Flow Net

Flow net diagram showing groundwater movement beneath a dam with flow lines and equipotential lines in a saturated aquifer

A flow net is a graphical representation of two-dimensional steady-state groundwater flow through aquifers. The construction of a flow net is commonly used to solve groundwater flow problems where analytical solutions are impractical due to complex geometry. It is widely applied in civil engineering, hydrogeology, and soil mechanics, particularly for analyzing seepage beneath hydraulic structures such as dams and sheet pile walls. A flow net consists of a grid formed by drawing a series of equipotential lines and flow lines, making it an important tool for analyzing two-dimensional irrotational flow problems. The flow net technique is therefore a graphical method used to represent and study groundwater flow behavior (Wikipedia).

Intensity-duration-frequency curve

Landscape IDF curve chart showing rainfall intensity versus storm duration for multiple return periods used in drainage design

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.