The Galena Fire burned about 16,788 acres of primarily ponderosa pine forest during July 5-8, 1988, in the Black Hills area of South Dakota. The fire burned primarily within the Grace Coolidge Creek drainage basin and almost entirely within the boundaries of Custer State Park. A U.S. Geological Survey gaging station with streamflow records dating back to 1977 was located along Grace Coolidge Creek within the burned area. About one-half of the gaging station's 26.8-square-mile drainage area was burned. The drainage basin for Bear Gulch, which is tributary to Grace Coolidge Creek, was burned particularly severely, with complete deforestation occurring in nearly the entirety of the area upstream from a gaging station that was installed in 1989.
A study to evaluate effects of the Galena Fire on streamflow, geomorphology, and water quality was initiated in 1988. The geomorphologic and water-quality components of the study were completed by 1990 and are summarized in this report. A data-collection network consisting of streamflow- and precipitation-gaging stations was operated through water year 1998 for evaluation of effects on streamflow characteristics, including both annual-yield and peak-flow characteristics, which are the main focus of this report.
Moderately burned areas did not experience a substantial increase in the rate of surface erosion; however, severely burned areas underwent surficial erosion nearly twice that of the unburned areas. The sediment production rate of Bear Gulch estimated 8 to 14 months after the fire was 870 ft3/acre (44 tons/acre). Substantial degradation of stream channels within the severely burned headwater areas of Bear Gulch was documented. Farther downstream, channel aggradation resulted from deposition of sediments transported from the headwater areas.
The most notable water-quality effect was on concentrations of suspended sediment, which were orders of magnitude higher for Bear Gulch than for the unburned control area. Effects on several other water-quality constituents, such as organic carbon and nitrogen and phosphorus nutrient constituents, probably were influenced by the large concentrations of suspended matter that were documented in initial post-fire, storm-flow events. The first post-fire stormflow produced the highest measured concentrations of specific conductance, nitrogen, phosphorus, organic carbon, calcium, magnesium, potassium, manganese, and sulfate in the burned areas. For most constituents sampled, differences in concentrations between burned and unburned areas were no longer discernible within about 1 year following the Galena Fire.
The effects of the Galena Fire on annual-yield characteristics of Grace Coolidge Creek were evaluated primarily from comparisons with long-term streamflow records for Battle Creek, which is hydrogeologically similar and is located immediately to the north. Annual yield for Grace Coolidge Creek increased by about 20 percent as a result of the fire. This estimate was based on relations between annual yield for Grace Coolidge Creek and Battle Creek for pre- and post-burn periods. Many of the post-burn data points are well beyond the range of the pre-burn data, which is a source of uncertainty for this estimate.
Substantial increases in peak-flow characteristics for severely burned drainages were visually apparent from numerous post-fire field observations. Various analyses of streamflow data indicated substantial increases in peak-flow response for burned drainage areas; however, quantification of effects was particularly difficult because peak-flow response diminished quickly and returned to a generally pre-burn condition by about 1991. Field observations of vegetation and analysis of remotely sensed data indicated that establishment of grasses and forbs occurred within a similar timeframe. Comparison of pre-fire peak flows to post-1991 peak flows indicates that these grasses and forbs were equally effective in suppressing peak flows as the predominantly ponderosa pine forest was prior to the Galena Fire.
Numerous peak-flow events with small recurrence intervals occurred within burned areas through 1990. Peak-flow events for Bear Gulch during this period were about one to two orders of magnitude larger than corresponding peaks for a small control drainage located along Grace Coolidge Creek upstream from the burn area. The small peaks do not provide quantitative information applicable to estimation of peak-flow magnitudes for larger events, however. Peak-flow events for Bear Gulch that occurred during 1991-98 were generally similar to those for the control drainage. A short-term increase in peak-flow potential also was documented for the longer-term gaging station located along Grace Coolidge Creek; however, peak-flow response was less pronounced than for Bear Gulch, which had nearly complete deforestation within a much smaller drainage area.
Abstract
Introduction
Purpose and Scope
Acknowledgments
Description of Study Area
Climate
Hydrogeology
Land Use
Timber Management and Burn Characteristics
Timber Management
Burn Characteristics
Previous Investigations
Data Sets Considered and Hydrologic Considerations
Data Sets Considered
Precipitation Data
Streamflow Data
Hydrologic Considerations
Hydrologic Effects of the Galena Fire
Effects on Geomorphology and Water Quality
Effects on Streamflow Characteristics
Effects on Annual-Yield Characteristics
Effects on Peak-Flow Characteristics
Summary
References
Supplemental Information
Suggested Citation:
Driscoll, D.G., Carter, J.M., and Ohlen, D.O., 2004, Hydrologic effects of the 1988 Galena Fire, Black Hills area, South Dakota: U.S. Geological Survey Water-Resources Investigations Report 03-4323, 67 p.
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Send questions or comments about this report to the author, D.G. Driscoll (605) 355-4560 ext. 211.
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