the effects of softening on nearshore erosion of a cohesive shoreline abstract a study designed to measure spatial and temporal variation in the shear strength of the surface of a till substrate in the nearshore was carried out on the south shore of lake ontario canada the primary goal was to determine whether softening or reduction in shear strength occurred during the study period and the significance of this as a control on the overall rate of vertical lowering of the cohesive profile characteristics of the nearshore environment and the substrate were determined through the collection of till shear strength measurements substrate cores and surficial sediment thickness along a 300 m long underwater profile changes in shear strength were monitored over a four month period in experimental plots in water depths of 1 6 3 5 and 4 75 m together with measurements of bed erosion softening of the till was evident from cores which showed a rapid increase in strength and corresponding decrease in moisture content to a depth of about 0 1 m below the till surface after which they became constant shear strength of the exposed till surface decreased during periods of low wave activity and similar results were found in laboratory experiments periods of high wave activity resulted in the removal of a layer of softened material thus exposing harder underlying till the results suggest that erosion during a storm is related to the thickness of the softened layer that develops during non storm periods because of the steep increase in strength with depth below the till surface maximum erosion during a storm is generally

aeolian sediment transport on a beach surface moisture wind fetch and mean transport abstract temporal and spatial changes in wind speed wind direction and moisture content are ubiquitous across sandy coastal beaches often these factors interact in unknown ways to create complexity that confounds our ability to model sediment transport at any point across the beach as well as our capacity to predict sediment delivery into the adjacent foredunes this study was designed to measure wind flow and sediment transport over a beach and foredune at greenwich dunes prince edward island national park with the express purpose of addressing these complex interactions detailed measurements are reported for one stormy day october 11 2004 during which meteorological conditions were highly variable wind speed ranged from 4 ms 1 to over 20 ms 1 wind direction was highly oblique varying between 60 and 85 from shore perpendicular and moisture content of the sand surface ranged from a minimum of about 3 by mass to complete saturation depending on precipitation tidal excursion and storm surge that progressively inundated the beach the data indicate that short term variations i e minutes to hours in sediment transport across this beach arise predominantly because of short term changes in wind speed as is expected but also because of variations in wind direction precipitation intensity and tide level even slight increases in wind speed are capable of driving more intense saltation events but this relationship is mediated by other factors on this characteristically narrow beach as the angle of wind approach becomes more oblique the fetch distance increases and allows greater opportunity for the saltation system to evolve toward an equilibrium transport state before reaching the foredunes whether the theoretically predicted maximum rate of transport is ever achieved depends on the character of the sand surface e g grain size slope roughness vegetation moisture content and on various attributes of the wind field e g average wind speed unsteadiness approach angle flow compression boundary layer development moisture content is widely acknowledged as an important factor in controlling release of sediment from the beach surface all other things being equal the rate of sediment transport over a wet surface is lesser than over a dry surface on this beach the moisture effect has two important influences a in a temporal sense the rate of sediment transport typically decreases in association with rainfall and increases when surface drying takes place and b in a spatio temporal sense shoreline excursions associated with nearshore processes such as wave run up storm surge and tidal excursions have the effect of constraining the fetch geometry of the beach i e narrowing the width of the beach because saturated sand surfaces such as found in the swash zone will only reluctantly yield sediments to aeolian entrainment the available beach surface across which aeolian transport can occur becomes narrower as the sea progressively inundates the beach under these constrained conditions the transport system begins to shut down unless wind angle becomes highly oblique thereby increasing fetch distance in this study maximum sediment transport was usually measured on the mid beach rather than the upper beach i e closer to the foredunes this unusual finding is likely because of internal boundary layer development across the beach which yields a decrease in near surface wind speed and hence transport capacity in the landward direction although widely recognized in the fluid mechanics literature this decrease in near surface shear stress as a by product of a developing boundary layer in the downwind direction has not been adequately investigated in the context of coastal aeolian geomorphology

