evaporation from cultivated soils containing rock fragments abstract evaporation from bare soil surfaces represents an important water loss for agriculture in semi arid regions numerous efforts have been undertaken to modify the topsoil characteristics mulching tillage in order to create a thin dry topsoil that reduces evaporation however little attention was paid to the role of natural rock fragments in topsoils with respect to evaporation this paper presents the results of laboratory experiments simulating evaporation from initially wet and air dry soils containing a range of rock fragment contents and compares them to field conditions evaporation was stimulated by blowing fans at one high evaporative demand eo 7 7 9 2 mm day 1 time domain reflectometry tdr was used to investigate the relation between the water content of the topsoil and the actual evaporation rate for soils at field capacity initial fine earth water content decreases with rock fragment content and consequently evaporation rates decrease in the same order for air dry soils that received a limited amount of rain 10 and 20 mm an opposite behaviour was observed initial fine earth water content and evaporation rates increase with rock fragment content a strong positive sigmoidal relation between relative evaporation rate actual over open pan evaporation rates and fine earth water content in the centre of the wetted soil section was observed during the laboratory experiments except for the columns covered with a mulch there were no systematic differences in this relation between the treatments a rock fragment mulch reduces evaporation rate at a given soil water content significantly these trends explain the often ambivalent effects of rock fragments on evaporation rates in the field

unsaturated hydraulic conductivity in limestone dolines influence of vegetation and rock fragments abstract vegetation and rock fragments have a profound impact on runoff generation in the dolines of the sierra de gador southeastern spain this study investigated the effect of vegetation and rock fragments on unsaturated hydraulic conductivity k h in three limestone dolines and examined whether variation in k h was consistent with differences in runoff from simulated rainfall tension infiltrometers were used to measure unsaturated hydraulic conductivity at three pressure heads h of 30 60 and 120 mm at 70 locations within the three dolines generally the trends of the k h were consistent with the simulated rainfall data and accounted for difference in runoff for the vegetated surfaces vegetation resulted in high infiltration with unsaturated hydraulic conductivities at 30 and 60 mm are significantly greater for the vegetated surface than for the rock fragment covered surface and bare soil surface rock fragments had no obvious effect on soil hydraulic conductivity as compared with bare soils the k h of the non crusted soil were 2 5 times higher than that of the crusted soil the k h decreased with increasing tensions k 60 and k 120 were only 8 4 and 0 89 respectively of k 30 for the vegetated surfaces and were about 30 and 8 7 respectively of k 30 for both rock fragment covered surfaces and bare soils suggesting that pores in the 0 5 to 1 mm diameter range dominate flow under unsaturated conditions there were significant differences in k h among the different topographic units of the dolines and k h tended to be higher in the upper position than in the lower position of the doline

flow structure modification and drag reduction induced by sediment stratification in coastal tidal bottom boundary layers abstract the karman prandtl logarithm formula of velocity distribution has been widely used to depict flow structures and estimate parameters including bed roughness length and friction velocity in coastal tidal bottom boundary layers however the basic assumptions are of homogeneous flow but the effects of stratification should be taken into account here field observations of hydrodynamics and sediment dynamics were carried out in the well mixed area outside of the changjiang estuary china during may 31 june 2 2011 velocity profiles within the 2 m bottom layer suggest that the flow structure is prominently influenced when the gradient of suspended sediment concentration reaches o 0 1 kg m 4 the direct application of the log fit method resulted in a pronounced deviation from the actual boundary parameters the extended log fit method was used to represent the tidally averaged vertical flow structure indicating that the modification of the flow structure diminishes down to the bed and the calculated z0 based on the lowest layer close to the bed 0 22 0 38 m above the bed in the observation approaches the real value the observed data were also used to examine the modified logarithmic velocity distribution model in which the flux richardson number is modified with an empirical constant a to parameterize the stratification effects it was found that the constant a is approximately 1 which is significantly different from previous studies results of a vertical one dimensional model supported the above findings the sediment stratification effects should be taken into account and the logarithmic velocity distribution model tends to be applicable in the water layers very close to the bed

a new late holocene sea level record from the mississippi delta evidence for a climate sea level connection abstract a detailed relative sea level rsl record was constructed for the time interval 600 1600 ad using basal peat to track sea level and containing 16 sea level index points that capture 60 cm of rsl rise the study area is in the mississippi delta where the spring tidal range is 0 47 m the impact of ocean currents on sea surface topography is limited and crustal motions are well constrained age control was obtained by ams 14 c dating and most ages represent weighted means of two subsamples sample elevations were determined by combining differential gps measurements with optical surveying all index points were plotted as error boxes using 2 confidence intervals for the ages plus all vertical errors involved in sampling and surveying as well as the indicative range of the samples a striking clustering of sea level index points between 1000 and 1200 ad suggests a possible acceleration in the rate of rsl rise removal of the long term trend 0 60 mm yr 1 allows for the possibility of a sea level oscillation with a maximum amplitude of 55 cm however given the size of the error boxes the possibility that oscillations did not occur cannot be entirely ruled out comparison of the new rsl record with various proxy climate records suggests that sea level in this area may have responded to hemispheric temperature changes including the medieval warm period and the little ice age however given the error margins associated with this reconstruction it is stressed that this causal mechanism is tentative and requires corroboration by high resolution sea level reconstructions elsewhere

late pleistocene and holocene palaeogeography of the lower tagus valley portugal effects of relative sea level valley morphology and sediment supply abstract because of the deep glacial incision the lower tagus valley hosts a sedimentary record since 20 000 cal bp making this a unique site along the european atlantic margin with respect to palaeogeographic and sea level changes based on nine cross sections and 55 radiocarbon dates together with a newly created relative sea level curve we constructed five palaeogeographic maps of the infill of the lower tagus valley since 20 000 cal bp we illustrate that relative sea level rise and fluvial sediment supply were the prime forcing factors determining the depositional history and palaeogeographic changes around 20 000 cal bp a deeply incised braided river existed which was directly connected to the ocean across the narrow continental shelf after that 12 000 cal bp the gradually moister and warmer climate caused a change to a single channel river during the following period 12 000 7000 cal bp relative sea level rise resulted in a transgression in the lower tagus valley and the establishment of extensive tidal environments after relative sea level rise had ended 7000 cal bp the valley was progressively filled by a fluvial wedge and tidally influenced bayhead delta since 1000 cal bp the valley fill history was dominated by increased sediment input due to human induced degradation of catchment slopes generally climate was of subordinate importance during the entire studied period merely causing a single channel river resulting from the change from the cold heinrich event 1 to the temperate bolling allerod interstadial despite the tectonic activity in the region neotectonic uplift or subsidence was limited as supported by the horizontal relative sea level curve since 7000 cal bp neotectonics played a minor role due to the large distance from the fennoscandian ice sheet and the narrow continental shelf which prohibited strong glacio and hydro isostatic movements

near field sea level variability in northwest europe and ice sheet stability during the last interglacial global sea level during the last interglacial lig marine isotope sub stage 5e peaked between c 5 5 and 9 m above present implying significant melt from greenland and antarctica relative sea level rsl observations from several far and intermediate field sites suggest abrupt fluctuations or jumps in rsl during the lig highstand that require one or more episodes of ice sheet collapse and regrowth such events should be manifest as unique sea level fingerprints recorded in far intermediate and near field sites depending on the source s of ice mass change involved to date though no coherent evidence of such fluctuations has been reported from near field rsl studies in northwest europe this is an important problem because rsl fluctuations during the lig are portrayed as warning signs for how polar ice sheets may behave in a future warmer than present world here we review the evidence for rsl change during the lig using stratigraphic data from the best resolved highstand records that exist in the near field of northwest europe from a range of settings that include lagoonal shallow marine tidal flat salt marsh and brackish water fluviatile environments consideration of previously published stratigraphic records from two sites in the eemian coastal marine embayment that existed in the central netherlands yields no clear indications for abrupt rsl change during the attainment of the near field highstand nor do we find any such indications common to other records from countries bordering the north sea the baltic sea and the white sea two modelling experiments that explore the global signal of hypothetical sea level oscillations caused by partial collapse and regrowth of either the greenland or antarctic lig ice sheet show that the north sea region is relatively insensitive to mass changes sourced from greenland but should clearly register events with an antarctic origin especially those that occur late in the lig the lack of evidence for abrupt sea level fluctuations at this time in northwest europe concurs with a lack of clear near field evidence for ice sheet collapse

holocene excursions of the northwest european geoid abstract computer assisted analyses of more than 600 radiocarbon dated sea level indicators from northwestern europe concentrated around the north sea margin indicate that vertical crustal movements are more important that eustatic sea level change in determining the locus of holocene shoreline positions through time for the past 14 000 radiocarbon years the divergence of sea level data for the northwest european sectors exceeds the maximum estimated sea level rise by a factor of two or more projecting these data to a single meridian demonstrates the remarkable variety of vertical crustal movement in northwestern europe accumulating radiocarbon dated sea level indicators into millennial cohorts we generate isobase maps which begin to specify areas of notable vertical crustal mobility these isobase maps appear to confirm that eustatic sea level rise is subordinate to postglacial geoidal excursions in determining the locus of contemporary northwestern european shorelines

turbulence spectra from the viscous sublayer and buffer layer at the ocean floor an experiment conducted on the oregon continental shelf has provided measurements of velocity fluctuations in the viscous sublayer and buffer layer of the boundary layer flow spectra from the viscous sublayer collapse considerably when scaled as suggested by bakewell lumley 1967 and buffer layer spectra collapse reasonably well with laboratory spectra when the scaling customarily used in the logarithmic layer is applied however in spite of the usefulness of the spectral scaling the scaled sublayer and buffer layer spectra from the ocean floor fall below the scaled laboratory spectra in the energy containing portion of the spectrum perhaps because the sea floor is not perfectly planar

