the impact of rapid coastline changes and sea level rise on the tides in the bohai sea china 1 the tidal regime in the bohai sea china is investigated using observations and an established numerical tidal model the area has recently experienced rapid coastline changes due to natural developments of the yellow river delta and large scale anthropogenic land reclamation these morphological changes are not reflected in most global bathymetric databases and are thus rarely incorporated into investigations of the bohai sea it is shown that there have indeed been significant changes in the tidal regime in the bohai sea over the last 35 years with m2 amplitudes changing up to 20 cm in some parts the model captures some of these changes when the appropriate bathymetries are used furthermore the simulations show that the tides in the bohai sea have become more sensitive to future sea level rise and the way in which it is implemented in the model i e whether or not flood defenses are included these sensitivity changes are due to the recent coastal developments

facies distribution and sedimentary processes on the modern baram delta implications for the reservoir sandstones of nw borneo the baram delta has been classified as wave dominated and as a modern analogue for the prolific tertiary sandstone reservoirs in the baram delta province of nw borneo however the delta s facies distribution and sedimentary processes indicate that sedimentation is presently occurring only on the large mouth bar and that the baram is more properly categorised as a mixed wave and tide influenced delta more than half of the surface area of the mouth bar is dominated by tidal currents and covered with tidally deposited sediments because a relatively large tidal prism controls the nearshore hydrodynamics conversely the widespread tertiary shoreface reservoir sandstones are clearly wave dominant and tidal signatures are absent consequently the baram delta is not an appropriate analogue for most shoreface reservoir sandstones in nw borneo

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

rapid consolidation characteristics of yellow river derived sediment geotechnical characterization and its implications for the deltaic geomorphic evolution abstract the yellow river which presently discharges into the western bohai sea has been widely recognized as having one of the highest sediment loads on earth understanding the consolidation characteristics of yellow river derived sediments is critical for improving our knowledge of the riverine sediment transport depositional processes and evolution of the yellow river delta morphology in this study we conducted in situ experiments from 2004 to 2008 at an abandoned subaqueous delta lobe diaokou lobe in order to investigate the consolidation process of the sediments our results show that the initial consolidation of yellow river derived sediment is a rapid process when the excess pore water pressure caused by sediment aggradation can completely dissipate in 1500 min the change in the physical and geotechnical properties during the consolidation endows the sediments with a certain shear strength however due to the hydrodynamic conditions the distribution of the sediment strength is both temporally and spatially inhomogeneous furthermore a hard layer can develop at the depths of 10 30 cm and the adjacent layer can become a potential sliding surface this study offers some insight into the formation and evolution processes of the yellow river delta s sedimentary and geomorphic forms

quantitative analysis of temporal variations on shoreline change pattern along ganjam district odisha east coast of india this research work describes the shoreline change rate variations of ganjam district of odisha east coast of india for the past 24 years seven shorelines were extracted from multidated satellite images and shoreline change rate has been calculated by using digital shoreline analysis system long term shoreline change rate 1990 2014 of the study area has been calculated using weighted linier regression method short term changes have been computed for different time scales i e 1990 1999 1999 2006 2006 2008 2008 2013 and 2013 2014 using end point rate method the results obtained from the study show that 71 65 of ganjam coast shows accretion pattern and 28 35 of coast falls under erosion category high erosion is mainly noticed in northern side of gopalpur port which is mainly due to recent construction activities short term results reveals that 2006 2008 period shows maximum erosion and 1999 2006 period exhibit maximum accretion in ganjam coast from short term analysis it is observed that shoreline in the study area shows cyclic nature of erosion and accretion pattern the study reveals that tropical cyclones and human activities such as port development construction of breakwaters and groins are the major factors responsible for shoreline erosion in the study area

1500 year cycle dominated holocene dynamics of the yellow river delta china the world s mega deltas are extremely important from a human perspective and attract considerable effort to reveal their evolution growth related driving forces and human impacts here we report a case study on the holocene deltaic evolution of the yellow river through development of a conceptual model which is compared with paleo proxy to analyze the forcing acting on the delta the main conclusion is that superlobe switching was modulated by the 1500 year cycle cooling in mongolia in response to strong bond ird events which is coincident with warming in eastern china due to a strong kuroshio current enhances the meridional temperature gradient which then increases cyclone frequency and activates dust storms and terrestrial erosion throughout the catchment enhanced erosion supplies great amounts of material to the yellow river and causes channel evulsion and superlobe development expressed as dominant 1500 year cycle at the same time summer monsoon and solar forcing are uncorrected with deltaic evolution on these timescales therefore we conclude that holocene dynamics of the delta on a millennial timescale was dominated by winter cyclone activity across northern china and mongolia

arctic mackenzie delta channel planform evolution during 1983 2013 utilising landsat data and hydrological time series arctic mackenzie delta channel planform evolution during 1983 2013 utilising landsat data and hydrological time series

patterns of erosion sedimentation heavy mineral concentration and grain size to interpret boundaries of littoral sub cells of the nile delta egypt abstract analyses have been undertaken of 68 beach nearshore profiles spanning the years 1971 1995 to interpret sub littoral cells of the nile delta that developed during cross shore and alongshore sediment transport bottom sediments of these profiles taken along the 240 km length of the delta coastline have been analyzed to determine seabed level changes textural and heavy mineral concentration distributions the spatial distribution of seabed depth changes linked with the heavy mineral concentration allows identification of three zones of erosion source areas associated with accretion sink areas erosion zones occur off the nile promontories at rosetta 20 to 50 cm yr burullus and damietta 0 to 20 cm yr accretion ranging from 0 to 40 cm yr occurs between erosion zones at abu quir bay the rosetta saddle gamasa embayments and along the western side of the jetty at the suez canal entrance port said this pattern was generally induced from the temporal variability in the direction and intensity of the incoming waves currents orientation of coastline seafloor morphology and local protective structures the correspondence among patterns of seabed depth change heavy mineral concentration and to some extent the texture of seabed sediments refine boundaries of littoral sub cells of the nile including sediment paths sources sinks nodal points and zones of sediment transport convergence and divergence this correspondence is not strongly correlated as might be expected in this deltaic system where sediment has been recycled between recent and relict seabed settings moving in the alongshore and cross shore directions nevertheless the present investigation shows that the relationship between seabed level changes heavy mineral concentration and to some extent mean grain size of the littoral zone can be practically applied in other deltaic settings to interpret sediment transport pathways particularly where there are less relict sediments

automatic extraction of shorelines from landsat tm and etm multi temporal images with subpixel precision abstract a high precision geometric method for automated shoreline detection from landsat tm and etm imagery is presented the methodology is based on the application of an algorithm that ensures accurate image geometric registration and the use of a new algorithm for sub pixel shoreline extraction both at the sub pixel level the analysis of the initial errors shows the influence that differences in reflectance of land cover types have over shoreline detection allowing us to create a model to substantially reduce these errors three correction models were defined according to the type of gain used in the acquisition of the original landsat images error assessment tests were applied on three artificially stabilised coastal segments that have a constant and well defined land water boundary a testing set of 45 images 28 tm 10 etm high gain and 7 etm low gain was used the mean error obtained in shoreline location ranges from 1 22 to 1 63 m and the rmse from 4 69 to 5 47 m since the errors follow a normal distribution then the maximum error at a given probability can be estimated the results confirm that the use of landsat imagery for detection of instantaneous coastlines yields accuracy comparable to high resolution techniques showing the potential of landsat tm and etm images in those applications where the instantaneous lines are a good geomorphological descriptor

testing morphodynamic controls on the location and frequency of river avulsions on fans versus deltas huanghe yellow river china a mechanistic understanding of river avulsion location and frequency is needed to predict the growth of alluvial fans and deltas the huanghe china provides a rare opportunity to test emerging theories because its high sediment load produces regular avulsions at two distinct nodes where the river debouches from the loess plateau avulsions occur at an abrupt decrease in bed slope and reoccur at a time interval 607 yrs consistent with a channel filling timescale set by the superelevation height of the levees downstream natural deltaic avulsions reoccur at a timescale that is fast 7 yrs compared to channel filling timescale due to large stage height variability during floods unlike the upstream node deltaic avulsions cluster at a location influenced by backwater hydrodynamics and show evidence for episodic downstream migration in concert with progradation of the shoreline providing new expectations for the interplay between avulsion location frequency shoreline rugosity and delta morphology

shoreline change of chongming dongtan and response to river sediment load a remote sensing assessment summary chongming dongtan located in the center of the yangtze estuary is a ramsar wetland of international importance and national nature reserve the dramatic decrease in river sediment load has attracted considerable scientific interest to this area but few studies have paid attention to the shoreline dynamics this study uses landsat images spanning from 1987 to 2010 and an orthogonal transect method which was previously developed by the authors to model the spatial and temporal characteristics of shoreline change and explore its relationship to reduced river sediment load by use of regression analysis on three different spatial scales results show a general decrease in the average rates of shoreline change throughout the entire study period the maximum average shoreline change rate of 115 5 m year occurred in the 1987 1990 interval and the minimum rate of 20 4 m year occurred from 2006 to 2008 based on average rates of shoreline change the coast of dongtan was divided into three segments the erosion segment eastern accretion segment and northern accretion segment the temporal pattern of the northern accretion segment is almost completely opposite to that of the eastern accretion segment the strongest correlation transects are located on the northern side of the eastern tip of dongtan and the next strongest transects are located on the south side other transects have a very low correlation transect 19 near the easternmost tip of dongtan has a near zero correlation r2 0 0045 but has the fastest accretion rate and in general an increase in the shoreline change rate the average rate of shoreline change and the net accretion area in dongtan as a whole are significantly associated with sediment discharge at datong station r2 0 69 and 0 75 respectively this implies that shoreline accretion in dongtan will probably slow down gradually if the river sediment load continues to decrease in the future the shoreline change rates achieved using our approach are consistent with previous studies but the relationship with the river sediment load is different from results in a previous study on intertidal wetland based on bathymetric maps the results and methods may be helpful in coastal management and understanding the evolution of the entire delta from the perspective of shoreline change

