Coasts Flashcards
Types of erosion at coasts
Hydraulic Action,
Abrasion, Corrosion, Attrition
What does the size and energy of a wave depend on?
Fetch, strength of wind and how long wind has been blowing.
Two different types of waves:
Destructive and Constructive
Characteristics of destructive waves
Weak swash and strong backwash. Backlash removes sediment from beach. Good at eroding the beach Steep wave gradient High frequency (10-12 per minute) Short wavelength (<20 metres) High energy
Characteristics of constructive waves
Strong swash and weak backwash
Good at pushing material up and depositing
Shallow wave has a gradient and crests far apart
Low frequency (6-8) per minute
Long wavelength (<100 meters)
Low energy
Describe the formation of a spit.
- Sediment is carried by longshore drift.
- When there is a change in the shape of the coastline, deposition occurs. A long thin ridge of material is deposited. This is the spit.
- A hooked end can form if there is a change in wind direction.
- Waves cannot get past a spit, therefore the water behind a spit is very sheltered. Silts are deposited here to form salt marshes or mud flats.
Describe the order of land forms that are formed in making a stump.
cave, arch, wave cut platform, stack, stump.
What is long-shore drift and how is it countered?
The movement of material along a coast by waves which approach at an angle to the shore but recede directly away from it.
It can be countered through the use of groynes.
Name 3 hard coastal protection methods.
Sea wall, groynes and gabions.
Name 3 soft coastal protection methods.
Beach nourishment, dune regeneration and beach re profiling.
Describe the formation of a bay and headlands
- There are alternating bands of soft and hard rock at a discordant coastline
- The soft rock is eroded backwards creating a bay
- The harder rock isn’t eroded as much, creating a headland
Describe the formation of a wave cut platform
- The sea erodes the base of the cliff
- A wave-cut notch is formed by erosional processes (e.g. abrasion and hydraulic action)
- As the notch increases in size, the cliff becomes unstable and collapses, leading to the retreat of the cliff face.
- The backwash carries away the eroded material, leaving a wave-cut platform.
- The process repeats. The cliff continues to retreat. The wave cut platform is often only visible at low tide
Describe how a cave, arch, stack and stump are formed
- Cracks and fissures are widened in the headland through erosional processes
- The cracks erode through and open up to form a cave.
- The cave becomes larger and eventually breaks through the headland to form an arch.
- The base of the arch continually becomes wider through further erosion, until its roof becomes too heavy and collapses into the sea.
- This leaves a stack
- The stack is undercut at the base until it collapses to form a stump.
Name 3 coastal landforms made by erosion
- Cave
- Arch
- Stack
- Stump
- Headlands and Bays
- Wave cut Notch
Name 3 coastal landforms made by deposition
- Spit
- Bars
- Tombolos
- Beaches
- Sand Dunes
What are the types of Erosion on coasts?
- Hydraulic Action
- Abrasion
- Attrition
- Solution
What is Managed Retreat?
It is where the land is allowed to flood naturally. This is normally done in areas of low econmic value
give 3 factors that affect waves
- the Length of the fetch
- How strong the wind is
- How long the wind has been blowing
At which type of coastlines do headland and bays form?
Discordant
What are the benefits of living near the coast?
- Port
- Tourism
- Less pollution
- Fishing
What is another name for corrasion
Abrasion
Explain how different erosional processes shape cliffs.
hydraulic action;
air in cracks compressed ;
corrasion/abrasion;
loose materials thrown at cliff by waves
corrosion;
rocks dissolved by chemicals in sea water
undercutting;
slumping/collapse;
as cliff cannot take weight of overhanging section
Main characteristics of mangrove swamps
Salt tolerant/live in brackish water/salty water/live in sea water/are halophytes;
Aerial roots;
Salt filtering roots;
Salt excreting leaves; Prop roots
Conditions required for coral reef growth
Warm water/temperatures between 18–27 degrees C
Shallow water/not more than 60 metres deep;
Water free from sediment/clear/clean/not polluted/sunlight able to penetrate the water;
Plentiful supply of oxygen in water;
Plentiful supply of plankton;
In areas of gentle waves/currents/calm/slow moving water; Neutral/high pH/alkaline water;
Salty water
What Factors effect longshore drift?
Backwash strength
(Constutive or Destructive wave)
Direction of prevailing wind
Tide
What are the two types of coastline?
Concordant
Discordant
Tourism at Chesil Beach/Weymouth
Historic Weymouth harbour - ships sailed to fight Spanish Armada from here
Home to sailing events of 2012 Olympics/Paralympics
Leisure at Chesil Beach/Weymouth
Leisure:
Weymouth beach one of top 10 in UK
Kayaking, paddling boarding through to deep sea diving
Residential at Chesil Beach/Weymouth
Average process paid for property is £262,000 - significantly lower than London
Average flat £189,000
Average terraced house £223,000
Fishing industry at Chesil Beach/Weymouth
In 2018 granted £8900 for an in-depth study into the needs of commercial fishing industry
Tourists visit unloading of fish in the summer
Old harbour side still hosts a fishing fleet with docks, unloading areas and until recently a cross-channel ferry terminal
As of 2018 the port was home to 36 under 10m fishing vessels
2016 57 tonnes of lobster worth £764,000 landed at Weymouth
Hazards at Chesil Beach/Weymouth
Chiswell village is loacted at the eastern end of Chesil Bank where the beach connects with Portland Bill. Chiswell is vulnerable to flooding during storm events and suffered flood and storm damage in 1979 and 2014
Coastal flooding occurs by percolation and as a results of waves overtopping the beach
2014 storm left a hole at the base of the seawall and in front of Quiddles Cafe. The loss of shingle meant that the foundation of the sea wall and blue-clay bed that lies beneath Chesil Beach were both exposed
Management of Hazards at Chesil Beach
Sea walls first built between 1958 and 1962 and later rebuilt in 1980s
Sea walls built to deflect wave energy and reduce flood risk during storm surges, and to protect against landslides and coastal erosion
Gabions were placed in a castle structure and a further 550m of mattress layers were placed on top to preevent the crest of the beach being lowered when waves overtop the beach
An interceptor
