WMS:Rational Method Computing Hydrographs

Rational Method Hydrographs dialog

The Rational Method equation is designed to compute peak flows. However, a hydrograph, based on the peak flow and basin (or outlet) time of concentration, can be computed using one of five different unit hydrographs. Furthermore, there are two different methods (traditional and route by summing) hydrographs can be computed at confluence points.

The Rational Method Hydrographs dialog is used to specify the dimensionless unit hydrograph method, and the way hydrographs at outlets are computed. The dialog can be accessed through the Rational Method dialog. Options include:

• Traditional method – Computes a peak flow at an outlet by determining composite C, t_c, and areas from upstream basins and tributaries.
• Route by summing – Computes peak flows and hydrographs for basins in the traditional manner, but hydrographs at outlet points are determined by combining or summing the hydrographs from upstream basins and tributaries.
• Hydrographaph computation method
  • "Rational Hydrograph"
  • "Modified Rational Hydrograph" – When this option is chosen, the following options need to be defined.
    • Recession limb coefficient
    • Storm duration
  • "Dekalb Rational Hydrograph"
  • "Universal Rational Hydrograph"
  • "User Defined Rational Hydrograph"

Related Topics

• Rational Method Edit Parameters