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Transcript of Coastal Management
Present and Future Management
In areas awaiting vegetation to take hold, jute mesh is now utilized to minimize scour on re-constructed areas in the short term. This has been removed in various areas that have been stabilized
Rebekah Chew 10GeoA
Coastal Management Research Plan
What is the issue ?
Sand Dune Erosion
To investigate dune erosion as an issue facing Cronulla Beach
What is the issue?
Why is it occurring?
How does it affect the environment and community?
How has it been managed in the past and how is it currently?
Dune erosion, Cronulla beach, issue
Dune erosion, Cronulla beach, processes
Dune erosion, Cronulla beach, effects, impact, complaints, problems
Dune erosion, Cronulla beach, management strategies, solutions
Why is it occurring?
To determine how dune erosion affects members of the community
Survey 10 people and graph
How often do you go to the beach?
How long do you stay at the beach?
What do you do at the beach?
What methods of dune protection have you been informed of or have seen?
How important on a scale of 1-5 is sand dune protection to you?
The beach sediment has been destabilized on a large scale from the removal of vegetation from the front and hind dunes and these are through human and natural causes
Large transgressive dunes have advanced inland at a rapid rate
Long term recession of the beaches will be the result of the inland loss of sand and imbalanced sediment budget for the embayment
Storms also result in mass erosion. A 1974 storm event combined with high tide had a huge impact on the beaches and a more recent storm occurred in August 2007 stripping bare beaches from Newcastle to Wollongong
The Importance of Sand Dunes at Cronulla
Dunes have been put in place artificially and naturally to hold the shoreline in place. It is both a management strategy for beach erosion and in need of management in the process of erosion.
The beach needs a dune's reservoir of sand to replenish itself after a storm as well as to absorb the effects of storms and surges.They are effective at protecting the inland-facing parts of barrier islands, which are often vulnerable to such natural disasters. They provide a foundation for ecosystems made up of a wide variety of coastal life and native species to Cronulla. For instance, sea turtles nest in these dunes, rodents carve out extensive burrows, and vegetation and insects of all kinds have adapted to live in a dune's sandy environment.
Aerial photo Cronulla 1970
Aerial Photo Cronulla 1988
Recent Aerial Photo
Sand Dunes at Cronulla Beach
The destabilization of dunes was due to the introduction of Bitou bush, brought in by ballast water released on the coast. The seeds were from South Africa and were far spreading at a high rate, planted initially for the purpose of stabilization. They soon out competed the native species, stubborn and impossible to uproot. As their fruit is attractive to birds and the seeds spread further through their waste, the cycle continues, seeds lasting for up to 10 years underground. This allowed the dunes to be eroded by Aeolian processes
The removal of vegetation allows for beach erosion through aeolian processes and this affects the progression of sand inland. Transgressive dune fields are formed as there is no obstruction.
Long shore drift and hydraulic action affected the area by eroding and depositing the sand else where to form sand dunes, sand bars and tombolo. The recession of the beach is the gradual result of this.
Natural disasters such as major storms cause permanent or increasing damage through mass destruction and erosion and to existing management strategies as well.
Short and steep with greater energy than constructive waves. The Backwash is more powerful and material is dragged down the beach, which makes it change shape
We damage and erode the dunes as a result of human activity which in turn has negative effects on the environment.
Local land use:
unrestricted access to the beaches
Regional Land Use:
The area south of Sydney Harbour was used for commercial, infrastructure and the CBD
The oil refinery at Kurnell built in that location for convenience of location near the city, cost effectiveness, sheltered bay and isolation
desalination plant of Prospect reservoir and Warragamba Dam was built because of cheap land and it was close to the city
Any development on the primary dune is at risk of storm damage in a normal beach erosion and build up cycle
The removal of sand and primary dunes was necessary in the process of incorporating infrastructure causing large scale damage
Kurnell was subject to explosions and accidents, threatening the nature of the dunes
These impact the native species of plants and animals which have to adapt or die out
population growth put more pressure on the beaches, adding to the gradual erosion
Large areas of the dune system were reclaimed for such purposes and dunes were removed or damaged
Beaches up the coast including Cronulla experienced thousands of tonnes of sand washed into the sea and swept inland by violent winter storms in the worst coastal erosion event in more than 30 years in August 2007
Receding 35m and losing 4m of depth, most of the sand the council dumped on the beaches from Narrabeen Lagoon was stripped
Around 1000 tonnes of sand was scraped up and moved back to Bondi and Tamarama after high winds swept it inland on to parks and roads.
Sand loss affected early season swimmers and beaches became more dangerous as storms dominated the coastline affecting surfers and tourists
The recovery of beaches to their pre-winter sizes takes up to several years even though seasonal erosion is a natural phenomenon
Effects of mass erosion mainly from natural disasters such as storms
We experience the negative effects of natural dune erosion processes
Huge swells tear up the promenade and original wall
Hazardous debris - surfers recall ocean bottom still lined with random huge chunks of concrete and steel girders for many months after wards
Social implications - expectation of a complete loss, or at the very least substantial damage, to the sand and shoreline, Cronulla Surf Life Saving Club and recreational facilities in South Cronulla. Assumption that the surf culture making Cronulla reknown, with learn to surf schools and professional surfing tournaments would be extinct
Post 1974 Storm
Greater impact from climate change will cause increasingly higher tides and gradually the effects of beach erosion will intensify. Without appropriate management, the effects will mean Cronulla beaches become non - existent.
