Using ReFH2 to Generate TUFLOW Boundary Inputs

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In 2016, the Centre of Ecology and Hydrology (CEH) and Wallingford Hydro Solutions (http://www.hydrosolutions.co.uk) released another version of the revitalised rainfall-runoff model (ReFH2) which allows users to generate design flows and hydrographs from given rainfall events for both catchment and development sites. ReFH2 is the 2nd version of the “Revitalised Flood Handbook”, created and developed by Wallingford Hydro Solutions. It’s a rainfall-runoff model specifically applicable to England, Wales and parts of Scotland. It takes inputs from the FEH 2013 website and generates design rainfall events and provides a method for calculating design runoff from subcatchments. For a full description of the approaches, the reader is referred to their document which can be freely accessed at:- http://files.hydrosolutions.co.uk/refh2/ReFH2_Technical_Report.pdf
To use the ReFH2, the software must be installed locally and a licence must be obtained from Wallingford HydroSolutions. The ReFH2 software can be installed from (http://files.hydrosolutions.co.uk/refh2/latest).

FEH 2013 Rainfall

FEH2013 is a new method for generating design rainfall hyetographs, superseding the FEH1999 method. In order to generate the design rainfall, the user obtains design rainfall depths from the FEH2013 web service at https://fehweb.ceh.ac.uk for pre-defined return periods/duration combinations. This requires a log on and user credits to purchase the data for the desired location. Data is available at a river catchment scale and as a point value. Both of these provide XML containing the rainfall depths. This is then imported into the ReFH2 software to generate hyetographs based on Flood Studies Reports (FSR) approaches (which have been published).

ReFH2 Runoff

ReFH2 is the new method for the calculation of runoff. It hasn’t changed significantly from the original ReFH approach for which equations are publicly available, although there has been a mass balance closure improvement to the runoff model. There has however, been a change to the initial conditions, BF0 and Cini (initial baseflow and initial soil moisture, C) and there is an additional parameter, alpha. The data contained in the XML from the FEH2013 website also provides the catchment descriptors to calculate the necessary model parameters within ReFH 2 from which the runoff hydrograph is developed.

Creating Design Rainfall and Runoff within ReFH2 for use with TUFLOW

To generate rainfall or runoff using ReFH2, firstly open the ReFH2 software and create a new ReFH project.


Use the ‘Import from file’ option to import the XML files. The XML data can be catchment values or point data. Importing the xml file will populate the parameters. When using point descriptors, these do not have an area associated with them. Therefore, you will need to specify the area of the plot that you are interested in (if required this can also be edited later). Once an area value has been provided then it is possible to generate the rainfall hyetographs and runoff hydrographs and apply to TUFLOW in the same manner as for catchment descriptors.

The user will then choose which country the data corresponds to. The ReFH2 programme included the development of Scotland specific algorithms to estimate the model parameters from the catchment descriptors. The choice of Scotland will mean that the alpha correction factor is not applied.

Once the parameters have been imported, and the country specified, apply the parameters and choose to move to the next page. On the next page you can choose which rainfall model to use, FEH1999 or FEH2013. It’s possible to specify the design rainfall return periods of interest and ReFH2 will automatically calculate the recommended duration and suggest an appropriate timestep that meets the requirement that the duration must be an odd multiple of the time step. The recommended duration should normally be used, although both values can be edited directly to provide the duration that is required. The XML file from the FEH2013 website contains the rainfall depths for a number of pre-defined return period/duration combinations. For those return period/duration combinations that are not pre-defined, ReFH2 undertakes a two-way interpolation process. ReFH2 will then generate the design rainfall hyetograph based on the rainfall depth and the FSR approach.

On the right hand side you can see the calculated Areal Reduction Factor and Seasonal Correction Factors which will be applied. The rainfall profile can vary depending on the season selected (summer or winter) and the seasonal correction factor and areal reduction factor are both applied to the rainfall hyetograph to obtain the correct design rainfall hyetograph. Once the Return periods and durations have been defined then click next. This brings up the various parameters together with the rainfall hyetographs and runoff hydrographs for the various return periods. The rainfall hyetographs and runoff are available as rural and urbanised scenarios.

Data can be viewed either as graphs or as grids. The available data includes the following for the selected return period and duration:-
1. Design Rainfall
2. Urban net rainfall
3. Rural net rainfall
4. Sewer Loss
5. Total net rain
6. Direct Runoff
7. Baseflow
8. Total Flow

The return period can be varied using the dropdown menu in the Rainfall section.

The catchment descriptors (BFIHOST, DPLBAR, DPSBAR, SAAR, PROPWET and Area) can all be edited should a sensitivity analysis be required.