sediment delivery after a wildfire we use a record of sedimentation in a small reservoir within the cerro grande burn area new mexico to document postfire delivery of ash other fine grained sediment carried in suspension within floods and coarse grained sediment transported as bedload over a five year period ash content of sediment layers is estimated using fallout 137 cs as a tracer and ash concentrations are shown to rapidly decrease through a series of moderate intensity convective storms in the first rainy season after the fire over 90 of the ash was delivered to the reservoir in the first year and ash concentrations in suspended sediment were negligible after the second year delivery of the remainder of the fine sediment also declined rapidly after the first year despite the occurrence of higher intensity storms in the second year fine sediment loads after five years remained significantly above prefire averages deposition of coarse grained sediment was irregular in time and was associated with transport by snowmelt runoff of sediment stored along the upstream channel during short duration summer floods coarse sediment delivery in the first four years was strongly correlated with snowmelt volume suggesting a transport limited system with abundant available sediment transport rates of coarse sediment declined in the fifth year consistent with a transition to a more stable channel as the accessible sediment supply was depleted and the channel bed coarsened maximum impacts from ash and other fine grained sediment therefore occurred soon after the fire whereas the downstream impacts from coarse grained sediment were attenuated by the more gradual process of bedload sediment transport

sediment source identification and residence times in the maroochy river estuary southeast queensland australia identification of sediment sources and associated nutrients and contaminants is crucial to the ecological management of aquatic systems a combination of geochemical and radionuclide tracing techniques and geostatistical modelling have been used to determine the primary source areas of fine sediment delivered to the maroochy river estuary the application of radionuclide 137cs and 210pb techniques indicate that approximately 70 of the sediment in the maroochy river estuary originates from subsoil erosion an average of 60 of sediment in the lower estuary originates from soils developed on the landsborough sandstone with 35 coming from soils developed on granitoids in the mid maroochy river estuary major contributions of fine sediment come from soils developed on landsborough sandstone 38 and granitoids 36 estimated sediment residence times in the maroochy river estuary are generally less than 30 years however one sample site near the estuary mouth had an estimated residence time of at least 30 years this indicates that sediment accumulation rates in mangroves along the estuary margins are relatively low results from this study will be used by catchment managers to better target remedial action to reduce fine sediment delivery to the maroochy river estuary

a tracer budget quantifying soil redistribution on hillslopes after forest harvesting managing the impacts of erosion after forest harvesting requires knowledge of erosion sources rates of sediment transport and storage as well as losses from the system we construct a tracer based 137cs sediment budget to quantify these parameters the budget shows significant redistribution storage and transport of sediment between landscape elements and identifies the snig tracks and log landings as the major impact sites in the catchment annual sediment losses from them were estimated to be 25 11 and 101 15 t ha 1 year 1 respectively however it is probable that most of this is due to mechanical displacement of soil at the time of harvesting the budget showed greatest net transport of material occurring from snig tracks representing some 11 4 of the 137cs budget of the latter amount 18 28 and 43 was accounted for within the cross banks filter strip and general harvest area gha respectively the 137cs budget also showed the gha to be a significant sediment trap the filter strip played a fundamental role in the trapping of material generated from the snig tracks the mass delivery to them from this source was calculated to be 1 7 0 6 kg m2 year 1 careful management of these remains critical overall we could account for 97 10 of 137cs this retention suggests that within errors the overall runoff management system of dispersing flow and sediment from the highly compacted snig tracks by cross banks into the less compacted and larger area gha and filter strips has effectively retained surface soil and sediment mobilised as a result of harvesting at this site

the effects of vegetative ash on infiltration capacity sediment transport and the generation of progressively bulked debris flows abstract through the alteration of the physical characteristics of a landscape such as the destruction of vegetation and the formation of a hydrophobic layer a fire can dramatically amplify erosion rates on the basis of field observations it has been proposed that the deposition of a layer of ash on the ground surface can enhance the erosion of mountainous terrain by surface runoff and might even be a necessary condition for the generation of progressively bulked debris flows in this study a flume was constructed to investigate the role of ash in increasing both the volume and the transport capacity of runoff the experiments demonstrated that the presence of ash on the soil surface reduces the ability of flowing water to infiltrate this effect is even greater when the ash has been pre wetted in addition the ability of ash slurries to infiltrate decreases with increasing ash concentration the results also indicate that the transport capacity of runoff is enhanced by the incorporation of ash into the flow because of the increased fluid density however the addition of ash reduces the boundary reynolds number such that at high ash concentrations and with fine grained sediment sediment transport declines as the flow becomes hydraulically smooth the experimental results were also used to evaluate the ability of steep flow fronts a common characteristic of debris flows and flash floods to increase sediment transport rates finally it is proposed that ash slurries may evolve into progressively bulked debris flows through a positive feedback between fluid density transport capacity and erosivity

sediment sources and transport pathways in a rural catchment herefordshire uk the relative significance of primary and secondary suspended sediment sources has been identified in a small 15 km2 agricultural catchment through the application of a linear unmixing model using mineral magnetic geochemical and radionuclide signatures of fine sediments roads appear to be important as a secondary source of suspended sediment and in the conveyance of topsoils to the river channel roads also alter the source signatures of sediment in transport especially that derived from agricultural topsoils modelling suggests that c 30 of the suspended sediment collected from suspended sediment traps in the river leadon were derived from or transported via roads relative contributions from primary sources of c 43 and c 27 were estimated from a combined subsoil and channel bank subsurface source and a combined arable and grassland topsoil source respectively

