sediment dynamics of an artificially deepened mesotidal coastal lagoon an environmental magnetic investigation of tauranga harbour new zealand abstract tauranga harbour new zealand s largest barrier enclosed coastal lagoon comprises two sub basins with separate catchments inlets and tidal channel systems this study sets out to assess and investigate the sediment dispersal system of tauranga harbour using standard environmental magnetic and sedimentological methods compilations of rock magnetic and grain size data of surficial sediments collected from inflowing rivers various estuarine environments estuaries tidal flats and tidal channels and the adjacent nearshore mirror the net and differential sediment fluxes into and through the two sub basins of this lagoon for all studied depositional environments the magnetogranulometric ratios sirm and arm are positively correlated with magnetic mineral content sirm arm in the sense that larger magnetic particles are associated with higher magnetic enrichment grain size analyses show that magnetic enrichment during particle transport and deposition can result from grain size as well as from grain density fractionation the periodically changing accumulation erosion conditions provide for a selective retention of specific grain sizes and an enhancement of the heavier magnetic mineral particles magnetic crystal size and clastic grain size correlate poorly over the whole study area but group within similar depositional environments coarser magnetic and clastic grain sizes and higher magnetite enrichment in the southern sub basin can be reconciled with episodic flood runoff of the wairoa river and a much larger artificially deepened southern tidal inlet which likely enables higher tidal current velocities our approach of combining magnetic and clastic grain size could be successfully implemented to establish a conceptual model of sediment dynamics and gravitational sorting within tauranga harbour

the influence of the layered character of snow cover on the triggering of slab avalanches one of the principal aims of avalanche warning is to prevent slab avalanches triggered by skiers other than explosives the best practical tool for stability evaluation is the rutschblock test whether the slab may be triggered by a skier depends on various slab characteristics important factors seem to be depth of the weak layer slab hardness and sublayering of the slab the stress distribution induced by a skier is calculated by the finite element method for typical snow cover configurations the additional shear stress is of the same order of magnitude as the shear strength of weak layers besides the critical weak layer prerequisite for a slab avalanche hard layers seem to be important the analysis suggests that a shear failure is most probable at the transition from a hard to a soft layer this corresponds well to observations of slab avalanche profiles the results may help to improve and quantify the analysis of snow profiles

a multivariate mixing model for identifying sediment source from magnetic measurements a sequential method for quantitative identification of sediment source components based on magnetic measurements has been developed and tested for sediments from the rhode river maryland simulated mixing tests and multiple regression were employed to establish numerical relationships between source component proportions and the magnetic measurements of mixtures on the basis of these multivariate mixing models source components of three estuarine sediment cores were estimated by linear programming the results strongly support the previous studies on this catchment which indicated a dramatic change in sediment source some 150 to 200 yr ago quantitative calculations are more useful and informative than purely qualitative descriptions

developments in the characterization of complex rock slope deformation and failure using numerical modelling techniques recent advances in the characterization of complex rock slope deformation and failure using numerical techniques have demonstrated significant potential for furthering our understanding of both the mechanisms processes involved and the associated risk this paper illustrates how rock slope analyses may be undertaken using three levels of sophistication level i analyses include the conventional application of kinematic and limit equilibrium techniques with modifications to include probabilistic techniques coupling of groundwater simulations and simplistic treatment of intact fracture and plastic yield such analyses are primarily suited to simple translational failures involving release on smooth basal rear and lateral surfaces where the principle active damage mechanisms are progressive failure and or asperity breakdown level ii analyses involve the use of continuum and discontinuum numerical methods in addition to simple translation level ii techniques can be applied to complex translational rock slope deformations where step path failure necessitates degradation and failure of intact rock bridges along basal rear and lateral release surfaces active damage processes in this case comprise not only strength degradation along the release surface e g asperity breakdown but also a significant component of brittle intact rock fracture level iii analyses involve the use of hybrid continuum discontinuum codes with fracture simulation capabilities these codes are applicable to a wide spectrum of rock slope failure modes but are particularly well suited to complex translation rotational instabilities where failure requires internal yielding brittle fracturing and shearing in addition to strength degradation along release surfaces through a series of rock slope analyses the application of varied numerical methods are discussed particular emphasis is given to state of the art developments and potential use of level iii hybrid techniques d 2005 elsevier b v all rights reserved

landslides induced by the wenchuan earthquake and the subsequent strong rainfall event a case study in the beichuan area of china abstract the wenchuan earthquake on may 12 2008 triggered massive landslides and a subsequent strong rainfall prompted the development of new landslides as well as the reactivation of some pre existing landslides the highest seismic intensity zone of the wenchuan earthquake in beichuan china was selected as a case study to analyze the influence of the earthquake and the subsequent heavy rains on landslide evolution we selected this study area 414 km 2 since it was close to the coseismic surface rupture and because it suffered strong ground motion based on the interpretation of high resolution aerial photographs and remote sensing imagery combined with field investigation 40 pre earthquake landslides and 2221 coseismic landslides were identified with total landslide areas of 2 68 km 2 and 30 81 km 2 respectively there were 134 large over 50 000 m 2 co seismic landslides that covered a surface area of 15 54 km 2 and represented approximately 50 4 of the total area of the co seismic landslides the coseismic landslides were mainly located on the hanging wall of the causative fault and on the steep valley sides of the jian river and its tributaries a strong rainfall event occurred four months after the wenchuan earthquake and induced 969 new landslides which covered a 6 90 km 2 area and enlarged 169 existing landslides 2 48 km 2 the landslides were identified in spot5 images ultimately we found that earthquake tremors and the subsequent rainstorm severely disturbed the surface strata resulting in a large number of landslides

