UG_210_21_1 - UG 210-21-1 ENG – EFH-2, Version 2.0.1, Computer Program
UG 210-21-1 ENG – EFH-2, Version 2.0.1, Computer Program
User Guide: 210-21-1 Date: March 8, 2021
Subject: ENG – EFH-2, Version 2.0.1, Computer Program


 
 
Purpose.  To announce the availability of the Engineering Field Handbook, Chapter 2 (EFH-2), version 2.0.1, computer program and provide instructions for obtaining the software.
 
Effective Date.  Effective Upon Receipt   
 

Background.  NRCS uses Title 210, National Engineering Handbook, Part 650, “Engineering Field Handbook,” Chapter 2, “Estimating Runoff Volume and Peak Discharge” (210-NEH-650-2) to determine runoff volumes and peak discharge for small single subarea watersheds in the design of on-farm conservation practices.

Special Instructions. The updated National Oceanic and Atmospheric Administration (NOAA) Atlas 14 rainfall data and the new NRCS-developed rainfall distributions are incorporated into EFH-2 version 2.0.1. The NOAA Atlas 14 rainfall values are available within EFH-2 version 2.0.1 for all States except Arizona, California (Area 2 and Area 4), Idaho, Montana, New Mexico, Oregon, Utah, Washington State, and Wyoming.

EFH-2 version 2.0.1 no longer uses the COUNTY.ST and TYPE.RF files.

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 210-NEH-650-2. Instead, EFH-2 version 2.0.1 uses 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. As a result, EFH-2, WinTR-20, and WinTR-55 should now produce identical results given identical input information.

EFH-2 version 2.0.1 uses a dimensionless unit hydrograph (DUH) with a peak rate factor of 484 as a default. It is identified as <standard> in the drop-down menu. Users should use this default unless State guidance (found in State Supplements to 210-NEH-650-2) dictates otherwise.

Please note EFH-2 version 2.0.1 is not backward or forward compatible with previous EFH-2 versions designated as version 1.X.X. EFH-2 version 2.0.1 cannot read input or output data files developed using previous versions and vice-versa.

Distribution. EFH-2 version 2.0.1 was tested and CCE certified on February 26, 2021, for deployment to NRCS workstations running Windows 10 x64. The project reference number is RFC#CRQ3915417.

This directive cancels, deletes, and replaces the previous notification, “User Guide UG-210-15-4, ENG-EFH-2, Version 1.1.2, Computer Program”, dated December 4, 2014.

NRCS users may obtain the EFH-2 version 2.0.1 computer program through the “Software Center” application for installation on NRCS computers. Installing EFH-2 version 2.0.1 will uninstall previous versions. It is not possible to have multiple versions of EFH-2 installed on a single computer.

Filing Instructions. NRCS does not distribute printed copies of EFH-2 version 2.0.1 program documentation. The EFH-2 version 2.0.1 program contains program documentation and help files. Users wishing to retain program documentation can print paper copies and place it in a three-ring binder adjacent to other NRCS technical directive.  

 
 

Contact.  Direct questions and comments regarding software operation to appropriate State-level staff or to Quan D. Quan, Hydraulic Engineer, West National Technical Support Center, at 301-504-3952 or quan.quan@usda.gov.

Direct general questions regarding this user guide notification to Claudia C. Hoeft, National Hydraulic Engineer, Conservation Engineering Division, at 202-720-0772 or claudia.hoeft@usda.gov

 
 

 /s/

DIANE GELBURD
Deputy Chief for Science and Technology   

 
 
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