landslide driven erosion and slope channel coupling in steep forested terrain ruahine ranges new zealand 1946 2011 abstract landslides are an important means of conveying sediment from slopes to channels in steepland environments but landsliding is a discontinuous process this means that any single assessment in time of their contribution to the sediment cascade is of limited value to better understand landscape dynamics and the contribution of landslides to slope channel coupling over time this paper quantifies connectivity over a time span of 65 years in small steep headwater catchments in the southern ruahine range new zealand temporal variability in landsliding and slope channel coupling was assessed using six sets of aerial photography flown between 1946 and 2011 from which over 6900 landslides were mapped in arcgis of which up to 78 connected with the stream network estimates of the volume of material delivered by landslide erosion to headwater channels were based on ground survey measurements of selected landslide scars and suggest that between 1946 and 2011 over 5 million m 3 of sediment was delivered from slopes to channels in the 221 km 2 study area forest cover is not sufficient to prevent this erosion these catchment systems are particularly vulnerable to high magnitude storm events which significantly elevate landslide intensity and enhance sediment delivery as occurred in the mid 1970s the legacy of these events remains in these headwater channels with ongoing consequences for stream and hazard management in and adjacent to the ranges

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

the fluvial sediment budget of a dammed river upper muga southern pyrenees abstract many rivers in the mediterranean region are regulated for urban and agricultural purposes reservoir presence and operation results in flow alteration and sediment discontinuity altering the longitudinal structure of the fluvial system this study presents a 3 year sediment budget of a highly dammed mediterranean river the muga southern pyrenees which has experienced flow regulation since the 1969 owing to a 61 hm 3 reservoir flow discharge and suspended sediment concentration were monitored immediately upstream and downstream from the reservoir whereas bedload transport was estimated by means of bedload formulae and estimated from regional data results show how the dam modifies river flow reducing the magnitude of floods and shortening its duration at the same time duration of low flows increases the downstream flow regime follows reservoir releases that are mostly driven by the irrigation needs in the lowlands likewise suspended sediment and bedload transport are shown to be notably affected by the dam sediment transport upstream was mainly associated with floods and was therefore concentrated in short periods of time i e 90 of the sediment load occurred in

slope channel linkage and sediment delivery on north carolina coastal plain cropland this paper presents the results of field measurements conducted in a small 19 4 ha agricultural basin on the north carolina coastal plain the overall objective of the study is to determine the magnitude of soil erosion and sediment delivery as a result of storm runoff the results suggest that erosion in the region is more rapid and extensive than previously thought fields at the site are experiencing accelerated soil loss with rates often comparable to those of the southeastern piedmont a region long recognized as having rapid and problematic soil loss this casts doubt on some assessments of the coastal plain as being a stable non eroding landscape however much of the soil mobilized is redistributed and stored within the watershed with only a small portion of the soil eroded from slopes leaving the basin on an event time frame copyright 2002 john wiley sons ltd

effects of temperature on silicate weathering solute fluxes and chemical weathering in a temperate rain forest watershed jamieson creek british columbia article i nfo article history accepted 7 september 2009 chemical weathering of silicate minerals has long been known as a sink for atmospheric co2 and feedbacks between weathering and climate are believed to affect global climate while warmer temperatures are believed to increase rates of weathering weathering in cool climates can be accelerated by increased mineral exposure due to mechanical weathering by ice in this study chemical weathering of silicate minerals is investigated in a small temperate watershed the jamieson creek watershed is covered by mature coniferous forest and receives high annual precipitation 4000 mm mostly in the form of rainfall and is underlain by quartz diorite bedrock and glacial till analysis of pore water concentration gradients indicates that weathering in hydraulically unsaturated ablation till is dominated by dissolution of plagioclase and hornblende however a watershed scale solute mass balance indicates high relative fluxes of k and ca indicating preferential leaching of these solutes possibly from the relatively unweathered lodgement till weathering rates for plagioclase and hornblende calculated from a watershed scale solute mass balance are similar in magnitude to rates determined using pore water concentration gradients when compared to the rio icacos basin in puerto rico a pristine tropical watershed with similar annual precipitation and bedrock but with dissimilar regolith properties fluxes of weathering products in stream discharge from the warmer site are 1 8 to 16 2 fold higher respectively and regolith profile averaged plagioclase weathering rates are 3 8 to 9 0 fold higher this suggests that the arrhenius effect which predicts a 3 5 to 9 fold increase in the dissolution rate of plagioclase as temperature is increased from 3 4 to 22 c may explain the greater weathering fluxes and rates at the rio icacos site however more modest differences in k and ca fluxes between the two sites are attributed to accelerated leaching of those solutes from glacial till at jamieson creek our findings suggest that under conditions of high rainfall and favorable topography weathering rates of silicate minerals in warm tropical systems will tend to be higher than in cool temperate systems even if the temperate system is has been perturbed by an episode of glaciation that deposits regolith high in fresh mineral surface area

