onset of scour below pipelines and self burial abstract this paper summarizes the results of an experimental study on the onset of scour below and self burial of pipelines in currents waves pressure was measured on the surface of a slightly buried pipe at two points one at the upstream side and the other at the downstream side of the pipe both in the sand bed the latter enabled the pressure gradient which drives a seepage flow underneath the pipe to be calculated the results indicated that the excessive seepage flow and the resulting piping are the major factor to cause the onset of scour below the pipeline the onset of scour occurred always locally but not along the length of the pipeline as a two dimensional process the critical condition corresponding to the onset of scour was determined both in the case of currents and in the case of waves once the scour breaks out it will propagate along the length of the pipeline scour holes being interrupted with stretches of soil span shoulders supporting the pipeline as the span shoulder gets shorter and shorter more and more weight of the pipeline is exerted on the soil in this process a critical point is reached where the bearing capacity of the soil is exceeded general shear failure at this point the pipe begins to sink at the span shoulder self burial it was found that the self burial depth is governed mainly by the keulegan carpenter number the time scale of the self burial process on the other hand is governed by the keulegan carpenter number and the shields parameter diagrams are given for the self burial depth and the time scale of the self burial process

a review of the superior province of the canadian shield a product of archean accretion abstract the superior province consists of northern and southern high grade gneiss subprovinces and a central region of alternating granite greenstone and metasedimentary belts subprovinces are commonly fault bounded and display contrasting lithological assemblages metamorphic and structural styles geophysical characteristics and ages they are comparable to phanerozoic suspect terranes the middle and late archean rocks of the superior province are of mantle and juvenile crustal origin with little evidence of inheritance of components older than ca 3 1 ga high grade gneiss subprovinces are mainly deeper level equivalents of the supracrustal rich belts but one minnesota river valley is part of an older ca 3 6 ga terrane that was juxtaposed late in the tectonic history granite greenstone terranes are characterized by low grade volcano sedimentary sequences tholeiitic komatiitic submarine lava plain tholeiitic calc alkalic submarine to subaerial central complexes early platform type quartz arenite stromatolitic carbonate late timiskaming type shoshonitic alkalic volcanic fluvial sediment that range in age from ca 3 0 ga to 2 7 ga the volcanics represent oceanic island arc and continental arc volcanism the quartz arenite carbonate sequences deposition on relatively stable early formed ca 3 0 ga crust and the timiskaming type sequences deposition in pull apart basins developed along strike slip faults late archean ca 2 75 2 70 ga greenstone sequences occur throughout the superior province middle archean ca 3 0 2 8 ga sequences are common in northern and central superior province rare or absent in the south volcanism was accompanied by mafic to trondhjemitic plutonism the metasedimentary belts consist of variably metamorphosed volcanogenic turbidites with detrital zircons ranging in age from ca 3 0 ga to 2 7 ga the metasediments were deposited after major volcanism and probably represent accretionary prisms late archean orogenesis accompanied and followed by calc alkalic plutonism youngs southward from about 2 73 2 72 ga to 2 70 2 68 ga it involved large scale north south compression and dextral transpression and displays thin to thick skinned transitions the contemporaneity of events along the lengths of the belts and their southward younging coupled with the evidence of major compression are consistent with subduction driven oblique accretion of oceanic and continental volcanic arcs accretionary sedimentary wedges older microcontinental fragments etc in a convergent margin setting analogous to parts of the pacific rim differences eg abundance of komatiites and tonalitic plutonic suites are attributable to a hotter archean mantle

comment on evidence for the biotic origin of seabed pockmarks on the australian continental shelf by r j mueller marine and petroleum geology 2015 doi 10 1016 j marpetgeo 2014 12 016 abstract the study of seabed depressions that may be related to fluid seepage requires a multi layer approach the application of a one hypothesis fits all approach to understanding seabed characteristics fails to critically assess information necessary to undertake a robust assessment here we contend that the broad brush approach assigning pockmark formation on the northwest shelf of australia to a single organism is insufficiently robust to assign a reliable interpretation of pockmark formation in this setting

