streaming potential observations using geothermal wells and in situ electrokinetic coupling coefficients under high temperature abstract in an attempt to detect streaming potentials induced by subsurface water flows we have observed the horizontal electric field self potential variations across stationary electric dipoles near geothermal wells in the takinoue geothermal area japan we observed variations of self potential which seem to be associated with the water flows in the aquifer induced by turning on and off the flow of the wells amplitudes of the variations are 3 5 mv across 60 200 m dipoles and can be explained well with a proposed electrokinetic model the streaming potential coefficient of 15 mv bar and or the potential of 50 to 100 mv in the aquifer are appropriate to explain the observed data by the model the obtained electrokinetic coupling coefficients are in situ ones and determined for crustal rock water system under high temperature 200 c condition the present results together with a laboratory study by ishido and mizutani 1981 give fundamental information on electrokinetic coupling coefficients in the earth s interior and are very important when we make quantitative interpretations of self potentials generated by geothermal activity on the basis of electrokinetic effects

chronology of late wisconsinan glaciation in middle north america abstract we propose a chronology of late wisconsinan glacial fluctuations in middle north america from alberta to wisconsin based on radiocarbon dates derived solely from wood previous chronologies of the southwestern margin of the north american continental ice sheet have depended to a considerable degree on radiocarbon dates from fine grained organic sediment this material is commonly contaminated with older carbon resulting in chronologic confusion by using only dates from wood much of the confusion disappears however because of the scarcity of wood dates only four of the sixteen identified fluctuations are accurately dated an advance into iowa about 14 000 to 13 500 bp an advance into south dakota and iowa about 12 300 bp an advance into the lake michigan basin about 11 700 bp and an advance into the lake superior basin about 9900 bp in addition the beginning of late wisconsinan glaciation before 20 000 bp is fairly well documented none of the fluctuations in the western part of the region are accurately dated

measuring bluff erosion part 1 terrestrial laser scanning methods for change detection human activities influence watershed sediment dynamics in profound ways often resulting in excessive loading of suspended sediment to rivers one of the primary factors limiting our ability to effectively manage sediment at the watershed scale has been our inability to adequately measure relatively small erosion rates on the order of millimeters to centimeters per year over annual and sub annual time scales on spatially extensive landforms such as river banks and bluffs terrestrial laser scanning tls can be employed to address this need tls collects high resolution data allowing for more accurate monitoring of erosion rates and processes and provides a new opportunity to make precise measurements of geomorphic change on vertical landforms like banks and bluffs but challenges remain this research highlights challenges and limitations of using tls for change detection on river banks and bluffs including the presence of vegetation natural surface crenulations and difficulties with creating benchmarks and provides solutions developed to overcome these limitations results indicate that data processing algorithms for change detection can have a significant impact on the calculated erosion rates with different methods producing results that can vary by over 100 the most accurate change detection technique compares a point cloud to a triangulated irregular network tin along a set of vectors that accommodate bluff curvature this paper outlines a variety of methods used to measure bluff change via tls and explains the accompanying error analysis that supports these methods copyright 2012 john wiley sons ltd

sediment loads and sources in heavily modified irish catchments a move towards informed management strategies abstract implementation of the eu water framework directive 2000 60 ec has forced regulatory authorities to take an integrated view of the link between water quality and catchment management in northern ireland concern over progressive habitat degradation of one of the province s prime salmon rivers the river bush provided the stimulus for a sediment monitoring programme the aims of this study were to quantify instream sediment loads and to identify sources of fine sediment feeding into the river channel this information would then be used to justify changes in the way the catchment s resources were managed sediment loads were assessed at four sampling stations on the river bush system over a one year period between 18 07 02 and 24 07 03 using sediment collection tubes and pit type traps these ranged between 0 196 and 4 98 t yr 1 for bed load and 1 70 and 102 t yr 1 for suspended load a combination of desktop studies erosion potential mapping monitoring visual observations bank erosion magnitude and yield and analytical work sediment fingerprinting was then applied in order to elucidate links between catchment sediment erosion and downstream sediment delivery bank erosion was highest in regions of the catchment with the least cohesive bank materials during high flow conditions livestock poaching and peak flows caused damage to banks at a localised scale and led to selective patches of bare land being susceptible to further erosion augmenting the sediment load approximately 2 of the annual suspended sediment and 60 of the annual bed load drainage maintenance work 60 and 30 forest clearfell 1 and 2 and ploughed land 37 and 8 also contributed to the annual suspended sediment and bed load respectively nine key actions were suggested in order to improve habitat quality in relation to sediment supply in the river bush these included wetland restoration prohibiting drainage maintenance work strategies to control conifer plantation felling reducing bare ground livestock access restrictions construction site management macrophyte clearance employment of a river warden and systematic dissemination of project recommendations to the general public to generate community involvement it was essential that these actions were both cost effective and practical in order to maximise catchment stakeholder uptake

