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16 October 2014

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Prediction Exercise
When rain falls there is a period of time between when the heaviest rain falls and the time the water gets into the river. This is known as lag time. The lag time is dependent on the type of land the rain falls on. Land covered in trees soak up the most water giving a long lag time and little chance of flooding. Land covered in housing and tarmac gives a short lag time and is more likely to flood.

The data shown in the table below is from SEPA. It shows the amount of rain that fell during the floods (mm) and volume of water flowing through the Mill Burn (Cumecs). This information can be put into a graph to show the relationship between the two. This type of graph is called a hydrograph.

Time in Hours	Rainfall in mm	Cumecs in cubic metres per second
7 Sept 2002
18	0.6	0.1
19	0.8	0.1
20	2.8	0.1
21	5.0	0.2
22	5.6	0.3
23	5.6	0.5
8 Sept 2002
00	2.4	0.6
01	2.6	1.1
02	25.4	2.4
03	5.6	5.4
04	1.4	4.5
05	0.0	3.7
06	0.0	2.5
07	0.0	1.8
08	0.6	1.5
09	0.6	1.3
10	0.0	1.1
11	0.4	0.9
12	1.4	0.8

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