impact of catastrophic events on small mountainous rivers temporal and spatial variations in suspended and dissolved solid fluxes along the choshui river central western taiwan during typhoon mindulle july 2 6 2004 abstract small mountainous rivers deliver disproportionately large quantities of suspended and dissolved solids to the global ocean often in response to catastrophic events such as earthquakes or floods here we report on the impact of a major flood on the choshui river central western taiwan generated by typhoon mindulle july 2 6 2004 five years after the nearby m w 7 6 chichi earthquake water samples taken at 3 h intervals at three stations along main stem as well as from two downriver tributaries allow us to delineate the temporal and spatial variability in concentrations and fluxes of suspended and dissolved constituents within the middle and lower portions of the river in response to this flood high suspended sediment concentrations some as high as 200 g l reflected the rapid erosion of landslide scars and debris deposits generated by super typhoon herb in 1996 and the 1999 chichi earthquake dissolved solid and suspended sediment discharges totaled 0 22 and 70 million tons mt 50 mt of which were discharged in just two days particulate organic carbon poc discharge most of which was pre modern in age was 195 000 t more than half of the discharged water poc and dissolved solids came from upriver whereas about 70 of the suspended sediment and 60 of the dissolved nitrate came from two downriver tributaries the chenyoulan and qingshui rivers spatial and temporal differences in the character and discharge of suspended and dissolved solids within and between rivers in the choshui drainage basin reflect different geologies landslide histories the effects of human impact and the abrupt draining of the tsaoling landslide lake in the qingshui basin as well as the possible shifting of importance of groundwater vs overland flow neither wind blown pollutants nor sea salts appear to have contributed significantly to dissolved solid character or discharge sediment contribution from the landslides in the chenyoulan basin generated by super typhoon herb and reactivated by the chichi earthquake declined during mindulle in contrast sediment erosion and discharge from the qingshui basin derived primarily from landslides generated during the chichi earthquake and reactivated during mindulle remained elevated for several more years

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

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

glaciers show direct linkage between erosion rate and chemical weathering fluxes field studies suggest a linkage between high physical erosion rates and rates of chemical denudation mechanical erosion by temperate glaciers is commonly an order of magnitude higher than in mountainous fluvial catchments leading to an expectation that chemical weathering fluxes should also be high from glacierized basins yet solute fluxes from glaciers are not found to be higher than non glacierized catchments application of a model of silicate weathering from glaciers based on mineral surface area production and mineralogy shows that solute fluxes are consistent with the low temperatures dilute water chemistry and high mineral surface area production in these environments low temperatures reduce silicate weathering rates this effect explains the difference between silica fluxes from glaciers and from non glacierized basins as in laboratory flow through reactors glacial solute flux should depend on surface area production and mineral weathering rate constants the surface area production is significant a typical glacial erosion rate and grain size distribution produces on the order of 104 km2 of mineral surface area per square kilometer per year this new surface area is highly reactive because mineral weathering rates decline with surface age application of the reactor model yields results largely consistent with measured solute fluxes for the example of bench glacier alaska the model underpredicts potassium fluxes probably due to accelerated initial dissolution of biotite strained by abrasion the success of the model in predicting other silicate weathering fluxes reflects the far from equilibrium conditions in glacial runoff such that mineral weathering rate constants are not limited by saturation state in a small data set from glacial catchments both annual silica fluxes and mean concentrations increase with water discharge this suggests that mineral surface area increases with water discharge from glaciers an effect plausibly linked to erosion rates those glaciers for which both erosion rate and silica flux data are available support the idea that production of new reactive mineral surface area by glacial erosion drives silicate weathering fluxes

