Burned Area Emergency Response Tools

Fire Enhanced Runoff and Gully Initiation (FERGI) Model

The FERGI model is used by a relatively small number of BAER team members in Region 4 (2%) (Foltz and others 2008). 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.

To use the FERGI model, you need to visit the FERGI model website .

Input Requirement

To use the FERGI model, the following information is required:

• location of three nearest weather stations selected from the FERGI input screen;
• depth to water repellent layer (mm);
• fractional water repellency (between 0 and 1);
• saturated hydraulic conductivity (mm h^-1);
• Slope (m m^-1);
• hillslope length;
• D₅₀ of soil surface (mm);
• storage capacity of barriers; and
• fraction of area trenched.

Steps

1. Visit the FERGI website (frames.nbii.gov/fergi).
2. Zoom to the area of interest.
3. Select each of the three weather stations.
4. Enter soil and hillslope parameters.

Advantages

The following were advantages to applying the FERGI for post-fire runoff and erosion estimation. FERGI:

• estimates rainfall excess, post-fire runoff, and gully length of a rectangular strip;
• provides an estimate of the effectiveness of contour felled logs/log barriers;
• is on-line accessible; and
• is, rocess-based and applicable to the western United States.

Disadvantages

The following were disadvantages to applying the FERGI for post-fire runoff and erosion estimation. FERGI:

• does not provide pre-fire rainfall excess, runoff amount, and gully initiation positions;
• does not estimate erosion;
• does not consider post-fire debris flow/torrent;
• is available only for Forest Service intranet;
• requires detailed soil parameter information;
• does not consider watershed shapes;
• considers only 24-hour storm duration; and
• uses only metric units.

Example Results

None

REFERENCES

Foltz, Randy B.; Robichaud, Peter R.; Rhee, Hakjun. 2008. A synthesis of post-fire road treatments for BAER teams: methods, treatment effectiveness, and decision-making tools for rehabilitation. Gen. Tech. Rep. RMRS-GTR. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station (in preparation).

Istanbulluoglu, Erkan; Tarboton, David G.; Pack, Robert T.; Luce, Charles. 2002. A probablistic approach for channel initiation. Water Resources Research. 38(12): 1325.

Istanbulluoglu, Erkan; Tarboton, David G.; Pack, Robert T.; Luce, Charles. 2003. A sediment transport model for incision of gullies on steep topography. Water Resources Research. 39(4): 1103.

Istanbulluoglu, Erkan; Tarboton, David G.; Pack, Robert T.; Luce, Charles. 2004. Modeling of the interactions between forest vegetation, disturbances, and sediment yields. Journal of Geophysical Research. 109: F01009.

Luce, Charles H. (2001 September 5-copyright date). FERGI: Fire Enhanced Runoff and Gully Initiation model [Homepage of FERGI], [Online]. Available: frames.nbii.gov/fergi [2010 September 8].

Luce, Charles H.; Tarboton, David G.; Istanbulluoglu, Erkan; Pack, Robert T. 2005. Reply to comment by Jonathan J. Rhodes on "Modeling of the interactions between forest vegetation, disturbances, and sediment yields". Journal of Geophysical Research. 110: F01013.

Luce, Charles. 2005. Land use and land cover effects on runoff processes: fire. Encyclopedia of Hydrological Sciences. 13: 1831-1837.

Rajagopalan, B.; Lall, U. 1999. A k-nearest-neighbor simulator for daily precipitation and other weather variables. Water Resources Research. 35(10): 3089-3101.

Rhodes, Jonathan J. 2005. Comment on "Modeling of the interactions between forest vegetation, disturbances, and sediment yields" by Erkan Istanbulluoglu and others. Journal of Geophysical Research. 110: F01012.

Shakesby, R. A.; Doerr, S. H.; Walsh, R. P. D. 2000. The erosional impact of soil hydrophobicity: current problems and future research directions. Journal of Hydrology. 231-232: 178-191.

USDA Forest Service - RMRS - Moscow Forestry Sciences Laboratory
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