Coasts Flashcards
The littoral zone
The wider coastal zone
Includes adjacent land areas and shallow parts of the sea just offshore
Cliff, FS, BS, OS, NS
Cliff profile
The height and angle of a cliff face as well as its features such as wave-cut notches or changes in slope angle
Coastal accretion
The deposition of sediment at the coast and the seaward growth of the coastline, creating new land
Often involves sediment deposition being stabilised by vegetation
Dynamic equilibrium
The balanced state of a system when inputs and outputs balance over time
If one element in the system changes because of an outside influence, the internal equilibrium is upset and other components change
Through feedback, the system adapts to change and the equilibrium is regained
Faults
Major fractures in rock produced by tectonic forces and involving the displacement of rocks on either side of the fault line
Holocene
The geological epoch that began about 12,000 years ago at the end of the last Pleistocene ice age
Early stages were marked by sea level rises of about 35m and a warming interglacial climate
Unconsolidated sediment
Material such as sand, gravel and clay and silt that has not been compacted and cemented to become sedimentary rock (has not undergone lithification) so it is easily eroded as it is loose
Pore water pressure
The pressure water experiences at a particular point below the water table due to the weight of the water above it
Swash
The flow of water up a beach as a wave breaks
Backwash
When water runs back down the beach to meet the next incoming wave
Fetch
The uninterrupted distance across water over which a wind blows, and therefore the distance waves have to grow in size
Beach morphology
The shape of a beach, including its width and slope (the beach profile) and features such as berms, ridges and runnels
It also includes the type of sediment (shingle, sand and mud) found at different locations on the beach
Blow hole
Forms when a coastal cave turns upward and breaks through the flat cliff top
Usually because of erosion especially at weak strata or the presence of a fault line
Currents
Flows of seawater in a particular direction driven by winds or differences in water density, salinity or temperature
Some are almost continuous, the global thermohaline circulation
Others more sporadic e.g. longshore currents
Some for hours e.g. rip currents
Mass movement
The downslope movement of rock and soil; it is an umbrella term used for a wide range of specific movements including a landslide, rockfall and rotational slide
Isostatic change
A local rise or fall in the land level
Eustatic change
Involves a rise or fall in water level caused by a change in volume of water
This is a global change
Affecting all the world’s connected seas and oceans
Accretion
This occurs when sediment is added to a landform, such as a river delta, by deposition. It can be built up to form new land, allowing a delta to grow out to sea
It tends to balance the subsidence caused by the weight of the newly deposited sediment
Post-glacial isostatic adjustment
Refers to the uplift experienced by land following the removal of the weight of the ice sheets
Often called post-glacial rebound or post-glacial readjustment
Ria
A drowned river valley in an unglaciated area caused by sea level rises flooding the river valley, making it much wider than would be expected based on the river flowing into it
Barrier islands
Offshore sediment bars, usually sand dune covered but, unlike spits, they are not attached to the coast
Foud 500km to 30km offshore and can be tens of KM long
Dredging
Involves scooping or sucking sediment up from the seabed or a river bed, usually for construction sand or gravel or to deepen a channel so that large boats can navigate it
Dissipation
Describes how the energy of a wave is decreased by friction with beach material during the wave swash up the beach
A wide beach slows waves down and saps their energy, so when they break most of the energy is gone
Megaproject
A very expensive (over US$1 billion) technically difficult and usually long-term engineering project
Many mega projects have multiple aims and often large environmental impacts
Return period
Recurrence interval
Refers to the frequency of a flood of a particular magnitude
a 1:100 flood event will occur on average every 100 years
There is a one per cent chance of that flood occurring in a given year
Environmental refugees
Communities forced to abandon their homes due to natural processes including sudden ones, such as landslides or gradual ones such as erosion or rising sea levels
Sustainable coastal management
Managing the wider coastal zone in terms of people and their economic livelihoods, social and cultural wellbeing and safety from coastal hazards, as well as minimising environmental and ecological impacts
Conflict
In the context of coastal management, conflict is disagreement over how the coast should be protected
Conflict exists between different stakeholders such as residents vs. the council
Littoral cells
Sediment cells
All coastlines divide up into littoral cells containing sediment sources, transport paths and sinks
Each littoral cell is isolated from adjacent cells and can be managed as a holistic unit
Outflanking
When erosion gets behind coastal defences at the point where they stop which leads to rapid erosion inland and undermining of defences
