flux and fate of small mountainous rivers derived sediments into the taiwan strait article i nfo high resolution chirp sonar profiles across the taiwan strait reveal a large silt sand dominated deltaic clinoform up to 50 m thick overlying the postglacial transgressive sea floor across the southeastern central and northern strait delta like configuration and internal depositional sequences indicate a northwestward progradation from western taiwan primarily from the choshui zhuoshui river grain size and mineral data confirm the sediment s taiwanese derivation the chirp profiles together with existing radiocarbon and geomagnetic dates suggest that the clinoform has formed over the past 10 kyr the estimated volume of 375 km 3 of sediment mainly sand and silt suggests a mean annual accumulation of 60 10 6 t yr presumably much of fine mud delivered by taiwanese rivers has been washed away by the local currents and escaped either northeastward into the southern okinawa trough or southward into the south china sea numerous shallow borings onshore over the central western taiwan coastal plain reveal an additional 350 km 3

isotopic evidence for the influence of typhoons and submarine canyons on the sourcing and transport behavior of biospheric organic carbon to the deep sea abstract export of biospheric organic carbon from land masses to the ocean plays an important role in regulating the global carbon cycle high relief islands in the western pacific are hotspots for such land to ocean carbon transport due to frequent floods and active tectonics submarine canyon systems serve as a major conduit to convey terrestrial organics into the deep sea particularly during episodic floods though the nature of ephemeral sediment transportation through such canyons remains unclear in this study we deployed a sediment trap in southwestern taiwan s gaoping submarine canyon during summer 2008 during which typhoon kalmaegi impacted the study area we investigated sources of particulate organic carbon and quantified the content of fossil organic carbon oc f and biospheric non fossil carbon ocnf during typhoon and non typhoon periods based on relations between total organic carbon toc isotopic composition 13 c 14c and nitrogen to carbon ratios n c of newly and previously reported source materials during typhoons flooding connected terrestrial rivers to the submarine canyon fresh plant debris was not found in the trap except in the hyperpycnal layer suggesting that only hyperpycnal flow is capable of entraining plant debris while segregation had occurred during non hyperpycnal periods the ocnf components in typhoon flood and trapped samples were likely sourced from aged organics buried in ancient landslides during non typhoon periods the canyon is more connected to the shelf where waves and tides cause reworking thus allowing abiotic and biotic processes to generate isotopically uniform and similarly aged ocnf for transport into the canyon therefore extreme events coupled with the submarine canyon system created an efficient method for deep sea burial of freshly produced organic rich material our results shed light on the ephemeral transport of organics within a submarine canyon system on an active tectonic margin

geology and geomorphology control suspended sediment yield and modulate increases following timber harvest in temperate headwater streams abstract suspended sediment transport is an important contributor to ecologic and geomorphic functions of streams however it is challenging to generalize predictions of sediment yield because it is influenced by many factors in this study we quantified the relevance of natural controls e g geology catchment physiography on suspended sediment yield ssy in headwater streams managed for timber harvest we collected and analyzed six years of data from 10 sites five headwater sub catchments and five watershed outlets in the trask river watershed western oregon united states we used generalized least squares regression models to investigate how the parameters of the ssy rating curve varied as a function of catchment setting and whether the setting modulated the ssy response to forest harvesting results indicated that the highest intercepts of the power relation between unit discharge and ssy were associated with sites underlain primarily by friable rocks e g sedimentary formations the greatest increases in ssy after forest harvesting up to an order of magnitude also occurred at sites underlain by the more friable lithologies in contrast basins underlain by resistant lithologies intrusive rocks had lower ssy and were more resilient to management related increases in ssy as such the impact of forest management activities e g use of forested buffers building of new roads on the variability in ssy was primarily contingent on catchment lithology sites with higher ssy or harvest related increases in ssy also generally had a lower mean elevation and slope b greater landscape roughness and c lower sediment connectivity we used principal component analysis pca to further explore the relationship between ssy and several basin physiographic variables the pca clearly separated sites underlain by friable geologic units from those underlain by resistant lithologies results are consistent with greater rates of weathering and supply of sediment to headwater streams in catchments with more friable lithologies and limited sediment supply in catchments underlain by resistant lithologies we hypothesize that a similar framework may aid in predicting the overall ssy of a catchment as well as its susceptibility to increases in ssy following forest harvesting

