Coasts as a system

Inputs,outputs, energy, stores/components, flows/transfers,positive/negative feedback,dynamic equilibrium

Inputs

Material or energy moving into the system from the outside

Examples

Precipitation

Wind

Output

Material or energy moving from the system to the outside

Example

Ocean currents

Rip tides

Sediment transfer

Evapouration

Energy

Power or driving force

Examples

Energy associated with flowing water

The effects of gravity on cliffs

Moving air

Stores/components

The individual elements or parts of a system

Examples

Beach

Sand Dunes

Nearshore sediment

Positive feedback

Where a flow/transfer leads to increase or growth

Coastal management can inadvertently lead to an increase in erosion elsewhere along the coast. Groynes trap sediment, depriving areas further down-drift of beach replenishment and this can exacerbate erosion. Seawalls can have the same effect by transferring high energy waves elsewhere along the coast

Negative feedback

Where a flow leads to decrease or decline

When the rate of weathering and mass movement exceeds the rate of cliff-foot erosion a scree slope is formed. Over time, this apron of material extends up the cliff face protecting the cliff face for sub aerial processes. This leads to a reduction in the effectiveness of weathering and mass movement

Dynamic equilibrium

This represents a state of balance within a constantly changing system

Coastal land forms and Landscapes

The concepts of Landforrm and landscapes and how related landforms combine to form characteristic landscapes

Landscape

The coastal landscape is the "big picture". It refers to the whole coastline that is being viewed and includes the coast and countryside linked to it. It is the broader picture and is made up different features including landforms

E.G - The Jurassic Coast

Different land forms combine to give unique coastal landscapes

Landforms

A landform is an individual component of the coastal landscape. They are a distinct part of the wider coastal landscape but must be viewed individually

E.g A stack

Helps form the landscape

Waves

The formation of waves and their size and shape is a result of the exchange of energy wind blowing over the sea. The longer the wind blows for, and greater the distance it blows over, the larger the waves that result and the greater their energy

The extent to which the shape of a beach or coast can be altered depends largely on the action of waves upon it. Waves can be gentle and infrequent or larger, more frequent and more powerful

Other factors include

Wave strenght

Time Wind blows for

Distance (fetch)

Key Terms

Wave fetch- The distance of open water over which a wave had passed. Maximum fetch is the distance from one coastline to the next landmass, it often coincides with prevailing wind direction

Wave crest-Highest point of a wave

Wave trough-Lowest point of the wave

Wave height- Distance between trough and crest(Amplitude)

Wave length-Distance between one crest/trough and the next

Swash- Water movement up a beach

Backwash-Water movement down a beach

Wave Refraction

It is very rare for waves to approach a regular uniform coastline, as most have a variety of bays, beaches and headlans

Because of these features, the depth of water around the coast varies and as a wave approaches a coast its progress is modified due to friction from the seabed,halting the motion of waves.

As waves approach a coast they are refracted so that their energy is concentrated around the headlands but reduced around bays. Waves then tend to approach the coastline parallel to it, and their energy decreases as water depth increases

Constructive waves

Long wavelength

low amplitude

Strong swash pushes sediment up the beach

Weak backwash

Strong Swash

Net impact - gain

Net process - deposition

Destructive waves-

Short wave length

Steep wave faces and high wave height

Backwash is very strong and drags material back down the beach

Backwash = strong

Swash = weak

Net process - erosion

Net impact - coastal loss

Tides

Causes

Gravitational pull of sun +moon

Moon = bigger influence

Moon impact varies every day - this is because the moon spins on a axis

Moon pulls water towards it creating high tides and there is a compensatory bulge on the other side of the earth - results in " high tides and 2 low tides

Spring Tides

1) as the moon orbits the earth the tide follows it. Twice in a lunar month when the sun-moon and earth are in a straight line, the tide raising force is the strongest

Produces the highest monthly tidal range

Neap tides

Twice a month the sun and moon are positioned at 90˚ to each other in relation to the earth

This alignment gives the month tidal range, or neap high tide

Tidal Range

This is the height between the low and high tide

Severn estuary = highest

Significant factor in the development of a coastline

Mediterranean Sea Tidal ranges are low

Restricts wave action to a narrow width of the coastal zone.

UK - ranges are high --> gives a wide zone of attack, resulting in the formation of wave cut platforms

Currents

movement of energy in water

Often follow a circular pattern

Move in similar patterns either side of the equator

Clockwise = northern hemisphere, Anit-clockwise = Southern hemisphere

Sediment Cells

Types of sediment

Clastic

Biogenic

Non-cohesive sediment

Cohesive sediment

Sources

Rivers

Cliffs - erosion

Longshore drift

Tides, waves, currents

Biogenic - marine organisms providing sediment such as skeletons

Run-off - saturated cliffs have surface water that runs off and brings sediment to the coast

What are sediment cells

movement of sand and shingle in the nearshore zone by longshore drift has been found to occur in discrete, functionally separate sediment cells

11 cells around UK coastline

Smaller sub cells idenified

Self-contained

Natural processes

Sub-arieal Weathering

Erosion

Mass movement- This is the movement of large areas of material downslope under the force of gravity (Cliff Collapsing)

Freeze-Thaw/mechanical-

Chemical-

Biological-

Abrasion-Sediment chipping away

Corrosion -

Transportation

Attrition-

Hydraulic Action - The sheer force of the waves

Suspension-

Solution-

Traction-Rolling of large sediment

Saltation -

Sediment budgets-

The material contained in a sediment cell can be viewed in the form of a budget

It has gains and losses

Sediment Gain-cliff erosion, river deposition, tidal deposition

Sediment loss- deposition in sediment sinks (stores) such as bars, spits, dunes or human dredging

Said to be in a state of dynamic equilibrium

Upsetting the balance- storms, flooding, human engineering

1) This is also called physical weathering/ freeze thaw weathering or frost shattering

2) It is the direct result of atmospheric - rainfall and temperature

3)It is common in the areas with a high diurnal temperature range

Diurnal- between day and night/hottest and coldest points

1) This involved the action of chemicals in weather conditions (acid rain) dissolving certain rock types over time. The decomposition is a result of chemical change

Oxidation

Hydration

Hydrolysis

Carbonation-one to refer to limestone and chalk

This is the result of organic agents

For example - tree roots growing into and widening a crack in rocks or the action of burrowing animals physically enlarging joints in weak rocks

Some Sea Creatures like piddocks actually drill into rocks leaving them pitted with holes

Salts within the seawater slowly dissolve carbon based rocks

Links with solution

Larger Sediments collide

Links with traction

Links to attrition

Slightly smaller sediment is flipped in the swash

Sediment held in the water - fine sediment -sandy

Links with Abrasion

Sediment that has been dissolved

Links with solution

Long shore Drift- The movement of sediment along a beach due to swash and backwash

Falls- rapid movement of material on vertical/steep slopes over 40 degrees

Slides- A type of mass movement where large areas of coastal rock and soil slide downwards from the cliff

Slump-Very similar to a slide only it usually involves a smaller distance of movement that is on curved axis

A rotational movement

Earth/mud flows- Saturated soil moving under its own weight on slopes 5-10 degrees

Soil creep-Very slow (1cm per year) movement of material due to raindrop impact, saturation and freeze-thaw expansion

Deposition