residual circulation in western long island sound 1 current salinity and temperature measurements from repeated ship transects complemented by observations from long duration current profilers are used to characterize the variability and structure of subtidal flow in western long island sound a region prone to seasonal hypoxia subtidal flow plays a leading role in the transport of oxygen and organic matter and must therefore be simulated as accurately as possible we show that during periods of light wind in march and july the subtidal along sound flow is vertically and horizontally sheared with lower salinity water in the top 7 m moving eastward toward the ocean at approximately 10 cm s 1 with a counterflow of similar magnitude elsewhere velocity contours were found to slope downward to the south and maximum eastward velocities were found near the surface on the southern half of the section we find that there is a net transport in the direction of the east river westward the velocity distribution is broadly consistent with theoretical predictions for the steady frictional baroclinic pressure gradient driven flow modified by coriolis acceleration despite its neglect of advective effects which were found to be important in the present observational analysis our estimates of the pressure gradient the coriolis acceleration and stress divergence have similar magnitudes observation based estimates of terms in the momentum balance suggest that advection is more important to along estuary momentum than across estuary momentum along estuary advection is overestimated in recent hydrodynamic simulations when compared to observed values at sampling locations

hydrothermal circulation beneath mount pelee inferred by self potential surveying structural and tectonic implications abstract self potential sp surveys were made on mount pelee volcano martinique island french west indies in 1991 and 1992 in order to recognize its hydrothermal system the associated groundwater channeling and the main superficial structures of the massif almost 70 km of profiles were carried out with an average sample spacing of 50 m measurements essentially reveal negative sp anomalies down to 1700 mv with high gradients 1 83 mv m due to the infiltration of meteoric water into the massif rims of summit calderas morne macouba and etang sec present sharp negative sp anomalies on the western northern and eastern flanks negative sp anomalies indicate no upward water flow beneath mount pelee summit on the southwestern volcano flank a 3 5 6 km horseshoe shaped structure corresponding to a southwest flank collapse event older than 25 000 years bp is clearly identified by the sp mapping high gradients border the inner southern rim from morne calebasse to st pierre town and the caribbean sea along the northern rim of the horseshoe shaped structure the negative sp anomalies give place to a positive sp anomaly up to 200 mv of sw ne trend this zone covers the area of two active hot springs sources chaudes and puits chaud 40 65 c marine magnetic surveys and bathymetry show that the horseshoe shaped structure spreads into the caribbean sea up to about 10 km from the coast buried structural discontinuities are evidenced inside the flank collapse structure the upper one deviates the groundwater flow coming from the summit toward the south flank where the flow finds an indentation to expand again downwards this discontinuity is either an old hypothetical caldera rim partly destroyed by the collapse of the south southwestern flank and covered by recent pyroclastic deposits or more probably the trace of a bulge landslide a circulation model of the hydrothermal waters is proposed rainfall 5 6 m year is partly drained inside the summital calderas and the flank collapse zone through pyroclastic flows down to an impermeable basement there the groundwater constitutes perched aquifers at the contact of the bulge landslide or of the hypothetical old caldera rim along the inner northern border of the flank collapse structure the phreatic water is reheated warm groundwater flows along the northern avalanche structure rim and discharges near the coast in ground and marine outcrops of medium temperature finally the main part of the meteoric water is channeled along the old caldera rim or along the bulge landslide towards the south flank of mount pelee where some gaps in the rim exist there the groundwater finds again a subhorizontal gravitational circulation along mount pelee slopes into the caribbean sea

insights into river bank erosion processes derived from analysis of negative erosion pin recordings observations from three recent uk studies recent studies of river bank erosion in three catchments in the uk have been characterized by the persistent occurrence of negative erosion pin results the cause of these negative recordings is considered with reference to field data from the afon trannon nant tanllwyth and river arrow and to a laboratory study of freeze thaw and desiccation processes it seems that there is potential for and in some cases evidence of a number of different circumstances that generate negative results but none of these alone is sufficient to explain all incidents factors considered include deposition of sediment during high flows soil fall from the upper parts of the bank on to lower erosion pins loosening of the soil surface and expansion contraction of the soil mass with fluctuations in temperature and moisture content movement of the erosion pin within the bank and human interference each has its own implications for the use of erosion pins further issues arise when including negative data in subsequent data analysis and it is demonstrated that attempts to correlate erosion rates with hydro meteorological data in order to ascertain causes of erosion will be influenced by the way in which negative data are handled it is thus suggested that any study of river bank erosion using erosion pins should state whether or not negative data were obtained and if so how they were included in data analysis failure to include this information could lead to comparison of mean erosion rates that reflect bank processes very differently the studies presented here offer a clear example of the value of anomalous field data results which do not appear to fit expected patterns can reveal as much about the processes in operation as those that do