a novel dynamic impact pressure model of debris flows and its application on reliability analysis of the rock mass surrounding tunnels abstract assessing the influence of the impact pressure exerted on surrounding rock mass by potential debris flows is one of the challenges in a mountain tunnel construction project this paper proposes an effective mathematical model for the assessment of impact pressure exerted by debris flows on obstacles the characteristics of the new model are analyzed and the parameters determination method for the new model are deduced also a new method for dynamic reliability analysis of the rock mass surrounding tunnels is proposed and is constituted into three key steps first by inputting impact pressure of debris flows generated by the aforementioned new model the flac3d is used as the dynamic analysis engine to obtain the time varying stress distribution of surrounding rock mass during the impact of debris flow second the factor of safety fos contours of surrounding rock mass are generated based on element states using the maximum tensile stress criterion and the mohr coulomb yield criterion third by using the time varying contours of the fos a failure probability and a reliability index are obtained from a reliability perspective a case study shows the complete analysis process and confirms the effectiveness of the above methodology in sum this paper provides new ideas new methods and a reference example for evaluating the influence of dynamic impact exerted by debris flows on the rock mass surrounding tunnels

impact of chi chi earthquake on the occurrence of landslides and debris flows example from the chenyulan river watershed nantou taiwan abstract the chenyulan river watershed in central taiwan was chosen for evaluating the impact of the chi chi earthquake on the occurrence of landslides and for exploring the initial conditions triggering debris flows interpretations of aerial photographs and spot images as well as field investigations were used to identify landslide and debris flow occurrences precipitation data were then utilized to investigate critical conditions leading to the debris flow comparison of five spot images taken between june 1996 before the july 1996 typhoon herb and september 1999 before the chi chi earthquake shows that the landslide area increased from 7 1 106 to 7 5 106 m2 during that time however by january 2000 after the chi chi earthquake the landslide area almost tripled to 20 8 106 m2 measurement of images taken in march and august 2001 reveals that the landslide area had further expanded to 24 2 106 and 27 5 106 m2 respectively significant differences before and after the earthquake are also noticed in 1 the intensity and amount of precipitation required for triggering debris flow 2 the size of contributing drainage basin in which debris flows occurred and 3 the frequency of debris flows after the chi chi earthquake maximum hourly rainfall intensity and critical accumulated precipitation necessary to initiate debris flow reduced to as low as 1 3 of the pre earthquake figures prior to the chi chi earthquake most debris flows occurred in gullies with slopes greater than 10 and in drainage basins larger than 0 1 km2 conversely after the earthquake debris flows were observed even in gullies with effective drainage area smaller than 0 03 km2 furthermore before the earthquake the debris flow recurrence time in the study area was greater than 5 years whereas six debris flow events have been observed in the 2 years since the earthquake

sediment sources and transport pathways in a rural catchment herefordshire uk the relative significance of primary and secondary suspended sediment sources has been identified in a small 15 km2 agricultural catchment through the application of a linear unmixing model using mineral magnetic geochemical and radionuclide signatures of fine sediments roads appear to be important as a secondary source of suspended sediment and in the conveyance of topsoils to the river channel roads also alter the source signatures of sediment in transport especially that derived from agricultural topsoils modelling suggests that c 30 of the suspended sediment collected from suspended sediment traps in the river leadon were derived from or transported via roads relative contributions from primary sources of c 43 and c 27 were estimated from a combined subsoil and channel bank subsurface source and a combined arable and grassland topsoil source respectively

prolonged impact of earthquake induced landslides on sediment yield in a mountain watershed the tanzawa region japan abstract to determine for how long a landslide affects sediment discharge the sediment yields of 15 check dam basins were compared with the time series of landslide distributions in a mountain basin in the tanzawa region central japan the distribution of sediment yield was quantitatively estimated from deposition in the sediment pools of check dams the relationship between the landslide history and sediment discharge in the nakagawa river basin was examined for an approximately 80 year period two major landslide events occurred during this period the 1923 kanto earthquake and the 1972 disaster caused by heavy rainfall the resulting trend in sediment discharge of the whole basin estimated using reservoir sedimentation in the miho dam at its base was nearly constant with high sediment discharge 2897 m 3 km 2 yr 1 in the intervening quarter century despite the recovery of vegetation on landslide areas in this period comparisons of the landslide distributions resulting from the two disasters the sediment yields of check dam basins and the sediment discharge of the whole basin indicate that recent sediment discharge contains landslide debris that was originated by the kanto earthquake that occurred over 80 years ago thus to understand high sediment discharge it is essential to investigate not only the current basin condition and recent events but also the landslide history of the basin for at least the previous 100 years

