sediment characteristics in the north branch of the yangtze estuary based on radioisotope tracers nuclide specific activity and sediment grain size were analyzed at locations along the north branch of the yangtze changjiang estuary the spatial distributions of various radioisotopes are presented along with the sources and applications of these nuclides for studies of the aquatic environment the specific activities of sediment radionuclides in the north branch increase toward the ocean indicating that the sediment is transported from the downstream side of the estuary into the north branch the 226ra 228ra ratio agrees well with the observed results and can be used to identify trends in erosion and accretion in the north branch

an improved method of sediment grain size trend analysis in the xiaoqinghe estuary southwestern laizhou bay china although deltas evolve with a regular cycle of growth and abandonment over centuries knowledge of these cycles and their effects is important given the fact that humans tend to locate near these areas this study examines sediment transport patterns in the xiaoqinghe estuary in southwestern laizhou bay china in order to identify the factors controlling the sedimentary environment in the estuary sediment samples collected from the bed of laizhou bay in 2007 were analyzed using the gao collins 2 d grain size pattern analysis method and two polymodal distribution functions the study identified three grain size subgroups 4 6 16 and 27 115 mu m and mapped the distribution of the relative percentage of the three components and the mean size distribution within each component the sediment transport trends for the three components were derived by a mathematical partitioning process generally the finest grains move from the local river mouths seaward in the north and south directions with a large anomaly suggesting input into the study area from the more distant huanghe river in the north in addition fine grained sediment is transported by marine hydrodynamic forces from the shallow sea areas toward the coast the medium sized grains move toward the river mouths settling over oyster beds and sandbars that create high turbulence zones while the fine silt grains move seaward in northerly and southerly directions the coarser grains tend to flow toward the coast brought in by seaward migration with some coarse material moving off the river mouths

morphological change and sediment dynamics of the beach step on a macrotidal gravel beach abstract the morpho sedimentary evolution of a pure gravel beach step over a tidal cycle is examined during fairweather conditions using detailed measurements of nearshore hydrodynamics morphological and sedimentary change and nearshore sediment transport the characteristics of the beach step are analysed with specific reference to the concurrent dynamics of the beachface a departure from previous studies which have treated the step as a feature isolated from the nearshore region as a whole the step and berm are both accretionary features strongly linked to tidal stage yet their temporal evolution is independent the relaxation time of the berm being linked to the spring neap tidal cycle and that of the more transient step linked to the semi diurnal tide over this time scale the beachface is a closed sedimentary unit although the beach step may be differentiated from the beachface using sedimentary moments indeed despite the location of the step in the region of wave breaking it has relatively stable sedimentology remaining characteristically coarser and more leptokurtic than the swash zone co spectral analysis between nearshore bed motion and cross shore current velocity reveals that significant nearshore sediment transport occurs at sub incident frequencies in response to wave groups motion of the nearshore bed is not a linear function of velocity magnitude or direction so it is likely that there is a role for the various mechanical properties of the bed therefore a better description of nearshore sediment transport in the region of the beach step would require instantaneous sediment size information allowing the use of a time variant friction factor

impacts of relative sea level rise on the shoreface deposition shuidong bay south china the influence of relative sea level rise on shoreface deposition helps to elucidate changes in beach and nearshore geomorphology in response to different forcing factors in this study two sets of sediment samples one from 1982 and one from 2004 from the shuidong bay of south china were analyzed to determine the changes in shoreface depositions an eof empirical orthogonal function method was used to examine how these depositions changed based on the relative sea level rise the results show that shoreface sediments of shuidong bay are mainly composed of sand fine grained sediments are distributed in the lower shoreface offshore area and coarse grained sediments are mainly found in the upper shoreface nearshore area due to the altered hydrological forcing caused by relative sea level rise the sand fraction in sediments increased from 84 7 in 1982 to over 90 in 2004 and the clay and silt fractions decreased from 11 8 in 1982 to 5 6 in 2004 grain size parameters in sediments in 2004 became coarser slightly more well sorted less skewed and had lower kurtosis than those in 1982 in addition the shoreface deposition of shuidong in 1982 and 2004 is distinctly different a polarized mode was described by the first eigenfunctions and a homogenized mode was described by the second eigenfunctions the former means that the sediment components developed towards the two opposite poles undergoing both coarsening and refining processes the second mode indicates that the secondary variation in sediment components was mostly in the three intermediate grained sand components in the future the shuidong bay shoreface may be subjected to even further erosion because of increases in the energy of the environment resulting from rapid relative sea level rise

an analysis of coastal erosion in the tropical rapid accretion delta of the red river vietnam abstract the largest plain in the north vietnam has formed by the redundant sediment of the red river system sediment supply is not equally distributed causing erosion in some places the paper analyzes the evolvement and physical mechanism of the erosion the overlay of five recent topographical maps 1930 1965 1985 1995 and 2001 shows that sediment redundantly deposits at some big river mouths ba lat lach and day leading to rapid accretion up to 100 m y typical mechanism of delta propagation is forming and connecting sand bars in front of the mouths erosion coasts are distributed either between the river mouths hai hau or nearby them giao long giao phong and nghia phuc the evolvement of erosion is caused by wave induced longshore southwestward sediment transport meanwhile sediment from the river mouths is not directed to deposit nearshore the development of sand bars can intensively reduce the erosion rate nearby river mouths erosion in hai hau is accelerated by sea level rise and upstream dams sea dike stability is seriously threatened by erosion induced lowering of beach profiles sea level rise typhoon and storm surge

sedimentation in the northern gulf of california after cessation of the colorado river discharge abstract the almost total elimination of sediment supply from the colorado river has produced a condition of sediment starvation in the entire northern gulf of california ngc textural and mineralogical analyses of 114 surface sediment samples collected in the area show that this situation has promoted alternate sediment sources to become more important in supplying and controlling the compositional characteristics of the sediments in the region by applying multivariate data analyses using q f ratios as well as heavy mineral and clay mineral content of samples four sedimentary provinces are identified colorado river delta province crdp concepcion river province ccrp transitional province tp and baja sonora province bsp the crdp dominates the regional distribution of sediments being mainly confined to the western side of the ngc the sediment source for this province is the deltaic structure of the colorado river sediment recycling through resuspension and reworking of the colorado delta and the shallow shelf of the upper gulf of california ugc is an important agent for supplying sediments to the ngc the ccrp reflects the mineralogical association of concepcion river while the tp contains a mineral association that is similar to crdp and ccrp but with intermediate values to these provinces this situation suggests that tp is a mixing zone between these two neighboring provinces the higher abundance of zircon and garnet in tp also suggests a clear contribution of sediment sources from the sonora desert in nw mexico clay mineral composition of these sediments indicates a greater abundance of smectite and chlorite relative to previous studies being mainly derived from eolian dust carried from the desert region of nw mexico and sw usa although eolian supply of fine grained sediments is important in the ngc colorado river delta sediments are still the largest single source of sediments to the region eolian supply of fine grained sediments is however more dominant in the southern half and along the eastern margin of the ngc the dispersion of sediments in the ngc is consistently cross basinal with a series of transport cells that follow a cyclonic circulation four depocenters were identified located all on the western side of the ngc and mainly associated to the deep basins the major effect that damming of the colorado river has had on the sedimentology of the area is that sediment dispersion is now cross basinal instead of long basinal this situation indicates that sediment dispersion at present is mainly controlled by oceanic forcing instead of fluvial processes as it was in the past

magnetic fingerprinting of hydrodynamic variations and channel erosion across the turbidity maximum zone of the yangtze estuary china abstract magnetic measurements were conducted on surface sediments and suspended particles collected across the turbidity maximum zone of the yangtze estuary in order to examine the spatial distribution of magnetic mineral assemblages and the factors responsible for this distribution the results indicate that magnetic properties are dominated by ferrimagnetic grains bulk magnetic susceptibility and saturation isothermal remanent magnetization sirm values show positive correlations with the proportion of the 63 m fraction in the north channel while anhysteretic remanent magnetization arm is significantly correlated with the proportion of the arm sirm ratios which is consistent with the coarsest particle size due to strong hydrodynamics i e currents within each channel and sirm values are higher in sediments from shallower water depth due to energetic conditions resulting from waves compared with surface sediments suspended particles have lower and sirm values but higher arm sirm ratios due to lower sand fractions the increasing trend of arm sirm of suspended particles along the pathway of sediment transport indicates weakening hydrodynamics from the inner estuary to the outer estuary diagenesis is another factor influencing magnetic properties in addition to particle size channel erosion leads to local exposure of buried sediments on the channel bed as a result of a stronger diagenetic imprint they show magnetic properties different from the recently deposited sediments our results indicate that magnetic properties cannot only indicate spatial variations in hydrodynamics but also provide insight into sediment erosion deposition processes combined granulometric and magnetic methods can therefore be used to interpret hydrodynamics and track changes in estuary morphology

issues with integrating carbonate sand texture data generated by different analytical approaches a comparison of standard sieve and laser diffraction methods abstract palaeoenvironmental reconstructive work relies on sediment texture information as a proxy for particle transport dynamics as the integration of data from multiple sources is often sought for studies at the regional scale a body of work exists that addresses compatibility levels of different analytical approaches past insights are derived predominantly from siliciclastic deposits this study instead addresses standard sieve and laser diffraction methods of texture analysis on a suite of carbonate beach sands from san salvador island bahamas while the near equant grain shapes of siliciclastic sands generate comparable results between methods our findings show that laser diffraction tends to overestimate the coarser fractions in carbonate sands given indiscriminate measurement of elongate particle axes peloidal grains that have width to length ratios on the order of 0 5 can pass through much smaller mesh sizes when sieved than diffraction would suggest the resulting deviation in analytical outputs significantly influences measures of skewness sorting and other derivative metrics which vary by up to several wentworth classes between procedures meaningful integration of texture data obtained by different methods is ill advised when dealing with carbonate beach sands similar problems are documented for muddy deposits wherein platy clay minerals favor size overestimation by laser diffraction and a size underestimation by settling tube technique an improved understanding of methodological biases resulting from application of different particle size methods is needed to help facilitate data reconciliation efforts this study provides a glimpse of issues facing the integration of carbonate sand texture information troublesome given prevalence of irregular grain shapes

