Characteristics of Debris-Flow Triggering Rainstorms Following Wildfire in Western New Mexico

McGuire, Luke A.; Rengers, Francis K.; Youberg, A.; Gorr, Alexander; Hoch, Olivia

doi:10.1130/abs/2022am-378676

Cited by 4 publications

(7 citation statements)

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“…The model requires the natural log of watershed area burned at moderate or high severity (Bmh) (Eq 1), so when Bmh equals zero, it is undefined and results in a predicted volume of 0 m 3 . This means that the Emergency Assessment model will always predict a volume of 0 m 3 if a watershed is not burned at moderate or high severity, even though watersheds burned at low severity may still be at an elevated risk for postwildfire debris flows [25].…”

Section: Resultsmentioning

confidence: 99%

Constraining post-fire debris-flow volumes in the southwestern United States

Gorr,

McGuire,

Youberg

2023

E3S Web of Conf.

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Debris flows pose a serious threat to human life and infrastructure in downstream areas following wildfire. This underscores the necessity for having a hazard assessment framework in place that can be used to estimate the impacts of post-wildfire debris flows. Current hazard assessments in the western United States (USA) use empirical models to assess the volume of potential post-wildfire debris flows. Volume models provide information regarding the magnitude and potential downstream impacts of debris flows. In this study, we gathered post-wildfire debris-flow volume data from 54 watersheds across the states of Arizona (AZ) and New Mexico (NM), USA, and compared these data to the output of a widely used empirical post-wildfire debris-flow volume model. Results show that the volume model, which was developed using data from the Transverse Ranges of southern California (CA), tends to overestimate observed volumes from AZ and NM, sometimes by several orders of magnitude. This disparity may be explained by regional differences between southern CA and AZ and NM, including differences in sediment supply. However, we found a power- law relationship between debris-flow volume and watershed area that can be used to put first-order constraints on debris-flow volume in AZ and NM.

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Section: Resultsmentioning

confidence: 99%

Constraining post-fire debris-flow volumes in the southwestern United States

Gorr,

McGuire,

Youberg

2023

E3S Web of Conf.

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“…Steep slopes and lack of accessibility likely preclude active restoration of these channels or any hill slope activities other than revegetation by hand labor. Frequent debris flows, a separate sediment transport mechanism, also complicates restoration in the headwater steep slopes (Porter et al 2023;McGuire et al 2023). The 430 nature of the channels (mostly G and F "Rosgen" type channels) indicate that the channel form is in the early stages of evolving to a stable form.…”

Section: Discussionmentioning

confidence: 99%

Post-wildfire sediment source and transport modeling, empirical observations, and applied mitigation: an Arizona USA case study

Schenk,

Wood,

Haden

et al. 2023

Preprint

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Abstract. Post-wildfire floods are receiving greater attention as wildland-urban interfaces become more common and as catastrophic wildfires have increased in frequency. Sediment sourcing, transport, and deposition in the post-fire environment receive attention due to the severity of risk caused by debris flows and concentrated sediment flood flows. This study provides a series of sediment model predictions based on MUSLE and the WARSSS suite of models that included: ERMIT, BANCS, and FLOWSED/POWERSED for the 2019 Museum Fire (809 Ha of steep slope Pinus ponderosa forest in the Spruce Wash watershed). A comparison is provided for the internet-based WEPPcloud post-fire sediment model. Empirical evidence from four floods in 2021 indicated 9,900 Mg of sediment yield to city of Flagstaff neighborhoods, the WEPP model estimated 3870 Mg/year, MUSLE predicted 4860 Mg/year (based on the four events), and the WARSSS suite of models predicted 4630 Mg/year. Both WEPP and WARSSS estimated more sediment yield from channels than hillslope (51 %/49 % and 60 %/40 % respectively) though the spatial patterns differ between the models. Sediment mitigation structures, or “work areas”, are discussed as real-world applications of sediment forecasting for reducing downstream impacts. Continued revisions of sediment forecasts, based on case studies such as this one, can provide managers and policy makers with tools for risk mitigation and emergency management.

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“…Upper elevations of some study watersheds, particularly on north-facing aspects, were located in a transition from Sonoran Desertscrub to chaparral. Our study watersheds, described in detail in [7], burned primarily at low severity (Figure 1), though pockets of soil burned at moderate severity were not uncommon on higher elevation, north-facing slopes. Rainstorms that produced debris flows were identified using postrainstorm surveys, pressure transducers, and time lapse cameras [7].…”

Section: Debris Flow Monitoringmentioning

confidence: 93%

“…Our study watersheds, described in detail in [7], burned primarily at low severity (Figure 1), though pockets of soil burned at moderate severity were not uncommon on higher elevation, north-facing slopes. Rainstorms that produced debris flows were identified using postrainstorm surveys, pressure transducers, and time lapse cameras [7]. Rainfall characteristics were quantified using tipping bucket rain gages.…”

Section: Debris Flow Monitoringmentioning

confidence: 93%

“…Post-fire debris flows in Arizona are often initiated by short-duration, high intensity rainfall associated with the North American Monsoon [6]. Monitoring at the Woodbury Fire builds directly from [7], who documented debris flows several months following the fire in a series of monitored watersheds in the Superstition Mountains to the east of Phoenix, Arizona. The Woodbury Fire burned over a large area and across a range of elevations that included a number of different plant communities.…”

Section: Debris Flow Monitoringmentioning

confidence: 99%

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Triggering rainfall intensities for post-wildfire debris flows in the Sonoran Desertscrub plant community

McGuire,

Youberg,

Gorr

et al. 2023

E3S Web of Conf.

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Wildfire makes landscapes more vulnerable to debris flows by reducing soil infiltration capacity and decreasing vegetation cover. The extent to which fire affects debris-flow processes depends on the severity of the fire, the climatology of intense rainfall, the pre-fire plant community, and sediment supply, among other factors. As fire expands into new plant communities and geographic regions, there is a corresponding need to expand efforts to document fire-induced changes and their impacts on debris-flow processes. In recent years, several large wildfires have impacted portions of the Sonoran Desertscrub plant community in Arizona, USA, a plant community where fire has been historically infrequent. Following two of these fires, we monitored debris-flow activity at the watershed scale and quantified wildfire-driven changes in soil hydraulic properties using in-situ measurements with mini disk tension infiltrometers. Results indicate that rainfall intensity-duration thresholds for the initiation of post-fire debris flows in recently burned watersheds within the Sonoran Desertscrub plant community are substantially greater than those in nearby areas dominated by other plant communities, such as chaparral. Results provide insight into the impact of fire on debris-flow processes in a plant community where it is likely to be more impactful in the future and help expand existing post-fire debris flow databases into a plant community where there is a paucity of observations.

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Characteristics of Debris-Flow Triggering Rainstorms Following Wildfire in Western New Mexico

Cited by 4 publications

References 0 publications

Constraining post-fire debris-flow volumes in the southwestern United States

Constraining post-fire debris-flow volumes in the southwestern United States

Post-wildfire sediment source and transport modeling, empirical observations, and applied mitigation: an Arizona USA case study

Triggering rainfall intensities for post-wildfire debris flows in the Sonoran Desertscrub plant community

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