transient seepage model for saturated unsaturated soil systems a geotechnical engineering approach a two dimensional finite element model is proposed to simulate transient seepage for complex groundwater flow systems the complete soil system is treated as a continuum encompassing flow in both saturated and unsaturated zones in the unsaturated zone the air phase is assumed to be continuous and open to atmospheric pressure the coefficient of permeability of the unsaturated soil is assumed to be a function of pore water pressure the governing differential equation is derived within a framework familiar to geotechnical engineers the stress state variables and the constitutive relationships for an unsaturated soil are used in the derivation the finite element solution to the governing differential equation is based on the galerkin weighted residual method the nonlinearity of the equation is solved by iterative procedures the finite element formulation is implemented into a computer model named trasee the model can be applied to a wide variety of problems involving complex boundary conditions and geo

horizontal structures in granulite terrains a record of mountain building or mountain collapse in many high temperature 800 c granulite terrains the development of characteristic horizontal structures occurred during the metamorphic culmination and was followed by isobaric cooling the absolute magnitude of isobaric cooling commonly 300 c implies cooling intervals of the order of the thermal time constant of the continental lithosphere 100 m y such prolonged isobaric cooling implies that no significant erosional denudation followed the development of the horizontal structures and thus precludes the prograde deformation being responsible for significant crustal thickening rather the prograde deformation more probably records bulk crustal thinning during extensional collapse of a previously thickened crust possibly triggered by detachment of a thickened thermal boundary layer at the base of the lithosphere

parameterization of stream channel geometry in the distributed modeling of catchment dynamics a simple and efficient procedure for incorporating the effects of stream channel geometry in the distributed modeling of catchment dynamics is developed at a station and downstream fluvial relationships are combined and the obtained laws of variability in space and time for water surface width and wetted perimeter are incorporated into a diffusion wave routing model based on the muskingum cunge method with variable parameters the parameterization obtained is applied to the approximately 840 km 2 sieve catchment central italian apennines to test the possibility of estimating channel geometry parameters from cross section surveys and to assess the impact of dynamic variations in the channel geometry on catchment dynamics the use of the estimated channel geometry in surface runoff routing produces a significant improvement in the flood hydrograph description at the catchment outlet with respect to less detailed network parameterizations in addition the results obtained from a downstream analysis of the velocity field indicate that the stream characteristics related to the locally varying cross section shape may have a strong control on flow velocities and thus they should be monitored and synthesized for a comprehensive description of the distributed catchment dynamics

successive overprinting granulite facies metamorphic events in the anmatjira range central australia the anmatjira range and adjacent reynolds range central australia comprise early proterozoic metasediments and othogneisses that were affected by three and possibly four temporally distinct metamorphic events m1 4 and deformation events d1 4 in the period 1820 1590 ma the north western portion of the range around mt stafford preserves the effects of 1820 ma m1 d1 and shows a spectacular lateral transition from muscovite quartz bearing schists to interlayered andalusite bearing migmatites and two pyroxene granofelses that reflect extremely low pressure granulite facies conditions over a distance of less than 10 km orthopyroxene cordierite garnet k feldspar quartz bearing gneisses occur at the highest grade implying peak conditions of 750 c and 2 5 0 6 kbar an anticlockwise p t path for m1 is inferred from syn to late d1 sillimanite overprinting andalusite petrogenetic grid considerations and quantitative estimates of metamorphic conditions for inferred overprinting assemblages the effects of m1 have been variably overprinted to the south east by a c 1760 ma m2 d2 event much of the central anmatjira range around ingellina gap comprises orthogneiss deformed during d2 and metapelites that have m1 andalusite and k feldspar overprinted by m2 sillimanite and muscovite the south eastern portion of the range around mt weldon comprises metasediments and orthogneisses that were completely recrystallized during m2 d2 with metapelitic gneisses characterized by spinel sillimanite k feldspar quartz bearing assemblages that suggest peak m2 conditions of 750 c and 5 5 1 kbar overprinting parageneses in metapelitic gneisses imply that d2 occurred during essentially isobaric cooling a third granulite facies event m3 affected rocks in the reynolds range immediately to the south of the anmatjira range at c 1730 ma a possible fourth event m4 with a minimum age of c 1590 my affected both ranges but resulted in only minor overprinting of m1 3 assemblages the superimposed effects of m1 4 mapped for the entire anmatjira reynolds range area indicate that only minor or no dislocation of the regional geology occurred during any of the metamorphic and accompanying folding events although the immediate cause of each of the metamorphic events involved advection the ultimate causes were external to the metasediments and most probably external to the crust