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

variations in fluvial discharge of rivers over the last millennium along the eastern coast of the liaodong peninsula china abstract sediments delivered by global rivers are of utmost importance to the morphological formation and ecosystem evolution of estuary coast shelf systems in this study numerical modeling supported by hydrological data was applied to quantify the impact of climate change and human activities on the water and sediments delivery of five rivers along the east coast of the liaodong peninsula to the north yellow sea simulation results indicate that the water discharge and sediment load of these five rivers during the past millennium reached 27 88 5 97 km3 y 1 and 5 97 3 26 mty 1 respectively climate change was the most significant driving factor altering water discharge in the study area with human activity producing an insignificant effect different from runoff variations in sediment loads are dominated by human activities in past millennium our results demonstrate that the soil erosion of five rivers induced by human activities increased sharply by up to 8 1 times over the past few centuries and that the total dam trapping efficiency for the eastern liaodong peninsula was 71 7 if no dams had been constructed in the study area between 1941 and 2012 the total sediment load of the five rivers would have reached 11 33 5 70 mty 1 this reflects an increase of 92 6 relative to the period between 1000 and 1850 5 88 2 93 mty 1 and would have been 3 5 times the actual sediment load during the period 1941 2012 3 21 4 61 mty 1

shoreline changes along the rosetta nile promontory monitoring with satellite observations abstract a study to test the effectiveness of satellite data for monitoring shoreline change is reported the rapidly changing rosetta promontory of the nile delta egypt being selected as the study area landsat multispectral scanner mss image data in the near infrared 0 8 1 1 m 80 m resolution covering a 15 year period 1972 1987 at roughly 3 year intervals were compiled these were digitally overlain registered and differenced relative to the initial 1972 shoreline and composite changes erosion and accretion are mapped the area studied is one undergoing both aggradation and degradation depending on location sediment supply and man made barriers it was found that the general trend of the regional processes can be monitored with landsat imagery due to its repetitive coverage and good spectral contrast of land and sea improved satellite imagery with higher resolution should be a valuable tool for complementing traditional shoreline monitoring surveys in easily eroded lowlying areas such as the nile delta

distribution and transport of suspended sediments off the yellow river huanghe mouth and the nearby bohai sea abstract hydrological and sedimentological investigations were carried out off the yellow river huanghe mouth and the nearby bohai sea during august september 2007 to examine the distribution and transport of suspended sediments our data witnessed that suspended sediments from the yellow river mouth primarily extend southerly and southeasterly during the flood season high suspended sediment concentration ssc occurs as turbid plume on both sides of the river mouth where it can reach 20 mg l 1 in the surface water and 40 mg l 1 in the bottom water accordingly salinity varies from 25 to 29 psu mean grain size dmz is 200 m and volume concentration vc is 100 l l 1 high ssc was concentrated in the river mouth area as two muddy patches i e the north mud and south mud consisting mostly of fine grained silt and clayey silt sediments our results have verified the larger extent of the south mud than that of the north one implicating south and southeastward sediment dispersal paths that prevail near the river mouth area the existing anti clockwise and clockwise flows in the river mouth area were synthesized as the major hydrodynamics responsible for forming the two muddy patches tidal and residual currents are considered as the key hydrodynamic factors controlling the sediment distribution and transport in the region

recent morphological changes of the yellow river huanghe submerged delta causes and environmental implications abstract the yellow river huanghe submerged delta yrsd has been under the threat of erosion and retreat during the anthropocene due to dramatic climatic and anthropogenic changes in the yellow river basin the analysis of field data shows that over the period of 1977 2005 the changes in climate decrease in precipitation and increase in air temperature and human interventions increase in water diversion projects throughout the watershed have resulted in the sharp reductions of river flow and sediment discharges into the bohai sea consequently over the decadal timescale morphological evolution of the yrsd has gone through three stages i e rapid accumulation 5 77 10 8 m 3 year in 1977 1985 moderate accumulation 3 80 10 8 m 3 year in 1986 1995 and slow accumulation 0 91 10 8 m 3 year in 1996 2005 climatic change within the catchment characterized by the rapid increase of air temperature contributed significantly to the transitions from the rapid accumulation to the moderate accumulation and to the subsequent slow accumulation the decadal morphological changes of the yrsd also show peculiar deposition erosion characteristics over the medium timescale under river input reduction within the three decades the patterns of the main sedimentary body exhibit irregular ellipses with the long axis parallel to the 5 or 10 m isobaths and short axis perpendicular to the isobaths the depocentres of the yrsd are located between the 10 and 15 m isobaths close to the respective river mouths with a high vertical accretion rate of 1 20 m year the time series data of annual volumetric change of the yrsd and river sediment load from 1977 to 2005 further demonstrate significant linear positive relationships between deltaic geomorphic change and fluvial input over shorter timescales annual and 3 year the critical sediment discharges for maintaining the deposition erosion equilibrium state of the yrsd over the annual and 3 year timescales are found to be 1 79 10 8 t year and 1 29 10 8 t year respectively the analysis from the latest hydrological data 2006 2015 suggests that over the decadal timescale the evolution state of the yrsd currently has transitioned from constructive to destructive due to the weakened fluvial input moreover there exists a close quantitative link between the progradation of the yellow river subaerial delta yrad and the yrsd over the five year timescale indicating that every 1 10 8 m 3 year increase of the yrsd s yearly volumetric change will result in a 3 28 km 2 year increase of the yrad s yearly land accretion area and the yrad will reach the extension retreat balance state when yearly morphological change of the yrsd is at 0 73 10 8 m 3 year

coast line evolution in portugal since the last glacial maximum until present a synthesis abstract an effort has been made to assemble a data set on the evolution of coastal morphology of the west iberian continental margin in portugal which has occurred since the last glacial maximum in this integrated review a particular attention was given to the analyses of coastline shaping phenomena on different time scales several overlapping processes such as shore erosion local sediment supply rate climatic changes anthropic impacts and mean sea level rise mslr were identified and their combined effects assessed the eustatic see level rise appears as a principal factor in shaping the shore line contour until mid holocene since then the non eustatic factors namely the terrigenous sediment supply rate and the dynamics of barriers and spits systems became dominant in the evolution of the near shore morphology since the 15th century ad the anthropogenic activities namely deforestation and land cultivation contributed decisively to the positive sedimentary balance in the portuguese coastal zone finally the multiple damming of the major rivers in 20th century and exploitation of sand and gravel from the river beds led to the sediment starving of the coastal zone and generalized shore line retreat

spatial variations in heavy minerals and patterns of sediment sorting along the nile delta egypt abstract sand samples were collected along 34 beach profiles spanning the 240 km length of the nile delta in order to examine the sorting patterns of heavy minerals that develop during cross shore and alongshore sediment transport factor analysis of the heavy mineral contents shows that two mineral factors or groups result from sorting due to the contrasting densities and sizes of the grains one factor is dominated by augite hornblende and epidote while the second factor consists of opaques garnet zircon rutile and monazite minerals of factor 1 are of lower densities and coarser sizes and represent the grains that are selectively entrained by waves and currents in areas of beach erosion and preferentially transported to zones of beach accretion where they are deposited the higher density minerals of factor 2 tend to become concentrated in areas of beach erosion accounting for the formation of black sand placers where the erosion has been greatest the spatial distributions of these two factors reflect the grain sorting patterns of the heavy minerals which coincide with the general trends of shoreline erosion versus accretion that exist along the length of the delta there is also a distinctive pattern of cross shore sorting with factor 2 containing the denser minerals being best developed within the inner surf zone generally with a maximum at the shoreline its development corresponds to the formation of black sand concentrates on the beach face where erosion has been greatest implying that grain sorting has taken place mainly within the swash zone there is a general decrease in factor 2 relative to factor 1 toward the offshore often with oscillations that are congruent with the beach topography factor 1 with the lower density minerals is greatest over offshore bars where deposition has prevailed

holocene evolution and anthropocene destruction of the krishna delta on the east coast of india delta lobe shifts human impacts and sea level history abstract the holocene evolution of the krishna delta was inferred using landform characteristics and 11 sediment cores with 59 accelerator mass spectrometry 14c dates the landform assemblages in a 5880 km2 area of the krishna delta indicate an upper landward river built fluvial plain and a lower seaward marine built beach ridge plain holocene sediment unconformably overlying a pleistocene basement consists of 11 sedimentary facies mainly shallowing upward and deltaic succession sea level indicators such as the basal mangrove peat layers above the pleistocene basement and the foreshore sediments indicate that the sea level rose from 9 m to 3 m during 8 3 6 3 cal ky bp and stabilised at the present level around 5 cal ky bp the 3539 km2 area of the krishna delta beach ridge plain developed in five major stages during the last 6 cal ky with distinct lateral and seaward migration of delta lobes depocentre shifts delta progradation accelerated in the last 500 years forming an out building lobate delta however predominant erosion along the sediment starved coast during the past five decades due to impoundment of riverine inputs at the burgeoning upstream dams has pushed the krishna delta into a persistent destruction phase

tidal constituents from remote sensing image sequences abstract we address the problem of obtaining tidal constituents from a series of shoreline positions derived from time sequential airborne imagery of the intertidal zone a multi sensor experiment bachmann et al 2012 conducted at the virginia coast reserve long term ecological research vcr lter site 1 supplied in situ and airborne data hyperspectral and infrared shoreline imagery of the vcr lter barrier islands shallow lagoons and mainland coastal areas as well as topographic lidar data were obtained from the same air platform over a nine day period and lidar and in situ topographic beach surveys were used to specify the beach bathymetry and derive a digital elevation model dem over the primary area focused on in this paper at wreck island va the dem and shoreline positions are used to obtain a time sequence of tidal heights these are found to be consistent with a time series from a gps equipped tide gage float anchored nearby a least squares fit of the five largest tidal constituents m 2 n 2 s 2 o 1 k 1 to this one week record indicates that the first three can be retrieved with only a 15 20 error as determined by the one year sea surface height time series from a nearby noaa sea surface height ssh station at wachapreague va the broader question of how many images are needed to obtain tidal constituents from an annual record is also addressed using ssh values from a noaa tide gage station as a surrogate for image derived ssh values we progressively decimate a yearlong tide record calculating its tidal constituents at each level of decimation we find that that only one image every ten days is needed to retrieve the five largest tidal constituents to within a 10 error