physical volcanology of the submarine mariana and volcano arcs narrow beam maps selected dredge samplings and surveys of the mariana and volcano arcs identify 42 submarine volcanos observed activity and sample characteristics indicate 22 of these to be active or dormant edifices in the volcano arc are larger than most of the mariana arc edifices more irregularly shaped with numerous subsidiary cones and regularly spaced at 50 70 km volcanos in the mariana arc tend to be simple cones sets of individual cones and volcanic ridges are elongate parallel to the trend of the arc or at 110 counterclockwise from that trend suggesting a strong fault control on the distribution of arc magmas volcanos in the mariana arc are generally developed west of the frontal arc ridge on rifted frontal arc crust or new back arc basin crust volcanos in the central mariana arc are usually subaerial large 500 km3 and spaced about 50 70 km apart those in the northern and southern marianas are largely submarine closer together and generally less than 500 km3 in volume there is a shoaling of the arc basement around iwo jima accompanied by the appearance of incompatible element enriched lavas with alkalic affinities the larger volcanic edifices must reflect either a higher magma supply rate or a greater age for the larger volcanos if the magma supply estimated at 10 20 km3 km of arc per million years at 18 n has been relatively constant along the mariana arc we can infer a possible evolutionary sequence for arc volcanos from small irregularly spaced edifices to large over 1000 km3 edifices spaced at 50 70 km the volcano distribution and basal depths are consistent with the hypothesis of back arc propagation into the volcano arc

diapirism during regional compression the structural pattern in the chibougamau region of the archean abitibi belt quebec the major fold pattern of the chibougamau region in the archean abitibi belt quebec is the result of two fold phases the principal f1 synclines first formed as subsiding fault troughs and were shortened in ns direction and molded around volcanic centers that had been consolidated by large synvolcanic plutons they have a general easterly direction but curve locally to the ne or se n trending f1 folds are locally present in the anticlinoria and are thought to have been produced by the upwelling of basement gneiss and or synvolcanic plutons the f2 folds have rather regular easterly trends their axial plane schistosity s2 is the predominant planar fabric element basin margin faults were transformed into east trending thrust faults during the f1 and f2 folding

sedimentation induced burial of subsea pipelines observations from field data and laboratory experiments abstract sediment transport induced changes to the embedment of three 26 km long sections of subsea pipeline are analysed and subsequently explained using model scale experiments rather than the scour and scour induced sinking and sagging traditionally thought to dominate post lay pipeline spanning and embedment change the change for these pipelines is shown to be caused by sedimentation the pipelines traverse a range of metocean and soil conditions the variation in embedment correlates well with the variation in metocean conditions with most change occurring in an area where multidirectional high velocity short duration flows associated with internal waves propagate at near perpendicular angles to the pipeline to understand the mechanism driving these changes a series of model scale tests in o tube flumes have been completed under flow conditions mimicking those recorded in the field good agreement is found between the field and laboratory results both in terms of the process timescale and the post sedimentation profile the consistency of the embedment changes between the pipelines their correlation with metocean conditions and the ability to replicate these changes in model scale tests suggests that such changes can be accounted for in more effective pipeline design spans are relatively rare along the pipelines but where they do occur fish rather than scour are shown to be the principal agent of span formation

internal tidal mixing as a control on continental margin ecosystems we show that a breaking internal tide at a shelf edge is a fundamental control on the structural and functional properties of ecosystems contrasts in vertical mixing of nitrate between the shelf and the open ocean correspond with horizontal and vertical changes in phytoplankton communities with largest cells found in surface waters at the shelf edge intense fishing activity is commonly seen at continental shelf edges targeting spawning fish stocks we suggest that the internal tide a globally ubiquitous physical process at steep shelf edge bathymetry supports shelf edge fisheries by providing large celled phytoplankton for first feeding fish larvae the repeatability of the internal tide removes fish from the need to time spawning with a spring bloom also with large phytoplankton cells dominating particulate organic carbon export the internal tides could be an important influence on spatial and temporal variability in patterns of global carbon sequestration in deep water and sediments citation sharples j c m moore a e hickman p m holligan j f tweddle m r palmer and j h simpson 2009 internal tidal mixing as a control on continental margin ecosystems geophys res lett 36 l23603 doi 10 1029 2009gl040683

