The Storm Hydrograph

The Storm Hydrograph

A storm hydrograph shows how a particular river responds to a storm.

• When a storm begins, discharge (amount of river water) does not increase immediately as only a little of the rain will fall directly into the channel.
• The first water to reach the channel after reaching the ground will be surface-runoff.
• The gap between the time of peak rainfall and peak discharge is called Lag Time. 
• A river with a short lag time and a high discharge is more likely to flood.