environmental controls on decadal morphologic behaviour of the holland coast a detailed comparison of alongshore variation in environmental variables along the holland coast with the observed marked regional differences in decadal nearshore morphologic behaviour reveals that neither offshore hydrodynamic parameters nor grain size are discriminating factors rather the abrupt alongshore changes in decadal behaviour coincide with sharp changes in shoreface morphology and the location of large man made structures these structures such as jetties and a protruding seawall appear to act as artificial headlands once they are built the coastal stretches on either side of the structure can develop independently of each other initially small differences in the development of the regions potentially may evolve into larger differences with time consequently on the long term large man made structures may affect the behaviour of coastal stretches over far larger distances than was previously known

linear evolution of a shoreface nourishment abstract the morphological evolution of a shoreface nourishment is investigated by interpreting the nourishment as a linear perturbation of the natural system the nourishment is projected onto the subset of linear eigenmodes with negative growth rates of the morphodynamical system the evolution of these linear modes then determines the temporal behaviour of the shoreface nourishment the method is presented and results are shown for shoreface nourishments of different length scales on a straight coast and subject to normal incidence shoreface nourishments are represented by their expansions according to the projection method on a 1 50 plane beach profile all nourishments are shown primarily to be diffusive features with long scale nourishments diffusing more slowly than shorter length scale nourishments long scale nourishments also exhibit a shoreward movement during their decay this all indicates that long length scale nourishments may be more beneficial in coastal engineering projects this study is a first step towards nonlinear projection to study shoreface nourishment behaviour

on wind wave current interactions during the shoaling waves experiment 1 this paper presents a case study of wind wave current interaction during the shoaling waves experiment showex surface current fields off duck north carolina were measured by a high frequency ocean surface current radar oscr wind wind stress and directional wave data were obtained from several air sea interaction spar asis buoys moored in the oscr scanning domain at several times during the experiment significant coastal currents entered the experimental area high horizontal shears at the current edge resulted in the waves at the peak of wind sea spectra but not those in the higher frequency equilibrium range being shifted away from the mean wind direction this led to a significant turning of the wind stress vector away from the mean wind direction the interactions presented here have important applications in radar remote sensing and are discussed in the context of recent radar imaging models of the ocean surface

the triassic and jurassic paleogeography and evolution of the qinghai xizang tibet plateau the kunlun qilian and qinling mountains already existed in embryonic form as coastal ranges in triassic times marine conditions predominated to the south the southern coastline is demarcated by the northern margin of the tertiary siwalik sediments the paleo landmass of longmenshan sichuan yunnan separated this sea from that of southwest china by jurassic times the coastline of the eurasian continent within what is now china had already moved southwards to a line along the kunlun and hengduan mountains mainly on the basis of differences between continental and oceanic crust several different seas can be distinguished the himalayan lhasa qiangtang hengduan and triangle seas together with the qaidam peninsula and xining bay triassic and jurassic transgressions and regressions of these seas are discussed in detail during carboniferous and permian times the lhasa and himalayan seas were joined together with the main gondwana plate to the south in triassic times when the india pakistan subconti

a survey of the jurassic system of china terrestrial jurassic rocks are widespread in china whereas marine jurassic rocks are confined to xizang tibet south qinghai south xinjiang and in limited parts of the sequence to west yunnan guangdong south hunan and east heilongjiang geographically occurrences of jurassic deposits may be divided into three regions and 13 districts i the xizang qinghai region with the south tethyan himalayan north tethyan himalayan lhasa xanza shiquanhe bangon dengqen karakorum tanggula and qamdo districts ii the coastal volcanic region of east china with the guangdong hunan fujian zhejiang heilongjiang and northeast china districts and iii the stable giant basin region of west china with the sichuan yunnan and northwest china districts these regions and districts are described briefly and preliminary biostratigraphic sequences and palaeogeography are presented the upper and lower boundaries of the jurassic system in china are briefly discussed the jurassic seas of china evidently were