plate tectonics and island arcs the plate tectonic concepts that developed rapidly in the late l960s made possible the understanding of island arcs before that time mobilistic concepts evolved slowly hindered particularly in the united states by an obstructionist geoscience establishment the volcanic belts of island arcs form about 100 km above subducting plates convergent plate boundaries evolve complexly with time and at any one time vary greatly along their lengths seismicity defines positions but not trajectories of descending slabs which sink more steeply than they dip and are overridden by advancing upper plates subduction occurs beneath only one side at a time of an internally rigid plate and the common regime in an overriding plate behind a surficial accretionary wedge is extensional except where a collision is underway back arc basin lithosphere is built behind or by migrating island arcs which lengthen and increase their curvatures a collision can involve two active arcs in which case intervening lithosphere sinks beneath both of them or an active margin and a passive one either type of collision generally is followed by the breaking through of new subduction beneath the composite mass of light crust from a new trench on the outside of the aggregate conversely a new subduction system commonly is a by product of collision a strip of back arc basin crust is in many cases left attached to the aggregate in front of the new trench and becomes the basement for a fore arc basin the leading edge of which is raised as melange is stuffed under it sedimentation in trenches is predominantly longitudinal and can be from distant sources accretionary wedges are dynamic being thickened at both toes and bottoms by tectonic accretion and thinned by gravitational forward flow melange is largely a product of tectonic imbrication and flowage driven by these conflicting processes not of submarine sliding high pressure metamorphic rocks form beneath overriding plates not within wedges in front of them arc magmas incorporate much material from the lithosphere through which they rise and vary correspondingly with the evolving composition of that lithosphere arc crust is inflated into geanticlines by intrusive rocks and thermal expansion submarine island arc volcanic rocks are widely spilitized with na enrichment and ca depletion by hydrothermal reaction with sea water the lower crust of mature island arcs consists of granulite facies rocks of mafic intermediate and felsic intermediate compositions the mohorovicic discontinuity may be primarily a constructional boundary representing the shallow limit off crystallization of voluminous rocks of ultramafic composition or plagioclase free mineralogy

generalized time scale for wave induced backfilling beneath submarine pipelines abstract this paper presents 25 new laboratory experiments involving the wave induced backfilling of wave induced scour holes beneath submarine pipelines so called wave to wave backfilling scenarios the experiments complement the previous 8 wave to wave backfilling experiments of fredsoe et al as well as recent current to wave backfilling experiments of bayraktar et al it is found that the wave induced backfilling time scale is generally an order of magnitude larger than for scour and is relatively insensitive to the initial current or wave induced pre backfilling scour profile based on this the data sets involving wave induced backfilling are collectively analyzed resulting in a new generalized expression for estimating the wave induced backfilling time scale beneath pipelines in the live bed regime this expression accounts for primary dependence on the shields parameter as well as secondary dependence based on the difference between the estimated or known initial and expected final equilibrium scour depth due to the backfilling wave condition

the tectonic evolution of the abitibi greenstone belt of canada based on structural geochemical sedimentological and geochronological studies we have formulated a model for the evolution of the late archaean abitibi greenstone belt of the superior province of canada the southern volcanic zone svz of the belt is dominated by komatiitic to tholeiitic volcanic plateaux and large bimodal mafic felsic volcanic centres these volcanic rocks were erupted between approximately 2710 ma and 2700 ma in a series of rift basins formed as a result of wrench fault tectonics the svz superimposes an older volcanic terrane which is characterized in the northern volcanic zone nvz of the abitibi belt and is approximately 2720 ma or older the nvz comprises basaltic to andesitic and dacitic subaqueous massive volcanics which are cored by comagmatic sill complexes and layered mafic anorthositic plutonic complexes these volcanics are overlain by felsic pyroclastic rocks that were comagmatic with the emplacement of tonalitic plutons at 2717 2 ma the tectonic model envisages the svz to have formed in a series of rift basins which dissected an earlier formed volcanic arc the nvz analogous rift environments have been postulated for the hokuroko basin of japan the taupo volcanic zone of new zealand and the sumatra and nicaragua arcs the difference between rift related submergent volcanism in the svz and emergent volcanism in the nvz resulted in the contrasting metallogenic styles the former being characterized by syngenetic massive sulphide deposits whilst the latter was dominated by epigenetic porphyry type cu au deposits

