Coastal systems Flashcards
what type of system is the coast?
open system
why is the coast considered an open system?
it receives inputs from outside the system and transfers outputs away from the coast and into other systems.
what other systems will outputs from the coast be transferred to?
terrestrial, atmospheric or oceanic systems and can include rock, water and carbon cycles.
what is a sediment cell?
a stretch of coastline usually bordered by two prominent headlands.
how can coastlines be split up?
coasts can be split up into sediment cells which are often bordered by prominent headlands.
how does sediment move within sections of a coast?
within these sections, the movement of sediment is almost contained and the flows of sediment act in a dynamic equilibrium.
what is a dynamic equilibrium?
dynamic equilibrium refers to the maintenance of a balance in the natural system, despite it being in a constant state of change.
describe dynamic equilibrium in a sediment cell
dynamic equilibrium in a sediment cell is where input and outputs of sediment are in a constant state of change but remain in balance.
how might the dynamic equilibrium be upset?
the dynamic equilibrium may be upset in the long term due to human intervention.
how might the dynamic equilibrium be interrupted?
in the short term, the dynamic equilibrium may be interrupted by natural variations.
what are inputs in a coastal system
may refer to material or energy inputs. Coastal inputs are not limited to but include three main areas.
what are the three main areas of inputs?
marine: waves, tides and salt sprays
atmosphere: sun, air pressure, wind speed and direction
humans: pollution, recreation, settlement and defences
what are outputs in a coastal system
may refer to material or energy outputs
names examples of outputs in coastal systems
ocean currents
rip tides
sediment transfers
evaporation
what are stores/sinks?
refers to stores/sinks of sediment and material
name examples of stores/sinks
Beaches
Sand Dunes
Spits
Bars and Tombolos
Headlands and Bays
Nearshore Sediment
Cliffs
Wave-cut Notches
Wave-cut Platforms
Caves
Arches
Stacks
Stumps
Salt Marshes
Tidal Flats
Offshore Bands and Bars
what are transfers/flows?
the process that links the inputs, outputs and stores in the coastal system
name examples of transfers/flows
wind-blown sand
mass-movement processes
longshore drift
weathering
erosion
- hydraulic action
- corrosion
- attrition
- abrasion
transportation
- bedload
- suspension
- traction
- solution
deposition
- gravity settlement
-flocculation
what is energy in coastal systems
the power and driving force behind the transfers and flows in the system
name examples of energy in the coastal system
wind
gravitational
flowing water
what are feedback loops?
the coastal systems has mechanisms which enhance changes within a system, taking away from dynamic equilibrium (positive feedback) or mechanisms which balance changes, taking the system back towards equilibrium (negative feedback).
what is a negative feedback loop?
a negative feedback loop lessens any change which has occurred within the system. for example, a storm could erode a large amount of a beach, taking the beach out of a dynamic equilibrium as there is a larger input of sediment into the system then output. a negative feedback loop will balance this excess of inputted sediment:
1. when the destructive waves from the storm lose their energy excess sediment is deposited as an offshore bar.
2. the bar dissipates the waves energy which
protects the beach from further erosion.
3. over time the bar gets eroded instead of the beach
4. once the bar has gone normal conditions ensue and the system goes back to dynamic equilibrium
what is a positive feedback loop?
this exaggerates the change making the system more unstable and taking it away from the dynamic equilibrium:
1. people walking over sand dunes destroy vegetation growing there and causes erosions.
2. as the roots from the vegetation have been holding the sand dunes together, damaging the vegetation makes the sand dues more susceptible to erosion. this increases the rate of erosion.
3. eventually the sand dunes will be completely eroded leaving more of the beach open to erosion taking the beach further away from its original state.
name the sediment sources
rivers
cliff erosion
wind
glaciers
offshore
longshore drift
describe rivers as sediment sources
most of the sediment in the coastal zone is a result of an input from rivers, especially in high-rainfall environments where significant rive erosion occurs.
sediment may be deposited in estuaries which are brackish (salty) areas where rivers flow into the sea. they are important wildlife habitats. the sediment is then transported throughput the coastal systems by waves, tides and currents
describe cliff erosion as a sediment source
very important areas with unconsolidated (uncompacted ad therefore unstable) cliffs that are erodes easily. in some areas, coastlines can retreat by up to 10m per year, providing a significant sediment input. most erosi9on occurs during the winter months due to more frequent storms.
describe wind as a sediment source
the wind is a coastal energy source and can cause sand to be blown along or up a beach. sediment transport y winds may occur where there are sand dines or in glacial and desert environments which provide sediment inputs.
describe glaciers as sediment sources
in some coastal systems such as Antarctica, Greenland, Alaska and Patagonia, glaciers flow directly into the ocean depositing sediment that was stored in the ice. this occurs when glaciers calve, a process where ice breaks off the glacier
