When is the peak flow typically highest during a storm event?

The peak flow during a storm event is typically highest during the rainfall's heaviest intensity. This is due to the fact that as rain falls more intensely, the volume of water entering a drainage area increases rapidly. When heavy rainfall occurs, the ground and surfaces become saturated, and runoff begins immediately, leading to increased flow in streams and rivers.

During periods of intense rainfall, the ability of the ground to absorb water is overwhelmed, and the runoff sharply rises, contributing to peak flow conditions. This increase in runoff can lead to potential flooding and other associated risks.

In contrast, the peak flow does not occur at the beginning of the storm, when rainfall is just starting and the ground may still absorb some of the water. Similarly, flow levels would decline after the storm has ended as water continues to drain away, and prior to the rain starting, there would be no runoff from rainfall because no rain has occurred. Hence, the most significant flow conditions correlate directly with the period of heaviest rainfall intensity.