the application of 137cs to post fire erosion in north west spain abstract wildfires are a frequent occurrence in the cantabrian mountain range in north west spain causing erosion and soil degradation with the aim of measuring this erosion 43 soil cores were taken from four slopes with different degrees of fire frequency and 137 cs concentration the four slopes are located in the same geographical area they have a quartzitic substrate with slopes of between 20 and 30 and share the same type of soil elevation and orientation however vegetation cover is different as a result of the action of fire maps of the area showing the burnt areas over the period 1984 to 2004 remote sensing data confirm the effects that fire has had soil cores were taken from transects on each slope and three reference samples were also taken from a high plateau in order to establish a reference value for 137 cs inventory soil redistribution rates erosion and deposit for the slopes could thus be calculated according to whether 137 cs inventory was higher or lower than the reference value the values obtained show that 137 cs inventory is lower for the slopes with shrubby vegetation than for the reference samples and its distribution indicates higher erosion rates for the upper slope samples mean erosion rates obtained for these slopes were 6 75 t ha 1 year 1 and 6 6 t ha 1 year 1 these data are compared with erosion rates for 137 cs obtained in areas with different climates and patterns of land use 137 cs redistribution was not found on slopes with tree cover suggesting that surface erosion has not occurred or at least not during the time period for which 137 cs can be measured 137 cs distribution was compared with the distribution of other variables and topographical indices distance from the hilltop accumulated flow slope curvature and cti the application of 137 cs in studies of post fire erosion is relatively novelty and it a useful technique in post fire erosion studies over long timescales and for study sites larger than point and plot scales

evidence of debris flow occurrence after wildfire in upland catchments of south east australia abstract numerous reports of flash floods mud torrents and landslides in burnt landscapes of south east australia were only recently linked to debris flows and recognised as a significant process that warrant more detailed investigation this paper provides a systematic documentation of high magnitude erosion events after wildfire in south east australia focusing on small

the use of mineral magnetism in the reconstruction of fire history a case study from lago di origlio swiss alps abstract the use of magnetic measurements in the detection of fire signals has been neglected since the work of rummery et al 1979 yet considerable developments have been made in the interpretation of magnetic measurements over the last 16 years this paper presents a study of the fire history of lago di origlio in the southern swiss alps the study utilises the technique of mineral magnetism alongside the stratigraphic pollen spore and charcoal records correlation between the various proxy records indicates that a magnetic fire record is present within the sediments for the last 4 ka the magnetic fire record has a distinct mineralogical and magnetic grain size signature that can be recognised against the background sedimentary signal the results suggest that magnetic measurements may be usefully employed in the reconstruction of fire history their application is rapid and non destructive and the results may provide additional information in relation to the links between catchment fire events and the sedimentary record

deriving hillslope sediment budgets in wildfire affected forests using fallout radionuclide tracers abstract information on post fire sediment and nutrient redistribution is required to underpin post fire catchment management decisions fallout radionuclide budgets 210 pb xs 137 cs and 7 be were derived to quantify soil redistribution and sediment yield in forested terrain following a moderately severe wildfire in a small 89 ha water supply catchment in se australia application of these techniques in burnt terrain requires careful consideration of the partitioning of radionuclides between organic and mineral soil components beryllium 7 and 210 pb xs were shown to be closely associated with ash litter and soil organic matter whereas 137 cs was more closely associated with subsurface coarse mineral soil comparison of the three tracer budgets indicated that the dominant sediment source areas were ridgetops and steep valley sideslopes from which burnt surface material was conveyed to the stream network via pre existing gullies erosion was predominantly driven by sheetwash enhanced by soil water repellency and modified by bioturbation which both supplies subsurface sediment and provides sinks for erosive overland flow footslope and riparian zones were not important sediment source areas the estimated event based wildfire and subsequent rainfall sediment yield is 58 25 t km 2 based on fallout 7 be measurements the upper estimate of total particulate phosphorus yield 0 70 kg ha 1 is more than 10 times that at equivalent unburnt sites this illustrates that soon after fire burnt eucalypt forest can produce nutrient loads similar to those of agricultural catchments the tracer budgets indicate that wildfire is an important control on sediment and phosphorus inputs to the stream network over the decadal timeframe and the pulsed nature of this release is an important concern for water quality management

the dominant erosion processes supplying fine sediment to three major rivers in tropical australia the daly nt mitchell qld and flinders qld rivers abstract the tropics of northern australia have received relatively little attention with regard to the impact of soil erosion on the many large river systems that are an important part of australia s water resource especially given the high potential for erosion when long dry seasons are followed by intense wet season rain here we use 137cs concentrations to determine the erosion processes supplying sediment to two major northern australian rivers the daly river northern territory and the mitchell river queensland we also present data from five sediment samples collected from a 100 km reach of the cloncurry river a major tributary of the flinders river queensland concentrations of 137cs in the surface soil and subsurface channel banks and gully samples were used to derive best fit probability density functions describing their distributions these modelled distributions are then used to estimate the relative contribution of these two components to the river sediments our results are consistent with channel and gully erosion being the dominant source of sediment with more than 90 of sediment transported along the main stem of these rivers originating from subsoil we summarize the findings of similar studies on tropical australian rivers and conclude that the primary source of sediment delivered to these systems is gully and channel bank erosion previously as a result of catchment scale modelling sheet wash and rill erosion was considered to be the major sediment source in these rivers identifying the relative importance of sediment sources as shown in this paper will provide valuable information for land management planning in the region this study also reinforces the importance of testing model predictions before they are used to target investment in remedial action

