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13/11/2019 13:07:01

Bob Potter, Development Manager - Flood Modeller, Jacobs

For this month’s tip of the month we wanted to highlight a particular component of a Flood Modeller model, namely the event file. This is an optional component that is defined as a 1D element but can be utilised in both 1D and 2D simulations.

What is it?

Event files are text format files that are a subset of a complete 1D network. They contain data for one or multiple 1D units, e.g. an alternative flow boundary (QTbdy). If you were to review an event file in a text editor, you would see it is identical to how the same unit would appear in a 1D network file.

The event files usually have file extension “.ied”, but it is also possible to use extension “.sec”. Usually the former extension is used when the event file contains alternative boundary units and the latter is used when the event file contains alternative section data (this is not a strict rule though).

Why use event files?

When you set up a 1D network it will include a single set of boundary data (upstream and downstream). These may correspond to a particular gauge record or a particular theoretical event, e.g. a 1 in a 100 year storm. Furthermore, the section data will correspond to a configuration, e.g. with or without proposed flood defences. Thus, utilising this network in a simulation would yield a single results dataset.

So, what if you then want to investigate a different storm event or a different channel configuration? You could make a copy of your 1D network, give it a different name and then edit this to incorporate the required changes. However, each new network might only change a single unit, e.g. an upstream boundary (to represent a different return period). It seems inefficient to have to copy everything from the original network to achieve this change. Furthermore, it makes it harder to manage all your simulations if each one uses a unique network. If you need to make a common change then having to edit many networks to achieve this could lead to user error.

Event files provide an effective solution to this problem. Using event files, you can define a baseline version of your 1D network and then for each variation set up one or multiple event files that only define the units that have changed from what’s in the baseline model. Thus, each 1D simulation (ief file) defines a unique combination of 1D baseline network and event files as shown below:

Tip of the month - 11/19 - Event file

Flood Modeller projects have a dedicated event data section. Therefore, you can set up your Flood Modeller project to contain less full networks and instead utilise multiple event files which are then incorporated into multiple 1D simulation files. The advantages of this are:

  • If any changes are required to the core network, then you only need to edit once to apply the same change across all your simulations
  • You can utilise different combinations of event data to create many different simulations. Flood Modeller provides a tool, the 1D Simulation Builder, that can automate the generation of many 1D simulations files to represent all combinations of event data within your project).

Tip of the month - 11/19 - Event file 2


Event files can also be utilised in 2D models to provide boundary data:

  • As standard boundaries – defining 1D time series boundary units, e.g. QTbdy or HTbdy, which can be read and used directly.
  • As standard boundaries – defining 1D hydrological boundaries which will be processed into a flow time series at run time (the 2D solver “calls” the 1D solver to do this)
  • As hydrological boundaries – defining 1D hydrological boundaries which include a rainfall time series which will be applied to the 2D domain (over a user specified area).

Examples of these are shown below:

Tip of the month - 11/19 - Event file 3

How do I create an event file?

Flood Modeller provides multiple methods for creating new event data files:

  1. Start from nothing – Right-click on the Event Data section of the Project Panel and you can define a new event file. After providing a name for your file you can proceed to build the contents of the event file in the same way as you would build a full 1D network, i.e. by utilising the tools on the 1D Build tab of the main toolbar.
  2. Build from the existing 1D network – within the active 1D network highlight the unit(s) required for your event file, right-click on the network table (panel to the right of the map view) and select File > Create event file from the displayed menu. You will be prompted for an event filename and then the new file will be automatically added to the Event Data section of the Project Panel.

If you want to edit an existing event file then it first must be added to the Event Data section of the Project Panel. You can then review or edit the contents of this file in two different ways, both of which are in the menu accessed by right-clicking on the event file:

  1. Set Active – this changes the active file in your map view and network table to your selected event file. You can then proceed to edit and review this in the same way as a full 1D network. In this case the Save Network button in the main toolbar will save any event file changes you make.
  2. List Contents – this displays the contents of your event file in a pop-up window. Double clicking on any unit listed will access the 1D properties window for that unit, enabling you to review and edit accordingly. When you close the window listing the event file contents you’ll then be prompted to save any changes you’ve made.


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