evidence for the biotic origin of seabed pockmarks on the australian continental shelf abstract the generally accepted formation mechanism of pockmarks worldwide is the expulsion of fluid at the seafloor but such a mechanism does not explain the close association between pockmarks and seabed infrastructure such as pipelines and wellheads within the stag oil field on the north west shelf of australia furthermore certain characteristics of the pockmarks such as conical mounds of sediment positioned around their perimeters are strongly suggestive of a biotic origin pockmarks in this case are typically 5 m in diameter and 1 m deep excavated within a sandy seabed in 45 m water depth inspection of rov footage acquired during oilfield operations within the stag field supports but does not entirely confirm without doubt the proposition that the pockmarks are created by fish of the genus epinephelus having determined the characteristic features of pockmarks within the stag field which mark them as biotic excavations data from commercial seabed surveys at 11 other sites on the north west shelf all of which reveal numerous pockmarks was reviewed for evidence of similar pockmark characteristics based on the review it appears likely that the majority of pockmarks on the shallow north west shelf between 40 m and 130 m water depth are representative of biological rather than geological activity the probability that pockmarks less than approximately 10 m in diameter throughout the remainder of the australian continental shelf are also the result of purely biological activity is high as demonstrated by the analysis of data from three further sites close inspection of seabed survey data from further afield could extend the findings of this paper throughout not only the tropical indo west pacific the range of the particular fish species implicated on the north west shelf but potentially worldwide if other species can be shown to display similar behaviour

differences between spontaneous and triggered earthquakes their influences on foreshock probabilities 1 in this study we investigate the foreshock probabilities calculated from earthquake catalogs from japan southern california and new zealand unlike conventional studies on foreshocks we use a probability based declustering method to separate each catalog into stochastic versions of family trees such that each event is classified as either having been triggered by a preceding event or being a spontaneous event the probabilities are determined from parameters that provide the best fit of the real catalogue using a space time epidemic type aftershock sequence etas model the model assumes that background and triggered earthquakes have the same magnitude dependent triggering capability a foreshock here is defined as a spontaneous event that has one or more larger descendants and a triggered foreshock is a triggered event that has one or more larger descendants the proportion of foreshocks in spontaneous events of each catalog is found to be lower than the proportion of triggered foreshocks in triggered events one possibility is that this is due to different triggering productivity in spontaneous versus triggered events i e a triggered event triggers more children than a spontaneous events of the same magnitude however further analysis on simulated data shows that such difference might be caused by the events triggered by smaller events below the magnitude threshold of the catalog even if the physical interpretation is unclear a clustering model where spontaneous events and triggered events have different triggering behaviors can be used to assess the risk of foreshocks and to avoid overpredicting

felsic fire fountaining beneath archean seas pyroclastic deposits of the 2730 ma hunter mine group quebec canada abstract the lapilli tuff breccias ltb 1 and ltb 2 of the archean hunter mine group in the south central part of the abitibi greenstone belt are inferred to be the product of subaqueous lava fountaining intercalated sub wave base iron formations interstratified turbiditic tuffs the absence of wave induced sedimentary structures and the stratigraphic position of lapilli tuff breccias beneath basaltic komatiites support this contention a complete eruptive sequence shows a tripartite division into a massive breccia b stratified lapilli tuff and c turbiditic tuff lapilli tuff division the massive breccia division is characterized by clusters of isolated and compressed irregular shaped clasts inferred to be deposited directly from the hot magmatic lava fountain abundant vesicular pyroclasts with a vesicle content of up to 60 exhibit locally coalescing vesicles indicating bubble nucleation prior to eruption the prevalence of irregular to amoeboid clast shapes suggests transport from the vent in a steamy rich high density current to the site under a self generated steam cupola ubiquitous subequant lapilli size pyroclasts of the stratified lapilli tuff division suggest that significant ingress of water into the fountain changed the prevalent fragmentation process from magmatic to hydrovolcanic the turbiditic tuff lapilli tuff division composed of pumice lithic fragments and vitric ash is envisaged to have formed by gravitational collapse of a subaqueous turbulent eruptive plume this type of eruptive mechanism constituted a minor but important process of volcanic construction on the ocean floor during the archean and possibly during incipient arc and backarc formation in modern day settings

a three dimensional perspective on the evolution of archaean crust lithoprobe seismic reflection images in the southwestern superior province in 1990 1991 the lithoprobe project completed 450 km of seismic reflection profiles across the late archaean crust of the southwestern superior province the results define a broad three fold division of crust upper crust in the abitibi greenstone belt is non reflective and is a 6 8 km veneer of volcanic and plutonic supracrustal rocks whereas in the sediment gneiss dominated pontiac subprovince upper crust comprises shallow northwest dipping turbidite sequences mid crust in both the abitibi and the pontiac subprovinces is interpreted as imbricate sequences of metasedimentary and metaplutonic rocks lower crust in both subprovinces has a horizontal layer parallel strycture which may represent interleaved mafic intermediate gneisses the seismic signature of the northern abitibi greenstone belt may be represented in an exposed 25 km crustal section in the kapuskasing stuctural zone preliminary tectonic models based on the seismic data are consistent with a plate tectonic scenario involving oblique subduction and imbrication of sedimentary plutonic and volcanic sequences the northern abitibi supracrustal sequences either represent an allochthon or overlie an allochthonous underthrust metasedimentary and plutonic sequence which may be equivalent to a metasedimentary subprovince such as the pontiac or quetico seismic velocities have yet to be defined however crustal thicknesses are relatively constant at 35 40 km the thinnest crust is adjacent to the grenville front where moho is very well defined