erosion rates for taiwan mountain basins new determinations from suspended sediment records and a stochastic model of their temporal variation abstract we estimate erosion rates from suspended sediment records for 11 basins in the eastern central range ecr of taiwan using methods based on mean measured sediment discharge a rating curve of sediment and water discharge and a rating curve corrected for periods of limited sediment due to the lack of landslide supplied sediment the preferred method for any basin depends on record length and sampling frequency with higher quality records being analyzed by the latter method erosion rate estimates range from 2 2 to 8 3 mm yr for records with varying sampling frequencies and durations between 8 and 27 yr this variation in erosion rates does not seem to reflect lithology tectonic environment or climate we interpret the variation in terms of natural stochastic variation in water discharge and sediment supply to assess the quality of the erosion rate estimates and to better understand the dependence of uncertainty on the duration and frequency of sampling we construct a stochastic model of sedi

new insights for the interpretation of ancient bog oak chronologies reactions of oak quercus robur l to a sudden peatland rewetting abstract subfossil bog oak material is an important palaeo climate and hydrology proxy for the holocene a correct interpretation of the subfossil material in terms of growth and population dynamics requires understanding of the underlying processes the catastrophic rewetting after dyke failure of a drained peatland forest in ne germany provides a unique natural laboratory to calibrate bog oak growth pattern with a known event growth differences among groups of currently vital damaged and dead oaks in the years before the flooding were used to estimate the adaptation potential in dependence on age tree size competition class and groundwater table dendrochronological analysis of growth patterns and wood anatomical parameters revealed changes in the wood in reaction to sharp hydrological shifts drainage and rewetting group specific chronologies were contrasted against instrumental data to evaluate the influence of climate and hydrology on radial growth of oak groundwater table proved to be the overriding factor influencing oak growth at our site already during times of intensive drainage results show an influence of micro site conditions elevation above soil water level along with a higher chance for slower growing and possibly former suppressed trees to survive the catastrophic rewetting these trees display a typical ring pattern with four to five years of depressed growth and a subsequent recovery characterised by a significant increase in ring width especially in the earlywood trees that died or were damaged following the rewetting typically show strongly reduced latewood width before they gradually die off our findings are discussed with regard to the interpretation of subfossil bog oak material and a modified version of release detection analysis is proposed as a tool to sharpen the identification of hydrological shifts in bog oak material the results of the study can contribute to a better understanding of ecophysiological mechanisms underlying growth reactions and adaptation potential of oaks to prevailing high water levels

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

review of erosion dynamics along the major n s climatic gradient in chile and perspectives abstract chile is an elongated country running in a north south direction for more than 30 along a subduction zone its climate is progressively wetter and colder from north to south this particular geography has been used positively by a growing number of studies to better understand the relationships between erosion processes and climate land use slope tectonics volcanism etc here we review the erosion rates factors and dynamics over millennial to daily periods reported in the literature in addition 21 new catchment mean erosion rates suspended sediment and 10be are provided and previous suspended sediment derived erosion rates are updated a total of 485 local and catchment mean erosion rates are reported erosion rates vary between some of the smallest values on earth 10 5 mm a to moderate values 0 5 mm a compared to other active ranges this review highlights strong limitations concerning the quantification of local erosion factors because of uncertainties in sampling point location slope and rainfall data for the mean erosion rates e for the millennial and decennial catchments a model of the form e s 1 s 0 6 2 r with 0 3 0 8 accounts for 40 to 70 of the erosion variance confirming a primary role of slope s compared to precipitation rate r over this time scale over the long term this review points to the long 5 to 10 ma response time of rivers to surface uplift in north central arid chile over millennia data provide evidence for the progressive contribution of extreme erosion events to millennial averages for drier climates as well as the link between glacier erosion and glacier sliding velocity in this period of time a discrepancy exists between the long term offshore sedimentological record and continental decennial or millennial erosion data for which no single explanation appears still little information is available concerning the magnitude of variation of millennial erosion rates over centuries data show the variable role of groundwater in the dynamics of suspended load and document a decrease in erosion over hundreds of years probably associated with historical harvesting