soil containing rock fragments effects on infiltration abstract infiltration is a very complex process rock fragments affect infiltration by their presence in the soil matrix and on the soil surface procedures for quantifying soil and surface rock fragments are reviewed within the soil the physical properties and hydraulic properties that affect infiltration are shown to be influenced by rock fragments physical properties discussed are bulk density porosity and water content hydraulic properties that affect infiltration are water retention saturated conductivity and unsaturated conductivity rock fragments on the soil surface have been reported to both increase or decrease infiltration rates and amounts

deciphering holocene sea level history on the u s gulf coast a high resolution record from the mississippi delta published holocene relative sea level rsl curves for the u s gulf coast are in mutual conflict with some characterized by a smooth rsl rise akin to widely accepted eustatic sea level curves versus others including several recent ones that are characterized by a conspicuous stair step pattern with prolonged millennium scale rsl stillstands alternating with rapid meter scale rises in addition recent work in texas and alabama has revitalized the notion of a middle holocene rsl highstand estimated at 2 m above present mean sea level an extensive sampling program in the mississippi delta louisiana focused on the collection of basal peats that accumulated during the initial transgression of the pre existing consolidated pleistocene basement we used stable carbon isotope ratios to demonstrate that many of these samples accumulated in environments affected by frequent saltwater intrusion in the 30 cm zone between mean spring high water and mean sea level and we selected plant macrofossils that were subjected to ams 14c dating nearly 30 sea level index points from a 20 km2 study area on the eastern margin of the delta suggest that rsl rise followed a relatively smooth trend for the time interval 8000 3000 cal yr b p thus questioning the occurrence of major rsl stillstands alternating with abrupt rises given the narrow error envelope defined by our data set any sea level fluctuations if present would have amplitudes of 1 m although a true middle holocene highstand never occurred in the mississippi delta the high level of detail of our time series enables a rigorous test of this hypothesis correction of our data set for a hypothetical tectonic subsidence rate of 1 1 mm yr 1 assuming a constant subsidence rate compared to the tectonically relatively stable adjacent coast of texas leads to sea levels near 2 m above present during the time interval 6000 4000 cal yr b p however this model also implies a rsl position near 2 m around 8000 cal yr b p which is inconsistent both with data of this age from texas as well as with widely accepted sea level data from elsewhere we therefore conclude that a middle holocene highstand for the u s gulf coast is highly unlikely and that the entire area is still responding glacio isostatically by means of forebulge collapse to the melting of the laurentide ice sheet

the modification of bottom boundary layer turbulence and mixing by internal waves shoaling on a barrier reef abstractresults are presented from an observational study of stratified turbulent flow in the bottom boundary layer on the outer southeast florida shelf measurements of momentum and heat fluxes were made using an array of acoustic doppler velocimeters and fast response temperature sensors in the bottom 3 m over a rough reef slope direct estimates of flux richardson number rf confirm previous laboratory numerical and observational work which find mixing efficiency not to be a constant but rather to vary with frt reb and rig these results depart from previous observations in that the highest levels of mixing efficiency occur for frt 1 suggesting that efficient mixing can also happen in regions of buoyancy controlled turbulence generally the authors find that turbulence in the reef bottom boundary layer is highly variable in time and modified by near bed flow shear and stratification driven by shoaling internal waves

vertical structure of surface gravity waves propagating over a sloping seabed theory and field measurements 1 theoretical predictions of the vertical structure of wave motion over a sloping seabed are compared with field observations close to the bed in the nearshore zone of particular interest is the effect of the local slope on the magnitude and phase of the vertical velocity field measurements of near bed velocity profiles on a 2 bed slope were obtained using a coherent doppler profiler the surface elevation was measured by a colocated upward looking acoustic sounder results are presented from two intervals of different wave energy levels during a storm event for wave height water depth ratios smaller than 0 3 and for ursell numbers smaller than 0 6 the local comparisons of magnitude and phase between the vertical velocity and surface elevation measurements are in good agreement with linear theory for a sloping bed but differ greatly from that for a horizontal bottom especially in the lower water column the sloping bottom however has little effect on the horizontal velocity linear theory appears to adequately describe the transfer function between the surface elevation and the near bed velocities not only at the peak frequencies but also at their harmonics however in relatively shallow water the local transformations of free and forced waves at the harmonic frequencies are indistinguishable in the lower water column therefore given surface elevation measurements at a particular location which reflect the integrated effects of nonlinearities associated with wave shoaling the vertical structure of the third moments of velocity fields estimated from linear theory is in reasonable agreement with the observations both theory and observations show that the skewness and asymmetry of the vertical velocity are subject to significant bottom slope effects whereas those of horizontal velocity are not index terms 4211 oceanography general benthic boundary layers 4203 oceanography general analytical modeling 4219 oceanography general continental shelf processes 4546 oceanography physical nearshore processes 4560 oceanography physical surface waves and tides 1255 keywords shoaling waves bottom slope vertical structure skewness asymmetry boundary layers citation zou q a e hay and a j bowen vertical structure of surface gravity waves propagating over a sloping seabed theory and field measurements j geophys res 108 c8 3265 doi 10 1029 2002jc001432 2003

holocene crustal movements and sea level changes in great britain crustal downwarping has occurred throughout southern and south eastern england and most of wales for at least the last 4000 years but the type of movement in some areas of southern and eastern england is more complicated than simple linear subsidence highest estimated rates of subsidence since 4000 bp are for the thames estuary and norfolk up to 2 mm yr glacio isostatic processes have resulted in uplift in northern england and mainland scotland the rates of uplift have decreased throughout the holocene estimates for the present range from zero in south lancashire and the tees estuary to over 1 mm yr though less than 2 mm yr in central scotland over 400 sea level index points from the databank of 904 cases collected for igcp project 200 are grouped into 15 main areas and used to investigate the nature of crustal movements in great britain since 8800 bp but there are significant deficiencies in available data which constrain the analysis

radiocarbon dated sediment sequences from the belgian coastal plain testing the hypothesis of fluctuating or smooth late holocene relative sea level rise the late holocene deposits of the coastal lowlands bordering the southern north sea were formed by a renewed expansion of the tidal environment replacing freshwater peats the sea level history during the last 2500 years inferred from the post peat deposits containing little to no datable organic material is characterized by two conflicting schools of thought the first one supports a smooth sea level curve the second approach underpins fluctuating sea level changes the fluctuating approach also uses facies variations recorded in the post peat deposits to provide a chronostratigraphical subdivision linked to transgressions and regressions this paper examines the controlling factors responsible for the facies variations in the post peat deposits in order to test the approach of the fluctuating sea level the results of sedimentological investigation coupled with radiocarbon dates of intertidal shells from four shallow outcrops located in nearby sand filled late holocene tidal channels in the belgian

near bed turbulence and relict waveformed sand ripples observations from the inner shelf 1 results are presented from a field investigation of near bed turbulence above degrading waveformed sand ripples in 17 m water depth on the inner shelf the heights of the 50 cm wavelength primary ripples were about 5 cm at the start of the observation period and decreased by a factor of 2 within 15 days the principal degradation mechanism involved fish making pits in the seafloor near bed turbulent kinetic energy dissipation rates are estimated both from the energy spectrum and from the vertical structure function within the inertial subrange and ranged from 0 1 10 6 to 3 10 6 w kg the friction velocity u at the bed ranged from 0 3 to 0 5 cm s and the wave friction factor fw from 0 017 to 0 02 the nearbed turbulence intensities and consequently the estimated values of u2 and fw are likely too small by a factor of 2 partly to satisfy the smooth wall constraint and partly to account for the effects of small scale turbulence within the finite volume range cells of the coherent doppler system used to make the turbulence estimates finally the results indicate that the hydraulic roughness of relict ripples is likely a function of both ripple height and steepness and that the relative roughness should also depend on the near bed wave orbital excursion for modeling purposes nielsen s ripple roughness formula is recommended with a reduced proportionality constant to account for the effects of irregular wave forcing and non equilibrium ripple history

holocene relative mean sea level changes in the wadden sea area northern netherlands although the netherlands has a long tradition of sea level research no holocene relative sea level curve is available for the north of the netherlands previous studies hypothesised that the relative sea level reconstruction for the western netherlands is also valid for the northern part of the country however glacial isostatic adjustment gia models predict a lower and steeper relative sea level curve because of greater postglacial isostatic subsidence long term data of relative sea level change are important to inform gia models and understand postglacial vertical land motion related to the rebound of fennoscandia and neotectonic activity we compiled and evaluated a set of basal peat radiocarbon dates to reconstruct the holocene relative mean sea level rise in the dutch wadden sea area for the early holocene this reconstruction is lower than the western netherlands curve after 6400 cal a bp the curve for the wadden sea is statistically indistinguishable from that for the western netherlands a result that conflicts with gia model results it remains to be investigated whether the problem lies with the gia model predictions or with the quality of the available data additional basal peat radiocarbon dates from suitable sites should be collected to further solve this problem

on the wave and current interaction with a rippled seabed in the coastal ocean bottom boundary layer interactions of currents and waves with a rippled seabed in the inner part of the coastal ocean bottom boundary layer are studied using particle image velocimetry adv and bottom roughness measurements mean velocity profiles collapse with appropriate scaling in the log layer but vary substantially in the roughness sublayer when wave induced motions are similar or greater than the mean current the hydrodynamic roughness z0 determined from velocity profiles is substantially larger than directly measured values the roughness signature in turbulent energy spectra persists with elevation when its scale falls in the dissipation range but decays in the log layer for larger roughness elements reynolds shear stress profiles peak in the lower parts of the log layer diminishing below it and gradually decaying at higher elevations in contrast wave shear stresses are negligible within the log layer but become significant within the roughness sublayer this phenomenon is caused by an increase in the magnitude and phase lag of the vertical component of wave induced motion no single boundary layer length scale collapses the reynolds stresses but both the prandtl mixing length and eddy viscosity profiles agree well with the classical model of linear increase with elevation especially near the seabed within the log region profiles of shear production and dissipation rates of turbulence converge below it dissipation rapidly increases peaking near the seabed conversely the shear production decays near the seabed in agreement with the eddy viscosity model but in contrast to both laboratory and computational rough wall studies

