modeling suspended sediment discharge from the waipaoa river system new zealand the last 3000 years hydrotrend a hydrologic transport model is used to simulate the water and suspended sediment discharge of the waipaoa river system over the last 3 kyr a time period in which a well documented sequence of natural events and anthropogenic activities that profoundly impacted drainage basin processes occurred comparisons between observed and simulated data show that the model output replicates the frequency and distribution of flow events and the suspended sediment concentration discharge relationship and the long term trends in suspended sediment discharge are consistent with the sediment record preserved on the middle shelf water discharge tracks precipitation and average annual discharge may have been up to 20 higher and 6 lower at different times in the past suspended sediment discharge changed from 2 3 4 5 to 14 9 8 7 mt yr 1 during the anthropocene increasing by 140 after polynesian arrival by 350 after european colonization and by 660 after the catchment headwaters were deforested

sources sinks and storage of river sediment in the atlantic drainage of the united states the history of sediment and its movement in the atlantic drainage demonstrate some of the difficulties of modeling sediment on a river basin scale soil erosion was accelerated by a factor of at least 10 when european settlers cleared forests and planted crops although increasing soil conservation practice and decreasing crop farming have since reduced the rates of erosion large quantities of eroded material are still stored on hillslopes and in stream valleys where they continue to augment the sediment loads of the rivers the sediment from this episode of erosion that is largely past can be expected to emerge from storage for many decades and perhaps even several centuries to come the reservoirs that have been built on many of the major rivers trap significant portions of the moving sediment which in some places may be remobilized by large floods essentially all the river sediment that reaches the atlantic coastal zone is trapped in estuaries and coastal marshlands probably less than 5 is deposi

chemical weathering in high sediment yielding watersheds new zealand 1 we have determined the chemical erosion yields for fifteen watersheds in new zealand ranging in size from 12 2 to 2928 km2 these rates coupled with previously measured physical erosion yields allow us to compare these two modes of landscape denudation the physical erosion yields are some of the highest measured in the world although in most instances the chemical erosion yields are only a small fraction of the total erosion yields the absolute values are very high our data strongly support the notion that chemical erosion rates are greatly influenced by the yield of physical erosion and that the rapid production of fresh surfaces as a result of high physical erosion rates and subsequent denudation is critical to the high chemical erosion yields observed

sediment accumulation patterns and fine scale strata formation on the waiapu river shelf new zealand abstract multiple sediment transport and reworking processes influence fine cm scale strata formation and long term accumulation on the waiapu river shelf new zealand gravity cores collected during two cruises in august 2003 and may 2004 were analyzed using 7 be and 210 pb geochronologies bulk carbon 13 c x radiographs and grain size to investigate sediment mixing and accumulation patterns the presence of 7 be on the inner and mid shelf regions 210 pb accumulation rates revealed that the middle to outer shelf 50 130 m acted as fine sediment repositories on longer time scales excess 210 pb accumulation rates were high with an area weighted average of 1 1 0 1 cm yr and ranging between 0 2 and 3 5 cm yr yet were localized such that only an estimated 23 ranging between 17 and 38 of the fluvial load was retained on the shelf between 40 and 200 m depths over the last 80 to 100 yr sediments not retained on the shelf were either transported to deeper waters or along the shelf beyond the sampling area several cores collected from the high sediment accumulation zone on the middle to outer shelf exhibited non steady state excess 210 pb profiles suggesting that multiple transport processes influenced fine scale strata formation layers of low excess 210 pb activity and predominantly terrestrial 13 c and c n values were likely formed during floods when sediments were rapidly deposited and buried on the shelf these event layers were sufficiently thick up to 20 cm such that all or a portion of the initial flood layer immediately transited through the surface mixing layer ensuring preservation in the sediment record sediments inter bedded with these event layers reflected a relatively marine source indicating either that they were not deposited rapidly or were significantly bioturbated a gradient of physical and biological mixing signatures extending radially from the waiapu river mouth suggested that high background accumulation rates and flood deposits negatively impacted the preservation of biological structures and enhanced preservation of event produced beds

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

magnitude and frequency of landsliding in a large new zealand catchment knowledge of long term average rates of erosion is necessary if factors affecting sediment yields from catchments are to be understood without such information it is not possible to assess the potential influence of extreme storms and therefore to evaluate the relative importance of various components of a sediment budget a study of the sediment budget for the waipaoa catchment north island new zealand included evaluation of long term rates of landsliding for six landslide prone land systems in the catchment the number of landslides per unit area generated by each of several storms was counted on sequential aerial photographs and correlated with the magnitude of the corresponding storm the resulting relationships were combined with magnitude frequency relationships derived for storms from 70 to 100 year rainfall records in the area to estimate a long term magnitude frequency relationship for landsliding for each land system the long term average values of the areal landslide frequency number of slides per unit area per unit time were then calculated from these relationships the volumes of a sample of landslide scars were measured in the field and the proportion of slides that deliver sediment to channels was determined from aerial photographs these measurements then allowed calculation of the long term average rate of sediment production to streams from landslides for different land systems and types of vegetation results suggest that shallow landslides currently contribute about 15 5 of the suspended sediment load in the waipaoa river above the kanakanaia gauging station and that 75 of the sediment production from the landslides occurs during storms with recurrence intervals of less than 27 years reforestation of 6 3 93 km2 of the slide prone lands in the catchment between 1990 and 1995 resulted in a calculated decrease in slide derived sediment of 10 calculations suggest that reforestation of an additional 3 66 km2 of the catchment in areas with the most sensitive combinations of land system and storm regime could decrease the total sediment inputs from landsliding by about 20

dispersal and transformation of organic carbon across an episodic high sediment discharge continental margin waipaoa sedimentary system new zealand abstract the rivers that drain active collisional margins of the southwest pacific deliver up to 35 of particulate organic carbon poc to the world ocean and are a key component of the global organic carbon flux however knowledge of the fate of terrestrial poc in the ocean is both limited and necessary for quantifying terrestrial and coastal ocean carbon budgets here the fate of terrestrial poc is determined off the high discharge waipaoa river sediment yield 15 mt y 1 based on a transect of seven cores from the river floodplain to the adjacent continental shelf and slope total organic carbon toc 13 c 14 c c n ratios and lipid biomarker compounds were used to determine biogeochemical characteristics of surface sediments from terrestrial source to marine sink and how these characteristics vary with river discharge complementary to surface sediments down core characteristics of three multi cores covering the shelf and slope regions were used to identify perturbations in sediment supply via major floods the presence of flood deposits allows us to compare their oc characteristics with non flood sediment thereby helping address the question of how flood events in the river catchment affect the transfer and fate of terrestrial oc through the marine environment results from this study show that as surface sediments are physically and biologically processed across the continental margin they gain a marine signature biomarker analyses of surface samples show decreases in terrigenous vascular plant sources with increasing distance offshore biomarkers also demonstrate that terrestrial oc is being transferred across the continental margin with plant sterols long chain alcohols and long chain fatty acids biomarkers indicative of vascular plants persisting as far offshore as the mid continental slope in contrast to ambient conditions represented by surface sediments rapid delivery by floods allows for more complete transfer of terrestrial carbon to the marine environment a 1 10 cm thick flood layer preserved from cyclone bola march 1988 contains a significant amount of terrestrially sourced oc which subsequently was rapidly buried by sediments delivered during less extreme conditions

contrasting fluid flow patterns at the bufa del diente contact metamorphic aureole north east mexico evidence from stable isotopes impure limestones with interstratified metachert layers were contact metamorphosed and metasomatized by the bufa del diente alkali syenite massive marbles exhibit mineralogical and stable isotope evidence for limited fluid infiltration confined to a 17 m wide zone at the contact influx of magmatic brines along most metacherts produced up to 4 cm thick wollastonite rims according to calcite cc quartz qz wollastonite wo co2 and were observed at distances of up to 400 m from the contact the produced co2 exsolved as an immiscible low density co2 rich fluid chert protolith isotope compositions were 18o qz 27 30 and 18o cc 24 27 many wollastonites in infiltrated metacherts have low 18o ranging from 11 17 and confirm that decarbonation occurred in presence of a magmatic signatured fluid large gradients in 18o wo across the rims may reach 6 the 18o of remaining quartz is often lowered to 15 20 whereas caleites largely retained their original compositions the isotopic reversals of up to 10 between quartz and calcite along with reaction textures demonstrate non equilibrium between infiltrating fluid in the aquifer and the assemblage calcite quartz wollastonite this is compatible with the assumption of a down temperature flow of magmatic fluids that occurred exclusively in the remaining quarzite layer the 13c cc and 18o cc of marble calcites measured perpendicular to two metachert bands reveal significant isotopic alterations along distances of 4 5 cm and 7 5 cm from the wollastonite marble boundary only into the hanging wall marble suggesting an advection process caused by a fluid phase which movel upwards covariation trends of 13c cc and 18o cc across the alteration front indicate that this fluid was co2 rich mass balance calculations show that all co2 rich fluid produced by the decarbonation reaction was lost into overlying marble the metachert aquifers did not leak with respect to water rich fluids

