site investigations to evaluate flow liquefaction slides at sand heads fraser river delta l ecoulement par liquefaction spontanee est un processus recurrent dans la progradation du delta du fleuve fraser une portion du delta a ete etudiee au moyen d essais de penetration au cone sismique et de resistivite et au moyen de l analyse spectrale de la methode des ondes de surface et de l echantiollonage de sol et de vapeur dans un effort pour determiner la stratigraphie du site l etat in situ et le degre de saturation afin explorer l enigme de l ecoulement par liquefaction spontanee un ensemble de capteur de pression interstitielle et d inclinaison a ete installe comme partie de l etude pour mesurer les effets de la vidange resultant du reflux de la maree les resultats ont indique que le lit de la mer a faible profondeur etait partiellement sature contenant un volume significatif de gaz methane qui affectait la reponse dynamique de la pression interstitielle durant le jusant une reduction de la contrainte effective atteignant 16 5 kpa a ete mesuree de meme qu un delai de 50 min entre le reflux de la maree et la reaction de la pression interstitielle ceci suggere que les effets de tampon sont un facteur significatif dans le declenchement de la liquefaction spontanee des sables l ches non viellis la ou ils reposent sur des pentes sous marines les resultats des essais in situ montrent que les sables nouvellement deposes du fleuve fraser ont une forte susceptibilite a l ecoulement par liquefaction

towards a protocol for laser scanning in fluvial geomorphology advances in spatial analytical software allow digital elevation models dems to be produced which accurately represent landform surface variability and offer an important opportunity to measure and monitor morphological change and sediment transfer across a variety of spatial scales many of the techniques presently employed aerial lidar edm theodolites gps photogrammetry suffer coverage or resolution limitations resulting in a trade off between spatial coverage and morphologic detail captured this issue is particularly important when rates of spatial and temporal change are considered for fluvial systems this paper describes the field and processing techniques required for oblique laser scanning to acquire 0 01 m resolution digital elevation data of an upland reach of the river wharfe in the uk the study site is variable with rapidly changing morphology diverse vegetation and the presence of water and these are evaluated with respect to laser data accuracy scan location frequency and distance are discussed with reference to survey accuracy and efficiency and a field protocol is proposed scan data cloud merging was achieved with a high degree of precision sub centimetre and positional data are shown to be very accurate for exposed surfaces vegetation and water decrease the accuracy as the laser pulse is often prevented from reaching the ground surface or is not returned copyright 2006 john wiley sons ltd

channel and floodplain response to recent abrupt climate change the tyne basin northern england this paper examines the timing nature and magnitude of river response in upland piedmont and lowland reaches of the tyne basin northern england to high frequency 20 30 year changes in climate and flood regime since 1700 ad over this period fluvial activity has been characterized by alternating phases of river bed incision and stability coinciding with non random decadal scale fluctuations in flood frequency and hydroclimate that appear to be linked to changes in large scale upper atmospheric circulation patterns episodes of widespread channel bed incision 1760 1799 1875 1894 1955 1969 result from a higher frequency of large floods 20 year return period and cool wet climate under meridional circulation regimes phases of more moderate floods 5 20 year return period corresponding to zonal circulation types 1820 1874 1920 1954 are characterized by enhanced lateral reworking and sediment transfer in upper reaches of the catchment and channel narrowing and infilling downstream rates of fluvial activity are reduced in intermediate periods 1800 1819 1895 1919 with no dominant circulation regime associated with lower flood frequency and magnitude the results of this study provide a valuable guide for forecasting probable drainage basin and channel response to future climate change

sediment characteristics of an extreme flood 1993 upper mississippi river valley the 1993 mississippi river flood was notable for its high magnitude long duration summer occurrence and low sediment discharge a field survey of a 70 km long reach in the vicinity of quincy illinois revealed that the event was characterized by 100 yr flood had remarkably little sedimentological or geomorphological impact on the flood plain within the study reach because the transport effectiveness of floods in large drainage basins is influenced by event sequencing in the same manner as floods in small watersheds and the cohesive flood plain soils were not susceptible to erosion

vertical accretion rates in fluvial systems a comparison of volumetric and depth based estimates a wide range of approaches has been adopted for collecting and reporting vertical accretion rates hence evaluation of results from different catchments or even from different reaches within the same basin is difficult as they may not be directly comparable the present study compares depth and volume based estimates of sediment accumulation for well dated vertical accretion sequences at broomhaugh island in the tyne basin northern england high resolution dating control based on heavy metal stratigraphy and cartography coupled with detailed reconstruction of channel geometry allows accumulation rates to be calculated for the last 300 400 years the results show a marked disparity in the magnitude and pattern of vertical accretion rates between the two approaches the average annual thickness of sediment increases progressively with a six fold difference between the seventeenth and twentieth centuries the volume figures are more consistent with a two fold difference between the highest and lowest rates both of which occurred in the twentieth century a major control on vertical accretion is found to be changing channel shape and capacity enlargement of the channel by 76 per cent since the seventeenth century associated with channel bed incision has resulted in fewer overbank flows hence floods with their associated suspended sediment loads which once inundated the floodplain are now confined within the channel the reduced areal extent of surfaces available for deposition has resulted in greater annual thickness of sediment accumulated despite an overall reduction in volume this study emphasizes that caution is needed when attempting to identify causal linkages between changes in sedimentation rates and catchment land use and or climatic factors and the geomorphological setting of the site must be taken into account copyright 2000 john wiley sons ltd

