Coastal Processes Lab

Land versus sea

A coastline is where land and sea fight it out. The sea erodes rock, transports the broken material along the shore, and deposits it elsewhere to build new features. Those three processes carve erosional landforms like caves and stacks, and build depositional ones like beaches and spits. Where people live on an eroding coast, protecting it means hard choices - and real conflict.

Four ways the sea erodes

Coastal erosion works in four distinct ways. Learn the exact names and mechanisms.

Match each process to how it works

Moving along the coast

In longshore drift, what carries sediment up the beach at an angle?

• The swash, driven by waves hitting the beach at the angle of the prevailing wind
• The backwash, running back down the beach
• Attrition between the pebbles
• Deposition of the sediment

How a stack forms

A resistant headland is eroded over time. Put the stages of forming a stack into order.

• Waves erode a crack or fault in the headland
• The crack is widened into a cave
• The cave is eroded right through to form an arch
• The arch roof collapses, leaving an isolated stack

Where the sediment lands

Longshore drift does not just move sediment - it builds things where the coast slows the water down: - A beach forms where sediment is deposited along the shore.\n- A spit grows where the coastline bends but drift carries sediment straight on into open water.\n- A bar can seal off a bay, trapping a lagoon behind it. These are depositional landforms - the opposite of the erosional caves, arches and stacks.

Erosion or deposition?

Which of these is a depositional landform?

• A spit
• A stack
• An arch
• A wave-cut platform

Hard vs soft engineering

To defend a coast, planners choose between hard engineering (build a barrier) and soft engineering (work with natural processes). Each has trade-offs in cost, effectiveness and impact.

Spot the hard defences

Select the TWO methods that are hard engineering.

• A sea wall
• Groynes
• Beach nourishment
• Managed retreat

Match each defence to its job

The longshore drift cycle

Put the steps of longshore drift moving sediment along a beach into order.

• The prevailing wind drives waves onto the beach at an angle
• The swash carries sediment up the beach at that angle
• The backwash drags sediment straight back down under gravity
• Repeated, the sediment zigzags along the coast

Manage the conflict

Three coastal management decisions on an eroding soft-clay coast. Pick the answer that reflects the real trade-offs.

• A village wants a sea wall to stop its cliffs eroding. What is the core conflict a planner must weigh?
• Environmental groups oppose expensive hard defences along a stretch of low-value farmland. What approach might suit?
• A council wants a long-term plan for the WHOLE coastline and all its users, not just one town. Which framework fits?

Evaluate the defences

The Holderness Coast in Yorkshire has soft boulder-clay cliffs and is one of the fastest-eroding coastlines in Europe. At Mappleton, groynes were built to trap sediment and protect the village, but this starved the coast further south, speeding up erosion there. Using this example, evaluate whether hard engineering is the best way to manage such a coast.

• Give one strength of the hard defence (e.g. it protects Mappleton and its road)
• Give one problem it causes (e.g. downdrift erosion further along the coast)
• Refer to the competing stakeholders (Mappleton residents vs communities to the south)
• Reach a justified judgement, considering soft engineering or ICZM as alternatives

Management is a conflict

Top coastal answers do two things. First, they treat management as a conflict with no single right answer: on somewhere like Holderness, protecting one village with groynes can speed up erosion for the next community along, so residents, businesses and environmental groups all pull different ways. Second, they weigh alternatives - hard engineering, soft engineering and Integrated Coastal Zone Management - against cost, sustainability and who benefits, rather than declaring one always best. (Remember this coastal topic also feeds your Topic 6 coastal fieldwork, so revise the two together.)