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EFH-2 Estimating Runoff Volume and Peak Discharge

The EFH-2, version 2.0.1 (February 2021) software implements the procedures described in Title 210, National Engineering Handbook 650 - Engineering Field Handbook, Chapter 2 (EFH-2), "Estimating Runoff Volume and Peak Discharge".  Required information includes watershed characteristics (drainage area, runoff curve number, watershed length, and watershed slope), rainfall amount and rainfall distribution.  The NOAA Atlas 14 rainfall values are not available for Arizona, California (Area 2 and Area 4), Idaho, Montana, New Mexico, Oregon, Utah, Washington State and Wyoming. 

In addition, EFH-2, version 2.0.1 no longer uses the unit peak discharge curves used for manual development of peak discharge as described in NEH 650 - Engineering Field Handbook, Chapter 2 (210-NEH-650-2).  Instead, EFH-2, version 2.0.1 uses the procedures described in 210-NEH-630, “Hydrology” to compute full hydrographs and report the peak discharge.  To accomplish this, EFH-2, version 2.0.1 uses the TR-20 computational engine common to both the WinTR-20, “Project Formulation Hydrology” and WinTR-55, “Small Watershed Hydrology” computer programs.  This necessitates the user select a dimensionless unit hydrograph (DUH) within EFH-2, version 2.0.1;  the default is the 484 DUH (designated as "" in the drop-down menu).

This program has restricted applications.  It may be applied when: 

  • Watershed is accurately represented by a single runoff curve number between 40 and 98.
  • Watershed area is between 1 and 2,000 acres.
  • Watershed length is between 200 and 26,000 feet.
  • Average watershed slope is between 0.5 and 64%.
  • No valley or reservoir routing is required.
  • Urban land use within the watershed does not exceed 10%.


Downloads

  EFH-2, Ver.2.0.1  (January 2021)

  EFH-20 User's Manual (under revision)

  EFH-2 User Guide

 

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