The 2000 Valley Complex wildfire burned in steep montane forests with ash cap soils in western Montana, USA. The effects of high soil burn severity on forest soil hydrologic function were examined using rainfall simulations (100mmh−1 for 1h) on 0.5-m2 plots. Infiltration rates, sediment yields and sediment concentrations were compared among three treatments: control (unburned and undisturbed); bare (unburned with all surface vegetation, litter, and duff removed prior to each simulation); and burned. Rainfall simulations were done immediately after the fire and repeated in 2001, 2002, and 2005. Soil moisture, water repellency, and understory canopy and ground cover were measured and related to infiltration rates and sediment yields. The unburned forest soil was water repellent at the mineral surface. This surface repellency was no longer detected after it was burned at high severity, but a post-fire water repellent soil layer was observed at 1–2cm below the surface. The control plots had high ground cover (90% overall), infiltration of 44–48mm, and very low sediment concentrations (median values of 0.1–0.6gL−1) and sediment yields (6–54gm−2) for all years despite changes in soil moisture and strong water repellency. The bare and control plots had similar water repellency values, but the interrill erosion in the bare plots was high throughout the study (624–1277gm−2). In the year of the fire, the burned sites had high rates of soil water repellency (88%) and little ground cover (10%). This resulted in low infiltration rates (30mm), high sediment concentrations (median value 21gL−1), and high sediment yields (1157gm−2). By 2005, the fire-altered water repellency decreased in occurrence (48%) and severity, and the ground cover increased (42%). This resulted in much greater infiltration (84mm), lower sediment concentration (median value 0.5gL−1), and lower sediment yields (15gm−2) on the burned plots. The importance of ground cover for preventing interrill erosion was demonstrated by the very low sediment yields on the control plots as compared to the bare and burned plots. The strength and occurrence of water repellency in both the unburned and burned sites decreased as soil moisture increased; however, strong soil water repellency was detected at the soil surface whenever unburned soils were dry. Fire-altered soil water repellency influenced the infiltration capacity and increased runoff rates immediately after the fire; however, the loss of protective ground cover was a more significant factor for the increased sediment concentrations and sediment yields.

Guidelines for the production and aerial application of wood shred mulch as a post-fire hillslope treatment were developed from laboratory and field studies, several field operations, and the evaluations of professionals involved in those operations. At two early trial sites, the wood shred mulch was produced off-site and transported to the area of use. At the 2010 Schultz Fire in Arizona, the wood mulches were produced on-site from burned hazard trees that were felled and skidded to a processing area where the logs were shredded by a horizontal grinder and piled. The subsequent aerial applications of the wood shreds were staged from the same landings where they were produced. At the 2010 Fourmile Canyon, 2012 High Park, and 2012 Waldo Canyon Fires in Colorado, wood shreds were produced from various combinations of on- and off-site burned and green trees that were generally shredded near the harvest or storage site. The wood shreds were transported by chip trucks to aerial application staging areas. The most challenging aspect of wood shred production was adjusting the grinder screens and through-put speed to maximize the proportion of shreds that were 2 to 8 inches (50 to 200 mm) in length. The same equipment and techniques used for aerial mulching with agricultural straw worked, with some adjustments in flight altitude and speed, for wood shreds. The Heli-Claw, an experimental device designed to replace the cargo net in aerial mulching, was tested and used to apply 80 percent of the wood shred mulch at the Beal Mountain mine reclamation site. Because wood shreds are four to six times heavier than agricultural straw, wood shred mulch took longer to apply than agricultural straw for the same area (25 to 35 ac [10 to 14 ha] per day for wood shreds; approximately 200 ac [81 ha] per day for straw). The additional flight time makes mulching with wood shreds cost three to four times more than with agricultural straw ($1700 to $2200 per ac [$4200 to $5500 per ha] for wood shreds; $500 to $700 per acre [$1200 to 1700 per ha] for straw). However, the advantages of wood shreds - on- or near-site availability, greater stability in high winds and on steep slopes, and lack of unwanted plant seeds from off-site - make wood shred mulch useful in areas where agricultural straw mulch may not be desirable.

