A low-cost method to measure the timing of post-fire flash floods and debris flows relative to rainfall

Water Resources Research
By: , and 



Data on the specific timing of post-fire flash floods and debris flows are very limited. We describe a method to measure the response times of small burned watersheds to rainfall using a low-cost pressure transducer, which can be installed quickly after a fire. Although the pressure transducer is not designed for sustained sampling at the fast rates ({less than or equal to}2 sec) used at more advanced debris-flow monitoring sites, comparisons with high-data rate stage data show that measured spikes in pressure sampled at 1-min intervals are sufficient to detect the passage of most debris flows and floods. Post-event site visits are used to measure the peak stage and identify flow type based on deposit characteristics. The basin response timescale (tb) to generate flow at each site was determined from an analysis of the cross correlation between time series of flow pressure and 5-min rainfall intensity. This timescale was found to be less than 30 minutes for 40 post-fire floods and 11 post-fire debris flows recorded in 15 southern California watersheds ({less than or equal to} 1.4 km2). Including data from 24 other debris flows recorded at 5 more instrumentally advanced monitoring stations, we find there is not a substantial difference in the median tb for floods and debris flows (11 and 9 minutes, respectively); however, there are slight, statistically significant differences in the trends of flood and debris-flow tb with basin area, which are presumably related to differences in flow speed between floods and debris flows.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title A low-cost method to measure the timing of post-fire flash floods and debris flows relative to rainfall
Series title Water Resources Research
DOI 10.1029/2011WR011460
Volume 48
Issue 5
Year Published 2012
Language English
Publisher AGU
Publisher location Washington, D.C.
Contributing office(s) Geologic Hazards Science Center
Description W05516
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Water Resources Research