Sand Dunes Development Plan

21915 words (88 pages) Essay

18th May 2020 Environmental Studies Reference this

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1.0 Introduction: 1.1 – The economic, cultural and natural importance of the chosen ecosystem

Sand dunes are large coastal features characteristically formed when windblown sand is trapped, accumulated and stabilised by vegetation. Sande dunes provide essential ecosystem services as habitats for native and endangered species, a site that provide high tourism value, groundwater recharge zones and protection of infrastructure and properties from wave erosion and storm surge flooding (Elko, et al, 2016). Coastal sand dunes form a natural buffer strip against strong wind and waves, protecting inland areas from storm damage. The structure and stability of sand dunes depends largely on stabilizing vegetation such as native dune grasses. Without these vegetations, the sand would simply erode as it does in areas that have been degraded by trampling and invasive species. As a component of sandy beaches, sand dunes are also popular recreation areas (Capital Regional District, n.d.). They also hold a cultural significance to Indigenous people that inhabited the area. Initially, sand dunes provided resources and shelter for aboriginal people, generating cultural values that remain important today (NSW Department of Land and Water Conservation, 2001). Economically, beach and dune systems are important for the coastal tourism industry and represent an important sand resource for the construction industry and beach replenishment works. They may also contain valuable heavy-mineral sand deposits (Brooke, n.d.). Heavy-mineral sand deposits are widely utlilised in aircraft engines and frames as well as medicine for joint replacements and dentistry for teeth implants (Iluka, 2018).

1.2 – A description of the natural area (including organisms and abiotic factors)

Image source: sanddunes.c20m.com, (n.d.). Evolution of sand dunes. Retrieved from http://www.sanddunes.20m.com/Evolution%20.htm

The sand dune vegetations zones reflect changes in the nutrient status and moisture content of dune soils as seen throughout the vegetation zonation where the plants are seen to grow in complexity as it continues landwards (figure 1&2). As established in the collected data, vegetations that colonise the strandline are extremely hardy and can tolerate salt spray, strong winds and sand abrasion. It’s common knowledge that sand dune vegetation are subjected to the constantly changing nature of the beach and dune environment. Hind dunes usually remain fairly intact when they are protected by a stable frontal dune and the plants in this zone have better access to soil moisture and nutrients than plants that colonise the fore dunes and strandline.

Information source: Mousley, J.G. (2012). Clarence Coast Dune Plants – A guide to selection for revegetation projects, Clarence Landcare Inc., Grafton NSW & Australian Govt. Caring for Our Country Program.

Three vegetation zones can be recognised: primary, secondary and tertiary. The primary vegetation zone is dominated by the beach spinifex, a pioneer coloniser. It has been recorded in figure 2 that the beach spinifex are the initial act for sand stabilization and dune formation and the primary species in the succession process. As the beach spinifex is located at the incipient foredune (refer to figure 1 & 2), it is open to the highest wind exposure (refer to figure 1), so they’re grown low to the ground as a reaction to incessant wind exposure (Liddy, n.d.). Increase in wind exposure and heat from the sun increases rate of evaporation which causes exposed plants to lose water hence why it has been observed that beach spinifexes have adapted to harsh conditions and developed silky hair on its grass blades (refer to figure 3). This physical attribute helps the plant to reduce the risk of evaporation by protecting the plant from high wind exposure and sun heat (Ross, 2018).

Image source: Newman, S. (n.d.). Ecosystems at risk case studies. Retrieved from http://www.mrstevennewman.com/geo/Stockton/Biophysical_Interactions/Biogeographical.htm

Beach spinifex play an important role in facilitating dune growth through colonization and trapping of windblown sand in place within the sand dune ecosystem. It has a very deep and expansive root system which stabilises frontal sand dune areas which reduce sand erosion from oncoming severe erosion events such as tidal surge and wave attacks (Council of the City of Gold Coast, n.d.). Signs of organisms in sand dunes is inconspicuous as they include amphipods; garter snakes; mammals such as mice and shrews; spiders, and insects such as caterpillars, beetles and flies. Sea birds such as the Plover nest among sand dunes as noted in the animal observations in figure 2 (CRD, n.d.). Sand dune mounds receive bird droppings that are rich in nutrients such as nitrates and phosphates which feed as good plant food (Newman, n.d.). This primary vegetation is the foundation and gives the stability for other vegetation to build up on and improves local conditions for other binders such as pigface and beach wattle to join in assisting stabalisation which as seen in figure 2, are located in the area behind the incipient foredunes (Newman, n.d.).

