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

study of dynamic behaviour of recession curves since brutsaert and neiber 1977 recession curves are widely used to analyse subsurface systems of river basins by expressing dq dt as a function of q which typically take a power law form dq dt kq where q is the discharge at a basin outlet at time t traditionally recession flows are modelled by single reservoir models that assume a unique relationship between dq dt and q for a basin however recent observations indicate that dq dt q relationship of a basin varies greatly across recession events indicating the limitation of such models in this study the dynamic relationship between dq dt and q of a basin is investigated through the geomorphological recession flow model which models recession flows by considering the temporal evolution of its active drainage network the part of the stream network of the basin draining water at time t two primary factors responsible for the dynamic relationship are identified i degree of aquifer recharge ii spatial variation of rainfall degree of aquifer recharge which is likely to be controlled by effective rainfall patterns influences the power law coefficient k it is found that k has correlation with past average streamflow which confirms the notion that dynamic dq dt q relationship is caused by the degree of aquifer recharge spatial variation of rainfall is found to have control on both the exponent and the power law coefficient k it is noticed that that even with same and k recession curves can be different possibly due to their different recession peak values this may also happen due to spatial variation of rainfall copyright c 2012 john wiley sons ltd

subsurface flow in a soil mantled subtropical dolomite karst slope a field rainfall simulation study abstract soil and epikarst co evolve resulting in complex structures but their coupled structural effects on hydrological processes are poorly understood in karst regions this study examined the plot scale subsurface flow characteristics from an integrated soil epikarst system perspective in a humid subtropical cockpit karst region of southwest china a trench was excavated to the epikarst lower boundary for collecting individual subsurface flows in five sections with different soil thicknesses four field rainfall simulation experiments were carried out under different initial moisture conditions dry and wet and rainfall intensities 114 mm h 1 high and 46 mm h 1 low on average the soil epikarst system was characterized by shallow soil overlaying a highly irregular epikarst surface with a near steady infiltration rate of about 35 mm h 1 the subsurface flows occurred mainly along the soil epikarst interface and were dominated by preferential flow the subsurface flow hydrographs showed strong spatial variability and had high steady state coefficients 0 52 and 0 36 for high and low rainfall intensity events irregular epikarst surface combining with high vertical drainage capacity resulted in high threshold rainfall depths for subsurface flows 67 mm and 263 mm for initial wet and dry conditions respectively the above results evidenced that the irregular and permeable soil epikarst interface was a crucial component of soil epikarst architecture and consequently should be taken into account in the hydrological modeling for karst regions

simulated effect of soil depth and bedrock topography on near surface hydrologic response and slope stability this paper explores the effect of hillslope hydrological behavior on slope stability in the context of transient subsurface saturation development and landslide triggering we perform a series of virtual experiments to address how subsurface topography affects the location and spatial pattern of slip surface development and pore pressure dynamics we use a 3d darcy richards equation solver hydrus 3 d combined with a cellular automata slope stability model to simulate the spatial propagation of the destabilized area our results showed that the soil bedrock interface and in particular bedrock depressions played a key role in pore pressure dynamics acting as an impedance for the downslope drainage of perched water filling and spilling of depressions in the bedrock surface microtopography induced localized zones of increased pressure head such that the development of pore pressure fields not predictable by surface topography lead to rapid landslide propagation our work suggests that landslide models should consider the subsurface topography in order to include a connectivity component in the mathematical description of hydrological processes operating at the hillslope scale copyright 2012 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

once again once again tidal friction topex poseidon t p altimetry has reopened the problem of how tidal dissipation is to be allocated there is now general agreement of a m2 dissipation by 2 5 terawatts 1 tw 1012 w based on four quite separate astronomic observational programs allowing for the bodily tide dissipation of 0 1 tw leaves 2 4 tw for ocean dissipation the traditional disposal sites since jeffreys 1920 have been in the turbulent bottom boundary layer bbl of marginal seas and the modern estimate of about 2 1 tw is in this tradition but the distribution among the shallow seas has changed radically from time to time independent estimates of energy flux into the marginal seas are not in good agreement with the bbl estimates t p altimetry has contributed to the tidal problem in two important ways the assimilation of global altimetry into laplace tidal solutions has led to accurate representations of the global tides as evidenced by the very close agreement between the astronomic measurements and the computed 2 4 tw working of the moon on the global ocean second the detection by ray and mitchum 1996 of small surface manifestation of internal tides radiating away from the hawaiian chain has led to global estimates of 0 2 to 0 4 tw of conversion of surface tides to internal tides measurements of ocean microstructure yields 0 2 tw of global dissipation by pelagic turbulence away from topography we propose that pelagic turbulence is maintained by topographic scattering of barotropic into baroclinic tidal energy via internal tides and internal waves previous estimates by baines 1974 baines 1982 of this conversion along 150 000 km of continental coastlines gave a negligible 0 02 tw evidently the important conversion takes place along mid ocean ridges the maintenance of the abyssal global stratification requires a much larger expenditure of power 2 tw versus 0 2 tw this is usually attributed to wind forcing if tidal power is to play a significant role here then the bbl estimates need to be reduced the challenge is to estimate dissipation from the energy flux divergence in the t p adjusted tidal models without prior assumptions concerning the dissipation processes

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

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

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

spatio temporal variability of piezometric response on two steep alpine hillslopes information on the main drivers of subsurface flow generation on hillslopes of alpine headwater catchments is still missing therefore the dominant factors controlling the water table response to precipitation at the hillslope scale in the alpine bridge creek catchment northern italy were investigated two steep hillslopes of similar size soil properties and vegetation cover but contrasting topography were instrumented with 24 piezometric wells sixty three 63 rainfall runoff events were selected over three years in the snow free months to analyse the influence of rainfall depth antecedent moisture conditions hillslope topographic characteristics and soil depth on shallow water table dynamics piezometric response expressed as percentage of well activation and water peak magnitude was strongly correlated with soil moisture status as described by an index combining antecedent soil moisture and rainfall depth hillslope topography was found to be a dominant control only for the convex divergent hillslope and during wet conditions timing of water table response depended primarily on soil depth and topographic position with piezometric peak response occurring later and showing a greater temporal variability at the hillslope bottom characterized by thicker soil the relationship between mean hillslope water table level and standard deviation for all wells reflected the timing of the water table response at the different locations along the hillslopes the outcomes of this research contribute to a better understanding of the controls on piezometric response at the hillslope scale in steep terrain and its role on the hydrological functioning of the study catchment and of other sites with similar physiographic characteristics copyright 2014 john wiley sons ltd