stability of streambanks formed in partially saturated soils and effects of negative pore water pressures the sieve river italy abstract streambanks of alluvial channels are usually composed of loose materials which are unsaturated in ambient conditions unsaturated soils are subject to negative pore water pressures which cause an apparent cohesion the latter is the main factor in allowing the stability of near vertical banks even during moderate in bank flow events the apparent cohesion can be strongly reduced as the material approaches full saturation therefore during the drawdown phase as the confining pressure of the water in the channel disappears a bank failure is likely to occur channel bed level lowering along the sieve river central italy has caused widespread bank instability a geomorphological reconnaissance of forms and processes was followed by in situ tests to determine the shear strength of the banks interpretation of the tests and a streambank stability analysis were based on concepts of soil mechanics for unsaturated soils in order to obtain relations between bank angle and height in limit equilibrium conditions a stability chart was obtained with curves for different apparent cohesion values and a stability analysis was performed taking into account the effects of flow events in order to investigate the pore pressure effects a series of piezo tensiometers were installed in a streambank of the sieve river data from a 1 year monitoring period show variations in pore water pressure and matric suction as a consequence of rainfall evapotranspiration and water stage variations a planar failure with a tension crack occurred in the upper cohesive part of the bank during december 1996 the safety factor has been expressed as a function of the geometry of the bank and of the shear strength of the material safety factor variations through time are therefore shown as a function of seasonal variations in matric suction

determining lateral migration rates of meandering rivers using fallout radionuclides abstract we explore the novel technique of using short lived fallout radionuclides to date fluvial surfaces with the goal of determining lateral migration rates specifically we use the fallout radionuclide 210pb half life t1 2 22 3 years to determine the lateral migration rates of meandering reaches on the winooski river vt the upper connecticut river nh and the genesee river ny we find that particularly near the channel 210pbex inventories are affected by the initial 210pbex inventories of freshly deposited sediment inheritance inheritance differs at each site with lower inheritance occurring at sites with larger upstream drainage areas after accounting for inheritance 210pbex inventories in surface sediments along a transect orthogonal to the channel yield migration rates of 0 7 3 1 and 4 7 m y for the winooski connecticut and genesee rivers respectively these rates agree well with values derived independently from historical aerial photography variations in 210pbex inventories along the transects also provide details of the channel migration histories not evident from the limited available aerial photographs including evidence for both nearly constant linear and episodic channel migrations results suggest the broad applicability and added value of our approach for quantifying decadal scale variations in fluvial surface ages

laboratory studies of electrical potential during rock failure we have investigated electrical potential and acoustic emissions signals associated with rock deformation five rock types were studied clashach bentheim and darley dale sandstones all quartz rich and a seljadur basalt and portland limestone both quartz free both air dry and the rocks were tested in distilled water shallow crustal conditions were simulated in a triaxial rock deformation cell with a confining pressure simulating depth of 40 mpa pore pressures ranging 5 35 mpa and strain rates 10 7 10 4 s 1 precursory electric potential signals prior to failure were observed in both saturated and dry samples of the quartz rich sandstones but only observed in the water saturated quartz free rocks co seismic electrical signals were obtained in all tests providing strong evidence that two of the main sources for precursory and co seismic signals are the piezoelectric and electrokinetic phenomena lowering the strain rate resulted in an increase in the number of acoustic emissions the pore volume changes during compaction and dilatancy remained approximately constant for all strain rates streaming potential generated by fluid flow across the sample was also measured at different stages of deformation the potential signals increased with the pore pressure gradient c 2005 elsevier ltd all rights reserved

measurement of river bank and cliff erosion from sequential lidar and historical aerial photography abstract the methodology and errors involved in determining the meander migration rates and amount of sediment produced by river bank and cliff erosion over five decades along a 16 and 28 km reach of the waipaoa river new zealand are described the reach average meander migration rates 0 22 and 0 12 m a 1 respectively are low by international standards for rivers of comparable size suggesting considerable stability of the river planform the contribution of sediment from bank and cliff erosion 74 3 and 23 3 kt a 1 respectively to suspended sediment load is also low

effects of silt clay content on the susceptibility of river banks to subaerial erosion abstract the aim of this paper is to demonstrate how subaerial processes vary with the silt clay content of river bank soil and to consider this variation in the context of erosion observed in the field in particular spatial and temporal variations in erosion interactions with other bank erosion processes and the implications for bank morphology are explored a number of soil blocks of known silt clay content were subjected to a series of freeze thaw and drying wetting cycles changes in the dimensions of the soil blocks were recorded and the mass of soil eroded from each block together with maximum size of eroding aggregates were measured limitations to this methodology are acknowledged including a limited ability to replicate the forces to which a river bank may be subject restrictions imposed by the available equipment in producing temperature and humidity cycles which reflect those occurring in the field and issues of scale the results indicate that river banks with high silt clay contents are the most susceptible to erosion by subaerial processes high susceptibility may influence spatial variations in bank erosion processes and rates including downstream changes in the effectiveness and significance of subaerial erosion a vertical zoning of processes on a river bank is recognised whereby the upper part of the bank is subject to subaerial erosion and the lower part to fluvial erosion given that a high silt clay content tends to indicate increased susceptibility to subaerial erosion but increased resistance to fluvial erosion this vertical zoning may have implications for bank morphology

