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AS and A Level: Hydrology & Fluvial Geomorphology
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Five things you need to understand about hydrology and fluvial geomorphology
- 1 Make sure you understand the concept of systems, and the difference between a closed system (the global hydrological cycle) and an open system (the drainage basin)
- 2 Learn the correct definitions of all the specialist terms (eg percolation, throughflow, hydraulic radius, etc.
- 3 Learn a case study which shows how the theory relates to an actual example of a real river basin.
- 4 Remember that rivers are not static – they are affected in the short term by weather patterns and human activity and in the long term by changes in climate, tectonic processes and sea levels.
- 5 Pay attention to scale: for example British rivers (and British floods) are tiny compared to the great rivers (and great floods) experienced in other parts of the world.
Common errors in hydrology and fluvial geomorphology essays
- 1 Although rivers near their source often look like they are flowing quickly, and rivers near their mouth look like they are flowing slowly, river velocity increases downstream. This is because there is more turbulence upstream (due to friction) and rivers flow more efficiently as they get further downstream (as friction reduces).
- 2 Infiltration is the movement of water into the soil. Percolation is the movement of water into the underlying rock. Students often confuse these two terms.
- 3 Landforms are often referred to as landforms of erosion (eg waterfalls) or landforms of deposition (eg deltas). However, it is important to remember that other processes (erosion, weathering, transportation, deposition, mass movement) also contribute to the formation of these features.
- 4 River valleys and river channels are not the same thing.
- 5 Remember that flooding can bring benefits as well as costs.
Top facts to use in your essay answers
- 1 Water covers approximately 71% of the Earth's surface
- 2 96.5% of the planet's water is found in oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air.
- 3 Only 2.5% of the Earth's water is freshwater, and 98.8% of that water is in ice and groundwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere.
- 4 The Amazon river is by far the largest in the world in terms of discharge (which is greater than the next seven largest rivers combined), and it has the world’s largest drainage basin. The Nile is generally recognised as the world’s longest river (approximately 6550 km).
- 5 River flooding has been the cause of some of the world’s worst environmental disasters. For example, the 1931 Yangtze floods in China may have killed up to 4 million people.
- Marked by Teachers essays 4
- Peer Reviewed essays 1
Temperate glaciers move very rapidly, e.g. The Franz Josef glacier in New Zealand moves approximately 300m per year. It is the basal temperature that determines the mechanism of movement. In what follows I will explain the factors influencing different mechanisms of movement. Temperate glaciers move mainly by basal sliding. If the basal temperature is at or above pressure melting point, a thin layer of meltwater will exist between the ice and the valley floor, therefore friction is reduced and enables the glacier to slide over the underlying land.
- Word count: 838
Discus to the extent to which you believe Carlisle floods 2005 were the result of intense rainfall rather than the physical characteristics of the drainage basin3 star(s)
This flow had returned again after approximately 175 years. Many geologists and people could say that the floods were cause by human impact, but in reality, that would be unlikely, but not impossible. It would not have been one of the major factors that cause the floods in Carlisle. However for example if, the vegetation in the river or around the river basin was removed or cut down, for the use of more land, or materialistic things, this could have affected the velocity of the river, as vegetation such as trees, act as an interception in the river causing its velocity to slow down.
- Word count: 648
In addition an argument against the management of Mississippi that floods have gotten worse was proved false as records at the time were inaccurate. It was also suggested that some levee's breaking may have saved towns further upstream. Furthermore the jobs created by the construction of levees, flood walls and wing dykes and other management techniques have boosted the economy. There was also extremely hazardous antecendent conditions that could not be predicted, there was 200% more rain than usual for the particular time of year and people were unprepared in the west were flooding is uncommon, this could not be accounted for when managing the floods for the Mississippi.
- Word count: 632
Long periods of rainfall are the main cause of flooding as the soil has become saturated it reaches its infiltration capacity and infiltration is reduced, therefore increasing the frequency of surface run off and the risk of flooding. In addition to the weather having a large impact on the inputs over a short period of time in and around the catchment area of the river basin the seasons also influence the levels of precipitation. For example in winter precipitation can fall in the form of snow and in summer the precipitation levels often decrease dramatically, due to the vast heat imposed on the surface of the land.
- Word count: 1507
Furthermore, the river starts as a stream in the upper course and flows through valleys. The middle course, however, is where the river starts to become wider and deeper. The land, which the river flows over, is becoming flatter and this is where the river starts to meander or bend in the middle course. The lower course is where the river becomes its widest and deepest. This course is found closest to the sea where the river has its mouth. The flat area of land by the riverbanks is known as a floodplain. Sometimes a river can also have an estuary or a delta as its mouth.
- Word count: 861