sediment trend models fail to reproduce small scale sediment transport patterns on an intertidal beach a rigorous test is presented of the application of sediment trend models to an intertidal beach environment characterized by bar morphology sediment samples were collected during low tide from a regular grid and their sediment fall velocity distributions obtained using a settling tube were analysed using moment analysis the net sediment transport direction determined from beach surveys hydrodynamic measurements wave ripple observations and sediment transport modelling was compared with predictions by sediment trend models based on the spatial distribution of sediment parameters it was found that the sediment transport pathways and patterns of sedimentation predicted using sediment trend models were at odds with field observations and varied significantly depending on whether surface or sub surface sediment samples were used the sediment trend models are thought to fail because in energetic and morphologically variable beach environments spatial patterns in sediment characteristics are mainly attributed to the presence of different hydrodynamic regions and associated morphology rather than sediment pathways the use of sediment trend models cannot replace the collection of morphological hydrodynamic and sediment transport data in the field to define relationships between flows forms and sedimentation patterns on a dynamic intertidal beach

much damage for little advantage field studies and morphodynamic modelling highlight the environmental impact of an apparently minor coastal mismanagement while coastal management activities have long been known to exert a strong influence on the health of marine ecosystems neither scientists nor administrators have realized that small interventions may lead to disproportionately larger impacts this study investigated the broad and long lasting environmental consequences of the construction of an ill planned although small only 12 m long jetty for pleasure crafts on the hydrodynamic conditions and on the meadow of the seagrass posidonia oceanica of an embayed cove in the ligurian sea nw mediterranean there p oceanica used to develop on a high 1 5 m matte a lignified terrace causing seafloor elevation in which the leaves reach the surface and form a compact natural barrier to waves in front of the beach such a so called fringing reef of p oceanica is today recognized of high ecological value and specific conservation efforts are required the construction of the jetty implied the cutting of the matte which directly destroyed part of the fringing reef in addition meadow mapping and sedimentological analyses coupled with morphodynamic modelling showed that the ecosystem of the whole cove had been greatly altered by the jetty we used the geometric planform approach a proper tool in the study of headland controlled embayment both to characterise the present situation of prelo cove and to simulate the original one before the jetty was built in the long term such a small jetty completely altered the configuration and the hydrodynamic conditions of the whole cove splitting the original pocket beach into two smaller ones and creating strong rip currents flowing seaward along the jetty these rip currents enhanced erosion of residual shallow portions of the meadow and further modified the sedimentary fluxes in shallow waters a century after the construction of the jetty an irreversible environmental damage has occurred as the slow growing rate of p oceanica implies that the high matte terrace and the fringing reef will hardly form again even after the removal of the jetty the lesson learnt from this study is that even such small and therefore reputed intrinsically innocent interventions on the coastal zone require accurate planning based on interdisciplinary studies to understand and respect the delicate interplay among morphological hydrodynamic and ecological components

grain size trends associated with net sediment transport patterns an example from the belgian continental shelf grain size trends in relation to net sediment transport pathways are examined using some commonly used grain size parameters the results of the trend analysis for 15 types of the trends are compared with a known net sediment transport pathways established on the basis of the sandbank hydro and sediment dynamics i e general water and sediment movement patterns and bedform asymmetry it is shown that 1 the results for grain size trends associated with a worsening in sorting along the transport pathways have little similarity to transport pathways 2 the results for grain size trends associated with an improvement in sorting along the transport pathways have relatively high degree of similarity to the identified pathways and 3 the residual pattern derived on the basis of a combined grain size trend used elsewhere gao and collins 1992 appears to be most similar and suitable for defining transport pathways

geostatistics and multivariate analysis as a tool to characterize volcaniclastic deposits application to nevado de toluca volcano mexico abstract grain size analysis of volcaniclastic deposits is mainly used to study flow transport and depositional processes in most cases by comparing some statistical parameters and how they change with distance from the source in this work the geospatial and multivariate analyses are presented as a strong adaptable geostatistical tool applied to volcaniclastic deposits in order to provide an effective and relatively simple methodology for texture description deposit discrimination and interpretation of depositional processes we choose the case of nevado de toluca volcano mexico due to existing knowledge of its geological evolution stratigraphic succession and spatial distribution of volcaniclastic units grain size analyses and frequency distribution curves have been carried out to characterize and compare the 28 ka block and ash flow deposit associated to a dome destruction episode and the el morral debris avalanche deposit originated from the collapse of the south eastern sector of the volcano the geostatistical interpolation of sedimentological data allows to realize bidimensional maps draped over the volcano topography showing the granulometric distribution sorting and fine material concentration into the whole deposit with respect to topographic changes in this way it is possible to analyze a continuous surface of the grain size distribution of volcaniclastic deposits and better understand flow transport processes the application of multivariate statistic analysis discriminant function indicates that this methodology could be useful in discriminating deposits with different origin or different depositional lithofacies within the same deposit the proposed methodology could be an interesting approach to sustain more classical analysis of volcaniclastic deposits especially where a clear field classification appears problematic because of a homogeneous texture of the deposits or their scarce and discontinuous outcrops our study is an example of the strong versatility of geospatial analysis to provide an effective and relatively clear methodology for the characterization of volcaniclastic deposits

the influence of grain size analysis methods and sediment mixing on curve shapes and textural parameters implications for sediment trend analysis abstract to this day deterministic physical models capable of explaining the evolution of grain size distributions in the course of transport are still lacking for this reason various attributes of particle frequency distributions in particular curve shapes and textural parameters have for many decades been investigated for potential information about transport behaviour and size sorting processes of sediments in numerous environments such approaches are essentially conceptual and hence rely heavily on the validity of the assumptions on which they are based a factor which has to date been largely ignored in this context is the fact that different methods of grain size analysis e g sieving laser absorption and diffraction settling velocity measurements when applied to the same sample material produce variable curve shapes and hence incongruous textural data this is illustrated by selected examples showing the differences between sieving and settling results conversion of settling velocities into equivalent settling diameters psi phi transformations and the influences of particle shape particle density and water temperature it is demonstrated that particle size distributions are not only method dependent but also dependent on the adopted post processing procedure as a result only frequency curves generated by the same method and subsequently processed by identical computational procedures can be meaningfully compared furthermore the computation of textural parameters from bi or multimodal size distributions produces spurious results which are unrelated to the processes leading to the mixing of different size populations frequently observed in nature in such cases only the decomposition of such distributions into individual populations and the spatial comparison of such populations makes any sense because a physical explanation for the generation of size distributions is lacking a particular curve shape of a grain size population has no meaning on its own only a systematic comparison of progressively changing curve shapes and associated textural parameters of sediments collected on a closely spaced grid can yield data suitable for sediment trend analysis

geochemistry and sedimentology of shelf and upper slope sediments of the south central black sea abstract eighty five surface samples from oxic suboxic and anoxic sites of the south central black sea shelf consist predominantly of clayey silts and silty clays reflecting the moderate to high energy wave dominated hydrological regime grain size data and net sediment transport patterns suggest that the western part of this shelf is an area of east directed active sediment transport with the exception of localized nearshore zones the eastern shelf is by contrast an area of major sediment deposition the sediment transport vectors are correlated with patterns of surface water circulation and storm generated longshore currents the sources of the shelf sediments are indicated by the total concentrations of 30 major minor and trace elements in 59 surface samples factor analysis shows that 99 1 of the total variance can be explained by five factors factor 1 as cu cr fe pb and zn reflects anthropogenic pollution by the etibank copper mine factor 2 mainly total organic carbon and s is linked to anoxia redox as saline conditions factor 3 mainly al si represents aluminosilicates whereas factor 4 sand and silt abundance total carbonate ca and sr represents the carbonate component factor 5 fe mn p cr ni and v tracks primary detrital delivery with strong overprints by redox dependent biogeochemical reactions within the anoxic sediments and the oxic suboxic bottom waters the combined data suggest that the sediments on the south central black sea shelf were largely derived from the north anatolian mountains and supplied to the shoreline by a network of small rivers

swell impact on reef sedimentary processes a case study of the la reunion fringing reef two surface sediment sampling campaigns were carried out in november and december 2003 before and after a strong swell event in the back reef area of a microtidal fringing reef on the western coast of la reunion indian ocean the spatial distributions of the mean grain size sorting and skewness parameters are determined and grain size trend analysis is performed to estimate the main sediment transport pathways in the reef the results of this analysis are compared with hydrodynamic records obtained in the same reef area during fair weather conditions and during swell events sediment dynamics inferred from the hydrodynamic records show that significant sediment erosion and transport occur only during swell events and under strongly agitated sea states under normal wave conditions there is a potential for onshore sediment transport from the reef flat to the back reef but this transport is episodic and occurs principally during high tide stages sediment transport trends revealed by the grain size trend analysis method show onshore and alongshore low energy transport processes that are in agreement with the hydrodynamic records the grain size trend analysis method also provides evidence of an offshore high energy transport trend that could be interpreted as a real physical process associated with return flow from the shore to the reef the impact of swell on the reef sediment dynamics is clearly demonstrated by onshore and alongshore transport considering different combinations of the vector transport trends computed through the grain size trend analysis approach more realistic and pertinent results can be obtained by applying an exclusive or operation xor case on the vectors the main results presented here highlight a trend towards the accumulation of carbonate sands in the back reef area of the fringing reef these sediments can only be resuspended during extreme events such as storms or tropical cyclones

sediment transport over an accretional intertidal flat with influences of reclamation jiangsu coast china this paper focuses on the hydrodynamic and suspended sediment transport processes in response to sequential reclamations over the intertidal flat jiangsu coast which used to be one of the widest intertidal flats in china investigations into the sediment transport patterns reveal that net suspended sediment fluxes increased from 102 kg m 1 on the upper intertidal flat to 103 4 kg m 1 on the lower intertidal flat per tidal cycle this variation was caused mainly by the phases of the current velocity suspended sediment concentration ssc local bed geomorphology inundation patterns and extreme weather conditions the longshore component of tidal currents intensifies seaward over the intertidal flat extreme weather conditions e g storms and strong winds were important factors affecting the current velocity structures the intensity of residual currents and the sscs the sscs were characterized by several peaks throughout the tidal cycle these peaks were associated with strong currents combined wave current interactions and intense turbulences due to the initial flood surge furthermore the suspended sediment was finer and contained more clay materials during the flood phase of the tidal cycle than during the ebb fine particles were transported within the upper water column by landward residual currents but coarse particles were transported within the lower water column by seaward residual currents overall residual currents were apt to transport fine grained sediment landward and coarse grained sediment seaward this pattern indicates that the suspended sediment fluxes are highly variable in the water column even for very shallow tidal environments the cross shore component accounted only for a small percentage of the total sediment flux however this part of sediment supply dominated accretion over the intertidal flat the intertidal flat has become narrower and steeper following sequential reclamations a negative feedback process existed to maintain the convex profile shape although the human activities i e reclamation could have modified the natural process the surficial sediment tended to become finer on the mid upper intertidal flat but coarser on the lower intertidal flat following reclamations in response to a reduction in the tidal currents over the intertidal zone and enhancement of wave action over the lower intertidal flat accretion with high rates was maintained by landward transport of sediment in such an accretional system with influences of reclamation the width or slope of the intertidal flat is adjusted continuously before the cease of reclamation the intertidal flat is unable to achieve an equilibrium shape

