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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 APart A

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Managing river and coastal environments: A continuing challenge

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Managing river and coastal environments: A continuing challenge

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Managing river and coastal environments: A continuing challenge

(Credit: Tsui Chung Pong David)

About 67% of the world population lives along rivers and in coastal areas.This is because rivers and coasts provide benefits to people.

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Managing river and coastal environments: A continuing challenge

1 AgricultureHow do people make use of rivers?

The flood plain in Loire Valley, France

Alluvium deposited on the flood plain forms fertile soil

Water from rivers is used for

____________irrigation

(Credit: Corbis)

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Managing river and coastal environments: A continuing challenge

2 Freshwater fisheryHow do people make use of rivers?

Freshwater fishery in Tai Hu along the Chang Jiang

Lake areas along rivers are converted into fish ponds for freshwater fishery

(Credit: China Features)

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Managing river and coastal environments: A continuing challenge

3 EnergyHow do people make use of rivers?

HEP plants can be built at the upper course of rivers,

where steep gradient provides great energy

Hydroelectric power (HEP) plant

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Managing river and coastal environments: A continuing challenge

4 Navigation and transportHow do people make use of rivers?

Rivers, if deep and large enough, can serve as an important inland river navigation network

Shipping along the Niagara River

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Managing river and coastal environments: A continuing challenge

4 Navigation and transportHow do people make use of rivers?

The shallow and narrow river channel in the upper course provides a cheap

transport route for timber

Transporting logs downstream

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Managing river and coastal environments: A continuing challenge

5 Industrial useHow do people make use of rivers?

The industrial plants along the river bank of the Yalu Jiang(Credit: Tsui Chung Pong David)

A river-side location is desirable for industries

Do you know why factories

often build by the rivers?

Do you know why factories

often build by the rivers?

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Managing river and coastal environments: A continuing challenge

6 TourismHow do people make use of rivers?

The natural beauty of Huanglong, Sichuan(Credit: Tsui Chung Pong David)

The beautiful landscape features and historical sites along rivers are

attractive tourist spots

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Managing river and coastal environments: A continuing challenge

1 Deforestation

How do these human activities alter river environments?

The forests in Guangxi were cleared to set up terraces for farming(Credit: Tsui Chung Pong David)

Forests in the river basin are cleared to obtain land for farming, industry, mining and the construction of HEP.

Forests are cut for domestic fuel.

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Managing river and coastal environments: A continuing challenge

2 Reclamation

How do these human activities alter river environments?

Lakes can be reclaimed for farming(Credit: Tsui Chung Pong David)

Lakes along rivers, e.g. Dongting Hu, are reclaimed for agricultural and urban uses.

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Managing river and coastal environments: A continuing challenge

1 FloodingWhat are the consequences of these?

Both deforestation and reclamation could induce flooding.

Flooding in the Chang Jiang basin in 1998 caused huge economic losses(Credit: Reuters)

Can you give some examples of the

effects of flooding?

Can you give some examples of the

effects of flooding?

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Managing river and coastal environments: A continuing challenge

1 FloodingWhat are the consequences of these?

A How does deforestation lead to flooding?

Vegetationcover

Infiltration

Interception

Overlandflow

Riverdischarge

When rain falls on deforested areas, the river discharge increases.

When the discharge exceeds the bankfull capacity, __________ occurs.

flooding

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Managing river and coastal environments: A continuing challenge

1 FloodingWhat are the consequences of these?

A How does deforestation lead to flooding?

Vegetationcover

Overlandflow

Soil erosionandmassmovement

Siltingofchannel

In deforested areas, rainwater hits the ground directly. The surface soil is easily eroded.

Slopes on river sides become unstable without vegetation cover, mass movement may occur.

Rainwater brings the eroded materials to the river channel. Silting reduces the bankfull capacity.

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Managing river and coastal environments: A continuing challenge

1 FloodingWhat are the consequences of these?

B How does reclamation lead to flooding?

Lakes can regulate water from tributaries and prevent flooding(Credit: Liang Wing Hang Yanchap)

Lakes can store water and act as buffer during flooding.

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Managing river and coastal environments: A continuing challenge

1 FloodingWhat are the consequences of these?

1644 - 1825

The changing size of the Dongting Hu at different periods

1826 - 19151916 - 19491950 - 19582000However, many lakes in the Chang Jiang, e.g. the Dongting Hu, are filled, drained or converted to other uses, such as freshwater fish ponds, farmland and settlement.

B How does reclamation lead to flooding?

