Using ReFH2 to Generate TUFLOW Boundary Inputs: Difference between revisions

Originally published in 1999, and subject to continuous development, the Flood Estimation Handbook (FEH) comprises the standard methods for estimating flood frequency. The rainfall-runoff model is one of two core handbook methods. In 20162015, the Centre of Ecology and Hydrology (CEH) and Wallingford Hydro Solutions (httphttps://www.hydrosolutions.co.uk) released anothera new version of the revitalisedRevitalised Flood Hydrograph 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 a rainfall-runoff model specifically applicable to England, Wales and parts ofthe ScotlandUK. It takes inputs from the FloodFEH2013 Estimationweb Handbook 2013service (FEH2013https://fehweb.ceh.ac.uk) website, and generates design rainfall events and provides a method for calculating design runoff from sites or contributing subcatchments.

For a full description of the approaches, the reader is referred to their documentguidance which can be freely accessed at:-

FEH2013 is athe newlatest methodDepth Duration Frequency (DDF) model for generating design rainfall hyetographs. CEH recommend the use of FEH2013, supersedingwhich supersedes the FEH1999 method. In order to generate the design rainfall, the user obtains FEH2013 design rainfall depths from the FEH2013FEH webWeb serviceService at https://fehweb.ceh.ac.uk for pre-defined return period/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 ReportsReport (FSR)/FEH approaches.

Use the '''‘Import from file’''' option to import the XML files. Importing the XML file will populate the parameters. The XML data is available is available in catchment data or point data format. When using the point data format, these do not have an area associated with them. Therefore, the user will need to specify the area of the plot that you are interested in (if required this can also be edited later). <br>

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.<br>

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 the user can choose which rainfall model to use, FEH1999 or FEH2013. Note that CEH recommend use of the improved FEH2013 model. 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 FEH2013FEH Web websiteService 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/FEH approach.<br>

On the right hand side of the above image, you can see the calculated Areal Reduction Factor and Seasonal Correction Factors which will be applied to the rainfall depth. 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 Returnreturn 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.<br>

The relevant data can then be copied into the TUFLOW bc_dbase folder and referenced by the '''bc_dbase.csv''' file as appropriate (see [[Tutorial_M06|Module 086]] for an example of applying direct rainfall boundary conditions for example).

Once the bc_base has been set up then a '''.tef''' file can be generated which populates the ARI variable above with the relevant ARI for the specific question. The '''TEF''' file also creates anewa new output folder for each return period.

This post provides instructions of how to obtain direct rainfall and inflow inputs from the ReFH2 software for use within a TUFLOW model. This requires the input of data from the FEH2013FEH websiteWeb Service and the selection of the appropriate return period, /duration combinations of which the user is interested. This outputs the time-varying rainfall and total runoff (as well as runoff contributions) which can be exported for use within TUFLOW. FutureIt developmentis inalso thispossible areato willuse lookTUFLOW event files to automateincrease someefficiency ofwhen thiscreating processmodels withfor amultiple return period/duration combinations. A ReFH2 to TUFLOW tool is available for the QGIS TUFLOW Viewer plugin, more details can be found on the [[QGIS_ReFH2_to_TUFLOW | QGIS ReFH2 to TUFLOW]] page.