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Coastal Erosion at Terrigal and Wamberal Beaches

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Michael Nutt

on 26 May 2014

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Transcript of Coastal Erosion at Terrigal and Wamberal Beaches

Coastal Erosion at Terrigal and Wamberal Beaches
What Is Coastal Erosion
Coastal erosion is the wearing away of land and the removal of beach or dune sediments by wave action, tidal currents, wave currents and drainage.
Nature Of The Issue
Coastal erosion worsens when natural defenses such as slopes, cliffs, etc. wear away, and then sediments from the coast slowly gets taken away by the waves crashing against the coast.
Why Does Coastal Erosion Happen
Coastal erosion is a natural process and has been happening for thousands of years. We are not able to stop it but we are able to slow it down.
Where are Terrigal and Wamberal Beaches
Wamberal and Terrigal beaches are located near Gosford on the central coast, approximately 80 kilometers from Sydney.
When Does Coastal Erosion Happen
Coastal erosion primarily happens and is alot worse during and just after large storms. This is because the waves are a lot larger and a lot more vicious
It is a natural process, but is primarily caused by wind, ocean waves, rivers, water runoff, rain, human and animal activity, plant growth and decay, the geology of the coastline and the geomorphology (or shape) of the coastline. These waves are primarily generated by wind, storms and fast moving motor craft.
Processes
There are 3 different processes:
- Erosion
- Transportation
- Deposition
Erosion
Erosion is where destructive waves wear away the coast. The three main causes of coastal erosion are
Corrasion/Abrasion
is when waves pick up beach material. such as pebbles, and hurl them at the base of a cliff

When waves hit the base of the cliff, the water compresses air into the cracks creating air pockets, when the waves retreats the air from the air pcokets come rishing out of the cracks. Often this will cause cliff material to break
away.

The process is also known as
hydraulic action.
Attrition
is when waves cause rocks and pebbles to bum into each other and break up.
Corrosion/Solution
is when certain types of cliffs erode, as a result of weak acids i the sea.
Transportation
Transportation is the movement of smaterials along the coast in the sea by waves. One of the main types of transportation is long shore drift. There is also solution, traction, suspension and saltation.
Deposition is when eroded material is dropped by weaker waves called constructive waves. Depositions creates a range of landforms.
Depostition
Longshore Drift
Longshore drift is the movement of material by wave action, this is also known as transportation
Longshore Drift happens when waves move towards the coat at am angle. The swash (or waves that are moving up the beach) carries materials up along the beach, and the backwash carries materials slowly back down the beach at a right angle. Longshore drift provides a link between erosion and deposition. This is becuase ,aterial is eroded in one place (erosion), gets arried down the coast (transportation or long shore drift), and then gets deposited elsewhere (deposition).
Fieldwork
There are 3 types of fieldwork to test erosion. They are:
Beach Profile
Testing for beach characteristics such as:
Wind speed and direction
Sand Grain size
Wave height
Creating a table of the vegetaion on sand dunes
Vegetation On The Dunes
This fieldwork measures in 1m² quadrants at 5m² intervals in a straight line; then the plants are identified and the coverage is estimated as a %. At each quadrant estimate the height of each quadrant. This is done to see what vegetation is in a certain area on sand dunes to be able to get the right plants for the area.
Constructing a Beach Profile
The shape of the beach is constantly changing as the sand is removed and deposited. The amount of sand moved can be estimated by analysing successive beach profiles. This is done by using a dumpy and a measuring tape and long (clearly readable) measuring stick. The height is measured by having one person hold the measuring stick and one person looking through the dumpy and reading the numbers that line up with the lines when you are looking through the dumpy; then the distance between the measuring stick and dumpy is measured. This is done on every spot on the beach that has a noticeable/dramatic change in height or in random intervals. At the end all of the information collected is graphed and the beach profile can be compared with previous beach profiles.

Beach Characteristics
This fieldwork measures:
o Wind direction and speed
o Size of the sand
o Testing the longshore drift
o Wave period
o Wave Height

First to match the sand (when beach nourishment is used to replenish the beaches) 100 ml’s of sand is measured. It is then sieved through sieves and the percentage of sand left in each sieve is written down.