experimental and numerical study of wave induced backfilling beneath submarine pipelines abstract this paper presents results of complementary experimental and numerical studies involving wave induced backfilling of current generated scour holes beneath submarine pipelines the laboratory experiments are conducted in a wave plus current flume utilizing laser doppler anemometry to measure velocities synchronized flow visualizations using digital image technology along with live bed scour and backfilling measurements each experiment is based on a two stage process 1 initial scour induced by a pure current followed by 2 backfilling induced by pure waves either regular or irregular the time series of scour depths are closely monitored through video recordings systematic analysis of these has resulted in a closed form expression for the backfilling time scale which is demonstrated to be a full order of magnitude greater than the well known time scale of scour with both governed primarily by the shields parameter the developed expression is strictly valid for the current to wave backfilling scenarios considered while likely serving as an upper limit for more general wave induced backfilling circumstances the experiments are complemented by similar backfilling simulations utilizing a fully coupled hydrodynamic and morphodynamic cfd model the numerical simulations demonstrate the ability of the model to predict backfilling towards expected equilibrium scour depths based on the new wave climate with time scales reasonably in line with experimental expectations

a new facility for studying ocean structure seabed interactions the o tube abstract this paper describes a unique new physical testing facility for studying ocean structure seabed interactions and in particular pipeline on bottom stability on erodible seabed under hydrodynamic loading the facility named the o tube due to its shape is a fully enclosed flume in which ambient and storm induced near seabed flows are generated by a computer controlled flow pump combined steady and oscillatory flow can be generated by alternating pump flow directions in a controlled manner and computer control also allows irregular flow to be generated the design of the o tube combines the capabilities of a conventional open channel flume which provides steady current with a u tube which provides oscillatory flow the facility is designed to physically model severe storm conditions as well as ambient or tidal flows when studying pipeline stability on erodible seabed under severe hydrodynamic loading conditions tests can be performed at a relatively large scale typically 1 5 for large diameter pipelines e g 40 in gas trunklines and at full scale for small diameter pipelines

tectonic evolution of the northern volcanic zone abitibi belt quebec the archean abitibi subprovince has been divided formally into a northern volcanic zone nvz including the entire northern part of the subprovince and a southern volcanic zone svz on the basis of distinct volcano sedimentary successions related plutonic suites and precise u pb age determinations the nvz has been further formally subdivided into i a monocyclic volcanic segment mvs composed of an extensive subaqueous basalt plain with scattered felsic volcanic complexes 2730 2725 ma interstratified with or overlain by linear volcaniclastic sedimentary basins and ii a polycyclic volcanic segment pvs comprising a second mafic felsic volcanic cycle 2722 2711 ma and a sedimentary assemblage with local shoshonitic volcanic rocks a sequence of deformational events d1 d6 over a period of 25 ma in the nvz is consistent with a major compressional event north south shortening was first accommodated by near vertical east trending folds and with continued deformation was concentrated along ma

lifelong embedment and spanning of a pipeline on a mobile seabed abstract seven years of field survey measurements of a subsea pipeline obtained using sonar profilers and underwater video indicate significant lowering of the pipeline into the seabed due to sediment mobility and scour the majority of the lowering occurs within 2 years of pipeline laying and appears to result from sustained ambient tidal and soliton currents as opposed to large storms the lowering results in an increase in pipeline embedment relative to the far field seabed of up to 0 8 times the pipe diameter referenced at a distance 8 d from the pipeline at most locations along the pipeline this increase in far field embedment is uniform and occurs after the formation of many closely spaced scour holes this suggests that the pipeline lowered mainly through sinking into the seabed at span shoulders rather than sagging into widely spaced scour holes for much of the pipeline length a beam bending analysis confirmed the dominance of sinking but did show some evidence of pipeline sagging calculating deflections of up to 0 3 pipeline diameters at the time of surveying in contrast to the traditional conception of span growth and self burial which conceives of complete pipeline burial as an endpoint this pipeline primarily appears to exhibit self lowering towards a mature state that consists of a pseudo static profile of alternating spanning and embedded sections that are distributed at regular intervals the observed changes appear to be predictable given sufficient pipeline setting data which suggests that they can be quantified in the stability design of new pipelines this opens up the possibility of more efficient on bottom stability design as the beneficial shielding and support provided by the self lowering process is not usually accounted for