distribution of magnetic properties of surface sediment and its implications on sediment provenance and transport in pearl river estuary abstract this study examines the magnetic properties of surface sediments and their implications on sediment provenance and transport in the lingding bay ldb which is the largest bay of pearl river estuary in china the concentration of magnetic and high coercivity minerals exhibits a low high low distribution pattern in the north middle south direction the western ldb is mainly covered by finer magnetic mineral particles whereas the eastern ldb is dominated by coarser particles three surface sediment provenances i e three groups are identified according to magnetic properties and particle size groups i and iii have terrestrial sources from the east river and west north river respectively whereas group ii is from a marine source in the adjacent sea the distribution of these three sediment provenances and their magnetic properties indicate that surface sediments are transported towards the southern direction with a sediment sink that occurs in the outer ldb as further confirmed by the grain size trend analysis results the main sediment depocenter moves southward because of human interventions the results further suggest that the ratio of saturation isothermal remanent magnetization to magnetic susceptibility sirm may be used as an indicator for distinguishing marine and terrestrial provenances and the s ratio s 100 may be employed as an indicator of sediment transport our findings demonstrate that sediment magnetic diagnosis provides an efficient approach to trace sediment provenance and transport and thereafter monitors the sediment process impacted by human intervention in estuaries worldwide

morphology of submarine barchans and sediment transport in barchans fields off the dongfang coast in beibu gulf submarine barchans in three new regions were described using new high resolution multibeam bathymetric data off the dongfang coast in beibu gulf currents seismic profiles of horns surface sediments and comparative surveys in 2007 and 2009 were obtained to study barchan mobility and sand transport in the barchan fields the submarine barchans occur at depths of 15 25 m reaching up to 551 9 m in horn length and 8 6 m in height most barchans have asymmetrical horns and display wider plane shapes than subaerial barchans for the same length and height the morphology of barchans exhibits regional variations that are mainly controlled by finite water depth daily reverse currents sand supply changes and interaction of dunes barchan asymmetries internal bedding inclinations and grain size changes are in agreement with the dominant current directions results show that submarine barchans migrated 5 43 m in two years 2007 2009 through comparison of bathymetric data because of the marginally cohesive fine sediment composition and long distance from contemporary sediment sources it is believed that barchans in region c are not of modern origin however these bedforms can be also affected by high energy flow regimes collisions limit barchan widths and provide efficient transport paths between barchans on their horns large sand supply through the horns increases the barchan heights and also changes their shapes some small dunes are identified that are moving away from the barchans field in 2007 and have departed from the host barchans in 2009 these small barchans were probably caused by the separation of the faster moving horn tails from the host barchans when extreme situations happen the mechanism gives a new explanation for sand loss and size determination of submarine barchans c 2014 elsevier b v all rights reserved

net sediment transport patterns over the bohai strait based on grain size trend analysis grain size trend analysis indicates two distinct characteristics of sediment transport in bohai strait eastward transport dominates the western area and along the coast of the shangdong peninsula this result supports the previous work which indicated that the yellow river sediments are transported from the bohai sea to the yellow sea through the south channel of bohai strait and dispersed into the southern yellow sea along the coast of shangdong peninsula in the central eastern bohai strait net deposition is taking place as indicated by the convergence of the grain size trends this result is consistent with current circulation pattern on bohai strait and the interpretation of strata disclosed by seismic reflection profile this study supports the use of grain size trend analysis for large scale areas on the continental shelf

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

application of grain size trend analysis for the determination of sediment transport pathways in intertidal areas abstract in this paper we apply the gao and collins procedure of grain size trend analysis for the first time in an intertidal sedimentary system our purpose is to evaluate a reliable method to determine residual transport directions in intertidal environments where sediment movement is not well understood residual transport patterns can be determined by grain size trend analysis if the following criteria are applied 1 a single sediment transport unit must be precisely defined and investigated 2 the thickness of sampling has to be chosen in order to investigate the most recent sedimentary event and 3 a regular mesh grid is sampled to avoid bias in the calculation of grain size trends the gao and collins method was undertaken simultaneously with a topographic survey and a tracer experiment during consecutive meteorological conditions of fair weather and a storm event the topographic changes observed between these two situations and the directions of sediment movement deduced from tracer tracking are coherent with the residual transport pattern calculated from the grain size trend analysis the method was tested on a ridge and runnel system which corresponds to the intertidal part of a macrotidal beach called la salie beach located along the southwest french coast in a high wave energy environment this study permits us to recognize two different residual transport patterns for this intertidal ridge and runnel system one for fair weather and a second for storm conditions during fair weather specific sites are subject to sand accretion while during storm conditions these sand stocks are subsequently spread out over the whole area and remain partly on the beach

mesospheric momentum flux studies at adelaide australia observations and a gravity wave tidal interaction model abstract we present here the results of an analysis of gravity wave momentum fluxes in the mesosphere and lower thermosphere inferred using a dual beam doppler radar near adelaide australia during june 1984 our analysis reveals that over 70 of the momentum flux and of the inferred zonal drag was due to gravity waves with observed periods less than one hour this suggests that it is the gravity waves with high intrinsic frequencies and small horizontal scales that are most effective at transporting momentum into the middle atmosphere the temporal variations in the momentum flux and flux divergence due to high frequency motions were also examined in detail in addition to daily variability a strong diurnal modulation was observed to occur this was found to be correlated with the phase of large amplitude diurnal tidal motions as a result of these observations a gravity wave tidal interaction model was proposed which accounts for all of the major features of the observed data including a reduction i

hydrodynamic implications of textural trends in sand deposits of the 2004 tsunami in sri lanka abstract field observations and sediment samples at a coastal plain setting in southeastern sri lanka were used to document the erosional and depositional impacts of the 2004 indian ocean tsunami and to interpret the hydrodynamic processes that produced an extensive sand sheet deposit tsunami deposit thicknesses ranged from 6 to 22 cm with thickness being controlled partly by antecedent topography the deposit was composed of coarse to medium sand organized into plane parallel laminae and a few laminasets vertical textural trends showed an overall but non systematic upward fining and upward thinning of depositional units with an upward increase in heavy mineral laminations at some locations repeated patterns in the vertical textural trends upward fining upward coarsening uniform were used to subdivide and correlate the deposit into five hydro textural stratigraphic units the depositional units were linked to hydrodynamic processes and upcurrent conditions such as rates of sediment supply and composition of the sediment sources vertical changes in grain size distributions recorded the depositional phases associated with flow acceleration initial unsteady pulsating flow relatively stable and uniform flow flow deceleration slack water and return flow or flow redirection study results suggest that vertical textural trends from multiple cross shore sections can be used to interpret complex tsunami flow histories but at the location examined interpretation of the lateral textural trends did not provide a basis for identifying the correct sediment transport pathways because flow near the landward boundary was multidirectional

sediment dynamic processes of the yuehu inlet system shandong peninsula china in order to investigate the sediment dynamic behavior of the yuehu a small inlet system characterized by abundant sediment supply and rapid sediment infilling measurements and sampling were undertaken to obtain data sets of tidal water levels current velocities suspended sediment concentrations grain size parameters deposition rates and organic carbon contents sediment budget and the time velocity asymmetry patterns of the inlet system were analyzed the results show that the deposition rates are relatively high within the tidal basin the total sediment flux cannot be balanced by the input from the open sea the aerosol and biological production rather the material from land which has been intensified by agricultural activities over the past several decades represents a major component for the balance thus the denudation rate must be reduced to protect the yuehu as a natural reserve furthermore it is found from the present study that the yuehu inlet system exhibits all of the four time velocity asymmetry patterns with varied frequencies of occurrence compared with the two asymmetry patterns identified for larger inlet systems such phenomena are partly due to the adjustment of entrance channel geometry this behavior may be representative of the small tidal inlets at their late stage of morphological evolution and therefore may be utilized to prolong the lifespan of small inlet systems c 2003 elsevier ltd all rights reserved

grain size components as markers of origin and depositional processes in the coastal zone of the golfe du lion mediterranean sea france abstract a study of beach and nearshore sands between the mouth of the river aude and cap d agde northwestern mediterranean sea shows the existence of four sediment types st st1 to st4 with st2 seemingly deriving from st1 revealed by grain size modal analysis and confirmed by a deconvolution program lognormal deconvolution of grain size grain size skewness is related to a much more persistent multimodality than graphic evidence can show multimodality results from mixtures of generally three sts and or variants the latter defining monotype grain size distributions monotype mixtures are unequally distributed in morphodynamic zones very abundant on the lower shoreface significantly present on the berm and inner bar but rare in the most dynamic zones i e the collision zone and outer bar on the berm and lower shoreface modal values of the three sedimentary variants retain a close grain size relationship on the berm where only bedload is present in the swash monotype grain size distribution trends towards a lognormal model this trend can also be observed on the lower shoreface where there are numerous monotype grain size distributions gsds possibly indicating a dominant process when compared with st1 dominated grain size distributions of the outer bar zone the distribution of the derived st2 on the lower shoreface has an added fine tail derived from the coarse skewed outer bar sands in addition positive skewness of the lower shoreface sands could indicate input of fine particles from deeper zones under the influence of shoaling waves and upwelling morphodynamic zones are approximately characterized by the distribution of grain size indices a change in the direction of the skewness sign can be observed between the shoaling zone and more energetic zones from the breaker zone up to the berm finally a more detailed description of the spatial properties of grain size distributions could first help explore possible mechanisms underlying sediment sorting in the coastal zone and second provide a set of indices that would be of use in paleogeographic reconstructions and organization of basin borders while improving discrimination and classification of environments