stratigraphic sequence and episodes of the ancient huanghe delta along the southwestern bohai bay since the lgm abstract the sedimentary evolution of the ancient huanghe yellow river delta in china is not well documented due to frequent river avulsions and limited deep cores in this paper 22 cores with lengths of 20 m at the coastal plain along the southwestern bohai bay were used the sedimentary facies were determined by grain size and microfossil analysis and carbon 14 dating the strata in the study area since the last glacial maximum lgm are divided into lowstand system tract lst transgressive system tract tst highstand system tract hst and retrograding system tract rst the lst which formed during the lgm to 10 8 ka bp consists of hard mud layer and overlying interfluvial lowland and flood plain deposits the tst that formed during 10 8 8 5 ka bp mainly include coastal marsh onshore sand bars and filled incised valleys the hst that formed during 8 5 2 6 ka bp mainly includes flood plain river channel delta front mouth bar and prodelta the rst that formed after 2 6 ka bp mainly includes crevasse splay interfluvial lowlands and distributary channel about eight episodes of the ancient huanghe delta are observed during the holocene and the names of the deltas are given by corresponding location names of cheniers 1 during 10 8 8 5 ka bp around ys3 and np1 cores without formation of cheniers during the transgression 2 during 8 5 7 4 ka bp around ys1 ys4 and np3 cores the dongsun shuiyicheng delta 3 during 7 4 6 1 ka bp around ck1 core the mashanzi delta 4 during 6 9 5 7 ka bp around gz3 core the miaozhuang zhaizhuang delta 5 during 4 6 3 5 ka bp around ys4 core the wuditai delta 6 during 3 0 2 6 ka bp around hh4 and hh1 cores the qikou delta 7 during 2 6 1 9 ka bp around ys7 and np1 cores the nanpaihe delta and 8 during 1034 bc 1099 bc around wangzidao and dakouhe the wangzidao delta

long term shoreline changes and the concentration of heavy minerals in beach sands of the nile delta egypt abstract analyses have been undertaken of shoreline positions established from beach profile surveys at 65 positions along the coastline of the nile delta spanning the years 1971 to 1990 the analyses identify long term linear trends as well as any cycles in the horizontal movement of shoreline positions the results reveal longshore patterns wherein erosion along a stretch of coast gives way to accretion in an adjacent stretch defining a subcell within the overall littoral system of the delta the rate of shoreline retreat has been greatest along the rosetta promontory 106 m yr and damietta promontory 10 4 m yr significant erosion has also occurred along the central bulge of the delta coast but at a lesser rate 6 5 m yr areas of accretion exist within the saddles or embayments between the promontories with the maximum shoreline advance averaging about 13 m yr the identified patterns of erosion versus accretion along the delta reflect the natural processes of wave induced longshore currents and sediment transport associated with this longshore sediment movement is a selective transport of different minerals according to their densities and grain sizes with the light minerals quartz and feldspar having the highest advection rates and the dense opaque minerals the lowest rates tending to remain behind as a lag within the erosion areas as a result of this longshore grain sorting paralleling the patterns of shoreline erosion versus accretion there are correlations between the rates of shoreline change and the heavy mineral contents and mean grain sizes of the beach sediments these large scale delta wide patterns are affected somewhat by local shoreline changes and mineral variations induced by the construction of jetties or shoreline protection structures

recent decadal growth of the atchafalaya river delta complex effects of variable riverine sediment input and vegetation succession abstract the mississippi river delta plain has experienced substantial wetland loss from subsidence erosion and sea level rise threatening coastal communities and the ecosystems that support them the atchafalaya river the largest distributary of the mississippi river has one of the few prograding delta features along the 200 km deltaic coastline understanding changes in the atchafalaya river delta complex ardc development has critical implications for future prediction and management strategy for the mississippi river delta plain this study was organized to answer two major questions 1 how did development of the ardc respond to fluctuation in riverine sediment supply over the period 1989 2010 and 2 has vegetation succession helped stabilize subaerial land the study quantified annual total suspended sediment yields to the two ardc subdeltas atchafalaya river subdelta arsd and wax lake outlet subdelta wlsd classified delta land cover using satellite imagery over 5 year intervals into three classes barren land vegetation and open water and investigated the relationship of delta land change with sediment yield and vegetation succession over the entire 21 year study period we found a net land gain of 59 km 2 with the arsd accounting for 58 of this gain and wlsd 42 sediment yield to the subdeltas decreased from an average annual of 38 megatonnes mt for arsd and 18 mt for wlsd during 1989 1995 to an average annual of 24 mt for arsd and 17 mt for wlsd during 2004 2010 corresponding to the decrease in riverine suspended sediment concentration concurrently total land growth rate decreased from 2 4 km 2 y 1 to 1 6 km 2 y 1 for arsd and 3 2 km 2 y 1 to 0 6 km 2 y 1 for wlsd however the ardc had a net land loss of 2 1 km 2 during 1999 2004 because of tropical system effects in conjunction with the lack of large river floods defined as discharge 13 800 m 3 s 1 on average more than 60 of newly vegetated land remained vegetated in subsequent years and when compared with barren areas vegetated land was less likely 7 3 vs 32 to be converted to water indicating vegetative stabilization effect however during the period without a major flood vegetation buffering against tropical system erosion was limited this indicates that over the period 1989 to 2010 land growth of the ardc was dictated by large flood events

morphodynamic impacts of large scale engineering projects in the yangtze river delta morphodynamics of world s river deltas are increasingly affected by human activities which are of great ecological economic and social implications however impacts of human interventions in deltaic regions are insufficiently understood especially superimposed upon diminishing sediment supplies this study uses the heavily interfered yangtze river delta as an example to address this issue the morphodynamic impacts of the deepwater navigation channel project dncp during 1997 2013 are investigated through process based modeling approach delft3d and bathymetric data analysis the dncp was implemented in the mouth bar area of the yangtze river delta including the twin dikes and 19 groynes with the total length of 132 0 km hydrodynamic simulations indicate that the training walls resulted in weaker tidal flow and longer slack period at the east hengsha shoal ehs and stronger tidal flow at the subaqueous delta thus the ehs is characterized as a sediment accumulation zone after the completion of the training walls subsequently morphological modeling shows enhanced accretion at the ehs and enhanced erosion at the subaqueous delta when the training walls are taken into account numerical experiments further demonstrate that the above changes are mainly attributed to the seaward half of the northern training walls constructed in 2002 2005 this is probably the reason for the observed accretion peak of the ehs in 2002 2007 and the gradual increase in the erosion rate of the subaqueous delta after 2002 the schematized paths of sediment transport after the dncp indicate that sediment eroded from the subaqueous delta serves as an important source for accretion of the mouth bar area it is suggested that siltation promoting projects within the mouth bar area increased shallow shoal accretion and aggravated erosion at the subaqueous delta with the overall erosion of the yangtze river delta due to river sediment reduction large scale estuarine engineering projects substantially increase the complicacy of its morphodynamic pattern which merits close attention for sustainable delta management

present day stress and neotectonic provinces of the baram delta and deep water fold thrust belt abstract we present the first present day stress orientation measurements across a delta and deep water delta toe fold thrust belt stress and neotectonic data for nw borneo reveal three discrete neotectonic provinces an inverted inner shelf province where present day maximum horizontal stress h is oriented margin normal an extensional delta top province h is margin parallel and a compressional delta toe province h is margin normal we interpret the delta top and delta toe data to reflect that compression in the fold thrust belt is coupled to delta top extension and that the inverted inner shelf province reflects the location of this system on an active margin

recent human impacts on the morphological evolution of the yangtze river delta foreland a review and new perspectives abstract this paper reviews the morphological change in the yangtze river delta due to increasing human impacts from three major aspects the first is the reduction of sediment supply to the ocean due to dam construction soil conservation and sand mining within the yangtze river basin the reduced sediment supply has decreased the progradation rate of the delta and triggered erosion in the front of the delta the second impact relates to the reclamation of intertidal wetlands by human activities since the 1950s approximately 1100 km 2 of intertidal land has been embanked resulting in the disappearance of salt marshes and even the entire intertidal zone along some sections of the coastline the third change in the delta due to human interference is the construction of deep waterway structures at the mouth bar which has greatly modified the local hydrodynamics and morphology sediment accretion has increased significantly in these areas as a result of sheltering by these deep waterway structures this review shows that human activities have severely altered the natural balance among the hydrodynamics and sediment supply affecting the morphological features of the yangtze river watershed and delta human impacts on the morphological evolution of deltaic coasts in general are becoming an increasingly concern and more attention should be paid to the management and mitigation of these effects

channel response to low water levels in the pearl river delta a multi decadal analysis abstract the pearl river delta is a composite delta with one of the densest channel networks in the world to analyze the internal erosion deposition characteristics of the net channel area this paper studies the upstream evolution characteristics using digital elevation model data from local channel sections we attempt to establish the relationship between the changes in low water level and erosion rate by using the accumulated data for the main stream and hydrological stations over the past 50 years including the distributions of flow and sediment at the top of the net channel area and the erosion deposition data of a typical channel section in fact the net channel area has been in a forced erosion state artificial sand excavation for a long time forcing the flow and sediment distributions at makou and sanshui stations to adjust from 1993 to the present although the incoming sedimentation is far less than the net erosion and there are similarities and differences in the sources of the incoming flow and sediment from the main stream the internal characteristics of the upper and lower reaches of the delta have not changed substantially they have always been stable slow deposition channels the forced undercutting is concentrated within width depth ratios of approximately 50 250 which still meets the evolution characteristics of the natural channel artificial sand excavation during the 1980s tended to enhance the characteristics however the sudden increase in the undercutting rate has forced chaotic changes in the low water level since 1990 and the sediment transport rate decreased sharply the phenomena of salt tides retrogression and retrogressive erosion generally happen the water level evolution in the net channel area is chaotic and continuous undercutting is still occurring

morphodynamics of a high discharge tropical delta san juan river pacific coast of colombia abstract the san juan river has one of the most extensive and best developed deltas on the pacific coast of south america measuring 800 km 2 the river drainage basin measures 16 465 km 2 and is located in one of the areas with the highest precipitation in the western hemisphere the annual rainfall varies from 7000 to 11 000 mm and as a result the san juan river has the highest water discharge 2550 m 3 s 1 sediment load 16 10 6 t yr 1 and basin wide sediment yield 1150 t km 2 yr 1 on the west coast of south america the san juan delta growth began approximately 5000 years bp the structure of the delta is determined by the interactions between fluvial deposition and the effect of 1 7 m significant swells mostly from the sw and strong tidal currents analysis of delta progradation indicates that during 1848 1992 the morphology of the delta was characterized by beach ridge accretion spit growth narrowing of inlets and a general advance of the delta shoreline during the past decade processes such as rapid erosion of the delta shore narrowing of barrier islands and breaching of a new inlet are the result of a long term relative sea level rise of 2 6 mm yr 1 due to tectonically induced subsidence coupled with a eustatic rise of sea level the delta also experiences strong oceanographic manifestations associated with the el nino la nina cycle causing regional sea level elevation of 20 30 cm during el nino years recent coastal subsidence in the delta is evidenced by 1 increased occurrence of non storm washover events 2 increased erosion of barrier islands with average loss of 11 m yr 1 during 1993 1997 and 3 a relative sea level rise of 3 4 mm yr 1 during 1991 1999 the morphology and recent evolution of the san juan delta are unique when compared to other deltas of south america because of the singular combination of extreme climatic geologic and oceanographic conditions under which the delta has formed and the absence of human induced impact in the drainage basin

