• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Water on the Land - Channel processes and landforms.

Extracts from this document...

Introduction

Geography Water on the Land Channel processes and landforms I. Distinguish between vertical and lateral erosion and examine where along the course of a river, each is likely to occur. (10 marks) Along the course of a river, there are various processes that take place, including several different types of erosion. Erosion is the wearing away of something over a period of time, and the two main types of erosion, upon which I will be focusing, are vertical and lateral erosion. Furthermore, there are four main processes of river erosion, which I will go into greater detail. Vertical erosion is specific to the upper course of a river, which is due to the high altitude and steep gradient of the source of the river, eroding in a downwards direction. It takes place at this point along the course of the river because the river is trying to find the quickest route to sea level and so cuts vertically through the rock in order to reach its mouth. Vertical erosion is a process which uses up a lot of the river's energy and so the structure of the river channel particular to this course of the river is generally very narrow and shallow, with large boulder strewn across it. The river channel generally does not increase in either width or depth as all of the river's surplus energy is used to erode vertically. The most common erosional process, which takes place in the upper course of the river, is corrasion. It is responsible for the vertical erosion of a river and corrasion is the term used for when pieces of rock are dragged along the riverbed by the flow of the water, and so in turn wear away the river channels bed and banks. The size of the load affects the amount of erosion, as larger pieces of rock create a more rapid rate of erosion, whereas smaller pebbles tend to round off edges of surfaces. ...read more.

Middle

The character of the material also influences the amount that can be carried, as finer particles such as silt and clay will be transported further in the state of suspension, than boulders or gravel. The Hjulstrom graph is model that shows different velocities are needed to erode, transport and deposit different types of material. The rock type of the land over which the water is flowing also has a lot to do with the size, type and amount of bed load found in a river channel along its course. Acidic water in the river channel has the ability to erode softer rocks such as Limestone and Chalk as the minerals in the rock are dissolved by the acidic components of the water. When the water is capable of eroding in this way, the minerals of the rock are carried by suspension and are moved along in the flow of water in a dissolved state. However, if the rock that the river is flowing over is of a much harder property, such as Granite, then corrasion will erode such rock and the transporting process of traction moves the larger rocks and boulders of Granite along the river bed. In certain circumstances, the larger of the boulders will only be capable of being moved in times of flood due to their size and the fact that a specific velocity is needed to transport them. Similarly, the factors of discharge and velocity play an important part in shaping the size, type and amount of load that a river carries. Discharge is the volume or flow of the water within the river channel, passing a particular point in the river at a specific time. Discharge therefore has an influence on the load that is carried by the river, as the greater the discharge, the larger the river's capacity to carry load. The velocity is the speed of the water's flow in the river channel and so has an effect on the load that the river can carry as the higher the velocity, the higher the amount of energy that the river potentially has to erode and transport. ...read more.

Conclusion

Deltas generally occur in calm, tideless seas such as where the Rh�ne enters the Mediterranean Sea. The periodic flooding of the river, which deposits further amounts of alluvium helping to build up lev�es, helps the formation of a delta. Finally, the process of flocculation, where river water meets the salt of the sea water has an electrical charge which causes molecules to stick to one another, increasing their mass and so causing them to deposit on the riverbed, helps to form the depositional feature known as a delta. There are two main types of deltas, and their shapes distinguish them. One known as a 'bird foot's delta, such as the Mississippi delta and the other is recognised as an 'arcuate' delta such as the Nile delta. A braided stream is a stream that has islands of build up deposited load within the river channel, known as eyots. Braiding tends to take place in streams where the load is made up of much heavier, coarser material such as sands and gravel's. The channel itself is generally straight in this course of the river, however, the eyots and smaller channels within this one river channel go through many changes in both shape, size and position. A characteristic of streams and rivers that have a varying discharge is the process of braiding and they tend to be very common in semi-arid areas or glacial-fed streams. Streams with high velocities and heavy loads are resultant of torrential downpours of rain, causing substantial overland flow, are typical of semi-arid areas. Evaporation and infiltration following the storm, lessening both the volume and velocity of the stream, cause the deposition of the load. Glacier-fed rivers have increased discharge due to the ice melting during hours of sunlight, however, at night and during winter, the discharge is noticeably less. During times of high flow, the river is capable of carrying and transporting a large load, though, when a stream's competence and capacity falls due to the decrease in velocity, the result is the load's deposition and over time, the formation of eyots. Joanna Lowe Page 1 Mrs Forkan ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Hydrology & Fluvial Geomorphology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Hydrology & Fluvial Geomorphology essays

  1. Peer reviewed

    Explain where and why depositional landforms occur along the course of a river.

    3 star(s)

    This is due to the following. Rivers and its landforms are formed and moulded over time chiefly by the processes of erosion, and by the transport and deposition of sediment. These are hydraulic variables, which occur in rivers. Rivers are able to work on the landscape through erosion, transport, and deposition.

  2. River channel processes.

    WATERFALLS - these result from a most resistant or tougher rock. A step will form because when the waterfalls erodes away the rock, the tougher rock will erode slower and so the rock before it will erode away quicker as opposed to that of the tougher rock and so this

  1. 'To what extent does the River Lyn conform to the Bradshaw model of River ...

    Rs can be used to discover if there is an association between two sets of measurements. The measurement levels I will use are interval levels. Fig. 24 This scatter graph shows the distance from the source and the velocity. Now I will draw a table to work out the Spearman's Rank Correlation Coefficient.

  2. 'How does the risk of flooding vary along the course of the River Eea?'

    to contain near the source, as it is still very small there. This may mean that the river will end up flooding. But near the source there is nothing apart from rough grazing or improved grazing around this part of the river.

  1. Investigating the river Caerfanell

    - The tape I used was easily moved by the fast moving current of the river so the end measurement could be inaccurate. - The water itself was very cold and so the person's measurement taking may have lead to hurried and imprecise measurements.

  2. Study the downstream changes of Loughton Brook.

    The gradient is then measured in degrees. Two ranging poles and a gun clinometer are required. Height of the Banks The height of the bank is measured from the water till the bank. A ranging pole goes in the water and the second ranging pole forms a right angle from

  1. Does the river Alyn follow Bradshaw's model?

    Knowing how river variables change can be useful in predicting how the river will react to heavy rainfall which can help with flood prediction and protection. Being able to measure the velocity and discharge at a point on a river is important when building dams so that your dam can provide the optimum amount of hydroelectric power.

  2. My hypotheses are:The character of the course of the River Bollin will change along ...

    On the inside of the bend, the water travels slower, an Depositation occurs) This final site was found at a place called "The Carrs" and so is referred to as "Site 3, The Carrs". When the data has been collected, it will be put into tables and graphs.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work