observations of turbulence in stratified flow abstract various theoretical properties of the structure function are evaluated additional functions are constructed to describe the overall influence of stratification the anisotropy and intermittency of the turbulence and the asymmetry of the main drafts these functions and the usual spectral decomposition are computed from aircraft measured turbulence data collected in nocturnal boundary layers and in turbulence over mountainous terrain certain features of the turbulence are found to depend more on stability than on the external situation three general types of turbulence are found 1 intermittent turbulence driven by shear driven overturning 2 continuous turbulence where strong drafts in the presence of shear are characterized by sharp boundaries or microfronts particularly on their upstream sides and 3 weaker continuous turbulence the costructure fields are generally consistent with vertical gradient transfer however the bora turbulence on larger scales is dominated by horizontal motio

ice moraine and landslide dams in mountainous terrain we review recent work on ice moraine and landslide dams in mountainous terrain thus complementing several comprehensive summaries on glacier dams in intracontinental and arctic areas of low relief we discuss the roles of tectonic and climatic forcing on ice moraine and landslide dam formation and sudden drainage and focus on similarities and differences between their geomorphic impacts on confined valleys drained by steep bedrock and gravel bed rivers despite numerous reported failures of natural dams in mountain belts throughout the world their relevance to long term dynamics of mountain rivers remains poorly quantified all types of dams exert local base level controls thus trapping incoming sediment and inhibiting fluvial bedrock incision pervasive geomorphic and sedimentary evidence of outburst events is preserved even in areas of high erosion rates suggesting that sudden dam failures are characterized by processes of catastrophic valley floor aggradation active channel widening and downstream dispersion of sediment during which little bedrock erosion seems to be achieved we find that in the absence of direct evidence of former dams a number of similarities among the geomorphic and sedimentologic characteristics of catastrophic outburst flows may give rise to ambiguous inferences on the dam forming process this is especially the case for tectonically active mountain belts where there is ample and comparable potential for the formation and failure of ice moraine landslide and polygenetic dams concomitant with climatic oscillations or earthquake disturbance hence the palaeoclimatic implications of erroneously inferring the cause of dam formation may be significant we recommend that future research on natural dams in mountainous terrain addresses a climate and earthquake controlled systematics in the pattern of formation and failure b quantification of response of mountain rivers to catastrophic outburst events and their concomitant process sequences c elaboration of a comprehensive classification of natural dams in mountainous terrain with special attention to polygenetic dams d physical based modelling of dam formation failure and routing of water and sediment outbursts and e quantitative controls on the contribution of natural dams to sediment budgets in mountainous terrain

energy dispersive x ray fluorescence analysis of haleakalā basalt adze quarry materials maui hawai i abstract one of hawai i s major prehistoric basalt adze quarries sihp 50 50 11 2510 is located in the summit region of haleakal maui situated at approximately 2750 m above sea level 9000 ft the quarry shares a similar high altitude setting with the mauna kea adze quarry on hawai i island adding to a growing energy dispersive x ray fluorescence edxrf database for the hawaiian islands we present the results from 255 geological and archaeological lithic samples from the haleakal quarry site we also briefly discuss why this non destructive xrf technique is particularly applicable in the hawaiian cultural context

influence of a large debris flow fan on the late holocene evolution of squamish river southwest british columbia canada cheekye fan is a large paraglacial debris flow fan in southwest british columbia it owes its origin to the collapse of mount garibaldi a volcano that erupted in contact with glacier ice near the end of the pleistocene epoch the fan extended across howe sound isolating a freshwater lake upstream of the fan from a fjord downstream of it squamish river built a delta into this lake during the holocene we use 28 radiocarbon ages to describe the final infilling of the lake and the subsequent evolution of the squamish river floodplain over the past 3300 years these events are recorded in fine grained lacustrine wetland river channel and overbank sediments exposed in the banks of squamish river over a distance of more than 10 km upstream of the fan we link these deposits to construction persistence and eventual degradation of the dam formed by cheekye fan and a smaller inset fan formed by cheakamus river into which cheekye river flows the coupled cheekye fan squamish river floodplain system is si

stability of composite river banks the stability of a river bank depends on the balance of forces motive and resistive associated with the most critical mechanism of failure many mechanisms are possible and the likelihood of failure occurring by any particular one depends on the size geometry and structure of the bank the engineering properties of the bank material the hydraulics of flow in the adjacent channel and climatic conditions rivers flowing through alluvial deposits often have a composite structure of cohesionless sand and gravel overlain by cohesive silt clay bank erosion occurs by fluvial entrainment of material from the lower cohesionless bank at a much higher rate than material from the upper cohesive bank this leads to undermining that produces cantilevers of cohesive material upper bank retreat takes place predominantly by the failure of these cantilevers three mechanisms of failure have been identified shear beam and tensile failure the stability of a cantilever may be analysed using static equilibrium and beam theory and dimensionless charts for cantilever stability constructed application of the charts requires only a few simple measurements of cantilever geometry and soil properties in this analysis the effects of cracks and fissures in the soil must be taken into account these cracks seriously weaken the soil and can invalidate a stability analysis by affecting the shape of the failure surface following mechanical failure blocks of soil must be removed from the basal area by fluvial entrainment if rapid undermining and cantilever generation are to continue hence the rate of bank retreat is fluvially controlled even though the mechanism of failure of the upper bank is not directly fluvial in nature this cycle of bank erosion undermining cantilever failure and fluvial scour of the toe operates over several flood events and has important implications for river engineering channel changes and the movement of sediment through fluvial systems

