analysis on residual coarse sediment transport in estuaries abstract the analytical expression for residual coarse sediment transport of van de kreeke and robaczewska 1993 is extended for estuaries the major extension concerns the contribution to sediment transport by residual current which is ignored by van de kreeke and robaczewska 1993 tidal constituents m 0 m 2 s 2 n 2 m 4 ms 4 mn 4 m 6 k 1 and o 1 are used to represent the collinear tidal current it is shown that interactions of m 0 and all tidal constituents contribute to residual sediment transport when m 0 is not negligible thus a representative tide based on m 2 and its overtides only is not sufficient to drive morphodynamic models in this case the present analysis also reveals that triad interactions of compound tides with their basic constituents i e ms 4 with m 2 s 2 and mn 4 with m 2 n 2 contribute to residual sediment transport besides interactions of m 0 and m 2 and of m 2 and its even overtides m 4 and m 6 the extended analytical expression is applied to determine residual sediment transport in the yangtze estuary it is demonstrated that a single representative tide does not exist for morphodynamic models in this case this conclusion is likely to also apply to other estuaries in which residual flow is not negligible

will river erosion below the three gorges dam stop in the middle yangtze abstract the environmental impact of the three gorges dam has been a subject of vigorous academic political and social debate since its inception this includes the key issue of post dam river channel erosion which was predicted by the feasibility study to extend to the river mouth in this paper we examine the geomorphic response of the channel of the middle yangtze for 660 km downstream of the dam using data on channel characteristics bed material and sediment transport we show that in the decade following the dam closure pre dam seasonal erosion has been replaced by year round erosion a pattern most marked at the upstream end of the study area the sediment carrying capacity of the river channel has been largely reduced below the dam the locus of bed scour has moved progressively downstream ceasing as the bed material became too coarse to be transported e g d 50 0 29 mm pre dam coarsened to 20 mm below the dam by 2008 about 400 km below the dam there is a reduction in channel slope that changes the sediment carrying capacity from 0 25 kg m 3 to only about 0 05 kg m 3 which is insufficient to move bed sediment the new long term hydro morphological equilibrium that will be established in this section of the middle yangtze will prevent the further incision downstream initiated by the three gorges dam the results suggest that the full extent of adverse environmental impact predicted by the pre dam studies will not eventuate

developments in the characterization of complex rock slope deformation and failure using numerical modelling techniques recent advances in the characterization of complex rock slope deformation and failure using numerical techniques have demonstrated significant potential for furthering our understanding of both the mechanisms processes involved and the associated risk this paper illustrates how rock slope analyses may be undertaken using three levels of sophistication level i analyses include the conventional application of kinematic and limit equilibrium techniques with modifications to include probabilistic techniques coupling of groundwater simulations and simplistic treatment of intact fracture and plastic yield such analyses are primarily suited to simple translational failures involving release on smooth basal rear and lateral surfaces where the principle active damage mechanisms are progressive failure and or asperity breakdown level ii analyses involve the use of continuum and discontinuum numerical methods in addition to simple translation level ii techniques can be applied to complex translational rock slope deformations where step path failure necessitates degradation and failure of intact rock bridges along basal rear and lateral release surfaces active damage processes in this case comprise not only strength degradation along the release surface e g asperity breakdown but also a significant component of brittle intact rock fracture level iii analyses involve the use of hybrid continuum discontinuum codes with fracture simulation capabilities these codes are applicable to a wide spectrum of rock slope failure modes but are particularly well suited to complex translation rotational instabilities where failure requires internal yielding brittle fracturing and shearing in addition to strength degradation along release surfaces through a series of rock slope analyses the application of varied numerical methods are discussed particular emphasis is given to state of the art developments and potential use of level iii hybrid techniques d 2005 elsevier b v all rights reserved

implications of flow control by the three gorges dam on sediment and channel dynamics of the middle yangtze changjiang river china the impacts of a dam on the river downstream in terms of hydrology and morphology are determined by a complex mix of variables that includes the patterns of release of water through the dam and the characteristics of the downstream channel scour of the downstream channel is a common response because large dams cause a significant interruption to sediment continuity here we show that in the case of china9s three gorges dam on the yangtze river the outcome is complicated as is commonly the case in large rivers the downstream channel and floodplain system compose an area of long term sediment accumulation and unstable channels with seasonally contrasting erosion and deposition patterns related to the migrating seasonal monsoon rainfall zones in achieving one of the main purposes of this dam that of flood control in the middle and lower basins the pattern of flows released from the dam will closely resemble those seasonal flows that are responsible for channel instability in the middle catchment thus effectively making erosive conditions the most common during a year there is obviously concern about the ultimate impact of sediment storage in the dam on the dynamics of the delta and adjacent coast and we show that this depends on the trajectory and duration of the erosive responses in the middle yangtze basin in this particular case the outcome is of great significance to the well being of the densely populated riparian areas of the river

shear fracture patterns and connectivity at geometric complexities along strike slip faults shear fracture patterns and connectivity at geometric complexities such as echelon fault steps and fault bends along strike slip faults are investigated by simulating shear fracture propagation paths using a displacement discontinuity boundary element method together with a maximum distortional strain energy density criterion it is shown that shear fracture patterns and connectivity depend on the specific geometric configurations the applied stress orientations and the coefficient of friction for a given initial configuration of the major faults the subsequent patterns of the associated shear fractures and their linkage can be predicted if the remote state of stress and the coefficient of friction are known the analyses of fault geometries commonly encountered in nature have important implications for evaluating the effect of faults on fluid flow and earthquake hazards associated with the geometric complexities along strike slip faults in the upper crust

effects of navigational works on morphological changes in the bar area of the yangtze estuary abstract to improve navigability of the major access channel into shanghai harbor a large scale deep waterway project was carried out in the north passage np of the yangtze estuary in this paper we investigate how the navigational works affected morphological changes of this channel as well as those of the adjacent north channel nc hengsha east shoal hes jiuduansha shoal jds and the south passage sp morphological changes were assessed by analyzing digitized bathymetric data of this area prior to and after execution of the engineering works the qualitative relations between these changes along with the hydrodynamic changes as a result of the construction of engineering works were subsequently investigated the results reveal that the construction of training walls groins and jetties resulted in decreased ebb transport in the upper reach of the np and increased ebb transport in the upper reach of the sp in turn this led to intensive upstream erosion with large amounts of sediment transported seaward in the sp and associated sedimentation in the downstream area at the same time intense siltation occurred in the upper reach of the np while the main channel of the np mainly experienced erosion caused by the construction of training walls and groins that concentrated ebb flow in the main channel the waterway deepened significantly in previously shallow areas small tidal channels in the hes which used to connect the np and the nc were cut off by the northern training wall consequently residual flow in the middle reach of the nc flowed directly toward the northern bank of the hes leading to local erosion flow obstruction by the southern training wall reduced the upstream propagation of the flood tide in the sp as a result a collection of small flood channels evolved under the flushing action of flood currents in the jds preventing the natural trend of horizontal extension of the jds however the flow obstruction enhanced the vertical accretion of the jds

