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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
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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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.
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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.
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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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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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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.
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There are however many different types of condensation just like there is for precipitation. Radiation cooling occurs when the ground loses heat very quickly through terrestrial radiation and the air that is in contact with it is cooled by conduction. If the air that is affected by this process is humid then fog or dew will form. This usually happens in the evenings when there is typically a clear and calm sky. Advection cooling is likened to radiation cooling because they involve horizontal rather than vertical movements of air, which means that the amount of condensation created as a result is much, lower.
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Flow I measured the flow of the river by firstly getting one member of my team to carefully stand in the river at the left side near the bank. That person then dropped one of the plastic balls into the water. When the ball had travelled the 10meter length I had measured for it to travel, I stopped the stopwatch and record time on my data sheet. I repeated this procedure three times for the left, middle and right side of the river of get an average to make it a fair result.
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This is where the river is straightened out bout in terms of its course and in terms of its bed and sides. This is done to reduce the friction that sides have on the water and this in turn increases the water velocity. A faster flowing river also prevents sediment dropping on the riverbed and reduces the need for dredging. This also has a knock-on effect in that it protects the banks from erosion, and protects upstream from flooding.
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The water that had risen was more than a foot over the danger level. The water that flooded the land was infested with many water born diseases, this water became mixed with the drinking water for many people. All of these problems are aimed to be stopped by the building of the 3 gorges dam. The main problem that the 3 gorges dam aims to solve is the major flood problem from the rivers. These floods are normally caused by the heavy rainfall in every monsoon season and making a massive increase in the river flow in June, July and August. This increase is added to from the snow melt from the Himalaya Mountains.
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Urbanisation on the flood plain was also a major factor as grass and tress have been covered over and concrete and tarmac. Replacing a permeable surface with an impermeable one has many effects on the river. Movement (transfer) of water into the soil from the surface (infiltration) is reduced dramatically along with throughflow, whilst surface run off is increased. This is because when trees were on the flood plain they had four jobs which helped keep the possibility of flooding to it's minimum a)
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There are lots of obstacles, stones and boulders for the water to flow over. As the river moves all the way through the upper course it cuts downwards. The steepness here is steep and the river channel is narrow. Vertical erosion in this highland part of the river creates steep sided V-shaped valleys and interlocking spurs. These are caused as the river erodes the landscape in the upper course, it winds and bends avoiding areas of hard rock. Therefore creating them they look a bit like the interlocking parts of a zip. The graphic shows how waterfalls and rapids are formed.
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According to Bradshaw's model, the hypothesis is that "Stream characteristics (i.e. cross-sectional area, discharge, velocity, efficiency, and gradient) all change along the course of the river and they are related to each other". Source Mouth The diagram above displays Bradshaw's model river. From this, we can see that the hypothesis briefly states that the characteristics of a river, namely cross sectional area, discharge, velocity, efficiency and gradient, all have a tendency to vary along with the movement of the river. Also, the hypothesis states that they are all interrelated: if one characteristic differs, then so will the others.
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Due to this the Severn, in particularly the Shrewsbury area is historically known for its proneness to flooding. It is expected on average for there to be a major flood in the area once every 10years, however there had been no such flood for over 30years. The urban area of Shrewsbury is built on higher ground to the flood plain of the river so there have been no floods of any severity. Unfortunately between October and December 2000, 3 major floods were experienced in the area. On the short term this had a huge impact to the busy market town.
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Stop 2 G.R.-512 805 This stop is similar to Stop 1. There are many different types of rocks and the river is still fast moving. Boulder clay is also present on top of which vegetation has formed . This stop also has its own micro climate compared to the mountain top because it is in a valley. This enables Mountain Ash to grow which is the first tree growing down the mountain because it is sheltered in the V-shaped valley. Some of the features found at this stop include interlocking spurs and V-shaped valley.
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This introduction is going to be about rivers and how they shape the landscape. Rivers are an important thing to study because the study of rivers
Some people would like to know the processes responsible for the development of selected landforms and the role of rock type and weathering', and the 'causes and effects of a related hazard (flooding or landslides) and human responses to it'. People also need to understand the uses of rivers. They can be as a source of water supply, the production of hydro-electric power and a place that hosts leisure activities that people like doing such as fishing, rowing etc. Rivers are also used as major transport systems and market routes e.g.
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A river nearby was a priority to Greg's hunt, 18th century only saw power as resource of energy. Being near Manchester was another constraint put down by Greg. Having all of the key elements for the mill; money, power (though employment was later undertaken) was. Using Burdett's map, Greg searched on horseback to find yet again a cheap, quick source of transportation and a place of allocating goods. Building materials needed to get to the locality for construction purposes. The quarry nearby was very useful for the building of the mill Styal and the Bollin seemed to have all the aspects and suitability's of Greg's requirements.
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By looking at The Afon Glaslyn we can see how and why these processes occur and landforms formed. The Upper Reaches 0-4km * Processes The main process in this section is erosion, in the form of: attrition, corrasion, hydraulic action and corrosion. Attrition is when the boulders collide with each other, breaking up into smaller pieces. Corrasion is when the ,material carried in suspension rubs against bank of river. Hydraulic action is the rivers force dislodging particles and finally corrosion is when acids dissolve rock.
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* Rock type * Topography * Vegetation- dense vegetation helps to intercept rainfall, because of infiltration capacity and prevent overland flow. This will inhibit channel development and thus the reduction of drainage density. * Rainfall amount, intensity and duration * Human activities * Time Stream order refers to stream hierarchy- the way the various stream channels in drainage fit together. Identification of the link in a stream network is by the process of stream ordering. Analysis of the stream order in a drainage basin can help in predicting the shape of hydrograph, and hence flood forecasting.
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With reference to the River Ganges case study, examine the international issues that arise as a result of river Management
The construction of the Farakka Barrage took place in 1977 at the head of the delta in West Bengal, it has caused mayor tension between India and Bangladesh. It was opened to decrease the risks of flooding from the Ganges as it would manage the water table of the river, to make sure it doesn't go over the 1 meter. Also the Damn would be used as a source of Hydroelectrically power, and supply excess water levels to the country to use for drinking, and managing their lands.
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There will be significant downward pressure acting on the glacier (gravity) which will increase levels of friction and consequently continued ablation. Cold or polar based glaciers also exhibit different types of movement. In very cold climates, the glacier will be frozen to its bed. Without any friction or an increase in pressure there will be no melting so internal flow is the primary type of movement. This occurs when proportions of ice within the glacier move past each other under the force of gravity.
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The loss of life can be divided into deaths from the primary and secondary effects of flooding. The primary deaths are directly inflicted by the flood and account for more of the deaths in L.E.D.C's because M.E.D.C's generally have a warning system in operation. Secondary fatalities e.g. diseases brought by things killed by the flood, is much greater in L.E.D.C's because they don't have the infrastructure to deal with it. * With the extreme excess of water, drainage and sewage is overloaded and all refuse and sewage that should be carried away by the drains overflows with the flood.
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In summer, the rainfall is concentrated in July and August, being highly variable. Prolonged and abnormally high rainfall may also increase the discharge of lower course of Huang He, allowing the floodwater to overflow its banks. The climatic condition throughout the year leads to the occurrence of flood. Topographically, there is a sudden decrease in gradient at Kaifeng, between the Loess Plateau and the North China Plain, which is therefore liable to flooding due to its topographic characteristics. It is a flood plain with gentle gradient and is extensive lowland. The river course is meandering with intense deposition and silting, raising the river bed.
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