particle dynamics the continuum of bedrock to alluvial river segments abstract particle dynamics refers to production erosion transport and storage of particulate material including mineral sediment and organic matter particle dynamics differ significantly between the end members of bedrock and alluvial river segments and between alluvial river segments with different grain size distributions bedrock segments are supply limited and resistant to change with relatively slow linear adjustments and predominantly erosion and transport particle dynamics in alluvial segments in contrast are transport limited and dominated by storage of mineral sediment and production of organic matter alluvial segments are resilient to change with relatively rapid multidirectional adjustments and stronger internal influences because of feedbacks between particles and biota bedrock segments are the governors of erosion within a river network whereas alluvial segments are the biogeochemical reactors fundamental research questions for both types of river segments center on particle dynamics which limit network scale incision in response to base level fall bedrock segments and habitat biogeochemical reactions and biomass production alluvial segments these characterizations illuminate how the spatial arrangement of bedrock and alluvial segments within a river network influence network scale resistance and resilience to external changes in relative base level climate and human activities

geomorphic and vegetative characteristics along three northern virginia streams geometry sediment and woody vegetation data were collected from bottomland geomorphic surfaces at valley sections along three gaged perennial streams of northern virginia the basins of the streams differ widely in topography and physiography mean discharges vary from 0 196 to 323 m3 per sec prevalent surfaces identified were the depositional bar the active channel shelf the flood plain and terraces the stages corresponding to active channel shelf levels were equivalent to flow durations of 5 to 13 stages corresponding to flood plain levels were equivalent to discharges with 1 4 to 2 0 yr recurrence intervals the discharge data and statistical tests of geomorphicsurface sediment and vegetative data suggest that the various alluvial features are formed and maintained by hydraulically controlled sorting processes analysis of woody plant and geomorphic data shows that each surface supports characteristic species some of which are nearly unique to a surface tests of sediment type with species distribution showed lower correlation than that of geomorphic surface with species it is inferred that plant distributions largely are controlled by flow frequency and intensity and that plants may help to identify geomorphic levels and potential for flood damage

anabranching rivers their cause character and classification anabranching rivers consist of multiple channels separated by vegetated semi permanent alluvial islands excised from existing floodplain or formed by within channel or deltaic accretion these rivers occupy a wide range of environments from low to high energy however their existence has never been adequately explained they occur concurrently with other types of channel pattern although specific requirements include a flood dominated flow regime and banks that are resistant to erosion with some systems characterized by mechanisms to block or constrict channels thereby triggering avulsion the fundamental advantage of an anabranching river is that by constructing a semi permanent system of multiple channels it can concentrate stream flow and maximize bed sediment transport work per unit area of the bed under conditions where there is little or no opportunity to increase gradient on the basis of stream energy sediment size and morphological characteristics six types of anabranching river are recognized types 1 3 are lower energy and types 4 6 are higher energy systems type 1 are cohesive sediment rivers commonly termed anastomosing with low w d ratio channels that exhibit little or no lateral migration they are divisible into three subtypes based on vegetative and sedimentary environment type 2 are sand dominated island forming rivers and type 3 are mixed load laterally active meandering rivers type 4 are sand dominated ridge forming rivers characterized by long parallel channel dividing ridges type 5 are gravel dominated laterally active systems that interface between meandering and braiding in mountainous regions type 6 are gravel dominated stable systems that occur as non migrating channels in small relatively steep basins anabranching rivers represent a relatively uncommon but widespread and distinctive group that because of particular sedimentary energy gradient and other hydraulic conditions operate most effectively as a system of multiple channels separated by vegetated floodplain islands or alluvial ridges

scale properties of microscale convection in the marine surface layer we analyze the scale distribution of coherent water vapor structures in the marine atmospheric boundary layer as measured by a shipboard raman lidar during the combined sensor program march 1996 using a two dimensional continuous wavelet transform coherent structures in the lidar measured water vapor concentration field correspond to locations where covariance with the wavelet is a local extremum scales of the significant structures are identified using a filtered wavelet variance detection density derived from 24 images in a horizontal plane a dominant radius of 14 m is identified using complimentary approaches to the analysis