linking the infilling of the north branch in the changjiang yangtze estuary to anthropogenic activities from 1958 to 2013 abstract many tidally dominated estuaries of the world are experiencing variations in bottom topography due to changes in natural forcings and intensive human activities here we focus on the morphological evolution of the north branch nb a tidally dominated distributary of the changjiang estuary our analysis is based on long term bathymetric and hydrological data collected between 1950 and 2010 the results show that mean water depth channel volume below 0 m and channel volume below 5 m have respectively decreased by 43 53 and 92 in the last 50 years a reduction of the whole estuarine surface with aggradation in elongated tidal sand bars and erosion at the mouth are the main morphological variations of the nb while a decrease in channel volume below 5 m due to infilling is the second mode of morphological change while the drastic decrease in sediment load from upstream is likely unrelated to the silting of the nb local land reclamation along the banks is directly responsible for the reduction of estuarine surface area and related tidal prism between 1958 and 2013 enhanced flood tide currents resulted in a large import of sediments from offshore into the nb triggering a sustained decrease in channel volume below 0 m it is argued that the recovery of the funnel shaped configuration of the estuary by restoring mud flats over 0 m dredging the southern part of the estuary bend and forbidding land reclamation could prevent the silting of the nb otherwise the nb will likely vanish in few decades

human influence and the changing geomorphology of mediterranean deltas and coasts over the last 6000 years from progradation to destruction phase the present geomorphology of the mediterranean s coasts is largely a product of an intricate long term relationship between nature and human societies a cradle of ancient civilisations the mediterranean has seen its shores occupied by humans since prehistory and is therefore a particularly pertinent unit of analysis the morphotectonic context and other forcing agents e g climate shaped out a highly diversified coastal morphology and generated a sediment supply regime potentially favourable to the formation of numerous open coast deltas and bay head deltas in infilled rias as sea level stabilised during the mid holocene this supply of riverine sediment has also been the key agent in mediating human occupation of the mediterranean s clastic coasts expressions of this relationship have been extensively archived in clastic coastal deposits including base level deltaic and estuarine sedimentary sinks which comprise records to explore the interactions between geosystems and the human environment the stratigraphic sequences in these coastal sedimentary archives comprise in many places a clearly identified anthropogenic signature notably in ancient harbours some of which underwent extremely rapid silting up due to massive sediment sourcing generated by new agricultural practices from the neolithic onwards increasing human influence especially over the last 3000 years has been in turn an important driver of changes in sediment supply strongly modulating deltaic development pulses of sediment supply from catchments rendered vulnerable by human perturbations during the roman period resulted in a new cycle of inception of many other deltas and in rapid delta growth e g the ebro the po the arno and the ombrone another progradation dynamic during the little ice age at a time of strong rural population growth river discharge increases technological developments and urbanisation further consolidated delta growth understanding the life cycle of these deltas since their initial formation is in turn key to unravelling the relative role of natural and anthropogenic forcing agents rapid climate changes are deemed to have contributed through both the stripping of landscapes rendered fragile by human activities and active fluvial sediment transport to the coast but disentangling climate change effects from human impacts in the mediterranean remains a challenge the patterns of subsequent deltaic growth and delta morphodynamics reflect adaptations to pulsed sediment supply river discharge variations the microtidal fetch limited context of the mediterranean and direct engineering interventions the progradation dynamic of the roman period and little ice age contrasts markedly with the situation of common coastal destabilisation over the last two centuries particularly well documented for the last 50 years this period has been characterised by reduced sediment flux to base level geosystems due to catchment reforestation retenion within reservoirs fluvial regulation and dredging resulting in the erosion of deltas and barrier lagoon and beach dune systems large stretches of shoreline and narrow coastal plains have been massively engineered for coastal defence and protection against erosion but also for the construction of marinas leisure harbours and artificial beaches resulting in the emergence of veritable artificial seafronts these interventions have collectively and progressively raised societies to a pervasive and overarching position in the geomorphic stability instability of the mediterranean s coasts a situation that will be exacerbated by pressures from sea level rise paving the way for rampant coastal erosion and delta destruction

how stable is the mississippi delta large deltas are commonly believed to exhibit rapid rates of tectonic subsidence largely due to sediment loading of the lithosphere as a result deltaic plains are prone to accelerated relative sea level rise coastal erosion and wetland loss hurricane katrina s devastation testifies to the severe threat that these processes pose to the mississippi delta but the relative role of tectonics versus other mechanisms causing land subsidence remains elusive relative sea level records derived from basal peat have the potential to quantify differential crustal movements over holocene time scales with exceptionally high accuracy and precision here we present new sea level index points from two study areas in the southwestern mississippi delta that essentially coincide with a recently published detailed relative sea level record from the eastern part of the delta our results show that differential vertical movements among the three study areas have been only 0 1 mm yr 1 w e compare our evidence with a recent sea level compilation from the caribbean to a large extent based on data from areas that are tectonically stable our sea level index points nearly coincide with the caribbean data showing surprising tectonic stability for considerable sections of the mississippi delta however the well documented high subsidence rates in and near the birdfoot of the mississippi delta indicate that different conditions prevail there the rapid wetland loss in coastal louisiana is likely due to a considerable extent to the compaction of holocene strata

flux and fate of yangtze river sediment delivered to the east china sea numerous cores and dating show the yangtze river has accumulated about 1 16 x 10 12 t sediment in its delta plain and proximal subaqueous delta during holocene high resolution seismic profiling and coring in the southern east china sea during 2003 and 2004 cruises has revealed an elongated similar to 800 km distal subaqueous mud wedge extending from the yangtze river mouth southward off the zhejiang and fujian coasts into the taiwan strait overlying what appears to be a transgressive sand layer this distal clinoform thins offshore from similar to 40 in thickness between the 20 and 30 m water depth to 1 2 in between 60 and 90 m water depth corresponding to an across shelf distance of less than 100 km total volume of this distal mud wedge is about 4 5 x 10 11 m 3 equivalent to similar to 5 4 x 10 11 t of sediment most of the sediment in this mud wedge comes from the yangtze river with some input presumably coming from local smaller rivers thus the total yangtze derived sediments accumulated in its deltaic system and east china sea inner shelf have amounted to about 1 7 x 10 12 t preliminary analyses suggest this longshore and across shelf transported clinoform mainly formed in the past 7000 yrs after postglacial sea level reached its mid holocene highstand and after re intensification of the chinese longshore current system sedimentation accumulation apparently increased around 2000 yrs bp reflecting the evolution of the yangtze estuary and increased land erosion due to human activities such as fanning and deforestation the southward flowing china coastal current the northward flowing taiwan warm current and the kuroshio current appear to have played critical roles in transporting and trapping most of yangtze derived materials in the inner shelf and hence preventing the sediment escape into the deep ocean c 2006 elsevier b v all rights reserved

