Postwildfire preliminary debris flow hazard assessment for the area burned by the 2011 Las Conchas Fire in north-central New Mexico

Tillery, Anne C.; Darr, Michael J.; Cannon, Susan H.; Michael, John A.

doi:10.3133/ofr20111308

Cited by 8 publications

(9 citation statements)

References 3 publications

(3 reference statements)

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“…In June and July of 2011, the Las Conchas fire burned 63 400 ha in the Jemez Mountains. At the time, it was the largest fire in New Mexico state history, and burned over areas previously burned by the Dome fire of 1996 and the Cerro Grande fire of 2000 (Tillery et al 2011). Over 90% of the Frijoles Canyon watershed was burned, and the middle of the watershed was especially damaged with high-severity burns.…”

Section: Study Sitesmentioning

confidence: 99%

Risk assessment of post-wildfire hydrological response in semiarid basins: the effects of varying rainfall representations in the KINEROS2/AGWA model

Sidman

Guertin

Goodrich

et al. 2016

Int. J. Wildland Fire

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Representation of precipitation is one of the most difficult aspects of modelling post-fire runoff and erosion and also one of the most sensitive input parameters to rainfall-runoff models. The impact of post-fire convective rainstorms, especially in semiarid watersheds, depends on the overlap between locations of high-intensity rainfall and areas of high-severity burns. One of the most useful applications of models in post-fire situations is risk assessment to quantify peak flow and identify areas at high risk of flooding and erosion. This study used the KINEROS2/AGWA model to compare several spatial and temporal rainfall representations of post-fire rainfall-runoff events to determine the effect of differing representations on modelled peak flow and determine at-risk locations within a watershed. Post-fire rainfall-runoff events at Zion National Park in Utah and Bandelier National Monument in New Mexico were modelled. Representations considered included both uniform and Soil Conservation Service Type II hyetographs, applying rain over the entire watershed and applying rain only on the burned area, and varying rainfall both temporally and spatially according to radar data. Results showed that rainfall representation greatly affected modelled peak flow, but did not significantly alter the model’s predictions for high-risk locations. This has important implications for post-fire assessments before a flood-inducing rainfall event, or for post-storm assessments in areas with low-gauge density or lack of radar data due to mountain beam blockage.

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Section: Study Sitesmentioning

confidence: 99%

Risk assessment of post-wildfire hydrological response in semiarid basins: the effects of varying rainfall representations in the KINEROS2/AGWA model

Sidman

Guertin

Goodrich

et al. 2016

Int. J. Wildland Fire

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“…Dendrochronology studies in VCNP have documented a shift in the fire regime from frequent, low-severity wildfires before 1900 to larger, high-severity fires post-1900 (Dewar, 2011). The recurrence interval of wildfires in the pre-1900 era was in the range of two to 25 years based on fire-scar records (Touchan et al, 1996;Dewar, 2011). Large, standreplacing, high-severity fires have become more common in the modern (post-1900) era with recurrence intervals estimated to be on the order of hundreds of years (Touchan et al, 1996).…”

mentioning

confidence: 99%

How do sediment yields from post‐wildfire debris‐laden flows depend on terrain slope, soil burn severity class, and drainage basin area? Insights from airborne‐LiDAR change detection

Pelletier

Orem

2014

Earth Surf Processes Landf

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We derived a high‐resolution, spatially continuous map of erosion and deposition associated with the debris‐laden flows triggered by the 2011 Las Conchas wildfire and subsequent rainstorms over a 197 km2 area in New Mexico, USA. This map was produced using airborne‐LiDAR‐derived bare‐earth digital elevation models (DEMs) acquired approximately one year before and one year after the wildfire. Differencing of the pre‐wildfire and post‐wildfire‐and‐rainstorm bare‐earth DEMs yielded a DEM‐of‐difference (DoD) map that quantifies the magnitude of ground‐surface elevation changes due to erosion/deposition within each 1 m2 pixel. We applied a 0.3 m threshold filter to our DoD to remove changes that could have been due to artifacts and/or imperfect georeferencing. The 0.3 m value for the threshold filter was chosen based on the stated accuracy of the LiDAR as well as a comparison of areas of significant topographic change mapped in aerial photographs with those predicted using a range of candidate threshold values for the DoD filter. We developed an automated procedure that accepts the DoD map as input and computes, for every pixel in the DEM, the net sediment volume exported through each pixel by colluvial and/or fluvial processes using a digital routing algorithm. An analysis of the resulting sediment volume map for the Las Conchas fire demonstrates that sediment volume is proportional to upstream contributing area. After normalized by contributing area, the average sediment yield (defined as the sediment volume divided by the contributing area) increases as a power‐law functions of the average terrain slope and soil burn severity class (SBSC) with exponents equal to approximately 1.5. Our analysis quantifies the relationships among sediment yield, average terrain slope, and average soil burn severity class at the watershed scale and should prove useful for predicting the geomorphic response of wildfire‐affected drainage basins. Copyright © 2014 John Wiley & Sons, Ltd.