constraining the transport time of lithogenic sediments to the okinawa trough east china sea the transport time of siliciclastic sediments from their continental sites of formation to their final location of deposition on the seafloor is an important parameter bearing on land sea interactions climate variability and understanding of marine sediment record 234u 238u activity ratios of the lithogenic fraction from late quaternary sediment deposited in the okinawa trough east china sea were reported in this study on basis of 234u 238u activity ratios the comminution ages and transport times were calculated using recoil loss factors f derived from different equations based on grain size distribution the transport times were longer approximately 200 100 kyr for the okinawa trough sediments deposited between 27 and 14 ka decreased gradually between 14 and 7 ka and stayed relatively short 100 kyr thereafter mineralogical geochemical and isotopic evidences indicate that changes in sediment transport time correspond well with the shift of sediment provenance predominantly from asia s interior prior to 14 ka to taiwan island after 7 ka this study offers the first and robust constraint on time scale of sediment transport process in east asia marginal sea which is constrained by unique sediment source to sink transport pattern the result illustrates the potential of this approach to decipher climate related changes in the mode of supply of lithogenic sediment to marginal seas it also highlights current difficulties in obtaining quantitative estimates of comminution age mostly because of uncertainties in estimating the recoil loss factor

a detrital heavy mineral viewpoint on sediment provenance and tropical weathering in se asia abstract understanding heavy mineral preservation is important for interpreting generation pathways provenance and geochemistry of sediments despite this many assumptions about heavy mineral stability are based on ancient strata and few studies consider modern sediments particularly those in tectonically active tropical areas such as se asia we report new heavy mineral data on 69 river sand samples from the malay peninsula and sumatra in which one aim was to find provenance indicators specific to these areas identifications were performed using optical microscopy and confirmed with sem eds in the malay peninsula heavy minerals record granitic and contact metamorphic provenance variable amounts of zircon tourmaline hornblende andalusite epidote monazite rutile and titanite and minor amounts of pyroxene apatite anatase garnet diaspore colourless spinel cassiterite and allanite are typical of this source area the composition of assemblages from sumatra indicates contributions from two major sources the modern volcanic arc i and the basement ii abundant pyroxene particularly hypersthene up to 70 is diagnostic of the volcanic arc source vesuvianite garnet andalusite tourmaline chrome spinel rutile anatase and corundum are present only in small amounts

geochemistry of river borne clays entering the east china sea indicates two contrasting types of weathering and sediment transport processes the east china sea is characterized by wide continental shelf receiving a huge input of terrigenous matter from both large rivers and mountainous rivers which makes it an ideal natural laboratory for studying sediment source to sink transport processes this paper presents mineralogical and geochemical data of the clays and bulk sediments from the rivers entering the east china sea aiming to investigate the general driving mechanism of silicate weathering and sediment transport processes in east asian continental margin two types of river systems tectonically stable continental rivers and tectonically active mountainous rivers coexist in east asia as the direct weathering products clays can better reflect the silicate weathering regimes within the two river systems provenance rock types are not the dominant factor causing silicate weathering intensity difference existed in the east asian rivers the silicate weathering intensity of tectonically stable river basins is primarily driven by monsoon climate and the sediment transfer is relatively slow because of natural trapping process and increasing damming effect the geochemistry of these river borne sediments can thus indicate paleo weathering intensities in east asian continent in contrast silicate weathering intensity in tectonically active mountainous rivers is greatly limited by strong physical erosion despite the high temperature and highest monsoon rainfall the factors controlling silicate weathering in tectonically active catchments are complex and thus it should be prudent to use river sediment records to decipher paleoclimate change these two different silicate weathering regimes and sediment transport processes are manifestations of the landscape evolution and overall dominate the sedimentation in asian continental margin

short term changes in seafloor character due to flood derived hyperpycnal discharge typhoon mindulle taiwan july 2004 during typhoon mindulle in early july 2004 the choshui river central western taiwan discharged similar to 72 mt of sediment to the eastern taiwan strait peak concentrations were g 200 g l similar to 35 40 of which was sand box core samples and chirp compressed high intensity radar pulse sonar records taken just before and after the typhoon indicate that the hyper pycnal sediment was first deposited adjacent to the mouth of the choshui subsequently resuspended and transported northward via the taiwan warm current and redeposited as a patchy coastal band of mud dominated sediment that reached thicknesses of 1 2 m within megaripples within a month most of the mud was gone probably continuing its northward transit but more mud appeared in late august in response to typhoon aere following autumn and winter storms the entire nearshore area was again sand dominated by early spring

