Due to its robustness, versatility, and open-source, EPA’s Storm Water Management Model (SWMM) has become one of the most popular applications used for urban hydraulics analysis nowadays. One reason that explains the model popularity is the ability to predict flow in complex stormwater systems with reasonable accuracy in realistic inflow conditions. However, in highly dynamic conditions associated with extreme inflows, recent research indicated that SWMM accuracy can be improved with spatial accuracy and smaller time steps. SWMM models using spatial discretization deviates from the traditional setting up that relies on a link-node, which comparatively require shorter computational times. Yet, even among approaches to representing stormwater systems using spatial discretization, there are alternative approaches regarding pressurization algorithms that are not fully understood. The aim of this work is to evaluate how modeled results of piezometric head and flow hydrograph in a stormwater tunnel are affected by varying discretization and pressurization algorithms in SWMM. Results from a combination of three different spatial discretization (link-node and 2 different spatial discretizations) and 3 different algorithms to solve pressurized flow (EXTRAN, original SLOT, and a custom SLOT with pressure wave celerity of 250 m/s) are presented. These alternative solutions are placed on a real-world stormwater tunnel subjected to a sequence of rain events. Contrasts in the results between the solutions are presented and discussed along with the accuracy limitations of the traditional link-node alternatives.
