sediment contributions from floodplains and legacy sediments to piedmont streams of baltimore county maryland abstract disparity between watershed erosion rates and downstream sediment delivery has remained an important theme in geomorphology for many decades with the role of floodplains in sediment storage as a common focus in the piedmont province of the eastern usa upland deforestation and agricultural land use following european settlement led to accumulation of thick packages of overbank sediment in valley bottoms commonly referred to as legacy deposits previous authors have argued that legacy deposits represent a potentially important source of modern sediment loads following remobilization by lateral migration and progressive channel widening this paper seeks to quantify 1 rates of sediment remobilization from baltimore county floodplains by channel migration and bank erosion 2 proportions of streambank sediment derived from legacy deposits and 3 potential contribution of net streambank erosion and legacy sediments to downstream sediment yield within the mid atlantic piedmont we calculated measurable gross erosion and deposition rates within the fluvial corridor along 40 valley segments from 18 watersheds with drainage areas between 0 18 and 155 km2 in baltimore county maryland we compared stream channel and floodplain morphology from lidar based digital elevation data collected in 2005 with channel positions recorded on 1 2400 scale topographic maps from 1959 1961 in order to quantify 44 46 years of channel change sediment bulk density and particle size distributions were characterized from streambank and channel deposit samples and used for volume to mass conversions and for comparison with other sediment sources average annual lateral migration rates ranged from 0 04 to 0 19 m y which represented an annual migration of 2 5 0 9 4 4 channel width across all study segments suggesting that channel dimensions may be used as reasonable predictors of bank erosion rates gross bank erosion rates varied from 43 to 310 mg km y median 114 and were positively correlated with drainage area measured deposition within channels accounted for an average of 46 28 75 of gross erosion with deposition increasingly important in larger drainages legacy sediments accounted for 6 90 of bank erosion at individual study segments represented about 60 of bank height at most exposures and accounted for 57 16 of the measured gross erosion extrapolated results indicated that first and second order streams accounted for 62 38 of total streambank erosion from 1005 km2 of northern baltimore county after accounting for estimated redeposition extrapolated net streambank sediment yields 72 mg km2 y constituted 70 of estimated average piedmont watershed yields 104 mg km2 y the results suggest that streambank sediments are a relatively large source of sediment from piedmont tributaries to the chesapeake bay

developments in monitoring and modelling small scale river bed topography recent research in fluvial geomorphology has emphasized the spatially distributed feedbacks amongst river channel topography flow hydraulics and sediment transport although understanding of the behaviour of dynamic river channels has been increased markedly through detailed within channel process studies less attention has been given to the accurate monitoring and terrain modelling of river channel form using three dimensional measurements however such information is useful in two distinct senses firstly it is one of the necessary boundary conditions for a physically based deterministic modelling approach in which three dimensional topography and river discharge drive within channel flow hydraulics and ultimately spatial patterns of erosion and deposition and therefore channel change secondly research has shown that an alternative means of estimating the medium term bedload transport rate can be based upon monitoring spatial patterns of erosion and deposition within the river channel this paper presents a detailed assessment of the distributed monitoring and terrain modelling of river bed topography using a technique that combines rigorous analytical photogrammetry with rapid ground survey the availability of increasingly sophisticated terrain modelling packages developed for civil engineering application allows the representation of topographic information as a landform surface intercomparison of landform surfaces allows visualization and quantification of spatial patterns of erosion and deposition a detailed assessment is undertaken of the quality of the morphological information acquired this allow some general comments to be made concerning the use of more traditional methods to monitor and represent small scale river channel morphology

correlations between topography and intraflow width behavior in martian and terrestrial lava flows local correlations between topography and width behavior within lava flows at puu oo mount etna glass mountain cerro bayo alba patera tyrrhena patera elysium mons and olympus mons were investigated for each flow width and slope data were both referenced via downflow distance as a sequence of points the data were then divided into collections of adjacent three point features and two point segments four discrete types of analyses were conducted 1 three point analysis examined positional correlations between width and slope features 2 two point analysis did the same for flow segments 3 mean slope analysis included segment slope comparisons and 4 sudden width behavior analysis measured abruptness of width changes the distribution of types of correlations compared to random combinations of features and segments does not suggest a significant correlation between flow widths and local underlying slopes and indicates that for these flows at least other factors have more influence on changes in width than changes in underlying topography mean slopes underlying narrowing widening and constant flow width segments were calculated an inverse correlation between slope and width was found only at mount etna where slopes underlying narrowing segments were greater than those underlying widening in 62 of the examined flows for the majority of flows at mount etna puu oo and olympus mons slopes were actually greatest under constant width segments this may imply a topographically dependent resistance to width changes the rate of change of width was also examined sudden width changes are relatively common at puu oo mount etna elysium mons and tyrrhena patera and relatively rare at glass mountain cerro bayo olympus mons and alba patera after correction for mapping scale puu oo mount etna olympus mons and alba patera appear to fall on the same trend glass mount exhibits unusually small amounts of sudden width behavior and tyrrhena patera exhibits a relatively large number of sudden width behavior occurrences

the distribution and residence time of suspended sediment stored within the channel margins of a gravel bed bedrock river previously undocumented deposits are described that store suspended sediment in gravel bedded rivers termed fine grained channel margin fgcm deposits fgcm deposits consist of sand silt clay and organic matter that accumulate behind large woody debris lwd along the margins of the wetted perimeter of the single thread gravel bed south river in virginia these deposits store a total mass equivalent to 17 to 43 of the annual suspended sediment load radiocarbon 210pb and 137c dating indicate that sediment in fgcm deposits ranges in age from 1 to more than 60 years reservoir theory suggests an average turnover time of 1 75 years and an annual exchange with the water column of a mass of sediment equivalent to 10 to 25 of the annual sediment load the distribution of ages in the deposits can be fitted by a power function suggesting that sediment stored in the deposits has a wide variety of transit times most sediment in storage is reworked quickly but a small portion may remain in place for many decades the presence of fgcm deposits indicates that suspended sediment is not simply transported downstream in gravel bed rivers in agricultural watersheds significant storage can occur over decadal timescales south river has a history of mercury contamination and identifying sediment sources and sinks is critical for documenting the extent of contamination and for developing remediation plans fgcm deposits should be considered in future sediment budget and sediment transport modeling studies of gravel bed rivers in agricultural watersheds copyright 2010 john wiley sons ltd

fluvial sediment budgets in the north carolina piedmont phillips j d 1991 fluvial sediment budgets in the north carolina piedmont geomorphology 4 231 241 sediment budgets for four large 1000 km 2 drainage basins in the piedmont physiographic province of north carolina were estimated from data compiled during erosion and sedimentation surveys budgets for the upper tar upper neuse haw and deep river basins showed broadly similar trends in allocation of eroded sediment among yield and storage sediment yield as a percentage of mean annual gross erosion within the basins averaged 10 this was less than the rate of alluvial storage which averaged 14 of annual gross erosion about 76 of the mean annual erosion was stored as colluvium on hillslopes there are relatively small differences in sediment delivery and storage ratios among the study basins this suggests that the relative order of magnitude of the allocation of eroded sediment for southern piedmont rivers is colluvial storage alluvial storage and yield of the sediment that does reach the streams more than half is stored as alluvium on an average annual basis aggrading channels and floodplains siltation of benthic habitats and sediment pollution problems are thus likely to persist unless dramatic reductions in upland erosion or in sediment delivery to streams are realized with respect to longer term basin evolution results point to the need for an improved understanding of the temporal scales of colluvial and alluvial sediment storage

viscosity of the dome of mount st helens abstract a sample of dacite from the dome of mt st helens has been studied experimentally and found to have a viscosity that declines from about 10 15 at 800 c to 10 3 poise at 1500 c its yield strength declines from about 2 10 6 dynes cm 2 at 800 c to less than the precision of our measurements 10 4 dynes cm 2 above 1050 c the geometrical form of the dome is approximately consistent with these properties if the internal temperature of the dome is between 900 and 1000 c the melting behavior of the crystalline dacite has been determined between 1000 and 1225 c data on the composition of the liquid fraction and sizes and proportion of crystals have been used to derive a set of equations for predicting the effective viscosity of crystal bearing magmas below their liquidus temperatures although of the bulk composition of the magma has changed little the increasing crystallinity and viscosity appear to have influenced eruptive behavior of the volcano during its most recent periods of activity

