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At least 451 records · Page 25Linked to original sources
USGS2017

Where you stand depends on where you sit: Qualitative inquiry into notions of fire adaptation

Wildfire and the threat it poses to society represents an example of the complex, dynamic relationship between social and ecological systems. Increasingly, wildfire adaptation is posited as a pathway to shift the approach to fire from a suppression paradigm that seeks to control fire to a paradigm that focuses on “living with” and “adapting to” wildfire. In this study, we seek insights into what it means to adapt to wildfire from a range of stakeholders whose efforts contribute to the management of wildfire. Study participants provided insights into the meaning, relevance, and use of the concept of fire adaptation as it relates to their wildfire-related activities. A key finding of this investigation suggests that social scale is of key importance in the conceptualization and understanding of adaptation for participating stakeholders. Indeed, where you stand in terms of understandings of fire adaptation depends in large part on where you sit.

Ecology and Society↗
USGS2018

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

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 dNB R 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.

New Mexico↗
USGS2001

Post-fire, rainfall intensity-peak discharge relations for three mountainous watersheds in the Western USA

Wildfire alters the hydrologic response of watersheds, including the peak discharges resulting from subsequent rainfall. Improving predictions of the magnitude of flooding that follows wildfire is needed because of the increase in human population at risk in the wildland-urban interface. Because this wildland-urban interface is typically in mountainous terrain, we investigated rainfall-runoff relations by measuring the maximum 30 min rainfall intensity and the unit-area peak discharge (peak discharge divided by the area burned) in three mountainous watersheds (17-26.8 km 2 ) after a wildfire. We found rainfall-runoff relations that relate the unit-area peak discharges to the maximum 30 min rainfall intensities by a power law. These rainfall-runoff relations appear to have a threshold value for the maximum 30 min rainfall intensity (around 10 mm h -1 ) such that, above this threshold, the magnitude of the flood peaks increases more rapidly with increases in intensity. This rainfall intensity could be used to set threshold limits in rain gauges that are part of an early-warning flood system after wildfire. The maximum unit-area peak discharges from these three burned watersheds ranged from 3.2 to 50 m 3 s -1 km -2 . These values could provide initial estimates of the upper limits of runoff that can be used to predict floods after wildfires in mountainous terrain. Published in 2001 by John Wiley and Sons, Ltd.

Hydrological Processes↗
USGS2019

Estimating forest canopy cover dynamics in Valles Caldera National Preserve, New Mexico, using LiDAR and Landsat data

Increasing tree canopy cover has led to increasing wildfire activity in conifer dominated areas of the southwestern United States. Estimating historical changes in the spatial distribution of tree canopy cover can provide further insights into the dynamics of forest and fuel conditions in these landscapes and help prioritize areas for restoration to mitigate wildfire risks and restore biological functioning. In this study, we explored the relationship between LiDAR derived canopy cover data and Landsat reflectance values, and derived a model to estimate percent canopy cover (PCC) on historical Landsat data from 1987 to 2015 for the Valles Caldera National Preserve (VCNP), located in the southwest Jemez Mountains of New Mexico. We developed a regression model between LiDAR generated canopy cover collected in June 2010 and Landsat Thematic Mapper (TM) reflectance values (bands 1–7 except band 6) and vegetation indices collected for the same date. About 5% (17,000) of the total LiDAR points (329,102) were used as training points and a separate, non-overlapping set of 17,000 points as test points to validate the regression model. A simple linear model with the red band (band 3; R 2 = 0.70) was selected as the best model to predict PCC in the rest of the images for 1987–2015. In general, we found a strong consistency between the spatial dynamics of modelled tree canopy cover based on historical Landsat data, wildfire events and forest management practicesthat occurred during the same period. Results showed that about 11% of the study area experienced an increase in PCC for the period of 1987–2015 while 41% of the study area experienced a reduction in PCC during the same time period, mostly in the areas which were affected by stand replacing wildfires in 2011 and 2013. The results indicate an overall increase in medium and high canopy cover classes in specific regions of the study area, which could lead to hazardous wildfires such as those in 2011 and 2013. In the context of ongoing ecological restoration of these montane forests, predicted PCC of contemporary forests could help local managers to identify the areas in the need of immediate restoration efforts by focusing management practices on the areas with closed canopy.

