velocity {transfR}

Streamflow velocity estimation

Description

Estimate streamflow velocity in average over the catchment.

Usage

velocity(hl, ...)

## Default S3 method:
velocity(hl, lagtime, method = "loire2016", ...)

## S3 method for class 'units'
velocity(hl, lagtime = NULL, method = "loire2016", ...)

## S3 method for class 'stars'
velocity(hl, ...)

## S3 method for class 'transfR'
velocity(hl, ...)

Arguments

hl

hydraulic length of class stars, matrix, vector or transfR. If no unit is provided, hl is assumed to be in [m].

...

further arguments passed to or from other methods

lagtime

lag time of the catchment. If no unit is provided, lagtime is assumed to be in [h].

method

character string describing the method to estimate the velocity. One of "loire2016" (default), "brittany2013" or "lagtime" (see details).

Details

Estimate the average streamflow velocity of the catchment from three different approaches. Method "lagtime" estimates the velocity from the ratio between the mean hydraulic length and the lag time of the catchment. Method "loire2016" estimates the velocity from a regression based on hydraulic length only:

a \cdot hl^b

where a=4.38e-4 and b=0.69 have been calibrated over the Loire river basin (de Lavenne et al. 2016). Method "brittany2013" used a similar regression calibrated for the French Brittany region where a=8.59e-4 and b=0.61 (de Lavenne 2013).

Value

A numeric value of class units, or if hl is a transfR object, the same transfR object incremented by the "uc" attribute.

References

de Lavenne A (2013). Modélisation hydrologique à base géomorphologique de bassins versants non jaugés par régionalisation et transposition d'hydrogramme. Ph.D. thesis, Agrocampus-Ouest Rennes. https://hal.inrae.fr/tel-02810356.

de Lavenne A, Skøien JO, Cudennec C, Curie F, Moatar F (2016). “Transferring measured discharge time series: Large-scale comparison of Top-kriging to geomorphology-based inverse modeling.” Water Resources Research, 52(7), 5555–5576. doi:10.1002/2016WR018716.

Examples

data(Oudon)
velocity(Oudon$hl[[1]], method = "loire2016")

object <- as_transfr(st = Oudon$obs, hl = Oudon$hl)
object <- velocity(object)
object$uc