sediment transport and trench development beneath a cylinder oscillating normal to a sandy seabed abstract the purpose of this study is to explore the conditions in which trenches form beneath oscillating cylinders such as pipelines cables or idealised chains close to the seabed experiments are conducted by oscillating a circular cylinder in a direction normal to an initially flat sandy bed across a relatively wide parameter space the transport patterns and trench geometries reveal three transport regimes that are linked to vortex dynamics and depend primarily on the ratio of oscillation amplitude to cylinder diameter k c number for k c 4 sediment motion results in bedload transport that is symmetric about the cylinder centreline this leads to the formation of two parallel trenches with a prominent ridge forming directly beneath the cylinder for 4 k c 9 sediment motion occurs via localised transport events which are associated with the motion of vortices shed from the cylinder these transport events are irregular but occur on both sides of the cylinder and lead to the formation of a symmetric trench geometry for 9 k c 12 the sediment motion is characterised by localised transport events and asymmetric bedload transport driven by overall vortex dynamics in terms of trench size the maximum equilibrium depth is found to increase with k c and a mobility number defined in terms of the maximum cylinder velocity the initial rate of trench development also increases with k c number and with an additional dependency on the cylinder number the cylinder motions required to initiate trenching are predicted well using continuity arguments and an oscillatory boundary layer assumption provided the k c number and minimum gap between the cylinder and the bed are relatively small the findings in this study provide insight into the mechanisms and prediction of trench formation in particular this study reveals that significant trenches can form in sandy seabeds solely due to fluid flow induced by pipeline cable chain motion without direct seabed contact which has implications for structural fatigue

paleogeographic and paleotectonic evolution of a basement controlled archean supracrustal sequence chibougamau caopatina quebec the 7 14 km thick archean volcano sedimentary sequence in the chibougamau caopatina region ccr composed of two mafic to felsic cycles and two thick essentially epiclastic successions is divided into a southern caopatina segment scs and northern chibougamau segment ncs the sedimentary units which evolved after cycle 1 volcanic rocks in the scs and after the combined cycles 1 and 2 in the ncs document a diachronous sedimentary basin evolution this criterion has been employed to distinguish an early evolutionary stage in the south and a late evolutionary stage in the north in each segment the basin episode represents a unique extensional event volcanism preceded the major sedimentary rifting event in both segments composition of sediments and sedimentary facies correlated with the interpreted basin margin faults support the interpretation of two phases of crustal extension volcanic construction and sill intrusion were the prevalent factors governing emergence of volcanic islands in the cc

numerical simulation of wave induced scour and backfilling processes beneath submarine pipelines abstract a fully coupled hydrodynamic morphodynamic numerical model is presented and utilized for the simulation of wave induced scour and backfilling processes beneath submarine pipelines the model is based on solutions to reynolds averaged navier stokes equations coupled with k turbulence closure with additional bed and suspended load descriptions forming the basis for sea bed morphology the morphological evolution is updated continuously rather than being based e g on period or other time averaging techniques simulations involving wave induced scour over the range of keulegan carpenter number 5 6 kc 30 demonstrate reasonable match with previous experiments both in terms of the equilibrium scour depth as well as the scour time scale wave induced backfilling processes are additionally studied by subjecting initial conditions taken from scour simulations with larger kc to new wave climates characterized by lower kc values the simulations considered demonstrate the ability of the model to predict backfilling toward expected equilibrium scour depths based on the new wave climate in line with experimental expectations the simulated backfilling process is characterized by two stages 1 an initial re distribution phase involving re organization of sediments in the immediate vicinity of the pipeline potentially followed by 2 a more lengthy backfilling evolution toward equilibrium scour depth the simulated backfilling time scales are of the same order of magnitude as in experiments though the multi stage process complicates a more systematic characterization the simulated sequences of scour and backfilling achieved within the present work are estimated to represent temporal durations of up to approximately 12 h at full practical scales