sediment transport predictions for the english channel using numerical models output from an hydrodynanmic numerical model salomon breton 1991 a b has been combined with various empirical formulae to derive sediment transport rates and directions the predictions are compared with radioactive sand tracer experiments demonstrating the applicability of gadd et al s 1978 expression the derived bedload transport pattern for the area is consistent with sedimentological and geomorphological evidence but provides improved resolution a bedload parting zone is identified for the central english channel this is well defined for sand movement but seabed material present over this area gravel is not predicted to move significantly the area is non erosive over which fine grained sediments are being transported a bedload convergence is located to the southwest of the dover strait not in the strait itself as proposed previously a transport pathway bypassing the convergence along the french coastline which is supported by radioactive tracer experiments could be responsible for sand transfer from the english channel to the southern north sea

polynomial and power functions for glacial valley cross section morphology an empirical evaluation of glacial trough cross section shape is performed on seven vertical cross sections in three sierra nevada valleys glaciated during the late quaternary power and second order polynomial functions are fitted by statistical regression power functions are very sensitive to subtle valley bottom topographic features and require precise specification of the valley bottom centre location this dependency is problematic given under representation of valley bottoms by conventional contour sampling methods and the common alteration of valley bottom morphology by non glacial processes power function exponents vary greatly in response to these and other non genetic factors and are not found to be reliable indicators of overall valley morphology second order polynomials express overall valley shape in a single robust function they are applied to both bedrock and sediment floored glacial valleys with negligible statistical bias except where side slopes are stepped or convex upward or where valley form is asymmetrical they can describe alluviated or severely eroded valleys and can objectively identify indi vidual components of polymorphic valleys because valley bottom and centre locations need not be specified mathematical expressions of parameters useful for geomorphic measurements and glaciological modelling are analytically derived from the polynomials as functions of the three polynomial coefficients these parameter equations provide estimates of valley side slopes mean and maximum depth midpoint location width area boundary length form ratio and symmetry

valley formation by fluvial and glacial erosion cross valley profiles from the west slope of the olympic peninsula washington are used to investigate the relative effects of fluvial and glacial erosion on valley formation unlike most ranges where glaciers and rivers sequentially occupied the same valleys neighboring valleys in the olympic mountains developed in similar lithologies but were subject to different degrees of glaciation allowing comparison of the net effect of glacial and fluvial processes integrated over many glacial cycles upslope drainage area was used to normalize comparisons of valley width ridge crest to valley bottom relief and valley cross sectional area as measures of net differences in the mass of rock excavated from below ridgelines for 131 valley spanning transects valley width relief and cross sectional areas are similar for glaciated partly glaciated and unglaciated fluvial valleys with drainage areas of 10 km 2 but diverge downslope glaciated valleys draining 50 km 2 reach two to four times the cross sectional area and have to 500 m greater relief than comparable fluvial valleys partly glaciated valleys have intermediate dimensions at distances of 5 km from valley heads the cumulative upstream volume of rock removed to form valleys is two to four times greater in glacially incised valleys than in fluvial valleys the finding of strong differences in the net result of valley excavation by fluvial and glacial erosion supports the interpretation that alpine glaciers are more effective erosional agents than are rivers and implies that large alpine valleys deepened and enlarged in response to pleistocene glaciation

natural and man induced stress evolution of slopes the monte mario hill in rome the paper deals with stress release effects induced by man made cuts or excavations into natural stiff clay slopes that experienced erosion in response to valley deepening the study was focused on the monte mario hill in rome italy which formed part of an area of recent urban expansion the methodology of the study relied on a reference engineering geology model which was developed on the basis of site and laboratory data and stress strain analyses the latter analyses were carried out with the finite difference code flac 4 0 numerical modelling was based on a sequential approach taking into account the main evolutionary stages of the tiber river valley in rome 9s urban area and then making cuts at the bottom of the slope located south of the monte mario astronomical observatory the simulation revealed the stress release effects that fluvial erosion and excavation fronts have caused on the investigated slopes and their consequent gravitational instabilities these processes appear with metre scale displacements followed by stress release cracks actually observed on the slopes under review in quantifying stress release deformations the simulation took into account the possible role of creep in the observed retardation of stress release effects

