potential consequences of a mid pleistocene impact event for the middle stone age occupants of dakhleh oasis western desert egypt abstract while it is expected that prehistoric populations experienced the effects of impacts by extraterrestrial objects there is little record of such events in occupied regions we discuss the ramifications of an impact between 100 and 200 ka into dakhleh oasis at that time experiencing humid phase conditions and inhabited by middle stone age people based on modeling of impact processes using estimated impact parameters the impact blast would likely have felled or dismembered most trees over 280 2400 km 2 of the oasis and inhabitants would have been injured over much of the region although severely only near the blast location the impact would not have vaporized much of the dakhleh paleolake s although some water was probably lost through boiling and through waves initiated by the impact blast water quality would have decreased as lake turbidity increased and soot from regional fires fell into the lake a relatively small event would not have immediately ignited much of the oasis vegetation but sedimentary evidence suggests that impact generated fires did spread to significantly affect the landscape the impact and resulting fires may have triggered mass wasting events as well as significant changes in erosion rates and have substantially affected human uses of the area

holocene fire related alluvial fan deposition and climate in ponderosa pine and mixed conifer forests sacramento mountains new mexico usa we employed 14c dating of alluvial fan deposits in ponderosa pine and mixed conifer forests of the sacramento mountains new mexico to document holocene fires and related geomorphic impacts rapid aggradation by charcoal rich debris flows occurred in the middle holocene 5800 4200 cal yr bp indicating episodic sedimentation following severe fires fire related deposition virtually ceased 4200 cal yr bp with most fan deposits indicating slower aggradation with cumulic soil development until 1800 cal yr bp from 1800 to 500 cal yr bp fire related sedimentation increased again although not to middle holocene levels a peak in fire related sedimentation c 650 cal yr bp corresponds to widespread severe drought in the southwestern usa limited fire related sedimentation is evident from 500 to 100 cal yr bp consistent with little ice age climate and tree ring records indicating frequent low severity fires although at least one severe fire burned in this interval increased fire related sediment

correction of deposit ages for inherited ages of charcoal implications for sediment dynamics inferred from random sampling of deposits on headwater valley floors abstract inherited age is defined herein as the difference between times of carbon fixation in a material and deposition of that material within sediments from which it is eventually sampled in order to estimate deposit age via radiocarbon dating inheritance generally leads to over estimation of the age by an unknown amount and therefore represents unquantified bias and uncertainty that could potentially lead to erroneous inferences inherited ages in charcoal are likely to be larger and therefore detectable relative to analytic error where forests are dominated by longer lived trees material is stored for longer periods upslope and downstream post fire delivery of that material is dominated by mass movements such as in the near coastal mountains of northwestern north america inherited age distribution functions were estimated from radiocarbon dating of 126 charcoal pieces from 14 stream bank exposures of debris flow deposits fluvial fines and fluvial gravels along a headwater stream in the southern oregon coast range usa in the region these 3 facies are representative of the nearly continuous coalescing fan fill complexes blanketing valley floors of headwater streams where the dominant transport mechanism shifts from debris flow to fluvial within each depositional unit and for each charcoal piece within that unit convolution of the calibrated age distribution with that of the youngest piece yielded an inherited age distribution for the unit fits to the normalized sums of inherited age distributions for units of like facies provided estimates of facies specific inherited age distribution functions finally convolution of these distribution functions with calibrated deposit age distributions yielded corrections to published valley floor deposit ages and residence time distributions from nearby similar sites residence time distributions were inferred from the normalized sums of distributions of 30 deposit ages at each of 4 sites 2 adjacent valley reaches 103 m long and within 102 m of 2 tributary confluences mean inherited ages from the observed distributions are 666 688 and 1506 yr for debris flow deposits fluvial fines and fluvial gravels respectively on average correction reduced estimates of individual deposit age means by a factor of 0 71 0 56 0 94 and increased standard deviations by a factor of 6 1 0 97 43 across sites mean residence times decreased by 24 0 and standard deviations by 12 5 on average corrected residence time distributions have thicker tails as indicated by gamma distribution fits with smaller shape factors and these changes are significant relative to the bootstrapped 95 confidence limits representing potential error in the sampling for inherited ages the ratio of the means of sediment age and residence time ranged from 1 03 to 1 80 across sites before correction and 1 21 to 2 18 after correction where a value of one implies that probability of evacuation from the reservoir comprising valley floor deposits is independent of time since deposition corrected values of this ratio therefore indicate that evacuation favors younger deposits at all sites whereas uncorrected results implied age independent evacuation from the more downstream valley reach

enhanced sediment delivery in a changing climate in semi arid mountain basins implications for water resource management and aquatic habitat in the northern rocky mountains the delivery and transport of sediment through mountain rivers affects aquatic habitat and water resource infrastructure while climate change is widely expected to produce significant changes in hydrology and stream temperature the effects of climate change on sediment yield have received less attention in the northern rocky mountains we expect climate change to increase sediment yield primarily through changes in temperature and hydrology that promote vegetation disturbances i e wildfire insect pathogen outbreak drought related die off here we synthesize existing data from central idaho to explore 1 how sediment yields are likely to respond to climate change in semi arid basins influenced by wildfire 2 the potential consequences for aquatic habitat and water resource infrastructure and 3 prospects for mitigating sediment yields in forest basins recent climate driven increases in the severity and extent of wildfire suggest that basin scale sediment yields within the next few years to decades could be greater than the long term average rate of 146 t km 2 year 1 observed for central idaho these elevated sediment yields will likely impact downstream reservoirs which were designed under conditions of historically lower sediment yield episodic erosional events massive debris flows that dominate post fire sediment yields are impractical to mitigate leaving road restoration as the most viable management opportunity for offsetting climate related increases in sediment yield however short term sediment yields from experimental basins with roads are three orders of magnitude smaller than those from individual fire related events on the order of 101 t km 2 year 1 compared to 104 t km 2 year 1 respectively for similar contributing areas suggesting that road restoration would provide a relatively minor reduction in sediment loads at the basin scale nevertheless the ecologically damaging effects of fine sediment material

the 17 march 2005 kuzulu landslide sivas turkey and landslide susceptibility map of its near vicinity landslides are common natural hazards in the seismically active north anatolian fault zone of turkey although seismic activity heavy rainfall channel incisions and anthropogenic effects are commonly the main triggers of landslides on march 17 2005 a catastrophic large landslide in sivas northeastern of turkey the kuzulu landslide was triggered by snowmelt without any other precursor the initial failure of the kuzulu landslide was rotational following the rotational failure the earth material in the zone of accumulation exhibited an extremely rapid flow caused by steep gradient and high water content the agnus creek valley where kuzulu village is located was filled by the earth flow material and a landslide dam was formed on the upper part of agnus creek the distance from the toe of the rotational failure down to the toe of the earth flow measured more than 1800 m with about 12 5 million m3 of displaced earth material the velocity of the kuzulu landslide was extremely fast approximately 6 m s the main purposes of this study are to describe the mechanism and the factors conditioning the kuzulu landslide to present its environmental impacts and to produce landslide susceptibility maps of the kuzulu landslide area and its near vicinity for this purpose a detailed landslide inventory map was prepared and geology slope aspect elevation topographic wetness index and stream power index were considered as conditioning factors during the susceptibility analyses the conditional probability approach was used and a landslide susceptibility map was produced the landslide susceptibility map will help decision makers in site selection and the site planning process the map may also be accepted as a basis for landslide risk management studies to be applied in the study area

post glacial range of variability in the conejos river valley southern colorado usa fluvial response to climate change and sediment supply effective river management strategies require an understanding of how fluvial processes vary both spatially and temporally here we examine the natural range of variability in the conejos river valley southern colorado through documentation of terrace morphostratigraphic and sedimentological characteristics as well as through investigation of sediment contributions from headwaters hillslopes and tributary streams additionally soil development and radiocarbon ages together with local and regional paleoclimate reconstructions were used to infer the range of processes acting in this system since de glaciation the conejos river has fluctuated between episodes of bedrock strath formation aggradation and vertical incision morphostratigraphic relationships soil development and radiocarbon ages enable us to propose a chronology for periods of alluvial deposition around 8 9 7 6 ka 5 5 ka and from 3 5 to 1 1 ka separated by intervals of fluvial incision we infer potential forcing mechanisms by utilizing multiple working hypotheses specifically we discuss the potential for increases in sediment supply during periods of 1 para glacial adjustment 2 climatic cooling 3 increased frequency of climate change and 4 increased fire frequency or severity we also consider the effects of changes in stream discharge and extreme storm occurrence we conclude that combinations of these processes operating at different times have contributed to sediment mobilization since de glaciation stream and landform morphology also varies longitudinally due to the influence of remnant glacial topography in particular valley bottom overdeepening at tributary junctions has resulted in incision and strath formation into unlithified glacial deposits i e fill cut terraces rather than bedrock in some reaches overall the conejos fluvial system has varied significantly both temporally and spatially since de glaciation and appears to be sensitive to changes in sediment supply related to holocene scale climate fluctuations this natural range of variability must therefore be a key consideration in any future stream management policies copyright 2012 john wiley sons ltd