morphological evolution of a rural headwater stream after channelisation in recent decades stream valleys have been profoundly modified by the construction of weirs and dams and by channelisation channelisation modifies the morphology of streams and induces changes in their energy regime and sediment transport capacity these types of changes in the channel morphology have to be quantified to allow the implementation of management strategies to regulate sediment transfer however studies over an entire stream using historical comparisons remain scarce and the associated uncertainties have not yet been resolved in this study the sedimentary response to channelisation on a medium time scale 42 years of a french river known as the ligoire is investigated this river is the main channel of a small rural headwater catchment that has been channelised over 21 km we have used the historical cross sections before and after channelisation and the current ones and the objectives of this study were as follows 1 to develop a methodology of cross section superposition and the associated uncertainties 2 to quantify the erosion and aggradation processes in the bed and on the banks along the bed profile and 3 to calculate a sediment budget for the entire stream and determine the relative contributions of the banks and the streambed to this budget a comparison of the cross sections before and after the channelisation shows that the morphology of the stream has been completely altered the main channel length was reduced by 10 the bankfull width was increased on average by 63 and the slopes were smoothed a total of 60 000 m3 of sediments was excavated during the channelisation works our results indicate that erosion is the dominant process over 63 of its length the streambed was incised by 0 41 m on average and over 60 of its length the banks were eroded by 0 20 m on average the successive patterns of erosion and deposition along the stream are the result of the cumulative effects of channelisation and of the presence of weirs and artificial knickpoints in the ligoire channel the vertical uncertainty of the elevation of the historical cross section is an important parameter for controlling the areas and sediment budget values using monte carlo methods we found that 1000 sediment budgets from different profile shiftings are necessary to obtain a variation coefficient below 0 1 the overall mean stream sediment budget for the period 1970 2012 is 9358 412 m3 with 66 originating from the banks and 34 from the streambed relative to the ligoire watershed surface the stream sediment yield is 2 71 0 12 m3 km 2 y 1 the approach developed in this study is easily replicable and relatively cheap and provides an integrated quantified overview of the morphological adjustments after channelisation works on a stream

seepage erosion in layered stream bank material current stream restoration practices often require anthropogenic manipulation of natural field soils to reconstruct stream banks in the absence of stabilizing vegetation for this study researchers conducted laboratory experiments on reconstructed non vegetated stream banks with layered soils experiencing seepage the objective of the study was to determine the effect of seepage pore water pressure and bank geometry on erosion and bank stability of layered streambanks the experimental design consisted of an intermediate size soil lysimeter packed with a sandy clay loam top soil and an underlying fine sand layer at three bank slopes 90 45 and 26 shallow groundwater flow and seepage resulted in bank failure of geometrically stable banks pop out failures liquid deformation and piping were all observed failure mechanisms in the underlying sand material dependent on the bank angle groundwater seepage processes created small scale failures of the underlying sand leading to larger scale failures of the overlying sandy clay loam the underlying sand layer eroded according to the initial bank angle and change in overburden loading the overlying loam layer failed along linear failure planes the gradually sloped bank i e 26 slope failed faster hypothesized to be due to less confining pressure and greater vertical seepage forces researchers analyzed the laboratory experiments using the bank stability and toe erosion model version 4 1 the model calculated an accurate shear surface angle similar to the failure angle observed in the lysimeter tests the model predicted failure only for the undercut 90 bank slope and indicated stable conditions for the other geometries steeper initial bank slopes and undercut banks decreased the bank factor of safety the observed failure mechanisms and measured saturation data indicated an interaction between overburden pressure seepage forces and bank slope on bank stability future bank stability modeling would benefit by incorporating lateral seepage erosion and soil liquefaction prediction calculations copyright 2009 john wiley sons ltd

influence of seepage undercutting on the stability of root reinforced streambanks several mechanisms contribute to streambank failure including fluvial toe undercutting reduced soil shear strength by increased soil pore water pressure and seepage erosion recent research has suggested that seepage erosion of noncohesive soil layers undercutting the banks may play an equivalent role in streambank failure to increased soil pore water pressure however this past research has primarily been limited to laboratory studies of non vegetated banks the objective of this research was to utilize the bank stability and toe erosion model bstem in order to determine the importance of seepage undercutting relative to bank shear strength bank angle soil pore water pressure and root reinforcement the bstem simulated two streambanks little topashaw creek and goodwin creek in northern mississippi simulations included three bank angles 70 to 90 four pore water pressure distributions unsaturated two partially saturated cases and fully saturated six distances of undercutting 0 to 40 cm and 13 different vegetation conditions root cohesions from 0 0 to 15 0 kpa a relative sensitivity analysis suggested that bstem was approximately three to four times more sensitive to water table position than root cohesion or depth of seepage undercutting seepage undercutting becomes a prominent bank failure mechanism on unsaturated to partially saturated streambanks with root reinforcement even with undercutting distances as small as 20 cm consideration of seepage undercutting is less important under conditions of partially to fully saturated soil pore water conditions the distance at which instability by undercutting became equivalent to instability by increased soil pore water pressure decreased as root reinforcement increased with values typically ranging between 20 and 40 cm at little topashaw creek and between 20 and 55 cm at goodwin creek this research depicts the baseline conditions at which seepage undercutting of vegetated streambanks needs to be considered for bank stability analyses copyright 2008 john wiley sons ltd