three component seismogram envelope synthesis in randomly inhomogeneous semi infinite media based on the single scattering approximation abstract we present a method for synthesizing three component seismogram envelopes of local earthquake in a randomly inhomogeneous semi infinite medium the method extends the single scattering model of sato sato h 1984 attenuation and envelope formation of three component seismograms of small local earthquakes in randomly inhomogeneous lithosphere j geophys res 89 1221 1241 by incorporating the effects of a free surface frequency dependent non spherical radiation from a double couple point source and non isotropic scattering including wave type conversion we synthesize seismogram envelopes the root mean square rms amplitude of seismograms at a receiver located on the free surface by dividing an inhomogeneous medium into many small cells and summing the energy of scattered waves from the cells on the isochronal scattering shells of different scattering modes for a given lapse time our main focus is the free surface effect which alters the shape of isochronal scattering shells and the amplitudes of incident waves synthesizing three component seismogram envelopes for different source receiver configurations we find that these effects on seismogram envelopes are not negligible and are pronounced at early s coda p coda envelope shape is not very sensitive to free surface incorporation because of dominant sp scattered waves which come from the source direction

sources of debris flow material in burned areas abstract the vulnerability of recently burned areas to debris flows has been well established likewise it has been shown that many if not most post fire debris flows are initiated by runoff and erosion and grow in size through erosion and scour by the moving debris flow as opposed to landslide initiated flows with little growth to better understand the development and character of these flows a study has been completed encompassing 46 debris flows in california utah and colorado in nine different recently burned areas for each debris flow progressive debris production was measured at intervals along the length of the channel and from these measurements graphs were developed showing cumulative volume of debris as a function of channel length all 46 debris flows showed significant bulking by scour and erosion with average yield rates for each channel ranging from 0 3 to 9 9 m 3 of debris produced for every meter of channel length with an overall average value of 2 5 m 3 m significant increases in yield rate partway down the channel were identified in 87 of the channels with an average of a three fold increase in yield rate yield rates for short reaches of channels up to several hundred meters ranged as high as 22 3 m 3 m debris was contributed from side channels into the main channels for 54 of the flows with an average of 23 of the total debris coming from those side channels rill erosion was identified for 30 of the flows with rills contributing between 0 1 and 10 5 of the total debris with an average of 3 debris was deposited as levees in 87 of the flows with most of the deposition occurring in the lower part of the basin a median value of 10 of the total debris flow was deposited as levees for these cases with a range from near zero to nearly 100 these results show that channel erosion and scour are the dominant sources of debris in burned areas with yield rates increasing significantly partway down the channel side channels are much more important sources of debris than rills levees are very common but the size and effect on the amount of debris that reaches a canyon mouth is highly variable

a morphometric analysis of gullies scoured by post fire progressively bulked debris flows in southwest montana usa in the fall of 2001 an intense thunderstorm in southwest montana triggered many debris flows in the burned area of sleeping child creek in most instances the debris flows cut deep gullies into previously unchannelized colluvial hollows and deposited large volumes of sediment onto the valley floor the presence of rill networks above the gullies as well as the absence of landslide features indicate that the gullies were scoured by progressively bulked debris flows a process in which dilute surface runoff becomes increasingly more laden with sediment until it transforms into a debris flow in this contribution we present a morphometric analysis of six of the gullies to better understand this relatively understudied process we find that the locations of the rill heads and gully heads conform to slope area thresholds that are characteristic of erosion by overland flow our data also suggest that the volumes of the debris flows increase exponentially with normalized drainage area thus lending support to an assumption used in a recently proposed debris flow incision law finally the debris flow fans have been relatively unaltered since deposition suggesting that the valley may be currently aggrading while the hillslopes are being denuded

magnetic enhancement in wildfire affected soil and its potential for sediment source ascription intense rainfall following wildfire can cause substantial soil and sediment redistribution with concern for the increasing magnitude and frequency of wildfire events research needs to focus on hydrogeomorphological impacts of fire particularly downstream fluxes of sediment and nutrients here we investigate variation in magnetic enhancement of soil by fire in burnt eucalypt forest slopes to explore its potential as a post fire sediment tracer low frequency magnetic susceptibility values lf of 10 m material sourced from burnt slopes c 8 0 10 4 10 6 m3 kg 1 are an order of magnitude greater than those of 10 m material derived from long unburnt areas 0 8 10 6 m3 kg 1 susceptibility of anhysteretic remanent magnetization arm and saturation isothermal remanent magnetization sirm values are similarly enhanced signatures are strongly influenced by soil and sediment particle size and storage of previously burnt material in footslope areas whilst observations indicate that signatures based on magnetic enhancement show promise for post fire sediment tracing problems arise with the lack of dimensionality in such data magnetic grain size indicators fd arm sirm and fd arm offer further discrimination of source material but cannot be included in numerical unmixing models owing to non linear additivity this leads to complications in quantitatively ascribing downstream sediment to source areas of contrasting burn severity since sources represent numerical multiples of each other indicating the need to involve additional indicators such as geochemical evidence to allow a more robust discrimination copyright 2005 john wiley sons ltd