late holocene climate change in the big belt mountains central montana usa carroll college and the helena national forest are working in a 6 year research partnership designed to investigate the relationship between paleoclimate change and human adaptation in the big belt mountains of central montana usa this ongoing project is designed to gather archaeological and paleoenvironmental data from three diverse ecosystems within one drainage basin high altitude park areas 1800 2100 m mid altitude conifer forests 1200 1500 m and low altitude locales under 1500 m along the missouri river these data will represent paleoecological and archaeological changes through time and will detect synchrony and diversity across an elevation gradient thus far excavation of two mid altitude sites dating to 2400 and 4500 bp and one high altitude site dated to 2400 bp revealed evidence of a significant drought period about 2000 years ago to date the excavated sites evidence a shift in pollen to drier species a shift to higher sedimentation rates and changes in snail and vertebrate

predicting gully rejuvenation after wildfire using remotely sensed burn severity data abstract the loss of surface vegetation and reduced infiltration caused by wildfires can trigger gully rejuvenation resulting in damage to downstream aquatic resources and risk to human life and property we developed a spatially explicit metric of burn severity the burn severity distribution index bsdi and tested its ability to predict post fire gully rejuvenation in 1st and 2nd order basins burned in the 2000 valley complex fires in the sapphire mountains of western montana the bsdi was derived from burn severity data interpreted from landsat 7 satellite imagery using the normalized burn ratio nbr method and ranged from 0 0 for completely unburned basins to 4 0 for basins burned entirely at high severity in july 2001 rainstorms with peak 30 minute intensities of up to 17 mm h 1 triggered gully rejuvenation in 66 of the 171 basins examined the frequency of gully rejuvenation was higher in basins with higher bsdi values increasing from zero for basins with a bsdi less than 1 3 to 67 for basins with a bsdi greater than 3 0 binary logistic regression indicated that bsdi was a more significant predictor of gully rejuvenation than basin morphometric variables the absence of gully rejuvenation in several basins with a high bsdi was attributed to low gradient dense riparian vegetation or concentration of high burn severity at lower elevations in the basin the presence of gully rejuvenation in several basins with a low bsdi was associated with false negative nbr classification errors in northwest aspects and concentration of severe burn impacts in the drainage headslopes bsdi is a useful metric for predicting gully rejuvenation after wildfire the use of the bsdi in burned area emergency response team assessments could improve the planning implementation and monitoring of burned area recovery treatments

frequency dependence of magnetic susceptibility as a proxy for fine grained iron minerals and aggregate stability of south chilean volcanic ash soils aggregate stability as is an important property controlling erodibility of volcanic ash soils and is known to be strongly affected by fine grained iron fe and aluminum al minerals assuming that frequency dependence of magnetic susceptibility ms is related to the amount of fine grained fe minerals and considering that formation of fine grained fe and al minerals is closely coupled in volcanic ash soils we hypothesized that the measurement of ms can be used to evaluate as of these soils to verify this we investigated volcanic ash soils along a 120 km transect in southern chile reaching from the andean southern volcanic zone svz to the pacific coastal range stability of 1 cm macroaggregates from topsoil 0 5 cm and subsoil 20 25 cm was determined by wet sieving combining long term water immersion and subsequent ultrasonic treatment ms was measured at 465 and 4650 khz to calculate its frequency dependence we found an increasing amount of organic matter fine grained fe and al minerals and clay and decreasing bulk density with increasing distance from the svz indicating progressing soil development along the transect likewise as increased with increasing distance from the svz and was found to be controlled primarily by soil organic matter and fine grained fe and al minerals while ms itself showed only slight variation its frequency dependence continuously increased with increasing distance from the svz indicating an increasing fraction of fine grained ferrimagnetic particles accordingly frequency dependence of ms was found to be linearly related to the amount of fine grained fe minerals as quantified by dithionite extraction and moreover due to the close linear relationship between fine grained fe and al phases it revealed to be suitable for estimating the total amount of both fine grained fe and al minerals analysis of underlying material 60 65 cm indicated that the increase in frequency dependence of ms with increasing distance from the svz was caused by fine grained ferrimagnetic particles of pedogenic and lithogenic origin although overall organic matter content turned out to be more closely related to the stability of the investigated aggregates we conclude that frequency dependence of ms can be used as an easily obtainable proxy for assessing the contribution of fine grained fe and al minerals to as

wildfire morphologic change and bed material transport at fishtrap creek british columbia abstract in 2003 a wildfire burned nearly two thirds of the fishtrap creek watershed including the forested floodplain annually repeated surveys of the stream channel combined with bed material tracer studies in 2006 and 2007 indicate that the channel has become unstable and that the bed material transport dynamics have changed since the fire using these data the morphologic changes have been quantified and event scale bed material transport rates have been estimated for four post fire freshets the immediate response of the channel during the 2005 and 2006 freshets was a progressive shift in channel morphology from a relatively featureless plane bed morphology devoid of significant sediment accumulations to a riffle pool morphology in which bars cover a significant proportion of the bed this transformation occurred in association with moderate bed material sediment transport rates and only minor bank erosion within the study reach extensive bank erosion occurred during the 2007 and 2008 freshets producing a dramatic change in channel morphology and increasing the local bed material transport rates by an order of magnitude post fire monitoring of streamflow and suspended sediment concentrations a surrogate for upstream sediment supply indicates that post fire increases are not detectable presented in eaton et al in press and our analysis demonstrates that major morphologic changes can occur following wildfire even when the common external drivers of stream discharge and sediment supply remain unchanged

persistent alluvial fanhead trenching resulting from large infrequent sediment inputs we present laboratory and field evidence that in mountainous catchment fan systems persistent alluvial fanhead aggradation and trenching may result from infrequent large sediment inputs we suggest that the river fan systems along the fault bounded range front of the western southern alps new zealand are likely to be in a dynamic equilibrium on 103 yr timescales superimposed on which their fanheads undergo long term cumulative episodic aggradation these fanheads are active only in rare events do not take part in the usual behaviour of the catchment fan system and require much longer to exhibit dynamic equilibrium than the rest of the fan these findings 1 increase our knowledge of the effects of extreme events on alluvial fan morphodynamics in humid climates 2 question the general applicability of inferring past climatic or tectonic regimes from alluvial fan morphology and stratigraphy and 3 provide a conceptual basis for hazard zonation on alluvial fans copyright 2006 john wiley sons ltd

geochemical evidence for the use of magnetic susceptibility as a paleorainfall proxy in the tropics abstract several workers have estimated paleomonsoonal rainfall using proxies that are related to wind strength upwelling productivity chemical weathering and pedogenesis in an earlier work on sediments of thimmannanayakanakere tk a lake in southern india shankar r prabhu c n warrier a k vijaya kumar g t sekar b 2006 a multidecadal rock magnetic record of monsoonal variations during the past 3700 years from a tropical indian tank journal of the geological society of india 68 447 459 we suggested that magnetic susceptibility lf may be used as a proxy to estimate the paleomonsoonal rainfall in tropical regions this was based on the positive correlation between magnetic susceptibility of tk sediments and instrumental rainfall data and backed up by historical records and paleoclimate proxy data from widely separated regions of india in this paper we provide geochemical data results of cbd extraction and elemental analysis and their statistical analysis pca to support our earlier proposition that lf may be used as a proxy for paleomonsoonal rainfall in the tropical regime the cbd treatment of sediment samples reduced the average lf from 132 to 64 10 8 m3 kg 1 average fd from 12 91 to 2 01 10 8 m3 kg 1 and average fd from 8 9 to 3 showing that the samples do contain pedogenic magnetite further samples of high low rainfall periods showed a higher lower reduction in the magnetic parameters suggesting a higher lower content of pedogenic magnetite metal al ratios fe al ti al na al mn al pb al zn al cu al k al ca al mg al and sr al are positively correlated most of them at the 1 level with lf suggesting that the tk sediments are derived mainly from the catchment in particular ti al k al and k na ratios that are good indicators of chemical weathering intensity cwi start increasing from 2 cal ka b p onwards corresponding to increasing lf increasing rainfall from this time as chemical weathering is principally driven by rainfall temperature being constant in tropical regions data on cwi indicators provide support to the hypothesis that lf estimates paleomonsoonal rainfall principal component analysis of geochemical and magnetic data shows that three important factors explain the variance in the data set terrigenous pedogenic rainfall and carbonate low rainfall or drought thus our data strengthen shankar et al s shankar r prabhu c n warrier a k vijaya kumar g t sekar b 2006 a multidecadal rock magnetic record of monsoonal variations during the past 3700 years from a tropical indian tank journal of the geological society of india 68 447 459 hypothesis that magnetic susceptibility may be used as a proxy for monsoonal rainfall in the tropical milieu we have proposed a model to explain pedogenesis chemical weathering intensity and carbonate precipitation which are all related to rainfall in the tk catchment

