Integration of the Illinois Transient Model (ITM) as a New Hydraulic Solver in the Storm Water Management Model (SWMM)
Conference
Leon, AS, Rossman, LA, Glovick, SJ. (2026). Integration of the Illinois Transient Model (ITM) as a New Hydraulic Solver in the Storm Water Management Model (SWMM)
. 606-621. 10.1061/9780784486931.050
Leon, AS, Rossman, LA, Glovick, SJ. (2026). Integration of the Illinois Transient Model (ITM) as a New Hydraulic Solver in the Storm Water Management Model (SWMM)
. 606-621. 10.1061/9780784486931.050
Although efforts have been made to simulate highly transient flows in pipes within the Storm Water Management Model (SWMM), these have achieved only limited success. The Illinois Transient Model (ITM) is a one-dimensional, shock-capturing, finite-volume model developed to analyze transient flows in circular closed conduits under dry-bed, gravity, mixed, and fully pressurized conditions. Since its introduction in 2008, ITM has been widely applied to the design and analysis of sewer systems in the United States and abroad. Recent upgrades include the implementation of the Harten-Lax-Leer + Source term (HLLS) Riemann solver, which enhances numerical stability and better preserves stationarity in sloped pipes, and the two-component pressure approach (TPA), which unifies gravity and pressurized flow within a single governing equation. The enhanced ITM version 2.0 effectively reduces spurious oscillations associated with realistic pressure-wave speeds in the TPA model and also supports additional boundary conditions and hydraulic elements, including orifices and weirs. This study integrates ITM v2.0 into SWMM to develop the coupled ITM–SWMM 1.0 framework and demonstrates its application through three example cases.