catastrophic erosion of hellas basin rim on mars induced by magmatic intrusion into volatile rich rocks 1 malea and hesperia plana form large sectors of the rim of hellas basin that display partly eroded volcanic shields and plains these regions have topographic profiles that appear to be several hundred meters lower than those of adjacent rim sectors and lack prominent massifs of remnant basement that would be expected to stand above the lava plains we interpret that before the volcanic edifices were constructed these regions were denuded by an early stage of voluminous sill intrusion into friable volatile rich impact breccia magma volatile interactions may have resulted in catastrophic generation of debris flows deposited into the adjacent basin particularly if co2 were involved later lavas covered the eroded terrain in turn the lavas were eroded locally by volatile interactions across mars huge channel systems erosional features in volcanic terranes and vast layered deposits may be due to magma volatile interactions

aeolian sediment transport on a beach thresholds intermittency and high frequency variability abstract during a field experiment designed to measure wind flow and sediment transport over the beach and foredune at greenwich dunes prince edward island national park measurements were made on october 11 2004 during a storm with wind speeds ranging from 4 ms 1 to over 20 ms 1 this paper examines thresholds of sand movement intermittency and the relationship between fluctuating winds and transport intensity based on high frequency measurements of wind speed and saltation wind speed was measured at four points across the beach profile using cup anemometers set at a height of 0 6 m the anemometers were co located with saltation probes set at a height of 0 02 m that measure the impacts of saltating sand grains the instruments were sampled at 1 hz during runs of 1 or 2 h over an eight hour period sand transport was highly intermittent early in the day when winds were only slightly above threshold and became more continuous towards the upper beach because of increasing fetch distance and decreasing surface moisture despite more continuous transport and increasing wind speed through the day a zone of highly intermittent transport migrated landward across the beach as water levels rose due to storm surge examination of three thresholds related to measures of wind speed the maximum wind speed without transport u tmax minimum wind speed with transport u tmin and the intermittency threshold u t showed that none provide a consistently robust measure of the threshold although they all provide some insight into conditions controlling entrainment while graphs of instantaneous saltation intensity crudely mimic the pattern of fluctuating wind speed statistical correlations over periods of 2 10 min were generally poor r 2

spatial and temporal controls on overwash occurrence on a great lakes barrier spit field measurements from 1985 to 1990 and sequential aerial photography since 1945 show that overwash plays an extremely important role in the dynamics of long point a large barrier spit on the north shore of lake erie overwash occurs primarily in the transgressive proximal and central zones of the spit which together account for some 65 of the total shoreline length of 41 km during periods of high lake level over 50 of the shoreline in these zones may be overwashed washover morphology ranges from continuous washover terraces in areas of low foredunes to isolated washovers with narrow throats and distinct fans where breaching has occurred through high dunes individual overwash events commonly produce deposits on the fan surface 0 25 0 75 m or more in thickness washover fan sediments are dominated by nearly horizontal planar bedding with deposits near the fan margins often having foreset bedding reflecting deposition in standing water of the bay or of interdune ponds the frequency of overwash oc

the influence of topography and approach angles on local deflections of airflow within a coastal blowout the spatial variability of air flow through complex topography is an important but not fully understood component of dune development and dynamics this study examines the spatial variability of the wind field in a linear blowout in coastal dunes at jockey s ridge state park on the outer banks of north carolina a spatial array of single height anemometers and wind vanes were placed within the blowout topography exerted a significant steering effect when onshore winds approached from directions within 50 of the blowout axis under those conditions wind flow in the blowout aligned to the axis regardless of approach angle maximizing the potential for erosion and transport in the trough in other locations aspect variations caused deflection both proportional and disproportional to changes in the approaching wind when prevailing winds approached from directions more oblique than 50 to the blowout axis topographic steering through the blowout trough was reduced and secondary flow generated by flow separation over the trough became more prominent during those approach angles wind directions and speeds within the upper blowout trough became erratic as vortices and turbulence dominated the flow minimizing transport potential the changing characteristics of airflow in the blowout relative to differing approach angles has implications on dune development and variations in transport potential under changing conditions copyright 2013 john wiley sons ltd

