Waves
Waves are generated by wind blowing over the sea. The characteristics of waves are determined by the strength of the wind, its duration and fetch (distance a wave travels). The stronger the wind the greater the friction on the surface of the sea and therefore the bigger the wave.
Constructive waves
Constructive waves are flat and low in height and have a long wave length. Their strong swash carries material up the beach, forming a berm. They have a low frequency of between 6 and 8 waves per minute. The wave energy dissipates over a wide area which results in a weak backwash.
Destructive waves
Destructive waves have a large wave height and short wave length. They have tall breakers that have a high downward force and a strong backwash. Their frequency is high with between 13 and 15 waves per minute. Their strong downward energy helps erode beach material and cliffs. The strong backwash results in narrow beach profiles.
Tides
Tides are the rise and fall of sea levels. Tides are caused by the gravitational pull of the moon and to a lesser extent the sun. When the earth, the moon and sun are aligned the gravitational pull is at it’s greatest. This creates a Spring tide. A Spring tide results in a high, high tide and low, low tide. This creates a high tidal range (difference between the highest and lowest tide) and results in stronger tidal currents than normal. Spring tides usually occur twice a month when there is a full moon.

When the sun and moon are at a right angle to the earth we experience Neap tides. The gravitational pull of the sun partially cancels the moon’s. This results in a low, high tide and a high, low tide. This creates a low tidal range and results in weaker tidal currents than normal.

Sub-Aerial Processes
Sub-aerial process are land based processes which alter the shape of the coastline. These are a combination of weathering and mass movement.
Sub-aerial processes – weathering
Weathering is the decay and disintegration of rock in situ. There are two main types of weathering that affect the coast. These are mechanical and biological weathering.
Mechanical (physical) weathering
Mechanical or physical weathering is the fracture and breakdown of rocks into fragments. Along the coast it may be caused by frost shattering (freeze-thaw), salt crystallisation, wetting and drying, or even biologically.
Mechanical weathering refers to physical processes such as freeze-thaw and biological weathering. Freeze-thaw occurs when water gets into cracks in rocks and freezes. This then expands by around 10%. The repeated freeze thaw action puts pressure on the rocks until they eventually crack and break the rock. Freeze-thaw usually occurs when the temperature oscillates around freezing point. The shattered angular fragments of rock accumulate around the base of the cliff as scree (talus). As coastal climates tend to be milder this process is only really effective during very cold winters.
A common type of mechanical weathering found at coasts is salt crystallisation. This is when salt crystals are deposited in cracks and over time the salt accumulates and applies pressure to the crack (similar to freeze-thaw weathering).
Wetting and drying is common along coastlines. Clay rich rocks are prone to expand when they are wet and contract when they dry. This results in cracks which are vulnerable to both freeze-thaw and salt crystallisation.
Biological weathering is mechanical when there is a physical effect. An example of this is when growing plant roots widen cracks as does the leverage created by bushes and trees swaying in strong winds. Burrowing animals and nesting birds excavate material in partially weathered and eroded cliffs.
Chemical weathering
Chemical weathering involves decomposition of rocks (literally, changing the minerals). Chemical weathering occurs as a result of a weak chemical reaction between water and rock. eg. with limestone. Rainwater mixed with carbon dioxide in the atmosphere forms Carbonic acid. This then reacts with calcium carbonate in limestone to form calcium bicarbonate. Bicarbonate is soluble in water and the limestone gets weathered when carbonation occurs.
The role of weathering is to weaken cliffs. This weakening speeds up the rates of erosion.
Sub-aerial processes – mass movement
Mass movement is the movement of material downslope as the result of gravity. This can be a slow process in the case of soil creep or fast in the case of rockfalls. Water commonly acts as a lubricant in mass movement.
Soil creep
Soil creep is a slow but continuous process. It typically occurs on most slopes over 5 degrees. Soil creep rarely exceeds speeds of 1cm per year. Creep occurs as the result of repeated expansion and contraction of material. Cycles of freeze thaw heave particles up on freezing and allow them to fall further down slope when the ice melts. Alternating hydration and dehydration have the same effect.
Earth flows
Earth flows tend to be faster than slow creep but less sporadic. Earthflows have a characteristic “hourglass” shape. The slope material liquefies and runs out, forming a bowl or depression at the head. The flow itself is elongate and usually occurs in fine-grained materials or clay-bearing rocks on moderate slopes and under saturated conditions. However, dry flows of granular material are also possible.
Mud flows
A mudflow is an earthflow consisting of material that is wet enough to flow rapidly and that contains at least 50 percent sand, silt, and clay-sized particles. In some instances, for example in many newspaper reports, mudflows and debris flows are commonly referred to as “mudslides.”

