What Are Post-Fire Debris-Flows? Do not require a discrete source of material (e.g. landslide), with a significant percentage of material originating from shallow erosion. Impact constrained to gullies, stream channels and immediately adjacent areas. Probability of occurrence not empirically related to antecedent moisture conditions. Volume and velocity have been experimentally linked via flume studies to antecedent moisture conditions, but not yet empirically demonstrated.
Recent Advances in Post-Fire Debris-Flow Hazard Assessment at
the U.S. Geological Survey Dennis M. Staley, Jason W. Kean, Greg M.
Smoczyk, Jacqueline A. Negri U.S. Geological Survey, Landslide
Hazards Program, Golden CO USA What Are Post-Fire Debris-Flows?
Initiate from surface runoff and erosion processes. Progressive
entrainment of sediment. Often exhibit evidence of both debris-flow
and flood processes. What Are Post-Fire Debris-Flows? Do not
require a discrete source of material (e.g. landslide), with a
significant percentage of material originating from shallow
erosion. Impact constrained to gullies, stream channels and
immediately adjacent areas. Probability of occurrence not
empirically related to antecedent moisture conditions. Volume and
velocity have been experimentally linked via flume studies to
antecedent moisture conditions, but not yet empirically
demonstrated. What Are Post-Fire Debris-Flows? Measured
debris-flows are generated within minutes after the start of
intense rainfall. Average time lag between recorded debris-flows
and 15-minute rainfall intensity is 0 minutes! First indication of
flow is often a major surge. Challenges for debris-flow
early-warning. What Arent Post-Fire Debris-Flows? May 2014 West
Salt Creek Landslide, Collbran CO Photo courtesy of Mesa County, CO
USGS Assessment Products - Past BAER Teams, NWS, and other
stakeholders use these maps for emergency planning and warning
Feedback from stakeholders Need digital geo-spatial data for
planning, not just a paper map. Need maps as soon as possible after
burn severity available (days after fire) Want assessments for more
than just a handful of fires every year Lesson Learned: Paper maps
and reports were not all that useful! USGS Assessment Products -
Present Feedback: Need digital geo-spatial data for planning, not
just a paper map. Interactive map Improvement: Interactive map
(casual users) and geospatial data (advanced users) are available
on website. USGS Assessment Products - Present Interactive Map Zoom
In / Out } Toggle Layers USGS Assessment Products - Present
Interactive Map USGS Assessment Products - Present Interactive Map
USGS Assessment Products - Present Feedback: Need digital
geo-spatial data for planning, not just a paper map. GIS files for
download Improvement: Interactive map (casual users) and geospatial
data (advanced users) are available on website. USGS Assessment
Products - Present Geospatial Data Basin-scale Predictions
(Polygons) Segment-scale Predictions (Lines) USGS Assessment
Products - Present Feedback: Need maps as soon as possible after
burn severity available (days after fire) Improvement: Leverage the
methods, tools and approach developed by USGS Earthquake Hazards
Program for online products (PAGER, ShakeMap, etc.) to rapidly
disseminate online assessments Typical OFR Timescale Web-based
Timescale (French Fire, CA) USGS Assessment Products - Present
Feedback: Need maps as soon as possible after burn severity
available (days after fire) Improvement: Leverage the methods,
tools and approach developed by USGS Earthquake Hazards Program for
online products (PAGER, ShakeMap, etc.) to rapidly disseminate
online assessments USGS Assessment Products - Present Feedback:
Increased Demand Number of hazards assessments conducted by year *
2007 Volume Maps Only # of assessments Move to the web 2015 More
anticipated in 2015 as word spreads, 28 so far 2014: More
assessments done in more states than any other year These hazards
assessments are now a standard operational product of the USGS
Landslide Hazards Program Insufficient time/$ to respond to fires
in these years * USGS Assessment Products Future (Near Term) More
Information: Google Us! post fire debris flow Citations: Cannon,
S.H., et al., Predicting the probability and volume of postwildfire
debris flows in the intermountain western United States. Geological
Society of America Bulletin 122, Gartner, J.E., et al., Empirical
models for predicting volumes of sediment deposited by debris flows
and sediment-laden floods in the transverse ranges of southern
California. Engineering Geology 176, Kean, J. W., et al "In situ
measurements of post-fire debris flows in southern California:
Comparisons of the timing and magnitude of 24 debris-flow events
with rainfall and soil moisture conditions." J. Geophys. Res.
116(F4): F Kean, J. W., et al "A low-cost method to measure the
timing of post-fire flash floods and debris flows relative to
rainfall." Water Resources Research 48(5): W Kean, J. W., et al
"Runoff-generated debris flows: Observations and modeling of surge
initiation, magnitude, and frequency." Journal of Geophysical
Research: Earth Surface 118(4): 2013JF Staley, D.M., Kean, J.W.,
Cannon, S.H., Schmidt, K.M., Laber, J.L., Objective definition of
rainfall intensityduration thresholds for the initiation of
post-fire debris flows in southern California. Landslides 10,
Staley, D. M., et al "Characterizing the primary material sources
and dominant erosional processes for post-fire debris-flow
initiation in a headwater basin using multi-temporal terrestrial
laser scanning data." Geomorphology 214(0): Contact Info:Phone:
Phone: Website: More Information: URL, Citations, Contact Info