geochemical fluxes and weathering of volcanic terrains on high standing islands taranaki and manawatu wanganui regions of new zealand abstract sediment fluxes from high standing oceanic islands hsis such as new zealand are some of the highest known milliman j d and syvitski j p m 1992 geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers j geol 100 525 544 recent geochemical work has suggested that along with their extremely high physical weathering yields many new zealand watersheds also have very high chemical weathering yields in new zealand the magnitude of both the physical and chemical weathering yields is related to the lithology of the watershed most of the previous work on this topic has been undertaken in southern alps watersheds of schist and greywacke and in east cape watersheds of semi consolidated marine sediments and greywacke we recently sampled north island watersheds in the taranaki and manawatu wanganui regions which have been subjected to volcanism since the miocene we sampled watersheds that contain both volcanic and sedimentary rocks a series of water and sediment samples was collected and analyzed for major minor and trace elements this was done to quantify the weathering intensities in the watersheds and to establish the relationship between physical and chemical weathering yields in volcanic lithologies our results reveal distinct chemical signatures for the different regions waters draining the taranaki region volcanics are significantly enriched in k and depleted in ca2 and sr2 compared to waters draining the manawatu wanganui region volcanics which also traverse expanses of sedimentary siltstones and mudstones the ca2 and sr2 depletions may reflect the relative absence of caco3 in the taranaki region watersheds in addition sediment samples from the taranaki region show significant enrichment in ti al ca fe mn mg ca and p and depletion in si and rb compared to those of the manawatu wanganui region from total dissolved solids concentrations and mean annual water discharge we calculate chemical weathering yields of 60 240 tons km 2 a 1 these weathering yields fall within the middle to upper range of those previously documented for the southern alps 93 480 tons km 2 a 1 and east cape 62 400 tons km 2 a 1 calculated silicate weathering yields of 12 33 6 tons km 2 a 1 and co2 consumption of 852 2390 103 mol km 2 a 1 for the rivers draining the taranaki volcanic region are higher than those previously reported for watersheds hosted in sedimentary and metamorphosed rock terrains on hsis co2 consumption is found to be within the range previously measured for the basaltic terrains of the deccan traps 580 2450 103 mol km 2 a 1 and reunion island 1300 4400 103 mol km 2 a 1 our calculated chemical weathering yields demonstrate the importance of hsis particularly those with volcanic terrains when considering global geochemical fluxes

oxygen isotopic compositions of relict and host grains in chondrules in the yamato 81020 co3 0 chondrite we report the oxygen isotope compositions of relict and host olivine grains in six high feo porphyritic olivine chondrules in one of the most primitive carbonaceous chondrites co3 0 yamato 81020 because the relict grains predate the host phenocrysts microscale in situ analyses of o isotope compositions can help assess the degree of heterogeneity among chondrule precursors and constrain the nebular processes that caused these isotopic differences in five of six chondrules studied the 17o 17o 0 52 18o compositions of host phenocrysts are higher than those in low feo relict grains the one exception is for a chondrule with a moderately high feo relict both the fayalite compositions as well as the o isotope data support the view that the low feo relict grains formed in a previous generation of low feo porphyritic chondrules that were subsequently fragmented it appears that most low feo porphyritic chondrules formed earlier than most high feo porphyritic chondrules although there were probably some low feo chondrules that formed during the period when most high feo chondrules were forming