a model for low pressure facies metamorphism during crustal thickening low pressure metamorphic facies i e high t p ratios are widespread in a wide range of tectonic settings explanations offered for the occurrence of these facies include extensional and or magmatic models however these fail to explain that the low p facies metamorphism is commonly coeval with a phase of pervasive crustal thickening with t p ratios increasing during or slightly lagging behind the thickening we propose an alternative explanation based on the approximate synchroneity of crustal thickening and erosion thinning of the mantle lithosphere

pressures and temperatures in precambrian metamorphic rocks modelp t estimates from nearly 100 precambrian rocks have been derived by comparing published descriptions of metamorphic mineral assemblages to a standard set of mineral stability data pressures temperatures and metamorphic geotherms show large variations nevertheless modelp t data reveal two distinct secular trends average metamorphic geotherms have declined through time and average metamorphic pressures have increased through time metamorphic geotherms and pressures from archean rocks average 54 c km and 4 1 kbar respectively corresponding figures for early proterozoic terranes are 47 c km and 4 3 kbar and for late proterozoic terranes 35 c km and 6 kbar these secular trends may reflect gradual cooling and thickening of the earth s crust at least in orogenic belts there are exceptions to both trends found in localities where mineral assemblages indicate high pressures 6 12 kbar and low metamorphic geotherms 20 30 c km these assemblages formed in archean crust that at least locally was thicker than 20 km during metamorphism

on the implementation of the surface conductance approach using a block centred surface subsurface hydrology model summary in physically based catchment hydrology models dynamic surface subsurface interactions are often represented using the surface conductance sc coupling approach guidance on sc parameterisation within block centred codes is limited and common practice is to express the sc coefficient as the quotient of the vertical saturated hydraulic conductivity and the half cell thickness of the uppermost layer this study evaluates the implementation of the sc approach utilising a popular block centred surface subsurface hydrology model modhms to simulate one dimensional infiltration experiments under hortonian conditions results show that defining the sc coefficient based on a half cell thickness of the uppermost subsurface cell inhibits accurate prediction of infiltration rates q e and the time to initiate surface runoff t ro for the adopted rainfall runoff scenario increasing the sc coefficient independently of the grid allows for accurate simulation of q e but not t ro the addition of a thin layer at the surface is shown to improve model accuracy substantially such that q e and t ro approach those obtained using an equivalent mesh centred model i e where the surface and upper subsurface nodes are coincident whilst the addition of a single thin layer in block centred codes allows improved prediction of surface subsurface interaction it does not provide a surrogate for fine discretisation throughout the subsurface that is necessary for accurate simulation of unsaturated zone flow this study offers guidance on the implementation of the sc approach in a block centred code and demonstrates the importance of systematic testing of parameters that are otherwise calibrated in physically based surface subsurface hydrology models

mechanisms of crustal deformation thirty sixthwilliam smith lecture the energy source for crustal deformation is isotopic heating and secular cooling of the mantle in a true solid heat would be lost to the surface by conduction however solid state creep processes allow the earth s solid mantle to exhibit a fluid behaviour thus thermal convection can convert heating into directed motion variations in temperature lead to variations in densitythrough thermal expansion and contraction although the resultant body forces are vertical horizontal variations in temperature lead to horizontal body forces at an ocean ridge the variations in the thickness of the lithosphere lead to the elevation of the ridge the result is a substantial horizontal ridge push force this force along with the trench pull force on the descending lithosphere is the primary force driving plate tectonics lithospheric thinning must occur beneath continental rifts and plateau uplifts i suggest that lithospheric thinning is caused by the diapiric penetration of hot asthenospheric rock to the crust mantle boundary this penetration may also cause lithospheric stoping and plateau uplifts lithospheric thinning leads to large tensional stresses above the zone of thinning these forces are generally much larger than the compressional forces generated by crustal thinning the forces generated by lithospheric thinning are quite large and may be responsible for the propagation of continental rifts in island arcs and andean type orogenic belts both lithospheric thinning and crustal thickening result in large tensional forces probably the most complex zone of crustal deformation is the continental collision variations in types of continental collisions are discussed