determining the reduction sequence of hawaiian quadrangular adzes using 3d approaches a case study from moloka i hawaiian adze manufacture requires a great deal of skill and undoubtedly required long apprenticeships to achieve the finesse seen in many finished prehistoric adzes despite the presence of more than two dozen adze quarries in hawai i and previous attempts at replicating adze preforms and positing reduction sequences in polynesia there is no detailed study that clearly defines the steps and stages of quadrangular adze preform manufacture the most common form in hawai i and the resulting characteristic debitage in this paper we examine the sequence of adze production for a population of 109 adzes from moloka i documenting the transition from blanks to preforms to the finished objects that were transported away from quarries reduction intensity is measured using the scar density index clarkson 2013 calculated from 3d scans we document the sequence of cumulative additions of characteristic features to adzes e g bidirectional edges bevel poll and tang as reduction intensity increases we also note the reasons for adze rejection at each stage of reduction our study provides the first detailed analysis of adze reduction in polynesia facilitated and standardised by 3d scanning technology hopefully it will serve as a useful benchmark for objectively and systematically comparing adze technology in other parts of hawai i and across polynesia leading to a better understanding of regional and temporal variation in adze technology

geochemical sourcing of basalt artifacts from kaua i hawaiian islands abstract we report on energy dispersive x ray fluorescence edxrf sourcing of 807 basalt artifacts and 34 basalt ecofacts recovered from stratified midden at nu alolo kai kaua i these data are compared with edxrf analyses of 473 alluvial pebbles from waimea canyon 34 adzes from the kaua i museum and published geochemical data for kaua i basalts formal tools such as adzes chisels and mirrors were predominantly manufactured from sources not available at nu alolo kai most adzes and chisels are consistent with sources available elsewhere on kaua i but two basalt mirrors are outside the expected geochemical range of kaua i basalts in contrast almost all expedient tools were manufactured from basalts available at nu alolo kai these findings support the existence of an island wide distribution system for adze material on kaua i and challenges extant models of pre contact hawaiian economics to consider the mechanisms through which specialized commodities were produced and distributed

organizational structure at the mauna kea adze quarry complex hawaii abstract the aim of this paper is to demonstrate that it is possible to define the organizational structure at prehistoric stone quarries by examining two aspects of stone tool production the spatial distribution of debitage and differential stoneworking skill analyses of debitage collected from the mauna kea adze quarry in hawaii will be compared with experimentally produced data to achieve the aim of the paper the results of these analyses indicate that the labour forces at the mauna kea adze quarry were well organized it is suggested that labour parties were organized into groups of two with expert craftsmen working where material was abundant and novices or apprentices working where they could practise their craft without wasting important resources

reconstructed summer degree days in central alaska and northwestern canada since 1524 abstract three time series based on precisely dated annual tree ring widths have been used to reconstruct june plus july degree days for the central alaska and northwestern canada region the time series are the longest recently developed chronologies for the area and represent 57 core samples from 27 trees the degree day reconstruction extending back to a d 1524 exhibits much year to year variation and extended warming and cooling trends including a general warming trend from about 1840 to 1960 the reconstruction is in agreement with some subaretic glacial information and with data of percentage melting from arctic ice cores this and similar reconstructions can provide quantitative information to compare with general circulation and energy budget models for longer time periods than are available in recorded meteorological data

prehistoric debris avalanches from mount cayley volcano british columbia reply an investigation of diamicton units exposed in an extensive accumulation of volcanic debris in the squamish valley west of mount cayley volcano has yielded evidence for at least three major debris avalanches initiated by the collapse of the western flank of mount cayley in the mid holocene radiocarbon ages obtained from tree fragments contained in the deposits indicate that the events took place at 4800 1100 and 500 bp all three debris avalanches dammed the squamish river and formed temporary lakes upstream of the debris failure of the cone took place after considerable dissection of the original edifice had exposed weak pyroclastic materials at the base of the steep upper slope of the volcano no evidence of older debris avalanches from mount cayley has been discovered smaller scale debris avalanches probably have been common and at least two have occurred in historic time 1963 and 1984 debris avalanches from mount cayley and the effects of a possible damming of the squamish river are major

initial investigations of microscale cellular convection in an equatorial marine atmospheric boundary layer revealed by lidar during the combined sensor program csp in march of 1996 the los alamos national laboratory lanl fielded an advanced scanning raman lidar the lidar was part of a larger suite of micrometeorological sensors to quantify processes associated with the ocean atmosphere interface including intermittency and coherent atmospheric features in the open quotes warm pool close quotes of the tropical western pacific twp near manus island 2 degree s lat 147 degree e long initial inspection of the data has revealed excellent information on the microscale vertical and horizontal spatial and temporal structure of the equatorial marine atmospheric boundary layer mabl the data from this experiment have added to the increasing body of measurements on surface layer convection and intermittency including for the first time the observation of microscale cellular convective structures such as hexagonal patterns associated with rayleigh b acute e nard cells copyright 1997 american geophysical union