residual sediment transport paths on a tidal sand bank a comparison between the modified mclaren model and bedform analysis abstract in order to evaluate the validity of the modified mclaren model for sand transport on a tidal sand bank 42 grab samples taken from the northern part of the kwintebank were decalcified sieved and analyzed for statistical parameters the areal distribution of mean grain size standard deviation and skewness were defined and used to determine the residual transport directions the grain size trends taken into consideration were that the sediment becomes finer better sorted and more negatively skewed along the transport pathways f b and the sediment becomes coarser better sorted and more positively skewed along the transport pathways c b these were compared with the transport paths inferred from bedform asymmetries obtained by side scan sonar records there were major differences between the sediment transport paths resulting from the two techniques when the f b trend and small dune asymmetries are compared only 5 out of 24 cases showed agreement 30 whereas in 9 cases the trends were 180 30 different there was even less agreement between the c b trend and the asymmetry of the small dunes only 1 out of 24 cases agreed 30 and almost half of the cases were 90 30 different the sediment transport directions deduced from the morphological analysis of the large dunes all point in the direction of the peak flood current the large dunes seem to be more suitable indicators of the sediment transport paths than the small ones however they conflict with the vectors resulting from the f b trend only one out of 20 cases agrees 30 while in 13 cases the vectors are 180 30 different and in three cases 90 30 neither do the transport directions from the c b trend agree with those deduced from the large dunes only one case agrees 30 while in four out of 20 cases the vectors point in opposite directions in four cases the vectors are 90 30 different the asymmetric cross section of the sand bank suggests sediment transport in a northwest direction it does not seem probable however that sediment transport occurs by migration of the whole sand bank the transport directions inferred from the bank morphology are quite different from the f b trend in 12 out of 42 cases the vectors agree 30 in four cases the vectors point in opposite directions and in 15 cases they are 90 30 different there is slightly more agreement between the c b trend and the transport directions deduced from the sand bank 16 out of 42 cases agree 30 in nine cases the vectors point in opposite directions and three cases are 90 30 different from this study it seems that the residual sediment transport directions can best be deduced from the morphological characteristics of the large dunes the departures between the results of the sediment trend analysis according to the modified mclaren model and the morphology of the subaqueous bedforms are partly explained by the location of the study area near the edge of the sand bank probably better results of the sediment trend analysis would be obtained if samples over the whole length of the sand bank were analyzed and compared perhaps a smaller spacing between the samples would improve the results as well and maybe the samples should not have been decalcified possibly the different transport patterns are attributed to different sediment transport processes which makes a comparison virtually impossible

classification of the australian continental shelf based on predicted sediment threshold exceedance from tidal currents and swell waves abstract estimates of significant wave height and period together with tidal current speed over a semi lunar cycle were used to predict the area on the australian continental shelf over which unconsolidated sediment was mobilised threshold exceedance these sediment entraining processes were examined independently to quantify their relative importance on the continental shelf using observed grain size data mobilisation from swell waves occurred on 31 and tidal currents on 41 of the continental shelf swell wave energy is sufficient to mobilise fine sand 0 1 mm diameter to a water depth of 142 m on the otway shelf near the western entrance to bass strait tidal currents in king sound northwest shelf are capable of mobilising large areas of medium sand 0 35 mm diameter 100 of the time superimposing the distribution of threshold exceedance by wave and tidal currents indicates that there are areas on the shelf where either wave induced or tidal currents dominate some areas where waves and tides are of relatively equal importance and still other areas where neither is significant we define six shelf regions of relative wave and tidal energy zero no mobility waves only wave dominated mixed tide dominated and tides only our results provide a predictive process based understanding of the shelf sedimentary system that has applications to marine engineering projects and to regional studies of pollution dispersal and accumulation where significant shelf sediment mobilisation is a factor