zeta potential estimation of volcanic rocks on 11 island arc type volcanoes in japan implication for the generation of local self potential anomalies 1 from streaming potential measurements we deduced the zeta potential of 73 volcanic rock samples collected in 11 volcanoes where self potential sp surveys had also been conducted experiments with crushed rock samples and 0 001 mol l nacl solution showed a large variation in streaming potential coefficient which ranged from 2860 to 2280 mv mpa deduced zeta potential ranged from 45 1 to 37 2 mv among the 73 samples 9 samples showed positive values and 11 samples showed small absolute values less than 10 mv even in a volcano the zeta potential values of rocks were sometimes highly variable to investigate the reason for the variation in zeta potential we performed x ray fluorescence xrf measurements on the rock samples however no significant correlations between zeta potential or isoelectric point and weight percentage of major elements were found implying that the zeta potential of the volcanic rocks is not controlled by chemical composition but by mineralogical composition or crystalline structure in volcanic areas rocks with positive or small absolute values of zeta potential which are considered to be unusual frequently exist in areas along with local positive sp anomalies although positive sp anomalies are usually interpreted as an indication of hydrothermal upflow this correlation suggests that in addition to the groundwater flow pattern the polarity of zeta potential should also be considered for interpretation of sp data therefore in cases where detailed zeta potential measurements have not been conducted local positive sp anomalies should be interpreted with caution

measuring bluff erosion part 2 pairing aerial photographs and terrestrial laser scanning to create a watershed scale sediment budget effectively managing and reducing high suspended sediment loads in rivers requires an understanding of the magnitude of major sediment sources as well as erosion and transport processes that deliver excess fine sediments to the channel network the focus of this research is to determine the magnitude of erosion from tall bluffs a primary sediment source in the 2880 km2 le sueur watershed minnesota usa we coupled analyses of seven decades of aerial photographs with four years of repeat terrestrial laser scanning tls to determine erosion rates on bluffs together these datasets provide decadal scale retreat rates throughout the entire watershed and high resolution geomorphic change detection on a subset of bluffs to both constrain erosion rates and document how environmental conditions affect bluff retreat erosion rates from aerial photographs and tls were extrapolated from 243 and 15 measured bluffs respectively to all 480 bluffs in the le sueur watershed using multiple techniques to obtain estimates of sediment loading from these features at the watershed scale despite different spatial and temporal measurement scales the aerial photograph and tls estimates yielded similar results for bluff retreat rate and total mass of sediment derived from bluffs with bluffs in the le sueur watershed yielding 135 000 39 000 mg yr of fine sediment comparing this value to the average annual total suspended solids tss load determined from gauging from 2000 to 2010 we determined that bluffs comprise 57 16 of the total tss load making bluffs the single most abundant fine sediment source in the basin copyright 2012 john wiley sons ltd

tank experiments with borehole self potential data despite their importance in the evaluation of petroleum and gas reservoirs measurements of self potential data under borehole conditions well logging have found only minor applications in aquifer and waste site characterization this can be attributed to lower signals from the diffusion fronts in near surface environments because measurements are made long after the drilling of the well when concentration fronts are already disappearing proportionally higher signals arise from streaming potentials that prevent using simple interpretation models that assume signals from diffusion only our laboratory experiments found that dual source self potential signals can be described by a simple linear model and that contributions from diffusion and streaming potentials can be isolated by slightly perturbing the borehole conditions perturbations are applied either by changing the concentration of the borehole filling solution or its column height parameters useful for formation evaluation can be estimated

self potential modeling from primary flows this paper discusses a new method for the investigation of self potentials sp based on induced current sources the induced current sources are due to divergences of the convection current which is driven in turn by a primary flow either heat or fluid as a result of using this approach there is a shift in emphasis toward the vector flow field and its interaction with current cross coupling structure when compared with the total potential approach of nourbehecht 1963 which emphasized the primary flow potential and the voltage cross coupling this shift in emphasis is advantageous because it is analogous to the actual physical processes for example fluid flow in the ground gives rise to drag convection currents and the interaction of the convection currents with the electrical structure gives rise to the electrical potentials sp this simple physical picture should aid in developing a better intuitive understanding of the generation of sp effects the convective current approach is easily ada

laboratory measurements anomalous 0 1 0 5 hz streaming potential under geochemical changes implications for electrotelluric precursors to earthquakes streaming potentials resulting from flow of various salt solutions in rock were measured on saturated sediments fontainebleau sandstones the streaming potential v was found to be proportional to the driving pore pressure p pulses of amplitude 15 40 mv in the frequency range of 0 1 to 0 5 hz were observed when the conductivity of the injected water was decreased and the fluid flow rate was relatively low corresponding to a darcian velocity of 17 to 30 cm h the amplitudes of these pulses are 47 to 133 of the corresponding steady components of the v values such geochemically induced effects may possibly be responsible for the frequency signals from 0 1 to 0 5 hz that were sometimes observed before an earthquake