fluvial sediment transport and deposition following the 1991 eruption of mount pinatubo the 1991 eruption of mount pinatubo generated extreme sediment yields from watersheds heavily impacted by pyroclastic flows bedload sampling in the pasig potrero river one of the most heavily impacted rivers revealed negligible critical shear stress and very high transport rates that reflected an essentially unlimited sediment supply and the enhanced mobility of particles moving over a smooth fine grained bed dimensionless bedload transport rates in the pasig potrero river differed substantially from those previously reported for rivers in temperate regions for the same dimensionless shear stress but were similar to rates identified in rivers on other volcanoes and ephemeral streams in arid environments the similarity between volcanically disturbed and arid rivers appears to arise from the lack of an armored bed surface due to very high relative sediment supply in arid rivers this is attributed to a flashy hydrograph whereas volcanically disturbed rivers lack armoring due to sustained high rates of sediment delivery this work suggests that the increases in sediment supply accompanying massive disturbance induce morphologic and hydrologic changes that temporarily enhance transport efficiency until the watershed recovers and sediment supply is reduced d 2002 elsevier science b v all rights reserved

a 184 year record of river meander migration from tree rings aerial imagery and cross sections abstract channel migration is the primary mechanism of floodplain turnover in meandering rivers and is essential to the persistence of riparian ecosystems channel migration is driven by river flows but short term records cannot disentangle the effects of land use flow diversion past floods and climate change we used three data sets to quantify nearly two centuries of channel migration on the powder river in montana the most precise data set came from channel cross sections measured an average of 21 times from 1975 to 2014 we then extended spatial and temporal scales of analysis using aerial photographs 1939 2013 and by aging plains cottonwoods along transects 1830 2014 migration rates calculated from overlapping periods across data sets mostly revealed cross method consistency data set integration revealed that migration rates have declined since peaking at 5 m year in the two decades after the extreme 1923 flood 3000 m 3 s averaged over the duration of each data set cross section channel migration occurred at 0 81 m year compared to 1 52 m year for the medium length air photo record and 1 62 m year for the lengthy cottonwood record powder river peak annual flows decreased by 48 201 vs 104 m 3 s after the largest flood of the post 1930 gaged record 930 m 3 s in 1978 declining peak discharges led to a 53 reduction in channel width and a 29 increase in sinuosity over the 1939 2013 air photo record changes in planform geometry and reductions in channel migration make calculations of floodplain turnover rates dependent on the period of analysis we found that the intensively studied last four decades do not represent the past two centuries

the july 29 1998 debris flow and landslide dam at capricorn creek mount meager volcanic complex southern coast mountains british columbia a very large debris flow was triggered during a period of record breaking high temperatures in upper capricorn creek within the mount meager volcanic complex a part of the garibaldi volcanic belt of the southern coast mountains the debris flow deposit impounded meager creek creating an 800 m long landslide dammed lake the total event volume was 1 2 106 m3 the debris flow was followed by three days of almost continuous hyperconcentrated flow surges which caused significant fluvial aggradation in the meager creek flood plain below the capricorn creek confluence within a few days of the formation of the landslide dam a spillway notch had been cut through the deposit thereby preventing the occurrence of a catastrophic dam break the landslide which triggered the debris flow originated in deep volcanic colluvium having a previous history of progressive slope deformation a consequence of glacial downwasting since the neoglacial maximum this paper highlights an important landslide response to rec

modelling site formation dynamics geoarchaeological chronometric and statistical approaches to a stratified rockshelter sequence polynesia formation processes and chronology are central to many archaeological endeavours and accuracy in the latter is dependent on control of the former here we consider how to integrate geoarchaeological and chronometric evidence to better understand the formational history along with the timing and duration of cultural activities at a regionally significant site in the southern cook islands polynesia which dates from 12th century ad initially we model natural and cultural processes of deposition using geoarchaeological evidence the results are integrated with 21 radiocarbon dates including nine new ams results on identified medium and short lived materials sample outliers are identified manually and statistically and a bayesian analysis helps to refine age estimates for the site s 12 stratigraphic zones the timing and rate of sediment accumulation is further considered through an age depth model finally the chronology developed from these combined approaches is used to address three key processes 1 initial site use potentially relevant to human colonisation of this polynesian island and archipelago 2 on site activities and patterns of resource use and 3 major marine deposition events which disrupted cultural activities and may have palaeoclimatological significance the approach developed here potentially has utility elsewhere particularly where human activities are recurrent and of limited duration

the little ice age as recorded in the stratigraphy of the tropical quelccaya ice cap the analyses of two ice cores from a southern tropical ice cap provide a record of climatic conditions over 1000 years for a region where other proxy records are nearly absent annual variations in visible dust layers oxygen isotopes microparticle concentrations conductivity and identification of the historical a d 1600 huaynaputina ash permit accurate dating and time scale verification the fact that the little ice age about a d 1500 to 1900 stands out as a significant climatic event in the oxygen isotope and electrical conductivity records confirms the worldwide character of this event