a mass conservative method for the integration of the two dimensional groundwater boussinesq equation 1 this work presents a new conservative finite volume numerical solution for the two dimensional groundwater flow boussinesq equation which can be used for investigations of hillslope subsurface flow processes and simulations of catchment hydrology the boussinesq equation which is integrated for each grid element can take account of the local variations of topography and soil properties within the individual elements the numerical method allows for wetting and drying of the water table without ad hoc assumptions the stability and convergence of the method is shown to be guaranteed a priori by the properties of the solver itself even with respect to the boundary conditions an aspect that has been neglected in previous literature the numeric solutions are validated against some approximate analytical solutions and compared to those of another 1 d numerical solver of the boussinesq equation the solver capabilities are further explored with simulations of the panola experimental hillslope where the bedrock topography which is accurately known causes complex wetting and drying patterns in this situation the importance of a two dimensional description of subsurface flows to obtain properly simulated discharges becomes clear finally a comparison is made between the results of the presented algorithm and the output of the geotop hydrological distributed model which simulates variably saturated soils the findings of the comparison are discussed

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

spatial and temporal variations in active layer thawing and their implication on runoff generation in peat covered permafrost terrain 1 the distribution of frost table depths on a peat covered permafrost slope was examined in a discontinuous permafrost region in northern canada over 4 consecutive years at a variety of spatial scales to elucidate the role of active layer development on runoff generation frost table depths were highly variable over relatively short distances 0 25 1 m and the spatial variability was strongly correlated to soil moisture distribution which was partly influenced by lateral flow converging to frost table depressions on an interannual basis thaw rates were temporally correlated to air temperature and the amount of precipitation input simple simulations show that lateral subsurface flow is governed by the frost table topography having spatially variable storage that has to be filled before water can spill over to generate flow downslope in a similar manner that bedrock topography controls subsurface flow however unlike the bedrock surface the frost table is variable with time and strongly influenced by the heat transfer involving water therefore it is important to understand the feedback between thawing and subsurface water flow and to properly represent the feedback in hydrological models of permafrost regions

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

a hydrometric and geochemical approach to test the transmissivity feedback hypothesis during snowmelt to test the transmissivity feedback hypothesis of runoff generation surface and subsurface waters were monitored and sampled during the 1996 snowmelt at various topographic positions in a 41 ha forested headwater catchment at sleepers river vermont two conditions that promote transmissivity feedback existed in the catchment during the melt period first saturated hydraulic conductivity increased toward land surface from a geometric mean of 3 6 mm h 21 in glacial till to 25 6 mm h 21 in deep soil to 54 0 mm h 21 in shallow soil second groundwater levels rose to within 0 3 m of land surface at all riparian sites and most hillslope sites at peak melt the importance of transmissivity feedback to streamflow generation was tested at the catchment scale by examination of physical and chemical patterns of groundwater in near stream discharge and hillslope recharge lateral flow zones and within a geomorphic hollow convergent flow the presence of transmissivity feedback was supported by the abrupt increase in streamflow as the water table rose into the surficial transmissive zone a flattening of the groundwater level vs streamflow curve occurred at most sites this relation had a clockwise hysteresis higher groundwater level for given discharge on rising limb than at same discharge on falling limb at riparian sites suggesting that the riparian zone was the dominant source area during the rising limb of the melt hydrograph hysteresis was counterclockwise at hillslope sites suggesting that hillslope drainage controlled the snowmelt recession end member mixing analysis using ca mg na dissolved organic carbon doc and si showed that stream chemistry could be explained as a two component mixture of groundwater high in base cations and an o horizon overland flow water high in doc the dominance of shallow flow paths during events was indicated by the high positive correlation of doc with streamflow r 2 a 0 82 despite the occurrence of transmissivity feedback hillslope till and soil water were ruled out as end members primarily because their distinctive high si composition had little or no effect on streamwater composition till water from the geomorphic hollow had a chemistry very close to streamwater base flow and may represent the base flow end member better than the more concentrated riparian groundwater during snowmelt streamwater composition shifted as this base flow was diluted not by shallow groundwater from the hillslope but rather by a more surficial o horizon overland flow water q 1999 elsevier science b v all rights reserved

on the base flow recession at the panola mountain research watershed georgia united states 1 there are two types of nonlinearity for recession slope curves 1 the data cloud of observed ln dq dt versus ln q along a straight line where the slope is not equal to 1 and 2 the data cloud of observed ln dq dt versus ln q is concave or convex from the 0 1 ha hillslope the 10 ha headwater subwatershed and the 41 ha watershed at the panola mountain research watershed pmrw the observed ln dq dt versus ln q changes from convex to concave this has been explained by the spatial heterogeneity of recession properties and nonlinearity of hillslope hydraulics hillslope bedrock leakage and return flow to the perennial riparian zone aquifer are important factors affecting the ln dq dt versus ln q relations and an assessment of this mechanism for explaining the observed base flow recessions at the pmrw is the sole focus of this research as a result the lower envelope and the upper envelope should be used to estimate the recession parameters for the 0 1 ha hillslope and the 41 ha watershed respectively and the recession at the 10 ha watershed is a mixture of them based on the recession analysis the leakage to the bedrock on the hillslope and return flow to the perennial stream riparian groundwater can be estimated and the estimation can be verified by other studies