heavy metal monitoring of beach sands through environmental magnetism technique a case study from vengurla and aravali beaches of sindhudurg district maharashtra india mineral magnetic geochemical and statistical analyses were carried on surface sediments collected from vengurla and aravali beach along west coast of india premonsoon prem monsoon m and postmonsoon pm magnetic concentration parameters lf arm sirm and hirm are strongly correlated within them prem during m and pm thermomagnetic analysis identifies titanomagnetite magnetite maghemite and hematite as the dominant magnetic mineralogy of the sediments strong correlation was deciphered between magnetic parameters and heavy metal cu cr zn and ni prem and pm which obliterated in m this shows influx of magnetic minerals and heavy metals is more in m than prem and pm the monsoonal influx is more haphazard and random in m because of enhanced weathering resulting in weak correlation between different mineralogical and geochemical entities this finding outlines the efficacy of simple rapid and non destructive magnetic measurement which can be used as an indicator for heavy metal contamination it can act as a proxy for measuring of heavy metal content in the coastal and beach environment

sediment sorting and beach erosion along a coastal foreland magnetic measurements in point pelee national park ontario canada abstract in situ and laboratory based magnetic measurements were made on sand samples from the beach on the eastern side of point pelee national park ppnp in northwestern lake erie in order to examine both the composition and spatial distribution of magnetic minerals magnetic remanence measurements on bulk and particle size fractions showed that the magnetic properties were dominated by multidomain ferrimagnetic grains probably magnetite and or maghemite particle size specific measurements on different grain size fractions showed that the

spatial distribution analysis of landslides triggered by 2008 5 12 wenchuan earthquake china abstract the 2008 5 12 wenchuan earthquake seismic magnitude mw 7 9 according to the usgs triggered a great number of landslides a spatial database of landslides is built by interpreting the remote sensing rs data which covers 11 counties severely damaged by the earthquake with area of about 31 686 12 km2 the geological settings of the study area are detailed mapped including geologic structure and lithology the digital elevation model dem of the study area with resolution of 30 m 30 m is presented to address the topographic characteristics correlations between the occurrence of landslides with geological settings i e active faults the coseismic surface ruptures geological unit slope gradient slope elevation as well as slope aspect are analyzed using spatial modeling in gis with the aids of field investigations it can be concluded that the distance to the causative faults and slope gradient are much more important than other factors landslides are clustered distributed along the causative faults of f2 and f3 and landslides incidence are dramatically decreasing with the increasing of the distance to the causative faults the landslides incidence has an obvious increase near the active faults i e f1 landslide concentration lc landslides km2 has an obvious exponent increase with slope gradient however lc has no obvious relationship with geological unit and slope elevation the difference of lc value in each geological unit each slope elevation category maybe have been the result affected by slope gradient for each geological unit each slope elevation category and distance of each geological unit each slope elevation category to causative fault zone isoseismal map reflects the incidence of landslides in some degree and lc increases dramatically with intensity increasing almost all landslides occurred in the region above vi degree statistics result also indicates that in the near field of causative faults landslides tend to have the initial sliding direction similar to the movement of the causative faults and preliminary study shows that landslides incidence varies in different slopes with different structure and consequent slopes and obsequent slopes have a higher landslides incidence than other layered slopes

winter regime of temperature and precipitation as a factor of snow cover distribution and its stratigraphy the investigation of spatial and temporal variability of the snow cover in northern eurasia snow depth density thermal characteristics water equivalent includes large scale fieldwork modelling and analysis of meteorological data of two winters 2004 05 and 2005 06 from 38 weather stations situated in different climatic conditions and physico geographical zones common regularities and features of snow cover variability are revealed for these winters despite their contrasting temperature and precipitation regimes and differences from an average winter as the time of appearance duration and depth of snow cover the number of snowfalls and date of melting the modelling of snow cover stratigraphy is based on viscous compression and recrystallization laws meteorological information temperature wind velocity and precipitation is used as input for the model the output is the specific snow cover stratigraphy according to positioning in different physical geographical regions and due to the possible variation as determined by winter temperature and precipitation regimes the peculiarity of snow cover stratigraphy at the regional scale depends on the meteorological conditions of its formation as well as on the character of landscapes a satisfactory correlation of the modelled typical columns of the snow cover formed in 2004 05 and 2005 06 in different regions of russia and of real columns is revealed

