Collaroy Narrabeen Beach Collaroy

Collaroy before the development of human infrastructure:

Before human intervention, the coast of Collaroy was a series of sand dunes. The beach carried out its natural process and was undisturbed by human activities and construction. The beach has always had extensive sand dunes behind them, however this did not create negative impacts because it was a natural occurrence and there was no infrastructure intruding onto the beach. This is evident in Source A (found on the next page) a photograph, displaying Collaroy during the early 1900s.

The negative consequences of erosion were virtually non-existent because there was no infrastructure on the shore of the beach. As shown in the image, the sand was expansive and naturally progressed into

bushland. This enabled natural coastal processes to occur and Collaroy was in a pristine state; untouched by human activity.

Wave patterns at this time were were carrying out their natural process which is a cycle of erosion and accretion of sand. Waves are important as they transport sand on and offshore and can also move sand along the shore. It is normal in winter for beach profiles to become steeper due to stronger wave action, which removes sand from the beach and deposits it onto offshore sandbars. In summer, calmer waves bring sand back to the beach. The nearshore currents, created by winds, waves, tides and river flows would transport large amounts of sand and alter the shape of offshore sandbars. These processes occurred without disruption at Collaroy before human interaction.

Source A: (secondary data)
Photograph of Collaroy Beach during the very early 1920s

Collaroy after the building of infrastructure, its current state & its coastal processes:

While Collaroy-Narrabeen Beach is exposed to natural erosion caused by tides, waves and wind, human infrastructure has been the key impact of erosion, due to the building of residential structures on the beachfront.

Not only has urban development faced damage from these coastal changes, however by changing coastal stability, development itself has increased erosion. Buildings, roads and homes built too close to the beach have become vulnerable to erosion due to extreme weather conditions. Furthermore, during storms, large waves cause severe erosion to this beach. Consequently, wave patterns change as they are are not naturally rolling onto the beach. Instead, they are smashing against built surfaces/structures (causing more erosion) and then are being violently pushed back.

Major erosion has been occurring in Collaroy for nearly 100 years; Major storms in 1913/14, 1944/5, 1966/67 and 1974 saw buildings damaged or washed away starting with the Collaroy Surf Lifesaving Club and Dressing Sheds in the summer of 1913/14. Since the 1920s, the council has still continued to allow massive over-development even after houses and structures had been damaged and washed away. Source B is a photograph from 1966 showing destruction caused to infrastructure as a result of building houses too close to the waterline, in spite of the risk of

erosion.

Overtime, erosion at Collaroy has become progressively worse and has made severe impacts on infrastructure.

Source C (below), an aerial image of Collaroy shows properties damaged by erosion at Collaroy beach after a storm event in June, 2016 caused by an east coast cyclone. The before and after shot displays the 10-15 metres of waterfront land that was washed away. In total, seven homes and a unit block in Collaroy were evacuated as 8 metre waves slammed the coast leading to major erosion. This image shows structures that have been destroyed, most notably a swimming pool. In the before picture, there was greenery and trees bordering the houses from the sand, however after the storm in the ‘after’ image they have disappeared and have been swept away by the waves. Source D (on the next page) depicts the destructive waves that crashed against the shore on Collaroy, causing structures to collapse. Due to the fact that the structures are located close to the foreshore, wave patterns have altered and instead of crashing onto an expanse of sand they are forced to smash against structures (causing erosion), and then are violently retreating back and repeating the same cycle. The white water, present in both Sources C and D, indicates that the waves were extremely violent leading to the collaspe and damage of properties. Swells from the storm coinciding with high tides increased the severity and size of the waves. These waves were large and broke directly on the shore, the white water from which carved out the sand and eroded the rocks, sand and structures. According to the Bureau of Meteorology, 410,000m3 of sand was moved from Collaroy beach during this time.

The beach erosion at Collaroy and large wave run up is strongly linked to the occurrence of high wave conditions with elevated ocean water levels. As a result, erosion and run up are more likely to be significant when large waves combine with a high tide. The peak wave height is predicted to be 8.8m for storm waves coming from the south and 9.3 for storm waves coming from the south-south-east. (According to a Warringah Council Report on Collaroy in 2014.)

Source C: (secondary data)
Before and after photograph of Collaroy Beach after the June 2016 storm

Source D: (secondary data)
Photograph of Collaroy Beach during the June 2016 storm

Currently, as of 2018 the beach is still suffering and has faced major destruction and erosion.