shallow groundwater response to rainfall on a forested headwater catchment in northern coastal california implications of topography rainfall and throughfall intensities on peak pressure head generation the pore water pressure head that builds in the soil during storms is a critical factor for the prediction of potential slope instability we report findings from a 3 year study of pressure head in 83 piezometers distributed within a 13 ha forested catchment on the northern coast of california the study s primary objective was to observe the seasonal and storm based dynamics of pressure head at a catchment scale in relation to observed rainfall characteristics and in situ topography to better understand landscape patterns of pressure head an additional goal was to determine the influence of the interaction between rainfall and forest canopy in altering delivery of water and pressure head during the large storms necessary to induce landsliding we found that pressure head was highly variable in space and time at the catchment scale pore pressures peaked close to maximum rainfall intensity during the largest storms measured the difference between rainfall and throughfall delivered through the canopy was negligible during the critical landslide producing peak rainfall periods pore pressure was spatially variable within the catchment and did not strongly correlate with surficial topographic features only 23 of the piezometers located in a variety of slope positions were found to be highly responsive to rainfall topographic index statistically explained peak pressure head at responsive locations during common storms but not during the larger storms with potential to produce landslides drainage efficiency throughout the catchment increased significantly in storms exceeding 2 to 7 months peak pressure head return period indicated by slowing or cessation of the rate of increase of pressure head with increasing storm magnitude this asymptotic piezometric pattern persisted through the largest storm measured during the study faster soil drainage suppressed pressure head response in larger storms with important process implications for pore pressure development and landslide hazard modelling copyright 2012 john wiley sons ltd

hydraulic properties of karst fractures filled with soils and regolith materials implication for their ecohydrological functions abstract in regions with shallow soils underlain by fractured bedrock hydrological processes of substrate are no longer only limited to soil layers however ecohydrological functions of bedrock fractures especially those filled with different soil and regolith materials have not been fully understood in this study we aimed to evaluate water transport and supplying capacities of the filled fractures through investigating hydraulic properties and explore their dominant influencing factors three typical fractures a vertical one filled with fine textured soil vsf a vertical one filled with soil and regolith materials vsrf and a non vertical one filled with coarse textured soil nsf were selected from a large newly excavated trench on a karst hillslope of southwest china stratified samples of fracture fillings were collected to measure saturated hydraulic conductivity k s water retention curves and basic physicochemical properties additionally twenty soil profiles in different topographic locations in the same study area were also analyzed in order to support the results derived from the filled fractures all fractures exhibited extremely high k s 87 149 mm h 1 in surface soil 0 10 cm which allowed rapid infiltration of rainwater into subsurface subsurface water transport was smooth when underlying fracture fillings were loamy with relatively high k s about 10 mm h 1 like in nsf but was blocked when they were clayey with low k s 1 like in vsf and vsrf all fracture fillings had abilities to hold water and available water was the most in nsf which provided an extra water source for plant growth in shallow soil regions the ecohydrological functions of the filled fractures often depend on the properties and layering of fracture fillings which was supported by those obtained from the twenty soil profiles these results are helpful for better understanding of the ecohydrological processes and functions of fractures filled with different materials in karst regions

threshold relations in subsurface stormflow 2 the fill and spill hypothesis analysis of subsurface stormflow from 147 storms at the 20 m long trench in the panola mountain research watershed by tromp van meerveld and mcdonnell 2006a showed that there was a distinct 55 mm precipitation threshold for significant subsurface stormflow production this second paper in the series investigates the processes responsible for this threshold response we installed a dense spatial array of maximum rise crest stage gauges and recording wells on the hillslope and studied the temporal and spatial patterns of transient saturation at the soil bedrock interface and its relation to subsurface stormflow measured at the trench face results show that while transient groundwater developed on parts of the hillslope during events smaller than 55 mm it was not until more than 55 mm of rain fell before bedrock depressions on the hillslope were filled water spilled over microtopographic relief in the bedrock surface and the subsurface saturated areas became connected to the trench when connectivity was achieved the instantaneous subsurface stormflow rate increased more than fivefold compared to before the subsurface saturated areas were connected to the trench face total subsurface stormflow was more than 75 times larger when connectivity was achieved compared to when connectivity was not achieved the fill and spill hypothesis presented in this paper is a process explanation for the observed threshold behavior of tromp van meerveld and mcdonnell 2006a thereby linking patterns and processes

topographic controls on shallow groundwater dynamics implications of hydrologic connectivity between hillslopes and riparian zones in a till mantled catchment hydrologic connectivity is regarded as one of the key controls in determining catchment rainfall run off response and has been linked to the export of solutes from uplands to streams we sought to identify the patterns of hydrologic connectivity within a small forested watershed by monitoring the shallow groundwater fluctuations of simple topographically defined landform sequences footslope backslope shoulder a spatially distributed instrument network was employed to continuously measure hydrometric responses of the shallow subsurface during seasonal wet up from summer through winter in a small till mantled research catchment we demonstrate that the spatial patterns of shallow water table extent and duration and therefore hydrologic connectivity had a strong seasonal signature during the low antecedent soil moisture conditions typically associated with the growing season water tables were patchy discontinuous and only the wettest near stream footslope areas were consistently hydrologically connected with the stream network during the dormant season footslopes and backslopes maintained water tables that persisted between storm events and were almost continuously connected with the stream network in the largest storm events the typically driest landforms shoulder slopes established shallow transient water tables suggesting that nearly the entire catchment was temporarily hydrologically connected with the stream network in addition we found significant differences p 0 05 in the magnitude and duration of groundwater responses to rainfall among landform groups both seasonally and during events these results have implications for using a similarity approach in representing characteristic hydrologic responses of topographically defined watershed elements determining hydrologic connectivity between watershed elements as well as for understanding solute transport in catchments copyright 2010 john wiley sons ltd

