© oxford university press 2009 quit part 2 managing river and coastal environments: a continuing...

© Oxford University Press 2009 Quit

Part 2 Managing river and coastal environments: A continuing challenge

2.52.5 How can humanHow can human activity influence andactivity influence and alter river and coastalalter river and coastal environments?environments?

Part BPart B



A bay in San Francisco, California, USA

How do people make use of the coastal areas?

Can you suggest how people make

use of the coastal areas?

Can you suggest how people make

use of the coastal areas?

Can the activities

you mentioned be found in

Hong Kong?

Can the activities

you mentioned be found in

Hong Kong?



How do people make use of the coastal areas?

In general, the following activities are found:

Tourism and recreation

Urban developmentPower generation

Industrial activities



How do people alter the coast?A Reclamation

The development of commercial and residential buildings in West Kowloon(Credit: Liang Wing Hang Yanchap)

Reclamation is carried out to obtain land for urban development.

It changes the shape and form of the coastline.

Reclamation has been carried out near old Star Ferry in Central for the construction of expressways



How do people alter the coast?B Dredging

A dredger(Credit: Liang Wing Hang Yanchap)

When deposition is active at a harbour, dredging is carried out to ensure that the port can accommodate large ships.

Dredging is also practised for obtaining materials for reclamation and construction.



Coastal erosion and deposition are continuing processes. They can shape the shoreline and this has

profound impact on human activities.

People need to manage the coast to ensure the continuance of

human activities. Two approaches are often used.

A Hard approach (structural response)

1. Groynes2. Breakwaters3. Sea walls4. Rock armour

B Soft approach (non-structural response)

1. Beach nourishment

2. Mangrove planting

3. Coral reef growing

4. Vegetation planting

5. Relocation and land use zoning

How do people manage the coast?



1 Reclamation

What are the consequences of coastal alterations?

In Hong Kong, reclamation projects on both sides of Victoria Harbour narrow the harbour.

It increases the speed of water currents and affects the safety of navigation.

It may also bury the habitats of aquatic organisms and disturb aquatic ecosystems.

The land at both sides of Victoria Harbour

Reclaimed land



2 Dredging


Dredging shingle would expose the coast to erosion, e.g. the case of Hallsands village in the UK.

Dredging may stir up sediment and pollutants from the seabed, which can disturb aquatic ecosystems.

1. Shingle beach before dredging of sand and shingle offshore

Sea

Sea level

2. Cliff eroded by sea after removal of shingle

3. Part of the village was destroyed

4. Present location of cliff

Hallsands village (abandoned)



3 Pollution and the ecological balance


Sewage and waste from homes, businesses, factories, hotels and other recreational facilities could upset marine ecosystems.

Structural work may block sediment movement. It leads to changes in the natural habitat. Tourist facilities along a beach in

Cancun, Mexico



What are the limitations of coastal management strategies?Groynes

Longshore drif

t

Groynes block longshore drift

Beaches further along the coast may be more vulnerable to wave erosion

Groynes in Dorset, UK (Credit: Rex Features)



What are the limitations of coastal management strategies?Breakwaters

Accumulation of sand behind the breakwater

Breakwater

Breakwaters protect the coast behind (Credit: Rex Features)



What are the limitations of coastal management strategies?Sea walls and rock armours

Expensive to build and maintain

A sea wall Rock armour

Expensive if rocks are imported

Rocks must be large and heavy enough to

remain stable

Dangerous to young children

(Credit: Tsui Chung Pong David)(Credit: Corbis)



What are the limitations of coastal management strategies?Beach nourishment

The beach of Repulse Bay

Sediment of the beach may lose

after a storm

Regular maintenance is

needed

Costly

(Credit: Getty Images)



What are the limitations of coastal management strategies?Mangrove planting and coral reef growing

Mangrove planting

Careful protection is needed for

young mangroves

Coral reef growing

Ensuring that the water is free from

pollution



What are the limitations of coastal management strategies?Vegetation planting, relocation and land use zoning

Vegetation planting

Planting vegetation on cliffs or poor soil is difficult

Relocation and land use zoning

People with investments and properties at the

coast are reluctant to move

Costly compensation



Rivers and coasts are our valuable resources.