morphodynamic response of a two barred beach to a shoreface nourishment abstract the response to a shoreface nourishment of the two bar system at noordwijk the netherlands is analyzed based on a daily data set of time exposure video images collected during about 6 years complemented with topographic and bathymetric surveys the 1 7 mm 3 nourishment implemented as a 3 km alongshore bump seaward of the outer bar migrated more than 300 m onshore in 4 years before losing its integrity furthermore the nourishment interrupted the autonomous seaward migration of both bars for the entire duration of the study period and allaying earlier fears did not intensify the three dimensional patterns in the bars such as the crescentic plan shape and rip channels the nourishment did result in clear head effects on both flanks with the bar becoming discontinuous and the flank section decaying or becoming attached to an offshore located bar while the section of bar landward of the nourishment became attached to a landward located bar this sequence of morphologies is known as bar switching each switching episode took almost one year to complete and can therefore not be ascribed to individual wave events we suspect that shoreface nourishments enhance the possibility of bar switching by creating alongshore variability in the position and depth of the outer bar and in its cross shore migration rate and direction the noordwijk nourishment did not influence the shoreline position as its trend did not undergo distinctive variations after 1998 differences in the response of the noordwijk sandbars to the shoreface nourishment compared with other dutch nourishments are attributed to the location and size volume per unit length of the nourishment with respect to the sandbars and to the median grain size of the nourished material

stratigraphic evolution of a late triassic to early jurassic intracontinental basin in southeastern south china a consequence of flat slab subduction abstract an intracontinental basin formed on a young orogen in south china during the late triassic to early jurassic t3 j1 a 2000 m thick siliciclastic sedimentary succession in the daxi section in northern guangdong province near the depocentre of the basin is correlated with the published zhuyuan section and three other sections the combined daxi zhuyuan sections record a marine influenced deltaic succession of carnian to early toarcian age spanning a period of 55 myr tectonic controls rather than eustasy and climate are interpreted to have played a primary role in the cyclic development of the basin fill four regional scale tectonostratigraphic stages are recognised stage 1 features a retrogradation progradation cycle characterised by increasing then slowly decreasing subsidence rates accompanied by slow to medium sedimentation rates stage 2 is broadly an aggradational cycle with multiple smaller scale retrogradational progradational cycles a complex interplay between moderate subsidence rates high sedimentation rates and eustasy is interpreted for this stage stage 3 represents a retrogradational aggradational progradational cycle during which the impact of global sea level was much reduced this period was characterised by mostly high sedimentation and high subsidence rates but a change to lower subsidence and sedimentation rates took place prior to the intracontinental uplift that inverted the basin stage 4 records continued uplift and the subsequent development of a late jurassic cretaceous basin and range province the temporal spatial evolution of the basin could be best explained by the gravitational pull of a subducted flat slab and its subsequent foundering

sand waves along the dutch coast sand waves defined as longshore wave like movements of the shoreline measured in a horizontal plane are described along several stretches of the shoreline of the netherlands they have a celerity in the order of 50 200 m yr a period of 50 150 years and an amplitude of 30 500 m they are found along the whole dutch shoreline analysis of sand waves shows that the assumed effect of groins might be very small along this shoreline there are indications that groins did not have any long term effect on coastal regression

nonlinear features of internal waves off baja california as observed from the seasat imaging radar the synthetic aperture radar sar on seasat has yielded well defined images of quasi periodic internal waves in the waters on the west side of baja california these waves occur in groupings separated by 15 23 km each group having 2 20 striations with wavelengths of the order of 300 m or longer they appear in water approximately 200 m deep shoreward of several banks at the continental shelf edge whose depths are as shallow as 15 m the wave surface signatures exhibit clear nonlinear features higher than linear group velocities and decreases in wavelength crest length and amplitude toward the rear of the packet environmental data for the area have been examined and these show a well developed mixed layer low winds and vigorous tidal action thus stratification wind speed tidal current and bottom topography apparently combine to establish proper conditions for tidal generation of internal waves the images have been analyzed from the standpoint of nonlinear wave theory and it is shown that the vertical displacement of an isopycnal surface can be estimated from a combination of sar imagery vertical density profiles and simple theoretical expressions numerical examples are given

