Catchment Descriptors

When a Calculation Point is created from either imported FEH catchment descriptors or a NRFA Peak Flow gauge, the Catchment descriptor tab will be populated with a full set of descriptors. The default / as imported version of the catchment descriptors is version 1, any changes to values will create a new version to enable change tracking.

Catchment descriptors should always be reviewed prior to use in calculation. Flood Modeller allows users to adjust catchment descriptors based on their review (for example adjusting URBEXT to reflect increased urbanisation in the catchment). Edits can be made to the selected version, displayed on the right-hand-side. Save will automatically create a new version of the catchment descriptors. It is strongly recommended that comments are applied alongside any changes to help document decisions made. Comments can be added to each descriptor value or to the version as a whole.

If comments are added to descriptors, but values remain unchanged, a new version will not be created. This is useful if you wish to document the checks/review you have undertaken of each descriptor. For example, adding a comment to AREA of "catchment area reviewed against Ordnance Survey contours and found to be correct, default value retained".

The descriptor version selected in the right hand menu will be used for subsequent ReFH2 and WINFAP analyses performed in the calculation point.

Both WINFAP and ReFH2 allow catchment descriptors to be edited/adjusted during analysis in the respective software. Flood Modeller will always check for changes to descriptors when importing ReFH/WINFAP analysis and a new descriptor version will be created if a change is identified to ensure consistency. All versions, whether created in Flood Modeller or ReFH/WINFAP will be displayed under this tab.

Further details of the catchment descriptor functionality is provided in the technical reference.