10.1 Introduction

This chapter discusses methods available for dynamically linking 1D and 2D domains, linking with external (third-party) 1D solvers, and linking 2D domains together using Classic’s Multiple 2D Domains feature. HPC’s Quadtree feature, whilst allowing variable 2D cell sizes, is essentially one 2D domain over which a full 2D solution is applied is discussed in Section 7.3.1. A comparison between Classic’s M2D feature and HPC’s quadtree grid is presented in Section 10.7.

The range of functionalities discussed in the Chapter offer numerous benefits, including greater model design flexibility, greater computational efficiency and performance, and ability to integrate TUFLOW domains within supported third-party 1D solvers and models.

1D-2D linked models utilise the individual benefits of 1D and 2D solution schemes. 1D schemes are typically used to represent culverts or sub-surface pipe networks, and sometimes rivers, where the flow is essentially one-directional. 2D schemes are suited to the representation of, for example, rivers and floodplains or estuarine and coastal waters, where the hydrodynamics can flow in multiple horizontal directions, which requires the ability to simulate flow in a two-dimensional plane.

TUFLOW’s 2D solutions (Classic and HPC) may be dynamically linked to a variety of different 1D solutions, including TUFLOW 1D (ESTRY), EPA SWMM (herein referred to as SWMM in this chapter), Flood Modeller (formerly ISIS), 12D Dynamic Drainage (DDA), and XPSWMM from Autodesk (formerly XP-Software then Innovyze).

Within the one model, 1D domains that are TUFLOW 1D (ESTRY) and other 1D domains that are an external 1D scheme can occur. This may be useful where different 1D solvers offer different capabilities. Further, linking of TUFLOW 1D (ESTRY) directly to either Flood Modeller or SWMM is also possible.

The software environment for the 1D Solver / TUFLOW 2D combination varies:

TUFLOW 1D (ESTRY) and SWMM are integrated within the TUFLOW executable. Model build tasks and result viewing associated with these linked 1D solvers is typically completed using traditional TUFLOW compatible GIS software.
12D Dynamic Drainage is developed by 12D Solutions. They have developed a TUFLOW interface within their own 12D GUI that offers GUI functionality for 1D and 2D modelling tasks. The interface provides users with the ability to build models and view results entirely within its GUI. Alternatively, existing TUFLOW files created in a GIS form can be imported and used in the 12D GUI.
Flood Modeller, developed by Jacobs (formerly the ISIS software developed by Halcrow), is not built into the TUFLOW executable. Flood Modeller must be purchased from Jacobs, installed and configured, and to link with TUFLOW, the Flood Modeller TUFLOW Link must also be purchased and installed. Flood Modeller accesses the TUFLOW solvers via the TUFLOW_LINK.dll that is part of the standard TUFLOW download. The Flood Modeller GUI is used for 1D model build tasks, and execution of the linked Flood Modeller 1D / TUFLOW model. The TUFLOW script (control) file and GIS environment is typically used for the TUFLOW 1D and 2D components.
XPSWMM functions in a fully independent GUI with TUFLOW fully embedded and operated “behind-the-scenes”. As such, the model development and results viewing information in this manual is not applicable and reference should be made to the XPSWMM documentation as supplied with the software. However, when XPSWMM runs a simulation with TUFLOW linked, all the standard TUFLOW script files, GIS layers and result outputs are written to disk should the user with to access these in their native formats.

Varying the 2D cell size within a single model enables use of smaller cell sizes (finer resolution) in areas where a more detailed assessment is required or a finer grid is required to accurately represent the hydraulics, with the larger cell sizes covering the remaining areas of the model. The ability to vary 2D cell sizes within the one model optimises the grid construct thereby reducing simulation times and the memory footprint compared to a model that adopts a fine resolution over the entire model domain.

Both TUFLOW Classic and HPC offer the ability to vary 2D cell sizes using two different approaches: - TUFLOW Classic offers 2D-2D linking of different 2D domains via the Multiple 2D Domains (M2D) Module. 2D-2D linked Classic models allow for a single model to contain multiple 2D domains of different cell sizes and different orientations. The 2D-2D link is via hidden TUFLOW 1D nodes that essentially pass the water from one 2D domain to another using HX links. The solution across the link is not a full 2D solution, rather a linked 2D-1D-2D solution results that may not be as accurate as a full 2D solution. - TUFLOW HPC doesn’t support Classic’s 2D-2D linking, but supports varying 2D cell sizes using a full 2D solution across a quadtree grid (the Quadtree Module, which purchase/licence wise is shared with Classic’s M2D Module, is required). The quadtree grid requires all 2D cells are on the same orientation and they can only vary in size by a factor of two when transitioning from a smaller cell to a larger cell.