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At least 757 records · Page 42Linked to original sources

USGS2000

Conditions for generation of fire-related debris flows, Capulin Canyon, New Mexico

Comparison of the responses of three drainage basins burned by the Dome fire of 1996 in New Mexico is used to identify the hillslope, channel and fire characteristics that indicate a susceptibility specifically to wildfire-related debris flow. Summer thunderstorms generated three distinct erosive responses from each of three basins. The Capulin Canyon basin showed widespread erosive sheetwash and rilling from hillslopes, and severe flooding occurred in the channel; the North Tributary basin exhibited extensive erosion of the mineral soil to a depth of 5 cm and downslope movement of up to boulder-sized material, and at least one debris flow occurred in the channel; negligible surface runoff was observed in the South Tributary basin. The negligible surface runoff observed in the South Tributary basin is attributed to the limited extent and severity of the fire in that basin. The factors that best distinguish between debris-flow producing and flood-producing drainages are drainage basin morphology and lithology. A rugged drainage basin morphology, an average 12 per cent channel gradient, and steep, rough hillslopes coupled with colluvium and soil weathered from volcaniclastic and volcanic rocks promoted the generation of debris flows. A less rugged basin morphology, an average gradient of 5 per cent, and long, smooth slopes mantled with pumice promoted flooding. Flood and debris-flow responses were produced without the presence of water-repellent soils. The continuity and severity of the burn mosaic, the condition of the riparian vegetation, the condition of the fibrous root mat, accumulations of dry ravel and colluvial material in the channel and on hillslopes, and past debris-flow activity, appeared to have little bearing on the distinctive responses of the basins. Published in 2000 by John Wiley and Sons, Ltd.

Earth Surface Processes and Landforms↗

USGS2019

Developing an expert elicited simulation model to evaluate invasive species and fire management alternatives

Invasive species can alter ecosystem properties and cause state shifts in landscapes. Resource managers charged with maintaining landscapes require tools to understand implications of alternative actions (or inactions) on landscape structure and function. Simulation models can serve as a virtual laboratory to explore these alternatives and their potential impacts on a landscape. To be useful, however, managers need to participate in model development to ensure that model structure can evaluate the response of key resources to plausible actions. Here, we detail development of a state‐and‐transition simulation model (STSM) to evaluate buffelgrass ( Cenchrus ciliaris L. syn Pennisetum ciliare (L.) Link) in Saguaro National Park (SNP), Arizona, USA, through collaboration between managers and researchers. We integrate expert knowledge and research to create and parameterize a stochastic, spatially explicit STSM to evaluate specific management objectives. We also develop a dynamic link between the STSM and a fire behavior model to allow exploration of potential novel processes introduced to the ecosystem by buffelgrass invasion. Our projections show that buffelgrass can be expected to increase on the landscape and that the integration of fire into the model accelerates the projected rate of invasion and increases degradation of resources of management concern. We highlight the benefit of engaging end users in the modeling process so that the model is targeted to evaluate management objectives, in this case retention of saguaro cacti ( Carnegiea gigantea (Engelm.) Britton & Rose) on the landscape. Being able to integrate an external model that can help address the unique characteristics of a problem such as the introduction of fire into the SNP desert ecosystem increases the ability of simulations to address complex ecological and management questions.

Ecosphere↗

USGS2022

Woody plant encroachment of grassland and the reversibility of shrub dominance: Erosion, fire, and feedback processes

Many grass-dominated ecosystems in dryland regions have experienced increasing woody plant density and abundance during the past century. In many cases, this process has led to land degradation and declines in ecosystem functions. An example is the Chihuahuan Desert in the southwestern United States, which experienced different stages of shrub encroachment in the past 150 years. Among a wide variety of mechanisms to explain the grass–shrub transitions in this dryland system, soil erosion (both wind and water) and fire are particularly well studied. Here, we synthesize recent developments on the drivers and feedback in the process of shrub encroachment in the Chihuahuan Desert through the intercomparison of two Long Term Ecological Research (LTER) sites, namely Jornada and Sevilleta. Experimental and modeling studies support a conceptual framework, which underscores the important roles of erosion and fire in woody plant encroachment. Collectively, research at the Jornada LTER provided complementary, quantitative support to the well-known fertile-islands framework. Studies at the Sevilleta LTER expanded the framework, adding fire as a major disturbance to woody plants. Conceptual models derived from the synthesis represent the general understanding of shrub encroachment that emerged from research at these two sites, and can guide management interventions aimed at reducing or mitigating undesirable ecosystem state change in many other drylands worldwide.