new statistics for estimating the bulk rheology of active lava flows puu oo examples downstream changes in lava rheology due to cooling crystallization and vesiculation have a strong influence on the final length and morphology of a lava flow three statistics are proposed to estimate the change in lava rheology with distance along the path of an active flow these statistics correspond to three separate models of the volumetric flow rate dependence on the thickness of the flow each statistic is based on flow dimensions and topographic data that are often available from field measurements or remote sensing one model assumes an elementary laminar newtonian flow a second empirical model often used to describe the flow of complex geologic materials such as lahars sediment laden floods and debris flows is also investigated for comparison a new volume loss model is also proposed to account for stationary components such as levees and stagnant areas the three statistics derived from these flow rate models are applied and interpreted for two well defined lobes from episodes 2 and 18 of the 1983 1984 puu oo eruption the power law dependence of the first two models results only in modest differences in the estimates of rheologic change along the flow path however the removal of lava from the active flow to construct stationary components produces significant differences in both the magnitude of computed rheologic changes and the ability to discern trends in rheologic changes along the path of the flow

early chromite mining and agricultural clearance opportunities for the investigation of agricultural sediment dynamics in the eastern piedmont usa many flood plains in the eastern piedmont usa are buried under deposits of sediment resulting from european agricultural clearance classic radioisotopic dating techniques cover temporal periods too short 137cs 210pb or too long 14c to reliably date sediments deposited during periods of local european activity 1660 1900 moreover many potential biomarkers such as pollen degrade in oxic flood plain sediments in the baltimore maryland usa region early chromite mining 1820 1880 occurred during periods of rapid agricultural clearance use of chromium cr chemostratigraphic profiles in flood plain sediments tied to historical mining activity can provide improved precision in overbank accumulation rates and timing sediment cores were collected from the red run basin which is part of the baltimore ecosystem study an urban long term ecological research site trace metal chemostratigraphic profiles were measured and peaks in cr concentration tied to historic mining activity dates from cr chemostratigraphic profiles were combined with 137cs dating to reconstruct flood plain sedimentation rates red run early sedimentation rates 1820 1880 were higher 0 45 1 19 cm yr than more recent 1880 1963 rates 0 08 0 46 cm yr this indicates that piedmont flood plain vertical sediment accumulation might have peaked before the peak in agricultural clearance earlier than assumed by regional models the cr chemostratigraphy is applicable to a wider region including much of the maryland and pennsylvania usa piedmont

limited carbon contents of centuries old soils forming in legacy sediment abstract accelerated erosion from european agriculture overwhelmed transport capacities of relatively low gradient piedmont watersheds and triggered widespread and massive sediment deposition on floodplains referred to as legacy sediments while erosion driven soil loss on the southern piedmont landscape has been widely studied the resultant legacy sediments deposited on hillslopes floodplains and in channels appear remarkably understudied in the interim between deposition and future remobilization legacy sediments are undergoing soil formation in ways that impact carbon stocks nutrient retention and a number of other soil sediment functions here we use a pedological framework to understand the dynamics of these legacy sediments by constraining the time since deposition and redevelopment of vegetation and the soil profile in this study we characterized the properties of legacy sediment and buried pre legacy sediment alluvium established the timing of legacy sediment deposition and its volume in a 600 ha watershed and analyzed the impact of accelerated sedimentation on floodplain soil carbon soc storage we found alluvial legacy sediment in the 6 km2 holcombe s branch watershed to range in thickness from 0 35 to 1 25 m averaging 1 01 m in depth n 20 cv 19 radiocarbon 14c dates from buried wood indicate that accelerated deposition began by the mid 1800s during the next century deposition rates increased and peaked at levels up to 40 higher than contemporary sedimentation rates by the mid 1900s accelerated deposition rates had slowed significantly as indicated by surficial distributions of 1960s fall out 137cs in sediments upstream floodplains are today less frequently flooded and function as abandoned floodplains or terraces in contrast downstream sites remain active floodplains and zones of deposition a century of pedogenesis has formed acidic well drained entisols characterized by incipient redeveloping a horizons over coarse textured c horizons buried pre legacy sediment alluvium have well developed redox features are lower in hue and chroma than legacy sediments and occasionally have moderate to strong aggregate structure a century old mixed pine hardwood forest has diminished subsoil carbon stocks and created a shallow vertical distribution of soc stocks that total 95 mg c ha 1 cv 25 in the upper 2 m legacy sediments have nearly doubled alluvial sediment in the catchment and account for 55 of soil carbon stock coarse texture and porous legacy sediment soils limit accumulation of mineral associated soil carbon a horizon morphology was preserved in buried a horizons underlying legacy sediment yet these horizons did not account for significant soc stocks at depth depth profiles of active light fraction organic carbon revealed differences in soc preservation between upstream and downstream sites the hydrogeomorphic change responsible for this difference from abandoned legacy sediment terraces upstream to active sedimentation on floodplains downstream will continue to impact soil sediment dynamics and functioning time since last deposition and revegetation are dominant forces in soc dynamics while gradients in soil moisture may be creating subtle longitudinal patterns in soc preservation at depth

calculation of lahar transit times using digital elevation data abstract volcanic debris flows or lahars represent a significant hazard because of their rapid emplacement long runout distances and tremendous destructive potential accurate knowledge of advance rates and flow depths is therefore critical to hazard mitigation in lahar prone areas with the increasing availability of digital topographic data models of lahar transit can now be applied to better representative descriptions of natural topography with the expectation of improved hazard predictions using an elementary model of lahar transport dynamics we have developed a mathematical treatment of lahar propagation over digital topography our results show that flow depths and transit times depend on the cumulative effects of changes in local slope along the flow path these cumulative effects can be significant in predicting lahar advance rates and transit times in adapting the continuum model to digital topography we treat the changes in elevation between each adjacent pair of elevations as contiguous inclined planes and establish new boundary conditions sequentially for all downstream intervals to satisfy both local and total volume conservation requirements thus we are able to derive transit times and the evolution of flow velocity and depth profile as a function of distance x and time t to illustrate the usefulness of this approach we have applied the model using parameters typical of large volume 10 6 to 10 7 m 3 long runout 25 50 km lahars at mt ruapehu new zealand by discretizing an analog topography model into n equal sized intervals we demonstrate that as n increases the predicted transit time over the digital topography decreases asymptotically several hundred intervals are required to achieve convergence thus yielding estimates of the minimum resolution of the digital topography 10 m vertical 250 m horizontal required to give accurate transit time assessments we also show that one cannot simply model irregular topography as a drop in elevation over a runout distance without risking significant errors in transit time predications the result that transit time predictions decrease with increasing topographic resolution has significant implications for both hazard assessment and the ability to provide timely warnings to communities in the flow paths of lahars

comparing landslides to fluidized crater ejecta on mars 1 we use the mars global surveyor and viking data sets to compare and contrast the geomorphology of four large martian landslides located in valles marineris to fluidized ejecta of seven fresh martian craters located in lunae planum both mass movements have flowed over the martian surface and possess characteristics seen in terrestrial mass movements we combine these comparisons with simple flow models to determine how the planar geometry of landslides and the cylindrical geometry of ejecta can generate different topographic expressions for the same input constraints our purpose is to better understand the emplacement processes of both types of mass movements our geomorphic analyses are consistent with previous views that the large martian landslides resemble large terrestrial long run out flows the planar flow model supports this inference martian landslides probably flowed as a basal glide where motion is limited to a narrow interface at the base of the mass movement geomorphic investigations of fresh multilayered ejecta indicate that their inner portions with their subtle rampart probably flowed like their landslide counterparts as a basal glide distal pronounced contiguous ramparts however resemble features akin to terrestrial debris flows the cylindrical flow model shows that differences in geometry can mask the dynamics of flow emplacement this model suggests as expected a basal glide origin for the inner portions of the ejecta surprisingly basal glide also best explains the topography of the distal ejecta ramparts

the sediment delivery problem abstract the linking of on site rates of erosion and soil loss within a drainage basin to the sediment yield at the basin outlet and improved knowledge and representation of the associated processes of sediment delivery represent a major research need within the field of erosion and sedimentation and also an important scale problem in drainage basin studies this paper reviews the limitations of the sediment delivery ratio concept by considering the problems of temporal and spatial lumping and its blackbox nature some recent advances in our understanding of the sediment delivery system and its modelling are described and the lack of detailed empirical investigations is highlighted the significance of recent concern for the role of sediments in the transport of nutrients and contaminants to sediment delivery studies is introduced and the need for further work in this field is emphasised

