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Post-Fire Peak Flow and Erosion Estimation ->
USGS Regression Methods
USGS Regression methods
The USGS Regression method
is the most commonly used post-fire runoff estimation method
by BAER team members (43%)
(Foltz and others 2008). The Department of Interior U.S. Geological Survey (USGS) has developed
a method to estimate magnitude and frequency of floods of both gaged and ungaged streams. The
flood-frequency relations at gaged and ungaged sites were developed for various hydologic regions
based on their stream gage records, basin characteristics, and numerous studies throughout the United
States. These flood-frequency relations are often called, and expressed as a form of, "USGS regression equations,"
since a regression analysis was used to develop the flood-frequency relations.
To use the USGS regression methods, you will need
StreamStats
or
USGS publications.
Input Requirement
To use the USGS Regression method, the following information is required:
- USGS Regression equations for the area of interests (burned sites);
- gaged data from the watershed of interests (if any);
- basin characteristics;
- design storm intensity, duration, and recurrence interval;
- size of high soil burn severity areas; and
- water repellency and surface runoff increase of high/moderate soil burn severity area.
Steps
- Find the USGS Regression equations for the area of interests.
- Collect the basin characteristics of burned areas.
- Collect information about the burned area,
such as percentage of high and moderate sil burn severity areas.
- Determine design/damaging storm, including
storm intensity, duration, and recurrence interval.
- Estimate pre-fire runoff assuming no fires and unburned area for the area of interest.
- Determine the
percent runoff increase for high and moderate soil burn severity area.
- Determine modifier that is defined as a ratio of
post-fire to pre-fire runnoff.
- Estimate post-fire runoff by multiplying the modifier and pre-fire
runoff (or use alternatives).
Advantages
The following were advantages to applying the USGS Regression method fo post-fire runoff and erosion estimation.
The USGS Regression Method:
- is applicable for estimating both pre- and post-fire peak flow;
- estimates peak flow, regardless of the storm duration and intensity;
- is appropriate for larger watersheds (>5 mi2);
- does not usually require detailed watershed information, such as soil and topography;
- is more accurate if gaged data is used from the watershed of interest; and
- is applicable to longer duration events, and snowmelt runoff events.
Disadvantages
the following were disadvantages to applying the USGS Regression method for post-fire runoff and erosion estimation.
- It does not estimate erosion.
- It does not consider post-fire debris flow/torrent.
- The user must find the adequate USGS Regression equations for the
watershed in the pre-fire condition.
- The user must find the adequate USGS Regression equations for the
watershed in the post-fire condition (if any).
- The user must determine the modifier, or the soil water
repellancy and post-fire runoff increase, for high and moderate burn severity areas.
- It uses only English units.
Example Results
The 2000 Skalkaho/Valley
Complex Fires in the Bitterroot National Forest, Montana
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).
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