holocene environmental changes of the godavari delta east coast of india inferred from sediment core analyses and ams 14c dating abstract the godavari delta in india is a major wave dominated delta of a tropical monsoon fed river with one of the largest sediment deliveries in the world while several earlier studies revealed the nature of landforms and progradation style of the delta plain during the holocene the present study attempts to reconstruct the depositional environment of the godavari delta through the analysis of core sediment and accelerator mass spectrometry ams 14c dating from three locations the sediment core obtained from a 27 06 m deep borehole at vilasavilli vv supported by 13 14c dates revealed the complete succession of the holocene deposits unconformably overlying pleistocene sediments textural analysis indicates the lower upward fining and upper upward coarsening units in the holocene succession total organic carbon toc total nitrogen tn ratios of 20 high content of toc around 1 5 2 5 and black to very dark colored sediment throughout the muddy part of the holocene succession indicated a predominance of terrigenous material the vv core and two other cores drp and sdg with 14 14c dates indicated the thickness of the holocene sediments in the godavari delta plain is in the order of 20 50 m unconformably resting on a seaward sloping pleistocene basement sediment facies and sediment accumulation of the three cores show the evolution of the godavari delta a transgressive phase is recognized as an upward fining succession in the vv core 8 4 8 0 cal ky bp followed by a low accumulation period 8 0 6 3 cal ky bp including the holocene maximum transgression in the godavari delta after 6 3 cal ky bp areas of high accumulation rates have changed laterally between the central part vv site and southwestern part drp and sdg sites may be controlled by the location of river mouths further analysis coupled with 11 more 14c dates compiled from earlier works indicated that the strandplain of the godavari delta prograded seaward in three stages and that the rate of progradation accelerated during the past 3 ky particularly in the last millennium however pronounced shoreline erosion led to a net negative growth of the delta during the recent decades due to sediment retention by upstream dams although this study provided insights into the sedimentation patterns and rate of seaward progradation of the godavari delta further studies on three dimensional volume analysis of the deltaic sediments are necessary to estimate the overall rates of past sediment discharge and the holocene growth of the godavari delta

sediment supply to the continental shelf by the major rivers of china the yalu luan the yellow changjiang and pearl rivers discharge 90 of china s total annual input of 20 14 10 8 t of sediment to the sea this huge volume of sediment is deposited in the river mouths and in the vicinity of the inner shelves in the form of deltas or submarine sandy ridges depending upon the dominant processes or dynamics of the area even though the continental shelves of the china seas were coastal plains during the late pleistocene modern river sediments rarely extend to the outer shelves except in response to changes in sea level

effects of hydrological events on morphological evolution of a fluvial system abstract this study quantifies morphological evolution of the dez river iran from 1955 to 2016 the approach uses a sequence of landsat images aerial photos and topographic maps in addition the hydrological data including average daily discharge and yearly maximum discharge at the dezful hydrological station for the period 1955 2016 were used the study reach was divided into 48 meander loops from upstream to downstream active channel width w was determined at 10 m intervals and changes assessed along the study reach of the dez river morphological indices including sinuosity index straight meander length centerline flow length erosion area erodible length channel migration centerline elongation and radius of curvature were calculated in the reach results showed that the study reach of the dez river changed dramatically in response to major floods although the general trend is towards a narrowing of active channel width by 38 in the period 1955 2016 results show that most of the meander loops in the study area extended and expanded between 1989 and 1995 all types of meander change were observed there was a direct correlation between the frequency of hydrological events flood days bigger than 2 years return period and elongation of bends

recent subsidence and northeast tilting of the nile delta egypt abstract sediment borings collected in the nile delta of egypt many of them radiocarbon dated indicate that the entire northern sector of this major depositional center in the eastern mediterranean is presently subsiding mapping of the base of the holocene deltaic facies which is dated at about 8000 6500 yrs b p reveals that differential lowering of the northern delta plain is preferentially accentuated toward the northeast long term subsidence rates at or near the coast averaged for the mid to upper holocene range from about 0 1 to 0 25 cm yr between alexandria and the north central delta margin rates increase markedly eastward to a maximum of about 0 5 cm yr in the port said manzala lagoon region and this rapid lowering explains the presence of thick marine delta lobe sequences of holocene age in cores in the northeastern delta in contrast only reworked remnants of holocene marine delta lobe deposits of the earlier river nile branches which once flowed to the north and northwest are preserved seaward of the present north delta coast subsidence has induced marked environmental changes particularly with respect to coastal erosion and salt water incursion the asymmetric pattern of saline ground water here attributed in part to the northeast tilt of the delta plain has serious implications for agricultural development in this intensely cultivated region

controls on quaternary coastal evolution of the east northeastern coast of brazil roles of sea level history trade winds and climate abstract east northeastern brazil has a wave dominated micro to meso tidal coast lying entirely within the southern atlantic trade wind belt integration of geologic mapping radiocarbon dating and vibracoring data shows that the quaternary coastal evolution of this area was controlled by three major factors 1 sea level history 2 trade winds and 3 climate change sea level history along the east northeastern coast of brazil relative sea level has fallen approximately 5 m during the last 5000 y correlation of this sea level history with the evolution of beach ridge lagoonal and coastal plain deposits shows that 1 sea level rise favours the formation of barrier island lagoonal systems and the construction of intralagoonal deltas 2 sea level lowering is not conductive to barrier island formation rather lagoons and bays become emergent and beach ridge plains rapidly prograde trade winds sediment dispersal systems along the coastal zone of east northeastern brazil have been highly persistent since pleistocene time as deduced from beach ridge orientation this persistence results from the fact that sediment dispersal in wave dominated settings is ultimately controlled by atmospheric circulation which for the east northeastern coast of brazil is associated with the south atlantic high pressure cell the remarkable stability of this cell through time has allowed the accumulation of extensive beach ridge plains at the longshore drift sinks located along the coast climate change effects of quaternary climate changes on coastal sedimentation are twofold climate changes may affect rainfall patterns thus exerting an important control on coastal dune development along the coast of northeastern brazil active coastal dunes are only present in those areas in which at least four consecutive dry months occur during the year mapping of these areas has shown that dune development during the holocene has been episodic these episodes being probably controlled by variations in rainfall patterns associated with climate changes secondly despite its overall stability the position of the high pressure cell has experienced small shifts in position during the holocene in response to climate changes changes in wind direction associated with these shifts have induced modifications in the coastal dispersion system which are recorded in the strandplains as small truncations in the beach ridge alignments these results have important implications in understanding accumulation of ancient sandstone shoreline sequences

sedimentary records off the modern huanghe yellow river delta and their response to deltaic river channel shifts over the last 200 years abstract the modern huanghe yellow river delta sedimentary complex has developed since 1855 when the lower river channel migrated northward from the yellow sea to the bohai sea as a result the river laden sediment accumulated rapidly on the lowlying plain and formed the mega delta here we present high resolution sedimentary sequences based on 137 cs and 210 pb dating and grain size parameters of two sediment gravity cores collected near the present river mouth core a11 and in adjacent laizhou bay core a26 based on these sedimentary sequences the different responses of the sediment records to natural and artificial channel shifts are presented the average sedimentation rates of the two cores a11 1951 2006 and a26 1808 2006 were estimated to be 2 25 cm year and 0 80 cm year respectively the results indicated that the geometry of the delta e g the location of river mouth and changing coastline and sediment supply from the river played an important role in the sedimentation of the subaqueous delta the channel shifts in 1976 and 1996 shortened the distances from the river mouth to the location of core a11 resulting in the local accumulations of relatively coarse particles from the river mouth the sedimentation of core a26 indicated four major channel shifts in 1855 1904 1947 and 1976 when the river mouth approached the core location the accumulated sediment became finer otherwise the active resuspension due to strong hydrodynamics resulted in the accumulation of coarser sediment the sediment records preserved in the two gravity cores illustrated different sedimentary responses to the lower channel shifts of the huanghe and sediment supply from the river at centennial scales which is critical to understanding the evolution of the modern huanghe delta in the past and to predicting the future trend

large rotaliid foraminifera as biostratigraphic and palaeoenvironmental indicators in northwest borneo an example from a late miocene section in brunei darussalam abstract palaeonvironmental interpretations and biostratigraphic zonations in northwest borneo are still a matter of debate but are important for petroleum related applications the outcrop of ambug hill a late miocene marine siliciclastic sequence in brunei darussalam has been investigated for its foraminifera assemblage from a 9 5 m clay rich interval 50 taxa have been recognized and classified whenever possible to species level the studied fauna is characterized by mostly hyaline foraminifera dominated by two rotaliid species cavarotalia annectens and heterolepa dutemplei additionally a number of miliolids lageniids bolivinids and also planktonic foraminifera are present but in much lower abundance the dominance of the rotaliids points to a sea floor rich in organic carbon characterized by muddy substrates with very low light penetration and the possible growth of patchy sea grass or macroalgae in the system as indicated by epiphytic foraminifera in the samples the results obtained give additional insights on how the environmental conditions might have been during the deposition of the deltaic sequences very widespread in the region and how the fauna coped with such settings throughout the investigated samples the dominance of the assemblages clearly shows alternating stress conditions typical of pro deltaic environments the large abundance of rotaliid foraminifera points toward possible biostratigraphic applications as several taxa within this group have short biozones in the region even though have strong facies dependency if their role as biostratigraphic indicators could be finally proven they might be used to date the large depositional sequences occurring in the region since planktonic index fossils are scarce due to the very proximal settings of the sediments