dunefoot dynamics along the dutch coast the dynamics of the dunefoot along a 160 km portion of the dutch coast has been investigated based on a data set of annual surveys dating back to as early as 1850 the linearly detrended or residual dunefoot positions comprise an alongshore uniform and an alongshore non uniform component the former is expressed as 10 to 15 m of landward retreat along extensive 10 km stretches of coast during years with severe storm surges and as up to 5 m of seaward advance during years without significant storm activity the latter alongshore non uniform component is organized in sandwave like patterns which may have a longevity of decades to up to the duration of the entire data set 150 years their wavelengths vary along the coast from 3 5 to 10 km migration rates are 0 200 m a 1 dunefoot sandwaves are shown to be the shoreward extensions of similar sandwave patterns in the beach position the non uniform dunefoot behaviour constitutes at least 80 per cent of the total residual dunefoot dynamics implying that along the dutch coast residual dunefoot variability is controlled by temporal and spatial variability in beach characteristics and not by storm induced uniform erosion various potential mechanisms causing beach sandwaves are discussed copyright 2002 john wiley sons ltd

nourishing the shoreface observations and hindcasting of the egmond case the netherlands abstract although beach nourishment policy in the netherlands is generally successful in maintaining the 1990 shoreline the efficiency of nourishments at several locations along the north sea coast is unacceptably low these locations are identified as erosion hotspots egmond aan zee is such a hotspot the bathymetric longshore irregularities make this coastal stretch highly susceptible to rip currents and horizontal circulations which transport large volumes of nourished sand to the sea in 1999 an alternative nourishment design was implemented this consisted of a shoreface nourishment at the outer bar at 7 5 m depth combined with a nourishment of the beach behind it high resolution bathymetric surveys carried out with the wesp revealed that the shoreface nourishment resulted in a significant shoreward migration of the outer bar during 1999 2001 after 2 years the system started to return to its natural dynamic equilibrium and lost the positive influence of the shoreface nourishment area shoreward movement of bars and increase of bar height which forms the first defense line of the mainland against the sea and positive contribution to the sand budget which increased as a result of the nourishment after 3 years may 1999 to april 2002 the sediment volume still had an increase of 477 500 m3 45 of the applied sand relative to may 1999 the shoreface nourishment area did not have a direct effect on the beach the shoreface nourishment area probably will have to be maintained to retain the sediment on the beach in the long run in egmond the shoreface nourishment started to disappear before the sediment could reach the beach the time scale of sediment feed to the beach zone probably is of the order of 5 10 years the shoreface nourishment seems to function as a reef creating a lee side effect that influences both cross shore and longshore sediment transport resulting in two main hypotheses firstly the longshore effect in which large waves break at the shoreface nourishment cause a calmer wave climate shoreward of the shoreface nourishment area and a reduction of the longshore current the shoreface nourishment partially blocks the wave driven longshore current secondly the cross shore effect in which shoaling waves generate onshore transport these hypotheses are supported by generated model results with both a process based profile model unibest tc and a process based coastal area model delft3d mor the unibest tc model was able to predict the detachment of the outer bar from the shoreface nourishment and to some extent the shoreward bar movements in the lee of the shoreface nourishment area the model found an increase in sediment confirming the shielding effect of the shoreface nourishment area the delft3d model found as a result of the shoreface nourishment area a decrease of the flow velocity and the wave height just shoreward of the shoreface nourishment area the model was able to predict the similar trend in sedimentation erosion pattern although the intensities were smaller in the lee of the shoreface nourishment area a clear sedimentation was found erosion was found south and seaward of the shoreface nourishment area the modeled profiles did not follow the measured profile changes the separation of the shoreface nourishment from the outer bar and the shoreward migration of the bars could not be accurately modeled because the cross shore transport caused by wave asymmetry is not taken into account in the standard version of delft3d these results were in line with the expectations

