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

cross shore wave transformation and mean flow circulation abstract an analysis of wave and current evolution in shoaling and breaking waves in the cross shore plane adopts the integral method used successfully for turbulent shear flows the field equations are integral conservation equations for mass momentum and energy which describe the cross shore flow as an initial value problem reynolds stress closure assumes added complexity as a result of the fluctuating wave motion for the wave fluctuations closure relationships consistent with the integral methodology are based on profiles of mean quantities established from steady fourier wave theory within the surf zone turbulence closure is dominated by breaking wave energy dissipation computations reproduce the trends of wave shoaling set up and undertow and the global trends compare favorably with field and laboratory data the various contributions to the complete balances of mass momentum and energy are examined in detail leading to an especially descriptive picture of the evolutionary processes in the complete nearshore zone from deep water through the shoaling breaker and surf zones to the beach

simulated headward erosion of bank gullies in the dry hot valley region of southwest china although the development and migration of gully headcuts can increase soil loss and accelerate landscape degradation considerably little attention has been paid to the spatiotemporal variations of the morphological characteristics of bank gully heads in the dry hot valley region of southwest china this study explored the in situ variations in soil loss rates and morphological characteristics in active bank gully heads testing the overland flow discharge with a range of 30 to 120 l min 1 in response to this flow actively migrating headcuts developed with retreat rates ranging from 2 6 to 7 9 mm h 1 all experimental runs resulted in a gradual increase in soil loss volume incision depth and retreat distance over time due to set flow rates for the gully beds and upstream areas of gully heads the soil erosion rates were greatest at the beginning of each run and progressively decreased during the scouring test non steady state soil erosion rates were observed in the headwall for the flow discharge levels examined for this study this was due to an abrupt slope collapse after long term scouring effects as degradation progressed similar trends emerged for temporal variations within the fractal dimensions of topographic surfaces in both the gully heads and upstream areas after the scouring was run for a period of 90 min asymptotic fractal dimensions of topographic surfaces were attained in the upstream areas and gully heads suggesting that steady state morphological characteristics had been realised it should be noted that headwall collapses are typically associated with a substantial increase in sediment yield where no other obvious change in morphological characteristics occurs in the headwall therefore even though a significant difference in the soil erosion rates and fractal dimensions of topographic surface values could be found between the bank gully heads and upstream areas the temporal variation in the morphological characteristics of bank gully heads was similar to those observed in upstream areas where ephemeral gullies developed c 2013 elsevier b v all rights reserved

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

mass flux and undertow in a surf zone abstract the mass of water carried shoreward by the breaking waves in a surf zone will in a two dimensional situation be compensated by a seaward return flow the undertow it is shown that the undertow is driven by the local difference between radiation stress and the set up pressure gradient which only balance each other in average over the depth turbulent shear stresses are required to maintain a steady situation comparison with measurements confirms the theoretical results

neodymium strontium isotopic evidence for extreme contamination in a layered basic intrusion abstract neodymium and strontium isotopic analyses from the kalka layered basic intrusion central australia are arrayed parallel to the sr axis of a nd sr isotopic correlation diagram and are removed from the normal basaltic field initial 143 nd 144 nd ratios are almost constant and typical of continental basalts whereas initial 87 sr 86 sr ratios vary greatly and range to high values 0 7049 0 7088 acidic granulites from the country rock lie upon the continuation of the kalka trend at higher 87 sr 86 sr ratios outlining a mixing system between granulite and normal basaltic magma if average granulite acted as a contaminant isotope dilution calculations show that amounts assimilated reached as high as 25 bulk contamination is confirmed petrologically by the abundance of orthopyroxene particularly as basal orthopyroxenites and the restriction of olivine to less contaminated levels analogies between kalka and several other major layered intrusions such as the bushveld complex suggest that large scale contamination was a significant aspect of their genesis