New Mexico↗
USGS2022

Divergent successional trajectories of soil seed bank and post-fire vegetation in a semiarid oak forest: Implications for post-fire ecological restoration

Wildfires are a major disturbance in forest ecosystems around the world and may lead to changes in vegetation succession trajectories. This study examined the impact of time since wildfires on the successional gradients of the degraded Zagros semi-arid oak forest in Iran. Here, we investigated the role of soil seed bank in postfire understory vegetation successional trajectories after wildfires and how time-since-fire influenced plant recovery of this disturbed site. Three adjacent high severity burned areas with different fire histories and the same physiographic conditions were considered. In sampling, we surveyed both aboveground understory vegetation and soil seed bank in all the 96 plots taken along the transects of each area. Soil samples were also collected from each plot and physicochemical properties were analysed in the laboratory. Species composition in the seed bank showed divergent successional trajectories compared to the aboveground vegetation after wildfire. The diversity of soil seed banks followed a gradual decrease, while aboveground understory plants revealed an increasing trend of diversity over time. In addition, the physical and chemical composition of soils was significantly altered by fire. This study presents important insights into soil seed bank dynamics compared to the corresponding aboveground vegetation during postfire succession. The observed changes in diversity and vegetation composition after wildfire can give important insights to management strategies involving prescribed fire in the restoration efforts of highly disturbed semiarid oak forest.

Ecological Engineering↗
USGS2024

Before the fire: Predicting burn severity and potential post-fire debris-flow hazards to Colorado River Cutthroat Trout (Oncorhynchus clarkii pleuriticus) conservation populations

Background Colorado River Cutthroat Trout (CRCT; Oncorhynchus clarkii pleuriticus ) conservation populations may be at risk from wildfire and post-fire debris flows hazards. Aim To predict burn severity and potential post-fire debris flow hazard classifications to CRCT conservation populations before wildfires occur. Methods We used remote sensing, spatial analyses, and machine learning to model 28 wildfire incidents (2016–2020) and spatially predict burn severity from pre-wildfire environmental factors to evaluate the likelihood (%) and volume (m 3 ) hazard classification of post-fire debris flow. Key results Burn severity was best predicted by fuels, followed by topography, physical ecosystem conditions, and weather (mean adjusted R 2 = 0.54). Predictions of high or moderate burn severity covered 1.1 (15% of study area) and 1.5 (19% of study area) million ha, respectively, and varied by watershed. Combined high or moderate debris flow hazard classification included 80% of stream reaches with conservation populations and 97% of conservation population point nodes. Conclusions Predicted burn severity and potential post-fire debris flow indicated moderate to high hazard for CRCT conservation populations native to the Green and Yampa rivers of the Upper Colorado River Basin. Implications Future management actions can incorporate predicted burn severity and potential post-fire debris flow to mitigate impacts to CRCT and other at-risk resource values before a wildfire occurs.

Colorado, Utah, Wyoming↗
USGS2026

Relationship of satellite-derived fire severity to archaeological fire severity and fire effects in the Jemez Mountains, New Mexico, USA