seasonal and annual variations in the volumetric sediment balance of a macro tidal salt marsh abstract this paper examines the spatial and temporal variability in the volumetric sediment balance of allen creek marsh a macro tidal salt marsh in the bay of fundy the volumetric balance was determined as the balance of inputs of sediments and organic matter via accretion on the marsh surface and outputs of sedimentary material primarily due to erosion of the marsh margin changes in marsh surface elevation were measured at 20 buried plates and 3 modified sediment elevation tables from 1996 2002 and detailed margin surveys were conducted in 1997 1999 and 2001 using a differential global positioning system changes in surface area were calculated using gis overlay analysis and used in conjunction with accretion and erosion data to derive volumetric estimates of gains and losses of sedimentary material in the marsh system currently the volumetric sediment balance at allen creek marsh is positive however the processes of erosion and accretion demonstrate seasonal annual and spatial variability inputs to the system include deposition on the marsh surface from sediment laden waters and from ice rafting of sediments sediment is deposited onto the marsh surface year round even during the winter when vegetation cover is sparse and the amount of deposition in general is not significantly correlated with the frequency of tidal inundations based on the data from 1996 to 2002 the mid and high marsh zones experience mean accretion rates of approximately 1 4 cm year 1 whereas accretion rates in the low marsh region are statistically significantly lower 0 8 cm year 1 the absolute amount of accretion varies between seasons and from year to year the main loss to the marsh is through erosion of the marsh margin cliffs which can remove a comparatively large volume of sedimentary material in one mass wasting event and which also decreases the vegetated surface area available for deposition from sediment laden waters the volume of material removed from the marsh margin almost tripled between 1997 169 m3 and 2001 502 m3 following breaching of the side of a tidal creek channel altering the patterns of margin erosion and deposition in the marsh system during this time however other sheltered areas of the marsh system such as along the tidal creek banks showed evidence of new vegetation growth increasing the amount of vegetated surface area available for deposition the processes of erosion and deposition on the marsh surface exhibit considerable spatial variability with different regions of the marsh being more or less sensitive to seasonal variability in the dominant controls influencing sediment deposition and erosion in this system namely wave activity vegetation ice and water depths a key factor in predicting how a marsh will evolve and respond to a number of different controls e g sea level rise or reduced sediment supply is to quantify both accretion of the marsh surface and erosion of the marsh margin evaluating the marsh system as a volumetric whole this study demonstrates that a marsh system should be assessed in three dimensions rather than simply as a surface of accumulation this is particularly important for open coastal marshes exposed to the erosive action of waves

geomorphic and sediment volume responses of a coastal dune complex following invasive vegetation removal this paper documents application of an established geostatistical methodology to detect significant changes in a foredune transgressive dune complex where parks canada agency pca implemented a dynamic restoration program to remove invasive marram grasses ammophila spp and enhance dynamic dune habitat for an endangered species detailed topographic surveys of a 10 320 m2 site in the wickaninnish dunes in pacific rim national park british columbia canada for the first year post treatment are compared to a pre restoration lidar baseline survey the method incorporates inherent spatial structure in measured elevation datasets at the sub landscape scale and models statistically significant change surfaces within distinct linked geomorphic units beach foredune transgressive dune complex seasonal and annual responses within the complex are discussed and interpreted all geomorphic units experienced positive sediment budgets following restoration treatment the beach experienced the highest differential volumetric change 1656 m3 and net sediment influx 834 m3 0 19 m3 m 2 mostly from supply to the supratidal beach and incipient dune this sediment influx occurred independent of the restoration effort and was available as a buffer against wave erosion and as supply to the landward dunes the foredune received 200 m3 0 13 m3 m 2 and its seaward profile returned to a similar pre restoration form following erosion at the crest from vegetation removal and scarping by high water events sediment bypassing and minimal change was evident at the mid stoss slope with appreciable extension of depositional lobes in the lee the transgressive dune complex experienced high accretion following restoration activity 201 m3 and over the year 284 m3 0 07 m3 m 2 mostly from depositional lobes from the foredune precipitation ridge growth along the downwind boundary and growth of existing lobes within the complex further integration of this methodology to detect significant geomorphic changes is recommended particularly for applications where sampling densities are limited or logistically defined copyright 2013 john wiley sons ltd

