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2.5 How can human activity influence and alter river and coastal

2.5 How can human activity influence and alter river and coastal environments?. Part A. About 67% of the world population lives along rivers and in coastal areas. This is because rivers and coasts provide benefits to people. (Credit: Tsui Chung Pong David).

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2.5 How can human activity influence and alter river and coastal

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  1. 2.5 How can human activity influence and alter river and coastal environments? Part A

  2. About 67% of the world population lives along rivers and in coastal areas. This is because rivers and coasts provide benefits to people. (Credit: Tsui Chung Pong David)

  3. How do people make use of rivers? 1 Agriculture Alluvium deposited on the flood plain forms fertile soil Water from rivers is used for ____________ irrigation The flood plain in Loire Valley, France (Credit: Corbis)

  4. How do people make use of rivers? 2 Freshwater fishery Lake areas along rivers are converted into fish ponds for freshwater fishery Freshwater fishery in Tai Hu along the Chang Jiang (Credit: China Features)

  5. How do people make use of rivers? 3 Energy HEP plants can be built at the upper course of rivers, where steep gradient provides great energy Hydroelectric power (HEP) plant

  6. How do people make use of rivers? 4 Navigation and transport Rivers, if deep and large enough, can serve as an important inland river navigation network Shipping along the Niagara River

  7. How do people make use of rivers? 4 Navigation and transport The shallow and narrow river channel in the upper course provides a cheap transport route for timber Transporting logs downstream

  8. How do people make use of rivers? 5 Industrial use A river-side location is desirable for industries Do you know why factories often build by the rivers? The industrial plants along the river bank of the Yalu Jiang (Credit: Tsui Chung Pong David)

  9. How do people make use of rivers? 6 Tourism The beautiful landscape features and historical sites along rivers are attractive tourist spots The natural beauty of Huanglong, Sichuan (Credit: Tsui Chung Pong David)

  10. How do these human activities alter river environments? 1 Deforestation Forests in the river basin are cleared toobtain landfor farming, industry, mining and the construction of HEP. Forests are cut fordomestic fuel. The forests in Guangxi were cleared to set up terraces for farming (Credit: Tsui Chung Pong David)

  11. How do these human activities alter river environments? 2 Reclamation Lakes along rivers, e.g. Dongting Hu, are reclaimed foragriculturaland urban uses. Lakes can be reclaimed for farming (Credit: Tsui Chung Pong David)

  12. Flooding in the Chang Jiang basin in 1998 caused huge economic losses (Credit: Reuters) What are the consequences of these? 1 Flooding Both deforestationandreclamationcould induce flooding. Can you give some examples of the effects of flooding?

  13. Vegetation cover When rain falls on deforested areas, the river dischargeincreases. When the discharge exceeds the bankfull capacity, __________ occurs. What are the consequences of these? 1 Flooding A How does deforestation lead to flooding? Infiltration Overland flow River discharge Interception flooding

  14. Vegetation cover Overland flow In deforested areas, rainwater hits the ground directly. The surface soil is easilyeroded. Slopes on river sides become unstable without vegetation cover,mass movementmay occur. Rainwater brings the eroded materials to the river channel.Siltingreduces the bankfull capacity. What are the consequences of these? 1 Flooding A How does deforestation lead to flooding? Soil erosion and mass movement Silting of channel

  15. What are the consequences of these? 1 Flooding B How does reclamation lead to flooding? Lakes can store water and act asbufferduring flooding. Lakes can regulate water from tributaries and prevent flooding (Credit: Liang Wing Hang Yanchap)

  16. However, many lakes in the Chang Jiang, e.g. theDongting Hu, are filled, drained or converted to other uses, such as freshwater fish ponds, farmland and settlement. What are the consequences of these? 1 Flooding B How does reclamation lead to flooding? 1826 - 1915 1916 - 1949 1950 - 1958 2000 1644 - 1825 The changing size of the Dongting Hu at different periods

  17. Chemical waste fromfarms, untreated sewage fromfactories and homescontaminate fresh river water. The water can become unsuitable fordrinking, not even forirrigation. What are the consequences of these? 2 Pollution Untreated sewage drained into rivers may contaminate river water

  18. Dams blocking the upstream and downstream movement of materials and creatures What are the consequences of these? 3 Disturbance to the ecosystem 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

  19. What are the consequences of these? 3 Disturbance to the ecosystem Fertilizers washed into rivers and lakes will causeeutrophication. This stimulates excessive growth of water plants and algae which uses up large amount ofoxygenin the water. Excess fertilizers are used Excess fertilizers are washed into rivers Pesticides washed into rivers contaminate thefood chain. Death of most living things More nutrients for water plants and algae Level of oxygen falls Rapid growth of algae

  20. Let’s look at the example of the Chang Jiang to see how people manage this river to prevent flooding and conserve the ecosystem.

  21. How do people manage the river? 1 Flood management A Regulate the discharge Regulating the river dischargehelps reduce the peak discharge. This is done by: The channel cannot hold the flood water The peak discharge is lowered building more reservoirs; Bankfull discharge prohibiting reclamation of lakes; and After regulating the river discharge Before regulating the river discharge recovering the reclaimed lakes.

  22. How do people manage the river? 1 Flood management B Increase the bankfull discharge Increasing the water-holding capacity of surrounding rivers helps increase thebankfull discharge. This is done by: prohibiting deforestationat the upper course regions; The channel cannot hold the flood water Bankfull discharge afforestation; soil conservation; prohibiting farming on steep slopes; After increasing the bankfull discharge Before increasing the bankfull discharge

  23. How do people manage the river? 1 Flood management B Increase the bankfull discharge Increasing the water-holding capacity of surrounding rivers helps increase thebankfull discharge. This is done by: straightening the course of the river toincrease the velocity and thereby reduce silting; and Bankfull discharge dredgingthe channel to lower the river bed. After increasing the bankfull discharge Before increasing the bankfull discharge

  24. How do people manage the river? 1 Flood management C Land use zoning Proper land use zoning can reduce the damage caused by flooding. Zone Flood risk Land use zone Development is prohibited I Highest Restricted development Moderate II Zone I Settlement is allowed III Lowest Zone II Zone III

  25. How do people manage the river? 2 Ecosystem conservation Preventing and reducingwater pollutionis the key to conserve ecosystems. This can be done throughlegislation, sewage treatmentand education.

  26. What are the limitations of river management strategies? (Credit: NASA) Sanxia Dam during construction The completed Sanxia Dam What are the problems of inundating river valleys?

  27. Inundating river valleys: Problem caused by dam construction • 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 The Sanxia Dam (Credit: Reuters)

  28. Inundating river valleys:Socio-economic problems caused by dam construction • Costly • Historical sites are lost • People lose their jobs • People are resettled The Sanxia Dam (Credit: Reuters)

  29. Problems caused by prohibiting logging Logging-associated industries, e.g. paper industry may decline. The supply of timber to local market drops. Local revenuefrom taxes drops. Afforestationincreases the economic burden on the government. Logging activities in Sichuan are no longer allowed Unemployment may causesocial unrest.

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

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