a comparison of time and frequency domain geomagnetic sounding summary a three site geomagnetic data set from the borders region of southern scotland is used to examine the empirical relationships established by differential geomagnetic sounding experiments a time domain analysis of such relationships reveals time domain transfer functions which appear to be almost independent of time a frequency domain analysis is then used to illustrate both a significant phase rotation and a significant dependence on period of the equivalent frequency domain response functions the formalism of conventional geomagnetic sounding is re examined it is found that difference fields are not required to establish the appropriate horizontal field relationships

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

crustal and upper mantle electrical conductivity structure in southern scotland summary magnetotelluric measurements were made during 1978 79 at nine sites on a linear traverse across south scotland extending from kinloch rannoch in the highlands to borthwickbrae in the southern uplands both one and two dimensional modelling of the apparent resistivities and phases indicate the existence of a low resisitivity 75 am zone at 20 90 km depth beneath the southern uplands rising closer to the surface beneath the midland valley to the north a zone of slightly higher resistivity 500s2m but still relatively conducting compared to the surrounding structure is shown to exist beneath the highlands the real part of the ratio of vertical to horizontal magnetic fields is shown to be suitably modelled by a combination of induction and conduction

natural electromagnetism in the rhine graben summary together with experiments by differential geomagnetic soundings magnetotelluric soundings have been performed in the rhine graben the results of the former have been presented and discussed before we try to show that it is not necessary to call upon the notion of induction in surrounding areas to justify the characteristics of the observed anomalous magnetic fields theoretical calculations of these fields on structures defined by the interpretation of magnetotelluric sounds or by geological and other geophysical data agree very well with experimental data we conclude that magnetotelluric experiments and interpretations are valid as the rhine graben is a well known region allowing us to verify our interpretation

influence of storm related sediment storage on the sediment delivery from tributary catchments in the upper waipaoa river new zealand although much is known about overall sediment delivery ratios for catchments as components of sediment production and sediment yield little is known about the component of temporary sediment storage sediment delivery ratios focused on the influence of storm related sediment storage are measured at matakonekone and oil springs tributaries of the waipaoa river basin east coast of new zealand the terrace deposits of both tributaries show abundant evidence of storm related sedimentation especially sediment delivered from cyclone bola a 50 year return rainfall event which occurred in 1988 the sediment delivery ratio is calculated by dividing the volume of sediment transported from a tributary to the main stream by the volume of sediment generated at erosion sites in the tributary catchment because the sediment delivery volume is unknown it can be calculated as the difference between sediment generation volume and sediment storage volume in the channel reach of the tributary the volume of sediment generated from erosion sites in each tributary catchment was calculated from measurements made on aerial photographs dating from 1960 1 44 000 and 1988 1 27 000 the volume of sediment stored in the tributary can be calculated from measurements of cross sections located along the tributary channel which are accompanied by terrace deposits dated by counting annual growth rings of trees on terrace surfaces sediment delivery ratios are 0 93 for both matakonekone catchment and oil springs catchment results indicate that oil springs catchment has contributed more than twice the volume of sediment to the waipaoa river than the matakonekone catchment 2 75 106 m3 vs 1 22 106 m3 although large volumes of sediment are initially deposited during floods subsequent smaller flows scour away much of these deposits the sediment scouring rate from storage is 1 25 104 m3 a 1 for matakonekone stream and 0 83 104 m3 a 1 for oil springs stream matakonekone and oil springs channels respond to extreme storms by instantaneously aggrading then gradually excavating the temporarily stored sediment results from matakonekone and oil springs streams suggest a mechanism by which event recurrence interval can strongly influence the magnitude of a geomorphic change matakonekone stream with its higher stream power is expected to excavate sediment deposits more rapidly and allow more rapid re establishment of storage capacity copyright 1999 john wiley sons ltd

a comparison of earthflow movement mechanisms on forested and grassed slopes raukumara peninsula north island new zealand abstract surface movement rates on forested earthflows are 2 3 orders of magnitude less than those on grassed earthflows subsurface deformation results largely from extension flow on grassed earthflows and from compression flow on forested earthflows a rafting mechanism in which blocks of roots from individual trees interact with those of neighbouring trees to retard surface movement is used to explain deformation profiles of forested earthflows the rheology of earthflow materials is changed by the presence of tree roots

supply and removal of sediment in a landslide dominated mountain belt central range taiwan abstract a strong coupling between hillslope and valley systems is often inferred for mountain landscapes dominated by bedrock landsliding we reveal the nature of this link using data sets on landsliding and sediment transport from two montane catchments draining the eastern central range of taiwan here the magnitude frequency distribution of landslides can be modeled by a robust power law but this scale invariance is not mirrored in the sediment discharge at the mountain front instead downstream sediment loads reflect a complex response to both sediment supply and ambient hydraulic conditions the rivers do not transport significant amounts of sediment unless it is provided by hillslope mass wasting in the catchment removal of landslide debris is a function of the transport capacity of the stream at the site of entry thus there is a dual supply and transport control on sediment loads in bedrock floored streams over a monitoring period of 25 yr the bulk of the sediment leaving the mountain bel

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

a study of the physics of telluric current flow at very low frequencies in the earth s crust summary interpretation of the effects of natural electromagnetic induction is often in terms of models in which changes in resistivity at great distances from the point of measurement are not taken into account in this paper we will try to show that this is not a valid approximation for very low frequency telluric currents flowing near the surface in the earth s crust when the material separating the crust from the mantle has a sufficiently high electrical resistance in this case the shape and dimensions of the circuit as well as the resistivity distribution along the whole length of the path followed by the currents play a part in determining the induced electromagnetic field a number of experimentally verifiable consequences follow from this

estimation of temporally averaged sediment delivery ratio using aggradational terraces in headwater catchments of the waipaoa river north island new zealand the sediment delivery ratio was estimated for two periods 28 years and eight years following reforestation of seven tributary catchments 0 33 to 0 49 km2 in the headwaters of the waipaoa river basin north island new zealand in these catchments gully erosion which largely resulted from clearance of the natural forest between 1880 and 1920 is the main source of sediment to streams reforestation commenced in the early 1960s in an attempt to stabilize hillslopes and reduce sediment supply efforts have been partially successful and channels are now degrading though gully erosion continues to supply sediment at accelerated rates in parts of the catchment data from the area indicate that the sediment delivery ratio sdr can be estimated as a function of two variables the product of catchment area and channel slope and ag the temporally averaged gully area for the period sediment input from gullies was determined from a well defined relationship between sediment yield and gully area sediment scoured from channels was estimated from dated terrace remnants and the current channel bed terrace remnants represent aggradation during major floods this technique provides estimates of sdr averaged over periods between large magnitude terrace forming events and with the present channel bed the technique averages out short term variability in sediment flux comparison of gully area and sediment transport between two periods 1960 1988 and 1988 1996 indicates that the annual rate of sediment yield from gullies for the later period has decreased by 77 per cent sediment scouring in channels has increased by 124 per cent and sediment delivered from catchments has decreased by 78 per cent however average sdr for the tributaries was found to be not significantly different between these periods this may reflect the small number of catchments examined it is also due to the fact that the volume of sediment scoured from channels was very small relative to that produced by gullies according to the equation for sdr determined for the waipaoa headwaters sdr increases with increasing catchment area in the case where ag and channel slope are fixed this is because the amount of sediment produced from a channel by scouring increases with increasing catchment area however this relationship does not hold for the main stem of the study catchments because sediment delivered from its tributaries still continues to accumulate in the channel higher order channels are in effect at a different stage in the aggradation degradation cycle and it will take some time until a main channel reflects the effects of reforestation and its bed adjusts to net degradation results demonstrate significant differences among even low order catchments and such differences will need to be taken into consideration when using sdr to estimate sediment yields copyright 2001 john wiley sons ltd