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

role of large particles in the transport of elements and organic compounds through the oceanic water column abstract during the past decade data from a variety of sources have been obtained which show conclusively that the relatively rare large particles sinking through the water column are responsible for the majority of the downward vertical mass flux in the sea this finding has important implications for understanding the transfer distribution and fate of elements and organic compounds in marine waters the large 100 m detrital particles responsible for vertical flux are primarily biogenic and range in size and composition from small discrete fecal pellets and plankton hard parts to large amorphous aggregates or snow which contain both organic and inorganic constituents depending on size shape and density these particles sink at rates ranging from 1000 m day 1 several methods have been developed for sampling these particles of which in situ sediment trapping has probably furnished the most comprehensive qualitative and quantitative information on the role large particles play in material transport flux studies have highlighted the importance of marine heterotrophs in packaging fine suspended particulate matter into large rapidly sinking particles which accelerate the movement of incorporated materials to depth large particle production via biological packaging is not restricted to the euphotic zone but can occur at all depths and information is now accruing on rates of production of large particles in the water column chemical analyses of sedimenting particles collected in sediment traps and those sampled by other means have allowed quantifying vertical fluxes and residence times of elements radionuclides and organic compounds natural and anthropogenic in various oceanic regimes pertinent studies dealing with the above aspects are reviewed and several areas for future research are suggested

process based morphodynamic modeling of the yangtze estuary at a decadal timescale controls on estuarine evolution and future trends abstract understanding the decadal morphodynamic evolution of estuaries and deltas and their controls is of vital importance regarding management for estuarine function and sustainable development this work addresses this issue by applying a process based model system delft3d to hindcast and then forecast the morphodynamic evolution of the yangtze estuary at a decadal timescale forced by the river and tides the model considers sand mud mixture and the variations of river water discharge and sediment discharge the morphodynamic model is validated against three periods i e an accretion period 1958 1978 an erosion period 1986 1997 and a recent accretion period with human activities 2002 2010 model results show good performance with respect to spatial erosion and deposition patterns sediment volume changes and hypsometry curves the model reveals quite different behaviors for mud transport between the dry and wet seasons which is subject to the prescription of river boundary conditions and bed composition we define six scenarios to project evolution to the year 2030 under decreased river inputs and increased relative sea level the simulations reveal that overwhelming amount of erosion will likely occur in the inner and mouth bar area of the estuary particularly the mouth zone will shift from net deposition before 2010 to net erosion by 2030 mainly because of decreasing sediment supply changes in water discharge have minor effects on the projected trend net erosion will be considerable when the sediment supply is extremely low 100 mt yr 1 due to the abundance of erodible modern sediment in the yangtze estuary erosion within the mouth bar area may be unexpected including the deepening of the tidal inlet at east chongming mudflat and the formation of a flood channel on the seaward side of jiuduansha shoal overall the model results provide valuable information for sustainable delta management under changing conditions for both the yangtze system and other similar estuaries and deltas with diminishing sediment supplies

the multi decadal morphodynamic changes of the mouth bar in a mixed fluvial tidal estuarine channel abstract inner channel mouth bars imb are common and vital geomorphological structures in estuaries that can efficiently promote the progradation of a fluvial delta however these significant structures face serious interferences by natural and human forces this study mainly focuses on imb deposited in the mixed fluvial tidal dominated south passage sp of the changjiang estuary between 1959 and 2018 to reveal how multidecadal morphodynamic variability in a mouth bar responds to natural forcing and human interferences the results show that the volume of the imb in the sp increased from 1128 106 m3 in 1959 to 1636 106 m3 in 1989 and then decreased to 462 106 m3 in 2018 meanwhile the evolution of the imb could be divided into five stages the growing phase 1959 to 1979 which showed a v shape the partial adjustment phase 1999 2003 which showed a crest dent shape the stable phase which showed a flat shape 2004 2010 the partial adjustment phase 2011 2017 when jiangyanan shola inserted into the sp and finally evolved into a flat shape in 2018 fluvial water discharge and suspended sediment discharge ssd did not control the variation in the mouth bar enso events were normally responsible for not only the periodic variations in the landward slope and the water depth of the crest of the imb but also occasional extreme changes in the imb moreover local sandbar insertion sediment from the seaside induced by strong tidal power and intensified engineering projects resulted in the continual shrinkage of the mouth bar by depositing more sediment at the mouth bar our work implies that understanding and governing this imb will bring additional economic benefits to this fast developing society but the protection of this delicate estuarine geomorphology system should still receive great attention

decline in suspended sediment concentration delivered by the changjiang yangtze river into the east china sea between 1956 and 2013 abstract the temporal evolution of suspended sediment concentration ssc in a river debouching into the ocean provides vital insights into erosion processes in the watershed and dictates the evolution of the inner continental shelf while the delivery of sediment from rivers to the ocean has received special attention in the recent past few studies focused on the variability and dynamics of river ssc especially in the changjiang yangtze river china the longest river in asia here variations in ssc delivered by the changjiang river to the east china sea and possible causes of its variability were detected based on a long term time series of daily ssc and monthly water discharge measured at the datong gauging station the ssc data are further compared to a hydrological analysis of yearly precipitation covering the entire catchment the results indicate the presence of a decline in ssc in the period 1956 2013 which can be divided into three phases i high ssc 0 69 kg m3 in the wet season and low ssc 0 2 kg m3 in the dry season from 1956 to 1970 ii relative high ssc 0 58 kg m3 in the wet season and low ssc 0 15 kg m3 in the dry season from 1971 to 2002 and iii low ssc 0 19 kg m3 in the wet season and very low ssc 0 09 kg m3 in the dry season after 2002 these three periods have a mean yearly ssc values of 0 62 0 42 and 0 18 kg m3 respectively compared with 1956 1970 the slope of the rating curve between ssc and water discharge decreased respectively by 2 and 30 during the period 1971 2002 and 2002 2013 soil erosion dam construction and banks reinforcement along the changjiang river are the main causes of ssc variations fluctuations in water discharge are also controlling the ssc long term variations specifically from 1956 to 1970 the effect of soil erosion overrules that of dam impoundment which is likely responsible for the high ssc during the period 1970 2002 the influence of dam impoundment increases while that of soil erosion decreases which together produce a small reduction in ssc since 2002 the impact of soil erosion further decreases and large scale sediment trapping behind the three gorges dam is responsible for the occurrence of extremely low ssc the results presented herein for the changjiang river can inform a better management strategy of sediment resources and water quality for both the river and the coast our conclusions can be well applied to other rivers discharging in the ocean subject to similar human activities

bathymetric evolution of the mersey estuary uk 1906 1997 causes and effects this paper examines how a continuous series of measurements and model studies have developed our understanding of the evolving interactions between tidal dynamics sediment regime and bathymetry of the mersey estuary among the most intensively monitored worldwide this includes familiar assessments of the capabilities of fine resolution 3 d models but is here extended to examine historical changes in tides sediments and estuarine bathymetries a century of bathymetric surveys indicates a net loss of estuarine volume of about 0 1 or 1 million cubic metres per year in contrast sea level rise of 1 2 mm a 1 represents only a 0 02 annual increase this relative stability persists in a highly dynamic regime with suspended sediment concentrations exceeding 2000 mg l 1 and spring tide fluxes of order 200 000 t detailed analyses of the bathymetric sequences indicate most significant changes occur in the upper estuary and in inter tidal zones a long period up to 63 years of tidal elevation records in the lower estuary shows almost no changes to the predominant m2 and s2 constituents the 3 d numerical model accurately reproduces both these elevation constituents and corresponding cross sectional distributions of currents simulation accuracies reduce upstream due to cumulative errors associated with relatively unstable bathymetries and increasing sensitivities to the bed stress coefficients impacts from increases in river flows of up to two or three times the long term mean value can only be detected in the upper estuary a detailed examination of sediment fluxes utilised a numerical simulation of conditions over a cross section in the narrows the 10 km by 1 5 km prismatic entrance channel the limited mobility of coarse sediments was contrasted with the near continuously suspended nature of the finest clay a sensible match between the net sedimentation rates indicated by the model and the net observed deposition rate was found to occur for silty sand corresponding directly with evidence from dredging records and from direct sampling while the model indicated sedimentation rates might increase by up to a factor of ten for much finer particles such occurrences are likely to be restricted by the limited availability of such material in the adjacent coastal zone the controlling mechanism for this import of fine sediments is via tidal pumping the nature of which depends critically on the phase lead of tidal currents relative to elevation however since this phase lead is determined by the large scale tidal energy balance of the estuary the conclusion is that stability of the overall tidal dynamics the associated sediment regime and bathymetry are likely to co exist and evolve slowly as indicated by the observed annual decrease in net volume suggestions are included for monitoring strategies in other estuaries to provide insight into such dynamics sediment bathymetry inter relationships

