subsurface lateral flow generation in aspen and conifer dominated hillslopes of a first order catchment in northern utah mountain headwater catchments in the semi arid intermountain west are important sources of surface water because these high elevations receive more precipitation than neighboring lowlands this study examined subsurface runoff in two hillslopes one aspen dominated the other conifer dominated adjacent to a first order stream in snow driven northern utah snow accumulation soil moisture trenchflow and streamflow were examined in hillslopes and their adjacent stream snow water equivalents swes were greater under aspen stands compared to conifer the difference increasing with higher annual precipitation semi variograms of shallow spatial soil moisture patterns and transects of continuous soil moisture showed no increase in soil moisture downslope suggesting the absence of subsurface flow in shallow 12 cm soil layers of either vegetation type however a clear threshold relationship between soil moisture and streamflow indicated hillslope stream connectivity deeper within the soil profile subsurface flow was detected at 50 cm depth which was sustained for longer in the conifer hillslope soil profiles under the two vegetation types varied with deep aspen soils having greater water storage capacity than shallow rocky conifer soils though swes were less under the conifers the soil profile had less water storage capacity and produced more subsurface lateral flow during the spring snowmelt copyright 2010 john wiley sons ltd

interactions among hydraulic conductivity distributions subsurface topography and transport thresholds revealed by a multitracer hillslope irrigation experiment interactions among hydraulic conductivity distributions subsurface topography and lateral flow are poorly understood we applied 407 mm of water and a suite of tracers over 51 hours to a 12 by 16 5 m forested hillslope segment to determine interflow thresholds preferential pathway pore velocities large scale conductivities the time series of event water fractions and the fate of dissolved nutrients the 12 hillslope featured loamy sand a and e horizons overlying a sandy clay loam bt at 1 25 m average depth interflow measured from two drains within an interception trench commenced after 131 and 208 mm of irrigation cumulative interflow equaled 49 of applied water conservative tracer differences between the collection drains indicated differences in flow paths and storages within the plot event water fractions rose steadily throughout irrigation peaking at 50 sixteen hours after irrigation ceased data implied that tightly held water exchanged with event water throughout the experiment and a substantial portion of pre event water was released from the argillic layer surface applied dye tracers bypassed the matrix with peak concentrations measured shortly after flow commencement indicating preferential network conductivities of 864 to 2240 mm h yet no macropore flow was observed near steady state flow conditions indicated average conductivities of 460 mm h and 2 5 mm h for topsoils and the bt horizon respectively low ammonium and phosphorus concentrations in the interflow suggested rapid uptake or sorption while higher nitrate concentrations suggested more conservative transport these results reveal how hydraulic conductivity variation and subsurface topographic complexity explain otherwise paradoxical solute and flow behaviors this article is protected by copyright all rights reserved

morphology structure and flow phases in soil pipes developing in forested hillslopes underlain by a quaternary sand gravel formation hokkaido northern main island in japan preferential flow pathways such as soil pipes are usually present in the soil of slopes subsurface flow through the soil pipes affects the subsurface drainage system and is responsible for sediment removal from slopes however a record of the inner structure of soil pipes has rarely been reported for slopes a fibrescope examination of the morphology and flow phases in soil pipes in hillslopes underlain by a quaternary sand gravel formation provided the following information the main pores of the soil pipes ran mostly parallel with the slope gradient the cross sections of the soil pipes were approximately circular and occurred on a few occasions with some triple junctions being present in addition both full flow and partly full depth conditions occurred simultaneously in the soil pipe the full flow condition has long been used in hydrological studies to model the pipe flow mechanism both the full flow condition and the partly full depth condition however must be examined closely in order to evaluate the subsurface hydrology in heterogeneous soil and the hydrogeomorphological processes of subsurface hydraulic erosion copyright 2000 john wiley sons ltd

hillslope storage and rainfall amount thresholds as controls of preferential stormflow summary shallow saturated subsurface flow is a dominant runoff mechanism on hillslopes of headwater catchments under humid temperate climate its timing and magnitude is significantly affected by the presence of preferential pathways reliable prediction of runoff from hillslope soils under such conditions remains a challenge in this study a quantitative relationship between rainfall stormflow and leakage to bedrock for hillslopes where lateral preferential runoff represents a dominant part of the overall response was sought combined effects of temporal rainfall distribution and initial hillslope saturation antecedent moisture conditions on stormflow leakage to bedrock and overall water balance were evaluated by conducting simulations with synthetic rainfall episodes a two dimensional dual continuum model was used to analyze hydrological processes at an experimental hillslope site located in a small forested headwater catchment long term seasonal simulations with natural rainfall indicated that leakage to bedrock occurred mostly as saturated flow during major runoff events the amount of rainfall needed to initiate stormflow appeared as a dynamic hillslope property depending on temporal rainfall distribution initial hillslope storage and the spatial distribution of soil water within the hillslope no single valued rainfall threshold responsible for triggering stormflow was found rainfall stormflow as well as rainfall leakage relationships were found highly nonlinear for low initial hillslope saturations temporal rainfall distribution affected the amount of rainfall necessary to initiate stormflow more than it did the amounts of stormflow or leakage to bedrock in spite of a simple hillslope geometry with constant slope and parallel soil atmosphere and soil bedrock interfaces considered in the analysis the applied model predicted a hysteretic behavior of storage discharge relationship the results showed a mutual interplay of components of hillslope water balance exposing a nonlinear character of the hillslope response the study provided a quantitatively coherent insight in the hydraulic functioning of hillslopes where preferential flow constitutes a dominant part of stormflow

impact of piping on gully development in mid altitude mountains under a temperate climate a dendrogeomorphological approach abstract gullies are complex geomorphic systems induced and transformed not only by surface erosion processes but also by subsurface processes such as piping however the transient nature of piping makes this process more difficult to observe and study especially when a pipe roof has totally collapsed this study aims at assessing piping impact on gully initiation and development using dendrogeomorphological analyses which are a novel approach in piping study the survey was carried out in a mountainous area under a temperate climate using the bere nica wyzna catchment in the bieszczady mts eastern carpathians as a case study we estimated the minimum age of pipe collapses and presented the transformation of pipe collapses in order to identify the direction of pipe and gully development we also verified the contribution of piping to gully development by the reconstruction of gully bottom deepening the analysis was based on changes in tree and root wood anatomy in diffuse porous deciduous angiosperm species i e common alder alnus glutinosa and field maple acer campestre the pipe collapses in the piping system studied are at least 19 to 23 27 years old and the pipe roof initially collapsed in the lower sections of the slope above the gully head and the pipe develops up the slope by headward erosion the gully that was analysed in forest had been deepened by piping during several episodes connected with high precipitation events in contrast the pipe located in grasslands collapsed 1 2 years after such events indicating that dense vegetation delays pipe collapse this study shows that dendrogeomorphological analyses based on diffuse porous deciduous angiosperm species may be a useful tool in piping research it provides information on pipe and gully development as well as enabling estimates to be made of the age of pipe collapses