We should manage them in a sustainable way.

To set up a sustainable management strategy, we need to

- examine the balance between four parties;

- carry out cost-benefit analysis.

SocietyEnvironment

Economy Government

What should people do to face the continued challenges posed by the management of river and coastal environments?



5. Investigate the balance between four aspects in

the management strategy

1. Define objectives

2. Consider the impact of human

3. Set indicators for use with

environmental-based management

4. Design effective assessment methods

6. Implement management strategy

7. Evaluate outcome

Let’s look at how the UK works out her shoreline

management plans (SMPs)!

Management strategy evaluation model











7. Evaluate outcome

Case study: Shoreline management plans (SMPs) in the UK


The aims of SMPs:1. Improve understanding of coastal

processes;2. Set up long-term planning of coastal

defences and land use.











7. Evaluate outcome


- Assessing the risk to people and the natural environment;

- Devising a sustainable management strategy with four policy options:• Do nothing• Hold the line• Advance the line• Retreat













7. Evaluate outcome




Case: SMP for Holderness coast- Rolston:1. Tackle wave erosion2. Major land use: agriculture3. Low population- Bridlington:1. Tackle wave erosion2. Major land use: holiday resorts,

nationally important place for seabirds











7. Evaluate outcome


Case: SMP for Holdernesscoast- Rolston:Option: Do nothing- Bridlington:Option: Hold the line(Methods: Promenade, sea

walls, groynes)




A The ‘hard’ approach: Structural response1 Groynes

Groynes are barriers built at right angle to the coastline to stabilize beach deposits.

Longshore

drif

t

Groynes

Longshore drift moves the sand deposits parallel to the shore.

Groynes in Dorset, UK

(Credit: Rex Features)



A The ‘hard’ approach: Structural response2 Breakwaters

Breakwaters are long piers built offshore to reflect and dissipate the energy of incoming waves.

The coastline is protected from erosion.

breakwaterstyphoon shelter

The Aberdeen Typhoon Shelter(Credit: Lam Man Lok)



A The ‘hard’ approach: Structural response3 Sea walls

Sea walls are built parallel to the shoreline to protect the coast by reflecting wave energy.The coastline is protected from wave erosion.

Curved concrete sea wall

Cliff

Wave energy is reflected by the

presence of the sea wall

Seabed Toe protection Sheet piling

(Credit: Corbis)



A The ‘hard’ approach: Structural response4 Rock armour

Rock armour is a barrier of large, irregular shaped rocks or concrete placed at the coastline.

They protect the coastline from wave erosion.

(Credit: Getty Images)Rock armour



High Island Reservoir, East Dam



B The ‘soft’ approach: Non-structural response1 Beach nourishment

Stabilizing the coastline by adding a large quantity of sand or shingle to the beach.

Repulse Bay in Hong Kong is an example of beach nourishment.

Repulse Bay is a famous tourist spot in Hong Kong(Credit: Getty Images)



B The ‘soft’ approach: Non-structural response2 Mangrove planting

Mangroves can protect the coast against erosion by strong waves and winds by binding the soil.

Mangroves can bind the soil and thereby prevent coastal erosion



B The ‘soft’ approach: Non-structural response3 Coral reef growing

Coral can reduce the speed of waves approaching the coast and thereby protect beaches against coastal erosion.

Coral reefs under the sea



B The ‘soft’ approach: Non-structural response4 Vegetation planting

Planting vegetation on cliffs can increase their stability and thereby stabilize the shore.

Structures on a sea cliff



B The ‘soft’ approach: Non-structural response5 Relocation and land use zoning

Removing or relocating coastal properties to safe ground helps prevent loss of life and property.

In the eroding coastal areas, only limited, or even no development, is allowed.

© oxford university press 2009 quit part 2 managing river and coastal environments: a continuing...

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