proterozoic granulite facies metamorphism in the southeastern reynolds range central australia geological context p t path and overprinting relationships in the southeastern reynolds range central australia a low p granulite facies metamorphism affected two sedimentary sequences the lander rock beds and the reynolds range group in the context of the whole of the reynolds range and the adjacent anmatjira range this metamorphism is m3 in a sequence m1 4 that occurred over a period of 250 ma in particular m1 affected the lander rock beds prior to the deposition of the reynolds group m3 has an areally restricted high grade area in the southeastern reynolds range affecting both the reynolds range group and the underlying lander rock beds the effects of m3 are characterized by spinel quartz bearing peak metamorphic assemblages in metapelites which imply peak conditions of 750 c and 4 5 1 kbar and involved isobaric cooling or compression with cooling it is concluded that one of a series of thermal perturbations caused by thinning of mantle lithosphere contemporaneous with crustal thickening was responsible for m3 in the southeastern reynolds range evidence of both the unconformity between the two rock groups and previous metamorphism deformation has been completely erased by recrystallization during m3 d3

the importance of hydraulic groundwater theory in catchment hydrology the legacy of wilfried brutsaert and jean yves parlange based on a literature overview this paper summarizes the impact and legacy of the contributions of wilfried brutsaert and jean yves parlange cornell university with respect to the current state of the art understanding in hydraulic groundwater theory forming the basis of many applications in catchment hydrology ranging from drought flow analysis to surface water groundwater interactions hydraulic groundwater theory simplifies the description of water flow in unconfined riparian and perched aquifers through assumptions attributed to dupuit and forchheimer boussinesq 1877 derived a general equation to study flow dynamics of unconfined aquifers in uniformly sloping hillslopes resulting in a remarkably accurate and applicable family of results though often challenging to solve due to its nonlinear form under certain conditions the boussinesq equation can be solved analytically allowing compact representation of soil and geomorphological controls on unconfined aquifer storage and release dynamics the boussinesq equation has been extended to account for flow divergence convergence as well as for nonuniform bedrock slope concave convex the extended boussinesq equation has been favorably compared to numerical solutions of the three dimensional richards equation confirming its validity under certain geometric conditions analytical solutions of the linearized original and extended boussinesq equations led to the formulation of similarity indices for baseflow recession analysis including scaling rules to predict the moments of baseflow response validation of theoretical recession parameters on real world streamflow data is complicated due to limited measurement accuracy changing boundary conditions and the strong coupling between the saturated aquifer with the overlying unsaturated zone however recent advances are shown to have mitigated several of these issues the extended boussinesq equation has been successfully applied to represent baseflow dynamics in catchment scale hydrological models and it is currently considered to represent lateral redistribution of groundwater in land surface schemes applied in global circulation models from the review it is clear that wilfried brutsaert and jean yves parlange stimulated a body of research that has led to several fundamental discoveries and practical applications with important contributions in hydrological modeling

