Time-area method
This is a form of catchment routing model in which a hyetograph of rainfall is combined with a time-area diagram to produce a flow hydrograph. All of these must use the same time step, Dt. The procedure effectively divides a catchment into a number of strips of land, and superimposes the individual flows from these sub-areas, allowing for time lags depending on their distance from the outlet.
This method can be employed with various loss models. In the Horton (ILSAX) hydrological model, the time-area diagram is considered to be a triangular shape, with the increase in area per time step being constant.
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