sediment supply from shoreface to dunes linking sediment transport measurements and long term morphological evolution a significant problem in current coastal research is the understanding of linkages between morphological phenomena occurring on different temporal and spatial scales morphodynamic processes in the nearshore typically exhibit nonlinear behaviour and consequently phenomena which occur on short temporal event scales as e g observed during field experiments have generally been difficult to upscale to provide an understanding of the long term behaviour of the coast on the time scale of seasons or decades this paper documents a persistent onshore migration of nearshore bar features over a period of 3 decades using a set of cross shore profile surveys from a barrier on the danish north sea coast the observed behaviour is consistent with experimental data obtained during weeklong field campaigns when sediment transport and bar migration were found to be landward directed during high energy dissipative conditions hydrodynamic and sediment transport processes leading to onshore bar migration and eventually welding of the bars are documented to provide an explanation for the observed long term evolutionary trends in addition bar welding and the resulting intertidal bar formation represent an onshore sediment storage which is subsequently available for aeolian transport observations on aeolian sediment transport indicate that transport rates and sediment supply to the foredunes critically depend on the presence of dry sand sources as represented by well drained intertidal bars measurements of long term accretion rates in foredunes indicate that volumes deposited on the crest and lee slope of the dunes are in reasonable correspondence with volumes supplied to the subaerial beach through the process of bar welding hence the data suggest that a persistent onshore directed sediment supply occurs from the shoreface across the surf and intertidal zones and into the dunes of the investigated barrier

morphology formation and migration of longshore sandwaves long point lake erie canada this paper describes the morphology and dynamics of features termed here longshore sandwaves which are developed on a large barrier spit in the great lakes the sandwaves are local beach protuberances with alongshore lengths of 500 2500 m and maximum widths at the downdrift end of 50 90 m which migrate alongshore in the direction of net drift at 150 300 m yr 1 they have a lifespan of 10 yrs or more and their spatial and temporal scales are an order of magnitude greater than the rhythmic topography associated with the nearshore bars and rip cells which are also characteristic of the littoral zone the sandwaves are initiated by the onshore movement and welding of inner nearshore bars during nonstorm periods in areas of local sediment abundance the alongshore movement of the sandwaves occurs through downdrift extension which is initiated by attachment of a landward migrating nearshore bar to the downdrift end of the sandwave and subsequent infilling of the trough landward of the bar the presence and movement of the sandwaves results in a complex spatial temporal pattern of beach and dune erosion and accretion with accretion occurring opposite the sandwave and erosion focused in the embayments between sandwaves

