COASTAL MANAGEMENT - Weebly



COASTAL MANAGEMENT

|WORDS |DEFINITIONS |

|Constructive waves |small low-energy waves that deposit sand onto beaches |

|Corrasion |occurs when waves crash over rock shelves and move rock and other material helping to erode the rock shelf |

| |away |

|Corrosion |the action of salt on minerals like iron that are contained in rock, weakening the rock and making it more |

| |susceptible to erosion |

|Deposition |the depositing of sand and rock particles caused by wind and wave action forming features such as beaches |

|Destructive waves |large waves formed by tropical cyclones and storms that erode material from beaches |

|Erosion |the removal of rock and sand particles as a result of wind and wave action |

|Fetch |the distance that wind travels over the ocean to form waves |

|Foredune |the closest dune to the ocean or the first dune in a sand dune system |

|Hydraulic action |where waves enter cracks in rocks, air is compressed by the force of the water causing erosion and forming |

| |features such as blow holes |

|Longshore drift |the process, caused by waves hitting the coast at an angle, that is responsible for moving sand along the |

| |coast |

|Refraction |the bending of waves around headlands and into bays |

|Surf and swash zone |the active part of the coast in terms of erosion and deposition of sand by wave action; the surf zone is |

| |immediately adjacent to the coast and the swash zone is at the shore once the waves have broken |

|Vegetation succession |the natural progression of vegetation from low-lying, salt-tolerant plants on the foredune, through to |

| |shrubs and established trees on the hind dunes |

|Wave height |the vertical distance between the trough and the peak of a wave |

|Wavelength |the horizontal distance between wave peaks |

GEOGRAPHICAL ISSUES IN THE COASTAL ENVIRONMENT

Australia is largely a nation of coastal dwellers with 85 per cent of the population living within just 50 kilometres of the coastal zone. The pressure of urban development along the coastline has caused a range of geographical issues involving various groups. Residents, tourists and commercial-related activities all need to be managed by geographers so that the development of the coastline is sustainable.

Pollution

Pollution from urban developments along the coastline is altering coastal ecosystems. Sewage outfalls add nutrients to the water and pollute the water. Without careful management the water can become unsuitable for swimming. In Sydney, urban stormwater is a major pollutant of the coastal environment—between Palm Beach and Cronulla over 200 stormwater outlets discharge water containing high levels of pollutants such as sediment, bacteria, heavy metals and organic chemicals into the ocean.

Pollution from urban developments can pose a health risk to humans. Without careful treatment of sewage and the management of stormwater, beaches can be unsuitable for swimming.

Tourism and recreational pressures

The coast is a popular destination for residents and tourists alike. Tourist developments and resorts are concentrated in particular areas along the coast. During holiday times the population of these areas can double, placing pressure on the infrastructure and environment of the area.

Recreational activities like four-wheel driving places pressure on the coastal environment. If not carefully managed, large dune areas and beaches where vehicles are given access can be highly susceptible to erosion.

Population growth

Overdevelopment and rapid growth of coastal areas occur due to the current Australian trend for people to move from large cities to smaller coastal towns and villages where the lifestyle is more relaxed. ‘Sea change’ is the name applied to this process. Some towns along the east coast of Australia have imposed residential caps or a population ceiling for their town in an effort to stop overdevelopment of the area.

Coastal rivers and lagoons

River entrances along the coast are prone to silting up as a result of both natural causes and human actions. Careful management of these river entrances ensures safe and navigable access for boating and provides tidal flushing of rivers and lagoons which keeps the environment healthy. This often involves dredging and river entrance clearance of the many rivers and lagoons along the coast. The entrance to the Murray River became so silted up it required four years of non-stop dredging to clear the river channel entrance.

Dredging of the Murray mouth continues today and is likely to be a part of the long-term management of the river entrance.

Introduced plants

Areas along the east coast have become invaded by introduced plants. The bitou bush or Chrysanthemoides monilifera was introduced into Australia from South Africa in 1908 to stabilise sand dunes and was used widely after sandmining activities in the 1950s. It can overtake native vegetation and does not offer sand dunes the same protection against wind erosion as those covered by native vegetation.