the origins of granulites a metamorphic perspective although many recent reviews emphasize a uniformity in granulite pressure temperature p t conditions and paths granulites in reality preserve a spectrum of important petrogenetic features which indicate diversity in their modes of formation a thorough survey of over 90 granulite terranes or occurrences reveals that over 50 of them record p t conditions outside the 7 5 1 kbar and 800 50 c average granulite regime preferred by many authors in particular an increasing number of very high temperature 900 1000 c terranes are being recognized both on the basis of distinctive mineral assemblages and geothermobarometry petrogenetic grid and geothermobarometric approaches to the determination and interpretation of p t histories are both evaluated within the context of reaction textures to demonstrate that the large range in p t conditions is indeed real and that both near isothermal decompression itd and near isobaric cooling ibc p t paths are important amphibolite granulite transitions promoted by the passage of co 2 rich fluids as observed in southern india and sri lanka are exceptional and not representative of fluid related processes in the majority of terranes it is considered on the contrary that fluid absent conditions are typical of most granulites at or near the time of their recorded thermal maxima itd granulites are interpreted to have formed in crust thickened by collision with magmatic additions being an important extra heat source erosion alone is not however considered to be the dominant post collisional thinning process instead the itd paths are generated during more rapid thinning 1 2 mm yr exposure related to tectonic exhumation during moderate rate or waning extension ibc granulites may have formed in a variety of settings those which show anticlockwise p t histories are interpreted to have formed in and beneath areas of voluminous magmatic accretion with or without additional crustal extension ibc granulites at shallow levels very rapid 5 mm yr extensional thinning subsequent to collision it is suggested that the preservation of ibc paths rather than itd paths in many granulites is primarily related to the rate and timescale of extensional thinning of thickened crust and that hybrid itd to ibc paths should also be observed most ibc granulites and probably many itd granulites have not been exposed at the earth s surface as a result of the tectonic episodes which produced them but have resided in the middle and lower crust for long periods of time 100 2000 ma following these events the eventual exhumation of most granulite terranes only occur through their incorporation in later tectonic and magmatic events unrelated to their formation

a seepage face model for the interaction of shallow water tables with the ground surface application of the obstacle type method this paper presents a model to simulate overland flow genesis induced by shallow water table movements in hillslopes variably saturated subsurface flows are governed by the richards equation discretized by continuous finite elements on unstructured meshes an obstacle type formulation is used to determine where saturation conditions and thus seepage face conditions are met at the ground surface the impact of hillslope geometry boundary conditions and soil hydraulic parameters on model predictions is investigated on two dimensional test cases at the metric and hectometric scales the obstacle type formulation is also compared with a more detailed model coupling subsurface and overland flow the latter being described by the shallow water equations in the diffusive wave regime

the synchronism of crustal thickening and low pressure facies metamorphism in the mount isa inlier australia 2 fast convective thinning of mantle lithosphere during crustal thickening the mount isa inlier is like some other northern australian early to middle proterozoic fold belts characterized by an anti clockwise p t t path i e regional prograde low p facies metamorphic assemblages grew during crustal thickening p t and were overprinted by a phase of essentially isobaric cooling p 0 t in this study two possible models for the synchronism of regional low p facies metamorphism and crustal thickening are quantitatively evaluated using a one dimensional finite difference technique 1 extreme elevation of isotherms immediately before the thickening event due to e g lithospheric extension magmatic activity or crust mantle delamination and 2 crustal thickening accompanied by convective thinning of the mantle lithosphere only the latter results in prograde low p facies metamorphism during crustal thickening it is the preferred model for the mount isa inlier

brittle frictional mountain building 3 low grade metamorphism an active fold and thrust belt in unchanging tectonic and climatic conditions exhibits a dynamic steady state with the flux of rocks accreted at the toe balanced by the flux of rocks eroded off the top rocks entering the toe are buried and heated before they are uplifted and eroded this results in a characteristic map pattern of low grade metamorphism on the surface metamorphic isograds are generally parallel to the regional strike of a fold and thrust belt with the grade increasing progressively from unmetamorphosed and zeolite facies near the deformation front up to greenschist facies in the highest mountains such a pattern is observed in the active fold and thrust belt of taiwan this paper examines the origin of this low grade syntectonic metamorphism using a previously developed mechanical and thermal model of a steady state fold and thrust belt as a basis to model the metamorphism we develop a petrogenetic grid for rocks of basaltic composition considering phases within the chemical system cao mgo al2o3 sio2 h2o equilibria diagnostic of stable low grade mineral assemblages are mapped onto a cross section of the taiwan fold and thrust belt using the calculated fluid pressure and temperature distributions within the wedge the variation of metamorphic grade along the surface is predicted by assuming that there is no retrograde metamorphism the most important mechanical factor controlling the degree of metamorphism in an active fold and thrust belt is the amount of frictional heating both on the basal decollement fault and within the deforming brittle wedge frictional heating raises temperatures in the deepest portions of the taiwan fold and thrust belt by 200 c to 250 c the resulting high temperatures in excess of 400 c are responsible for the extensive greenschist facies metamorphism the amount of heating is well constrained by the observed heat flow anomaly geochronological data and the critical wedge taper the best fitting coefficient of basal friction in taiwan is b 0 5 0 2 underplating of footwall rocks by the assimilation of duplexes along the decollement fault is not considered to be a significant process in taiwan because of the observed balance between the accretionary influx at the toe and the erosive efflux off the top in other fold and thrust belts however underplating can significantly increase the outcrop width of higher metamorphic grades on the surface by increasing the flux of rocks through the higher fluid pressure and temperature regions within the wedge