the sediment delivery problem abstract the linking of on site rates of erosion and soil loss within a drainage basin to the sediment yield at the basin outlet and improved knowledge and representation of the associated processes of sediment delivery represent a major research need within the field of erosion and sedimentation and also an important scale problem in drainage basin studies this paper reviews the limitations of the sediment delivery ratio concept by considering the problems of temporal and spatial lumping and its blackbox nature some recent advances in our understanding of the sediment delivery system and its modelling are described and the lack of detailed empirical investigations is highlighted the significance of recent concern for the role of sediments in the transport of nutrients and contaminants to sediment delivery studies is introduced and the need for further work in this field is emphasised

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

deep sea sedimentation offshore eastern taiwan facies and processes characterization recent sedimentary facies and processes along the offshore slope of east taiwan are investigated using a large set of geophysical and sedimentological data the taiwan orogen is often considered as one of the most tectonically active regions in the world and also suffers important climatic activity with an average of four typhoons per year we have mapped in details the morphosedimentary features and characterized the sedimentary facies along offshore eastern taiwan there we show that the slope is driven by a variety of erosional processes from mass wasting to turbidity current mass movements such as slides or mass transport deposits mtds are ubiquitous and affect the whole east coast off taiwan detailed core investigations such as grain size analysis chemical and mineralogical composition revealed that turbidite facies range from thin fine grained turbidites to thick massive turbidite facies the detailed analysis of turbidite beds allow us to discuss the controlling factors of turbidity current generation turbidity currents represent an important sedimentary process that governs the slope morphology off east taiwan triggering mechanisms likely range from slope instabilities related to earthquakes shaking to failure relative to climatic controlled pulses of sediment supply we propose that at least two end members are characteristics in our turbidite records in term of controlling factor 1 turbidity currents likely generated by tectonic activity and earthquakes shaking in particular and 2 turbidity currents likely generated by climatic activity such as typhoon induced floods

climate driven bedrock incision in an active mountain belt measurements of fluvial bedrock incision were made with submillimeter precision in the east central range of taiwan where long term exhumation rates and precipitation driven river discharge are independently known they indicate that valley lowering is driven by relatively frequent flows of moderate intensity abrasion by suspended sediment is an important fluvial wear process and channel bed geometry and the presence of widely spaced planes of weakness in the rock mass influence erosion rate and style

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

cyclone driven deep sea injection of freshwater and heat by hyperpycnal flow in the subtropics china 973 program 2009cb421200 program of introducing talents of discipline to universities b07034 academia sinica thematic program afobi taiwan nsc 98 2116 m 001 005

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

trace metal fluxes to the ocean the importance of high standing oceanic islands 1 trace metal analyses of river channel sediments from taiwan and new zealand provide new estimates for global budgets of trace metal inputs to the world s ocean mean trace metal values from high standing island river sediments are less chemically weathered than observed in sediments collected from large continental rivers and more similar to upper continental crust ucc values our mean values for cu mn co and pb are similar to the ucc zn ni and cr are more highly enriched compared to ucc values our new estimates of global trace metal budgets combining previous estimates with these new data show that geochemical fluxes of metals into the oceans are lower than previous estimates ranging from 9 lower for co to 24 lower for cu

early interglacial carbonate dilution events in the south china sea implications for strengthened typhoon activities over subtropical east asia abstract a compilation of many late quaternary marine sediment records from the northern south china sea scs continental slope confirms 15 50 reductions in sedimentary calcium carbonate concentrations between 11 0 and 8 5 ka bp in the early holocene this low carbonate event occurred at a time when the regional sea level rose from 50 m to 10 m which drowned large areas of continental shelves especially those near and within the taiwan strait this event is associated with a significant increase in bulk sedimentation rates on the upper continental slope and the relative abundance of fine grained detritus sediment provenance analyses suggest a dominant terrigenous input from taiwan and a minor contribution from luzon during the low carbonate event similar to the background terrigenous deposition in other periods of the holocene two comparable low carbonate events respectively from the beginning of marine isotope stages 5 5 and 7 3 have also been recognized pointing to similar causal factors while carbonate dissolution and carbonate accumulation rate should not have been responsible increased terrigenous input and dilution is considered as the main cause for the recurrent low carbonate events in early interglacials we further hypothesize that during early interglacials fluvial sediment discharge from taiwan and luzon intensified due to stronger typhoon activities and massive fine grained sediments from these two end members may have been transported to the northern scs continental slope via surface and deep ocean currents the conjecture of strengthened typhoon activities over east asia during the early holocene is supported by high ocean heat contents in the west pacific warm pool area with the prevailing la nina like conditions