backwater controls on the evolution and avulsion of the qingshuigou channel on the yellow river delta abstract as rivers approach base level their water and sediment dynamics are affected by a transitional reach known as the backwater zone at low flows backwater zones cause flow deceleration and in channel sedimentation but at high flows they cause flow acceleration and erosion over many floods the dynamics of deposition and erosion in the backwater zone are thought to control the locations of avulsions on some large deltaic channels however in various studies the role of the backwater is often inferred or modeled and directly observed evidence of how backwater affects channel dynamics at avulsion sites remains scarce in this study we show how the backwater zone impacts the evolution and avulsion of the qingshuigou channel a recent lobe on the yellow river delta using four decades 1976 2015 of data from systematic surveys of water discharge sediment load cross sectional profiles and water surface elevation the results show that the channel was commonly eroded during flood seasons and aggraded during nonflood seasons erosion rates generally decreased in the downstream direction along the lower channel reach during flood seasons primarily due to downstream channel widening and the subsequent decrease in sediment transport capacity the erosion rate reached zero at the cross sections farthest downstream which is contrary to expectations under hydrodynamic backwater effects where drawdown causes erosion to increase downstream during high flows during nonflood seasons maximum sedimentation occurred upstream of the backwater zone possibly due to impacts of local topography of meandering bends or constriction from dikes morphodynamic backwater accompanied by the deposition and gradual progradation of a mouth bar resulted in downstream increasing sedimentation superelevation and lateral migration rates along the lower channel reach from 1985 to 1996 the predicted avulsion location was near cross sections q6 or q7 with an avulsion length of 20 30 km upstream of the shoreline which was consistent with those for historical avulsions we emphasize the close interplay between backwater effects and channel geometry and argue that morphodynamic backwater may play a more important role than hydrodynamic backwater in setting up and triggering avulsions on the yellow river delta

sedimentary transition of the yangtze subaqueous delta during the past century inspiration for delta response to future decline of sediment supply abstract how the yangtze delta responds to riverine sediment decline has become a hot research topic and an urgent issue to be addressed especially after the impoundment of the three gorges dam in 2003 this study investigated sedimentary features through the sediment granularity of surficial samples and short cores over the entire yangtze subaqueous delta aiming to better understand the spatial response of the subaqueous delta to sediment supply decline and local hydrodynamic adjustment of the estuary the results show that four sedimentary zones of estuarine sand bar zone i prodelta zone ii delta shelf transition zone zone iii and residual sand zone iv are distributed from the estuary to the shelf characterised by first fining from zone i to zone ii and then coarsening from zone ii to zone iv on grain size of surficial sediments in the past few hundred years the subaqueous delta has been generally prograded seaward following this sedimentary system spatially manifested by generally fining upwards in the cores of the main subaqueous delta however sediment coarsening occurs on the top of the cores in the delta shelf transition zone zone iii implying a recent retrogradation process based on the results of 210pb and 137cs the sedimentary transition from progradation to retrogradation occurred since 1950s and was intensified after 1980s in the north part of zone iii mainly caused by channel shrinking of the north branch and riverine sediment decline comparatively such a sedimentary transition is not significant in the south part of zone iii but it is worth noting that surficial coarsening in the core of the south part of zone iii is probably related to drastic sediment decline since 2003 when the three gorges dam closed which means that the yangtze subaqueous delta has probably been in a full sedimentary transition the sedimentary transition of the north subaqueous delta can provide an insightful reference for the sedimentary response of the yangtze delta to further decline of sediment supply in the future

changes in morphometric meander parameters identified on the karoon river iran using remote sensing data abstract river meander dynamics and mobility are important indicators of environmental change related to climate changes and anthropogenic activities at local and river basin scales the aim of the present study is to identify morphological changes of the karoon river in iran using high accuracy maps and landsat satellite images by analyses during the time period 1989 2008 in this study 20 meandering reaches were analyzed over a 128 km long river reach located in the middle part of the karoon river iran morphometric indicators such as river width w meander neck length l axis length a radius of curvature r water flow length s and sinuosity of meander c were extracted for the identified meanders the results of a paired t test showed that river width w and meander neck length l have significantly changed during the study period 1989 2008 with an increase of 3 5 m for w and a decrease of 274 m for l spearman correlation analysis has shown that meander parameter changes are highly correlated to each other the parameters that do not have significant correlation together are c with w and l w and l and l with s and a during the period of the study the flow length and river sinuosity decreased for the whole river reach by 4 77 km and 0 11 respectively analysis of land use land cover categories 1989 and 2008 using the support vector machine svm and kernel function method served as one of the tools for interpretation of the meander parameter changes these changes can be attributed not only to lu lc riparian vegetation to agriculture area ratio but also to dam construction in the upstream part of the river that leads to major hydrological regime and sediment transfer alteration sediment extraction may also be an important factor

crustal sources involved in continental arc magmatism a case study of volcan mocho choshuenco southern chile volcan mocho choshuenco a pleistocene holocene basaltic andesite to dacite shield volcano located at lat 40 s in the southern volcanic zone svz of the andes is built on the thinnest svz continental crust 30 km which consists largely of paleozoic sedimentary and metamorphic rocks and mesozoic plutons sr pb nd and o isotopic ratios of mocho choshuenco lavas 87 sr 86 sr 0 70399 to 0 70422 206 pb 204 pb 18 57 to 18 61 207 pb 204 pb 15 60 to 15 63 208 pb 204 pb 38 45 to 38 57 143 nd 144 nd 0 512787 to 0 512881 18 o 5 8 to 6 8 standard mean ocean water are similar to those of other svz centers and exhibit no correlation with indices of differentiation however incompatible trace element systematics indicate that evolved lavas have been contaminated by crustal plutonic rocks by 5 to 15 rb ba k ba rb la and k la ratios increase with increasing sio 2 content as a result of assimilation of orogenic calc alkalic plutonic rocks enriched in rb and k relative to ba and la xenoliths of plutonic rocks recovered from mocho choshuenco lavas are slightly more radiogenic in 87 sr 86 sr less radiogenic in 143 nd 144 nd and comparable in pb isotopic ratios and they have variable 18 o contents 87 sr 86 sr 0 70482 to 0 70557 206 pb 204 pb 18 60 to 18 64 207 pb 204 pb 15 60 to 15 62 208 pb 204 pb 38 53 to 38 56 143 nd 144 nd 0 512686 18 o 3 3 to 5 5 smow contamination of mocho choshuenco parental magmas by crustal melts with small isotopic contrast imposed little variation on isotopic heterogeneities existing in the parental compositions these heterogeneities probably were produced during magma crust interaction at the crust mantle boundary or in the lower crust

temporal trends of aliphatic and polyaromatic hydrocarbons in the bohai sea china evidence from the sedimentary record abstract this work reports the historical trends and sources of aliphatic hydrocarbons ahs and polycyclic aromatic hydrocarbons pahs in two 210 pb dated sediment cores extracted from the central mud areas of bohai sea bohai the toc tn ratio of the bulk organic matter om and the composition of the n alkanes suggest that the sedimentary organic matter was of mixed marine and terrigenous sources the coarser sediment grain size and decreasing c n ratios since 1976 could be attributed to the relocation of the yellow river mouth causing a decreased influence of yellow river derived sediments and associated om into the central bohai the concentration of total 16 pahs in the two cores ranged from 34 2 202 ng g mean 91 5 for bc1 and from 53 3 186 ng g mean 103 for bc2 with a high abundance of 2 3 ring pahs perylene in the two cores mainly originated from terrigenous sources via riverine discharge and thus could be potentially related to changes in the sediment load from the yellow river into the bohai over time petroleum inputs could be revealed by ratios of methylphenanthrenes to phenanthrene mp p and the patterns of more stable geochemical biomarkers hopanes and steranes along the two cores in addition to the presence of unresolved complex mixtures ucm in the surface layers source diagnostic ratios of pahs indicated a pyrogenic origin from biomass and coal combustion with a minor petroleum contribution downcore trends of compositional pahs profiles were in agreement with the socio economic development in china in the past decades this temporal variation of sedimentary pahs can also reflect a different evolution stage of energy structure in china as compared with those of the western developed countries

recent changes in sediment delivery by the huanghe yellow river to the sea causes and environmental implications in its estuary summary over the past 60 years climate change and human activities in the huanghe yellow river basin have changed the river system in particular construction of large reservoirs and soil conservation practices within the river basin have reduced sediment flux to the sea by 90 and increased the grain size of suspended sediment delivered to the sea 30 m now versus 18 m before in median grain size scouring of the channel in the lower reaches has added a new sediment source to those derived from the loess region of the middle reaches before construction of the xiaolangdi reservoir at the downstream end of the middle reaches suspended sediment concentrations at station lijin the last hydrographic station before the river enters the sea were high enough 35 kg m 3 in the flood season to offset the density contrast between freshwater and ambient seawater thus hyperpycnal flows developed along the subaqueous slope at the river mouth during the flood season observations from two cruises near the huanghe river mouth one before and one after the operations of the xiaolangdi reservoir suggest that buoyant hypopycnal plumes rather than hyperpycnal plumes have occurred at the river mouth since the dramatic changes in concentration and grain size of suspended sediment discharged to the sea the rapid decrease of sediment discharge to the sea and the increase of grain size of suspended sediments not only changed the sediment dispersal pattern at the river mouth but also modified the shoreline and subaqueous slope the effects of climate change and human activities in the river basin have been transferred along the hydrological pathway to the estuary and delta and have changed estuarine sediment dynamics and delta morphology the huanghe presents an illustrative example of river basin coastal zone interactions in the context of climate change and human activities

temporal and spatial changes in coastline movement of the yangtze delta during 1974 2010 abstract the evolution of the yangtze delta where the largest economic zone e g shanghai in china is located directly affects the regional economic development and ecoenvironment the mean high tide lines as the coastline delineated from multi temporal remote sensing data of landsat during 1974 2010 at intervals of about 8 years were used to examine the shoreline progradation and recession of the yangtze delta in the past four decades our results show that significant parts of the shoreline in the yangtze delta in the past four decades and particularly after the operation of the three gorges reservoir tgr the world s largest hydropower project ever built experienced continual progradation despite a substantial decrease in the yangtze sediment input during 1974 2010 the area of the yangtze subaerial delta increased by 667 km2 with a net progradation rate of 18 5 km2 yr and the maximum progradation occurred at the eastern parts of chongming island and nanhui bank where the coastline advanced seaward about 8 and 6 km respectively with mean net progradation rates of 0 22 and 0 17 km yr respectively an important probably dominant reason for the yangtze shoreline progradation despite markedly decreased riverine sediment supply is coastal engineering such as sea reclamation works filling project and wharf constructions