floodplain dynamics of a wandering river dendrochronology of the morice river british columbia canada dendrochronological techniques are used to develop a history of flood occurrence and relative stage for the middle section of the morice river based on flood scars bank undercutting dates and tree establishment dates on fluvial features the morice river is the major tributary of the bulkley river skeena river system northwest british columbia canada reach 2 of the morice river drainage area 3499 km2 is forested and little disturbed by human activity it is presently a wandering multiple channel river and shows evidence of frequent channel changes which have reworked most of the floodplain several times in the last 180 years airphoto analysis and dendrochronology demonstrate that many channels show evidence of two or more periods of activity reoccupation and re excavation of pre existing channel segments is more frequent than development of new channels thirty one significant floods over the past 105 years were detected through dendrochronology of flood scarred trees on the morice river flood scars are predominantly caused by flood transported logs abundant log transport results in damage to channel margin trees during events only slightly above bankfull discharge the record of flood scars on channel margin trees and establishment dates of forest stands on abandoned channels and surfaces show that the morice river has maintained its present regimen for the past 115 years during the neoglacial the morice river was more active than in recent times and its channels occupied twice the present area tree establishment dates show that neoglacial surfaces and channels of the morice river were abandoned during the 1820 s the modern floodplain configuration was assumed by 1870

british columbia flood scars maximum flood stage indicators abstract flood scars abundant along rivers of heavily forested northern british columbia provide records of flood occurrence and magnitude in a region with few and relatively short gaging records log transport during floods is episodic and occurs almost immediately preceding and during peak stage impact wounds form during this transport stage many of these logs are sequestered in bankside vegetation where they form abrasion wounds on trees by rubbing up and down in the turbulent waters from may 30 through june 2 1990 an approximate 9 year nival flood occurred on the skeena river at cedarvale b c this flood damaged many trees within a few tree spacings of the bank margin immediately after the flood the peak stage line along 170 m of shoreline was marked in september 1992 48 flood scarred trees were selected and their locations and flood scar heights surveyed the mean height of the top of the flood scars sampled is 20 3 cm below the peak stage on the adjacent bank flood scar heights range from 9 to 80 cm compared to the peak stage on the adjacent bank a regression line for the floodscar top elevations is roughly parallel to the peak stage elevations along the shoreline and approximately 20 cm below it data from usk the nearest gaging station on the skeena river demonstrate that the stage was high enough to form the flood scars for only 24 to 36 hours most of the flood scars had to form in less than 24 hours field observations suggest that the time of flood scar formation was even more restricted

channel response to sediment wave propagation and movement redwood creek california usa redwood creek north coastal californa usa has experienced dramatic changes in channel confguation since the 1950s a series of large floods in 1955 1964 1972 and 1975 combined with the advent of widespread commercial timber harvest and road building resulted in extensive erosion in the basin and contributed high sediment loads to redwood creek since 1975 no peak flows have exceeded a 5 year recurrence interval twenty years of cross sectional survey data document the downstream movement of a sediment wave in the lower 26 km of this gravel bedded river at a rate of 800 to 1600 m a i durng this period of moderately low flows higher transit rates are associated with reaches of higher unit stream power the wave was initially deposited at a site with an abrupt decrease in channel gradient and increase in channel width the amplitude of the wave has attenuated more than i m as it moved downstream and the duration of the wave increased from eight years upstream to more than 20 years downstream channel aggradation and subsequent degradation have been accommodated across the entire channel bed channel width has not decreased significantly after initial channel widening from large 25 year recurrence interval floods three sets of longitudinal surveys of the streambed showed the highest increase in pool depths and frequency in a degrading reach but even the aggrading reach exhbited some pool development through time the aggraded channel bed switched from functioning as a sediment sink to a significant sediment source as the channel adjusted to high sediment loads from 1980 to 1990 sediment eroded from temporary channel storage represented about 25 per cent ofthe total sediment load and 95 per cent of the bedload exported from the basin

geomorphic control of persistent mine impacts in a yellowstone park stream and implications for the recovery of fluvial systems a half century after mine closure metal contamination from sulfide ore mining in the headwaters continues to impair riparian vegetation and aquatic macroinvertebrates along soda butte creek yellowstone national park a tailings dam failure in 1950 emplaced metal rich sediment at high flood plain levels above 50 yr to 100 yr flood stages in 1996 and 1997 these large natural floods removed only a small part of the contaminated sediment through bank erosion they also failed to lower in channel cu concentrations because increased erosion of mine waste during high flows balances increased inputs of uncontaminated sediments generating no net change in concentrations geomorphic processes controlling movement of contaminated sediments indicate that mine impacts will persist for centuries in soda butte creek and imply long lasting impacts in similarly affected streams worldwide