a comparison of reef protected environments in western australia the central west and ningaloo coasts variability in the regional setting and morphology of cuspate forelands on the west coast of western australia is examined in this paper in accordance with this aim principal differences in the geologic and geomorphologic setting of three prominent sites on the west coast were established and their association with historical changes and contemporary oceanographic processes was examined the cuspate forelands investigated are jurien bay winderabandi point and turquoise bay the most significant differences in geologic setting are associated with the structure and location of an extensive offshore reef system morphologically the reef alters from south to north changing from a discontinuous ridge parallel to the shore along the central west coast to a nearly continuous fringing reef at ningaloo the reefs vary in distance from the shore being farthest in the south and closest in the north and they impound a series of inshore basins or lagoons the deeper southern basins are dominated by locally generated wind waves and wind generated currents the shallower northern basins are most markedly affected by tidal currents and wave pumping across the reef flats the large cuspate foreland at jurien on the central west coast has undergone shoreline configuration change in response to changing phases of storminess as well as in response to a change in focus for sediment deposition as a result of offshore reef erosion at winderabandi point on the ningaloo coast relict pleistocene limestone has provided the focus for sedimentation and morphology has been controlled by a balance in refracted wave energy and nearshore currents driven by tidal and wave set up variability at turquoise bay where the lagoonal basin is most shallow and narrow the morphology of the foreland suggests that it may at some stage have been migratory but its present asymmetrical shape is maintained by strong northerly longshore drift and strong currents exiting the lagoon through a nearby gap in the reef crest fundamental differences between the two coastal regions include the structure of the offshore reef processes driving flow of water within the lagoons and the role of storminess in evolution of coastal landforms although many questions regarding storm surge dynamics and landform change remain unanswered this research provides a significant contribution to the understanding of the evolution of morphological systems in low wave energy protected environments copyright 2000 john wiley sons ltd

hydrodynamics and sedimentation induced by large scale coastal developments in the keum river estuary korea abstract the macro tidal keum river estuary located in the eastern yellow sea has been suffering siltation and morphological change since 1994 to understand the effects of the large scale coastal developments on the sedimentation processes in the estuary hydrodynamic and sedimentary data collected from 1985 to 2002 were analyzed and numerical experiments of hydrodynamics were performed the sedimentation rate in the estuary increased by a factor of 1 9 from 3 5 10 6 to 6 7 10 6 m 3 y 1 after the construction of a dam in the upper reaches of the estuary in 1994 large part of the estuary is veneered by the muddy sediments noticeably which were rarely found before dam construction since then siltation has concentrated in the upper estuary rather than the lower the upstream transport and accumulation of fine grained sediments is due to 1 the change to flood dominance in the main channel i e the relative intensification of flood current and the flood directed residual current and 2 the decrease in transport capacity in the upper estuary i e the marked decrease in current velocity which was induced by dam construction the former has resulted in the ebb dominance of the gaeya channel a distributary in the north of the main channel the tidal pumping of fine sediments was reinforced not by the freshwater saltwater interaction but by the residual tidal circulation the sediment fluxes observed in 2001 2002 demonstrate year round net inflow both at the entrance of the jetties and at the gaeya channel which implies that the sediments delivered by the keum river are entirely confined to the estuary incapable of escaping to the sea the net inward transport of fine sediments may accumulate pollutants adsorbed to or absorbed in the sediment grains in the estuary thus deteriorating the benthic environment gradually and the water quality eventually

sediment transport pathways in a dredged ria system southwest england abstract the fowey ria system southwest england comprises the river fowey catchment the fowey estuary the cliffs and bays adjacent to the ria mouth and part of the inner continental shelf of the english channel previously large quantities of sediment were introduced into the upper ria by ore mining activity today in common with other rias the fowey receives a low riverine sediment input material from maintenance dredging in the lower ria is dumped in a spoil ground outside the ria mouth the sediments of the system are investigated using an integrated approach to determine sediment distribution and sediment transport pathways surface sediments are analysed for grain size and mineralogy grain size trend analysis is used to examine sediment dispersal patterns away from the locus of deposition in the spoil ground archived data are used to investigate the seabed morphology and to determine long term 100 year bathymetric changes within the ria mixing of sediment from several sources occurs in the upper reaches riverine and locally eroded sediment is transported seawards towards the main area of commercial activity sand and finer grained material moves into the ria from offshore the bed of the inner continental shelf comprises interfluves covered by a thin veneer of sediment with a natural composition of locally derived lithic fragments and biogenic material the area is mainly low non depositional in character except within the partially infilled palaeovalley and its tributaries sediments dumped in the spoil ground disperse in a complex pattern coarse grained material is moved by the action of waves and tidal currents towards the southwest and northeast fine grained material is transported either to the east or the west depending upon the prevailing wave and tidal current regime because of its geomorphology the lower ria acts as an efficient sediment trap retaining a riverine material and sediment eroded from the upper reaches and b sediment entering the ria from offshore despite being subjected to major anthropogenic disturbance from past mining and present day dredging activities the fowey ria conforms to the general sediment model for southwest england rias castaing p guilcher a 1995 geomorphology and sedimentology of rias in perillo g m e ed geomorphology and sedimentology of estuaries developments in sedimentology no 53 elsevier science amsterdam pp 69 111 a conceptual model of sediment transport pathways for the fowey ria system is presented as the basis for further investigations

comparing spatial grain size trends inferred from textural parameters using percentile statistical parameters and those based on the log hyperbolic method abstract the folk ward f w and the log hyperbolic methods are applied to a small and easy to overlook number of typical sand sized grain size distributions from the danish wadden sea the sand originates from the same source and the pattern of change in the grain size distributions is therefore exclusively linked to dynamic sorting in general the f w parameters reflect the observed grain size trends far better than the corresponding log hyperbolic parameters the log hyperbolic typical log grain size is sensitive to changes in skewness and cannot replace mean grain size mz in grain size trend analysis the four log hyperbolic parameters describing dispersion 1 1 and are not able to give an unambiguous picture of spreading trends the f w sorting parameter sd can therefore not be replaced by any of the log hyperbolic parameters in grain size trend analysis in skewed grain size distributions there seems to be a general defect in the log hyperbolic approximation of the best represented tail this makes less sensitive to indicate the correct sign of slightly skewed grain size distributions than sk however when examining trends the relative change between and sk by and large seems to be the same the log hyperbolic peakedness parameter is preferable to the f w peakedness kurtosis parameter kg because the latter is hypersensitive to small insignificant variations in a grain size distribution by contrast the concept of peakedness as defined by seems to relate more directly to sedimentary environmental conditions in conclusion the log hyperbolic method has both advantages and disadvantages when compared with the f w method it is thus suggested that a sensible combination of the two methods could be advantageous to sediment trend analysis

grain size trends used to assess the effective discharge for floodplain sedimentation river waal the netherlands abstract the importance of floods of different magnitude on floodplain sedimentation can be estimated from sedimentation measurements carried out during a series of floods however because these measurements represent sediment accumulation during the entire flood they cannot be used to estimate the importance of individual flood stages on sediment deposition in this study the importance of different flood stages on floodplain sedimentation was assessed from analysis of spatial variations in grain size distributions which are indicative of sediment transport directions as a secondary objective the applicability of grain size trend analysis to fine grained floodplain sediments was tested the grain size trend analyses were carried out in a geographical information system and applied to sediment deposited on an embanked floodplain section along the river waal in the netherlands during a large flood in december 1993 because flow patterns at the studied floodplain section vary with flood stage comparison of the identified sediment transport pathways with computed flow patterns indicates at which discharge most sediment is deposited the results indicate that large discharges with a recurrence time of more than two years are most effective in depositing suspended sediment on floodplain areas enclosed by a minor river dike on floodplain sections that directly border the main channel moderate discharges with a recurrence time of about one year seem to be more efficient contrary to the results of floodplain sedimentation models low but increasing discharges with a recurrence time of less than one year and during which only low lying areas near residual channels are inundated appear important for deposition of suspended sediment in these low lying areas this observation is confirmed by measurements of spatial concentration gradients and by floodplain sedimentation measurements comparison of the trends with additional information on sediment transport directions indicates that trends in which sediment becomes finer better sorted and more negatively skewed when measured in units are most suitable for defining transport pathways on river floodplains trends may however deviate up to 90 from true transport directions flocculation does not seem to have any negative effects on the applicability of grain size trend analysis

sediment characteristics and water physicochemical parameters of the lysimachia lake western greece in the present paper we present the sedimentological characteristics and the water physicochemical parameters of lysimachia lake which is one of the most important lakes of western greece as it is protected by international conventions and is listed in the natura 2000 european network sedimentological analysis involved grain size analyses moment measures total organic carbon toc total nitrogen tn and total phosphorus tp measurements as well as determination of the clay minerals content water physicochemical parameters such as ph temperature conductivity and dissolved oxygen were measured in situ with portable equipment while nutrients such as nitrates nitrites phosphates and ammonium ions as well as toc and tn were analyzed in a time period of 1 year seasonal monitoring geographical distribution of grain size and geochemical parameters indicated a clear partition in the northern and southern parts of the lake this phenomenon can related to the discharging of a channel into the lake the discharging of sewage effluents from agrinio city during the last years as well as the type of clay minerals distribution clay minerals analyses indicated that smectite predominates in the northern part of the lake whereas chlorite is more abundant in the southern parts this explain the higher amounts of toc and tn observed in the northern part of the lake and can be correlated with the higher external surface and adsorption capacity of minerals in the smectite rich sediments the four seasons monitoring of water physicochemical parameters indicates a relatively higher values of toc and tn in the northern part of the lake while nutrient concentrations indicate a uniform geographical distribution along the lake

an alternative approach to the identification of net sediment transport paths based on grain size trends abstract progressive changes in grain size parameters have long been linked to net sediment transport paths however the methods employed to date suffer from limitations potentially leading to serious interpretational errors which necessitate the formulation of an integrated quantitative technique the approach advocated here is a step in this direction as it eliminates some of the problems inherent in the older methods previously trend vectors were obtained by comparing the grain size parameters of only two sampling stations at a time which gives a low probability of identifying the actual transport direction in the proposed method groups of five stations comprising a central station and four satellite stations are used for each trend vector grain size parameters are first combined in such a way that bias towards any one of them is climated the resultant dimensionless numbers are then substituted for the proportional frequencies of recorded directions in conventional vector analysis the satellite stations must be located equally far from the central station on radials 90 from each other which is seldom the case an iterative trigometric technique is therefore employed to determine the combined grain size parameters at these localities conventional vector analysis adapted to the situation of using four raials instead of 10 sectors allows the calculation of a vector mean azimuth and vector magnitude

peculiarities of interannual changes in the mean wind and gravity wave characteristics in the mesosphere over shigaraki japan results are presented of month by month measurements of the mean wind and intensity and momentum fluxes of internal gravity waves igws with the middle and upper atmosphere radar mu radar at the altitudes 65 80 km at shigaraki japan 35 n 136 e in 1986 1997 the mean zonal wind is eastward in winter and westward in summer but the amplitude of these annual variations is different in different years having a minimum in 1992 1994 the mean meridional wind shows substantial quasi bi annual variations igw intensities and momentum fluxes had a maximum in 1991 1994 some possible reasons for such interannual changes are discussed