New Mexico↗

USGS2023

Guidance for parameterizing post-fire hydrologic models with in situ infiltration measurements

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) can be used to estimate soil hydraulic properties, such as field-saturated hydraulic conductivity ( K fs ) and wetting front potential ( H f ), and their spatial variability following wildfire. However, the small (point-scale) footprint of MDI measurements makes it challenging to use these data to parameterize hydrologic models at the hillslope and watershed scales where hydrologic hazards, such as debris flows, initiate. Here, we designed numerical experiments to estimate spatially constant or watershed-scale effective hydrologic parameters (EHPs) that approximate the response of spatially variable hydrologic parameters with distributions derived from MDI measurements at five sites in the southwestern United States. We found that it is possible to define EHPs for both K fs and H f based on the MDI measurements that lead to reasonable approximations of run-off hydrographs at the outlets of small watersheds (<1 km 2 ). We found that watershed EHPs are functions of rainfall characteristics, although they are most sensitive to rainfall intensity and relatively less sensitive to the temporal distribution of rainfall. EHPs are lower than the arithmetic mean of the MDI measurements and are better approximated by the median or geometric mean of the MDI measurements, particularly for storms with recurrence intervals of approximately 1 year or less that commonly initiate post-fire debris flows. This work demonstrated that using the proposed upscaling method to estimate watershed-scale EHPs, as opposed to approximating EHPs based on the arithmetic mean of the MDI measurements, improved the ability of a hydrologic model to identify storms that are likely to produce debris flows. Results improved our ability to link point-scale MDI measurements and watershed-scale EHPs in post-fire settings and helped guide our ability to use MDI data to parameterize post-fire hydrologic models.

Arizona, New Mexico↗

USGS2013

Infiltration and runoff generation processes in fire-affected soils

Post-wildfire runoff was investigated by combining field measurements and modelling of infiltration into fire-affected soils to predict time-to-start of runoff and peak runoff rate at the plot scale (1 m 2 ). Time series of soil-water content, rainfall and runoff were measured on a hillslope burned by the 2010 Fourmile Canyon Fire west of Boulder, Colorado during cyclonic and convective rainstorms in the spring and summer of 2011. Some of the field measurements and measured soil physical properties were used to calibrate a one-dimensional post-wildfire numerical model, which was then used as a ‘virtual instrument’ to provide estimates of the saturated hydraulic conductivity and high-resolution (1 mm) estimates of the soil-water profile and water fluxes within the unsaturated zone. Field and model estimates of the wetting-front depth indicated that post-wildfire infiltration was on average confined to shallow depths less than 30 mm. Model estimates of the effective saturated hydraulic conductivity, K s , near the soil surface ranged from 0.1 to 5.2 mm h −1 . Because of the relatively small values of K s , the time-to-start of runoff (measured from the start of rainfall), t p , was found to depend only on the initial soil-water saturation deficit (predicted by the model) and a measured characteristic of the rainfall profile (referred to as the average rainfall acceleration, equal to the initial rate of change in rainfall intensity). An analytical model was developed from the combined results and explained 92–97% of the variance of t p , and the numerical infiltration model explained 74–91% of the variance of the peak runoff rates. These results are from one burned site, but they strongly suggest that t p in fire-affected soils (which often have low values of K s ) is probably controlled more by the storm profile and the initial soil-water saturation deficit than by soil hydraulic properties.

