•Peak flow compared to Base flow
•Recovery rate, back to Base flow
You need to refer to:
Basin lag time
0 12 24 36 48 30 72
Hours from start of rain storm
Interpretation of Storm
Recap on Hydrographs
• Have a go at the Living Hydrograph exercise
…where do you think each statement would be
best placed on the graph?
• Now watch this video
Two different Hydrographs A & B – can
you describe them?
1. Amount and type of precipitation
• Short intense rainstorms can produce
rapid overland flow and steep rising limb.
• Snow will be stored on the ground and not
effect the hydrograph until it melts. This
means in spring there may be steep rising
• Snow on the ground can act as a store
producing a long lag time and shallow rising
limb. Once a thaw sets in the rising limb
will become steep.
• If there have been extreme temperatures,
the ground can be hard (either baked or
frozen) causing rapid surface run off.
6. Land Use
• Urbanisation - concrete and tarmac form
impermeable surfaces, creating a steep
rising limb and shortening the time lag
• Afforestation (planting trees) -
intercepts the precipitation, creating a
shallow rising limb and lengthening the lag
What could cause 2 peaks in a