11. Geography: Coastal change and management

Question 1

What are ecosystems? What is hinterland? What is dynamic equilibrium? What is mass wasting?

Answer 1

• ecosystems:- systems formed
  by the interactions between the
  living organisms (plants, animals,
  humans) and the physical
  elements of an environment
• hinterland :- the land behind a
  coast or shoreline extending a few
  kilometres inland
• dynamic equilibrium :- when the
  input of a coastal system such
  as winds and waves moving
  sediments onshore is equal to
  the output that moves sediments
  offshore, the system is said to be
  in a steady state. It is therefore
  not unstable and it has a dynamic
  equilibrium.
• mass wasting :-the movement of
  rock and other debris downslope
  in bulk, due to a destabilising
  force such as undermining
  compounded by the pull of gravity

Answer 2

The Importance of the Coast in Australia
* The coast is a dynamic natural system with over 85% of Australians living within 50km of it.
* Human activities can impact coastal landforms and ecosystems.
* Australia’s coasts need to be managed for sustainable living and conservation.

The Coastal Zone
* The coastal zone includes coastal waters and hinterland.
* The Australian coast, approximately 37000km long, includes various environments like plains, rivers, lakes, rainforests, wetlands, mangrove areas, estuaries, beaches, coral reefs, seagrass beds, and sea life.
* Many of Australia’s World Heritage sites are located in these diverse coastal environments.
* The coast is important for human settlement, urban complexes, ports, and harbors.

Coasts as Natural Systems
* Coasts are natural systems consisting of landforms and biotic elements.
* They are in a state of dynamic equilibrium, constantly changing.
* Small-scale agents of change include tides, ocean currents, and wave action.
* Large-scale agents include continental drift, uplift and sinking of land, movement of sea levels, and creation of islands by volcanic activity.

Answer 3

Coastal Landforms and Ocean Processes

Coastal Landforms:
* Various marine and terrestrial structures found at the coast, including beaches, bays, dunes, cliffs, fiords, and structures under the sea.
* Ocean processes include waves, tides, currents, rips, storm surges, and tsunamis.

Range of Coastal Landforms:
* Dune blowouts: Loose sand is blown from dunes due to vegetation removal.
* Waves refracted towards headlands, forming caves where weak rocks are eroded.
* Erosion between low and high tides undercuts rocks, forming a rock platform that eventually collapses, creating a cliff.
* Longshore drift moves sand and other material along a beach, extending along the coastline forming a spit.
* Estuaries: Tidal parts of a river that catch mud, sand, and nutrients.
* Lagoons: formed when a sandbar begins to develop, closing an estuary.
* Beaches: formed when material is brought to the shore by waves.
* Dunes: formed when sand on a beach is stabilised by vegetation.
* Caves: developed in places exposed to sea and waves, water rushes in and can cause pressure to build at the back of the cave.
* Tombolos: spits that join two land areas.
* Headlands: formed when coastal rocks are hard and resist erosion from the waves.

Waves and Waves:
* Waves are generated by winds out at sea, creating swells.
* Waves in storm conditions are destructive-waves, leading to increased erosion of coastal forms.
* Waves translate into a swash, or forward movement, and a backwash, or return to the sea, after encountering the land.

Answer 4

Erosional and Depositional Coastal Forms

Erosional Forms
* Erosional landforms are created by waves’ hydraulic action or weight and pressure.
* Headlands and bays are formed by differential erosion, with harder rocks resisting erosion.
* Cliffs and platforms are created by waves’ erosive powers, causing cliffs to collapse into the sea and coastline retreating inland.
* Caves, arches, blowholes, and stacks are features created by erosion due to differences in rock hardness and fractures.

Depositional Forms
* Depositional coastal forms include beaches, sand dunes, bars and barriers, spits, sand islands, tombolos, and lagoons.
* Beaches are formed from sediments and sands eroded from cliffs and sediments brought down by rivers.
* Beaches are easily eroded in storms, but sands taken offshore will return when calmer conditions return and constructive waves can move the sediments back.

Answer 5

Dunes and Other Depositional Coastal Forms

Dunes Formation
* Sandy sediments dry out at the beach and above high tide zones.
* Wind picks up these and moves them onshore and inland.
* Fore dunes form, depressions inland, and secondary dunes may form.
* Coastal dune vegetation succession is crucial for stabilizing dunes.
* Dunes are fragile and need careful management to prevent pedestrian traffic from disturbing plant life.

Other Depositional Coastal Forms
* Spits are sandy extensions of beaches formed by longshore drift currents.
* Bars and barriers are sandy offshore structures parallel to the coast, with lagoons or wetlands behind them.