the effect of rock fragment size and position on topsoil moisture on arid and semi arid hillslopes abstract rock fragments on arid hillslopes affect rainwater redistribution and overland flow through various hydrological processes the present study focuses on the evolution of topsoil moisture content under rock fragments following rain events measurement was taken under rock fragments in various sizes large and small and positions on top of the soil surface and partially embedded within the soil surface at north and south facing hillslopes in arid and semi arid areas the main findings 1 the topsoil moisture content under rock fragments was higher over time than that of bare soil areas 2 rock fragments affect the topsoil moisture content for a longer time in semi arid areas than in arid areas and 3 large rock fragments and partially embedded ones are favorable micro environments for accepting and retaining rainwater and overland flowing water this may have eco geomorphic implications regarding the mosaic like patterns of source and sink areas on arid hillslopes

vertical structure of dissipation in the nearshore abstract the vertical structure of the dissipation of turbulence kinetic energy was observed in the nearshore region 3 2 m mean water depth with a tripod of three acoustic doppler current meters off a sandy ocean beach surface and bottom boundary layer dissipation scaling concepts overlap in this region no depth limited wave breaking occurred at the tripod but wind induced whitecapping wave breaking did occur dissipation is maximum near the surface and minimum at middepth with a secondary maximum near the bed the observed dissipation does not follow a surfzone scaling nor does it follow a log layer surface or bottom boundary layer scaling at the upper two current meters dissipation follows a modified deep water breaking wave scaling vertical shear in the mean currents is negligible and shear production magnitude is much less than dissipation implying that the vertical diffusion of turbulence is important the increased near bed secondary dissipation maximum results from a decrease in the tu

the melting history of the late pleistocene antarctic ice sheet spatial and temporal variations in the sea levels of the past 20 000 years around the globe place constraints on the melting history of the major late pleistocene ice sheets the antarctic ice sheets provided a significant contribution to the sea level rise at a rate that was approximately synchronous with the melting of the laurentide ice sheet except for the interval 9 000 6 000 years ago when it may have lagged behind minor melting of the antarctic ice sheet continued throughout the holocene

a suspended sediment stratification correction for combined wave and current flows a simple model for the near bottom combined wave and current flow over a moveable sediment bed is presented the model is an extension of the grant and madsen 1979 combined wave and current model with moveable bed effects on the physical bottom roughness included as by grant and madsen 1982 the unsteady conservation of fluid momentum and sediment mass equations which are coupled through an eddy diffusivity closure scheme are solved for the wave and current velocity profiles along with the suspended sediment concentration and transport profiles sample runs are presented to illustrate the effect of varying wave conditions on the current the mean sediment concentration and the mean sediment transport results show that for fine to medium sands self stratification of the flow can be important during storms owing to the large amount of sediment suspended by the waves and the enhanced turbulent mixing associated with the wave current interaction the theory easily can be generalized for inclusion in a full ekman layer model

modeling bottom roughness in the presence of wave generated ripples 1 near bottom wave current and microtopography measurements have been obtained at the leo 15 site off the southern coast of new jersey the measurements are used in conjunction with a recently calibrated continental shelf bottom boundary layer model to refine estimates of bottom roughness for a rippled bed under combined wave and current flows in the presence of nearly two dimensional wave generated ripples application of the grant and madsen 1979 type bottom boundary layer model produces estimates of the bottom roughness felt by the current that are several times greater than established formulations for rippled beds under waves modifying one of the primary length scales in the eddy viscosity profiles returns estimates that are more consistent with the wave roughness results application of the roughness model in conjunction with a refined empirical ripple geometry model produces highly accurate estimates of measured shear velocities and apparent roughnesses during a moderate storm the demonstrated accuracy of this simple combined roughness and ripple geometry formulation reveals its utility when considering applications of coupled bottom boundary layer shelf circulation models

effects of rock fragments on infiltration and evaporation in hilly purple soils of sichuan basin china this paper presents the results of laboratory experiments showing the effects of rock fragments contained in three different purple soils of the sichuan basin of southwest china the experiments investigated how these rock fragments alter the soil s physical chemical and agronomical characteristics such as infiltration and evaporation we found that the infiltration rate whether horizontal or vertical in the three soils has the following order gray brown purple soil reddish brown purple soil brown purple soil with increasing rock fragment contents the accumulated infiltration decreases while the total time decreases first and then increases the minimum occurs at approximately 10 20 of fragment content by weight the infiltration rate also changes with the distance in the 0 5 cm range the initial infiltration rate increases with increasing rock fragment contents while in the 5 10 cm range the slope of infiltration curve increases with increasing rock fragment contents with increasing distance the slope gradually decreases and finally reaches a stable value the presence of rock fragments reduces soil water content the minimal value appearing when the rock fragments were on top of the soil column soil rock sample decreasing with increasing rock fragments for other samples mixed with fragments under the constant 40 c temperature the accumulated evaporation and evaporation rate are minimal for soils covered by rock fragments and the accumulated evaporation decreases with increasing rock fragment for other soil samples however the evaporation rate increases with increasing rock fragments in the first 4 days and decreases thereafter

reconstruction of holocene relative sea level change and residual uplift in the lake inba area japan abstract we collected and analyzed fossil diatoms and volcanic ash and determined 14 c ages in core samples from the lowlands around lake inba in the eastern kanto plain central japan an area where late quaternary sea level change fluvial erosion and tectonic uplift have affected a region of archeological interest we inferred holocene paleoenvironmental changes and relative sea levels on the basis of indicators such as high tide levels derived from fossil diatom assemblages as well as the stratigraphic positions of 14 c dated samples and the k ah tephra our results lead to estimates of the upper half tidal range during 6800 7000 cal yr bp of 1 7 m the holocene highstand took place at approximately 6400 6500 cal yr bp and mean sea level reached an elevation of 1 9 m however the timing of this sea level rise is earlier in the lake inba area than documented in previous studies and it is suggested that the timing of the holocene highstand may appear at least 1000 years earlier as a result of holocene residual uplift after this sea level fell abruptly around 4000 cal yr bp we also recognized a sea level fall corresponding to the yayoi regression at about 2600 cal yr bp during which the mean relative sea level may have been as low as 2 5 m after compensating for uplift subsidence or geomorphologic effects in this area

field experiments on the transport of rock fragments by animal trampling on scree slopes qualitative observations in an area with steep scree slopes in turkey suggested that trampling by goats and sheep may contribute significantly to the downslope movement of rock fragments in these environments therefore a series of field experiments was set up to determine the rate of rock fragment transport caused by trampling the experimental results allowed the calculation of a unit displacement distance from each trampling experiment which may then be used to extrapolate the measured transport rates over longer time periods and larger areas although such extrapolations should be interpreted with great caution the results demonstrate that trampling contributes significantly to rock fragment transport in such environments as calculated yearly displacement distances are equal to or higher than those reported in the literature for other geomorphic processes the observed travel distance distributions are not well described by a negative exponential distribution trampling causes a weak downslope sorting the coarsest clasts move farther but has a significant effect on vertical sorting and is one of the factors which can explain the layered structure of the scree slopes in the area

holocene relative sea level change and crustal movement in the southwestern netherlands abstract sea level data collected by jelgersma 1961 from zeeland in the southwestern netherlands show an anomalously high time depth position with respect to sea level curves established for the rest of the netherlands until now it was not clear whether this was related to differential crustal movements a higher tidal range and or to groundwater influenced peat growth above contemporaneous sea level new radiocarbon dates from the base of the basal peat in zeeland and the adjacent estuarine flood plain of the river scheide in belgium have a considerably lower time depth position than the original data of jelgersma 1961 comparison of the lowest mean sea level msl time depth points from the study area with a reference msl error band for the western netherlands yields a maximum crustal uplift of zeeland relative to the western netherlands of about 0 17 m 1000 yr over the last 8000 yrs cal b p a regional msl envelope for the southwestern netherlands has been constructed by correcting the reference msl error band with this maximum rate of relative uplift the new regional maximum msl error band plots significantly below the zeeland curve and the zeeland data points of jelgersma 1961 1966 but is still higher than msl curves established for the rest of the netherlands the remaining vertical distance of the data of jelgersma to the new zeeland msl error band is attributed to early basal peat growth above contemporaneous msl primarily due to a groundwater gradient effect on the gently inclined pleistocene subsoil the sea level index points with the lowest time depth position all come from locations close to or within the late pleistocene palaeovalley of the river scheide this was probably due to the slope of the regional groundwater table towards the palaeovalley resulting in better drainage conditions on the valley sidewalk peat could only develop under the direct influence of the river water level which was controlled by sea level rise this suggests that comparable palaeovalleys on other coastlines of the north sea or elsewhere offer considerable potential for sea level research if the topography of the compaction free substratum is well known

lagoa da apulia a residual lagoon from the late holocene nw coastal zone of portugal the lagoa da apulia is a unique feature in the nw coastal zone of portugal a remaining form from a lagoon complex system that during the late holocene was dominant in the region this system was mainly neotectonically controlled occupying a depressed area bounded by faults on a palaeozoic rocky lower platform today observable on beaches at low tide with the intention of knowing the main architecture of the palaeo lagoon geophysical prospecting with gpr and resistivity was carried out accordingly six cores were taken and the sedimentary and mineralogical facies and diatom and foraminifer contents were analysed and five rich organic layers were dated by radiocarbon analysis with the data an evolutionary environment reconstruction model was created for this palaeo lagoon and the main structural features of the neighbouring area

