SGP - Coastal Erosion - Full marks SGP for Yr 11 PDF

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Full marks SGP for Yr 11...

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COASTAL EROSION

TABLE OF CONTENTS

2 INVESTIGATION & BACKGROUND 3 JUSTIFICATION & EVIDENCE OF ISSUE 4 AIMS AND HYPOTHESES 5 METHODOLOGIES 7 PRIMARY RESULTS 13 PRIMARY PHOTOGRAPHS 18 SECONDARY PHOTOGRAPHS 21 QUESTIONNAIRE RESULTS 23 RESEARCH FINDINGS 29 EVALUATION 32 CONCLUSION 33 ACKNOWLEDGEMENT & REFERENCES

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To investigate the coastal erosion at Collaroy-Narrabeen Beach and the impact of the erosion on its surrounding environment and vegetation.

Coastal erosion is the removal or loss of coastal land due to the removal of sediments from the shoreline. Beaches are temporary landforms that commonly undergo cycles of coastal erosion in response to varying sea conditions and other factors such as sediment reductions, submergence and poor planning.The Collaroy – Narrabeen Beach is located on Sydney’s Northern Beaches, 16km north of the CBD. It is the interconnecting 3.6km coast of Collaroy Beach and Narrabeen Beach. The lengthy coastline stretches from the 20m high Narrabeen head in the north to the low cliffs at Collaroy Point.

Figure 1: Google Maps image of Narrabeen Beach to Collaroy Beach

A number of coastal processes operate within the embayment which contribute to the long-term recession of the coastline. At North Narrabeen, the waves average a height of 1.5m as well as the most intense rips. Whilst waves average 1m-1.5m from North Narrabeen to the South Narrabeen surf club, then dropping to less than a metre at Collaroy where the rips often infill.The Collaroy – Narrabeen Beach has always had a long history of storm damage and coastal erosion. Over the past decades, the coastal erosion at Collaroy – Narrabeen Beach has significantly worsened and had caused the coastline to recede in drastically. This intensifying coastal erosion has been caused by factors such as poorly planned coastal development, increasing climatic conditions, intense and larger waves and increasing population. The coastline is still increasingly preceding inland despite the actions the local council and other organisations have taken to stop, control and prevent the coastal erosion from impacting the surrounding environment. The strategies and management plan they have created are ineffective and weaker against the natural environment.

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Coastlines and beach environments are important to the humans, flora and fauna who are impacted by the ecosystem. Coasts provide habitats from mangroves, beaches, bays, gulfs to estuaries, for many different species, such as the yellow-crested Cockatoos, terns, pelicans and eagles. Australia’s coasts are what allows Australians to achieve social, economic and environmental benefits. As one of the most urbanised nations in the world, more than 85% of the population resides within 50km of the coast. As the population is growing and becoming more urbanised, the importance and the sustainability of coastal environments has become an increasing concern. Coastal ecosystems are becoming increasingly vulnerable and at risk to coastal processes, specifically coastal erosion. Coastlines are moving further inland and negatively impacting its surrounding environments.

In Australia, the Collaroy-Narrabeen Beach has been determined as the third area that is most at risk to coastal processes; especially coastal erosion. Whilst in NSW it is the coastal area most at risk, and the most highly capitalised shoreline in NSW. The Northern Beaches are particularly susceptible to erosion caused by tides and waves. It led to a number of properties to be evacuated and other properties to be at imminent risk to other storm events. Such erosion has occurred over the years and is forecast to continuously increase and intensify.However, such erosion has not deterred people from buying more and more properties in the area with the lure of the oceanic views. With the population increasing outside of metropolitan areas, it has added pressures on local councils to agree to inappropriate development along coastal edges. The highest increase in urbanisation has occurred near the coast, all throughout Australia, with the population density increasing by 14% from 2001 – 2009.

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1.) To investigate the coastal erosion at Collaroy-Narrabeen Beach by conducting tests on longshore drift, vegetation transects, beach profiles, and the use of other sources to determine the presence of coastal erosion at Collaroy-Narrabeen Beach.

2.) To identify and analyse the impacts and the primary causes of coastal erosion at Collaroy-Narrabeen, its consequences on the surrounding environment and, the Northern Beaches Council'sresponse in controlling the coastal erosion.