holocene sea level change and delta growth fraser river delta british columbia the fraser river has been building its delta into the strait of georgia in southwestern british columbia for about the last 9000 years this period encompassed a relative sea level rise of some 13 m this study concerns the effects of the rise in sea level on the depositional evolution of the delta the lithostratigraphy of the delta was established by a series of drill cores four major lithostratigraphic units were defined peat organic rich silt interbedded silts and sands and massive sands these units were interpreted in terms of the delta s contemporary depositional environments including peat bog floodplain and intertidal zone analysis of the delta s depositional architecture and chronology indicates that the delta continued to prograde during the rise in sea level a marine transgression accompanied by the landward migration of marine and intertidal facies did not occur growth of the delta during the rise in sea level was accomplished by both vertical accretion and lateral progradation ver

the characteristics of overbank deposits associated with a major flood event in the catchment of the river ouse yorkshire uk overbank floodplain deposits associated with a major flood which occurred in 1995 were collected shortly after the event from transects at 14 locations within the catchment of the river ouse yorkshire uk at most sites the sediment deposited nearest to the channel consisted primarily of sand sized material and the absolute particle size composition of the mineral fraction of the deposits evidenced fining with increasing distance from the channel most of the sand sized material was deposited within 20 to 40 m of the channel although at some sites sand was present at distances 100 m from the channels there was no obvious downstream trend in the texture of the sediment deposited on the floodplains in most places the overbank sediment was considerably coarser than the suspended sediment transported in the study rivers although at several sites thed50 of the latter was similar to that of overbank sediment deposited furthest from the channel although the c n ratio of the organic fraction of the overbank sediment was approximately constant across the width of the floodplain the organic carbon and137cs content of the deposited sediment increased with distance from the channel and both properties were positively related to the magnitude of the 63 m fraction the texture of sediment in cores collected from two of the sites in 1994 was generally finer than that of the overbank deposits from the 1995 flood at the same locations confirming the extreme nature of the 1995 flood event

the seismic facies of a tidally influenced holocene delta boundary bay fraser river delta b c abstract the tidally influenced fraser river delta in southwestern british columbia is actively prograding into the strait of georgia to investigate the geometry stratigraphy and structure of the post glacial fraser river delta sediments a high resolution shallow seismic reflection survey was carried out during the summer of 1987 in the boundary bay region of the delta twenty kilometers of optimum offset seismic reflection data were collected these high resolution seismic profiles were shot with 3 m spacing between geophones and a two way travel time of 200 ms four seismic facies were identified representing foreset topset slope failure and distributary channel deposits the foreset seismic facies has reflections that dip at angles of 1 to 7 towards boundary bay along strike the reflections have horizontal or mounded patterns horizontal continuous reflections typify the topset seismic facies the slope failure facies is located within the foreset seismic facies and consists of upper convex reflections and broken internal reflections the distributary channel seismic facies is characterized by concave downward reflections and is incised into the top of the foreset facies

the topographic data source of digital terrain models as a key element in the accuracy of hydraulic flood modelling funded by european commision grant number evg1 ct 1999 00010 cicyt grant number ren2001 1633 ries

the chemical and physical speciation of trace metals in fine grained overbank flood sediments in the tyne basin north east england deposition of fine sediment contaminated by heavy metals on floodplains in the tyne basin north east england during a major flood in august 1986 provided an unusual opportunity to investigate the chemical and physical speciation of metals in overbank fines selective extractions and heavy liquid analyses were used to assess the chemical forms of sediment associated metal and the relationship between grain size density and metal concentration and to identify sources of metalliferous material generally the highest concentrations of trace metals were found in the 500 250 m size range and in the heavier density fractions 3 3 gml 1 though more than 60 of metals reported to the lightest 3 3 gml 1 density product the principal source of metals appeared to be reworked alluvium contaminated by historic mining activity metal concentrations in flood sediment decrease downstream from former mining areas though at varying rates depending on the physical propeties and chemical phase of individual metals with the exception of cu dominated by lithogenic fraction metals are primarily associated with fe mn oxides pb zn and to a lesser extent with carbonates cd zn organic matter zn cu and an operationally defined exchangeable cd component in the upper and middle parts of the tyne basin physical processes of downstream sediment metal content reduction were found to predominate while in the lower reaches of the tyne sediment metal transport appears to be governed by chemical sorption desorption processes associated with fe mn oxides and organic material finally the results of the study are discussed in a wider context of particulate metal transport in rivers and recommendations are made for refining density based models of metal dispersal

sedimentary environments and postglacial history of the fraser delta and lower fraser valley british columbia the fraser river delta which is about 1000 km2 in area above low tide level has been built into the strait of georgia in southwestern british columbia during the holocene present day sedimentary

airborne lidar in support of geomorphological and hydraulic modelling this paper considers the application of airborne laser altimetry lidar to the provision of elevation data at accuracies and spatial densities commensurate with the current generation of high resolution hydraulic models three sets of issues are addressed with reference to a telemac 2d model of a morphologically complex estuary in eastern england first the quality of airborne lidar data is assessed via multiscale calibration against surveyed sections and supplementary control points second image processing techniques are used for i identification of multiple regions of interest within large lidar mosaics ii subregional infilling of voids left by data drop outs iii filtering and subsampling to match topographic information content with model resolution and the density of the computational mesh third the implications of improved terrain data are considered with reference to the estimation of elevations and potential tidal volumes for a number of discrete flood compartments and the modelling of hypothetical inundation scenarios after minor offset correction to ensure registration with local benchmarks the quality of lidar elevation data within a 12 km x 4 kin coverage is found to be consistent with the published specification 0 10 to 0 15 m image processing tools provide an efficient means of managing information content and interfacing this with the gis based functionality of the preprocessing software used in conjunction with the hydraulic model the accuracy and spatial resolution of the lidar data allow the identification of subtle but important topographic variations between adjacent flood compartments in many cases differences in model results obtained using these data relative to previously estimated average flood compartment elevations are small importantly however lidar provides topographic information at an accuracy and resolution close to the present limits of model representation reliable representation of form allows the modeller to concentrate on the physical aspects of model parameterization whilst minimizing the conflation of parameter effects with those of poorly constrained geometric representation copyright c 2003 john wiley sons ltd