linking lithology and land use to sources of dissolved and particulate organic matter in headwaters of a temperate passive margin river system a number of rivers have been found to transport highly aged organic matter om however the sources of this aged material remain a matter of debate one potential source may be erosion and weathering of headwater lithologies rich in ancient sedimentary om in this study waters suspended particulates streambed sediments rocks and soils from fourteen small headwater watersheds of a mid size temperate passive margin river were sampled and characterized by d 14 c d 13 c and poc tpn ratios to identify sources of particulate and dissolved om delivered to the river mainstem these headwater sites encompass a range in lithology om rich shales om lean carbonate mudstone facies and om free crystalline rocks and land use types forested and agricultural and allow investigation of the influence of agriculture and bedrock types on stream om characteristics streams draining large areas of both agricultural land use and om rich lithology contain particulate om pom that is more 14 c depleted than streams draining forested shale free watersheds however this is not sufficient to account for the significantly lower d 14 c poc measured in the river mainstem dissolved om dom d 14 c are in all cases enriched compared to pom from the same stream but are otherwise highly variable and unrelated to either land use or lithology poc tpn ratios were likewise highly variable poc and doc d 13 c signatures were similar across all watersheds based on isotope mass balance 14 c free fossil om sources contribute 0 12 of total stream pom although these results do not unequivocally separate the influences of land use and lithology watershed coverage by shale and agriculture are both important controls on stream d 14 c poc thus export of aged particle associated om may be a feature of river systems along both

catchment scale influences on riverine organic matter in southern new zealand abstract riverine particulate organic matter pom is a critical vector for nutrient cycling of carbon at both regional and global scales pom and suspended sediment ss are transported concomitantly through rivers and their concentrations change in association to landscape transformations and natural fluctuations the proportion of pom to ss mobilised in rivers under base flow is an important component of carbon flux to oceans and is a useful metric for understanding hillslope river coupling and hydraulic connectivity we quantified pom during base flow conditions in southern new zealand to assess the role of different catchment characteristics that control the spatial variability of organic matter in the fluvial environment the proportion of pom to total suspended material tsm can be

tropical cyclone driven erosion of the terrestrial biosphere from mountains the transfer of organic carbon from the terrestrial biosphere to the oceans via erosion and riverine transport constitutes an important component of the global carbon cycle measurements of particulate organic carbon load and composition in the liwu river taiwan during cyclone triggered floods suggest that tropical cyclones may facilitate the delivery of non fossil particulate organic carbon to the ocean and its subsequent burial the transfer of organic carbon from the terrestrial biosphere to the oceans via erosion and riverine transport constitutes an important component of the global carbon cycle1 2 3 4 more than one third of this organic carbon flux comes from sediment laden rivers that drain the mountains in the western pacific region3 5 this region is prone to tropical cyclones but their role in sourcing and transferring vegetation and soil is not well constrained here we measure particulate organic carbon load and composition in the liwu river taiwan during cyclone triggered floods we correct for fossil particulate organic carbon using radiocarbon and find that the concentration of particulate organic carbon from vegetation and soils is positively correlated with water discharge floods have been shown to carry large amounts of clastic sediment6 non fossil particulate organic carbon transported at the same time may be buried offshore under high rates of sediment accumulation7 8 9 we estimate that on decadal timescales 77 92 of non fossil particulate organic carbon eroded from the liwu catchment is transported during large cyclone induced floods we suggest that tropical cyclones which affect many forested mountains within the intertropical convergence zone10 may provide optimum conditions for the delivery and burial of non fossil particulate organic carbon in the ocean this carbon transfer is moderated by the frequency intensity and duration of tropical cyclones

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

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

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

the role of effective discharge in the ocean delivery of particulate organic carbon by small mountainous river systems recent research has shown that small mountainous river systems smrs account for a significant fraction of the global flux of sediment and particulate organic carbon poc to the ocean the enormous number of smrs precludes intensive studies of the sort conducted on large systems necessitating development of a conceptual framework that permits cross system comparison and scaling up herein we introduce the geomorphic concept of effective discharge to the problem of source to sink poc transport this idea recognizes that transport effectiveness is the product of discharge frequency and magnitude wherein the latter is quantified as a power law relationship between discharge and load the rating curve an analytical solution for effective discharge qe identifies two key variables the standard deviation of the natural logarithm of discharge sq and the rating exponent of constituent i bi data from selected smrs are used to show that for a given river qe poc qesediment qe for different poc constituents e g pocfossil vs pocmodern differs in predictable ways and qe for a particular constituent can vary seasonally when coupled with the idea that discharge peaks of small rivers may be coincident with specific oceanic conditions e g large waves wind from a certain direction that determine dispersal and burial these findings have potentially important implications for poc fate on continental margins future studies of poc transport in smrs should exploit the conceptual framework provided herein and seek to identify how constituent specific effective discharges vary between rivers and respond to perturbations delivery of particulate organic carbon poc from the land to the sea by rivers and its eventual burial in ocean sediments are critical processes in the global carbon cycle sequestration of poc in marine sediments is a major long

storage and release of fossil organic carbon related to weathering of sedimentary rocks abstract the biogeochemical carbon cycle which plays an undeniable role in global climate change is defined both by the size of carbon reservoirs such as the atmosphere biomass soil and bedrock and the exchange between them of various mineral and organic carbon forms among these carbon forms fossil organic carbon foc i e the ancient organic matter stored in sedimentary rocks is widely observed in modern environments but is not included in the supergene carbon budget using a digitized map of the world and an existing model of co 2 consumption associated with rock weathering we establish the global distribution of foc stored in the first meter of sedimentary rocks and a first estimation of annual foc delivery to the modern environment resulting from chemical weathering of these rocks results are given for the world s 40 major river basins and extended to the entire continental surface with a mean value of 1100 10 9 t mainly controlled by shale distribution the global foc stock is significant and comparable to that of soil organic carbon 1500 10 9 t the annual chemical delivery of foc estimated at 43 10 6 t yr 1 and controlled by the areal distribution of shales and runoff is of the same order of magnitude as the foc output flux to oceans chemical weathering of bedrock within the amazon basin produces one quarter of the total global flux of foc derived from chemical weathering and thus is expected to govern foc release on a global scale these results raise important questions concerning the role of foc in the modern carbon cycle as well as the origin and the budget of carbon in soils and rivers