1.) The coastal erosion at Collaroy-Narrabeen Beach is severe and with a much more significant presence at Collaroy Beach thatis continuing to worsen.

2.) That the exacerbating coastal erosion at Collaroy-Narrabeen Beach will continue to impact the vegetation and animals, as well as the coastal assets and properties that reside near the beach. In addition, the Northern Beaches Council has acknowledged the issue, but their plans and strategies havebeen relatively weak.

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1.Primary methodology will include quantitative measurements, photos and qualitative observations of the environment surrounding CollaroyNarrabeen Beach. Quantitative measurement will include the longshore drift (rates and time). A beach profile is the second primary method, which will provide a better understanding of the extent coastal erosion has on the beach terrain. A vegetation transect is the third primary method to show the extent of the impact of erosion of the surrounding natural vegetation. The fourth primary method is the photography of the CollaroyNarrabeen Beach, providing detailed views of the most impacted areas to erosion; it will avoid bias to the previous methods stated. The final primary method will be an online questionnaire to residents that live within the Northern Beaches region to provide an insight look into the effects the erosion has on people susceptible to it.Secondary methods include analysing studies that involve coastal processes amongst Collaroy-Narrabeen Beach to allow comparison between the results obtained. Coastal erosion at Collaroy-Narrabeen Beach will also be investigated through secondary research using news articles, government studies, weather and coastal websites, satellite images of the beach and the local council’s website, and its management plans. By studying the local council’s sources, the extent of their response to coastal erosion can be analysed and evaluated. The satellite images can be used to compare the distances of the shoreline to the end of the beach from the past, to its current state, in order to identify the impact coastal erosion has given rise to.

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1.Sampling points along the width of the beach 2.Place a ranging pole at the start and finish of each point. (first point should be the low tide mark) 3.Note down the main changes in slope angle up the beach 4.Use the clinometer at each change in slope angle to take a bearing. (bearings can be taken from the eye level of a person of a similar height holding the ranging pole) 5.Measure the distance of the ground of each section, and record 6.Repeat steps four and five for each change in slope

1.Mark a point with a ranging pole in the breakwater zone 2.Place the float (tennis ball) into the water in the breakwater zone at the start point 3.Set a timer for 5 minutes and observe the object’s movement 4.With a person holding the starting pole, place another pole where the float ended at 5.Measure the distance between the two poles 6.Repeat steps 2 to 5, three more times

1.Lay a tape measure across the width of the beach, marking the transect route from the pioneer zone towards the end of the beach. 2.Place ranging poles at the major changes in slope angle 3.Sample the vegetation cover and the coverage of different plant species at each point 4. Record abundance level

Google forms survey https://docs.google.com/forms/d/1XoFk-o WoPua-sN5Mx1LyzvK8UazMrJJV-NtjgkyWlo/edit

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Testing rates of longshore drift at Collaroy Beach TRIAL 1 (17/04/20)

Testing rates of longshore drift at Collaroy Beach TRIAL 2 (29/04/20)

Testing rates of longshore drift at Collaroy Beach TRIAL 3 (05/05/20)

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Testing rates of longshore drift at Narrabeen Beach TRIAL 1 (17/04/20)

Testing rates of longshore drift at Narrabeen Beach TRIAL 2 (29/04/20)

Testing rates of longshore drift at Narrabeen Beach TRIAL 3 (05/05/20)

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BEACH PROFILES

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BEACH PROFILES

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VEGETATION TRANSECT

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VEGETATION TRANSECT

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Figure 2: The distance from the end of the ‘dunes’ to the shoreline at Collaroy Beach

Figure 3: Erosion control blanket placed over hottentot fig and brachychiton rupestris seedlings at Collaroy Beach

Figure 4: The general terrain and slope at Collaroy Beach

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Figure 5: Structures built very close to the shoreline at Collaroy Beach

Figure 6: Residential homes nearing the shoreline at Collaroy Beach have seawalls

Figure 7: Residential homes nearing the shoreline at Collaroy Beach have seawalls

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Figure 8: A large apartment complex built near the shoreline at Collaroy Beach also has seawalls