impacts of pre vs postcolonial land use on floodplain sedimentation in temperate north america abstract this paper evaluates the relative importance of anthropogeomorphic sedimentation on floodplains in the mid latitudes of north america before and after the arrival of euroamericans geohistorical and geoarchaeological theories have emerged that have conflicts concerning the relative effectiveness of pre and postcolonial anthropogeomorphic change in north america many geoarchaeologists paleoecologists historians and cultural geographers have concluded that intensive precolonial land use resulted in substantially humanized landscapes prior to the arrival of colonists this presents a geomorphic paradox to fluvial geomorphologists and river restorationists who interpret buried floodplain soils as evidence of landscape stability evidence for these theories is reviewed from a geomorphic perspective while making distinctions between ecological and geomorphic change and recognizing spatial and temporal variability in some locations mid millennial land use generated erosion and floodplain sedimentation subsequent indigenous population declines and reductions in land use intensity may have been followed by precolonial geomorphic stability and pedogenesis an abandoned landscape hypothesis that floodplain soils developed on precolonial anthropogenic alluvium and were subsequently buried should be considered where indigenous populations and land use activities were high variability is also noted in postcolonial floodplain sedimentation many stratigraphic studies show that rates of sedimentation increased greatly after colonization in response to land clearance for agriculture timbering and mining an inventory of studies that document postcolonial floodplain sediment shows strong spatial patterns most studies of postcolonial sedimentation cluster in the eastern usa from the mid atlantic southward and in the mississippi valley from wisconsin to mississippi but many occurrences of mining sediment are scattered throughout the west few of the studies reviewed in the west document anthropogenic floodplain sediment from agriculture or logging although more thorough regional inventories could change that vast areas of temperate north america do not have historical deposits that are well represented in the scientific literature so assumptions that legacy sediment on floodplains is ubiquitous are ill founded spatial and temporal variations in pre and postcolonial floodplain sedimentation are complex and more research is needed to fill in the knowledge gaps

flume experiments on lower flow regime bed forms in coarse sand thirty five runs were made in a recirculating channel 11 5 m long and 0 92 m wide with four sizes of very well sorted coarse sand to study geometry migration and hydraulics of bed configurations in equilibrium with steady uniform open channel flows at flow depths of about 15 cm equilibrium energy slope and sediment transport rate were measured as well bed phases kinds of bed configurations studied were ripples low flow velocity flat beds with sand transport and dunes identical with megaripples current velocities in none of the runs were high enough for development of an upper flow regime flat bed a plot of mean flow velocity versus sand size for all the runs shows that at low flow velocities the ripple field narrows with increasing sand size and pinches out at about 0 7 mm the field for flatbed transport narrows with decreasing sand size and pinches out at about 0 5 mm just above the ripple field at high flow velocities dunes are the stable phase for all sand sizes studied dune configurations are divided into two subphases two dimensional dunes 2d dunes with fairly straight continuous even crests and no strong localized scour in troughs are formed at relatively low flow velocities three dimensional dunes 3d dunes with strongly sinuous discontinuous uneven crests and strong localized scour pits in troughs are formed at relatively high flow velocities 3d dunes tend to be higher than 2d dunes have larger height spacing ratios and show less variability in height spacing and migration rate dunes can be viewed as kinematic shock waves differences between 2d dunes and 3d dunes lie in the differing importance of shock wave coupling and of sand transport in bed form troughs in both geometry and hydraulic ralationships the 2d dunes and 3d dunes in our flume runs correspond to the relatively regular megaripples at low flow velocities and relatively irregular megaripples at high flow velocities described by other authors from intertidal environments

travel of pyroclastic flows as transient waves implications for the energy line concept and particle concentration assessment abstract we here consider the precept that pyroclastic flows travel as transient waves or pulses we provide simple geometric models to estimate the wave height that may form under specified conditions and how it may vary with progression away from the vent a main uncertainty is the length of the wave relative to the total travel distance but the simple sequence of segregation layers observed in many ignimbrites may enable crude constraints to be placed on the wavelength application of these models to actual ignimbrites suggests wave heights of tens to hundreds of meters a corollary is that a wave is able to surmount obstacles less high than itself irrespective of its velocity the wave may also possess momentum which confers an additional landscape surmounting capability thus a part of the obstacle crossing ability of a pyroclastic flow is due to the height of the wave and a part is due to the velocity of the wave another corollary is that the deposit will normally be much thinner than the wave height estimates of the degree of expansion of pyroclastic flows or surges based on the relationships of the height of a trimline to the depth of a deposit may therefore be invalid this is important as at el chichon when diagnosing whether a deposit was laid down by a pyroclastic flow or surge care must also be taken not to confuse a trimline or upper limit of a veneer which exists and is a wave height level with an energy line which is a theoretical concept application of the wave concept helps explain many observed features of pyroclastic flows and their deposits for example drainage of a wave off topographic highs to generate the secondary valley ponds such as were observed in the mount st helens 1980 blast flow deposit

conclusion recommendations and findings of the red seed working group red seed stands for risk evaluation detection and simulation during effusive eruption disasters and combines stakeholders from the remote sensing modelling and response communities with experience in tracking volcanic effusive events the group first met during a three day long workshop held in clermont ferrand france between 28 and 30 may 2013 during each day presentations were given reviewing the state of the art in terms of a volcano hot spot detection and parameterization b operational satellite based hot spot detection systems c lava flow modelling and d response protocols during effusive crises at the end of each presentation set the four groups retreated to discuss and report on requirements for a truly integrated and operational response that satisfactorily combines remote sensors modellers and responders during an effusive crisis the results of collating the final reports and follow up discussions that have been on going since the workshop are given here we can reduce our discussions to four main findings 1 hot spot detection tools are operational and capable of providing effusive eruption onset notice within 15 min 2 spectral radiance metrics can also be provided with high degrees of confidence however if we are to achieve a truly global system more local receiving stations need to be installed with hot spot detection and data processing modules running on site and in real time 3 models are operational but need real time input of reliable time averaged discharge rate data and regular updates of digital elevation models if they are to be effective the latter can be provided by the radar photogrammetry community 4 information needs to be provided in an agreed and standard format following an ensemble approach and using models that have been validated and recognized as trustworthy by the responding authorities all of this requires a sophisticated and centralized data collection distribution and reporting hub that is based on a philosophy of joint ownership and mutual trust while the next chapter carries out an exercise to explore the viability of the last point the detailed recommendations behind these findings are detailed here

lava flows are fractals we have conducted a preliminary investigation of the fractal nature of the plan view shapes of lava flows in hawaii based on field measurements and aerial photographs as well as in idaho and the galapagos islands using aerial photographs only our results indicate that the shapes of lava flow margins are fractals in other words lava flow shape is scale invariant at least within the range of scale measured 0 5m to 2 4km this observation has important implications for understanding the fluid dynamics of lava flows it suggests that nonlinear forces are operating in them because nonlinear systems frequently produce fractals furthermore a a and pahoehoe flows can be distinguished by their fractal dimensions d the majority of the a a flows we measured have d between 1 05 and 1 09 whereas the pahoehoe flows generally have higher d 1 14 1 23 we have extended our analysis to other planetary bodies by measuring flows from orbital images of venus mars and the moon all are fractal and have d consistent with the range of terrestrial a a and pahoehoe values combining the terrestrial and extraterrestrial data the fractal nature of lava flow outlines holds for over five orders of magnitude in scale 0 5m to 60km