non energy minerals and surficial geology of the continental margin of maryland abstract the surficial sediments have been mapped and the shallow geologic framework outlined of the maryland inner continental shelf the initial study encompassed a small area offshore of assateague island but was extended northward to include the ocean city area and eastward across several linear shoals the surficial sediments are predominantly sand with mean grain sizes ranging from 0 40 to 2 89 mud and gravel are the mappable components of the surficial sediments muds are distributed along a n s trending band seaward of the shoreface gravels are mapped farther offshore in 18 22 m of water four distinct seismic units are identified from seismic reflection profiles the lowermost unit t1 exhibits high angle clinoforms truncated at the top by a locally prominent near horizontal reflector above this reflector are concordant strata with parallel to subparallel bedding designated as q2 incised into q2 is an extensive channel q3 that trends both coast parallel and coast normal the upper unit q4 overlaps portions of units q2 and q3 along the eastward edges of the study area and is represented in the nearshore by holocene inlet channeling adjacent to the shoreface note that this excludes the modern shelf and sheet

evolution of a classic sand ridge field maryland sector north american inner shelf the ridge and swale topography of the middle atlantic bight is best developed on the delaware maryland inner shelf here sand ridges can be seen in all stages of formation several aspects of the ridge field are pertinent to the problem of ridge genesis the first is ridge morphology there is a systematic morphologic change from shoreface ridges through nearshore ridges to offshore ridges which reflects the changing hydraulic regime as successively more seaward ridges are examined maximum side slope decreases the ratio of maximum seaward slope to maximum landward slope decreases and the cross sectional area increases these changes in ridge morphology with depth and distance from shore appear to be equivalent to the morphologic changes experienced by a single ridge during the course of the holocene transgression a second aspect is the change in bottom sediment characteristics that accompanies these large scale morphologic changes megaripples sand waves and mud lenses appear in the troughs between nearshore and offshore ridges these changes indicate that the storm flows which maintain ridges are less frequently experienced in the deeper sector and that the role of high frequency wave surge becomes less important relative to the role of the mean flow component in shaping the sea floor a third aspect is the systematic relationship of grain size to topography grain size is 90 out of phase with topography so that the coarsest sand lies between the axis of the landward trough and the ridge crest while the finest sand lies between the ridge crest and the axis of the seaward trough this relationship is characteristic of large scale bedforms finally flow was measured and transport calculated on the same ridge during a one month period november 1976 threshold was exceeded only during storm events mean transport was southerly and a little seaward with respect to both the ridge crest and the shoreline these flow measurements are in conformity with the pattern of smaller bedforms a 43 year time series of bathymetric change for this ridge reveals a systematic pattern of landward flank erosion seaward flank deposition and seaward crest migration sand ridges are considered the consequence of constructive feedback between an initial topography and the resulting distribution of bottom shear stress the relationship between grain size and topography supports this model but does not account directly for the oblique angle of the ridge with respect to the coastline this feature may be due to a more rapid alongshore migration rate of the inshore edge of the ridge than the offshore edge and the relationship between this migration rate and the rate of shoreface retreat

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

the dominance of dispersion in the evolution of bed material waves in gravel bed rivers bed material waves are temporary zones of sediment accumulation created by large sediment inputs recent theoretical experimental and field studies examine factors influencing dispersion and translation of bed material waves in quasi uniform gravel bed channels exchanges of sediment between a channel and its floodplain are neglected within these constraints two factors influence relative rates of dispersion and translation 1 interactions between wave topography flow and bed load transport and 2 particle size differences between wave material and original bed material our results indicate that dispersion dominates the evolution of bed material waves in gravel bed channels significant translation requires a low froude number which is uncharacteristic of gravel bed channels and low wave amplitude which for a large wave can be achieved only after substantial dispersion wave material of small particle size can promote translation but it primarily increases bed load transport rate and thereby accelerates wave evolution copyright 2001 john wiley sons ltd

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

quantitative determination of the activity of within reach sediment storage in a small gravel bed river using transit time and response time abstract reach scale sediment storage is rarely quantified in sediment budget studies yet it has a considerable effect on the sediment delivery ratio at the basin scale and on the accuracy of morphological methods of bedload estimation at the reach scale deployment of magnetic tracer particles allows accurate characterisation of sediment fluxes in gravel bed rivers and provides the opportunity to quantify storage activity using reservoir theory activity was quantified at reach and sub reach scales in two reaches of a small gravel bed river and the possibility of quantifying the activity of smaller scale sediment stores is explored reach scale transit time functions were derived from the cumulative output of sediment against age or time the shape of the functions in both reaches was determined by flood incidence and magnitude hydraulics sediment tracer availability grain size and local morphology accurate transit time functions were difficult to determine due to reliance upon tracer output and the associated problems of tracer exhaustion over time and imperfect tracer recovery rates in addition if tracers of different ages are allowed to mix for example where upstream input is possible then the resultant transit time distributions age are not comparable with the timing of the hydraulic processes responsible unless the hydraulic conditions are constant these results suggest that transit time is difficult to determine from tracer studies in gravel bed rivers consequently a refinement of transit time the response time is introduced and is defined as the time after the initial input of tracer sediment when cumulative tracer output exceeds the amount of tracer sediment remaining in storage whilst still based upon tracer output the calculation of response time also utilises storage data and is expressed relative to time since the start of the study rather than age it is therefore directly comparable with the incidence of hydraulic conditions this provides a more informative measure of activity which is readily available from tracer data in gravel bed rivers and allows evaluation of the importance of flood incidence and magnitude grain size morphology and reach characteristics stability like transit time response time estimates are hindered by mixing of sediment of different ages at the sub reach scale however it does account for errors from less than 100 recovery and tracer exhaustion more effectively than transit time quantification of absolute and relative size effects in transport is also possible from response time

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

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

redwoods restoration and implications for carbon budgets abstract the coast redwoods sequoia sempervirens of california have several unique characteristics that influence interactions between vegetation and geomorphic processes case studies using a combination of in channel wood surveys and an air photo inventory of landslides illustrate current conditions in a redwood dominated watershed undergoing restoration work and the influence of wood loading and landslides on the carbon budget redwood trees have extremely large biomass trunk wood volumes of 700 to 1000 m3 and are very decay resistant consequently they have a large and persistent influence on in channel wood loading large wood surveys indicate high wood loading in streams in uncut forests 0 3 0 5 m3 m2 of channel but also show that high wood loading can persist in logged basin with unlogged riparian buffers because of the slow decay of fallen redwoods through a watershed restoration program redwood national park increases in channel wood loading in low order streams but the effectiveness of this technique has not yet been tested by a large flood another unique characteristic of redwood is its ability to resprout from basal burls after cutting so that root strength may not decline as sharply following logging as in other types of forests an air photo inventory of landslides following a large storm in 1997 indicated 1 that in the redwood creek watershed the volume of material displaced by landslides in harvested areas was not related to the time elapsed since logging suggesting that the loss of root strength was not a decisive factor in landslide initiation 2 landslide production on decommissioned logging roads was half that of untreated roads and 3 landslides removed an estimated 28 mg of organic carbon km2 from hillslopes the carbon budget of a redwood dominated catchment is dominated by the vegetative component but is also influenced by the extent of mass movement erosion control work and in channel storage of wood

