Tuesday, 25 September 2007

Flood hydrographs

On Friday, we had a look at flood hydrographs - composite graphs that show changes in river discharge in relation to storm events.

You (well, some of you!) plotted graphs with time in hours on the horizontal axis, and two vertical axes - one for precipitation and one for discharge. You plotted your precipitation as a bar graph, and your river discharge as a line graph. Most of you managed to label the peak rainfall, peak discharge, lag time, rising limb and falling limb onto your graph.

If you need a reminder, go back and revisit the BBC Scotland site that we looked at before:


We also had a quick look at factors that affect the shapes of hydrographs - e.g. geology, antecedent weather conditions, drainage basin size/shape, vegetation, relief, drainage density, etc. Make sure you can talk about each of these factors, and that you understand how each one would affect the shape of the hydrograph.

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