a general framework for modeling sediment supply to coastal dunes including wind angle beach geometry and fetch effects a series of spatially explicit equations are derived that form the foundation of a modeling framework that provides insight into how the interaction of the fetch effect and angle of wind approach leads to tradeoffs that govern the magnitude of aeolian sediment transport across beaches of different geometry the spatial distribution of sediment transport rate per unit width at any point on the beach is shown to vary predictably as a function of wind angle critical fetch and beach geometry and this has evident implications for the total volume and distribution of sediment transport into the dunes behind the beach as well as the proportion of sediment lost from the beach dune system at the downwind margin as the wind field shifts from onshore shore perpendicular to oblique shore parallel approach angle total sediment transport rate across a dune line segment will reflect a tradeoff between transport reduction because of the cosine effect and transport enhancement because of potentially longer fetch distances traversed by the wind prior to encountering the dune line this tradeoff is most evident on long narrow beaches when beach width is less than the critical fetch for such beaches and with onshore winds the total sediment transport rate across the dune line will be less than that predicted for a wide beach because of the constraint imposed by the fetch effect however as the angle of wind approach becomes oblique the available fetch becomes progressively longer transport limitations imposed by the fetch effect are negated and transport enhancement across the dune line is to be expected with very large angles of wind approach the cosine effect dominates the interaction and transport reductions across the dune line occur until the wind is shore parallel and sediment supply to the dunes ceases altogether this sequence of adjustments and tradeoffs were only partially understood prior to this study and yet they form the foundation of coastal dune modeling the framework proposed in this paper serves to place future studies of process form interaction in beach dune systems on a robust theoretical foundation it also facilitates the testing of various alternative hypotheses regarding the uneven spatial and temporal distribution of dune height and growth rate in coastal environments

annual to decadal morphodynamics of the foredune system at greenwich dunes prince edward island canada the purpose of this study was to quantify relationships between season sediment availability sediment transport pathways and beach foredune morphology at greenwich dunes pei this was done for periods ranging from a few days to multiple decades using erosion pins bedframe measurements annual surveys and digital photogrammetry using historical aerial photographs the relative significance of seasonal annual processes versus response of the foredune system to broader geomorphic controls e g relative sea level rise storms etc was also assessed the data show that there are clear seasonal differences in the patterns of sand supply from the beach to the foredune at greenwich and that there are differences in sediment supply to the foredune between the east and west reaches of the study area resulting in ongoing differences in foredune morphology they also demonstrate that models that incorporate wind climate alone or even models that include other factors like beach moisture would not be able to predict the amount of sediment movement from the beach to the foredune in this environment unless there were some way to parameterize system morphology especially the presence or absence of a dune ramp finally the data suggest that the foredune can migrate landward while maintaining its form via transfers of sediment from the stoss slope over the crest and onto the lee slope although the rate of foredune development or recovery after disturbance changes over time due to morphological feedback the overall decadal evolution of the foredune system at greenwich is consistent with and supports the davidson arnott 2005 conceptual model of dune transgression under rising sea level copyright 2012 john wiley sons ltd

respiration dissolution and the lysocline 1 here i synthesize the results of several types of measurements of organic carbon respiration and calcium carbonate dissolution rates in pelagic seafloor sediments measurements of pore water oxygen demonstrate that most of the respiration takes place very near the sediment water interface with a scale depth of a few millimeters the remainder of the oxic respiration occurs much deeper in the sediments with a scale depth of several centimeters all measures of respiration from locations as disparate as the tropical pacific and atlantic and the subtropical north atlantic agree that pelagic seafloor rates of oxic respiration of organic carbon are relatively independent of depth and location with the exception of sediments beneath the pacific eastern equatorial upwelling zone calcite dissolution in seafloor sediments requires forcing by respiration produced co2 and rates are consistent with a first order dependence on pore water undersaturation solubility as determined by mucci 1983 at atmospheric pressure and locally variable mass specific dissolution rate constants respiration driven calcite dissolution fluxes predicted by this combination of respiration and dissolution rate expressions are significantly lower than many previous estimates comparison of dissolution fluxes in the oligotrophic open ocean measured by other researchers with benthic chamber incubation techniques with those predicted by this combination of rate expressions is within stated uncertainties in agreement in all but one case questioning the need for complicated mechanisms such as surface buffering or authigenic precipitation to explain seafloor calcite diagenesis applying these kinetics to a simple one dimensional steady state model of the bulk calcite content and sediment accumulation rates of the sediment mixed layer yields results consistent with observations of the seafloor lysocline the region of transition from high calcite to low calcite sediments on the ceara rise in the western tropical north atlantic and the ontong java plateau in the western equatorial pacific scenarios ignoring dissolution driven by respiration produced co2 in pore waters and using the high order dependence on undersaturation and very large dissolution rate constants implied by some earlier laboratory studies do not simulate these observations while the scheme represented here does in fact imply a strong shift in the locus of carbonate dissolution toward the sediment water interface as bottom water saturation decreases as implied by the observations of martin et al 2000 no simple combination of sediment transport coefficients and reaction kinetics can reproduce the observation of increasing 14c age as dissolution progresses these results emphasize the importance of accurate knowledge of the kinetics of respiration and dissolution to interpretation of either the present day or paleolysocline

