FIRE EFFECTS GUIDE - National Wildfire Coordinating Group

western Montana (DeByle and Packer 1972) found that sediment returned to
preburn levels after about four years. Erosion rates in the Montana study remained
below 0.01 tons per acre per year throughout the study.
Methods for mitigating accelerated sedimentation due to fire have not been fully
developed. Sedimentation may be reduced by the protection of steep slopes,
retention of wide buffers along water courses, rapid revegetation, the presence of
residual fuel and duff, and the exclusion of use until recovery.
Fire may induce sudden changes in water chemistry. Such changes probably
result from nutrients that are carried into water courses from burned areas.
Typically, several forms of nitrogen, phosphorus, and most cations show increases
in stream water after burning (Tiedemann et al. 1979). Chemistry is most often
altered during the first few storms following fire. Changes include increases in
bicarbonates, nitrates, ammonium, and organic nitrogen (Chandler et al. 1983).
These nutrients usually are not hazardous to humans but may contribute to
eutrophication or algal blooms. Water quality typically returns to preburn levels
within one to two years. Some fire retardant chemicals used during fire
suppression may be toxic to aquatic animals; the addition of these chemicals near
or in water courses should be avoided until specific consequences are clarified.
Stream temperatures also often increase after fire occurs. Usually the temperature
increase is due to the removal of overhead protective vegetation rather than direct
heat flux from the fire. Elevated stream temperatures are detrimental to most cold
water fish species. Therefore, protection of streamside vegetation, and quick
revegetation of burned areas, are critical to stream rehabilitation.
C. Resource Management Considerations
1. Expertise on Interdisciplinary (I. D.) Teams. Expertise in soils and hydrology
is required on interdisciplinary teams.
a. A soil scientist, knowledgeable about fire effects, should be assigned to
interdisciplinary teams involved with fire prescription development, site selection,
emergency fire rehabilitation projects, and wildland fire suppression activities.
b. A hydrologist should be assigned to the I.D. team, or at least consulted, if wild
or prescribed fire might affect water quality, on or off-site.
2. Statistical Analysis. Statistical analysis is necessary to assess the effects of
fire on soils and hydrology.
a. Physical and chemical characteristics of soils typically are extremely variable.
Fire effects can vary significantly around a site because of differences in the
amount of soil heating. A biometrist or statistician should be consulted before any
sampling is undertaken.