Background Archaeological attributes important for determining cultural affiliation, site age, or artifact origin can be damaged or destroyed by wildfires. Satellite-derived fire severity products are used in post-fire rapid response to prioritize and guide stabilization and preservation activities, but their ability to predict archaeological fire impacts has not yet been tested. We compared the severity of fire from Burned Area Reflectance Classification (BARC) maps with ground-based observations of fire severity (“archaeological fire severity”) and archaeological impacts for 904 prehistoric or historic sites within three wildfires in the Jemez Mountains of north-central New Mexico, U.S. Results from this unique study inform archaeological preservation in the context of wildfires and fire management. Results We found a statistically significant, moderately strong association between BARC and archaeological fire severity and a high likelihood that sites with a low BARC fire severity also had a low archaeological fire severity designation. Sites of moderate or high BARC severity were less likely to have a matching severity classification in post-fire assessments, and BARC maps tended to identify as unburned areas where archaeologists determined that sites were burned at low severity. Wildfire of any severity resulted in measurable impacts to archaeological architecture, features, or artifacts at some sites, with increasing proportion of sites impacted at moderate versus low BARC severity, but fire impacts were also observed at sites classified by BARC as unburned. Conclusions Generally, BARC maps provide good assessment of the severity of fire and its effects on archaeological resources, particularly for areas burned at low severity. In areas of moderate or high fire severity, BARC maps may not consistently identify sites with a high need for assessment, and archaeological fire effects can also be present at sites classified by BARC as unburned. Adoption of standardized post-fire archaeological assessments across wildfires and regions, exploration of alternative fire mapping products, and continued research on the fire environments that produce archaeological fire effects can enhance archaeological preservation and post-fire response.

New Mexico↗
USGS2026

Size of modern megafire not unprecedented and a cumulative fire deficit persists

Background The area burned by wildfires in western North American forests has grown since the 1980s, largely driven by individual “megafires.” Despite breaking state records for fire size, it remains uncertain whether these large fires are unprecedented, owing to limited knowledge of the area burned during historical fire regimes (pre-1900). We used new methods and 14 tree-ring fire-scar sites to evaluate whether the area burned by Arizona’s largest fire on record – the 217,741 ha 2011 Wallow Fire – was unprecedented in a multi-century context. Using the 375-year reconstruction of annual area burned, we also assessed the departure of the modern fire regime by introducing cumulative fire deficit, calculated as the cumulative sum of 20-year area burned anomalies. Results The size of the Wallow Fire was exceptional in the modern era, but comparable to the extent of burning in 1748, 1847, and 1851 on the same landscape. Notably, years of extensive fire (50,000–100,000 ha) were common on this landscape prior to 1900. The average return interval for fires exceeding 100,000 ha was just 20 years. By contrast, the 2011 Wallow Fire was the only modern fire > 10,000 ha in our study area ( n = 129, 1970–2024), leading to an 85% reduction in average annual area burned. This exceptional departure from the historical fire regime generated a cumulative fire deficit exceeding 2.0 million hectares by 2011, which continues to increase despite the occurrence of the large Wallow Fire. Conclusions Although the modern wildfire crisis is characterized by large, severe wildfires, historical fire regimes also included extensive fires. On an Arizona landscape, the sizes of several historical fires were on par with the largest wildfire on record. Similar historical precedent of large fires is likely true elsewhere in dry conifer forests of western North America. These findings underscore that future wildfire events could be even larger, and likely more severe, as fuels accumulate and the climate grows warmer and drier. Forest restoration aimed at reestablishing characteristic disturbance regimes, including frequent, large, low-severity fires, could be used to assist recovery of these ecosystems resulting from the cumulative fire deficit.

Arizona↗
USGS2026

Resources to inform the 2026 Colorado Climate Preparedness Roadmap: Compound hazards and associated public health implications

