Shorelines Flashcards
What are the two types of Coastline?
Emergent and Submergent
What is an emergent coastline?
Emergent or eroding coasts include features such as raised beaches, high cliffs, headlands, exposed bedrock, steep slopes, rocky shores, arches, stacks, tombolos, wave-cut platforms, and wave notches.
What is a submergent coastline?
Submergent coasts are subsiding, they occur where sea levels rise relative to land. This may be due to tectonic subsidence—when the Earth’s crust sinks—or when sea levels rise due to glacier melt. Features associated with submergent coasts include flooded river mouths, fjords, barrier islands, lagoons, estuaries, bays, tidal flats and tidal currents.
What are the five main shoreline zones
-Offshore
-Nearshore
-Surf Zone
-Foreshore
-Backshore
Offshore
Not affected by active wave turbidity currents
Nearshore
Affected by the waves with water depth is ~1/2 wavelength so depend on wavelength and water depth;
* upper shoreface where normal wave action occurs (finely laminated and cross-bedded sand),
* lower shoreface where storm waves can produce hummocky cross-stratified sand.
Surf Zone
are of actively breaking waves
Foreshore
Periodically wet and dry due to waves and tides. Well-sorted sand shows planar laminations. Low ridges above the beach face in the foreshore zone are called berms, summer berms are closer to the water and are replaced by winter berms produced in high energy water.
Back Shore
Typically always above sea level. In the backshore zone, onshore winds may blow
sand behind the beach and the berms, creating dunes.
What drives the evolution of the coast?
The balance between sediment supply and demand.
What causes erosion of the beach and dunes?
Storm water level surge causes dunes to collapse and be transported away by the sea
What is soft engineering and what are examples
Soft engineering uses natural management techniques to tackle erosion, not artificial structures.
- Dune Nourishment: Plants to increase biodiversity and create a barrier
- Reprofiling: movement of sediment around beach to limit erosion.
What is hard engineering and what are examples
When erosion cannot be managed through soft engineering building artificial structures is required.
- Sea walls and promenades : Walls made of concrete
- Groynes: Wooden or stone structures built on the beach extending into the water
-Rock armour or Rip Rap : Large piles of boulders or rock placed at the bottom of cliffs
What is wave movement caused by and what does it transmit?
Caused by wind and transfers energy through friction
What are possible sources of Sediment?
- river sediment input,
- onshore transport of sediment from offshore marine deposits,
- and inflow through longshore transport.
- human interference through deposition of sand from dredging may also form an important input.