holocene valley floor deposition and incision in a small drainage basin in western colorado usa the valley floor of a 33 9 km 2 watershed in western colorado experienced gradual sedimentation from before 6765 to 500 cal yr bp followed by deep incision renewed aggradation and secondary incision in contrast at least four terraces and widespread cut and fill architecture in the valley floor downstream indicate multiple episodes of incision and deposition occurred during the same time interval the upper valley fill history is atypical compared to other drainages in the colorado plateau one possible reason for these differences is that a bedrock canyon between the upper and lower valley prevented headward erosion from reaching the upper valley fill another possibility is that widespread sand rich clay poor lithologies in the upper drainage limited surface runoff and generally favored alluviation whereas more clay rich lithologies in the lower drainage resulted in increased surface runoff and more frequent incision twenty two dates from valley fill charcoal indicate an approximate forest fire recurrence interval of several hundred years similar to that from other studies in juniper pinon woodlands results show that closely spaced vertical sampling of alluvium in headwater valleys where linkages between hillslope processes and fluvial activity are relatively direct can provide insight about the role of fires in alluvial chronologies of semi arid watersheds

a combined study of radar facies lithofacies and three dimensional architecture of an alpine alluvial fan illgraben fan switzerland alluvial fans serve as useful archives that record the history of depositional and erosional processes in mountainous regions and thus can reveal the environmental controls that influenced their development economically they play an important role as groundwater reservoirs as well as host rocks for hydrocarbons in deeply buried systems the interpretation of these archives and the evaluation of their reservoir architecture however are problematic because marked heterogeneity in the distribution of sedimentary facies makes correlation difficult this problem is compounded because the accumulated sedimentary deposits of modern unconsolidated fan systems tend to be poorly exposed and few such systems have been the focus of investigation using high resolution subsurface analytical techniques to overcome this limitation of standard outcrop analogue studies a geophysical survey of an alpine alluvial fan was performed using ground penetrating radar to devise a scaled three dimensional subsurface model radar facies were classified and calibrated to lithofacies within a fan system that provided outcropping walls and these were used to derive a three dimensional model of the sedimentary architecture and identify evolutionary fan stages the illgraben fan in the swiss alps was selected as a case study and a network of ca 60 km sections of ground penetrating radar was surveyed seven radar facies types could be distinguished which were grouped into debris flow deposits and stream flow deposits assemblages of these radar facies types show three depositional units which are separated by continuous fan wide reflectors they were interpreted as palaeo surfaces corresponding to episodes of sediment starvation that affected the entire fan an overall upward decline in the proportion of debris flow deposits from ca 50 to 15 and a corresponding increase in stream flow deposits were identified the uppermost depositional unit is bounded at its base by a significant incision surface up to 700 m wide which was subsequently filled up mostly by stream flow deposits the pronounced palaeo surfaces and depositional trends suggest that allocyclic controls governed the evolution of the illgraben fan making this fan a valuable archive from which to reconstruct past sediment fluxes and environmental change in the alps the results of the integrated outcrop geophysical approach encourage similar future studies on fans to retrieve their depositional history as well as their potential reservoir properties

a comparison and integration of tree ring and alluvial records of fire history at the missionary ridge fire durango colorado usa we used tree ring and alluvial sediment methods to reconstruct past fire regimes for a mixed conifer forest within a 1 km2 drainage basin which was severely burned by a wildfire near durango color

fire prone plant communities and palaeoclimate of a late cretaceous fluvial to estuarine environment pecinov quarry czech republic the botanical identity and facies distribution of fossil charcoal is described from middle to late cenomanian 90 94 ma fluvial to estuarine units at pecinov quarry near prague czech republic braided alluvial facies associations contain charred conifer woods family pinaceae possibly derived from upland forest fires and abundant charred angiosperm woods flowers and inflorescences families lauraceae and platanaceae derived from riparian gallery forest fires unit 2 retrogradational coastal salt marsh facies associations contain abundant charred conifer wood families cheirolepidiaceae and cupressaceae taxodiaceae derived from fires in halophytic backswamp forest and rare pinaceous charred cones and lauraceous angiosperm wood washed downstream from fires further inland units 3 4 progradational coastal facies associations within an estuary mouth setting contain abundant charred conifer wood family cupressaceae taxodiaceae common taxodiaceous conifer and angiosperm leaves fern rachises and lycopsid stems derived from fires in mesic backswamp taxodiaceous forests and supra tidal fern lycopsid thickets unit 5 growth rings in angiosperm and conifer woods leaf physiognomy and computer models indicate that climate was equable warm and humid but that there was a short annual dry season most fires probably occurred during these annual drought periods the abundance of charcoal and the diversity of taxa preserved in this state indicate that nearly all plant communities were fire prone physiognomically the pecinov flora resembles present day seasonally dry subtropical forests where fires are a common occurrence

geologic versus wildfire controls on hillslope processes and debris flow initiation in the green river canyons of dinosaur national monument abstract as in many areas of high relief debris flows are an important process linkage between hillslopes and the green river in the canyons of the eastern uinta mountains yet the physical conditions that lead to debris flow initiation are unknown a recent episode of enhanced debris flow and wildfire activity provided an opportunity to examine the geomorphic impact of fire and the processes by which weathered bedrock is transported to the green river field investigations and analysis of elevation and precipitation data were undertaken in 15 catchments with recent debris flows to determine how surficial geology wildfire topography bedrock strength and meteorology influence hillslope processes the recent debris flows were triggered by intense summer rainstorms the dominant debris flow initiation mechanism the firehose effect occurred when overland flow generated on bedrock hillslopes cascaded down steep cliffs onto colluvium causing failure sixty percent of the debris flows occurred in unburned catchments however 15 of the burned catchments in the study area produced debris flows over the study period whereas only 7 of the unburned catchments did thus fire was not the primary driver of debris flows but fire related events did contribute to the increased debris flow activity the geomorphic impact of wildfire in the eastern uinta mountains is not as great as in transport limited settings with regolith mantled hillslopes the strong rocks and dry climate of the study area cause hillslopes to be very steep and weathering limited with high runoff ratios and a dearth of regolith as a result there is little vegetation and thus we hypothesize that burning does little to change hillslope processes the suite of hillslope processes in the eastern uintas are like those documented in the similarly dry grand canyon but differ from other locations in the western u s where wildfire is a primary control on debris flow processes

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

particle size and analytical considerations in the mineral magnetic interpretation of soil loss from cultivated landscapes abstract prior research has highlighted the potential for using soil magnetism as a rapid estimator of total cumulative soil loss on cultivated land in this study the influences of particle size choice of magnetic measurement and initial conditions on a proposed model linking surface soil magnetism and soil loss are described and evaluated output model curves are generated for several parameter sets corresponding to different model assumptions and physical scenarios output is also compared to a new high resolution surfacial magnetism data set from a cultivated site gilbert farm in northwestern alabama usa to further evaluate the model magnetic susceptibility values at gilbert farm range from 150 to 220 10 8 m 3 kg 1 in a control soil profile the original model output ranges from 180 to 192 10 8 m 3 kg 1 and many magnetism values in the cultivated area fall outside this range introduction of a particle size sorting correction factor decreases the range of output values and results in even greater numbers of out of range observations however there is evidence suggesting that particle size distributions in the upper soil at this site are not strongly affected by differences in water erosion mechanism lower tillage depths cause magnetic susceptibility values to come in range but may be unrealistic and create a twin value problem for complex magnetic profiles use of the remanence sirm volume susceptibility lf ratio profile with values ranging from 35 to 120 ma m 1 10 5 si instead of magnetic susceptibility as used in the original model was found to eliminate out of range and twin value anomalous magnetism values were identifiable and treatable on the high resolution magnetism maps but other types of natural spatial variation remain at issue

