1. River Conwy - hydrographs
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2. Introduction.
Click on the image below to learn more about Hydrographs.

3. Llanrwst and Trefriw have suffered from flooding in recent years.
The hydrographs on the next slides show rainfall events in 2009 and 2015 and the rivers reaction to each event.

4. Hydrograph 1

5. River Conwy Hydrograph (2009)
Use the pen tool to complete the hydrograph
River Conwy Hydrograph (2009)
100
200
400
500
600
300
Rainfall (mm)
Flow ( m3/sec)
Date and time
Click on the pen tool icon (bottom left) and select Pen.
You can now annotate the screen with a whiteboard pen or a mouse.
Turn the pen tool off by clicking on the pen tool icon and select Arrow.
Click the Hydrograph button to see the complete hydrograph and see how close was your line. Click on ‘i’ again to hide this message.
Hydrograph

6. River Conwy Hydrograph (2009)
100
200
400
500
600
300
Peak
discharge
Peak rainfall
Lag time
Rainfall (mm)
Flow ( m3/sec)
Date and time
Hydrograph
Labels

7. Activity 1
1. Describe the rainfall pattern Estimate how much rain fell between mid-day on the 16/11 and mid-day on the 17/ What was the peak rainfall and when did it occur? 4. What was the peak flow and when did it occur? 5. Estimate the difference in time between peak rainfall and peak flow. (Lag time)
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8. Hydrograph 2

9. River Conwy Hydrograph (2015)
Use the pen tool to complete the hydrograph
River Conwy Hydrograph (2015)
Rainfall (mm)
Flow ( m3/sec)
Date and time
Click on the pen tool icon (bottom left) and select Pen.
You can now annotate the screen with a whiteboard pen or a mouse.
Turn the pen tool off by clicking on the pen tool icon and select Arrow.
Click the Hydrograph button to see the complete hydrograph and see how close was your line. Click on ‘i’ again to hide this message.
Hydrograph

10. River Conwy Hydrograph (2015)
Peak discharge
Peak rainfall
Lag time
Rainfall (mm)
Flow ( m3/sec)
Date and time
Hydrograph
Labels

11. Activity 2
1. Describe the rainfall pattern When did the peak rainfall and peak flow occur? 3. What was the lag time between these peaks? 4. When did a second peak rainfall and peak flow occur? 5. What was the lag time for these second peaks?
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