Source E displays a large wire fence that collapsed as well as damaged chairs and umbrellas sprawled about. Furthermore, Source F shows two images of the destruction of a property. The cream coloured steel fence has been completely demolished, along with a wooden structure. A rusted steel structure (in the second image) is laying on a horizontal angle and pieces of tree trunks are also clustered into a dishevelled pile.
Source E: (primary data)
Photograph of damage at Collaroy Beach, April 2018

Source F: (primary data)
Photographs (below) of a house and its fence destruction at Collaroy Beach, April 2018

Source G (below) exhibits tree damage in front of a property, also surrounding it is junk and destruction. The tree roots are exposed and it looks like it will fall over if it is not removed. It is a danger hazard that could cause even more disruption to the surrounding area. This demonstrates that by human’s building so close, the natural environment (tree) has no room to grow and is now positioned on the steep formation which continues to erode.
Source G: (primary data)
Photograph of tree damage at Collaroy Beach, April

2018

Source H: (primary data)
Photographs of steep erosion escarpment
at Collaroy Beach, April 2018

These images of erosion from Source H show the steep escarpment at Collaroy. The first image illustrates the effects of wave action on the shoreline of the beach. The second image shows how far the waves have reached and crashed against the shoreline, resulting in the formation of a vertical sand wall.

Observations (primary data):

Interviews - Locals and Professionals (primary data):

Management implemented to reduce damage at Collaroy:

As of 2018, most of the affected properties at Collaroy have been fronted by makeshift seawalls to guard against erosion. These seawalls were placed there to decrease the erosion and damage to residences. However, it is evident that they are insufficient and cannot protect against the erosion. Additionally, these defences can exacerbate further erosional problems, with seawalls reflecting and concentrating wave energy and erosion.

During the 1980’s the Pittwater Council made a decision to refuse any new Development Applications for beachfront properties as the Council did not want to be responsible for any future damage to property. The Council also adopted a defensive strategy of buying the worst effected properties and demolishing any buildings. The land acquired was turned into public parkland. However due to the large growth in property prices, this strategy quickly became unaffordable for the Council.

Furthermore, in the late 1980’s an expensive plan to build a sea wall, to be jointly funded by the NSW Government, the Council and residents, was made. However after much dispute the residents failed to agree to fund the plan and it was never implemented. In addition to the cost, the disadvantages of sea walls include visual impact and increased erosion due to waves reflecting. Around the same time, dune rebuilding and stabilisation with vegetation was undertaken but was ultimately had no long term benefit.

More recently, in 2014, a management plan was established, “The Coastal Zone Management Plan (CZMP) for Collaroy-Narrabeen and Fishermans Beach” which outlined how both beaches will be managed for current and future generations. The CZMP recognised that Collaroy is exposed to coastline hazards, specifically erosion. This plan was prepared in accordance with the NSW Government.

According to a report by the Warringah Council, the objective of the CZMP is to preserve the beach environments while limiting the impact of coastal processes on public and private assets. The key aims are to:
“Protect and preserve beach environments and beach amenity
Manage current and projected future risks from coastal hazards
Ensure continuing and unfinished public access to beaches, headlands and waterways
Protect or promote the culture and heritage of both beaches”

On observation, this project does not seem to be in action. Perhaps the council is carrying out further planning and designing because the fieldwork and data collected does not show improvement of the area or any signs of offical reconstruction and protection methods.

Moreover, the strategy of beach nourishment, whereby sand offshore of the Narrabeen Lagoon entrance is dredged and pumped to the middle and Southern parts of the beach, has been undertaken periodically since the 1990’s to the current day. However, this strategy has been problematic for the following reasons;
It is very expensive to operate and manage
It is never possible to pump enough sand
The movement of sand is dictated by the direction and timing of future storms which is unpredictable. For example, if 2 storms in a row come from the same direction the beach may not have time to recover between the storms, therefore the strategy is ineffective.

Some individual property owners have taken steps to protect their own properties by using boulders, sandbags, gravel and rubble. While these tactics may be somewhat good for protecting their properties, they can create increased turbulence and adversely affect the neighbouring properties. These actions also normally result in a loss of sand and can make the beach very steep which is negative for recreational users of the beach.
Source I: (primary data)
Photograph of makeshift rock seawall at Collaroy Beach, April 2018
Source I showcases a house fronted by a makeshift seawall made of large sandstone rocks. While this is providing some protection to the property, it is not able to properly defend the house from destruction. In the image, there is a fence falling over and rocks are not stable.

Source J: (primary data)
Photograph of makeshift sandbag seawall
at Collaroy Beach, April 2018
Source J is a photo of a steep makeshift seawall constructed using sandbags. This wall is not supportive enough and in the case of a violent storm, it would not withstand the conditions. Source I and J reveal that residents of Collaroy have been so greatly affected that they have been forced to build their own seawalls in order to conserve their properties.