After the 2009 Terrace Mountain fire near Kelowna, BC, Canada, wood shred and agricultural straw mulch effects on post-fire runoff and sediment yields were compared using three experimental techniques: rainfall simulations on 1-m2 plots, concentrated flow (rill) simulations on 9-m long plots, and sediment yields from natural rainfall on 30-m2 plots. All experimental plots were located on and along a planar hillslope burned at high severity. Experiments were conducted once a year for three consecutive years beginning in Sep 2009, except for the rainfall simulations which only were conducted the first two years. Although results varied by experiment and time since fire, both agricultural straw and wood shred mulch treatments performed similarly for reducing runoff and sediment; thus were combined into a single "treated" class for analyses. The mulch treatments were effective in reducing sediment yields as compared to the controls in all three experiments in 2009. In the rill simulation experiment, the mulch treatments significantly reduced overland flow velocity and increased the proportion of overland flow that infiltrated the soil before reaching the plot outlet. The elapsed time since the fire, which was strongly related to the increase in vegetative ground cover, was a significant factor for predicting sediment yields in the statistical models. Favorable spring rainfall in 2010 and 2011 supported rapid regrowth of vegetation, which recovered similarly on all plots regardless of treatment. The runoff and sediment yields on the treated plots were similar to those measured on the control plots a year later; we concluded that the mulch was, in effect, a surrogate for a year of recovery. Given that agricultural straw mulch is an established and effective post-fire hillslope treatment, it was important to find that wood shred mulch was similarly effective in reducing post-fire runoff and sediment yields. Thus, the choice of agricultural straw or wood shreds for a post-fire mulch treatment may be based on the performance characteristics (longevity, potential to carry invasive species seeds, cost, etc.) that best fit the needs of the site.

Agricultural straw, hydromulch, and wood shred or wood strand mulches increasingly are being used as post-fire hillslope treatments, but the differences in effectiveness among these mulch treatments are not fully understood. Following the 2002 Hayman fire in central Colorado and the 2003 Cedar fire in southern California, matched catchments were monitored for five to seven post-fire years to determine the effectiveness of wheat straw mulch (Hayman fire only) and hydromulch in reducing post-fire runoff, peak flow rates, and sediment yields from natural rainfall. Measured runoff and sediment yields were caused by short duration high intensity summer storms at the Hayman fire and long duration winter rains at the Cedar fire.The wheat straw mulch treatment significantly reduced peak flow rates and sediment yields at the Hayman fire. The annual peak flow rates in the first two post-fire years in the straw mulch catchment were 4.5 and 3.9 m(3) s(-1) km(-2) (respectively) as compared to 4.3 and 7.1 m(3) s(-1) km(-2) (respectively) in the control. In post-fire years one and two, the maximum event sediment yields in the straw mulch catchment were 7.2 and 10 Mg ha(-1), respectively, which were less than half of the maximum event sediment yields in the control catchment (19 and 24 Mg ha(-1), respectively). The straw mulch catchment had no detectable runoff or sediment yield after the second post-fire year, but the control catchment continued to have measurable runoff and sediment yields through the seventh post-fire year. The straw mulch treatment effect in runoff reduction was not Significant in the statistical model. Total ground cover was 80% immediately after the application of straw mulch, and decreased to 10% by the end of first post-fire year, yet total ground cover values remained high as litter and vegetation, including invasive cheatgrass, increased.The hydromulch cover at both fires declined rapidly and provided less than 10% of the ground cover within 2.5 months after application at which point the catchment was presumed to be untreated. Due to differences in precipitation, the three catchments at the Cedar fire had significantly different hydrologic responses during the presumed untreated portion of the study, which precluded evaluation of treatment effectiveness during the short treated period. The peak flow responses from the hydromulch and control catchments at the Hayman fire were also different during the presumed untreated period and were not tested. Although the runoff and sediment yields did not differ during the presumed untreated period and were tested for treatment effects, the Hayman hydromulch treatment did not significantly affect either response during the first post-fire year the presumed treated period.Unit-area sediment yields from the catchments were similar to those measured on hillslope plots at both the Hayman and Cedar fires in the first post-fire years, but in later years the sediment yields from the catchments were at least double the sediment yields measured on hillslope plots. The longer periods of greater erosion rates in the catchments likely reflect the addition of channel erosion processes and a difference in hydrologic connectivity at the catchment scale. Published by Elsevier B.V.