drowning of the mississippi delta due to insufficient sediment supply and global sea level rise global sea level rise reduced sediment supply and subsidence threaten the stability of the mississippi delta calculations of riverine sediment load and storage indicate that 10 000 13 500 km2 of the delta could be submerged by ad 2100

a statistics based discrete element modeling method coupled with the strength reduction method for the stability analysis of jointed rock slopes abstract the stability of jointed rock slopes can be effectively analyzed using the discrete element method dem however the criteria for terminating the dem iterative calculation process and determining the factor of safety fos are not well defined in this paper a displacement statistics based discrete element modeling method dsdm is proposed to analyze the stability of jointed rock slopes by coupling with the shear strength reduction method srm in the presented dsdm two important criteria are defined 1 a statistics based criterion for terminating the iterative calculation process of the dem modeling in the stability analysis of jointed rock slopes and 2 a statistics based criterion for determining the fos of a jointed rock slope when coupling dem and srm the novelty of the proposed dsdm is that statistical information of the global displacements around the potential slip surface of the jointed slope rather than the local displacements of several characteristic points are utilized to define the criteria for terminating the dem iterative calculation process and determining the fos to verify the effectiveness of the proposed dsdm the fos of a simplified jointed rock slope is first calculated using the proposed dsdm and then compared with the fos obtained using the finite difference method fdm moreover the proposed dsdm is applied to analyze the stability of a real high steep bedding rock slope the numerical simulation results for the real rock slope are consistent with the in situ observations the proposed dsdm is thus capable of effectively analyzing the stability of jointed slopes with potential slip surfaces

detailed analysis of acoustic emission activity during catastrophic fracture of faults in rock abstract the detailed time space distribution of acoustic emission ae events during the catastrophic fracture of rock samples containing a pre existing joint or potential fracture plane is obtained under triaxial compression using a high speed 32 channel waveform recording system and the results are discussed with respect to the prediction and characterization of catastrophic fault failure ae activity is modeled quantitatively in terms of the seismic b value of the magnitude frequency relation the self excitation strength of the ae time series and the fractal dimension of ae hypocenters consistent with previous studies on rock samples containing a fracture plane with several asperities the present analyses reveal three long term phases of ae activity associated with damage creation on heterogeneous faults each clearly identifiable based on the above parameters a long term decreasing trend and short term fluctuation of the b value in the phase immediately preceding dynamic fracture are identified as characteristic features of the failure of heterogeneous faults based on the experimental results it is suggested that precursory anomalies related to earthquakes and other events associated with rock failure are strongly dependent on the heterogeneity of the fault or rock mass a homogeneous fault or rock mass appears to fracture unpredictably without a consistent trend in precursory statistics while inhomogeneous faults fracture with clear precursors related to the nature of the heterogeneity

secular bathymetric variations of the north channel in the changjiang yangtze estuary china 1880 2013 causes and effects abstract as the interface between the fluvial upland system and the open coast global estuaries are facing serious challenges owing to various anthropogenic activities especially to the changjiang estuary since the establishment of the three gorges dam tgd currently the world s largest hydraulic structure and certain other local hydraulic engineering structures the changjiang estuary has experienced severe bathymetric variations it is urgent to analyze the estuarine morphological response to the basin wide disturbance to enable a better management of estuarine environments north channel nc the largest anabranched estuary in the changjiang estuary is the focus of this study based on the analysis of bathymetric data between 1880 and 2013 and related hydrological data we developed the first study on the centennial bathymetric variations of the nc it is found that the bathymetric changes of nc include two main modes with the first mode representing 64 of the nc variability which indicates observable deposition in the mouth bar and its outer side area lower reach the second mode representing 11 of the nc variability which further demonstrates channel deepening along the inner side of the mouth bar upper reach during 1970 2013 further recent erosion observed along the inner side of the mouth bar is caused by riverine sediment decrease especially in relation to tgd induced sediment trapping since 2003 while the deposition along the lower reach since 2003 can be explained by the landward sediment transport because of flood tide force strengthen under the joint action of tgd induced seasonal flood discharge decrease and land reclamation induced lower reach narrowing generally the upper and lower nc reach are respectively dominated by fluvial and tidal discharge however episodic extreme floods can completely alter the channel morphology by smoothing the entire channel the results presented herein for the nc enrich our understanding of bathymetric variations of the changjiang estuary in response to human activities which can be well applied to other estuaries subject to similar interferences

morphological evolution of the south passage in the changjiang yangtze river estuary china abstract estuarine morphology of the world s major large rivers have experienced great changes due to intensive anthropogenic activities and natural forcings especially in the changjiang estuary located at the end of the longest river in asia this study focuses on morphological changes of the south passage sp which is one of the 4 channels in the branching estuary at the mouth of the changjiang yangtze river china a multivariate analysis technique of empirical orthogonal eigen function eof method was used to examine the major modes of change in the long term over 26 years water depth data the results show that the morphological changes at the sp could be divided into two stages between 1987 and 1997 the sp had a single stable channel with closure of a cross channel between 1997 and 2012 sp displayed southeastward elongation of a spit into the main channel and westward shoal incision by a cross channel the opening of the sp developed a two channel morphology which stabilized and showed infilling during 2003 2012 the average deposition rate was 10 cm yr in the past 30 years the most dominant morphological changes of sp included the deposition around the upstream opening of the channel the second most important pattern of morphological change was related to the downstream elongation retreat and lateral migration of the spit of the jiangyanan shoal which resulted in the two channel configuration of the sp additionally these morphological changes were not triggered by the decline of the distal sediment source from the upstream but due to the input of proximal sources of the shoal at the upstream opening of the sp and spill over sediment from the north passage via a short cut channel

