Subject: What are the Equations for Weirs in SWMM 5, Part 2?
There are four types of Weirs in SWMM 5: Transverse, Sideflow, V Notch and Trapezoidal. The trapezoidal weir is a combination of the Sideflow and V Notch Weir and the Sideflow acts like a Transverse Weir when the flow is reversed (Figure 1). The Weirs can have zero, one or two end contractions (Figure 2) and the Weir Length is a function of the Weir Setting and Horizontal Weir Length. A V Notch weir works as Trapezoidal Weir when the Weir RTC Setting is less than 1.0
Figure 2. Valid Number of End Contractions
Figure 3. Weir Length Calculations