influence of mixtures of grain size populations on the parametric and modal characteristics of coastal sands herault mediterranean sea france abstract grain size distributions in lower beach and nearshore sands of a segment of the coast of the golfe du lion france were analyzed by a parametric method and by modal analysis the results have been considered both in a spatial framework delineating geographically distinct sedimentary compartments and cells and in a morphodynamic framework separating the dynamic components of the shoreline berm collision zone inner bar outer bar lower shoreface modal statistics indicate that a mixture of three dominant components end members contributes to the grain size distribution gsd of the sediments fine sand sedimentary type i modal value 0 195 mm i 0 35 medium and coarse sand st ii modal value 0 680 mm i 0 8 and very coarse sand and gravel st iii i modal value 2 3 mm i 1 5 quasi log normal one component gsds form a minority group and mixtures produce various apparently unimodal sands and bimodal sediments a large variation of grain size indices results from mixing a simulation of mixing of log normal populations close to the end members shows the great sensitivity of parameters sorting skewness and kurtosis to small changes in the compositional formula of the mixture the procedure followed supplies a good preliminary tool enabling rapid identification and localization of the main sand sources on a regional scale these components derive from potential sources available in the region well known from previous studies st i originates from the river rhone and provides the textural base for most of the sediments st ii and iii form a local component originating either from fluvial input aude orb and herault rivers or from the nearshore reworking of ancient quaternary sediments and late holocene beachrocks each st takes on local aspects in relation to the morphological environment but the regional scale of the study was too large to precisely reflect the local morphodynamic regime a significant change in the st i sorting of bar sands is however observed probably due to the net offshore migration reported for the bar system

variations in chemical composition and particle size of dune sediments along the west coast of jutland denmark abstract geochemical and textural variations in frontal dune sediments along the western coast of jutland denmark have been investigated in order to identify possible sediment provinces and transport pathways an understanding of sediment sources and sinks is important for both for an understanding of the nature of sedimentary environments and for applied coastal engineering and management purposes four coastal sectors were identified on the basis of geochemical composition one sector is compositionally different from the other three units having higher concentrations of the trace elements ni cr v sc zn pb ba zr and many rare earth elements dune sediments on this section of coast also have higher al2o3 to k2o ratios and lower al2o3 to fe2o3 ratios reflecting a lower content of feldspar and higher content of heavy minerals it is inferred that different or additional sediment source s have supplied sediment to this section of coast beach nourishment has contributed to the observed compositional differences but previous data obtained from the lodbjerg area indicate that aeolian sands on this section of coast naturally have a relatively high si fe and ti content reflecting high quartz feldspar ratio and relatively high content of heavy minerals compared with those on other sections of the coast frontal dunes along the most northern section show high abundances of k2o rb and ba reflecting a relatively high k feldspar content derived from local sources alongshore trends were also identified in the mean particle size and sorting of the frontal dunes although there is no direct correspondence with the observed geochemical differences three coastal units can be identified on the basis of particle size frontal dune sediments in the middle section are relatively coarser and less well sorted than those to the north and south probably reflecting both the addition of beach nourishment material and greater exposure to strong westerly winds which are a capable of transporting a wide range of particle sizes the three units defined on this basis do not correlate directly with the units defined on the basis of geochemical composition

on the annual variation of tropospheric zonal winds observed above christmas island in the central equatorial pacific observations of tropospheric winds have been made nearly continuously since early 1986 in the altitude range 2 18 km using a 50 mhz vhf wind profiler at christmas island 2 n 157 w tropospheric zonal winds observed at christmas island show a pronounced annual variation in the middle to upper troposphere with westerly winds typically observed during northern winter the annual variation is strongest during la nina and weakest during el nino the amplitude of the cycle has a broad peak in the upper troposphere empirical orthogonal function eof analysis of the vertical structure of the annual variation shows that the principal mode explains nearly 90 of the variance in the 90 to 365 day frequency band we attribute the annual variation in zonal winds to the annual variation in deep tropical heating associated with deep convection the annual variation in tropical convection gives rise to annual variations in the surface pressure and pressure difference between darwin and tahiti the pressure difference is greatest during northern hemisphere winter months other measures of the annual variation in tropical convection are provided by the tropical tropopause height and by highly reflective clouds hrc the tropical tropopause is highest during the northern hemisphere winter months when convection is most active over the maritime continent western pacific warm pool region and lowest in northern summer when convection is most active over the land masses of the northern hemisphere the hrc show an annual migration in the centers of active convection the annual latitudinal migration of the active centers of convection over the western pacific with respect to the equatorial waveguide appears to be an important factor in determining the annual variation evident in the remote response of the zonal winds observed over christmas island

pattern of sediment transport in a microtidal river mouth using geostatistical sediment trend analysis abstract we perform a grain size trend analysis gsta to investigate sediment transport mechanisms in the grand rhone microtidal mouth during various hydroclimatic conditions the objective is to determine the efficiency of this method to explain the directions of residual transport pattern and mode of distribution of the fluvial sediment input in an environment that is very difficult to equip with instrumentation during extreme events the known biases of this sedimentological approach are reduced by using enriched geostatistical processing and choosing periods of sampling subject to unequivocal hydrodynamic forcings the modeling results and grain size distributions of surface sediments clearly show three vector fields during periods of low river discharge the first vector field corresponds to an upstream zone under fluvial influence the second field is characteristic of a mixing zone confined inside the river mouth and marked by heterogeneous sedimentation this sector is interpreted as the confrontation zone between alluvial and marine dynamics farther offshore the vectors are oriented towards the river and at counter slope in deeper zones the vectors reflect the sediment transport generated by wave refraction at the top of the mouth bar at the delta front bathymetry from 5 m to 20 m the vectors are interpreted as representing a lag deposit the periods of medium and extreme floods are associated with storms the marine dynamic regime generates a longshore drift current which brings sediments onto the mouth bar during medium flood events only the inner part of the mouth bar is highly influenced by the river during extreme flood events the river influences both the eastern part of the mouth and the wave regime in the central part consequently the gsta method shows that even during flood events the river solid discharge is not transferred towards the adjoining upper shoreface in the context of a wave dominated delta the distribution of surface sedimentation in a microtidal mouth remains controlled mainly by the swell even in periods of flood when the intensity of river dynamics is exacerbated finally all these results are similar to the known hydro sedimentological behaviours of the rhone river mouth nevertheless gsta results seem not self sufficient to explain all the processes but this method proposes an alternative approach to traditional methods used to measure bed load sediment transfer during extreme events

downdrift coarsening of beach foreshore sediments at tidal inlets an example from the coast of new jersey analysis of grain size statistics of upper foreshore sediments on sand beaches at two tidal inlets in new jersey u s a reveals that sediments are coarser at beaches flanking the inlets than updrift although sediments become finer downdrift at the broad regional scale the local reversal of the regional trend in size grading is attributed to 1 the offshore diversion of the finer sands along the surf zone on the ebb tidal delta and 2 the removal of the finer sands from the inlet flank beach caused by low wave energy conditions at low stages of the tide and by deflation sediments thus become coarser at inlet beaches as a result of alterations in the interaction of waves with the beach and as a result of aeolian processes not solely as a result of increased tidal current velocities as previously reported the distance along the new jersey barrier islands over which inlet processes are likely to affect changes in sediment size updrift averages less than 1100 m but the impacts of inlets on the sedimentary record can be extended greater distances as a result of inlet migration

progressive grain size sorting along an intertidal energy gradient abstract along a 2 km nw se transect along the energy gradient of an intertidal sand body of the back barrier tidal flats of spiekeroog island german wadden sea southern north sea three sets of closely spaced surface sediment samples were taken at different times to investigate whether the effects of progressive size sorting could be identified in the textural parameters and size frequency curves of the sediments grain sizes analyses were carried out with a high resolution settling tube having an internal resolution of 1 50 psi intervals the settling velocity data were subsequently transformed numerically into equivalent settling diameters on the basis of a quartz sphere standard at this high resolution it was possible to visualize subtle changes in textural parameters which would not have been resolved by standard 0 25 phi sieve analyses the first two sample sets of 1992 and 1994 show similar trends of progressive fining in the sediment combined with a slight decrease in skewness and sorting in the direction of decreasing energy ten years later in 2003 the sediments were slightly coarser but still reflected the hydrodynamic energy gradient by a distinct fining trend along the transect however in contrast to the former data sets the skewness values now remained constant whereas the sorting values revealed the existence of two overlapping hydrodynamic energy regimes on the tidal flat the better sorting in the coarser size fractions and the general coarsening trend in the central part of the tidal flat are interpreted to reflect an increase in the hydrodynamic energy level since the first two sample sets were collected this observation suggests that some of the finer particles in the grain size spectrum on the tidal flat were winnowed out by wave action without however completely obliterating the former trend this interpretation is supported by an increase in the frequency and duration of strong winds as recorded by the national weather bureau since the early 1990s the results of the study demonstrate that the intertidal sediments of the wadden sea respond rapidly and sensitively to gradual changes in the hydrodynamic energy regime

analysis of sediment distribution and transport for mitigation of sand deposition hazard in tam quan estuary vietnam tam quan estuary in the binh dinh province of vietnam provides shelter for about 2000 boats recently erosion and accretion associated with the mouth of the estuary have badly affected marine transportation and economic development an 850 m long jetty was constructed to mitigate the hazard however sand deposition still continues to be an ongoing problem this paper aimed to assess the reasons for sand deposition in the estuary based on sediment distributions and transport pathways following an investigation of topography geological and hydrodynamic conditions and sediment characteristics an analysis of sediment transport trends was undertaken results show that medium sand is distributed along the coast from the shoreline to 2 5 m water depth fine sands are found in deeper areas of 10 13 m where there are also medium sand deposits thought to be of ancient origin sand deposition has intensively occurred in the estuary due to a dominant north to south longshore sediment transport regime sediment from this regime is presently trapped by the jetty and deposited in the navigation channel as a solution it is suggested that a properly designed jetty stemming from the headland on the north side of the estuary could effectively control the patterns of sediment transport enabling the sand to bypass the entrance thereby avoiding entrapment inside its mouth

