ARF: Areal reduction factor (ARF)

In UKFE: UK Flood Estimation

Areal reduction factor (ARF)

Description

The results of applying, to a rainfall depth, the ratio of the rainfall over an area to the rainfall depth of the same duration at a representative point in the area.

Usage

ARF(Depth, Area, D)

Arguments

Depth	depth of rainfall
Area	catchment area in km2
D	duration in hours

Details

The ARF and it's use is detailed in the Flood Estimation Handbook (1999), volume 2. The DDF model is calibrated on point rainfall and the areal reduction factor converts it to a catchment rainfall for use with a rainfall runoff model such as ReFH (see details for ReFH function). The ReFH model includes a design rainfall profile for winter and summer but the depth duration frequency (DDF) model is calibrated on annual maximum peaks as opposed to seasonal peaks. A seasonal correction factor (SCF) is necessary to convert the DDF estimate to a seasonal one. The final depth, therefore is; Depth = DDFdepth x ARF x SCF.

Value

the rainfall depth or rainfall return period

Author(s)

Anthony Hammond

Examples

#Derive the ARF for a depth of 30, an area of 500km2 and a duration of 12 hours
ARF(30, 500, 12)

UKFE documentation built on Nov. 6, 2023, 1:07 a.m.