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

water and sediment discharge from small mountainous rivers taiwan the roles of lithology episodic events and human activities national science council of taiwan nsc96 2628 m 001 028 u s national science foundation and naval oceanographic office

distribution of organic carbon and lignin in soils in a subtropical small mountainous river basin abstract as a unique biomarker of terrigenous organic matter om lignin has provided valuable information for tracing the sources of om in land to ocean transfer oceanian small mountainous rivers smrs are characterized by extremely high erosional rate and quick change in microclimate within watershed which may potentially affect the distribution of soil oc and lignin concentrations and compositions bulk oc and lignin were determined on surface soils and soil profiles from a taiwanese smr jhuoshuei river and nearby region along a large altitudinal gradient 3 3176 m to investigate the influence of microclimate on soil oc and lignin both surface soils oc and lignin increased in higher altitude suggesting higher preservation of om in the cold region variations in lignin vegetation indices s v and c v in surface soils generally reflect the vegetation change in this river basin and were more affected by precipitation seasonality than mean annual precipitation lignin concentration decreased with depth along with a decrease in s v and c v and an increase in degradation indices ad al v and dhba v reflecting a decreased input and or biodegradation of lignin in subsoils our survey on soil lignin in taiwan smr provided the basis for utilizing lignin to trace the source of oc in land to ocean transfer as well as paleo climate and paleo vegetation reconstruction study in taiwan smrs

the danube river inception evidence for a 4 ma continental scale river born from segmented paratethys basins before reaching the black sea the danube river passes through a string of para tethyan vienna pannonian and western and eastern dacian basins the key question is when and how did the danube river became a continental scale river with a drainage similar to present new data presented here show that the late miocene deep water strata in the black sea have a significant sediment source and depositional style change at about 4 ma however the presence of active miocene basins within the danube catchment raises questions about the timing of danube river inception and whether the upstream palaeogeography would have allowed or disallowed delivery of large sediment volumes to the deep water black sea stratigraphic analyses in the pannonian and dacian basins reveal a phase of coeval sedimentary fill of the basins along the danube at about 4 ma this multi basin observation points to a concurrent basin fill model rather than the basin fill and spill or messinian type lowstand models previously proposed for danube inception this article is protected by copyright all rights reserved

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

earthquake triggered increase in sediment delivery from an active mountain belt in tectonically active mountain belts earthquake triggered landslides deliver large amounts of sediment to rivers we quantify the geomorphic impact of the 1999 mw 7 6 chi chi earthquake in taiwan which triggered 20 000 landslides coseismic weakening of substrate material caused increased landsliding during subsequent typhoons most coseismic landslides remained confined to hillslopes downslope transport of sediment into the channel network occurred during later storms the sequential processes have led to a factor of four increase in unit sediment concentration in rivers draining the epicentral area and increased the magnitude and frequency of hyperpycnal sediment delivery to the ocean four years after the earthquake rates of hillslope mass wasting remain elevated in the epicentral area

hyperpycnal sediment discharge from semiarid southern california rivers implications for coastal sediment budgets southern california rivers discharge hyperpycnal river density greater than ocean density concentrations of suspended sediment 40 g l according to buoyancy theory during flood events mostly during el nino southern oscillation enso conditions because hyperpycnal river discharge commonly occurs during brief periods hours to occasionally days mean daily flow statistics often do not reveal the magnitude of these events hyperpycnal events are particularly important in rivers draining the transverse range and account for 75 of the cumulative sediment load discharged by the santa clara river over the past 50 yr these events are highly pulsed totaling only 30 days 0 15 of the total 50 yr period observations of the fate of sediment discharge although rare are consistent with hyperpycnal river dynamics and the high likelihood of turbidity currents during these events we suggest that much of the sediment load initially bypasses the littoral circulation cells and is directly deposited on the adjacent continental shelf thus potentially representing a loss of immediate beach sand supply during particularly exceptional events 100 yr recurrence intervals flood underflows may extend past the shelf and escape to offshore basins