a new interpretation of kinematic stormflow generation the paper reviews a number of possible fast and slow hydrological flow mechanisms to account for rapid runoff generation within a catchment a new interpretation of the kinematic wave process is proposed which develops some of these concepts to explain rapid subsurface flow from a watershed evidence for the process is provided by the results from a laboratory soil core experiment and an investigation of the hydrology of a dartmoor hillslope a tension response was monitored in the soil core in which pressure waves were propagated downwards and expelled water from the base the transmission of the wave down the core was considerably faster than the movement of a chloride tracer the concept of this kinematic wave process and associated water flux was then extended to the dartmoor watershed raindrops reaching the wet soil surface caused pressure waves to travel laterally downslope during large rainstorms the hillslope became hydrologically highly connected and the pressure waves forced existing water from seepage faces into the saturated area adjacent to the stream contributing substantially to the stream discharge a kinematic contributing area was defined as determined by both rainfall runoff ratios and geostatistical analyses of hillslope soil moisture contents which extended over at least 65 of the catchment area this kinematic wave theory is consistent with results of translatory flow and macropore flow models and stable isotope field studies of old new water copyright 2002 john wiley sons ltd

tracer and hydrometric study of preferential flow in large undisturbed soil cores from the georgia piedmont usa we studied the temporal patterns of tracer throughput in the outflow of large 30 cm diameter by 38 cm long undisturbed cores from the panola mountain research watershed georgia tracer breakthrough was affected by soil structure and rainfall intensity two rainfall intensities 20 and 40 mm hr 1 for separate cl and br amended solutions were applied to two cores one extracted from a hillslope soil and one extracted from a residual clay soil on the ridge for both low and high rainfall intensity experiments preferential flow occurred in the clay core but not in the hillslope core the preferential flow is attributed to well developed interpedal macrochannels that are commonly found in structured clay soils characteristic of the ridge site however each rainfall intensity exceeded the matrix infiltration capacity at the top of the hillslope core but did not exceed the matrix infiltration capacity at the middle and bottom of the hillslope core and at all levels in the clay core localized zones of saturation created when rainfall intensity exceeds the matrix infiltration capacity may cause water and tracer to overflow from the matrix into macrochannels where preferential flow occurs to depth in otherwise unsaturated soil

piezometric response in zones of a watershed with lateral preferential flow as a first order control on subsurface flow characterizing zones of a watershed based on the water table is used to understand and predict internal watershed processes in watersheds dominated by lateral preferential flow the water table response typically shows a distinct hydraulically limited pattern this response is characterized by a capping of the rising water table when the lateral preferential flow features are activated and subsurface flow still increases we expected that this response would be related to the contributing area since nearby hillslope excavations showed that the development of preferential flow network was positively correlated with the contributing area the watershed was stratified into three predetermined zones and installed 25 piezometers to measure the water table dynamics the objectives were 1 to characterize the water table runoff relationship 2 to prove preferential flow by observable characteristics and 3 to test the feasibility of identifying areas within a watershed that are dominated by lateral preferential flow watershed zones were not well defined and there was no strong relationship between the hydraulically limited response and observable watershed characteristics although zones might still be useful for grouping the hillslope processes the piezometric response may not be an appropriate indicator for mapping the watershed into areas with runoff dominated by lateral preferential flow copyright 2010 john wiley sons ltd

soil pipe distribution and hydrological functioning within the humid tropics a synthesis some of the most responsive runoff systems in the world are found within the humid tropics these runoff responses are likely to be affected by the presence of natural pipes within the soil this study provides a synthesis of the hydrological aspects of these phenomena within the humid tropics of the studies reporting the presence of soil piping within the humid tropics most are associated with ultisol soils and locally most pipe outlets are observed on the lower sections of hillslopes while the drainage role of pipes has been observed providing faster and slower components of stream hydrographs the mechanism of their recharge remains less clear in part this is because their spatial extent is poorly mapped within the hillslopes of the humid tropics further studies quantifying the length and recharge of soil pipe networks within the humid tropics are needed

pipes and pipe flow process in an upland catchment wales abstract the results of observations on the spatial localisation origin and function of soil pipes in an upland catchment are discussed the pipes occur in distinct zones in the brown earth soils of the lower slopes and form a hydrological link conducting water between an upslope zone of highly permeable skeletal soils and the stream channel it is proposed that in this catchment pipes develop from an initial network of mole burrows modified by hydraulic activity to produce an efficient downslope transmission network a conceptual model for the pipe slope segment is proposed which recognises the importance of this transmission role slope discharge controls switching between saturated throughflow pipe flow and overland flow each of which has a specific threshold value for operation attempts to investigate the significance of pipe flow at the catchment scale met with limited success but it appears to be important in increasing both contributing area and duration of storm flow

when interflow also percolates downslope travel distances and hillslope process zones copyright 2014 john wiley sons ltd introduction in hillslopes with soils characterized by deep regoliths such as ultisols oxisols and alfisols interflow occurs episodically over impeding layers near and parallel to the soil surface such as low conductivity b horizons e g newman et al 1998 buttle andmcdonald 2002 du et al in review till layers mcglynn et al 1999 bishop et al 2004 hardpans mcdaniel et al 2008 c horizons detty and mcguire 2010 and permeable bedrock tromp van meerveld et al 2007 as perched saturation develops within and above these impeding but permeable horizons flow moves laterally downslope but the perched water also continues to percolate through the impeding horizon to the unsaturated soils and saprolite below perched water and solutes will eventually traverse the zone of perched saturation above the impeding horizon and then enter and percolate through the impeding horizon in such flow situations only lower hillslope segments with sufficient downslope travel distance will deliver water to the riparian zone within the time scale of a storm farther up the slope lateral flow within the zone of perched saturation will act mainly to shift the point of percolation location where a water packet leaves the downslope flow zone in the upper soil layer and enters the impeding layer down the hillslope from the point of infiltration in flatter parts of the hillslope or in areas with little contrast between the conductivities of the upper and impeding soil layers lateral flow distances will be negligible from darcy s law we can estimate the downslope travel distance for quasi steady state conditions within the saturated layer assuming boussinesq slope parallel flow above the restrictive layer and normal flow perpendicular to the slope through the restrictive layer to unsaturated soils below figure 1 using a downslope flow vector we must employ an orthogonal normal vector and avoid harr s 1977 mistake of adding non orthogonal and non independent gradient vectors in calculating flow directions weassume that each layer is isotropic and the impeding layer is saturated or nearly so and drains freely to an unsaturated layer below pressure head equals zero at the base of the impeding layer we assume diffuse porosity within the impeding layer so percolation is not restricted to randomly spaced discontinuities with these assumptions generally applicable to hillslopes with deep regoliths and a low conductivity layer paralleling the soil surface we will calculate downslope travel distances for reasonable combinations of slopes conductivities and impeding layer thicknesses evaluate these distances with respect to typical slope lengths map the downslope travel distances on watersheds with soil and slope conditions matching these assumptions and discuss how couplingboussinesq downslope flow and percolation affect our understanding of the potential zonation of lateral flow processes