Changing environmental conditions are increasing the frequency and severity of extreme weather and environmental hazards, including heat waves, wildfires, drought, reduced water quality, and degraded air quality from ozone (O3) and fine particulate matter pollution (AghaKouchak et al., 2020; Bolinger et al., 2024; Colorado Health Institute, 2023a; Fann et al., 2015; IPCC, 2023a; Nagamoto et al., 2024; Nolte et al., 2018, 2021; Zscheischler et al., 2020). Strong scientific evidence indicates that climate change will increase risks to public health and safety throughout the 21st century, particularly through compound climate events (AghaKouchak et al., 2020; Cascio, 2018; Childs et al., 2022; Ebi, 2025; IPCC, 2023a, 2023b; Ma et al., 2024; Marlier et al., 2026; National Academy of Medicine, 2025; Reid et al., 2016; Reid & Maestas, 2019; Simpson et al., 2023; van den Hurk et al., 2023; Volckens, 2024; Zscheischler et al., 2018, 2020). Compound hazards, which are co-occurring or sequential hazards such as heat waves occurring alongside drought, wildfire, and poor air quality from smoke, can amplify public health risks beyond the effects of individual hazards alone (Marlier et al., 2026; Zscheischler et al., 2020). In Colorado, compound climate events with clear implications for public health are already evident (see “Core definitions” section for additional context on compound climate events). Recent statewide assessments have documented increasing heat waves, drought, and wildfires linked to rising temperatures, while emerging data show that climate change is reversing decades of air quality improvements through increased O3 and fine particulate matter pollution due to wildfire, and increased aerosolized topsoil (i.e., dust) due to drought (Bolinger et al., 2024; Childs et al., 2022; Fann et al., 2015; Ghanbari et al., 2023; Larsen et al., 2022; Nolte et al., 2018, 2021; Volckens, 2024). These environmental shifts are associated with increases in eye and kidney-health related concerns, heat-related illness, exacerbations of asthma and other respiratory conditions, increased risk of infectious disease, cardiovascular stress, and mental health impacts, with disparities in risk for children, older adults, outdoor workers, and communities with existing health and economic vulnerabilities (Baraghoshi et al., 2023; Butler-Dawson et al., 2026; Cascio, 2018; Cleland et al., 2022; Colorado Health Institute, 2023a; Grover et al., 2024; Lee et al., 2023; Ma et al., 2024; Macaluso et al., 2024; Marlier et al., 2026; National Academy of Medicine, 2025; Patnaik et al., 2024; Peters et al., 2019; Reid et al., 2016; Reid & Maestas, 2019). The state is actively pursuing strategies to mitigate the risks of these compound climate events on the public, including expanding climate and health surveillance, strengthening early-warning systems and public communication around smoke and air quality, and developing integrated policy agendas that link climate mitigation, adaptation, and health equity (CDPHE, 2025; Colorado Health Institute, 2023b; Zemaitis & Bailey, 2024). For example, state and partner organizations have articulated cross-sector goals to prepare for health impacts related to extreme heat, wildfires, flooding, drought, declines in water quality, and poor air quality, including updating workplace safety protocols, enhancing community-based resilience, adapting clinical care assessments to include climate-related stressors, and improving access to mental and behavioral health services following climate-related disasters (Colorado Health Institute, 2023b; CDPHE, 2025; Zemaitis & Bailey, 2024). To better prepare for current risks and make informed decisions, more information is needed, including methods to analyze historical and projected conditions in near real time, characterize interactions among compound hazards, and translate climate and air quality science into actionable guidance for public health agencies, health care systems, and communities across Colorado (Ebi, 2025; Marlier et al., 2026; National Academy of Medicine, 2025; Simpson et al., 2023; Zscheischler et al., 2018). For this report, we focus on extreme heat and outdoor air quality (ozone [O3] and fine particulate matter [PM2.5]) as the main compound hazards causing compound climate events, given that 1) the state of Colorado has experienced poor air quality for some time, 2) these climate events are affecting large population numbers, and 3) there is capacity to consider and respond to these climate-driven events.

Colorado↗
USGS2014

Potential postwildfire debris-flow hazards: a prewildfire evaluation for the Sandia and Manzano Mountains and surrounding areas, central New Mexico