Slide / Slumps
One of the most common types of mass movement along the coast are rotational slumps. The image below shows slumping at Tunstall, Holderness Coast.
Slumps happen because of a number of factors. Firstly, marine processes erode and undermine the base of the cliff. Rainwater infiltrates the cliff through unconsolidated, porous material (e.g. boulder clay). This then creates a slip plane. The weight of the saturated clay causes the material to slump along the slip plane. The process is illustrated in the diagram below.
Rockfall
Rockfalls are usually associated with near vertical slopes. Only more resistant rock can sustain these angles on the coast. They are most commonly triggered by undercutting in the inter-tidal zone or freeze-thaw weathering.
Run-off
Run-off has the ability to move fine material downslope, particularly where overland flow occurs as a thin, continuous layer (sheet flow) and washes silt and clay sized particles.

Marine Processes
Marine processes are those associated with the action of waves.
Erosion
Erosion refers to the wearing away of the land surface and removal of materials by river and sea water, ice and wind. There are four main processes of erosion along the coast. These are hydraulic action, abrasion and corrasion, attrition and solution.
Hydraulic action
Waves breaking at the foot of a cliff force air in cracks to be compressed. Loose rocks are dislodged and removed. When the wave retreats the compressed air rushes out of the crack and can further weaken faults in the cliff face.
Abrasion
Abrasion is the sandpaper effect of loose rocks being scraped along bare rock. It often smooths and polishes the rock.
Corrasion
Corrasion is when rock caught up in surging waves are hurled at a cliff face – causing it to be chipped and gauged.
Attrition
Attrition is when rocks carried by seawater collide – gradually making them smaller and smoother.

Transportation
Transportation is movement of sediment by the action of waves.
Traction
Traction involves the rolling of large and heavy rocks along the seabed.
Saltation
Saltation involves smaller material being bounced along the seabed.
Suspension
Suspension is when lighter sediment is suspended within the water. This often discolours the water close to the shore.
Solution
Sediment that has dissolved completely will be transported in solution.

Deposition
Deposition occurs when energy levels decrease in environments such as bays and estuaries. Where deposition occurs on the inside of a spit a salt marsh can form.
Longshore Drift (littoral drift)
Longshore drift is a process responsible for moving significant amounts of sediment along the coast. This usually occurs in one direction as dictated by the prevailing wind. For example the prevailing wind along the Holderness Coast is north-easterly. As the result waves break on to the beach obliquely at an angle of around 45 degrees. The swash moves beach material along the beach and the backwash, under gravity, pulls the material back down the beach at right angles to the coastline. Over time this creates a net shift of material along the coast.
Where the removal of beach material exceeds the supply erosion occurs. This is illustrated in the photograph below where a large rock groyne at Mappleton stops the supply of new beach material. As the result longshore drift transports material from the beach to the south of the groyne and is not replenished. This leads to a lack of beach material and therefore protection for the soft, boulder clay cliffs.

Landforms of deposition
Landforms of deposition occur where accumulation of sand and shingle is greater than it is removed. This is particularly the case where constructive waves are prevalent or where there is an abundant amount of beach material supplied. Beaches and associated features: berms, runnels and cusps
Beaches are dynamic environments which for the buffer between land and sea. They have 3 main components, the nearshore (where the land begins to affect the sea), the foreshore (surf zone) and the backshore (usually above the high tide mark). The backshore typically features the material deposited by storm waves.