climate and floods still govern california levee breaks 1 even in heavily engineered river systems climate still governs flood variability and thus still drives many levee breaks and geomorphic changes we assemble a 155 year record of levee breaks for a major california river system to find that breaks occurred in 25 of years during the 20th century a relation between levee breaks and river discharge is present that sets a discharge threshold above which most levee breaks occurred that threshold corresponds to small floods with recurrence intervals of 2 3 years statistical analysis illustrates that levee breaks and peak discharges cycle broadly on a 12 15 year time scale in time with warm wet storm patterns in california but more slowly or more quickly than enso and pdo climate phenomena respectively notably these variations and thresholds persist through the 20th century suggesting that historical flood control effects have not reduced the occurrence or frequency of levee breaks

suitability of lidar point density and derived landform curvature maps for channel network extraction this study uses landform curvature as an approach for channel network extraction we considered a study area located in the eastern italian alps where a high quality set of lidar data was available and where channel heads and related channel network were mapped in the field in the analysis we derived 1 m dtms from different ground lidar point densities and we used different smoothing factors for the landscape curvature calculation in order to test the suitability of the lidar point density and the derived curvature maps for the recognition of channel network this methodology is based on threshold values of the curvature calculated as multiples 1 3 times of the standard deviation of the curvature our analyses suggested that i the window size for curvature calculations has to be a function of the size of the features to be detected ii a coarse ground lidar point density could be as useful as a finer one for the recognition of main channel network features and iii rougher curvature maps are not optimal as they do not explore a sufficient range at which features occur while smoother curvature maps overcome this problem and are more appropriate for the extraction of surveyed channels copyright 2010 john wiley sons ltd

a delta plain sheet sand in the fraser river delta british columbia canada abstract borehole data in the fraser river delta demonstrate that a nearly continuous sand unit generally 8 to 20 m thick underlies the surficial silts and sands of most of the delta plain the sand unit consists of one or more sharp based fining upward sequences and is interpreted to be a complex of distributary channel deposits distributary channel migration and the resulting accumulation of channel sands has occurred primarily in a tidal flat environment due to the interaction of tidal and fluvial processes and the high proportion of sand in the sediment load this sand unit thus provides a model for sand rich river and tide dominated delta plains jetties now maintain the position of the main channel of the fraser river where it crosses the tidal flats and prevent channel migration and further storage of sand in the lower delta plain as a result more of the available sand is being transported directly to the river mouth where failures transport the sand downslope consequently these structures contribute to instability at the river mouth

the use of overbank sediment for geochemical mapping and contamination assessment results from selected english and welsh floodplains abstract overbank sediment profiles from floodplains in england and wales contain a record of both natural geochemical patterns and those showing the influence of man s activities it has been suggested that this characteristic can be used to allow maps to be compiled which show human impact on the fluvial geochemical environment studies reviewed in this paper however show that a single overbank profile very rarely spans the period from before anthropogenic disturbance through to the industrial revolution and later significant lateral variations in metal concentrations occur also over a relatively small area in overbank sediments of the same general age these and the nature of vertical changes in chemistry make the choice of sample sites and sampling interval within a profile difficult even sediments which appear uncontaminated may record anthropogenic influences from activities such as deforestation and agriculture a means of dating the sediment and an appreciation of river erosion and sedimentation histories are shown to be essential in order to ensure that maps intended to depict natural geochemical variations are based on material deposited before disturbance of the catchment by human activity these considerations and associated costs may render overbank sediment non viable as a regional geochemical mapping medium

assessing levee stability with geometric parameters derived from airborne lidar abstract a methodology to assess levee structural integrity using high resolution airborne light detection and ranging lidar data is investigated for a 16 km reach of the sacramento river within the sacramento san joaquin river delta california levee geometric parameters levee crown width height and water and landside slopes were extracted from 0 5 m resolution lidar derived digital ground models deviation of these parameters from minimum levee design standards was used to calculate a levee stability index stability maps were generated and those areas that did not meet usace geometric shape standards were identified results show that 2 out of the 4 geometric parameters do not meet the minimum value required in 48 and 43 of profiles on the east urban adjacent and west farmland adjacent margins respectively most importantly the crown width in 99 of the levee profiles located on the urban side was below the minimum required the paper also points out the importance of evaluating all four geometric parameters not just the elevation of the levee by assessing its level of performance through a geometric assessment

