Why Some Coasts Erode Faster: The Five Factors
Part of Coastal Processes and Landforms — GCSE Geography
This causation covers Why Some Coasts Erode Faster: The Five Factors within Coastal Processes and Landforms for GCSE Geography. Revise Coastal Processes and Landforms in Physical Landscapes in the UK for GCSE Geography with 15 exam-style questions and 22 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 6 of 14 in this topic. Use this causation to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 6 of 14
Practice
15 questions
Recall
22 flashcards
⛓️ Why Some Coasts Erode Faster: The Five Factors
Not all coastlines erode at the same rate. Comparing Holderness (losing 1.7 m/year) with the granite cliffs of Land's End (barely changing in recorded history) illustrates that erosion rate is determined by a combination of factors — not just wave energy alone.
This is usually the dominant factor. Hard, resistant rocks such as granite and basalt erode extremely slowly — they are crystalline structures with few cracks to exploit, and they do not dissolve. Softer rocks such as boulder clay, sand and shale erode much faster. Boulder clay — the material that makes up the Holderness cliffs — is a glacial deposit: a mixture of clay, sand and unsorted rock material left by retreating ice sheets. It has no internal structure to hold it together. When it gets wet, it becomes unstable and liable to slump. When waves remove material from the cliff base, the saturated material above simply flows down. Chalk and limestone are chemically vulnerable to solution erosion as well as mechanical attack, making them softer than they appear.
The size and energy of waves arriving at a coast depends on fetch. East-facing coasts in Yorkshire and Lincolnshire face the North Sea — with a fetch of up to 700 km across to Norway. South-west-facing coasts in Cornwall face the North Atlantic — fetch of 3,000 km or more. High-energy waves with long fetches have more power to erode, transport and deposit. The alignment of a stretch of coastline relative to the prevailing wind determines how directly it receives the full force of dominant wave energy.
A wide, deep beach is one of the most effective natural defences a cliff can have. Waves expend much of their energy travelling across a beach before they reach the cliff base — the beach absorbs and dissipates wave energy. Where longshore drift strips sediment from a beach (or human-built groynes and sea walls interrupt sediment supply), the cliff behind is exposed to the full force of waves. The Holderness coast has very little beach in many places precisely because longshore drift removes sediment southward faster than erosion can supply it.
Sea walls, rock armour and groynes can dramatically slow erosion where they are built. But coastal management in one location almost always has knock-on effects. A sea wall reflects wave energy rather than absorbing it — this can scour the beach in front of the wall and increase erosion at its ends. Groynes trap sediment on the updrift side but starve the beach downdrift. Development on cliff tops adds weight and increases the risk of slope failure. In general, human interference with the natural sediment budget tends to shift erosion problems rather than solve them.
Sea level rise — currently approximately 3 mm per year globally, but accelerating — means waves reach further up cliffs and beach sediment is submerged. More frequent and intense storms bring destructive waves more often. In the UK, projections suggest sea levels could rise by up to 1 metre by 2100 under high-emission scenarios. For soft-rock coasts like Holderness, this would significantly accelerate already rapid erosion rates. Climate change does not just threaten future generations — the acceleration is already measurable on vulnerable coastlines now.