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“…The thresholds in gravel fraction for 0–1 cm depth and for silt + clay at 0–1 cm both correspond to transitions into high burn severity for the MTBS and BARC 4 thematic burn severity (Figure a,d; Table ). Prior work has documented elevated magnitudes of post wildfire overland flow generation and geomorphic response in the area affected by the 2011 Las Conchas Fire (Dahm et al, ; ICMN, ; NPS, ; Orem & Pelletier, ; Pelletier & Orem, ; Reale et al, ; Sherson et al, ; Tillery et al, ). Hydraulic erosion associated with the elevated surface runoff generation preferentially erodes finer silt and clay size particles, leaving an armoured surface lag with coarser materials including gravel and stone fragments (Canfield, Lopes, & Goodrich, ; Nearing, Simanton, Norton, Bulygin, & Stone, ; Poesen, van Wesemael, Bunte, & Benet, ; Simanton, Renard, Christiansen, & Lane, ).…”

Section: Discussionmentioning

confidence: 99%

“…The Las Conchas wildfire also increased sediment yields (Orem & Pelletier, , ; Pelletier & Orem, ). Debris flow assessments suggested that the area would be problematic for water‐related hazards for years following the wildfire (Tillery, Darr, Cannon, & Michael, ).…”

Section: Field Area and Burn Severity Methodsmentioning

confidence: 99%

Thresholds and relations for soil‐hydraulic and soil‐physical properties as a function of burn severity 4 years after the 2011 Las Conchas Fire, New Mexico, USA

Ebel

Romero

Martin³

2018

Hydrological Processes

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Wildfire effects on soil-physical and -hydraulic properties as a function of burn severity are poorly characterized, especially several years after wildfire. A stratified random sampling approach was used in 2015 to sample seven sites representing a spectrum of remotely sensed burn severity in the area impacted by the 2011 Las Conchas Fire in New Mexico, USA. Replicate samples from each site were analysed in the laboratory.Linear and linear indicator regression were used to assess thresholds in soil-physical and -hydraulic properties and functional relations with remotely sensed burn severity.Significant thresholds were present for initial soil-water content (θ i ) at 0-6 cm depth between the change in the Normalized Burn Ratio (dNBR) equal to 618-802, for bulk density (ρ b ) at 3-6 cm between dNBR equal to 416-533, for gravel fraction at 0-1 cm between dNBR equal to 416-533, for fines (the silt + clay fraction) at 0-1 cm for dNBR equal to 416-533, and for fines at 3-6 cm for dNBR equal to 293-416. Significant linear relations with dNBR were present between ρ b at 0-1 cm, loss on ignition (LOI) at 0-1 cm, gravel fraction at 0-1 cm, and the large organic fraction at 1-3 cm.No thresholds or effects on soil-hydraulic properties of field-saturated hydraulic conductivity or sorptivity were observed. These results suggest that ρ b and LOI at 0-1 cm have residual direct impacts from the wildfire heat impulse. The θ i threshold is most likely from delayed groundcover/vegetation recovery that increases evaporation at the highest burn severity sites. Gravel and silt + clay thresholds at 0-1 cm at the transition to high burn severity suggest surface gravel lag development from hydraulic erosion. Thresholds in ρ b from 3 to 6 cm and in silt + clay fraction from 3 to 6 cm appear to be the result of soil variability between sites rather than wildfire impacts.This work suggests that gravel-rich soils may have increased resilience to sustained surface runoff generation and erosion following wildfire, with implications for assessments of postwildfire hydrologic and erosion recovery potential.

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Postwildfire preliminary debris flow hazard assessment for the area burned by the 2011 Las Conchas Fire in north-central New Mexico

Cited by 8 publications

References 3 publications

Risk assessment of post-wildfire hydrological response in semiarid basins: the effects of varying rainfall representations in the KINEROS2/AGWA model

Risk assessment of post-wildfire hydrological response in semiarid basins: the effects of varying rainfall representations in the KINEROS2/AGWA model

How do sediment yields from post‐wildfire debris‐laden flows depend on terrain slope, soil burn severity class, and drainage basin area? Insights from airborne‐LiDAR change detection

Thresholds and relations for soil‐hydraulic and soil‐physical properties as a function of burn severity 4 years after the 2011 Las Conchas Fire, New Mexico, USA

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