the evolution of buctouche spit new brunswick canada buctouche spit is an 11 km long sandy spit on the northeast shore of new brunswick canada it is a typical flying spit having a narrow proximal section which is characterized by a single foredune that is prone to overwash and transgression and a much wider prograding distal section which is characterized by a well developed foredune backed by a series of relict foredunes an optical luminescence dating method in which infrared stimulation is used on potassium feldspars was developed for this study it is a very promising method for dating holocene deposits yielding good resolution and having simplicity of measurement the luminescence ages obtained indicate that buctouche spit extended at a rate of 4 m yr 1 between 715 45 years ago and 240 25 years ago this extension rate equates to a distal end accumulation rate of 56 000 m3 yr 1 for this period at this rate of accretion the present buctouche spit would have formed during the past 2000 years the core data indicate that the spit is 2200 years old which is consistent with the preceding estimate since 240 25 years ago the rate of sediment accumulation at buctouche spit has apparently been falling the accumulation rate between 1839 and 1945 was 23 000 m3 yr 1 less than half of the historic rate of 56 000 m3 yr 1 since 1945 the distal end of buctouche spit has not prograded extended measurably this is because buctouche spit s present vertical growth rate is at most equal to the rate of relative sea level rise at the spit and may be as little as half of the rate of relative sea level rise present sediment supply to buctouche spit is probably 16 000 m3 yr 1 it is likely that the much larger sediment supply required to sustain an historic accretion rate of 56 000 m3 yr 1 was derived from the reworking of a former sandy barrier located seaward and possibly updrift of the present spit buctouche spit is now in a limited sediment supply situation and it has become a constrained spit sediment is being eroded from the centre section of the spit transported to the distal end and then carried away by ebb tidal currents the centre section of the spit will likely breach within the next hundred years if a breach or breaches becomes permanently established in the centre section of the spit the distal end will suffer significant erosion and may be destroyed after this the cycle of rebuilding and landward migration would likely start again at a new location landward of the present spit as relative sea level continues to rise it is concluded that the key to understanding buctouche spit s long term evolution is recognizing that it is migrating landward both by continuous processes like overwash and by the more discrete and catastrophic process of overstepping

high frequency sediment transport responses on a vegetated foredune wind flow and sand transport intensity were measured on the seaward slope of a vegetated foredune during a 16 h storm using an array of sonic anemometers and wenglor laser particle counters the foredune had a compound seaward slope with a wave cut scarp about 0 5 m high separating the upper vegetated portion from the lower dune ramp which was bare of vegetation wind direction veered from obliquely offshore at the start of the event to obliquely onshore during the storm peak and finally to directly onshore during the final 2 h as wind speed dropped to below threshold sand transport was initially inhibited by a brief period of rain at the start of the event but as the surface dried and wind speed increased sand transport was initiated over the entire seaward slope transport intensity was quite variable both temporally and spatially on the upper slope as a result of fluctuating wind speed and direction but overall magnitudes were similar over the whole length ten minute average transport intensity correlates strongly with mean wind speed measured at the dune crest and there is also strong correlation between instantaneous wind speed and transport intensity measured at the same locations when the data are smoothed with a 10 s running mean transport on the beach for onshore winds is decoupled from that on the seaward slope above the small scarp when the wind angle is highly oblique but for wind angles 45 from shore perpendicular some sand is transported onto the lower slope copyright 2012 john wiley sons ltd

