- Copyright © 2017, Environmental & Engineering Geoscience
Compilation of a database of debris-flow peak discharges (Q) allowed for a comparison with the expected basin discharge as computed using the rational equation, Q=CIA. The observed values of Q for debris flows in unburned and burned areas were divided by the computed Q values of runoff using the rational method. This ratio is the bulking factor for that debris-flow event. Unburned and burned basins constitute two distinct populations, analysis shows that the bulking factors for burned areas are consistently higher than unburned basins. Previously published bulking factors for unburned areas fit the dataset in about 50% of the observed cases in our compiled dataset. Bulking factors for burned areas that were found in the published literature were well below the observed increases in peak discharge in over 50% of the cases investigated. If used for design purposes , these bulking factors would result in a significant underestimation of the peak discharge from a burned basin for the given rainfall intensity. Peak discharge bulking rates were found to be inversely related to basin area.