sediment transport under waves and tidal currents a case study from the northern bristol channel u k bed load transport under tidal currents and waves and waves alone is predicted from near bed self recording current meter data and observations from a wave rider buoy transport rates and paths are derived using seven different unidirectional transport formulae and those of bagnold 1963 bijker 1967 and madsen and grant 1976 for combined flows predicted rates are compared with the results of a fluorescent sand tracer study the data are available from swansea bay a high tidal and wave energy embayment on the british continental shelf sediment transport paths in this region had been determined previously using a variety of techniques including bedform orientation and sea bed drifter recovery patterns transport is enhanced under the superimposed effect of waves and in some circumstances the direction of the resultant vector is altered such storm induced catastrophic transport is different to that predicted under tidal currents alone this could provide a mechanism for long term sediment supply in some areas there is correspondence between bedform orientation and storm induced transport paths in others there is opposition

holocene evolution of bottom sediment distribution on the continental shelves of the bohai sea yellow sea and east china sea abstract coastline shifts due to transgression and regression can remodel tidal fields of continental shelves and this can control transport of sediments and modulate sediment distribution accordingly tidal currents have become the dominant hydrodynamic processes on the continental shelves of the bohai sea yellow sea and east china sea byecs since the transgression after the last glacial maximum lgm to examine the evolution of the bottom sediment distributions on the continental shelves of the byecs we simulated patterns of tides and tidal currents sediment transport and bottom sediment types sand mud and mixed sediments for five periods corresponding to sea level lowstands of 80 m 52 m and 30 m below present the holocene transgression maximum htm and the present the simulation shows that both sediment transport and shelf sediment distribution patterns were controlled by the strength type and asymmetry of tidal currents in the byecs since the lgm evolution of shelf sediment distribution patterns occurred in two stages 1 sediment emplacement and formation stage before the htm and 2 local adjustment after the htm the marked changes in coastline configuration since the lgm are the dominant factor controlling tide and tidal current evolution distribution of shelf sediment types in the byecs is closely related to tidal current fields during transgression after the lgm

tectonics fracturing of rock and erosion 1 we argue that by fracturing rock not by raising it relative to base level tectonics plays its most important role in causing rapid incision of valleys and rapid erosion of hillslopes tectonic deformation riddles the upper crust with fractures which not only provide avenues for water flow and thus promote weathering and further disintegration of rock but also fragment bedrock into debris that is readily extracted and transported by surface processes bends in active faults require straining of adjacent rock masses aftershocks that occur subsequent to slip on primary faults reflect penetrative brittle deformation of the upper crust at least some aftershocks must nucleate or lengthen cracks which contribute to the comminution of these rock masses scaling rules suggest that dimensions of ruptures for very small m 2 earthquakes can be meters or less the gutenberg richter recurrence relationship implies that such earthquakes are common as high magnification seismographs in low noise environments confirm moreover large differences among fault plane solutions for aftershocks show that the small faults on which they occur are not parallel to one another some faults must intersect thus the upper crust in tectonically active regions should be fragmented into blocks down to the scale of boulders or smaller dismembered rock arrives at the earth s surface already prepared to be transported away as a corollary both deeply exhumed lower crust and posttectonic igneous rock never deformed under brittle conditions and not deformed recently should be less susceptible to detachment and subsequent transport than fractured rock

estimation of annual bedload flux in a macrotidal estuary bristol channel u k sedimentological data from the bristol channel indicate that mutually evasive ebb and flood dominant zones of net bedload transport are present to test this hypothesis long term observations of currents from the channel are combined with empirical formulae to estimate annual bedload transport rates under the combined influence of tidal currents and surface wind waves extrapolating these values over the ebb and flood dominant zones sand flux to the upper part of the channel is estimated at about 64 105 t yr 1 with supply and removal being of nearly equal magnitude such patterns of sand and water movement may be typical of tidally dominated estuaries and embayments

estimating global shelf sediment mobility due to swell waves global climate models gcms such as those produced at the european centre for medium range weather forecasts ecmwf generate data that are relevant to the study of marine sedimentary processes we used estimates of significant wave height and period derived from an ecmwf gcm to predict for the first time the area of continental shelves over which sediment is mobilised the wave climatology was such that 0 1 mm diameter quartz sand had the potential to be mobilised on at least one occasion between july 1992 and july 1995 over 41 6 of the earth s continental shelves the north atlantic region has the most energetic global wave climate strong enough to mobilise 0 1 mm diameter quartz sand to water depths of up to 234 m at least once over a 3 year period

