UKFE (version 0.2.2)

Pool: Create pooling group

Description

Function to develop a pooling group based on catchment descriptors

Usage

Pool(
  CDs = NULL,
  AREA,
  SAAR,
  FARL,
  FPEXT,
  N = 500,
  exclude = NULL,
  iug = FALSE,
  DeUrb = FALSE
)

Value

A data.frame of the pooling group with site refence row names and 24 columns each providing catchment & gauge details for the sites in the pooling group.

Arguments

CDs

catchment descriptors derived from either GetCDs or ImportCDs

AREA

catchment area in km2

SAAR

catchment standard average annual rainfall (1961-1990) in mm

FARL

catchment flood attenuation from reservoirs & lakes

FPEXT

catchment floodplain extent. The proportion of the catchment that is estimated to be inundated by a 100-year flood

N

minimum Number of total gauged record years for the pooling group

exclude

sites to exclude from the pooling group. Either a single site reference or a vector of site references (numeric)

iug

iug stands for 'include urban gauge'. It's a logical argument with default of FALSE. TRUE will over-ride the default and add the closest site in catchment descriptor space to the CDs provided if it has URBEXT2000 >= 0.03

DeUrb

logical argument with a default of FALSE. If true, the Lcv and LSkew of the top site in the pooling group will be de-urbanised

Author

Anthony Hammond

Details

A pooling group is created from a CDs object, derived from GetCDs or ImportCDs, or specifically with the catchment descriptors AREA, SAAR, FARL, & FPEXT (see arguments). To change the default pooling group one or more sites can be excluded using the 'exclude' option, which requires either a site reference or multiple site references in a vector. If this is done, the site with the next lowest similarity distance measure is added to the group (until the total number of years is at least N). Sites with URBEXT2000 (urban extent) > 0.03 are excluded by default. If a gauged assessment is required and the site of interest is urban it can be included by setting iug = TRUE. In which case the user may wish to de-urbanise the subject site's Lcv and Lskew (L-moment ratios) by setting DeUrb = TRUE. If the user has more data available for a parcticular site within the pooling group, the Lcv and Lskew for the site can be updated after the group has been finalised. An example of doing so is provided below. The pooling method is outlined in Science Report: SC050050 - Improving the FEH statistical procedures for flood frequency estimation.

Examples

#Get some catchment descriptors
CDs.73005 <- GetCDs(73005)
#Set up a pooling group object called Pool.73005 excluding sites 79005 & 71011.
#Then print the group to the console
Pool.73005 <- Pool(CDs.73005, exclude = c(79005, 71011))
Pool.73005
#Form a pooling group, called PoolGroup, with the catchment descriptors specifically
PoolGroup <- Pool(AREA = 1000, SAAR = 800, FARL = 1, FPEXT = 0.01)
#Form a pooling group using an urban catchment which is intended for enhanced
#single site estimation - by including it in the group.
CDs.39001 <- GetCDs(39001)
Pool.39001 <- Pool(CDs.39001, iug = TRUE, DeUrb = TRUE)
#Change the Lcv and LSkew of the top site in the pooling group to 0.19 & 0.18,
#respectively. Lcv and Lskew are in columns 16 & 17.
Pool.39001[1,c(16, 17)] <- c(0.19, 0.18)