effects of soil depth and subsurface flow along the subsurface topography on shallow landslide predictions at the site of a small granitic hillslope shallow landslides are affected by various conditions including soil depth and subsurface flow via an increase in the pore water pressure in this study we evaluate the effect of soil depth and subsurface flow on shallow landslide prediction using the shallow landslide stability shalstab model three detailed soil depth data the average soil depth weathered soil depth and bedrock soil depth were collected using a knocking pole test at a small hillslope site composed of granite in the republic of korea the shalstab model was applied to a ground surface topographic digital elevation model dem using the three soil depths and upslope contributing area sca assuming subsurface flow calculated from four dems a ground surface topography gsto dem weathered soil topography wsto dem bedrock topography bsto dem and low level bedrock topography ebsto dem the model performance was measured using a receiver operating characteristic roc analysis while evaluating the effect of the soil depth with sca using gsto dem it was found that the bedrock soil depth had higher prediction accuracy compared to that of the average soil depth or weathered soil depth to evaluate the saturated subsurface flow between the soil and bedrock scas calculated using wsto and bsto dems were applied from these simulations we found that sca from bsto dem and the bedrock soil depth affect the shallow landslide prediction however these prediction effects are not significantly increased by large differences in the elevation between the lowest and highest elevation values therefore we considered the influence of the bedrock depression and sca from ebsto dem in applying sca from ebsto the prediction accuracy was significantly increased compared to the other predictions our results demonstrate that the influence of the bedrock topography on the prediction of shallow landslides may be particularly significant at the scale of a hillslope

snowmelt runoff pathways in a boreal forest hillslope the role of pipe throughflow abstract on an instrumented slope of the lac laflamme basin we observed that during snowmelt season 1 the unsaturated matrix flow seems to be a negligible component of the downslope flow through the soil horizons 2 the groundwater flow from an aquifer in till a few meters thick is the major pathway for rain melt inputs and 3 when groundwater levels are high a turbulent pipe throughflow occurs at the mineral and organic soils interface gauging one of the subsurface streams showed that although its discharge is correlated and synchronized with nearby groundwater levels its hydrograph often reflected that of rain melt input according to our calculations pipe throughflow does not carry more than one fifth of the seasonal rain melt input during short periods hourly basis however it may become the main source of water input to the lake the water delivered by pipe throughflow forms a distinct 0 5 1 m thick acidic layer ph 4 4 4 8 that invades the lake just beneath the lake ice cover and is susceptible to affect the fish spawning ground

influence of subsurface flow by lidar dems and physical soil strength considering a simple hydrologic concept for shallow landslide instability mapping abstract high resolution dems and physical soil strength among other factors have significant effects on the shallow landslide instability mapping subsurface flow in soil mantle normally is assumed by slope parallel flow based on resolution of dems and measuring soil strength which is affected by subsurface flow within the soil mantle is difficult in both the field and the laboratory thus the aims of this study are to investigate the effect of subsurface flow by high resolution lidar dems and the effect of physical soil strength attributes on shallow landslide instability mapping respectively in this study two dems with 1 m and 5 m resolutions were used and physical soil strength was calibrated using a simple subsurface hydrological concept with lidar and field survey data in order to quantify the influence of soil strength on shallow landslide instability mapping to this end various field surveys were performed at woomyeon mountain seoul republic of korea where shallow landslides occurred in 2012 the physical shallow landslide stability shalstab model were applied the modified success rate msr method were applied to assess the predicted results in the first series of simulations using the two dems and experimentally derived soil strength values relatively low msr values of 0 42 0 468 for the 1 m dem and 0 42 0 47 for the 5 m dem were recorded in the second series of simulations using soil strength calibrated using a simple theoretical approach the msr for the 1 m dem was 0 78 0 823 and the msr for the 5 m dem was 0 723 0 80 these results indicated that soil strength had a more important role in shallow landslide instability mapping than assuming subsurface flow by topographic resolution therefore it may be useful to apply field collected soil strength data using hydrological concepts to improve the accuracy of predictive models based on high resolution surface data

hillslope dynamics modeled with increasing complexity summary few studies have investigated how much model complexity is needed to simulate both the hillslope outflow and the internal hillslope dynamics we studied the influence of model complexity on simulations for the panola mountain trenched hillslope we analyzed the influences of the inclusion of bedrock permeability variable soil depth and preferential flow on modeled hillslope responses we found that without the inclusion of bedrock leakage the long term subsurface flow response measured at the trenchface and the threshold relation between total precipitation and total subsurface flow could not be simulated adequately individual events could still be represented acceptably showing the importance of long time series for model calibration and validation the use of spatially constant bedrock conductivity allowed us to simulate spatially variable bedrock leakage rates because of the spatially variable depths of saturation without variable soil depth the spatial variability of subsurface flow along the trenchface and its temporal dynamics during events could not be represented in addition the spatial patterns of saturation at the soil bedrock interface did not agree with the observed patterns and responses to smaller events were underestimated inclusion of preferential flow mainly influenced the distribution of the maximum saturation depths at the soil bedrock interface and increased peak flows and recessions soil moisture measurements were less useful for model validation for the panola hillslope than measurements of the spatial patterns of saturation and subsurface flow we plea for a new blue print for the set up of hillslope experiments such that their data is useful for studies on hillslope model complexity and for model validation and rejection

evolution of the lower saxony basin abstract the lower saxony basin is a 300 km long and 65 km wide late jurassic and early cretaceous trough which parallels the northern margin of the rhenish massif this basin became inverted during the senonian and paleocene the lower saxony basin is the most important oil province of germany past production amounts to 200 10 6 t of oil 1 5 10 9 bbl the lower saxony basin is superimposed on the late carboniferous variscan foredeep basin and the frontal structures of the variscan fold belt during the permian to middle jurassic the area formed part of the northwest european basin differential subsidence of the lower saxony basin was initiated during the late jurassic and persisted till albian time this involved reactivation of permo carboniferous fracture systems by divergent wrenching a major aptian deep seated laccolith is evident in the western part of the lower saxony basin during the senonian and paleocene sinistral convergent wrenching induced uplift of the basin floor and folding of its sedimentary fill the margins of the inverted lower saxony basin are thrust over the adjacent stable platform areas the differential subsidence of the lower saxony basin can be related to a period of major crustal extension in the north sea rift basin inversion coincides with important orogenic events in the alpine system and is thought to have been induced by intra plate compressional stresses

estimating average fracture spacing in subsurface rock knowledge of the spacing of fractures in reservoir rocks i e the distance between parallel fractures in a subsurface joint set can lead to a better understanding of the production characteristics of a reservoir and serve to quantify the relative degree of deformation in subsurface rocks in this paper i present a new method for estimating the spacing of subsurface fractures this new method is easy to use from the standpoint of both data collection and data analysis the average fracture spacing method can be applied with boreholes of any orientation relative to a fracture set the method is especially powerful when it is used for the relatively common case of a borehole nearly parallel to a fracture set e g vertical borehole intersecting vertical fractures average fracture spacing is estimated from an analytical solution based on observed borehole fracture intersections and observed fracture porosity the only data required are the dimensions of the core or imaged borehole and the total height of all sampled fractures because the likelihood of intersecting fractures increases when a well is deviated perpendicular to the fractures of a set fracture reservoirs commonly are candidates for deviated boreholes an informed decision on borehole deviation requires predicting the fracture intersection frequency as a function of both deviation magnitude and direction a new method based on probabilities of borehole fracture intersections uses spacing and height data from subsurface joint like fractures and the borehole diameter to predict fracture intersection frequencies for all possible well deviations fracture intersection frequency solutions are presented with respect to a conventional geographic reference frame thus simplifying even the most complex three dimentional situations

