Rivers
Definitions
Hydraulic Action
This process involves the force of water against the bed and banks. Abrasion This is the process by which the bed and banks are worn down by the river’s load. The river throws these particles against the bed and banks, sometimes at high velocity. Attrition Material (the load) carried by the river bump into each other and so are smoothed and broken down into smaller particles. Corrosion (Chemical Solution) This is the chemical action of river water. The acids in the water slowly dissolve the bed and the banks. |
SAMPLE ESSAY -Human Interaction with River Processes
Q. 1 a) Name ONE way that humans interact with a river.
b) Discuss 2 advantages of this c) Discuss 2 negatives of this (10 marks) A. 1 a) One way that humans interact with rivers is by building dams. Eg 3 Gorges Dam in China or Ardnacrusha Dam R. Shannon, Ireland b) 2 advantages of building: (PICK ANY 2) i) it can generate HEP (Hydro Electric Power) ii) it can prevent flooding iii)Recreation and Tourism i)HEP- Hydro Electric power is created when the Dam forces the river through a narrow opening. There is a turbine in this opening which is connected to a generator. The water spins this turbine and the electricity is then used in nearby towns and cities. HEP a renewable energy source that does not pollute the environment unlike fossil fuels. This can be very beneficial to the economy as we do not need to import expensive fossil fuels that will eventually run out. ii) Building Dams can also prevent flooding. Eg Ardnacrusha. During a period of heavy rain the water table levels rise. This means that the ground can no longer absorb large amounts of water. It also means that the rivers and lakes are at risk of flooding. At these times the openings in the Dam can be enlarged to allow more water through to ensure the river upstream does not burst its banks. These spillways allow humans to control the river and reduce the chance of flooding along the Shannon. iii)Recreation and Tourism- When dams are constructed they block off part of a river and reduce the flow of the river. This creates a large lake called a reservoir behind it which can be used for leisure purposes. Eg. Poulaphuca and the Blessington lakes Co. Wicklow are a popular tourist destination where they can do a variety of activities including fishing and watersports such as kayaking, sailing etc. This lake was also the location for the Vikings TV series which has been filmed there over the past few years. c) 2 disadvantages of building: (PICK ANY 2) i) negative effect on local wildlife ii)can cause flooding iii) reduction in alluvium i)Many animals depend on the river to survive. When the natural course or processes are interfered with it can effect these animals. Eg The salmon. The Atlantic salmon is native to Ireland. It returns to the place of its birth by swimming upstream to lay its eggs. If it cannot reach these breeding grounds due to the dam blocking its way, it may effect stock numbers in that river. The Yangtze River dolphin became extinct in China in 2007 due to the construction of the 3 Gorges Dam. ii)Flooding- although dams are built to prevent flooding they can also cause flooding. At the time of construction, the rivers flow is reduced. This causes the water to become backed up behind the concrete structure creating a lake or reservoir. This means that previously useful land becomes flooded. Farmers may loose land and people may loose their homes. 1.5 million people were forced to move when the 3 Gorges Dam was being built. iii)Reduction in Alluvium- A river carries a certain amount of fine sediment in its load. This is transported to the lower course where it is deposited on the floodplain during times of flooding. This rich alluvium is very fertile and excellent for growing crops in. The dam blocks this natural process of transportation and causes the sediment to build up behind the concrete structure. This means that it is no longer transported downstream. Farmers on the Yangtze river now have to buy expensive the fertilizer due to the construction of the 3 Gorges Dam. |
Ardnacrusha
3 Gorges Dam, Yangtze River China
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Upper Course Landform- Waterfall
Middle Course Landforms- Meander & Ox-Bow Lake
rivers.._visual_exam.pdf | |
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