buffers barriers and blankets the dis connectivity of catchment scale sediment cascades abstract catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency this paper introduces the concept of landform impediments termed buffers barriers and blankets that impede sediment conveyance by limiting the connectivity between landscape compartments buffers restrict sediment delivery to channels barriers inhibit sediment movement along channels and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment these features operate as a series of switches which turn on off processes of sediment delivery determining the effective catchment area at any given time using previously documented examples the role of these features in affecting the operation of sediment cascades in a low relief passive landscape setting such as the australian landmass is contrasted to examples from high relief uplifting settings in new zealand the australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since european settlement have impacted upon landscape sensitivity and prospects for river recovery this approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting

landslide occurrence as a response to land use change a review of evidence from new zealand abstract vegetation cover is an important factor influencing the occurrence and movement of rainfall triggered landslides and changes to vegetation cover often result in modified landslide behaviour however it is difficult to relate the occurrence of landslides directly to variations in land use especially in some european countries in contrast new zealand provides a good opportunity to investigate geomorphic responses to anthropogenic land cover changes before european settlers first arrived in the 1840s hilly regions were only marginally influenced by human activity the maoris new zealand s first settlers lived largely on coastal plains or near lakes and rivers they influenced general vegetation cover only through localized burning practices in contrast european settlers moved into the back country and converted extensive hill areas from native forest and bush to pasture this reduced the strength of the regolith and rendered the slopes more susceptible to landslides pulses of natural sedimentation in the pre european period have been related to volcanic activity climatic variability including changes in frequency of cyclonic storms and wind erosion and fluvial erosion following forest fires initiated either by volcanic eruptions or lightning strikes since european deforestation began sediment production has largely been determined by landslide events on unstable slopes thousands of landslides were triggered by high magnitude low frequency climatic events during storms with estimated return periods in excess of 50 years in contrast low magnitude high frequency rainfall events have caused gully and channel erosion examples from different parts of new zealand indicate changes in sediment generating processes following land use modifications after deforestation landslides have contributed significantly to sediment sequences in depositional basins such as lakes swamps estuaries coastal wetlands and the nearshore and offshore zones of continental platforms

a lacustrine record of early holocene watershed events and vegetation history corvara in badia dolomites italy the early middle holocene lacustrine succession of corvara in badia italian dolomites 1521 m a s l records landslides and other watershed events before the onset of human pressure the sensitivity of this archive to relate climate change watershed processes and vegetation dynamics in the catchment has been explored through a stratigraphic study including the analysis of sedimentological features magnetic properties palaeobotanical records and radiocarbon dating a palaeolake existed between 10 1 k and 7 k cal yr bp and was surrounded by a dense conifer forest long term forest dynamics driven by ecological processes and by climatic conditions favourable to upward forest expansion is recorded throughout the pollen record within the fine clastic sedimentation distinct layers enriched in organic debris of terrestrial origin have been attributed to instant events produced by mass movements their age fits the chronology of large landslide events already known in the catchment enabling correlation of the field evidence of landslides with the lacustrine record landslide frequency is controlled by geological and structural factors but it is significantly modulated by the centennial millennial climatic phases that characterise the holocene in the alps the taphonomical properties of pollen and macroremains provided valuable insight on the mechanism of watershed processes copyright 2006 john wiley sons ltd

signals of watershed change preserved in organic carbon buried on the continental margin seaward of the waipaoa river new zealand abstract holocene sediments buried on the continental shelf seaward of the waipaoa river northeastern new zealand preserve a stratigraphic record of terrestrial environmental change the well characterized long term record of storms volcanism and human disturbance in this region provides an opportunity to examine how such changes are reflected in the character of organic carbon oc buried on the continental margin complimentary evidence obtained from analyses of the 14 c content and the elemental and stable carbon isotopic composition of different sedimentary fractions including charcoal wood and clay sized isolates indicates that these perturbations led to mobilization of oc components with variable storage histories in the watershed charcoal transported in the modern waipaoa river and buried in offshore depocenters includes a highly aged component that has apparently been slowly released from storage in soil or alluvial terraces the charcoal fraction ages become dramatically younger in sediments deposited after the taupo volcanic eruption 1717 cal yr bp and then polynesian settlement ca 700 cal yr bp both signaling biomass burning the mean age of woody plant fragments and clay bound oc deposited on the shelf also varies over time with older material having accumulated in the middle holocene and since human occupation deposition of older than average wood fragments and clay bound oc between about 5 and 3 6 kyr bp correlates with evidence for a period of increased storm frequency in the region and may reflect the enhanced delivery of aged soil and sedimentary rock mobilized from hill slopes via earthflows and or deep seated landslides similarly the deposition of older wood and clay bound oc commensurate with the first anthropogenic disturbance ca 700 years ago is consistent with accelerated mass wasting due to deforestation at the same time a change in the elemental and stable isotopic composition of bulk and clay bound oc buried on the shelf may reflect increased marine primary productivity and or mobilization of oc from deep levels in soil profiles deforestation of the waipaoa headwaters by european settlers beginning in the middle 19th century is evinced by a sharper rise in the age of clay associated oc buried offshore today deep gully incision into fractured sedimentary bedrock is a major source of sediment and kerogen to the river and this process has left its mark on the age of sedimentary oc delivered to the adjacent margin

a source to sink perspective of the waipaoa river margin abstract a fundamental goal of the earth science community is to understand how perturbations on earth s surface are preserved in the stratigraphic record recent source to sink s2s studies of the waipaoa sedimentary system wss new zealand are synthesized herein to provide a holistic perspective of the processes that generate transport and preserve sedimentary strata and organic carbon on the waipaoa margin in the late quaternary rapid uplift associated with subduction processes and weak sedimentary units have conspired to generate rapid rates of incision and erosion in the waipaoa catchment since the last glacial maximum lgm we show that although much of the sediment exported offshore during this time interval originated from valley excavation a substantial portion emanated from hillslopes mostly through deep seated landslide and earthflow processes that were vigorous during periods of rapid fluvial incision just prior to the pleistocene holocene transition lacustrine sediments deposited in naturally dammed 7 ky old lake tutira provide a record of holocene environmental controls on upper catchment sedimentation in the wss with 1400 storms identified storm frequency is modulated by the waxing and waning of atmospheric teleconnections between the tropics and antarctica furthermore clear long term changes in sediment yield are evident from the lake tutira record following human settlement as conversion to pasture is accompanied by a 3 fold increase in the long term lake sediment accumulation rate whereas there is ample evidence that waipaoa river flood deposits are routinely deposited offshore in the sheltered confines of poverty bay over the longer term waves and currents subsequently resuspend and transport these deposits both landward sandy fraction and seaward finer fraction thus the timing of sediment supply to areas of net sediment accumulation is more often driven by wave events that are not associated with river flooding therefore we conclude that asynchronicity of river sediment delivery and of wave resuspension in most instances precludes the direct preservation of flood events in the stratigraphic record of the waipaoa shelf over the longer term the sediment package preserved on the shelf and slope since the lgm can be explained in large measure by sequence stratigraphic models forced by varying sea level and ongoing tectonic deformation of the margin as sea level rose sediment supply to the slope was reduced by about a factor of 5 due to shelf trapping despite this reduction turbidites are found at similar frequency throughout the lgm present as the dominant trigger appears to be subduction earthquakes with large ones having a return interval of about 200 100 years sediment budget exercises that consider both modern river discharge versus centennial accumulation rates and post lgm terrestrial production versus offshore isopachs mass balances indicate that about half of the total sediment production from the waipaoa escapes the study area moreover a coupled sediment transport hydrodynamic model and observations of textural trends on the shelf indicate that a large fraction of the sediment is carried outside the study area along the shelf to the northeast by the river plume or by combined current wave activity therefore we conclude that the wss is an open system with sediment escape from the present day through the lgm the organic matter associated with sediment as it moves from upland source to marine sink is a product of particle history and provides a record of materials that have cycled over timescales of days to millions of years the ubiquity of fossil organic carbon oc in both the terrestrial and marine realms of the waipaoa attests both to the chronic nature of its source crumbling mudstones further destabilized by land use and its biogeochemical recalcitrance modern oc persists by virtue of its continual production along the s2s transit and is buried and preserved within the adjacent marine depocenters the waipaoa contrasts with dispersal systems on wide energetic shelves e g the amazon and fly rivers where sediment is extensively refluxed in oxygenated overlying water resulting in the biogeochemical incineration of particulate oc the waipaoa like other small mountainous rivers on active margins exhibits a high riverine oc preservation efficiency 50 in its marine depocenters because of the relatively rapid event driven accumulation of sediment

quantifying sediment connectivity in an actively eroding gully complex waipaoa catchment new zealand abstract using a combination of airborne lidar 2005 and terrestrial laser scanning 2007 2008 2010 2011 sediment delivery processes and sediment connectivity in an 20 ha gully complex which significantly contributes to the waipaoa sediment cascade are quantified over a 6 year period the acquisition of terrain data from high resolution surveys of the whole gully fan system provides new insights into slope processes and slope channel linkages operating in the complex raw terrain data from the airborne and ground based laser scans were converted into raster dems with a vertical accuracy between surveys of 3 of sediment annually with a standard deviation of 20 806 m 3 the volumes of debris eroded from those areas dominated by surface erosion processes were higher than in areas dominated by landslide processes over the six year study period sediment delivery from the source zones to the fan was a factor of 1 4 times larger than the volume of debris exported from the fan into te weraroa stream the average annual volume of sediment exported to te weraroa stream varies widely from 23 195 to 102 796 m 3 fluctuations in the volume of stored sediment within the fan rather than external forcing by rainstorms or earthquakes account for this annual variation no large rainfall events occurred during the monitoring period therefore sediment volumes and transfer processes captured by this study are representative of the background conditions that operate in this geomorphic system

