USDA Forest Service

United States Department of Agriculture Forest Service Enterprise Program
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Equivalent Roaded Acreage (ERA) Model Overview


The ERA Model was developed years ago. Today’s model has been refined and improved by continuously incorporating advances in GIS technology throughout the years. The ERA model called ERODA compiling GIS spatial data from hydrology, soils, harvest history, site preparation, fire history, range management, recreation, and mining history in a spreadsheet format.

Cumulative watershed effects such as mass wasting events (landslides) are known as a “threshold of concern”. A threshold of concern is established for each watershed based on the natural sensitivity index (NSI) spreadsheet that tracks the amount of sensitive areas within the watershed. including: Soils with a high erosion hazard rating, hydrological groups C and D, inner gorge areas, and the number of streams. The ERODA spreadsheet file compiles the information from various GIS intersects to account for timber harvests, site preparation, cultural treatments, transportation, range management, fire history, impervious areas, and watershed improvements. Additional spreadsheet tabs display the future threshold of concern conditions based on proposed project alternatives.

Because many Forest Service GIS datasets GIS layers often are clipped to the forest boundary, omit lands that are not national forest, or aren’t updated to current existing conditions, they are unable to complete a thorough ERA analysis.

TEAMS Offers the latest in ERA Analysis

TEAMS Enterprise Unit has developed a methodology to complete an ERA analysis in your project area that captures the full impact of all past, present, and future activities in all the watersheds. TEAMS GIS staff have successfully updated hundreds of watersheds with this methodology to provide NEPA planning teams with cutting edge current and future watershed conditions.

We create an integrated harvest history that combines FACTS with private timber harvests, older plantations, and remote sensing techniques to capture the past 30 years of known harvest history. What’s more, TEAMS will fill in the data gaps from other sources such as transportation networks outside national forest lands to account for all management activities.


TEAMS GIS staff can provide:

  • An integrated harvest layer showing Forest Service and private landowner timber harvests
  • ERA GIS layers for the project watersheds showing features such as transportation, range management, or fire history
  • ERODA spreadsheets showing the ERA values by year for all management activities occurring on the watershed for both existing and future conditions
  • Threshold of Concern spreasheets summarizing the TOC calculation derived for each watershed
  • Analysis review of the ERA model outputs by a TEAMS experienced hydrologist

Contact us today for a complimentary estimate!

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US Forest Service - TEAMS Enterprise Unit
Last Modified: Thursday, 17 September 2015 at 16:39:17 CDT

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