nearshore circulation over transverse bar and rip morphology with oblique wave forcing there is a paucity of field data to describe the transition in nearshore circulation between alongshore meandering and rip current systems a combination of in situ current meters and surf zone drifters are used to characterize the nearshore circulation over a transverse bar and rip morphology at pensacola beach florida in the presence of relatively low energy oblique waves current speeds vary in response to the relative wave height ratio hs h which defines the degree and extent of breaking over the shoal in the absence of wave breaking the nearshore circulation was dominated by an alongshore current driven by the oblique waves as waves begin to break across the shoal 0 2 0 5 the meandering current is replaced by an unsteady rip circulation that moves offshore between the shoals before turning alongshore in the direction of wave advance outside the surf zone the increase in wave dissipation is associated with an increase in very low frequency vlf variations in the current speed across the shoal and in the rip channel that caused the circulation to oscillate between an offshore and an alongshore flow the unsteady nature of the nearshore circulation is responsible for 55 of all surf zone exits under these more dissipative conditions in contrast only 29 of the drifters released from the shoal exited the surf zone and bypassed the adjacent shoal with the alongshore meandering current while the currents had a low velocity maximum of 0 4 m s 1 and would not pose a significant hazard to the average swimmer the results of this study suggest that the transverse bar and rip morphology is sufficient to create an alongshore variation in wave dissipation that forces alongshore meandering and low energy rip circulation systems under oblique wave forcing copyright 2013 john wiley sons ltd

aeolian dynamics over a coastal foredune prince edward island canada near surface airflow over a morphologically simple vegetated 8 m high foredune with a small wave cut scarp was measured for onshore to oblique onshore conditions during a low moderate 5 6 m s 1 wind event and a high velocity 11 18 m s 1 sand transporting gale event flow across the foredune was characterized by significant flow compression and acceleration up and across the foredune during both events during the gale a pronounced jet speed bulge developed at the foredune crest which increased in magnitude with increasing wind speed the vertical w velocity component of the 3d flow field was positive upwards across the stoss slope under low wind conditions but negative downwards during gale wind conditions with upslope acceleration during the low velocity event there was speed down within the vegetation canopy as would be expected for a porous roughness cover during the strong wind event there was speed up in the lower portion of the vegetation canopy and this was found up the entire stoss slope sediment transport during the gale force event was substantial across the beach and foredune despite the moderate vegetation cover and minimum fetch aeolian suspension was evident in the lee of the dune crest the observations presented herein show that strong storm winds are an effective mechanism for translating sediment landwards across a high vegetated foredune contributing sediment to the stoss slope crest and leeward slopes of the foredune and backing dunes copyright 2013 john wiley sons ltd

recalibrating aeolian sand transport models a quality controlled data set comprising measurements of aeolian sand transport rates obtained at three disparate field sites is used to evaluate six commonly employed transport rate models those of bagnold kawamura zingg owen hsu and lettau and lettau and to recalibrate the empirical constants in those models shear velocity estimates were obtained using the von karman constant and an apparent von karman parameter models were recalibrated using non linear regression and non linear regression with least squares lines forced through axes origins recalibration using the apparent von karman parameter and forced regression reduced the empirical constants for all models the disparity between the predictions from the different models is reduced from about an order of magnitude to about a quarter of an order of magnitude the recalibrated lettau and lettau model provided the greatest statistical agreement between observed and predicted transport rates with a coefficient of determination of 0 77 evaluation of the results suggests that our estimations of threshold shear velocity may be too slow causing errors in predicted transport rates copyright 2012 john wiley sons ltd

