QMED {UKFE}

QMED (median annual maximum flow) estimate from catchment descriptors

Description

Estimated median annual maximum flow from catchment descriptors and donor sites

Usage

QMED(
  CDs = NULL,
  Don1 = NULL,
  Don2 = NULL,
  UrbAdj = FALSE,
  DonUrbAdj = FALSE,
  AREA,
  SAAR,
  FARL,
  BFIHOST,
  URBEXT2000 = NULL
)

Arguments

CDs

catchment descriptors derived from either GetCDs or CDsXML

Don1

numeric site reference for the a single donor (for donor candidates see DonAdj function)

Don2

vector of two site references for two donors (for donor candidates see DonAdj function)

UrbAdj

logical argument with a default of FALSE. True applies an urban adjustment

DonUrbAdj

logical argument with a defailt of FALSE. If TRUE, an urban adjustement is applied to the donor/s QMEDcds estimate.

AREA

catchment area in km2

SAAR

standard average annual rainfall (mm)

FARL

flood attenuation from reservoirs and lakes

BFIHOST

baseflow index calculated from the catchment hydrology of soil type classification

URBEXT2000

measure of catchment urbanisation

Details

QMED is estimated from catchment descriptors: QMED = 8.3062*AREA^0.8510 0.1536^(1000/SAAR) FARL^3.4451 0.0460^(BFIHOST^2) as derived in Science Report: SC050050 - Improving the FEH statistical procedures for flood frequency estimation. The single donor method is from the same paper. The method for two donors is outlined in 'Kjeldsen, T. (2019). Adjustment of QMED in ungauged catchments using two donor sites. Circulation - The Newsletter of the British Hydrological Society, 4'. When UrbAdj = TRUE, urban adjustment is applied to the QMED estimate according to the method outlined in the guidance by Wallingford HydroSolutions: 'WINFAP 4 Urban Adjustment Procedures'. Urban donors should be avoided, but in the case that the subject catchment is rural, and the donor is urban, the QMEDcd estimate of the donor (or donors) can be urban adjusted by setting the DonUrbAdj argument to TRUE. For flexibility there is the option to input the relevant catchment descriptors directly rather than a CDs object.

Value

An estimate of QMED from catchment descriptors. If two donors are used the associated weights are also returned

Author(s)

Anthony Hammond

Examples

#Get some catchment descriptors and calculate QMED as if it was ungauged, with
#no donors, one donor, and two donors
CDs.55004 <- GetCDs(55004)
QMED(CDs.55004)
QMED(CDs.55004, Don1 = 55012)
QMED(CDs.55004, Don2 = c(55012, 60007))
#Get CDs for urban gauge and calculate QMED with urban adjustment
CDs.27083 <- GetCDs(27083)
QMED(CDs.27083, UrbAdj = TRUE)