fld.frq: Flooding frequency
In VulnToolkit: Analysis of Tidal Datasets

Description Usage Arguments Details Value See Also Examples

Calculates the frequency of high tides flooding an elevation of interest.

1	fld.frq(z, ht, units = "percent")

`z`	elevation of interest
`ht`	a numeric vector of high tide levels
`units`	units for output. Default is `percent`; the proportion of tides flooding elevation `x`. Alternatively, `tides` will return the number of flooding tides in the dataset

Calculates the frequency of high tides flooding an elevation of interest.

value the number or percent of high tides in vec that fall above z

fld.dur

# get a dataset of high/low tides
HT.NL <- HL(level = NL_6min_2013[, 2], time = NL_6min_2013[, 1], tides = "H")
a <- fld.frq(z = 0.9117, ht = HT.NL[, 1], units = "tides") # number of flooding tides at MHW
a / length(HT.NL[, 1]) # flooding tides as a percentage of all tides in time period

fld.frq(0.9117, HT.NL[,1], units = "percent") # check 

b <- as.numeric((NL_6min_2013[nrow(NL_6min_2013), 1] - 
NL_6min_2013[1, 1])) / 365.242 # fraction of year covered by dataset

elev.frq <- data.frame(elev = seq(from = 0, to = 1.5, by = 0.005))

# error thrown if units = "tides" and length(x) > length(ht)
fld.frq(elev.frq$elev, HT.NL[, 1], units = "tides") 

# a work-around
elev.frq$frq <- fld.frq(elev.frq$elev, HT.NL[, 1], units = "percent") * 
length(HT.NL[, 1]) / b 

plot(elev.frq$frq ~ elev.frq$elev, pch = 19, 
ylab = "flooding frequency (tides per year)", xlab = "elevation (m; MLLW)")