assessment of river bank erosion in southern minnesota rivers post european settlement article i nfo river bank erosion is one of the major sources of sediment for many rivers around the world with the cur rent emphasis on developing total maximum daily loads tmdls for impaired waters in the united states there is heightened interest in quantifying background sediment levels in rivers in this study we assessed variations in river bank erosion over time using a combination of 1855 public land survey system plats aerial photographs from 1938 to 2009 and light detection and ranging lidar data from 2005 to 2009 for sediment impaired rivers in southern minnesota results showed that bank erosion was episodic making comparisons of erosion rates from dissimilar time intervals unreliable for comparable time intervals average river bank retreat rates 0 51 m yr 1 from 1855 to 1938 vs 0 37 m yr 1 from 1938 to 2009 were statistically similar t 2 13 p 0 14 suggesting that bank erosion rates have remained stable since european settlement comparisons over shorter time intervals of 1938 1971 and 1971 2009 also showed similar statistical trends t 0 76 p 0 45 with average river bank retreat rates of 0 57 and 0 50 m yr 1 respectively however additional 145 observations of bank retreat were found in the period 1971 2009 relative to 1938 1971 in dicating that the number of actively eroding river banks may have increased over time contrary to assump tions made in the literature bank erosion measurements using lidar data showed a poor relationship r 2

self potential observations during hydraulic fracturing 1 the self potential sp response during hydraulic fracturing of intact sierra granite was investigated in the laboratory excellent correlation of pressure drop and sp suggests that the sp response is created primarily by electrokinetic coupling for low pressures the variation of sp with pressure drop is linear indicating a constant coupling coefficient cc of 200 mv mpa however for pressure drops 2 mpa the magnitude of the cc increases by 80 in an exponential trend this increasing cc is related to increasing permeability at high pore pressures caused by dilatancy of microcracks and is explained by a decrease in the hydraulic tortuosity resistivity measurements reveal a decrease of 2 prior to hydraulic fracturing and a decrease of similar to 35 after fracturing an asymmetric spatial sp response created by injectate diffusion into dilatant zones is observed prior to hydraulic fracturing and in most cases this sp variation revealed the impending crack geometry seconds before failure at rupture injectate rushes into the new fracture area where the zeta potential is different than in the rock porosity and an anomalous sp spike is observed after fracturing the spatial sp distribution reveals the direction of fracture propagation finally during tensile cracking in a point load device with no water flow a sp spike is observed that is caused by contact electrification however the time constant of this event is much less than that for transients observed during hydraulic fracturing suggesting that sp created solely from material fracture does not contribute to the sp response during hydraulic fracturing

ten conceptual models of large scale legacy sedimentation a review abstract considerable interest has been directed toward the recognition and documentation of legacy sediment i e anthropogenic sediment in fluvial systems little has been written however to identify implicit or explicit theories about how these deposits form and evolve over decennial to centennial time scales this review attempts to redress this void by examining conceptual models of the physical behavior and characteristics of catchment scale anthropic fluvial sedimentation events these concepts which are not unique to anthropogenic sediment include cascades sediment delivery ratios waves aggradation degradation episodes residence times budgets connectivity stream power nonlinear dynamical systems and geohistorical geoarchaeological and chronostratigraphic principles a broad definition of legacy sediment as episodically produced anthropogenic sediment is adopted that includes early episodes of large scale human induced sedimentation throughout the world the models apply to a variety of environments so the examples from north america following the introduction of european settlement can be related to other post settlement sedimentation episodes elsewhere during aggradation episodes rates of erosion and sedimentation often increased an order of magnitude in response to land clearance for agriculture timbering or mining these sediments may remain as a lasting geomorphic legacy that provides evidence of anthropogenic change and governs modern rates of sediment production and nonpoint source pollution