effects of fire induced water repellency on soil aggregate stability splash erosion and saturated hydraulic conductivity for different size fractions forest fires can alter several soil properties influencing soil erosion and runoff processes in addition to removing all or part of the vegetative cover these include organic matter content aggregate stability and water repellency soil erodibility and saturated hydraulic conductivity depend on these properties and their response varies according to aggregate size the objective of the study was to investigate how forest fires affect key soil properties and determine the potential impact of these on runoff and erosion processes the a horizon of an acidic sandy loam was collected and subjected to a pine litter fire the burned and control soil samples were separated into 4 size fractions bulk 5 0 mm 0 4 0 4 2 0 and 2 0 5 0 mm organic matter om aggregate stability mean weight diameter mwd and water drop penetration time wdpt were measured for each size class each size fraction sample was subjected to 0 5 h of simulated rainfall 55 mm h 1 for splash erosion measurements saturated hydraulic conductivity k measurements were performed on the same samples burning the litter decreased soil om content but increased mwd and wdpt splash erosion increased greatly for the bulk and 0 4 mm samples mwd increased for the 0 4 2 0 and 2 0 5 0 mm size fractions despite a loss in om and clay content in the burned soil a surface crust never formed on the water repellent fine fraction leaving plenty of non cohesive material available for soil detachment increased water repellency reduced k for all size fractions the data support the need for a specific soil erodibility index for post forest fire soils copyright 2007 john wiley sons ltd

effect of surface roughness on runoff and erosion in a mediterranean ecosystem the role of fire mechanisms at the micro patch scale influencing runoff and erosion processes following a forest fire were investigated the study was conducted in a mediterranean mountainous region with a mean annual rainfall of 690 mm terra rossa soil and vegetation composed of a dense shrubland of pinus halepensis and quercus calliprinos simulated rainfall experiments were carried out on plots representing different intervals of time elapsed since a fire i e immediately after fire two weeks after fire one year after fire unburned plots were also used for comparison at a local scale great variability was found whereby some patches produced high runoff and sediment yields following fire while others did not the conclusion is that the main effect of fires of low to moderate intensity is to produce a mosaic like surface containing both rough patches in which there is almost no chance for runoff generation and relatively smooth patches in which fire can subsequently lead to higher runoff and erosion rates

determining the sources of suspended sediment in a forested catchment in southeastern australia 1 knowledge is scarce regarding the relative contributions from harvested areas and unsealed roads to sediments in forested catchments we investigate the source composition of suspended sediment using sediment tracers and an improved multivariate mixing model sediment samples were collected during six rainfall events geochemical and radiometric tracer properties were corrected for particle size and organic content as well as conservativeness during erosion and sediment delivery the mixing model incorporates variability of the tracer properties using a monte carlo simulation technique mean sediment contribution from the undisturbed forest was 50 70 harvested areas gravel surfaced roads and ungravelled roads contributed 5 15 6 14 and 12 25 respectively the unsealed roads contribute 20 to 60 times more sediment than the undisturbed forest and about 10 times more sediment than the harvested areas on a per unit area basis harvested areas contribute 1 to 5 times greater sediment than the undisturbed forest these results support other studies that identify unsealed roads as important sediment sources in forested catchments

fingerprinting suspended sediment sources in the catchment of the river ouse yorkshire uk statistically verified composite fingerprints and a multivariate mixing model have been employed to establish the main sources of the suspended sediment transported through the lower non tidal reaches of the river ouse and one of its main tributaries the river wharfe during the period 1994 1997 in the case of the suspended sediment samples collected from the river ouse the load weighted mean contributions from uncultivated topsoil cultivated topsoil and channel bank sources were estimated to be c 25 38 and 37 respectively while for the river wharfe these sources contributed c 70 4 and 23 respectively c 4 was derived from woodland topsoil suspended sediment samples collected during higher flows evidenced a greater contribution from channel banks than samples collected during lower flows source materials were also differentiated according to the three main geological source areas carboniferous permian and triassic and jurassic and their load weighted mean contributions were estimated to be c 24 41 and 35 for the river ouse and c 91 9 and 0 there are no jurassic rocks in this catchment for the river wharfe respectively when suspended sediment samples from tributary streams were used to characterize each geological source area the equivalent results for the river ouse were c 30 46 and 24 considering the three main tributaries that contribute to the river ouse the load weighted mean contributions from the rivers swale ure and nidd were estimated to be 82 15 and 3 respectively these values have been compared with estimates of the relative magnitude of the annual suspended sediment loads of these three rivers for the years 1995 and 1996 derived from continuous monitoring of discharge and turbidity differences between the two sets of results are ascribed to the different periods of record involved and to the timing of suspended sediment sampling relative to the overall storm hydrograph and thus the degree to which the available samples are representative of the overall suspended sediment flux although a number of limitations must be recognized the fingerprinting approach to source ascription is seen as providing valuable information regarding suspended sediment sources in the study catchments copyright 1999 john wiley sons ltd

