According to Wikipedia, an intensity–duration–frequency curve (IDF curve) is a mathematical function that relates the intensity of an event, such as rainfall, to its duration and frequency of occurrence. Frequency is the inverse of the probability of occurrence. These curves are commonly used in hydrology for flood forecasting and in civil engineering for urban drainage design. However, IDF curves are also analyzed in hydrometeorology due to interest in the time concentration or time structure of rainfall, and they can also be defined for drought events. Additionally, applications of IDF curves to risk based design are emerging outside hydrometeorology. For example, some authors have developed IDF curves for food supply chain inflow shocks to cities in the United States.