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

groundwater dynamics in a till hillslope flow directions gradients and delay knowledge of groundwater dynamics is important for the understanding of hydrological controls on chemical processes along the water flow pathways to increase our knowledge of groundwater dynamics

role of epikarst in near surface hydrological processes in a soil mantled subtropical dolomite karst slope implications of field rainfall simulation experiments epikarst exerts a strong control on run off generation in karst regions but it is still unclear in karst regions our study aimed to demonstrate the effect of epikarst on near surface hydrological processes in a subtropical cockpit karst region of southwest china using plot scale rainfall simulation experiments with different rainfall intensities low and high and antecedent moisture conditions dry and wet a trench excavated to the epikarst lower boundary allowed identification of flow pathways in the entire soil epikarst architecture system thus facilitating the water balance calculations using a conceptual model with the assumption of a two stage hydrological evolution more than 70 of the total rainfall water moved vertically through the shallow soil layer and then was redistributed by the epikarst as subsurface flow occurring on the soil epikarst interface depression filling on epikarst surface water held by epikarst and deep percolation epikarst water regulation capacity defined as the sum of depression filling on epikarst surface water held by epikarst epikarst seepage flow and deep percolation was 58 mm wet antecedent condition and 223 mm dry antecedent condition total run off from the soil epikarst system was dominated by saturated subsurface flow showing a threshold process controlled by epikarst storage capacity storing as much as 181 mm of rainfall water under dry antecedent condition our study proved that despite the epikarst being relatively poorly developed and covered by a soil mantle it still exerted a strong influence on near surface hydrological processes and thus should be adequately considered in future modelling of water recharge and depletion dynamics in this integrated soil epikarst system copyright 2015 john wiley sons ltd

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

interflow dynamics on a low relief forested hillslope lots of fill little spill author s du e rhett jackson c klaus j mcdonnell jj griffiths na williamson mf greco jl bitew m abstract 2016 we evaluated the occurrence of perching and interflow over and within a sandy clay loam argillic horizon within first order low relief forested catchments at the savannah river site srs in the upper coastal plain of south carolina we measured soil hydraulic properties depths to the argillic layer soil moisture shallow groundwater behavior interflow interception trench flows and streamflow over a 4 year period to explore the nature and variability of soil hydraulic characteristics the argillic topography and their influence on interflow generation perching occurred frequently within and above the restricting argillic horizons during our monitoring period but interflow was infrequent due to microtopographic relief and associated depression storage on the argillic layer surface high percolation rates through the argillic horizon particularly through soil anomalies also reduced the importance of interflow interflow generation was highly variable across eleven segments of a 121 m interception trench hillslopes were largely disconnected from stream behavior during storms hillslope processes were consistent with the fill and spill hypothesis and featured a sequence of distinct thresholds vertical wetting front propagation to the argillic layer saturation of the argillic followed by local perching filling of argillic layer depressions and finally connectivity of depressions leading to interflow generation analysis of trench flow data indicated a cumulative rainfall threshold of 60 mm to generate interflow a value at the high end of the range of thresholds reported elsewhere

time and the rivers flowing fluvial geomorphology since 1960 fluvial geomorphology has been the largest single subdiscipline within geomorphology for many decades fluvial geomorphic expertise is integral to understanding and managing rivers and to developing strategies for sustainable development this paper provides an overview of some of the significant advances in fluvial geomorphology between 1960 and 2010 with respect to conceptual models fluvial features and environments being studied tools used by fluvial geomorphologists geomorphic specialty groups within professional societies journals in which fluvial geomorphic research is published and textbooks of fluvial geomorphology during this half century fluvial geomorphology broadened considerably in scope from a focus primarily on physical principles underlying process and form in lower gradient channels with limited grain size range to a more integrative view of rivers as ecosystems with nonlinear behavior and great diversity of gradient substrate composition and grain size the array of tools for making basic observations analyzing data and disseminating research results also expanded considerably during this period as did the diversity of the fluvial geomorphic community

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

quantifying the morphology of flow patterns in landslide affected and unaffected soils summary in mountainous regions landslides are a common natural phenomenon they are often triggered by a combination of steep relief and long lasting rainfalls therefore hydrological conditions in the soil are crucial for their initiation because direct measurements of water flow are difficult and model predictions uncertain we used a dye to visualise flow patterns directly we combined dye tracer experiments with field observations root density and rock fragment content and measurements of soil properties bulk density soil water retention curve and saturated hydraulic conductivity we quantified the morphology of flow patterns by image indices and mutual information that measures the overall dependency between variables and compared two shallow landslides of different ages with a landslide unaffected hillslope our results showed that flow patterns on the landslides were more fragmented and contained larger stained objects than on the landslide unaffected site we relate these findings to a larger stone content and a stronger macropore soil matrix interaction moreover we detected a fissure network on the younger landslide that probably affects its hydrological behaviour field observations soil hydraulic properties and dye tracer studies describe different hydrological aspects of the studied sites and complement the information provided by the morphological image indices

soil pipe collapses in a loess pasture of goodwin creek watershed mississippi role of soil properties and past land use little is known about the association of soil pipe collapse features with soil properties or land use history three loess covered catchments in northern mississippi usa were characterized to investigate these relationships soil pipe collapses were characterized for their size type feature and spatial location along with soil properties across the three catchments although mapped as the same soil one of the catchments did not contain pipe collapse features while the other two had 29 4 and 15 4 pipe collapses per hectare these loess soils contained fragipan layers that are suspected of perching water thereby initiating the piping processes pipe collapses associated with subsurface flow paths were not always consistent with surface topography the surface layer tended to be non erodible while layers below even the upper fragipan layers were susceptible to erosion by pipeflow soil properties of the lowest fragipan layer were highly variable but tended to prevent further downward erosion of soil pipes and thus formed a lower boundary for gullies middle to lower landscape positions in one of the piped catchments contained anthropic soils that were highly erodible these anthropic soils were previously gullies that were filled in in the 1950s when forested areas assumed to have been established when land was previously converted from crop to forest land were converted to pasture three decades after this land use change from forest to pasture pipe collapses became evident in contrast the adjacent catchment that does not exhibit pipe collapse features experienced severe sheet and rill erosion prior to the 1930s while in cotton production the surface horizons above the lower fragipan layer were completely removed during this period thus the top soil layer that tends to form a bridge above soil pipes in the more erodible subsoil layers was removed this study showed that knowledge of soil characteristics or topography alone do not explain the distribution of soil pipe collapses as past land use can play a definitive role copyright 2015 john wiley sons ltd

