Expected Peak Flow Calculator

Formula

The formula to calculate the Expected Peak Flow is:

$Q = \frac{C \times I \times A \times 640}{12}$

Where:

$Q$ is the peak flow (cubic feet/second)
$C$ is the runoff coefficient
$I$ is the rainfall intensity (inches/hour)
$A$ is the catchment area (square miles)

What is Expected Peak Flow?

Expected peak flow is the maximum rate at which water is expected to flow from a catchment area during a rainfall event. It is a critical factor in hydrology for designing drainage systems, culverts, and other infrastructure to manage stormwater and prevent flooding. The peak flow is influenced by the size of the catchment area, the intensity of the rainfall, and the runoff coefficient, which reflects the proportion of rainfall that is not absorbed by the ground and thus contributes to runoff.

Example Calculation

Let's assume the following values:

Runoff Coefficient (C) = 0.5
Rainfall Intensity (I) = 2 inches/hour
Catchment Area (A) = 1 square mile

Using the formula:

$Q = \frac{0.5 \times 2 \times 1 \times 640}{12} = 53.33 \, \text{cubic feet/second}$

The Expected Peak Flow (Q) is 53.33 cubic feet/second.