bottom currents interpreted from iceberg ploughmarks revealed by multibeam data at tromsoflaket barents sea abstract multibeam data have been acquired on eastern tromsoflaket a bank in the southwestern barents sea comprising a plateau detailed examination of the multibeam backscatter data however reveals a high variability of sediments especially in and around iceberg ploughmarks we observe coarser sediments on the levees either side of the ploughmarks than inside the furrows moreover we frequently note asymmetries in the distribution of fine sediments across these ploughmark features drawing inspiration from previous studies of bottom currents which use the distribution of sediments across bedforms e g sand waves we have interpreted the direction of bottom currents on tromsoflaket by examining the local distribution of fine sediments across iceberg ploughmarks which are the most prominent bedform in this area further integration of our results with existing grain size current speed models have allowed estimates of the bottom current speeds to be obtained such interpretations are particularly valuable in this area where availability of bottom current measurements sparse our approach makes valuable and novel use of multibeam data and results show good agreement with the limited set of available current data and models we can identify near bottom pathways for the norwegian atlantic current and norwegian coastal current the two major current systems in this region and the patterns of circulation help to explain the sedimentation regime and identify recent erosion and deposition areas

behavior of grain size characteristics on reflective and dissipative foreshores broken bay australia abstract beach morphology wave current dynamics or sediment attributes such as grain size changes and sorting processes intrinsically characterize each other the extreme cases of the morphological spectrum include reflective beaches which are steep and devoid of inshore topographic expression or surf zone circulation and dissipative beaches which are flat and have inshore barred topography with attendant longshore currents and rips for a study of four beaches in broken bay australia representing these morphological extremes four facts become obvious first reflective beaches have rapid variaiton in foreshore grain size alongshore mean settling velocity changes greater than 0 3 log10 cm sec km grain size changes greater than 0 2 mm km whereas dissipative beaches have weak r variation mean settling velocity changes approximate 0 1 log10 cm sec km grain size changes less than 0 1 mm km second the pattern on reflective foreshores remains fixed over time whereas the pattern on dissipative foreshores varies to the point that size gradients can reverse direction within one year third this temporal variation reflects the directional width of the incoming wave spectra and not changes in the level of wave power reflective beaches have waves approaching almost shore normal because of the nullification of deep water variation by wave refraction or by the sheltering effects of headlands wave approach on dissipative beaches varies daily and the beach planform and sediment must respond over time to this variation fourth grain size changes fit one of two postulates the energy postulate states that grain size and sorting increase along a foreshore as energy increases the drift postulate states that grain size increases downdrift the energy postulate is more appropriate on reflective beaches whereas the drift postulate accounts for the difference in the magnitude of grain size changes alongshore between reflective and dissipative beaches on reflective foreshores coarse material is naturally concentration at the base of the swash zone because of gravity effects or shear sorting in backwash larger grains here move faster alongshore than finer ones near the top of the foreshore because longshore currents at the base of the swash are stronger than the zigzag motion of swash drift further up the beach face this drift sorti g produces strong longshore size gradings on the foreshore this effect is negated on dissipative beaches by swash bore transport of coarse grains upslope by dilution with inshore sediment that has undergone preferential movement of fines alongshore in suspension and by locally reversed longshore currents near rips

concepts in gravel beach dynamics abstract the dominant processes in gravel beach dynamics are reviewed highlighting some common themes which unify the various components of the gravel beach system the repercussions of which impart on how gravel beach dynamics might be understood conceptually in particular gravel beach dynamics are thought to be highly dependent on the temporal and spatial variation in grain size and the continual adjustments made by an active beach step both of which act not only as the expression of changing morphodynamic conditions but also as a controlling influence morphodynamics the notion that the exchanges on beaches between the hydrodynamics sediment transport and morphological change takes the form of reciprocal relationships which are mediated through feedback mechanisms in such a way that they cannot be thought of or studied independently is not a new one yet it appears that for the gravel beach morphodynamics must be re defined to describe conditions where variations in sediment size are thought to deserve parity rather than as merely a sequent entity or boundary condition morpho sedimentary dynamics is a phrase coined to intuit such cause and effect detailing the co evolution of morphology hydro hydraulics and sediment properties whilst acknowledging causative pluralism feedbacks and multiplier effects this is the recommended conceptual framework within which to crystallise thought and organise further research for the gravel beach essentially it increases the minimum number of parameters needed to describe the state of the gravel beach as a physical system therefore it is advised that simplicity will be most expedient in our future modelling efforts if complexity is to be adequately encapsulated

sedimentological sectorization of an estuarine system in a regressive coast southeast brazil abstract multivariate statistical analysis can be applied in order to group sediments with similar characteristics and be an important tool for the interpretation of sedimentary facies for a given depositional environment this study investigates the use of multivariate analysis to produce a sectorization of an estuarine system located along a regressive coast espirito santo southeast brazil results of cluster analysis and principal component analysis were compared to qualitative sediment interpretation based on well known sediment classifications multivariate analysis defined four distinct sedimentary groups for the estuarine and adjacent inner shelf system these groups reflect distinct sedimentary facies found along the system inner estuarine facies outer estuarine facies fluvial coastal facies and shelf facies this sectorization is used to propose a sedimentary facies model for the system sedimentological variables used in the sectorization were shown to be good indicators of depositional environments indirectly expressing the hydrodynamic energy

sediment sorting at the sand motor at storm and annual time scales bed sediment composition with a focus on the median grain size d50 was investigated at a large scale nourishment the sand motor at the dutch coast 21 5 million m3 sand considerable alongshore heterogeneity of the bed composition d50 was observed as the sand motor evolved over time with 1 coarsening of the exposed part of the sand motor 90 to 150 m and 2 a depositional area with relatively fine material 50 m finer just north and south of the sand motor the alongshore heterogeneity of the measured d50 values was most evident outside the surfzone i e seaward of msl 4 m coarsening of the bed after construction of the sand motor was attributed to hydrodynamic sorting processes because the alongshore heterogeneity of the d50 showed a similar spatial pattern as the mean bed shear stresses the observed alongshore heterogeneity of the d50 and correlation of d50 with modelled mean bed shear stresses suggest that preferential erosion of the finer sand fractions has taken place the selective transport of finer sand fractions results in a coarser top layer of the bed at the sand motor the preferential transport is most dominant during mild and moderate conditions when hydrodynamic forcing conditions are close to the critical bed shear stresses for transport the measurements also show the impact of a storm which consists of a 40 m finer d50 of the offshore bed composition in front of the sand motor i e where a considerably coarser bed was in place additionally storms may generate a temporary zone with fine bed material at the toe of the deposition profile this means that the coarsening of the bed is reduced by storms as a result of the mobilization of both coarse and fine sediment and mixing of the bed with the relatively finer substrate

remote triggering of fault strength changes on the san andreas fault at parkfield a 20 year seismological record of from the parkfield area of the san andreas fault has been used to identify two occasions when long term changes in fault strength seem to have been induced remotely by large seismic events the 2004 sumatra andaman and the 1992 landers earthquakes in both cases two changes occurred that are consistent with variations in fault strength variation in the properties of seismic scatterers with time reflecting stress induced migration of fluids and systematic variation in the characteristics of repeating earthquake sequences these findings suggest that the largest earthquakes have a global influence on the strength of the earth s fault systems in support of that hypothesis an unusually large number of m 8 earthquakes occurred in the three years following the 2004 sumatra andaman earthquake changes in fault strength over time can increase or decrease the likelihood of failure and the ultimate triggering of seismic events observation of the parkfield area at the san andreas fault over the years 1987 2008 now reveals two occasions the 2004 sumatra andaman earthquake and the 1992 landers earthquake where long term changes in fault strength have probably been induced remotely by large seismic events fault strength is a fundamental property of seismogenic zones and its temporal changes can increase or decrease the likelihood of failure and the ultimate triggering of seismic events although changes in fault strength have been suggested to explain various phenomena such as the remote triggering of seismicity1 there has been no means of actually monitoring this important property in situ here we argue that 20 years of observation 1987 2008 of the parkfield area at the san andreas fault have revealed a means of monitoring fault strength we have identified two occasions where long term changes in fault strength have been most probably induced remotely by large seismic events namely the 2004 magnitude m 9 1 sumatra andaman earthquake and the earlier 1992 m 7 3 landers earthquake in both cases the change possessed two manifestations temporal variations in the properties of seismic scatterers probably reflecting the stress induced migration of fluids and systematic temporal variations in the characteristics of repeating earthquake sequences that are most consistent with changes in fault strength in the case of the 1992 landers earthquake a period of reduced strength probably triggered the 1993 parkfield aseismic transient2 3 4 5 as well as the accompanying cluster of four m 4 earthquakes at parkfield the fault strength changes produced by the distant 2004 sumatra andaman earthquake are especially important as they suggest that the very largest earthquakes may have a global influence on the strength of the earth s fault systems as such a perturbation would bring many fault zones closer to failure it should lead to temporal clustering of global seismicity this hypothesis seems to be supported by the unusually high number of m 8 earthquakes occurring in the few years following the 2004 sumatra andaman earthquake

transport of riverine sediment from different outlets in the pearl river estuary during the wet season abstract riverine sediment is important for the development of river deltas and for carrying both nutrients and contaminants into estuaries and coasts previous studies of sediment transport have focused on single sourced estuaries and paid less attention to multi sourced estuaries estuaries with multiple river discharge sources in this study we used the coupled ocean atmosphere wave sediment transport coawst modeling system to study the sediment transport in the pearl river estuary pre where riverine sediments come from four different outlets during a typical wet season 2007 about 6 8 million tons of riverine sediments were discharged into the pre most of which were trapped in shoals during neap tides while about 11 8 by mass was transported out of the estuary during spring tides the proportions of the multi sourced sediments trapped in the pre or escaping from the estuary depended on the morphology of the estuary and the location of the outlets in relation to the estuarine morphology the distributions of different riverine sediments were mostly independent in neap tides but overlapped more in spring tides the seaward sediment transport was dominated by river freshwater discharge in the upper estuary and by tidal forcing in the lower channels while tides and winds controlled the sediment transport in the lower shoals this study aids our understanding of sediment transport processes in multi sourced estuaries and has implications for coastal environmental management

modelling of bed sediment composition changes at the lower shoreface of the sand motor abstract large perturbations in the coastline such as the sand motor nourishment 21 million m3 at the holland coast can initiate considerable spatial and temporal changes in the median grain size d 50 of the sea bed on the lower shoreface the relevance of hydrodynamic conditions for the development of the heterogeneity in d 50 at large scale nourishments was assessed with a numerical model delft3d which required a validation against 2 5 years of d 50 measurements a good representation of the observed spatial pattern of d 50 was obtained independent of a 2dh or 3d approach and initial condition for the d 50 of the bed five sediment size fractions and a multi layer administration of the bed composition were used the extent and magnitude of the coarsening of the bed is related to the velocity of the horizontal tide while a far less pronounced coarsening takes place during energetic conditions i e h m 0 3 m differential suspension behaviour between the size fractions which are all mobilized at the bed causes a preferential transport of fine sediment in alongshore direction away from the sand motor at the lower shoreface i e seaward of msl 6 m storm conditions may induce a partial removal of the coarse top layer due to mobilization of all of the size fractions and mixing with the relatively fine substrate material simulations also show that transport of the fine sand fraction extents to much deeper water than for the medium and coarse sand fractions models with multiple sediment fractions are therefore required for the assessment of environmental impacts of large scale coastal structures or land reclamation s and sediment transport on the lower shoreface