Situated behind the wall of the foredune is an area called a swale which nurtures conditions for nutrients to build up and other plants to grow and develop. The pioneer plants located in the fore dunes that have adapted to exposure to high salinity and wind exposure assisted in establishing the swale which provides a leeway for a new variety of low sand-holding plants like the beach wattle, banksia, pigface, goat’s foot and guinea flowers.

Image & information source: Marine Discovery Centre, (2018). Dunes – Nature’s way of defending the coast. Retrieved from http://www.marinediscoverycentre.com.au/Marine_Discovery/zone/Dunes-Natures-Way-Of-Defending.html

Proceeding into the secondary vegetation zone which is situated on the foredune and swale area contain secondary species such as shrubs, grass and small trees. These include vegetation such as beach wattle, banksia, pigface, guinea flowers, goat’s foot, red tip grass and bob grass. They have adapted to grow in areas with poor soils and accumulating phosphates and against salt winds and dehydration (Newman, n.d.). The beach wattle has developed an adaptation where it has a vine type root system which helps with its grip on the sand dunes, contribute to stabilisation and branching out for nutrients (figure 3). The main function of this zone and its vegetation is to stabilise the accumulated sand and generally improve soil conditions to enable a wider range of plant species to establish later (Council of the City of Gold Coast, n.d.). Species within the secondary vegetation zone are more complex than those in the pioneer zone as the presence of more nutrients means that such plants are able to be supported (Beachapedia, 2013). In comparison to the primary vegetation zone located on the incipient foredune, there is weaker winder exposure in terms of strength and speed where in the incipient foredune it’s 10km/h compared to 6.4km/h (figure 1). However, moderate wind and sun exposure are apparent (figure 1), so these shrub-typed plants have developed adaptations to survive in the sand dune environment. The beach wattle has waxy cuticles on its leaves to minimise desiccation and their leaves are modified to contain less stomata which also prevents the occurrence of evaporation (figure 3). While similarly to the beach spinifex, the guinea flower is a plant that grows low to the ground to aid in minimising exposure (Department of Environment and Science, Queensland, 2019). Presence of organisms distribution were more apparent behind the incipient dunes, landward of the sand dunes. There were sighting of plentiful kangaroo droppings located throughout the swale and secondary dune (figure 2 – animal observations). This may due to kangaroos feeding on the more appropriate and abundant vegetation that is located in this area (Official North Stradbroke Island website, 2019). 

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The hind dunes comprise of the tertiary vegetation zone, a stable zone where trees and more complex vegetation tend to dominate. Within this area, vegetation is protected from the wind and salt spray and the soils are characterised with organic matter. Since this area is more protected, it makes it easier or less hardy and specialised trees to survive. The more complex species in this area result in more humus and organic matter produced, thus providing sufficient nutrients for more species (Beachapedia, 2013). These types of vegetation include woodland plants including windswept shrub, stunted tree, coastal heath and forest plants. Plants identified in the recent expedition included guinea flower, casuarina seeds, she oak, grass, banksia and coast tea tree (refer to figure 2). Shading by taller vegetation means that woody species out-compete species from earlier seral stages, and so the resulting species diversity is lower (Field Studies Council, 2016). Most nutrients have leached from the high dunes by rain waters and the soils are thus infertile in the agricultural sense. These dunes, however, generally support tall open forests trees of the open forests and smaller trees like the she-oaks and tea trees and shrubs including acacias such as the coastal banksias (Banksia aemula and B. integrifolia). These banksias attract nectar eating birds such as the friar bird and insects (refer to figure 2, animal observations) when flowering (Liddy, n.d.). As the wind blows in from the ocean, the initial defence is the primary vegetation found on the incipient foredune. As the wind progresses through each zone, it is deflected up and over the foredune to move much of the strong salty wind over the non-resilient vegetation within the hind dune area (Newman, n.d.). This is seen in figure 1 where strong winds of similar strength and speed are seen to reach the hind dune area with the incipient fore dunes receiving wind speeds of 10km/h and that of the hind dune having similar results with a speed of 9.7km/h and 9km/h.

