How do V-notch weirs work in SWMM 5?
Hi Keith, As you change the Length which is actually the Top Width you change the area and hydraulic radius of the Weir.
The height of a V-Notch weir is the Height Value in the SWMM 5 Weir Property Dialog (Figure 1)
The Length in the Dialog for a V-Notch is the Top Width of Triangular Shaped V-Notch Weir.
The slope of the sides of the V-Notch Weir is Square Root (1 + Top Width / Height / 2 * Top Width / Height / 2)
The full area is the Height * Height * Side Slope
The hydraulic radius is the Height / ( 2 * Height * Side Slope)
The two values Height and Length for a SWMM 5 V-Notch Weir determines the area, hydraulic radius and side slope of the weir.
Figure 1. Parameters for a V-Notch Weir in SWMM 5