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

morphometric controls and geomorphic responses on fans in the southern alps new zealand morphometric variables associated with 41 debris ow and 18 uvial fans and their basins in the southern alps of new zealand are examined the results show statistically signi cant differences in the area maximum elevation relief and ruggedness melton s r of the basin and the area gradient and apex and toe elevations of the fan between debris ow and uvial sites concavity of the fan longitudinal pro le also differs between the two fan types although this could not be tested statistically most of these morphometric differences re ect differences in processes and environmental controls on them discriminant analysis indicates that basin area and fan gradient best differentiate the two fan types by process moderately strong correlations exist on both debris ow and uvial fans between basin area or melton s r and fan area correlations between basin area or melton s r and fan gradient are generally weaker the results of this study also indicate that on debris ow prone fans the fan gradient and basin melton s r have lower thresholds which overlap little with upper thresholds associated with basins where only stream ow reaches the fan these thresholds may therefore have value in preliminary morphometric assessments of debris ow hazard on fans in the southern alps copyright 2004 john wiley sons ltd

on the construction of geomagnetic timescales from non prejudicial treatment of magnetic anomaly data from multiple ridges summary when marine magnetic anomaly data are used to construct geomagnetic polarity timescales the usual assumption of a smooth spreading rate function at one seafloor spreading ridge forces much more erratic rate functions at other ridges to eliminate this problem we propose a formalism for the timescale problem that penalizes non smooth spreading behaviour equally for all ridges specifically we establish a non linear lagrange multiplier optimization problem for finding the timescale that 1 agrees with known chron ages and with anomaly interval distance data from multiple ridges and 2 allows the rate functions for each ridge to be as nearly constant as possible according to a cumulative penalty function the method is applied to a synthetic data set reconstructed from the timescale and rate functions for seven ridges derived by cande kent 1992 under the assumption of smooth spreading in the south atlantic we find that only modest changes in the timescale less than 5 per cent for each reversal are needed if no one ridge is singled out for the preferential assumption of smoothness future implementation of this non prejudicial treatment of spreading rate data from multiple ridges to large anomaly distance data sets should lead to the next incremental improvement to the pre quaternary geomagnetic polarity timescale as well as allow a more accurate assessment of global and local changes in seafloor spreading rates over time

anti clockwise hysteresis in suspended sediment concentration during individual storms holbeck catchment yorkshire england abstract analysis of the flow sediment hysteresis shape may assist in determining the sediment source area in a small basin a clockwise hysteresis occurs when sediment is derived from the bed and banks of the channel or areas adjacent to the channel whereas an anti clockwise hysteresis occurs when the upper part of the slopes is the sediment source area

process type identification in torrential catchments in the eastern alps abstract torrential hazards are omnipresent in the alpine regions as it frequently causes damage to infrastructures in some cases even people s lives are endangered the classification of these processes takes place according to factors like sediment concentration and flow behaviour and ranges from fluvial process types including water floods and fluvial sediment transport processes to fluvial mass movements such as debris flows following the hypothesis of this study a context exists between basic geomorphological disposition parameters and potential dominant flow process types in a steep headwater catchment thus examined catchments were selected based on a historical event documentation of torrential events in the austrian alps in total 84 catchments could be analysed and 11 different morphometric parameters were considered to predict the dominant torrential process type within a catchment a naive bayes classifier a decision tree model and a multinomial regression model was trained against the compiled geomorphological disposition parameters all models as well as their combination were compared based on bootstrapping and complexity we present the classification model with the lowest prediction error for our data that might help to identify the most likely torrential process within a considered catchment