near synchronous and delayed initiation of long run out submarine sediment flows from a record breaking river flood offshore taiwan subsea fiber optic telecommunication cables can break under fast sediment flows that travel 100s of kilometers through the deep ocean in response to earthquakes and submarine landslides similar flows are inferred to form from major river floods whose sediment laden waters plunge and travel along the seabed however the complex initiation of flood related flows and their hazard potential have not been observed until now here we use cable fault data from the gaoping canyon manila trench off taiwan to show that a major river flood formed during typhoon morakot 2009 generated two long run out destructive sediment flows one during peak flood and the other 3 days later the latter flow was more damaging with speeds and run out similar to that of landslide triggered turbidity currents formed in the same catchment if the second flow was due to remobilized canyon sediment it occurred during low earthquake mw 2 0 activity suggesting other triggering mechanisms

rare earth elements in fine grained sediments of major rivers from the high standing island of taiwan thirty eight sediment samples from 15 primary rivers on taiwan were retrieved to characterize the rare earth element ree signature of fluvial fine sediment sources compared to the three large rivers on the chinese mainland distinct differences were observed in the ree contents upper continental crust normalized patterns and fractionation factors of the sediment samples the average ree concentrations of the taiwanese river sediments are higher than those of the changjiang and huanghe but lower than the zhujiang light rare earth elements lrees are enriched relative to heavy rare earth elements hrees with ratios from 7 48 to 13 03 we found that the variations in la lu ucc gd lu ucc and la yb ucc gd yb ucc are good proxies for tracing the source sediments of taiwanese and chinese rivers due to their distinguishable values our analyses indicate that the ree compositions of taiwanese river sediments were primarily determined by the properties of the bedrock and the intensity of chemical weathering in the drainage areas the relatively high relief and heavy rainfall also have caused the rees in the fluvial sediments from taiwan to be transported to the estuaries down rivers from the mountains and in turn delivered nearly coincidently to the adjacent seas by currents and waves our studies suggest that the ree patterns of the river sediments from taiwan are distinguishable from those from the other sources of sediments transported into the adjacent seas and therefore are useful proxies for tracing the provenances and dispersal patterns of sediments as well as paleoenvironmental changes in the marginal seas

three dimensional observation of carbonaceous chondrites by synchrotron radiation x ray ct quantitative analysis and developments for the future sample return missions abstract carbonaceous chondrites were observed by synchrotron radiation x ray computed tomography sr ct three dimensionally we analyzed the chemical composition of the components of the carbonaceous chondrites such as chondrules matrix and iron inclusions from the linear attenuation coefficient lac of x rays histograms of the lac were used for the analysis of chemical composition of the internal material and we could find a clear relation of the compositions between the chondrules and matrix we also analyzed the size distribution of low fe inclusions chondrules using image processing of ct images cumulative size distribution of chondrules shows power law distribution and slopes of the distribution changed for different chondrite classes results of these analyses show that the chondrule and matrix would have formed from the same precursor and were incorporated into the parent bodies without large scale mixing in the solar nebula the method will also provide important information for the analysis of future sample return missions our examinations demonstrate great potential of the quantitative determination of chondrite class nondestructively by sr ct

effects of topography lithology rainfall and earthquake on landslide and sediment discharge in mountain catchments of southeastern taiwan abstract from 1996 through 2007 several heavy typhoons and earthquakes precipitated landslide hazards in southeast taiwan in the present study we analyze the impact of topography lithology rainfall and earthquakes on landsliding and sediment transport by quantifying the landslide ratio ratio of landslide area to catchment area and the sediment discharge for the sinwulu and luye upstream catchments of the peinan river the steep topography in these two catchments causes a large proportion of landslide ratios on slopes to exceeding 50 a condition which accelerates the delivery of landslide debris to the downslope channel the landslide ratios of 0 84 2 30 are obviously related to the rock strength and discontinuity density of the terrain but we find the magnitude of landsliding and sediment discharge to vary with the occurrence of earthquakes typhoon induced rainstorms generate the bulk of sediment discharge in the study catchments though the landslide debris is transported by the huge amounts of runoff produced by rainstorms a contributing factor is the recent occurrence of severe earthquakes which weakened the geomaterial leading in turn to further increases of fluvial sediment during subsequent typhoons additionally the finding that eventual reduction of unit sediment concentration after high magnitude earthquake events reveals that the downslope transport of landslide debris associated with earthquake activity and subsequent typhoon events precipitates a relatively short term 1 3 year increase of erosion rates in these two study areas in southeastern taiwan

