SWMM5 modelling of staggered flume with internal orifice-weir plate

Abstract

A new approach uses soft computing to model an orifice-weir system inside open-source drainage software. As climate change alters urban runoff patterns, innovative nature-based engineering solutions like staggered detention ponds are increasingly necessary. Still, intricate hydraulics typically demand high-end simulation tools many working engineers lack access to. For this reason, a basic setup emerges through adjustments in SWMM 5, modifying a weir element with defined bottom entry spacing to reflect both orifice and overflow behaviour at once. Verified using experimental data from a hydraulic flume alongside hand-based calculations, the model lines up with expected mass balance behaviour. The experimental results match theoretical mass conservation principles, and empirical testing identifies an optimal discharge coefficient of 0.40 for the structure. Though flow and water level outputs stay close to observed values when inflow is high, lower inflows see the model fall short on predicting actual depths. One core constraint stands out which the setup cannot capture hydraulic jumps forming further down. Despite this, the approach offers engineers a practical way forward, fitting complex water control features into everyday drainage planning without demanding advanced tools. What matters most is practical forecasting for how much stormwater systems can be handled, built on straightforward methods.