linking rainfall induced landslides with debris flows runout patterns towards catchment scale hazard assessment abstract debris flows and landslides induced by heavy rainfall represent an ubiquitous and destructive natural hazard in steep mountainous regions for debris flows initiated by shallow landslides the prediction of the resulting pathways and associated hazard is often hindered by uncertainty in determining initiation locations volumes and mechanical state of the mobilized debris and by model parameterization we propose a framework for linking a simplified physically based debris flow runout model with a novel landslide hydro mechanical triggering lht model to obtain a coupled landslide debris flow susceptibility and hazard assessment we first compared the simplified debris flow model of perla 1980 with a state of the art continuum based model ramms and with an empirical model of rickenmann 1999 at the catchment scale the results indicate that predicted runout distances by the perla model are in reasonable agreement with inventory measurements and with the other models predictions of localized shallow landslides by lht model provides information on water content of released mass to incorporate effects of water content and flow viscosity as provided by lht on debris flow runout we adapted the perla model the proposed integral link between landslide triggering susceptibility quantified by lht and subsequent debris flow runout hazard calculation using the adapted perla model provides a spatially and temporally resolved framework for real time hazard assessment at the catchment scale or along critical infrastructure roads railroad lines

towards more systematic perceptual model development a case study using 3 luxembourgish catchments the synthesis of experimental understanding of catchment behaviour and its translation into qualitative perceptual models is an important objective of hydrological sciences we explore this challenge by examining the cumulative understanding of the hydrology of three experimental catchments and how it evolves through the application of different investigation techniques the case study considers the huewelerbach weierbach and wollefsbach headwater catchments of the attert basin in luxembourg subsurface investigations including bore holes and pits analysis of soil samples and electrical resistivity tomography measurements are presented and discussed streamflow and tracer data are used to gain further insights into the streamflow dynamics of the catchments using end member mixing analysis and hydrograph separation based on dissolved silica and electrical conductivity we show that the streamflow generating processes in all three catchments are controlled primarily by the subsolum and underlying bedrock in the huewelerbach the permeable sandstone formation supports a stable groundwater component with little seasonality which reaches the stream through a series of sources at the contact zone with the impermeable marls formation in the weierbach the schist formation is relatively impermeable and supports a fill and spill type of flow mechanism during wet conditions it produces a delayed response dominated by pre event water in the wollefsbach the impermeable marls formation is responsible for a saturation excess runoff generating process producing a fast and highly seasonal response dominated by event water the distinct streamflow generating processes of the three catchments are represented qualitatively using perceptual models the perceptual models are in turn translated into quantitative conceptual models which simulate the hydrological processes using networks of connected reservoirs and transfer functions more generally the paper illustrates the evolution of perceptual models based on experimental fieldwork data the translation of perceptual models into conceptual models and the value of different types of data for processes understanding and model representation copyright 2014 john wiley sons ltd

pairing geophysical techniques improves understanding of the near surface critical zone visualization of preferential routing of stemflow along coarse roots abstract there is compelling evidence from aboveground observations that trees considerably affect precipitation partitioning through the critical zone however due to the lack of appropriate methods the role of root systems the hidden half of trees on redistributing precipitation and infiltration into and routing through the soil remains inadequately visualized and understood here we designed a novel experiment to pair two non invasive geophysical techniques ground penetrating radar gpr and electrical resistivity tomography ert to trace stemflow through the soil in a forested hillslope after water was released on the trunk of an american beech fagus grandifolia ehrh to induce stemflow we used gpr to locate lateral coarse roots and gpr and ert together to confirm the wetting areas in response to the non uniform transport of stemflow signal changes between time lapse geophysical images were used to reveal both the response time and location of stemflow infiltration into and redistribution through the soil this first known study to investigate the subsurface routing of stemflow by combining gpr and ert revealed that the belowground funneling of stemflow along laterally oriented coarse roots transported water 2 8 m downslope from the study tree in 30 min after stemflow was initiated in situ excavation validated the distribution of lateral roots and lateral root derived preferential flow paths identified in geophysical images confirming the utility of pairing gpr and ert to gain insights into the temporal dynamics and spatial distribution of subsurface routing of stemflow the proposed method visualized and confirmed the funneling effect of roots on belowground water redistribution that contributed to subsurface lateral flow pairing gpr and ert provides a useful combination of geophysical methods to advance our understanding of the complex interactions between plant and soil such as the role of tree roots in soil hydrological process by revealing areas of funneling in the hidden part of the critical zone

identifying hydrologic flowpaths on arctic hillslopes using electrical resistivity and self potential shallow subsurface flow is a dominant process controlling hillslope runoff generation soil development and solute reaction and transport despite their importance the location and geometry of these flow paths are difficult to determine in arctic environments shallow subsurface flow paths are limited to a thin zone of seasonal thaw above permafrost which is traditionally assumed to mimic the surface topography we have used a combined approach of electrical resistivity tomography ert and self potential sp measurements to map shallow subsurface flow paths in and around water tracks drainage features common to arctic hillslopes ert measurements delineate thawed zones in the subsurface that control flow paths whereas sp is sensitive to groundwater flow we have found that areas of low electrical resistivity in the water tracks were deeper than manual thaw depth estimates and varied from the surface topography this finding suggests that traditional techniques might underestimate active layer thaw and the extent of the flow path network on arctic hillslopes sp measurements identify complex 3d flow paths in the thawed zone our results lay the groundwork for investigations into the seasonal dynamics hydrologic connectivity and climate sensitivity of spatially distributed flow path networks on arctic hillslopes

effects of soil spatial variability at the hillslope and catchment scales on characteristics of rainfall induced landslides spatial variations in soil properties affect key hydrological processes yet their role in soil mechanical response to hydro mechanical loading is rarely considered this study aims to fill this gap by systematically quantifying effects of spatial variations in soil type and initial water content on rapid rainfall induced shallow landslide predictions at the hillslope and catchment scales we employed a physically based landslide triggering model that considers mechanical interactions among soil columns governed by strength thresholds at the hillslope scale we found that the emergence of weak regions induced by spatial variations of soil type and initial water content resulted in early triggering of landslides with smaller volumes of released mass relative to a homogeneous slope at the catchment scale initial water content was linked to a topographic wetness index whereas soil type varied deterministically with soil depth considering spatially correlated stochastic components results indicate that a strong spatial organization of initial water content delays landslide triggering whereas spatially linked soil type with soil depth promoted landslide initiation increasing the standard deviation and correlation length of the stochastic component of soil type increases landslide volume and hastens onset of landslides the study illustrates that for similar external boundary conditions and mean soil properties landslide characteristics vary significantly with soil variability hence it must be considered for improved landslide model predictions

