Using ReFH2 to Generate TUFLOW Boundary Inputs: Difference between revisions

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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>

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[[File:Catchment_Descriptors.png]]<br>

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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.<br>

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[[File:FEH_2013_Design_Rainfall.png]]<br>

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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.<br>

[[File:ReFH2_Results.png]]<br>

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Data can be viewed either as graphs or as grids. The available data includes the following for the selected return period and duration:-

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

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[[File:Catchment_Descriptors_Key.png]]<br>

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The model parameters section allows the user to specify the seasonality and other parameters, again for sensitivity analysis. Changing the seasonality will change the seasonal correction factor for the rainfall.<br>

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[[File:Model_Parameters.png]]<br>

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The urbanisation tab allows the user to estimate the impact of urbanisation for catchments as well as greenfield and post development peak runoff rates for development sites.<br>

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[[File:Urbanisation.png]]<br>

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The grids can then be exported to csv using the ‘Export Grid’ option. This exports the time-varying grids for all return periods and all design outputs.<br>

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[[File:ReFH2 Outputs.png]]<br>

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The relevant data can then be copied into the TUFLOW bc_dbase folder and referenced by the bc_dbase.csv file as appropriate (see Module 08 for an example of applying direct rainfall boundary conditions for example).

The gross design rainfall or total net rainfall can be applied to directly to the 2D domain using a 2D_RF polygon to distribute the rainfall. Multiple RF polygons can be used to spatially distribute the rainfall if required.

The total runoff (or rainfall) can be applied directly to a 2D_SA polygon, to apply the inflow to an area of the 2D mesh. There are a number of options for distributing flows in this instance, these are:-

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*Flow is distributed firstly to the lowest cell and then to the wet cells,