hydrodynamics of a large oil sand tailings impoundment and related environmental implications oil sand mine tailings are primarily contained by dykes constructed of permeable sand tailings the environmental impacts of process waters released from these tailings facilities are controlled by

saturated area formation on nonconvergent hillslope topography with shallow soils a numerical investigation prediction of saturated area formation is important for hydrologic modeling of watersheds with shallow highly pervious soils this simulation study examines the relative importance of hillslope properties and rainfall rate on the evolution of saturated source areas during wetting the study focuses on homogeneous nonconvergent hillslope topography with constant slope the two dimensional variably saturated groundwater model vs2d healy 1990 lappala et al 1993 is used to simulate saturated area formation under the action of steady uniform rainfall the study methodology systematically varies four hillslope properties depth to impervious layer slope length slope angle and average saturated hydraulic conductivity and the rainfall rate results indicate that the fraction of the hillslope length that is saturated at equilibrium is a function of a parameter which is defined as the rainfall rate multiplied by the slope length divided by the slope angle soil thickness and saturated hydraulic conductivity the temporal evolution of saturated area is analyzed in terms of the equilibrium time nonlinearity in the unsaturated zone and differences in hillslope properties result in a nonunique time to equilibrium relation the time to equilibrium is maximum when factors that tend to cause surface saturation are in approximate balance with those that tend to dissipate surface saturation the temporal evolution of surface saturation during wetting follows a wide variety of trajectories equivalent hillslope soil water storage ratios on slopes with different properties can result in a wide range of surface saturation conditions hillslopes with shallower soils and smaller slope angles are most susceptible to saturated area formation however sudden changes in surface saturation are possible on steep hillslopes when 1 6

low pressure granulite facies metapelitic assemblages and corona textures from macrobertson land east antarctica the importance of fe2o3and tio2in accounting for spinel bearing assemblages low pressure granulite facies metasedimentary gneisses exposed in macrobertson land east antarctica include hercynitic spinel bearing metapelitic gneisses peak metamorphic mineral assemblages include spinel rutile ilmenite sillimanite garnet spinel ilmenite sillimanite garnet cordierite ortho pyroxene magnetite ilmenite garnet spinel cordierite biotite ilmenite and orthopyroxene cordierite biotite each with quartz k feldspar and melt the presence of garnet biotite and cordierite orthopyroxene bearing assemblages implies crossing tie lines in afm projection for the k2o feo mgo al2o3 sio2 h2o kfmash system this apparent contradiction and the presence of spinel rutile and ilmenite in the assemblages is acounted for by using the kfmash tio2 o2 system i e afm tio2 fe2o3 we derive a petrogenetic grid for this system applicable to low pressure granulite facies metamorphic conditions retrograde assemblages are interpreted from corona textures on hercynitic spinel and fe ti oxides the relative positions of the peak and retrograde metamorphic assemblages on the petrogenetic grid suggest that corona development occurred during essentially isobaric cooling

some remarks on high temperature low pressure metamorphism in convergent orogens many high temperature low pressure high t low p metamorphic terranes show evidence for peak mineral growth during crustal thickening strain increments at pressures near the maximum attained during the heating cooling cycle such terranes are not readily explained as the conductive response to crustal thickening since the resulting moho temperatures would greatly exceed the crustal liquidus and because heating due to conductive equilibration on length scales appropriate to lithospheric scale strains must greatly outlast the deformation consequently high t low p metamorphism may be generated during crustal thickening only when significant heat is advected within the crust as for example may occur during the segregation of granitic melts we show that without the addition of asthenospheric melts and at strain rates appropriate to continental deformation the conditions required for significant lower crustal melting during deformation are only likely to be attained if heat flow into the lower crust during crustal thickening is increased substantially for example by removing the mantle part of the lithosphere a simple parameterization of lithospheric deformation involving the vertical strain on the scale of the crust c and the lithosphere 1 respectively allows the potential energy of the evolving orogen to be readily evaluated using this parameterization we show that an important isostatic consequence of the deformation geometries capable of generating such high t low p metamorphism during crustal thickening with c1 is an imposed upper limit to crustal thicknesses which is much lower than for homogeneous deformations fc f1 for the same initial lithospheric configuration