reconstruction of floodplain sedimentation rates a combination of methods to optimize estimates reconstruction of overbank sedimentation rates over the past decades gives insight into floodplain dynamics and thereby provides a basis for efficient and sustainable floodplain management we compared the results of four independent reconstruction methods optically stimulated luminescence osl dating caesium 137 cs 137 dating heavy metal analysis and flood bed interpretation applied at three embanked floodplain sites along lower rhine river distributaries in the netherlands all methods indicate significant sedimentation rates on the floodplains varying between 2 7 mm a in the distal zones and 3 9 mm a in the proximal zones on a rapidly developing sand bar along a natural levee sedimentation rates of 9 to 25 mm a were found except for some minor inconsistencies in cs 137 dating results all methods show decreasing sedimentation rates with increasing distance from the river channel intercomparison of the results of the different dating methods revealed the potential errors associated with each method particularly where disagreement among the results were found uncertainties may arise due to 1 grain size dependent downward migration of cs 137 2 smoothing of the vertical heavy metal and cs 137 profiles 3 delayed sediment associated input of cs 137 in addition to direct atmospheric fall out 4 overestimation of the burial age in os l dating due to incomplete resetting of the osl signal or 5 non linear relationships between sediment deposition and flood magnitude in the count from the top correlation between sediment lamination and past observed flood records still taking the uncertainties associated with each method into account the results are generally in good agreement using the results we indicate the optimal spatial range of application of each method depending on sediment texture and sedimentation rate the optimal spatial and temporal ranges differ for each method but show significant overlap a combination of the methods will thus provide maximum information for accurate estimation of sedimentation rates on a decadal time scale

the foreslope hills large scale fine grained sediment waves in the strait of georgia british columbia abstract the foreslope hills are a set of 20 m high 5 km long ridges at 230 350 m water depth in the south central strait of georgia occupying a 60 km 2 area at the base of the fraser river delta foreslope they are composed of clay silt and fine sand previous authors have interpreted them as 1 a single mass slide deposit 2 mud diapirs 3 in situ rotational failures and 4 creep deformation features but collaborative evidence for these interpretations is lacking seafloor surface morphological renders derived from recent multibeam sonar bathymetry data show linear evenly spaced symmetrical ridges with ridge bifurcation resembling wave ripples but on a much larger scale detailed multichannel and single channel seismic reflection data show sinusoidal internal reflections suggesting upslope migration the ridges occur within the uppermost portion of the holocene section in a very high sedimentation rate environment consequently they are probably less than 3000 years old moored current meter records for the region show reversing currents largely oriented normal to the ridge crests averaging 10 cm s with a maximum of 50 cm s this evidence combined with increasing documentation of large scale sedimentary bedforms in slope and rise environments suggests that the foreslope hills should be re interpreted as sediment waves upslope migration is typical of many large scale fine grained sediment waves the preferred physical interpretation for the creation and maintenance of the foreslope hills as sediment waves is the lee wave model requiring a phase shift in density stratified flow as it passes over the wavy topography maximum measured bottom currents are easily strong enough to entrain silt and clay delivered to the site by turbidity currents or by sediment plume fallout from fraser river outflow either strong flood tides or severe biannual density intrusions due to their intense stratification may be susceptible to lee wave formation and the creation of sediment waves leading to the observed pattern of upslope migration

sediment routing analyses based on chronological changes in hillslope and riverbed morphologies recent studies of sediment delivery and budgets in the united states indicate that upland erosion rates at a given time may not explain contemporaneous sediment yields from a drainage basin this suggests temporal discontinuities in sediment delivery associated with hillslope and channel storage processes integration of sediment production storage and transport is essential to understand sediment routing in basins we analysed each process chronologically using aerial photographs monitoring data of sediment movement and annual tree rings and then compared estimated temporal changes in sediment production from hillslopes floodplain disturbance areas and sediment transport in river channels toeslopes floodplains and alluvial fans together contained 59 per cent of sediment eroded from uplands over the last 30 years monitoring results of riverbed changes showed that the volume of stored sediment on floodplains decreased exponentially with succeeding floods the age distribution of floodplain deposits reflected the disturbance history of a river channel and followed an exponential decrease with age the results of this study may have important implications for sediment control plans for watersheds in steep regions

episodes of vertical accretion and catastrophic stripping a model of disequilibrium flood plain development this paper describes flood plains formed episodically by vertical accretion along high energy laterally stable channels in southeastern australia overbank deposition gradually builds a flood plain of fine textured alluvium over a period of hundreds or thousands of years following which catastrophic erosion by a single large flood or a series of more moderate floods strips the flood plain to a basal lag deposit from which it slowly reforms this periodic destruction appears due to the progressive development of large levee banks and flood plain surfaces of highly variable relief as the levees and flood plain grow overbank flow is gradually displaced from the broad flood plain into the main channel and flood plain backchannels with a resulting concentration of erosional energy eventually high flows greatly exceed erosional thresholds and wholesale scour of the channel boundary and flood plain occurs vertical accretion flood plains at different stages of development result in a wide range of bankfull recurrence intervals even along the same river some of these flood plains are so infrequently flooded that they can be mistaken for terraces formed under a prior flow regime the almost random but catastrophic nature of this flood plain erosion means that sediment supply and transport are highly variable and probably impossible to predict this model of flood plain formation is seen as only part of a continuum of alluvial environments ranging from vestigial coarsegrained traction load flood plains along high energy rivers in narrow gorges to extensive low gradient flood plains in which alluvial stratigraphy is dominated by fine grained overbank deposition

geomorphology and potential slope instability on the fraser river delta foreslope vancouver british columbia le delta du fleuve fraser est localise dans une des regions ayant les plus hauts risques sismiques au canada et comprend pour une bonne part des sables fluviaux meubles tres connus comme possedant un potentiel eleve de liquefaction sismique des etudes recentes de la rive ouest du delta du fraser indiquent que la liquefaction cyclique durant un fort tremblement de terre est possible engendrant potentiellement des deformations incluant des extensions laterales un ramollissement cyclique et possiblement une coulee l on presente une evaluation preliminaire de la stabilite statique des pentes apres secousse dans laquelle les analyses ont ete limitees aux valeurs estimees des resistances au cisaillement ultimes ou a l etat d equilibre deduites de correlations avec les donnnees du terrain et aux contraintes de cisaillement calculees en partant de la bathymetrie du lit de mer existant l on a trouve que le coefficient postliquefaction de securite contre le glissement etait inferieur a l unite pour la pente de la terrasse superieure roberts en supposant une limite inferieure de resistance au cisaillement ultime equivalente a 0 06 p 0 les donnees pour evaluer la validite de cette hypothese sont insuffisantes cependant il y a abondance de depots de rupture le long de la base de la pente du delta