static and seismic stability assessment of 3d slopes with cracks abstract the majority of extant analyses on slope stability assumed a two dimensional plane strain condition and or an intact slope however slope failures typically exhibit three dimensional 3d characteristics and cracks are commonly present in cohesive slopes this study develops a framework based on the kinematic limit analysis method for static and seismic stability evaluation of 3d slopes with cracks a pseudo static approach is adopted to represent seismic effects two types of cracks are considered cracks prior to slope failure open cracks and cracks forming contemporaneously with slope failure formation cracks a 3d horn like collapse mechanism including a vertical crack is used to represent the slope collapse a comparison with previous studies is conducted to validate the proposed approach a series of stability charts is presented for the ease of direct use results show that consideration of seismic effects and existence of cracks lead to a significant reduction in slope stability whereas the inclusion of 3d effects yields a greater safety factor the influence of cracks becomes more significant for slopes with greater inclination angles and higher levels of soil cohesion this study considers a more realistic situation the results of which can serve as a reference tool in the seismic design of slopes

rapid human induced siltation of the macro tidal ord river estuary western australia field studies on the sediment dynamics of the two arms of cambridge gulf tropical western australia were undertaken the system is macro tidal with 8 m tides the west arm is the estuary of the durack and pentecost rivers which are largely untouched by human activities the east arm is the estuary of the ord river affected by land clearing which started 100 years ago and by two river dams constructed 30 years ago prior to damming of the ord river the natural flow in all rivers was highly seasonal characterized by small at times negligible flow during the dry season which lasts eight months and occasional river floods during the wet season which lasts four months the river flow has been regulated in the east arm as a result of damming this resulted in suppressing large river floods the salinity intrusion length has decreased by about 50 in the east arm following river damming the east arm has silted measurably over the last 30 years with the stream cross sectional area decreasing by about 50 field and numerical studies suggest that this is due to the dam induced suppression of large river floods which has in turn allowed a greater amount of tidal pumping of sediment into the east arm from cambridge gulf since tidal pumping is increasing as the system is silting the east arm appears to now be geomorphologically unstable as a result of human activities numerical studies suggest it may take as little as 100 years for the ord river to reach a new equilibrium modelling suggests that this equilibrium may be characterized by a salinity intrusion length half that before damming a channel width and depth reduced by 70 and a much stronger tidal asymmetry characterized by an increasing size of the tidal bore the west arm appears to be at equilibrium since there has been no net loss or gain of sediment for the last 111 years tidal dynamics and river floods appear responsible for self scouring this channel

off fault plasticity favors the arrest of dynamic ruptures on strength heterogeneity two dimensional cases we study the effects of a plastic behavior of the volume around the fault on in plane and anti plane 2d rupture dynamics both rupture modes exhibit similar answer to off fault yielding in terms of modification of the kinematics of the rupture front and in terms of energy lost outside the fault plane we then compare the ability of the rupture to propagate through a barrier on the interface the plastic behavior responsible for a linear increase of the global fracture energy during dynamic crack growth enhances the rupture front sensitivity to a static resistance increase on the fault consequently the rupture arrest is more easily provoked in heterogeneous models that include a plastic yielding even with relatively small variations of frictional resistance along the fault plane

the first deep sea mooring station in the eastern levantine basin deeplev outline and insights into regional sedimentological processes abstract the eastern levantine basin elb is an ultra oligotrophic warm and saline marine system significantly affected by climate change during the past several decades the deployment of the first moored station at the elb deeplev at 1500 m water depth 50 km offshore haifa israel aimed at enhancing synchronized measurements of physical and biogeochemical dynamics the station carries an array of sediment traps and sensors that measure physical chemical and biological attributes along the water column here we describe the station and present sediment flux data from the first 1 5 years of operation since november 2016 we show that despite deeplev s offshore location and the open sea characteristics of the water column lateral transport from the continental margin contributes the greatest fraction of particulate flux to the seafloor at this site this mostly occurs via intermediate nepheloid layer plumes entering the study area between depths of 180 and 800 m bottom currents are weak average sd 3 5 2 cm s 1 and are unlikely to cause significant resuspension based on sedimentation rates obtained from nearby sediment cores and sediment particle fluxes sampled in the traps calculated accumulation rates of total particulate matter and of particulate organic carbon at the seafloor were 95 108 g m 2 y 1 and 0 5 0 6 g m 2 y 1 respectively offshore changes in sedimentation rates and in surface sediment elemental ratios indicate that sediment originating from the continental margins is transported at least 100 km offshore

fluvial and marine controls on combined subaerial and subaqueous delta progradation morphodynamic modeling of compound clinoform development 1 fluviodeltaic systems commonly display a compound clinoform geometry that consists of a subaerial subaqueous delta couplet the extent of subaqueous delta development varies significantly and in modern systems is a function of fluvial input and basin hydrodynamics we present a model of fluviodeltaic progradation in which the repeated occurrence of characteristic terrestrial floods and large coastal storms drives fluvial and shallow marine morphodynamics respectively we couple fluvial and shallow marine sediment dynamics via the surf zone which we collapse to a shock condition and treat as a moving boundary with steady sediment supply and sea level and simple basin geometry our model naturally develops prograding deltas with compound clinoform geometries the subaerial delta grows via fluvial aggradation and shoreface progradation whereas the subaqueous delta expands through foreset progradation with only minor topset aggradation the interplay of fluvial input with the wave current field controls the basic partitioning of sediment between subaerial and subaqueous deltas and by extension the compound clinoform geometry increasing the frequency or magnitude of coastal storms decreasing flood frequency or discharge and reducing grain size all increase the fraction of sediment delivered to the shallow marine environment and the extent of subaqueous delta progradation relative to subaerial delta development our model which emphasizes the intrinsic coupling of fluvial and shallow marine sediment dynamics and downplays the importance of allogenic fluctuations can explain many of the first order morphologic features of natural delta systems including significant lateral separation of the shoreline and clinoform rollover and differing rates of subaerial and subaqueous delta progradation

accelerated oxygen consumption in eastern mediterranean deep waters following the recent changes in thermohaline circulation 1 using an intercalibrated set of oxygen data for the eastern mediterranean 1987 1999 we study the evolution of oxygen concentrations that accompanied the recent changes in the thermohaline circulation of this sea the so called eastern mediterranean transient emt we find that by way of massively transferring oxygen rich near surface waters into the deep layers the emt by 1995 had raised oxygen concentrations considerably relative to the pre emt situation in 1987 between 1995 and 1999 however the oxygen concentrations decreased noticeably we identify oxygen decreases of about 5 mol kg for the layers below 2200 m and between about 500 and 1000 m depth for which layers previous work found vanishing or little replenishment during 1995 1999 supporting evidence for absence of replenishment is obtained from the temporal evolution of tritium 3he ages the oxygen decreases convert into utilization rates of approximately 1 3 mol kg yr an even higher rate 2 3 mol kg yr is obtained for the deep waters of the cretan sea below 1000 m the utilization rate found for the deepest waters significantly exceeds the pre emt value of 0 53 mol kg yr we propose that the massive invasion of near surface waters affected by the emt made available large amounts of dissolved organic carbon with an unusually high fraction of labile material which in turn enhanced oxygen consumption supporting evidence is obtained from data of dissolved organic carbon and from mesozooplankton ecology data the enhanced oxygen utilization represents a further example of emt related disturbances in the biogeochemistry of the eastern mediterranean