typhoon impacts on chemical weathering source provenance of a high standing island watershed taiwan abstract chemical weathering source provenance changes associated with typhoon mindulle 2004 were identified for the choshui river watershed in west central taiwan using radiogenic sr isotope 87 sr 86 sr and major ion chemistry analysis of water samples collected before during and following the storm event storm water sampling over 72 h was conducted in 3 h intervals allowing for novel insight into weathering regime changes in response to intense rainfall events chemical weathering sources were determined to be bulk silicate and disseminated carbonate minerals at the surface and silicate contributions from deep thermal waters loss on ignition analysis of collected rock samples indicate disseminated carbonate can compose over 25 by weight of surface mineralogy but typically makes up 2 3 of watershed rock 87 sr 86 sr and major element molar ratios indicate that typhoon mindulle caused a weathering regime switch from normal flow incorporating a deep thermal signature to that of a system dominated by surface weathering the data suggest release of silicate solute rich soil pore waters during storm events creating a greater relative contribution of silicate weathering to the solute load during periods of increased precipitation and runoff partial depletion of this soil solute reservoir and possible erosion enhanced carbonate weathering lead to increased importance of carbonates to the weathering regime as the storm continues major ion data indicate that complex mica weathering muscovite biotite illite chlorite may represent an important silicate weathering pathway in the watershed deep thermal waters represent an important contribution to river solutes during normal non storm flow conditions sulfuric acid sourced from pyrite weathering is likely a major weathering agent in the choshui river watershed

interpreting sediment delivery processes using suspended sediment discharge hysteresis patterns from nested upland catchments south eastern australia in this study suspended sediment concentration ssc and discharge q hysteresis patterns recorded at the outlets of two nested upland catchments in south eastern australia were examined detailed monitoring of sediment flux was undertaken in a 1 64 km2 sub catchment located within a 53 5 km2 catchment for which sediment yield was measured and the extent of incised channels mapped the analysis of ssc q hysteresis patterns was supplemented by these additional datasets to contribute to the explanation of observed patterns clockwise ssc q hysteresis loops with the suspended sediment peak leading the discharge peak were recorded most frequently at both sites this was attributed to initial rapid delivery of sediment from channel banks the dominant sediment source in the sub catchment and probably also for the catchment in conjunction with remobilization of in channel fine sediment deposits sediment exhaustion effects were considered to enhance clockwise hysteresis with reduced ssc on the falling limb of event hydrographs pronounced exhaustion effects were observed on some multi rise events with subsequent flow peaks associated with much reduced sediment peaks to compare ssc q hysteresis patterns between the two catchments a dimensionless similarity function sf was derived to differentiate paired event hysteresis patterns according to the extent of pattern similarity this analysis coupled with the other datasets provided insight into the function of erosion and sediment delivery processes across the spatial scales examined and indicated the dependency of between scale suspended sediment transfer on defined flow event scenarios quantitative measures of event ssc q hysteresis pattern similarity may provide a mechanism for linking the timing and magnitude of process response across spatial scales this may offer useful insights into the between scale linkage of dominant processes and the extent of downstream suspended sediment delivery copyright 2009 john wiley sons ltd

catchment scale weathering fluxes in the southern alps new zealand abstract the dissolved and suspended sediment flux in a small headwater in the southern alps new zealand over a 16 month period showed that mass transferred as dissolved load 91 t km 2 a 1 is a significant flux relative to the suspended sediment flux 210 t km 2 a 1 export of dissolved load occurs mostly under baseflow with 268 t being transported over 10 discrete events relative to a total load of 1171 t over the experimental observation period which is equivalent to 23 of the ionic flux occurring during event flow storm events contribute 2420 t of suspended sediment accounting for 90 of the total suspended sediment flux the chemical weathering flux was 43 of the physical weathering flux and much higher than previous estimates of 1 9 for the southern alps such a high relative rate of chemical weathering is unlikely to be indicative of the full southern alps extent but suggests that in some regions of the eastern southern alps mass loss via chemical weathering may be a significant portion of overall flux during storm events temporal exhaustion of sediment occurred and inferred limited sediment source production rather than limited connectivity with the hillslope environment similar supply limitation is expressed in the ionic flux where rainfall events do not usually express hysteretic behaviour and event flow is dominated by a simple dilution recession

