Waves

Wave mechanism
Destructive strom waves and life risking surfing







CoastsThe following document explains the main coastal features like cliffs, wave-cut platforms, caves, arches, stacks, bays, headland coastlines, beaches, spits, and coastal sand dunes, and the common hazards including coastal erosion and tropical storms.



Marine Erosional Processes

Hydraulic Action
Occurs due to the force of air and water acting in joints and cracks. It occurs as the waves breaks onto cliffs, any air trapped in cracks of the cliff will be under great pressure. As the waves retreats, the pressure is released with explosive force and the rocks will weaken and will be shattered by the storm waves.
Corrasion or Abrasion
Whereby a breaking waves hurls pebbles and shingles against a coast and erodes it.
Attrition
Wearing away of the load itself. Gradual reduction in the size of the loads as it crashes with other particles.
Solution or Corrosion
Chemical erosion in chalk and limestone rocks where acidic water dissolve rock.
Refer to: http://www.geographyalltheway.com/in/gcse-coasts/wave_processes.htm


Wave Refraction and Long Shore Drift



Formation of Marine Erosional Landforms



Marine Transportation Processes
Traction
Large boulders and pebbles are carried along the sea bed
Saltation
Small pebbles and stones are bounced or roll along the bed
Suspension
Fine light materials are suspended in the sea water
Solution
Fine light materials are dissolved in the sea water, involves chemical change

Overview of coastal landforms
Spit Formation






Coastal Vegetation in Salt Marshes and Sand Dunes
Type
Characteristics
Adaptation mechanism
Halophytes (salt tolerant)
Have a number of ways to cope with the daily changes in the levels of salinity, submergence by water and rapidly shifting sediments.

Able to tolerate the waterlogged situation two times a day during high tides.
Deep root to anchor the plant in the mud.

Ability to extract nitrogen directly from the air.

Example: Mangrove vegetation in tropics and sub tropics.
Xerophyte (drought resistant)
Condition on the foreshore is harsh, saline, windy and arid, due to the presence of the permeable sand.
Two most common species: Sea couch and Marram grass

Sea couch store water in its succulent leaves

Marram has deep tap roots


Salt Marshes

Coastal Management
Hard Engineering* Building artificial structures such as sea wall, Groynes, rock armor aimed at controlling natural processes
  • Trying to win over the forces of nature
  • Immediate solution to protect high value properties
  • Very costly and may have adverse environmental impact

Soft Engineering* A suitable approach to manage the coast without using artificial structure. For example, beach nourishment
  • Try to fit in and work with the natural processes
  • Often low maintenance cost - both economically and environmentally
  • Managed retreat or coastal realignment:
    • Allowing controlled flooding of low lying coastal areas where the value of land is low


Cliff side erosion: need of coastal management
Fun video on coastal management





Coral Reefs


Amazing biodiversity in the Coral reef ecosystem


Click here to see National Geographic coverage on Great Barrier Reef