multiple seepage faces on layered slopes and their implications for slope stability analysis this study provides an analysis of the water table configuration and pore pressure distribution in layered hillsides a finite element model was used to simulate two dimensional saturated unsaturated steady state flow through layered slopes a laboratory sand tank experiment was used to verify the physical foundation of the mathematical model it is shown that layered slopes feature multiple seepage faces perched water tables and wedge shaped unsaturated zones the pore pressure distribution and the distribution of multiple seepage faces are strongly dependent on the position of the impeding layers and their hydraulic properties predictions of pore pressure fields based on homogeneous saturated analyses may be significantly in error when applied to problems on layered slopes slope stability analyses on layered slopes that do not take into account the presence of unsaturated wedges beneath the impeding layers can lead to overdesign of the stable slope angle key words groundwater conditions unsatu

predicting reservoir scale faults with area balance application to growth stratigraphy a reservoir that appears to lack faults at one scale of resolution or at one sampling density may nevertheless contain faults that are below the resolution of the observations the area depth relationship from a balanced cross section is shown to contain the necessary information for predicting the sub resolution fault heave existing area depth theory is extended to include growth units allowing structural length and thickness changes to be separated from the depositional changes the technique is validated with a numerical model of a growth full graben and a sand box model of a half graben then field tested in the gilbertown graben a growth structure within the regional peripheral fault trend along the northern margin of the gulf of mexico a cross section developed from wells alone is used to infer the abundance of sub resolution faults by the area balance technique a small but significant amount of sub resolution extension is predicted and then confirmed with a highresolution seismic line q 2003 elsevier science ltd all rights reserved

metamorphic evolution of the bunger hills east antarctica evidence for substantial post metamorphic peak compression with minimal cooling in a proterozoic orogenic event the bunger hills east antarctica experienced a low pressure granulite facies orogenic event during the proterozoic the stable coexistence of the s1 foliation parallel m1 assemblages garnet cordierite spinel ilmenite and garnet sillimanite spinel ilmenite rutile in quartz bearing pelitic gneisses is evidence for metamorphic peak pressures of around 4 kbar during m1 at temperatures of about 800 c the growth of massive reaction coronas of garnet and cordierite around hercynitic spinel and iron titanium oxides during m2 is evidence for the destabilization of the m1 assemblages during compression thermodynamic calculations on the m2 assemblages indicate formation pressures of 6 7 kbar at temperatures of about 750 c thus the gneisses from the bunger hills indicate about 2 kbar or more of compression during minimal cooling such a p t path is different from that of many other proterozoic terranes which are characterized by isobaric cooling or decompression a large charnockite body which is undeformed was intruded at 950 c towards the end of compression the low pressures during m1 can be best explained by metamorphism at mid crustal levels in thin continental crust in thin lithosphere above a thermal perturbation in the underlying asthenosphere we suggest that the compression during cooling was a result of gravitational backflow in which the action of body forces between adjacent normal thickness crust and the thin crust of the bunger hills is switched on by the thermal perturbation within such a model the timing of intrusion of the charnockite exposed in the bunger hills is consistent with its generation by partial melting during the metamorphic maximum of the lowermost crust