physical modeling investigation of rainfall infiltration in steep layered volcanoclastic slopes abstract infiltration processes in layered slopes can be strongly affected by the different hydraulic properties of the soils constituting the layers with potential downslope flow diversion that can have effects on slope stability as well as on runoff generation and groundwater recharge in this respect volcanoclastic soil covers represent a typical example as layers with strongly contrasting textures are deposited during the various eruptive phases in this paper the results of a transient infiltration test carried out in a densely instrumented physical model of a layered volcanoclastic sloping cover are presented the soil cover was constituted by a layer of gravelly pumices interbedded between two layers of finer ashes sandy loams even with such an extreme contrast in texture capable of significantly delaying the advancement of infiltration through the layer of pumices flow diversion occurred only temporarily at the interface between the upper layer of ashes and the pumices in fact although a long lasting intense rainfall was applied into an initially dry soil profile the downslope diverted water volume in form of a subsurface runoff was just a small fraction of the total applied rainfall in fact the accumulation of water above the upper edge of the pumices responsible of the subsurface runoff soon led to the establishment of a large water potential gradient which redirected the infiltrating flow through the pumices and stopped the downslope flow diversion

sediment detachment and transport processes associated with internal erosion of soil pipes subsurface flow can be an important process in gully erosion through its impact on decreasing soil cohesion and erosion resistance as soil water content or pressure increases and more directly by the effects of seepage forces on particle detachment and piping the development of perched water tables in duplex soils fosters lateral flow that can result in seepage at the surface of hillslopes and or formation of soil pipes by internal erosion of lateral preferential flow paths continued internal erosion of soil pipes can lead to gullies dam and levee failures however the processes involved in particle and aggregate detachment from soil pipe walls and transport processes within soil pipes have not been well studied or documented this paper reviews the limited research on sediment detachment and transport in macropores and soil pipes and applies the knowledge learned from the much more extensive studies conducted on streams and industrial pipes to hydrogeologic conditions of soil pipes knowledge gaps are identified and recommendations are made for future research on sediment detachment and transport in soil pipes

influence of antecedent soil moisture on hydraulic conductivity in a series of texture contrast soils antecedent soil moisture significantly influenced the hydraulic conductivity of the a1 a2e and b21 horizons in a series of strong texture contrast soils tension infiltration at six supply potentials demonstrated that in the a1 horizon hydraulic conductivity was significantly lower in the wet treatment than in the dry treatment however in the a2e horizon micropore and mesopore hydraulic conductivity was lower in the dry treatment than the wet treatment which was attributed to the precipitation of soluble amorphous silica in the b21 horizon desiccation of vertic clays resulted in the formation of shrinkage cracks which significantly increased near saturated hydraulic conductivity and prevented the development of subsurface lateral flow in the dry treatment in the wet treatment the difference between the hydraulic conductivity of the a1 and b21 horizons was reduced however lateral flow still occurred in the a1 horizon due to difficulty displacing existing soil water further down the soil profile results demonstrate the need to account for temporal variation in soil porosity and hydraulic conductivity in soilwater model conceptualisation and parameterisation

hydrology of subarctic canadian shield soil filled valleys the canadian shield landscape includes bedrock uplands and valleys infilled with soil a site near yellowknife in subarctic canada was studied to elucidate the hydrological behaviour of soil filled valleys a suite of hydrological processes was found to be important in the studied valley including snowmelt and rainfall ground frost development evaporation infiltration lateral inflow from adjacent uplands and surface and subsurface flows valley storage requirements during snowmelt are met by local meltwater infiltration but lateral inflows in the summer are needed to satisfy the storage before runoff can be generated from the valley the valleys perform three functions of collecting vertical and lateral water inputs retaining and losing the water held in storage and transferring water down the valley and generating local outflow unlike channel flows in humid areas runoff from the upper valley has to meet the storage demands of the lower valley segments often causing seepage loss along flow paths to render the flows intermittent a fill and spill runoff system is proposed in which the valley physiography results in a series of segments with varying storage conditions as water is supplied to the valley each segment has to be filled until its storage threshold for runoff is exceeded then subsurface or surface flows will be generated but these flows may be arrested to furnish water to satisfy the storage requirements of the segments downstream such a flow system applies also to other valleys in the shield environment

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

catchment properties function and conceptual model representation is there a correspondence this study investigates the possible correspondence between catchment structure as represented by perceptual hydrological models developed from fieldwork investigations and mathematical model structures selected on the basis of reproducing observed catchment hydrographs three luxembourgish headwater catchments are considered where previous fieldwork suggested distinct flow generating mechanisms and hydrological dynamics a set of lumped conceptual model structures are hypothesized and implemented using the superflex framework following parameter calibration the model performance is examined in terms of predictive accuracy quantification of uncertainty and the ability to reproduce the flow duration curve signature our key research question is whether differences in the performance of the conceptual model structures can be interpreted based on the dominant catchment processes suggested from fieldwork investigations for example we propose that the permeable bedrock and the presence of multiple aquifers in the huewelerbach catchment may explain the superior performance of model structures with storage elements connected in parallel conversely model structures with serial connections perform better in the weierbach and wollefsbach catchments which are characterized by impermeable bedrock and dominated by lateral flow the presence of threshold dynamics in the weierbach and wollefsbach catchments may favour nonlinear models while the smoother dynamics of the larger huewelerbach catchment were suitably reproduced by linear models it is also shown how hydrologically distinct processes can be effectively described by the same mathematical model components major research questions are reviewed including the correspondence between hydrological processes at different levels of scale and how best to synthesize the experimentalist s and modeller s perspectives copyright 2013 john wiley sons ltd

