Hydrology

Flood Estimation Handbook (FEH)

As mentioned above, we would generally use the latest version of the Flood Estimation Handbook (FEH) software for the hydrological assessment of flood flows in watercourses. This is produced by the UK Centre for Ecology and Hydrology and Wallingford HydroSolutions Limited and is the industry standard method for this type of work.

We would also generally follow the advice set out in the Environment Agency's document, 'Flood Estimation Guidelines' and this could include the use of the statistical or the ReFH rainfall-runoff methods as appropriate. The statistical method can produce estimates of the peak flood flow and in many ways is the preferred methodology for this. The ReFH method on the other hand, can also produce peak flood flow estimates but in addition can also generate design flood hydrographs.

Uses of FEH Study

An FEH study of the flow in a watercourse is often used in other engineering processes such as being a preliminary to the hydraulic modelling of a river or stream. This process, in turn, is often an element of a flood risk assessment in England or a flood consequence assessment in Wales.

Greenfield Runoff

The greenfield runoff rate, (that is the estimated runoff rate from an undeveloped site), is an important consideration in the design of drainage systems for new developments. This is often used as the limiting flow from a proposed site to ensure that there is no increase in the flood risk downstream once the site is completed.

As well as following the recommendations set out in the R Kellagher document mentioned above, we can also use the FEH ReFH2 software to calculate plot scale greenfield runoff rates.

Further information

The preparation of a hydrological study is site specific so please contact us for further information.