Hydrological Processes↗

USGS2017

A micro-UAS to start prescribed fires

Prescribed fires have many benefits, but existing ignition methods are dangerous, costly, or inefficient. This paper presents the design and evaluation of a micro-UAS that can start a prescribed fire from the air, while being operated from a safe distance and without the costs associated with aerial ignition from a manned aircraft. We evaluate the performance of the system in extensive controlled tests indoors. We verify the capabilities of the system to perform interior ignitions, a normally dangerous task, through the ignition of two prescribed fires alongside wildland firefighters.

Conference Paper↗

USGS2009

The increasing wildfire and post-fire debris-flow threat in western USA, and implications for consequences of climate change

In southern California and the intermountain west of the USA, debris flows generated from recently-burned basins pose significant hazards. Increases in the frequency and size of wildfires throughout the western USA can be attributed to increases in the number of fire ignitions, fire suppression practices, and climatic influences. Increased urbanization throughout the western USA, combined with the increased wildfire magnitude and frequency, carries with it the increased threat of subsequent debris-flow occurrence. Differences between rainfall thresholds and empirical debris-flow susceptibility models for southern California and the intermountain west indicate a strong influence of climatic and geologic settings on post-fire debris-flow potential. The linkages between wildfires, debris-flow occurrence, and global warming suggests that the experiences in the western United States are highly likely to be duplicated in many other parts of the world, and necessitate hazard assessment tools that are specific to local climates and physiographies.

Book chapter↗

USGS1998

The interactive effects of fire and herbivory on a coastal marsh in Louisiana

Both vertebrate herbivores and fire have long been known to have dramatic and important effects on wetland vegetation. However, the interactive effects of burning and herbivory have received less attention. In this study, conducted in the coastal marshes of the Pearl River Basin in Louisiana, USA, both the effects of herbivory and fire as well as the interaction between these effects were examined in three marsh community types: Sagittaria lancifolia, Panicum virgatum , and Spartina patens . At five sites for each of the three community types, the effects of burning and fencing to exclude herbivores were determined over two years. Results showed that total biomass was reduced by burning but increased by fencing, with no interactive effects on total biomass. Species density (the number of species per unit area) was enhanced in plots that were both burned and fenced. Spartina patens was an important component in all three communities. Cover estimates indicated that S. patens responded to burning and fencing differently from the other dominant species. In the Panicum virgatum community, P. virgatum cover was enhanced by burning and fencing while S. patens cover was reduced. In the Sagittaria lancifolia community, S. lancifolia and Vigna luteola were enhanced by burning and fencing while S. patens was reduced. In the S. patens community, Scirpus americanus was enhanced by fencing, but burning had no significant effect on cover of either dominant species. These and other data are generally consistent with the hypothesis that herbivory favors S. patens while burning favors other dominant species. Thus, the relative effects of fire and herbivory have an influence (along with other factors such as salinity) on the dominance of S. patens in coastal marshes.

Louisiana↗

USGS2016

Holocene vegetation and fire history of the mountains of northern Sicily (Italy)

Knowledge about vegetation and fire history of the mountains of Northern Sicily is scanty. We analysed five sites to fill this gap and used terrestrial plant macrofossils to establish robust radiocarbon chronologies. Palynological records from Gorgo Tondo, Gorgo Lungo, Marcato Cixé, Urgo Pietra Giordano and Gorgo Pollicino show that under natural or near natural conditions, deciduous forests ( Quercus pubescens , Q. cerris , Fraxinus ornus , Ulmus ), that included a substantial portion of evergreen broadleaved species ( Q. suber , Q. ilex , Hedera helix ), prevailed in the upper meso-mediterranean belt. Mesophilous deciduous and evergreen broadleaved trees ( Fagus sylvatica , Ilex aquifolium ) dominated in the natural or quasi-natural forests of the oro-mediterranean belt. Forests were repeatedly opened for agricultural purposes. Fire activity was closely associated with farming, providing evidence that burning was a primary land use tool since Neolithic times. Land use and fire activity intensified during the Early Neolithic at 5000 bc , at the onset of the Bronze Age at 2500 bc and at the onset of the Iron Age at 800 bc . Our data and previous studies suggest that the large majority of open land communities in Sicily, from the coastal lowlands to the mountain areas below the thorny-cushion Astragalus belt (ca. 1,800 m a.s.l.), would rapidly develop into forests if land use ceased. Mesophilous Fagus - Ilex forests developed under warm mid Holocene conditions and were resilient to the combined impacts of humans and climate. The past ecology suggests a resilience of these summer-drought adapted communities to climate warming of about 2 °C. Hence, they may be particularly suited to provide heat and drought-adapted Fagus sylvatica ecotypes for maintaining drought-sensitive Central European beech forests under global warming conditions.

