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

A flood hydrograph

Extracts from this document...

Introduction

A flood hydrograph is a graph of two axis, 'discharge' and 'time'. Plotted on the graph is the amount of discharge over a period of time. By looking at a hydrograph, a lot of information and data can be gathered about the river, the precipitation, the surrounding area and vegetation etc. The gradient, height and length of a line can tell you a lot of this information. There are many different factors that can affect the appearance and shape of a hydrograph. Certain conditions can cause the line on the hydrograph to be tall and thin and other conditions can cause it to be short and wide. Peak discharge is the term used to describe the maximum amount of discharge from the river over the period of time recorded; this peak discharge can be high or low depending on a lot of conditions. Climatic factors are the most obvious conditions that can affect the flood hydrograph. ...read more.

Middle

The rates of evapotranspiration affect the nature of a flood hydrograph. If there are high rates of evapotranspiration then the peak discharge maybe lower and the lag time greater. If the rates are low then the graph will not be affected by this factor. Soil types and characteristics can have a large impact on a hydrograph. If the soil is dry and permeable then it can hold lots of water and the hydrograph is more likely to look like line B on the right. If the soil is impermeable or it is a high antecedent soil that is already waterlogged the line is more likely to look like line A on the right. If the drainage basin has steep slopes then despite other factors the ascending limb can be a very steep gradient because the rainfall flows directly downhill to the river/streams without having time to infiltrate into soil. ...read more.

Conclusion

Vegetation prevents the water infiltration the ground as quick and reaching the river by means of overland flow or groundwater flow. If the drainage basin is greatly vegetated then the lag time is likely to be greater, the limbs are likely to be gentler and the length of the flood is likely to be longer. Forests and woodland intercept much rainfall and the roots encourage infiltration. If the drainage basin is bare and has little vegetation then there is likely to be more surface water. If there are lakes and backwater swamps upon the drainage basin then the movement of water to the channel is slowed. Another factor affecting the flood hydrograph is if the snow or ice that feeds the stream and rivers is melting quickly or slowly, this is decided by the weather. Flood hydrographs are useful and there are many different factors that can affect its from. Flood hydrographs could be slightly more useful if they were supplied with information about the precipitation, e.g. duration. ?? ?? ?? ?? Jonathan Burch 02/05/2007 Geography Essay 1 of 3 ...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. Explain what is measuredon a flood hydrograph and outline the factors that affect its ...

    reaches the river very quickly and all in a short period of time, this gives the immediate steep ascending limb on the hydrograph. Reasons for large amounts of rainfall becoming overland flow can be little vegetation and maybe impermeable rock below the surface.

  2. Hydrology and Fluvial geomorphology. (Q&A)

    There are no inputs and outputs from the system as a whole - it is self-contained. About 2% of global water is stored as polar ice, snow and glaciers; 0.7% is fresh water in the form of rivers and lakes (surface storage, 0.1%), soil moisture and groundwater in aquifers (0.6%), or atmospheric moisture (water vapour)

  1. Edexcel Geography B Unit 3 Coursework

    Vertical erosion brings about large bed load but due to the small increases in these variables, rooted from the small size of the river, there is little change and range in the depth downstream. 4th Hypothesis: There is a significant relationship between velocity and hydraulic radius downstream across the River Holford.

  2. Compare the impact and responses to a major flood in an MEDC and LEDC.

    railways and irrigation systems were damaged, preventing access to many areas which disabled many emergency services and aid from reaching people in need. The flood caused damages around $2.2billion, a huge sum for a country which has an extremely low GDP.

  1. To what extent the flood alleviation scheme has had on the environment and people ...

    the concrete and tarmac ground which makes infiltration impossible and increases the speed of the surface runoff. The seas tides add to the problem as during high tides the waves run into the river. To the North if Swanage lays Clayton which is impermeable and has a great surface run off.

  2. Describe and Explain the Factors that Influence the Flood Hydrograph, with particular reference to ...

    Looking at figure 3, I can see that the rainfall in Birmingham is relatively constant during the year. Evapotranspiration is increased by high temperatures in the summer and therefore results in water deficit. Recharge in water is increased in autumn caused by an increased rainfall.

  1. Geography investigation - The River Skirfare located in the Littondale region in the Yorkshire ...

    Will show how much the river is affected by the forces of friction against the banks and bed. Enables me to work out the hydraulic radius. Calculates the amount of friction on the river. Taken from the cross-sectional area. So the same weaknesses apply.

  2. Do the Characteristics of a river change downstream?

    I would expect the river channel at this point is V-shaped due to the water vertically eroding into the ground. This is known as vertical erosion and takes place in streams that occur on the upper course of a river.

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