tracing sediment movement in interrill overland flow on a semi arid grassland hillslope using magnetic susceptibility experiments were undertaken to determine the feasibility of tracing sediment movement in interrill overland flow crushed magnetite was introduced as a source line 10 cm wide by 8 m long on a runoff plot 18 m wide by 29 m long located in southern arizona initial magnetic susceptibilities along this source line and along three transects located 0 25 2 95 and 5 m downslope of the source line were measured movement of the magnetite in response to three rainfall simulation experiments was monitored during the first two experiments overland flow discharge was sampled at miniature flumes located along two cross sections on the plot downslope of the source line and at a supercritical flume at the plot outlet magnetic susceptibilities along the source line and transects were measured after all three experiments results show that the magnetite moves very early in the experiments and that it reaches one of the flumes 2 m downslope of the source line in 3 min most of the tracer moves a very short distance 29 7 per cent is deposited within 25 cm of the source line and only 2 2 per cent is deposited 2 95 m away the deposition rate appears to decrease exponentially away from the source line very little magnetite is recorded in the flow through the miniature flumes in general it makes up less than 1 per cent of the total sediment load no temporal pattern in these percentages is observed magnetite appears to be an effective tracer of sediment movement in interrill overland flow though its higher density than natural soil may affect its detachment and transport

a comparison of different magnetic methods for determining the relative grain size of magnetite in natural materials some results from lake sediments abstract a new rapid method for identifying relative grain size variations in magnetic involves the parameter anhysteretic susceptibility arm i e specific arm obtained in a 1 oe steady field which is particularly sensitive to the single domain sd and small pseudo single domain psd grains of the finer magnetite fraction a second parameter low field susceptibility is relatively more sensitive to the coarser magnetite fraction larger psd and smaller multidomain md grains we can then obtain a measure of the ratio of coarse to fine grain magnetite for large numbers of samples by plotting arversus a simple idealized model based on sized magnetite samples is proposed to explain the use of the armversus plot for detecting relative grain size changes in the magnetic content of natural materials the sediments of three lakes that contain magnetite or a similar magnetic carrier and have a wide range of values of arm and are used to test the model the model is used to interpret the magnetic variations observed and the interpretations are supported by high field hysteresis measurements of the same sediments the combination of the high field hysteresis method of day et al 1 and the arm vs method is a powerful technique allowing the rapid identification of both the relative grain size and domain state for large numbers of samples containing magnetite the armvs method should be used as an intial means of identifying distinct groups of samples the high field hysteresis method should then be applied to a few representative samples from each group to confirm the initial interpretation

modeling of the interactions between forest vegetation disturbances and sediment yields in the idaho batholith are investigated through numerical modeling the model simulates soil development based on continuous bedrock weathering and the divergence of diffusive sediment transport on hillslopes soil removal is due to episodic gully erosion shallow landsliding and debris flow generation in the model forest vegetation provides root cohesion and surface resistance to channel initiation forest fires and harvests reduce the vegetation vegetation loss leaves the land susceptible to erosion and landsliding until the vegetation cover reestablishes in time simulation results compare well with field observations of event sediment yields and long term averages over 10 000 years when vegetation is not disturbed by wildfires over thousands of years sediment delivery is modeled to be less frequent but with larger event magnitudes increased values of root cohesion representing denser forests lead to higher event magnitudes wildfires appear to control the timing of sediment delivery compared to undisturbed forests erosion is concentrated during the periods with low erosion thresholds often called accelerated erosion periods following wildfires our modeling suggests that drainage density is inversely proportional to root cohesion and that reduced forest cover due to wildfires increases the drainage density we compare the sediment yields under anthropogenic harvest and natural wildfire disturbances disturbances due to forest harvesting appear to increase the frequency of sediment delivery however the sediment delivery following wildfires seems to be more severe these modeling based findings have implications for engineering design and environmental management where sediment inputs to streams and the fluctuations and episodicity of these inputs are of concern index terms 1625 global change geomorphology and weathering 1824 1886 1815 hydrology erosion and sedimentation 1824 hydrology geomorphology 1625 keywords sediment yield wildfires forest management hydrology

lake catchment based studies of erosion and denudation in the merevale catchment warwickshire u k sediment yields estimated from contemporary stream monitoring of suspended sediment in the merevale forested catchment north warwickshire were compared with the sediment yield record obtained from analysis of lake sediment in the downstream reservoir total sediment volume and mass for nine periods since 1861 were calculated by extrapolation of synchronous levels in 54 cores identified from magnetic susceptibility and other magnetic measurements and by using 210pb and 137cs analysis to provide an absolute sediment chronology sediment yield estimated from the two methods show comparable but low 50 200 kg ha 1 yr 1 levels of sediment loss while suggesting that lake sediments can be a useful means for extending the period over which contemporary monitoring exists the study stresses the need for detailed historical records of land use and climate against which long term sediment yield records can be evaluated

holocene alluvial fan development in the macgillycuddy s reeks southwest ireland holocene alluvial landforms in the macgillycuddy9s reeks southwest ireland were investigated to determine the controls and timing of postglacial geomorphic activity detailed geomorphologic analysis of three alluvial fan and debris cones within high level cirque basins demonstrates evidence of episodic phases of late holocene surface aggradation and incision radiocarbon dates from peat horizons above and below inorganic units show that phases of aggradation cluster into two distinct periods the first after 230 790 calibrated cal yr a d and the second from 1510 cal yr a d to the present an additional phase of fan aggradation at one site is dated after 1040 1280 cal yr a d all three phases coincide with episodes of enhanced late holocene valley floor alluviation and debris flow activity from upland britain alluvial fans and debris cones have developed primarily as a result of the resedimentation of late midlandian wisconsin drift and talus slopes and mobilization of materials involved flooding transitional flow and debris flow processes pollen analysis of peat horizons interbedded with alluvial fan and debris cone sediments indicates that land use changes were an important factor in lowering the threshold for local slope erosion phases of aggradation also coincide with well documented episodes of climate change and hence fan development is probably a function of both anthropogenic and climatic forcing a sequence of events may have involved initial slope destabilization due to overgrazing and removal of vegetation that was followed by debris mobilization and fan aggradation during intense rainstorms associated with climate change

a sediment transport model for incision of gullies on steep topography 1 we have conducted surveys of gullies that developed in a small steep watershed in the idaho batholith after a severe wildfire followed by intense precipitation we measured gully length and cross sections to estimate the volumes of sediment loss due to gully formation these volume estimates are assumed to provide an estimate of sediment transport capacity at each survey cross section from the single gully forming thunderstorm sediment transport models commonly relate transport capacity to overland flow shear stress which is related to runoff rate slope and drainage area we have estimated the runoff rate and duration associated with the gully forming event and used the sediment volume measurements to calibrate a general physically based sediment transport equation in this steep high shear stress environment we find that a shear stress exponent of 3 corresponding to drainage area and slope exponents of m 2 1 and n 2 25 match our data this shear stress exponent of 3 is approximately 2 times higher than those for bed load transport in alluvial rivers but is in the range of shear stress exponents derived from flume experiments on steep slopes and with total load equations the concavity index of the gully profiles obtained theoretically from the area and slope exponents of the sediment transport equation c m 1 n agrees well with the observed profile concavity of the gullies our results although preliminary because of the uncertainty associated with the sediment volume estimates suggest that for steep hillslopes such as those in our study area a greater nonlinearity in the sediment transport function exists than that assumed in some existing hillslope erosion models which calculate sediment transport capacity using the bed load equations developed for rivers

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

predicting the probability and volume of postwildfire debris flows in the intermountain western united states empirical models to estimate the probability of occurrence and volume of postwildfire debris flows can be quickly implemented in a geographic information system gis to generate debris flow hazard maps either before or immediately following wildfires models that can be used to calculate the probability of debris flow production from individual drainage basins in response to a given storm were developed using logistic regression analyses of a database from 388 basins located in 15 burned areas located throughout the u s intermountain west the models describe debris flow probability as a function of readily obtained measures of areal burned extent soil properties basin morphology and rainfall from short duration and low recurrence interval convective rainstorms a model for estimating the volume of material that may issue from a basin mouth in response to a given storm was developed using multiple linear regression analysis of a database from 56 basins burned by eight fires this model describes debris flow volume as a function of the basin gradient aerial burned extent and storm rainfall applications of a probability model and the volume model for hazard assessments are illustrated using information from the 2003 hot creek fire in central idaho the predictive strength of the approach in this setting is evaluated using information on the response of this fire to a localized thunderstorm in august 2003 the mapping approach presented here identifies those basins that are most prone to the largest debris flow events and thus provides information necessary to prioritize areas for postfire erosion mitigation warnings and prefire management efforts throughout the intermountain west