hydrology of a forested hillslope during storm events abstract subsurface flow from a 0 47 ha hillslope subcatchment at the upper most reach of the west fork 38 ha of walker branch watershed was monitored throughout 1988 stormflow in the first order stream draining the west fork responded simultaneously with the initiation of subsurface flow through 0 to 2 5 m depth from the hillslope subsurface flow from the upper hillslope was only 1 3 of total precipitation for 1988 however individual storms yielded as much as 12 5 of precipitation as subsurface flow the west fork had 10 4 of precipitation observed as storm flow with an additional 29 as baseflow individual storms exhibited up to 71 of precipitation as storm flow in the west fork illustrating the significant increase in percent rain converted to subsurface flow in lower landscape positions as compared to upper hillslopes peak subsurface flow preceded peak streamflow and occurred primarily through the 1 0 2 5 m depth bt2 horizons due to perched water tables preferential flow from hillslopes through macro and mesopores was concluded to be the predominant stormflow mechanism the contributions of the various size pores was reasoned to be dependent upon the position within the soil profile and the stage of the hydrograph preferential flow occurred at extreme soil water conditions with the response due to perched water tables under wet conditions and believed to be due to hydrophobic conditions under extremely dry conditions intermediate soil water conditions resulted in infiltration into soil matrix pores precluding subsurface stormflow

evolution of the northeast german basin inferences from a 3d structural model and subsidence analysis abstract a 3d structural model of the northeast german basin was evaluated with special emphasis on its evolution as an intracontinental depression the study includes investigations on subsidence history and structural setting of the basin thickness evolution and calculated tectonic subsidence volumes of permian to quaternary sediments in the northeast german basin indicate that the subsidence history was related to five stages of basin evolution which differ in their subsidence mechanisms for the initial rift phase in the late carboniferous to early permian a dominant thermal event and subordinate horizontal stresses were indicated by thickness variation evolution and by structural evidence the main part of basin subsidence occurred in a nw se oriented basin in the subsequent phase of thermal relaxation with maximum subsidence from early permian rotliegend to middle triassic muschelkalk from middle triassic the thermal subsidence pattern was superposed by further tectonic events in the middle triassic regional extension led to a reconfiguration of the southern part of the basin where new nne ssw trending troughs rheinsberg and gifhorn troughs developed in the jurassic the northwestern part of the basin was uplifted while in the south the keuper subsiding areas continued to sink and nw se trending depressions related to salt margins became important differentiation continued into cretaceous times when regional compression caused uplift of the southeastern part of the basin and basin margins a final subsidence phase occurred in the cenozoic this was accompanied by intensive salt movement recent basin configuration reflects the superposition of structural elements resulting from different evolution stages the main structural characteristics of the basin are 1 a vertical tectonic zonation in a pre zechstein succession which lacks significant internal structures and a strongly deformed post zechstein succession which was decoupled due to the thick zechstein salt and 2 a marked asymmetry of the basin with a shallow northern slope and a steep bounding fault at the southern margin elbe fault system the northwestern part of the basin shows the structural properties of an intracratonic sag basin with persisting subsidence and with minor salt mobilisation in contrast initial structures in the southeastern part are strongly overprinted by younger tectonic events including middle triassic to jurassic extension late cretaceous inversion and late to post cretaceous salt movements tectonic elements that deform the whole sedimentary succession are restricted to the basin s southern eastern and northeastern margins where salt thickness decreases combined volumetric and backstripping investigations show that 2 3 of the total subsidence was induced by the sediment load and 1 3 was caused by tectonics the tectonic subsidence history varies laterally across the basin while tectonic subsidence curves in the northwestern part of the basin show fast subsidence during the permian and early triassic decreasing exponentially with time subsidence curves in the southeastern part indicate repeated tectonic activity however the tectonic subsidence volume created during permian to late triassic is significantly higher than the tectonic subsidence during younger phases of basin history

runoff generation processes estimated from hydrological observations on a steep forested hillslope with a thin soil layer abstract in order to understand runoff generation processes on a forested hillslope involving large heterogeneities this study monitored runoff from a steep hillslope with a thin soil layer as well as matric potential within it and analyzed their responses to storm rainfall a comparison of storm runoff responses from the study slope with those from two adjacent catchments one of which includes it showed that physical properties of the slope reflected the runoff characteristics although no responses occurred in very dry conditions because of the absence of wet zones near the stream the area contributing to storm runoff more rapidly extended to the whole slope due to its topographic properties they also caused its steep hydrographs produced in the wettest condition where almost all the rainfall contributed to storm runoff in this wettest condition tensiometric responses near bedrock showed the vertical quick propagation of the rainfall pulse and a good agreement of storm hydrograph simulated through a kinematic wave runoff model suggested that runoff from the slope was produced by a lateral flow on the bedrock receiving the quick propagation in a transition process from dry to the wettest conditions the development of the lateral flow producing smaller responses at the downslope end was estimated from decreasing of matric potential near bedrock from high negative to low values with increasing cumulative rainfall

development of crystal morphology during unitaxial growth in a progressively widening vein ii numerical simulations of the evolution of antitaxial fibrous veins the development of fibrous morphology and capability of fibres for tracking the opening trajectory were investigated using numerical simulations of a natural antitaxial fibrous vein starting from a non unique best case variation of fracture opening velocity grain size wall roughness growth anisotropy and crystal growth velocity shows that these parameters differ in importance for crystal morphology and tracking capability fibrous veins can be simulated using crack seal opening of the fracture grain boundaries track the opening trajectory if the wall roughness is high opening increments are small and crystals touch the wall before the next crack increment starts

lateral subsurface stormflow and solute transport in a forested hillslope a combined measurement and modeling approach preferential flow dominates water movement and solute transport in boreal forest hillslopes however only a few model applications to date have accounted for preferential flow at forest sites here we present a parallel and coupled simulation of flow and transport processes in the preferential flow domain and soil matrix of a forested hillslope section in kangaslampi finland using a new three dimensional physically based dual permeability model our aim is to simulate lateral subsurface stormflow and solute transport at the slope during a chloride tracer experiment and to investigate the role of preferential flow in the tracer transport the model was able to mimic the observed tracer transport during tracer irrigation but overestimated the dilution velocity of the tracer plume in the highly conductive soil horizons near the soil surface after changing the irrigation to tracer free water according to the model 140 times more chloride was transported downslope in the preferential flow domain than in the soil matrix during the tracer irrigation the simulations showed together with reference simulations with a traditional one pore domain model that a two pore domain approach was required to simulate the observed flow and transport event the event was characterized by the transmissivity feedback phenomenon and controlled by preferential flow mechanisms in particular by lateral by pass flow according to our results accounting for the slow flow and fast flow domains of soil as well as the water and solute exchange between the domains is essential for a successful simulation of flow and solute transport in preferential flow dominated hillslopes

hillslope threshold response to rainfall 1 a field based forensic approach summary hillslope threshold response to storm rainfall is poorly understood basic questions regarding the type location and flow dynamics of lateral subsurface flow remain unanswered even at our most intensively studied field sites here we apply a forensic approach where we combined irrigation and excavation experiments at the well studied maimai hillslope to determine the typology and morphology of the primary lateral subsurface flowpaths and the control of bedrock permeability and topography on these flowpaths the experiments showed that downslope flow is concentrated at the soil bedrock interface with flowpath locations controlled by small features in the bedrock topography lateral subsurface flow is characterized by high velocities several orders of magnitude greater than predicted by darcy s law using measured hydraulic conductivities at the site we found the bedrock to be moderately permeable and showed that vertical percolation of water into the bedrock is a potentially large component of the hillslope water balance our results suggest that it is the properties of the bedrock topography and permeability that control subsurface flow at maimai and the soil profile plays a less significant role than previously thought a companion paper incorporates these findings into a conceptual model of hydrological processes at the site to explore the generalities of whole hillslope threshold response to storm rainfall

