What is the FEH statistical method?
The Flood Estimation Handbook, produced by the Institute of Hydrology in 1999 effectively replaced Flood Studies Report in the UK.
The following QMED equation is from a revision to the statistical approach in 2008 (Kjeldsen et al, 2008).
Qmed = 8.3062 x (0.01 x AREA)0.851 x 0.1536(1000 / SAAR) x FARL3.4451 x 0.0460(BFIHOST x BFIHOST), m3/s
where:
- Qmed is the median annual flow rate; the 1:2 year event.
- AREA is the area of the catchment in ha.
- SAAR is the standard average annual rainfall for the period 1941 to 1970 in mm.
- FARL is a reservoir attenuation function and is set at 1.0 and therefore has effectively been ignored. This means that areas with water bodies which attenuate the runoff will over-predict the greenfield runoff rate.
- BFIHOST is the base flow index derived using the HOST classification.