Influencing decision-making

Making decisions on the appropriate use and management of coastal areas involves detailed knowledge of the natural processes that shape and form them. In addition a wide range of perspectives or viewpoints about how the coast should best be used or developed need to be considered. On occasions, residents and interested groups need to take action to influence decision-makers such as councils, governments and developers. Geographers play an essential role in determining the suitability of developments and ensuring the sustainable use of the coastline.

Inappropriate development

Much of the appeal of the coast comes from the views and lifestyle offered by the location. A balance needs to be achieved between development and the natural beauty or visual amenity of the area. Government planning now includes strict rules in an effort to ensure appropriate development. However, there are still poorly planned developments that alter the natural environment. Sand mining and the construction of breakwaters, for example, have interrupted the natural cycles that have shaped the coast. Large complexes such as the Holdfast Shores accommodation development in Adelaide are appreciated by residents and tourists but opposed by many local residents because of the loss of amenity to the beach front.

Activities

Knowledge

1 Describe how the settlement pattern of Australia is related to issues in the coastal environment.

2 Why is the sustainable development of the coastline the aim of coastal management strategies?

3 What trend has been labelled ‘sea change’?

4 Describe one government response to ‘sea change’.

5 Select four of the geographical issues facing the coastal environment presented in this unit. For each issue identify the human actions that cause the issue.

6 What role do geographers play in developing management solutions to issues in coastal environments?

Application

7 Study the inappropriate development image. Select one of the viewpoints below and write a letter to the local paper about the advantages and/or disadvantages of the development.

a a resident of one of the new developments shown in the picture

b a long-time local resident of the area who appreciates the coastal views.

WAVES – WATER ON THE MOVE

When we think of coasts we usually think about waves. Waves are one of the most identifiable features and are one of the key natural forces that shape coastal environments. They are a way in which energy is transferred from one place to another. For effective coastal management a clear understanding of the way waves shape the shoreline is essential.

The formation of waves

Waves are formed by the action of the wind blowing across the ocean. First the wind forms ripples, then these form wavelets and finally waves. The distance the wind travels over the ocean to form a wave is called the fetch. The size and speed of the waves is influenced by the strength of the wind and the length of the fetch.

Natural wind energy forms the waves. As the waves travel towards the coast they take the energy from the wind with them. Watching a buoy in the open ocean, waves cause it to move in an up-and-down motion only.

When the waves enter shallow water the energy in the waves starts to interact with the sea floor. The wave speed decreases, the wavelength becomes shorter and the wave height increases. Eventually the wave peak travels faster than the wave base and the waves break and release the energy they contain (see 7.5).

A broken wave forms the surf and swash zone. This is the active part of the coast in terms of erosion and deposition of sand. As waves travel across the open ocean they form what is called a swell. If waves travel only a short distance before they hit land they form a wind swell. A wind swell is marked by a short wavelength and high frequency of waves hitting the coast. A ground swell forms when waves have travelled across a greater distance of ocean before hitting the coast. A ground swell has a longer wavelength and the waves hit the coast less frequently.

PAGE 154-156 4 DIAGRAMS

Activities

Knowledge

1 Outline the three stages in the formation of a wave.

2 What is the fetch? Why is it an important factor in determining the size and speed of a wave?

3 How do waves in the open ocean differ from waves closer to the shore?

4 Draw an annotated diagram showing wavelength and wave height.

5 Draw an annotated diagram explaining how a wave breaks.

6 Explain the difference between the three different types of waves.

7 Explain the difference between a wind swell and a ground swell.

Skills

8 Interpret the synoptic charts that tracked Tropical Cyclone Wati in the Coral Sea from 24–28 March 2006.

Application

9 A tourist to Australia has asked you to advise them on the best areas for swimming at local beaches. Write a letter that explains to them the three types of waves and how to identify them.

10 Imagine you are the lifesaver on duty at a busy Sydney beach during a large cyclone swell. Write an account of the day’s events.

GEOGRAPHICAL PROCESS SHAPING THE COASTAL ENVIRONMENT

The three key geographical processes that shape the coastal environment are erosion, transportation and deposition. Waves and wind act to erode headlands and shape beaches. These same forces then transport sand and other material to be deposited in other coastal areas forming landforms like beaches and sand dunes.

Erosion of headlands

As waves approach the coast they bend or refract due to headlands and the contours of the ocean floor. In the open ocean, wave energy is distributed evenly along the entire wave. Wave refraction causes the wave energy to be concentrated in particular areas and less intense in others, as shown in 7.7.