Wildfire can drastically increase the probability of debris flows, a potentially hazardous and destructive form of mass wasting, in landscapes that have otherwise been stable throughout recent history. Although there is no way to know the exact location, extent, and severity of wildfire, or the subsequent rainfall intensity and duration before it happens, probabilities of fire and debris-flow occurrence for different locations can be estimated with geospatial analysis and modeling efforts. The purpose of this report is to provide information on which watersheds might constitute the most serious, potential, debris-flow hazards in the event of a large-scale wildfire and subsequent rainfall in the Sandia and Manzano Mountains. Potential probabilities and estimated volumes of postwildfire debris flows in the unburned Sandia and Manzano Mountains and surrounding areas were estimated using empirical debris-flow models developed by the U.S. Geological Survey in combination with fire behavior and burn probability models developed by the U.S. Department of Agriculture Forest Service. The locations of the greatest debris-flow hazards correlate with the areas of steepest slopes and simulated crown-fire behavior. The four subbasins with the highest computed debris-flow probabilities (greater than 98 percent) were all in the Manzano Mountains, two flowing east and two flowing west. Volumes in sixteen subbasins were greater than 50,000 square meters and most of these were in the central Manzanos and the western facing slopes of the Sandias. Five subbasins on the west-facing slopes of the Sandia Mountains, four of which have downstream reaches that lead into the outskirts of the City of Albuquerque, are among subbasins in the 98th percentile of integrated relative debris-flow hazard rankings. The bulk of the remaining subbasins in the 98th percentile of integrated relative debris-flow hazard rankings are located along the highest and steepest slopes of the Manzano Mountains. One of the subbasins is several miles upstream from the community of Tajique and another is several miles upstream from the community of Manzano, both on the eastern slopes of the Manzano Mountains. This prewildfire assessment approach is valuable to resource managers because the analysis of the debris-flow threat is made before a wildfire occurs, which facilitates prewildfire management, planning, and mitigation. In northern New Mexico, widespread watershed restoration efforts are being carried out to safeguard vital watersheds against the threat of catastrophic wildfire. This study was initiated to help select ideal locations for the restoration efforts that could have the best return on investment.

New Mexico↗
USGS2016

Potential postwildfire debris-flow hazards—A prewildfire evaluation for the Jemez Mountains, north-central New Mexico

Wildfire can substantially increase the probability of debris flows, a potentially hazardous and destructive form of mass wasting, in landscapes that have otherwise been stable throughout recent history. Although the exact location, extent, and severity of wildfire or subsequent rainfall intensity and duration cannot be known, probabilities of fire and debris‑flow occurrence for given locations can be estimated with geospatial analysis and modeling. The purpose of this report is to provide information on which watersheds might constitute the most serious potential debris - flow hazards in the event of a large - scale wildfire and subsequent rainfall in the Jemez Mountains. Potential probabilities and estimated volumes of postwildfire debris flows in both the unburned and previously burned areas of the Jemez Mountains and surrounding areas were estimated using empirical debris - flow models developed by the U.S. Geological Survey in combination with fire behavior and burn probability models developed by the U.S. Forest Service. Of the 4,998 subbasins modeled for this study, computed debris-flow probabilities in 671 subbasins were greater than 80 percent in response to the 100 - year recurrence interval, 30-minute duration rainfall event. These subbasins ranged in size from 0.01 to 6.57 square kilometers (km 2 ), with an average area of 0.29 km 2 , and were mostly steep, upstream tributaries to larger channels in the area. Modeled debris-flow volumes in 465 subbasins were greater than 10,000 cubic meters (m 3 ), and 14 of those subbasins had modeled debris‑flow volumes greater than 100,000 m 3 . The rankings of integrated relative debris - flow hazard indexes for each subbasin were generated by multiplying the individual subbasin values for debris - flow volume, debris‑flow probability, and average burn probability. The subbasins with integrated hazard index values in the top 2 percent typically are large, upland tributaries to canyons and channels primarily in the Upper Rio Grande and Rio Grande-Santa Fe watershed areas. No subbasins in this group have basin areas less than 1.0 km 2 . Many of these areas already had significant mass‑wasting episodes following the Las Conchas Fire in 2011. Other subbasins with integrated hazard index values in the top 2 percent are scattered throughout the Jemez River watershed area, including some subbasins in the interior of the Valles Caldera. Only a few subbasins in the top integrated hazard index group are in the Rio Chama watershed area. This prewildfire assessment approach is valuable to resource managers because the analysis of the debris-flow threat is made before a wildfire occurs, which facilitates prewildfire management, planning, and mitigation. In north‑central New Mexico, widespread watershed restoration efforts are being done to safeguard vital watersheds against the threat of catastrophic wildfire. This study was designed to help select ideal locations for the restoration efforts that could have the best return on investment.

