4: Long-term Beach Change and Sand Barriers Flashcards
Why are beaches in Australia typically more susceptible to beach rotation?
Because there is a limited estuarine sediment input and instead the beaches (particularly on the east coast) respond more to the ENSO phenomenon
What is a major feature of Australian beaches due to the stronger ENSO influence instead of estuarine sediment input?
Beach rotation
What distinguishes the different beach-change processes?
Time scale and spatial scale of operation
What are 4 classes of beach change processes based on their temporal and spatial scale?
Geological (long timescales and large spatial scales e.g. delta dynamics), Historical (dune and cliff changes), Event (ENSO), instantaneous (waves and ripples)
What is sediment budget?
The modal amount of sediment that is in a beach system at any time because if too high then it will adjust and similarly if too low
What does it mean if a beach has a positive sediment budget?
The total amount of sediment for a beach is increasing over time
Given an example of a beach with a positive sediment budget
Moruya Beach
What does a beach’s sediment budget look like if it is undergoing beach rotation?
It will switch between negative and sediment budgets, but is important to consider the timescale of these switches as it could just be switching in response to daily weather occurences
What does a stable beach sediment budget look like?
The beach is in a steady-state equilibrium
What can the beach sediment budget be an indication of?
General geographic transportation method i.e. if a beach further north has a positive sediment budget then this may reflect the transportation of sediment further north up the coastline which may also coincide with a negative sediment budget seen further down the coastline
What is the definition of a sand barrier?
Elongated, tide-, wave-, wind- built ridges composed predominantly of sand and gravel and protect the adjacent mainland from open-water processes
What is a transgressive sand barrier?
These are sand barriers that rise and retreat in response to successive sea level rises
What is a regressive sand barrier?
These are sand barriers that experience creation of new ridges in response to successive falls of sea level
What can some sand barriers wrongly be interpreted as? Why?
Spits/tombolos because the ridges from a regressive barrier build out