el nino southern oscillation signal associated with middle holocene climate change in intercorrelated terrestrial and marine sediment cores north island new zealand a synchronous textural variation in intercorrelated high resolution sediment records from floodplain continental shelf and continental slope settings of the eastern north island new zealand provides evidence of increased storminess after ca 4 ka an upcore change in sediment texture reflects the transition to landsliding which supplanted fluvial incision as the dominant mode of sediment production in the middle holocene this signal which appears in all three records indicates a regional response to external forcing and records the impact of an intensified atmospheric circulation marking the establishment of the contemporary climate that is strongly influenced by the el nino southern oscillation the change in climate was a hemispheric event and in the southern hemisphere its timing is confirmed by independent proxy records from elsewhere in new zealand and the circum south pacific region

channel change bankfull and effective discharges on a vertically accreting meandering gravel bed river along the lower reaches of the waipaoa river new zealand cross section survey data indicate there was a 23 per cent decrease in bankfull width and a 22 per cent reduction in channel cross section area between 1948 and 2000 as the channel responded to increased inputs of fine suspended sediment following deforestation of the headwaters in late c19 and early c20 we determined the bankfull discharge within a 39 km long reach by routing known discharges through the one dimensional mike 11 flow model the model runs suggest that the bankfull discharge varies between 800 and 2300 m3 s 1 and that the average recurrence interval is 4 2 years on the annual maximum series by contrast the effective flow 360 m3 s 1 is equaled or exceeded three times a year the variability in bankfull discharge arises because the banks tend to be lower in places where flood flows are constricted than in reaches where overbank flow is dispersed over a wide area and because scour has counteracted aggradation in some locations there is no downstream variation in shields stress or in relative shear stress within the study reach bankfull shear stress is on average five times greater than the shear stress required to initiate motion at the effective discharge it is more than twice the threshold value the effective discharge probably has more relevance than the bankfull discharge to the overall picture of sediment movement in the lower reaches of the waipaoa river but because width is constrained by the stability and resistance of the bank material to erosion during high flows that also scour the bed the overall channel geometry is likely determined by discharges at or near bankfull copyright 2006 john wiley sons ltd

downstream fining in a rapidly aggrading gravel bed river downstream changes in particle size that occur in the waipaoa river a 104 km long gravel bed river in which rapid aggradation in the historic post 1800 period was triggered by the conversion of native forest to pasture are summarized in this paper the textural data presented are unique for a field situation not only because of the spatial resolution and extent of the sampling program but also because they provide information about the pattern of fining at different points in time they are supported by equally comprehensive topographic survey data from which local rates of aggradation can be derived despite variability induced by lateral sediment inputs there is an essentially continuous pattern of fining along the entire length of the river fining occurs in both the fine and coarse size fractions of the bed material the highest rates of fining occur in the larger percentiles of the subsurface bed material and in the surface bed material downstream fining in the waipaoa river appears to be a response to changes in flow hydraulics that are regulated by the concave configuration of the long profile the fining gradient developed rapidly in 45 years it does not appear to be influenced by the rate of aggradation nor the overall rate of sediment supply to the channel system because in the short term aggradation has a negligible impact on the inherited form of the long profile

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

controlling factors of the size and location of large gully systems a regression based exploration using reconstructed pre erosion topography abstract the role of different factors potentially affecting the size and location of large gully systems is explored in two tributary basins of the tagus river s portugal the hillslopes of these basins corresponding to tertiary sedimentary formations are affected by hundreds of large gully systems varying in extent from somewhat 2 to 3 ha a study set of 90 gully systems were vectorized from aerial ortophotos and analysed in relation to a set of potential control variables obtained by reconstructing the pre erosion topography multiple linear regression and logistic regression were combined in order to investigate controls over the general morphometry of these landforms area perimeter and sinuosity and their location in the respective basins results indicate that gully systems initiated as bank gullies in response to an incision by the drainage network in both basins and then evolved as a function of upslope contributing area developing progressively more sinuous outlines as a result of headcut bifurcation pre erosion topographic form was shown to have only a marginal effect with results suggesting gully systems have grown essentially through mass movements in headcuts and sidewalls influenced by subsurface water

characteristics of sediments and their dispersal systems along the shelf and slope of an active forearc margin eastern hokkaido northern japan abstract this study revealed sediment distributions and their dispersal systems in a shelf slope setting along an active forearc margin off eastern hokkaido northern japan where the pacific plate is being subducted beneath the okhotsk north american plate at the 7 km deep kuril trench the findings were based on analyses of the textures and structures of surface sediments components of the sampled sand fractions high resolution acoustic reflection records and sediment budgets the studied margin has a 20 30 km wide shelf and steep 5 10 slope marked by faults and folds associated with transpressional tectonics the shelf sediments are classified into gravelly coarse to fine sand from the shelf edge to the uppermost slope 110 1000 m water depth gravel and coarse sand on the shelf off hanasaki fine sand on the middle outer shelf off kiritappu and very fine sand on the shelf off akkeshi the coarse sediments on the eastern shelf off hanasaki and the shelf margin are interpreted to represent lag deposits from coastal erosion associated with a post glacial transgression across topographic highs the two depocenters of shelf sediments subsequent to the last glacial maximum are situated in the middle outer shelf off kiritappu and in the inner middle shelf off akkeshi these are interpreted as transgressive highstand sequences whose locations were controlled by ridges on the shelf margin and topographic highs on the shelf the shelf sediment thickness reaches 20 m and the total volume is estimated at ca 6 km3 the slope sediments are grouped into medium fine sand on the uppermost and upper slopes 150 2000 m water depth and mud dominated sediments on the upper to middle slope 1000 3000 m water depth the sandy sediments on the slope at water depths greater than 1000 m are regarded as being derived from the shelf break by gravitational redistribution the occurrence of diamictite like sediments around gullies that incise into the slope indicates that mass movement and sediment gravity flows play an important role in the redistribution of sediments upon the slope on the upper middle slope hemipelagic fallout and advection of turbid water from the shelf edge provide a supply of suspended material the main contributor of sediment supply to the area is coastal erosion 1 81 mt y 1 along with a lesser contribution from fluvial input 0 10 mt y 1 during the latest quaternary the rates of sediment accumulation upon the shelf are estimated to have been 0 47 mt y 1 the remainder of the material transported into the sea is probably redistributed to deeper parts of the slope via gravitational sediment flows or transported outside of the study area by alongshore and tidal currents the studied shelf that kept less than a quarter of the mass from land is comparable with other active margin shelves of new zealand and california although they are fed by high sediment laden rivers

reaction and relaxation in a coarse grained fluvial system following catchment wide disturbance abstract the waiapu river catchment drainage area of 1734 km2 is one of the most prolific conveyors of sediment in the world annually delivering roughly 35 mt of fine material to the ocean from eroding gullies hillslopes and reworked sediment on valley floors tectonic and geologic influences in combination with a dynamic climate influenced by tropical cyclones and clearance of vegetation from steep hillslopes predisposes this region to high rates of erosion the bedload sediment regime of the river is strongly influenced by several exceptionally large gullies and gully complexes that produce a coarse grained poorly sorted sediment mixture rapid abrasion and breakdown leads to high rates of suspended sediment yield a wave of bedload material manifesting as elevated bed levels and significant widening of active alluvial fills has been triggered by large inputs of hillslope material from a few key tributary catchments following cyclone bola in 1988 we review the evidence for the relaxation process of the sedimentary system in the subsequent 29 years appraising some of the legacy effects that may endure as associated with reworking of the considerable alluvial stores within the waiapu system we use structure from motion sfm techniques and archival aerial photos to quantify changes in sediment storage at the base of two major gully systems in recent decades a record of over 850 cross section surveys at 62 sites on 10 rivers throughout the catchment 1958 2017 indicates recent transition from a trend of continuous accumulation to downcutting and remobilisation of valley bottom deposits the channel cross sections provide a minimum estimate of sediment flux from source areas to the lower reaches of the river giving a rudimentary but spatially extensive picture of the wave of material cascading through the drainage network the largest impacts occur in the upper steepland rivers closest to the landslide derived sediment supply transport rates here as inferred from cross section change are at a maximum during an aggradational phase following cyclone bola then taper off despite the large sediment accumulations remaining in the system as of 2017 the river is in the process of incising the upper extents of this deposit on a trajectory of recovery toward pre bola conditions the compilation of cross section data provides us with new insights into the sensitivity of particular sites in the landscape as well as the changing relationship between reach sediment storage and transport rates during the response and relaxation phase of a major disturbance in a large catchment