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

watershed control on the carbon loading of marine sedimentary particles abstract previous investigations of the factors governing organic carbon burial on continental margins have pointed toward the important apparently protective association of carbon with mineral particles these studies have also revealed dramatic transformations of carbon particle relationships at the land sea interface riverine particles in some settings lose a large portion of their loads of sorbed terrestrial carbon upon discharge to the ocean and gradually reload to similar levels with marine carbon the eel river in northern california and the adjacent continental shelf were selected as an ideal system to investigate the rates of these processes the river is episodically subject to large floods and the shelf stratigraphy preserves a record of the resultant large pulses of sediment and carbon input to the marine environment carbon isotopic carbon to nitrogen and carbon to surface area ratios of particles in flood deposits were expected to reflect the rapid unloading of terrestrial carbon from discharged particles whereas nonflood sediments that have accumulated at slower rates on the shelf were expected to carry higher loads of marine carbon our results indicate however that particles on the eel shelf have retained their loads of terrigenous carbon and that a significant portion of the particle sorbed carbon buried on the shelf is kerogen derived from the mesozoic tertiary franciscan complex we hypothesize that rates of uplift and mass wasting in the eel watershed and rates of particle delivery to and burial on the continental shelf are so rapid that kerogen is not completely oxidized and is recycled instead the loading of carbon on clay sized particles delivered to the shelf moreover is dependent on river discharge and may reflect the relative importance of different mass wasting processes during precipitation events of varying intensity the eel river system is likely to be representative of other small mountainous rivers and indicates that processes on land may play an important role in governing the amount and character of carbon being buried on the continental margins

slope channel coupling in steepland terrain a field based conceptual model from the tarndale gully and fan waipaoa catchment new zealand abstract connectivity between an actively eroding gully complex and upper waipaoa catchment via a steep 1 km long alluvial fan is assessed using digital elevation models dems of the tarndale fan derived from 10 high resolution gps surveys between 2004 and 2008 repeat dem analysis provides a means of assessing transfer of sediment supplied from the tarndale gully through the fan to the te weraroa stream and thus inferring connectivity between these landscape components from which a conceptual coupling model is derived analysis indicates the operation of two critical junction switches at the i gully fan and ii fan stream nexus which contribute to considerable complexity in patterns of erosion and deposition on the fan as it responds to sediment supply or starvation from the tarndale gully and evacuation to the te weraroa stream described in fuller and marden 2010 the fan does not respond as a coherent unit each of six fan feeder tributaries behaves independently according to sediment supplied from six discrete source areas within the gully complex this reflects sediment production within specific activity zones of tarndale gully mass movements triggered by single rainstorm events and or wet periods contingent upon sediment availability and intrinsic slope mechanics frequently deliver sediment to the upper fan tributaries this enhanced gully fan coupling during storms or wetter periods promotes rapid fan aggradation with each feeder tributary responding to its discrete source zone infilling may propagate down fan in response to upper fan incision once the gully fan switch deactivates transferring sediment as far as the te weraroa stream coupling the fan with the stream system floods generated in the te weraroa stream may also activate the junction switch at the fan stream nexus by trimming the lower fan prompting up fan incision via head cutting in response to changed local base level slope channel coupling in this environment is a function of a range of slope and channel processes responding to discrete storms and intrinsic gully dynamics the high rates of geomorphic activity in this environment mean the tarndale system provides a natural laboratory in which to assess key slope channel coupling processes beyond the plot or discrete event scale

climatic and geomorphic controls on the erosion of terrestrial biomass from subtropical mountain forest 1 erosion of particulate organic carbon poc occurs at very high rates in mountain river catchments yet the proportion derived recently from atmospheric co2 in the terrestrial biosphere pocnon fossil remains poorly constrained here we examine the transport of pocnon fossil in mountain rivers of taiwan and its climatic and geomorphic controls in 11 catchments we have combined previous geochemical quantification of poc source accounting for fossil poc from bedrock with measurements of water discharge qw and suspended sediment concentration over 2 years in these catchments pocnon fossil concentration mg l 1 was positively correlated with qw with enhanced loads at high flow attributed to rainfall driven supply of pocnon fossil from forested hillslopes this climatic control on pocnon fossil transport was moderated by catchment geomorphology the gradient of a linear relation of pocnon fossil concentration and qw increased as the proportion of steep hillslopes 35 in the catchment increased the data suggest enhanced supply of pocnon fossil by erosion processes which act most efficiently on the steepest sections of forest across taiwan pocnon fossil yield was correlated with suspended sediment yield with a mean of 21 10 tc km 2 yr 1 at this rate export of pocnon fossil imparts an upper bound on the time available for biospheric growth of 800 yr over longer time periods pocnon fossil transferred with large amounts of clastic sediment can contribute to sequestration of atmospheric co2 if buried in marine sediments our results show that this carbon transfer should be enhanced in a wetter and stormier climate and the rates moderated on geological timescales by the regional tectonic setting

landslide impact on organic carbon cycling in a temperate montane forest in humid forested mountain belts bedrock landslides can harvest organic carbon from above ground biomass and soil ocmodern while acting to refresh the landscape surface and turnover forest ecosystems here the impact of landslides on organic carbon cycling in 13 river catchments spanning the length of the western southern alps new zealand is assessed over four decades spatial and temporal landslide maps are combined with the observed distribution and measured variability of hillslope ocmodern stocks on average it is estimated that landslides mobilized 7 6 2 9 tc km 2 yr 1 of ocmodern 30 of which was delivered to river channels comparison with published estimates of ocmodern export in river suspended load suggests additional erosion of ocmodern by small shallow landslides or overland flow in catchments the exported ocmodern may contribute to geological carbon sequestration if buried in sedimentary deposits landslides may have also contributed to carbon sequestration over shorter timescales 100 years 5 4 3 0 tc km 2 yr 1 of the eroded ocmodern was retained on hillslopes representing a net carbon sink following re vegetation of scar surfaces in addition it was found that landslides caused rapid turnover of the landscape with rates of 0 3 of the surface area per decade high rates of net ecosystem productivity were measured in this forest of 94 11 tc km 2 yr 1 which is consistent with rapid landscape turnover suppressing ecosystem retrogression landslide ocmodern yields and rates of turnover vary between river catchments and appear to be controlled by gradients in climate precipitation and geomorphology rock exhumation rate topographic slope copyright 2011 john wiley sons ltd