rheology of a long lava flow at pavonis mons mars 1 dimensions of lava flows can be used to unravel the relative roles of viscosity changes and concurrent formation of levees stationary margins and stagnant zones this approach is applied to data derived from the mars orbiter laser altimeter mola experiment for a long lava flow on the plains north of pavonis mons mars we obtain a formula for the relative change in viscosity on the basis of a steady state newtonian flow rate our approach features a new length scale that describes the transfer of lava from the active advancing component to passive components this length scale can be determined from planetary image and topographic data by estimating the volume fraction of lava contained in flow margins relative to the total flow volume we find only modest changes in viscosity over the distal 175 km of the pavonis flow allowing the flow to also lose volume through degassing resulting in a density increase does little to affect the overall viscosity change thickening and widening of the flow with distance are as expected for a single coherent isothermal viscous flow this dynamic regime features a balance between the formation of an outer skin and shedding of lava into stationary zones requirements for attaining such a regime include a thick flow shallow slopes over extended distances and preexisting surface roughness that is small compared to flow thickness this style of emplacement may explain why many of the long thick sheet like flows on the plains of mars often exhibit an unexpected lack of thickening with distance

risk evaluation detection and simulation during effusive eruption disasters lava ingress into a vulnerable population will be difficult to control so that evacuation will be necessary for communities in the path of the active lava followed by post event population infrastructural societal and community replacement and or relocation there is a pressing need to set up a response chain that bridges scientists and responders during an effusive crisis to allow near real time delivery of globally standard products for a timely and adequate humanitarian response in this chain the scientific research groups investigating lava remote sensing and modelling need to provide products that are both useful to and trusted by the crisis response community requirements for these products include a formats that can be immediately integrated into a crisis management procedure and b in an agreed and stable standard a review of current capability reveals that we are at a point where the community can provide such a response as is the aim of the red seed risk evaluation detection and simulation during effusive eruption disasters working group this book is the first production of this group and is intended not only as a directory of current capabilities and operational service providers but also as a statement of intent and need while providing a simulation designed to demonstrate how a truly pan disciplinary response to an effusive crisis could work

exposed tree root analysis as a dendrogeomorphic approach to estimating bank retreat at the south river virginia abstract we use a biometric approach based on anatomical changes in the wood of exposed tree roots to quantify riverbank erosion along south river virginia a site where commonly applied techniques for determining bank erosion rates are either not appropriate because of the required spatial scale of analysis i e erosion pins traditional surveys lidar analysis or have failed to detect obvious erosion i e photogrammetric techniques we sampled 73 exposed roots from 22 study reaches and identified the year of exposure macroscopically 2 to 20 times magnification and microscopically 20 to 100 times magnification comparing the estimated erosion rates between levels of magnification and to those obtained with photogrammetric techniques we found no statistical differences between the results of macroscopic and microscopic analyses t test 0 01 but encountered difficulty in identifying the year of root exhumation in some samples when comparing exposed root analysis to photogrammetric techniques the results indicate that the exposed root approach is a feasible and effective method for estimating annual to decadal scale bank erosion in addition to producing erosion rates statistically indistinguishable from photogrammetric techniques at sites with erosion rates large enough for detection using historical aerial photographs regression analysis and t test 0 01 exposed root analysis was able to estimate erosion rates at sites where photogrammetric techniques failed we also identify deciduous species well suited for this approach fraxinus pennsylvanica and others that prove more problematic e g acer negundo celtis occidentalis acer saccharinum this study is significant because it describes a robust tool that provides insights into annual to decadal scale erosion where other commonly applied techniques may not be appropriate or easily applied

cambrian biostratigraphy of the tal group lesser himalaya india and early tsanglangpuan late early cambrian trilobites from the nigali dhar syncline precise biostratigraphic constraints on the age of the tal group are restricted to 1 a basal level correlative with the anabarites trisulcatus protohertzina anabarica assemblage zone of southwest china 2 a level near the boundary of the lower and upper parts of the tal group correlative with the early tsanglangpuan stage drepanuroides zone and 3 an interval low in the upper part of the tal group correlative with later in the tsanglangpuan stage palaeolenus zone these correlations are based on small shelly fossil and trilobite taxa other chronostratigraphic constraints include the marked negative 13 c isotopic excursion coincident with the transition from the krol group to the tal group this excursion is used as a proxy for the precambrian cambrian boundary in several sections worldwide and if applied to the lesser himalaya indicates that the boundary is at or just above the base of the tal group the upper parts of the tal group may be of middle or late cambrian age and might form proximal equivalents of sections in the zanskar spiti region of the tethyan himalaya both faunal content and lithological succession are comparable to southwest china furthering recent arguments for close geographic proximity between the himalaya and the yangtze block during late neoproterozoic and early cambrian time trilobites from the uppermost parts of the sankholi formation from the nigali dhar syncline are described and referred to three taxa one of which drepanopyge gopeni is a new species they are the oldest trilobites yet described from the himalaya

imaging short period variations in lava flux short period e g 1 h variations in lava effusion rate have been detected previously on mount etna sicily but the causes and effects of such changes are poorly understood because of difficulties in obtaining suitably high frequency measurements over long periods here we report short period flux variations in active lava flows recorded in dense time series imagery over a 7 night period using modified remote trail cameras the sequences of night time images show significant pulses of enhanced incandescence interpreted as short period increases in lava flux travelling down channel at velocities of 10 20 m min 1 pulse generation decreased from an average of one pulse per hour on the first night to approximately one per night within a few nights effusion rate changes on these timescales are considered to reflect instabilities in magma ascent and consequently could provide insight into subsurface flow processes

simulation of inflated pahoehoe lava flows a new stochastic model simulates late stage pahoehoe lobes where random processes dominate emplacement the model prescribes probabilistic rules for determining where and when parcels of lava move within the lobe unlike a classical brownian motion random walk the model allows individual parcels to remain dormant but fluid for multiple time steps the randomness of parcel volume transfers within the lobe interior as well as at the margins qualitatively reflects inflation processes observed in the field the fraction of inflated volume to total volume increases with the total volume with greater than 75 of the lobe volume contributed through inflation for typical lobes the influence on planform shape and topographic cross sectional profiles of total volume source area and shape topographic confinement and sequential breakouts at the lobe margins are all explored with the stochastic model each of these factors influences the overall lobe thickness and width the model provides a means for assessing the relative importance of these processes through comparisons with field data for the first time gaussian and parabolic functions are quantitatively fit to field measurements of pahoehoe lobes both functional forms provide adequate description of the cross sectional flow shapes when comparing simulated lobes to field data sequential breakouts at the lobe margins are found to be an important process controlling the final topographic distribution of observed pahoehoe lobes

topographic and stochastic influences on pahoehoe lava lobe emplacement a detailed understanding of p hoehoe emplacement is necessary for developing accurate models of flow field development assessing hazards and interpreting the significance of lava morphology on earth and other planetary surfaces active p hoehoe lobes on k lauea volcano hawai i were examined on 21 26 february 2006 using oblique time series stereo photogrammetry and differential global positioning system measurements during this time the local discharge rate for peripheral lava lobes was generally constant at 0 0061 0 0019 m3 s but the areal coverage rate of the lobes exhibited a periodic increase every 4 13 0 64 min this periodicity is attributed to the time required for the pressure within the liquid lava core to exceed the cooling induced strength of its margins the p hoehoe flow advanced through a series of down slope and cross slope breakouts which began as 0 2 m thick units i e toes that coalesced and inflated to become approximately meter thick lobes the lobes were thickest above the lowest points of the initial topography and above shallow to reverse facing slopes defined relative to the local flow direction the flow path was typically controlled by high standing topography with the zone directly adjacent to the final lobe margin having an average relief that was a few centimeters higher than the lava inundated region this suggests that toe scale topography can at least temporarily exert strong controls on p hoehoe flow paths by impeding the lateral spreading of the lobe observed cycles of enhanced areal spreading and inflated lobe morphology are also explored using a model that considers the statistical likelihood of sequential breakouts from active flow margins and the effects of topographic barriers

the piedmont landscape of maryland a new look at an old problem the piedmont upland of maryland has been variously interpreted as a peneplain a series of peneplains a surface of marine planation and a landscape in dynamic equilibrium these different perspectives of landform evolution are related to different scales of time and space both equilibrium and episodic erosion features can be recognized in the modern landscape an equilibrium condition is suggested by adjustment of first and second order streams to rock structure and lithology entrenchment of some streams against gneiss domes altitudinal zonation of rock types around gneiss domes correlation of lithology with overburden thickness on uplands decreasing overburden thickness on uplands related to decreasing degree of metamorphism of crystalline rocks and correlation of secondary mineral assemblages with subsurface drainage and slope the long term episodic character of erosion is suggested by clastic wedges on the adjacent coastal plain an upland of low relief that truncates non carbonate rocks of different lithologies isovolumetric chemical weathering of alumino silicate rocks clastic deposition in marble valleys and weathering profile truncation by modern drainage the maryland piedmont may have been an area of positive relief subject to subaerial erosion since triassic and possibly permian time the upland surface preserved in the eastern piedmont developed by the late cretaceous in the interval from the late cretaceous to the late miocene low input of terrigenous sediments to the coastal plain dominance of marine sedimentation and spotty evidence of saprolite formation on crystalline rocks suggest that the maryland piedmont was an area of low relief undergoing intense weathering incised valleys were formed during a cycle of erosion probably initiated in the late miocene and extensive colluvial sediments were deposited on hillslopes by periglacial processes during the pleistocene