New Mexico↗
USGS2022

Estimating soil moisture, actual evapotranspiration, climatic water deficit, and groundwater recharge during periods of drought for current and future climate conditions in Hawaiʻi

Mid- and end-of-century climate projections for the Hawaiian Islands indicate that rainfall is projected to decrease across large areas. In areas affected by drought or where the future climate becomes drier, reduced groundwater recharge can affect freshwater availability. Reduced rainfall can also reduce soil moisture, which can increase the risk of wildfire. Cloud-water interception, or fog drip, is the process by which cloud-water droplets are captured on the leaves and branches of plants with some of the captured cloud water subsequently dripping to the ground. Studies in Hawaiʻi indicate that fog drip can contribute substantially to total precipitation and may have the potential to lessen the negative effects of drought or a drying climate on freshwater availability and wildfire risk. Wildfire danger assessments in the continental United States have used estimates of soil moisture, evapotranspiration, and climatic water deficit (that is, the evaporative demand that exceeds available water) to improve the identification of areas at risk for wildfires. In this study, water-budget models developed for the islands of Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi were used to quantify the effects of severe drought, future climate conditions, and reducing or eliminating fog drip on groundwater recharge, soil moisture, evapotranspiration, and climatic water deficit. Island-wide summaries of groundwater recharge, soil moisture, evapotranspiration, and climatic water deficit were developed to (1) illustrate changes between recent, drought, and future climate conditions, (2) illustrate the effects of reducing or eliminating fog drip for recent, drought, and future climate conditions, and (3) highlight areas of increased potential risk for wildfire during drought and future climate conditions. The results of these analyses can be used by natural resource managers in Hawaiʻi.

Hawaii↗
USGS2022

The wildland-urban interface in the United States based on 125 million building locations

The wildland-urban interface (WUI) is the focus of many important land management issues, such as wildfire, habitat fragmentation, invasive species, and human-wildlife conflicts. Wildfire is an especially critical issue, because housing growth in the WUI increases wildfire ignitions and the number of homes at risk. Identifying the WUI is important for assessing and mitigating impacts of development on wildlands and for protecting homes from natural hazards, but data on housing development for large areas are often coarse. We created new WUI maps for the conterminous U.S. based on 125 million individual building locations, offering higher spatial precision compared to existing maps based on U.S. census housing data. Building point locations were based on a building footprint dataset from Microsoft®. We classified WUI across the conterminous U.S. at 30-m resolution using a circular neighborhood mapping algorithm with a variable radius to determine thresholds of housing density and vegetation cover. We used our maps to (1) determine the total area of the WUI and number of buildings included, (2) assess the sensitivity of WUI area included and spatial pattern of WUI maps to choice of neighborhood size, (3) assess regional differences between building-based WUI maps and census-based WUI maps, and (4) determine how building location accuracy affected WUI map accuracy. Our building-based WUI maps identified 5.6% – 18.8% of the conterminous U.S. as being in the WUI, with larger neighborhoods increasing WUI area but excluding isolated building clusters. Building-based maps identified more WUI area relative to census-based maps for all but the smallest neighborhoods, particularly in the north-central states, and large differences were attributable to high numbers of non-housing structures in rural areas. Overall WUI classification accuracy was 98.0%. For wildfire risk mapping and for general purposes, WUI maps based on the 500-m neighborhood represent the original Federal Register definition of the WUI; these maps include clusters of buildings in and adjacent to wildlands and exclude remote, isolated buildings. Our approach for mapping the WUI offers flexibility and high spatial detail, and can be widely applied to take advantage of the growing availability of high-resolution building footprint datasets and classification methods.

