Flood Modeller Tutorial Module01 Provisional

Introduction

In this module we will link an existing 2D TUFLOW domain to an existing Flood Modeller 1D model. The 2D TUFLOW domain will represent the floodplain in the study area, and the 1D Flood Modeller model will represent the watercourse and all online structures.

1D-2D linked models are able to utilise the individual benefits of 1D and 2D solution schemes. In this example, the 1D Flood Modeller scheme is used to represent the watercourses where the flow is essentially uni-directional. A 2D scheme is suited to the representation of floodplains where more complex flow patterns may occur.

As discussed in Module 1 of the TUFLOW Tutorial Model, the main watercourse channel is not very well represented using the 5m 2D cell size. In parts, the watercourse is only 5-10m wide and the 5m cell size could be considered too coarse to accurately represent the watercourse topography.

Using a cell size that is coarse relative to the width of the watercourse channel may reduce the accuracy of the conveyance in the channel. There are two options for improving the representation of the creek channel:

• decrease the width of the 2D cells; and/or
• model the channel as a 1D network, dynamically linked to the 2D domain (the floodplain).

In the optional section of Module 1 of the TUFLOW Tutorial Model, we looked at reducing the cell size to get a better representation of the channel. In this module we will adopt the second approach of modelling the creek as 1D elements using Flood Modeller.

TUFLOW may be dynamically linked to 1D networks using the hydrodynamic solutions of ESTRY (TUFLOW 1D), Flood Modeller, XP-SWMM and 12D Solutions’ Dynamic Drainage.

Setting up a 1D/2D model where the 1D channel cuts through the 2D domain is probably the most time-consuming type of a model to setup. However, the reduction in simulation time can be beneficial and make this a good approach. For this module, the complete Flood Modeller 1D model has been provided, to allow for progressing through the module in a relatively short period of time.

Existing Model Data

This tutorial builds upon the 2D TUFLOW domain that was constructed as part of Module 1 and Module 2 of the TUFLOW Tutorial Model.
The model developed in these tutorial modules already contains some culverts modelled as 1D elements. The culverts are modelled in ESTRY, TUFLOW's internal 1D engine. One of these culverts will be kept in ESTRY and the other will be added to the Flood Modeller model.
The 2D boundary conditions (upstream inflows and downstream stage-discharge boundary) will be removed from the model. These will instead be represented in Flood Modeller as it is a more typical schematisation for a 1D/2D linked model.
The existing TUFLOW model consists of:

• Definition of Active/In-Active Areas
• Definition of Land Use
• 1D ESTRY culverts
• 1D/2D boundary links to connect the 1D ESTRY culverts to the 2D TUFLOW domain.

For further information on these elements, please refer to Module 1 and Module 2 of the TUFLOW Tutorial Model.