debris flow initiation by runoff in a recently burned basin is grain by grain sediment bulking or en masse failure to blame postwildfire debris flows are frequently triggered by runoff following high intensity rainfall but the physical mechanisms by which water dominated flows transition to debris flows are poorly understood relative to debris flow initiation from shallow landslides in this study we combined a numerical model with high resolution hydrologic and geomorphic data sets to test two different hypotheses for debris flow initiation during a rainfall event that produced numerous debris flows within a recently burned drainage basin based on simulations large volumes of sediment eroded from the hillslopes were redeposited within the channel network throughout the storm leading to the initiation of numerous debris flows as a result of the mass failure of sediment dams that built up within the channel more generally results provide a quantitative framework for assessing the potential of runoff generated debris flows based on sediment supply and hydrologic conditions

empirical models to predict the volumes of debris flows generated by recently burned basins in the western u s abstract recently burned basins frequently produce debris flows in response to moderate to severe rainfall post fire hazard assessments of debris flows are most useful when they predict the volume of material that may flow out of a burned basin this study develops a set of empirically based models that predict potential volumes of wildfire related debris flows in different regions and geologic settings the models were developed using data from 53 recently burned basins in colorado utah and california the volumes of debris flows in these basins were determined by either measuring the volume of material eroded from the channels or by estimating the amount of material removed from debris retention basins for each basin independent variables thought to affect the volume of the debris flow were determined these variables include measures of basin morphology basin areas burned at different severities soil material properties rock type and rainfall amounts and intensities for storms triggering debris flows using these data multiple regression analyses were used to create separate predictive models for volumes of debris flows generated by burned basins in six separate regions or settings including the western u s southern california the rocky mountain region and basins underlain by sedimentary metamorphic and granitic rocks an evaluation of these models indicated that the best model the western u s model explains 83 of the variability in the volumes of the debris flows and includes variables that describe the basin area with slopes greater than or equal to 30 the basin area burned at moderate and high severity and total storm rainfall this model was independently validated by comparing volumes of debris flows reported in the literature to volumes estimated using the model eighty seven percent of the reported volumes were within two residual standard errors of the volumes predicted using the model this model is an improvement over previous models in that it includes a measure of burn severity and an estimate of modeling errors the application of this model in conjunction with models for the probability of debris flows will enable more complete and rapid assessments of debris flow hazards following wildfire

fire storms and erosional events in the idaho batholith in late december 1996 the south fork payette river basin in west central idaho experienced a prolonged storm that culminated on january 1 1997 with intense rain on melting snow that triggered slide failures producing debris flows and sediment charged floods failures occurred in saturated cohesionless grussy colluvium derived from weathered idaho batholith granitic rocks many failures along the south fork payette river originated in ponderosa pine forests burned in the 1989 stand replacing lowman fire an example is the 0 49 km 2 jughead creek basin where a single large colluvial failure produced almost 40 of the total volume eroded from the basin and generated a massive and rapid debris flow failures also occurred in steep unburned and unforested drainages such as hopkins creek in this south facing 0 58 km 2 basin 15 colluvial hollows failed but no single failure produced more than 10 of the total eroded volume sediment transport in hopkins creek occurred by prolonged sediment charged sheetflooding despite vegetation differences sediment yields from the geomorphically similar hopkins creek 42 000 mg km 2 and jughead creek 44 000 mg km 2 basins were quite similar these 1997 erosion events are equivalent to several thousand years of sediment yield at low rates 2 7 30 mg km 2 year 1 measured by short term sediment trapping and gauging in idaho batholith watersheds if similar large events were solely responsible for sediment export recurrence intervals ris of several hundred years would account for higher sediment yields averaged over 10 4 year from idaho batholith watersheds dating of small fire induced sheetflooding events in an early holocene tributary junction fan of jughead creek indicates that frequent small sedimentation events ri 33 80 year occurred between 7400 and 6600 cal year bp with an average yield not greatly exceeding 16 mg km 2 year 1 compared with the holocene average erosion rates during that 800 year period were unusually low suggesting that sediment yields have not been constant over time and that climatic variations and related fire regime changes may exert a strong influence on the probability of major erosional events copyright 2001 john wiley sons ltd

use of mineral magnetic measurements to investigate soil erosion and sediment delivery in a small agricultural catchment in limestone terrain abstract understanding sediment delivery at the hillslope scale requires information on the spatial distributions and magnitudes of erosion and deposition empirical models such as the rusle may be useful for predicting erosion but are poorly suited for quantifying deposition cesium 137 cs 137 is useful for quantifying both erosion and deposition but is costly to inventory over a large area and directly gauges soil redistribution only for recent decades the use of rapidly acquired magnetic measurements represents a relatively new potential means of mapping and measuring soil redistribution in this study variations in surface magnetism are analyzed to determine patterns of erosion and sedimentation in a small agricultural catchment in northwestern alabama usa magnetic indicators of erosion are combined with published soil morphology cs 137 and short term suspended sediment data from this former experimental watershed to evaluate long term sediment delivery all magnetic parameters measured could be related to soil erosion although their patterns in space are not identical magnetic evidence suggests approximately 30 cm of soil loss on the steepest mid slope portions of the catchment distributing soil loss across space according to magnetic patterns gives average long term values lower than a prior estimate based on cs 137 data long term sediment delivery calculated using soil morphology to determine depositional volume ranges up to 45 depending on the magnetic parameter used to index soil loss and assumptions regarding deposit geometry these results suggest the need for continued refinement of magnetic techniques for purposes of erosion model validation and general sediment tracing applications

lithological factors affecting magnetic susceptibility of subtropical soils zhejiang province china abstract magnetic susceptibility was measured on subtropical soils formed on a range of parent materials in zhejiang province china to demonstrate the influence of parent material lithologies on the amount and vertical distribution of in the soils we found that the values of soils vary by up to two orders of magnitude with their parent material lithologies soils formed on igneous rocks with high values showed high absolute and distinctly decreased compared with values of parent materials the values of soils formed on basalt andesite and granodiorite were 250 10 8 m 3 kg 1 the values of soils formed on granite and other neutral and acid igneous rocks ranged from 50 10 8 to 120 10 8 m 3 kg 1 in most of the soils formed on sedimentary rocks enhancement in upper horizons of soils was found compared with parent material this enhancement was believed to be pedogenic formation of superparamagnetic sp stable single domain ssd magnetic grains which are characterized by high values of frequency dependent susceptibility fd and anhysteretic remanent magnetization arm soils formed on sedimentary rocks with a very low initial and iron content showed a low value throughout the profile it was found that there is a highly significant relationship between the values of soils and their dithionite citrate bicarbonate solution dcb soluble iron contents fe d the values of soils in chronosequences formed on alluvium and two marine deposits increased as soils became older it is suggested that the values can be used as a tool for determining the relative age in chronosequence studies

predicting sediment delivery from debris flows after wildfire abstract debris flows are an important erosion process in wildfire prone landscapes predicting their frequency and magnitude can therefore be critical for quantifying risk to infrastructure people and water resources however the factors contributing to the frequency and magnitude of events remain poorly understood particularly in regions outside western usa against this background the objectives of this study were to i quantify sediment yields from post fire debris flows in southeast australian highlands and ii model the effects of landscape attributes on debris flow susceptibility sediment yields from post fire debris flows 113 294 t ha 1 are 2 3 orders of magnitude higher than annual background erosion rates from undisturbed forests debris flow volumes ranged from 539 to 33 040 m3 with hillslope contributions of 18 62 the distribution of erosion and deposition above the fan were related to a stream power index which could be used to model changes in yield along the drainage network debris flow susceptibility was quantified with a logistic regression and an inventory of 315 debris flow fans deposited in the first year after two large wildfires total burned area 2919 km2 the differenced normalised burn ratio dnbr or burn severity local slope radiative index of dryness ai and rainfall intensity from rainfall radar were significant predictors in a susceptibility model which produced excellent results in terms identifying channels that were eroded by debris flows area under curve auc 0 91 burn severity was the strongest predictor in the model auc 0 87 when dnbr is used as single predictor suggesting that fire regimes are an important control on sediment delivery from these forests the analysis showed a positive effect of ai on debris flow probability in landscapes where differences in moisture regimes due to climate are associated with large variation in soil hydraulic properties overall the results from this study based in the southeast australian highlands provide a novel basis upon which to model sediment delivery from post fire debris flows the modelling approach has wider relevance to post fire debris flow prediction both from risk management and landscape evolution perspectives