first time landslides in vashon advance glaciolacustrine deposits puget lowland u s a abstract advance glaciolacustrine qglv deposits from the last continental glaciation are widespread in the densely populated puget lowland and are prone to shallow landsliding much less frequently in historic time new landslides propagate deeply within intact qglv deposits the exceptional volume and highly mobile nature of the 22 march 2014 state route 530 oso landslide generated considerable uncertainty and public concern about the likelihood for similar deep seated failures initiating from most any slope where these deposits crop out the primary study objectives are to utilize geotechnical data from the small data set of available published and public domain investigations to characterize in general terms hydrogeologic geotechnical and geomorphic factors and their relative contribution to initiating deep seated landslides within intact qglv deposits and to inform future hazard and risk assessments for first time landslides within these deposits qglv deposits are overconsolidated very stiff to hard laminated to massive silt and clay shear strength is anisotropic with cohesion being a significant component of bedding parallel strength and friction dominating strength perpendicular to bedding hydraulic conductivity is likely also anisotropic multi year records of pore pressures within qglv deposits show no to minor seasonal flux only minor pore pressure responses to multi day to multi week episodes of heavy precipitation have been detected back analyses using limit equilibrium methods and peak anisotropic strength under drained conditions demonstrate initial stability of the slopes instability occurs near the fully softened strength we conclude that over the long term loss of cohesive strength rather than hydroclimatic pore pressure response is the more important contributor to diminishing stability and in some cases initiation of first time landslides in qglv deposits the shape and location of the slide surface is strongly influenced by strength anisotropy and stress state sliding surfaces developed near the basal contact of the qglv deposits in all of the five studied landslides higher stress states associated with increasing sequence thickness of the landslide masses decrease stability the length of the basal slide surface and thus the aspect ratio of the landslide mass appears to increase proportionally with sequence thickness of the landslide mass

fire related sedimentation events on alluvial fans yellowstone national park u s a abstract we document initiation and flow processes deposit facies and geomorphic effects of forest fire related sedimentation on small alluvial fans in yellowstone national park brief intense convective storm precipitation on steep basins burned in the 1988 fires produced sedimentation events involving a variety of depositional processes on fans over the course of all documented events flows on fans progressed from higher to lower sediment concentration events were often dominated by either debris flows or relatively sediment poor streamflow processes in some events however flows ranging a over wide spectrum of sediment concentration produced significant fan deposits debris flows were generated by progressive sediment bulking involving pervasive surface runoff and rill erosion on st ep upper basin slopes followed by deep incision as flows progressed down channels debris flow deposits show a marked decline in thickness and coarse gravel content downfan often with extensive distal gravel poor facies we recognized a relatively minor percentage of noncohesive debris flow and hyperconcentrated flow facies with sorting and stratification intermediate between muddy debris flow and streamflow facies these were deposited where dilute flows bulked with coarse sediment by eroding channel alluvium or earlier deposits of the event below incised fan channels streamflows expanded as sheetfloods which prograded lower fans with distally fining deposits basins 3 km2 typically produced streamflow events on fans but sediment texture and availability on slopes and in channels are primary factors determining flow processes on fans of smaller basins burned soil surfaces provided abundant silt and clay for debris flow generation but because soil surface sediment was stripped and or compacted over time the lack of available fines resulted in dominance of streamflow processes in later events

quantitative sediment source ascription using magnetic measurements in a reservoir catchment system near nijar s e spain the magnetic properties of sediments from a dried out reservoir and its inflowing streams were measured to provide a basis for sediment source determination quantitative estimates of source component proportions in the reservoir sediments were made using linear programming procedures the study confirms that this type of research must be based on a detailed knowledge of the relationship between magnetic properties and particle size in both the sediments and the potential sources in the case of the site studied the isabel ii reservoir near nijar s e spain the sediments generated by contemporary surface processes within the reservoir catchment fail to reflect fully the 19th century material largely responsible for the rapid infill of the reservoir an additional source type namely unweathered schist derived material not represented in the fine sediments sampled within channels upstream from the reservoir has to be included in the model before calculations of source component contributions can be made it is inferred that one or more high magnitude low frequency event outside the amplitude of the most recently operating processes was largely responsible for the infilling of the reservoir

establishing fire incidence in temperate soils using magnetic measurements abstract natural unburnt topsoil samples from the cotswolds region of england and samples from archaeological contexts in the uk and hungary some of which are known to have been affected by burning have been used to identify a distinctive magnetic signature linked to the effects of fire on magnetic properties a combination of bulk low field lf and frequency dependent fd magnetic susceptibility and normalized anhysteretic remanent magnetization arm measurements have been used on both unburnt and experimentally burnt samples from the cotswolds and on the archaeological samples complementary determinations were made for both sets of samples of the maximum potential susceptibility max and hence percentage fractional conversion conv which provides independent evidence of burning the results show that the ferrimagnetic mineral assemblages produced as a result of fire have a significantly finer grain size than those arising from weathering and soil formation alone burning thus gives rise to a distinctive envelope of values on a bilogarithmic plot of arm fd versus arm lf such a diagram provides a convenient basis for identifying magnetic signatures in soils archaeological materials and palaeosols that have arisen mainly through burning