Impacts
The following are impacted by coastal erosion at Terrigal & Wamberal Beaches:
Recreation & Tourism
Local Residents
Beach Users
Recreation & Tourism
Terrigal & Wamberal Beaches are big tourist destinations.
The coast has been used to improve Tourism & Recreation in Australia.
Many things have been built to improve recreation & tourism, but even these positive things that have been built there are negative impacts on the environment and coastal areas.
If the coast erodes, the beaches then will reduce in size and many tourists go to Terrigal and Wamberal for the beaches, if the numbers of tourists drop the shops will lose buisness, then will need to raise there prices which will mean locals will buy from there shops less often which will then cause them to close.
Local Residents
As numbers in tourism drops and shops close, local residents will move away. This is because the area will be less appealing and the residents will need to travel further to get to essentials (such as shops) causing many residents to move away.
Once people move away from the area no other people will want to move into the area because of the lack of shops, restaurants and other buisnesses.
Another impact affecting the local residents is, as the coast erode some houses will need to be either knocked down, moved or abandoned and left to fall into the sea.
Beach Users
If the beach erodes the beach will slowly disappear and eventually become unappealing and/or unusable.
This will then start to crowd other beaches become crowded from people that don't want to go to Terrigal & Wamberal beaches.
As people use other beaches and other beaches over crowed will then cause other beaches to erode, and slowly will make more and more beaches unappealing and/or unusable.
This will eventually make beaches unappealing and/or unusable and change australian culture forever!
Perspectives
The perspectives of people affected by the erosion include:
Members of parliment
Residents
Tourists
Visitors to the area
Conservationists
Inland Residents
They live away from busy areas like sydney seeking a quiet and peaceful life style, the erosion doesnt affect their houses.
They believe that the home owners should be responsible for the problems they have because of disasters, as they should of known the consequences for building houses so close to the coast.
They are against any stratergies proposed to prevent and/or slow down the erosion, because they know there rates will go up to pay for it
Local
Councillers
They are sympathetic on homeowners living on the dune, but they know that the council doesn't have sufficient funds to meet the requirements of the proposed strategies.
They have to deal with all of the fore dune residents that want the council to pay for the damage for and/or prevention of disasters.
Fore Dune Residents
Fore dune residents live along the coast.
They usually believe the council is to blame because they gave them the correct permission to build their houses where they are.
They believe the local council have a responsibility to protect rate players for such disasters
They also want the erosion to be slowed or stop becaus eof tourism ad tourism is a prime buisness around the are they live, and tourism allows them to have a nice area to live with many businesses near by.
Environmental Minister
They are sympathetic to the residents, they also see the value of tourism and want to preserve tourism, they also see that further loss of beaches and homes would then produce negative publicity for the government.
They also know that the government doesn't have funds to help prevent or slow down the issue.
Strategies
Some strategies include:
Beach nourishment
Groynes
Sea walls
Offshore breakwater
Purchase the properties
What is Beach Nourishment
Beach nourishment is where beach is brought down from other beaches to replace sand that has been lost at a beach
Advantages
Low environmental impact at the beach
Sand is used that bes matches the sand at the beach
Disadvantages
Mus be done on a continuous basis, therefore requires continuous funds.
The sand needs to come from another beach and there will be environmental impacts on that beach
Trucks are required to carry the sand down which will cost alot and polute the air.
What are Groynes
Groynes are artificial structures that are designed to trap sand being moved by longshore drift, therefore protecting the beach.
Groynes can be built with rock, timber and steel pilings.
Advantages
Traps sand which maintains the beach.
Disadvantages
They are a visual eyesore and will make tourist avoid the area.
Groynes do not stop sand movement off shore.
What is Off Shore Break Water
A structure that is parallel to the shore.
It gets placed in the water at a depth of about 10 meters.
Advantages
The waves at the beach break in deeper water. This reduces their energy at the shore.
Disadvantages
It has and extremely high cost.
Destroys the surfing amenity of the coast.
Requires large boulders in large quantities, this will mean the government has to find a place to get the boulders and has to find a way to get to the correct area.
Purchasing The Properties
This is basically the government buying all of the threatened and near threatened properties on the coast.
Then the government knocks down the threatened and near threatened structures.
Advantages
Low environmental impact at the beach
Sand is used that bes matches the sand at the beach
Disadvantages
Mus be done on a continuous basis, therefore requires continuous funds.
The sand needs to come from another beach and there will be environmental impacts on that beach
Trucks are required to carry the sand down which will cost alot and polute the air.
Sources
http://961030052817253669.weebly.com/uploads/1/8/5/4/18544338/6650722.jpg?373
http://en.wikipedia.org/wiki/Coastal_erosion
Geo Active 2
Virtual Fieldwork Slide Show accessed on sharepoint.
http://www.coastalwatch.com/environment/4524/impact-of-coastal-erosion-in-australia
http://fluswikien.hfwu.de/index.php/Group_K_-_Collaborative_Climate_Adaption_Project
http://coastalcare.org/sections/inform/beach-nourishment/
http://hamptonroads.com/2011/05/36-million-beach-nourishment-begins-nags-head
http://www.southampton.ac.uk/~imw/Portland-Harbour.htm
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processes

http://www.s-cool.co.uk/a-level/geography/coastal-processes/revise-it/features-of-coastal-
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http://www.s-cool.co.uk/a-level/geography/coastal-processes/revise-it/coastal-transportation

http://www.s-cool.co.uk/a-level/geography/coastal-processes/revise-it/coastal-deposition

http://www.tutor2u.net/blog/index.php/geography/comments/the-physical-causes-of-coastal-
erosion/

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http://www.marbef.org/wiki/human_causes_of_coastal_erosion

http://en.wikipedia.org/wiki/Coastal_erosion

http://www.wrl.unsw.edu.au/site/projects/australian-coastal-observation-network/

http://www.genkin.org/blog/2009/02/11/the-skillion-terrigal-central-coast-nsw-australia/

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http://en.wikipedia.org/wiki/Coastal_erosion

http://www.htmltemplates.net/

http://www.landscapephotographeronline.com/photo/wamberal-beach-sunset-4-oct-2013-img-

0090-1680-panorama-v2
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