assessment of aeolian desertification trends from 1975 s to 2005 s in the watershed of the longyangxia reservoir in the upper reaches of china s yellow river abstract global climate change will affect the ecology and environment of the qinghai tibet plateau thus increasing attention is being paid to the aeolian desertification that is occurring in the watershed that supplies the longyangxia reservoir in the upper reaches of china s yellow river we must assess the aeolian desertification trends before developing a plan to restore the region s degraded eco environment in this study land suffered from aeolian desertification was classified into four levels slight moderate severe and extremely severe using a series of indices interpretation of landsat mss and tm data from 1975 s 1989 s and 2005 s was used to establish databases of aeolian desertified land at these three times we then derived the aeolian desertification trends during the study period by overlaying the consecutive databases and we analyzed the driving factors responsible for the observed aeolian desertification the results show a total of 1 721 478 02 ha of aeolian desertified land in 2005 s accounting for 13 of the region s total area from 1975 s to 1989 s the area of aeolian desertified land increased by 229 307 26 ha which represents a 15 increase compared to the 1975 s area and from 1989 s to 2005 s the area of aeolian desertified land decreased by 19 079 87 ha which represents a 1 decrease compared to the 1989 s area the main driving factors responsible for this increased aeolian desertification were climate factors high wind velocity and an increase in annual temperature combined with low precipitation and high evaporation as well as unsustainable human activities and inappropriate policy measures a series of key national projects initiated to combat degradation of the study area s eco environment led to a decrease of aeolian desertified land through obvious restoration of vegetation

impact of river discharge on hydrodynamics and sedimentary processes at yellow river delta abstract during the anthropocene regulating river discharge by high dams may have met the need for water demands in river basins but resulted in carrying less freshwater and sediment to the sea inducing land degradation and shoreline retreat in worldwide mega river deltas in land ocean interaction tide response to water discharge changes plays an important role and is crucial for the river laden sediment transfer and dispersal affecting both nearshore and estuarine deposits the yellow river delta yrd which is under an increasing pressure of the new discharge regime of the yellow river has undergone drastic changes in terms of sediment dynamics and morphologic evolution to gain a better understanding of the overall fluvial and marine hydrodynamics and morphodynamic processes in the yrd in this study a full scale numerical model is built to investigate the interaction and impacts of changing environmental forcing and dynamics on flow and sediment transport in the estuary of yrd and its adjacent coasts the results show that the river discharge strongly affects the tidal dynamics and morphology of the delta particularly in the close vicinity of the outlet and the intertidal zone tidal constituents m2 and k1 which are the most significant ones in the yrd are found to be noticeably affected with a decreasing trend when the river discharge increases the model results also indicate that river discharge affects the location and intensity of the shear front that occurs in the nearshore areas of the yrd increasing the river discharge can induce a seaward movement of the shear front reduce its width and concentrate its shear intensity it is found that the reverse of the flow direction at each side of the shear front and strong longshore tidal current can act as a barrier for the sediment dispersal process by keeping suspended sediment in the inner zone thus to form a particular sediment deposition zone and the depo center

the heterogeneity of mudflat erodibility the prediction of the erosion of mudflats is hampered by inaccurate estimates of the erodibility distribution of the sediment bed to investigate how erodibility varies in space and what the vertical distribution over the sediment depth is comprehensive observations of the sediment properties hydrodynamics and bed level changes were conducted on an intertidal flat in the western scheldt estuary the netherlands the erosion potential on a mudflat is determined by the critical shear stress for erosion e erosion rate coefficient m and local hydrodynamic conditions a clear difference in hydrodynamic forcing was observed leading to significant bed level variations at the low water line where erosion often occurs during very shallow water condition and a nearly constant bed level at the upper part the erosion parameters e and m could be determined over a sediment bed of 12 cm at the low water line the erosion coefficient m can be considered constant with depth although there is a large spreading a clear vertical variation of e was found e increased significantly downward from 0 10 pa at the sediment surface to 1 13 pa at 12 cm below the surface additionally there was a strong indication that the presence of diatoms enhanced e in the upper 2 mm of sediment by five times of the abiotic e from 0 09 pa to 0 46 pa these findings lead to the following improvement for predicting morphological changes of tidal mudflats 1 very shallow conditions should be better simulated 2 the vertical distribution of e should be considered otherwise erosion rates can be overestimated especially during extreme events because exposure of the deeper well consolidated layer likely occurs and 3 an appropriate description of the effect of diatoms should be considered as part of the bottom boundary condition

changing pattern of accretion erosion of the modern yellow river huanghe subaerial delta china based on remote sensing images abstract the yellow river shifted from the diaokou course to the qingshuigou course in 1976 and shifted again at the north bank of the qingshuigou course in 1996 as a result the entire modern yellow river delta has experienced complicated patterns of erosion and accretion multitemporal remote sensing data of landsat mss and tm from 1976 to 2000 totaling twenty scenes were used to examine the changing pattern of accretion and erosion of the modern yellow river subaerial delta with gis tools during the period 1976 to 2000 the maximum erosion occurred at the head of the last two abandoned promontories diaokou and shenxiangou promontories where the coastline retreated landward over 7 and 4 5 km respectively with mean net erosion rates of 0 29 and 0 19 km a respectively in contrast the maximum accretion occurred at the head of the qingshuigou promontory where the coastline advanced seaward over 20 km with a mean net accretion rate of 0 83 km a the coastline at the head of the q 8 promontory also advanced seaward 7 km with a mean net accretion rate of 0 29 km a during the period 1996 to 2000 total area of the diaokou and shenxiangou promontories was reduced by 141 3 km 2 with a mean net erosion rate of 6 03 km 2 a total area of the qingshuigou and q 8 promontories increased by 384 16 and 11 88 km 2 respectively with mean net accretion rates of 16 4 and 3 03 km 2 a respectively relative to the diaokou shenxiangou and qingshuigou promontories the west area of the diaokou promontory and south area of the qingshuigou promontory were relatively stable although minor erosion occurred the general pattern of accretion and erosion of the modern yellow river subaerial delta was divided into three stages rapid accretion stage 1976 1984 accretion erosion adjustment stage 1985 1995 and slow erosion stage 1996 present the factors affecting the pattern of erosion and accretion over the yellow river delta such as structural geology the yellow river sediment discharge coastal processes meteorological conditions human activity sea level rise and land subsidence were summarized the cumulative area of increase over the entire subaerial delta is closely correlated with the cumulative yellow river sediment discharge wave induced longshore current is the major driving force to transport sediment from eroded areas along the last two abandoned promontories diaokou and shenxiangou promontories mostly westerly and partially easterly together with these coastal processes is the geographical shift of the yellow river course associated with its discharge regime after 1976 leading to the accretion along the present qingshuigou promontory and then the q 8 promontory

balancing deformation in nw borneo quantifying plate scale vs gravitational tectonics in a delta and deepwater fold thrust belt system abstract recent gps measurements demonstrate that nw borneo undergoes 4 6 mm of plate scale shortening a year which is not accommodated by plate scale structures the only geological structure in nw borneo described to accommodate on going shortening is the baram delta system located on the outer shelf to basin floor delta toe fold thrust belts are commonly thought to be caused by margin normal compressional stresses generated by margin parallel upslope gravitational extension the baram delta system is divided into three neotectonic provinces 1 an inactive onshore and inner shelf region of inversion superimposed on an older extensional deltaic province 2 an outer shelf region of present day deltaic extension and 3 a compressional delta toe however it is uncertain whether compression in the delta toe area is purely driven by gravity i e shortening is less than upslope extension or if there is a component of regional shortening involved which can only be demonstrated if shortening is greater than upslope extension in order to quantify the balance between the shortening related to the upslope gravitational extension and the shortening related to the regional geodynamic framework in the baram delta system we have used a geomechanical code based on the finite element method and conservation of mass and momentum dynel 2d this enabled us to reconstruct the tectonic evolution of the delta and to demonstrate for the first time that the total shortening observed in the delta toe does not balance against the active extension in the delta top with the system exhibiting 1 8 shortening overall or 2 0 km this additional shortening is therefore attributed to plate scale shortening across nw borneo produced by far field compression using a convergence rate of 4 mm y 1 demonstrated by gps measurements the delta toe has accommodated far field compression only in the last 0 5 my

sedimentation in the yellow river delta part ii suspended sediment dispersal and deposition on the subaqueous delta abstract rapid deposition and suspended sediment dispersal off the modern yellow river mouth has been examined from the data of topographic maps 1 25 000 suspension and bed sediments current and salinity which were measured in the field the results show that the sedimentation rate of the mouth bar is the highest of all the environments of deposition in the modern yellow river delta about 30 40 of the sediment that the river transports into the sea has been deposited within the mouth bar area rapid deposition of the mouth bar results mainly from kinetic energy dissipation of the river under the influence of three ambient mechanisms these three mechanisms occur simultaneously as shear front movement which obstructs the river s jet like flow small scale circulations where large velocity gradients occur and the bulldozer effect of the tide sensitive zone in the estuary at ebb based on the analysis of morphologic changes the mouth bar can be divided into two morphologic types one is the double lobe and single channel type and the other double channel and single lobe type weak hyperpycnal plumes with small density differences between the river flow and ambient water dissipate rapidly and deposit about 20 of the river sediments on the delta front slope while hyperpycnal underflows from the river mouth can go through the steep delta front slope to form a rise apron along the upper part of the prodelta grain size analysis of suspended sediment shows that the flow can be divided into three layers a tide layer in the upper part and a hyperpycnal layer in the lower part these two layers are normally graded and a transition layer with inverse grading in the mid part the fine suspended sediments have been transported in the hypopycnal plume layer into the prodelta and deep sea such as the north huanghai sea north yellow sea this study indicates that the tidal current field has dominated the distribution of deposition of sediment on the subaqueous delta and the movements of the river effluent and hyperpycnal underflows