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Managing river and coastal environments: A continuing challenge

2 PollutionWhat are the consequences of these?

Untreated sewage drained into rivers may contaminate river water

Chemical waste from farms, untreated sewage from factories and homes contaminate fresh river water.

The water can become unsuitable for drinking, not even for irrigation.

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Managing river and coastal environments: A continuing challenge

Dams could reduce downstream movement of sediment and organic matter. It leads to a degradation of fish habitats

Construction of dams could block some fish species from migrating up or down

the rivers to spawn, e.g. salmons

Dams blocking the upstream and downstream movement of materials and creatures

3 Disturbance to the ecosystemWhat are the consequences of these?

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Managing river and coastal environments: A continuing challenge

Excess fertilizers are washed into rivers

More nutrients for water plants and algae

Rapid growth of algae

Level of oxygen falls

Death of most living things

Excess fertilizers are used

3 Disturbance to the ecosystemWhat are the consequences of these?

Fertilizers washed into rivers and lakes will cause eutrophication. This stimulates excessive growth of water plants and algae which uses up large amount of oxygen in the water.

Pesticides washed into rivers contaminate the food chain.

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Managing river and coastal environments: A continuing challenge

Let’s look at the example of the

Chang Jiang to see how people

manage this river to prevent flooding and conserve the

ecosystem.

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Managing river and coastal environments: A continuing challenge

1 Flood managementHow do people manage the river?

A Regulate the dischargeRegulating the river discharge helps reduce the peak discharge. This is done by:

building more reservoirs;

prohibiting reclamation of lakes; and

Bankfull discharge

The channel cannot hold the flood water

Before regulating the river dischargeAfter regulating the river discharge

The peak discharge is

lowered

recovering the reclaimed lakes.

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Managing river and coastal environments: A continuing challenge

1 Flood managementHow do people manage the river?

B Increase the bankfull dischargeIncreasing the water-holding capacity of surrounding rivers helps increase the bankfull discharge. This is done by:

prohibiting deforestation at the upper course regions;

afforestation;

soil conservation;

The channel cannot hold the flood water

Before increasing the bankfull discharge

Bankfull discharge

After increasing the bankfull discharge

prohibiting farming on steep slopes;

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Managing river and coastal environments: A continuing challenge

1 Flood managementHow do people manage the river?

B Increase the bankfull discharge

Before increasing the bankfull discharge

Bankfull discharge

After increasing the bankfull discharge

straightening the course of the river to increase the velocity and thereby reduce silting; and

dredging the channel to lower the river bed.

Increasing the water-holding capacity of surrounding rivers helps increase the bankfull discharge. This is done by:

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Managing river and coastal environments: A continuing challenge

1 Flood managementHow do people manage the river?

C Land use zoningProper land use zoning can reduce the damage caused by flooding.

Zone

I

II

III

Flood risk

Highest

Moderate

Lowest

Land use zone

Development is prohibited

Restricted developmentSettlement is allowed

Zone I

Zone II

Zone III

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Managing river and coastal environments: A continuing challenge

2 Ecosystem conservationHow do people manage the river?

Preventing and reducing water pollution is the key to conserve ecosystems.

This can be done through legislation, sewage treatment and education.

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Managing river and coastal environments: A continuing challenge

(Credit: NASA)

What are the problems of

inundating river valleys?

What are the problems of

inundating river valleys?

What are the limitations of river management strategies?

The completed Sanxia DamThe completed Sanxia Dam

Sanxia Dam during constructionSanxia Dam during construction

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Managing river and coastal environments: A continuing challenge

Inundating river valleys: Problem caused by dam construction

The Sanxia Dam

Behind the dam- Farmlands are inundated- Natural landscape is inundated- Rare plants and animals are lost- Reproduction of fish species is affected- Factories are inundated- Historical sites are inundated- Settlements are resettled

Downstream- Dam may collapse, threatening the settlement downstream- Infertile soil downstream

(Credit: Reuters)

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Managing river and coastal environments: A continuing challenge

The Sanxia Dam

Inundating river valleys: Socio-economic problems caused by dam construction

- Costly- Historical sites are lost- People lose their jobs- People are resettled

(Credit: Reuters)

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Managing river and coastal environments: A continuing challenge

Problems caused by prohibiting logging

Logging activities in Sichuan are no longer allowed

Logging-associated industries, e.g. paper industry may decline. The supply of timber to local market drops.

Unemployment may cause social unrest.

Afforestation increases the economic burden on the government.

Local revenue from taxes drops.

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Managing river and coastal environments: A continuing challenge

In Part B, we will explore: how people alter the coast; how we manage the river and coastal environments.