a hybrid model for leveed lava flows implications for eruption styles on mars 1 many channelized lava flows on the plains of mars have substantial embanking margins and levees inferred to have been stationary while the central channel was active levee formation can be attributed to two end member processes during emplacement construction during passage of the flow front and growth along the entire length of the flow while it is active it is shown here that the amount of lava that can be deposited by the flow front alone is limited estimates of the levee volume for many mars plains flows exceed this limit and must have formed by processes that continued after the passage of the front experimental studies of analogous laboratory flows also indicate a combination of both modes of emplacement a model that combines both modes of levee formation is presented including a method for estimating volumetric flow rate eruption duration and viscosity six lava flows on the plains of the tharsis volcanic province are used as illustrative examples crustal thicknesses for the six flows examined range from 9 to 23 m estimated emplacement times required to cool crusts of these thicknesses range from 1 year to 10 years corresponding viscosities are on the order of 105 106 pa s effusion rates range from 25 to 840 m3 s 1 and are all within the range of terrestrial observations therefore the large leveed plains flows on mars are not dramatically different in eruption rate or lava viscosity from large terrestrial analogs

numerical simulations of flood basalt lava flows roles of parameters on lava flow morphologies using a three dimensional numerical simulation model of lava flow we studied the effects of parameters on the morphologies of simple flood basalt lava flows the model can provide a more realistic description of morphologies of lava flows than two dimensional models because it can evaluate the complex relationship between erupted volume and length of lava by considering lateral spreading of flows moreover our model can calculate lava morphologies on a very moderate slope or even on a flat plane without mesh direction dependency it can simulate not only small scale flows on individual volcanoes but also large scale 100 km flows without numerical instability although the length of a lava flow is controlled by many parameters including rheological properties and eruption rate the length is not a simple function of these parameters we confirm that small changes in parameters such as slope angle and viscosity can affect the length of the flow increasing the eruption rate up to 107 m3 s makes basaltic lava flows longer however at eruption rates higher than 107 m3 s on 0 3 slopes flow length does not increase beyond that of the 107 m3 s eruption rate due to volume conservation of erupted lava thus eruption conditions cannot be estimated from the length of a lava flow alone therefore the estimated eruption rate obtained by previous two dimensional models which essentially estimate eruption rate from the length of the flow will not always reveal useful values on the other hand the width of a simple lava flow is a good measure of its eruption rate because the width is mainly controlled by the eruption rate and yield strength a simple lava whose width is greater than 100 km was almost certainly emplaced at eruption rates higher than 107 m3 s if the yield strength of the flow is in a basaltic range

floodplain width adjustments in response to rapid base level fall and knickpoint migration abstract geomorphology has long been engaged in characterizing the form and understanding the evolution of floodplains this study primarily examines floodplain width in four tributaries to the minnesota river in southern minnesota namely the maple le sueur and blue earth rivers and seven mile creek the tributary systems are relatively young having formed after retreat of the wisconsinan ice sheet and are rapidly evolving in response to a base level fall of nearly 70 m 13 400 ybp as a result the lower reaches of all four river channels are aggressively incising this study applies a new freely available open code plug in for arcgis to measure floodplain width as a function of elevation above the geomorphic top of bank systematic changes are observed in all four systems above the steep incising knickzone reaches of each of the tributaries relatively wide and mostly unconfined floodplains are observed within the knickzone floodplains progressively narrow to between 25 60 of their width above the knickzone despite the fact that sediment loads increase significantly in the downstream direction a power law relationship is consistently observed between floodplain width and the ratio of local channel slope to contributing drainage area to about the negative one third power in all four rivers this same power law relationship is observed for two other rivers that differ significantly from our study systems in climatic and tectonic environment as well as base level history

floodplain sedimentation in the upper mississippi valley natural versus human accelerated abstract understanding the time scales and pathways for response and recovery of rivers and floodplains to episodic changes in erosion and sedimentation has been a long standing issue in fluvial geomorphology floodplains are an important component of watershed systems because they affect downstream storage and delivery of overbank flood waters and they also serve as sources and temporary sinks for sediments and toxic substances delivered by river systems here 14c and 137cs isotopic dating methods are used along with ages of culturally related phenomena associated with mining and agriculture to determine rates of sedimentation and morphologic change for a reach of the upper mississippi river and adjacent tributaries in southwestern wisconsin and northwestern illinois the most important environmental change that influenced fluvial activity in this region during last 10 000 years involved the conversion of a late holocene mosaic of prairie and forest to a landscape dominated by cropland and pastureland associated with euro american settlement results presented herein for the upper mississippi valley umv show that the shift from pre agriculture natural land cover to landscape dominance by agricultural land use of the last 175 200 years typically increased rates and magnitudes of floodplain sedimentation by at least an order of magnitude accelerated overbank flooding led to increased bank heights on tributary streams and in turn contributed to more frequent deep flows of high energy these high energy flows subsequently promoted bank erosion and lateral channel migration and the formation of a historical meander belt whose alluvial surface constitutes a new historical floodplain inset against the earlier historical floodplain the new historical floodplain serves as a flume like channel that provides efficient downstream transport of water and sediment associated with moderate and large magnitude floods floodplains on lower tributaries however continue to experience rates of overbank sedimentation that are of anomalously high magnitude given improved land cover and land conservation since about 1950 this lower valley anomaly is explained by minimal development of historical agriculture period meander belts because of relatively low stream power in these channel and floodplain reaches of relatively low gradient in general long term pre agriculture rates of vertical accretion between about 10 000 and 200 years ago averaged about 0 2 mm yr 1 in tributary watersheds smaller than about 700 km2 and about 0 9 mm yr 1 on the floodplain of the upper mississippi river where the contributing watershed area increases to about 170 000 km2 on the other hand rates of historical vertical accretion during the period of agricultural dominance of the last 200 years average between 2 and 20 mm yr 1 with short episodes of even higher rates during times of particularly poor land conservation practices significant hydrologic effects of mining and agricultural started by the 1820s and became widespread in the study region by the mid 19th century the hydrologic and geomorphic influences of mining were relatively minor compared to those related to agriculture high resolution dating of floodplain vertical accretion deposits shows that large floods have frequently provided major increments of sedimentation on floodplains of tributaries and the main valley upper mississippi river the relative importance of large floods as contributors to floodplain vertical accretion is noteworthy because global atmospheric circulation models indicate that the main channel upper mississippi river should experience increased frequencies of extreme hydrologic events including large floods with anticipated continued global warming instrumental and stratigraphic records show that coincident with global warming a shift to more frequent large floods occurred since 1950 on the upper mississippi river and these floods generally contributed high magnitudes of floodplain sedimentation

upland sediment supply and its relation to watershed sediment delivery in the contemporary mid atlantic piedmont u s a abstract we use sediment accumulation in ponds and reservoirs to examine upland sediment sources and sinks in the piedmont physiographic region of maryland usa in zero order and first order watersheds sediment yield is greatest from suburban land cover followed by agriculture and forest the idea that sediment yield is small from mature suburban development appears to not be correct first order channel enlargement is an important sediment source causing sediment yield to increase from zero order to first order watersheds nonchannel sources provide one third to two thirds of the upland sediment load long term sediment accumulation in a reservoir at fifth order indicates that cumulative sediment load from upland areas is reduced by one quarter by net valley bottom sedimentation if upland supply exceeds the load delivered from a watershed sediment must accumulate along valley bottoms in our study watershed net sedimentation rate sedimentation less erosion averaged over valley bottom area is 2 6 mm y a value that is similar to independent direct measurements of sedimentation and erosion in a nearby watershed evaluation of the relative contributions to sediment mass balance of upland supply valley bottom sedimentation and erosion and watershed delivery indicates that if valley bottom rates of sedimentation exceed erosion as indicated by recent studies then the proportion of watershed sediment delivery derived from stream banks is necessarily small although sediment yield estimated from stream gage records is similar in magnitude to that from ponds for watersheds smaller than 20 km 2 sediment yield from reservoir sedimentation is a factor of five larger than that estimated from gage records for watersheds larger than 140 km 2 this observation confirms that the different methods provide very different estimates of sediment yield this possibility is reinforced by a sediment yield of 14 mg km 2 y from a gage immediately above a reservoir with a yield of 142 mg km 2 y based on reservoir accumulation