investigating the linkage between streamflow recession rates and channel network contraction in a mesoscale catchment in new york state the rate of recession dq dt in a given time interval has long been plotted in log log space against the concurrent mean discharge qavg recent interpretations of these dq dt qavg plots have sought to look at curves for individual events instead of the data cloud from all the data points together these individual recession curves have been observed to have near constant slope but to have varying intercepts features hypothesized to possibly be explained by the nature of the contraction of the active channel network during recession for a steep 150 ha forested catchment in central new york state with an 8 8 km channel network changes in the active channel network were mapped between april and november 2013 streamflow recession occurred in a matter of days but changes in the active channel network occurred over a matter of weeks thus in this catchment it does not appear that channel contraction directly controls recession additionally field observations indicate that dry down did not occur in a spatially organized sequential way such that the upper end of higher order streams dried first instead the location of groundwater seeps in part controlled the active portion of the channel network consistent with the presence of different types of flow contributing zones the paper presents a conceptual model that consists of multiple parallel reservoirs of varying drainage rate and varying degrees of recharge at different times of the year this conceptual model is able to reproduce a slope of 2 and a seasonal shift in intercept typical of individual recession curves copyright 2015 john wiley sons ltd

effect of climate change and mining on hydrological connectivity of surficial layers in the athabasca oil sands region this is the peer reviewed version of the following article kompanizare m petrone rm shafii m robinson dt rooney rc effect of climate change and mining on hydrological connectivity of surficial layers in the athabasca oil sands region hydrological processes 2018 32 3698 3716 https doi org 10 1002 hyp 13292 which has been published in final form at https doi org 10 1002 hyp 13292 this article may be used for non commercial purposes in accordance with wiley terms and conditions for use of self archived versions

threshold behavior in a fissured granitic catchment in southern china 2 modeling and uncertainty analysis 1 in general preferential flow occurring in forest catchments cannot be reasonably described using classical partial differential equations as a result linear or nonlinear reservoir models are widely used in hillslope and catchment hydrology currently few studies have simulated the hydrological threshold behavior that has been observed in many experimental catchments in this study five models with different structures were constructed using linear reservoir method to explore the inherent mechanisms of threshold behavior and to analyze the uncertainty of model structure in threshold simulations according to the model results the average bedrock depression storage over the study catchment 0 99 km2 which can be represented using the height of the lowest lateral outlet from the reservoir bottom h1 was 1 5 5 1 mm substantial movable water percolated into the fissure bedrock and was discharged into the streamflow as base flow after storm events illustrating why the slope of the linear relationships between the total event precipitation plus the antecedent soil moisture index p asi and the event quick flow depth above the rising threshold was less than one streamflow was simulated effectively by all five models with h1 0 or without h1 0 bedrock depression storage however different ratios of annual infiltration into bedrock to annual interflow discharged to the stream were obtained by models with h1 0 2 5 2 8 and h1 0 1 8 1 9 namely the calculated infiltration into bedrock was larger by models with h1 0 than that by models with h1 0 at the storm event scale the simulated total bedrock flow was larger than the interflow for models with h1 0 by a ratio of 1 0 7 whereas for models with h1 0 the ratio was 1 1 5

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

karst aquifer characterization using storm event analysis for black dragon springshed beijing china beijing is a megacity suffering from acute water shortage the characterization of karst aquifers in beijing s outlying districts is critical to inform sustainable policies and practices in groundwater development we captured spring hydrogeochemical dynamics during an intense storm event 721 storm by installing a data logger in the weir which presents an opportunity for defining and characterizing the recharging sources of discharge from black dragon bd springshed multivariate techniques including pca 2d hca heat map and piper diagram were used to characterize the waters and investigate their geochemical evolution the results in combination with hydrological evidence suggest bd spring was dominated by interaction with dolomite host limestone rock during dry season whereas it was fed by a second water supply dolomite aquifer during storm events the infiltration coefficients were calculated based on the water balance model and it was found that the 721 storm has resulted in less infiltration due to the high rainfall intensity we presented a novel methodology combining high frequency data sets and routine manual flow measurements with traditional geochemical sampling techniques this methodology appears to be very efficient at characterizing a karst aquifer and seems to be potentially applicable to other karst aquifers

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

scaling and physiographic controls on streamflow behaviour on the precambrian shield south central ontario summary relationships explaining streamflow behaviour in terms of drainage basin physiography greatly assist efforts to extrapolate streamflow metrics from gauged to ungauged basins in the same landscape the dorset environmental science centre desc has monitored streamflow from 22 small basins 3 4 190 5 ha on the precambrian shield in south central ontario in some cases since 1976 the basins exhibit regional coherence in their interannual response to precipitation however there is often a poor correlation between streamflow metrics from basins separated by as little as 1 km this study assesses whether inter basin variations in such metrics can be explained in terms of basin scale and physiography several characteristics annual maximum minimum and average flow exhibited simple scaling with basin area while magnitude range and timing of annual maximum daily runoff showed scaling behaviour consistent with the representative elementary area rea concept this rea behaviour is partly attributed to convergence of fractional coverage of the two dominant and hydrologically contrasting land cover types in the desc region with increasing basin size three principal components pcs explained 82 4 of the variation among basin physiographic properties and several runoff metrics magnitude and timing of annual minimum daily runoff mean number of days per year with 0 streamflow exhibited significant relationships with one or more pc significant relationships were obtained between basin quickflow qf production and the pcs on a seasonal and annual basis almost all of which were superior to simple area based relationships basin physiography influenced qf generation via its control on slope runoff water storage and hydrologic connectivity however this role was minimized during spring when qf production in response to large rain on snow events was relatively uniform across the desc basins the pc based relationships and inter seasonal changes in their form were consistent with previous research conducted at point slope and basin scales in the desc region and perceptions of key hydrological processes in these small basins may not have been as readily obtained from scaling studies using streamflow from larger basins this process understanding provides insights into scaling behaviour beyond those derived from simple scaling and rea analyses the physiography of the study area is representative of large portions of the precambrian shield such that basin streamflow behaviour could potentially be extended across much of south central ontario this would assist predictions of streamflow conditions at ungauged locations development and testing of hydrological models for this landscape and interpretation of inter basin and intra annual differences in hydrochemical behaviour on the southern precambrian shield

