Factors Affecting Landform Change
Why Some Landforms Change Faster
Two stretches of UK coast can sit only a short drive apart and erode at completely different rates. The Holderness coast in East Yorkshire is losing nearly two metres of cliff a year, while the chalk cliffs of the Seven Sisters lose only a few centimetres. The pattern is not random — three factors decide how fast a river or coastal landform changes: geology, climate and human activity.
Geology — Rock Type and Structure
The kind of rock at the surface decides how easily waves and rivers can break it down. Hard, well-cemented rocks like granite or chalk resist erosion. Soft, weakly-cemented rocks like clay and sand are stripped away quickly. The arrangement of these rocks matters too.
A concordant coastline has rock bands running parallel to the sea, so a single rock type forms long stretches of cliff. A discordant coastline has rock bands running at right angles to the sea, so soft rocks erode into bays between hard headlands.
A concordant coast looks regular and straight. The Lulworth coast in Dorset is partly concordant, with hard Portland limestone protecting softer rocks behind. A discordant coast looks crinkly. Studland Bay further east in Dorset shows it: hard chalk forms the headland at Old Harry Rocks while softer clays form Studland Bay just to the north. Geology also affects rivers — a waterfall like High Force on the Tees only exists because hard Whin Sill dolerite sits above softer limestone.
Climate — Wind, Waves and Storms
Climate sets the energy environment. The prevailing south-westerly wind drives most large UK waves onto the south and west coasts of Cornwall, Devon and west Wales. The further the wind has blown over open sea, the more powerful the waves — this distance is called fetch. Cornish beaches face an Atlantic fetch of over 5,000 km, so even a modest gale produces waves that pound the cliffs.
Most UK landform change happens in short, dramatic bursts during extreme weather. The winter of 2013–14 was one of the stormiest on record. Storms tore down the railway sea wall at Dawlish in Devon, the chalk cliff at Birling Gap in East Sussex lost up to seven years' worth of erosion in a single stormy winter, and rivers like the Thames and Severn flooded for weeks. Climate change is expected to bring more frequent storms and higher sea levels, accelerating both river and coastal erosion.
River discharge is also climate-driven. Heavy rain over saturated upland catchments — common in winter — produces sharp peaks in flow. These short, intense events do most of the erosion. In summer, low river levels mean little material moves and deposition can briefly dominate even in upper-course rivers.
Human Activity — Speeding Up and Slowing Down
Humans both protect and disturb landforms. Defences such as sea walls, groynes and rock armour are designed to slow erosion. They often work locally, but they can speed up erosion further along the coast.
A clear example is Mappleton on the Holderness coast. In 1991, two large rock groynes were built to trap sand on the village beach, with rock armour along the foot of the cliff between them. The groynes worked — the village stopped collapsing into the sea — but they cut off the supply of sand moving south along the coast. Within a few years, cliffs at Cowden and Aldbrough just to the south began retreating much faster than before, leaving farms and roads at risk. The groynes saved one place by accelerating loss elsewhere.
Coastal defences interrupt the natural longshore drift, a process called terminal groyne syndrome. Sediment is trapped behind the structure, and the next stretch of coast is starved of sand — so it erodes faster.
Rivers Feel Human Pressure Too
River landforms also speed up or slow down because of what people do. Removing trees from upland catchments allows rain to reach rivers faster, sharpening flood peaks. Straightening river channels (channelisation) makes water flow more quickly, so erosion accelerates downstream. Dams and reservoirs do the opposite — they trap sediment and starve floodplains of new alluvium. The lower River Severn, controlled by reservoirs in mid-Wales, deposits less than it did a century ago.
Holderness illustrates all three factors at once. Geologically, the cliffs are made of soft boulder clay left behind by the last ice age — weak material that crumbles easily. Climatically, the coast faces a 700 km North Sea fetch and a stormy wind from the north-east. Socially, defences at Hornsea and Mappleton trap sand and starve the cliffs further south. Together these explain why the coast loses around two metres a year — one of the fastest erosion rates in Europe.