seismoelectric measurements in a porous quartz sand sample with anisotropic permeability seismoelectric coupling coefficients are difficult to predict theoretically because they depend on a large numbers of rock properties including porosity permeability tortuosity etc the dependence of the coupling coefficient on rock properties such as permeability requires experimental data in this study we carry out a set of laboratory measurements to determine the dependence of seismoelectric coupling coefficient on permeability we use both an artificial porous sandstone sample with cracks built using quartz sand and berea sandstone samples the artificial sample is a cube with 39 porosity its permeability levels are anisotropic 14 7 d 13 8 d and 8 3 d in the x y and z directions respectively seismoelectric measurements are performed in a water tank in the frequency range of 20 khz 90 khz a piezoelectric p wave source is used to generate an acoustic wave that propagates through the sample from the three different x y and z directions the amplitudes of the seismoelectric signal induced by the acoustic waves vary with the direction the highest signal is in the direction of the highest permeability and the lowest signal is in the direction of the lowest permeability since the porosity of the sample is constant the results directly show the dependence of seismoelectric coefficients on permeability seismoelectric measurements with natural rocks are performed using berea sandstone 500 and 100 samples because the berea samples are nearly isotropic in permeability the amplitudes of the seismoelectric signals induced in the different directions are the same within the measurement error because the permeability of berea 500 is higher than that of berea 100 the amplitude of the seismoelectric signals induced in berea 500 is higher than those in berea 100 to determine the relative contributions of porosity and permeability on seismoelectric conversion we carried out an analysis using pride 1994 formulation and kozeny carman relationship the normalized amplitudes of seismoelectric coupling coefficients in three directions are calculated and compared with the experimental results the results show that the seismoelectric conversion is related to permeability in the frequency range of measurements this is an encouraging result since it opens the possibility of determining the permeability of a formation from seismoelectric measurements

streaming potential properties of westerly granite with applications this paper reports on laboratory measurements of the streaming potential properties of common minerals and in particular of westerly granite data are presented for these solids in contact with simple electrolytic solutions and in one case for temperature variation in the range 5 70 c for 1 1 electrolytes the ratio of the streaming potential coupling coefficient to fluid resistivity was approximately 4 mv atm m and for 2 1 electrolytes 2 mv atm m the effect of temperature was small 0 05 mv c temperature increase and indicates that the zeta potential was independent of temperature preliminary experimental results using mixed electrolytic solutions nacl cacl2 and two phase fluid flow are also described two phase flow can enhance streaming potentials by as much as a factor of 3 or 4 the laboratory data are used to interpret streaming potentials in geological problems such as earthquake prediction geothermal prospecting using the self potential method and surface conductivity contribution to the electrical resistivity of rocks

bank and near bank processes in an incised channel abstract gravitational forces acting on in situ bank material act in concert with hydraulic forces at the bank toe to determine rates of bank erosion the interaction of these forces control streambank mechanics hydraulic forces exerted by flowing water on in situ bank toe material and failed cohesive material at the bank toe are often sufficient to entrain materials at relatively frequent flows and to maintain steep lower bank profiles seepage forces exerted on in situ bank material by groundwater downward infiltration of rainwater and lateral seepage of streamflow into and out of the bank are critical in determining bank strength data from a study site on goodwin creek ms usa clearly show the temporal variability of seepage forces and the lag time inherent in reductions in shear strength due to losses of matric suction and generation of positive pore water pressures negative pore water pressures matric suction have also been shown to increase the resistance of failed cohesive blocks to entrainment by fluid shear a stable bank can be transformed into an unstable bank during periods of prolonged rainfall through 1 increase in soil bulk unit specific weight 2 decrease or complete loss of matric suction and therefore apparent cohesion 3 generation of positive pore water pressures and therefore reduction or loss of frictional strength 4 entrainment of in situ and failed material at the bank toe and 5 loss of confining pressure during recession of stormflow hydrographs relatively small frequent flows during the winter have the ability to erode failed bank materials maintain oversteepened unstable bank surfaces and promote prolonged periods of bank retreat channel migration and high yields of fine grained sediment confining pressures provided by stormflow are not as significant in maintaining bank stability as the counteracting force of fluid shear on the bank toe which steepens the bank for example more than 2 m of bank retreat occurred during the study period at the research site on goodwin creek northern mississippi the loss of matric suction negative pore pressures due to infiltrating precipitation has been found to be as significant as the development of excess pore pressures in contributing to mass bank instability apparent cohesion friction angle soil bulk unit weight and moisture content were measured in situ matric suction was measured continuously in situ with a series of five pressure transducer tensiometers a bank failure algorithm which combines the mohr coulomb approach for saturated conditions and the fredlund modification for unsaturated conditions was developed for layered cohesive streambanks the resulting equation has been used successfully to investigate the role of matric suction positive pore water pressures and confining pressure for layered streambanks composed of cohesive materials

river channel planform change software for historical analysis abstract er mapper an image processing system was used to manipulate scanned maps plans and aerial photographs to enable detailed analysis of historical river channel planform change the er mapper package offers the opportunity to spatially reference each item of planform data into the same scale and co ordinate space as a base map using a warping algorithm and operator selected ground control points once all the data are in the same co ordinate space and at the same scale a given point can be returned to over time and a number of indices can be easily calculated to examine past channel behaviour here lateral shift channel width sinuosity and area of sedimentation within the reach were used as the maps and aerial photographs themselves are used the errors associated with digitising vectors are avoided and a more flexible approach towards analysis and the identification of important indices can be adopted at the outset results obtained for the cleekhimin burn a site in southern scotland are briefly presented and discussed and the advantages of the package and the limitations of the historical database are also outlined