slip slidin away a post glacial environmental history of the waipaoa river basin abstract the dramatic changes that occurred to the post glacial landscape in the headwaters of the waipaoa river basin are a consequence of perturbations about the equilibrium that exists between the rate of tectonic uplift and fluvial incision at times when the amount of coarse sediment delivered to channels exceeds the capacity of streams to remove it the channel bed rises at the rate of tectonic uplift once bedload overcapacity is replaced by undercapacity and the alluvial cover is depleted streams reestablish contact with bedrock and recuperate the time lost to fluvial incision the first major perturbation occurred during the final phase of the last glaciation ca 33 17 5 cal ka when aggradation was driven by a climate forced variation in the relative supplies of sediment and water we suggest that the subsequent transformation of channels in the headwaters of the waipaoa river basin from alluvial to bedrock occurred as the atmospheric and oceanic circulation converged on their contemporary patterns ca 12 cal ka a second major perturbation that continues to the present began ca 1910 1912 ce when a massive increase in sediment load was accompanied by a modest increase in water discharge after the native vegetation cover in the headwaters was replaced by pasture the processes of terrace creation and incision are inherently unsteady and in five interim cases incision was arrested by a transient increase in the thickness of the alluvial cover that was a response to climatic forcing events that disrupted the native vegetation cover in the headwaters also modulated patterns of sediment dispersal and accumulation in other parts of the fluvial system and caused rapid storm driven infilling of the poverty bay flats tectonic subsidence dictates the course of the waipaoa river across poverty bay flats which because the modern rate of floodplain construction by vertical accretion is rapid relative to the amount of destruction by lateral channel migration has remained virtually unchanged for the past 100 years during this time the channel assumed a narrower deeper form that is in equilibrium with the contemporary supply of sediment and hydraulic regime

the magnitude and frequency characteristics of fluvial transport in a devon drainage basin and some geomorphological implications summary magnitude and frequency analysis of fluvial transport based on long and detailed record has been lacking for british rivers continuous monitoring of suspended sediment and solute concentrations for the river creedy devon since october 1972 has provided an opportunity to establish the medium term magnitude and frequency characteristics of river transport in a sizeable 262 km 2 drainge basin results reveal the importance of solute removal substantial variations in the relative magnitude of annual dissolved and suspended sediment yields clear differences in the temporal distribution of sediment and solute removal and contrasts in the magnitude and recurrence of extreme values of dissolved and suspended solids transport consideration of discharge levels most effective for transporting river loads in relation to a natural channel cross section has stressed the importance of events of moderate magnitude and frequency in this drainage system

altered regional sediment transport regime after a large typhoon southern taiwan analyses of river suspended sediment response to record breaking regional rainfall in southern taiwan during typhoon morakot 7 9 august 2009 reveal systematic changes in the regional sediment transport regime as characterized by rating curve parameters with decreasing b typically considered to be a constant for a given gauging station and increasing intercept k values in concentration discharge c q relations c kq b these changes result in much greater sediment concentration and thus sediment transport in subsequent low flow events after the typhoon an effect that amplifies and extends the influence of such extreme events through increased low flow sediment transport our finding that the exponent b is not constant contrasts with the conventional assumption that large events influence sediment yields through increased intercept k values thereby supporting the interpretation that basin sediment delivery influences both rating parameters and increases post event low flow sediment transport surveys of landslide density and riverbed grain sizes before and after typhoon morakot support the interpretation that the observed decrease in b values and the synchronous shift from an inverse correlation between k and mean catchment slope before the typhoon to a positive correlation afterward reflect an altered sediment transport regime and a change from channel migration and bank erosion to reworking of landslide debris and enhanced bed mobility as the dominant processes supplying fluvial sediment

quantifying human impacts on rates of erosion and sediment transport at a landscape scale establishing background geologic rates of erosion is prerequisite to quantifying the impact of human activities on earth s surface here we present 10 be estimates of background erosion rates for ten large 10 000 100 000 km 2 river basins in the southeastern united states an area that was cleared of native forest and used intensively for agriculture these 10 be based rates are indicative of the pace at which the north american passive margin landscape eroded before european settlement 8 m m y comparing these background rates to both rates of post settlement hillslope erosion and to river sediment yields for the same basins we find that following peak disturbance late 1800s and early 1900s rates of hillslope erosion 950 m m y exceeded 10 be determined background rates more than one hundred fold although large basin sediment yields during peak disturbance increased 5 10 above pre settlement norms rivers at the time were transporting only 6 of the eroded material work by others suggests that the bulk of historically eroded material remained and still remains as legacy sediment stored at the base of hillslopes and along valley bottoms because background erosion rates such as we present here reflect the rate at which soil is generated over millennial time scales they can inform and enhance landscape management strategies

organic carbon in floodplain alluvium signature of historic variations in erosion processes associated with deforestation waipaoa river basin new zealand 1 we use c org and 13c to trace the origin of the alluvium deposited on the waipaoa river floodplain at mcphail s bend between 1853 and 2002 the overbank deposits exhibit a more positive range of 13c values 26 3 0 6 than contemporary suspended sediment in transport at intermediate flows 27 8 0 2 when gully erosion releases most material to stream channels reflecting the greater contribution made by shallow landsliding in the headwaters during large precipitation events overbank sediment associated with recent floods contains a higher 50 amount of organic carbon than alluvium deposited by pre 1927 floods which was derived from outcrops of weathered bedrock on steep riparian hillslopes that were the primary sediment source before the soil mantled hillslopes elsewhere in the headwaters of the basin were destabilized by deforestation the recent alluvium resembles the bw horizon of soils present on these hillslopes sediment deposited during floods generated by localized storms and an overbank event that did not feature widespread shallow landsliding also has a distinctive signature that provides an indication of its provenance the organic carbon associated with the alluvium appears to be old 4031 40 b p in the case of the carbon associated with sediment deposited in 2002 and to be derived from weathered cretaceous and tertiary sedimentary rocks

badass gullies fluvio mass movement gully complexes in new zealand s east coast region and potential for remediation abstract this paper reviews gully erosion in the east coast region of new zealand s north island and conceptualises fluvio mass movement gully complexes as badass gully systems tectonic setting and lithological control with steep slopes and a climate influenced by tropical cyclones predispose hill country in the east coast region to gully erosion the clearance of indigenous forest since the late 1800s has dramatically increased catchment erosion and paved the way for development of large scale fluvio mass movement gully complexes these features are a composite of fluvial and mass movement processes they are conceptualised as badass by not conforming to any existing gully model and by generating disproportionate results in east coast catchment sediment cascades their remediation is discussed but their nature means that prevention is better than a cure

suspended sediment transport response to upstream wash load supply in the sand bed reach of the upper yellow river china summary wash load is a major component of suspended sediment transport in the sand bed reach of the upper yellow river china this wash load sediment originates from the loess region with the high runoff mainly originating from the rock mountains of its upstream basin these characteristics result in a mismatch between water and sediment sources and a low probability of high runoffs meeting high suspended sediment concentration ssc flows as a result higher runoff with lower ssc levels hr ls and lower runoff with higher ssc values hs occur whose sscs do not follow the typical power form for flow discharges c i q where c i and q are ssc and flow discharge respectively here we modify the traditional power form with an upstream wash load supply function c 1 to satisfy the relation between the water and wash load sediment concentrations in water sediment mismatched cases c i q c 1 where c is an input flow s ssc using the daily flow discharges and sscs of nine typical hr ls flows and 18 hs flows in our study reach from 1960 to 2012 we find that changes in response to input flow conditions and downstream transport distances when the downstream transport distance is between 360 and 663 5 km varies between 0 3 and 0 6 in a hs input flow condition while in the hr ls input flow case tends to be greater than 0 6 between 0 74 and 0 65 the entrainment rate of an hr ls flow and the deposition rate of an hs flow appear to be asymmetrically balanced establishing a primary mechanism for channel aggradation and upward fining of floodplains in our study reach

production storage and output of particulate organic carbon waipaoa river basin new zealand 1 we compute the particulate organic carbon poc yield of the waipaoa river new zealand using sediment rating curves in conjunction with measurements of the carbon content of the suspended sediment to ascertain the source of the carbon and the extent to which the poc flux is tied to different erosion processes we determined the stable isotopic carbon composition 13c and carbon to nitrogen c n ratio of weathered bedrock soil and regolith most poc is derived from suspended sediment generated by gully erosion incision into weathered bedrock supplemented by landsliding during extreme events the specific yield of poc from the headwaters drainage area 1580 km2 is 55 g m 2 yr 1 which is very high by global standards and by comparison with other turbid steep land rivers the annual loss to floodplain storage is 4 3 6 kt of the mean annual poc yield 86 7 kt thus the waipaoa river is a very effective conduit for transporting poc to the ocean