mechanisms for linear sandbank formation and maintenance in relation to dynamical oceanographic observations abstract theories associated with flow in the vicinity of headlands and sandbanks together with proposed mechanisms for sandbank formation and maintenance are reviewed to exemplify water and sand movement around a sandbank on a tidally dominated shelf tidal currents in the vicinity of a headland associated linear sandbank are described these data are integrated with sedimentological information on bedforms and grain size distributions the sandbank under detailed investigation the scarweather sands is located along the northern coastline of the bristol channel uk which is an area susceptible to high energy inputs the maximum spring tidal range here is around 10m and a 6000km fetch is available for storm wave approach from the atlantic ocean but the area is 460km from the shelf break detailed observations are presented from 11 long term current meter stations located within 10km of the sandbank currents are described in terms of residual water circulation shallow water harmonics and tidal ellipse characteristics bedload transport paths are inferred from the distribution of bedforms grain size and m2 m4 tidal current interactions transport vectors are predicted from near bed current meter observations combined with empirically derived formulae it is demonstrated that water circulation and sand transport paths form part of a clockwise eddy system around the sandbank mechanisms controlling the location and the characteristics of this particular sandbank are shown to be explicable in terms of a combination of models for sandbank formation and maintenance the results of the present study are thought to be applicable directly to headland associated sandbanks elsewhere it is shown on the basis of theoretical considerations that the pattern of residual water movement and possibly sand transport around this sandbank could be extended to continental shelves on a global basis

glacial landscape and paleoglaciation in terra sabaea evidence for a 3 6 ga polythermal plateau ice cap abstract in a previous study we demonstrated with a comparative morphometrical analysis the first morphometric evidence of a glacial landscape composed of glacial cirques and glacial valleys in the south of terra sabaea at an elevation 1000 m in two impact craters and one mountain the purpose of this study is to use the same method to seek other geomorphologic evidence of glacial landscapes elsewhere in terra sabaea based on a comparison between current and old glacial landscapes on earth and mars we identified 81 glacial valleys and possible evidence for a former plateau ice cap dated at 3 6 ga at the highest elevation in terra sabaea the identified glacial valleys have the same morphometric properties as terrestrial and martian glacial valleys with u shaped cross sectional profiles a v index 0 2 a length to with ratio 1 and a cross sectional area to drainage area ratio four times higher than the fluvial ones moreover these properties are different from terrestrial and martian fluvial valleys we did not find well preserved glacial cirques in this area this absence questions the origin of glacial valleys however the presence of an extensive flat plateau from which the long valleys radiate could have hosted an ancient plateau ice cap which was the source of these glacial valleys a comparison with the cantal and the shaluli shan in the southeastern tibetan plateau on earth reveals morphometrical similarities with our study area in fact long glacial valleys originating radially from a plateau at higher elevation are characteristics of an ancient plateau ice cap this analysis allowed us to propose a polythermal regime for martian glacial landscape namely a cold based ice cap except at the margin where the regime is warmed based due to the steeper topography this topography created shear stress which increased the heat at the base of the ice and created the outlet glacial valleys near the plateau the radial valleys are u shaped with a v index 0 2 but downstream to the low elevation area these valleys become more v shaped with a v index around 0 1 this hypothesis is supported by the presence of an open basin paleolake making the transition between inlet glacial valleys upstream and an outlet v shaped valley downstream so the morphometry of the radiating valleys suggests that liquid water played a role in the formation of this landscape

sediment dynamics of the severn estuary and inner bristol channel net sediment transport pathways have been determined in many environments by studying grain size trends this approach is extended here to an inner shelf environment with improved statistical techniques patterns of net surficial sediment transport are proposed indicating that the area is dominated by up estuary transport exceptions exist in the form of radial mud transport at the river mouths and clockwise sand circulation around linear sandbanks six different sedimentary environments are defined on the basis of the shape of the transfer function and its relationship to the grain size distributions erosion takes place along the axis of the estuary dynamic equilibrium is reached around the linear sandbanks whilst accretion occurs at the head of the estuary and where there are riverine inputs the results are compared with numerical model outputs representing water movement and sediment transport over the seaward part of the study area there is agreement between the two approaches contradictions increase however towards the upper reaches of the estuary the discrepancies can be attributed to 1 inherent differences between patterns of water and sediment movement 2 difficulties in modelling intertidal boundary conditions 3 inadequate representation of river influences in the models and 4 time scale differences associated with sediment transport processes