driving mechanisms of coastal change peat compaction and the destruction of late holocene coastal wetlands abstract this paper examines the role of peat compaction as a driving mechanism behind the widespread inundation of a late holocene coastal wetland in southeast england uk detailed stratigraphic and dating evidence lithology grain size foraminifera pollen and radiocarbon dates from a sample site in romney marsh documents the gradual inundation of a coastal wetland after 1263 1085 cal yr bp c 700 850 ad and the establishment of a saltmarsh shortly thereafter there was a rapid increase in water depth that was associated with the deposition of nearly 4 m of laminated intertidal mudflat and tidal channel sediments prior to site reclamation from the sea by ad 1460 grain size data and statistical analysis of sand and mud laminae thicknesses suggest the laminated sediments accumulated rapidly c 0 2 m per year as heterolithic tidal rhythmites rapid compaction of the thick peat bed that underlies the study site provided the accommodation space for their deposition this process began with the gradual tidal inundation of the site but accelerated following the widening of a breach in a coastal barrier in the 13th century compaction lowered the peat surface by at least 3 m and was associated with widespread landscape change the study demonstrates the powerful influence that compaction had on the evolution of the late holocene landscape at this site and we believe at many other coastal lowlands in northwest europe this process is likely to have been a key driving mechanism behind rapid late holocene coastal change far exceeding the longer term effects of either eustatic change or crustal uplift subsidence

insect evidence for environmental and climate changes from younger dryas to sub boreal in a river floodplain at st momelin st omer basin northern france coleoptera and trichoptera the st omer area is a rapidly subsiding basin in which long sequences of weichselian and holocene sediments are preserved a core 21 m long extracted from near st momelin about ten km north of st omer has been analysed for insect fossils four faunal units smi 1 to smi 4 are described based on changes in both coleopteran and trichopteran assemblages the basal faunal unit smi 1 includes many cold adapted species and is attributed to the younger dryas chronozone the transition to holocene sedimentation was abrupt faunal units smi 2 to smi 4 are attributable to the holocene they lack all the cold adapted species found in the basal sediments and in their place are insect assemblages very similar to the present day fauna in this region this sequence spans the period from the pre boreal to the sub boreal faunal unit smi 2 includes insects from the pre boreal the boreal and most of the atlantic periods this fauna was fairly sparse and made up largely of species living in freshwater habitats the faunal unit smi 3 includes the insect assemblages from the late atlantic to sub boreal periods this fauna was much more diverse and indicated a river meandering across its floodplain and bordered by a mature forest at a time when the climate was warmer than that of the present day this chronostratigraphical sequence of events is supported by 14c dates and by lithological data thermal climatic conditions have been quantified using the mutual climatic range method during the younger dryas period smi 1 tmax the mean july temperature was in the region of 10 c and tmin the mean temperature of january february was close to 11 12 c after the sudden climatic amelioration at the start of the holocene smi 2 to smi 4 tmax probably fluctuated throughout the early holocene between 16 c to 19 c and tmin between 0 c to 5 c figures that are close to those of the present day this climatic history is compared with others in northern europe

geoarchaeological records in temperate european river valleys quantifying the resource assessing its potential and managing its future throughout the quaternary episodes of glaciation and associated low sea level have resulted in the connection of the terrestrial landmasses of britain and mainland europe the river systems that established themselves across these newly emergent land surfaces of the coastal plain would have created important migration corridors for both animals and humans a point corroborated by the affinity of palaeolithic remains across britain and europe technological developments within the last decade have allowed these now submerged valley floors and adjacent terrestrial landscapes associated with the last cold stage and early and middle parts of the current holocene interglacial to be explored and their archaeological legacies unravelled providing geoarchaeologists with an opportunity to contribute to major cultural debates however in order to maximize knowledge it is essential that geoarchaeologists working within river valleys across both britain and the european continent are addressing similar research questions by collecting data using comparable methodologies this paper reviews the approach taken in different regions and provides a baseline assessment to allow the development of a coherent european wide framework for alluvial geoarchaeology and geoprospection particularly with respect to the holocene record

vertical distribution of wave shear stress in variable water depth theory and field observations 1 a generalized analytical model is developed to describe the vertical distribution of wave induced shear stress in the presence of bottom slope bottom friction and depth induced wave breaking in the shoaling region and surf zone the theory is compared to data obtained on an unbarred beach in 3 7 m mean water depth over a 2 bottom slope bottom slope and bottom friction are incorporated in the theory by including the wave energy dissipation by bottom friction in a potential wave theory for variable water depth and coupling the wave theory with a wave bottom boundary layer wbbl theory over a sloping bottom the effect of wave breaking is included through a periodic bore dissipation model previous studies have considered some but not all of these effects each of the three components sloping bottom bottom friction and wave breaking exhibits a different vertical structure the contributions due to bottom slope and bottom friction attain maximum strength in the wbbl and decay with distance above the bed approaching smaller but nonzero values at the surface in contrast the contribution from wave breaking is maximal at the surface and decays linearly with depth becoming zero at the bed the vertical structure of the cross shore u and vertical w components of wave orbital velocity was measured using a coherent doppler acoustic profiler the measured velocity fields were used to obtain the ensemble averaged wave shear stress profiles that extend across the wbbl to a height of 30 cm above the bed close to the seabed the observed and predicted uw profiles are similar confirming the sensitivity of wave stress to frictional and bottom slope effects within the wbbl farther from the bed however the observed profiles fall off more rapidly with height as w approaches quadrature with u faster than predicted wave breaking induced shear stresses were not observed

sequence mapping of holocene coastal lowlands the application of the streif classification system in the belgian coastal plain a geological map of the holocene deposits of a portion of the western belgian coastal plain is presented the map differs from a conventional geological map which is of little use for coastal lowlands because of the high lateral and vertical variability in lithology in the subsoil the method of sequence maps was chosen because these maps allow the representation of the entire vertical sequence of the holocene deposits a sequence map is constructed on the basis of profile types consisting of the vertical succession of the various mapping units in order to produce a user friendly map preference was given to lithogenetic units instead of formal lithostratigraphic units for the determination of mapping units the organisation of the mapping units was established according to the streif classification system the application of the system is demonstrated with two different sequence maps each constructed on a different level of the hierarchic system a general sequence map and a special sequence map showing further differentiation

the high resolution holocene sea level curve for northwest germany global signals local effects or data artefacts a few years ago a new relative sea level curve for northwest germany was constructed for the entire german north sea coast it is characterised by several suspected sea level fluctuations to test this curve for local effects it was broken down into five relative sea level curves representative for five coastal sections the relative sea level curves were corrected for tidal effects and also a rough first correction for compaction was applied the five curves all differ from the original curve and from each other most of the suspected sea level fluctuations in the original curve cannot be supported and are discussed as data artefacts or local effects around ad 800 1000 all curves show stagnation or drop of sea level thus this signal is discussed as of over regional stratigraphic meaning this study is a first step 1 to show that several curves are needed to demonstrate the holocene sea level history of such a big area as the entire german north sea coast and 2 to establish reliable relative sea level curves for the german north sea coast further research is necessary to apply detailed corrections especially with respect to compaction prone data and to improve the individual curves

holocene evolution of a wetland in the lower seine valley marais vernier france estuaries like that of the seine river in nw europe developed in incised fluvial valleys after the last glacial maximum since the 1940s several authors have studied the largest wetland of the seine estuary the marais vernier to understand depositional environments during holocene infilling we reinterpret previous research based on new and published data for example fill thickness and material source to 1 describe facies and depositional environments 2 reconstruct palaeoenvironmental evolution 3 show the influence of local and global forcing on depositional environments before 7000 6000 cal bc terrestrial material was deposited because of catchment erosion related to changes in climate just before 7000 6000 cal bc estuarine material began to be deposited in low lying areas in response to sea level rise while terrestrial material still settled at higher elevations after this but before 5850 5710 cal bc estuarine material areas began to accumulate at both high and low elevations this marked a general flooding of the marais vernier synchronous with that at the seine estuary mouth soon after peat accumulated over a wide area as a response to a local change in accommodation and a worldwide drop in sea level a tidal channel developed to the west of the marais vernier providing minerogenic material after 1130 900 cal bc human influence becomes increasingly clear in the record this record of regional change during the holocene can serve as a reference for further studies in the area

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

rock fragments in top soils significance and processes this introductory paper reviews various aspects of rock fragments in top soils such information is required for various reasons and in particular for predicting the impact of climatic or landuse changes on the response of these soils particular attention is paid to the definition and measurement of rock fragment content in top soils the density of soils containing rock fragments the spatial distribution and movement of rock fragments in top soils the effects of rock fragments on some key hydrological processes thermal properties of top soils physical soil degradation soil erosion and soil productivity

changes in coastal zone processes at a high sea level stand a late holocene example from belgium this paper presents the results of an investigation of late holocene deposits on the belgian coastal plain the upper clastic deposits overlying the uppermost intercalated peat bed were studied on the basis of lithology radiocarbon dates and foraminiferal assemblages to determine why silting up phases or peat beds are lacking and to establish the evolution of the sedimentary environments as well as the age of the deposits two contrasting sites in quite different locations and showing a different stratigraphy were studied it appears that the coastal evolution was not gradual and continuous but characterised by short periods with high energy conditions alternating with long periods where low energy conditions and little sedimentation prevailed the evolution is determined mainly by tidal channel activity at about 3400 cal yr bp the peat was eroded in narrow zones by the main tidal channels and this until the landward limit of the plain the peat was only partly flooded and mudflats fringed the channels with time new tributaries formed and the channel network progressively enlarged the channels were rapidly filled followed by a period of little sedimentation which lasted at least until 1400 1200 cal yr bp the following channel activity is characterised by lateral sedimentation rather than vertical erosion together with increased sediment reworking the mechanisms of coastal change in the late holocene might be similar over the entire plain but the timing of the changes is certainly not copyright 2002 john wiley sons ltd

bottom stress estimates from vertical dissipation rate profiles on the continental shelf abstract measurements of the near bottom distribution of the turbulent dissipation rate on the continental shelf west of vancouver island are used to calculate bottom stress a free failing vertical profiler with microstructure shear probes was used to measure the dissipation rate from near the surface to within 0 15 m of the bottom the shear probes measure velocity gradients at scales within the viscous subrange of the turbulence and therefore directly measure the rate at which kinetic energy is dissipated by viscosity friction velocities are computed from the formula uast z where the dissipation rate is measured in the constant stress layer the technique is more reliable than estimates of the dissipation rate obtained by fitting spectral slopes to velocity spectra at scales in the inertial subrange near bottom current measurements indicate that the bottom stress values obtained from the turbulent measurements are well correlated with the current magnitude an estimate of the drag coeff