The gradient of the beach tends to change during the year. Beaches are typically steeper in summer. This is because constructive waves are more common in summer, but destructive waves are more common in winter.
The strong swash of a constructive wave deposits the largest material at the top of the beach. As the upper beach builds up, the backwash becomes even weaker because a greater proportion of the water drains away by percolation, rather than running down the beach.
The weak swash of a destructive wave deposits material at the base of the beach. It cannot advance further up the beach because it is destroyed by the backwash from the previous breaking wave.
Ridges and runnels form parallel to the shore line in the foreshore zone. Ridges are areas of the foreshore that are raised above the adjacent shore which dips into a Runnel.

If you were to look at the cross-section (see below) it would appear similar to that of hills and valleys but at a much smaller scale.
Ridge and runnel systems are formed due to the interaction of tides, currents, sediments and the beach topography. They only form on beaches with a shallow gradient. They form as a simple drainage route for tides. Water flows in and out via the runnel.
Spring tides often form a storm ridge which consists of the largest material thrown up by the strong swash of the larger waves. Following tides often cannot reach these features therefore they remain largely untouched. There are often a series of smaller ridges formed beneath the storm ridge known as berms. These mark the successive high tides that follow the spring tide through to the neap tide.

Cusps are crescent-shaped indentations that form on beaches of mixed sand and shingle. They are formed where there is a junction between sand and shingle. Once the curving shape is created, swash is concentrated in the small bay that forms in the centre of the cusp. This creates a stronger backwash that removes material down the beach.

Spits are formed where the coast suddenly changes direction e.g. across a river mouth. Longshore drift continues to deposit material across the mouth of a river which results in the formation of a long bank of sand and shingle forming. The image below shows Spurn Head which has been formed by the deposition of material transported by longshore drift from north to south along the Holderness Coast. Where the coast changes direction where it meets the mouth of the Humber Estuary this material continues to be deposited forming Spurn Head. A salt march has formed on the inside, sheltered side of Spurn Head (right of the picture).
Changes in the prevailing wind and wave direction can cause a spit to form a recurved end. Over time several recurved ends may form as waves return to their dominant direction. Where the wind is strong enough to lift sediment of the beach dunes may form which adds stabilisation to the spit when pioneer plants such as marram grass anchor the sand.
Bars and Tombolo
A bar is a spit that joins together two headlands. Bars are particularly obvious at low tide when they become exposed. At high tide bars make the water shallow which often causes waves to break early. A lagoon may be formed within a bay as the result of a bar. Where a spit links the mainland and an island a tombolo is formed.
Dunes are landforms formed from sand deposits that have been blown off the beach. Where sufficient sand is deposited and dries in the intertidal zone (foreshore – area between the high and low tide marks) it is then transported by saltation by the blowing wind. Sand dunes only form where the rate of beach deposition is greater than erosion (positive sediment budget).
When the dried sand reaches the top of the beach it can be trapped by debris such as driftwood, dead seaweed or rocks and pebbles. If the sand is not eroded again it may become colonised by small plants, or trap other windblown debris, increasing its size and thus trapping even more sand. The PH of the sand is very alkaline here (carbonate from sea shells) and only the most hardy plants such as lyme grass and sand couch colonise.
The first dunes to form are known as embryo dunes. They contain species such as lyme grass, sand couch and marram grass. These species survive by growing upwards through accumulating wind blown sand. These plants add organic matter to the dunes making the dunes more hospitable for plants that later grow. These dunes tend to grow to around 1m.
The next stage in the sequence of sand dune development is the formation of foredunes or yellow dunes. These are initially yellow but darken as organic material adds humus to the soil. The dunes remain slightly alkaline. Foredunes tend to grow to around 5m in height and around 20% of the sand is exposed (this is down from around 80% of embryo dunes). Very little moisture exists in this area.
The next stage is the formation of grey dunes and dune ridges. By this stage the dunes are more fixed. The soil becomes increasingly acidic as more humus forms which in turn increases water retention. Combined this allows new species of plants to thrive e.g. creeping willow and dewberry. Less than 10% of the sand is exposed on these dunes which tend to be between 8-10m high.
Very little sand from the beach accumulates beyond the grey dunes and dune ridges which leads to the formation of wasting dunes. Here the soil is more acidic, water retentive and rich in humus. Typical vegetation here includes heather and gorse. Dune height here is usually between 6-8m high.