flood.length.max {hydrostats}

Calculates the maximum flood length in a time series.

Description

Calculates the maximum flood length above a user defined threshold in a time series. Used with ddply (from the plyr package) it can be used to return a vector of maximum flood lengths for multiple gauges or for multiple years (see examples). Alternatively, the function high.spell.lengths can be used to return the length of all events above a threshold.

Usage

flood.length.max(flow.ts, threshold, ind.days = 5)

Arguments

flow.ts

Dataframe with date and discharge data in columns named "Date" and "Q" respectively. Date must be in POSIX format (see ts.format)

threshold

A user supplied threshold for defining spells. This would typically be derived from hydraulic models or similar knowledge pertaining to a gauge site

ind.days

Periods between spells of less than ind.days (default 5) are considered to be 'in spell' for the purpose of further calculations. A value of 0 means spells 1 day apart are considered indpedendent

Value

A dataframe with one column (flood.length.max).

Author(s)

Nick Bond <[e-mail]>

Examples

data(Cooper)
Cooper<-ts.format(Cooper)

flood.length.max(Cooper, threshold = 50000, ind.days = 5)

# Return annual maximum flood length based on calendar year using ddply (from plyr package) 
require(plyr)
Cooper$Year=format(Cooper$Date, format="%Y")
ddply(Cooper, .(Year), flood.length.max, threshold = 50000)

require(dplyr)
Cooper %>%
dplyr::group_by(Year) %>%
dplyr::do(flood.length.max(., threshold = 50000))


# Based on hydrologic year.
Cooper<-hydro.year(Cooper)
plyr::ddply(Cooper, .(Year), flood.length.max, threshold = 50000)