erosive water level regime and climatic variability forcing of beach dune systems on south western vancouver island british columbia canada increases in the frequency and magnitude of extreme water levels and storm surges are correlated with known indices of climatic variability cv including the el nino southern oscillation enso and the pacific decadal oscillation pdo along some areas of the british columbia coast since a shift to a positive pdo regime in 1977 the effects of enso events have been more frequent persistent and intense teleconnected impacts include more frequent storms higher surges and enhanced coastal erosion the response of oceanographic forcing mechanisms i e tide surge wave height wave period to cv events and their role in coastal erosion remain unclear particularly in western canada as a first step in exploring the interactions between ocean atmosphere forcing and beach dune responses this paper assembles the historic erosive total water level twl regime and explores relations with observed high magnitude storms that have occurred in the tofino ucluelet region wickaninnish bay on the west coast of vancouver island british columbia canada extreme events where twl exceeded an erosional threshold i e elevation of the beach foredune junction of 5 5 m acd are examined to identify dominant forcing mechanisms and to classify a regime that describes erosive events driven principally by wave conditions 61 5 followed by surge 21 8 and tidal 16 7 effects furthermore teleconnections between regional cv phenomena extreme storm events and by association coastal erosion are explored despite regional sea level rise eustatic and steric rapid crustal uplift rates have resulted in a falling relative sea level and in some sedimentary systems shoreline progradation at rates approaching 1 5 m a 1 over recent decades foredune erosion occurs locally with a recurrence interval of approximately 1 53 years followed by rapid rebuilding due to high onshore sand supply and often in the presence of large woody debris and rapidly colonizing vegetation in the backshore copyright 2012 john wiley sons ltd

the effects of surface moisture on aeolian sediment transport threshold and mass flux on a beach this paper presents results from a study designed to explore the effects of beach surface moisture and fetch effects on the threshold of movement intensity of sand transport by wind and mass flux the experiment was carried out over a period of five weeks at greenwich dunes prince edward island canada in may and june 2002 moisture content was measured with a delta t moisture probe over a 50 m by 25 m grid established on the beach measurements of wind speed and direction were made with arrays of cup anemometers and a two dimensional sonic anemometer transport intensity was measured at a height of 2 4 cm above the bed using omnidirectional saltation probes which count the impact of saltating grains on a piezoelectric crystal anemometers and saltation probes were sampled at 1 hz sand transport was measured with vertical integrating sand traps over periods of 10 20 minutes results show that where there is a considerable supply of dry sand the saltation system responds very rapidly 1 2 s to fluctuations in wind speed i e to wind gusts where sand supply from the surface is limited by moisture mean transport rates are much lower and this reflects in both a reduction in the instantaneous transport rate and in a transport system that becomes increasingly intermittent threshold wind speed is significantly correlated with an increase in surface moisture content near the upwind end of the beach fetch but the relationship is not significant at the downwind end where sediment transport is initiated primarily by saltation impact from upwind mass flux increases with increasing fetch length and the relationship is described best by a power function further work is necessary to develop a theoretical function to predict the increase in transport with fetch distance as well as the critical fetch distance copyright 2007 john wiley sons ltd

influence of varying tidal prism on hydrodynamics and sedimentary processes in a hypertidal salt marsh creek recent initiatives directing tidal power development in the bay of fundy have raised questions about far field environmental impacts related to energy extraction it is understood that commercial scale tidal power installations in the minas passage will result in an overall decrease in tidal amplitude in the minas basin corresponding changes in sedimentation patterns may or may not be within the natural range of variability and it is hypothesized that intertidal sedimentation rates will demonstrate a non linear response to modification of the tidal energy regime this research considers acoustic doppler velocimeter adv and optical backscatter sensor obs data from a sheltered tidal creek in the minas basin for analysis of tidal characteristics in a hypertidal creek environment over spring and neap tidal cycles sediment deposition in the creek was also measured results show a first order control of topography on flow magnitude in the tidal creek which impacts net sediment deposition through resuspension and removal of newly introduced material this study demonstrates that tides which peak around the bankfull level show reduced early ebb stage turbulence and flow velocity and encourage an extended depositional period the dynamics of marshfull tides may be responsible for the maximum sediment deposition in tidal creeks providing large amounts of material that is eventually distributed to and deposited on marsh surfaces copyright 2012 john wiley sons ltd