long term morphological change and its causes in the mersey estuary nw england changes in the morphology of the mersey estuary and their possible causes have been investigated using historical trend analysis and expert geomorphological assessment historical bathymetric charts were digitised and analysed within a gis to provide quantitative estimates of changes in areas and sediment volumes above and below selected elevation planes the results show that the estuary experienced major changes over the last 150 years notably between the late 19th century and ca 1950 an analysis of data relating to possible natural and human factors which could have influenced these changes suggests that training wall construction and dredging in the outer estuary and liverpool bay was the most significant factor contributing to change during this period these activities modified the hydrodynamic and sediment transport regime in a way which enhanced an existing natural tendency for movement of sediment from liverpool bay and the outer estuary into the inner estuary changes in other factors including sea level tidal range wind wave climate freshwater flow and embanking land reclamation were of relatively minor importance between 1950 and 1977 the rate of sediment accumulation in the inner estuary declined as the estuary approached a new condition of dynamic equilibrium and since 1977 there has been a slight net loss of sediment under these conditions the changes in natural forcing factors such as sea level and storminess are likely to have a relatively greater effect on the estuary than in the past

decadal morphological response of an ebb tidal delta and down drift beach to artificial breaching and inlet stabilisation abstract the morphodynamic response of a mixed energy ebb tidal delta guadiana estuary southern portugal and its down drift barrier island canela island to channel relocation and stabilisation by jetties is examined using a series of sequential bathymetric maps and vertical aerial photographs spanning five decades morphological analysis indicates that the ebb delta is in an immature state characterised by weak sediment bypassing landward migrating shoals on the swash platform have been produced by the jetty induced artificial bank breaching and by the collapse of the eastern portion of the delta the welding of these shoals has largely controlled the evolution of the coast with local accretion and erosion lasting for years and large amounts of regional accretion occurring over decades due to sand accumulation against jetties located further down drift these observations provide insights into the potential response of a coast to very large locally concentrated sand nourishment in the form of shoals the main effects of the jetties on the coast are observed at the centre of canela island with the production of an erosion hot spot associated with a temporally persistent and divergent longshore transport providing sand to the adjacent areas significant accretion is anticipated for the next decade along the entire island due to the ongoing attachment of the presently observed shoals after the depletion of this sediment source and in the context of weak sediment bypassing the most severe down drift erosion induced by the jetties is predicted to occur some decades after their construction this study demonstrates that the geomorphic response of an ebb tidal delta to jetty construction must be considered at multiple temporal and spatial scales when assessing the impacts of jetties on the down drift coast

long term morphological change in the ribble estuary northwest england morphological change in the ribble estuary northwest england has been studied using bathymetric charts topographical surveys and remote sensing data a sediment budget has been prepared from the analysis of these data the results reveal a net accretional trend over the last 150 years the main channels experienced major infilling sediment also accumulated in higher parts of the intertidal zone salt marshes and sand banks while the sediment volume in the lower intertidal zone remained essentially the same there were both zones of net erosion and deposition in the outer estuary with a small net gain in subtidal sediment volume infilling associated with major morphological change was accelerated in the nineteenth century and early twentieth century principally as a result of human activities the triggering factors for increased sedimentation were embankment construction and reclamation after 1810 which progressively reduced the intertidal area tidal prism and current velocities within the estuary additionally construction of a trained channel between 1847 and 1910 to secure navigation and maintenance of this channel by dredging concentrated the ebb flow in this overdeepened channel and reduced periodic scour over the sand banks on both sides enhancing sedimentation thus the effects of human activities have outstripped those of changes in natural forcing factors on the morphological development in the area

long term morphodynamic evolution and the equilibrium mechanism of a flood channel in the yangtze estuary china the stability of flood channels has attracted considerable attention because of their complicated interactions with the prevailing hydrodynamics and importance in ship navigation this research examines long term morphodynamic evolution in the yangtze estuary from 1861 to 2002 and the equilibrium mechanism of the xinqiao channel in the yangtze estuary by digitizing 15 selected maritime charts and calculating the volume of the channel although the total period of channel development is much longer than the historical data used in this paper three stages are identified during the study period the first embryonic stage 66 years the second formation stage 33 years and the third equilibrium stage 45 years variations in coastline location channel volume and hydrodynamics in the channel during the three stages indicate that the channel equilibrium was reached and maintained when the channel direction was aligned with the direction of offshore tidal wave propagation variations in river and sediment discharges affect erosion and deposition in the channel and thus channel geometry however future reduction in sediment supply by 10 33 due to the ongoing river engineering projects would increase the volume of the xinqiao channel only by 1 3 it seems unlikely that the above change in sediment discharge will disrupt the equilibrium of the xinqiao channel

seismicity on a fault controlled by rate and state dependent friction with spatial variations of the critical slip distance 1 we perform systematic simulations of slip using a quasi dynamic continuum model of a two dimensional 2 d strike slip fault governed by rate and state dependent friction the depth dependence of the a b and l frictional parameters are treated in an innovative way that is consistent with available laboratory data and multidisciplinary field observations various realizations of heterogeneous l distributions are used to study effects of structural variations of fault zones on spatiotemporal evolution of slip we demonstrate that such realizations can produce within the continuum class of models realistic features of seismicity and slip distributions on a fault we explore effects of three types of variable l distributions 1 a depth dependent l profile accounting for the variable width of fault zones with depth 2 uncorrelated 2 d random distributions of l with different degrees of heterogeneity and 3 a hybrid distribution combining the depth dependent l profile with the 2 d random l distributions the first type of l distribution with relatively small l over the depth range corresponding to the seismogenic zone and larger l elsewhere generates stick slip events in the seismogenic zone and ongoing creep above and below that region the 2 d heterogeneous parameterizations generate frequency size statistics with event sizes spanning 4 orders of magnitude our results indicate that different degrees of heterogeneity of l distributions control 1 the number of simulated events and 2 the overall stress level and fluctuations other observable trends are 3 the dependency of hypocenter location on l and 4 different nucleation phases for small and large events in heterogeneous distributions

simulation of the frictional stick slip instability a lattice solid model capable of simulating rock friction fracture and the associated seismic wave radiation is developed in order to study the origin of the stick slip instability that is responsible for earthquakes the model consists of a lattice of interacting particles in order to study the effect of surface roughness on the frictional behavior of elastic blocks being rubbed past one another the simplest possible particle interactions were specified corresponding to radially dependent elastic brittle bonds the model material can therefore be considered as round elastic grains with negligible friction between their surfaces although breaking of the bonds can occur fracturing energy is not considered stick slip behavior is observed in a numerical experiment involving 2d blocks with rough surfaces being rubbed past one another at a constant rate slip is initiated when two interlocking asperities push past one another exciting a slip pulse the pulse fronts propagate with speeds ranging from the rayleigh wave speed up to a value between the shear and compressional wave speeds in agreement with field observations and theoretical analyses of mode ii rupture slip rates are comparable to seismic rates in the initial part of one slip pulse whose front propagates at the rayleigh wave speed however the slip rate is an order of magnitude higher in the main part of pulses possibly because of the simplified model description that neglected intrinsic friction and the high rates at which the blocks were driven or alternatively uncertainty in slip rates obtained through the inversion of seismograms particle trajectories during slip have motions normal to the fault indicating that the fault surfaces jump apart during the passage of the slip pulse normal motion is expected as the asperities on the two surfaces ride over one another the form of the particle trajectories is similar to those observed in stick slip experiments involving foam rubber blocks bruneet al 1993 additional work is required to determine whether the slip pulses relate to the interface waves proposed by brune and co workers to explain the heat flow paradox and whether they are capable of inducing a significant local reduction in the normal stress it is hoped that the progressive development of the lattice solid model will lead to realistic simulations of earthquake dynamics and ultimately provide clues as to whether or not earthquakes are predictable