the effects of wildfires on the magnetic properties of soils in the everglades we present results of a rock magnetic study of soils that were affected by wildfires that burned portions of the everglades in the spring of 2008 soils at sites that were extensively burned exhibit a pronounced surface magnetic enhancement effect with magnetizations of surface samples up to 16 times greater than that observed at depth 7 cm at these sites the increase in magnetization results from an increased abundance of a low coercivity phase maghemite that occurs at the expense of the abundance of a high coercivity phase goethite these results indicate that fire induced heating caused goethite in the surface soils to convert into a more magnetic low coercivity phase such as maghemite goethite is an excellent adsorber of phosphorus and therefore we hypothesize that the destruction of goethite as a result of burning may have important implications for phosphorus cycling in the everglades ecosystem copyright 2010 john wiley sons ltd

improving precision in sediment source and erosion process distinction in an upland catchment south eastern australia abstract analysis of sediment sources is an important component in the development of catchment sediment budgets and in determining links between erosion from sources and sediment delivery to catchment outlets in this study 137cs and 210pbex were used to determine surface and sub surface source contributions of fine sediment in a small upland headwater catchment 1 6 km2 in south eastern australia the findings from this analysis are employed in an adjustment procedure to better differentiate sediment source erosion processes by utilising channel survey and erosion pin data this improved the precision of estimates of sediment source erosion process contributions from hillslopes and channel gully walls a mean of 74 of in channel deposits and suspended sediment exiting the study catchment was derived from sub surface sources and when adjusted for erosion process this increased to 81 which may be attributed to channel and gully wall erosion alone net erosion of the channel floor was low and constitutes only a small part of the total channel source input to sediment flux variability in sediment source contributions within the catchment was high with rapid transition from hillslope to channel source dominance of sediment flux with distance downstream in the study catchment

tracing crop specific sediment sources in agricultural catchments abstract a compound specific stable isotope cssi sediment tracing approach is evaluated for the first time in an agricultural catchment setting against established geochemical fingerprinting techniques the work demonstrates that novel cssi techniques have the potential to provide important support for soil resource management policies and inform sediment risk assessment for the protection of aquatic habitats and water resources analysis of soil material from a range of crop covers in a mixed land use agricultural catchment shows that the carbon cssi signatures of particle reactive fatty acids label surface agricultural soil with distinct crop specific signatures thus permitting sediment eroded from each land cover to be tracked downstream high resolution sediment sampling during a storm event and analysis for cssi and conventional geochemical fingerprints elucidated temporal patterns of sediment mobilisation under different crop regimes and the specific contribution that each crop type makes to downstream sediment load pasture sources 65 of the catchment area dominated the sediment load but areal yield 0 13 0 02 t ha 1 was considerably less than that for winter wheat 0 44 0 15 t ha 1 while temporal patterns in crop response matched runoff and erosion response predictions based on plot scale rainfall simulation experiments comparison of biomarker and geochemical fingerprinting data indicated that the latter overestimated cultivated land inputs to catchment sediment yield due to inability to discriminate temporary pasture in rotation from cultivated land this discrepancy however presents an opportunity since combination of the two datasets revealed the extremely localised nature of erosion from permanent pasture fields in this system estimated at up to 0 5 t ha 1 the novel use of cssi and geochemical tracers in tandem provided unique insights into sediment source dynamics that could not have been derived from each method alone research into cssi signature development plant and soil processes and the influence of cultivation regimes are required to support future development of this new tool

discriminating fine sediment sources and the application of sediment tracers in burned catchments a review wildfire can cause substantial changes to runoff erosion and downstream sediment delivery processes in response to these disturbance effects the main sources of sediment transported within burned catchments may also change sediment tracing offers an approach to determine the proportional contributions of fine sediment typically 63 m from burned catchment sources in this paper we review the application of various sediment tracers to discriminate fine sediment sources following wildfire fallout radionuclides provide the most effective tracers for discriminating hillslope surface and sub surface usually channel bank sources previous tracer studies quantifying contributions from these sources after wildfire are based exclusively on radionuclides the potential for fallout radionuclides to discriminate spatial sources defined according to burned and unburned areas depends on burn related changes in surface soil concentrations tracing of burned and unburned source areas will be problematic where most radionuclides in surface material are bound to ash rather than soil geochemical properties of surface soils are probably too susceptible to natural and burn related variability to consistently discriminate burn defined spatial sources mineral magnetic properties have shown potential for discriminating soil burned at different severities as well as unburned areas more research is needed to assess the use of soil organic compounds as tracers of burned source areas linking fallout radionuclide based hillslope and channel source discrimination with process measurements and monitoring after fire can provide enhanced insight into fine sediment transfer and related water quality impacts adopting such integrated and multi scale approaches would contribute to improved understanding of hydrological and geomorphological responses to wildfire copyright 2012 john wiley sons ltd