Sicily↗

USGS2020

Runoff-initiated post-fire debris flow Western Cascades, Oregon

Wildfires dramatically alter the hydraulics and root reinforcement of soil on forested hillslopes, which can promote the generation of debris flows. In the Pacific Northwest, post-fire shallow landsliding has been well documented and studied, but the potential role of runoff-initiated debris flows is not well understood and only one previous to 2018 had been documented in the region. On 20 June 2018, approximately 1 year after the Milli fire burned 24,000 acres, a runoff-initiated debris flow occurred on the flanks of Black Crater in the Oregon Cascade Range. The debris flow was initiated via dispersed rilling on > 30-degree slopes near the crater rim and traveled > 1.5 km downslope. We measured exceptionally low soil infiltration rates at the study site, likely due to high burn severity during the Milli fire. Based on nearby 5-min rain gage data, we quantified rainfall rates for the storm event that triggered the debris flow. Our results show that peak 15-min rainfall rates were 25.4 mmh −1 , equaling or exceeding the measured infiltration rates at the study site, which had a geometric mean of ~ 24 mmh −1 . Field mapping shows that high burn severity resulted in the initiation of the debris flow and that convergent and steep topography promoted the development of a debris flow at this site. As wildfires increase in frequency and intensity across the western USA, the Pacific Northwest could become more susceptible to runoff-initiated debris flows. Therefore, characterization of the conditions that resulted in this debris flow is crucial for understanding how runoff-initiated debris flows may shape terrain and impact hazards in the Pacific Northwest.

Oregon↗

USGS2007

Prescribed fire and cutting as tools for reducing woody plant succession in a created salt marsh

This paper reports on efforts to reduce woody successional growth by the native shrub Iva frutescens L. in a created salt marsh by using prescribed fire and cutting. Experimental treatments included a winter burn, cutting plants at ground level, and a combination burn-and-cut treatment, with replicate plots of each. Iva frutescens proved to be extremely hardy, with zero mortality following the cutting, burning, or combination treatment; similar levels of regrowth were observed for all treatments. Individual shrub response, however, was found to be related to initial plant size, ground water level and salinity, and two fire characteristics (total heating >60??C and total heat index >60??C). Fire severity, sediment nutrient concentrations, and other abiotic factors had no observable effects. ?? 2007 Springer Science+Business Media B.V.

Wetlands Ecology and Management↗

USGS2006

Radiometric ages of the Fire Clay tonstein [Pennsylvanian (Upper Carboniferous), Westphalian, Duckmantian]: A comparison of U-Pb zircon single-crystal ages and 40Ar/39Ar sanidine single-crystal plateau ages

The Fire Clay tonstein [Pennsylvanian (Upper Carboniferous), Westphalian Series, Duckmantian Stage]-a kaolinized, volcanic-ash deposit occurring in Kentucky, West Virginia, Tennessee, and Virginia-is the most widespread bed in the Middle Pennsylvanian of the central Appalachian basin, USA. A concordant single-crystal U-Pb zircon datum for this tonstein gives a 206Pb/238U age of 314.6 ?? 0.9 Ma (2??). This age is in approximate agreement with a mean sanidine plateau age of 311.5 ?? 1.3 Ma (1??, n = 11) for the Fire Clay tonstein. The difference between the two ages may be due to bias between the 40K and 238U decay constants and other factors. The age of the Fire Clay tonstein has important implications for Duckmantian Stage (Westphalian Series) sedimentation rates, correlations with the Westphalian Series of Europe, Middle Pennsylvanian volcanic events, and the late Paleozoic time scale. ?? 2006 Elsevier B.V. All rights reserved.

