Coastal Systems and Landscapes
Define the concept of a coastal sediment budget.
EXAM ANSWER
The coastal sediment budget is the balance between sediment inputs (sources such as cliff erosion or fluvial discharge) and sediment outputs (sinks such as offshore bars or dredging) within a coastal cell. A positive budget indicates accretion, while a negative budget leads to coastal recession.
Pro Tip: Always use the term ‘dynamic equilibrium’ when discussing how coastal systems adjust to changes in the sediment budget.
EASY ANSWER
It is like a bank account for sand. If more sand arrives than is taken away by waves, the beach grows. If more sand leaves than arrives, the beach disappears.
Distinguish between eustatic and isostatic sea-level change.
EXAM ANSWER
Eustatic change is a global change in sea level caused by variations in water volume (e.g., thermal expansion or ice melt). Isostatic change is a local change in land level relative to the sea, caused by the weighting or unweighting of the Earth’s crust, such as post-glacial rebound.
Pro Tip: In questions about climate change, prioritise eustatic sea-level rise due to thermal expansion and its global impact.
EASY ANSWER
Eustatic is when the water level rises or falls everywhere (like filling a bathtub). Isostatic is when the land itself moves up or down (like a person sitting on or getting off a mattress).
Explain the process and impact of wave refraction.
EXAM ANSWER
As waves approach an irregular coastline, they slow down in shallower water off headlands but continue at speed in deeper water off bays. This causes the wave crests to bend (refract), concentrating wave energy on headlands (causing erosion) and dissipating energy in bays (causing deposition).
Pro Tip: If asked to draw a diagram, ensure the wave crests are perpendicular to the direction of travel to show energy concentration on headlands.
EASY ANSWER
When waves hit a bumpy coast, they wrap around the parts sticking out (headlands). This focuses all the power on the headlands and makes the water calmer in the curved bits (bays).
What is a sediment cell and why is it considered a ‘closed system’?
EXAM ANSWER
A sediment cell is a distinct length of coastline where the movement of sediment is largely self-contained. It is theoretically a closed system because sediment does not cross the boundaries (usually headlands or deep-water trenches), meaning inputs and outputs are balanced within the cell.
Pro Tip: Reference the UK’s 11 major sediment cells to demonstrate locational knowledge in your case studies.
EASY ANSWER
A sediment cell is like a self-contained neighbourhood for sand. Most of the sand stays within those borders and doesn’t move to the next ‘neighbourhood’ along the coast.
Compare Rias and Fjords as submergent landforms.
EXAM ANSWER
Rias are drowned river valleys formed by rising sea levels, typically V-shaped in cross-section and winding in plan view. Fjords are drowned glacial troughs with steep, U-shaped sides and deep basins, often featuring a shallow ‘threshold’ at the mouth where the glacier met the sea.
Pro Tip: Mention that rias reflect the original dendritric drainage pattern of the river system for top marks.
EASY ANSWER
A ria is a flooded river valley that looks like a wide, wiggly river. A fjord is a flooded valley carved by a glacier, so it is much deeper and has very steep cliffs on either side.
Describe the process of rotational slumping in coastal landscapes.
EXAM ANSWER
Rotational slumping is a form of mass movement where saturated material moves downwards along a curved slip plane. It often occurs on cliffs composed of incompetent rock (like clay) when heavy rainfall increases pore water pressure, reducing friction and causing the material to slide under gravity.
Pro Tip: Always mention ‘pore water pressure’ as the lubricant that triggers mass movement on clay cliffs.
EASY ANSWER
When a cliff gets soaked with rain, a huge chunk of it slides down in a curved way, like a person sliding down the back of a sofa. It leaves behind big ‘steps’ in the land.
Contrast high-energy and low-energy coastal environments.
EXAM ANSWER
High-energy coasts (e.g., North Atlantic) have powerful waves, high fetch, and dominant erosional processes, resulting in landforms like stacks and stumps. Low-energy coasts (e.g., the Mediterranean) have calmer waves, limited fetch, and dominant depositional processes, creating landforms like spits and salt marshes.
Pro Tip: Link the energy level to the ‘fetch’ (the distance the wind blows over the water) to explain why some coasts are more powerful than others.
EASY ANSWER
High-energy coasts are wild and stormy with big waves that smash cliffs. Low-energy coasts are peaceful where sand builds up and creates flat beaches and marshes.
Evaluate the difference between hard and soft engineering.
EXAM ANSWER
Hard engineering involves man-made, solid structures (e.g., sea walls, groynes) to resist natural processes; these are often expensive and can disrupt natural systems. Soft engineering (e.g., beach nourishment, managed retreat) works with natural processes to manage risks, generally being more sustainable and cost-effective.
Pro Tip: Use the Shoreline Management Plan (SMP) terminology such ‘Hold the Line’ or ‘Managed Realignment’ when discussing these strategies.
EASY ANSWER
Hard engineering is building walls and fences to fight the sea. Soft engineering is working with nature, like adding more sand to a beach or letting the sea flood certain areas on purpose to protect others.