hillslope hydrology and wetland response of two small zero order boreal catchments on the precambrian shield two precambrian shield zero order catchments were monitored from january 2003 to july 2004 to characterize their hydrological and biogeochemical characteristics prior to a forest management experiment hydrometric observations were used to examine temporal trends in hillslope wetland connectivity and the hillslope runoff processes that control wetland event response the hillslope groundwater flux from the longer transect e1 was continuous throughout the study period groundwater fluxes from a shorter and steeper hillslope e0 were intermittent during the study period large depression storage elements termed micro basins located on the upper hillslope of the e1 catchment appeared to be at least partly responsible for the observed rapid wetland runoff responses these micro basins were hydrologically connected to a downslope wetland by a subsurface channel of glacial cobbles that functioned as a macropore channel during episodic runoff events the runoff response from the hilltop micro basins is controlled by antecedent water table position and water is quickly piped to the wetland fringe through the cobble channel during high water table conditions during periods of low water table position seepage along the bedrock soil interface from the hilltop micro basin and other hillslopes maintained hillslope wetland connectivity the micro basins create a dynamic variable source area runoff system where the contributing area expands downslope during episodic runoff events the micro basins occupied 30 of the e1 catchment and are a common feature on the precambrian shield copyright 2007 john wiley sons ltd

magma dynamics of 2007 stromboli effusive eruption as revealed by high precision location of seismic events stromboli is considered one of the most active volcanoes in the world and its persistent but moderate explosive activity is only interrupted by occasional episodes of more vigorous activity accompanied by lava flows a new effusive eruption began in late february 2007 and was characterized by intense seismic activity throughout the whole period the accurate seismic signals analysis showed the presence of families of events with similar waveform signatures i e multiplets located beneath the crater region since traditional location techniques do not allow obtaining reliable hypocenters our analysis focused on high precision locations of the seismicity in order to better define the source geometry of the events hypocenters therefore have been relocated considering two steps the first based on a robust probabilistic approach is used to find the absolute position of the clusters and the second exploits a master event concept for the relative location of the events finally the shape of the clusters and the temporal migration of the foci were correlated with the eruptive phases the results show that the occurrence of a cluster of events is related to the opening and closure of a vent opened in the sciara del fuoco slope and in particular to the intrusion of a dike injected by central conduit in a radial direction whereas another cluster lies in a narrow vertical volume positioned under the crater area the geometry of the clusters suggests a source region depicting the shallower feeding system overall the results highlight that the high precision locations method is an efficient and quick tool to obtain a better understanding of the magmatic processes occurring during an ongoing eruption

gypsies in the palace experimentalist s view on the use of 3 d physics based simulation of hillslope hydrological response as a fundamental unit of the landscape hillslopes are studied for their retention and release of water and nutrients across a wide range of ecosystems the understanding of these near surface processes is relevant to issues of runoff generation groundwater surface water interactions catchment export of nutrients dissolved organic carbon contaminants e g mercury and ultimately surface water health we develop a 3 d physics based representation of the panola mountain research watershed experimental hillslope using the tough2 sub surface flow and transport simulator a recent investigation of sub surface flow within this experimental hillslope has generated important knowledge of threshold rainfall runoff response and its relation to patterns of transient water table development this work has identified components of the 3 d sub surface such as bedrock topography that contribute to changing connectivity in saturated zones and the generation of sub surface stormflow here we test the ability of a 3 d hillslope model both calibrated and uncalibrated to simulate forested hillslope rainfall runoff response and internal transient sub surface stormflow dynamics we also provide a transparent illustration of physics based model development issues of parameterization examples of model rejection and usefulness of data types e g runoff mean soil moisture and transient water table depth to the model enterprise our simulations show the inability of an uncalibrated model based on laboratory and field characterization of soil properties and topography to successfully simulate the integrated hydrological response or the distributed water table within the soil profile although not an uncommon result the failure of the field based characterized model to represent system behaviour is an important challenge that continues to vex scientists at many scales we focus our attention particularly on examining the influence of bedrock permeability soil anisotropy and drainable porosity on the development of patterns of transient groundwater and sub surface flow internal dynamics of transient water table development prove to be essential in determining appropriate model parameterization copyright 2010 john wiley sons ltd

are all runoff processes the same copyright 2013 john wiley sons ltd introduction research on runoff processes to date has focused on the differences between the main divisions of runoff partitioning indeed our major advancements in runoff theory have come with new differentiations of different forms of overland flow and subsurface stormflow these studies of how runoff processes are different have resulted in our current summaries of runoff regimes conceptually e g the variable source area vsa concept and codified in our models e g topmodel and its derivatives such summaries are captured in iconic figures in textbooks that we teach new generations of hydrologists the most popular of which is shown in figure 1 from dunne 1983 and reproduced more recently in wagener et al 2007 and mirus and loague 2013 although such process differentiation was useful as new dominant forms of runoff were discovered in different climates with different soils slope morphologies and vegetation cover continued differentiation does not appear helpful for improved understanding of runoff dynamics and streamflow generation we seem to have exhausted the main list of runoff classes infiltration excess overland flow saturation excess overland flow and subsurface stormflow some decades ago with perhaps the last wave of minor updates to these processes coming in the 1980s and early 1990s in response to isotope tracing demonstration of the importance of stored water and clarification of differences between hydrologic and hydraulic time scales see reviews by bonell 1993 1998 and in bachmair and weiler 2011 in the spirit of sivapalan 2009 i wonder if it is more useful now to change our organizing question from how are runoff processes different to how are runoff processes similar in many ways i am simply building upon and restating what others have said in recent useful statements on the importance of boundary conditions and flux closures beven 2006 the need for new theory e g troch et al 2008 and new ways of considering runoff systems spence 2010 asking if all runoff processes are the same conceptually is a possible new way to come at runoff process research to aid improved process measurement understanding and prediction through new flexible model structural approaches similar to fenicia et al 2011 across diverse regions it opens up new research questions such as what can we learn about subsurface stormflow from overland flow and vice versa can we recognize things on the surface where boundary conditions are visible that may help guide new theory for the subsurface where such boundary controls are hidden here i present a simple analogical reasoning that shows how all runoff processes are similar this comes following the viewing of many dozens of hillslopes and catchment sites across the world for 25 years especially although i do note that pioneering work in the 1990s in deglaciated landscapes particularly in canada has shown new behaviours outside of these three classes largely linked to groundwater and wetland processes see branfireun and roulet 1998 peters et al 1995 and others