transgressive systems tract development and incised valley fills within a quaternary estuary shelf system virginia inner shelf usa abstract high frequency quaternary glacioeustasy resulted in the incision of six moderate to high relief fluvial erosion surfaces beneath the virginia inner shelf and coastal zone along the updip edges of the atlantic continental margin fluvial valleys up to 5 km wide with up to 37 m of relief and thalweg depths of up to 72 m below modern mean sea level cut through underlying pleistocene and mio pliocene strata in response to drops in baselevel on the order of 100 m fluvially incised valleys were significantly modified during subsequent marine transgressions as fluvial drainage basins evolved into estuarine embayments ancestral generations of the chesapeake bay complex incised valley fill successions are bounded by or contain up to four stacked erosional surfaces basal fluvial erosion surface bay ravinement tidal ravinement and ebb flood channel base diastem in vertical succession these surfaces combined with the transgressive oceanic ravinement that generally caps incised valley fills control the lateral and vertical development of intervening seismic facies depositional systems transgressive stratigraphy characterizes the quaternary section beneath the virginia inner shelf where six depositional sequences sequences i vi are identified depositional sequences consist primarily of estuarine depositional systems subjacent to the transgressive oceanic ravinement and shoreface shelf depositional systems highstand systems tract coastal systems are thinly developed the quaternary section can be broadly subdivided into two parts the upper part contains sequences consisting predominantly of inner shelf facies whereas sequences in the lower part of the section consist predominantly of estuarine facies three styles of sequence preservation are identified style 1 represented by sequences vi and v is characterized by large estuarine systems ancestral generations of the chesapeake bay that are up to 40 m thick have hemicylindrical wedge geometries and occur within large coast oblique trending depressions paleo estuaries style 1 is dominated by fluvial through estuary mouth depositional systems seismic facies 1 4 style 2 sequence preservation represented by sequences iii and ii is dominantly an inner shelf and shoreface succession with a seaward thickening tabular wedge geometry that does not exceed 15 m in thickness these shoreface and inner shelf depositional systems of the upper transgressive systems tract seismic facies 9 and highstand systems tract seismic facies 7 and 11 are not associated with paleo estuaries style 3 sequence preservation is represented by sequence i the holocene sequence it consists of lower transgressive systems tract fluvial estuarine lagoonal and tidal inlet fill deposits seismic facies 1 6 and 8 overlain by upper transgressive systems tract shelf and shoreface sands seismic facies 9 style 3 has a crenulated wedge geometry and is thickest beneath and seaward of the modern chesapeake bay mouth it thins northward and landward onto late pleistocene interfluvial highs on the basinward side of the southern delmarva peninsula

electrical conductivity from australian magnetometer arrays using spatial gradient data quiet daily magnetic variations recorded by magnetometer arrays in australia are analysed to obtain electromagnetic response parameters for two parts of the australian continent remote from electrical conductivity anomalies the parameters are based on measurements of vertical field and horizontal field spatial gradient and three different methods are followed in their computation the response parameters are checked for consistency with a compilation of globally determined earth apparent resistivities and are then interpreted for one dimensional conductivity structure in the two different parts of the continent there is evidence that the rise in electrical conductivity from 10 1 s m 1 to 100 s m 1 which occurs at a depth of order 500 km beneath central australia may occur at a substantially shallower depth of order 230 km beneath southeast australia

gravel sediment routing from widespread low intensity landscape disturbance current river basin missouri during the last 160 years land use changes in the ozarks have had the potential to cause widespread low intensity delivery of excess amounts of gravel sized sediment to stream channels previous studies have indicated that this excess gravel bedload is moving in wave like forms through ozarks drainage basins the longitudinal areal distribution of gravel bars along 160 km of the current river missouri was evaluated to determine the relative effects of valley scale controls tributary basin characteristics and lagged sediment transport in creating areas of gravel accumulations the longitudinal distribution of gravel bar area shows a broad scale wave like form with increases in gravel bar area weakly associated with tributary junctions secondary peaks of gravel area with 1 8 4 1 km spacing disturbance reaches are superimposed on the broad form variations in valley width explain some but not all of the short spacing variation in gravel bar area among variables describing tributary drainage basin morphometry present day land use and geologic characteristics only drainage area and road density relate even weakly to gravel bar areal inventories a simple channel network based sediment routing model shows that many of the features of the observed longitudinal gravel distribution can be replicated by uniform transport of sediment from widespread disturbances through a channel network these results indicate that lagged sediment transport may have a dominant effect on the synoptic spatial distribution of gravel in ozarks streams present day land uses are only weakly associated with present day gravel inventories and valley scale characteristics have secondary controls on gravel accumulations in disturbance reaches copyright 1999 john wiley sons ltd

recent studies of time variations of natural electromagnetic fields in scotland abstract a series of geomagnetic induction studies has been undertaken in scotland since 1973 it includes the operation of two geomagnetic arrays one over northern scotland and the other over southern scotland subsequent individual station and small scale geomagnetic array studies and three sets of magnetotelluric soundings which traverse scotland from the lewisian foreland to the english border the problems associated with the interpretation of induction data from an island located in the subauroral region are discussed qualitatively and the manner in which both coast and source field effects can be accounted for is described the geomagnetic deep sounding data gds from all the observation sites have been collated and examples of hypothetical event contour maps and traverses across the great glen and of individual events from the northern array are presented they indicate that significant lateral variations in electrical conductivity structure within the crust and upper mantle are associated with the major geological faults in the region examples of the results of the magnetotelluric soundings are also presented together with an outline of the procedure used for one and two dimensional modelling models of the geo electric structure in both northern and southern scotland have been obtained these show distinctive features which are compatible with the qualitative interpretation of the magnetovariational data for example the major granitic blocks are highly resistive while regions of relatively low resistivity exist at upper crustal depths near the great glen highland boundary and southern uplands faults a zone of low resistivity exists at lower crust uppermost mantle depths throughout much of the region the lowest value occurring under the southern uplands

organic carbon fluxes to the ocean from high standing islands the transfer of terrestrially derived yet poorly quantified organic carbon to the oceans is an important yet unagreed upon proportion of the world s carbon budget the few data that exist suggest that high standing oceanic islands in the southwest pacific may make important contributions to the overall terrestrial flux of particulate organic carbon poc to the oceans we have determined the poc flux from several streams in new zealand with those data and previous measurements from taiwan and papua new guinea we estimate the poc flux from high standing islands in the southwest pacific to be 48 1012 g c yr 1 a value slightly lower than previous estimates these islands which make up only 3 of earth s landmass contribute 17 35 of the estimated poc entering the world s oceans annually and thus may be important sources of terrestrial carbon to the ocean anthropogenic activities especially deforestation and forest harvesting have probably exacerbated the natural flux few to no data exist for many of these islands and thus a more detailed assessment awaits further measurements

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

effects of land use change on channel morphology in northeastern puerto rico between 1830 and 1950 much of northeastern puerto rico was cleared for agriculture runoff increased by 50 and sediment supply to the river channels increased by more than an order of magnitude much of the land clearance extended to steep valley slopes resulting in widespread gullying and landslides and a large load of coarse sediments delivered to the stream channels a shift from agriculture to industrial and residential land uses over the past 50 yr has maintained the elevated runoff while sediment supply has decreased allowing the rivers to begin removing coarse sediment stored within their channels the size abundance and stratigraphic elevation of in channel gravel bar deposits increases channel depth decreases and the frequency of overbank flooding increases downstream along these channels this is presumed to be a transient state and continued transport will lead to degradation of the bed in downstream sections as the channel adjusts to the modern supply of water and sediment a downstream decrease in channel size is contrary to the expected geometry of self adjusted channels but is consistent with the presence of partially evacuated sediment remaining from the earlier agricultural period reverse downstream decreasing channel morphology is not often cited in the literature although consistent observations are available from areas with similar land use history identification of reverse channel morphology along individual watercourses may be obscured in multiwatershed compilations in which other factors produce a consistent but scattered downstream trend identification of reverse channel morphology along individual streams in areas with similar land use history would be useful for identifying channel disequilibrium and anticipating future channel adjustments