shoreline variability via empirical orthogonal function analysis part i temporal and spatial characteristics empirical orthogonal functions eofs or principal components were used to extract the significant modes of shoreline variability from several data sets collected at three very different locations although eofs have proven to be a valuable tool in the analysis of nearshore data most applications have focused on the ability of the technique to describe cross shore or profile variability here however eofs were used to help identify the dominant modes of longshore shoreline variability at duck north carolina the gold coast australia and at several locations within the columbia river littoral cell in the u s pacific northwest in part one of this analysis characteristic patterns of shoreline variability identified by the eof analysis are described in detail at each site the dominant modes consisting of the first four eigenfunctions were found to describe nearly 95 of the total shoreline variability at both duck and the gold coast several interesting longshore periodic features suggestive of sand waves were identified while boundary effects related to natural headlands and navigational structures entrances dominated the pacific northwest data sets

a comparison of mechanical behavior and frequency energy relations for two kinds of echelon fault structures through numerical simulation heterogeneities of faults and rock blocks were included in the present numerical simulation to study differences between the compressive and extensional echelon fault structures released elastic strain energy due to shear and tensile failures of elements was calculated an event is defined as a failed element releasing energy for calculation of the frequency energy relation whose negative slope was labled b0 value a cut off factor used to delete a few larger events and a classification factor used to group the remaining events into several grades were introduced the evolution of b0 value at different stages was obtained three kinds of changes in b0 value were found in the compressive echelon fault structure no remarkable change in b0 value is observed during the outward propagation of tensile failure zones also during the jog failure in the extensional fault structure this is due to the fact that tensile failure only increases the number of small events that are originally larger in the compressive echelon fault structure a rapid decrease of b0 value is found during the jog failure since a shear failure zone links two fault tips leading to the occurrence of larger events for both kinds of echelon fault structures b0 value is found to decrease continuously during the fault reactivation this is related to stress or strain enhancement over a larger area in the extensional fault structure a recovery in b0 value in the vicinity of the stress peak is found after a global minimum which is similar to phenomena caused by aftershocks moreover evolution of b0 value at different stages for the same echelon fault structure and that at the same stage for different echelon fault structures are compared and analyzed it is found that the change in fault structure may not lead to the change in b0 value to obtain a more continuous and less fluctuant b0 value curve the suggested values of the cut off and classification factors are 1 8 1 2 and 3 4 respectively the proposed method can also be used to analyze the mechanical behavior and frequency energy relations for other typical or complex fault structures our work can contribute to identify the regions where abnormalities or precursors can be monitored and to assess the positions of larger events

from the highest to the deepest the gaoping river gaoping submarine canyon dispersal system abstract there are many different source to sink dispersal systems around the world and the gaoping river gpr gaoping submarine canyon gpsc provides an example especially as a canyon captured system the gpr a small mountainous river having an average gradient of 1 150 and the gpsc which links the river catchment to the deep sea basin represent two major topographic features around sw taiwan together they constitute a terrestrial to marine dispersal system that has an overriding impact on the source to sink transport of sediment in this region the gpsc extents from the mouth of the gpr through the shelf and slope and into the northeastern manila trench a distance of about 260 km it is a major conduit for the transport of terrestrial sediment and carbon to the south china sea and the landward transport of particles of marine and biological origin in the gpsc the dominant mode of suspended sediment transport is tidal oscillations and the net direction is up canyon in contrast sediment transport associated with episodic gravity driven events is down canyon the steady sedimentation of the tidal regime results in hemipelagic mud across the canyon floor whereas the gravity driven hyperpycnal regime causes turbidite erosion and deposition along the canyon thalweg typhoon induced river floods often lead to hyperpycnal plumes at the river mouth which directly and indirectly ignite hyperpycnal turbidity currents in the canyon forming an effective agent for transporting large amounts of terrestrial organic material modern and fossil carbon to the south china sea basin therefore the gpr gpsc represents a source to sink system in which terrestrial sediment in a mountainous catchment is promptly removed and transported to the deep sea by episodic gravity flows this is also a pathway by which modern terrestrial organic carbon is quickly and effectively delivered to the deep sea

a thirteen year record of bathymetric changes in the north passage changjiang yangtze estuary article i nfo the mouths of major rivers in the world have always been important waterways and as a result subject to significant human intervention therefore it is necessary to understand the coupling of natural processes and human intervention in the sediment movement and deposition to determine long term morphodynamic evolution in the mouth regions of major rivers a multivariate technique was used to analyze high resolution bathymetric data from the north passage of changjiang yangtze river which is the vital shipping channel in the mouth region and for the entire changjiang waterway our findings show that there are two modes of bathymetric changes the first mode represents 85 of the variability which includes the deposition in the peripheral groin fields along the shipping channel and deepening of the shipping channel which is primarily due to the channel maintenance the second mode represents 6 of the variability of the river mouth shoal seaward migration and size reduction attributable to the declining sediment discharge of the changjiang

use of continuous turbidity sensor in the prediction of fine sediment transport in the turbidity maximum of the trent estuary uk results from continuous monitoring of turbidity and water level at burringham on the tidal river trent uk are presented for the period 18 may 1997 to 9 february 1998 these measurements together with detailed readings of velocity and suspended sediment concentration over an individual tidal cycle near the opposite bank at derrythorpe help to describe the mechanisms and behaviour of the turbidity maximum tm it is demonstrated that there is a distinct pattern of fine sediment movement that reflects a predictable system response to changing hydraulic features it is shown that the tm in this system is highly mobile and its location depends on antecedent fresh water flow and tidal range approximate representative flood and ebb tide suspended sediment concentrations of up to 13 g l over this nine month period have been derived from the data and plotted against fresh water flow and tidal range in order to show the relationship between these parameters three semi empirical polynomial regression models have been tested for goodness of fit against available data it was found that a partitioning approach whereby data are grouped into different categories depending on antecedent fresh water flow yielded the lowest standard error for the period analysed analysis of detailed observations of suspended sediment concentration and velocity measured over an individual tidal cycle also help to elucidate the mechanism of tidal pumping within this system these results also help to give an estimate of the relative magnitude of suspended sediment fluxes during typical low fresh water flow conditions it is estimated that for low fresh water flow conditions a typical spring tide can mobilise at least an order of magnitude more sediment than a neap tide

fault geometry and earthquakes in continental interiors abstract although large earthquakes in continental interiors are much less frequent than those along plate boundaries they have been responsible for a disproportionate amount of destruction i present a testable model for strain accumulation and seismicity in the upper crust of continental interiors intersecting faults provide a focus for strain build up resulting in local pockets of high strain accumulation rigid plates typically deform at strain rates 10 10 to 10 9 strain yr 1 but at intersecting fault zones strain accumulates at anomalously high rates of 10 8 to 10 7 strain yr 1 i e the strain rates are comparable with those at plate boundaries the resulting large earthquakes are associated with relatively short return times hundreds of years typically one of the intersecting faults appears to split and to offset the other main fault defined as a fault on which the larger offset occurs forming two parallel strands separated by a jog i also observe a rotation of one leg of the main fault with respect to the other the region of intersection is usually associated with intense fracturing increased microseismicity and uplift