great expectations flow restoration and sediment transport in the waimea river kaua i abstract conventional and novel observations made in the waimea river basin between 1960 and 1995 permit the total riverine mass flux to be estimated and the influence that flow restoration will have on sediment dynamics in the river s lower reaches to be assessed flows between the threshold for sediment transport 6 0 m3 s 1 and the most effective flow 80 7 m3 s 1 recur annually and transport 60 of the waimea river s suspended sediment load discharges of this magnitude essentially were unaffected by plantation era agricultural diversions of 2 3 0 7 m3 s 1 the modern day mass flux from the waimea river basin is 155 38 t km 2 y 1 and comparison with an independent cosmogenic nuclide based estimate implies that it has remained at about this level for the past 10 ky previous work indicated that i most of the sand the waimea river transports to the coast is derived from steep rapidly eroding sparsely vegetated bedrock dominated hillslopes and ii the sediment transport regime of the waimea river is supply limited at very high discharges recurrence interval 2 5 years consequently major floods tend to remove sand from the estuary climate change has caused a statewide decline in heavy rainfall and a commensurate decline in the magnitude of peak flows in the basin s pristine undiverted headwaters over the past 97 years the effect this secular change in climate presently is having on streamflow was foreshadowed in the late 1970s by a naturally occurring warm pacific decadal oscillation phase reduction in the magnitude of flows with low exceedance probabilities additionally the controlling base level at the river mouth has risen and been displaced seaward simple proportionality approximations show that for a constant sediment supply aggradation will occur if either the magnitude of flows with a low exceedance probability declines and or base level rises thus anthropogenic stresses on waimea river s lower reaches are not derived from the within basin influence agricultural diversions exert on the flow regime and will not be resolved by restoring flow to the river these stresses primarily accrue from extrinsic factors that will continue to influence the river s hydrologic and sediment transport regimes until global offsetting climate ameliorating measures are implemented

floodplain construction by recent rapid vertical accretion waipaoa river new zealand the rate of vertical accretion typically 14 18 mm h 1 during eight floods in the waipaoa river basin with recurrence intervals of 5 to 60 years was determined by relating the floodplain stratigraphy at mcphail s bend to the 1948 1995 flood history overbank deposits remaining after a flood that occurred in march 1996 suggest a rate of vertical accretion of 15 mm h 1 by contrast because the flow velocity across the floodplain was too high to permit deposition from suspension during the record flood of march 1988 the rate of vertical accretion was only 6 mm h 1 the sequence of deposition is highly discontinuous and the rapid vertical accretion is a response to a late 19th to early 20th century phase of deforestation in the headwaters that probably initiated a far greater change in suspended sediment yield than in discharge cross section surveys conducted since 1948 indicate that the high suspended sediment load of the waipaoa river also promoted in channel deposition which effected a progressive reduction in bankfull channel width although due to the overbank deposition channel capacity remained constant 1998 john wiley sons ltd

erosion thresholds and suspended sediment yields waipaoa river basin new zealand characteristics of the suspended sediment load in the waipaoa river new zealand and in two of its tributaries mangatu and te arai rivers are examined for evidence of different dominant erosion processes in the basins upstream different shapes of the suspended sediment concentration water discharge relations lead to differences in long term average yield event yield magnitude frequency relations and relative importance of large flows and rare events in the mangatu river frequent runoff events 2 1 are relatively more important to the long term yield 11 540 t km yr half of the long term average load is transported by events with return periods less than 1 year and there is little evidence of an erosion threshold limitation on sediment supply this is consistent with the predominance in the mangatu basin of hillslope erosion processes that involve scour by surface and channelized runoff particularly gully erosion this contrasts with the te arai river where sediment concentration tends to be much lower at low and moderate flows frequent runoff events transport less of the long term yield 4600 t km 2 yr than do rarer large magnitude flood events event sediment yields are an order of magnitude lower during events with subannual return periods and half of the long term average load is transported during events with a return period of 2 years some of these characteristics appear to result in part from two populations of runoff events in the te arai basin nonetheless they are consistent with field evidence that most of the sediment supplied to the te arai stream network is generated by shallow landslides which are activated once a rainfall threshold is exceeded

sediment budget to assess the geomorphic effect of a cyclonic storm new zealand abstract a short term sediment budget was constructed to assess the erosion response of a soft rock hill country watershed to an intense rainstorm event the watershed is located in a landslide prone area on the east coast of the north island new zealand during march 1988 753 mm of rain was recorded over a four day period with 320 mm and 329 mm on successive days known as cyclone bola this was the largest rainstorm event in the tutira watershed in the 93 year rainfall record the budget quantifies the total sediment generated during the storm the relative contribution of erosion processes involved the amount of sediment held in storage and the amount discharged into two lakes within the watershed a landform map of the watershed was constructed and the contribution of each landform type to the total budget was calculated a total of 1 35 0 13 million m3 of sediment was generated during the storm at an average of 420 m3 ha this is equivalent to a denudation value of 42 mm for the total watershed 3208 ha and 83 mm for the landforms severely affected by landsliding 1427 ha of the sediment generated 21 remained on hillslopes 22 was deposited on valley floors 51 was deposited on the lakebeds and the remaining 6 was discharged from the watershed via the lake outlet most of the sediment generated during the storm was from primary source areas on hill slopes with sediment in secondary storage providing only a small contribution landslide erosion was the main process accounting for 89 of the sediment generated channel tunnel gully and sheet erosion were only minor contributors to the budget six hillslope landforms which occupy only 44 of the watershed generated 90 of the sediment the results of this sediment budget when put in context with the storm magnitude frequency history being analysed from lake cores contribute to the identification of sustainable land use and management of soft rock hill country

stratigraphic modeling of the western taiwan foreland basin sediment flux from a growing mountain range and tectonic implications abstract sediment flux signals from source to sink in foreland basins preserve a record of tectonics sea level and climate through erosion and sedimentation however longitudinal sediment transport often occurs in foreland basins thus removing part of the orogenic material flux from foreland basin records here we use mass balance calculation and stratigraphic simulations of sediment fluxes for the taiwan orogen to provide an order of magnitude estimate of how much orogenic material may bypass a foreland basin our results indicate a significant potentially more than 50 mismatch between sediment volume currently preserved in the basin and the amount of material presumably eroded from the orogen since the onset of collision in taiwan this suggests either a significant overestimation of average erosion rates over the period concerned with orogenic development of taiwan or it supports previous paleogeographic work suggesting that longitudinal sediment transport in the paleo taiwan strait served as a major bypass conduit of importance for the establishment of a steady state orogen we identify candidate submarine topography in the south china sea that may preserve taiwan s missing erosional mass

impact of coarse sediment supply from hillslopes to the channel in runoff dominated dryland fluvial systems sediment supply from hillslopes to channels is an important control on basin functioning and evolution however current theoretical frameworks do not adequately consider processes of runoff driven hillslope sediment supply which affect river channels spatially and temporally mountainous dryland basins exhibit an important manifestation of these processes because their debris mantled hillslopes produce coarse sediment and because rainfall is delivered as infrequent high intensity short duration rainstorms this paper combines field measurements and modeling to explore runoff driven coarse sediment supply from hillslopes to the channel and assesses a range of plausible storms on the longitudinal patterns of sediment load and its caliber over a dryland basin reach our results show that modeled sediment load and its grain size distribution are determined by the nonlinear interaction between rainfall characteristics and hillslope attributes resulting in longitudinal fluctuations in sediment supply the relative magnitude and location of which varies between storms results suggest that long hillslopes are most sensitive to rainfall and they exhibit large variations in supplied sediment load and grain size for different runoff characteristics short and steep hillslopes are less sensitive to rainfall variations as gradient effects dominate over the role of length in modulating runoff accumulation furthermore the signal of the median fraction d50 of modeled sediment supplied by the hillslope is preserved in the coarse fraction of the measured in channel grain sizes d90 finally we propose a simple index which provides new insights into the effectiveness of different rainstorms in terms of the impact of hillslope sediment supply on the channel

environmental impact of the 1 8 ka taupo eruption new zealand landscape responses to a large scale explosive rhyolite eruption abstract large scale ignimbrite eruptions from rhyolitic caldera volcanoes can trigger geologically instantaneous changes in sedimentary systems over huge areas by either burying existing environments or overloading them with vast quantities of unconsolidated particulate material the post eruption readjustment of the landscape to such perturbations is one of the most dramatic processes in physical sedimentology exemplified here by the 1 8 ka taupo eruption in the central north island of new zealand this eruption generated voluminous fall deposits then climaxed with emplacement of a c 30 km 3 non welded ignimbrite over a near circular area of c 20 000 km 2 approximately 90 of the area but the headwaters of many of the north island s largest rivers were impacted by both the primary pyroclastic fall and flow material large scale post eruption remobilisation of this material coupled with the re establishment of fluvial systems occurred in a distinct sequence as recorded by the evolution of sedimentary facies in different sub environments following an initial period dominated by mass flows re establishment of fluvial systems began with the headward erosion of box canyons through the ponded ignimbrite deposits a process often associated with the break out of temporary lakes aggradational streams developed in these channels rapidly evolved from shallow ephemeral sediment laden outbursts associated with flash flood events to deeper permanent braided rivers before declining sediment yields led to retrenchment of single thread rivers and a return to pre eruption gradients and bedloads years to decades later typically the modern profile of many streams and rivers follow closely their pre eruption profiles and incision and erosion is overwhelmingly confined to the deposits of the eruption itself although the general remobilisation pattern is similar for all impacted river systems detailed studies of the waikato rangitaiki mohaka ngaruroro and whanganui catchments show that the relative timing and scale of each eruption response phase differs between each catchment these reflect differences in catchment physiography and hydrology and the volume and type of pyroclastic material deposited in each ultimately the landscape response reflects the relative spatial distributions of and the volumetric ratios between the volumes of pyroclastic debris water and accommodation space in the basin cf kataoka and manville this volume