annual fossil organic carbon delivery due to mechanical and chemical weathering of marly badlands areas a key issue in the study of the carbon cycle is constraining the stocks and fluxes in and between c reservoirs among these the role and importance of fossil organic carbon foc release by weathering of outcropping sedimentary rocks on continental surfaces is still debated and remains poorly constrained our work focuses on foc fluxes due to chemical and mechanical weathering of marls in two experimental watersheds with typical badlands geomorphology draix watersheds laval and moulin alpes de haute provence france organic matter from bedrock soil litter and riverine particles are characterized by rock eval 6 pyrolysis foc fluxes due to mechanical weathering are then estimated by monitoring the annual particulate solid exports at the outlets of the watersheds 1985 2005 period foc fluxes from chemical weathering were calculated using ca2 concentrations in dissolved loads year 2002 to assess the amount of foc released by the dissolution of the carbonate matrix results show that foc delivery is mainly driven by mechanical weathering with a yield ranging from 30 to 59 t km 2 yr 1 in the moulin 0 08 km2 and laval 0 86 km2 catchments respectively 1985 2005 average the release of foc attributed to chemical weathering was 2 2 to 4 2 t km 2 for the year 2002 these high foc fluxes from badlands are similar to those observed in tectonically active mountain catchments at a regional scale badland outcropping within the durance watershed does not exceed 0 25 in area of the rhone catchment but could annually deliver 12 000 t yr 1 of foc this flux could correspond to 27 of the total particulate organic carbon poc load exported by the rhone river to the mediterranean sea at a global scale our findings suggest that erosion of badlands may contribute significantly to the transfer of foc from continental surfaces to depositional environments copyright 2012 john wiley sons ltd

river sediment discharge to the oceans present day controls and global budgets empirical relationships between river sediment yields and a large number of hydroclimatic biological and geomorphological parameters are investigated at the global scale for a set of 60 major world river basins the environmental characteristics were extracted from various global computer data sets and natural river sediment fluxes were taken from the literature it is found that sediment yields can be best correlated by forming the products of hydroclimatic and geomorphological factors that is runoff intensity basin slope an index characterizing rock hardness and an index characterizing rainfall variability over the year the best parameter combination varies to some extent when the rivers are grouped according to their average climatic situation but it is always a combination of the above mentioned parameters that yields the most significant models in arid climates however regression coefficients are greater than in humid climates indicating that erodibility is much greater than in arid climates when extrapolated to the total continental area on the basis of the corresponding data sets the empirical models result in a total sediment flux of about 16 gigatons discharged to the oceans every year which is in good agreement with previous estimates derived from compilations of world wide river data consequently two global maps are proposed showing the spatial distributions of river sediment yields on the continents as well as the inputs of these sediments to the oceans in a grid point scale by far most of the sediments originate from the young orogenic belts of the continents mainly due to a combination of steep morphologies and high runoff intensities

riverine particulate organic carbon from an active mountain belt importance of landslides 1 we investigate the routing and transfer of particulate organic carbon poc from the western southern alps new zealand using organic carbon corg and nitrogen norg concentrations and stable carbon isotopes 13corg in this active mountain belt sediment discharge is dominated by landslide derived material landsliding acts to homogenize the geochemically diverse hillslope poc mixing poc from the standing biomass and soil with the fossil poc from bedrock as a result the poc in river sediment at the mountain front is a binary mixture of fossil and nonfossil carbon sourced from many landslide deposits we calculate that nonfossil biogenic poc makes up 63 7 of the total poc in the suspended load of rivers draining the western southern alps the erosional flux of biogenic poc from these catchments represents a transfer of 39 tc km 2 a 1 of atmospheric co2 averaged over the west flank of the mountain belt if more than 10 of this poc is preserved in sediments on geological timescales then this process is the most significant way in which the southern alps and similar tectonically active mountain belts with restricted alluvial aprons consume atmospheric co2

incision and morphologic evolution of an alluvial channel recovering from hydraulic mining sediment hydraulic gold mining in the sierra nevada california produced such a large volume of sediment from 1853 to 1884 that channels could not carry a substantial proportion of the delivered sediment the lower bear river aggraded as much as 5 m and underwent a major avulsion during the 1870s channel morphology continues to respond to these changes more than 100 years after the cessation of most hydraulic mining textures of mine tailings and older alluvium are contrasted and channel incision and channel shape changes from 1930 to 1985 are documented unlike the yuba and sacramento rivers the lower bear river had not returned to pre mining base levels by 1950 as sediment loads decreased nor were incision rates or morphological change governed by reduced sediment loads below dams built in 1928 and in the mid 1960s channel stability was due to resistance of a cohesive stratum on the channel bed an episode of channel down cutting was instigated by a moderately large flood in december 1955 that pierced the cohesive layer and was sustained through the 1970s by moderate magnitude floods the 1955 flood did not directly erode large volumes of sediment but it destabilized the channel allowing smaller floods to erode the channel at an accelerated rate episodic channel bed incision is contrasted to progressive morphologic changes cross section shape narrowed and deepened steadily from 1930 through the mid 1970s as the channel was superimposed onto cohesive older alluvium progressive deepening set up a positive feedback that ensured the ultimate penetration of the paved bed channel morphologic readjustment from the avulsion thus was both progressive and episodic

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

rapid channel response to variability in sediment supply cutting and filling of the tarndale fan waipaoa catchment new zealand abstract in the headwaters of the waipaoa catchment fluvio mass movement gully complexes are currently significant contributors of sediment delivery of which is buffered by fans which have developed in the small tributaries that lead from the gully complexes biannual channel cross section surveys made since 1983 show seasonal aggradation incision cycles channels generally incise in summer and infill during the winter months this seasonal pattern of cutting and filling is driven by variations in sediment supply from the gully complexes in this paper to better understand patterns and processes of sediment delivery at the top of the sediment cascade we examine cut and fill cycles on the 11 ha tarndale fan over a two and a half year period analysis of sequential dems compiled from survey data obtained between december 2004 and august 2007 indicates cutting and filling may involve up to 47 000 tonnes of sediment over as little as three months during discrete severe rainstorm and or wet weather periods mass movements in the gully complex are enhanced and contribute large quantities of sediment to the fan via debris flows and landslides which infill channels during drier periods mass movement activity is inhibited and runoff incises the feeder channels

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

occurrence of fossil organic matter in modern environments optical geochemical and isotopic evidence abstract this study relates to the input and fate of fossil organic matter fom in the modern environment and focuses on two experimental watersheds overlying jurassic marls le laval and le brusquet 1 km2 in area located near digne alpes de haute provence france considering that fom delivery is mainly a result of different processes affecting sedimentary rocks bio chemical and mechanical weathering samples from different pools were collected bedrocks weathering profiles soils and riverine particles the samples were examined using complementary techniques optical palynofacies methods geochemical rock eval 6 pyrolysis c n ratio molecular gas chromatography mass spectrometry and isotopic stable c isotopic composition as a result fom markers were identified and tracked through the different pools the results highlight the contribution of fom which can be found in all the studied pools transfer of fom between bedrocks weathering profiles governed mainly by chemical weathering and bedrocks riverine particles governed mainly by mechanical weathering reveals any qualitative change weathering profiles soils transition governed by bio chemical weathering is characterized by alteration of the fom which is difficult to describe because fossil material is mixed with recent organic matter rom despite this latter point the study provides evidence for a relative resistance of fom to weathering processes and points to its contribution to the modern geosystem and the c cycle