present day stress control on fluid migration pathways case study of the zechstein fractured carbonates nw germany abstract understanding the orientation and connectivity of fracture systems in tight reservoirs is essential to reduce uncertainties in reservoir development and production however the actual flow potential of the fractures can be controlled by the present day stress field dilation and slip tendency analyses can improve fracture permeability evaluations and thus aid in estimating the hydrocarbon recovery of a field this study focuses on a naturally fractured relatively tight matrix permeabilities of 0 01 1 md and gas producing late permian zechstein reservoir in the southern permian basin northern germany fracture data are obtained from resistivity image log data of a 775 m long horizontal well and show principal ne sw orientation with main dip angles steeper than 70 to quantify the potential of those fractures that contribute to the flow within the reservoir dilation td and slip ts tendencies are calculated two different stress scenarios are defined based on known variations in the orientation of the horizontal stresses between formations below and above the zechstein salt in an offset field approximately 5 km away results of td and ts strongly depend on the strike and dip angle of the fractures with sub vertical fractures showing highest potential to dilate while fractures with dip angles of 60 are favorably oriented for slip fractures with orientations parallel to the principal horizontal stress have highest slip and dilation tendencies adding this information to the calculation of fracture permeability results in a significant reduction of the calculated flow potential due to the influence of the stress field thus incorporating stress field data helps reducing risks in field development planning

baroclinic developments in jet entrances and exits i linear normal modes this study examines the effect of the ageostrophic circulations associated with jet entrance and exit regions on the structure and growth rates of baroclinic normal modes a linearized gcm is used to find the most unstable normal mode disturbances for a zonally symmetric basic state consisting of a zonal jet and meridional circulation normal mode growth rates are reduced by up to 20 for realistic strengths of meridional overturning and normal mode structures are significantly affected for example the normal mode poleward tilt with height varies affecting the conversion of basic state available energy a mechanism for the change in poleward tilt is proposed ageostrophic meridional circulations may play a significant role in determining the magnitude and length of mid latitude storm tracks

conceptualizing lateral preferential flow and flow networks and simulating the effects on gauged and ungauged hillslopes 1 one of the greatest challenges in the field of hillslope hydrology is conceptualizing and parameterizing the effects of lateral preferential flow our current physically based and conceptual models often ignore such behavior however for addressing issues of land use change water quality and other predictions where flow amount and components of flow are imperative dominant runoff processes like preferential subsurface flow need to be accounted for in the model structure this paper provides a new approach to formalize the qualitative yet complex explanation of preferential flow into a numerical model structure we base our examples on field studies of the well studied maimai watershed new zealand we then use the model as a learning tool for improved clarity into the old water paradox and reasons for the seemingly contradictory findings of lateral preferential flow of old water where applied line sources of tracer appear very quickly in the stream following application we evaluate the model with multiple criteria including ability to capture flow hydrograph composition and tracer breakthrough we generate output ensembles with different pipe network geometries for model calibration and validation analysis surprisingly the range of runoff response among the ensembles is narrow indicating insensitivity to specific pipe placement our new model structure shows that high transport velocities for artificial line source tracers can be reconciled with the dominance of preevent water during runoff events even when lateral pipe flow dominates response the work suggests overall that preferential flow can be parameterized within a process based model structure via the structured dialog between experimentalist and modeler

mechanisms and pathways of lateral flow on aspen forested luvisolic soils western boreal plains alberta canada rainfall simulation experiments by redding and devito 2008 hydrological processes 23 4287 4300 on two adjacent plots of contrasting antecedent soil moisture storage on an aspen forested hillslope on the boreal plain showed that lateral flow generation occurred only once large soil storage capacity was saturated combined with a minimum event precipitation of 15 20 mm this paper extends the results of redding and devito 2008 hydrological processes 23 4287 4300 with detailed analysis of pore pressure soil moisture and tracer data from the rainfall simulation experiments which is used to identify lateral flow generation mechanisms and flow pathways lateral flow was not generated until soils were wet into the fine textured c horizon lateral flow occurred dominantly through the clay rich bt horizon by way of root channels lateral flow during the largest event was dominated by event water and precipitation intensity was critical in lateral flow generation lateral flow was initiated as preferential flow near the soil surface into root channels followed by development of a perched water table at depth which also interacted with preferential flow pathways to move water laterally by the transmissivity feedback mechanism the results indicate that lateral flow generated by rainfall on these hillslopes is uncommon because of the generally high available soil moisture storage capacity and the low probability of rainfall events of sufficient magnitude and intensity copyright 2010 john wiley sons ltd

a note on induced stress changes in hydrocarbon and geothermal reservoirs abstract earthquakes have been induced by oil and gas production where pore pressures have decreased in some cases by several tens of mpa it has previously been suggested that such earthquakes are caused by poroelastic stressing of crust surrounding the reservoir induced earthquakes are also common in geothermal fields such as the geysers where strong correlations between both steam production and condensate injection and earthquake activity have been observed over the last several decades stress measurements within hydrocarbon reservoirs show that the least horizontal stress decreases with declining reservoir pressure as predicted by poroelasticity for circular disk shaped reservoirs isothermal reduction in pore pressure induces a relative horizontal tension within the reservoir production induced stressing may promote frictional sliding on pre existing faults within the reservoir itself normal faulting is promoted if the regional stress is extensional and the biot coefficient is sufficiently large 0 85 for reasonable coefficients of friction on the other hand dilatant fracturing and normal faulting are always promoted in extensional environments near the edge of the reservoir or in regions of high pore pressure gradient it is suggested that such fracturing could enhance fracture permeability in tight rocks adjacent to portions of the reservoir that experience large reductions in pore pressure due to production in regional compressional environments production modestly favors reverse faulting above and below the reservoir the ratio of thermal to poroelastic stress can be quite large in geothermal reservoirs such as the geysers reservoir wide energy balance considerations suggest that the average temperature has declined at the geysers by 6 c during the past 20 years reservoir average stress changes are thus on the order of 2 mpa and are certainly much larger near injection wells and steam producing fractures

threshold behavior in a fissured granitic catchment in southern china 1 analysis of field monitoring results 1 an experimental granitic catchment in southern china was instrumented to continuously monitor the hydrologic processes within which two plots 5 m 10 m were equipped observed rainfall and corresponding responses of surface water soil water and groundwater were used to examine the hydrological threshold behaviors new hydrological thresholds were determined on the spatial scales of plot and catchment and on the temporal scales of storm event and month namely those between 1 the sum of total event precipitation p and the antecedent soil moisture index asi hereafter p asi and the total event interflow at plots a soil depth 200 250 cm and b soil depth 50 90 cm and between p asi and deep interflow at plot a within which an aquitard exists 2 p asi and event peak flow 3 the normalized maximum well water level nmwwl and event peak flow at the catchment scale and 4 p asi and monthly streamflow depth in addition thresholds between p asi nmwwl and event quick flow depth were identified in accordance with findings of previous studies based on the hydrometric observations we believed that the soil moisture deficit and bedrock depression storage were the main reasons for the threshold behavior in the study catchment below a specific threshold of p asi none or little interflow was generated on hillslopes and contributed to streamflow while interflow generated at the soil bedrock interface on hillslopes started to contribute to streamflow when it was above the threshold and the runoff contributing areas expanded from the near stream zone to hillslopes