International Journal of Coal Geology↗

USGS2011

Modeling hydrologic and geomorphic hazards across post-fire landscapes using a self-organizing map approach

Few studies attempt to model the range of possible post-fire hydrologic and geomorphic hazards because of the sparseness of data and the coupled, nonlinear, spatial, and temporal relationships among landscape variables. In this study, a type of unsupervised artificial neural network, called a self-organized map (SOM), is trained using data from 540 burned basins in the western United States. The sparsely populated data set includes variables from independent numerical landscape categories (climate, land surface form, geologic texture, and post-fire condition), independent landscape classes (bedrock geology and state), and dependent initiation processes (runoff, landslide, and runoff and landslide combination) and responses (debris flows, floods, and no events). Pattern analysis of the SOM-based component planes is used to identify and interpret relations among the variables. Application of the Davies-Bouldin criteria following k-means clustering of the SOM neurons identified eight conceptual regional models for focusing future research and empirical model development. A split-sample validation on 60 independent basins (not included in the training) indicates that simultaneous predictions of initiation process and response types are at least 78% accurate. As climate shifts from wet to dry conditions, forecasts across the burned landscape reveal a decreasing trend in the total number of debris flow, flood, and runoff events with considerable variability among individual basins. These findings suggest the SOM may be useful in forecasting real-time post-fire hazards, and long-term post-recovery processes and effects of climate change scenarios.

Environmental Modelling and Software↗

USGS2023

Interactions among rainfall, fire, forbs and non-native grasses predict occupancy dynamics for the endangered Pacific pocket mouse (Perognathus longimembris pacificus) in a Mediterranean-type ecosystem

It is important to understand species-habitat relationships to implement effective adaptive management for rare species. However, it can be challenging to assess habitat associations and their relationships to abiotic stressors in dynamic habitats without the insights that can be gained from long-term monitoring. We report results from the first six years of extensive track tube monitoring of the largest two of three remaining extant populations of federally endangered Pacific pocket mouse ( Perognathus longimembris pacificus ) in a coastal Mediterranean-type ecosystem on Marine Corps Base, Camp Pendleton in southern California, USA. We used dynamic occupancy and structural equation modeling to assess potential drivers of population trends that included habitat, fire history, rainfall, disturbance, and the presence of other small mammals. We found that the variables that best predicted mouse occupancy were moderate to high forb and perennial herb cover (40–80%), and moderate to high open ground (20–70%) and low non-native grass cover (<20%), Non-native grass cover (>20%) was also a strong predictor of lower PPM colonization and increased extinction probabilities, with the extent of non-native grass cover being strongly influenced by annual rainfall and recency of fire. Our study adds to the growing literature on effects of invasive annual grasses on native species in Mediterranean-type ecosystems. We suggest that habitat management could be based upon promotion of open forb and perennial herb dominated habitats with reduction of non-native grasses by prescribed fire and other methods. These types of spatial and temporal monitoring programs can support land managers by creating a monitoring and management feedback loop. They can reveal landscape and environmental variables associated with species persistence, inform habitat management goals, and help managers to assess the success of management actions on populations of conservation concern.

California↗

USGS2017

Prediction of spatially explicit rainfall intensity–duration thresholds for post-fire debris-flow generation in the western United States

Early warning of post-fire debris-flow occurrence during intense rainfall has traditionally relied upon a library of regionally specific empirical rainfall intensity–duration thresholds. Development of this library and the calculation of rainfall intensity-duration thresholds often require several years of monitoring local rainfall and hydrologic response to rainstorms, a time-consuming approach where results are often only applicable to the specific region where data were collected. Here, we present a new, fully predictive approach that utilizes rainfall, hydrologic response, and readily available geospatial data to predict rainfall intensity–duration thresholds for debris-flow generation in recently burned locations in the western United States. Unlike the traditional approach to defining regional thresholds from historical data, the proposed methodology permits the direct calculation of rainfall intensity–duration thresholds for areas where no such data exist. The thresholds calculated by this method are demonstrated to provide predictions that are of similar accuracy, and in some cases outperform, previously published regional intensity–duration thresholds. The method also provides improved predictions of debris-flow likelihood, which can be incorporated into existing approaches for post-fire debris-flow hazard assessment. Our results also provide guidance for the operational expansion of post-fire debris-flow early warning systems in areas where empirically defined regional rainfall intensity–duration thresholds do not currently exist.