extended finite element simulation of step path brittle failure in rock slopes with non persistent en echelon joints abstract the aim of this paper is to investigate the brittle failure mechanism of rock slopes with non persistent en echelon joints using the extended finite element method xfem in the research a novel geometrical method distinguished from the conventional level set method is proposed to describe the cracks in the xfem the numerical form of the j integral considering the effect of the bode force and the frictional contact force is provided moreover a refined coalescence method is proposed then the state function employed to define the state of the crack and the method used to define the crack growth increment are introduced next some numerical tests are carried out to validate the feasibility of the xfem finally two typical rock slope modes are provided to illustrate the mechanism of the step path brittle failure of rock slopes

vertical distribution of mesozooplankton and its δ15n signature at a deep sea site in the levantine sea eastern mediterranean in april 1999 1 mesozooplankton samples were collected throughout the water column in the 4270 m deep ierapetra basin 30 nm se off crete in april 1999 information on trophic relationships within mesozooplankton size classes 0 5 0 5 1 1 2 and 2 5 mm and the sources of diet were obtained by measuring the composition of stable nitrogen isotopes of size fractionated zooplankton and particles collected by sediment traps compared to data from the arabian sea the 15n values of zooplankton were markedly lower in the levantine sea data from the upper 250 m 2 3 suggest that n2 from the atmosphere was used by diazotroph cyanophycea as a nitrogen source for primary production a loop system is hypothesized by which isotopically light nh4 is recycled and used by phytoplankton in the deep mesopelagic zone an increase in 15n with increasing depth was observed in the deep bathypelagic zone the 15n values were more or less stable and indicate a trophic level of 2 5 a first zooplankton analysis revealed that juveniles of the calanoid copepod lucicutia longiserrata one of the rare true deep sea species in the levantine basin were predominant in this zone the taxonomic composition as well as the vertical distribution of zooplankton in the large habitat zones resembled that in january 1987 before the onset of a hydrological shift in the eastern mediterranean we therefore suggest that the situation in april 1999 does not characterize the mode of nitrogen transfer during the emt

numerical simulation of large shear strain drops during jog failure for echelon faults based on a heterogeneous and strain softening model abstract for two kinds of echelon faults with different spacings we numerically model the spatiotemporal distribution of large shear strain drops using a heterogeneous and strain softening model implemented in flac fast lagrangian analysis of continua nine quantities regarding large shear strain drops and released energy due to shear or tensile failure are calculated during the jog failure it is found that the largest shear strain drops are created upon the jog failure for both kinds of echelon faults suggesting the occurrence of large cracking or slip events for the compressive echelon faults the number of elements undergoing large shear strain drops and the sum of all large drops exhibit pronounced responses upon the jog failure but not for the extensional echelon faults this means that whether abnormalities are apparent during the jog failure depends on types of echelon faults large shear strain drops have superiority over some quantities used commonly such as the number of failed elements and corresponding energy due to failure this is due to the fact that the failure of an element storing high elastic strain energy can lead to unloading responses of its surrounding elastic elements namely an input for a system results in many outputs whereas these common quantities can only reflect the information of failed elements for the compressive echelon faults large events occur in the vicinity of the jog appropriate for detecting abnormalities related to the jog failure however for the extensional echelon faults they occur at faults thus the jog may not be appropriate based on the present model without shear dilatation and pore fluid a small fault spacing equal to overlap leads to the fact that the jog fails easily and early for the compressive echelon faults responses of some quantities become less apparent during the jog failure as fault spacing increases

decadal link between longitudinal morphological changes in branching channels of yangtze estuary and movement of the offshore depo center in estuaries the morphology of inland and offshore areas usually evolves synergistically this study examines the decadal link between longitudinal changes in morphology of branching channels and movement of the offshore depo center where sediment deposition rate is maximum of the yangtze river estuary under intense human interference integrated data analysis is provided on morphology runoff discharge and ebb partition ratio from 1950 to 2017 channel volume reductions and change rates between isobaths in branching channels reflect the impact of estuarine engineering projects ebb partition ratio and duration of discharge 60 000 m3 s 1 act as proxies for the water excavating force in branching channels and runoff intensity it is found that deposition occurs in the lower upper sub reaches or further downstream upstream channels of the inland north south branching channels and the offshore depo center moves southward or southeastward as runoff intensity grows the reverse occurs as runoff intensity declines this is because the horizontal circumfluence in the yangtze estuary rotates clockwise as ebb partition ratios of the north south branching channels increase decrease for increasing runoff and conversely rotates anticlockwise for decreasing runoff land reclamation activities the deepwater channel project and the qingcaosha reservoir have impacted greatly on longitudinal changes of morphology in the north branch and the south passage and on ebb partition ratio variations in the north south channel and the north south passage dam induced runoff flattening has enhanced deposition in the upper lower sub reaches of the north south branching channels and caused northward movement of the offshore depo center except in areas affected by estuarine engineering projects dam induced longitudinal evolution of branching channel morphology and offshore depo center movement will likely persist in the future given the ongoing construction of large cascade dams in the upper yangtze and the completion of major projects in the yangtze estuary

evaluating failure mechanisms of dip slope using a multiscale investigation and discrete element modelling abstract this study proposed an in depth multiscale analysis procedure to identify the dip slope area and assess dip slope stability and influencing area the proposed analysis procedure comprised five stages 1 identifying the potential area of a dip slope 2 analyzing the possible failure types of the dip slope 3 evaluating slope activity 4 analyzing dip slope stability under the influence of possible triggering factors and 5 assessment of the deformation and deposition area to validate the proposed procedure the chaochouhu region of taiwan was analyzed as a dip slope case in stages 1 to 3 the scale of the utilized map and the precision of associated data were evaluated to identify the potential area of a dip slope the possible failure types and the activity of each slope unit in stages 4 and 5 the processes of deformation and sliding in a high activity slope unit were simulated using the discrete element method the numerical model was first verified using in situ monitoring data obtained from inclinometers subsequently the model was used to predict the slope behavior under conditions of wetting deterioration of geomaterial the multiscale analysis revealed comprehensive information regarding the dip slope the application of the proposed approach would be useful to civil engineers for evaluating dip slope stability as well as to relevant authorities for planning hazard mitigation strategies

climatic changes in the aegean sea influence the eastern mediterranean thermohaline circulation 1986 1997 recent changes of water mass characteristics in the south aegean sea have considerably influenced the eastern mediterranean thermohaline circulation a combination of salinity increase 1987 92 and temperature drop 1992 94 caused massive dense water formation and strong outflow towards the deep and bottom parts of the eastern mediterranean this climatic shift the most important since the existence of observations in the basin is a combined effect of extreme meteorological events superimposed on large scale trends it has initiated a series of modifications in the hydrology and dynamics of the entire eastern mediterranean with possible influence on the mediterranean outflow in the north atlantic ocean