Figure 1

 

Sun

Shade

Figure 2

Plant species

0m

30m

60m

90m

120m

Spinifex

Pigface

Beach wattle

Goat’s foot

Seedlings

Red tip grass

Weeds

Guinea flower

Bob grass

Casuarina seeds

She oak

Grass

Pandanus palms

Banksia

Coast tea tree

Estimated % coverage in 1m2

60%

90%

75%

90%

10%

Animal observations

Sea eagles

Lady bug

Ants

Kangaroo droppings

Friar bird

Grasshopper

Ants

Plover

Snake

Figure 3

Plant species

Adaptations to the sand dune environment

Beach Spinifex

-Low growing to avoid excessive wind exposure

-Narrow leaves to minimise desiccation

-Shallow not system to absorb, fresh-water rain which doesn’t soak deep into soil

Beach wattle

-vine type root system, branches out for nutrients

-Wax cuticle on leaves to minimise water evaporation

-Leaves are modified stems with less stomata = less evaporation

Guinea flower

-Thick leaves for water storage

-Low growing to the ground to avoid excessive wind exposure

Banksia

-Sorating drops seeds after fire clears out completion

Casuarina

-Needles have minimal surface from which to lose moisture

-Wax cuticle on leaves to minimise desiccation

1.3 – A description and evaluation of data collection methods used in the field

Data was progressively collected along the sand dunes transect line. A measuring tape was used to measure the distance from the high-water mark in 30 metre increments. In this way, plant distribution and characteristics, taking note of zonation was accordingly recorded across the vegetation zones of the sand dune. When measuring the plant coverage in 1m2

areas, a quadrant was placed on the ground to seclude a sample of the sand dune to extract data from. Though, there were some apparent flaws within the fieldwork that has affected the data collected. There were no attempts at multiple trials in collecting a wide range of data which meant limited data was available. There were no prior instructions given of how to use equipment and material effectively and the time restraint in which this work was conducted limited the amount of data that can be collected. An alternative offered to fix these flaws in forming a sand dune profile was to use a previous year’s data collection of the sand dune measurements as recent slope data collected was not useful as it was not understood. As a result, relationships between biotic, abiotic and position along the sand dune aren’t close and accurate. There is an apparent discrepancy between dune profile and the biotic and abiotic factors as the dune data was collected in the previous year. This is due to the fact that the data of the sand dune profile was extracted from last year, the wind data recently recorded will not coincide with the previous topography of the sand dunes, hence a shifted alignment across the graph is presented when current data is inputted.

1.4 A summary of the proposed issue

This report is intended to outline the broad issues where the proposed development of pole houses on foredunes and the environmental/social impacts on sand dunes are concerned.

2.0 Discussion

2.1 Describe the likely effects of the proposed issue on the area (e.g. erosion). Analyse your data and draw conclusions.

If the pole houses were to be built on the sand dunes, inevitably the presence of human activities will have a large environmental impact. It’s observed that sand dunes are highly sensitive to any sort of human activities therefore it’s generally understood that sand dunes need to have very minimal interaction with humans for their portection and survival (NSW DLWC, 2001). Human impacts can quickly advance from minor to highly significant adverse effects. Minor effects can include pedestrian trampling, constructing footpaths, and off-road vehicle tracks, to highly more significant effects such as the construction of roads, car parks, houses and ground water extractions of sand dunes. On top of human activities, natural process will continue to operate within sand dune environments such as storms, floods, sea level change and sediment supply changes (Meulan, 1996). Two main risks are very likely to occur if this proposal is to go ahead. The first risk is stability which is a result of the mobile nature of sand which makes up the sand dune. The second risk is locational risk that derives from this proposal as the proximity of sand dunes to the sea create immediate risks in tidal surges (Shoalhaven City Council, n.d.). The removal of important vegetation will increase the chances of erosion and expose species to harsh conditions which eventually lead to destruction of sand dunes. Some issues involved are that the urban development encroaching on what were once active frontal dune areas, excavation of native sand dune species to create views and gardens which in turn destabilise the sand dune. Uncontrolled access in active forming sand dune areas result in instability and disruption to dune formation. The loss of vegetation with their heights and arrangements that come with the distribution of different vegetation species will affect the whole structure and stability of the sand dune. Property and parkland are susceptible to damage in the event of a natural incident such as erosion or other standard environmental conditions of the sand dune. Urban development on foredunes can have adverse impacts on coastal dunes. Covering foredunes with buildings and then the construction of rock walls, groynes and breakwaters to protect these properties locks up this source of sand, which disrupts the natural beach sediment budget. As a consequence, the morphology of beaches can change and they may become more prone to erosion because the volume of sand circulating within the beach systems is reduced (Brooke, n.d.).

