6.1 Introduction

This chapter of the manual is written in USA English for the predominantly USA centered SWMM user base.

TUFLOW has supported 1D/2D dynamic coupling since its initial 2D solver development in 1989. Traditionally, 1D (1 Dimensional) linking and associated modeling has been applied using the ESTRY 1D solver (see Section 5). As of the 2023-03-AF release, TUFLOW’s 1D linking and solver options have been expanded to support the EPA Storm Water Management Model (referred to herein as SWMM). As such, 1D pipe networks can be modeled using either the ESTRY, SWMM, or a combination of the two 1D solvers. In addition to this, extra functionality, such as SWMM hydrology and SWMM Low-impact developments (LIDs) features, can be used in TUFLOW.

SWMM is a widely used software program for simulating urban and non-urban watersheds’ hydrologic and hydraulic behavior. Developed in the early 1970s by the Environmental Protection Agency (EPA), the model has since undergone numerous updates and enhancements to become one of the most used 1D stormwater runoff and water quality analysis tools globally, particularly in North America.

The primary uses of SWMM include designing and evaluating stormwater management practices, planning, and assessing low-impact development techniques, and developing models for floodplain mapping and emergency response planning. The software allows users to simulate a wide range of storm events and analyze the impact of a range of factors, such as land use changes, climate variability, and water quality control measures, on the performance of stormwater management systems. More information about SWMM can be found on the EPA website.

6.1.1 TUFLOW-SWMM Capabilities

Combined TUFLOW (2D) and SWMM (1D) models have a variety of applications and capabilities. Features built into TUFLOW-SWMM include:

  • 1D/2D SWMM/TUFLOW linkage through direct connections (TUFLOW HX and SX).
  • All inbuilt SWMM stormwater inlet types are supported, including a wide variety of shapes. Both on-sag and on-grade stormwater inlet connections are also supported.
  • SWMM Inlets can surcharge into the TUFLOW 2D domain if the 1D pressure head exceeds the 2D water level.
  • SWMM 1D inflows can be sourced from: external boundary conditions specified in SWMM, rainfall routed through SWMM subcatchments, or via 2D linkages from TUFLOW to SWMM.
  • SWMM hydrology subcatchment routing, including allowance for infiltration, groundwater levels, evaporation, and snow melt.
  • Low-impact developments (LIDs) features for modeling green infrastructure.
  • Scenario support through the ability to combine multiple SWMM project files (inp) in a single TUFLOW model. This feature is a powerful way to explore multiple setup options without duplicating information.

The TUFLOW QGIS Plugin has been expanded to assist with building SWMM models, linking TUFLOW-SWMM models, and viewing SWMM outputs in a GIS environment. The SWMM GIS tools are discussed in Section 6.3.

Currently, TUFLOW does not connect the AD (advection-diffusion) module or the TUFLOW groundwater (interflow) capability to the SWMM network.

6.1.2 Additional SWMM User Resources

This manual documentation does not duplicate SWMM information available elsewhere. Useful additional SWMM resources are listed below: