The enhanced probability of catastrophic wildfires has increased our need to understand the risk of floods, erosion, and debris and contaminant transport in burned watersheds. This project investigates the relation between rainfall intensity and peak discharge; erosion and deposition processes; and water-quality impacts to minimize the loss of life and property resulting from post-wildfire floods.
SCIENTIFIC QUESTIONS
The enhanced probability of catastrophic wildfires in the western United States and elsewhere in the world has increased the need to understand the flooding risk and the erosion and depositional responses of burned watersheds. In addition, surface water flowing from burned areas may carry increased levels of sediment, organic debris, and chemicals that may contribute to significant degradation of municipal water supplies and aquatic habitats. Our project has three main thrusts: (1) we are investigating the relation between rainfall intensity and peak water discharge from burned watersheds, a relation that depends on the size of the rainstorm, the size of the burned area and burn severity, and the changes in infiltration capacity of the soil; (2) we are investigating the hillslope and channel erosion and deposition processes after wildfire with a focus on predicting these processes on a watershed or landscape scale rather than on a single hillslope plot or channel cross-section scale; and (3) we are examining the water quality impacts of wildfire and are synthesizing post-fire water-quality sampling protocols.
RESEARCH GOAL
An extensive body of literature exists on the effects of wildfire on watersheds. Wildfires have burned across the landscape of the western United States for centuries, but the magnitude of the geomorphic effect on the landscape is unknown. By understanding the magnitude of the runoff response and the erosion and deposition responses of recent wildfires, we can provide data for landscape evolution models in areas prone to wildfire. In addition, an understanding of the runoff response will contribute to better methods of predicting post-fire flooding to minimize the loss of life and property. Watershed-scale predictions of erosion and deposition from these natural disasters can be used by land managers to prioritize forest treatments based on erosion potential before and after wildfires. Moreover, we hope to contribute to an understanding of wildfire as an element of an ecosystem’s disturbance regime.
Selected USGS Publications
Infiltration and runoff generation processes in fire-affected soils
Wildland fire ash: Production, composition and eco-hydro-geomorphic effects
Current research issues related to post-wildfire runoff and erosion processes
Variations in soil detachment rates after wildfire as a function of soil depth, flow properties, and root properties
Rethinking infiltration in wildfire-affected soils
Soil-water dynamics and unsaturated storage during snowmelt following wildfire
Difference infiltrometer: a method to measure temporally variable infiltration rates during rainstorms
Hyper-dry conditions provide new insights into the cause of extreme floods after wildfire
Hydrologic conditions controlling runoff generation immediately after wildfire
An analytical method for predicting postwildfire peak discharges
Plot-scale sediment transport processes on a burned hillslope as a function of particle size
Spatial variability of steady-state infiltration into a two-layer soil system on burned hillslopes
- Overview
The enhanced probability of catastrophic wildfires has increased our need to understand the risk of floods, erosion, and debris and contaminant transport in burned watersheds. This project investigates the relation between rainfall intensity and peak discharge; erosion and deposition processes; and water-quality impacts to minimize the loss of life and property resulting from post-wildfire floods.
SCIENTIFIC QUESTIONS
The enhanced probability of catastrophic wildfires in the western United States and elsewhere in the world has increased the need to understand the flooding risk and the erosion and depositional responses of burned watersheds. In addition, surface water flowing from burned areas may carry increased levels of sediment, organic debris, and chemicals that may contribute to significant degradation of municipal water supplies and aquatic habitats. Our project has three main thrusts: (1) we are investigating the relation between rainfall intensity and peak water discharge from burned watersheds, a relation that depends on the size of the rainstorm, the size of the burned area and burn severity, and the changes in infiltration capacity of the soil; (2) we are investigating the hillslope and channel erosion and deposition processes after wildfire with a focus on predicting these processes on a watershed or landscape scale rather than on a single hillslope plot or channel cross-section scale; and (3) we are examining the water quality impacts of wildfire and are synthesizing post-fire water-quality sampling protocols.
RESEARCH GOAL
An extensive body of literature exists on the effects of wildfire on watersheds. Wildfires have burned across the landscape of the western United States for centuries, but the magnitude of the geomorphic effect on the landscape is unknown. By understanding the magnitude of the runoff response and the erosion and deposition responses of recent wildfires, we can provide data for landscape evolution models in areas prone to wildfire. In addition, an understanding of the runoff response will contribute to better methods of predicting post-fire flooding to minimize the loss of life and property. Watershed-scale predictions of erosion and deposition from these natural disasters can be used by land managers to prioritize forest treatments based on erosion potential before and after wildfires. Moreover, we hope to contribute to an understanding of wildfire as an element of an ecosystem’s disturbance regime.
The Buffalo Creek Fire in May 1996 burned 4,690 hectares in the mountains southwest of Denver, Colorado. This wildfire lowered the erosion threshold of the watershed. As a consequence of this wildfire, a 100-year rainstorm in July 1996 caused erosion upstream and deposition of this alluvial fan at the mouth of a tributary to Buffalo Creek. Buffalo Creek is flowing to the right at the bottom of the photograph. (Credit: R. H. Meade, USGS.) A consequence of wildfire is the increased probability of flash floods. This flash flood occurred in Spring Creek on July 29, 1997, within the area burned by the Buffalo Creek Fire. The view is upstream and the discharge is about 5.0 cubic meters per second from a maximum 30-minute rainfall intensity of about 19 millimeters per hour. Rainfall-runoff relations suggest a rainfall threshold at about 10 millimeters per hour above which much larger flash floods occur. (Credit: John A. Moody, USGS.) Another consequence of wildfires and subsequent rainfall is erosion. This erosion of a drainage created an incised channel after the Cerro Grande Fire near Los Alamos, NM. The view is upstream and the blue backpack is about 1-meter tall. The maximum 30-minute rainfall intensity was about 20 millimeters per hour. The incision seen in this photo was after the wildfire and rain storm; prior to the storm this drainage had no definite banks. (Credit: John A. Moody, USGS.) Channels draining burned areas have zones of erosion and zones of deposition. This deposition was downstream from an erosion zone shown in the previous photo. The peeled bark indicates the highest level of water and debris during a flash flood. Sediment is coarse sand and gravel. The view is downstream and the blue backpack is about 1-meter tall. (Credit: John A. Moody , USGS.) Water being released from Strontia Springs Dam after wildfire-related flooding. Organic debris and sediment were deposited in Strontia Springs Reservoir, which supplies drinking water to the cities of Denver and Aurora. This debris came from two watersheds (Buffalo Creek and Spring Creek) burned by the 1996 Buffalo Creek Fire. Associated with this debris was an increase in manganese, which increased the chlorine demand of water treated for municipal usage. (Credit: John A. Moody, USGS.) Rill erosion on a burned hillslope after the Buffalo Creek Fire. (Credit: John A. Moody, USGS.) - Publications
Selected USGS Publications
Filter Total Items: 30Infiltration 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 m2). 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 iAuthorsJohn A. Moody, Brian A. EbelWildland fire ash: Production, composition and eco-hydro-geomorphic effects
Fire transforms fuels (i.e. biomass, necromass, soil organic matter) into materials with different chemical and physical properties. One of these materials is ash, which is the particulate residue remaining or deposited on the ground that consists of mineral materials and charred organic components. The quantity and characteristics of ash produced during a wildland fire depend mainly on (1) the toAuthorsMerche B. Bodi, Deborah A. Martin, Victoria N. Balfour, Cristina Santin, Stefan H. Doerr, Paulo Pereira, Artemi Cerda, Jorge Mataix-SoleraCurrent research issues related to post-wildfire runoff and erosion processes
Research into post-wildfire effects began in the United States more than 70 years ago and only later extended to other parts of the world. Post-wildfire responses are typically transient, episodic, variable in space and time, dependent on thresholds, and involve multiple processes measured by different methods. These characteristics tend to hinder research progress, but the large empirical knowledAuthorsJohn A. Moody, Richard A. Shakesby, Peter R. Robichaud, Susan H. Cannon, Deborah A. MartinVariations in soil detachment rates after wildfire as a function of soil depth, flow properties, and root properties
Wildfire affects hillslope erosion through increased surface runoff and increased sediment availability, both of which contribute to large post-fire erosion events. Relations between soil detachment rate, soil depth, flow and root properties, and fire impacts are poorly understood and not represented explicitly in commonly used post-fire erosion models. Detachment rates were measured on intact soiAuthorsJohn A. Moody, Peter NymanRethinking infiltration in wildfire-affected soils
Wildfires frequently result in natural hazards such as flash floods (Yates et al., 2001) and debris flows (Cannon et al., 2001a,b; Gabet and Sternberg, 2008). One of the principal causes of the increased risk of post-wildfire hydrologically driven hazards is reduced in filtration rates (e.g. Scott and van Wyk, 1990; Cerdà, 1998; Robichaud, 2000; Martin and Moody, 2001). Beyond the reduction in peak infilAuthorsBrian A. Ebel, John A. MoodySoil-water dynamics and unsaturated storage during snowmelt following wildfire
Many forested watersheds with a substantial fraction of precipitation delivered as snow have the potential for landscape disturbance by wildfire. Little is known about the immediate effects of wildfire on snowmelt and near-surface hydrologic responses, including soil-water storage. Montane systems at the rain-snow transition have soil-water dynamics that are further complicated during the snowmeltAuthorsBrian A. Ebel, E.S. Hinckley, Deborah A. MartinDifference infiltrometer: a method to measure temporally variable infiltration rates during rainstorms
We developed a difference infiltrometer to measure time series of non-steady infiltration rates during rainstorms at the point scale. The infiltrometer uses two, tipping bucket rain gages. One gage measures rainfall onto, and the other measures runoff from, a small circular plot about 0.5-m in diameter. The small size allows the infiltration rate to be computed as the difference of the cumulativeAuthorsJohn A. Moody, Brian A. EbelHyper-dry conditions provide new insights into the cause of extreme floods after wildfire
A catastrophic wildfire in the foothills of the Rocky Mountains near Boulder, Colorado provided a unique opportunity to investigate soil conditions immediately after a wildfire and before alteration by rainfall. Measurements of near-surface (< 6 cm) soil properties (temperature, volumetric soil-water content, θ; and matric suction, ψ), rainfall, and wind velocity were started 8 days after the wildAuthorsJohn A. Moody, Brian A. EbelHydrologic conditions controlling runoff generation immediately after wildfire
We investigated the control of postwildfire runoff by physical and hydraulic properties of soil, hydrologic states, and an ash layer immediately following wildfire. The field site is within the area burned by the 2010 Fourmile Canyon Fire in Colorado, USA. Physical and hydraulic property characterization included ash thickness, particle size distribution, hydraulic conductivity, and soil water retAuthorsBrian A. Ebel, John A. Moody, Deborah A. MartinAn analytical method for predicting postwildfire peak discharges
An analytical method presented here that predicts postwildfire peak discharge was developed from analysis of paired rainfall and runoff measurements collected from selected burned basins. Data were collected from 19 mountainous basins burned by eight wildfires in different hydroclimatic regimes in the western United States (California, Colorado, Nevada, New Mexico, and South Dakota). Most of the dAuthorsJohn A. MoodyPlot-scale sediment transport processes on a burned hillslope as a function of particle size
Soil moisture, rainfall, runoff, and sediment transport data were collected from four 1-m2 hillslope plots after the 2000 Hi Meadow Fire in Colorado. Data were collected daily during three summers, two of which were affected by drought. Maximum 30-minute rainfall intensities, I30, were less than 20 mm h-1 and the average runoff volumes per plot were less than 4.7 L per storm. The data were separatAuthorsJohn A. MoodySpatial variability of steady-state infiltration into a two-layer soil system on burned hillslopes
Rainfall-runoff simulations were conducted to estimate the characteristics of the steady-state infiltration rate into 1-m2 north- and south-facing hillslope plots burned by a wildfire in October 2003. Soil profiles in the plots consisted of a two-layer system composed of an ash on top of sandy mineral soil. Multiple rainfall rates (18.4-51.2 mm h-1) were used during 14 short-duration (30 min) andAuthorsD.A. Kinner, J. A. Moody