R/utils.R

In FlowWest/cvpiaHabitat: Estimate Spawning and Rearing Habitat

#' WUA to Area in Square Meters
#' @description Function converts a Weighted Usable Area (WUA) to an
#' area in square meters by multiplying the WUA by the stream's length used by the species.
#' The lengths were obtained through expert outreach in 2017 and are available here
#'  \code{\link{watershed_lengths}}.
#' @param wua WUA in square feet per 1000 feet
#' @param watershed watershed
#' @param species species, "fr" - fall run or "sr" - spring run or "st" - steel head
#' @param life_stage life stage
wua_to_area <- function(wua, watershed_name,  life_stage, species_name) {
  stream_length <- dplyr::pull(dplyr::filter(cvpiaHabitat::watershed_lengths,
                                    watershed == watershed_name,
                                    species == species_name,
                                    lifestage == life_stage), feet)
  if (length(stream_length) == 0) {
    stream_length <- dplyr::pull(dplyr::filter(cvpiaHabitat::watershed_lengths,
                                               watershed == watershed_name,
                                               species == 'fr',
                                               lifestage == life_stage), feet)
  }

  ((stream_length/1000) * wua)/10.7639
}


#' Square Meters to Acres
#' @description Function converts area in square meters to area in acres
#' @param sq_meters area in square meters
#' @examples
#' hab_sq_meters <- set_instream_habitat('Merced River', 'fr', 'fry', 425)
#' square_meters_to_acres(hab_sq_meters)
#'
#' @export
square_meters_to_acres <- function(sq_meters) {
  sq_meters * 0.000247105
}

#' Acres to Square Meters
#' @description Function converts area in acres to area in square meters
#' @param acres area in square meters
#' @export
acres_to_square_meters <- function(acres) {
  acres / 0.000247105
}

#' Duration of Floodplain Inundation
#' @description Function returns number of weeks of floodplain inundation given a flow for a watershed
#' @param ws name of CVPIA watershed
#' @param flow_cfs monthly mean flow in cubic feet per second
#' @return integer value for number of weeks
#' @export
#'
#' @details
#' These relationships between number of days inundated and the mean monthly flow
#' are stored in \code{\link{weeks_inundated}} and referenced by this function.
#' For watersheds without a defined relationship, a two week inundation duration is assumed.
#'
#' @examples
#' weeks_flooded('Yuba River', 900)
#'
weeks_flooded <- function(ws, flow_cfs) {

  flow_thresholds <- cvpiaHabitat::weeks_inundated[cvpiaHabitat::weeks_inundated$watershed == ws, 'flow_threshold']
  if (length(flow_thresholds) == 0) {
    return(2)
  }

  # select closest number of weeks inundated given flow without going over
  v <- flow_thresholds[!is.na(flow_thresholds)]
  number_of_weeks <- (0:4)[!is.na(flow_thresholds)]
  i <- which.min(abs(v - flow_cfs))
  closest_threshold_index <- ifelse(flow_cfs < v[i], i - 1, i)

  number_of_weeks[closest_threshold_index]
}