Premium
Amplification of postwildfire peak flow by debris
Author(s) -
Kean J. W.,
McGuire L. A.,
Rengers F. K.,
Smith J. B.,
Staley D. M.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl069661
Subject(s) - debris flow , surface runoff , debris , bedrock , hydrology (agriculture) , geology , flow (mathematics) , flood myth , drainage , environmental science , geomorphology , geotechnical engineering , mechanics , geography , ecology , oceanography , physics , archaeology , biology
In burned steeplands, the peak depth and discharge of postwildfire runoff can substantially increase from the addition of debris. Yet methods to estimate the increase over water flow are lacking. We quantified the potential amplification of peak stage and discharge using video observations of postwildfire runoff, compiled data on postwildfire peak flow ( Q p ), and a physically based model. Comparison of flood and debris flow data with similar distributions in drainage area ( A ) and rainfall intensity ( I ) showed that the median runoff coefficient ( C = Q p / AI ) of debris flows is 50 times greater than that of floods. The striking increase in Q p can be explained using a fully predictive model that describes the additional flow resistance caused by the emergence of coarse‐grained surge fronts. The model provides estimates of the amplification of peak depth, discharge, and shear stress needed for assessing postwildfire hazards and constraining models of bedrock incision.