A Suite of Tools for Efficient SWMM Modeling of Complex Systems

The USEPA SWMM model uses a non-linear reservoir algorithm to compute runoff and dynamically routes flows accounting for backwater and pressurized flow conditions. These abilities of SWMM enable detailed modeling of complex urban collection systems. As complexity increases, the detailed representation of the system is often limited by the abilities of the available tools to prepare large input datasets as well as their ability to perform quality assurance checks. Moreover, such complexities cannot be handled by automated methods or readily available software. Our experiences with modeling large urban collection systems suggest that a “one-size fits all” concept does not always work. This presentation describes customized tools using SAS statistical software for hydrologic and hydraulic modeling of complex urban setups using SWMM 5.

Examples of custom built tools are presented here from SWMM applications for large, complex combined and separated sewer systems with several thousand subcatchments. Such models should be able to handle different topographic slope categories, hundreds of orifices with multiple real time control rules and outfalls with time series boundary conditions. The continuous simulation for the example setup uses radar-corrected virtual precipitation gages, area-weighted for each subcatchment. Also, the presented SWMM setup utilizes multiple inflow time series for groundwater and base wastewater from an external file for each sewershed connection in the system. A typical model application for such systems requires validation of hundreds of sewersheds, continuous simulations, and management of hundreds of multi-year time series. These procedures are not easily handled using only the USEPA SWMM 5 interface or other available software. In this work we describe customized SAS tools for building input files, production of graphics for flow validation, and computing useful statistics for all conduits and nodes simultaneously. We present examples ranging from plotting inflow-outflow for all combined sewer overflow regulator structures, to computing combined sewer overflows statistics at all outfalls, illustrating the usefulness and effectiveness of these tools to model and evaluate complex urban hydrologic and hydraulic systems.