evolution of the rhone delta plain in the holocene abstract the delta plain of the rhone shows many sandy beach ridges cropping out at the surface we propose here a radiocarbon chronology for the accumulation of the sedimentary bodies and an interpretation of the morphology of the mouth lobes that they form morphologies of the lobes depend on four principal factors 1 the variation of the relative sea level which constitutes the morphogenic base level 2 the fluvial input volume of water discharge and sedimentary input number and position of the mouths 3 marine dynamics volume and direction of the longshore drift dominant wave direction 4 the accommodation space created by the rise of relative sea level along with the paleobathymetry onto which the lobe will prograde immediately in front of the delta and at sea our conclusions are the main holocene paleo delta lobes of ulmet and saint ferreol were contemporaneous being deposited from 4000 to 2000 yr bp however the fluvial style of their downstream channel meandering for ulmet channel and linear for saint ferreol and the lobe morphologies of both channels are contrasted rounded in the case of ulmet and elongated for saint ferreol the role of the accommodation space is confirmed by two recent drillholes traversing the entire holocene succession which reveal a prior stage of sedimentary filling in the case of the saint ferreol lobe thus limiting the accommodation space and favouring a rapid and pointed progradation of this lobe the decoupling between hydrological activity and progradation of lobe indicates the complexity of mechanisms in the large catchment basin of rhone however the high rate of progradation of saint ferreol lobe after 2900 bp is probably a consequence of the increase of human activity after this date the variation of relative sea level remains an important factor controlling the evolution of the rhone delta after 6000 bp the local stabilization of the relative sea level between 4585 bp and 3520 bp played an important role in the triggering of coastal progradation saint ferreol lobe eastern margin rhone delta

variation of rock fragment cover and size along semiarid hillslopes a case study from southeast spain abstract the spatial variation of rock fragment cover rc and rock fragment size rs along semiarid hillslopes and transects in the mediterranean is largely controlled by hillslope gradient total rock fragment cover rc 5 mm often increases in a convex upward curve with hillslope gradient while the d50 of the surface rock fragments 5 mm increases linearly with hillslope gradient on south facing slopes rc 5 mm is slightly higher than on north facing slopes lithology controls the size distribution of the stone pavement rather than its cover percentage spatial variation of rock fragment cover reflects spatial variation in past erosion and deposition rates hillslope sections that are steep south facing or have been abandoned a long time ago have undergone intense interrill and rill erosion and thus have high rock fragment covers tillage erosion leads to high rock fragment covers on convex hillslopes in intensively cultivated areas thus using information on hillslope gradient aspect lithology and landuse we have been able to describe the spatial variation of rock fragment cover and size along semiarid hillslopes in southeast spain such information is crucial for understanding and modelling the spatial variation of the hydrological and erosion response of semiarid hillslopes under environmental change especially in semiarid environments of the mediterranean where vegetation cover is predicted to decrease due to climatic or landuse changes and rock fragments at the surface become the only soil surface stabilisers

observations of bed form evolution with field scale oscillatory hydrodynamic forcing 1 the evolution of rippled beds in response to irregular waves was examined over short temporal scales observations of natural irregularly rippled beds and the oscillatory two dimensional time varying velocity field were collected using a submersible particle image velocimetry piv system bed form evolution regimes characterized by the ripple radius of curvature were examined relative to measures of the nondimensional bed stress the grain roughness shields parameter the nondimensional pressure gradient the sleath parameter and the water column coherent structure formation from the ripples the swirling strength bed forms were found to respond to individual waves by modulating amplitude as wave groups passed the bed form approached its initial geometry following the passage of a group even when the critical value of the shields parameter for sheet flow was exceeded however when the sleath parameter exceeded the critical value for plug flow the bed form profile flattened requiring significant time after the wave group passed to rebuild the ripples these observations suggest that the ability to predict bed form geometry with respect to wave forcing is possible but requires knowledge of the initial bed form geometry as well as the flow field evolution

mid and late holocene sea level changes in roudsea marsh northwest england a diatom biostratigraphical investigation diatoms vascular vegetation sediment data and water salinity from contemporary intertidal environ ments in roudsea marsh northwest england are used to define altitudinal relationships between diatom assem blages and reference water levels comparison of these data with the high resolution diatom biostratigraphy of a fossil marsh sequence allows identification of fluctuations of relative sea level in the mid and late holo cene two oscillations in relative sea level are recorded a rise in sea level 0 6 m led to the inundation of the site after 6000 bp and was followed by a fall in sea level c 1 m around 4700 bp a second rise in sea level 0 5 m occurred before 2420 bp and was followed by a relatively stable or smaller rise of sea level during the last millennium the use of diatom groups based on marsh altitude was successful

how subsoil morphology and erodibility influence the origin and pattern of late holocene tidal channels case studies from the belgian coastal lowlands abstract this paper aims at a better understanding of the late holocene re entrance of the tidal system in the belgian coastal plain after a 2 3 ka years long period of peat growth the re entrance was associated with the development of deeply incised tidal channels the initial cause of the re entrance still a missing link in the understanding of the late holocene coastal change is investigated by focusing on the specific location of the young tidal channels the research though based in the western belgian coastal plain is relevant to the lowlands of the southern north sea and english channel the investigation combines stratigraphic radiocarbon and sedimentological data together with maps showing the morphology of the pre holocene surface the distribution of the holocene deposits and the erosional surface produced by the late holocene channels it appears that the young channels re occupied the same position as their early and mid holocene predecessors the re entrance of the tidal system began by a removing of the upper part of the older channels which originated from the mainland once the channels were cleaned of sediment tidal waters could re enter and rework the easily erodable sand of the older channels and pleistocene deposits

distribution of energy spectra reynolds stresses turbulence production and dissipation in a tidally driven bottom boundary layer abstract seven sets of 2d particle image velocimetry data obtained in the bottom boundary layer of the coastal ocean along the south carolina and georgia coast at the south atlantic bight synoptic offshore observational network sabsoon site are examined covering the accelerating and decelerating phases of a single tidal cycle at several heights above the seabed additional datasets from a previous deployment are also included in the analysis the mean velocity profiles are logarithmic and the vertical distribution of reynolds stresses normalized by the square of the free stream velocity collapse well for data obtained at the same elevation but at different phases of the tidal cycle the magnitudes of u u w w and u w decrease with height above bottom in the 25 160 cm elevation range and are consistent with the magnitudes and trends observed in laboratory turbulent boundary layers if a constant stress layer exists it is located below 25 cm elevation two methods for estimating dissipatio

middle holocene alluvial forests and associated fluvial environments a multi proxy reconstruction from the lower scheldt n belgium analyses of pollen plant macrofossils seeds fruits wood and mosses molluscs diatoms and vertebrate mainly fish remains allowed a detailed reconstruction of a middle holocene alluvial forest and its associated hydrological conditions the use of multiple proxies resulted in a taxonomically more detailed and environmentally more comprehensive understanding of terrestrial as well as aquatic habitats the results demonstrate possible biases in palaeoecological reconstructions of alluvial and estuarine environments drawn from single proxies many locally occurring woody taxa were underrepresented or remained undetected by pollen analyses seeds and fruits also proved to be inadequate to detect several locally important taxa such as ulmus and hedera helix apparently brackish conditions inferred from diatoms pollen and other microfossils conflicted strikingly with the evidence from molluscs fish bones and botanical macroremains which suggest a freshwater environment brackish sediment and the microfossil indicators is likely to have been deposited during spring tides or storm surges when estuarine waters penetrated more inland than usual despite the reworking and deposition of estuarine and saltmarsh sediment well above the tidal node at such events local salinity levels largely remained unaffected

concentrated flow erosion rates as affected by rock fragment cover and initial soil moisture content abstract concentrated flow experiments using a small hydraulic flume and a constant flow discharge and bed slope have been conducted in order to investigate the effects of rock fragment cover rc on sediment yield for an initially wet and an initially air dry loamy topsoil the experimental results indicate that rc reduces concentrated flow erosion rates e in an exponential way i e e e brc which is similar to previously reported relations for other water erosion processes such as interrill erosion and sheet rill erosion measured on runoff plots the decay rate b of this exponential relationship increased throughout the experiments because of scour hole development and bed armouring the concentrated flow erosion rates and b values also depend on the initial moisture content of the topsoil depending on rc mean concentrated flow erosion rates were 20 to 65 less on initially wet compared to initially air dry topsoils the mean value for b was 0 032 for the initially wet but only 0 017 for the initially air dry topsoil indicating that a rock fragment cover is less efficient in reducing concentrated flow erosion rates when the topsoil is initially air dry than when it is initially wet the results help explain the data scatter in reported relationships between rc and interrill rill erosion rates they also indicate that a given surface rock fragment cover will offer more protection to wet topsoils than to dry topsoils which are very common in mediterranean environments event based water erosion models should incorporate effects of antecedent soil moisture content as well as those of rc on concentrated flow erosion rates

water level changes in the flevo area central netherlands 5300 1500 bc implications for relative mean sea level rise in the western netherlands abstract the younger post 4000 cal bc part of the water level curve for the eastern flevo area central netherlands runs below the relative mean sea level msl curve for the western and northern netherlands mededelingen rijks geologische dienst 36 1 1982 93pp we investigated if this difference can be attributed to i root rejuvenation of the bulk dated basal peat samples on which the curve for the eastern flevo area is based and or ii underestimation of the water depth in which the dated peat accumulated it appears that these potential sources of error did not influence significantly the results obtained by roeleveld and gotje de holocene laagveenontwikkeling in de randzone van de nederlandse kustvlakte noordoostpolder unpublished ph d thesis vrije universiteit amsterdam 1993 pp 76 86 on the basis of new and recently published water level data from the eastern and southwestern flevo area we confirm refine and tentatively extend the water level rise reconstruction by roeleveld and gotje and establish a relative msl trend curve for the central netherlands the systematic age differences of our radiocarbon dates on various fractions of four new basal peat samples from the eastern flevo area support the interpretation by roeleveld and gotje that the younger part of the 1982 msl curve may be based on basal peat samples all from the rotterdam area that have been dated 100 200 yr too old if this interpretation is correct the fact that the relative msl curve for the central netherlands lies below the 1982 msl curve cannot be interpreted to indicate less crustal subsidence for the rhine meuse delta as predicted by geophysical modeling j quat sci 17 2002 535

