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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.
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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.
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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.
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Describe the changes of characteristics of the river channel after channelization. Evaluate the pros and cons of channelization on the river channel and its neighbouring areas. Suggest ways to reduce the negative effects that may have occurred.
Thirdly, because the river was made less meandering, the channel length would become shorter than before. Fourthly, channel gradient would be increased and it will be steeper. Fifthly, the rugged channel bed will be smoothened after channelization taking place. These changes were contributed by the removal of obstructions along the river channel by human effort. As a result, the river flow would become faster and the capacity of the river would increase. There are different advantages for rivers to be channelized, firstly, it will provide more navigable waterways for ships. The stream will be more suitable for navigation and large ships which previously cannot pass through the channel can now pass through the river.
- Word count: 759
Also, there is a similar problem due to the river being used for transport. Fisherman cannot fish when there are big containers being shipped down the river. Also, these containers often disturb the fish, causing them to swim away from the fishermen. The extraction of sand and gravel from the Thames bed can also effect fishing, as the fish lay eggs in the river bed, and so when the sand and gravel is extracted this sometimes kills the eggs, lowering fish stocks.
- Word count: 1459
The positioning of the sun can also affect if there is or is not a microclimate. Places with small towns and countryside will be much cooler than large cities. This affect is called "Urban Heating Island Effect". Microclimates can exist everywhere if the appropriate conditions occur. There could be a microclimate in the two courtyards in between the senior building, or in the junior school inner playground. There could be a microclimate where any of the appropriate conditions might exist. Hypotheses Write 4 hypotheses to test. Here are some examples of how to write a hypothesis: i.
- Word count: 1173
How may knowledge of the hydrological cycle and its components assist in devising flood prevention measures?
This way, flooding can be prevented. Precipitation in the form of snow would spend longer time on the land as it flows into channels only when they melt. Knowledge of the volume of water contained in the snow and the time taken for the melting would help assess if the area has the capacity to hold the water formed from snow melt. Flood can be prevented by attempting to melt some of the snow 1 during the winter time and allowing greater discharge during the season so that when summer comes, the discharge do not increase too much suddenly.
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and get smaller and more rounded downstream. 2. The change in the bed load will be partly due to an increase in velocity downstream, which will increase hydraulic action on the bed load, eroding it in size and angularity. A higher velocity downstream will also increase the process of attrition, which occurs when the rocks knock into one another, which causes them to erode. It will be interesting to compare my results to the Bradshaw model. This model shows the characteristics that rivers usually follow from source to mouth, based on data from rivers from all over the world.
- Word count: 3553
Key questions: * Is there a gradual increase or decrease in the velocity downstream in the River Holford? * Is there a gradual increase or decrease in the hydraulic radius downstream in the River Holford? * Is there a gradual increase or decrease in the average depth downstream in the River Holford? * Is the velocity affected by the change in hydraulic radius across the River Holford? * Is average depth affecting the velocity at each separate interval within the River Holford?
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Using simple rain gauges, emptied and measured every 24 hours, we can measure rainfall and from that, work out how much water the river will have to cope with. Large amounts of rainfall can mean that problems with the river such as small blockages or thin channels can be multiplied. However, rainfall reaching the river can be affected by other factors. Interception plays an important part in flood risk, as it dictates how much water will reach the soil to be carried as surface run-off or slower processes.
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Temperature also needs to be considered because if temperatures are higher it will increase the rates of evapotranspiration, resulting in less water flowing into the river. The landscape can include the relief of the land (is it flat / mountains / steep or gentle slopes?) and the geology, both of which can affect the river regime. For example, permeable rocks will allow some water to flow through them, meaning there is less water flowing in the river channel while impermeable rocks will increase the amount of water in the river, as water cannot sink through them to travel as groundwater.
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The zone of net ablation is usually at lower altitudes where the temperature is higher. If net accumulation in a year is higher than net ablation then the glacier will appear to grow and retreat forwards as the amount of ice added to the glacier is greater than that which has melted. However if net ablation is higher than net accumulation in a year the glacier will appear to shrink, since the glacial ice is melting and evaporating faster than snow is falling. This is usually true for the snout of the glacier where the temperature is warmer.