the effect of a submarine canyon on the river sediment dispersal and inner shelf sediment movements in southern taiwan abstract this study examines the influence of a submarine canyon on the dispersal of sediments discharged by a nearby river and on the sediment movement on the inner shelf the study area includes the head region of the kao ping submarine canyon whose landward terminus is located approximately 1 km seaward from the mouth of the kao ping river in southern taiwan within the study area 143 surficial sediment samples were taken from the seafloor six hydrographic surveys along the axis of the submarine canyon were also conducted over the span of 1 yr three different approaches were used in the analysis of grain size distribution pattern they include 1 a combination of filtering and the empirical orthogonal eigen function eof analysis technique 2 the mclaren model and 3 the transport vector technique the results of the three methods not only agree with one another they also complement one another this study reveals that the kao ping submarine canyon is relatively a stratified and statically stable environment the hydrographic characteristics of the canyon display seasonal variability controlled primarily by the temperature field and the effluent of the kao ping river the hydrographic condition and the bottom topography in the canyon suggest the propagation of internal tides during the flood season summer of the kao ping river the submarine canyon acts as a trap and conduit for mud exchange between the kao ping river and offshore near the head of the canyon there is a region of sediment transport convergence this region is also characterized by high mud abundance on the seafloor that coincides with the presence of high suspended sediment concentration ssc spots in the bottom nepheloid layer outside the submarine canyon on the shelf where the evidence of wave reworking is strong the northwestward alongshore transport dominates over the southeastward transport which is a common theme on the west coast in southern taiwan

the use of grain size trend analysis in macrotidal areas with breakwaters implications of settling velocity and spatial sampling density abstract in a macrotidal environment with offshore breakwaters elmer west sussex a new approach for the identification of the sediment transport pathways with grain size trend analysis gsta was undertaken using statistical parameters mean sorting and skewness directly derived from settling velocities distributions the same samples were analysed with sieving quarter and half phi resolution and gsta was performed again in order to directly compare the resultant sediment transport directions derived with the two analytical techniques furthermore both regular and irregular sampling distributions were used to recalculate gsta hydrodynamic data were collected in different locations around the breakwaters and net sediment transport directions were calculated in order to assess the accuracy of the sediment transport pathway directions derived with the different analytical techniques the accuracy of settling velocity in determining the statistical parameters of the grain size distribution is identified especially for the fine medium sand sediments settling velocities produced better results than the sieving the quarter phi resolution producing the poorer results in comparison with the coarser half phi resolution the results for the different spatial sampling strategies are found to depend upon the number of samples utilised that shows that the accuracy of the gsta is based upon the ability of representing adequately the spatial distribution of the sediment parameters

radio frequency identification rfid technology applied to the definition of underwater and subaerial coarse sediment movement abstract in this paper radio frequency identification technology has been applied to track both underwater and subaerial displacement of pebbles along an artificial coarse beach at marina di pisa italy several preliminary laboratory tests have been performed to adapt the rfid technique for underwater use which has been the primary impediment to this promising approach to the study of coarse sediment transport and movement tests showed the reliability of low frequencies for this kind of work since they enable good signal transmission and reception through water passive abs plastic transponders were inserted into about 100 pebbles and released onto the beach in march 2009 a core 125 reader was chosen as the operating antenna to continuously transmit low frequency 125 khz signals an acoustic signal toned whenever a pebble was detected while the unambiguous identification code of the pebble is shown immediately on the screen of a laptop connected to the reader the positions of the pebbles were recorded with a total station after two months may 2009 74 marked pebbles were retrieved 77 of the total the positions of the retrieved pebbles were also recorded with the total station thus allowing calculation of the coarse sediment transport tendency about 60 of the recovered pebbles 44 out of 74 were found on the upper shoreface the analysis of the marked pebble trajectories revealed a divergent transport movement in the northernmost sector of the beach this movement was probably triggered by an irregularity of the submerged breakwater fronting the shoreline the southern sector is characterised by chaotic pathways related to the formation and evolution of beach cusps this outcome highlights and confirms the importance of a complete definition of the beach system with no separation between the underwater and the subaerial portion of the shore when it comes to sediment transport and movement this successful application of rfid technology to the underwater environment provides a chance to broaden understanding of a topic in need of further study

net sediment transport patterns inferred from grain size trends based upon definition of transport vectors reply abstract a new approach to the analysis of the grain size trends associated with net sediment transport directions in shallow marine environments is developed here two specific trends modified from mclaren and bowles 1985 on the basis of a literature review are used to define a grid of trend vectors such vectors are filtered and transformed into transport vectors it is suggested that an ordered pattern of the transport vectors represents net transport paths the orderliness of the derived pattern is examined on the basis of a significance test using the average length of the transport vectors as a criterion both the filtering operation and the significance test procedure are based upon the assumption that the trend vectors which are not associated with net transport have the same probability of being in any direction the technique is applied to data from yangpu harbour southern china the technique can be applied to inner continental shelf and coastal environments for such an analysis the area under investigation should be sampled at an interval large enough to reflect the real grain size trends resulting from net sediment transport but small compared with the dimensions of the sedimentary environment the time scale of the results depends upon the sampling depth applicability of the technique is likely to be somewhat limited where the environment is highly variable over short distances furthermore due to its statistical character the analysis may fail to identify net transport patterns

deriving transport pathways in a sediment trend analysis sta abstract sediment trend analysis sta is a technique that enables patterns of net sediment transport to be determined by relative changes in grain size distributions of all naturally occurring sediments in addition sta can determine the dynamic behaviour of bottom sediments with respect to erosion accretion or dynamic equilibrium the data requirements for sta are the full grain size distributions taken from sediment grab samples collected at a regular spacing over a particular area of interest two types of methods are presently used in the derivation of the transport pathways a line by line approach in which transport pathways are determined by searching for sample sequences in which the distributions change in a statistically acceptable manner and various vector approaches in which each sample is compared to neighbouring sites from which a vector sum is calculated the basic assumption for sta is that the processes that cause sediment transport will affect the statistics of sediment distributions in a predictable way in reality this type of analysis is complicated through the inclusion of a number of uncertainties or noise the goal of sta is to extract the information the transport pathways from the noisy signal the grain size distributions an approach that is made difficult because neither the nature of the information nor the noise is known because of this obtaining results by simply applying its theory in a black box approach may provide poor solutions the line by line approach to sta draws from communications theory to achieve a solution in some communications systems the information from many sources is combined into one signal the resulting signal is from a statistical viewpoint nothing but noise the extraction of specific information assumes that information is indeed present and determines if that assumption is consistent with the received signal for sta the procedure is to assume a transport direction over an area comprising many sample sites from this assumption the predicted sediment trends are compared with the pathways determined by the actual samples the assumed transport direction is repeatedly modified until the best fit is achieved vector techniques may be very helpful to provide insights and guidance to the line by line approach however the approach is ultimately necessary to finalize a credible solution as well as providing important further information on the dynamic behaviour of the sediments and to delineate specific sediment transport environments

residual transport model in correlation with sedimentary dynamics over an elongate tidal sandbar in the gironde estuary southwestern france abstract this study qualitatively describes by a multidisciplinary approach hydrodynamic and residual sediment transport over a sandbar in a macrotidal environment the sandbar is elongated and attached to a headland that is located in the gironde estuary southwestern france bathymetric surveys side scan sonar sonograms grain size trends of surficial sediment and 2dh numerical simulations of current patterns were used to define a conceptual model for the dynamics of this sandbar the sandbar is oriented anticlockwise with respect to the main flow the channel oriented bar face is ebb dominated whereas the opposite face is flood dominated resulting in a clockwise residual transport the line of sediment flux convergence corresponds to the crest of the bar the residual flow over the bar appears to originate from the regional estuarine flow the dominant process responsible for the maintenance of the sandbar seems to be the depth averaged main tidal flow rather than secondary circulation due to headlands or the interaction between the tidal flow and the seabed to generalize this regional conceptual model a qualitative comparison is made with the theories of sandbar dynamics due to tidal currents pingree and maddock 1979 zimmerman 1981 huthnance 1982 and others the seabed stability approach developed by huthnance 1982 seems to be the most reliable theory to explain the saint georges bank dynamics even though many natural factors are not taken into account

the grain size characterisation of coastal sand from the somme estuary to belgium sediment sorting processes and mixing in a tide and storm dominated setting abstract sand rich holocene to modern clastic deposits in the eastern english channel and the southern north sea coasts of france and belgium occur extensively as nearshore sand bank estuarine tidal flat aeolian dune and beach sub environments sand samples n 665 collected from these deposits suggest the presence of three different populations a largely dominant 83 medium to fine quartz sand population b and finer 14 and coarser grained 4 populations respectively c and a the distribution of these populations among the four sub environments reflects tide and storm dominated sorting and transport processes and a variable degree of mixing these populations are derived from a mixture of very fine to very coarse grained fluvial outwash and paraglacial sediments deposited on the beds of the eastern english channel and southern north sea during the late pleistocene lowstand the nearshore sand bank environment which also corresponds to the main offshore source area of the coastal deposits exhibits population heterogeneity reflecting the variability of hydrodynamic conditions and sediment sorting in this zone the nearshore topography of tidal ridges banks and troughs in these tidal seas leads to variable bed and tide and storm induced shear stress conditions these conditions only allow for the mobilisation and onshore transport of some of the finer fractions populations b and c leaving an offshore mixture of these finer populations with coarser less mobilisable sediments population a once in the coastal zone these two finer populations undergo further hydrodynamic sorting and segregation variably sorted very fine sands to silts population c are trapped in the low energy estuarine tidal flat sub environment while the highly homogeneous population b is further sorted in aeolian dune and beach sub environments this sorting occurs via a coastal sand transport pathway linking the somme estuary mouth to the southern north sea bight where tidal range and wave energy decrease relative to the english channel since this sand transport pathway enables longshore transport of hydrodynamically sorted medium to fine sand derived directly from the immediate nearshore zone it has further contributed to a net flux of this sand population from the eastern english channel sea bed to the southern north sea