centennial eolian cyclicity in the great plains usa a dominant climate pattern of wind transport over the past 4000 years proxy evidence at decadal resolution from late holocene sediments from pickerel lake northeastern south dakota shows distinct centennial cycles 400e700 years in magnetic susceptibility contents of carbonate organic carbon and major elements abundance in ostracodes and d 18 o and d 13 c values in calcite proxies indicate cyclic changes in eolian input productivity and temperature maxima in magnetic susceptibility are accompanied by maxima in aluminum and iron mass accumulation rates mars and in abundances of the ostracode fabaeformiscandona rawsoni this indicates variable windy and dry conditions with westerly wind dominance including during the medieval climate anomaly maxima in carbonates organic carbon phosphorous and high d 13 c values of endogenic calcite indicate moister and less windy periods with increased lake productivity including during the little ice age and alternate with maxima of eolian transport times of the maunder sporer and wolf sunspot minima are characterized by maxima in d 18 o values and aluminum mars and minima in d 13 c values and organic carbon content we interpret these lake conditions during sunspot minima to indicate decreases in lake surface water temperatures of up to 4e5 c associated with decreases in epilimnetic productivity during

slope grain size and roughness controls on dry sediment transport and storage on steep hillslopes existing hillslope sediment transport models developed for low relief soil mantled landscapes are poorly suited to explain the coupling between steep rocky hillslopes and headwater channels here we address this knowledge gap using a series of field and numerical experiments to inform a particle based model of sediment transport by dry ravel a mechanism of granular transport characteristic of steep hillslopes we find that particle travel distance increases as a function of the ratio of particle diameter to fine scale 1 m topographic variability associated with rocky landscapes applying a 2 d dry ravel routing model to lidar derived surface topography we show how spatial patterns of local and nonlocal transport control connectivity between hillslopes and steep headwater channels that generate debris flows through failure of ravel filled channels following wildfire our results corroborate field observations of a patchy transition from soil mantled to bedrock landscapes and suggest that there is a dynamic interplay between sediment storage roughness grain sorting and transport even on hillslopes that well exceed the angle of repose

the use of magnetic susceptibility to measure long term soil redistribution abstract several studies have documented the severity of recent soil erosion on the canadian prairies where cultivation started about a century ago little quantitative information is available on erosion before 1960 this study attempts to quantify post and pre 1960 soil erosion in a small cultivated basin near saskatoon saskatchewan canada by measuring 137cs and magnetic susceptibility distribution with depth soil cores were collected along six transects three across closed depressions and three across the drainage channel in the cultivated field and one transect across an uncultivated depression the cores were sliced into 3 cm layers and the soil analyzed for 137cs and organic and inorganic c high variability in with depth in eroding areas as indicated by 137cs made it impossible to use to quantify past soil losses in these locations however these eroding upper and middle slope positions have a much higher than lower slope areas where soil deposition occurs and where the variability in with depth could be used to estimate soil deposition estimating soil deposition from the vs depth profiles was more successful in the closed depressions than in the drainage channel where the profiles may reflect the variable source areas of the materials rather than the pedological conditions the data indicated that soil deposition since 1960 has been about 30 to 50 of that prior to 1960 this suggests that soil deposition rates and by implication soil erosion rates have been relatively steady since cultivation of these soils started although there are clear indications that the spatial pattern of deposition has varied

the effects of particle breakage and abrasion on the magnetic properties of two soils as mineral magnetism is used as a tracer for sourcing river and dam sediments changes in the magnetic properties that may occur during transport between the source and sink must be considered abrasion and breakage of particles will occur during transport these processes were examined in simulation experiments with a granitic and a sedimentary soil the effects of these processes on the magnetic properties of a granitic and a sedimentary soil were examined using a simulated breakage abrasion experiment breakage and or abrasion had substantial effects on the magnetic properties of both soils all particle sizes were affected but the magnitude varied through the size range of derived particles the major effect was on the concentration of magnetic minerals with differences between the concentrations in particle sizes of the original material and those generated by the experiments being as much as 20 times the effect on the granite soil was to reduce the concentrations i e derived material was less than original material whereas for the sedimentary soil the derived particles had higher concentrations the effect on magnetic grain size as indicated by the magnetic ratios was less than the effect on the mass magnetic properties but still substantial for some ratios for some sizes 1998 john wiley sons ltd

recent sediment flux and erosional processes in a welsh upland lake catchment based on magnetic susceptibility measurements abstract single sample magnetic susceptibility measurements are used to correlate synchronous levels in 16 cores of dated 210 pb 137 cs recent sediment taken from the deep and oligotrophic llyn peris n wales in order to provide a basis for calculating total sediment and chemical influx through time results show that sediment influx has steadily increased since c 1750 a d to reach peak levels in the period 1966 1976 a d equivalent to a rise in erosion in the catchment from c 5 t km 2 yr 1 to c 42 t km 2 yr 1 comparison of down core susceptibility fluctuations with sediment pollen and organic pigment data indicates that maximum susceptibility values relate to periods of channel erosion and minimum susceptibility values relate to periods of slate debris inwash from spoil tips in the catchment a study of historical records reveals that pre twentieth century peak levels of erosion were due to the effects of extractive industries while twentieth century erosion has been caused by overgrazing increased trampling pressure and heavy construction works in the catchment

vegetation modulated landscape evolution effects of vegetation on landscape processes drainage density and topography 1 topography acts as a template for numerous landscape processes that include hydrologic ecologic and biologic phenomena these processes not only interact with each other but also contribute to shaping the landscape as they influence geomorphic processes we have investigated the effects of vegetation on thresholds for channel initiation and landform evolution using both analytical and numerical approaches vegetation is assumed to form a uniform ground cover runoff erosion is modeled based on a power function of excess shear stress in which shear stress efficiency is inversely proportional to vegetation cover this approach is validated using data plant effect on slope stability is represented by additional cohesion provided by plant roots vegetation cover is assumed to reduce sediment transport rates due to physical creep processes rainsplash dry ravel and expansion and contraction of sediments according to a negative exponential relationship vegetation grows as a function of both available cover and unoccupied space by plants and is killed by geomorphic disturbances runoff erosion and landsliding and wildfires analytical results suggest that in an equilibrium basin with a fixed vegetation cover plants may cause a transition in the dominant erosion process at the channel head a runoff erosion dominated landscape under none or poor vegetation cover may become landslide dominated under a denser vegetation cover the sign of the predicted relationship between drainage density and vegetation cover depends on the relative influence of vegetation on different erosion phenomena with model parameter values representative of the oregon coast range ocr numerical experiments conducted using the channel hillslope integrated landscape development child model confirm the findings based on the analytical theory a highly dissected fluvial landscape emerges when surface is assumed bare when vegetation cover is modeled landscape relief increases resulting in hollow erosion dominated by landsliding interestingly our simulations underscore the importance of vegetation disturbances by geomorphic events and wildfires on the landscape structure simulated landscapes resemble real world catchments in the ocr when such disturbances are considered

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

10 000 yr record of extreme hydrologic events well dated lacustrine sediments provide a hydrologic record indicating that the frequency and magnitude of runoff events and by inference storms have varied over the past 10 k y in northern new england we used five sediment cores and radiocarbon dating to develop a chronology of holocene hydrologic events for the ritterbush pond basin northern vermont chemical and physical analyses allow us to identify 52 distinct layers of predominately inorganic sediment that represent terrestrially derived material delivered to the pond by runoff events the thickness of some layers suggests hydrologic events at least equal in size to and probably much larger than any storm or flood recorded during nearly 300 yr of written regional history layer thickness and frequency and by analogy storm size and recurrence change through the holocene the largest events occurred 2620 6840 and 9440 calibrated 14c years before present cal 14c yr b p the most frequent hydrologic events occurred in three periods 1750 to 2620 6330 to 6840 and 8600 cal yr b p the recurrence interval of layer deposition during stormy periods averages 130 100 cal yr whereas the recurrence interval during less stormy periods is longer 270 170 cal yr the ritterbush pond event record illustrates the potential of inorganic lacustrine sediment to serve as a proxy record for estimating paleoflood frequency and deciphering climate change

a mineral magnetic study of holocene sediment yields and deposition patterns in the llyn geirionydd catchment north wales mineral magnetic investigations of sediment cores and catchment materials from llyn geirionydd north wales form the basis of a study of holocene sediment yields and deposition patterns catchment soils and bedrock materials are highly variable in magnetic concentration in contrast the lake sediments are more homogenous in magnetic concentration magnetic hysteresis properties of catchment materials bulk sediments and magnetic extracts demonstrate that the occurrence of authigenic greigite fe3s4 in early holocene sediments is responsible for differences between the magnetic characteristics of sediments older than 5000 bp and the more recent sediments and catchment materials a whole lake stratigraphy based on core correlation using magnetic measurements pollen stratigraphy and 14c age determinations indicates sediment yields which increase almost threefold from the early holocene to the period from c ad 500 1850

