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Burned Area Emergency Response Tools
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Details of FERGI Model
The FERGI model was developed by the U.S. Forest Service's Rocky Mountain Research Station, Boise Aquatic Sciences Lab (Luce 2001), and is based on several scientific research papers (Istanbulluoglu and others 2002; Istanbulluoglu and others 2003; Istanbulluoglu and others 2004; Luce 2005; Luce and others 2005; Rajagopalan and Lall 1999; Rhodes 2005; Shakesby and others, 2000). The FERGI model is a physically-based mathematical description of hillslope hydrologic and geomorphic response to a set of weather events, and the model is applicable to any part of the western United States. FERGI estimates the probability of post-fire rainfall excess (mm), runoff generation amount (m3 s-1 m-1), and gully initiation positions (m) on hillslopes with and without mitigations using contour felled logs/log barriers.
The FERGI model reports on the following:
This output is provided as graphs (percent reduction of rainfall excess, hillslope runoff, and gully length) and tables of text file.
Users can choose three nearest weather stations, which are wind, rainfall intensity, and COOP (Cooperative Weather Program; NOAA 2006) stations.
The proportion of the area that is underlain by water repellent soils after a fire.
Average length of hillslope before flow begins to accumulate into channels.
The amount of precipitation that can be stored by the barriers, i.e., the volume of water storage behind barriers divided by the total area over which the measured barriers are applied.
The total length of scalping times the width of scalped area divided by the total area of the site.
The model results are based on a rectangular strip with unit width.
The model provides the effectiveness as a function of storm return periods.
No pre-fire results are available; therefore, users cannot compare pre- and post-fire changes.
FERGI assumes a rectangular hillslope.
FERGI considers only 24-hour storm duration; therefore, it is not applicable to the regions where the damaging storm duration is much shorter, such as 15 or 30 minutes.
USDA Forest Service - RMRS - Moscow Forestry Sciences