Block 1 (The Operation Of The Coast As A System) Flashcards
Define system
- Set of interrelated components working towards a process
- Made up of: inputs, processes (stores + transfers), outputs
Define coast
Point where land, sea and atmosphere meet
What are the three types of systems?
- Open
- Closed
- Isolated
Define open system
Energy and sediment can be input/output
E.g. coast
Define closed system
Energy (not sediment) can be input/output
E.g. sediment cells (in theory)
Define isolated system
Nothing can be input/output
E.g. the Universe
What type of system is the coast?
Dynamic, open system
What are the processes by which energy and sediment can be input/output?
- Sea (waves, tides, currents)
- Fluvial (rivers, estuaries) (BIGGEST FACTOR)
- Aeolian (wind)
- Anthropogenic (human - e.g. nourishment and dredging)
How can sediment be stored?
Coastal landforms
How can sediment be transferred?
- Transportation methods in water: solution, suspension, saltation, traction
- Transportation methods on land: suspension, saltation, creep
- LSD
What are the supplies of sediment (where the sediment comes from)?
- Terrestrial (land) - coastal erosion
- Offshore (sea) - seabed, offshore landforms (bars, etc)
- Other (river + estuaries - 85% sediment from here) (humans)
Define sediment budget
Balance between inputs, stores and outputs of sediment
How do you calculate the sediment budget?
Sediment input - sediment output
If answer is negative - erosion increased
Define sediment cell
A length of coastline and its associated nearshore area within which the movement of course sediment is largely self contained
What type of system are sediment cells?
Closed - in theory only energy is transferred
BUT - finer sediment can sometimes move between cells
How many sediment cells are there in England + Wales
11
Give an example of a sediment cell
- Sediment cell 3
- NE Norfolk
- The Wash - The River Thames
What separates sediment cells?
- Headlands
- Deep water
- Convergence of currents or LSD
Define sub cells
Largely self-contained sediment within a cell - e.g. beaches
Define equilibrium in a system
Equal inputs and outputs
What are the 3 types of coastal equilibrium
- Steady state
- Meta-stable
- Dynamic
What is steady state equilibrium
Variations in energy and the morphological (land) responses don’t deviate much from long-term average
- Flat graph
- E.g. beach profile maintains same average gradient
What is meta-state equilibrium
Coastal system switches between two or more states of equilibrium, stimulated by a trigger
- Flat, increase, flat, decrease, flat graph
- E.g. summer and winter beach
What is a dynamic equilibrium
State of equilibrium gradually changes over long period
- Gradually rising graph
- E.g. climate change causing coasts to slowly change due to rising sea levels
What is negative feedback?
Feedback processes reduce the effect of the change - helping coast return to original state
- E.g. erosion of toe causes landslides, more material on beach, decreases erosion rates
What is positive feedback?
Feedback processes amplify the initial change
- E.g. wave energy increases, erosion removes vegetation, erosion rates increase further as wind able to blow away more sand
Outline a case study example of a sediment cell
North-East Norfolk Location: - NE Norfolk - East coast of England - Sediment cell 3 - The Wash-River Thames
Sediment mostly self contained
Sources include:
- Other-rivers
- Terrestrial-cliff erosion
- Offshore
Sinks include:
- Landforms, e.g. spit - Blakeney Point
Type of equilibrium:
- Naturally dynamic (sea levels rising, erosion increasing)
- Humans are trying to enforce steady state (hard defences, e.g. groynes) (disrupting sediment movement within cell)