bed level changes on intertidal wetland in response to waves and tides a case study from the yangtze river delta short term bed level variability in tidal wetlands has important implication both for ecology and engineering in this study we combined in situ measurements with model simulations to quantify short term bed level changes on a meso macrotidal wetland in the yangtze river delta on the middle flat we observed erosion during neap to mean tides under onshore moderate to strong winds and bed recovery during subsequent spring tides when winds were both offshore and weaker suggesting that winds can overturn the neap spring cyclicity of bed level changes even on meso macrotidal mudflats the magnitude of bed level changes was smaller on both sides of the middle flat while the smallest changes occurred on the salt marsh observed bed level changes were reconstructed using a single point bed level change model which incorporates in situ measured parameters of hydrodynamics waves and currents suspended sediment concentrations and bed sediment properties we conclude that the relative importance of waves and tides in intertidal wetland erosion and accretion can vary temporally due to changes in balance between wave and tidal energies and spatially because of changes in elevation and vegetation in the cross shore profile our study also reflects the advantage of combination of in situ measurement with simulation in detecting short term variability of tidal flats

sedimentation in the yellow river delta part i flow and suspended sediment structure in the upper distributary and the estuary abstract a 44 year data record measured by lijin hydraulic station on the yellow river shows that sediment concentration has been increasing while river discharge has been decreasing into the delta since the 1970s these changes are important because flood waters of the yellow river which are heavily laden with sediment must be used to supply dongying city and shengli oil company which are located on the delta based on the analyses of data of velocity sediment concentration salinity and sediment grain size from four cross section measurements at lijin station and one 8 vessel simultaneous measurement cruise in the estuary structural characteristics of the river flow and suspended sediments throughout the upper distributary and the estuary have been studied and discussed results show that when sediment concentrations of the yellow river exceed 100 kg m 3 in the lower layer of the river flow during the flood period the river flow structure does not coincide with the logarithmic law of wall and becomes vertically layered and the vertical distributions of suspended sediment do not coincide with the diffusion law the channel length influenced by the tide wave is less than 15 km and there is no tidal intrusion flow only weak osmosis of salinity occurs inside the river mouth during the flood period of the yellow river simultaneous 8 vessel measurements and simulation using the method of preissman show that there is a tidal sensitive zone inside the river mouth bar with a length of 6 7 km when the discharge is as large as 1100 m 3 s and an area of very active sedimentation the tidal sensitive region near the river mouth becomes a low velocity zone that traps a large amount of river sediment which rapidly forms a plastic bed at flood tide and a high velocity zone with a strong hydrodynamic action to erode the new bed and transport the sediments into the sea at ebb tide

sedimentation in the yellow river delta part iii seabed erosion and diapirism in the abandoned subaqueous delta lobe abstract historical bathymetry satellite remote sensing and river discharge data have been used to examine the evolution of an abandoned delta lobe in the northern area of the modern yellow river delta results show three stages of evolution in the subaqueous delta slope after lobe abandonment 1 rapid erosion stage 2 slow erosion stage and 3 erosion accumulation adjustment stage according to 1 10 000 bathymetry data and high resolution seismic profiles diapirism in the subaqueous abandoned delta lobe is closely related to seabed erosion which mainly occurs in the middle part of subaqueous delta slope diapirism results from the deformation of soft fine grained prodeltaic sedimentary stratum when the accumulation body on the soft stratum is removed in rapid erosion stage the maximum accumulation centre in the delta lobe during growth coincides with the maximum erosion centre in the delta lobe abandonment phase the diapir body occurs there distinguishing from diapirism in the mississippi delta three stages of the soft stratum deformation and diapirism are established in the yellow river delta the mobile strata and its diapirism are destructive to the offshore engineering facilities

historical changes in the yellow river delta china abstract the lower yellow river delta has experienced numerous avulsions during the last 2000 years and the floodplain can be divided into four provinces alluvial fan western plain middle plain and eastern plain coastal deltas the yellow river delta complex is composed of several delta superlobes resulting from shifts in the lower river channel and each delta superlobe consists of several smaller lobes formed by shifts in the distributary channels these two kinds of channel shifts have resulted in a complicated imbrication pattern in the delta complex two imbricated delta superlobes are divided by a reworked bed and buried shelf deposits shelly ridges form the surface boundaries between the various delta superlobes the delta superlobes passed through an active stage a reworking stage and were then finally overlain by later superlobes

detrital fine grained sediment contribution from taiwan to the northern south china sea and its relation to regional ocean circulation article i nfo results of clay mineralogy in 140 samples collected in major rivers and lakes in southwestern taiwan and on the seafloor off taiwan in the northeastern south china sea scs combined with clay mineral records of the pearl river drainage basin rivers in luzon and the south china shelf and slope are used to semi quantitatively evaluate the detrital fine grained sediment contribution of taiwan to the northern scs the clay mineral assemblage of the taiwan sourced sediments consists dominantly of illite average 56 and chlorite 41 with very scarce kaolinite and smectite their respective distribution from the rivers and lakes to the seafloor off taiwan does not show obvious basin wide differences linear correlations of illite chemistry index with illite crystallinity and of illite crystallinity with kaolinite present two end members of provenances the pearl river and taiwan for the south china shelf and slope assuming that kaolinite in the northern scs is provided completely from the pearl river the contribution of taiwan in clay minerals is evaluated as 29 to the south china shelf and 23 to the south china slope respectively accordingly the contribution of the pearl river to the south china shelf and slope is 52 and 31 respectively the luzon arc accounts for the rest of clay mineral components for the northern scs mainly by providing smectite the bashi strait crossed branches of the southward deep north pacific deep water and the northward surface kuroshio current in the western pacific may transport taiwan sourced suspended sediments westwards to the northern scs

asymmetry in holocene river deltas patterns controls and stratigraphic effects abstract understanding controls on sediment distribution in river deltas is paramount to predicting facies relationships and stratal architecture most classifications of deltas have focused on subaerial plan morphology as a simplistic function of river tide and wave energy new work however is revealing the importance of subaqueous deposits and in particular shore parallel sediment redistribution in the shaping of delta planform delta asymmetry has emerged as an important characteristic reflective of patterns of alongshore sediment dispersal asymmetry has been described from onshore and offshore environments from several different types of modern deltas but aspects of asymmetry have not been fully documented and the degree to which these patterns are recorded in deltaic strata is not yet known this study is a comprehensive literature review of sediment distributions in modern deltas focusing on studies with high resolution geomorphic geophysical and geochronological datasets we reviewed 27 deltas using over 100 papers primarily from the past 15 20 years morphological facies and stratigraphic aspects were analyzed across the entire spectrum of deposits from the delta apex to the most distal muds of the prodelta we define quantifiable indices of asymmetry describing upcurrent vs downcurrent distribution of sediment volume sediment area sediment caliber and distributary channels most deltas are asymmetrical to some degree with respect to one or more of these parameters many deltas are increasingly skewed toward the downcurrent side from proximal to distal sub environments i e delta plain delta front prodelta some deltas are skewed toward the upcurrent side in one sub environment and toward the downcurrent side in another sub environment sand is preferentially deposited on the downcurrent side of most deltas but distributary channels tend to develop toward the upcurrent side the highest sand mud ratios are often on the upcurrent side in the lower delta plain but in the delta front these ratios are highest on the downcurrent side these complex patterns of asymmetry reflect different combinations of controls including discharge partitioning lobe abandonment and localized transgression plume deflection by coastal currents dominance of longshore current direction variable subsidence and other factors these processes may result in upcurrent downcurrent variations in clinoform geometry rates of progradation and stratal lapping relationships asymmetry has multiple aspects manifestations and controls even within a single delta but the long term preservation potential of these patterns likely varies depending on depositional setting and shoreline trajectory studies of ancient deltas will be better informed by recognizing the wide variety of controls on sediment distribution and avoiding the tendency toward a single model of delta asymmetry

enhanced bioturbation on the down drift flank of a turonian asymmetrical delta implications for seaway circulation river nutrients and facies models extant models predict delta front environments down drift of river mouths as unfavourable for organisms because of the physico chemical stresses caused by sediment and fresh water influx this study however finds evidence for near optimal living conditions down drift of contemporaneous mouth bars and distributary channels as well as at the tops of abandoned lobes in part of the asymmetrical notom delta complex of the ferron sandstone turonian south eastern utah usa presented herein is a sedimentological and ichnological model using thirty two detailed measured sections along a 16 km transect through two continuously exposed ca 10 m thick allomembers containing delta front mouth bar and distributary channel facies azimuths from sedimentary structures show south eastward deflection of near shore palaeocurrents relative to the inferred north south shoreline as well as minor reversal of flow two end member trace fossil suites are recognized in delta front sandstones i a stressed suite of low abundance low diversity diminutive traces reflecting mobile deposit feeding resting and locomotion behaviours and ii a comparatively unstressed high abundance moderate diversity suite with a regular heterogeneous distribution of deep vertical or u shaped suspension feeding burrows which in places thoroughly homogenize the sandstones the down drift side of the delta was colonized by suspension feeders during seasonal reversal of the seaway gyre when mud plumes were swept northward or when river derived nutrients were sufficiently concentrated relative to fresh water and sediment input during normal seaway circulation very high sedimentation rates and mud laden wave dampened waters down drift of the river mouths heightened the preservation potential of the pervasively bioturbated facies up drift of the river mouths these bioturbated facies were either not preserved or not developed until the lobe was abandoned this alternative model for delta planform asymmetry contributes to the refinement of facies models for deltaic systems and provides a framework for predicting the distribution of bioturbation enhanced porosity and permeability in lobe deflected deltas

assessing morphological changes of the ganges river using satellite images abstract using eight dry season satellite images of landsat mss 1973 1984 landsat tm 1993 2003 and irs liss 2009 this study assessed morphological changes of the ganges river within bangladesh as a typical alluvial river morphological changes of the ganges river had been a common phenomenon in the 1973 2009 study period with its morphologically dynamic nature the ganges river had undergone considerable changes in its river banks and its vegetated islands the bankline movement rates m y and erosion accretion rates ha y of the river were analyzed under four time periods 1973 1984 1984 1993 1993 2003 and 2003 2009 the results indicate that both the left and the right banks of ganges have changed significantly due to varying erosion and accretion rates that had occurred on a whole the left bank was more prone to accretion while the right bank to erosion the magnitude of bank erosion along the ganges river is closely related to the erodibility of riverbank materials which vary spatially in 1973 1984 the average river width and the overall islands area had decreased considerably due to a net river bank accretion which resulted in an increase of 6790 ha of land area however afterwards both river width and islands area continue to increase to the end of this study period 2009 because of a net erosion loss of 18 830 ha of land furthermore from 1984 to 2009 the sinuosity of ganges had generally increased and was related to increased river width caused by a net bank erosion compared to other major rivers ganges has a very high erosion rate probably because its river banks are primarily composed of highly erodible materials and its high discharge rate especially during the monsoon season