geomorphic changes in a complex gully system measured from sequential digital elevation models and implications for management high resolution digital elevation models dems were derived from sequential aerial photography of an active uvio mass movement gully complex in new zealand s north island east coast region to measure geomorphic changes over approximately one year the gully showed a complex behaviour combining uvial and mass movement erosion deposition and reworking of materials stored in an active debris fan during the measurement period 5200 1700 m3 of material were eroded from the 8 7 ha gully complex and 670 180 m3 from the 0 8 ha depositional fan giving a total of 5870 1710 m3 for the entire gully complex fan system the results provide a high resolution description of gully behaviour over a short time period and also demonstrate that mass movement slumping and debris ows accounted for almost 90 per cent 4660 200 m3 of the sediment generated this erosional response is described in terms of gully evolution by comparing the gully complex to other systems in the region in various stages of development the effect of gully evolution on geomorphic coupling between the gully complex and channel system is described and coupling is also shown to vary with the magnitude and frequency of rainfall events from a land management perspective the success of strategies such as tree planting to mitigate against gully erosion depends on the stage of gully development particularly on whether or not mass movement erosion has begun in contrast to gully rehabilitation efforts elsewhere basin wide afforestation in the early stages of gully incision is favoured over riparian planting given that mass movement assisted by excessive groundwater pressure is the main process leading to uncontrollable gully expansion to protect land effectively against continuing gully erosion of headwater catchments and resulting downstream aggradation it is necessary for land managers to understand the spatial and temporal variability of gully development fully so that mitigation efforts can be targeted appropriately copyright 2003 john wiley sons ltd

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

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

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

cross shore mean flow in the surf zone abstract the seaward mean returnflow or undertow in the surf zone which compensates for the shoreward mass flux above the wave trough level is found to be driven by the force imbalance between the wave momentum flux on the one hand and the set up on the other hand in qualitative agreement with the model of dyhr nielsen and sorensen 1970 a model which quantifies this imbalance is shown to yield theoretical results in good accordance with experiments when the proper boundary conditions are accounted for

coastal landslide material loss rates associated with severe climatic events deep seated landslides along the california coast deliver large amounts of material to the nearshore littoral environment landslide movement a combined result of slope base undercutting by waves and ground saturation is highly episodic movement occurs primarily during periods of high rainfall and large waves such as those associated with el nino events this analysis applies remote sensing techniques to quantify the volumetric net loss rates at three specific landslide sites along the big sur coast over three approximately decadal time periods two of which contained the largest el nino events of the twentieth century high resolution historical terrain models were compared in order to provide surface elevation change data for each landslide complex to determine the material influx to the littoral system the landslide complexes were divided into upper and lower slopes and the surface elevation change was converted to a volume loss some material lost from the upper slope was deposited at the slope base not into the littoral system we describe a method to calculate the net loss that omits the deposition volumes from the upper slope loss rates were found to be substantially higher during the periods in which el nino events occurred this is especially true during the period of the 1997 1998 el nino when 75 of the total material volume was lost and loss rates were as much as sixteen times higher than during non el nino periods

a sm nd isotopic study of the south harris igneous complex the outer hebrides sm nd geochronology may be used to bracket the age of metamorphism in rocks which are difficult to date by other methods by coupling whole rock sm nd analyses of the principal members of the south harris igneous complex with sm nd mineral isochrons on two anothositic gabbros the age of granulite facios metamorphism has been defined whole rock analyses of three pairs of closely spaced samples of the anorthosite give consistent ages averaging 2 18 0 06 gyr but in general the data from the anorthosite do not define an isochron as a result of variable contamination of the evolving magma chamber whole rock data on the tonalite indicate that it is younger than 2 06 gyr its mean tchur age is 1 86 0 05 gyr garnet pyroxene amphibole plagioclase mineral isochrons on two anorthosite samples give identical 1 87 0 04 gyr ages which date cooling after the high pressure granulite facies metamorphism together with the tonalite whole rock data this defines the age of that metamorphism and confirms dearnley s original assignment of an early laxfordian age

cross shore currents in surf zone modelling abstract the paper discusses two aspects of the problem of incorporating the cross shore circulation into mathematical numerical nearshore models that also predict wave heights and set up one aspect is related to the proper choice of boundary conditions for the undertow the other one to the determination of the mean bottom shear stress b two methods are compared for b and found to yield comparable results both are based on the assumption of the existence of a bottom boundary layer with an eddy viscosity much smaller than that created at the surface by breaking waves both methods also yield results that very accurately reproduce measured undertow velocity profiles and hence confirm the basic ideas finally it is found that both methods can be used as parts of comprehensive nearshore models this on the other hand does not seem to be the case for the undertow theory suggested by stive and wind 1986 in which the no slip condition at the bottom is substituted by specification of a mean shear stress at wave trough level