Improved Strategies and Innovation
Recycled product is used to for pavements as a substitute for timber. These are for access of maintenance and emergency vehicles or beach users providing a more environmentally friendly and safer access to them. It has a more flexible nature and splinters and slipperiness are avoided.
In the mid 1800s Kurnell was covered in timber and brought by Thomas Holt, then cleared. He grew grass imported from Germany, allowing the grazing of sheep and later cattle. By 1970 there was no vegetation and it was decided to re establish it. The local council fenced off the dunes, provided specific pathways, education, signs and rules and threatened people with fines. Platforms were built in particular for surfers who wanted to overlook the ocean to spot the best surf spots.
Dune forming fences
Marram Grass Planting 1977
Stabilized dunes 1987
Infrastructure built on the primary dunes were exposed to impact of storm waves. Sea walls which were simple concrete walls to reduce impact were built and this was often ineffective if the sand grounding the wall was eroded away, therefore allowing it to come crashing down.
Grenfell. J. R. ENGLISH. 12th July 1950
"Men who, like myself, have had a life-long experience of surfing and surf beaches, have never been in
doubt as to the cause of the trouble. Not only does the sea-wall destroy the beach, but it creates strong "back currents" whose scouring action makes deep holes in the sea bed in the vicinity of the wall. These holes make the area danger- ous for any but the most experi- enced surfers, and preventing the even roll of the waves to the beach."
Letters of complaint of dis function in use of sea walls
"Sir,-The Cronulla beaches and sea walls have never recovered from the damage done to them at the direction of the defence authorities at the time Japan entered the war. Sand was scooped away from the foundations of the sea walls and the sea was invited to scour the beaches from the deep channels then made for very doubtful reasons. It was from this moment that the notice- able deterioration of beaches and walls took place. So far as North Cronulla is concerned, we are witnessing the result of the rapid decimation of the high sand hills at the back of the beach. Sand carters and shell grit gatherers are permitted by one Government authority or another to remove and wear away these hills to an alarming degree and in a manner that will be irreparable."
(Mrs.) M. DAVIS. Sydney.
15th July 1950
The concrete sea walls which were constructed in the 1920s and 1930s in North and South Cronulla suffered severe damage during the 1941 - 1950 storms and the current wall seen today began its construction in 1986 costing $1.7 million. It has been modified many times since, built on an angle to spread out the impact and covered in holes to absorb the impact. The top wall is curved to deflect waves.
In 2006 Cronulla experienced much development in comparison to 1974 for upmarket and commercial purposes. Wealthy people and tourists were attracted to the coast and a revetment wall of rocks helped to prevent erosion and damage
Fenced and stabilized
Signs, education and warnings
'The Impacts and management of coastal erosion on The Kurnell Peninsula' NSW Government, http://www.gemsevents.com.au/iecaconf2013/Resources/Laboyrie.pdf
C. Toddmiller, S. Howden, 'Beaches washed away by Storms,' News, The Daily Telegraph, http://www.dailytelegraph.com.au/beaches-washed-away-by-storms/story-e6freuy9-1111114167657
'Sand Dunes,' Coastal Care, http://coastalcare.org/educate/sand-dunes/
'Why are sand dunes important to coastal areas?' Ecosystems, Curiosity.com, http://curiosity.discovery.com/question/why-dunes-coastal-areas
Grenfell. J. R.'Effect of Sea Walls,' Beach Erosion, Letters, Trove Digitalised Newspapers and More, http://trove.nla.gov.au/ndp/del/article/18166068
(Mrs.) M. DAVIS. 'Beach Erosion,' Trove Digitalised Newspapers and More, http://trove.nla.gov.au/ndp/del/article/18159455
'North Cronulla,' Cronulla Surf Museum, Sub Rosa Creative, http://cronullasurfmuseum.com.au/tag/north-cronulla/
D. Shoebridge MLC, 'Cronulla Beach,' Sydney's Beaches, Beach Saver, http://beachsaver.org.au/sample-page/cronulla-beach/
10 people, mixed gender, were chosen at random to answer the following survey questions. They live in various areas of the Sydney vicinity, all differing in ages and occupations.
Results show that most people on average go to the beach depending on the weather and season, mostly summer. The public does visit the coast on a regular basis though.
The most common activities the general public share are swimming, walking and exercising and lying or sitting on the sand. Dune erosion affects the ability to use the coast for such purposes making the beaches less of an attraction to people.
Dune protection: Awareness and Importance
Only half of those asked noticed or knew what dune protection and the management strategies were and more than half rated the protection of dunes in terms of importance on a scale of 1 - 5, 1.
Many people are unaware of the issue because they are uneducated, have not cared about it.