The Flood Estimation Handbook (FEH) was published in 1999 by the Institute of Hydrology, and largely supercedes the Flood Studies Report (1975). The Modified Rational Method of the 'Wallingford Procedure' was partially developed from the FSR. The FEH is made up of four volumes and is available from the Institute of Hydrology.

There has been comment that this new document invalidates the existing methods of surface water drainage design. This is not true for the type of design in which Public Health Engineers tend to be involved (see notes below). In these cases, the traditional methods of design are still valid, and should be used.

In the Introductory volume (Vol.1) of the FEH, the following points are made (paragraph numbers in parentheses):

• The FEH techniques are not applicable to small catchments i.e. those less than 50 Ha.(3.1.2)
• They are not applicable in heavily urbanised areas (3.1.3)
• Ideally, storm durations must be within the range of 1 hour to 8 days. With care, this data can be extrapolated to 30 mins, or even 15 mins. (3.1.4)

It can be seen from the above that these exceptions represent the majority of the drainage schemes that PHEs have to design or develop, and thus the techniques of the FEH would not appear to be generally applicable to PHEs.

The FEH is a major step in the field of hydrology and flood prevention, and it would be a valuable experience for PHEs engaged in surface water drainage design to have a look at the volumes (Vol 4 - "Restatement and application of the Flood Studies Report rainfall-runoff method" is well worth a look). Its main target seems to be those engaged in designing large structures for flood prevention, rather that the PHE draining a small housing estate.

FEH data may be added to a configuration file (.CNF) if it is available and used in subsequent calculations.