coastal progradation and sediment partitioning in the holocene waipaoa sedimentary system new zealand abstract over the late holocene highstand the shoreline at poverty bay nz migrated 12 km seaward fed by sediment from the waipaoa river paleo shorelines indicate steadily decelerating progradation possibly signaling changes in forcing on the waipaoa sedimentary system to isolate the cause of this progradation slowdown we reconstruct late holocene tectonics and stratigraphy over the waipaoa coastal plain and nearshore from 7 ka present we find that decreasing rates of sediment storage by coastal progradation were driven by increasing tectonic storage in the steadily subsiding but rapidly growing coastal plain such that net terrestrial storage remained constant at 0 8 mt yr hence changes in shoreline migration were due to autogenic increases in accommodation rather than allogenic changes in forcing furthermore while the waipaoa sediment load is primarily mud reconstructions suggest that progradation was largely controlled by the supply of coarse grained sediment our results suggest that in coastal systems such as the waipaoa where progradation is confined and wave energy is high net accumulation of muds occurs only behind the prograding sandy shoreface which shelters them from wave attack accounting for mud storage in the waipaoa coastal plain and poverty bay suggests that export of muddy sediment to the waipaoa shelf remained roughly constant at 2 0 mt yr from 7 ka until the onset of anthropogenic deforestation in the 19th century

terrestrial sources and export of particulate organic carbon in the waipaoa sedimentary system problems progress and processes abstract the composition of particulate organic carbon in sedimentary systems can provide information concerning sources of materials and their history the nsf margins source to sink study of the waipaoa sedimentary system in new zealand provides a platform to calibrate the particulate organic carbon sedimentary record by linking chemical characteristics to terrestrial and marine sedimentary processes this report is a preliminary evaluation of the available organic carbon concentration elemental c n ratio and c isotopic composition data for the terrestrial portion of the system samples analyzed were rocks soils floodplain sediments and riverine suspended sediments measurements confirm previous conclusions that a portion of the riverine particulate organic carbon is derived from sedimentary rocks the rock c kerogen concentration is relatively invariant 0 25 from rock source to riverine and floodplain sediments the non rock c is derived from c3 vegetation in most of the watershed the exception being the floodplain in which local c4 plant inputs are detected the non rock organic carbon has a mean 14c age of approximately 1000 years which reflects a mixture of modern and aged components the presence of aged non rock c which is chronic in its supply to the river indicates storage of particulates within the watershed remobilized colluvial and alluvial deposits are among the possible sources systematic differences are found between 13c databases generated by various groups while there may be natural explanations for these differences methodological artifacts have to be considered standardization of methods that cross source to sink boundaries is recommended

postshield stage transitional volcanism on mahukona volcano hawaii age spectra from 40ar 39ar incremental heating experiments yield ages of 298 25 ka and 310 31 ka for transitional composition lavas from two cones on submarine mahukona volcano hawaii these ages are younger than the inferred end of the tholeiitic shield stage and indicate that the volcano had entered the postshield alkalic stage before going extinct previously reported elevated helium isotopic ratios of lavas from one of these cones were incorrectly interpreted to indicate eruption during a preshield alkalic stage consequently high helium isotopic ratios are a poor indicator of eruptive stage as they occur in preshield shield and postshield stage lavas loihi seamount and kilauea are the only known hawaiian volcanoes where the volume of preshield alkalic stage lavas can be estimated

application of the shetran basin scale landslide sediment yield model to the llobregat basin spanish pyrenees the first application of the shetran basin scale landslide erosion and sediment yield model is carried out for a major landsliding event in the upper 505 km2 of the llobregat basin in the eastern spanish pyrenees in november 1982 the model simulates the spatial distribution of shallow landslides and their sediment yield acknowledging uncertainty in the model parameter evaluation the aim of the application was not to reproduce the observed occurrence of landslides as accurately as possible with one simulation but to bracket the observed pattern with several simulations representing uncertainty in the key input conditions bounds on the landslide simulations were thus determined as a function of uncertainty in the vegetation root cohesion used in the model factor of safety calculations the resulting upper bound considerably overestimates the observed pattern 17 000 landslides compared with an observation of around 700 but it reproduces several of the principal clusters in the observed pattern the lower bound contains around 500 landslides the sediment yield estimates 2670 14 630 t km 2 are comparable to measurements elsewhere in the pyrenees for extreme events the results demonstrate an ability to simulate the basin scale landslide response to a rainfall event and the resulting sediment yield they also highlight the need for further research in setting the uncertainty bounds and in avoiding large overestimates of landslide occurrence arising in part from a current inability to model small scale controls for a basin of the given size copyright 2006 john wiley sons ltd

coupling fine particle and bedload transport in gravel bedded streams abstract fine particles in the silt and clay size range are important determinants of surface water quality since fine particle loading rates are not unique functions of stream discharge this limits the utility of the available models for water quality assessment data from 38 minimally developed watersheds within the united states geological survey stream gauging network in california usa reveal three lines of evidence that fine particle release is coupled with bedload transport first there is a transition in fine particle loading rate as a function of discharge for gravel bedded sediments that does not appear when the sediment bed is composed of sand cobbles boulders or bedrock second the discharge at the transition in the loading rate is correlated with the initiation of gravel mobilization third high frequency particle concentration and discharge data are dominated by clockwise hysteresis where rising limb discharges generally have higher concentrations than falling limb discharges these three observations across multiple watersheds lead to a conceptual model that fine particles accumulate within the sediment bed at discharges less than the transition and then the gravel bed fluidizes with fine particle release at discharges above the transition discharge while these observations were individually recognized in the literature this analysis provides a consistent conceptual model based on the coupling of fine particle dynamics with filtration at low discharges and gravel bed fluidization at higher discharges

geology geography and humans battle for dominance over the delivery of fluvial sediment to the coastal ocean abstract sediment flux to the coastal zone is conditioned by geomorphic and tectonic influences basin area and relief geography temperature runoff geology lithology ice cover and human activities reservoir trapping soil erosion a new model termed bqart in recognition of those factors accounts for these varied influences when applied to a database of 488 rivers the bqart model showed no ensemble over or underprediction had a bias of just 3 across six orders of magnitude in observational values and accounted for 96 of the between river variation in the long term 30 years sediment load or yield of these rivers the geographical range of the 488 rivers covers 63 of the global land surface and is highly representative of global geology climate and socioeconomic conditions based strictly on geological parameters basin area relief lithology ice erosion 65 of the between river sediment load is explained climatic factors precipitation and temperature account for an additi

sediment flux from a mountain belt derived by landslide mapping in humid uplands landsliding is the dominant mass wasting process in the western southern alps of new zealand landslides are scale invariant and have a power law magnitude frequency distribution independent studies from other regions suggest that this is a general property of landsliding this observation is of critical importance to the evaluation of the impact of events of different length scales over different time intervals on landscape evolution it is particularly useful when estimating regional geomorphic rates because it constrains the frequency and overall significance of extreme events which cannot otherwise be evaluated by integrating the complete response of the system we estimate the regional denudation rate due to landsliding to be 9 4 mm yr 1 sediment discharge from the western southern alps is dominated by landslide derived material

modern sediment dispersal and accumulation on the outer poverty continental margin abstract the poverty margin was sampled in 2005 and 2006 as part of an international initiative to examine the terrestrial and marine sedimentary response to natural and human impacts on dispersal systems at mud dominated coasts the nsf margins source to sink initiative 210pb accumulation rates generally decrease from 1 g cm2 y in the mid shelf depocenter on the outer shelf to 0 1 g cm2 y on the mid slope plateau range 0 04 2 53 g cm2 y higher accumulation rates are observed all along the outer poverty shelf extending over the shelf break onto the upper poverty slope in canyons and gullies rates are fast in gullies that incise into the shelf edge 0 75 1 g cm2 y particularly in the area between waipaoa canyon and poverty canyon and in the axis of poverty canyon 1 29 1 89 g cm2 y below 1200 m water depth rates in the axis of poverty canyon are no more rapid than those found at open slope cores in similar water depths 0 12 0 15 g cm2 y excess 210pb profiles generally exhibit steady state characteristics except in the axis of poverty canyon where non steady state 210pb profiles are observed 137cs was not found above minimum detection limits or above statistical background levels in any cores from the poverty margin 7be was found distributed widely along and across the margin during both summer and winter periods observed to depths of up to 4 cm widespread presence of 7be on the margin in both winter and summer suggests that terrestrially derived sediment is reaching the outer shelf and upper slope throughout the year a sediment budget based on 210pb accumulation rate data shows that approximately 13 18 of the waipaoa annual discharge is accumulating on the outer poverty margin as a whole and approximately 11 15 of the annual discharge is accumulating on the continental slope alone notably approximately 28 of the sediment annually accumulating in the outer margin is being sequestered in slope gullies and canyons although they represent only 6 of the area of the outer margin

residence time of alluvium in an aggrading fluvial system relationships between the surface area and age of alluvial deposits were used to estimate the residence time of alluvium in the 2205 km2 waipaoa river basin new zealand the contemporary waipaoa river is an efficient transporter of sediment to the continental shelf but the basin has been characterized by rapid channel and valley aggradation in the historic period and by extensive mid to late holocene alluvial storage in the lower reaches the area weighted mean age of alluvial deposits in the lower part of the river basin is 4400 yr these deposits comprise terrace remnants isolated by downcutting and holocene to recent sediments that are potentially remobilizable by the modern river even though the amount of storage is small relative to downstream transport the majority of the potentially remobilizable alluvium is likely to remain in storage for 100 yr and its half life time for 50 per cent removal is 2000 yr within the confines of the flfloodplain the apparent loss of older deposits is due primarily to burial but losses of the most recent deposits are due almost entirely to remobilization 30 40 per cent with the remainder preserved in the alluvial record for at least 104 yr most of this sediment is likely to remain in storage until there is a shift to a degradational state copyright 2006 john wiley sons ltd