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

channel processes following land use changes in a degrading steep headwater stream in north island new zealand abstract in headwater streams in steep land settings narrow and steep valley floors provide closely coupled relationships between geomorphic components including hillslopes tributary fans and channel reaches these relationships together with small catchment sizes result in episodic changes to the amount of stored sediment in channels major sediment inputs follow high magnitude events subsequent exponential losses via removal of material can be represented by a relaxation curve the influence of hillslope and tributary processes on relaxation curves and that of altered coupling relations between components were investigated along a 1 3 km reach of a degrading channel in the 4 8 km2 weraamaia catchment new zealand extensive deforestation in the late 19th and early 20th centuries followed by invasion of scrubs and reforestation induced changes to major erosion types from gully complexes to shallow landslides changes in the size and pattern of sediment slugs from 1938 to 2002 were analysed from air photographs tied to detailed field measurement the rate and calibre of sediment flux changed progressively following substantive hillslope input in a storm in 1938 subsequently the channel narrowed and incised decoupling tributary fans from the main stem thereby scaling down the size of sediment slugs as a consequence the dominant influence on the behaviour of sediment slugs and associated relaxation processes changed from tributary fans to the type and distribution of bedrock outcrops along the reach

gully formation and the role of valley floor vegetation southeastern australia attempts to understand the causes of gully erosion have been hampered by a poor understanding of quantitative changes to the force of flows and the resistance to scour we used flume experiments on an unincised valley floor to determine flow resistance and the critical shear stress for scour under natural and degraded vegetation covers applying the results to sites of gully formation in southeastern australia demonstrates the crucial role that reduced vegetation cover plays in increasing the susceptibility of valleys to channel incision widespread and rapid gully formation in the 19th century required degradation of valley floor vegetation and was not solely the result of land use or climatically induced increases in discharge

kinematics of active earthflows revealed by digital image correlation and dem subtraction techniques applied to multi temporal lidar data earthflow type landslides are persistent natural hazards having deep socio economic and environmental consequences they have significantly contributed to the geomorphic evolution of mountainous slopes in europe since the late glacial an understanding of their complex kinematics is crucial to better constrain the processes governing their occurrence and mobility in this work we explored the possibility to quantify displacement vectors on a spatially distributed basis and to quantify volumetric transfer at the slope scale with regard to a large flow type landslide located in the northern apennines of italy for this purpose we applied digital image correlation dic and digital elevation model differencing demod techniques to multi temporal airborne lidar surveys of 2006 2007 and 2009 the dic was applied to greyscale slope gradient maps retrieved after precise co registration of lidar surveys thereby movement patterns over various sectors of the landslide were reconstructed and quantified most notably up to 20 m in the head zone up to 51 m in the lower main track and up to about 27 m at the landslide toe the demod analysis revealed significant mass transfer from the source to the tracks and toe zone with the upper flow tracks acting as temporal storage of large amounts of material the mass balance indicated that significant amounts of advancing landslide debris were eroded by a local stream an integrated analysis of demod and dic results allowed for a discussion of governing processes such as the transition from slide to flow the influence of underlying topography on earthflow mobility and the role of undrained loading as a mechanism of toe zone reactivation in conclusion the successful application of dic and demod to the case study underlines the added value of high resolution dems in the analysis of earthflow kinematics toward a better understanding of their role in the geomorphic evolution of slopes copyright 2012 john wiley sons ltd

the kalka layered intrusion central australia the kalka intrusion central australia has a 5000 m thick layered sequence comprising pyroxenite norite and anorthosite zones an olivine gabbro zone is enclosed by and has a facies relationship with the norite zone contamination is evidenced by high initial 87sr 86sr ratios 0 708 in the lower four fifths of the intrusion and resulted in pyroxenite rather than peridotite as a basal crystal accumulate after an early phase of erratic buildup in contamination due to assimilation of ragged granulite wall rock armouring of the walls and mixing produced an homogeneous norite zone threshold magma body crystallising opx cpx plag within the succeeding 3500 m of section plagioclase an values have a general decline up sequence an74 60 feldspar threshold with superimposed short term digressions to more calcic compositions initial 87sr 86sr ratios also fall very gradually 0 7081 0 7078 isotopic threshold with transient fluctuations to distinctly lower values maxima in plagioclase an contents and 87sr 86sr minima may be correlated with the spasmodic appearance of olivine and pronounced lithological variation such features are explained by the ponding of fresh bodies of uncontaminated magma on the floor of the chamber these formed a hybrid with threshold magma that temporarily dominated crystallisation thereby perturbing plagioclase and isotopic compositions eventually mixing of the hybrid into the overlying threshold magma returned crystallisation to its initial state the facies controlled olivine gabbro zone is the physical expression of ponded basal hybrid magmas the onset of the anorthosite zone is marked by a pronounced decline in 87sr 86sr ratios to around 0 705 registering a major influx of new magma in this instance the new magma dominated the system and a change to plagioclase as the dominant liquidus phase indicates a drastic change in input magma composition the evolution of kalka was determined by an interplay of crystal fractionation fresh magma pulses and magma mixing with the latter effects producing both increases and decreases in plagioclase an contents the complete process can only be revealed by combined mineral composition and isotopic data

