Lag time

Lag time is the time between peak rainfall and peak discharge.

The lag time between peak rainfall and peak discharge becomes shorter, increasing the chance that discharge will exceed what the channel can contain.

Lag time is the interval between peak rainfall and peak discharge. The discharge peak usually comes later because water takes time to travel through the drainage basin.

These conditions produce a short lag time and a ‘flashy’ response: river discharge can rise rapidly after heavy rain. The sudden rise is sometimes called the Tees roll or Tees wave; the river level can rise by about one metre in 15 minutes.