The Standard Rational method produces a triangular runoff hydrograph that gives the peak inflow at time = Tc and falls to zero flow at time = 2xTc. This hydrograph represents a storm whose duration equals …

The runoff volume from the pre-development hydrograph is subtracted from each of the runoff volumes (areas under the Trapezoid), for each storm duration. The greatest difference in volume between the …

Mar 2, 2020 · Method Description: The Modified Rational Method can estimate peak flows at critical points in basins with numerous subbasins. The Modified Rational Method can give a triangular and …

Jun 18, 2025 · The Rational Routing Model is a triangular Unit Hydrograph Routing Model with the following characteristics: Tp (Time of Peak): Equal to Tc (Time of Concentration)

The rational formula is one of the oldest and most commonly used methods to predict peak flows. It was originally used to estimate peak flows only, but a triangular shaped hydrograph has also been used …

Aug 26, 2021 · FHWA HDS 2 proposes a simple way to calculate the required storage volume using triangular shape hydrograph of modified rational method as shown in Figure 3A, in which the …

The recurrence frequencies of rainfall intensities and durations provide the basis for the Rational Method computation of peak discharge using the Intensity-Duration-Frequency (IDF) Curves. Linear …

Using the Modified Rational method and running it with the Static Runoff Type will return: A triangular hydrograph if the Duration of Peak is equal to the Time of Concentration.

The Rational method is appropriate for estimating peak discharges for small drainage areas of up to about 200 acres (80 hectares) with no significant flood storage. The method provides the designer …

Sep 27, 2007 · The Rational Method has been applied to the estimation of runoff volume by assuming a hydrograph of a specific shape (NRCS/SCS, triangular, etc) and fitting the hydrograph to the peak …