development of the late proterozoic to mid paleozoic intracratonic amadeus basin in central australia a key to understanding tectonic forces in plate interiors the intracratonic amadeus basin in central australia is a complex composite basin covering 17 000 km with at least nine distinct episodes of evolution between 900 and 300 ma these have been identified in neighboring central australian basins and are characterized by intervals of renewed subsidence followed by intervals of erosion and changes in basin shape several unconformities separating the tectonostratigraphic sequences represent periods of mild regional uplifts and correlate with major episodes of compressive tectonism at the evolving margin of the early australian plate in the absence of direct geological evidence for thermal events in the amadeus basin after the initial period of subsidence ended possibly at about 800 ma the correlations found between events in the amadeus basin those in the neighboring interconnected basins and tectonic events at the continental or plate margins emphasize that regional horizontal stress fields contribute significantly to primary basin forming mechanisms this suggests that stresses generated at continental or plate margins may propagate to the plate interior with the lithosphere acting as a stress guide throughout the history of the amadeus basin both periods when compressional stresses were dominant and when extensional tectonics controlled subsidence can be identified there were also transitional periods when neither compression nor extension dominated so that other processes masked the effects of weak horizontal stresses the most recent compressional thrust belt concentrated at the northern margin between 300 and 400 ma and has partly obscured the record of earlier basin shape and size

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

estimation of regional material yield from coastal landslides based on historical digital terrain modelling high resolution historical 1942 and recent 1994 digital terrain models were derived from aerial photographs along the big sur coastline in central california to measure the long term volume of material that enters the nearshore environment during the 52 year measurement time period an average of 21 000 3100 m3 km 1 a 1 of material was eroded from nine study sections distributed along the coast with a low yield of 1000 240 m3 km 1 a 1 and a high of 46 700 7300 m3 km 1 a 1 the results compare well with known volumes from several deep seated landslides in the area and suggest that the processes by which material is delivered to the coast are episodic in nature in addition a number of parameters are investigated to determine what influences the substantial variation in yield along the coast it is found that the magnitude of regional coastal landslide sediment yield is primarily related to the physical strength of the slope forming material coastal highway 1 runs along the lower portion of the slope along this stretch of coastline and winter storms frequently damage the highway the california department of transportation is responsible for maintaining this scenic highway while minimizing the impacts to the coastal ecosystems that are part of the monterey bay national marine sanctuary this study provides environmental managers with critical background data on the volumes of material that historically enter the nearshore from landslides as well as demonstrating the application of deriving historical digital terrain data to model landscape evolution published in 2005 by john wiley sons ltd

magnitude and cross shore distribution of bed return flow measured on natural beaches abstract field measurements of cross shore currents 0 25 m from the bed were made on two natural beaches under a range of incident wave conditions the results indicated the presence of a relatively strong offshore directed mean current both within and seaward of the surf zone typical velocities within the surf zone were of the order of 0 2 0 3 m s this bed return flow or undertow represents a mass conservation response returning water seaward that was initially transported onshore in the upper water column primarily above the trough of the incident waves the measurements demonstrated that the bed return flow velocity increases with the incident wave height in addition the crossshore distribution of the bed return flow is characterised by a mid surf zone maximum which exhibits a strong decrease in velocity towards the shoreline and a more gradual decay in the offshore direction several bed return flow models based on mass continuity were formulated to predict the cross shore distribution of the bed return flow under an irregular wave field and were compared with the field data best agreement was obtained using shallow water linear wave theory after including the mass transport associated with unbroken waves the contribution of the unbroken waves enables net offshore directed bottom currents to persist outside the region of breaking waves providing a mechanism other than rip currents to transport sediment offshore beyond the surf zone