structural constraints on the proterozoic reworking of archaean crust in the rayner complex macrobertson and kemp land coast east antarctica abstract the high grade metamorphic rocks exposed along the macrobertson and east kemp land coasts consist of in the west archaean gneisses reworked during a ductile mid proterozoic deformation and in the east foliated proterozoic charnockite gneiss containing large remnants of gneiss of probable archaean age evidence for three folding events is recognized in the reworked gneisses an early recumbent terrain is deformed by two upright events possessing near vertical axial surfaces the charnockite gneiss preserves evidence of only the final event these three events comprise the rayner structural episode which was a consequence of the ductile thrusting of archaean gneiss westward toward a stable archaean block the napier complex kinematic indicators are consistent with formation of the proterozoic recumbent terrain by dominantly shear deformation dissection of both the rayner and napier complexes by retrograde shear zones and mylonite pseudotachylite zones was a consequence of the northward thrusting of the two complexes during the cambrian

a numerical procedure for unsaturated seepage analysis in rock mass containing fracture networks and drainage holes abstract it is computationally difficult to model unsaturated flow through a highly fractured rock system that contains porous rock matrix densely distributed fracture networks and narrowly spaced drainage holes we present an efficient numerical procedure that uses a three dimensional finite element model to solve richards equation with embedded zero thickness elements for fractures and line elements for drainage holes a mixed boundary condition is applied at potential seepage surfaces and a water retention relation with extremely narrow unsaturated zone is specified to precisely locate the phreatic surface the procedure compares favorably with results from other numerical solutions and experimental data a case study is developed to evaluate seepage through a densely fractured rock slope the simulated results demonstrate that fractures disorder the hydraulic potential distribution with fracture patterns acting as significant influential factors and drainage holes dramatically lower the phreatic surface due to the effects of drainage and depressurization the proposed numerical procedure shows to be capable of investigating the unsaturated flow in highly fractured rock mass

the development of multiple seepage faces on layered slopes this study provides an analysis of the water table configuration and hydraulic head distribution in layered hillsides a finite element model was used to simulate two dimensional saturated unsaturated steady state flow through layered slopes a laboratory sand tank experiment was used to verify the physical foundation of the mathematical model it is shown that layered slopes feature multiple seepage faces perched water tables and wedge shaped unsaturated zones the hydraulic head distribution and water table configuration are strongly dependent on the position of the impending layers and the ratio of the hydraulic conductivity between adjacent layers this work has geotechnical implications with regard to slope stability and the control of groundwater inflows into excavations it has hydrogeological implications with regard to flow path analysis in contamination studies it has geomorphological implications with respect to landform development by mass movements and surface water erosions and to drainage network development through piping

instability caused by a seepage impediment in layered fill slopes the underlying cause of loose fill slope failures in hong kong has been attributed to static liquefaction during heavy rainfall a series of centrifuge model tests and numerical analyses were condu

surface subsurface flow modeling with path based runoff routing boundary condition based coupling and assimilation of multisource observation data received 21 october 2008 revised 2 september 2009 accepted 16 september 2009 published 13 february 2010 1 a distributed physically based model incorporating novel approaches for the representation of surface subsurface processes and interactions is presented a path based description of surface flow across the drainage basin is used with several options for identifying flow directions for separating channel cells from hillslope cells and for representing stream channel hydraulic geometry lakes and other topographic depressions are identified and specially treated as part of the preprocessing procedures applied to the digital elevation data for the catchment threshold based boundary condition switching is used to partition potential atmospheric fluxes into actual fluxes across the land surface and changes in surface storage thus resolving the exchange fluxes or coupling between the surface and subsurface modules nested time stepping allows smaller steps to be taken for typically faster and explicitly solved surface runoff routing while a mesh coarsening option allows larger grid elements to be used for typically slower and more compute intensive subsurface flow sequential data assimilation schemes allow the model predictions to be updated with spatiotemporal observation data of surface and subsurface variables these approaches are discussed in detail and the physical and numerical behavior of the model is illustrated over catchment scales ranging from 0 0027 to 356 km 2 addressing different hydrological processes and highlighting the importance of describing coupled surfacesubsurface flow