the role of lateral pipe flow in hillslope runoff response an intercomparison of non linear hillslope response the importance of lateral pipe flow on runoff generation in wet steep hillslopes has been described in many case studies from around the world however most hillslope studies are done in isolation and usually focus on the idiosyncrasies of individual hillslope characteristics and pipe flow response at a single site consequently the first order controls on pipe flow responses remain poorly understood we present a new intercomparison of pipe flow response to storm rainfall at four well instrumented sites panola georgia usa toinotani kyoto japan jozankei hokkaido japan and hakyuchi tokyo japan our objective was to minimize the complexities of lateral pipe flow on hillslopes by looking for commonality across different hillslope types despite the large differences between the study sites in topography climate soil type and soil matrix hydraulic conductivity we found several common pipe flow responses to storm rainfall 1 the relationship between total rainfall amount and total pipe flow volume was highly non linear at each site 2 initiation of measurable pipe flow was threshold dependent controlled by the total rainfall amount and the pre storm wetness 3 once significant pipe flow response occurred the maximum pipe flow rate was sensitive to the measured rainfall intensity and 4 the ratio of total pipe flow to total hillslope discharge for each site was constant regardless of total rainfall amount once the precipitation threshold for significant pipe flow response was reached we used these results to develop a decision tree to determine the general conditions necessary for significant pipe flow to occur the controls derived from our comparisons agree largely with the controls reported by the previous individual hillslope pipe flow studies in the literature the commonality of response between our four very different forested hillslope settings indicates that site intercomparison may be effective for extracting common first order controls on complex hillslope processes we argue that a decision tree may be a useful organizational framework to summarize and organize comparative analyses and may provide a structure for defining the hierarchy of process controls necessary for model development

the role of soil pipes as a slope runoff mechanism subarctic yukon canada pipeflow in subarctic slopes provides a preferential runoff mechanism that bypasses the soil matrix rapidly conveying water to the stream extensive soil piping occurs in the central wolf creek basin yukon at the interface of the organic and mineral horizons flow in these pipes are ephemeral transmitting water only when the water table is within or above the zone where pipes occur during snowmelt pipeflow began several days after the onset of surface runoff pipeflow contribution increased until ground thaw lowered the water tables leaving matrix flow within the organic layer as the dominant mode of runoff pipeflow accounted for 21 of runoff during the 15 day melt period of 1997 following melt pipeflow recurred only during two intense summer rainstorms each yielding different pipeflow response characteristics during melt pipeflow closely followed the daily snowmelt cycles and responded earlier than the integrated slope runoff in the summer pipeflow hydrographs rose and fell much quicker than direct storm runoff from the entire slope which was dominated by fast matrix flow within the organic layer pipeflow contributing areas were relatively small but their extent changed with hillslope wetness analysis revealed that the manning flow formula can be combined with contributing areas to simulate pipeflow discharges unlike temperate environments where frozen ground is not a factor the frost table position significantly controls the position of the phreatic surface and must be considered in any models of pipeflow in permafrost slopes

late cretaceous intraplate thrusting in central europe effect of africa iberia europe convergence not alpine collision a well established event of intraplate basin inversion and basement thrusting affected central europe in late cretaceous time it is widely accepted to have resulted from the collision of the alpine orogen with europe s margin at that time an early alpine orogen located on the leading edge of the adria microplate still lay far southeast of its present day position and had entered a phase of extension after a first orogenic event characterized by w to nw directed thrusting this configuration is not likely to have induced ssw nne directed thrusting and folding in the future european foreland that was still separated from the alpine wedge by a strip of oceanic lithosphere by contrast the onset of intraplate contraction coincides with an important change in relative motion between the european and african plates at ca 90 ma africa s sse directed sinistral transform motion relative to europe changed to ne directed convergence this agrees well with the timing and kinematics of intraplate thrusting in central europe structures of similar age and kinematics occurring in southern france spain and north africa suggest that the late cretaceous pulse of contraction was caused by pinching west central europe s thin lithosphere between baltica and africa only since the onset of n directed thrusting in the alps in paleocene or eocene time are the kinematics of the alps and their european foreland compatible indicating that mechanical coupling between africa europe and the adria microplate had been achieved

dye tracer visualization of flow patterns and pathways in glacial sandy till at a boreal forest hillslope abstract dyes are valuable tracers in visualizing flow patterns and pathways in soil we applied the dye acid blue 9 to unsaturated and saturated soil profiles at a boreal forest hillslope consisting of glacial sandy till and determined the soil physical properties from soil samples the objective was to characterize preferential flowpaths investigate their porosity extent and connectivity and complement earlier findings on subsurface flow formation at the site according to the results preferential flowpaths were formed by roots erosion related to soil water flow freezing thawing cycles and soil fauna the role of roots and stones in the formation of preferential flowpaths was emphasized porosity of preferential flowpaths was 5 1 1 8 and they extended to a depth of about 55 cm from the soil surface the deepest roots reached the same depth when the soil saturated individual preferential flowpaths self organized into continuous and well connected lateral flow systems along the slope at the slope shoulder preferential flow network covering the entire soil profile as well as preferential flowpaths on the underlying bedrock surface were considered crucial for runoff generation in the midslope area runoff generation was characterized by lateral preferential flow and the transmissivity feedback phenomenon at the slope foot preferential flowpaths in soil below the eluvial horizon were the major runoff contributors a full saturation of the soil profile at the slope is unlikely under natural conditions however lateral flow was found to occur also in unsaturated soil

hydrological and hydrochemical processes observed during a large scale infiltration experiment at the super sauze mudslide france rainfall is one of the major triggering factors of landslides and its pattern controls their temporal behaviour characterization of the groundwater processes and possible preferential infiltration of rainfall is necessary challenging and very relevant for landslide hazard analysis the objective of this paper is to identify the groundwater dynamics matrix flow and preferential flow within highly heterogeneous and fissured reworked black marl material using a large scale infiltration test the artificial rainfall experiment over a 100 m2 infiltration plot monitored with several hydrological hydrochemical and geophysical equipments was carried out on the super sauze mudslide south french alps high resolution groundwater and water quality measurements were collected artificial rainfall was applied over a period of 14 days conservative tracers br and cl were used successively during the infiltration period the mean rainfall intensity was 8 5 mm h 1 with a mean tracer concentration of 100 mg l 1 the hydrodynamic and hydrochemical responses of the tracing experiments allowed us to get a new insight into 1 the horizontal and vertical variability of the rain infiltration in unstable black marl hillslopes 2 the effect of shallow fissuration on the groundwater recharge 3 the role of piston flow on the rate of water level changes and the increase of pore water pressures and 4 the effect of material heterogeneity in the development of preferential water flows and local perched water tables copyright 2011 john wiley sons ltd

subsurface flow velocities in a hillslope with lateral preferential flow 1 our understanding of hillslope subsurface flow relies on assumptions about how storm characteristics affect the hillslope runoff response experiments in hillslopes dominated by preferential flow features often show that runoff is dynamic and is affected by antecedent conditions rainfall conditions and position of the slope we applied tracers to a hillslope under natural and steady state flow boundary conditions to determine the relationship between lateral tracer velocities and various hillslope lengths and storm indicators tracer velocities were similar to the fastest velocities measured in other similar experiments the velocities were dependent on the boundary conditions and slope length and the subsurface flow velocity was most closely related to the 1 h rainfall intensity unlike some studies there was little correlation between our measured flow velocities and storm volume or antecedent conditions we attributed this to the hillslope characteristics and the relatively consistent wet antecedent conditions during the experiments this experiment showed that the connectivity of the hillslope preferential flow network is an important factor governing the average subsurface flow velocity