predicting the topographic limits to a gully network using a digital terrain model and process thresholds a digital terrain model is used with process thresholds to predict the extent of a stable gully network in a 5 km2 catchment of the southeastern highlands of australia the model developed by dietnch et al 1992 1993 predicts the topographic controls on channel networks and interprets these in terms of a critical shear stress for channel incision c applied by saturation overland flow we adapt the model slightly to compare the shear stress applied by hortonian overland flow to that applied by saturation overland flow the limits to gully erosion in the catchment are controlled strongly by a topographic threshold that has an inverse relationship between upslope catchment area and local gradient the topographic threshold for channel incision is reproduced using a simple model of hortonian overland flow and a c appropriate for incision into a degraded grass surface c 245 dyn cm2 this is consistent with historical evidence for the timing of gully erosion the study confirms a strong topographic control on the extent of the channel network in a catchment significantly different from the western north america catchments where the topographic threshold was first demonstrated despite its simplicity the model for incision by overland flow appears capable of distinguishing the hydrological processes responsible for channel incision when these are reflected in the relationship between channel network and landscape morphology the model requires relatively simple inputs suggesting it may be useful for mapping gully erosion hazard in actively eroding catchments

strontium isotopic constraints on the origin of proterozoic anorthosites abstract the proterozoic giles complex central australia contains an almost complete range of anorthosite types from minor or major layers in gabbronorite intrusions to large anorthosite troctolite bodies to small orthopyroxene anorthosite massifs each type has a distinctive sr isotopic signature anorthosite dominated masses have a regular relationship between ferromagnesian mineralogy initial 87 sr 86 sr and anorthite contents in plagioclase anorthosite troctolite bodies have significant olivine relatively low initial 87 sr 86 sr 0 7038 0 7043 and an 50 69 orthopyroxene dominant anorthosites have relatively high 87 sr 86 sr 0 7045 0 7063 and an 45 60 the pattern is found worldwide detailed study of one intrusion demonstrates that contamination by wall rock granulite produces the higher 87 sr 86 sr values anti correlation between 87 sr 86 sr and an and determines olivine orthopyroxene proportions olivine bearing anorthosites form from a primary aluminous tholeiite magma with plagioclase dominating the liquidus progressive contamination of this parent magma produces a gradation to orthopyroxene anorthosites

slope control on the frequency distribution of shallow landslides and associated soil properties north island new zealand the extrapolation of results from field trials to larger areas of land for purposes of regional impact assessment is an important issue in geomorphology particularly for landform properties that show high stochastic variability in space and time such as shallow landslide erosion it is shown in this study that by identifying the main driver for spatial variability in shallow landslide erosion at field scales namely slope angle it is possible to develop a set of generic functions for assessing the impact of landslides on selected soil properties at larger spatial scales and over longer time periods research was conducted within an area of pastoral soft rock tertiary hill country in the north island of new zealand that is subject to infrequent high intensity rainfall events producing numerous landslides most of which are smaller than several hundred square metres in size and remove soil to shallow depths all landslides were mapped within a 0 6 km2 area and registered to a high resolution 2 m slope map to show that few landslides occur on slopes 24 the areal density of landslides from all historical events showed an approximately linear increase with slope above 24 integrating landslide densities with soil recovery data demonstrates that the average value of a soil property fluctuates in a saw tooth fashion through time with the overall shape of the curve controlled by the frequency of landslide inducing storm events and recovery rate of the soil property between events despite such fluctuations there are gradual declines of 7 5 in average total carbon content of topsoil and 9 5 in average soil depth to bedrock since the time of forest clearance results have application to large scale sediment budget and water quality models and to the new zealand soil carbon monitoring system cms copyright 2012 john wiley sons ltd

assessing the sources of sediment transported in gully systems using a fingerprinting approach an example from south east china abstract eroded sediment is an important feature of permanent gully s development however obtaining the specific characteristics of the sediment transport in the gully can be difficult thus a composite fingerprinting technique incorporating uncertainty analysis has been employed to investigate the mean relative contribution of sediment sources in permanent gullies in this study 31 tracers were measured at 62 different sampling sites from three layers of a gully wall surface layer sl sandy soil layer ssl and semi weathering rock layer swl and 36 sediment samples from the slumping deposit and alluvial fan of the gullies the sediment source tracing procedure was therefore used to assess the relative contribution of each source the mean relative contribution from the sl to the sediment of the slumping deposit is higher in the active gully g1 and is relatively lower in the potentially stable g2 and stable gullies g3 thus there was no obvious gully bank retreat in g2 and g3 in different places of the g1 alluvial fan the mean relative contribution of the sl ssl and swl ranged from 9 11 36 43 and 46 55 respectively however the sediment contribution of the sl increased in g2 and g3 due to the changes in the erosion type the mean relative contributions of the sl were 33 5 g2 and 30 3 g3 these findings have important implications for the establishment of a scientific basis for permanent gully sediment transport management and control policies