analysis of the scale of errors in nearshore bathymetric data most studies of nearshore hydrodynamics sediment transport and morphology focus on bathymetric variability within a narrow band of spatial and temporal scales typically these studies rely on bathymetry estimates derived from field observations consisting of discrete samples in space and time with varying degrees of measurement error sampling limitations which result in aliasing and measurement errors can significantly contaminate variability at resolved scales and may lead to large errors in the representation of the scales of interest using a spectral analysis interpolation errors were analyzed for three different nearshore bathymetric data sets each of which targeted a different range of spatial scales bathymetric features that were unresolved or poorly resolved e g beach cusps introduced the potential for contamination in two of the data sets this contamination was significantly reduced using an appropriate scale controlled interpolation method leading to more accurate representations of the actual bathymetry an additional benefit of using scale controlled interpolation is that interpolation errors may be estimated independently of actual observations which allows one to design bathymetric sampling strategies that ensure that dominant scales are either resolved or largely removed finally interpolation errors corresponding to a particular sample design can be used to determine which interpolated values contribute usefully to a band limited analysis of bathymetric variability

morphodynamic response of nearshore bars to a shoreface nourishment abstract the autonomous nearshore bar behaviour along the barrier island of terschelling the netherlands is characterised by the presence of net seaward cyclic migrating sand bars generated near the shoreline in 1993 a perturbation of the cyclic bar system was introduced by the implementation of a 2 mm 3 shoreface nourishment supplied to the nearshore bar zone filling up the trough between the middle and outer bar the morphodynamic response of the nearshore bars to the nourishment perturbation is investigated using a bathymetric data set with an alongshore extent of 12 km and sampled for 10 years bar behaviour is quantified in terms of bar crest position in relation to morphometric parameters such as bar depth height width and volume along with a pronounced development of a three dimensional bar system unseen in the autonomous behaviour the nearshore bars exhibited a 6 7 year arrest in their migrational behaviour during which bar morphology remained stable at immediate pre nourishment morphometric values at the subsequent onset of bar movement bars resumed their migration at a rate predicted by autonomous behaviour in parallel development with morphometric parameters along their predicted trends it is shown that the observed onshore transport of nourished sediment in the 6 7 year arrest results from a gradual deepening of troughs cross shore sediment transport modelling is used to assess the effect of the nourishment on yearly averaged onshore short wave nonlinearity and offshore undertow sediment transport rates the gradual reappearance of the pre nourishment bar trough morphology is shown to engender a normalisation in the cross shore distribution of sediment transport rates to pre nourishment rates

alongshore variability of the multiple barred coast of terschelling the netherlands abstract the alongshore variability of the behaviour of a multiple bar system in the nearshore zone along the barrier island of terschelling the netherlands is investigated using a bathymetric data set with an alongshore extent of 12 km sampled annually for 28 yr the spatial and temporal variability of bar behaviour is quantified in terms of bar crest position in relation to morphometric parameters such as bar depth height width and volume along the entire study area the bars were generated close to the shore migrated seaward and eventually degenerated at the outer margin of the nearshore the interannual migrational patterns of the nearshore sandbars are analysed in terms of time of residence migration rates and return periods within the life cycle of a bar the cross shore nearshore bar behaviour was found to vary alongshore for instance cross shore migration rates gradually increased from 35 to 70 m yr from one end of the study area to the other concurrently the duration of net seaward migration increased from 9 to 15 yr the return period and total life span of bars were however found to be alongshore uniform on the order of 10 12 yr and 22 yr respectively morphological characteristics of the nearshore bar zone such as slope and width also exhibit gradually alongshore varying patterns a strong causal association is established between nearshore slope and both bar migration rates and duration of net seaward migration it is hypothesised that alongshore increasing wave heights at the seaward end of the bar zone is coupled with a corresponding increase in nearshore slope the presence of an important updrift ebb tidal shoal is identified as key controlling factor in the variability of bar behaviour along the adjacent shoreline of terschelling

