Enter the length of flow, slope, and Manning’s n value into the calculator to determine the sheet flow rate. This calculator uses Manning’s equation for sheet flow to evaluate the flow rate.
Sheet Flow Formula
The following formula is used to calculate the sheet flow rate:
Q = (1.49 / n) * L^0.6 * S^0.3
Variables:
- Q is the flow rate (cubic feet per second)
- n is Manning’s n value (dimensionless)
- L is the length of flow (feet)
- S is the slope (expressed as a decimal)
To calculate the sheet flow rate, use Manning’s equation for sheet flow by inputting the length of flow, slope as a decimal, and Manning’s n value.
What is Sheet Flow?
Sheet flow is the overland flow of water that occurs when excess stormwater spreads out over the ground surface in a thin, even layer. This type of flow is common in the early stages of runoff and occurs before the water collects into a defined channel. Understanding sheet flow is important for designing effective drainage systems and managing stormwater runoff in urban and rural areas.
How to Calculate Sheet Flow?
The following steps outline how to calculate the sheet flow rate:
- First, determine the length of flow (L) in feet.
- Next, determine the slope (S) as a percentage and convert it to a decimal for the calculation.
- Next, determine Manning’s n value (n), which is a coefficient that accounts for the roughness of the surface.
- Use the formula Q = (1.49 / n) * L^0.6 * S^0.3 to calculate the flow rate (Q).
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem:
Use the following variables as an example problem to test your knowledge.
Length of flow (L) = 100 feet
Slope (S) = 2%
Manning’s n value (n) = 0.013