partitioning sediment flux by provenance and tracing erosion patterns in taiwan we critically evaluate the potential and limitations of an alternative way to calculate erosion rates based on petrographic and mineralogical fingerprints of fluvial sediments coupled with gauged sediment fluxes our approach allows us to apportion sediment loads to different lithological units and consequently to discriminate erosion rates in different tectonic domains within each catchment our provenance data on modern taiwanese sands indicate focused erosion in the backbone range and tananao complex of the retrowedge lower rates are inferred for the northern part of the island characterized by tectonic extension and for the western foothills in the prowedge the principal factor of uncertainty affecting our estimates is the inevitably inaccurate evaluation of total sediment load because only the suspended flux was measured another is the assumption that suspended load and bed load are derived from the same sources in fixed proportions additional errors are caused by the insufficiently precise definition of lithologically similar compositional end members and by the temporal variability of sediment composition at the outlet of each catchment related to the spatial variability of erosional processes and triggering agents such as earthquakes typhoons and landslides to evaluate the robustness of our findings we applied a morphometric technique based on the stream power model the results obtained are broadly consistent with local discrepancies ascribed to poorly constrained assumptions and choices of scaling parameters our local erosion estimates are consistent with gps uplift rates measured on a decadal timescale and generally higher than basin wide results inferred from cosmogenic nuclide and thermochronology data

estimating river sediment discharge to the ocean application to the eel margin northern california abstract hydrotrend a synthetic river discharge numerical model can simulate the natural variability daily annually and longer in the flux of water and sediment delivered to the coastal ocean the numerical model is designed to make discharge predictions based on climate even though field measurements of river flow are not available provided that appropriate assumptions are made regarding past climate the model can predict how a river may have behaved in the geological past sediment load is determined from a river s rating coefficients when applied to the flood dominated eel river northern california hydrotrend captures the intermonthly and interannual variability of discharge and loads over a century or more hydrotrend is applied to the ice age paleo eel river when sea level was lower and climate much cooler and wetter the paleo eel river at 18 000 year bp would see its hinterland runoff increase but not the magnitude of the peak discharges the post dicted sediment load of the paleo eel river was 25 greater than today s although basin precipitation was 45 greater and the hinterland area 4 greater through sea level lowering a method is provided to obtain sediment discharge rating coefficients for unmonitored modern rivers and paleo rivers the relationship q s g 1 2 h 3 2 a 1 2 provides for an estimate of a river s sediment load q s to within a factor of 3 over 7 orders of magnitude from knowledge of basin relief h and basin area a rating coefficients are determined from this estimate of q s and the power law rating curve q s aq b 1 where q is discharge

sediment trapping in deltas of small mountainous rivers of southwestern taiwan and its influence on east china sea sedimentation abstract taiwan s setting of high mountains steep gradients frequent earthquakes erodible lithology and heavy rainfall represents an ideal site to focus on sedimentary processes of the deltas of small mountainous rivers smrs several smrs in southwestern taiwan have deposited a thick sedimentary succession in the composite southwest taiwan delta swtd since the middle holocene evidence from the swtd can help to determine its trapping efficiency and assess the role of smrs in sediment transport to the sea we used historical nautical charts bathymetric data satellite radar data and 14c dates to calculate the sediment volume of the swtd on millennial and decadal scales the 14c dates of core samples indicate deposition of thick deltaic sediment in subsiding areas since the time of the maximum flooding surface about 7 cal ka bp the paleo shoreline changes of the swtd suggest a steady westward progradation since 7 cal ka bp in contrast the nautical charts suggest minor volume reduction of the offshore part of the swtd with a deepening trend and retreating shorelines during the last seven decades the results show that at least 201 72 13 90 km3 3 23 105 mt of sediment has been trapped in the swtd since 7 cal ka bp and that the delta has shifted to a destructive phase during the past seven decades as human influences such as construction of reservoirs dams and weirs in the hills have reduced the sediment supply the birth of the taiwan warm current and following continuous sediment supply from the western rivers of taiwan to the east china sea since 7 3 cal ka bp have played a crucial role in the sedimentation of the east china sea particularly in the okinawa trough and the japan sea through the tsushima warm current