Gradex method

{
  "id": "MLC-T-MET-006015",
  "term": "Gradex method",
  "field": "Meteorology and atmospheric science",
  "definition": "A hydrological method, proposed in France by Guillot and Duband in the late 1960s, for estimating the frequency of very rare floods by extrapolating beyond the observed record. Past a pivot return period of roughly ten years or more, it assumes the catchment is saturated, so extra rainfall runs off in full and the flood volume distribution gains the same slope as the rainfall distribution on a Gumbel plot, called the gradex. It is applied to dam spillway design.",
  "url": "https://mlchart.com/terminology/meteorology/gradex-method/"
}