2.2 Predict what the immediate and long-term implications could be for the biotic and abiotic factors in the local and wider area. Analyse your data and make links between biotic and abiotic factors.

Excavation of the sand dune from construction will inevitably cause the removal of primary vegetation of the fore dunes, the beach spinifex. Coastal sand dune systems are highly vulnerable to disturbance by trampling. Pedestrians and motor vehicles can compact the sand and crush vegetation. For example, native dune grass dies when its roots are crushed. Without the stabilizing vegetation, the sand is blown away, susceptible to erosion and eventually the dune will disappear. This can leave the shoreline more prone to damage from storm surges (CRD, n.d.). Plant species (like the hardy species) that experience harsh weather conditions are susceptible to change so it can’t survive being trampled by vehicle or man. So important vegetation such as the beach spinifex snaps easily when trampled or driven upon as part of its resistance to salinity and drying conditions the plant has developed a thick brittle stalk (Delaware.gov, n.d.). Loss of several beach spinifex, the centre of fore dune and overall sand dune stabilisation, will be fatal in terms of destabilising the grounds on which the pole houses will be built upon. Vegetation removal will also remove the natural habitat for the organisms that live there. For example, the Plover birds that nest among sand dunes will be harmed as the carrying capacity will be reduced so that populations will decline (Encyclopedia Britannica, 2019). It could also leave the sand exposed to the elements, resulting in blowouts and increased erosion. Blowouts, an erosional hollow, basin, trough or swale within a dune complex created by wind removal of sand. Blowout characteristics are controlled by 2 factors: vegetative cover and dune geomorphology. Generally, species composition and percentage cover modify the erosive capacity of wind but once the vegetation is destroyed, the size and orientation of blowouts are dependent on the interaction between geomorphology and characteristics of wind (Maun, 2009). The construction of pole houses will also lead household chemicals into the soil which can affect the pH levels of soil, which can prevent vegetation from taking up nutrients through the roots (Pearson, 2019).

2.3 Discuss the effect on the organisms present and how this could affect the local and wider area.

The proposed issue presents the introduction of pole houses, the rate at which the exposure of sunlight reaches the vegetations would decrease significantly and in turn, reducing photosynthesis and vegetation. This will ultimately inhibit the plant’s ability to survive on the foredune due to the light intensity being outside the optimum or tolerant range. This would directly impact organisms that rely on the vegetation for food and nesting. (find a source?) Coastal dunes already low tolerance to intensive recreational use, and if this proposal were to go ahead, then careless pollution by leaching chemicals and oils can critically impair this first line of defence that the sand dunes provide. Rubbish left on coast especially of the non-biodegradable variety can get back out to sea and there reach their damaging effects on wildlife e.g. plastic bags. Unlike the beach the frontal dune is extremely fragile. Destruction of its vegetation established by even moderate pedestrian use or grazing by domestic animals can quickly undo the evolutionary process of succession. Even tiny patches of frontal dune loss can leave much bigger areas open to destruction as strong on shore winds target the small discrepancy. These winds can result in Blow out, then transgressive mobile dunes, resulting in a completely unstable dune system rapidly moving inland. Ecosystems adjacent inland establish by dune formation and stabilisation are extremely vulnerable to dune breakdown, sand swamping by the inland march of a transgressive dune kills established Woodland, Heathland and Forests. The whole process of succession must be repeated all over again before their ecology can hope to re-establish its original biodiversity unless these destroyed regions are nurtured, fertilised, replanted and stabilised manually and artificially by us (Marine Education Society of Australasia, 2015).