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

the isotopic composition of particulate organic carbon in mountain rivers of taiwan small rivers draining mountain islands are important in the transfer of terrestrial particulate organic carbon poc to the oceans this input has implications for the geochemical stratigraphic record we have investigated the stable isotopic composition of poc 13corg in rivers draining the mountains of taiwan in 15 rivers the suspended load has a mean 13corg that ranges from 28 1 0 8 to 22 0 0 2 on average 37 samples per river over the interval of our study to investigate this variability we have supplemented suspended load data with measurements of poc in bedrock and river bed materials and constraints on the composition of the terrestrial biomass fossil poc in bedrock has a range in 13corg from 25 4 1 5 to 19 7 2 3 between the major geological formations using coupled 13corg and n c we have found evidence in the suspended load for mixing of fossil poc with non fossil poc from the biosphere in two rivers outside the taiwan central range anthropogenic land use appears to influence 13corg resulting in more variable and lower values than elsewhere in all other catchments we have found that 5 variability in 13corg is not controlled by the variable composition of the biomass but instead by heterogeneous fossil poc in order to quantify the fraction of suspended load poc derived from non fossil sources fnf as well as the isotopic composition of fossil poc 13cfossil carried by rivers we adapt an end member mixing model river suspended sediments and bed sediments indicate that mixing of fossil poc results in a negative trend between n c and 13corg that is distinct from the addition of non fossil poc collapsing multiple fossil poc end members onto a single mixing trend as an independent test of the model fnf reproduces the fraction modern fmod in our samples determined from 14c measurements to within 0 09 at the 95 confidence level over the sampling period the mean fnf of suspended load poc was low 0 29 0 02 n 459 in agreement with observations from other mountain rivers where physical erosion rates are high and fossil poc enters river channels the mean 13cfossil in suspended poc varied between 25 2 0 5 and 20 2 0 6 from catchment to catchment this variability is primarily controlled by the distribution of the major geological formations it also covers entirely the range of 13corg found in marine sediments which is commonly thought to derive from mixing between marine and terrigenous poc if land sourced poc is preserved in marine sediments then changes in the bulk 13corg observed offshore taiwan could instead be explained by changes in the onshore provenance of sediment the range in 13corg of fossil organic matter in sedimentary rocks exposed at the surface is large and given the importance of these rocks as a source of clastic sediment to the oceans care should be taken in accounting for fossil poc in marine deposits supplied by active mountain belts

terrestrial sedimentation and the carbon cycle coupling weathering and erosion to carbon burial this paper examines the linkages between the carbon cycle and sedimentary processes on land available data suggest that sedimentation on land can bury vast quantities of organic carbon roughly 1015 g c yr 1 to evaluate the relative roles of various classes of processes in the burial of carbon on land terrestrial sedimentation was modeled as a series of 864 scenarios each scenario represents a unique choice of intensities for seven classes of processes and two different global wetland distributions comparison was made with presumed preagricultural conditions the classes of processes were divided into two major component parts clastic sedimentation of soil derived carbon and organic sedimentation of autochthonous carbon for clastic sedimentation masses of sediment were considered for burial as reservoir sediment lake sediment and combined colluvium alluvium and aeolian deposits when the ensemble of models is examined the human induced burial of 0 6 1 5 1015 g yr 1 of carbon on land is entirely plausible this sink reaches its maximum strength between 30 and 50 n paddy lands stand out as a type of land use that warrants future study but the many faces of rice agriculture limit generalization in an extreme scenario paddy lands alone could be made to bury about 1 1015 g c yr 1 arguing that terrestrial sedimentation processes could be much of the sink for the so called missing carbon is reasonable such a hypothesis however requires major redesign of how the carbon cycle is modeled unlike ecosystem processes that are amenable to satellite monitoring and parallel modeling many aspects of terrestrial sedimentation are hidden from space

controls on carbon and nitrogen export in an eroding catchment of south eastern queensland australia effects of gully and channel erosion on the export of sediments are in general well understood but the effects on carbon c and nitrogen n export remain an open question we examined these effects and the role of flow magnitude total wet season rainfall catchment size and the c and n content and solubility of most probable sediment sources in a subtropical catchment we sampled the baseflow and the rising stage of high flow events for one wet season and analysed 5 years of water quality data from event sampling stations total suspended sediment was the main variable explaining n export followed by rainfall flow and catchment size n was exported mainly in particulate organic form and c in dissolved form the quality of most probable sediment source fractions explains these results and points to fractionation during transport into c and n richer and c and n poorer fractions with travel distance ultimately determining the average quality of transported sediment for different flow magnitudes erosion would have caused a lower c and n concentration in sediments a lower proportion of mineralized n a larger proportion of dissolved organic c and a larger c n ratios of the soluble fraction as compared with unincised grassed valleys this would alter the rates of nutrient cycling and energy flow within and across ecosystem compartments in streams receiving this export copyright 2014 john wiley sons ltd

climate regulates the erosional carbon export from the terrestrial biosphere erosion drives the export of particulate organic carbon from the terrestrial biosphere pocbiosphere and its delivery to rivers the carbon transfer is globally significant and can result in drawdown of atmospheric carbon dioxide co2 if the eroded pocbiosphere escapes degradation during river transfer and sedimentary deposition despite this recognition we lack a global perspective on how the tectonic and climatic factors which govern physical erosion regulate pocbiosphere discharge obscuring linkages between mountain building climate and co2 drawdown to fill this deficit geochemical 13c 14c and c n hydrometric water discharge suspended sediment concentration and geomorphic slope measurements are combined from 33 globally distributed forested mountain catchments radiocarbon activity is used to account for rock derived organic carbon and reveals that pocbiosphere eroded from mountain forests is mostly 1300 14c years old annual pocbiosphere yields are positively correlated with suspended sediment yields confirming results from taiwan and a recent global analysis and are high in catchments with the steepest slopes based on these relationships and the global distribution of slope angles 3 arc second it is suggested that topography steeper than 10 16 of the continental area may contribute 40 of global pocbiosphere erosional flux climate is shown to regulate pocbiosphere discharge by mountain rivers by controlling hydrologically driven erosion processes in catchments where discharge measurements are available 8 of the 33 a significant relationship exists between daily runoff mm day 1 and pocbiosphere concentration mg l 1 r 0 53 p 0 0001 the relationship can be described by a single power law and suggests a high connectivity between forested hillslopes and mountain river channels as a result annual pocbiosphere yields are significantly correlated with mean annual runoff r 0 64 p 0 0001 a shear stress pocbiosphere erosion model is proposed which can explain the patterns in the data the model allows the climate sensitivity of this carbon flux to be assessed for the first time for a 1 increase in annual runoff pocbiosphere discharge is predicted to increase by 4 in steeper catchments pocbiosphere discharge increases more rapidly with an increase in annual runoff for comparison a 1 increase in annual runoff is predicted to increase carbon transfers by silicate weathering solute fluxes in mountains by 0 4 0 7 depending on the fate of the eroded pocbiosphere river export of pocbiosphere from mountains may act as an important negative feedback on rising atmospheric co2 and increased global temperature erosion of carbon from the terrestrial biosphere links mountain building and climate to the geological evolution of atmospheric co2 while the carbon fluxes are sensitive to predicted changes in runoff over the coming century