extended cooling and viscous flow of large hot rhyolite lavas implications of numerical modeling results abstract a common misconception about rhyolite lava flows is that they cannot advance far from their vents and are constrained to be small due to their high viscosities although a high viscosity lava will indeed flow quite slowly it may advance a great distance if the lava efficiently retains heat and thus mobility and if the available magma supply is large to evaluate this possibility a finite difference numerical model was used to determine the rate of heat loss from units interpreted to be large rhyolite lavas cooling of such 100 300 m thick units is very slow and is further retarded by a vesicular carapace and by evolution of latent heat thermal history alone suggests that large thick lava flows could remain active for several decades to constrain the duration of flow advance of these units their inferred apparent viscosities are compared with those of active lava flows mean flow velocity of some large rhyolites in southwestern idaho usa was estimated based on the observation that the units must still have been advancing by viscous flow at the start of spherulite crystallization indicating perhaps a 10 to 18 year flow duration based on studies of obsidian dome california mean flow velocities would have been roughly 0 59 to 2 5 km yr and calculated average apparent viscosities of the flows ranged from 1 8 to 3 6 orders of magnitude greater than the viscosity of the lava itself this relationship also holds for active andesite and basaltic andesite block lava flows which have apparent viscosities 2 7 to 4 orders of magnitude greater than lava viscosities this implies that large rhyolites may indeed have been emplaced in the same manner as less silicic block lavas and that long distance viscous flow is not unrealistic for rhyolite lavas a good example of a large volume lava is the 15 km 3 rhyolite of the badlands sw idaho where vent relations show that lava effused from a fissure and advanced up to 9 km more extensive rhyolites could also be emplaced solely by effusion extended flow of these lavas may lead to the remelting and removal of basal crumble breccias and to the formation of welded shard textures in their margins both processes tending to obscure the lava flow origin of the units the great dimensions of lava like rhyolitic units with volumes of 10 to at least 200 km 3 are not a sufficient reason to assume they erupted as ignimbrites

flow and instability of a viscous current down a slope if viscous fluid is released on a horizontal surface it rapidly takes up a circular plan form as it spreads this form is observed1 2 to be stable to any small disturbances which are initiated on the front due for example to irregularities in the horizontal surface or to chance perturbations alternatively if some fluid is released onto a sloping surface for example some liquid detergent on a slanted plate a quite different plan form occurs one two or more extended regions of fluid develop downslope as shown in fig 1a b a situation intermediate between these two is now discussed consider a broad band of viscous fluid uniform in depth across a slope released so as to flow down a constant slope by following the motion which is initially independent of the cross slope coordinate the speed of advance and the depth of the flow before it breaks up into a series of waves of ever increasing amplitude can be determined i present an expression for the wavelength of the front which is determined by surface tension and is independent of the coefficient of viscosity

quantifying the effect of rheology on lava flow margins using fractal geometry this study aims at quantifying the effect of rheology on plan view shapes of lava flows using fractal geometry plan view shapes of lava flows are important because they reflect the processes governing flow emplacement and may provide insight into lava flow rheology and dynamics in our earlier investigation bruno et al 1992 we reported that flow margins of basalts are fractal having a characteristic shape regardless of scale we also found we could use fractal dimension d a parameter which quantifies flow margin convolution to distinguish between the two endmember types of basalts a a d 1 05 1 09 and pahoehoe d 1 13 1 23 in this work we confirm those earlier results for basalts based on a larger database and over a wider range of scale 0 125 m 2 4 km additionally we analyze ten silicic flows sio2 52 74 over a similar scale range 10 m 4 5 km we note that silicic flows tend to exhibit scale dependent or non fractal behavior we attribute this breakdown of fractal behavior at increased silica contents to the suppression of small scale features in the flow margin due to the higher viscosities and yield strengths of silicic flows these results suggest we can use the fractal properties of flow margins as a remote sensing tool to distinguish flow types our evaluation of the nonlinear aspects of flow dynamics indicates a tendency toward fractal behavior for basaltic lavas whose flow is controlled by internal fluid dynamic processes for silicic flows or basaltic flows whose flow is controlled by steep slopes our evaluation indicates non fractal behavior consistent with our observations

accuracy assessment of georectified aerial photographs implications for measuring lateral channel movement in a gis aerial photographs are commonly used to measure planform river channel change we investigated the sources and implications of georectification error in the measurement of lateral channel movement by testing how the number 6 30 and type human versus natural landscape features of ground control points gcps and the order of the transformation polynomial first second and third order affected the spatial accuracy of a typical georectified aerial photograph error was assessed using the root mean square error rmse of the gcps as well as error in 31 independent test points the rmse and the mean and median values of test point errors were relatively insensitive to the number of gcps above eight but the upper range of test point errors showed marked improvement i e the number of extreme errors was reduced as more gcps were used for georectification using more gcps thus improved overall georectification accuracy but this improvement was not indicated by the rmse suggesting that independent test points located in key areas of interest should be used in addition to rsme to evaluate georectification error the order of the transformation polynomial also influenced test point accuracy the second order polynomial function yielded the best result for the terrain of the study area gcp type exerted a less consistent influence on test point accuracy suggesting that although hard edged points e g roof corners are favored as gcps some soft edged points e g trees may be used without adding significant error based upon these results we believe that aerial photos of a floodplain landscape similar to that of our study can be consistently georectified to an accuracy of approximately f5 m with 10 chance of greater error the implications of georectification error for measuring lateral channel movement are demonstrated with a multiple buffer analysis which documents the inverse relationship between the size of the buffers applied to two channel centerlines and the magnitude of change detected between them this study demonstrates the importance of using an independent test point analysis in addition to the rsme to evaluate and treat locational error in channel change studies d 2005 published by elsevier b v

legacy sediments and historic land use chemostratigraphic evidence for excess nutrient and heavy metal sources and remobilization major and trace element geochemistry of sediment cores of legacy deposits i e sediments eroded from upland areas starting in colonial times reflecting intensive land use that have altered pre colonial environments and are impairing modern environments from behind former mill dams in different land use sub watersheds of the yellow breeches creek cumberland county pennsylvania usa provide insight into the origins of elements with multiple natural and anthropogenic sources in comparing a forested land use watershed with an agriculturally affected one we find similar elemental ratios with al for pre settlement and early legacy sediments but increasing trends of nutrient elements and select trace metals through time in the agriculturally affected legacy deposit likely sources of excess p cu and pb over background are fertilizer pesticides and other soil amendments pb trends show smaller increases over time in the forested land use subwatershed mostly due to the input of leaded gasoline emissions to the atmosphere and ubiquitous fallout to all watersheds the agriculturally affected subwatershed cores show significantly more pb suggesting multiple sources the continued remobilization of legacy sediments from thousands of mill ponds in the eastern united states suggests that this source of nutrients and trace elements may add significantly to the degradation of downstream ecosystems such as the chesapeake bay

natural streams and the legacy of water powered mills gravel bedded streams are thought to have a characteristic meandering form bordered by a self formed fine grained floodplain this ideal guides a multibillion dollar stream restoration industry we have mapped and dated many of the deposits along mid atlantic streams that formed the basis for this widely accepted model these data as well as historical maps and records show instead that before european settlement the streams were small anabranching channels within extensive vegetated wetlands that accumulated little sediment but stored substantial organic carbon subsequently 1 to 5 meters of slackwater sedimentation behind tens of thousands of 17th to 19th century milldams buried the presettlement wetlands with fine sediment these findings show that most floodplains along mid atlantic streams are actually fill terraces and historically incised channels are not natural archetypes for meandering streams

