What This Tutorial Covers

This tutorial serves as a hands-on guide for professionals using GeoSWMM, with a focus on the practical application of combined sewer system modeling and Combined Sewer Overflow (CSO) analysis. It is intended for users who already have a working knowledge of hydrology, hydraulics, stormwater management modeling, model input data in ArcGIS Pro and the use of EPA SWMM elements and flow routing methods for representing drainage systems.

The tutorial walks users through the modeling of combined sewer systems, where both sanitary wastewater and stormwater are conveyed through the same pipe network. It emphasizes the behavior of these systems during moderate to heavy rainfall events, when pipe and treatment capacity can be exceeded, resulting in Combined Sewer Overflows (CSOs). These skills are especially relevant for engineers and planners working with older urban drainage systems where combined sewers remain common and where overflow events can create significant operational and environmental challenges.

Users will learn how to represent combined flow conditions in GeoSWMM, analyze system performance during wet-weather events, and evaluate the circumstances under which CSOs may occur. This tutorial complements the GeoSWMM User’s Manual by offering a structured, example-driven walkthrough of real-world modeling scenarios.

The following section begins a step-by-step demonstration of the worked example project, guiding users through each stage of setting up and analyzing a combined sewer system and CSO scenario in GeoSWMM.