RMRS - BAER Road Treatment Tools - USGS Regression Methods Example

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BAER Tools -> Post-Fire Road Treatment Tools -> Post-Fire Peak Flow and Erosion Estimation -> USGS Regression Methods -> Example

Example Results for USGS Regression Methods: the 2000 Skalkaho/Valley Complex Fires in the Bitterroot National Forest, Montana

The Bitterroot National Forest had the Skalkaho/Valley Complex fires in 2000, and had a 10 yr, 24 hour storm event on 1 September 2001. It was assumed that 1/3 of the high soil burn severity areas had soil water repellency and a 10-fold increase in surface runoff for the same year, and 1/6 of the areas for one year after the fires. USGS Regression method (Omang 1992) was used to calculate peak flows in the unburned condition (unpublished data, Story 2002). Observed and estimated peak flows are provided below.

Watershed	Acres	% high	Observed	Estimated	Estimated	Estimated
(Creek)		burn	Q₁₀	Q₁₀	Q₁₀	Q₁₀
			2001	unburned¹	burned	burned
					2000²	2001³
			(cfs)	(cfs)	(cfs)	(cfs)

Medicine Tree	4,918	30	307	102	173	⁴122
Doran	4,064	70	574	86	226	126
Lyman	3,975	15	485	84	113	92
Laird	6,222	60	613	125	300	175
Reimel (entire)	6,154	30	210	150	255	180
Maynard	3,395	60	377	89	214	125
Reimel	5,050	30	187	126	214	151
Camp	5,299	10	103	132	163	141
Cameron	21,844	20	282	381	559	432
Warm Spring	6,712	20	312	134	197	152

¹	from Omang (1992)
²	Assumed that 1/3 of the high soil burn severity areas have soil water repellency and a 10 times increase in surface runoff
³	Assumed that 1/6 of the high soil burn severity areas have soil water repellency and a 10 times increase in surface runoff
⁴	Estimated Medicine Tree Creek Q₁₀ in 2001
	=	(unburned Q₁₀)×(% high burn)×(1/6)×(10 times runoff increase) + (unburned Q₁₀)×(100% - % high burn)
	=	(102 cfs)×(30%)×(1/6)×(10) + (102 cfs)×(100% - 70%)
	=	122 cfs

REFERENCES

Omang, R. J. 1992. Analysis of the magnitude and frequency of floods and the peak-flow gaging network in Montana. Water-Resources Investigations Report 92-4048. Denver, CO: U.S. Geological Survey. 70 p.

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