how do disconnected macropores in sloping soils facilitate preferential flow runoff from hillslopes is generated by processes such as infiltration excess and saturation overland flow subsurface stormflow and subsurface return flow preferential flow through macropores can affect any one of these runoff generation processes field studies at the hitachi ohta experimental watershed in japan have noted that self organization processes may manifest the connectivity of such subsurface flow paths particularly via macropores from hillslopes to stream channels it is well established from soil physics principles that the connectivity of macropore networks depends on soil wetness and this has been shown experimentally at hitachi ohta where subsurface flow and streamflow respond to thresholds of wetness numerical solutions to the three dimensional richards equation are derived for a sloping soil block containing a population of disconnected macropores of various sizes shapes and orientations solutions for the case of steady water flux applied to the surface of the soil block are evaluated to determine the conditions where the disconnected macropores become active in the flow process results show that subsurface flow is directed through the preferential flow network in the saturated portion of the soil but bypasses the macropores in the drier regions the preferential flow network expands as the degree of saturation increases the expanding network of active macropores leads to less resistance to overall flow in the domain and access to increased volumes of the flow domain although the individual macropores are disconnected it is argued that large localized hydraulic gradients can potentially lead to preferred zones of subsurface erosion in addition to the importance of these findings related to stormflow generation in catchments they add support to the concept of self organization of subsurface flow systems in soils copyright 2010 john wiley sons ltd

assessment of grass root effects on soil piping in sandy soils using the pinhole test abstract soil piping is an important land degradation process that occurs in a wide range of environments despite an increasing number of studies on this type of subsurface erosion the impact of vegetation on piping erosion is still unclear it can be hypothesized that vegetation and in particular plant roots may reduce piping susceptibility of soils because roots of vegetation also control concentrated flow erosion rates or shallow mass movements therefore this paper aims to assess the impact of grass roots on piping erosion susceptibility of a sandy soil the pinhole test was used as it provides quantitative data on pipeflow discharge sediment concentration and sediment discharge tests were conducted at different hydraulic heads i e 50 mm 180 mm 380 mm and 1020 mm results showed that the hydraulic head was positively correlated with pipeflow discharge sediment concentration and sediment discharge while the presence of grass roots expressed as root density was negatively correlated with these pipeflow characteristics smaller sediment concentrations and sediment discharges were observed in root permeated samples compared to root free samples when root density exceeds 0 5 kg m 3 piping erosion rates decreased by 50 compared to root free soil samples moreover if grass roots are present the positive correlation between hydraulic head and both sediment discharge and sediment concentration is less pronounced demonstrating that grass roots become more effective in reducing piping erosion rates at larger hydraulic heads overall this study demonstrates that grass roots are quite efficient in reducing piping erosion rates in sandy soils even at high hydraulic head 1 m as such grass roots may therefore be used to efficiently control piping erosion rates in topsoils

fill and spill hillslope runoff representation with a richards equation based model integrated surface subsurface hydrological models isshms are well established numerical tools to investigate water flow and contaminant transport processes over a wide range of spatial and temporal scales however their ability to correctly reproduce the response of hydrological systems to natural and anthropogenic forcing depends largely on the accuracy of model parameterization including the level of detail in the representation of the bedrock this latter is typically incorporated in some way via the bottom boundary of the model domain issues of bedrock topography variable soil depth and the resulting hillslope storage distribution representation in isshms are vitally important but to date have received little attention a standard treatment of the bottom boundary especially in large catchment and continental scale applications is to model it as a flat or inclined e g parallel to the surface impermeable base sometimes with some simple leakage term this approach does not allow the model to correctly reproduce bedrock controlled threshold responses such as the fill and spill process as observed across many hillslope and catchment scale field studies it is still unclear whether richards equation based numerical models are actually able to generate such responses here we use a richards equation based model cathy to simulate internal transient subsurface stormflow dynamics observed at the well characterized panola experimental hillslope in georgia usa soil and bedrock properties were calibrated starting from values reported in previous studies at the site our simulation results show that the model was able to reproduce threshold mechanisms which in turn affected both the integrated and distributed hydrologic responses of the panola hillslope we then developed a set of virtual experiments with modified boundary conditions and base topography at the soil bedrock interface to explore the bedrock boundary control on transient groundwater flow patterns our results show that accurate representation of the lower boundary is crucial for isshm simulations of hillslope scale storm runoff and for connectivity of transient groundwater we summarize our findings with the development of a new bedrock topographic wetness index that takes into account the unsaturated infiltration dynamics the index is able to help represent the spatial variability of water table response over the bedrock surface compared to standard surface topography based indices this new index may be useful in larger scale isshm applications where an exact bedrock topography representation is not feasible or possible

hydrological processes letters topographic controls on subsurface storm flow at the hillslope scale for two hydrologically distinct small catchmetns controls on hillslope ow pathways are still not well understood despite the many di erent studies reported since the pioneering work of hewlett 1961 in a wide range of recent modelling studies it has been assumed that ow directions can be related to hydraulic gradients derived from surface topography this assumption leads to believable maps of predictions of soil saturation and is convenient because of the increasing availability of digital terrain maps dtms the validity of the resulting spatial patterns throughout the watershed however have not been fully assessed although see the discussion in beven et al 1995 and the recent studies of nyberg 1996 and crave and gascuel odoux 1997 this results from the di culty of obtaining adequate spatial coverage of hydrological variables and the scale problem of relating point measurements to predictions at the dtm grid scale recent hillslope analyses of soil moisture distributions have identi ed that ow paths do not necessarily converge to hollow regions anderson 1982 that they may require dynamic spatial representations barling et al 1994 and that their prediction using topographically derived indices have had mixed results burt and butcher 1986 moore and thompson 1996 spatial representations of topographically driven indices therefore need further exploration a possible way forward is to conduct more detailed studies of the dynamics of subsurface ow at the hillslope scale analysis of a natural hillslope combines integrated trench ow and point scale soil moisture measurements coupled with a detailed understanding of surface and subsurface features such data provide a more comprehensive assessment of the assumption used in many modelling studies that hillslope ow is controlled by surface topography in this letter we address the question of whether it is appropriate to use surface topography to describe hillslope ow paths or if it is not more appropriate to use subsurface gradients relating to the soil bedrock interface or the hydrologically impeding layer we present examples for two hillslopes in di erent hydrogeological climatic settings analyses of the distribution of topographic index patterns derived from digital terrain analysis for both surface and subsurface topography are related to observational patterns of subsurface storm ow along arti cial trench face sections