onshore record of the subduction of a crustal salient example of the nw borneo wedge terra nova 23 232 240 2011 abstract subduction of oceanic highs has been described in offshore accretionary wedges thanks to bathymetric and seismic data and simulated in sand box models where documented it is limited to oceanic subduction of small culminations seamounts however tracing this phenomenon in ancient and or uplifted belts remains a challenge based on structural geomorphological and thermal analysis we describe a subducted horst in the nw borneo wedge this is evidenced by the occurrence of several geomorphological anomalies a strong bend of the structural trend of the rajang crocker belt and an area with hummocky texture representing dismantled packages of sediments some specific structural features large back and out of sequence thrusts in the internal zones complex folds rooted on shear structures in the accretionary wedge also occur in this central part of the nw borneo wedge the central area of the related deformation zone records several thermal anomalies terra nova 00 1 9 2011

riverbank migration and island dynamics of the braided jamuna river of the ganges brahmaputra basin using multi temporal landsat images as one of the largest braided rivers in the world the jamuna river jm of the lower brahmaputra regularly undergoes significant erosion causing major bankline migration making thousands of families homeless and sizeable land loss every year e g the dynamic nature of jamuna causes great suffering to the people living along its course and on its islands therefore gaining a better understanding of the river s behavior should contribute to mitigate these sufferings and also to reduce the possible damage of the river to public infrastructure in this study using thirteen selected images of landsat mss and tm acquired from 1973 to 2003 the riverbank migration patterns and island dynamics of jm resulted from accretion erosion processes for 30 years were investigated for short term analysis the migration rate from one landsat image to the next is estimated for long term analysis the migration rates are based on the difference between the 1973 image as the reference and subsequent images for the short term long term analysis the average erosion and accretion rates are 227 and 271 m y 90 and 104 m y on the left bank and 187 and 148 m y 75 and 50 m y on the right bank of jamuna respectively because of human interventions and the averaging effect of erosion and accretion the long term migration rate is lower than that of the short term migration rate on both banks the short term rate of accretion erosion on the left right bank follows the general pattern of river bank migration while the accretion erosion of the right left bank does not follow such a pattern on the other hand the long term erosion and accretion processes for both banks partly follow the general pattern of river bank migrations from one flood to another large islands tend to be more stable with little changes but smaller islands underwent more changes from results obtained from analyzing multi temporal landsat images this study provides new and accurate information about the riverbank migration of jm

present day stress orientations and tectonic provinces of the nw borneo collisional margin received 23 september 2009 revised 17 may 2010 accepted 9 june 2010 published 16 october 2010 1 borehole failure observed on image and dipmeter logs from 55 petroleum wells across the nw borneo collisional margin were used to determine maximum horizontal stress sh orientations combined with seismic and outcrop data they define seven tectonic provinces the baram delta deepwater fold thrust belt exhibits three tectonic provinces its inner shelf inverted province sh is nw se margin normal its outer shelf extension province sh is ne sw margin parallel and its slope to basin floor compression province sh is nw se margin normal in the inverted province sh reflects inversion of deltaic normal faults the sh orientations in the extension and compression provinces reflect deltaic gravitational tectonics the shale and minibasin provinces have been recognized in offshore sabah in the shale province sh is n010 e which aligns around the boundary of a massif of mobile shale currently no data are available to determine sh in the minibasin province in the balingian province sh is ese wnw reflecting ese absolute sunda plate motions due to the absence of a thick detachment seen elsewhere in nw borneo the central luconia province demonstrates poorly constrained and variable sh orientations these seven provinces result from the heterogeneous structural and stratigraphic development of the nw borneo margin and formed due to complex collisional tectonics and the varied distribution and thicknesses of stratigraphic packages

monitoring changing position of coastlines using thematic mapper imagery an example from the nile delta coastline movement due to erosion and deposition is a major concern for coastal zone management very dynamic coastlines such as sections of the nile delta coast pose considerable hazards to human use and development and rapid replicable techniques are required to update coastline maps of these areas and monitor rates of movement the synoptic capability of landsat thematic mapper imagery enables monitoring of large sections of coastline at relatively coarse 30 m spatial resolution by comparing positions of the nile delta coast in 1984 1987 and 1990 1991 mapped using a region growing image segmentation technique areas of rapid change can be identified and targeted for more detailed monitoring in the field or using higher resolution images rates of erosion and deposition can be estimated crudely and areas where change appears to be accelerating can also be identified areas of severe erosion along the nile delta coast are found to be confined to the promontories of the present day mouths of the nile at rosetta and damietta eroding shorelines are mostly flanked by accreting shorelines showing that some of the eroded material is redistributed along the coast the technique outlined here has potential to augment conventional field based surveying for monitoring shoreline changes over short timescales

updrift river mouth migration on cuspate deltas two examples from the coast of tuscany italy the configuration of the arno and ombrone deltas italy is evaluated the terminal courses of the rivers forming these deltas face the dominant wave orthogonal this configuration came about during rapid delta progradation as a consequence of increased river sediment input due to widespread deforestation within the catchment area a prevailing phenomenon from the early middle ages to the xviii century the rivers attained and maintained their directions as the result of the increased accretion rate on the less exposed downdrift side of the delta on the more exposed updrift side delta growth caused the shoreline to gradually rotate so that it directly faced the waves approaching the coast here due to the lower refraction wave energy per shore unit increased whilst accretion rate decreased this rotation of the shoreline induced longshore inversion on the updrift side whereas today cusp erosion is restoring the original drift direction

nile delta extreme case of sediment entrapment on a delta plain and consequent coastal land loss abstract accelerated erosion of egypt s nile delta coast during this century has generally been attributed to construction of two dams at aswan entrapment of sediment in lake nasser behind the high dam and effects of barrages and river control structures on river nile deposition below aswan also considered important are natural factors including delta subsidence rising sea level and strong coastal current processes this study proposes that more influential in controlling coastal land loss is the near complete entrapment of modern and reworked nile sediment on the nile delta plain sediment is primarily retained in an extremely dense network of irrigation and drain channels and also in wetlands in the northern delta the increased number of artificial canals more than 10 000 km of waterway is a response to egypt s drive to augment its much needed agricultural production by perennial irrigation the drastically reduced amount of sediment now reaching the sea discharged primarily from lagoon outlets and several canal mouths is removed by strong easterly directed coastal and innermost shelf currents the nile delta is an extreme example of a depocenter which has been completely altered by man from an active prograding delta to a locally eroding coastal plain

subsidence in the northeastern nile delta rapid rates possible causes and consequences holocene fluvial and marine deposits have accumulated in a graben like structure on the northeastern margin of the nile delta this part of the delta which includes lake manzala port said and the northern suez canal has subsided rapidly at rates of up to 0 5 centimeter per year since about 7500 years ago this subsidence has diverted at last four major distributaries of the nile river into this region the combined effects of continued subsidence and sea level rise may flood a large part of the northern delta plain by as much as 1 meter by the year 2100 the impact of continued subsidence now occurring when sediment input along the coast has been sharply reduced because of the aswan high dam is likely to be substantial particularly in the port said area and as far inland as south of lake manzala

spatial and temporal shoreline changes of the southern yellow river huanghe delta in 1976 2016 abstract in this study 364 landsat satellite images were utilized to study the spatial and temporal shoreline changes of the southern yellow river delta in 1976 2016 and a new method revised and improved after zhang et al 2016 was proposed by employing that method the calculated sea levels calculated from simulated tidal heights and instantaneous shoreline positions rather than simulated tidal heights were used to correct fluctuations in instantaneous shoreline positions caused by tidal height and seasonal sea level changes and other random sea level fluctuations when calculating the shoreline erosion rates and beach slopes a statistical analysis of a large number of corrected shoreline positions was used to reduce the influence of random errors that were mainly caused by waves and other casual factors the shoreline erosion rates and beach slopes presented in this paper are therefore more precise and reliable than those derived in previous studies which only used two satellite images the results of this study show that the shoreline of the southern yellow river delta primarily experienced gradual erosion during 1976 2016 with an average erosion rate of 26 9 m year the average shoreline erosion rate increased from 24 9 m year in 1976 1996 to 34 9 m year in 1996 2016 an increase of 40 probably due to the reduction in sediment discharge and shifting northward course of the yellow river after 1996 the shoreline erosion rate of the central coast decreased from 50 2 m year in 1976 1996 to 27 1 m year in 1996 2016 a decrease of 46 probably due to the protection offered by coastal hard structures the average shoreline erosion rate caused by relative sea level rise was 8 5 m year or 32 of the total average shoreline erosion rate relative sea level rise plays an important role in the erosion of the southern yellow river delta due to its flat beach the beach slope of the southern yellow river delta was flat and stable in 1976 2016 and the average slope over most of the beach was 0 043

the dramatic changes and anthropogenic causes of erosion and deposition in the lower yellow huanghe river since 1952 the yellow river has been considerably altered over the past half century from human activities these perturbations provide a rare opportunity to document how this natural system has responded to anthropogenic impacts on channel hydrodynamics using a six decade record data set i analyze and summarize changing patterns in erosion and sedimentation of a downstream channel with three units km 3 y gt y and cm y and the response to human impacts upstream the changing pattern of channel bed erosion and deposition in the lower reach during 1952 2007 is divided into five phases in terms of erosion and deposition rates and human activities 1 a rapid and quasi natural deposition phase 1952 1959 0 25 km 3 y or 10 cm y with few main human effects 2 a rapid erosion phase 1960 1964 0 36 km 3 y or 14 cm y in response to heavy sedimentation in the sanmenxia reservoir 3 a rapid deposition phase 1965 1973 0 32 km 3 y or 13 cm y in response to sediment release from the sanmenxia reservoir 4 a moderate erosion and deposition phase with a net deposition 1974 1999 0 10 km 3 y or 4 cm y in response to the sanmenxia reservoir practice of storing clear water and discharging turbid water since 1974 and the intensified soil and water conservation since the 1970s and 5 a slow erosion phase 2000 2007 0 15 km 3 y or 6 cm y in response to the water and sediment regulation and the initial operation of xiaolangdi reservoir the total reduction in sediment delivery by this river is 41 0 gt giga tons during 1959 2007 the sediment delivery reduction are dams and reservoirs 51 soil and water conservation 25 increased water consumption 19 and channel sedimentation 13