profile_chi: Compute chi parameter along a single river

In VincentGodard/gtbox: A Geomorphology Toolbox With Various Functions For The Analysis of Topography and Surface Processes

Compute chi parameter along a single river

Description

Compute chi parameter along a single river

Usage

profile_chi(area, distance, aref, mn)

Arguments

area	drainage area (m2)
distance	distance along stream (m)
aref	reference drainage area (m2)
mn	m/n ratio

Value

a vector (same length as the inputs) with chi values along the river

Examples

# get river data
# see DEM processing vignette for example of the extraction of such data from a DEM
data("rivers_cevennes",package = "gtbox")

# get DEM (for plotting)
data("dem_cevennes",package = "gtbox")
dem = rast(dem_cevennes)
rm(dem_cevennes)

df = rivers_cevennes[rivers_cevennes$river==1,] # select a river
df = df[order(df$dist),] # order data according to distance along river
df$area = df$acc*30^2 # compute drainage area
df$chi = profile_chi(df$area,df$dist,aref=1000,mn=0.5) # compute chi
df$z2 = profile_smooth(df$dist,df$z,span=0.1,radius=10e3) # smooth profile
df$z3 = profile_gaussian(df$dist,df$z2,span=0.1,sigma=500) # filter profile
df$gradient = profile_gradient(df$dist,df$z3,window=200) # compute gradient

par(mfrow=c(2,2))
plot(dem)
lines(df$x,df$y,lwd=3,col="blue")
par(mar = c(4,4,0.5,0.5))
plot(df$dist,df$z,type="l",xlab="Distance along river (m)",ylab="Elevation (m)")
lines(df$dist,df$z2,col="firebrick")
lines(df$dist,df$z3,col="dodgerblue")
legend("topleft",c("Raw","Smoothed","Filtered"),lty=1,col=c("black","firebrick","dodgerblue"))
plot(df$dist,df$gradient,type="l",xlab="Distance along river (m)",ylab="Gradient (m/m)")
plot(df$chi,df$z,type="l",xlab="Chi (m)",ylab="Elevation (m)")

VincentGodard/gtbox documentation built on Sept. 4, 2022, 3:46 a.m.