Figure 9: Longshore drift testing with the float (tennis ball) at Collaroy Beach

Figure 10: Terrain and slope of the dunes at Narrabeen Beach

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Figure 11: Terrain and slope of the dunes at Narrabeen Beach

Figure 12: Longshore drift testing with float (tennis ball) at Narrabeen Beach

Figure 13: A wide view of a section of the dunes at Narrabeen Beach

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Figure 14: Spinifex sericeus and gazania rigens are dominant in the dunes at Narrabeen Beach

Figure 15: Scaevola calendulacea and sesuvium portulacastrum are also dominant in the dunes at Narrabeen Beach

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Figure 16: Schematic representation of a preerosion/storm profile

Figure 17: Schematic representation of a posterosion/storm profile

Figure 18: Flight Deck apartment undermined by waves in 1967

Figure 19: Erosion in front of South Narrabeen SLC in 1966

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Figure 20: Pre and post UAV surveys at Collaroy Beach after the June 2016 East Coast Low

Figure 21: Pre and post cross-section of Narrabeen-Collaroy Beach after the June 2016 East Coast Low

Figure 22: Population comparison of Collaroy

Figure 22: Population comparison of Narrabeen

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Figure 23: Objectives of the Coastal Zone Management Plan prepared for Collaroy-Narrabeen Beach

Figure 24: Protestors form a 1km human chain from Narrabeen to Collaroy beach to protest a sea wall in 2002

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Coastal erosion questionnaire results – Graph 1

Coastal erosion questionnaire results – Graph 2

Coastal erosion questionnaire results – Graph 3

Coastal erosion questionnaire results – Graph 4

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Coastal erosion questionnaire results – Graph 5

Coastal erosion questionnaire results – Graph 6

Coastal erosion questionnaire results – Graph 7

Coastal erosion questionnaire results – Graph 8

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The primary testings conducted at Collaroy-Narrabeen Beach provided results which overall support the hypotheses that were aimed to be investigated.Collaroy – Narrabeen Beach is a stable closed system; the most significant coastal processes that influence beach recessions and fluctuations are cross-shore and longshore sediment transport. The longshore drift testing which occurred in three separate trials showed similar results, of a much faster speed of longshore drift at Collaroy Beach when compared to Narrabeen Beach. Even though Narrabeen Beach has larger waves and more violent sea conditions than Collaroy Beach’s, however the longshore drift is more prevalent at Collaroy. Collaroy Beach has an average speed of longshore drift at 2.17m/min, a noticeably faster rate of longshore drift compared to Narrabeen Beach’s 1.44m/min. Longshore drift, which is the movement of materials (sediments) along the shore caused by wave action. It involves the swash and backwash of material which provides a link between erosion and deposition. The speed at which the waves approach the shore is also linked to the features of the shoreline, such as the angle of the shore. When a wave breaks at a steeper incline, longshore currents increase in velocity, whilst a gentler and wider breaking angle results in a slower velocity. The beach profile of Collaroy and Narrabeen Beach influences the longshore drift at each beach. Collaroy maintains a flatter, narrower and rugged beach profile with a sharp incline towards the backshore/dunes, the sharp incline increases the speed of the longshore drift when waves reach the backshore which causes the destruction of many properties that are lined along the backshore/dunes. Narrabeen has a very smooth, wide and gentle sloped beach profile with no sharp inclines or drops, therefore providing for a slower speed of longshore drift. The abundance of debris left on the two beaches effectively shows the contrast between the vastly different longshore drift speeds. From Figures 2 to 5, there is evidence of a large amount of debris (from rocks to environmental waste) that have been transported by longshore currents. Whilst in comparison, in Figures 10 to 13, there is almost no debris that can be spotted on the stretch Narrabeen Beach.

