topdist: Distributes soil moisture by topographic wetness

In ilyamaclean/ecohydrotools: hydrogical modelling for ecological applications with R

Description

topdist distributes soil moisture, typically within a basin, by the topograhic wetness index of each basin grid cell

Usage

topdist(tx, sm, p = 0.25, Smin = 0.091, Smax = 0.419)

Arguments

tx	a vector or marix of topographic wetness index values
sm	a single numeric value of the mean soil water fraction
p	a single numeric value of to power adjustment to apply to topographic wetness index values (see details)
Smin	a single numeric value of the residual soil water fraction (see soilparams())
Smax	a single numeric value of the saturated soil water fraction (see soilparams())

Details

the coefficient p scales the relationship between topographic wetness and the distribution of soil moisture values. If p = 1, soil moisture is strongly concentrated in cells with a high topographic wetness. If p = 0, soil moisture is evenly distributed across the basin. The correct choice of p depends on sub-grid scale variation in topographic wetness, and on complex lateral flows, and thus best determined empirically, by measuring soil moisture across a catchment. A choice of 0.25 for surface soil layers and 0.15 for sub-surface soil layers is likely to provide a reasonable approximation.

Value

a vector or matrix of soil moisture values of each grid cell of tx

See Also

topidx(), soilparams()

Examples

library(raster)
tpx <- topidx(dtm100m)
tp1 <- topdist(is_raster(tpx), 0.3, p = 0.25)
tp2 <- topdist(is_raster(tpx), 0.3, p = 0.15)
# NB - not distributed by basin
plot(if_raster(tp1, dtm100m))
plot(if_raster(tp2, dtm100m))

ilyamaclean/ecohydrotools documentation built on June 10, 2019, 5:45 a.m.