spatial characteristics of avalanche activity in an alpine valley a gis approach a dataset of daily avalanche activity observed consistently or 14 years in the surroundings ofzuoz in the engadine valley eastern swiss alps is analyzed all medium sized and larger avalanches had been mapped by the local snow and avalanche observer they were digitized into a geographic information system gis and linked to the daily snow and avalanche observations thus the avala nche activity and its spatial distribution could be analyzed and yisualized a classification for avalanche size and a a lanche activity is proposed in 52 of the potential starting zones an avalanche is released at least once in 14 years the avalanche area decreases strongly with the frequency of ava lanche occurrence preliminary analysis of the relation of daily avalanche activity to weather snow and snow cover reyealed a wide variety of contributory factors even for large amounts of new snow snow cover conditions prior to snowfall or temperature evo lution might decide the extent of the aval anche activ ity for six examples the avalanche hazard five degree european scale is visualized by means of avalanche activity the gis approach will be followed to build a tool for local avalanche forecasting in zuoz

the use of mineral magnetic analyses in the study of glacial diamicts a pilot study mineral magnetic methods of characterising glacial diamicts and their associated sediments are applied to deposits within the manx quaternary sequence the possible advantages of these techniques over more traditional methods of sediment characterisation are outlined and the results obtained in a pilot study are examined results show that both distinctions and similarities exist within the magnetic mineral assemblages of the four diamict units studied the possible implications of these results for interpreting the late quaternary history of the isle of man and the future potential of the techniques are briefly discussed

snowpack characteristics associated with avalanche accidents reports of 93 fatal avalanche accidents in canada between 1972 and 1991 indicate that most of them involved dry snow slabs and were triggered by people slab thicknesses averaged 0 86 m and over half the slabs included snow deposited prior to the most recent storm two persistent microstructures of snow namely surface hoar and faceted grains were commonly reported in the weak layers believed to have released the overlying slabs the people that had difficulty recognizing or evaluating instabilities involving surface hoar and faceted grains include amateur recreationists as well as professional forecasters and guides this suggests that present field tests and forecasting techniques may be unsatis factory for assessing the stability of slabs which overlie layers of surface hoar or faceted grains key words avalanche accident avalanche forecasting critical weak layer slab avalanche snowpack microstructure avalanche trigger

modelling magnetization data using simplex two new approaches to modelling magnetization data are described the first approach models the magnetic properties of natural materials in terms of mixtures of possible source materials the second approach models the magnetic properties of natural materials in terms of mixtures of magnetite and haematite crystals of varying concentrations and grain sizes in the second approach the magnetic characteristics of magnetite and haematite and their variation with grain size are described by bicubic spline functions the methods are applied to remanence and susceptibility measurements on a suite of lake sediment particle size fractions and on a set of samples from a soil profile

a computer based system simulating snowpack structures as a tool for regional avalanche forecasting this paper describes the current state of a complete automatic system of three numerical models that simulate snow cover stratigraphy and avalanche risks for operational avalanche forecasting the first model safran estimates relevant meteorological parameters affecting snowpack evolution the second crocus is a snow numerical model which simulates the physical processes inside the snowpack and its stratigraphy the last model mepra is an expert system based on an assessment of snowpack stability it deduces natural and accidental avalanche risks to describe the great variability of the snowpack and the associated avalanche risks this automatic system simulates snow cover evolution and its stability for many typical slopes elevations and aspects representative of the different french massifs to achieve this result different kinds of validations have been carried out since winter 1981 they are mainly based on comparisons with different sets of measurements and on the opinion of users although the routinely obtained results do not yet take into account all small scale effects such as wind transport they have been considered as valuable information by avalanche forecasters since 1992 93 and used operationally since then

the zymoetz river rock avalanche june 2002 british columbia canada abstract on june 8 2002 the pacific northern gas pipeline in the zymoetz river valley was severed by a large debris flow the event initiated as a rock avalanche in glen falls creek a tributary of the zymoetz river the rock avalanche involved 1 106 m3 of volcaniclastic bedrock and travelled through a complex flow path to finally deposit a large fan in the main zymoetz river approximately half of the debris volume was deposited in the cirque basin at the head of the valley with the rest deposited in the channel and the fan examination of the initiation zone showed a very persistent slightly curved joint set that forms the main sliding surface for the failed block with a dip of 45 and dip direction of 300 a geographic information system gis was used to examine the event and allowed for further interpretation of field data preliminary dynamic analysis indicates that the event reached velocities of up to 34 m s comparison of the zymoetz river rock avalanche zrra with other similar events from the literature indicates that it exhibited similar mobility and velocities as evidenced from the literature these long runout events can cause significant damage and have the potential to be a very high risk as forestry and recreation activities spread further into remote areas

magnetic mineral transport and sorting in the swash zone northern lake erie canada a combined field and laboratory study in northern lake erie has provided new insights into the origin and dynamics of heavy mineral placer deposits on beaches consisting primarily of non magnetic sediment work was conducted on the cross shore and longshore transport of heavy magnetic minerals using magnetic susceptibility and fluorescent paints to trace the movement in the field of samples of magnetic magnetite and non magnetic quartz and calcite grains respectively laboratory experiments examined how the burial of small dense magnetic minerals is affected by the grain size of the non magnetic host material and how grain burial affects magnetic susceptibility measurements at the surface the field experiments demonstrated that the magnetic mineral tracers were buried rapidly beneath coarser non magnetic grains under low to moderate wave conditions and subsequently were unable to move in the longshore or cross shore directions the laboratory experiments showed that the magnetic susceptibility rapidly decreased with the rate and depth of burial of the magnetic minerals and that magnetic grain burial was most effective beneath coarser rather than finer non magnetic sand and for the latter sediments under less rather than more energetic conditions the results imply that magnetic mineral concentrations develop in this area through magnetic grain burial under fairly mild conditions and subsequent settling exposure and concentration in the upper swash zone during more energetic periods when the non magnetic grains are eroded it is probably during these erosional periods when the magnetic minerals are exposed in fairly homogeneous deposits that longshore and cross shore transport takes place