fracture density in the deep subsurface techniques with application to point arguello oil field because monterey formation reservoirs rely on fractures joints for permeability quantitative information on fracture spacing is important to exploration strategies and for understanding reservoir behavior density of joints in cores of four wells from the point arguello reservoir has been determined with a new probability based method and these subsurface joint densities are compared with joint densities measured at nearby outcrops my measure of joint density is the fracture spacing index which is the slope of the trend of layer thickness to joint spacing a single set of extension joints that strike parallel to bedding dip predominates at outcrops likewise the cores contain a single set of extension joints perpendicular to the anticline axis and parallel to present day maximum horizontal compressive stress in core and at outcrop the only lithologic control on joint density is between nonjointed mudstone and harder more brittle jointed rocks within each well the fracture spacing index is the same for all hard rocks though it varies between wells in the reservoir joint density relates to structural position the most densely jointed strata fracture spacing index 0 45 are from the hinge of a minor anticline where its plunge steepens a less steeply plunging anticlinal nose has lower joint density fracture spacing index 0 30 the lowest joint density fracture spacing index 0 095 and 0 12 is in cores from gently dipping areas at outcrops in various structural settings the fracture spacing index is the same approximately 1 29 in chert dolostone and porcelanite and siliceous shale these rocks may be saturated with joints so that differences in brittle strain due to local structural variations have been overwhelmed as joints continued to form during unroofing of these strata chert looks more fractured than other lithologies because of thin bedding fracture spacing index is used to compute such parameters as fracture porosity and volume of fractures that directly contact the well bore these parameters may be important when trying to model the behavior of a petroleum reservoir or when trying to assess the feasibility of strongly deviating wells to improve the performance of a fracture reservoir

role of upslope soil pore pressure on lateral subsurface storm flow dynamics 1 the role of upslope soil pore water pressure on lateral subsurface storm flow dynamics is poorly understood further development of hillslope hydrologic models requires new understanding from field understanding in particular we need new quantifiable measures that link upslope soil pore pressure and water table dynamics to the timing and volume of subsurface storm flow here we examine the relationship between hillslope scale pore pressure and lateral outflow from slope base using the fine temporal resolution hydrometric data 10 min interval from two steep unchanneled concave hillslopes one hillslope fudoji covered by relatively high hydraulic conductivity sandy soil and the other toinotani covered by relatively low hydraulic conductivity clay soil in both hillslopes pore pressures in the area close to the slope base were only weakly related to subsurface storm flow dynamics during periods of storm flow production hillslope discharge was strongly related to the cross sectional area of the upslope saturated layer during slope seepage periods between events hillslope discharge from the highly permeable hillslope was still related to the upslope cross sectional subsurface saturated area however during this same period at the low permeability site hillslope discharge was not related to the upslope subsurface saturated area through intersite comparison we show that the soil matrix permeability has a large impact on the hydrological extension of preferential flow and hence the linkage between upslope pore pressure and subsurface storm flow dynamics

throughflow variability on a forested hillslope underlain by compacted glacial till this study examined the spatial and temporal variability of throughflow in a shallow forest oil in terms of the controls exerted by topography soil properties and the shape of the water table hillslope outflow was measured at nine troughs installed at a road cut and hydraulic head was measured at 37 piezometers installed to the confining till surface at the base of the soil at the lowest flows the distribution of throughflow across the hillslope conformed reasonably to the distribution of upslope contributing area computed from the topography of the confining basal till layer at higher flows however the distribution of throughflow shifted partly as a result of changes in the orientation in flow tubes as the piezometric surface changed at high flows surface topography appeared to provide a reasonable proxy for the shape of the water table shunting of water through discrete macropores however can apparently overwhelm topographic controls on throughflow at least for slope widths less than about 10 m effective hydraulic conductivities computed at the scale of the troughs varied over two orders of magnitude and displayed no consistent relationship with the thickness of the saturated layer estimates at the plot scale c 10 m hillslope width were far less variable and for higher flows displayed an approximately linear relationship with saturated zone thickness copyright 2000 john wiley sons ltd

deep seated complex tunnel systems a hydrological study in a semi arid catchment loess plateau china abstract during 1989 1990 delailed monitoring of deep seated complex tunnel systems was conducted in yangdaogou a subbasin in the hilly loess region shanxi which has a catchment area of 0 203 km2 it was found that tunnel flow hydrological processes were characterized by a quick response to rainfall an early flow peak and a short duration all the tunnel discharge was derived from overland flow entering via inlets however discharge is not significantly related to rainfall parameters in some tunnels which is contrary to observations on surface plots field surveys show frequent blockages of tunnels caused by collapses inside the tunnels which could be reopened in subsequent events as well as the occasional abrupt opening of new inlets as a result tunnel discharge was highly erratic in some of the monitored events partial damming within the tunnel systems may also be involved hence instability in the tunnel systems is one of the key factors affecting their hydrologic response during the period of monitoring fifteen events occurred and on average at least 43 ranging from 0 to 78 of the total basin water discharge was routed through four major tunnel systems which account for 90 of the catchment area of all tunnel systems in the basin the deep seated tunnel systems in this area seem not to be developed from the micro pipes close to the surface instead they are most likely formed in some catastrophic storms and expanded in subsequent storms 1997 elsevier science b v

runoff process on a steep forested slope abstract three slope units are defined by combining nine basic slope types a convergent slope unit is called a zero order basin because it combines a slope and a stream field measurements of the runoff process of stormflow on pliocene slopes are presented pipe flow and saturated overland flow play an important part on convergent colluvial slope units surface soils significantly influence saturated throughflow on creeping middle slopes the depth of weathering has a major effect on initial moisture storage for residual and creeping slopes a subsurface storm flow pattern on a typical pliocene slope is reconstructed based on the field measurements

piping and pipeflow in a deep peat catchment abstract natural pipes are common in many upland blanket peats yet little is known about pipe network morphology or pipeflow processes most information on soil piping comes from the shallow peaty podzols of the welsh uplands where monitoring suggests that pipes may be important contributors to streamflow this paper presents information on piping and pipeflow from a deep upland blanket peat catchment in the pennine hills of northern england pipe outlets are found throughout the soil profile ranging from the underlying substrate at 3 m depth to pipes which are within a few centimetres of the surface mean pipe diameters range from 3 to 70 cm some pipes are over 150 m long slopes in the catchment are less steep than those usually associated with soil piping continuous flow records were obtained from 15 gauging sites on 8 separate pipes the pipeflow response from deep blanket peat was found to be different to that reported in the shallow peaty podzols of the welsh uplands the distinction between ephemeral and perennial pipe types does not appear to be useful within the deep pennine blanket peat response times from all of the pipes are short even from pipes deep within the peat at the same time pipes have a prolonged recession limb such that they maintain low flow for longer periods than most other runoff production processes within the catchment pipeflow contributes around 10 of the streamflow volume but can at times contribute up to 30 soil pipes may therefore be far more important in some upland peat catchments than previous work has hitherto suggested

stress orientations found in north east germany differ from the west european trend knowledge about the acting stresses is of crucial importance for understanding the tectonics of a region data about the stress field in north eastern germany used to be very rare in general it was assumed that the orientation of the larger horizontal principal stress sh is similar to that found for western germany and central west europe i e nw se to check this several borehole logs of the late 1980s were analysed for information on the principal horizontal stress orientations they include four arm dipmeter and borehole televiewer data from 15 boreholes the depth range of our stress results reaches from 1500 to 6700 m they were compared to a few other data especially from hydraulic fracturing and to recent findings on the stresses in the northwest german basin in contrast to expectation sh derived from breakout orientations below the salt layers displayed n to ne orientation the latter was found at 10 locations spread over the ne german basin from berlin to the baltic sea from the polish border to the former border between east and west germany moreover this stress rotation in the subsaline formations seems to be the continuation of a trend found in the nw german basin