relative sea level rise and neotectonic events during the last 6500 yr on the southern eastern rhone delta france abstract the analysis of peat formations from the eastern limit of the rhone delta allows us to follow relative sea level changes over the last 6300 yr the curve represents two periods of rapid relative sea level rise about 2 mm yr the first between 6295 50 and 4585 45 bp and then the second between 2120 55 and 1200 55 bp these two periods are separated by a period of stability between 4085 60 and 3520 55 bp the comparison with data from the rocky coast to the east of marseille indicates a negative difference of between 1 5 and 0 5 m then rapid adjustment after 2120 55 bp the existence of an incompressible substrate along with the thinning out of the holocene deposits along the limits of the deltas restricted the effects of subsidence and compaction we prefer the hypothesis that tecto subsident movements account for these differences as well as the rapid rise in relative sea level during this second period this is compatible with the network of post miocene faults that account for the differences in altitude of the roman quarries carved out from the miocene layers

the streif classification system a tribute to an alternative system for organising and mapping holocene coastal deposits the classification system for organising and mapping holocene coastal deposits as introduced by streif is highlighted with respect to mapping requirements apart from the requirements such as a user friendly legend and map the linkage of the classification system with the history of deposition is demonstrated for the tide dominated lowlands of the southern north sea and english channel the linkage becomes obvious when considering the effect of the changes in the rate of relative sea level rise the difficulties that surrounded the lithostratigraphy of holocene coastal deposits and the principles of the classification system which eventually made an end to the well known and long standing debate about the lithostratigraphy are briefly recalled

sedimentology and stratigraphy of a tidal sand bank in the southern north sea abstract a set of 125 vibrocores collected on the basis of a dense grid of high and very high resolution seismic coverage over a tidal sand bank the middelkerke bank provides a unique opportunity to reconstruct the stratigraphy and sedimentary facies succession of such a large tidal sand body five sedimentary facies are distinguished they range from clay to pebble and display various types of bedding and lithologies corresponding to different depositional environments a succession of four late quaternary units are defined on the basis of the stratigraphic framework given by the seismic grid the first unit represents the infill of a palaeovalley system by tidally influenced sedimentary facies it is followed by extensive and thick lagoonal or sub tidal deposits the third unit reveals the development of a landward prograding storm dominated sand bar this unit is dominated by clean fine sand the last unit corresponds to the present day tidal sand bank it shows the typical offshore tidal sand bank facies cross bedded sand prograding in an offshore direction like other banks located in a more offshore position the middelkerke bank is a composite bank incorporating facies which do not occur in classic tidal sand banks

holocene sea level database for the rhine meuse delta the netherlands implications for the pre 8 2 ka sea level jump abstract this paper provides the most accurate sea level index points slips for the rhine meuse delta rmd the netherlands identified amidst a wealth of data accumulated in sixty years of research following documented protocols 106 selected radiocarbon dates from peat beds from transgressed valley floor upper estuarine and back barrier lagoonal settings were first listed individually then screened in ensemble on quantified age depth position and inshore palaeotidal setting the database contains 50 slips and 56 upper limiting data points spanning a depth range of 34 to 1 5 m the dates in the database originate from dedicated sea level research which kept surface elevation and sampling depth uncertainty small and sampling of basal peat beds was favoured keeping compaction uncertainties small too the slips cover an age range of 8 8 3 0 ka bp and are available from greater rotterdam and its near offshore for upper limiting data points the coverage extends offshore tracing the rhine palaeovalley and reaches back to 11 5 ka bp the age depth data density and spatial concentration of subsets of dates allow to perform bayesian radiocarbon calibration and to reduce temporal uncertainty by 25 for the average sample 1 age uncertainty 75 cal yr when depth position and rates of relative sea level rise rslr are used to assign sequence order between 8 0 4 5 ka bp rates of rslr gradually decreased from 9 to 1 mm yr in the millennium before rates of rslr were much higher on average 10 mm yr and marked by a sea level jump between 8 45 8 2 ka bp a two phased nature of this jump starts to be resolved with local magnitudes of 1 7 0 6 m 1 first phase and 0 2 0 2 m second phase corresponding to globally averaged jumps of 2 5 m 0 9 m for the first and 0 3 0 3 m for the second phase for the pre 9 ka bp period only offshore upper limiting data points are currently available until new offshore data are gathered trends of rslr before 9 ka bp can only be estimated fed with global insights in post glacial eustasy regional estimates regarding rates of glacio isostatic adjustments and tectonic subsidence and sedimentary geological interpretations of scattered basal peat presence

full scale observations of wave induced vortex generation over a rippled bed 1 our understanding of vortex generation over rippled beds is largely based on small scale laboratory studies the insight provided by such studies has been considerable although questions remain regarding the applicability to the field this paper presents observations from a full scale investigation of wave induced vortex generation events over a movable sediment bed observations of the two dimensional time varying velocity field were obtained with a submersible particle image velocimetry piv system in a field scale experimental environment at the o h hinsdale wave research laboratory the observations were obtained over an irregularly rippled bed with ripple height and wavelength of roughly 0 01 m and 0 1 m respectively the vortices generated during offshore directed flow over the steeper bed form slope were regularly ejected into the water column and were consistent with conceptual models of the oscillatory flow over a backward facing step the observations allowed for an examination of the generation and subsequent ejection of individual vortical structures vortical structures are identified with a measure of the flow field that estimates the time for a complete revolution of a vortex called swirling strength an analysis of these structures reveals that the swirling strength nondimensionalized by the wave period is correlated to the keulegan carpenter these results offer new insight into fluid sediment interaction over rippled beds

estimating hydrodynamic roughness in a wave dominated environment with a high resolution acoustic doppler profiler 1 hydrodynamic roughness is a critical parameter for characterizing bottom drag in boundary layers and it varies both spatially and temporally due to variation in grain size bedforms and saltating sediment in this paper we investigate temporal variability in hydrodynamic roughness using velocity profiles in the bottom boundary layer measured with a high resolution acoustic doppler profiler pcadp the data were collected on the ebb tidal delta off grays harbor washington in a mean water depth of 9 m significant wave height ranged from 0 5 to 3 m bottom roughness has rarely been determined from hydrodynamic measurements under conditions such as these where energetic waves and medium to fine sand produce small bedforms friction velocity due to current u c and apparent bottom roughness z0a were determined from the pcadp burst mean velocity profiles using the law of the wall bottom roughness kb was estimated by applying the grant madsen model for wave current interaction iteratively until the model u c converged with values determined from the data the resulting kb values ranged over 3 orders of magnitude 10 1 to 10 4 m and varied inversely with wave orbital diameter this range of kb influences predicted bottom shear stress considerably suggesting that the use of time varying bottom roughness could significantly improve the accuracy of sediment transport models bedform height was estimated from kb and is consistent with both ripple heights predicted by empirical models and bedforms in sonar images collected during the experiment

estimating bottom stress in tidal boundary layer from acoustic doppler velocimeter data bed stresses in the bottom boundary layer of the york river estuary virginia were estimated from three dimensional near bottom velocities measured by acoustic doppler velocimeters advs and also by a profiling array of electromagnetic current meters by assuming the measurements were made in a constant stress layer four methods of stress estimation were evaluated using advs direct covariance cov measurement turbulent kinetic energy inertial dissipation utilizing the kolmogorov spectrum and log profile the four methods yielded similar estimates of frictional velocity u based on adv output from both 14 cm and 44 cm above bed all eight estimates of average u were consistent with the overall mean of 1 10 cm s to within the 95 confidence interval for individual burst estimates the cov method worked slightly better nearer the bed possibly because of the sensitivity of cov to the upper limit of the constant stress layer the inertial dissipation method performed marginally well at 14 cm above bed likely because of sediment induced stratification and insufficient separation of turbulent production and dissipation scales the log profile method was the most variable and appeared most sensitive to stratification and to the thickness of the constant stress layer the turbulent kinetic energy method was the most consistent at both heights and appears most promising for further development results encourage future use of the adv in estuarine environments but also favor the simultaneous use of several methods to estimate bottom stress

holocene relative sea level change isostatic subsidence and the radial viscosity structure of the mantle of northwest europe belgium the netherlands germany southern north sea abstract a comprehensive observational database of holocene relative sea level rsl index points from northwest europe belgium the netherlands northwest germany southern north sea has been compiled in order to compare and reassess the data collected from the different countries regions and by different workers on a common time depth scale rsl rise varies in magnitude and form between these regions revealing a complex pattern of differential crustal movement which cannot be solely attributed to tectonic activity it clearly contains a non linear glacio and or hydro isostatic subsidence component which is only small on the belgian coastal plain but increases significantly to a value of ca 7 5 m relative to belgium since 8 cal ka bp along the northwest german coast the subsidence is at least in part related to the post glacial collapse of the so called peripheral forebulge which developed around the fennoscandian centre of ice loading during the last glacial maximum the rsl data have been compared to geodynamic earth models in order to infer the radial viscosity structure of the earth s mantle underneath nw europe lithosphere thickness upper and lower mantle viscosity and conversely to predict rsl in regions where we have only few observational data e g in the southern north sea a very broad range of earth parameters fit the belgian rsl data suggesting that glacial isostatic adjustment gia only had a minor effect on belgian crustal dynamics during and after the last ice age in contrast a narrow range of earth parameters define the southern north sea region reflecting the greater influence of gia on these deeper older samples modelled rsl data suggest that the zone of maximum forebulge subsidence runs in a relatively narrow wnw ese trending band connecting the german federal state of lower saxony with the dogger bank area in the southern north sea identification of the effects of local scale factors such as past changes in tidal range or tectonic activity on the spatial and temporal variations of sea level index points based on model data comparisons is possible but is still complicated by the relatively large range of earth model parameters fitting each rsl curve emphasising the need for more high quality observational data

