Derive and plot rainfall Depth Duration Frequency curves.
Source:R/RainfallAnalysis.R
DDFExtract.RdDerive and plot rainfall Depth Duration Frequency curves from an input of rainfall data.
Arguments
- x
A data.frame with POSIXct in the first column and rainfall in the second. The data must have an hourly or sub-hourly sampling rate.
- Plot
Logical argument with a default of TRUE. If TRUE, the DDF curves are plotted.
- main
Title for the plot (character string). The default is no title.
- Truncate
Logical argument with a default of TRUE. If TRUE the extraction of annual maximum process truncates the data to incorporate only full hydrological years. If there is significant rainfall within a partial year it will not be included unless Truncate = FALSE. If Truncate = FALSE, ensure that there are at least 92 hours of data available in the partial years or the function will fail.
Value
A dataframe with hours (1 to 96) in the first column then depths associated with a range of return periods (2 to 1000) in the remaining nine columns. If Plot = TRUE, a plot of the DDF curves is also returned.
Details
The function works by extracting the annual maximum sample (by hydrological year - starting Oct 1st) of rainfall for a range of sliding durations (1 hour to 96 hours). It then calculates the median annual maximum rainfall depth (RMED) and a GEV growth curve for each duration. To ensure RMED increases with duration a power curve is fit as a function of duration to provide the final RMED estimates. Then the average growth factor for each return period (across the durations) is assumed.
Examples
# Extract all available 15-minute rainfall from the St Ives (Cambridgeshire)
# rain gauge (WISKI ID = 179365).
if (FALSE) { # \dontrun{
st_ives <- GetDataEA_Rain(WISKI_ID = "179365", Period = "15Mins")
} # }
# Apply the DDF function.
if (FALSE) { # \dontrun{
DDFExtract(st_ives)
} # }