how accurate are rivers as gauges of chemical denudation of the earth surface examination of the behavior of oxygen and hydrogen during weathering reactions shows that river dissolved load although widely used is an imperfect tracer of chemical denudation at the current state of knowledge none of the metrics for river total dissolved loads such as the silicate derived total dissolved solids tds sil ca 2 mg 2 na k sio 2 converted or not to equivalent oxides account in a mechanistic manner for the transfer of oxygen and hydrogen between the solid and fluid phase during weathering reactions we assess that chemical denudation derived from tds sil will significantly overestimate the true chemical denudation for weathering of ca feldspar to kaolinite whereas weathering of water rich sedimentary rocks will be characterized by an underestimation of chemical denudation by tds sil for a handful of field sites we estimate that the bias is lower than 10 the sign and extent of the bias depends on the nature of bedrock and on weathering conditions altogether our analysis questions the broadly accepted concept of chemical denudation rate

chemical weathering in active mountain belts controlled by stochastic bedrock landsliding in active mountain belts erosion is driven by bedrock landsliding river water chemistry in new zealand s southern alps suggests that stochastic mass wasting processes also enhance chemical weathering in such environments a link between chemical weathering and physical erosion exists at the catchment scale over a wide range of erosion rates1 2 however in mountain environments where erosion rates are highest weathering may be kinetically limited3 4 5 and therefore decoupled from erosion in active mountain belts erosion is driven by bedrock landsliding6 at rates that depend strongly on the occurrence of extreme rainfall or seismicity7 although landslides affect only a small proportion of the landscape bedrock landsliding can promote the collection and slow percolation of surface runoff in highly fragmented rock debris and create favourable conditions for weathering here we show from analysis of surface water chemistry in the southern alps of new zealand that weathering in bedrock landslides controls the variability in solute load of these mountain rivers we find that systematic patterns in surface water chemistry are strongly associated with landslide occurrence at scales from a single hillslope to an entire mountain belt and that landslides boost weathering rates and river solute loads over decades we conclude that landslides couple erosion and weathering in fast eroding uplands and thus mountain weathering is a stochastic process that is sensitive to climatic and tectonic controls on mass wasting processes

hydrologic connectivity as a framework for understanding biogeochemical flux through watersheds and along fluvial networks abstract hydrologic connections can link hillslopes to channel networks streams to lakes subsurface to surface land to atmosphere terrestrial to aquatic and upstream to downstream these connections can develop across vertical lateral and longitudinal dimensions and span spatial and temporal scales each of these dimensions and scales are interconnected creating a mosaic of nested hydrologic connections and associated processes in turn these interacting and nested processes influence the transport cycling and transformation of organic material and inorganic nutrients through watersheds and along fluvial networks although hydrologic connections span dimensions and spatiotemporal scales relationships between connectivity and carbon and nutrient dynamics are rarely evaluated within this framework the purpose of this paper is to provide a cross disciplinary view of hydrologic connectivity highlighting the various forms of hydrologic connectivity that control fluxes of organic material and nutrients and to help stimulate integration across scales and dimensions and collaboration among disciplines

the sediment budget of a highly dynamic mesoscale catchment the river isabena the paper presents the sediment budget of the isabena basin a highly dynamic 445 km2 catchment located in the central pyrenees that is patched by highly erodible areas i e badlands the budget for the period 2007 2009 is constructed following a methodology that allows the interpolation of intermittent measurements of suspended sediment concentrations and enables a subsequent calculation of sediment loads data allow specification of the contribution of each subbasin to the water and sediment yield in the catchment outlet mean annual sediment load was 235 000 t y 1 specific sediment yield reached 2000 t km 2 y 1 a value that indicates very high sedimentary activity especially in the case of villacarli and lascuarre subcatchments were most badlands are located the specific sediment yield obtained for the entire isabena is 527 t km 2 y 1 a high value for such a mesoscale basin results show that a small part of the area i e 1 controls most of the catchment s gross sediment contribution sediment delivery ratio ratio between sediment input from primary sources and basin export has been estimated at around 90 while in channel storage represents the 5 of the annual load on average the high connectivity between sediment sources i e badlands and transfer paths i e streamcourses exacerbates the influence of the local sediment production on the catchment s sediment yield a quite unusual fact for a basin of this scale