Conterminous United States↗
USGS2017

Meta-analysis of field-saturated hydraulic conductivity recovery following wildland fire: Applications for hydrologic model parameterization and resilience assessment

Hydrologic recovery after wildfire is critical for restoring the ecosystem services of protecting of human lives and infrastructure from hazards and delivering water supply of sufficient quality and quantity. Recovery of soil-hydraulic properties, such as field-saturated hydraulic conductivity ( K fs ), is a key factor for assessing the duration of watershed-scale flash flood and debris flow risks after wildfire. Despite the crucial role of K fs in parameterizing numerical hydrologic models to predict the magnitude of postwildfire run-off and erosion, existing quantitative relations to predict K fs recovery with time since wildfire are lacking. Here, we conduct meta-analyses of 5 datasets from the literature that measure or estimate K fs with time since wildfire for longer than 3-year duration. The meta-analyses focus on fitting 2 quantitative relations (linear and non-linear logistic) to explain trends in K fs temporal recovery. The 2 relations adequately described temporal recovery except for 1 site where macropore flow dominated infiltration and K fs recovery. This work also suggests that K fs can have low hydrologic resistance (large postfire changes), and moderate to high hydrologic stability (recovery time relative to disturbance recurrence interval) and resilience (recovery of hydrologic function and provision of ecosystem services). Future K fs relations could more explicitly incorporate processes such as soil-water repellency, ground cover and soil structure regeneration, macropore recovery, and vegetation regrowth.

Hydrological Processes↗
USGS2021

The timing and magnitude of changes to Hortonian overland flow at the watershed scale during the post-fire recovery process

Extreme hydrologic responses following wildfires can lead to floods and debris flows with costly economic and societal impacts. Process-based hydrologic and geomorphic models used to predict the downstream impacts of wildfire must account for temporal changes in hydrologic parameters related to the generation and subsequent routing of infiltration-excess overland flow across the landscape. However, we lack quantitative relationships showing how parameters change with time-since-burning, particularly at the watershed scale. To assess variations in best-fit hydrologic parameters with time, we used the KINEROS2 hydrological model to explore temporal changes in hillslope saturated hydraulic conductivity ( K sh ) and channel hydraulic roughness ( n c ) following a wildfire in the upper Arroyo Seco watershed (41.5 km 2 ), which burned during the 2009 Station fire in the San Gabriel Mountains, California, USA. This study explored runoff-producing storms between 2008 and 2014 to infer watershed hydraulic properties by calibrating the model to observations at the watershed outlet. Modelling indicates K sh is lowest in the first year following the fire and then increases at an average rate of approximately 4.2 mm/h/year during the first 5 years of recovery. The estimated values for K sh in the first year following the fire are similar to those obtained in previous studies on smaller watersheds (<1.5 km 2 ) following the Station fire, suggesting hydrologic changes detected here can be applied to lower-order watersheds. Hydraulic roughness, n c , was lowest in the first year following the fire, but increased by a factor of 2 after 1 year of recovery. Post-fire observations suggest changes in n c are due to changes in grain roughness and vegetation in channels. These results provide quantitative constraints on the magnitude of fire-induced hydrologic changes following severe wildfires in chaparral-dominated ecosystems as well as the timing of hydrologic recovery.

California↗
USGS2011

Simultaneous speciation of arsenic, selenium, and chromium: species, stability, sample preservation, and analysis of ash and soil leachates