channel and woody debris characteristics in adjacent burned and unburned watersheds a decade after wildfire park county wyoming abstract large variability in responses of stream sediment and large woody debris lwd to severe fire has limited the accurate prediction of the magnitude and duration of fire effects on streams conditions in one absaroka range stream that was severely burned in 1988 were compared to those in an adjacent undisturbed stream to improve understanding of fire effects on channel and lwd characteristics beyond the first few years ten reaches of each stream were sampled during summer 1999 average bankfull channel width was greater in burned jones creek than in unburned crow creek lwd frequency and overall frequency of lwd accumulations were greater in crow creek than jones creek debris jam frequency was greater in jones creek after accounting for differences in the frequency of pieces with length greater than channel width larger piece size and better anchoring contributed to more frequent small accumulations of lwd in crow creek differences between streams in lwd frequency are consistent with greater mobility of debris in burned jones creek lwd associated fine sediment deposits were thicker but less frequent along jones creek than crow creek

timing and style of deposition on humid temperate fans vermont united states fans in the once glaciated mountainous landscape of humid temperate new england preserve a long and unique record of deposition and thus of hillslope erosion by using multiple backhoe trenches and radiocarbon dating of wood and charcoal we determined the history of five small fans 1900 14 850 m 3 that range in age from historic to 13 320 calibrated cal 14 cy r

comparing mineral magnetic properties of sediments in two reservoirs in strongly and mildly eroded regions on the guizhou plateau southwest china a tool for inferring differences in sediment sources and soil erosion shibanqiao reservoir 0 24 km 2 and xiaohe reservoir 0 28 km 2 have catchments of 6 00 km 2 and 22 69 km 2 respectively they essentially represent strongly eroded shibanqiao and mildly eroded xiaohe regions in guizhou plateau southwestern china sediment cores were retrieved from the two reservoirs and soils were also sampled from their catchments mineral magnetic measurements were performed on the sediments and soils and the particle size analysis of selected sediment cores and soil profiles were also made sirm versus chi if was used to compare sediment and soil samples in addition correlations between percentages of different particle size fractions and magnetic parameters ratios of sediment samples were also checked these results revealed differences in sediment sources and soil erosion in these two representative catchments the sediments in shibanqiao reservoir are derived from both the topsoil and subsoil when erosion is relatively weak it is limited to the topsoil and preferentially transports the relatively finer magnetic grains into the reservoir which may imply rain splash and or sheet erosion in this relatively steep catchment stronger erosional forces are capable of not only moving relatively coarser ferrimagnetic grains from the topsoil but also incising the subsoil and moving anti ferromagnetic minerals into the reservoir which seems to hint at not only sheet wash but also rill and gully erosion as there are no stable streams nor channel networks developed in this mountainous catchment contributions from river bank erosion to sediment yield are almost negligible the sediments in xiaohe reservoir which has a lower relief are predominately derived from topsoil erosion here erosion is concentrated to the topsoil and preferentially transports the relatively fine magnetic grains into the reservoir when erosional forces are weak however even when erosional forces increase in this relatively flat catchment erosion is still restricted to the topsoil thus relatively coarser ferrimagnetic grains from the topsoil are transported to the reservoir but the subsoil remains undisturbed and there are no significant changes in the proportion of anti ferromagnetic minerals in the sediments consequently only sheet washing occurs even when erosion is intensifying in this hilly plain catchment in general the more effective erosion in the shibanqiao catchment is probably due to its steeper topography than xiaohe catchment although higher and more seasonal rainfalls and lower percentages of woodlands may also contribute to the differences in susceptibility to erosional forces c 2011 elsevier b v all rights reserved less

holocene palaeofire records in a high level proximal valley fill wilson bog mount lofty ranges south australia an elevated valley fill peat bog wilson bog near mount lofty south australia failed in november 2005 following a flooding event and exposed representative sections of the sediment infill two

field measurement of basal forces generated by erosive debris flows 1 it has been proposed that debris flows cut bedrock valleys in steeplands worldwide but field measurements needed to constrain mechanistic models of this process remain sparse due to the difficulty of instrumenting natural flows here we present and analyze measurements made using an automated sensor network erosion bolts and a 15 24 cm by 15 24 cm force plate installed in the bedrock channel floor of a steep catchment these measurements allow us to quantify the distribution of basal forces from natural debris flow events that incised bedrock over the 4 year monitoring period 11 debris flow events scoured the bedrock channel floor no clear water flows were observed measurements of erosion bolts at the beginning and end of the study indicated that the bedrock channel floor was lowered by 36 to 64 mm the basal force during these erosive debris flow events had a large magnitude up to 21 kn which was approximately 50 times larger than the concurrent time averaged mean force high frequency greater than 1 hz fluctuating component we interpret these fluctuations as flow particles impacting the bed the resulting variability in force magnitude increased linearly with the time averaged mean basal force probability density functions of basal normal forces were consistent with a generalized pareto distribution rather than the exponential distribution that is commonly found in experimental and simulated monodispersed granular flows and which has a lower probability of large forces when the bed sediment thickness covering the force plate was greater than 20 times the median bed sediment grain size no significant fluctuations about the time averaged mean force were measured indicating that a thin layer of sediment 5 cm in the monitored cases can effectively shield the subjacent bed from erosive impacts coarse grained granular surges and water rich intersurge flow had very similar basal force distributions despite differences in appearance and bulk flow density these results demonstrate that debris flows can have strong control on rates of steepland evolution and contribute to a foundation needed for modeling debris flow incision stochastically

heavy metal release by peat erosion in the peak district southern pennines uk upper north grain ung is a heavily eroding blanket peat catchment in the peak district southern pennines uk concentrations of lead in the near surface peat layer at ung are in excess of 1000 mg kg 1 for peatland environments these lead concentrations are some of the highest globally high concentrations of industrially derived atmospherically transported magnetic spherules are also stored in the near surface peat layer samples of suspended sediment taken during a storm event that occurred on 1 november 2002 at ung and of the potential catchment sources for suspended sediments were analysed for lead content and the environmental magnetic properties of anhysteretic remanent magnetization arm and saturation isothermal remanent magnetization sirm at the beginning of the storm event there is a peak in both suspended sediment and associated lead concentration sirm arm values for suspended sediment samples throughout the storm reveal that the initial lead flush is associated with a specific sediment source namely that of organic sediment eroded from the upper peat layer using the magnetic fingerprinting approach to discrimination of sediment sources this study reveals that erosion of the upper peat layer at ung is releasing high concentrations of industrially derived lead and by inference other toxic heavy metals associated with industrial particulates into the fluvial systems of the southern pennines climate change scenarios for the uk involving higher summer temperatures and stormier winters may result in an increased flux both of sediment associated and dissolved heavy metals from eroding peatland catchments in the southern pennines adversely affecting the quality of sediment and water entering reservoirs of the region copyright 2005 john wiley sons ltd

identification of mechanisms for landslide type initiation of debris flows the modelling of debris flow initiation in slopes is addressed in this paper first possible factors governing debris flow initiation are established then a coupled hydro mechanical model for deformable porous media with two pore fluids that is used to assess the problem of the debris flow initiation in slopes is briefly outlined various ways to identify failure and to approach the transition of the failed mass into a debris flow are discussed in the framework of small strain theory and elasto plastic behaviour a parametric study was carried out to evaluate the relative importance of the most commonly cited parameters that are assumed to influence debris flow initiation it was found that the slope angle is of minor importance in the development of slope instability under loading due to internal water supply transient behaviour was found to be decisive and some critical combinations of water supply over time yielded situations that were likely to encourage the onset of debris flow the significant role of permeability as a function of the degree of saturation in relation to the water supply is demonstrated the proposed three phase model is shown to be an adequate and promising way to address debris flow initiation