testing presence of relict fractures in granitoid saprolites by centrifuge modeling abstract granitoid saprolites formed from the chemical weathering of granitoid rocks contain relict fractures however saprolites may be considered as homogeneous soils because these relict fractures are not as visible as those in rock masses the presence of these fractures is not as widely accepted as those that occur in stiff and expansive clays while they can play an important role in slope excavation in this study the centrifugal modeling technique is employed to verify the presence of relict fractures in granitoid saprolites by demonstrating their effect on the displacement and force induced by excavation in cut slopes centrifugal tests are carried out using four slope models one homogeneous and three fracture containing and the displacement and force induced by excavation are monitored a comparative analysis of the results for different models shows that the presence of relict fractures has a significant effect on the excavation induced behavior of cut slopes the displacement and force generated during centrifuging are distinctly larger in the fracture containing models than in the homogeneous model particularly for the model with outward dipping fractures experimental results are used to confirm the presence and mechanical implications of relict fractures in granitoid saprolite slopes

outlet glacier trough size drainage area relationships fiordland new zealand abstract this paper examines relationships between the area supplying ice to fiord troughs and various measures of fiord size such as depth width and length in fiordland new zealand the size of the outlet troughs was found to be adjusted to the discharge of ice following a similar relationship to that encountered with fiords developed under essentially cold based ice sheets in british columbia however the fiordland outlet troughs were substantially shorter and shallower than their counterparts in british columbia this difference may reflect contrast in mode of erosion in each case although the major dimensions of the fiords undoubtedly reflect the controlling influence of the pre glacial lanscape upon which ice caps were superimposed with their rediating outlet glaciers

bed load transport under waves and currents the data from the flume experiments of kalkanis 1964 and abou seida 1965 giving the rates of accumulation of sand in recessed traps in oscillating sand beds have been reassessed in contrast to the work of madsen and grant 1976 the accumulation rate is interpreted as a measure of the average concentration of bed load per unit area during the period of oscillation for which the shields number t exceeds the threshold shields number th for the experimental runs where the reynolds number 35 the volume concentration of bed load c t cm3 cm 2 was found to be directly proportional to the excess shields number ex t t th c t 0 09 0 03 ext and the volume transport rate q t under instantaneous flow velocity u t was therefore q t 0 09 0 03 ex t u t for t th the rate of transport predicted by this equation was tested against the data of manohar 1955 and good agreement found showing a closer match between calculated and observed transport at high rates than found by the equation of madsen and grant 1976 the form of the transport rate equation proposed here q t u2 t u2th u t is compared with the form of the bedload transport equation for unidirectional flow and is found to have a firmer physical basis than some other wave transport equations presently in use

estimation of building damage due to excavation induced ground movements building damage due to excavation induced ground movement is evaluated using a damage criterion based on the average state of strain in the distorting portion of the structure and by considering the effect of building shear stiffness on the distortions imposed by the ground settlement profile physical model tests and numerical simulations correlated with case studies of building distortion and damage have been used to evaluate these relationships for masonry bearing wall structures the distinct element method was used to numerically model each masonry unit as a block with the contacts between blocks having the stiffness and strength characteristics of mortar in plane displacements at the corners of the wall sections permitted determination of the average state of strain and the components of rigid body tilt angular distortion lateral strain at the base and the contribution of bending strain to the lateral strain in the upper portion of the wall the increase in angular distortion with increase in the ratio of ground structure shear stiffness decrease in building shear stiffness was examined for both elastic and cracked building walls cracking significantly reduced effective wall stiffness making the wall more conformable to the ground settlement profile which increased angular distortion causing it to approach the distortion change in ground slope that would occur in the absence of the structure