Geomorphology↗

USGS2020

The recurrence interval of post-fire debris-flow generating rainfall in the southwestern United States

In the southwestern United States, post-fire debris flows commonly initiate during short bursts of intense rainfall. To date, the frequency of the rainfall rates has not been quantified. Here, we combine an existing database of debris-flow occurrences and corresponding peak storm intensities with a geospatial library of rainfall recurrence interval (RI) information and climate type to determine the distribution of the estimated frequencies of the rainfall associated with 316 observed post-fire debris flows in the southwestern United States. Our results indicate that a majority (77%) of the observed debris flows were triggered by rainfall intensities with RI less than 2 years. Climatic and geographic differences in RI were evident in our analysis. Debris flows in most of the analyzed climates within California, Colorado, and New Mexico were primarily associated with 1-year or less RI intensities, whereas debris flows in arid portions of Arizona, Colorado, and Utah tended to be generated during storms greater than 2-year RI. Event consequence, as defined by the impact on downstream communities and infrastructure, was not directly related to RI, as very destructive debris flows were initiated at a wide range of RI intensities. Our results highlight that post-fire debris-flow initiation can be expected during common rainstorms in the southwestern United States, therefore emergency management plans and risk mitigation efforts must focus on both extreme and frequent rainstorms.

Arizona, California, Colorado, Nevada, New Mexico,↗

USGS2021

Predicting the spatiotemporal exposure of aquatic species to intrusions of fire retardant in streams with limited data

Because fire retardant can enter streams and harm aquatic species including endangered fish, agencies such as the U.S. Forest Service (USFS) must estimate the downstream extent of toxic effects every time fire retardant enters streams (denoted as an “intrusion”). A challenge in estimating the length of stream affected by the intrusion and the exposure time of species in the affected reach is the lack of data typically available on the stream's geometry and flow characteristics. Previously, the USFS estimated the affected reach length assuming instantaneous mixing of the retardant over the reach; however, this approach neglects key river mixing processes. An approach is described that accounts for advection and dispersion of the retardant as well as the downstream growth of the stream. Applied to 13 intrusions documented by the USFS, the new approach shows affected reach lengths range between 8.0 and 362 km; all 13 cases exceeded previous estimates from an instantaneous mixing model. The time that a stationary individual in the affected reach is exposed to concentrations above a pre-defined toxicity threshold (10% of 96-hour LC 50 , for example) ranges from 0.17 to 2.73 h, with all but one case having a maximum exposure time less than 1.5 h. Results from 1152 hypothetical intrusions provided by the USFS confirm that exposure times rarely exceed 5 h. This result suggests that 96-hour tests to determine toxicity (LC 50 ) to various species should be reconsidered. Although the approach described can be improved in several ways, it provides a first estimate of the effects of fire retardant intrusions.

Science of the Total Environment↗

USGS2011

Fire and the origins of Mediterranean-type vegetation

The mediterranean-type climate (MTC) is widely agreed to have been in place in all five MTC regions since at least the late Pliocene (see Fig. 9.1), ~2 Ma, with much of the contemporary mediterranean-type vegetation (MTV) present and contributing to a highly fire-prone environment. There is far less agreement on: (1) the timing of the origin of the MTC, (2) the timing of and factors responsible for the origins of MTV, and (3) the paleohistory of fire and extent to which it has played a role in the origins of MTV. Ample evidence exists to suggest a much earlier origin of MTC and MTV. A widely held paradigm is that many of the woody sclerophylls that comprise MTV are much older than the Pliocene and thus have not adapted to contemporary fire-prone MTC conditions (Axelrod 1989; Herrera 1992; Verdú et al . 2003; Ackerly 2004a). Most of these have origins in the Tertiary Period of the early Cenozoic and are viewed as relictual taxa that represent evolutionary inertia and are present today merely by chance avoidance of random extinctions.

Book chapter↗