---
title: "V-Notch Weir"
canonical: "https://help.innovyze.com/space/infodrainage2021v1/16548482/V-Notch%20Weir"
format: markdown
---
**V-Notch Weir flow** is calculated using the following formula:

![image](media://13901254-7bc3-4ec1-ac13-783da17fb723)

where

*C*<sub>*d*</sub> = Coefficient of Discharge

*vang* = internal angle of the V (degrees)

g = acceleration due to gravity (9.81 m²/s)

*H* = height of water above weir invert


When the downstream level is above the crest level the software will use the Villemonte equation to simulate the submerged nature of the flow:

![image](media://62b8063c-e1f0-427e-b884-2b45be7aef32)

where:

Qs = Submerged Flow Rate

Q = Free-flow rate at H

Yd = Depth downstream

H = Water Depth at point of measurement

Note: Discharge exponent of 2.5 (5/2) used for V-Notch weirs.

## V-Notch Weir: Specifications 

**Angle of V **- Enter the angle of the V in degrees.

**Coefficient of Discharge** - Enter the discharge coefficient of the weir. A default value of 0.59 is given.

**Invert Level **- The invert level of the Weir.


![image](media://08ec6246-8083-4b5b-a913-5f721b4349cb)