debris flow runout predictions based on the average channel slope acs prediction of the runout distance of a debris flow is an important element in the delineation of potentially hazardous areas on alluvial fans and for the siting of mitigation structures existing runout estimation methods rely on input parameters that are often difficult to estimate including volume velocity and frictional factors in order to provide a simple method for preliminary estimates of debris flow runout distances we developed a model that provides runout predictions based on the average channel slope acs model for non volcanic debris flows that emanate from confined channels and deposit on well defined alluvial fans this model was developed from 20 debris flow events in the western united states and british columbia based on a runout estimation method developed for snow avalanches this model predicts debris flow runout as an angle of reach from a fixed point in the drainage channel to the end of the runout zone the best fixed point was found to be the mid point elevation of the drainage channel measured from the apex of the alluvial fan to the top of the drainage basin predicted runout lengths were more consistent than those obtained from existing angle of reach estimation methods results of the model compared well with those of laboratory flume tests performed using the same range of channel slopes the robustness of this model was tested by applying it to three debris flow events not used in its development predicted runout ranged from 82 to 131 of the actual runout for these three events prediction interval multipliers were also developed so that the user may calculate predicted runout within specified confidence limits

a high resolution late holocene palaeo environmental record from the central adriatic sea a multi proxy study of a holocene sediment core rf 93 30 from the western flank of the central adriatic in 77 m of water reveals a sequence of changes in terrestrial vegetation terrigenous sediment input and benthic fauna as well as evidence for variations in sea surface temperature spanning most of the last 7000 yr the chronology of sedimentation is based on several lines of evidence including ams 14c dates of foraminifera extracted from the core palaeomagnetic secular variation pollen indicators and dated tephra the temporal resolution increases towards the surface and for some of the properties measured is sub decadal for the last few centuries the main changes recorded in vegetation sedimentation and benthic foraminiferal assemblages appear to be directly related to human activity in the sediment source area which includes the po valley and the eastern flanks of the central and northern appenines the most striking episodes of deforestation and expanding human impact begin around 3600 bp late bronze age and 700 bp medieval and each leads to an acceleration in mass sedimentation and an increase in the proportion of terrigenous material reflecting the response of surface processes to widespread forest clearance and cultivation although human impact appears to be the proximal cause of these changes climatic effects may also have been important during these periods signs of stress are detectable in the benthic foram morphotype assemblages between these two periods of increased terrigeneous sedimentation there is smaller peak in sedimentation rate around 2400bp which is not associated with evidence for deforestation shifts in the balance between terrigenous and authigenic sedimentation or changes in benthic foraminifera the mineral magnetic record provides a sensitive indicator of changing sediment sources during forested periods of reduced terrigenous input it is dominated by authigenic bacterial magnetite whereas during periods of increased erosion anti ferromagetic minerals haematite and or goethite become more important as well as both paramagnetic minerals and super paramagnetic magnetite analysis of the alkenone u37k record provides an indication of possible changes in sea surface temperature during the period but it is premature to place too much reliance on these inferred changes until the indirect effects of past changes in the depth of the halocline and in circulation have been more fully evaluated the combination of methods used and the results obtained illustrate the potential value of such high resolution near shore marine sedimentary sequences for recording wide scale human impact documenting the effects of this on marine sedimentation and fauna and potentially disentangling evidence for human activities from that for past changes in climate

intensity duration threshold of rainfall triggered debris flows in the wenchuan earthquake affected area china the ms 8 0 wenchuan earthquake has greatly altered the rainfall threshold for debris flows in the affected areas this study explores the local intensity duration i d relationship based on 252 post earthquake debris flows it was found that i 525 d 0 76 accounts for more than 98 of the debris flow occurrences with rainfall duration between 1 and 135 h therefore the curve defines the threshold for debris flows in the study area this gives much lower thresholds than those proposed by the previous studies suggesting that the earthquake has greatly decreased the thresholds in the past years moreover the rainfall thresholds appear to increase annually in the period of 2008 2013 and present a logarithmic increasing tendency indicating that the thresholds will recover in the future decades c 2015 elsevier b v all rights reserved