river adjustment to changes in sediment load the effects of tin mining on the ringarooma river tasmania 1875 1984 the mining of alluvial tin in the ringarooma basin began in 1875 reached a peak in 1900 20 and had virtually ceased by 1982 during that time 40 million m3 of mining waste were supplied to the main river quickly replacing the natural bed material and requiring major adjustments to the channel based on estimates of sediment supply from more than 50 widely scattered mines and the frequency of flows capable of transporting the introduced load the river s transport history is reconstructed using a mass conservation model because of the lengthy time period 110 years and river distance 75 km involved the model cannot predict detailed change but it does reproduce the main pattern of sediment movement in which successive phases of aggradation and degradation progress downstream peak storage is predicted in that part of the river where braiding and anastomosis are best developed aggradation was most rapid in the upper reaches close to major supply points becoming slower and later with distance downstream channel width increased by up to 300 per cent where the valley floor was broad and braiding became relatively common bridges had frequently to be replaced while bed levels were still rising in lower reaches degradation began in upper ones notably after 1950 and by 1984 had progressed downriver over 30 km rates of incision reached 0 5 m yr 1 especially in the early 1970s when record high flows occurred as a result of degradation the bed material became gravelly through either reexposure of the original bed or lag concentration of coarser fractions also a narrower unbraided channel has developed the river is beginning to heal itself and upper reaches now have reasonably stable beds but at least another 50 years will be required for the river to cleanse its channel of mining debris

x ray fluorescence analysis and intra island exchange in the society island archipelago central eastern polynesia abstract we apply x ray fluorescence xrf geochemical analysis to a collection of opunohu valley lithic artifacts from mo orea island to investigate the local scale of raw material procurement adze production use and exchange within the society island archipelago we use these data to document the distribution of non local versus local volcanic artifacts in opunohu valley house sites ritual sites and specialized sites as a means for establishing intra site production and consumption patterns and access to exotic possibly superior stone resources and how these two themes correlate with site function or household wealth and status overall 30 of the artifacts analyzed via wdxrf derive from non local sources notably two other islands in the archipelago outside of the political boundaries of moorean chiefdoms our case study thus provides the first direct material evidence of intra archipelago trade and exchange in the society islands intra archipelago trade in adzes was certainly in place by as early as a d 1350 if not earlier and continued up until the time of european contact in addition our analyses have identified a local adze production locale in the afareaitu district of mo orea island the patterns of local versus non local adze production and exchange strongly suggest that dual interaction spheres were involved the correlation between adzes and adze related debris produced from off island sources and sites with specialized use which were often reserved for the social ritual and political elites in ma ohi society suggests that some of the exotic adzes derived from gift exchange between mo orea and ruling elites in tahiti and the leeward islands these adzes from afar would have solidified socio political and ideological alliances between elites in the windward and leeward sectors of the archipelago

an experimental approach to distinguishing different stone artefact transport patterns from debitage assemblages this paper experimentally demonstrates the ability of a set of indices to distinguish between different stone artefact transport patterns represented in debitage assemblages stone artefacts were transported extensively in the past and this is an important component of technological organisation however most stone artefacts occur as part of debitage assemblages from these assemblages where mostly non transported artefacts remain it can be challenging to identify what artefacts if any were transported in anticipation of future use a series of indices the cortex ratio volume ratio flake to core ratio non cortical to cortical flake ratio and flake core diminution tests are presented to meet this challenge these are tested on an experimental assemblage where three different transport scenarios are simulated results suggest that the indices are sensitive to artefact transport and are capable of empirically distinguishing between the three transport scenarios even when raw material form varies the results also indicate that artefact transport is capable of exerting a significant influence on stone artefact assemblage formation

measuring stone artefact transport the experimental demonstration and pilot application of a new method to a prehistoric adze workshop southern cook islands this paper presents a new method based on the calculation of a cortex ratio capable of contributing towards measures of stone artefact transport in polynesia a set of ratios can be calculated by comparing the observed amount of cortical surface area and volume in an assemblage with what is expected should all the products of reduction remain because raw material shape and size is controlled for using geometric equations an estimate for the number of preforms produced from an assemblage also is possible the method is experimentally demonstrated and applied to an archaeological early stage adze manufacturing assemblage from moturakau rockshelter aitutaki island in the southern cook islands application of the method in combination with geochemical and chronological analyses shows that the number of preforms produced and transported as well as the frequency of their transport changed over time but the geographic scale of distribution remained the same essentially local to aitutaki

establishing statistical confidence in cortex ratios within and among lithic assemblages a case study of the middle paleolithic of southwestern france abstract recent studies have demonstrated the usefulness of the cortex ratio for quantifying the cortex composition in lithic assemblages and as a viable index of prehistoric artifact transport yet the lack of means for assigning statistical confidence to archaeologically observed cortex ratios inhibits the approach s utility for objective comparisons and interpretation here we derive statistical confidence for archaeological cortex ratios through monte carlo and resampling techniques experimental data with known geometric properties and measured cortex values were employed as a reference for attaching a probability to an archaeological assemblage s cortex ratio the method is demonstrated on assemblages from the middle paleolithic sites of roc de marsal pech de l aze iv and combe capelle bas in southwestern france