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The beach profile of Collaroy Beach shows a larger and a dominant presence of coastal erosion compared to the beach profile of Narrabeen Beach, which shows a milder presence of coastal erosion. By looking at Figure 16, the beach profile of Collaroy Beach is almost identical to the post-erosion/storm profile, especially due to the steep incline towards the dunes (or where the dunes should be located). The Collaroy Beach struggles to recover from the intensified erosion caused by the continuous, destructive storms due to the lack of dunes. The lack of dunes is primarily contributed by the inappropriate urban development that is present right next to the edge of Collaroy beach. Although Narrabeen has milder coastal erosion than Collaroy and tends to fare better than Collaroy Beach, the two beaches share a long history of inappropriate urban development and issues with dunes. In Figure 18, the Flight Deck apartment (which still exists) an inappropriately built residential apartment building, built on the sand of Collaroy Beach was undermined by waves in the 1960’s. Cohesively, in Figure 19, it shows a large steep incline manifested from very intense erosion in front of the South Narrabeen SLC and although the structures were not entirely impacted, the erosion had reached the structures which hence shows the close proximity of man-made structures to the beach. The proximity between man-made structures to the beach and the continuous inappropriate development has always been an ongoing issue at Collaroy-Narrabeen Beach; especially at Collaroy, with structures built on the sand in the areas where dunes are meant to vegetate. The results of the vegetation transect testing shows a positive impact of an abundance of dune vegetation. The vegetation transect of Collaroy Beach shows a meagre number of hottentot fig seedlings, hilaria jamesii and brachychiton rupestris that have looked to be recently planted on an erosion control blanket.

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The scarce and almost non-existent dunes at Collaroy Beach contribute to the major impacts many residentials receive from the coastal erosion. Dunes naturally limit the inward intrusion of waves, wind and salt spray, which can all increase erosion. They act as natural buffers against oceanic inundation and provide a natural transition from marine to terrestrial environments. The coastal erosion at Collaroy Beach has led to not only the loss of land, but it has removed the little vegetation that was once present; especially after the frequent violent storm events. In Graph 6, it shows 56% of residents believe that the vegetation has eroded over the years due to erosion, with a few responses stating it is not a problem if the dunes and the vegetation were left alone. In Figure 21, the large loss of sand within a few days shows the intensity of the coastal erosion at Collaroy-Narrabeen Beach. The most recent violent storm event was in early February of 2020, with more than 25m of sand lost from the Collaroy-Narrabeen strip. In many news articles, it mentions Collaroy Beach and the impacts of the erosion caused by the storm events, with very minor mentions of Narrabeen Beach. From Figure 20, the scarce dune vegetation that was once present at Collaroy Beach was completely obstructed by the erosion. In a length of four years, there has yet to be any growth in any of the dunes at Collaroy Beach, with the majority of the vegetation being seedlings. The miniscule dunes at Collaroy Beach compared to Narrabeen Beach prove to be effective in preventing destruction of nearby properties and landforms. Dunes minimise coastal erosion, hence justifying the weaker coastal erosion and impacts of it at Narrabeen Beach compared to Collaroy Beach. This worsening coastal erosion impacts the surrounding environment immensely, from the terrain to the inhabitants, including humans, native animals and plants species. Coastal erosion in general terms refers to the loss or displacement of sediments along the coastline, leading to long term removal of land from the beach.

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A diminishing coastline would cause more development to occur in order to remove and rebuild structures that have been built very close or on top of the beach. The population of Collaroy and Narrabeen is also steadily growing which is causing more urban development around the areas; many residents believe the cause of this population growth is due to the internal migration to these suburbs. A beach is considered a prime location; hence, it is a pull factor for many people and the major reason most people live near beaches. However, the two main causes of coastal erosion at Collaroy – Narrabeen Beach is inappropriate urban development and climate change/intensifying weather events, which can also be seen in the responses of residents in Graph 3.Coastal urban development, especially poorly planned and inappropriate development, places increasing pressure on the natural environment due to the land clearings and pollution urban development causes. Building along the foreshore and the sand dunes interferes with the natural terrain, which affects the coastal processes and the natural movement of sand. Coastal development results in increasing erosion, which calls for the need for beach nourishment and revegetation of native plants. Inappropriate coastal development interrelates with climate change and the intensifying weather events. Coastal structures are more susceptible to rising sea levels, storm events and tropical cyclones. With intense weather events becoming more frequent over the years, Collaroy-Narrabeen Beach has lost over 50m of the beach in 2016 and more than 25m in 2020. The residents that live along the beach are particularly vulnerable to the loss in land, as the sea draws closer and closer to their properties. It leads to the destruction of coastal structures and properties which can lead to an increase in coastal development to repair, restructure and relocate those properties. Sea level rise and accelerated erosio...