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

Explain what it is meant by, in a drainage basin, by the terms drainage density and stream order

Extracts from this document...

Introduction

A) Explain what it is meant by, in a drainage basin, by the terms drainage density and stream order. The drainage basin is an area of land drained by a river and its tributaries. Drainage Density represents an approach to the quantitative analysis of drainage basin. It is the average length of channel per unit area of the drainage basin. It is calculated as shown below. Drainage density is a qualitative analysis of the areal properties of a river basin . Drainage density is useful as a measure of frequency and spacing of streams within the drainage basin. It also helps to determine the texture of dissection of a drainage basin- the extent to which the landscape is cut into by river valleys and in turn influence slope development. Generally, there are 4 categories of drainage density and corresponding texture of dissection. Very low- less than 8km/km sq coarse Medium low- 8-20 medium High density- 20- 200 fine Very high density- more than 200 ultra fines Drainage density and texture of dissection varies in response to these factors: * Permeability of surface- a highly permeable material such as sand tends to give low drainage density because of high infiltration capacity and little water is available as surface runoff to maintain channels. ...read more.

Middle

Have the results been always beneficial? Human activities on rivers can either be deliberate or advertent. The river is an efficient pathway between places and any actions in one place may be transmitted like a chain reaction to have consequences across time and space. Although it is not of man's intentions to bring about disastrous consequences on rivers, their actions are often not beneficial to the environment. Deliberate actions are made to regulate rivers. Dam constructions have been encouraged by growth in water and energy demands and advances in technology. Most dams have achieved their aims of regulating discharge. They are also highly successful in meeting the needs of surrounding communities. However, dams have many environmental consequences that are not beneficial to man. Dams are able to retain high amounts of sediments and this is detrimental to the environment. Since the construction of Aswan High Dam on River Nile, the silt load is lowered throughout the year and the seasonal peak is removed. The Nile now only transports about 8 % of its natural sediments below the dam. ...read more.

Conclusion

For example, the Mississippi basin is reinforced by levees. Yet catastrophic flooding still took place in 1993 that destroyed 7 million hectares of farmland. This shows that flood protection policy may backfire causing worst damage. Advertent changes like urbanization have many negative impacts on rivers. The increase in concrete surfaces and efficient sewage system will promote high and fast discharge. This will in turn lead to an increase in peak flood flows of a river. The below shows the contrast between storm hydrographs of an area before and after urbanizations. A flashier storm hydrograph will make the area more prone to flooding. Chinese experts believe that local deforestation, uncontrolled building and lack of flood control have led to massive floods that threaten loves and homes of millions. Clearing of land for cultivation may cause soil erosion which result in large quantities of sediments being moved into channels and floodplains. Mining can also lead to very major change in channel morphology. As mining often requires the use and deposition of large quantities of water, thus high amount of waste is moved to rivers. Both human activities may lead to the aggradations of the channel bed- the building up of land surface. 1 ...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. Marked by a teacher

    Analyse How the Inputs and Outputs from a River Basin Can Vary Over Time

    3 star(s)

    because in a large river basin, the water has much further to travel (lag period) than that in a small river basin before it reaches the main river channel, and therefore compared to a river with a small river basin, the total river discharge is smaller.

  2. How does the Efficiency and Cross-Sectional Area of a River Change Down Stream?

    would have a Rs value of -1.0. No correlation would be mid way between these values, or 0. This can be seen in the figure 3. Site CSA (m�) Rank Hydraulic Radius Rank Difference between ranks (d) Difference squared (d�)

  1. How does Loughton Brook change as it moves downstream?

    This is natural as there is more space for the water to travel through. The cross sections also shows the increase in efficiency as we move downstream as I got a few cross section that were of meander shape

  2. With Reference to your case study of flooding in a large scale drainage basin, ...

    This affected 2.5 million farmers and due to the loss of the rice crop the food supplies were seriously affected.

  1. I am going to study the characteristics of rivers and how they change as ...

    If two 2nd order streams join up a 3rd order stream is made. The stream ordering doesn't necessarily need to stop at stream order 3; it can go on much higher. That explains how stream ordering is done. The diagram below shows how the stream ordering would look like: I

  2. Identify and explain how human intervention in the drainage basin can increase the risk ...

    This can be seen in the below diagram, it happens because there is less water reaching the channel by through flow and base flow and more by overland flow. Water companies and local authorities will need to respond to these problems to prevent flooding in the river basin.

  1. The Drainage Basin - Bangladesh

    * DAMS: these hold water back in the upper course but may alter the river's flow so that poor farmers are faced with irrigation reductions and silt gets trapped behind the dam rather than on their land. * TIDAL BARRAGE ACROSS BAY OF BENGAL: this has been proposed but is an expensive option.

  2. Potential conflicts caused by the use of the Thames basin

    Also, transportation may be effected as there may be so much waste in the river large containers may not be able to be used anymore. Waste disposal can also effect sand and gravel extraction, as the quality of the sand can be decreased if a lot of waste it dumped in the river.

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