seabed instability due to flow liquefaction in the fraser river delta les ruptures par liquefaction de depots de sables l ches peuvent representer une menace importante pour les structures cotieres on a evalue a partir des concepts d etats stationnaires les contributions possibles de divers mecanismes de declenchement lors d une rupture par liquefaction qui a eu lieu en 1985 a l embouchure du chenal principal de la riviere fraser parmi les mecanismes qui ont pu declencher le glissement par liquefaction en 1985 on a etudie la sedimentation les vagues de surface et les marees basses l analyse montre qu une sedimentation rapide genere des contraintes de cisaillement dans la pente mais ne pourrait pas faire demarrer des ruptures par liquefaction lorsqu on evalue l effet des vagues de surface et leur capacite a causer des glissements de type coulee profonde on trouve qu il ne s accumule pas de pressions interstitielles significatives dues aux vagues de surface pouvant exister dans la region les marees basses ne peuvent pas non plus declencher de rupture dans des sables submerges et completement satures l apparition de gaz provoque cependant la desaturation des sediments ce qui peut induire des pressions interstitielles residuelles pendant les marees basses on emet donc l hypothese que c est la combinaison de sediments l ches de faibles quantites de gaz et de marees basses qui favorise les ruptures par coulees liquefiees dans le delta ces ruptures conduisent a des glissements regressifs

effectiveness of natural zeroing of the thermoluminescence in sediments the last exposure to sunlight of detrital feldspars and quartz grains in quaternary sediments can be dated directly by thermoluminescence tl methods but the effectiveness of zeroing of the light sensitive tl signal by daylight varies widely depending upon details of the sedimentation processes to document this variability and to help develop objective criteria useful for future sample selection and laboratory procedures i have collected and analyzed several eolian fluvial marine deltaic and lacustrine samples from less than 100 year old deposits as well as suspensions from sediment plumes also underwater spectral irradiance was measured during recovery of suspensions tl properties of polyrnineralic feldspar dominated 2 4 m and 4 11 m size fractions were measured in the laboratory unexpectedly some light sensitive tl was found to remain in all samples however the light sensitive tl was more effectively zeroed in some samples a proximal loess a sandy braided channel deposit tidal flat and upper delta front muds and thin clayey lacustrine laminae than in others a silty braided channel deposit submarine fan muds and silt bearing lacustrine laminae for the first group the minimum relict paleodose obtained with the partial bleach technique is about 0 4 0 3 gy corresponding to a relict tl age estimate of about 200 years for these sediments thus similar sediments excluding fluvial deposits as young as about 2 ka can be accurately and routinely dated without significant correction for a zero point error if one uses the partial bleach technique coupled with integrated optical bleaching energy fluences of less than 1 j cm 2 and wavelengths only above about 550 nm also some simple optical bleaching tests are reported that have a potential use in sample selection and in provenance studies of some surficial detrital sediments finally a simple mathematical model is presented that helps account for the gross features of the observed bleaching response curves

uncertainty assessment of multi temporal airborne laser scanning data a case study on an alpine glacier in glaciology volumetric changes from multi temporal digital elevation models dems serve to validate and calibrate glacier mass balances from traditional in situ measurements in this study we provide a thorough uncertainty assessment of multi temporal airborne laser scanning dems based on a applying a statistical error model b comparing laser echoes to reference points and surfaces and c developing a physical error propagation model the latter model takes into account the measurement platform characteristics components of the measurement process and the surface properties such a model allows the estimation of systematic and stochastic uncertainties for single laser echoes as well as for distributed surfaces in every part of the study site independent of the reference surfaces the full error propagation framework is applied to multi temporal dems covering the highly undulating terrain in the findelengletscher catchment in canton valais switzerland this physical error propagation model is able to reproduce stochastic uncertainties in accordance with measurements from reference surfaces the high laser point density in the study site reduces the stochastic uncertainties over the whole glacier area to negligibly small values however systematic uncertainties greatly influence the calculation of mass changes and lead to corrections of the thickness change of up to 35

human induced sedimentation patterns of a channelized lowland river channelization of the severely polluted odra and vistula rivers in poland induced intensive accumulation of fine grained deposits rich in organic matter and heavy metals these sediments have been identified in vertical profiles in a narrow zone along river banks both in groyne created basins and on the floodplain grain size organic matter zinc zn lead pb copper cu content and cesium 137 137cs was used for sediment dating and stratigraphy and chemistry have been diagnostic features for these deposits named industrial alluvium in the most polluted river reaches stabilized by bank reinforcements and groynes 2 m thick slack water groyne deposits are composed of uniform strata of polluted silts with organic matter content over 10 zn content over 1000 mg kg and average cu and pb over 100 mg kg the average rate of sediment accretion in groynes is higher than on the floodplain and reaches 5 cm yr stratification which appears at higher levels in the groyne fields and on the levees reflects a change from in channel to overbank deposition and is typified by dark layers separated by bright sandy and less polluted strata stratified 4 m thick sediment sequences have been found in groyne fields of incised river reaches the average rate of sediment accretion in these reaches is of the order of 5 cm yr in stable and relatively less polluted river reaches vertical accretion organic deposits are finely laminated and the average rate of deposition amounts to a few millimeters per year investigations indicate that groyne construction favors conditions for long term storage of sediments at channel banks for this reason groynes should be considered as structures that efficiently limit sudden release of sediment associated heavy metals stored in channels and in floodplains of the historically polluted rivers copyright 2014 john wiley sons ltd