the metamorphic evolution of granulites at fyfe hills implications for archaean crustal thickness in enderby land antarctica granulites at fyfe hills in enderby land antarctica crystallized at temperatures in excess of 850 c and possibly as high as 1000 c and at pressures of 8 10kbar during the mid to late archaean a number of features including repeated retrograde metamorphism at 5 5 8kbar retrograde reaction textures and rimward zoning in pressure sensitive systems suggest that following peak metamorphism the granulites stabilized at a depth of 18 26 km after stabilization the granulites cooled near isobarically to temperatures of 600 700 c assuming a total crustal thickness of 35 40 km during this late archaean interval of isobaric cooling the peak metamorphic crustal thickness is estimated at 35 56 km this estimate is significantly less than the 60 70 km obtained by summing the depths of the present levels of exposure 26 34 km and the thickness of the crust presently beneath fyfe hills approxi mately 35km and is therefore consistent with independent evidence for extensive post archaean thickening of the enderby land crust

examination of the seepage face boundary condition in subsurface and coupled surface subsurface hydrological models a seepage face is a nonlinear dynamic boundary that strongly affects pressure head distributions water table fluctuations and flow patterns its handling in hydrological models especially under complex conditions such as heterogeneity and coupled surface subsurface flow has not been extensively studied in this paper we compare the treatment of the seepage face as a static dirichlet versus dynamic boundary condition we assess its resolution under conditions of layered heterogeneity we examine its interaction with a catchment outlet boundary and we investigate the effects of surface subsurface exchanges on seepage faces forming at the land surface the analyses are carried out with an integrated catchment hydrological model numerical simulations are performed for a synthetic rectangular sloping aquifer and for an experimental hillslope from the landscape evolution observatory the results show that the static boundary condition is not always an adequate stand in for a dynamic seepage face boundary condition especially under conditions of high rainfall steep slope or heterogeneity that hillslopes with layered heterogeneity give rise to multiple seepage faces that can be highly dynamic that seepage face and outlet boundaries can coexist in an integrated hydrological model and both play an important role and that seepage faces at the land surface are not always controlled by subsurface flow the paper also presents a generalized algorithm for resolving seepage face outflow that handles heterogeneity in a simple way is applicable to unstructured grids and is shown experimentally to be equivalent to the treatment of atmospheric boundary conditions in subsurface flow models

cretaceous crustal structure and metamorphism in the hinterland of the sevier thrust belt western u s cordillera combined structural and geochronologic studies to the west of the sevier belt at lat 39 degree 40 degree n indicate that peak metamorphism of the upper 15 km of crust occurred during the late cretaceous 70 90 ma overlapping in time with the intrusion of muscovite bearing granites and pegmatites metamorphism was accompanied by penetrative deformation top to the east layer parallel shear both were localized at the currently exposed structural levels resulting in impressive vertical and lateral strain gradients and t sub max gradients of 50 c km inception of thrust faulting in the sevier belt may have predated peak metamorphism and intrusion of granites in the hinterland by 10 15 m y but it continued during and ended simultaneously with the end of metamorphism at about 70 ma the rise of muscovite bearing granites and hot fluids generated by metamorphism and crustal anatexis at greater depth provides and explanation for the observed localized metamorphism and deformation at relatively high structural levels

evidence of an emerging levee failure mechanism causing disastrous floods in italy a levee failure occurred along the secchia river northern italy on 19 january 2014 resulting in flood damage in excess of 500 million in response to this failure immediate surveillance of other levees in the region led to the identification of a second breach developing on the neighboring panaro river where rapid mitigation efforts were successful in averting a full levee failure the paired breach events that occurred along the secchia and panaro rivers provided an excellent window on an emerging levee failure mechanism in the secchia river by combining the information content of photographs taken from helicopters in the early stage of breach development and 10 cm resolution aerial photographs taken in 2010 and 2012 animal burrows were found to exist in the precise levee location where the breach originated in the panaro river internal erosion was observed to occur at a location where a crested porcupine den was known to exist and this erosion led to the collapse of the levee top this paper uses detailed numerical modeling of rainfall river flow and variably saturated flow in the levee to explore the hydraulic and geotechnical mechanisms that were triggered along the secchia and panaro rivers by activities of burrowing animals leading to levee failures as habitats become more fragmented and constrained along river corridors it is possible that this failure mechanism could become more prevalent and therefore will demand greater attention in both the design and maintenance of earthen hydraulic structures as well as in wildlife management

on slope instability induced by seepage erosion this paper is focused on seepage erosion causing liquefaction processes and rapid slope failures one case history which occurred along an old fluvial terrace in the po plain northern italy is