About This Application Manual

This manual is intended as a practical application guide for modelers who already have a solid understanding of hydrology, storm water management modeling and the use of GeoSWMM’s hydraulic elements and flow routing methods to simulate surface drainage systems. Especially you must know how to develop a GeoSWMM model using GIS data, to set simulation options and prepare model input data in ArcGIS Pro, and to run simulation and interpret model results under various design and planning scenarios. For detailed explanations of GeoSWMM’s interface, modeling features, and configuration settings, you are encouraged to keep the GeoSWMM User's Manual handy while working through this application guide.

This tutorial focuses on modeling a continuous simulation in GeoSWMM using a long-term rainfall record. The goal is to evaluate the performance of the stormwater drainage system and a BMP detention pond designed in Tutorial 03 for a 48.78-acre residential site. In Tutorial 03, the detention pond was originally designed to serve two purposes: capturing the Water Quality Capture Volume (WQCV) and controlling peak post-development runoff rates to match pre-development runoff rates for the 2-year, 10-year, and 100-year design storms. In this tutorial, the model same model file (Tutorial_03.gdb) will be used to simulate the pond’s behavior over a 10-year period. This simulation incorporates evaporation rates and a continuous precipitation record to better assess long-term system performance. This tutorial will also demonstrate how to use GeoSWMM’s Statistics tool to analyze continuous simulation results.

For context, drainage systems are typically designed using synthetic design storms. These single event design storms do not take into account varying patterns of rainfall duration and intensity, variation of time between storms, changing antecedent soil and storage conditions within the watershed, and the effect of evaporation. Continuous simulation addresses these limitations by using historical rainfall data to evaluate the system’s performance over time. This approach provides a more robust and realistic understanding of long-term water balance and the hydrologic performance of various stormwater management strategies.

In the next chapter, the worked-out tutorial with illustrations is detailed.