coupling between hillslopes and channels in upland fluvial systems implications for landscape sensitivity illustrated from the howgill fells northwest england abstract the sensitivity of upland fluvial systems depends on the magnitude and frequency of sediment and flood producing events modified by the internal coupling characteristics of the system this paper assesses the role of hillslope channel coupling for the sensitivity of upland geomorphic systems using evidence from a 30 year monitoring programme of geomorphic change in the carlingill valley howgill fells northwest england in the hillslope zone there is little sediment supply to the stream system locally slope failures occur in response to extreme events six such events in 30 years within the ca 6 km 2 carlingill valley in the footslope coupling zone basally induced gullies are major sediment sources to the stream sediment production events occur ca 30 times per year feeding sediment to basal debris cones stream floods which can entrain these sediments occur once every ca 2 5 years stream channel morphology is adjusted to this regime downstream of gullies channels are wide and braided elsewhere they are narrow and single thread as the gullies develop however this coupling weakens and the eroding slopes eventually stabilise by revegetation over the 30 year monitoring period there has been a progressive trend towards gully stabilisation and an associated reduction in channel instability massive destabilisation may occur in response to rare extreme flood events such an event return period 100 years occurred in neighbouring langdale and bowderdale valleys in june 1982 that event destabilised the system causing slope failures fan deposition and in some places a switch in channel style to wide braided channels since 1982 there has been a progressive recovery by slope stabilisation and single thread sinuous channels have become reestablished a different style of extreme event occurred in carlingill in october 1998 in response to the wettest week in the 30 year period a slope failure fed debris flows 400 m downslope almost coupling with the channel system future climatic change could render the system prone to destabilisation through either extreme flood events or through major slope failures

sm nd and pb isotopic study of mafic rocks associated with early proterozoic continental rifting the peropohja schist belt in northern finland the perapohja schist belt in northern finland rests unconformably on archaean granitoids and marks the early stages of proterozoic crustal evolution in the fennoscandian baltic shield 2440 ma old layered mafic intrusions predate the supracrustal and ca 2200 ma old sills of the gabbro wehrlite association intrude the lowest quartzites and volcanics runkaus of the sequence the sm nd mineral isochron of the penikat layered intrusion gives an age of 2410 64 ma the initial nd values of the penikat intrusion nd 2440 1 6 and the runkausvaara sill nd 2200 0 suggest that these mafic magmas were contaminated by older crustal material the sm nd and pb isotopic results on the 2 44 2 2 ga old runkaus volcanics indicate mobility of pb fractionation of sm nd during late greenschist facies metamorphism and crustal contamination the pb pb data provide an age of 1972 80 ma with a high initial 207pb 204pb ratio 1 8 49 while scattered sm nd data result in an imprecise age of 2330 180 ma with an initial nd value of about zero secondary titanite gives an u pb age of ca 2250 ma the jouttiaapa basalts in contrast ascended from the mantle without interaction with older crust these lree depleted tholeiites mark a break in continental sedimentation and yield a sm nd age of 2090 70 ma their initial nd 4 2 0 5 implies that the subcontinental early proterozoic mantle had been depleted in lree for a long period of time the first lava flows are strongly depleted in lree suggesting that their source was significantly more depleted than the source of mid ocean ridge basalts today

bar generating cross shore flow mechanisms on a beach random waves normally incident on a dissipative beach induce a variety of cross shore flows such as asymmetric oscillatory flow wave grouping induced long wave flow breaking induced turbulent flow and momentum decay induced undertow these flows are identified analyzed and hindcasted in a set of laboratory experiments with the aim of revealing the role of each of the flow mechanisms in the two dimensional case of bar generation on a beach

age and origin of anorthosites charnockites and granulites in the central virginia blue ridge nd and sr isotopic evidence rb sr isotopic data for anorthosites charnockites ferrodioritic to quartz monzonitic plutons and high grade gneisses of the blue ridge of central virginia show evidence of post emplacement metamorphism but in some cases retain grenville ages the pedlar river charnockite suite yields an isochron age of 1021 36 ma initial 87sr 86sr ratio of 0 7047 6 which agrees with published u pb zircon ages five samples of that unit which contain paleozoic mylonitic fabrics define a regression line of 683 ma interpreted as a mixing line with no age significance samples of the roseland anorthosite complex show excessive scatter on a rb sr evolution diagram probably due to paleozoic 475 m y metamorphism data from the ferrodioritic to quartz monzonitic plutons of the area yield an age of 1009 26 ma inital ratio 0 7058 4 which is in the range of the u pb zircon ages of 1000 1100 ma the stage road layered gneiss yields an age of 1147 34 ma initial ratio of 0 7047 5 sm nd data for the pedlar river charnockite suite reflect a pre grenville age of 1489 118 ma nd 6 7 1 2 data for the roseland anorthosite complex and the ferrodioritic to quartz monzonitic plutons yield grenville isochron ages of 1045 44 ma nd 1 0 0 3 and 1027 101 ma nd 1 4 1 0 respectively two roseland anorthosite samples plot far above the isochron demonstrating the effects of post emplacement disturbance of sm nd systematics while mylonitized pedlar river charnockite suite samples show no evidence of sm nd redistribution the disparity of the sm nd age and other isotopic ages for the pedlar river charnockite suite probably reflects a sm nd source age suggesting the presence of an older crust within this portion of the ca 1 ga old basement

