3: Beach Change Flashcards
What determines whether a beach is defined as macrotidal or microtidal?
Microtidal means that they have a low tidal range relative to wave height whereas the opposite holds true for macrotidal beaches
What are 3 major things that are affected/changed from a macrotidal to a microtidal beach?
Swash, surf zone and shoaling
What are the 4 types of beach depending on their tidal range and what is the associated RTR of these beaches?
Wave-dominated (RTR<3) Tide-modified (RTR: 3-12) Tide-dominated (RTR: 12-50) Tidal flats (RTR>50)
How do you calculate relative tidal range?
Tidal range/Height of waves
What are the 3 types of tide-modified beaches?
Reflective + low tide terrace
Reflective + bars and rips
Ultra-dissipative
What are reflective + low tide terrace (tm) beaches characterised by?
- most common
- Steep cusps at high tide
- Rips at low tide with a terrace before shoreline
- RTR ~9
What are reflective + bars and rips (tm) beaches characterised by?
- Highest energy
- Coarser sand
- Rips and scour channels
- RTR~4
What are ultra-dissipative (tm) beaches characterised by?
- Wide intertidal zone (200-400m)
- Wide spilling surf zone
- Plane beach
- RTR~10
What are the 3 types of tide-dominated beaches?
- Beach + sand ridge flats
- Beach + sand flats
- Tidal sand/mud flats
What are beach + sand ridges (td) characterised by?
- Steep cusped beach at high tide
- Shore parallel ridges
- Low gradient
- RTR ~9
What are beach + sand flats (td) beaches characterised by?
- Small steep high tide beach
- intertidal sand flats
- featureless apart from a few small wave ripples
- RTR~20
What are tidal sand/mud flats and mud flats (td) characterised by?
- Lowest energy
- Small steep high tide beach
- Sand/mud
- RTR 30-50
What is not uncommonly found at the back of mud flats?
Mangroves
What are reflective + rock/reef flats characterised by?
Beach is overshadowed by large rocky outcrops just in front of the beach
Give an example of a reflective + rock/reef flat?
Ningaloo Reef
What are the 3 main controls upon what determines a beach type?
Wave height, sand size, relative tidal range
What is the difference between littoral compartments and cells?
Compartments are larger essentially (e.g. pocket beach) whereas cells are essentially operating within or between compartments (e.g. rip currents, tidal inlets and submarine canyons)
Who has adopted the idea of beach compartments and cells as a way of managing the coastline?
Australian government
What are the 3 types of compartment outlined in Australian coastal planning?
Primary = large landforms (e.g. headlands and river) Secondary = sediment movement on shoreface within and between beaches Tertiary = Sediment movements in the near shore area
What is each compartment type adopted in the Australian government suitable for in terms of planning/managing?
Primary = large scale engineering and strategic plans (e..g boating) Secondary = regional planning and engineering decisions (e.g. housing) Tertiary = detailed impact studies and local management plans for vulnerable areas
What are 3 sediment sources and sinks within the secondary beach compartment? What are 2 examples of where things are both?
Sources = Biogenic sources (e.g. reef critters) and alongshore source and anthropogenic Sinks = lagoon sink, dune sink, alongshore sink Both = surf zone and shoreface
What is defined as a leaky beach?
prominent influence of longshore drift
What is defined as a closed beach?
The beach system is relatively closed with little input/output
What beach has been identified as a major leak?
Kingscliff
What has the Kingscliff leakage inspired?
Tweed River Bypass Scheme
What is beach rotation?
When depending on the conditions at the time, sediment can be transported from one end of the beach to the other but this can later switch in response to a stimulant that results in the sediment being transported/removed back the other way hence rotation.
What is a good paper that talks about beach rotation?
Ranasinghe et al. (2004)