a process for fire related debris flow initiation cerro grande fire new mexico in this study we examine factors that pertain to the generation of debris flows from a basin recently burned by wildfire throughout the summer 2000 thunderstorm season we monitored rain gauges channel cross sections hillslope transects and nine sediment runoff traps deployed in a steep 0 15 km 2 basin burned by the may 2000 cerro grande fire in new mexico debris flows were triggered in the monitored basin during a rainstorm on july 16 2000 in response to a maximum 30 min rainfall intensity of 31 mm h 1 return period of approximately 2 years eleven other storms occurred before and after the july storm these storms resulted in significant runoff but did not generate debris flows the debris flows generated by the july 16 storm initiated on a broad open hillslope as levee lined rills the levees were composed of gravel and cobble sized material supported by an abundant fine grained matrix debris flow deposits were observed only on the hillslopes and in the first and second order drainages of the monitored basin no significant amounts of channel incision were measured following the passage of the debris flows indicating that most of the material in the flows originated from the hillslopes sediment runoff concentrations of between 0 23 and 0 81 kg l 1 with a mean of 0 42 kg l 1 were measured from the hillslope traps following the debris flow producing storm these concentrations however were not unique to the july 16 storm the materials entrained by the july 16 storm contained a higher proportion of silt plus clay sized materials in the 2 mm fraction than the materials collected from storms that produced comparable sediment runoff concentrations but not debris flows the difference in materials demonstrates the critical role of the availability of fine grained wood ash mantling the hillslopes in the runoff dominated generation of post wildfire debris flows the highest sediment runoff concentrations again not unique to debris flow production were produced from maximum 30 min rainfall intensities greater than 20 mm h 1

fallout radionuclide tracers identify a switch in sediment sources and transport limited sediment yield following wildfire in a eucalypt forest abstract fire can alter sediment sources and transport rates in river basins changing landforms and aquatic habitats and degrading downstream water quality variability in the response between environments between fires and with time since fire makes predicting the catchment scale effect of individual fires difficult this study applies the fallout radionuclides 137cs and 210pbxs to trace the sources and transport of fine sediment through a river network following a wildfire of moderate to extreme severity in the 629 km2 eucalypt forested nattai river water supply catchment near sydney australia the tracer analysis showed that post fire erosion caused a switch in fine

137cs losses from a loamy surface water gleyed soil inceptisol a laboratory simulation experiment abstract 137 cs was applied with simulated rainfall to 0 25 m 2 soil boxes at an intensity of 20 mm hr 1 for 30 minutes ten simulations were performed on six soil boxes at 2 and 4 slopes soil was compacted in one box to simulate the effects of tractor wheelings the depth distribution of 137 cs was analysed in six soil cores in addition a 1 m long 16 cm wide soil trough was placed under the simulator until a constant rate of overland flow was generated 137 cs was added at four locations at increasing distance from the trough outflow overland flow drainage water and suspended sediments were collected and analysed separately for 137 cs in all experiments at 2 slopes the highest proportion of the 137 cs input was lost by drainage at 4 slopes and with compaction the greatest amount of 137 cs was eroded with sediment approximately 10 of the added 137 cs was lost from the compacted soil over the ten simulations 137 cs retention in the upper 10 cm of the profile ranged from more than 95 compacted soil to less than 45 uncompacted soils results from the trough experiment suggested that 137 cs could be preferentially adsorbed by sediments entrained in overland flow

determining sources and transit times of suspended sediment in the murrumbidgee river new south wales australia using fallout 137cs and 210pb sediment budgets typically require an estimate of the proportional yield from erosion sources to sediments in transport and storage this becomes increasingly difficult as catchments become larger and erosion storage and deposition processes become more complex we demonstrate how fallout radionuclides can be used to estimate the proportional contributions to sediment load from a tripartite classification of erosion sources in a large catchment the mid murrumbidgee 13 500 km2 the three major potential sources of sediment within this catchment are cultivated lands 22 of the surface area uncultivated pastoral lands 78 and the numerous channels and gullies found in this region concentrations of the fallout radionuclides 210pbex and 137cs in representative samples from each of these three sources are significantly different employing these values in a simple mixing model shows that the largest contribution of material is currently derived from subsoil channel gully sources alterations to the suspended sediment 210pbex signature by in situ labeling and decay are also considered applying the model with different concentrations of 210pbex decayed as a function of residence time in channels suggests that the mean residence time of fine grained material within this system is 10 5 years however differences in 137cs concentrations observed between flood and low flow sediments and the presence of the short lived cosmogenic 7be suggest that residence time of some of this fine grained material may be of the order of only weeks to months

combining suspended sediment monitoring and fingerprinting to determine the spatial origin of fine sediment in a mountainous river catchment an excess of fine sediment grain size 2 mm supply to rivers leads to reservoir siltation water contamination and operational problems for hydroelectric power plants in many catchments of the world such as in the french alps these problems are exacerbated in mountainous environments characterized by large sediment exports during very short periods this study combined river flow records sediment geochemistry and associated radionuclide concentrations as input properties to a monte carlo mixing model to quantify the contribution of different geologic sources to river sediment overall between 2007 and 2009 erosion rates reached 249 75 t km 2 yr 1 at the outlet of the bleone catchment but this mean value masked important spatial variations of erosion intensity within the catchment 85 5000 t km 2 yr 1 quantifying the contribution of different potential sources to river sediment required the application of sediment fingerprinting using a monte carlo mixing model this model allowed the specific contributions of different geological sub types i e black marls marly limestones conglomerates and quaternary deposits to be determined even though they generate locally very high erosion rates black marls supplied only a minor fraction 5 20 of the fine sediment collected on the riverbed in the vicinity of the 907 km2 catchment outlet the bulk of sediment was provided by quaternary deposits 21 66 conglomerates 3 44 and limestones 9 27 even though bioengineering works conducted currently to stabilize gullies in black marl terrains are undoubtedly useful to limit sediment supply to the bleone river erosion generated by other substrate sources dominated between 2007 and 2009 in this catchment