soil properties controlling seepage erosion contributions to streambank failure the majority of sediment leaving catchments may be from streambank failure seepage erosion of unconsolidated sand above a restrictive layer is an important erosion process in incised streams that leads to streambank failure by undercutting banks the objective of this study was to determine the impact of soil properties on seepage erosion and the resulting streambank failure seepage flow and sediment concentrations were measured in situ at eight locations along the banks of a deeply incised stream in northern mississippi using field observations as a guide the soil profile conditions of a shallow 45 cm streambank consisting of 30 cm of topsoil a 10 cm conductive layer and a 5 cm restrictive layer were mimicked in laboratory lysimeter experiments to quantify the hydrologic properties controlling seepage erosion and bank failure under a 40 cm head the time to flow initiation and the flow rate were linearly related to the slope of the restrictive layer seepage erosion began within minutes of flow initiation and resulted in substantial 3 to 34 cm undercutting of the bank sediment concentrations of seeps were as high as 660 g l 1in situ and 4500 g l 1 in the lysimeters sediment concentrations were related to the layer slope thereby indicating the importance of detailed site characterization the usda ars streambank stability model demonstrated the increase in instability of banks due to undercutting by seepage erosion but failed to account for the sediment loss due to sapping for stable banks and overestimated the sediment loads for failed banks published in 2006 by john wiley sons ltd

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

volumetric measurement of river bank erosion from sequential historical aerial photography abstract understanding of the relative contribution of bank erosion to sediment budgets in new zealand is limited few measurements of bank erosion rates exist and this is a major limitation to the development of a locally calibrated model of bank erosion the new zealand sediment budget model sednetnz predicts bank erosion based on preliminary data and this study aims to underpin the development of an improved model for bank erosion photogrammetric techniques and lidar were used to collect data on bank erosion rates for five different river reaches ranging from 3 to 14 km in length in the kaipara catchment northland new zealand changing river channel planform between the 1950s and 2015 was assessed using four to five well spaced dates of historical aerial photographs changes in planform were combined with bank height to calculate erosion and accretion volumes which were compared with sednetnz modelled estimates erosion and accretion is relatively evenly balanced in the study sites the largest difference in terms of relative proportions of erosion and accretion are found along the tangowahine river 13 4 km reach length where 492 000 m3 of sediment eroded between 1956 and 2015 compared to 364 000 m3 of accretion lateral migration rates erosion for the five river reaches range between 0 14 m yr 1 and 0 21 m yr 1 and are comparable with those measured by previous assessments in new zealand the migration rates in channel widths per year for the three larger rivers stream order 5 6 range between 0 4 and 0 8 of channel width per year in contrast the smaller streams stream order 3 4 are retreating more rapidly with width averaged rates of 1 7 and 3 0 current sednetnz modelling tends to underestimate the bank height and greatly overestimates the migration rate

electrokinetic and magnetic fields generated by flow through a fractured zone a sensitivity study for la fournaise volcano a number of electric and magnetic signals have been observed on la fournaise volcano attributed to electrokinetic effects a simple model is proposed here to check this hypothesis the volcano is idealized as a 2d heterogeneous structure composed of a fractured zone located between two porous zones through which meteoritic waters flow downwards flow occurs predominantly in the fractured zone and induces electromagnetic fields correct orders of magnitude are obtained for the measured surface fields the importance of the heterogeneous character of the underground medium is demonstrated local measurements of various quantities are recommended

piping sapping erosion ii identification diagnosis although erosion of streambanks and other shorelines by emergent seepage is widespread this erosion mechanism termed piping or sapping has not been recognized as important to the overall erosion process the mechanism is complex and interactions with other bank and shore processes tend to mask the effects of piping sapping direct evidence water emerging from a soil face and carrying away soil particles is rarely encountered several types of indirect evidence are presented and illustrated in this paper including cavities formed by piping deposits of dislocated particles below piping zones blind gullies staining produced by persistent seepage outflow and particular types of localized failures slab toppling block shearing and tensile falls caused by undercutting due to piping sapping the interactions of this erosion mechanism with other erosion deposition processes are described the purpose of this paper is to facilitate identification and evaluation of piping sapping erosion particularly

seismoelectric and seismomagnetic measurements in fractured borehole models seismoelectric and seismomagnetic fields generated by seismic waves in fluid saturated fractured borehole models are experimentally investigated with an electrode and a hall effect sensor in a borehole with a horizontal fracture the stoneley and flexural waves induce seismoelectric and seismomagnetic fields on the borehole wall and an electromagnetic wave propagating at light speed at the horizontal fracture in a borehole with a vertical fracture the acoustic field generated by a monopole or dipole source is similar to that in a borehole without a vertical fracture however the acoustic wave propagating along the vertical fracture induces seismoelectric and seismomagnetic fields whose apparent velocities are equal to that of a stoneley wave experimental results show that two different kinds of electric and magnetic fields are generated by acoustic waves in borehole models with horizontal and or vertical fractures one is an electromagnetic wave propagating with light speed the second is a stationary or localized seismoelectric and seismomagnetic field seismoelectric and seismomagnetic measurements might be a new logging technique for exploring fractures in a borehole