rainfall induced debris flows in pyroclastic deposits campania southern italy abstract a combination of empirical and physically based hydrological models has been used to analyze historical data on rainfall and debris flow occurrence in western campania to examine the correlation between rainfall and debris flow events rainfall data from major storms recorded in recent decades in western campania were compiled including daily series from several rain gauges located inside landslide areas supplemented by hourly rainfall data from some of the principal storms a two phase approach is proposed during phase 1 soil moisture levels have been modelled as the hydrological balance between precipitation and evapotranspiration on a daily scale using the method of thornthwaite geograph rev 38 1948 55 phase 2 is related to the accumulation of surplus moisture from intense rainfall leading to the development of positive pore pressures these interactions take place on an hourly time scale by the leaky barrel lb model described by wilson and wiezoreck env eng geoscience 1 1995 11 in combination with hourly rainfall records the lb model has been used to compare hydrological effects of different storms the critical level of retained rain water has been fixed by the timing of debris flow activity related to recorded storm events new rainfall intensity duration thresholds for debris flow initiation in western campania are proposed these thresholds are related to individual rain gauge and assume a previously satisfied field capacity condition the new thresholds are somewhat higher than those plotted by previous authors but are thought to be more accurate and thus need less conservatism

impacts of the chi chi earthquake on subsequent rainfall induced landslides in central taiwan abstract the influence of the chi chi earthquake on subsequent rainfall induced landslides was evaluated by comparing the occurrence of landslides in the choushui river watershed through eight spot images that covered the period from 1996 to 2001 the chi chi earthquake not only triggered serious coseismic landslides itself but also extensively disturbed surface strata around the epicentral area after surface strata have been highly disturbed heavy rainfalls in 2000 and 2001 have triggered more landslides than the earthquake itself compared with the data obtained from images before the earthquake it is obvious that the density of rainfall induced landslides increased significantly after the earthquake and the places where landslides occurred changed as well although typhoon herb in 1996 brought more precipitation than typhoon toraji in 2001 only 9 77 km 2 landslides were induced by herb while 48 8 km 2 landslides almost five times larger than those caused by herb were triggered by toraji besides landslides induced by herb were mainly distributed in mid slope areas with slopes of 20 30 after the chi chi earthquake the rainfall induced landslides occurred mainly in places with slopes between 40 and 50

formation of magnetite enriched zones in and offshore of a mesotidal estuarine lagoon an environmental magnetic study of tauranga harbour and bay of plenty new zealand 1 magnetic iron minerals are widespread and indicative sediment constituents in estuarine coastal and shelf systems we combine environmental magnetic sedimentological and numerical methods to identify magnetite enriched placer like zones in a complex coastal system and delineate their formation mechanisms magnetic susceptibility and remanence measurements on 245 surficial sediment samples collected in and around tauranga harbour the largest barrier enclosed tidal estuary of new zealand reveal several discrete enrichment zones controlled by local hydrodynamic conditions active magnetite enrichment takes place in tidal channels which feed into two coast parallel nearshore magnetite enriched belts centered at water depths of 6 10 m and 10 20 m a close correlation between magnetite content and magnetic grain size was found where higher susceptibility values are associated within coarser magnetic crystal sizes two key mechanisms for magnetite enrichment are identified first tide induced residual currents primarily enable magnetite enrichment within the estuarine channel network a coast parallel fine sand magnetite enrichment belt in water depths of less than 10 m along the barrier island has a strong decrease in magnetite content away from the southern tidal inlet and is apparently related to active coast parallel transport combined with mobilizing surf zone processes a second less pronounced but more uniform magnetite enrichment belt at 10 20 m water depth is composed of non mobile medium coarse grained relict sands which have been reworked during post glacial sea level transgression we demonstrate the potential of magnetic methods to reveal and differentiate coastal magnetite enrichment patterns and investigate their formative mechanisms

snow avalanche formation 1 snow avalanches are a major natural hazard endangering human life and infrastructure in mountainous areas throughout the world in many countries with seasonally snow covered mountains avalanche forecasting services reliably warn the public by issuing occurrence probabilities for a certain region however at present a single avalanche event cannot be predicted in time and space much about the release process remains unknown mainly because of the highly variable layered character of the snowpack a highly porous material that exists close to its melting point the complex interaction between terrain snowpack and meteorological conditions leading to avalanche release is commonly described as avalanche formation it is relevant to hazard mapping and essential to short term forecasting which involves weighting many contributory factors alternatively the release process can be studied and modeled this approach relies heavily on snow mechanics and snow properties including texture while the effect of meteorological conditions or changes on the deformational behavior of snow is known in qualitative or semiquantitative manner the knowledge of the quantitative relation between snow texture and mechanical properties is limited but promising developments are under way fracture mechanical models have been applied to explain the fracture propagation and micromechanical models including the two competing processes damage and sintering have been applied to explain snow failure there are knowledge gaps between the sequence of processes that lead to the release of the snow slab snow deformation and failure damage accumulation fracture initiation and fracture propagation simultaneously the spatial variability that affects damage fracture initiation and fracture propagation has to be considered this review focuses on dry snow slab avalanches and shows that dealing with a highly porous media close to its melting point and processes covering several orders of scale from the size of a bond between snow grains to the size of a mountain slope will continue to be very challenging