a system for measuring bottom profile waves and currents in the high energy nearshore environment abstract a new data acquisition system capable of measuring waves currents and the nearshore profile in breaking waves as high as 5 m has been developed and successfully field tested components of the mechanical system are a sled carrying a vertical mast a double drum winch placed landward of the beach and a line that runs from one drum of the winch around three blocks which are the corners of a right triangle to the other drum of the winch the sled is attached to the shore normal side of the triangular line arrangement and is pulled offshore by one drum of the winch and onshore by the other the profile is measured as the sled is towed along the shore normal transect using an infrared rangefinder mounted landward of the winch and optical prisms mounted on top of the sled s mast a pressure sensor and two axis electromagnetic current meter are mounted on the frame of the sled these data are encoded on the sled and telemetered to a receiving recording station onshore preliminary results suggest that near bottom offshore flowing currents during periods of high energy swell are important in forcing changes to the configuration of the nearshore profile

development of gullies and sediment production in the black soil region of northeastern china abstract gully erosion is an important environmental hazard in the black soil region of northeastern china it is a primary sediment source in the region which needs appropriate soil conservation practices gully incision in rolling hills typical of this region was monitored using real time kinematic gps to assess the rates of gully development and the resultant sediment production from 2002 to 2005 gully heads in the study area retreated between 15 4 and 33 5 m giving an average retreat rate of 8 4 m yr 1 field measurements showed that total sediment production due to gully erosion during the three years ranged between 257 and 1854 m3 yr 1 which is equivalent to 326 to 2355 t yr 1 with gully head retreat accounting for 0 to 21 7 4 4 in average the sediment delivery ratio was especially high during the summer rainy season 56 in average sediment production by ephemeral gullies and permanent gullies was 1 5 times greater than that from surface erosion gully heads retreated faster in the spring freeze thaw period than in the summer the stage of gully development could be identified based on short term changes in the gully erosion rate

evolution of debris flow activities in gaojiagou ravine during 2008 2016 after the wenchuan earthquake abstract the 2008 wenchuan earthquake in sichuan china triggered numerous landslides in the stricken area the loose landslide materials retained on mountain slopes and in gullies are prone to reactivation and may transform into debris flows in the rainy season nine years after the wenchuan earthquake debris flows are still active in gaojiagou ravine 16 5 km north of the epicentre on 14 august 2010 3 july 2011 13 july 2013 and 6 july 2016 four large scale debris flows were triggered by heavy storms in gaojiagou ravine the four debris flows blocked the minjiang river twice and caused severe damage to nearby villages and reconstruction sites several questions arise from these repeated debris flows did the level of triggering rainfall change in the four debris flow events how did the initiation mechanism evolve over time what are the differences in the runout characteristics in the four events how did the check dams constructed in 2012 function in the subsequent debris flows in this paper we evaluated the loose deposit volumes in gaojiagou ravine before and after each of the four debris flows and the runout volumes and analysed the triggering rainfall intensities initiation mechanisms and runout characteristics of the four debris flows the rainfall threshold for the debris flows in gaojiagou ravine increased over time and the initiation mechanisms evolved from landslides to channel bed failure and subsequently to channel bank erosion the mobility of the debris flows decreased from 2010 to 2016 as the initiation positions moved lower and the particle size of the runout materials became coarser