integration of bed characteristics geochemical tracers current measurements and numerical modeling for assessing the provenance of beach sand in the san francisco bay coastal system abstract over 150 million m3 of sand sized sediment has disappeared from the central region of the san francisco bay coastal system during the last half century this enormous loss may reflect numerous anthropogenic influences such as watershed damming bay fill development aggregate mining and dredging the reduction in bay sediment also appears to be linked to a reduction in sediment supply and recent widespread erosion of adjacent beaches wetlands and submarine environments a unique multi faceted provenance study was performed to definitively establish the primary sources sinks and transport pathways of beach sized sand in the region thereby identifying the activities and processes that directly limit supply to the outer coast this integrative program is based on comprehensive surficial sediment sampling of the san francisco bay coastal system including the seabed bay floor area beaches adjacent rock units and major drainages analyses of sample morphometrics and biological composition e g foraminifera were then integrated with a suite of tracers including 87sr 86sr and 143nd 144nd isotopes rare earth elements semi quantitative x ray diffraction mineralogy and heavy minerals and with process based numerical modeling in situ current measurements and bedform asymmetry to robustly determine the provenance of beach sized sand in the region

influence of suspended kelp culture on seabed sediment composition in heini bay china abstract kelp aquaculture activities occupy large nearshore areas with significant effects on sediment properties primarily caused by the influence of the suspended kelp on local hydrodynamics changes in sediment composition and grain size distributions were investigated prior to and following the commencement of kelp aquaculture activities in heini bay in eastern china seabed sediment types and the particulate matter in suspension during the kelp seeding and harvesting periods and in sediment cores were analyzed while suspended sediment in the kelp aquaculture area was up to 20 organic material sediment organic content on the seabed remained at similar levels as areas lacking aquaculture the composition of the seabed sediment in the kelp aquaculture area became finer grained by the capture of fine particles within the kelp aquaculture area the sediments are poorly sorted and positively skewed whereas at the shoreward and seaward of the aquaculture area the sediments are relatively coarse grained well sorted and nearly symmetrically distributed therefore the kelp aquaculture activities not only increase the fine particulate fraction in the sediments within the aquaculture area but also result in similar deposits seaward of it indicating that seabed erosion and accretion is also controlled by the sediment source and the hydrodynamic conditions the analysis of sediment cores showed that kelp culturing refines the sediment by preferentially capturing particles in the 38 40 m size class while having no effect on the

sediment transport patterns inferred from grain size trends and trace metal dispersion near the santa rosalia mining district gulf of california abstract the transport of continental materials of natural and or anthropic origin as well as their dispersion and final deposition in marine environments can be inferred from the analysis of the textural tendencies of sediments the exploitation of copper ore since the 19th century in the santa rosalia mining district has caused the accumulation of potentially toxic elements ptes in sediments off the western coast of the gulf of california however after several decades of mining little is known about the mobilization and final destination of these ptes in the present work the net sedimentary transport and dispersion of cu and zn is inferred in front of the mining district of santa rosalia at the western margin of the gulf of california net sedimentary transport is dominantly towards the southeast with a change towards the east of the port of santa rosalia the spatial distribution of cu and zn showed the same pattern as the net sediment transport which suggests that the dispersion of ptes is controlled by the textural tendencies of the sediments and their transport corroborated by hydrodynamic models of the marine currents at the western margin of the gulf of california

distal mud deposits associated with the pearl river over the northwestern continental shelf of the south china sea abstract continental shelf mud deposits represent an important archive of the holocene earth history such deposits are usually associated with large rivers that transport a large quantity of suspended sediment the pearl river has formed a distal shore parallel holocene mud deposit on the northwestern continental shelf of the south china sea investigations into its spatial distribution and evolutionary history are necessary for an improved understanding of such sedimentary systems seabed sediment sampling in situ tidal cycle measurements seismic survey and the associated data analyses reveal that the distal mud deposit associated with the pearl river occupies an area of approximately 8 87 10 3 km 2 with a modern deposition rate of 1 27 to 5 66 mm yr 1 evidence from sediment balance environmentally sensitive components sediment transport processes and regional shelf circulation patterns indicates that the pearl river is a major sediment source for the mud deposit this distal mud deposit represents an initial stage of its development the fining upward pattern and the negative skewness values in the layer are indicative of the pearl river influence and the 210 pb age is younger than 10 2 yr the main body of the holocene deposit of the region is not related directly to the modern pearl river sediment for most of the holocene periods the pearl river has been trapping the sediment to fill its extensive estuarine waters and therefore the formation of the distal mud is a recent event a regional characteristic is that the timing of the formation of distal muds associated with large rivers depends on the estuarine morphological evolution and the quantity of sediment discharge

sediment transport patterns determined from grain size parameters overview and state of the art abstract grain size trends have been applied in many diverse sedimentary environments to determine sediment transport paths generally coinciding with information from tracer studies current measurements and the orientation of sedimentary structures the different methods proposed to date are critically analysed and compared with reference to recent field studies it is concluded that the two dimensional methods produce comparable results and may in fact complement each other in spite of the advances several problems still exist which include the sampling method and density the choice of trend types the relative weight of grain size parameters and the interpretation of results these are discussed together with possible solutions

a reconstruction of late pleistocene relative sea level in the south bohai sea china based on sediment grain size analysis future anthropogenic sea level rise and its impact on coastal regions is an important issue facing human civilizations due to the short nature of the instrumental record of sea level change development of proxies for sea level change prior to the advent of instrumental records is essential to reconstruct long term background sea level changes on local regional and global scales here we employ numerical methods to partition sediment grain size using a combined database of marine surface and core samples and to quantitatively reconstruct sea level variation since the late pleistocene in the south bohai sea china our sea level reconstruction indicates that relative sea level changes in the southern bohai sea track global sea level variation for the duration of the record the results also indicate substantial regression from 70 to 30 cal kyr bp and potentially subarial exposure from 38 to 20 cal kyr bp our results document the feasibility of reconstructing relative sea level change by numerical partitioning of sediment grain size data demonstrating the potential for future applications c 2012 elsevier b v all rights reserved

influence of trace metals in recent benthic foraminifera distribution in the pearl river estuary this work analyzed the distribution of trace metals and benthic foraminifera in the pearl river estuary and studied the influence of environmental parameters i e trace metals organic matter and sediment grain size on the total living plus dead benthic foraminiferal assemblages the results indicate that the distribution patterns of co cr cu ni pb and zn are strongly related to the behavior of the sedimentary clay fraction kaolinite and illite and are dispersed with sedimentary material whereas ba sr v and zr follow different trends the study area is moderately to severely polluted with co cr cu ni pb and zn and maximum values were found in the upstream and on the western side of the estuary where the lowest levels of h s fisher alpha index and number of species are situated analyses of species abundance and community diversity as well as the subsequent canonical redundancy analysis were conducted to reveal the relationship between the foraminifera data and environmental parameters two assemblages were established by cluster analysis and were distributed in relation to bathymetry the distribution of foraminiferal assemblages was mainly determined by cu zn and pb while sand may exert an influence on particular species ammonia tepida haplophragmoides canariensis and elphidium nakanokawaense are tolerant to the metal enrichment while the abundances of the other species decline and are prejudiced this study indicates that benthic foraminifera can be used as a bio indicator of trace metal pollutants in the pearl river estuary and the results promote a better understanding of the response of benthic foraminifera to human induced pollution in estuaries c 2014 elsevier b v all rights reserved

evaluating the influence of tidal currents on the distribution of silt in nara inlet central great barrier reef australia a simple model is developed to infer flood tide dispersal of silt during fair weather conditions from spatial grain size variation of mixed carbonate siliciclastic silt on the bed of nara inlet a 3 km long shallow tropical embayment on the mid shelf of the central great barrier reef region australia the model uses settling velocities calculated for three dominant silt modes 23 28 and 41 m and measured tidal current data to predict the headward transport of silt by a large flood tide modelling was aided by the use of wind and currents 2000 wc2000 freeware a visualisation and analysis tool for vectorial data the model predicts the 23 28 and 41 m modes will be transported minimum headward distances of 1250 950 and 500 m respectively and compares well with the observed silt distribution on the bed the results indicate that under fair weather conditions flood tides control the distribution of silt consistent grain size trends of bulk and siliciclastic silt implies that siliciclastic and carbonate silt sized grains may exhibit similar hydraulic behaviour during transport by flood tides in nara inlet the model may be applied to embayments where fine sediment transport is dominated by flood tides it may also have application in identifying the controls on dispersal and accumulation of particle associated contaminants in embayments characterised by mixed carbonate and siliciclastic sediments

sediment distribution and transport at the nearshore zone of the red river delta northern vietnam abstract the coast between ngason and haiphong is largely formed by accretion of the red river system in the region five main surface sediment types sand sandy silt silt mud and sand at shoals could be defined which differ from one another in their sedimentary characteristics sand dominates along the shoreline between 0 and 15 m water depth down to a water depth of about 25 30 m the sediment is dominantly silt further offshore the surface sediments are mainly sandy silt and sand of older units early middle holocene late pleistocene net sediment transport directions are defined by grainsize analysis according to the method of gao and collins gao s collins m 1992 net sediment transport patterns inferred from grain size trends based upon definition of transport vectors sedimen geol 80 47 60 1992 at river mouths directions of sediment transport are variable where the depths are shallower than 5 m from 5 to 10 m water depth sediments are mainly transported southeastward at the ba lat lach and day mouths northeastward at the tra ly mouth and eastward at the thai binh mouth recently the hai hau erosional shoreline is not supplied with sediment from the ba lat mouth and sediments are transported southwestward alongshore in the region shallower than 5 m the region of depths from 10 to 30 m is specified by southward sediment transport

application of image based granulometry to siliceous and calcareous estuarine and marine sediments abstract grain size analysis has long been used as a descriptor of transport and depositional processes this paper presents the possibility of using image based granulometries not yet widely used in the earth sciences to characterize granulometric composition of unconsolidated estuarine and marine sediments to test the method conventional sediment analysis of siliceous and calcareous sediments are compared to image based analysis of sediments obtained along the ore estuary northern sweden and the adriatic sea croatia and italy these grains have different textural characteristics composition roundness and specific surface area granulometric parameters are calculated using both a graphical method and the mathematical method of moments grains have been imaged using a microscope and mathematical granulometries have been applied to the digital data image based granulometric moment descriptors are compared with sieve coulter counter derived moments although it is not claimed that digital imaging should be the only method used in sedimentology the results show the potential of applying digital electronic imaging to granulometric analysis of sediments in this way sampling for granulometric analysis and sieving processes combined with coulter counter analysis of fraction