high position debris flow a long term active geohazard after the wenchuan earthquake after the 12 may 2008 wenchuan earthquake in sichuan a special type of long term active compounded geohazard namely high position debris flow frequently occurred in the seismic area 136 high position debris flow gullies were recognized from the 796 active debris flow gullies to investigate distinctive characteristics of such debris flows in terms of their geomorphological conditions spatial distribution and causal factors they usually initiate at high steep slopes and have high mobility and long runout high position debris flows have significantly larger magnitude and destructive force than those of common debris flows observed in the regions not affected by recent large earthquake the high position debris flows have been recognized as the most threatening geohazards among post earthquake geological disasters in the wenchuan earthquake region detailed investigation on 45 debris flows suggests three quantitative indices for recognizing the high position debris flows i the height difference between the material source and the debris flow exit or gully mouth should be larger than 350 m ii the volume of source debris accumulation should be bigger than 1 0 x 10 6 m 3 and iii the gradient ratio of a debris flow channel should be steeper than 270 parts per thousand the spatial distribution of high position debris flows was highly controlled by the seismogenic fault due to the abundant loose materials caused by earthquake the rainfall threshold triggering high position debris flows was found to have decreased at least 36 4 63 7 when compared to the pre earthquake one three disaster forming models have been identified for the high position debris flows in the wenchuan earthquake region the long term post earthquake effect of high position debris flow is becoming more concerned in the area of high intensity the characteristics of long term activity of high position debris flows using a case study indicate a 15 years of extremely active period after a strong earthquake such as the wenchuan one a number of issues regarding the classification investigation runout prediction and controlling measures for high position debris flow are discussed to provide insight into the foundation for high position debris flow mitigation and its risk assessment c 2014 elsevier b v all rights reserved

rotational translational landslides in the neogene basins at the northeast margin of the tibetan plateau abstract rotational translational landslides are common in neogene basins throughout the world and are of high risk to the public to understand the mechanism of rotational translational failure the spatial distribution and deformation of rotational translational landslides in the northeast of the tibetan plateau are investigated in this study the spatial distribution of these landslides is dependent on the regional tectonics and geomorphology crustal stresses and lithological properties the rotational translational landslides are concentrated in the neogene mudstone basins and the intensities of these landslides are observed to gradually decrease from the hinterland of the plateau to the marginal basins the bedding parallel shear zones within the location of the rotational translational landslides are present in the overconsolidated neogene mudstones with high clay content nearly horizontal tectonic stresses and erosion cause the formation of horizontal shear stresses in the sliding masses in this stress environment materials with low internal friction angle

the thermal conductivity of seasonal snow twenty seven studies on the thermal conductivity of snow k eff have been published since 1886 combined they comprise 354 values of k eff and have been used to derive over 13 regression equation and predicting k eff vs density due to large and largely undocumented differences in measurement methods and accuracy sample temperature and snow type it is not possible to know what part of the variability in this data set is the result of snow microstructure we present a new data set containing 488 measurements for which the temperature type and measurement accuracy are known a quadratic equation where is in g cm 3 and k eff is in w m 1 k 1 can be fit to the new data r 2 0 79 a logarithmic expression can also be used the first regression is better when estimating values beyond the limits of the data the second when estimating values for low density snow within the data set snow types resulting from kinetic growth show density independent behavior rounded grain and wind blown snow show strong density dependence the new data set has a higher mean value of density but a lower mean value of thermal conductivity than the old set this shift is attributed to differences in snow types and sample temperatures in the sets using both data sets we show that there are well defined limits to the geometric configurations that natural seasonal snow can take

mass wasting triggered by the 2008 wenchuan earthquake is greater than orogenic growth shallow earthquakes lead to the uplift of mountain ranges but also trigger landslides that remove mass an analysis of the 2008 wenshuan earthquake suggests that more material was removed from the orogen by widespread landslides than was added by coseismic uplift

effects of strong ground motion on the susceptibility of gully type debris flows abstract typhoon herb in 1996 caused widespread debris flows in central taiwan the 7 3 chi chi earthquake on september 21 1999 which also took place in central taiwan induced many landslides in the region these landslides turned into debris flows when typhoon toraji struck taiwan in 2001 this research selects three regions which suffered a ground motion class of 5 6 and 7 on the richter scale during the chi chi earthquake as study areas air photos from 1997 and 2001 of these regions are used to map the gully type debris flows that took place after typhoons herb and toraji respectively the gullies adjacent to the debris flow but without a trace of debris flows are also mapped as the non debris flow data the topography hydrogeology and rainfall factors where debris flow occurred and in which there was no occurrence of debris flows in these gullies were retrieved from dtm geological maps and iso countour maps and of rainfall through gis processing these characteristic are introduced into a probabilistic neural network to build a predicting model for the probability of the occurrence of debris flows three series of cross analyses are conducted to compare the probability of the occurrence of debris flows of the same dataset predicted by different prediction models the results reveal that the susceptibility of debris flows was elevated after the chi chi earthquake struck the upsurge of susceptibility was more obvious for the regions that received a higher class of ground motion