vertical and horizontal structure in cross shore flows an example of undertow and wave set up on a barred beach greenwood b and osborne p d 1990 vertical and horizontal structure in cross shore flows an example of undertow and wave set up on a barred beach coastal eng 14 543 580 eulerian measurements of the horizontal cross shore velocity field in the lowermost meter of the water column in association with measurements of waves and the mean elevation of the water surface across a nontidal low relief barred surf zone reveal a spatially coherent patterns of the timeaveraged first second and third moments of the velocity field which vary temporally in direct response to the incident waves b large asymmetries in the flow field with offshore directed mean flows upto 0 20 m s a and onshore directed velocity skewness the third moment normalized by the standard deviation upto 0 60 c mean flows decrease and oscillatory flows measured by the standard deviation of the velocity field increase towards the water surface d a fourth order polynomial provides the best fit to the cross shore set up reflecting the influence of variable energy dissipation due to topographic controls on wave breaking e significant linear correlations exist between the cross shore mean velocities and the maximum set up of the still water surface near to the shoreline upto 82 of the observed variability in the former can be accounted for by linear regressions f set up is highly correlated with the incident wave height 86 of the observed variability in the former can be accounted for by a linear regression g gradients in the mean water surface are significantly less than those predicted by a linear function of beach slope as originally proposed by bowen et al even using an appropriate breaking criterion 0 4 0 6 for the spilling breakers recorded cross shore circulation over the low relief barred nearshore slope is predominantly two dimensional over the outer bar in this case study the near bed mean flow is an undertow responding to the balance between the wave generated depth dependent momentum flux directed onshore the stress induced by the onshore mass transport under waves and wind and the hydraulic pressure gradient induced by set up of the mean water level

the response of slope and channel systems to various types of extreme rainfall a comparison between the temperate zone and humid tropics abstract the mountain slopes and river channels of the temperate zone and of the humid tropics are modelled by various types of extreme rainfall in the flysch carpathians the leading role is played by continuous rains causing floods and landslides rainy seasons wet years mobilizing deep landslides and to a smaller degree by local downpours in the darjeeling himalaya with young relief and uplift tendency the main influence on modelling the mountain slopes and river channels have been the extreme continuous rains separated by several decades of normal rainy season playing the preparatory or relaxation role with simultaneous transformation of slopes and river channels in both cases human impact has caused the acceleration of runoff and mobilization of sediment the higher extremes of precipitation and steep slopes in the humid tropics are balanced to some extent in temperate zones by the lower infiltration rates and lower thresholds of mass mobility on the gentle slopes originated in the periglacial environment

upb and rbsr geochronology and geological evolution of the harts range ruby mine area of the arunta inlier central australia abstract supracrustal and meta igneous rock units from the ruby mine area of the harts range eastern arunta inlier central australia have been dated by the zircon u pb and rb sr total rock tr and mica methods a well defined zircon discordia for a weakly deformed specimen of the bruna granite gneiss yields an age of emplacement of 1748 4 5 ma thereby constraining the minimum age of the irindina supracrustal assemblage metapelitic gneiss within the supracrustals and a meta igneous ultramafic boudin from the associated harts range meta igneous complex yield highly discordant zircon data revealing a strong early palaeozoic overprint rb sr tr data from anorthositic gneisses associated with the ultramafic boudin are highly disturbed also apparently during the lower palaeozoic however rb sr model age calculations and the zircon u pb data suggest a maximum age of about 2000 ma for the supracrustal and meta igneous rocks and argue for new proterozoic crust formation zircon u pb data from a deformed pegmatite emplaced in the meta igneous complex yield an emplacement age of 520 4 5 ma further pointing to lower palaeozoic magmatism and deformation correlations of u content and calculated 206 pb 238 u age for the ultramafic boudin zircons suggest that new growth of low u zircons occurred during retrogression associated with this event the sr isotope systematics of the anorthositic gneisses can also be interpreted in terms of introduction of palaeozoic sr our data suggest lower palaeozoic possibly delamerian tectonothermal activity to be more important in the evolution of the harts range area than previously recognised on the other hand rb sr mica ages for deformed and undeformed pegmatites and tr isochrons for the latter show that pervasive tectonothernal activity had ceased by about 315 ma and that regional cooling occurred between about 345 and 325 ma local shear zone biotite resetting may have persisted to about 300 ma consistent with the previously recognised alice springs orogeny possible dilational pb loss in the bruna zircons occurred at about 103 ma

the interaction between the undertow and the boundary layer flow on a beach the theoretical result for undertow in a surf zone found by svendsen 1984a is combined with a boundary layer solution at the bottom and it is shown that in this boundary layer the eddy viscosity is small relative to that produced by the breaking the proper eddy viscosity t between the surface and the bottom boundary layer is determined by comparison with measurements which leads to quite accurate reproduction of the velocity profiles the model also predicts the mean flow in the boundary layer and the mean bottom shear stress and the results are analyzed for sensitivity to inaccuracies in the basic assumptions