controls on slope to channel fine sediment connectivity in a largely ice free valley hoophorn stream southern alps new zealand there has been little work to date into the controls on slope to channel fine sediment connectivity in alpine environments largely ice free for most of the holocene characterization of these controls can be expected to result in better understanding of how landscapes relax from such perturbations as climate shock we monitored fine sediment mobilization on a slope segment hydrologically connected to a stream in the largely ice free 8 3 km2 hoophorn valley new zealand gerlach traps were installed in ephemeral slope channels to trap surficial material mobilized during rainfall events channel sediment flux was measured using turbidimeters above and below the connected slope and hysteresis patterns in discharge suspended sediment concentrations were used to determine sediment sources over the 96 day measurement period sediment mobilization from the slope segment was limited to rainfall events with increasingly larger particles trapped as event magnitude increased less than 1 of the mass of particles collected during these events was fine sediment during this period 714 t of suspended sediment was transported through the lower gauging station 60 of it during rainfall events channel sediment transfer patterns during these events were dominated by clockwise hysteresis interpreted as remobilization of nearby in channel sources further suggesting limited input of fine sediment from slopes in the lower valley strong counterclockwise hysteresis representing input of fine sediment from slope segments was restricted to the largest storm event jd2 2009 when surfaces in the upper basin were activated the results indicate that the slopes of the lower hoophorn catchment are no longer functioning as sources of fine sediment but rather as sources of coarse material with flux rates controlled by the intensity and duration of rainfall events although speculative these findings suggest a shift to a coarse sediment dominated slope to channel transfer system as the influence of pre holocene glacial erosion declines copyright 2011 john wiley sons ltd

climatic and tectonic controls on chemical weathering in the new zealand southern alps abstract climatic and tectonic controls on the relative abundance of solutes in streams draining the new zealand southern alps were investigated by analyzing the elemental and sr isotope geochemistry of stream waters bedload sediment and hydrothermal calcite veins the average relative molar abundance of major cations and si in all stream waters follows the order ca2 50 si 22 na 17 mg2 6 k 5 for major anions the relative molar abundance is hco3 89 so42 7 cl 4 weathering reactions involving plagioclase and volumetrically small amounts of hydrothermal calcite define the ionic chemistry of stream waters but nearly all streams have a carbonate dominated ca2 and hco3 mass balance stream water ca sr and 87sr 86sr ratios vary from 0 173 to 0 439 mol nmol and from 0 7078 to 0 7114 respectively consistent with the ionic budget these ratios lie solely within the range of values measured for bedload carbonate ca sr 0 178 to 0 886 mol nmol 87sr 86sr 0 7081 to 0 7118 and hydrothermal calcite veins ca sr 0 491 to 3 33 mol nmol 87sr 86sr 0 7076 to 0 7097 streams draining regions in the southern alps with high rates of physical erosion induced by rapid tectonic uplift and an extremely wet climate contain 10 more ca2 and 30 more sr2 from carbonate weathering compared to streams draining regions in drier more stable landscapes similarly streams draining glaciated watersheds contain 25 more sr2 from carbonate weathering compared to streams draining non glaciated watersheds the highest abundance of carbonate derived solutes in the most physically active regions of the southern alps is attributed to the tectonic exhumation and mechanical denudation of metamorphic bedrock which contains trace amounts of calcite estimated to weather 350 times faster than plagioclase in this environment in contrast regions in the southern alps experiencing lower rates of uplift and erosion have a greater abundance of silicate versus carbonate derived cations these findings highlight a strong coupling between physical controls on landscape development and sources of solutes to stream waters using the southern alps as a model for assessing the role of active tectonics in geochemical cycles this study suggests that rapid mountain uplift results in an enhanced influence of carbonate weathering on the dissolved ion composition delivered to seawater