An analytical method using high-performance liquid chromatography separation with inductively coupled plasma mass spectrometry (ICP-MS) detection previously developed for the determination of Cr(III) and Cr(VI) has been adapted to allow the determination of As(III), As(V), Se(IV), Se(VI), Cr(III), and Cr(VI) under the same chromatographic conditions. Using this method, all six inorganic species can be determined in less than 3 min. A dynamic reaction cell (DRC)-ICP-MS system was used to detect the species eluted from the chromatographic column in order to reduce interferences. A variety of reaction cell gases and conditions may be utilized with the DRC-ICP-MS, and final selection of conditions is determined by data quality objectives. Results indicated all starting standards, reagents, and sample vials should be thoroughly tested for contamination. Tests on species stability indicated that refrigeration at 10&deg; C was preferential to freezing for most species, particularly when all species were present, and that sample solutions and extracts should be analyzed as soon as possible to eliminate species instability and interconversion effects. A variety of environmental and geological samples, including waters and deionized water [leachates] and simulated biological leachates from soils and wildfire ashes have been analyzed using this method. Analytical spikes performed on each sample were used to evaluate data quality. Speciation analyses were conducted on deionized water leachates and simulated lung fluid leachates of ash and soils impacted by wildfires. These results show that, for leachates containing high levels of total Cr, the majority of the chromium was present in the hexavalent Cr(VI) form. In general, total and hexavalent chromium levels for samples taken from burned residential areas were higher than those obtained from non-residential forested areas. Arsenic, when found, was generally in the more oxidized As(V) form. Selenium (IV) and (VI) were present, but typically at low levels.

Analytical and Bioanalytical Chemistry↗
USGS2022

A progressive flow-routing model for rapid assessment of debris-flow inundation

Debris flows pose a significant hazard to communities in mountainous areas, and there is a continued need for methods to delineate hazard zones associated with debris-flow inundation. In certain situations, such as scenarios following wildfire, where there could be an abrupt increase in the likelihood and size of debris flows that necessitates a rapid hazard assessment, the computational demands of inundation models play a role in their utility. The inability to efficiently determine the downstream effects of anticipated debris-flow events remains a critical gap in our ability to understand, mitigate, and assess debris-flow hazards. To better understand the downstream effects of debris flows, we introduce a computationally efficient, reduced-complexity inundation model, which we refer to as the Progressive Debris-Flow routing and inundation model (ProDF). We calibrate ProDF against mapped inundation from five watersheds near Montecito, CA, that produced debris flows shortly after the 2017 Thomas Fire. ProDF reproduced 70% of mapped deposits across a 40 km 2 study area. While this study focuses on a series of post-wildfire debris flows, ProDF is not limited to simulating debris-flow inundation following wildfire and could be applied to any scenario where it is possible to estimate a debris-flow volume. However, given its ability to reproduce mapped debris-flow deposits downstream of the 2017 Thomas Fire burn scar, and the modest run time associated with a simulation over this 40 km 2 study area, results suggest ProDF may be particularly promising for post-wildfire hazard assessment applications.

Landslides↗
USGS2025

The influence of postfire root strength decay on shallow landslide susceptibility in western Oregon

Severe wildfires can increase the potential for postfire landslides, partly due to the loss of vegetation and root reinforcement. This study investigates the multi-year dynamics of root strength following wildfire in coniferous forests of western Oregon and evaluates implications for postfire slope stability. Root tensile strength was measured through laboratory testing of 969 roots collected from 26 test pits over four postfire timeframes: unburned conditions, 4–12 months postfire (Cedar Creek, 2022), 24–35 months postfire (Holiday Farm, 2020), and 59–67 months postfire (Eagle Creek, 2017). Variables analyzed include root diameter, tensile thread strength, stiffness, progressive tensile strength with displacement, time-dependent strength and ductility, root area ratio, and cohesion. Results indicate a 50% reduction in root strength after wildfire, with the lowest values occurring around 4 years postfire. Projections indicate it could take 10–22 years following fire for root strength to recover to 70% and 90% of the prefire original root strength, respectively. This timeline indicates a multi-year window of vulnerability for shallow landslides that reaches a maximum approximately 4 years following fire. Brittle failure behavior was observed in burned root systems compared to unburned root systems, signaling a more abrupt loss of strength at yield. Simple slope stability analyses show that reduced root strength can lead to instability on more gentle slopes and under less saturation in comparison to unburned conditions. These findings highlight the critical role of root reinforcement in postfire slope stability and the long-term implications of wildfire disturbance on landslide susceptibility.

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