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BAER Tools -> Post-Fire Road Treatment Tools -> Post-Fire Peak Flow and Erosion Estimation -> Rule of Thumb by Kuyumjian -> Example

Example for Rule of Thumb: Rendija Canyon after the 2000 Cerro Grande Fire, New Mexico

Approximately 4.8 mi2 of the Rendija Canyon watershed were burned by the 2000 Cerro Grande Fire: 82% at high severity, 10% at moderate severity, 6% at low severity, and 2% was unburned (Gallaher and Koch 2004). Seven subwatersheds were monitored for rainfall intensity and discharge in 2001 and 2002 (Moody and others 2001). Four subwatersheds had 581 ± 5% of ΔNBR Differenced Normalized Burn Ratio) value that was considered high or moderate-high burn severity (Cocke and others 2005; Key and Benson 2006). The ΔNBR incorporates reflectance measurements from Landsat imagery and was designed to measure the fire effects on vegetation and soil characteristics. It is now the primary method for mapping large remote fires on public lands (Key and Benson 2006).

Assuming the entire drainage area was high severity burn area, peak flow per unit drainage area (cfs mi-2) can be calculated based on rainfall intensity (inch/h) that is greater than 0.5 inch. The Rule of Thumb by Kuyumjian estimated less than a half (47%) of peak flow within ± 50% of observed values, which can be from uncertainty associated with discharge and rainfall intensity measurements or natural variation that the Rule of Thumb cannot consider.

 

Watershed
Date
Rainfall intensity
Observed
Estimated
Number
I30
peakflow
peakflow1
per unit area
per unit area
(inch/h)
(cfs mile-2)
(cfs mile-2)

3
2 Jul
2.07
686
622
3
13 Jul
0.88
151
263
3
9 Aug
1.50
405
449
9
2 Jul
0.90
41
269
9
26 Jul
1.45
777
435
9
9 Aug
0.59
28
177
9
11 Aug
0.90
154
270
11
2 Jul
1.69
461
508
11
26 Jul
1.30
333
389
11
11 Aug
1.28
333
384
13
2 Jul
0.65
65
195
13
2 Jul
1.13
182
339
13
2 Jul
1.10
43
331
13
11 Jul
0.73
39
219
13
11 Aug
1.28
264
384

 

1 Bulking factor is not included for estimated peak flow calculation so that comparisons between observed and estimated peak flows can be made.

 

REFERENCES

Cocke, Allison E.; Fulé, Peter Z.; Crouse, Joseph E. 2005. Comparison of burn severity assessments using Differenced Normalized Burn Ratio and ground data. International Journal of Wildland Fire. 14(2): 189-198.

Gallaher, B. M.; Koch, R. J. 2004. Cerro Grande Fire impacts to water quality and stream flow near Los Alamos National Laboratory: Results of four years of monitoring. LA-14177. Springfield, VA: U.S. Department of Commerce, National Technical Information Service. 195 p.

Key, Carl H.; Benson, Nathan C. 2006. Landscape assessment: Sampling and analysis methods. In: Lutes, Duncan C., eds. FIREMON: Fire Effects Monitoring and Inventory System. Gen. Tech. Rep. RMRS-GTR-164-CD. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 1 CD.

Moody, John A.; Martin, Deborah A. 2001. Hydrologic and sedimentologic response of two burned watersheds in Colorado. Water-Resources Investigations Report 01-4122. Denver, CO: U.S. Geological Survey. 142 p.

 

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