lava flows as kinematic waves a recently proposed model for the emplacement of lava flows is reinterpreted as a kinematic wave theory for the depth of the flow with this interpretation the longitudinal profile of an advancing flow is considered to be a propagating waveform with its length limited continuously by the amount of lava extruded the application of kinematic wave formalism provides new insights into the effects of time dependent source behavior on the shape and extent of the wave eruption behavior with a period of increasing flow depth at the source is shown to produce so called breaking points in the depth profile where the kinematic wave model itself could be invalid two models of such eruption behavior are investigated and this is shown not to be the case specifically when the conservation of lava volume is imposed the breaking points always reside beyond the front of the wave in general it is found that source behavior propagates downstream faster than the flow advances thus only a fraction of the source time dependence is reflected in the shape of the kinematic wave the remainder of the time dependent source effects must be deposited in the flow front lateral margins or solidifying crust or be dissipated irretrievably by processes not included in the model the fraction of eruption history contained in the advancing waveform depends crucially on the nature of the flow rate flow depth relation for the lava distal surface waves budding at the nose of the flow distal levee collapse and other volcanological observations may be manifestations of time dependent source behavior that advanced beyond the kinematic wave front

fluvial processes morphology and sediment budgets in the coon creek basin wi usa 1975 1993 sediment budget processes in coon creek wisconsin from 1975 to 1993 changed only moderately generally continuing the trends that were evident in 1975 perhaps most importantly sediment yield to the mississippi river appears to be unabated with much of this clearly coming from storage loss especially stream bank erosion vertical accretion continued on the lower new floodplains inset within their meander plains in tributaries and the upper main valley the lower main valley also continued to aggrade but at the rate of about 6 of that occurring in the 1920s and 1930s the major revision from earlier studies is that the upper main valley is a less significant net source of sediment than previously thought and the earlier prognostications of it being a significant net source of sediment in the future may be wrong perturbations have been caused by changes of riparian vegetation and much more importantly by the introduction of fish shelter structures and protected cut banks along the stream system reaching downstream to the end of the upper main valley because these structures do not permit natural stream migration bank erosion and downstream sediment transfer the coon creek basin has lost much of its suitability as a natural laboratory of fluvial processes

a self replication model for long channelized lava flows on the mars plains 1 a model is presented for channelized lava flows emplaced by a self replicating levee building process over long distances on the plains of mars such flows may exhibit morphologic evidence of stagnation overspills and upstream breakouts however these processes do not inhibit the formation and persistence of a prominent central channel that can often be traced for more than 100 km the two central assumptions of the self replication model are 1 the flow advances at the average upstream velocity of the molten core and 2 the fraction of the lava that travels faster than the average upstream velocity forms stationary margins in the advancing distal zone to preserve the self replication process for an exemplary 300 km long flow north of pavonis mons the model indicates that 8 m of crust must have formed during emplacement as determined from the channel and levee dimensions when combined with independent thermal dynamic estimates for the crustal growth rate relatively narrow constraints are obtained for the flow rate 2250 m3 s 1 emplacement duration 600 d and the lava viscosity of the molten interior 106 pa s minor transient overspills and breakouts increase the emplacement time by only a factor of 2 the primary difference between the prodigious channelized martian flows and their smaller terrestrial counterparts is that high volumetric flow rates must have persisted for many hundreds of days on mars in contrast to a few hours or days on earth

deposition and storage of fine grained sediment within the main channel system of the river tweed scotland thispaperassessestheimportanceofdepositionandstorageoffine grained c 150m sedimentonthefloodplainsand bedsofthemain non tidal channelsoftherivertweed 4390km 2 scotland andtwoofitstributaries riverteviotand ettrick water caesium 137 analysis of floodplain sediment cores has been used to estimate average rates of overbank sedimentation during the last 30 to 40 years average values for individual transects ranged from 016 to 218 kg m 2 a 1 013to2 2m ma 1 themeanforthe10transectsinvestigatedwas129kgm 2 a 1 1 3m ma 1 thetotalamountoffine sediment deposited was estimated to be about 44 000 t a 1 the fine grained sediment stored in the channel bed was quantifiedusingresuspensiontechniques averagevaluesforindividualsitesrangedfrom012to096kgm 2 themeanfor the10sitesinvestigatedwas056kgm 2 thetotalamountofsedimentstoredonthechannelbedofthemainchannelsystem at the time of sampling was estimated to be about 4300 t comparison of these estimates of floodplain and channel storage with the estimated suspended sediment loadfor the river tweed at the downstream gauging site atnorham indicates that floodplainsedimentationandchannelbedstoragerepresentabout40and4percent respectively oftheannualloadoffine sedimentdeliveredtothemainchannelsystem erosionofchannelbankswillreintroducetheequivalentofabout30percent of the floodplain deposited sediment back into the channel the residence time of the fine grained sediment stored on the channel bed is probably less than one year but that of sediment deposited on the floodplain is likely to be considerably longer conveyance losses associated with overbank deposition have important implications for the routing of sediment throughfluvialsystemsandtheinterpretationofdownstreamsedimentyields copyright 1999johnwiley sons ltd

effective timescales of coupling within fluvial systems this paper presents a review of the coupling concept in fluvial geomorphology based mainly on previously published work coupling mechanisms link the components of the fluvial system controlling sediment transport down the system and the propagation of the effects of base level change up the system they can be viewed at several scales at the local scale involving within hillslope coupling hillslope to channel coupling and within channels tributary junction and reach to reach coupling at larger scales coupling can be considered as zonal coupling between major zones of the system or as regional coupling relating to complete drainage basins these trends are illustrated particularly by the examples of hillslope to channel coupling in the howgill fells northwest england badland systems in southeast spain alluvial fans in spain usa and uae and base level induced dissection of neogene sedimentary basins in southeast spain as the spatial scales increase so do the timescales involved effective temporal scales relate to magnitude and frequency characteristics recovery time and propagation time the relative importance changing with the spatial scale for downsystem coupling at the local scale the first two are important with propagation time increasing in importance in larger systems especially in those involving upsystem coupling related to base level change the effective timescales range from the individual event with a return period of decades through decadal to century timescales for downsystem coupling to tens to hundreds of thousands of years for the basinwide response to base level change the effective timescales influence the relative importance of factors controlling landform development

time dependent profiles of lava flows this work investigates the combined effects of a time dependent effusion rate and a spatially varying viscosity on the thickness profile of a flowing lava we formulate relatively simple governing equations as a primitive dynamical model for these two influences on lava flow morphology free boundary solutions for the profile of the flow and its extent are presented and analyzed for different boundary conditions at the source of the flow and several models for the spatial dependence of the viscosity the results presented here suggest that time dependence in the flow depth at the source and the form of the viscosity variation are significant influences on the morphology and dimensions of lava flows moreover this analysis implies that time dependent source conditions may contribute to the scatter in plots of eruption rate versus flow length and disparities between field and laboratory estimates of lava viscosity

the measurement of river bank erosion and lateral channel change a review a detailed review and chronological survey is presented of the various techniques which have been used for the measurement of river bank erosion and channel change the techniques are classified according to the time scales involved long intermediate and short and each is discussed with respect to accuracy and repeatability the methods covered include sedimentological evidence botanical evidence historical sources planimetric resurvey repeated cross profiling erosion pins and terrestrial photogrammetry prospects for future developments are also discussed

on lava dome growth with application to the 1979 lava extrusion of the soufriere of st vincent abstract a theoretical analysis is presented for the spread of a viscous liquid flowing under its own hydrostatic pressure on a horizontal surface in order to model lava dome formation two situations are considered in detail the spreading of a constant volume of liquid and the case where the amount of liquid is continually increased experiments with silicone liquids show close agreement with theory the formation of a basaltic andesite lava extrusion in 1979 on the crater floor of the soufriere of st vincent west indies provided the motivation for and an application of the model the extrusion reached a diameter of 868 m and a height of 133 m over a period of 150 days over the first 90 days the growth relationships were consistent with those predicted by theory application of the theory to the soufriere dome suggests an effective viscosity of 2 x 10 12 poise for the basaltic andesite lava the large effective viscosity calculated for the lava may be attributed to the dominant influence of a high viscosity skin which forms at the margins of the flow as it cools after 70 days the rate of growth of the extrusion markedly decreased because a substantial collar of rubble accumulated at the flow front due to this collar the growth of the extrusion ceased after 150 days from approximately two weeks after the initiation of the extrusion the discharge rate of lava decreased approximately linearly with increasing dome height this observation suggests that the lava ascended under a decreasing hydrostatic driving pressure and that extrusion ceased when the lava column reached hydrostatic equilibrium