quantifying sources of fine sediment supplied to post fire debris flows using fallout radionuclide tracers fine sediment supply has been identified as an important factor contributing to the initiation of runoff generated debris flows after fire however despite the significance of fines for post fire debris flow generation no investigations have sought to quantify sources of this material in debris flow affected catchments in this study we employ fallout radionuclides 137cs 210pbex and 239 240pu as tracers to measure proportional contributions of fine sediment 10 m from hillslope surface and channel bank sources to levee and terminal fan deposits formed by post fire debris flows in two forest catchments in southeastern australia while 137cs and 210pbex have been widely used in sediment tracing studies application of pu as a tracer represents a recent development and was limited to only one catchment the ranges in estimated proportional hillslope surface contributions of fine sediment to individual debris flow deposits in each catchment were 22 69 and 32 74 the greater susceptibility of 210pbex to apparent reductions in the ash content of channel deposits relative to hillslope sources resulted in its exclusion from the final analysis no systematic change in the proportional source contributions to debris flow deposits was observed with distance downstream from channel initiation points instead spatial variability in source contributions was largely influenced by the pattern of debris flow surges forming the deposits linking the tracing analysis with interpretation of depositional evidence allowed reconstruction of temporal sequences in sediment source contributions to debris flow surges hillslope source inputs dominated most elevated channel deposits such as marginal levees that were formed under peak flow conditions this indicated the importance of hillslope runoff and fine sediment supply for debris flow generation in both catchments in contrast material stored within channels that was deposited during subsequent surges was predominantly channel derived the results demonstrate that fallout radionuclide tracers may provide unique information on changing source contributions of fine sediment during debris flow events

artificial magnetic enhancement of stream bedload a hydrological application of superparamagnetism abstract laboratory heat treatment of natural rocks alters their mineralogy and produces a characteristic magnetization that can be used as a simple persistent tracer workers have shown that natural magnetic enhancements occur in soils on a wide range of bedrocks including limestones granites shales and sandstones the artificial magnetic enhancement tracing method may consequently be expected to be applicable to many localities in our study magnetite and hematite were grown in naturally paramagnetic mudstones and slates by rapid heating in air to 900 c and then quenching studies of magnetic remanence viscosity hysteresis and coercivity m ssbauer spectroscopy and the effect of temperature on magnetization have been used to determine the dominant processes affecting the magnetic mineralogy during heat treatment these are the growth of single domain magnetite followed by the formation of superparamagnetic magnetite probably by both the breakdown of the single domain magnetite and the growth of new crystals simultaneously with the formation of hematite the fine magnetite particles dominate most of the magnetic properties of the heat treated samples although hematite is produced in greater abundance the mineralogical changes of the magnetic grains are complex and depend on many interrelated variables however a very simple but effective heat treatment procedure has been developed that optimizes the enhancement of magnetic susceptibility and permits practical hydrological field experiments to be performed this work is concerned with stream bedload movement but the artificial magnetic enhancement method could also be useful in studying other sedimentological processes such as movement of sand waves and beach sands and the silting of harbours

wildfire related debris flow initiation processes storm king mountain colorado a torrential rainstorm on september 1 1994 at the recently burned hillslopes of storm king mountain co resulted in the generation of debris flows from every burned drainage basin maps 1 5000 scale of bedrock and surficial materials and of the debris flow paths coupled with a 10 m digital elevation model dem of topography are used to evaluate the processes that generated fire related debris flows in this setting these evaluations form the basis for a descriptive model for fire related debris flow initiation the prominent paths left by the debris flows originated in 0 and 1st order hollows or channels discrete soil slip scars do not occur at the heads of these paths although 58 soil slip scars were mapped on hillslopes in the burned basins material derived from these soil slips accounted for only about 7 of the total volume of material deposited at canyon mouths this fact combined with observations of significant erosion of hillslope materials suggests that a runoff dominated process of progressive sediment entrainment by surface runoff rather than infiltration triggered failure of discrete soil slips was the primary mechanism of debris flow initiation a paucity of channel incision along with observations of extensive hillslope erosion indicates that a significant proportion of material in the debris flows was derived from the hillslopes with a smaller contribution from the channels because of the importance of runoff dominated rather than infiltration dominated processes in the generation of these fire related debris flows the runoff contributing area that extends upslope from the point of debris flow initiation to the drainage divide and its gradient becomes a critical constraint in debris flow initiation slope area thresholds for fire related debris flow initiation from storm king mountain are defined by functions of the form acr tan 3 s where acr is the critical area extending upslope from the initiation location to the drainage divide and tan is its gradient the thresholds vary with different materials