numerical modelling of tsunamis generated by hypothetical landslides in the strait of georgia british columbia a modified and corrected version of the viscous slide model of jiang and leblond 1994 is used to assess the tsunami risk associated with hypothetical underwater slope failures in two coastal areas of british columbia having potentially unstable sediment deposits a malaspina strait separating the mainland coast and texada island in the central strait of georgia and b roberts bank on the foreslope of the fraser river delta in the southern strait of georgia the intent of this study is to demonstrate the capability of the model for tsunami risk assessment and to improve upon previous studies of tsunami risk in the region based on reasonable submarine landslide scenarios the potential risk from tsunamis associated with slide failures has been examined but the likelihood of failure events themselves was not considered for the malaspina strait scenarios simulated tsunamis are generated by failure of a lobe of perched sediment situ ated on the slope of eastern texada island failure as a flow slide of the estimated 1 250 000 m3 of sediment generates wave troughs reaching 4 9 m and trough to crest heights of 6 to 8 m along the coast of texada island at cape cockburn on the opposite side of the strait wave heights of 1 5 to 2 0 m are produced for roberts bank simulated waves are examined for two separate failure scenarios the larger slide case 1 involves the failure of a sediment lobe with lateral dimensions of 7 3 km2 and volume of 0 75 km3 while the smaller slide case 2 fails a sediment lobe with dimensions of 4 2 6 km2 and volume of 0 23 km3 computations were made both for high 3 m and low 3 m tide conditions for both failure volumes maximum wave amplitudes up to 18 m for case 1 and 8 m for case 2 occur on the coasts of mayne and galiano islands opposite the source area wave amplitudes are much smaller 1 to 4 m on the mainl and coast because of the reflection of the initial waves from roberts bank additional numerical experiments were conducted for both regions to estimate the sensitivity of the computed tsunami wave heights to input parameters such as slide viscosity bulk density and slide position

floodplain sedimentation quantities patterns and processes this paper presents the result of measurements of floodplain sedimentation using sediment traps the study was carried out on two embanked floodplains along the rivers rhine and meuse in the netherlands during a 3 day flood in january 1993 raster maps of sediment accumulation were made by interpolating the measurements from the traps using block kriging the sediment maps show clear patterns in sediment accumulation together with the estimated interpolation errors average sediment accumulation ranges between 0 57 and 1 0 kg m 2 high sediment accumulation is found on the levees 4 kg m 2 or more and on low lying areas 1 6 kg m 2 sediment accumulation decreases with distance from the main channel the sedimentation patterns are related to floodplain topography and sediment transporting mechanisms sediment transport by turbulent diffusion as well as by convection can be recognized also flood duration and the process of sediment settling out in ponding water in closed depressions are important the applied method allows comparison of the results with raster based sedimentation models

channel floodplain connectivity during an extreme flood event implications for sediment erosion deposition and delivery the term connectivity has emerged as a powerful concept in hydrology and geomorphology and is emerging as an innovative component of catchment erosion modeling studies however considerable confusion remains regarding its definition and quantification especially as it relates to fluvial systems this confusion is exacerbated by a lack of detailed case studies and by the tendency to treat water and sediment separately extreme flood events provide a useful framework to assess variability in connectivity particularly the connection between channels and floodplains the catastrophic flood of january 2011 in the lockyer valley southeast queensland australia provides an opportunity to examine this dimension in some detail and to determine how these dynamics operate under high flow regimes high resolution aerial photographs and multi temporal lidar digital elevation models dems coupled with hydrological modeling are used to assess both the nature of hydrologic and sedimentological connectivity and their dominant controls longitudinal variations in flood inundation extent led to the identification of nine reaches which displayed varying channel floodplain connectivity the major control on connectivity was significant non linear changes in channel capacity due to the presence of notable macrochannels which contained a 3000 average recurrence interval ari event at mid catchment locations the spatial pattern of hydrological connectivity was not straight forward in spite of bankfull discharges for selected reaches exceeding 5600m 3 s 1 data indicate that the main channel boundary was the dominant source of sediment while the floodplains where inundated were the dominant sinks spatial variability in channel floodplain hydrological connectivity leads to dis connectivity in the downstream transfer of sediments between reaches and affected sediment storage on adjacent floodplains consideration of such variability for even the most extreme flood events highlights the need to carefully consider non linear changes in key variables such as channel capacity and flood conveyance in the development of a quantitative connectivity index copyright c 2013 john wiley sons ltd

space geodesy subsidence and flooding in new orleans a subsidence map of the city offers insight into the failure of the levees during hurricane katrina

a river mouth submarine channel and failure complex fraser delta canada abstract high resolution seismic and side scan sonar surveying combined with coring of the fraser delta slope seaward of the main fluvial distributary has revealed a complex suite of morphologic units which include undisturbed delta slope sediments shallow rotational slides relict and active slope channels debris accumulations and ponded turbidites sediment transport through the main submarine channel is thought to be primarily by debris flows rather than by turbidity currents although this is a seismically active region the instability related features described here are probably due primarily to rapid sediment deposition on the upper delta slope at the river mouth