3.0 Conclusion and recommendations 

3.1 Summarise the main issues with the proposal (those outlined in the discussion)

The construction process of houses can have a substantial effect on sand dune stability and disrupt the ecosystem. Human encroachment on the coasts is extensive and expected to increase with the construction of pole houses that are to be inhabited. If it were to be built on the foredunes, the proximity to the sea, coupled with potentially more frequent and eustatic sea level rise and consequently human life and infrastructure are susceptible. It also goes without saying that an increase in human activity will result in high impact and degradation of the coastal sand dune. This ecosystem is particularly threatened by the impact of human activities which include recreational use, establishment of environmentally inappropriate exotic vegetation, roads, car parks, beach access tracks, waste disposal and housing. Sand dunes and the vegetation that grow in them have a limited capacity to recover from intensive use without assistance and care from the community.

3.2 How could the proposal be modified to protect the site? Are there any alternatives which are more viable?

If the proposal were to go ahead, it would be best suggested that the construction of the pole houses should occur on the high dune instead of the foredunes. This is because would reduce the ecological impact of the project, eliminate the risk of inducing coastal erosion and ensure the security of any sand in which building foundation are to be constructed. The construction of houses should occur at low densities, in order to allow for sufficient sunlight penetration to the remaining vegetation. It should be endeavored that development is to be restricted on sand dunes within plausible reach of a storm with a high probability. Infrastructure may also be affected by waves and stronger wind due to proximity to the sea. It is strongly advised that this development plan is to be re-evaluated for any possible damage to sand dunes and to buildings. The building plan process should be consulted with a Structural Engineer experience in coastal engineering. Any loss and damaged plants should be replanted with the correct species. When constructing the pole houses, cut and fill operations should be limited to ensure little damage is done to the sand dunes (Shoalhaven, n.d.). Sand dunes are not to be reshaped unless approved by the relevant Council.

3.3 Make recommendations on what should be done to minimise the effect at the chosen area

In the event of building houses on sand dunes, clearing of vegetation should be kept to an absolute minimum and should be consulted with the Council prior to carrying out any work. The replanting of bare areas with recommended species and gradually remove other vegetation that is not appropriate. This work should only be done in consultation with the council in charge. Those who wish for the proposal to go ahead should be prepared for undertaking methods and approaches to keep the damage to the sand dune area to a minimum. Some of these should include things such as the installation of water tanks to harvest rainwater which is highly recommended as a way to protect and conserve groundwater extraction. When the mains water is no longer accessible, it will serve as an easy access to clean water if filtration with chlorination is installed as a precaution against any harmful bacteria that might be present in the water tank due to poor maintenance or accidental pollutants (Clark Tanks, 2018). Wooden sand fences have been seen to help with retaining and control the flow of sand and other important material essential for a stable sand dune ecosystem. This in turn, will reduce the risk of erosion and help rebuild and lost sand by drawing more sand into it. It’s a low cost for a simple addition in protecting the sand dunes (Discount Fence Supply, 2014).

4.0 Appendices  

Plants and organisms identification

Quadrat no. and sand dune category

Plant species

Estimated % cover in 1m2

Animal observations

Quad 1 – 0m

(foredune top)

Beach spinifex

60%

Sea eagle

Quad 2 – 30m

Slender vine

Beach wattle

Guinea flower

Weeds

Bob grass

90%

Quad 3 – 60m

Intermediate (secondary) top

Slender vine

Guinea flower

Red tip grass

75%

Quad 4 – 90m

Hind dune seaward side

Beach wattle

Slender vine

Red tip grass

90%

Friar bird

Quad 5 – 120m

High dune top “blowout” zone

Grass

Seedlings

She oak

10%

Grasshopper

Ants

Quad 6 – 150m

Hind dune landward

Casuarina seeds

Guinea flowers

Tea tree

Banksia

90%

Abiotic – physical parameters

0m

30m

60m

90m

120m

150m

Temperature of air

19.1˚c

22.6 ˚c

20.5 ˚c

19.6 ˚c

18.3 ˚c

19.3

Temperature –10cm depth

19.6 ˚c

20.2 ˚c

20.5 ˚c

19.5 ˚c

18.9 ˚c

20.8 ˚c

Wind strength (nil, low, moderate, strong)

10km/h

Strong

1.8km/h

Low

6.4km/h

Moderate

9.7km/h

Strong

9km/h

Strong

0.3km/h

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