detailed measurements of velocities and suspended sand concentrations over full scale ripples in regular oscillatory flow the knowledge and modeling of wave induced sand transport over rippled beds still has significant shortcomings which is partly related to a lack of measurements of the detailed processes from controlled laboratory experiments we have carried out new measurements of the detailed time dependent velocity and suspended sand concentration field around vortex ripples for regular oscillatory flow conditions the fact that the ripples were mobile and the flow conditions were full scale makes these measurements unique we made velocity measurements for 14 different flows and concentration measurements for three of these flows the velocity and concentration field above ripples are dominated by the generation and ejection of vortices on the ripple flanks around the time of flow reversal vortex formation results in near ripple flow reversals ahead of free stream reversals and velocity maxima near the ripple crest that are much higher than the free stream maxima asymmetry in the free stream produces steady circulation cells with dominant offshore mean flow up the ripple lee slope balanced by weaker onshore streaming up the ripple stoss slope as well as higher up in the flow the time and bed averaged horizontal velocity profile comprises an offshore streaming near the bed and an onshore drift higher up in the flow the vortices are responsible for three main concentration peaks one just after on offshore flow reversal associated with the passage of a sand laden vortex followed by two smaller peaks due to advected suspension clouds generated by vortex action at the neighboring onshore ripples the sand flux field measured for one typical asymmetric flow condition is dominated by an offshore flux associated with the suspended sand cloud generated by vortex shedding from the ripple s lee slope around the time of on offshore flow reversal the net time averaged current related and wave related horizontal sand fluxes are generally offshore directed and mostly contained within 1 5 ripple heights above the ripple crest the wave related suspended transport component is larger but the contribution of the current related suspended sand transport cannot be neglected in addition to the measured offshore net transport of suspended sand there is an onshore directed transport very close to the ripple surface the total net transport is in the offshore direction for this specific asymmetric flow condition

chironomid responses insect diptera to younger dryas and holocene environmental changes in a river floodplain from northern france st momelin st omer basin lateglacial to holocene subfossil chironomids from the st omer basin at st momelin northern france were analysed at the end of the lateglacial stratigraphic and chironomid sequences indicate a shallow oligotrophic and slow flowing freshwater stream with abundant aquatic macrophytic vegetation cold water adapted taxa indicate a cold climate during the early holocene from about 9500 to 7700 conventional radiocarbon yr bp climate improvement is marked by an increase in warm water adapted taxa and a decrease in cold water fauna however the cold water fauna persist probably because of both the instability and continentality of the climate during the mid holocene from about 7700 to 6000 bp the marine transgression strongly influenced the river s hydrological regime and consequently the chironomid assemblages at that time eutrophic warm and shallow stagnant water conditions occured throughout the basin from 6000 to 3200 bp the st momelin basin was subjected to a marine regression chironomids indicate a hydrological regime marked by an alternance of phases with either a dominance of rheophilous or limnophilous fauna during this period equivalent percentages of warm and cold adapted taxa may be explained by cold water input in context of a temperate climate

spatial distribution of rock fragments in dolines a case study in a semiarid mediterranean mountain range sierra de gador se spain abstract rock fragments rfs at the soil surface have great effects on the intensity of various hydrologic and geomorphic processes however little information is available on the spatial distribution of rock fragments rf in the dolines which may be of importance in understanding overland flow and subsequent recharge in limestone karst landscapes this study analysed spatial variability of rf cover and size in different topographic positions top upper middle and lower position in three dolines in sierra de gador almeria province south east spain the results indicated that cover percentage of small rfs 5 20 mm increased but large rf cover 250 600 mm and 600 mm decreased from the upper position to the lower position of the dolines small rfs were usually resting on the soil surface while most large rfs tended to be partly embedded in the soil surface total rf cover and d 50 median diameter of the surface rfs greater than 5 mm tended to increase with slope gradient

holocene evolution of relative sea level and local mean high water spring tides in belgium a first assessment abstract holocene age depth data from the belgian coastal plain basal peat data particularly are assessed in terms of local water and tide levels basal peat formation was generally induced by sea level rise effects of local seepage were limited and significant river gradient effects were absent no relation was found between the timing of basal peat inception and substrate permeability in general edaphic moisture conditions were unfavourable for organic accumulation prior to sea level related rise of the groundwater table error envelopes for the minimum level of local mean high water spring tides and for upper and extreme lower relative mean sea level limits during the last 9400 solar years 8400 yrs b p are presented these indicate that the rate of relative sea level rise showed marked retardations at ca 7500 7000 yrs cal b p 6650 6100 yrs b p and ca 5500 5000 yrs cal b p 4400 yrs b p a eustatic explanation appears to be plausible particularly for the former prior to ca 4000 yrs cal b p ca 3600 yrs b p the relative sea level rise in belgium differs noticeably from that established for the western netherlands with both diverging progressively back in time this implies that considerable differential crustal movement occurred between the two areas in the early holocene

a new holocene relative sea level curve for western brittany france insights on isostatic dynamics along the atlantic coasts of north western europe abstract this study presents new relative sea level rsl data that were obtained in the finistere region western tip of brittany france and the implications those data have for the understanding of the isostatic dynamics across north western europe and more specifically along the atlantic and channel coasts new stratigraphic sequences were obtained and analyzed to derive 24 new sea level index points in which 6 are basal these new data considerably increase the knowledge we have of the rsl evolution along the coasts of western brittany since the last 8 kyr b p from this new dataset rsl was estimated to rise continuously over the last 8 kyr with a major inflection at ca 6 kyr cal bp our results show large vertical discrepancies between the rsl records of brittany and south western uk with the latter plotting several meters below the new data from this comparison we suggest that the two regions underwent a very different pattern and or amplitude of subsidence during the last 8 kyr which has implications for the spatial and temporal pattern of the peripheral bulge of the european ice sheets we compared our data against predictions from glacio isostatic adjustment models gia models there are large misfits between rsl observations and the predictions of the global ice 5g vm2a peltier 2004 glac1 b tarasov and peltier 2002 tarasov et al 2012 briggs et al 2014 and regional uk models biis bradley et al 2009 bradley et al 2011 kuchar kuchar et al 2012 which can t be resolved through significant changes to the deglaciation history and size of the british irish ice sheet paleo tidal modelling corrections indicate regional changes in the tidal ranges played a negligible role in the data model misfits hence we propose that the misfits are due to some combination of i unaccounted mass loss of far field ice sheets antarctic ice sheet or laurentide ice sheet ii unresolved differences in the deglaciation history and size of the fennoscandian ice sheet or more likely iii significant lateral variations in the earth s structure across the english channel

sediment supply and barrier dynamics as driving mechanisms of holocene coastal change for the southern north sea basin the combined effects of climate change and human impact lead to regional and local coastal responses that pose major challenges for the future resilience of coastal landscapes increasing the vulnerability of communities infrastructure and nature conservation interests using the suffolk coast southeast england as a case study we investigate the importance of sediment supply and barrier dynamics as driving mechanisms of coastal change throughout the holocene litho bio and chronostratigraphic methods are used to decipher the mechanisms of coastal change from the record preserved within coastal stratigraphy results suggest that local coastal configuration and sediment supply were the most influential in determining coastal change during the mid and late holocene against a background control of sea level rise the importance of sedimentological and morphological factors in shaping holocene coastal changes in the southern north sea basin must therefore be considered when using the database of evidence from this region as an analogue for future change under accelerated sea level rise

evidence for ubiquitous preferential particle orientation in representative oceanic shear flows in situ measurements were undertaken to characterize particle fields in undisturbed oceanic environments simultaneous co located depth profiles of particle fields and flow characteristics were recorded using a submersible holographic imaging system and an acoustic doppler velocimeter under different flow conditions and varying particle concentration loads typical of those found in coastal oceans and lakes nearly one million particles with major axis lengths ranging from 14 m to 11 6 mm representing diverse shapes sizes and aspect ratios were characterized as part of this study the particle field consisted of marine snow detrital matter and phytoplankton including colonial diatoms which sometimes formed thin layers of high particle abundance clear evidence of preferential alignment of particles was seen at all sampling stations where the orientation probability density function pdf peaked at near horizontal angles and coincided with regions of low velocity shear and weak turbulent dissipation rates furthermore pdf values increased with increasing particle aspect ratios in excellent agreement with models of spheroidal particle motion in simple shear flows to the best of our knowledge although preferential particle orientation in the ocean has been reported in two prior cases our findings represent the first comprehensive field study examining this phenomenon evidence of nonrandom particle alignment in aquatic systems has significant consequences to aquatic optics theory and remote sensing where perfectly random particle orientation and thus isotropic symmetry in optical parameters is assumed ecologically chain forming phytoplankton may have evolved to form large aspect ratio chains as a strategy to optimize light harvesting

the indicative meaning of diatoms pollen and botanical macro fossils for the reconstruction of palaeoenvironments and sea level fluctuations along the coast of lower saxony germany abstract interdisciplinary studies carried out on marine and terrestrial deposits such as tidal flats lagoonal deposits and salt marshes have provided the basis for interpreting holocene sea level fluctuations along the southern north sea coast radiocarbon dating provides the timeframe for the studies the employed palaeoecological techniques include analysis of pollen diatoms and botanical macro remains benefits and constraints of each technique are discussed using examples of sediment cores from around the southern north sea sea level index points have been defined using the results of these interdisciplinary studies and then employed to reconstruct the sea level oscillations of the last two millennia