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

tracing movements of topsoil by magnetic measurements two case studies an array of magnetic measurements is used to trace the occurrence of magnetically enhanced topsoil in two different environmental settings the first is a cultivated slope section where the results confirm that movements of topsoil have occurred but that identification of specific erosional processes is problematic the second is a lake catchment system where measurements on soils and sediments allow a partial reconstruction of soil movements from different sources over the last 200 y the study highlights both the need to analyse the magnetic mineralogies of different particle size fractions and the difficulties that may be encountered in trying to discriminate between topsoil and subsoil material on the basis of demagnetization parameters alone

upland ecology of some late carboniferous cordaitalean trees from nova scotia and england abstract permineralised logs and charcoal fragments composed of dadoxylon type wood and derived from cordaitalean trees are described from the upper carboniferous westphalian of nova scotia and england they exclusively occur in sandstone bodies interpreted as the deposits of braided meandering and anastomosing river channels the architecture and ecology of this type of cordaitalean has not yet been satisfactorily described estimates of tree height using an allometric approach suggest that the largest trees attained an approximate height of ca 45 m the absence of true growth rings in the logs indicate that they grew under non seasonal humid tropical conditions however the presence of charred wood fragments implies that droughts of sufficient intensity to permit wildfire did occasionally occur the charcoal fragments are usually associated with incised poorly sorted chaotically bedded channel facies interpreted as flood deposits dramatic increases in runoff and sediment discharge are known to follow the destruction of vegetation in modern wildfire events and the high energy charcoal bearing channel facies described may represent a similar geomorphic response to cordaitalean vegetation fires geomorphic sensitivity to fire is greatest for steeply sloping terrains and it is therefore probable that the cordaitaleans described in this paper occupied upland settings this palaeoecological interpretation is supported by occurrence of the cordaitalean remains in river channel deposits immediately downstream of regions of palaeo upland and by the palynological record the presence of upland forests in late carboniferous times has important implications for numerical modelling of global geochemical cycles

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

erosion under climate and human pressures an alpine lake sediment perspective we review the scientific efforts over the last decades to reconstruct erosion from continuous alpine lake sediment records we focused both on methodological issues showing the growing importance of non destructive high resolution approaches xrf core scanner as well as progresses in the understanding of processes leading to the creation of an erosion signal in lakes we distinguish continuous records from event records both provide complementary information but need to be studied with different approaches continuous regionally relevant records proved to be particularly pertinent to document regional erosion patterns throughout the holocene in particular applying the source to sink approach event based approaches demonstrated and took advantage of the strong non linearity of sediment transport in high altitude catchment areas this led to flood frequency and intensity reconstructions highlighting the influence of climate change upon flood dynamics in the mountain the combination of different record types both in terms of location high vs low elevation sedimentology high vs low terrigenous contribution and significance local vs regional is one of the main outputs of this paper it allows the establishment of comprehensive histories of nw french alps erosion but also and consequently soil dynamics and hydrological patterns throughout the holocene we also discuss the influence of glacier dynamics one of the major agents of erosion in the alps a major feature is the growing human influence upon erosion at a local scale since at least the middle of the bronze age 3500 cal bp however and according to the regional record from lake bourget only few periods of rising erosion at local scales generated a regional record that can be discriminated from wetter climatic periods among them the period between 200 bce and 400 ad appeared to be marked by a generalised rise in human triggered erosion at local scales in the northern french alps this review highlights the importance of modern high resolution and interdisciplinary studies of lake sediments in order to better understand the complex relationships between humans climate and the earth system in general we strongly argue that regional integration of data is now required to move a step further such an integration is easier with cost and time effective methods as well as after a better definition of approaches and their limits this should lead to a stronger collaboration between paleo data producers and modellers in the near future

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

conditions for generation of fire related debris flows capulin canyon new mexico comparisonoftheresponsesofthreedrainagebasinsburnedbythedomefireof1996innewmexicoisusedtoidentifythe hillslope channelandfirecharacteristicsthatindicateasusceptibilityspecificallytowildfire relateddebrisflow summer thunderstorms generated three distinct erosive responses from each of three basins the capulin canyon basin showed widespreaderosivesheetwashandrillingfromhillslopes andseverefloodingoccurredinthechannel thenorthtributary basin exhibited extensive erosion of the mineral soil to a depth of 5 cm and downslope movement of up to boulder sized material andatleastonedebrisflowoccurredinthechannel negligiblesurfacerunoffwasobservedinthesouthtributary basin thenegligiblesurfacerunoffobservedinthesouthtributarybasinisattributedtothelimitedextent andseverityof the fire in that basin the factors that best distinguish between debris flow producing and flood producing drainages are drainage basin morphology and lithology a rugged drainage basin morphology an average 12 per cent channel gradient andsteep roughhillslopescoupledwithcolluviumandsoilweatheredfromvolcaniclasticandvolcanicrockspromotedthe generation of debris flows a less rugged basin morphology an average gradient of 5 per cent and long smooth slopes mantled with pumice promoted flooding flood and debris flow responses were produced without the presence of waterrepellentsoils thecontinuityandseverityoftheburnmosaic theconditionoftheriparianvegetation theconditionofthe fibrous root mat accumulations of dry ravel and colluvial material in the channel and on hillslopes and past debris flow activity appearedtohavelittlebearingonthedistinctiveresponsesofthebasins publishedin2000byjohnwiley sons ltd

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

post fire hillslope debris flows evidence of a distinct erosion process abstract after wildfire a hitherto unexplained erosion process that some authors have called miniature debris flows on hillslopes and that leave behind levee lined rills has been observed in some regions of the world despite the unusual proposition of debris flow on planar hillslopes the process has not received much attention the objectives of this study were to 1 accumulate observational evidence of hillslope debris flows hdf as we have defined the process to 2 understand their initiation process by conducting runoff experiments on hillslopes to 3 propose a conceptual model of hdf and to 4 contrast and classify hdf relative to other erosion and transport processes in the post wildfire hillslope domain hdf have been observed at relatively steep slope gradients 0 4 0 8 on a variety of geologies and after fire of at least moderate severity and consist of a lobe of gravel to cobble sized material 0 2 1 m wide that is pushed by runoff damming up behind it during initiation runoff moved individual particles that accumulated a small distance downslope until the accumulation of grains failed and formed the granular lobe of the hdf hdf are a threshold process and runoff rates of 0 5 l s 1 2 l s 1 were required for their initiation during the experiments the conceptual model highlights hdf as a geomorphic process distinct from channel debris flows because they occur on planar unconfined hillslopes rather than confined channels hdf can erode very coarse non cohesive surface soil which distinguishes them from rill erosion that have suspended and bedload transport on a matrix of slope and grain size hdf are enveloped between purely gravity driven dry ravel and mostly runoff driven bedload transport in rills

debris flow initiation in proglacial gullies on mount rainier washington article i nfo effects of climate change retreating glaciers and changing storm patterns on debris flow hazards concern managers in the cascade range usa and mountainous areas worldwide during an intense rainstorm in november 2006 seven debris flows initiated from proglacial gullies of separate basins on the flanks of mount rainier gully heads at glacier termini and widespread failure of gully walls imply that overland flow was trans formed into debris flow along gullies we characterized gully change and morphology and assessed spatial distributions of debris flows to infer the processes and conditions for debris flow initiation slopes at gully heads were greater than 0 35 m m 1 19 and exhibited a significant negative relationship with drainage area a break in slope drainage area trends among debris flow gullies also occurs at 0 35 m m 1 representing a possible transition to fluvial sediment transport and erosion an interpreted hybrid model of debris flow initi ation involves bed failure near gully heads followed by sediment recruitment from gully walls along gully lengths estimates of sediment volume loss from gully walls demonstrate the importance of sediment inputs along gullies for increasing debris flow volumes basin comparisons revealed significantly steeper drainage networks and higher elevations in debris flow producing than non debris flow producing proglacial areas the high slopes and elevations of debris flow producing proglacial areas reflect positive slope elevation trends for the mount rainier volcano glacier extent therefore controls the slope distribution in proglacial areas and thus potential for debris flow generation as a result debris flow activity may increase as glacier termini retreat onto slopes inclined at angles above debris flow initiation thresholds

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

characterizing the primary material sources and dominant erosional processes for post fire debris flow initiation in a headwater basin using multi temporal terrestrial laser scanning data abstract wildfire dramatically alters the hydrologic response of a watershed such that even modest rainstorms can produce hazardous debris flows relative to shallow landslides the primary sources of material and dominant erosional processes that contribute to post fire debris flow initiation are poorly constrained improving our understanding of how and where material is eroded from a watershed during a post fire debris flow requires 1 precise measurements of topographic change to calculate volumetric measurements of erosion and deposition and 2 the identification of relevant morphometrically defined process domains to spatially constrain these measurements of erosion and deposition in this study we combine the morphometric analysis of a steep small 0 01 km 2 headwater drainage basin with measurements of topographic change using high resolution 2 5 cm multi temporal terrestrial laser scanning data made before and after a post fire debris flow the results of the morphometric analysis are used to define four process domains hillslope divergent hillslope convergent transitional and channelized incision we determine that hillslope divergent and hillslope convergent process domains represent the primary sources of material over the period of analysis in the study basin from these results we conclude that raindrop impact induced erosion ravel surface wash and rilling are the primary erosional processes contributing to post fire debris flow initiation in the small steep headwater basin further work is needed to determine 1 how these results vary with increasing drainage basin size 2 how these data might scale upward for use with coarser resolution measurements of topography and 3 how these results change with evolving sediment supply conditions and vegetation recovery