use of fused airborne scanning laser altimetry and digital map data for urban flood modelling flood modelling of urban areas is still at an early stage partly because until recently topographic data of sufficiently high resolution and accuracy have been lacking in urban areas however digital surface models dsms generated from airborne scanning laser altimetry lidar having sub metre spatial resolution have now become available and these are able to represent the complexities of urban topography this paper describes the development of a lidar post processor for urban flood modelling based on the fusion of lidar and digital map data the map data are used in conjunction with lidar data to identify different object types in urban areas though pattern recognition techniques are also employed post processing produces a digital terrain model dtm for use as model bathymetry and also a friction parameter map for use in estimating spatially distributed friction coefficients in vegetated areas friction is estimated from lidar derived vegetation height and unlike most vegetation removal software the method copes with short vegetation less than 1 m high which may occupy a substantial fraction of even an urban floodplain the dtm and friction parameter map may also be used to help to generate an unstructured mesh of a vegetated urban floodplain for use by a two dimensional finite element model the mesh is decomposed to reflect floodplain features having different frictional properties to their surroundings including urban features such as buildings and roads and taller vegetation features such as trees and hedges this allows a more accurate estimation of local friction the method produces a substantial node density due to the small dimensions of many urban features copyright 2007 john wiley sons ltd

patterns of legacy sediment deposits in a small south carolina piedmont catchment usa abstract anthropogeomorphic changes to channels and floodplains occurred in response to destructive agricultural practices following the arrival of european settlers into the americas the southeastern piedmont physiographic region of the usa experienced severe erosion and sedimentation after settlement in the 1700s and farming up through the 1930s in places deep floodplain aggradation formed uninterrupted alluvial deposits that extend many kilometers this research examines anthropogenic impacts of land use change on valley bottom sedimentation in the chicken creek watershed of south carolina abrupt contacts between precolonial floodplain soils and a thick overburden of historical legacy sediment are common and well exposed throughout the two km study reach and provide clear evidence of extensive postcolonial sedimentation soil stratigraphic and sedimentologic evidence are presented to identify and contrast pre and postcolonial sediment characteristics and thicknesses lidar based spatial analysis is used to examine patterns of legacy sediment deposition and floodplain storage and together with field observations of bank stratigraphy examine the environments in which this occurred precolonial geomorphic stability is indicated by a buried soil epipedon ab horizon and other features on precolonial floodplain surfaces legacy sediment 2 to 4 m thick rests on top of exposed precolonial soils throughout the stream corridor with the pre postcolonial contact 1 5 m above the channel bed on average linear regression analysis shows that legacy sediment thickness varies statistically with changes in valley width and proximity to tributary sediment sources thin precolonial alluvium over bedrock suggests modest erosion and sedimentation rates prior to the arrival of euroamerican settlers mean grain sizes are similar between the pre and postcolonial alluvium but substantial contrasts in the degree of stratification and bulk density document differences between the respective depositional environments and post depositional changes to the two units channel adjustments since the time of maximum aggradation include bed incision to at least as low as the precolonial longitudinal profile and widening that is ongoing

earthquake induced liquefaction near lake amatitlan guatemala one of the effects of the february 4 1976 guatemala earthquake was the extensive liquefaction which occurred at the settlement of la playa on the northeast shore of lake amatitlan ground accelerations in the area resulting from the magnitude 7 5 earthquake are estimated to be of the order of 0 12 g to 0 15 g the characteristics of the sand are investigated including its standard penetration resistance and its cyclic loading characteristics despite the fact that the sand is somewhat lighter in weight than sand deposits which have liquefied in other earthquakes its liquefaction characteristics are apparently influenced by the same factors as other sand deposits its overall behavior is consistent with that exhibited by other sands the high degree of liquefaction at the la playa site was probably due in large measure to the lightweight nature of the pumiceous sands

dynamic changes and processes in the mississippi river delta research in the modern delta of the mississippi river has revealed short term changes and processes that are of significant magnitude deltaic lobes each lobe covering an area of 30 000 sq km and having an average thickness of 35 km switch sites of deposition on an average of every 1 500 yr through short periods of geologic time this process results in a relatively thick accumulation of stacked deltaic cycles covering extremely large areas within a single delta lobe and operating on an even higher frequency are bay fills and overbank splays bay fills having areas of 250 sq km and thickness of 15 m require only 150 yr to accumulate four major events have taken place in the modern balize delta since 1838 overbank splays are much smaller covering areas of less than 2 sq km and having thicknesses of 3 m but are associated with high floods on the river at the river mouth continued progradation of the distributary channel can form distributary mouth sand bodies that have dimensions of 17 km long 8 km wide and a thickness of 80 m in a period of only 200 yr differential sedimentary loading at the river mouth results in formation of diapirs that display vertical movements in excess of 100 m in a period of 20 yr on the subaqueous delta platform sediment instabilities operate nearly continuously mass moving large quantities of shallow water deposits to deeper water environments via arcuate rotational slides and mudflow gullies and depositional lobes all of these changes and processes operate at differing spatial and temporal scales but all result in deposition of large volumes of sediment over extremely short periods of time

