The Pooled & QMED Analysis is the WINFAP main modelling tool and can be accessed via the r-click menu items associated with the Site of Interest. In essence, the Flood Frequency Curve (FFC) for your site is estimated as the product of a pooled estimate of an 'as rural' growth curve and the index flood, QMED. WINFAP is an application of the FEH statistical method, including the Enhanced Single Site (ESS) site method, as presented in detail by Kjeldsen et al., 2008. This report should be read in conjunction with the Flood Estimation Handbook.
In most cases your Site of Interest is unlikely to have sufficient at-site peak flow data for use in the analysis thus QMED and the growth curve are often estimated using the 'ungauged' methods:
The most common approach to estimate the QMED is to use the FEH QMED catchment descriptor equation to first estimate the rural QMED and then adjust these using the Multiple Donor Adjustment procedure. The latter enables you to incorporate local data from observed QMED estimates from multiple donor stations deemed as suitable for QMED estimation. WINFAP includes additional methods for estimating QMED as detailed in the QMED Estimation Methods guidance.
If no site data is available your growth curve is estimated using the ungauged Growth Curve Estimation method. This estimates the growth curve based on observed data at hydrologically similar gauging stations; collectively referred to as the 'pooling group'. The WINFAP sidebar provides comprehensive options for reviewing and refining the pooling group. More details are provided in the Growth Curve Estimation guidance.
WINFAP enables you to estimate both 'as rural' and 'urbanised' FFCs using the urban adjustment procedures.
Where available, at-site data may be incorporated into the pooling group and QMED estimation procedures for both urban and rural catchments. The dashboard provides you with options to specify the explicit use of available at-site data for Growth Curve and/or QMED estimation. Where AM data is available, for example for NRFA Peak Flow Dataset stations, WINFAP maximises the use of the at-site data in the estimation procedure. The default methods selected are conditional upon the NRFA suitability indices, record length and the degree of urbanisation. See Growth Curve Estimation and QMED for further details. You can override these rules through manual selection.
Other sources of at-site data can be incorporated directly for QMED Estimation.
Historic data can also be incorporated into an extended single site analysis through the r-click on your Site of Interest in the sidebar, Historic Data....
Copy and paste graphs, diagrams, maps and tables
Most of the graphs, diagrams and maps can be copied to the clipboard using r-click to select 'Copy chart' to then paste into external software.
For tables, highlighting the top left corner of the table will select the table and allow Ctrl + c for copy and pasting into external software. Data can also be copied and pasted similarly by selecting the cells of interest or individual rows.
Tip: double clicking on a pooling group station in the sidebar opens the Single Site Analysis dashboard. The dashboard and graphs update if you cycle though stations in the pooling group. This is a valuable tool when reviewing and revising pool membership in the next step. For example, you can open the single site flood frequency graph and the graph updates as you click through the catchments in the pooling group.