1 - operation of coast as a system Flashcards
what is needed in a system?
INPUTS - energy and sediment
OUTPUTS - sediment removed by longshore drift deposited as landforms
TRANSFERS - erosion/transportation moves sediment
STORES - sediment deposited in landforms
what kind of a system is the coast?
a dynamic open system - energy/sediment moves from system boundary into environment nearby
what is the sediment budget?
balance between input and output
= input - output
what are the major sediment suppliers in less resistant geology and low lying coastlines ?
less resistant geology = cliffs
low lying coastlines = fluvial sediment transported by rivers
what is an AOELIAN input?
any sediment blown by wind
what human influences change the sediment budget?
- hard engineering (groynes) = increases output of sediment
- soft engineering (beach nourishment) =. increases input of sediment
how does sediment budget reach steady state equilibrium?
when inputs = outputs (equal/balanced)
if humans affect budget it is INBALANCED
what is the effect of an imbalance?
if one system out of place can increase EROSION down coastline
what are the inputs in the coastal sediment budget?
- from coastal stores
- from offshore
- cliffs
- rivers
- longshore drift in
- beach feeding
- dune building
what are the transfers in the coastal sediment budget?
- NATURAL
- ANTHROPOGENIC (human)
what are the outputs in the coastal sediment budget?
- to coastal stores (marshes/dunes)
- to offshore during storms
- estuarine sedimentation
- land claim
- dredging
- beach mining
- longshore drift out
what property do all coastlines have?
stores of material and processes that operate as flows to move the stores
coastlines constantly changing because of erosion, transportation and deposition
what are the inputs, outputs and transfers of beach and cliff sub systems?
BEACH:
—> inputs - subaerial processes
—> transfers - cliff collapse
—> outputs - transportation of sediment
CLIFF:
—> inputs - accumulation of sediment from longshore drift
—> transfers - transportation of sand by wind
—> outputs - removal of sediment by destructive waves
what is a sediment cell
‘a length of coastline and its associated nearshore area within which the movement of coarse sediment is largely self contained’
both open and functional systems as movement exists across longshore drift divides
where does coastal sediment come from
85% - river channels and estuaries (erosion)
5% - sea bed
5% - beaches
5% - cliff erosion
offshore bars and sandbanks act as sediment stores
give 2 examples of sediment cells in the UK
Portland Bill -> Land’s End
Flamborough Head -> The Wash
explain steady state equilibrium
variations in energy and morphological responses not deviating from long term average
cliff profile and beach gradient remaining fairly constant and equal marine and atmospheric energy received each year
explain meta stable equilibrium
coastal system switches between 2 or more states of equilibrium, stimulated by trigger
hard engineering rapidly switching coastal system from one state to another
what is dynamic equilibrium
balanced state of a system when its inputs and outputs are equal and sediment cells help achieve this
by feedback process, system adjusts to change and regains equilibrium
what is positive and negative feedback
NEGATIVE - self regulation which restores equilibrium to a system
POSITIVE - an initial change in system amplified and causes further change
