R/coefficient_of_the_exponential_function_of_flow_increase.R

In FannyVille/hydroSEG: Hydrograph segmentation and discretization between natural event or hydropeak

#' coefficient_of_the_exponential_function_of_flow_increase
#' @description
#' *Courret (2014)* shows that in natural hydrology the rise and fall times of hydrographs follow an exponential law.
#' \eqn{Q= 4 * exp(-a * t^b)}
#' The value of the coefficient **a** can be expressed according to the module of the river.
#' This function give the **a** coefficient
#' @param Stream_Module A numeric value corresponding to the average inter annual flow rate ""module"".
#'
#' @return A number
#' @export
#'
#' @examples
#' coefficient_of_the_exponential_function_of_flow_increase(10)
coefficient_of_the_exponential_function_of_flow_increase <- function(Stream_Module) {
  if (Stream_Module <1) {
    return("Outside the limits of the method" )
  }
  else if (Stream_Module <= 50) {
    return(1/(0.0000257411*Stream_Module^3+0.00339408*Stream_Module^2+0.0371028*Stream_Module+0.422078))
  }
  else {
    return(1/(0.0000257411*50^3+0.00339408*50^2+0.0371028*50+0.422078))
  }
}