geomorphologic controls on the age of particulate organic carbon from small mountainous and upland rivers 1 to assess the role that erosion processes play in governing the character of particulate organic carbon poc discharged from small mountainous and upland rivers a suite of watersheds from oregon california and new zealand was investigated the rivers share similar geology tectonic setting and climate but have sediment yields that range over 3 orders of magnitude the 14c age of the poc loads is highly correlated with sediment yield carbon isotope mass balances reveal that the rivers carry bimodal mixtures of modern plant and ancient rock derived oc at lower yields modern plant oc dominates the material delivered to the river by sheetwash and shallow landsliding with increasing yield a progressively larger part of the poc is contributed directly from bedrock erosion via deep gully incision our results support the inference that active margin watersheds are important sources of aged poc to the ocean

last glacial aggradation and postglacial sediment production from the non glacial waipaoa and waimata catchments hikurangi margin north island new zealand abstract the sediment flux generated by postglacial channel incision has been calculated for the 2150 km 2 non glacial waipaoa catchment located on the tectonically active hikurangi margin eastern north island new zealand sediment production both at a sub catchment scale and for the waipaoa catchment as a whole was calculated by first using the tensioned spline method within arc map to create an approximation of the aggradational waipaoa 1 surface contemporaneous with the last glacial maximum and second using grid calculator functions in the gis to subtract the modern day surface from the waipaoa 1 surface the waipaoa 1 surface was mapped using stereo aerial photography and global positioning technology fixed the position of individual terrace remnants in the landscape the recent discovery of kawakawa tephra within waipaoa 1 aggradation gravels in this catchment demonstrates that aggradation was coincidental with or began before the deposition of this 22 600 14 c year old tephra and using the stratigraphic relationship of rerewhakaaitu tephra the end of aggradation is dated at ca 15 000 14 c years ca 18 000 cal years bp the construction of the waipaoa 1 terrace is considered to be synchronous and broadly correlated with aggradation elsewhere in the north island and northern south island indicating that aggradation ended at the same time over a wide area subsequent downcutting a manifestation of base level lowering following a switch to postglacial incision at the end of glacial age aggradation points to a significant southern hemisphere climatic warming occurring soon after ca 15 000 14 c years ca 18 000 cal years bp during the older dryas interval elevation differences between the waipaoa 1 c 15 ka terrace and the level of maximum channel incision i e before aggradation since the turn of the 20th century suggest about 50 of the topographic relief within headwater reaches of the waipaoa catchment has been formed in postglacial times the postglacial sediment flux generated by channel incision from waipaoa catchment is of the order of 9 5 km 3 of which 6 6 km 3 is stored within the confines of the poverty bay floodplain thus although the postglacial period represented a time of high terrigenous sediment generation and delivery only 30 of the sediment generated by channel incision from waipaoa catchment probably reached the marine shelf and slope of the hikurangi margin during this time the smaller adjacent waimata catchment probably contributed an additional 2 6 km 3 to the same depocentre to give a total postglacial sediment contribution to the shelf and beyond of 5 5 km 3 sediment generated by postglacial channel incision represents only 25 of the total sediment yield from this landscape with 75 of the estimated volume of the postglacial storage offshore probably derived from hillslope erosion processes following base level fall at times when sediment yield from these catchments exceeded storage

input of river derived sediment to the new zealand continental shelf i mass abstract the input of river borne sediments to the new zealand continental shelf has been calculated for all the major rivers and basins in new zealand south island yields 284 40 106 tonnes per year of sediment from a land area of 152 977 km2 and north island yields 105 9 4 106 tonnes per year from a land area of 114 621 km2 particularly high discharges are noted off the west coast of south island and east coast of north island and result in higher offshore sedimentation there the data are compatible with measured sedimentation rates on the new zealand continental shelf the specific sediment yield from south island is amongst the highest previously recorded

glacial interglacial control of terrigenous and biogenic fluxes in the deep ocean off a high input collisional margin a 139 kyr record from new zealand abstract sediment input to the deep ocean off the new zealand collisional plate boundary is large and variable as revealed by a 139 kyr old record from the 34 92 m long core md97 2121 mass accumulation rates mars were derived for terrigenous and biogenic carbonate and silica sedimentary components with temporal control from a stable isotope age model verified by tephra and radiocarbon ages terrigenous mars changed in phase with glacio eustatic fluctuations of sea level highest rates 30 g cm 2 kyr coincided with the late regressive lowstand early transgressive phase of marine isotope stage mis 2 when rivers discharged at or near the shelf edge lesser but still high terrigenous rates 20 30 g cm 2 kyr characterized peak warm phases of early mis 5 and 1 when a strengthened subtropical inflow probably introduced sediment from fluvial and seabed sources to the north of md97 2121 however during prolonged highstands the flux declined as more sediment was retained on a tectonically subsiding shelf with a shore parallel current paradoxically the lowest mars 10 5 g cm 2 kyr occurred in mis 4 either sea level was too high to allow much sediment to escape off shelf or the fluvial input was modest or both these factors despite the terrigenous dominance biogenic mars are high and are 2 4 times larger than sw pacific ocean rates mars were lowest during mis 4 and 3 possibly due to reduced marine production under a lowered input of fluvial micronutrients in contrast mars increased irregularly though glacial maxima to peak at 5 6 g cm 2 kyr carbonate and 2 2 5 g cm 2 kyr silica in early mid mis 5 and 1 such rates reflected the interaction of macronutrient rich subantarctic waters sourced from the south with local micronutrient rich subtropical waters production also responded to warmer temperatures elevated nutrient runoff and a more stratified surface ocean later in mis 5 and 1 fluxes reduced as less productive subtropical waters prevailed that biogenic and aeolian mar profiles are out of phase suggests fe fertilization by aerosolic dust was not a major influence

shelf sedimentation on a tectonically active margin a modern sediment budget for poverty continental shelf new zealand abstract the combination of high sediment yields and the prevalence of tectonically controlled accommodation on collision margins such as that adjacent to the waipaoa river nz create the potential for these areas to contain high resolution records of natural and anthropogenic signals this study describes modern 100 yr sedimentation patterns off the waipaoa and quantifies a sediment budget for the continental shelf which is compared to long term holocene trends 210 pb and 239 240 pu geochronologies reveal three main shelf depocenters two of these depocenters are located in subsiding synclinal basins on the mid shelf landward of the actively deforming ariel and lachlan anticlines the depocenters exhibit accumulation rates ranging from 0 75 to 1 5 cm yr 1 and display both steady state and non steady state 210 pb activity profiles textural characteristics of the non steady state cores indicate the possible preservation of flood event layers the third depocenter is located near the shelf break and has accumulation rates as high as 1 0 cm yr 1 the inner shelf and central mid shelf are characterized by low uniform 210 pb activity profiles and low accumulation rates indicating that sediment is bypassing the inner shelf region and being deposited on the mid to outer shelf the modern sedimentation patterns seen in this study are similar to those for the holocene suggesting that regional tectonics are the major influence on poverty shelf sedimentation a modern bulk sediment budget estimates that 3 6 0 9 10 6 t yr 1 of sediments remains on the shelf amounting to only 25 of the 15 mt of sediments discharged from the river per year this indicates massive export of sediments from the study area to the adjacent slope or along the shelf in contrast studies of the mid late holocene sediment budget in the same area indicate that the sediment input and shelf trapping have been roughly in balance when compared with the modern budget this suggests an extraordinarily rapid shift from shelf trapping to shelf bypassing most likely driven by increasing sediment discharge in response to deforestation

influence of anthropogenic land use change on hillslope erosion in the waipaoa river basin new zealand european settlement of the poverty bay region resulted in deforestation and conversion of 90 of the landscape to pastureland the resulting loss of vegetation triggered a rapid increase in hillslope erosion as widespread landslide complexes and gully systems developed on weak lithologic units in the waipaoa basin to quantify the rate and volume of historic hillslope degradation we used a 1956 2010 sequence of aerial photographs for a 16 km2 catchment to map temporal changes in the spatial extent of active landslides then we created a turf index based on the extent and style of pastoral ground disruption which correlates with downslope velocity based on the movement of trees and other features we assigned average velocities to the turf classes as follows 1 minimal disrupted ground 0 6 m yr 2 a mix of disrupted ground and intact blocks 3 4 m yr and 3 no intact blocks or vegetation 6 m yr we then calculated the average annual sediment flux using these turf derived velocities the width of the landslide channel intersection and an average toe depth of 4 4 1 3 m mean standard deviation sd from 37 field measurements the resulting catchment averaged erosion rates are mean sd 29 9 12 9 mm yr 1956 28 8 13 7 mm yr 1969 13 4 4 9 mm yr 1979 17 0 6 2 mm yr 1988 and 9 9 3 6 mm yr 2010 compared with long term post 18 ka erosion rates 1 6 mm yr and the long term uplift rate 1 mm yr for this site the 50 year anthropogenically driven rate is an order of magnitude larger 20 mm yr previously we measured an increase in erosion over the past 3 4 kyr 2 2 mm yr and here we demonstrate this increase could be primarily due to human land use change showing that a century of rapid erosion superimposed on the background geologic rate can profoundly skew the interpretation of erosion rates copyright 2016 john wiley sons ltd