The main erosional features found on coasts are around headlands. They are shaped by three processes that are all related to waves.

• Hydraulic action—Waves crash against a headland. Waves enter cracks in the rock and air is compressed into the crack by the force of the water being pushed by the wave. As the air is compressed it acts to erode rock. Blow holes are a common feature formed by hydraulic action.

• Corrasion—Waves crash over rock shelves. The wave action moves rock and other material across the rock shelf and wears away the rock in an abrasive fashion.

• Corrosion—In rocks along the coast there are minerals like iron. When waves break they wet the rocks. As the rock dries the salt in the sea water crystallises and acts on the minerals in the rock to erode material.

PAGE 156-157 3 DIAGRAMS

[pic] [pic]

Famous Australian ‘apostle’ lost to the waves

On the Great Ocean Road in Victoria are some of Australia’s most distinctive coastal landforms—the Twelve Apostles. These are seastacks in Port Campbell National Park that are made of rock formed up to 20 million years ago. They were created by the sea gradually eroding the soft limestone cliffs.

Waves erode coastal headlands but the rate depends on the type of rock. One of the famous ‘apostles’—a 45-metre stack—collapsed into the sea in July 2005.

The stack that collapsed in 2005 was not the first to disappear into the sea. In January 1990 the feature called London Bridge, which was a natural arch that linked the mainland to offshore rocks, also collapsed.

Deposition and transportation along the coast

Once material is eroded away by the wind and waves it is transported to other places to be deposited. Depositional landforms include beaches and coastal dunes, which are shaped by the action of the wind, waves and prevailing ocean currents.

PAGE 158 1 DIAGRAM

Beaches

Beaches are one of the most obvious depositional landforms of the coastal environment. Formed from eroded rock and shell material they are accumulations of sand that occur along the shoreline. They are a dynamic environment as they are constantly being reshaped.

During severe storms beaches can lose large quantities of sand through erosion by waves. Often the eroded sand will be deposited offshore, forming a sand bar off the beach where it helps to limit the impact of the erosive waves on the coast. The sand that is removed will be eventually returned naturally by smaller constructive waves, restoring the beach to its former state in what is called the erosion-accretion cycle.

Coastal dunes

Coastal dunes are formed by the action of the wind. Once sand is deposited on the beach it is then subject to aeolian (wind) transportation.

The wind blows the sand landward, which is then trapped by low-lying vegetation like coastal spinifex. The foredune is a store of sand. It may be eroded away, or it may continue to increase in size depending on wave and wind action.

The foredune provides a buffer zone for the fragile dune vegetation located on the hind dunes. Easily eroded, the plant communities can quickly recolonise and stabilise the area after periods of erosion, allowing the dune to quickly form again. In this way dunes play a vital role in the protection of property and developments from erosion.

PAGE 159 1 DIAGRAM

ACTIVITIES

Knowledge

1 Name the three key geographical processes that shape the coastal environment.

2 What is wave refraction and why does it occur?

3 Use a diagram to explain how wave refraction leads to the uneven distribution of wave energy along the coastline.

4 Name the most common erosional landforms found along the coastline.

5 Describe the three wave action processes that shape headlands.

6 Explain the operation of the erosion–accretion cycle.

7 Name the three forces that shape depositional landforms on beaches.

8 Name the most common depositional landforms found along the coastline.

9 Explain the process that forms coastal dunes. What role does vegetation play in their formation?

10 With the aid of a diagram describe the process of longshore drift. What role does this process play in transporting sand along the coast?

11 Select two erosional and two depositional landforms found on coasts. Sketch them into your notes and describe the processes that have formed each landform.

12 What role does the foredune play in protecting coastal areas?

13 Read the snapshot about the loss of one of the Twelve Apostles and use your knowledge of the coastal environment to answer the following:

a Where are the Twelve Apostles located?

b Why are they a popular tourist destination?

c Describe how the Twelve Apostles were formed.

d What was London Bridge? What happened to this landform in 1990?

e Do you think the collapse of the landforms along the coast could have been prevented? Explain your answer.

Application

14 Imagine you are a park ranger employed at Port Campbell National Park. Prepare a brief talk that explains the formation and eventual destruction of the Twelve Apostles.