boundary layer dynamics and sediment transport under storm and non storm conditions on the scotian shelf abstract near bed measurements of waves currents seabed responses and ripple migration rates were obtained using an instrumented tripod at a water depth of 39 m on the scotian shelf during the winter of 1992 93 these data and the grant and madsen s 1986 grant w d madsen o s 1986 the continental shelf bottom boundary layer annu rev fluid mech 18 265 305 combined flow boundary layer model are used to examine wave current interaction various sediment dynamic thresholds and sediment transport on an exposed high energy continental shelf the seabed was found to be rippled for most time of the deployment and thus the ripple enhanced combined skin friction shear velocity had to be used to determine the initiation of bedload transport under combined flows this indirectly indicates adequate predictions of the skin friction shear velocities inside the wave boundary layer by the grant and madsen model at high transport stages bedload roughness must be added to the grain size roughness to obtain a transportrelated combined shear velocity in order to predict correctly the onsets of saltation suspension and sheet flow transports otherwise the initiation of suspended load transport and the total sediment transport rates will be severely under estimated the comparison between the prediction by the grant and madsen 1986 model and the calculation of a quadratic stress law suggests that the total current shear velocity was enhanced by a factor of 2 3 due to the wave current interaction during storms while the apparent bottom roughness was increased by more than an order of magnitude the non linear coupling between waves and currents also causes a 20 increase of the combined skinfriction shear velocity inside the wave boundary layer this non linear coupling is most important when waves and currents are roughly equal in magnitude and the angles between them are less than 30 four sediment transport formulae were tested while the engelund hansen total load and yalin bedload methods did not perform well the einstein brown and bagnold formulae were found to respectively give reasonable predictions of the bedload and total load sediment transport rates under the observed combined flow conditions the predicted sediment transport direction is also in good agreement with the observed ripple migration direction the gsc sediment transport model sedtrans92 predicts that the net daily transport rates during the storms reached 822 kg m 1 day 1 and were 2 3 orders of magnitude higher than the non storm transport suggesting the dominance of storm processes in sediment transport on the scotian shelf these values are in good agreement with the results from sand tracer experiments conducted in this region we thus conclude that sedtrans92 can properly simulate boundary layer dynamics and sediment transport on continental shelves

preliminary study of the dynamic origin of the distribution pattern of bottom sediments on the continental shelves of the bohai sea yellow sea and east china sea the bottom sediment types in the bohai sea yellow sea and east china sea byecs are diversified and their distribution pattern is very complicated however the bottom sediment types can be simplified to be sandy sediment clayey sediment and mixed sediment which comprise the complicated distribution pattern of bottom sediment in the byecs the continental shelves of the byecs are broad with shallow water depths and tidal currents which are permanent and dominate the marine dynamics in the byecs based on numerical simulation of tidal elevations and currents in the byecs the rates of suspended load transport and bed load transport during a single tidal cycle for sediments of eight different grain size ranges are calculated the results show that any sediment whose threshold velocity is less than that of tidal current has the same transport trend suspended load transport rare bed load transport rate and the ratio of the former to the latter decrease with grain size becoming coarser and coarser the erosion accretion patterns of sediments with different grain sizes are determined by the sediment transport rate divergences and the results show that the patterns are the same for sediments with different grain sizes three main bottom sediment types i e sandy sediment mainly composed of fine sand clayey sediment mainly composed of silty clay and mixed sediment mainly composed of fine sand silt and clay are obtained by computation the three bottom sediment types and their distribution pattern are consistent not only with sediment transport field and the sea bed erosion accretion pattern obtained by simulation but also with field data of bottom sediment types and divisions in the byecs sand ridges form mainly in the areas with strong rectilinear tidal currents sand sheets form mainly in the areas dominated by strong rotatory tidal currents and clayey sediments i e mud patches form mainly in the areas with weak tidal currents hence not only the sandy sediments but also the clayey sediments in the byecs are formed under the control of the whole tidal current field of the byecs the three main bottom sediment types are not isolated respectively in fact they constitute a whole tidal depositional system under the condition with no cyclonic cold eddy the clayey sediments in the byecs can form in weak tidal current environments therefore a cold eddy is not necessary for the deposition of clayey sediments in the byecs c 2000 academic press

