rise by 2100 according to the IPCC?

Between 26-77 cm.

What impact would a 50cm sea level rise have?

It would impact 800 million people and put £120 billion worth of infrastructure at risk in the UK.

What has been observed about the frequency and intensity of tropical cyclones since the 1970s?

The frequency and intensity of the strongest tropical cyclones have increased.

What is the role of vegetation in reducing flood risk?

Vegetation traps sediment, reduces wave height, and absorbs wave energy.

What percentage of salt marshes and mangroves have been lost since the 1950s?

50% of salt marshes and 35% of mangroves.

What human activities contribute to the removal of coastal vegetation?

Reclamation for development, coastal management, tourism, and shrimp farming.

What is a depression in meteorological terms?

An area of low pressure that forms due to rising air, leading to clouds and rain.

How do depressions move in the northern hemisphere?

West to east in an anticlockwise direction.

What is the significance of the IPCC report (2013) regarding tropical cyclones?

It states that the intensity of tropical cyclones is likely to increase.

What is the importance of evaluating multiple risk factors in flood risk assessments?

It provides a comprehensive understanding of how different factors contribute to flood risk.