on the determination of characteristics of the interior ocean dynamics from radar signatures of internal solitary waves in this paper we discuss two different methods of inferring characteristics of the interior ocean dynamics from radar signatures of internal solitary waves visible on synthetic aperture radar sar images the first one consists in the recognition and the interpretation of sea surface patterns of internal solitary waves the second one consists in the analysis of the modulation depth of the normalized radar backscattering cross section nrcs associated with internal solitary waves for this purpose we consider a data set composed of sar and in situ measurements carried out from 1991 to 1997 in the region of the strait of messina the recognition and the interpretation of sea surface patterns of internal solitary waves in the strait of messina can be used to study characteristics of the density distribution in the area the internal wave field varies with seasonal variations in the vertical density stratification and with remotely induced variations i e variations induced by the larger scale circulation in the horizontal density distribution in order to inquire into the possibility of inferring parameters of the interior ocean dynamics by analyzing the modulation of the nrcs associated with internal solitary waves several numerical simulations are carried out using a radar imaging model these simulations are performed by assuming different wind conditions and internal wave parameters it is shown that an accurate knowledge of wind conditions is crucial for deriving internal wave parameters and hence parameters of the interior ocean dynamics from the modulation of measured nrcs associated with internal solitary waves

the late jurassic oblique collisional orogen of sw japan new structural data and synthesis the structural configuration of sw japan mainly reflects a late jurassic early cretaceous orogeny the region is divided into an inner belt and an outer belt on the japan sea and pacific ocean sides respectively by a strike slip fault the median tectonic line mtl both consist of a series of stacked nappes the inner belt is divided into a jurassic olistostrome known as the tanba zone and a hinterland area comprising continental triassic jurassic sediments the tanba zone is sliced into two units a lower one with late jurassic matrix and triassic early jurassic radiolarite olistoliths tectonically overthrust by an upper unit comprising an olistostrome with middle jurassic matrix and blocks which include late paleozoic limestone basic lava and radiolarite the tanba zone is overthrust by a paleozoic nappe complex derived from the hinterland the basal sole of the nappe corresponds to a peculiar unit called the ultra tanba zone in the chugoku area the hinterland is divided into an upper nappe the oga nappe formed by permo carboniferous limestone and permian clastic rocks and a lower one the sangun maizuru nappe formed by paleozoic high pressure hp metamorphics the sangun schists the permian maizuru olistostrome and the dismembered paleozoic yakuno ophiolites in the northern part of sw japan the tanba zone is in faulted contact with the circum hida and the hida zones the former is interpreted as the equivalent of the oga and sangun maizuru nappes of the chugoku domain crushed by post cretaceous tectonics the latter consists of paleozoic high temperature ht metamorphic rocks and late triassic early jurassic granite locally mylonitized and covered by early jurassic sandstone the outer belt is formed by a superficial nappe similar to the tanba zone thrust upon a deep domain characterized by a synmetamorphic ductile deformation the deep domain is divided into a lower unit the oboke unit formed by continental derived arenites and a green schist nappe consisting of oceanic sediments and resedimented ophiolites the green schist nappe overthrusts the oboke unit under synmetamorphic conditions with an eastward displacement the two belts are separated by the ryoke zone which corresponds to the southern part of the tanba zone affected by a cretaceous ht metamorphism and sharply cut by the mtl a geodynamic model is proposed for the jurassic orogeny of sw japan assuming that the evolution of the inner and outer belts are linked in the late triassic early jurassic sw japan is an active plate margin the upper plate or south china block consisted of the hinterland and the tanba belt a forearc basin the lower plate consisted of an oceanic area and the south japan continent the basic mechanism of the orogeny is ascribed to the oblique subduction and collision of the south japan continent