15 The local council has decided to buy back residential property located on a headland and a neighbouring foredune that is subject to severe erosion. Local residents who own the property say the council is depriving them of their spectacular views, relaxed lifestyle and valuable property.

Write a newspaper article that evaluates the council’s decision to buy back the properties. The article should present facts and consider a range of opinions about the issue. As a part of the article you will need to present an opinion on the property buy-back proposal.

MANAGING THE COASTAL ENVIRONMENT

Coastal management involves developing strategies that are designed to protect and preserve the coastal environment. Human actions have altered the operation of the natural coastal processes. Intervention is often necessary in order to protect property, make areas safe for boating and restore the environment.

Coastal management strategies

Management strategies involve careful consideration of the geographical processes that shape and transform the environment. There are a number of coastal management strategies that have been developed to manage coastal environments around Australia. Often a combination of some or all of the following strategies will be used to manage coastal areas.

Construction of protective barriers and walls

Using rocks and concrete to create structures which stop erosion are a frequent management strategy used along the coast. There are three basic types of constructed walls.

• Sea walls—Used to stop erosion of the coastline and protect property. Sea walls often replace the foredune, which is an essential part of the beach erosion– accretion cycle and the scenic appeal of the beach may be reduced by their construction.

• Breakwaters—Constructed at the entrances to rivers, they extend into the ocean in order to stabilise river entrances and provide safe access for boating by keeping the river entrance clear of sand build-up. However, these breakwaters can act to dramatically alter patterns of erosion, transportation and deposition of sand along the coastline.

• Groynes—Constructed along beaches (almost at right angles to the shore) to catch sand and make beaches wider. As a management technique they rely on the sand carried by longshore drift. They protrude into the ocean and are designed primarily to slow down the rate of longshore drift. However, sand tends to accumulate on one side only, creating a different beach from its natural shape. Groynes were traditionally made out of wood or rocks and concrete. Textile bags filled with sand are now being used instead in many areas.

Beach nourishment

Beach nourishment involves the movement of sand by machines. Large quantities of sand are moved from a point where it accumulates to a point where it has been eroded. As a beach management technique it is expensive and needs to be ongoing. Dredging river mouths along the coast is a common source of sand for beach nourishment.

Coastal dune preservation

Coastal dunes play a vital role in the coastal environment and there are a number of strategies used to manage these areas.

• Limiting any new developments that occur in coastal dune areas. This allows the dunes to play their natural role as a buffer between the beach and the land and avoids councils having to develop and build elaborate sea walls to protect property.

• Constructing fences to control access of pedestrians and vehicles across sand dune areas. This helps stop erosion as trampling vegetation removes the protective covering.

• Revegetation to help stabilise the dunes when the natural vegetation has been removed.

Group and community involvement in coastal management

The coast is a popular recreational environment that all Australians enjoy. It is essential that the area be preserved for future generations. Coastal management schemes need to be not only based on a sound understanding of the natural coastal processes that operate but also ensure access to the coastal areas for the community. For this reason it is essential that coastal management schemes have the support of all levels of government as well as community groups.

ACTIVITIES

Knowledge

1 In your own words describe what coastal management involves.

2 List the coastal management techniques discussed in this unit.

3 Prepare a table of coastal management strategies listing the advantages and disadvantages of each:

Brief description of management strategy Advantages Disadvantages

4 Why do effective coastal management schemes often involve a combination of management techniques in order to protect and preserve the coastal area?

Application

5 Outline the most appropriate coastal management strategy for the following issues along the coastline:

Description of problem Proposed management solution/s

Fishermen from a coastal village anchor their

boats in a small river. Recently the river mouth

has been eroded by the ocean and the river

entrance is no longer safe for ships to use.

A tourist development has been built behind

a well-preserved sand dune system. Tourists

wanting to access the beach are trampling and

destroying fragile dune vegetation.

Developments along the coast have changed

the shape of a safe swimming beach popular

with families. It is often dangerous to swim.

Hotel owners are demanding that the beach be

restored to how it was before the developments.

Storm waves frequently threaten to destroy

property along the foredune of a beach.

TO BE USED WHEN FOCUS TOPIC

TWO CASE STUDIES IN THE TEXTBOOK GEO FOCUS 2

1. GOLD COAST

2. TWEED HEADS (THE ENTRANCE)

3. FIELD WORK ACTIVITIES

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