Mulch treatments often are used to mitigate post-fire increases in runoff and erosion rates but the comparative effectiveness of various mulches is not well established. The ability of mulch treatments to reduce sediment yields from natural rainfall and resulting overland flow was measured using hillslope plots on areas burned at high severity following four wildfires in the western United States. Wheat straw mulch, wood strand mulch, and hydromulch were evaluated along with untreated control plots on multiple fires for 4 to 7 years after burning. Needle cast from fire-killed conifer trees was evaluated in an area of moderate burn severity at one fire, and seeding with genetically native seed was tested, with and without hydromulch, at another fire. Rainfall, ground cover, and soil water repellency were measured in each treatment site at all 4 fires. Mean sediment yields on the control plots ranged from 0.3 to 7.5 Mg ha− 1 in the first post-fire year, from 0.03 to 0.6 Mg ha− 1 in the second, and from 0 to 0.4 Mg ha− 1 in the third and fourth post-fire years. Assuming a linear fit between sediment yield and rainfall intensity, storms with equivalent rainfall intensities produced nearly an order of magnitude less sediment on the control plots in the second post-fire year as compared to the first post-fire year. Large storms (at least a 2-year return period, 10-min maximum rainfall intensity) produced sediment on all fires in all years where they occurred; however, sediment yields produced by large storms that occurred in the first post-fire year were larger than the sediment yields from equivalent storms that occurred in later years at the same fire. Sediment yields decreased as ground cover increased and all the mulch treatments increased total ground cover to more than 60% immediately after application. However, the longevity of the mulches varied, so that the contribution of the treatment mulch to total ground cover varied by mulch type over time. The wood strand mulch was the most long-lived of the mulch treatments and was observed in ground cover assessments throughout the study period (4 and 7 years) at two fires. The wheat straw mulch decreased nearly twice as fast as the wood strand mulch, and no hydromulch was detected after the first post-fire year on either fire where it was tested. Mulch treatment effectiveness varied when data were analyzed separately for each fire. Wood strand mulch reduced sediment yields at both fires where it was tested, wheat straw mulch reduced sediment yields at 2 of the 4 fires where it was applied, and the hydromulch tested at 2 fires did not reduce sediment yields on either. When data were normalized and analyzed by treatment across all fires, wood strand mulch reduced sediment yields for the first four post-fire years, but wheat straw mulch and hydromulch did not significantly reduce sediment yields in any post-fire year. The greater variability in the combined data resulted in fewer statistically significant treatment effects being observed as compared to the individual fire analyses. We believe the fire-specific results provide the more accurate representation of potential post-fire mulch treatment effectiveness.

Mulch treatments often are used to mitigate post-fire increases in runoff and erosion rates but the comparative effectiveness of various mulches is not well established. The ability of mulch treatments to reduce sediment yields from natural rainfall and resulting overland flow was measured using hillslope plots on areas burned at high severity following four wildfires in the western United States. Wheat straw mulch, wood strand mulch, and hydromulch were evaluated along with untreated control plots on multiple fires for 4 to 7 years after burning. Needle cast from fire-killed conifer trees was evaluated in an area of moderate burn severity at one fire, and seeding with genetically native seed was tested, with and without hydromulch, at another fire. Rainfall, ground cover, and soil water repellency were measured in each treatment site at all 4 fires. Mean sediment yields on the control plots ranged from 0.3 to 7.5 Mg ha(-1) in the first post-fire year, from 0.03 to 0.6 Mg ha(-1) in the second, and from 0 to 0.4 Mg ha(-1) in the third and fourth post-fire years. Assuming a linear fit between sediment yield and rainfall intensify, storms with equivalent rainfall intensities produced nearly an order of magnitude less sediment on the control plots in the second post-fire year as compared to the first post-fire year. Large storms (at least a 2-year return period, 10-min maximum rainfall intensity) produced sediment on all fires in all years where they occurred; however, sediment yields produced by large storms that occurred in the first post-fire year were larger than the sediment yields from equivalent storms that occurred in later years at the same fire. Sediment yields decreased as ground cover increased and all the mulch treatments increased total ground cover to more than 60% immediately after application. However, the longevity of the mulches varied, so that the contribution of the treatment mulch to total ground cover varied by mulch type over time. The wood strand mulch was the most long-lived of the mulch treatments and was observed in ground cover assessments throughout the study period (4 and 7 years) at two fires. The wheat straw mulch decreased nearly twice as fast as the wood strand mulch, and no hydromulch was detected after the first post-fire year on either fire where it was tested.Mulch treatment effectiveness varied when data were analyzed separately for each fire. Wood strand mulch reduced sediment yields at both fires where it was tested, wheat straw mulch reduced sediment yields at 2 of the 4 fires where it was applied, and the hydromulch tested at 2 fires did not reduce sediment yields on either. When data were normalized and analyzed by treatment across all fires, wood strand mulch reduced sediment yields for the first four post-fire years, but wheat straw mulch and hydromulch did not significantly reduce sediment yields in any post-fire year. The greater variability in the combined data resulted in fewer statistically significant treatment effects being observed as compared to the individual fire analyses. We believe the fire-specific results provide the more accurate representation of potential post-fire mulch treatment effectiveness. Published by Elsevier B.V.