the influence of raw material size on stone artefact assemblage formation an example from bone cave south western tasmania this paper specifically examines the influence of raw material size on stone artefact assemblage formation in conjunction with two behavioural assemblage formation processes reduction intensity and artefact transport the aim is to establish whether raw material size can influence the way in which reduction intensity and artefact transport form a stone artefact assemblage and should a significant influence be established whether this has any bearing on human behavioural reconstructions this is first investigated in an experimental setting followed by an archaeological setting using a quartzite and chert assemblage from bone cave in south western tasmania reduction intensity and artefact transport are respectively measured using the scar density index flake to core ratio non cortical to cortical flake ratio and cortex ratio while tool blank sizes are also reconstructed the combined experimental and archaeological analyses find that raw material size variation is capable of exerting a substantial influence on stone artefact assemblage formation this particularly with reference to the nature of change in stone artefact assemblages both reduction intensity and artefact transport will alter assemblage composition at faster rates when nodule sizes are smaller this can have significant implications for intra and inter site reconstructions of past human behaviour

the lillooet terraces of fraser river a palaeoenvironmental enquiry the history of holocene fluvial terraces was investigated by stratigraphic morphological and palaeohydrologic methods the terraces were formed in glaciofluvial and glaciolacustrine sediments by the fraser river degradation alternated with episodes of stability and aggradation the uppermost terraces four nonpaired surfaces were occupied by a braided river vertical stability was controlled either by the water and sediment discharge of the river or by backwater effects from downstream landslides the lower terraces two paired surfaces and associated fluvial sediments provide evidence for at least two cycles of aggradation and downcutting these can be attributed to the effects of landslides that occurred a short distance downstream climatic variations may also have influenced terrace formation but direct evidence is lacking palaeohydraulic investigations based on gravel texture terrace gradients and geometry of palaeochannels provide results that although approximate conform with conclusions

effective timescales of coupling within fluvial systems this paper presents a review of the coupling concept in fluvial geomorphology based mainly on previously published work coupling mechanisms link the components of the fluvial system controlling sediment transport down the system and the propagation of the effects of base level change up the system they can be viewed at several scales at the local scale involving within hillslope coupling hillslope to channel coupling and within channels tributary junction and reach to reach coupling at larger scales coupling can be considered as zonal coupling between major zones of the system or as regional coupling relating to complete drainage basins these trends are illustrated particularly by the examples of hillslope to channel coupling in the howgill fells northwest england badland systems in southeast spain alluvial fans in spain usa and uae and base level induced dissection of neogene sedimentary basins in southeast spain as the spatial scales increase so do the timescales involved effective temporal scales relate to magnitude and frequency characteristics recovery time and propagation time the relative importance changing with the spatial scale for downsystem coupling at the local scale the first two are important with propagation time increasing in importance in larger systems especially in those involving upsystem coupling related to base level change the effective timescales range from the individual event with a return period of decades through decadal to century timescales for downsystem coupling to tens to hundreds of thousands of years for the basinwide response to base level change the effective timescales influence the relative importance of factors controlling landform development

catastrophic landslides and their effects on the upper indus streams karakoram himalaya northern pakistan abstract the paper examines the nature and geomorphic influences of deposits from rock avalanches that obstruct rivers most of the 115 rockslide rock avalanche events identified in the karakoram himalaya straddled one or more stream valleys at least 73 of these landslides formerly dammed the indus or its tributaries upstream of the barriers remnants exist of once very extensive lacustrine deposits the stability and long term survival of dams from large rock avalanches is addressed and the reasons for the gradual or phased rather than catastrophic and sudden breaching case histories emphasise the erosional and depositional forms associated with the barriers they are reconstructed in terms of the emplacement and properties of the deposits from rock avalanches and the response of the river to interruption by them these barriers have exerted a substantial control over stream response and development for most of the holocene at least today they are associated with distinctive features of channel form and thalweg river terrace systems intermontane sediment sinks and sources and local erosional forms in bedrock more broadly the landslide barriers have created a naturally fragmented river system deposition and erosion in the lower few tens or hundreds of meters of the upper indus stream valleys have been dominated by epicycles of aggradation trenching and downcutting that mainly reflect the scale timing and history of each barrier the landforms involved are only indirectly related to the late glacial and paraglacial conditions that have hitherto been regarded as the main explanation

measuring core reduction using 3d flake scar density a test case of changing core reduction at klasies river mouth south africa a new core reduction index is presented calculated as the ratio of flake scar number to 3d surface area sdi the index is tested experimentally on five types of core blade discoid levallois biface and multiplatform cores and then applied to the core assemblages from five sub stages of the middle stone age at klasies river mouth south africa preliminary results indicate that the sdi possesses the desirable attributes of a successful reduction index and is a significant improvement on traditional proxy measures of core reduction the results of the archaeological case study confirm previous untested observations that cores from the howiesons poort and msaiii sub stages are more heavily reduced than preceding and following stages and that local and exotic raw materials as well as different types of cores are all more heavily reduced during these periods the sdi fills a significant lacuna in available core reduction measures