improving methodology for high resolution reconstruction of sea level rise and neotectonics by paleoecological analysis and ams 14c dating of basal peats abstract sea level research in several submerging coastal regions has traditionally been based on 14 c dating of basal peats that overlie a compaction free substratum and can be related to paleo ground water levels provided that an unequivocal relationship between ground water level and sea level can be assumed this approach contains two sources of uncertainty 1 the paleoenvironmental interpretation of samples is usually based on inherently inaccurate macroscopic descriptions in the field and 2 14 c ages of bulk peat samples may be erroneous as a result of contamination due to the uncertainties in both the altitude and the age the two crucial sources of evidence necessary to arrive at accurate sea level curves sea level index points are therefore represented by considerable but typically not quantified error boxes accelerator mass spectrometry ams opens new perspectives for this type of sea level research as illustrated by a paleoecological and ams 14 c study of basal peats from a small study area in the rhine meuse delta the netherlands where previous conventional work revealed highly problematic results a detailed macrofossil analysis has two purposes 1 an inferred paleoecological succession indicates a relatively accurate level of paludification of the site and hence rise of the ground water level 2 suitable macrofossils from that specific level are then selected for ams 14 c dating in spite of very small sample sizes our results are consistent and indicate that this approach can constitute a step forward in high resolution reconstruction of sea level rise the new results further enable a revision of holocene ground water gradient lines for the rhine meuse delta a knickpoint in these gradient lines can be related to the effect of faulting this approach therefore also has considerable potential to unravel and quantify neotectonic activity in submerging coastal settings

movable bed roughness in unsteady oscillatory flow a model to predict the roughness in unsteady oscillatory flows over movable noncohesive beds is presented the roughness over movable beds is shown to be a function of the boundary shear stress rather than a fixed geometrical scale as is the case for fully rough turbulent boundary shear flows over immobile beds the model partitions the roughness into two distinct contributions these two contributions are due to the form drag around individual bed forms and to the near bed sediment transport the form drag over the bed forms is treated explicitly as a function of the boundary geometry and shear stress the ripples are predicted as a function of the local skin friction and a semiempirical expression is derived using standard law of the wall arguments which gives the ripple or form roughness as a function of the boundary geometry the ripple roughness is found to be proportional to the product of the ripple steepness and height favorable comparison of the form drag model with the results of bagnold s 1946 fixed ripple study is found the value of z0 associated with intense sediment transport in oscillatory flow over a flat bed is determined from carstens et al s 1969 experiments this value is found to be 7 or 8 grain diameters an expression is derived for the roughness associated with the maximum thickness of a near bottom sediment transporting layer consistent with owen s 1964 roughness hypothesis for saltation of uniform grains in air at large values of the boundary shear stress relative to the critical value for initial sediment motion the derived expression is similar to the results of smith and mclean s 1977 unidirectional flow approach modified for oscillatory flow the total roughness model is found to compare favorably with carstens et al s 1969 data in contrast to smith and mclean s 1977 steady flow findings the results here show that when ripples are present they account for a significant portion of the boundary roughness

comments on shoreface sand supply and mid to late holocene aeolian dune formation on the storm dominated macrotidal coast of the southern north sea by e j anthony m mrani alaoui and a hequette marine geology 276 2010 100 104 abstract anthony et al 2010 published a recent paper in marine geology on the origin and chronology of an inland dune for which they presented an explanation for the regional pattern of mid to late holocene coastal development this explanation contradicts other data collected from this coastal area it is moreover in contrast to our current understanding of holocene coastal evolution of the southern north sea the data used by anthony et al 2010 includes a number of inconsistencies that led the authors to incorrect conclusions this discussion reports on our critical evaluation of data and reasoning in antony et al 2010 we propose an alternative model of coastal evolution which is in line with the current knowledge about mid to late holocene coastal evolution

the effects of coal gangue and fly ash on the hydraulic properties and water content distribution in reconstructed soil profiles of coal mined land with a high groundwater table soil water systems have been severely degraded in coal mined and subsiding land where a shallow groundwater table is also present the present paper discussed the effects of fly ash fa and coal gangue cg as filling materials on the hydraulic properties and water content distribution in a profile for the purpose of rehabilitating subsided lands the saturated water content water characteristic curve and water diffusivity of local soil fa cg and a mixture of fa and cg mixed filling were characterized a column experiment was conducted to investigate the changes of water content in profiles reconstructed from the combination of soil and filling materials including soil only fa cg and a mixture of fa and cg which were used to fill the lower part of the reconstructed profile the mixture of fa and cg was found to possess similar hydraulic properties to those of the soil particularly high water holding capacity and permeability moreover the volumetric water contents in the whole profile containing the mixture of fa and cg were consistent with those of the profile reconstructed with soil only as a result it is recommended to adopt the mixture of fa and cg for reconstructing the lower profile of the land to alleviate or rehabilitate subsided land in coal mines

turbulence characteristics and dissipation estimates in the coastal ocean bottom boundary layer from piv data abstract turbulence characteristics in the coastal ocean bottom boundary layer are measured using a submersible particle image velocimetry piv system with a sample area of 20 20 cm2 measurements are performed in the new york bight at elevations ranging from 10 cm to about 1 4 m above the seafloor recorded data for each elevation consists of 130 s of image pairs recorded at 1 hz after processing the data at each elevation consist of 130 instantaneous spatial velocity distributions within the sample area the vertical distribution of mean velocity indicates the presence of large scale shear even at the highest measurement station the flow also undergoes variations at timescales longer than the present data series spatial spectra of the energy and dissipation are calculated from individual vector maps the data extend well beyond the peak in the dissipation spectrum and demonstrate that the turbulence is clearly anisotropic even in the dissipation range the vector maps are also patched together to

field observations of the wave bottom boundary layer this paper presents a comprehensive set of velocity and suspended sediment observations in the nearshore wave bottom boundary layer collected during the duck94 field experiment on the outer banks of the north carolina coast cross shore velocity measurements in the wave bottom boundary layer were made using five hot film anemometers nominally spaced from 1 to 5 cm above the bed in 2 m of water depth the time varying location of the seabed was estimated to roughly 1 cm with a stacked set of bed penetrating fiber optic backscatter sensors the instrument array was intermittently located in the surf zone on the crest of a bar the location of the bottom varied several centimeters over a 34 min data run even over 4 min segments of quasi steady statistics occasional large waves caused short erosion and redeposition events complicating the definition of bottom location and causing the root mean square velocity statistics to be nonzero below the mean bed location this leads to obvious difficulties in comparisons with two one dimensional time dependent eddy viscosity wave bottom boundary layer models for example bed shears based on rms amplitude decay were lower than predicted the observations show some evidence for a velocity overshoot region within the wave bottom boundary layer the observations were compared with two linear eddy viscosity models larger estimates of a constant eddy viscosity and smaller than predicted phase leads are indicative of more rapid mixing of momentum than predicted by the models the phase and amplitude frequency response estimated with frequency domain empirical orthogonal functions shows a nonlinear response of the wave bottom boundary layer over the incident band these observations are among the first coherent looks at the wave bottom boundary layer under conditions of significant sediment response they highlight the added complexity of the dynamics in natural environments

conservation of soil moisture by different stone covers on alpine talus slopes lassen california abstract this study reports on the influence of stone covers with different clast sizes on the soil moisture of alpine talus slopes in lassen california fifteen four plot sets were sampled in the dry season july 1990 in sandy areas and in talus covered with pebbles cobbles or blocks between 2740 and 2775 m three depths 0 5 5 10 10 15 cm were sampled field moisture content increased gradually with depth in all soil profiles and also in plots covered by increasingly larger rocks surface soils in sand areas were very dry but under rocks had water contents 6 to 14 times greater differences among plots decreased with depth but subsoil samples in sand were still drier than those beneath any stone cover at similar depths blocks were most effective in conserving moisture water content below them was higher than even in deep 10 15 cm sand soils soil temperatures were recorded in sand and under blocks for an 11 day period minima were not significantly different but average maxima were 5 6 c lower under blocks than in sand which reached highs 4 4 c lower than the air differences in soil moisture among talus types are ascribed to lower evaporation losses under stones due to both disruption of capillarity by the coarse particles which prevented water flow to the talus surface and to their efficient reduction of maximum temperatures an irrigation experiment was conducted at 2110 m on a steep talus on the chaos crags from july 18 to aug 2 1993 four 100 75 cm plots with the same surface types than at lassen received 22 5 mm water moisture content was then periodically sampled watering produced similar water distributions among soil depths and talus types to those in lassen evaporation occurred quickly in bare soils due to high air and soil temperatures the sand surface was already dry 2 days after watering but stone covered plots remained moist until day 15 when soils under blocks still retained 77 97 of the water content percent by weight at the start of the test

late quaternary sea level change and isostatic and tectonic land movements along the belgian dutch north sea coast geological data and model results early and middle holocene sea level data from belgium plot ca 2 m above data from the western netherlands reflecting differential tectonic and isostatic movements the total uplift rate of belgium relative to the western netherlands decays gradually from 0 66 m kyr 1 at 7500 cal yr bp to less than 0 25 m kyr 1 since 5000 cal yr bp the tectonic component of this relative movement inferred from eemian sea level data is in the order of 0 06 to 0 16 m kyr 1 the isostatic component of the uplift is related to the last phase of the collapse of a peripheral bulge under the netherlands and the dutch and german sectors of the north sea and to hydroisostatic subsidence of the north sea basin caused by water loading as sea level rose comparisons with isostatic rebound models show that they predict well the holocene isostatic movement between belgium and the western netherlands and that the predictions are improved when the tectonic component is removed from the observations preliminary evaluation of sea level data from the dutch sector of the north sea shows that glacio hydroisostatic subsidence relative to belgium was significantly greater than for the western netherlands coastal area and spatially highly variable copyright 2002 john wiley sons ltd

influence of rock fragments on the water retention and water percolation in a calcareous soil abstract the water retention properties of a calcareous soil containing rock fragments have been determined in the laboratory thanks to pressure plate measurements done on both the fine earth and the rock fragments from the soil the available water content awc has been calculated from these data we have shown that when the rock fragments are neglected the awc can be overestimated by 39 when we do not neglect their volume but when their hydraulic properties are not considered the awc can be underestimated by 34 by using a reservoir model we have also calculated the effect of rock fragments on water percolation to groundwater depending of the climatic characteristics of the year the underestimation of percolation when we neglect the rock fragments can reach up to 14 9 and the overestimation when we neglect their hydraulic properties can be equal to 15 8 these findings emphasise the role of the rock fragments on the water supply in stony soils