the transfer of modern organic carbon by landslide activity in tropical montane ecosystems 1 geomorphic processes play an important role in the transfer and storage of carbon within steep mountainous terrain among these mass wasting stands out because of its impact on above and below ground carbon pools and its potential for releasing or sequestering carbon a combined remote sensing and gis modeling approach was used to quantify the amount and spatial redistribution of modern organic carbon mobilized by mass wasting activity in a tropical mountain setting the study focused on a population of hundreds of shallow translational landslides triggered by hurricane mitch 1998 on seven watersheds draining the southern flank of the sierra de las minas mountain range slm in central eastern guatemala results illustrate that mass wasting contributed to the transfer of 43 104mgc or 3 of the pre event c in above ground vegetation and soils for an equivalent carbon flux rate of 0 08 0 33 mgc ha 1 y 1 depending on whether we consider hurricane mitch to be a landslide triggering event with a 20 year or an 80 year recurrence interval while 30 of this carbon was delivered to hillslopes or first order streams with a presumed high potential for long term sequestration the remaining 70 was delivered to higher order streams with unknown carbon retention capabilities therefore the ultimate fate of the carbon released by landsliding is very uncertain but depending on the proportion sequestered by colluvial deposits the recurrence interval of landslide triggering events and the rate of ecosystem recuperation at the landslide failure sites mass wasting could be either a net source or sink of carbon in a simulated setting based on the slm study results in which all carbon transferred by landslides from all tropical mountains of the globe is released to the atmosphere it would represent an amount equivalent to 1 11 of the global carbon currently being released by the burning of fossil fuels meanwhile in a projected scenario where a significant proportion of the carbon transferred by landslides is retained within sedimentary deposits sequestration rates would equal 2 19 of the residual land sink

event suspended sediment characteristics and the generation of hyperpycnal plumes at river mouths east coast continental margin north island new zealand abstract steepland rivers draining small coastal watersheds often have very high suspended sediment loads but the event characteristics of suspended sediment concentration and yield in this class of river is not well documented continuous monitoring at four sites in the waipaoa river basin new zealand demonstrates that during individual and composite events suspended sediment concentration versus water discharge relations typically show clockwise hysteresis and that event maximum concentration is poorly related to event peak discharge the signature of different erosion processes is also imprinted on the event yield magnitude frequency distributions gully dominated tributary basins produce relatively high yields at all frequencies reflecting greater sediment availability whereas in tributary basins where shallow landsliding is the dominant erosion process there is a steep increase in yields in relation to return period we estimate that flood discharges from the waipaoa river approach or exceed

gully erosion impacts factors and control gully erosion attracts increasing attention from scientists as reflected by two recent international meetings poesen and valentin eds catena 50 2 4 87 564 li et al 2004 gully erosion under global change sichuan science technology press chengu china 354 pp this growing interest is associated with the increasing concern over off site impacts caused by soil erosion at larger spatial scales than the cultivated plots the objective of this paper is to review recent studies on impacts factors and control of gully erosion and update the review on dgully erosion and environmental change importance and research needst poesen et al 2003 catena 50 2 4 91 134 for the farmers the development of gullies leads to a loss of crop yields and available land as well as an increase of workload i e labour necessary to cultivate the land gullies can also change the mosaic patterns between fallow and cultivated fields enhancing hillslope erosion in a feedback loop in addition gullies tend to enhance drainage and accelerate aridification processes in the semi arid zones fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion in this respect tracers such as carbon nitrogen the nuclear bomb derived radionuclide 137 cs magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment recent studies conducted in australia china ethiopia and usa showed that the major part of the sediment in reservoirs might have come from gully erosion gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess european belt chinese loess plateau north america and sandy soils sahelian zone north east thailand or in soils prone to piping and tunnelling such as dispersive soils most of the time the gullying processes are triggered by

carbon isotope geochemistry of the santa clara river the santa clara river is a prototypical small mountainous river with a headwater height greater than 1000 m and a basin area smaller than 10 000 m 2 although individual small mountainous rivers export trivial amounts of sediment and carbon to the ocean as a group these rivers may export a major fraction as much as 50 of the total global river sediment flux milliman and syvitski 1992 making their geochemistry relevant the study of the ocean s carbon cycle in addition many small rivers export sediment in a few high flux events causing massive sporadic discharge of carbon onto coastal shelves discharge conditions very different from those of large rivers this class of rivers is an end member of the river ocean carbon exchange system opposite the earth s largest river the amazon the carbon mass and isotopic properties of the santa clara river are significantly different from previously studied large rivers during the 1997 1998 winter all santa clara carbon pools were old with flux weighted average l4c values of 428 76 for particulate organic carbon 73 31 for dissolved organic carbon and 644 58 for black carbon the age of exported carbon is primarily due to the deep erosion of old soils and not to inclusion of fossil fuel carbon additionally the 13c signatures of exported carbon pools were high relative to terrestrial carbon bearing a signature quite similar to marine carbon average particulate organic carbon poc 13c 22 2 0 8 the santa clara s estuary is small and drains onto the narrow eastern pacific coastal margin exporting this old soil organic matter directly into the ocean if the santa clara export patterns are representative of this class of rivers they may be a significant source of refractory terrestrial carbon to the ocean

stochastic forcing of sediment routing and storage in channel networks the stochastic field of sediment supply to the channel network of a drainage basin depends on the large scale interactions among climatically driven processes such as forest fire and rainstorms topography channel network topology and basin scale during infrequent periods of intense erosion large volumes of colluvium are concentrated in parts of a channel network particularly near tributary junctions the rivers carry bed material and wash load downstream from these storage sites at different rates the bed material travels slowly creating transient patterns of sediment transport sediment storage and channel morphology along the channel network as the concentrations of bed material migrate along the network their waveforms can undergo changes by diffusion interference at tributary junctions and loss of mass through temporary sediment storage in fans and terraces and through particle abrasion which converts bed material to wash load we investigated how these processes might influence the sediment mass balance in channels of third and higher order in a 215 km 2 drainage basin within the oregon coast range over a simulated 3000 year period with a climate typical of the late holocene we used field measurements and a simulation model to illustrate interactions between the major controls on large scale processes functioning over long periods of time in complex drainage basins

gully erosion and sediment production te weraroa stream new zealand conversion to pasture early in the twentieth century was ameliorated by reforestation that commenced in 1962 estimates of sediment production were made using the change in gully area observed in sequential aerial photographs channel storage was assessed from stream cross section surveys at its peak gully erosion affected 6 of the total catchment area the amount of sediment contributed from gullies declined by 62 as the forest became established but of the 28 7 mt of sediment generated by gully erosion between 1950 and 1988 48 was stored in the channel along the lower 8 km of te weraroa stream even if the amount of sediment generated by gully erosion continues to decline it likely will be many decades before the gravel is released from storage index terms 1815 hydrology erosion and sedimentation 1824 hydrology geomorphology 1625 1878 hydrology water energy interactions keywords channel storage gully erosion sediment production citation gomez b k banbury m marden n a trustrum d h peacock and p j hoskin gully erosion and sediment production te weraroa stream new zealand water resour res 39 7 1187 doi 10 1029 2002wr001342 2003