landslide induced river channel avulsions in mountain catchments of southwest new zealand pulsed or chronic supply of landslide debris to valley floors has historically caused substantial aggradation and channel instability in several alpine catchments of sw new zealand in this regional investigation of landslide impacts on river morphology three types of landslide induced channel avulsion are discerned i upstream backwater avulsions ii contact avulsions and iii downstream loading avulsions the basis for this qualitative geomorphic process response framework is the principal direction of fluvial response with respect to its position relative to the causative landslide emplacement site downstream avulsions have the highest damage potential to land use and infrastructure on unconfined mountain fringe alluvial fans in the wake of such events catastrophic aggradation may obliterate up to several km2 of mature floodplain forests by burial under several metres within a few decades estimates of mean aggradation rates are high 220 mm year 1 and exceed long term 103 year trends of fluvial degradation by an order of magnitude future potential avulsion routeways may be detected by geomorphic mapping of abandoned channels which are preferentially reactivated in the wake of landslide induced sediment waves

record of recent river channel instability cheakamus valley british columbia rivers flowing from glacier clad quaternary volcanoes in southwestern british columbia have high sediment loads and anabranching and braided planforms their floodplains aggrade in response to recurrent large landslides on the volcanoes and to advance of glaciers during periods of climate cooling in this paper we document channel instability and aggradation during the last 200 years in lower cheakamus river valley cheakamus river derives much of its flow and nearly all of its sediment from the mount garibaldi massif which includes a number of volcanic centres dominated by mount garibaldi volcano stratigraphic analysis and radiocarbon and dendrochronological dating of recent floodplain sediments at north vancouver outdoor school in cheakamus valley show that cheakamus river aggraded its floodplain about 1 2 m and buried a valley floor forest in the early or mid 1800s the aggradation was probably caused by a large ca 15 2510 6 m 3 landslide from the flank of mount garibaldi 15 km north of our study site in 1855 or 1856 examination of historical aerial photographs dating back to 1947 indicates that channel instability triggered by this event persisted until the river was dyked in the late 1950s our observations are consistent with data from many other mountain areas that suggest rivers with large but highly variable sediment loads may rapidly aggrade their floodplains following a large spike in sediment supply channel instability may persist for decades to centuries after the triggering event crown copyright d 2002 published by elsevier science b v all rights reserved

channel response to increased and decreased bedload supply from land use change contrasts between two catchments abstract the catchments of pine creek idaho usa 200 km 2 and the drome river in the drome department france 1640 km 2 illustrate contrasting changes in land use bedload sediment production and channel response hard rock mining began in the catchment of pine creek near the end of the 19th century and together with road construction timber harvest and historically heavy grazing of uplands resulted in increased tributary bedload yield increased bedload migrating to the channel combined with removal of large cedar trees on the floodplain resulted in channel instability which propagated downstream over a period of decades on many reaches of pine creek active channel width has increased by over 50 since 1933 over roughly the same time period the drome river catchment was extensively reforested after at least one century of denudation and heavy grazing and numerous check dams were constructed on torrents to reduce erosion as a result the drome river has experienced a reduction in bedload sediment supply since the late 19th century in addition gravel has been extracted from some reaches consequently the channel has degraded and gravel bars have been colonized with woody riparian vegetation channel widths in wide braided reaches decreased from 1947 to 1970 by 60 on pine creek channel instability has resulted in bank erosion exposing contaminated mine tailings and increased flood hazard on the drome river degradation has undermined bridges and embankments and lowered the water table in areas dependent on groundwater for irrigation resulting in loss of 6 million m 3 of groundwater storage since 1960 though they differ in drainage area by nearly an order of magnitude pine creek and the drome river provide an excellent contrast in that they represent two sides of an epicycle of alluvial sedimentation set off in each case by land disturbance in both cases the most recent channel changes though in opposite directions were viewed as negative by river managers on pine creek managers have removed or protected from erosion mine tailings and have attempted to train the stream into a more stable channel and most rock waste piles the principal sediment sources have recently been controlled on the drome river managers have prohibited gravel mining and adopted new policies to permit coarse sediment to migrate through the river system

the quaternary stratigraphic record of british columbia evidence for episodic sedimentation and erosion controlled by glaciation the terrestrial quaternary stratigraphic record of british columbia is largely a product of brief depositional events separated by long periods of nondeposition and erosion thick stratified quaternary sediments are present mainly in valleys and coastal lowlands and accumulated during periods of growth and decay of the cordilleran ice sheet at glacial maxima till was deposited over large areas of low and moderate relief however at the same time much of the landscape was eroded by glaciers sedimentation has been more restricted and has occurred at lower rates during nonglacial periods than during glaciations on land the only important sediment accumulation sites during nonglacials have been lakes floodplains and fans however large amounts of sediment have accumulated offshore especially in fjords and basins such as the strait of georgia because of the restricted aspect of sedimentation during nonglacials the stratigraphic record of these periods is meagre in most places true nonglacial uni