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EXAMINE THE IMPACT OF PROCESSES OF GLACIIAL EROSION ON THE LANDSCAPE (20 MARKS) There are two main processes of glacial erosion which take place as the glacier moves forward; and which mainly occur in upland areas. The first of these processes is called plucking and is when melt water freezes between the glacier and the underlying rocks causing the glacier to become attached to the rock. As the glacier advances the rock is then "plucked" from the valley floor or side.
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Describe and explain the variety and location of fluvioglacial landforms (20 marks) When glaciers begin to melt they produce large amounts of melt water which often results in extreme erosion and the transportation of debris, leading to the formation of distinctive landforms. Fluvioglacial deposits vary greatly to glacial deposits. They are deposited by melt water streams, which run beneath and then beyond the glaciers' snout, and in the same manner as any other stream they loose energy as their velocity or volume decreases. As their energy is lost they begin to deposit the debris that they are carrying, largest first followed by the smaller particles as more energy is lost.
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This resulted in the orange absorbing a lot of water into it and therefore all the extra water increases the drag making the velocity slower. The problems to the pebble collection are that we may have been unsuccessful with the pebbles which we collected as these may have possibly been not the average pebble for that site. This might be because someone's desire is often to select pebbles, most of the times they go for the big and smooth ones.
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Technique Data Collected Purpose Method Limitations Suggestions on expanding data Date Photographic Evidence Photographs taken at 12 sites of river. To show size and shape of river at each site. Also to show management. Photographs were taken at best angle using a digital camera if each site. Weather and foliage may have affected quality of photographs. Only one photo taken at each site. More photographs taken. 10/10/07 Velocity Survey 10 speed measurements measured in seconds To work out the average speed of the river down stream Dog biscuits were thrown into river and timed how long it took to float just below the surface over 10 metres.
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It also tend to be less deep, between 10 and 50 meters deep. The surface shows a significant depth of melting in the summer, forming an active layer. The last type is sporadic permafrost which occurs where there is more talik than permafrost. The mean annual temperature in these areas may be around 0�C B) Describe and explain the variety and location of periglacial landforms. There are a number of periglacial landforms caused by permafrost. One of the largest, as a single object, would be pingos. These are rounded ice-cored hills that can reach up to 90 meters high.
- Word count: 666
Artificial levees, which make up over 500km of the Mississippi's banks can be seen to greatly enhance the flood damage rather than reduce it. These are extensions to nature's raised river banks, which are caused by the sediment deposited by high water levels. Coarser material builds up closer to the river and alluvium, being lighter, is transported further away from the banks. The water that transported this sediment then gradually infiltrates back into the river in a downwards fashion through the ground, creating a floodplain.
- Word count: 1325
Erosional processes occur as glaciers move forward; advance downhill due to gravity. This movement and subsequent erosion can have impacts on a wide variety of scales, and varying implications can be seen over short and long periods of time, or repeated cycles of glaciations. This essay will attempt to describe and explain the processes of glacial erosion and the significance of the impacts on landscapes and their development. Examples will be drawn upon with reference to areas currently undergoing glaciations as well as areas that were once, but are no longer glacial regions.
- Word count: 2936
It flows southwest across the Colorado Plateau into Utah, where the confluence with the Green River in the Canyon lands region brings waters from the northernmost reaches of its drainage basin in Wyoming. Downstream in northern Arizona, the main trunk of the Colorado's branching canyon system- the Grand Canyon- reaches 18 miles in width and cuts down through layers of sedimentary rock that record 2 billion years of geological history. Below the canyon after exiting the plateau, the course turns southwards, forming the California- Arizona state line.
- Word count: 645
With Reference to your case study of flooding in a large scale drainage basin, examine the effects of flooding on people, property and the land.
Overall 1040 people died in the floods this death toll resulted from a number of things as well as people by drowning in the flood waters, the water supplies were contaminated for a quarter of million people because of polluted wells, flooded latrines and floating bodies of people and cattle; the young and elderly were most at risk. The problems increased because of the build up of waste that could not be disposed of while the floodwaters remained. A quarter of million people were affected by cholera and typhoid.
- Word count: 849