A considerable investment in post-fire research over the past decade has improved our understanding of wildfire effects on soil, hydrology, erosion and erosion-mitigation treatment effectiveness. Using this new knowledge, we have developed several tools to assist land managers with post-wildfire assessment and treatment decisions, such as prediction models, research syntheses, equipment and methods for field measurements, reference catalogues and databases of past-practice, and spreadsheets for calculating resource valuation and cost–benefit analysis. These tools provide relevant science to post-fire assessment teams and land managers in formats that often can be directly entered into assessment and treatment decision-making protocols. Providing public access to these tools through the internet not only has increased their dissemination, but also has allowed them to be updated and improved as new knowledge and technology become available. The use of these science-based tools has facilitated a broader application of current knowledge to post-fire management in the United States and in other fire-prone areas around the world.

This synthesis of post-fire treatment effectiveness reviews the past decade of research, monitoring, and product development related to post-fire hillslope emergency stabilization treatments, including erosion barriers, mulching, chemical soil treatments, and combinations of these treatments.In the past ten years, erosion barrier treatments (contour-felled logs and straw wattles) have declined in use and are now rarely applied as a post-fire hillslope treatment.In contrast, dry mulch treatments (agricultural straw, wood strands, wood shreds, etc.) have quickly gained acceptance as effective, though somewhat expensive, post-fire hillslope stabilization treatments and are frequently recommended when values-at-risk warrant protection.This change has been motivated by research that shows the proportion of exposed mineral soil (or conversely, the proportion of ground cover) to be the primary treatment factor controlling post-fire hillslope erosion.Erosion barrier treatments provide little ground cover and have been shown to be less effective than mulch, especially during short-duration, high intensity rainfall events.In addition, innovative options for producing and applying mulch materials have adapted these materials for use on large burned areas that are inaccessible by road.Although longer-term studies on mulch treatment effectiveness are on-going, early results and short-term studies have shown that dry mulches can be highly effective in reducing post-fire runoff and erosion.Hydromulches have been used after some fires, but they have been less effective than dry mulches in stabilizing burned hillslopes and generally decompose or degrade within a year.

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The predicted continuation of strong drying and warming trends in the southwestern United States underlies the associated prediction of increased frequency, area, and severity of wildfires in the coming years. As a result, the management of wildfires and fire effects on public lands will continue to be a major land management priority for the foreseeable future. Following fire suppression, the first land management process to occur on burned public lands is the rapid assessment and emergency treatment recommendations provided by the Burned Area Emergency Response (BAER) team. These teams of specialists follow a dynamic protocol to make post-fire treatment decisions based on the best available information using a range of landscape assessment, predictive modeling, and informational tools in combination with their collective professional expertise. Because the mission of a BAER team is to assess burned landscape and determine if stabilization treatments are needed to protect valued resources from the immediate fire effects, the evaluation of treatment success generally does not include important longer term ecological effects of these treatments or the fates of the materials applied over the burned landscape. New tools and techniques that have been designed or modified for BAER team use are presented in conjunction with current post-fire treatment effectiveness monitoring and research. In addition, a case is made to monitor longer term treatment effects on recovering ecosystems and to make these findings available to BAER teams.

Wildfire effects include loss of vegetative cover and changes to soil properties that may lead to secondary effects of increased runoff, erosion, flooding, sedimentation, and vulnerability to invasive weeds. These secondary effects may threaten human life and safety, cultural and ecological resources, land use, and existing infrastructure. Current Burned Area Emergency Response (BAER) assessment procedures require identification and valuation of values-at-risk (VAR) from the potential secondary effects of wildfires. However, guidelines to estimate the monetary value of these resources are limited and difficult to apply. This project examined current methods for post-fire assessment of VAR and sought methodologies to standardize and simplify the complex valuation task. A spreadsheet-based “VAR Calculation Tool” supports this valuation framework. It is expected to improve defensibility of VAR valuation and post-fire emergency treatment decisions.

Our team was asked to analyze and comment on the existing knowledge and science related to postfire rehabilitation treatments, with particular emphasis on the known effectiveness of these treatments. The general effects of fire on Western forested landscapes are well documented (Agee 1993; DeBano and others 1998; Kozlowski and Ahlgren 1974) and have been thoroughly discussed in other chapters of this report. However, postfire erosion and rehabilitation treatment effectiveness have not been studied extensively.