geomorphic change detection using historic maps and dem differencing the temporal dimension of geospatial analysis abstract the ability to develop spatially distributed models of topographic change is presenting new capabilities in geomorphic research high resolution maps of elevation change indicate locations processes and rates of geomorphic change and provide a means of calibrating temporal simulation models methods of geomorphic change detection gcd based on gridded models may be applied to a wide range of time periods by utilizing cartometric remote sensing or ground based topographic survey data to measure volumetric change advantages and limitations of historical dem reconstruction methods are reviewed with a focus on coupling them with subsequent dems to construct dems of difference dod which can be created by subtracting one elevation model from another to map erosion deposition and volumetric change the period of dod analysis can be extended to several decades if accurate historical dems can be generated by extracting topographic data from historical data and selecting areas where geomorphic change has been substantial the challenge is to recognize and minimize uncertainties in data that are particularly elusive with early topographic data this paper reviews potential sources of error in digitized topographic maps and dems although the paper is primarily a review of methods three brief examples are presented at the end to demonstrate gcd using dods constructed from data extending over periods ranging from 70 to 90 years

erosion of the eastern united states observed with 10be the problem of identifying areas of accelerated erosion in a dynamic landscape is complicated the limited history of sediment yield measurements makes this task difficult even if geomorphic evidence is available beryllium 10 a cosmogenic isotope produced by cosmic rays interacting with the earth s atmosphere and surface has chemical and physical properties that make it useful as a tracer for erosion and sediment transport processes the rarity of the stable isotope 9be allows 10be to be detected with accelerator mass spectrometry in natural materials at extremely low levels backgrounds for rocks and sediments below 105 atom per g are now attainable a value to be compared with an average deposition rate of 1 3 106 atom cm 2 yr 1 the affinity of be for the components of soil and sediment is sufficiently high that it is effectively immobilized on contact thereby allowing 10be to function as a tracer of sediment transport to a good approximation all the 10be transport out of a drainage basin is on the sediment leaving it the number of 10be atoms passing the gauging station can be determined by measuring the concentration of the isotope in the sediment if the annual sediment load is known the ratio of the 10be carried from the basin by the sediment to that incident upon it called the erosion index has been determined for 48 drainage basins within the same physiographic province which allows them to be reasonably compared all of which have sediment yield data basins located in the atlantic coastal plain have an average index of 0 3 with the maximum observed being 0 9 basins located between the fall line and the mountains a region called the piedmont have an average value of 2 2 with individual values ranging from 0 6 to 6 7 this marked difference is thought to result from two centuries of farming on land of moderate gradient basins in the highland regions reflect local conditions with low indices for those in grass and timber and high indices associated with destructive land use the data allow an estimate of the erosion index for the pre colonial piedmont which then allows the pre colonial sediment yield to be calculated a number of basins have also been examined world wide with similar conclusions derived an important deviation from the rule is noted for rivers that erode large regions of loess such as the mississippi hwang ho and yangtze large aeolian deposits were laid down during the ice age in these basins deposits that brought inherited 10be with them and that are easily eroded

recent and historic sediment dynamics along difficult run a suburban virginia piedmont stream abstract suspended sediment is one of the major concerns regarding the quality of water entering the chesapeake bay some of the highest suspended sediment concentrations occur on piedmont streams including difficult run a tributary of the potomac river draining urban and suburban parts of northern virginia accurate information on catchment level sediment budgets is rare and difficult to determine further the sediment trapping portion of sediment budget represents an important ecosystem service that profoundly affects downstream water quality our objectives with special reference to human alterations to the landscape include the documentation and estimation of floodplain sediment trapping present and historic and bank erosion along an urbanized piedmont stream the construction of a preliminary sediment balance and the estimation of legacy sediment and recent development impacts we used white feldspar markers to measure floodplain sedimentation rates and steel pins to measure erosion rates on floodplains and banks respectively additional data were collected for from legacy sediment thickness and characteristics mill pond impacts stream gaging station records topographic surveying and sediment density texture and organic content data were analyzed using gis and various statistical programs results are interpreted relative to stream equilibrium affected by both post colonial bottomland sedimentation legacy and modern watershed hardening associated with urbanization six floodplain channel sites from high to low in the watershed were selected for intensive study bank erosion ranges from 0 to 470 kg m y and floodplain sedimentation ranges from 18 to 1369 kg m y m refers to meters of stream reach upstream reaches are net erosional while downstream reaches have a distinctly net depositional flux providing a watershed sediment balance of 2184 kg m y trapped within the system the amounts of both deposition and erosion are large and suggest nonequilibrium channel conditions both peak discharge and number of peaks above base have substantially increased since the mid 1960s when urbanization of the watershed began deposition patterns are most closely correlated with channel gradient sinuosity and channel width floodplain width for recent and historic periods the substantial amounts of fine grained sediment deposited on the floodplain over the past two centuries or so do not appear to be closely related to historic mill pond presence or location the floodplain continues to provide the critical ecosystem service of sediment trapping in the face of multiple human alterations trends in sediment deposition erosion may react rapidly to land use practices within the watershed and offer a valuable barometer of the effects of management actions

near channel versus watershed controls on sediment rating curves predicting riverine suspended sediment flux is a fundamental problem in geomorphology with important implications for water quality land and water resource management and aquatic ecosystem health to advance understanding we evaluated environmental and landscape factors that influence sediment rating curves srcs we generated srcs with recent total suspended solids tsss and discharge data from 45 gages on 36 rivers throughout the state of minnesota usa watersheds range from 32 to 14 600 km2 and represent distinct settings regarding topography land cover and geologic history rivers exhibited three distinct src shapes simple power functions threshold power functions and peaked or negative slope functions we computed src exponents and coefficients describing the steepness of the relation and the tss concentration at median flows respectively in addition to quantifying watershed topography climate hydrology geology soil type and land cover we used lidar topography to characterize the near channel environment upstream of gages we used random forest models to analyze relations between src parameters and attributes of the watershed and the near channel environment the models correctly classify 78 of src shapes and explain 37 60 of variance in src parameters we find that src steepness exponent is strongly related to near channel morphological characteristics including near channel relief channel gradient and presence of lakes along the local channel network but not to land use in contrast land use influences tss concentrations at moderate and low flow these findings suggest that the near channel environment controls changes in tss as flows increase whereas land use drives median and low flow tss conditions

image based measurement of flux variation in distal regions of active lava flows 1 understanding the processes involved with the advance of lava flows is critical for improving hazard assessments at many volcanoes here we describe the application of computer vision and oblique photogrammetric techniques to visible and thermal images of active a flows in order to investigate distal flow processes at mount etna sicily photogrammetric surveys were carried out to produce repeated topographic data sets for calculation of volumetric lava flux at the flow fronts velocity profiles from a distal channel were obtained by rectification of a thermal image sequence and are used to investigate the rheological properties of the lava significant variations of the magma flux were observed and pulses of increased flux arrived within the flow front region on timescales of several hours the pulses are believed to be the distal result of more frequent flux changes observed in the vent region hence they reflect the importance of flow processes which are believed to cause the coalescence of flux pulses along the channel system as well as short period variations in effusion rate in considering advance processes for the individual flow fronts it must be assumed that they were fed by a highly unsteady flux which was volumetrically at least an order of magnitude lower than that observed near the vent

disequilibrium of holocene sediment yield in glaciated british columbia it is generally supposed that specific sediment yield the quantity of sediment passing a monitored river cross section per unit area drained upstream of that section declines as the area drained increases1 3 part of the sediment mobilized from the land surface is supposed to go back into storage at field edges and on footslopes and floodplains in contrast we show here that data from british columbian rivers reveal a pattern of increasing specific sediment yield at all spatial scales up to 3 104 km2 this results from the dominance of secondary remobilization of quaternary sediments along river valleys over primary denudation of the land surface the result controverts the conventional model which has been derived from studies of small highly disturbed agricultural catch ments the rivers are still responding to the last glaciation giving a landscape relaxation time greater than 10 kyr this holds pro found implications for geomorphological theory and for studies of erosion