the use of multi temporal lidar to assess basin scale erosion and deposition following the catastrophic january 2011 lockyer flood se queensland australia advances in remote sensing and digital terrain processing now allow for a sophisticated analysis of spatial and temporal changes in erosion and deposition digital elevation models dems can now be constructed and differenced to produce dems of difference dod which are used to assess net landscape change for morphological budgeting to date this has been most effectively achieved in gravel bed rivers over relatively small spatial scales if the full potential of the technology is to be realised additional studies are required at larger scales and across a wider range of geomorphic features this study presents an assessment of the basin scale spatial patterns of erosion deposition and net morphological change that resulted from a catastrophic flood event in the lockyer creek catchment of se queensland seq in january 2011 multitemporal light detection and ranging lidar dems were used to construct a dod that was then combined with a one dimensional flow hydraulic model hec ras to delineate five major geomorphic landforms including inner channel area within channel benches macrochannel banks and floodplain the lidar uncertainties were quantified and applied together with a probabilistic representation of uncertainty thresholded at a conservative 95 confidence interval the elevation change distribution ecd for the 100 km2 study area indicates a magnitude of elevation change spanning almost 10 m but the mean elevation change of 0 04 m confirms that a large part of the landscape was characterised by relatively low magnitude changes over a large spatial area mean elevation changes varied by geomorphic feature and only two the within channel benches and macrochannel banks were net erosional with an estimated combined loss of 1 815 149 m3 of sediment the floodplain was the zone of major net deposition but mean elevation changes approached the defined critical limit of uncertainty areal and volumetric ecds for this extreme event provide a representative expression of the balance between erosion and deposition and importantly sediment redistribution which is extremely difficult to quantify using more traditional channel planform or cross sectional surveys the ability of lidar to make a rapid and accurate assessment of key geomorphic processes over large spatial scales contributes to our understanding of key processes and as demonstrated here to the assessment of major geomorphological hazards such as extreme flood events

stability of the fraser river delta front the distributary front deposits of the delta consist mainly of interlayered sand and silt and lie in one of the most seismically active zones in canada subsurface deposits at the north tend to be siltier than those at the south sediments on the surface of the delta slope range from clayey silts at the north to pure sands at the south slope angles vary from 23 at the head of the slope to 1 2 within 2 km beyond the tidal flats hydraulic bedforms observed on the sandy slopes southeast of the main channel gradually increase in size from small ripples to large asymmetric sand waves 2 3 m high and approximately 30 m long they are generated primarily by flood tidal currents which scour the seabed to a water depth in excess of 100 m formation of gullies which crease the delta slope probably is initiated principally by failure of oversteepened deposits at a channel mouth previous studies have suggested that the large hummocks or ridges at the base of the slope off the main channel have been formed by the co

relation of sediment load and flood plain formation to climatic variability paria river drainage basin utah and arizona suspended sediment load flow volume and flood characteristics of the paria river were analyzed to determine their relation to climate and flood plain alluviation between 1923 and 1986 flood plain alluviation began about 1940 at a time of decreasing magnitude and frequency of floods in winter summer and fall no floods with stages high enough to inundate the flood plain have occurred since 1980 and thus no flood plain alluviation has occurred since then the decrease in magnitude and frequency of floods appears to have resulted from a decrease in frequency of large storms particularly dissipating tropical cyclones and not from a decrease in annual or seasonal precipitation suspended sediment load is highest in summer and fall whereas flow volume is highest in winter fall shows the greatest interannual variability in suspended sediment load flow volume and flood size because climatic conditions are most variable in fall the relation between sediment load and discharge apparently did not change within the period of sediment sampling 1949 1976 even though the channel elevation and width changed significantly annual suspended sediment loads estimated for periods before and after 1949 1976 show that decrease in suspended sediment load caused by floodplain alluviation in the paria river and other tributaries could have been a significant part of the decrease of suspended sediment load in the colorado river in the early 1940s

integration of high resolution topographic data with floodplain flow models two dimensional hydraulic models of floodplain flow are at the forefront of current research into flood inundation mechanisms but they are however currently constrained by inadequate parameterization of topography and friction primarily due to insufficient or inaccurate data this paper reviews the effects of topographic representation on flood inundation extent prediction and presents initial results of a flood simulation using a new topographic parameterization surface produced from airborne lidar laser induced direction and ranging data copyright 2000 john wiley sons ltd

use of fallout pb 210 measurements to investigate longer term rates and patterns of overbank sediment deposition on the floodplains of lowland rivers the potential for using fallout unsupported pb 210 210pb measurements to estimate rates of overbank sediment deposition on the floodplains of lowland rivers is explored a model which distinguishes the contribution from direct atmospheric fallout and the catchment derived input associated with the deposition of suspended sediment has been developed to interpret the fallout pb 210 inventories at floodplain sampling sites and to estimate average sediment accumulation rates over the past 100 years the approach has been successfully used to estimate rates of overbank sedimentation on the floodplains of the rivers culm and exe in devon u k a detailed investigation of the pattern of longer term sedimentation rates within a small reach of the floodplain of the river culm indicated a range of deposition rates between 0 07 and 0 59 g cm 2 a 1 which was in close agreement with estimates of current sedimentation rates obtained using sedimentation traps

postglacial deltaic sediments southern fraser river delta british columbia the fraser river delta the largest delta on the west coast of canada has been built into the strait of georgia during the holocene drill hole and seismic reflection records reveal a succession of sedimentary units deposited during early holocene progradation of the delta these overlie an irregular surface developed on pleistocene drift mud and silt similar to sediments presently accumulating off the mouth of fraser river in the southern strait of georgia are conformably overlain by a thick unit of sandy foreset beds dipping gently to the south southwest into boundary bay and deposited in a foreslope environment the foreset unit is sharply overlain by a much thinner topset sequence comprising silt and sand deposited in intertidal fluvial channel and overbank environments and peat deposited in swamps and bogs fifteen accelerator mass spectrometry radiocarbon dates on shell and wood indicate that most of the deltaic sediments south of the main channel of fraser river were deposited between ca 7