Beach Characteristics Flashcards
What determines the nature of the beach characteristic?
The angle at which waves approach the coastline.
Which direction are drift-aligned beaches orientated?
Parallel to the direction of dominant longshore drift.
Where do drift aligned beaches generally develop?
Where the coastline is fairly regular, or where the predominant wave direction is at an angle to the beach.
Give an example of a drift aligned beach.
A spit
What happens to drift aligned beaches if there is a sudden change in the direction of the coastline?
The coastline can extend outwards.
What are drift aligned beaches formed by?
Longshore drift.
Which way are swash aligned beaches orientated?
Parallel to the incoming wave crests.
How much longshore drift occurs on swash aligned beaches?
There is a minimal amount of longshore drift.
Where can swash aligned beaches be found?
They can be found on irregular coastlines where longshore drift is impeded.
What type of beaches are produced by swash aligned beaches?
Smoothly curved, cancaved beaches
What are the four conditions that lead to marine deposition?
Low energy waves.
Constructive waves break early and spill onto the shore.
Sheltered environment.
Water loses energy through percolation.
Do large pieces of shingle produce a large or small gradient?
The larger the size of the material, the steeper the gradient.
What limits backwash in shingle beaches?
Water can
rapidly percolate through the shingle.
What type of gradient is produced by a sandy beach?
A gentle gradient is produced.
Where do ridges and runnels develop?
On sandy beaches
How long do ridges and runnels stay on the beach for?
They are a temporary feature.
What produces ridges and runnels?
This is caused by the spreading out of the waves energy across a wide area of beach. This produces ridges and intervening depressions at sandy, shallow beaches.
Whereabouts do ridges and runnels develop?
By the low water mark.
What causes ridges and runnels?
Swash and backwash
Which way do ridges and runnels run?
Parallel to the shore.
What may drain water off the beach?
Channels
What are berms?
These are beach ridges that are built up by constructive waves. They are small ridges that develop at the high tide marks this is from the deposition of the material from the top of the swash.
What do berms show?
The successive tides from spring to neap. These get successively lower.
What is a storm beach?
This is a ridge composed of the biggest boulders thrown by the largest waves above the high tide mark.
What is below the storm beach?
Below this is a series of ridges marking the successively lower tides as the cycle goes from spring to heap.
What are beach cusps?
These are semi-circular depressions that form when the waves break directly onto the beach and swash and backwash are strong.
Where on the beach can you see beach cusps?
Where sand and shingle meets.
What part of the cusps channel incoming swash into the centre of the embayment?
The sides of the cusps channel incoming swash into the centre of the embayment which produces a stronger backwash in the central area which drags material down the beach, deepening the cusp.
Where do ripples occur?
They occur below the cusps.
What are ripples?
These develop on sand as a result of wave action or tidal currents.
What are spits?
These are long, narrow elongated pieces of land that extend from the mainland to the sea or across an estuary.
On what type of coasts are spits found?
Drift aligned coasts
What are the four factors that affect spit formation?
LSD
Wave energy
Prevailing wind
Currents
What shape are simple spits?
They are either straight or recurred.
Do simple spits have minor spits or recurved ridges along their landward edge?
No
What shape do compound spits have?
They have a number of recurved ridges and or minor spits along their landward side.
What can the minor spits in compound spits how about their past?
They show where the spit may have previously terminated.
Give an example of a compound spit.
Sandy Hook Spit, New Jersey, USA
What are tombolos?
These are spits that join an island to the mainland.
What are the four factors that affect tombolo formation?
LSD
Prevailing wind
Type of wave
Distance between mainland and island
What is a bar?
This is where a spit extends past a bay to form a lagoon.
What may happen to the lagoon overtime?
It may silt up.
What may some bars be a result of?
They may be the result of onshore migration of material from offshore as sea levels rose after the last ice age.
What is an offshore bar?
This is where a ridge of beach material can be submerged by incoming tides. When it returns semi submerged it accumulates seawards of the breaker zone, it is known as an offshore bar.
What are barrier beaches?
These are elongated banks of deposited beach material that lie parallel to the coastline. They are not submerged by incoming tides.
What are barrier islands?
These are formed when the barrier beach bank is high enough to allow sand dunes to develop. A lagoon is often formed in sheltered areas.
What are the four factors that affect barrier beach and island formation?
Fetch
Distance between headland
LSD
Prevailing winds
Give an example of a barrier beach or island?
Lido of Venice