the influence of sea level and tectonics on late pleistocene through holocene sediment storage along the high sediment supply waipaoa continental shelf abstract we present geophysical and core evidence showing how subsidence caused by forearc shortening has accommodated late pleistocene and holocene sediments supplied to the tectonically active waipaoa shelf nz limiting off shelf export during the early sea level highstand the last glacioeustatic fall and subsequent rise exposed and then flooded a shelf segmented into subbasins separated by zones of uplift leaving key stratigraphic markers of shoreline regression and transgression that vary strongly in character across the shelf highstand sediment isopachs tied to piston cores dated using tephra correlation and a radiocarbon age model provide a sediment budget at 2000 yr intervals from the mid holocene 5500 cal yr bp to present sediment load estimates from our shelf budget are in agreement with published model estimates for suspended sediment discharge from the waipaoa river for the past 3000 yr but importantly do not show the 6 fold increase in the waipaoa s sediment output that began with human settlement 700 yr ago and accelerated with deforestation over the last century bypassing of waipaoa sediment to the slope may therefore be a recent phenomenon caused by unnaturally high sediment loads a conclusion supported by data reported elsewhere in this volume our study also reveals evidence for 1 a relatively thick mid shelf transgressive section deposited during the last eustatic rise that may correlate to estuarine sequences reported from numerous sites on the modern coastline of the north island 2 a slight decrease in total basin filling rates during the highstand and 3 variability in the partitioning of highstand sediments between individual subbasins that may reflect differing degrees of tectonic accommodation

seafloor structural geomorphic evolution of the accretionary frontal wedge in response to seamount subduction poverty indentation new zealand abstract high quality swath bathymetry and seismic reflection data reveal that the steep forearc slope along the northern sector of the obliquely convergent hikurangi subduction zone is characteristic of non accretionary and tectonically eroding continental margins with reduced sediment supply in the trench relative to further south and the presence of subducting seamount relief on the hikurangi plateau these seamounts influence the subduction process and the structurally driven geomorphic development of the over riding margin of the australian plate frontal wedge the origin of the poverty indentation on the inboard trench slope is attributed to multiple seamount impacts over the last c 1 myr period accompanied by canyon incision thrust fault propagation into the trench fill and numerous large scale gravitational collapse structures with multiple debris flow and avalanche deposits ranging in downslope length from a few hundred metres to more than 40 km the indentation is directly offshore of the waipaoa river which is currently estimated to have a high sediment yield into the marine system the poverty canyon stretches 70 km from the continental shelf edge directly offshore from the waipaoa to the trench floor incising into the axis of the indentation the sediment delivered to the margin from the waipaoa catchment and elsewhere during sea level high stands including the holocene has remained largely trapped in a large depocentre on the poverty shelf while during low stand cycles sediment bypassed the shelf to develop a prograding clinoform sequence out onto the upper slope the formation of the indentation and the development of the upper branches of the poverty canyon system has led to the progressive removal of a substantial part of this prograding wedge by mass movements and gully incision sediment has also accumulated in the head of the poverty canyon and episodic mass flows contribute significantly to continued modification of the indentation by driving canyon incision and triggering instability in the adjacent slopes prograding clinoforms lying seaward of active faults beneath the shelf and overlying a buried inactive thrust system beneath the upper slope reveal a history of deformation accompanied by the creation of accommodation space the middle to lower poverty canyon represents a structural transition zone within the indentation coincident with the indentation axis the lower to mid slope south of the canyon conforms more closely to a classic accretionary slope deformation style with a series of east facing thrust propagated asymmetric anticlines separated by early stage slope basins north of the canyon system seamount impact has resulted in frontal tectonic erosion associated with the development of an over steepened lower to mid slope margin fault reactivation and structural inversion and over printing

posteruption suspended sediment transport at mount st helens decadal scale relationships with landscape adjustments and river discharges received 11 december 2002 revised 30 september 2003 accepted 18 november 2003 published 17 january 2004 1 widespread landscape disturbance by the cataclysmic 1980 eruption of mount st helens abruptly increased sediment supply in surrounding watersheds the magnitude and duration of the redistribution of sediment deposited by the eruption as well as decades to centuries old sediment remobilized from storage have varied chiefly with the style of disturbance posteruption suspended sediment transport has been greater and more persistent from zones of channel disturbance than from zones of hillslope disturbance despite the severe landscape disturbances caused by the eruption relationships between discharge magnitudes and frequencies and suspended sediment transport have been remarkably consistent discharges smaller than mean annual flows generally have transported 5 but locally 15 of the annual suspended sediment loads and infrequent p 0 01 large floods have transported as much as 50 of the annual suspended sediment loads in a single day however moderate magnitude discharges those greater than mean annual flows but less than 2 year floods have transported the greatest amounts of sediment from all disturbance zones such discharges have transported on average 60 to 95 of the annual suspended sediment loads usually within cumulative periods of 1 3 weeks each year although small magnitude and largemagnitude discharges have locally and episodically transported considerable amounts of suspended sediment there has not been any notable change in the overall nature of the effective discharges moderate magnitude flows have been the predominant discharges responsible for transporting the majority of suspended sediment during 20 years of posteruption landscape adjustment index terms 1824 hydrology geomorphology 1625 1815 hydrology erosion and sedimentation 1860 hydrology runoff and streamflow keywords sediment yield suspended sediment transport mount st helens erosion volcano geomorphology

development of a new zealand sednet model for assessment of catchment wide soil conservation works abstract much hill country in new zealand has been converted from indigenous forest to pastoral agriculture resulting in increased soil erosion following a severe storm that hit the manawatu wanaganui region in 2004 and caused 62 000 landslides the horizons regional council have implemented the sustainable land use initiative slui a programme of widespread soil conservation we have developed a new zealand version sednetnz of the australian sednet model to evaluate the impact of the slui programme in the 5850 km2 manawatu catchment sednetnz spatially distributes budgets of fine sediment in the landscape it incorporates landslide gully earthflow erosion surficial erosion bank erosion and flood plain deposition the important forms of soil erosion in new zealand modelled suspended sediment loads compared well with measured suspended sediment loads with an r2 value of 0 85 after log transformation a sensitivity analysis gave the uncertainty of estimated suspended sediment loads to be approximately plus or minus 50 at the 95 confidence level it is expected that by 2040 suspended sediment loads in targeted water management zones will decrease by about 40 the expected decrease for the whole catchment is 34 the expected reduction is due to maturity of tree planting on land at risk to soil erosion the 34 reduction represents an annual rate of return of 20 on 20 million nz of investment on soil conservation works through avoided damage to property and infrastructure and avoided clean up costs

provenance of fluvial terrace sediments within the waipaoa sedimentary system and their importance to new zealand source to sink studies late pleistocene fluvial terrace deposits within the waipaoa river system of north island new zealand provide some insight into the fluvial history of the region that can be potentially translated to the marine sedimentary record pebble counts and sand detrital modes from terrace remnants suggest significant compositional differences between these terraces and the modern stream deposits the terrace deposits are enriched in sandstone lithics sand and gravel as well as monomineralic quartz and feldspar sand in contrast the modern waipaoa river is dominated by mudstone fragments mainly products of gullying in the waipaoa river headwaters region both the terrace and modern river sand show a compositional dependency on grain size with increasing lithic components in the coarse sand fractions carbonate lithic content and proportions of lithic types in the modern river and terrace sediments can be related to the distribution of calcareous geological units across the region for example the calcareous lithics sand and gravel in the mangatu river a major tributary of the waipaoa are derived from deep water facies allochthon that dominate the catchment these carbonate facies are petrographically distinct from the marl calcareous mudstone that dominates elsewhere in the waipaoa river system such as the pliocene units in the waimata river catchment the combined petrologic data sets from the modern rivers and terraces in the waipaoa river system provide a model to interpret the provenance of sandy deposits in the offshore marine realm

eel river margin source to sink sediment budgets revisited abstract the eel river coastal margin has been used as a representative source to sink sediment dispersal system owing to its steep high sediment yield river and the formation of sedimentary strata on its continental shelf one finding of previous studies is that the adjacent continental shelf retains only 25 of the eel river fine grained sediment less than 63 m discharged over time scales of both individual floods and the 20th century thus suggesting that the eel shelf trapping efficiency is uniquely lower than other similar systems here i provide data and analyses showing that sediment discharge relationships in the eel river have varied strongly with time and include substantial decreases in suspended sediment concentrations during the latter 20th century including these trends in margin wide sediment budgets i show that previous eel river sediment discharge rates were overestimated by a factor of two thus revised sediment budgets shown here reveal that the eel shelf retained 50 of the discharged river fine grained suspended sediment during intensively sampled events of 1995 97 and over the 20th century in light of this hypotheses about high rates of sediment export away from the primary shelf depocenter should be reevaluated