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How to resolve common error messages in Flood Modeller

Error messages are a pain! There is no denying it – when you set up everything carefully to get your simulation running and then are hit with an error message, it can ruin your day! What should you do now?


The first thing may sound obvious; READ THE MESSAGE. Flood Modeller details possible issues within the error messages to aid you. These are provided both in the exy (seen directly at runtime) and the diagnostics file (zzd). Be aware that the exy sometimes needs to use a more generic and/or truncated version of the error message in the zzd, and therefore it is always recommended you check the full diagnostics to gain as much detail as possible.


In this article, we provide details of some of the more common error messages, and approaches to resolve these.

Figure 1: Details of warnings and errors are provided directly at simulation runtime.


Model stability errors


If you encounter the following error messages or issues, it is likely that an instability has occurred.

  1. E1020 Water level exceeded maximum section data level dflood ( X.00m). Check model, extend section data or increase dflood

  2. E1100 Model is diverging. No solution has been found with the current time step. You should try decreasing the time step or improving the initial conditions

  3. E1066 Channel has gone dry. Try increasing the slot depth checking the initial conditions or checking downstream boundary levels are above the bed

Following an instability, the error message may report section has run dry or the parameter Dflood has been exceeded - often the location is not where problem actually lies! This is because the instability can oscillate up and down the channel before creating the model failure.


What to do to stabilise your model can involve a multitude of techniques. Our recent model stability article provides 5 tips and tricks for resolving instability issues within 1D networks and may help you resolve these errors.


Hydrological boundary errors


If you encounter the following messages, there is likely an issue with your hydrological boundary.

  1. Errors caused by hydrological boundaries

  2. Issue with ReFH2 unit showing different results

Many issues we experience with hydrological boundaries are due to incorrect input data. In the first instance, we recommend you carefully check all of the data entered in your units.


However this is not always the case. In particular, the ReFH2 boundary is developed externally to Flood Modeller, and therefore outputs can sometimes differ due to newer updates provided in the unit to adjust the data.


There are certain issues that instead involve a workaround, for example, if the methodology you desire is unavailable. The easiest workaround for these issues is to simply copy the final hydrograph data into a flow-time (QT) boundary instead. Ensure you adjust the time unit appropriately.


This functionality is especially helpful for if considering hydrological methodologies currently unavailable in Flood Modeller. For example, for standard Irish hydrology methods, the FSU Portal can still be utilised to create your initial flow hydrograph and this can simply be pasted into the QT boundary.

Figure 2: Outputs from external sources such as the Office of Public Works (Ireland) FSU Portal can be simply copied and pasted into a Flood Modeller flow-time (QT) boundary.