the critical role of climate and saprolite weathering in landscape evolution landscapes evolve in response to external forces such as tectonics and climate that influence surface processes of erosion and weathering internal feedbacks between erosion and weathering also play an integral role in regulating the landscapes response our understanding of these internal and external feedbacks is limited to a handful of field based studies only a few of which have explicitly examined saprolite weathering here we report rates of erosion and weathering in saprolite and soil to quantify how climate influences denudation by focusing on an elevation transect in the western sierra nevada mountains california we use an adapted mass balance approach and couple soil production rates from the cosmogenic radionuclide crn 10be with zirconium concentrations in rock saprolite and soil our approach includes deep saprolite weathering and suggests that previous studies may have underestimated denudation rates across similar landscapes along the studied climate gradient chemical weathering rates peak at middle elevations 1200 2000 m averaging 112 3 9 7 t km 2 y 1 compared to high and low elevation sites 46 8 5 2 t km 2 y 1 measured weathering rates follow similar patterns with climate as those of predicted silica fluxes modeled using an arrhenius temperature relationship and a linear relationship between flux and precipitation furthermore chemical weathering and erosion are tightly correlated across our sites and physical erosion rates increase with both saprolite weathering rates and intensity unexpectedly saprolite and soil weathering intensities are inversely related such that more weathered saprolites are overlain by weakly weathered soils these data quantify exciting links between climate weathering and erosion and together suggest that climate controls chemical weathering via temperature and moisture control on chemical reaction rates our results also suggest that saprolite weathering reduces bedrock coherence leading to faster rates of soil transport that in turn decrease material residence times in the soil column and limit soil weathering copyright 2009 john wiley sons ltd

sand transport under the combined influence of waves and tidal currents an assessment of available formulae abstract various formulae are used to predict the transport of sand under the combined influence of waves and currents these approaches include the use of the unidirectional formulae of einstein 1950 frijlink 1952 yalin 1963 engelund and hansen 1967 sternberg 1972 ackers and white 1973 and gadd et al 1978 modified for the presence of waves in accordance with the techniques described by bijker 1967 and swart 1976 and those of bagnold 1963 madsen and grant 1976 and vincent et al 1981 predicted rates are compared with measurements based upon fluorescent sand tracer studies in an area of high tidal current and wave energy northern bristol channel u k in general predicted rates are lower than those measured and only the formulae of madsen and grant 1976 and the modified formula of sternberg 1972 appear to provide realistic estimates of transport under wave and tidally induced currents in comparison with the field measurements

quantifying bedrock fracture patterns within the shallow subsurface implications for rock mass strength bedrock landslides and erodibility 1 the role of bedrock fractures and rock mass strength is often considered a primary influence on the efficiency of surface processes and the morphology of landscapes quantifying bedrock characteristics at hillslope scales however has proven difficult here we present a new field based method for quantifying the depth and apparent density of bedrock fractures within the shallow subsurface based on seismic refraction surveys we examine variations in subsurface fracture patterns in both fiordland and the southern alps of new zealand to better constrain the influence of bedrock properties in governing rates and patterns of landslides as well as the morphology of threshold landscapes we argue that intense tectonic deformation produces uniform bedrock fracturing with depth whereas geomorphic processes produce strong fracture gradients focused within the shallow subsurface additionally we argue that hillslope strength and stability are functions of both the intact rock strength and the density of bedrock fractures such that for a given intact rock strength a threshold fracture density exists that delineates between stable and unstable rock masses in the southern alps tectonic forces have pervasively fractured intrinsically weak rock to the verge of instability such that the entire rock mass is susceptible to failure and landslides can potentially extend to great depths conversely in fiordland tectonic fracturing of the strong intact rock has produced fracture densities less than the regional stability threshold therefore bedrock failure in fiordland generally occurs only after geomorphic fracturing has further reduced the rock mass strength this dependence on geomorphic fracturing limits the depths of bedrock landslides to within this geomorphically weakened zone

comparisons of measured and predicted sediment transport rates in tidal currents abstract this paper describes bedload transport measurements in a large scale sedimentary system on the british continental shelf steady flow sediment transport theories are applied to oscillatory tidal currents and various equations are compared with measured transport rates from tracer dispersion experiments the effects of waves on both measured and predicted rates are briefly considered and the predicted directions of sediment movement compared with those inferred from sedimentological data