Abstract Wildfire‐induced changes to soil and vegetation promote runoff‐generated debris flows in steep watersheds. Postfire are most commonly observed watersheds during the first wet season following a wildfire, but it is unclear how long elevated threat of flow persists why debris‐flow potential recovering burned areas. This work quantifies rainfall intensity‐duration (ID) thresholds for initiation change with time since burning provides mechanistic explanation these changes. We...

First posted June 30, 2016 For additional information, contact: Center Director, Geologic Hazards Science CenterU.S. Geological SurveyBox 25046, MS 966Denver, CO 80225-0046http://geohazards.usgs.gov/ Wildfire can significantly alter the hydrologic response of a watershed to extent that even modest rainstorms generate dangerous flash floods and debris flows. To reduce public exposure hazard, U.S. Survey produces post-fire debris-flow hazard assessments for select fires in western United...

Abstract Predicting the timing of overland flow in burned watersheds can help to estimate debris‐flow and location initiation. Numerical models produce predictions, but they are limited by our knowledge appropriate model parameters. Moreover, opportunities test calibrate parameters post‐wildfire settings available data (measurements rare). In this study, we use a unique set rainfall flow‐timing extent which be generalized from an individual watershed other (0.01 km 2 >1 k m ) within area....

Abstract Wildfire significantly alters the hydrologic properties of a burned area, leading to increases in overland flow, erosion, and potential for runoff‐generated debris flows. The initiation flows recently areas is well characterized by rainfall intensity‐duration (ID) thresholds. However, there currently paucity data quantifying intensities required trigger post‐wildfire flows, which limits our understanding how why ID thresholds vary different climatic geologic settings. In this study,...

Abstract Debris flows pose a significant hazard to communities in mountainous areas, and there is continued need for methods delineate zones associated with debris-flow inundation. In certain situations, such as scenarios following wildfire, where could be an abrupt increase the likelihood size of debris that necessitates rapid assessment, computational demands inundation models play role their utility. The inability efficiently determine downstream effects anticipated events remains...

Abstract Climate and land use changes have led to recent increases in fire size, severity, and/or frequency many different geographic regions ecozones. Most post‐wildfire geomorphology studies focus on the impact of a single wildfire but changing regimes underscore need quantify effects repeated disturbance by subsequent impacts system resilience. Here, we examine two successive wildfires soil hydraulic properties debris flow hazards. The 2004 Nuttall‐Gibson Complex 2017 Frye Fire affected...

Abstract In steep landscapes, wildfire‐induced changes to soil and vegetation can lead extreme hazardous geomorphic responses, including debris flows. The mechanisms that heightened however, depend on many site‐specific factors regional climate, vegetation, texture, burn severity. As climate land use change drive in fire regime, there is an increasing need understand how alters particularly areas where has been historically infrequent. Here, we examine differences the initiation, magnitude,...

Abstract. Moderate- or high-severity fires promote increases in runoff and erosion, leading to a greater likelihood of extreme geomorphic responses, including debris flows. In the first several years following fire, majority flows initiate when rapidly entrains sediment on steep slopes. From hazard perspective, it is important be able anticipate where watershed responses will dominated by rather than flood Rainfall intensity averaged over 15 min duration, I15, particular, has been identified...

Flooding and erosion after wildfires present increasing hazard as climate warms, semi-arid lands become drier, population increases, the urban interface encroaches farther into wildlands. We quantify post-wildfire in a steep, initially unchannelized, 7.5 ha headwater catchment following 2011 Horseshoe 2 Fire Chiricahua Mountains of southeastern Arizona. Using time-lapse cameras, rain gauges, repeat surveys by terrestrial laser scanner, we response burned landscape to subsequent precipitation...

Abstract Wildfire influences geomorphic process rates, increasing the potential for runoff‐generated debris flows in steep watersheds. Runoff‐generated postfire (PFDFs) often initiate when overland flow rapidly mobilizes sediment from hillslopes and channels. Fire effects on soil hydraulic properties, including their magnitude temporal persistence, can therefore play an influential role determining degree to which fire increases debris‐flow time period heightened hazards following fire....

Scientists and practitioners have identified research priorities to improve scientific understanding of postfire debris flows meet decisionmaking challenges posed by this growing hazard.

DATA REPORT article Front. Earth Sci., 13 April 2021 | https://doi.org/10.3389/feart.2021.649938

Abstract. Debris flows transport large quantities of water and granular material, such as sediment wood, this mixture can have devastating effects on life infrastructure. The proportion woody debris (LWD) incorporated into be enhanced in forested areas recently burned by wildfire because wood recruitment channels accelerates forests. In study, using four small watersheds the Gila National Forest, New Mexico, which 2020 Tadpole Fire, we explored new approaches to estimate flow velocity based...

Abstract Burned slopes are susceptible to runoff‐generated debris flows in the years following wildfire due reductions vegetation cover and soil infiltration capacity. Debris can pose serious threats downstream communities, so quantifying variations flow properties along debris‐flow runout paths is needed improve both conceptual quantitative models of behaviour help anticipate mitigate risk associated with these events. Changes that follow fire may be particularly dramatic, since they...

Abstract Wildfire can alter soil‐hydraulic properties, often resulting in an increased prevalence of infiltration‐excess overland flow and greater potential for debris‐flow hazards. Mini disk tension infiltrometers (MDIs) be used to estimate soil hydraulic such as field‐saturated conductivity ( K fs ) wetting front H f ), their spatial variability following wildfire. However, the small (point‐scale) footprint MDI measurements makes it challenging use these data parameterize hydrologic models...

Abstract The 2019 Museum Fire burned in a mountainous region near the city of Flagstaff, AZ, USA. Due to high risk post‐fire debris flows and flooding entering city, we deployed network seismometers within burn area downstream drainages examine efficacy seismic monitoring for flows. Seismic instruments were during 2019, 2020, 2021 monsoon seasons following fire recorded several flow flood events, as well signals associated with rainfall, lightning wind. Signal power, frequency content, wave...

Fluvial channels in metamorphic core complexes are preferentially oriented parallel and perpendicular to the direction of tectonic extension. This pattern has been variably attributed such causes as tilting during extension, channel elongation by slip along range-bounding detachment fault, exploitation extension-related joint sets incision. In this paper we use field measurements, digital elevation model analyses, numerical modeling test hypotheses for structural control fluvial complexes,...

ABSTRACT The extreme heat from wildfire alters soil properties and incinerates vegetation, leading to changes in infiltration capacity, ground cover, erodibility, rainfall interception. These promote elevated rates of runoff sediment transport that increase the likelihood runoff-generated debris flows. Debris flows are most common year immediately following wildfire, but temporal magnitude not well constrained. In this study, we combine measurements soil-hydraulic with vegetation survey data...

Heavy rainfall on 27–31 July 2006 led to record flooding and triggered an historically unprecedented number of debris flows in the Santa Catalina Mountains north Tucson, Ariz. The U.S. Geological Survey (USGS) documented floods along four watercourses Tucson basin, at least 250 hillslope failures spawned damaging area where less than 10 small had been past 25 years. At 18 destroyed infrastructure heavily used Sabino Canyon Recreation Area...

The role of pyrogenic carbon (PyC) in the global cycle is still incompletely characterized. Much work has been done to characterize PyC on landforms and soils where it originates or “terminal” reservoirs such as marine sediments. Less known about intermediate streams rivers, few studies have characterized hillslope in-stream erosion control structures (ECS) designed capture sediments destabilized by wildfire. In this preliminary study, organic (OC), total nitrogen (N), stable isotope...