an energy and mass model of snow cover suitable for operational avalanche forecasting a numerical model has been developed to simulate energy and mass evolution of snow cover at a given location as a function of meteorological conditions precipitation air temperature humidity wind velocity and incoming short wave and long wave radiation this model named crocus was first tested on a well instrumented field during a whole winter showing its ability to simulate the important phenomena affecting the evolution of the snow layers high temperature gradients wetting compaction and melting freezing cycles a second test was conducted at two locations in the french network used for operational avalanche forecasting though the weather observations are made there only twice daily the snow profiles calculated by the model were very close to those obtained once a week by a pit observation crocus proved itself sufficient to be considered now as a useful objective tool for operational avalanche forecasting

problems associated with quantitative magnetic sourcing of sediments of the scarborough to mablethorpe coast northeast england u k there are many problems associated with beach tracing and sand provenance in coastal studies over short and long timescales here an attempt has been made to trace the source sediments of the beaches along the holderness and humberside coastline of northeast england between scarborough and mablethorpe using rapid field and laboratory magnetic techniques the methodology employed involves classification and modelling of sediment sources and mixtures based on their magnetic properties focus is given to a strong ferrimagnetic black sand heavy mineral which dominates the magnetic signal of the beach mixtures delimiting the spatial extent quantifying and tracing of this mineral may give a good indication of wave energy and sediment movement processes along this coastline this paper represents results obtained during a short time scale survey

frequency of debris flows and their relation with precipitation a case study in the central alps italy abstract debris flows are very important and widespread mass movements and represent a remarkable geomorphological hazard this research deals with debris flows in an alpine environment studied using dendrogeomorphological dating techniques outlining their relation with precipitation and analysing possible changes in their frequency and intensity over time the study area is the upper valle del gallo northern italy a typical high mountain environment dominated by mass wasting processes where many debris flow fans occupy the valley bottom dendrogeomorphological research was conducted on twelve of these fans and two channels located on slopes tree growth anomalies abrasion scars compression wood and abrupt growth changes were used as dating methods two hundred and thirty nine debris debris flow events between 1875 and 2003 were dated using 757 trees pinus montana mill analysis between dated events and precipitation suggests that debris flows in the study area could be triggered by 20 30 mm of rain concentrated in a few hours the debris flow frequency tends to increase gradually but the highest value seems to have occurred in the period 1974 1983 this trend agrees with the historical occurrence of flooding events in northern italy as inferred by literature and with similar studies conducted in the swiss alps the results of this research are intended as a contribution for understanding the response of geomorphological processes to climatic changes

dda validation of the mobility of earthquake induced landslides abstract this paper studies the run out of earthquake induced landslides there are more than 20 mechanical models to explain long run out of rapid landslides including some earthquake induced landslides however notably few of them considered the effect of seismic loading on the run out of landslides in a previous study we have proposed a model which is called the multiplex acceleration model mam to interpret the long run out mechanism and a shaking table test has been performed to verify the mam because the previous mam is a conceptual model and only a single stone has been examined under sine waves by the shaking table test the mam needs to be extended and further verified in this paper the mam was extended by introducing the movement change that was induced by the so called trampoline effect of earthquake loading and the latest practical numerical simulation program discontinuous deformation analysis dda was used to verify the mobility of earthquake induced landslides after a conceptual landslide model was used to verify the effect of seismic loading on the mobility the donghekou landslide which was a typical long run out landslide that was induced by the 2008 wenchuan earthquake was analyzed the results show that the seismic loading could be one of the factors that could eventually help increase the run out of landslides

laboratory experiments on shear failure of snow using a direct simple shear apparatus snow samples 115 mm in diameter 16 18 mm in height taken from a so called homogeneous layer small rounded particles density 290 kg m 3 were tested in a cold laboratory experiments were performed for strain rates between 7 10 6 s 1 and 5 10 3 s 1 at test temperatures of 5 c 10 c and 15 c the effects of strain rate and temperature on failure stress failure strain stiffness initial tangent modulus and toughness were studied the transition between the ductile and brittle sudden fracture state of failure was found to be at about 1 10 3 s 1 for the snow types tested independent of temperature stiffness proved to be the most temperature dependent property of alpine snow it strongly increases with decreasing temperature failure strain and toughness decrease with decreasing temperature failure stress was found to increase slightly with decreasing temperature the effect is not very distinct but close to statistically significant and might be partly hidden by the scatter in the stress data due to variations inherent in sampling and testing

holderness coast erosion and the significance of ords a sample ord a low section of beach characteristic of the holderness coast is examined as it moved southwards between 1977 and 1983 and its significant role in coast erosion is demonstrated the reduction in beach level at the cliff foot by up to 3 9 m enabled most hwn tides to reach it as compared with only some hws tides along the inter ord beach and the volume of till eroded from the cliffs increased by eight times to an annual mean of 72m3m 1 the holderness tills are shown to be composed of 31 per cent sand and coarser sediment which is the sediment range of the beaches where an ord is sited the massive injection of beach sediment goes to form the ord s most prominent constructional feature the lower beach ridge which extends southwards from the centre of the ord analysis of 12 months observer wave data collected at withernsea in 1969 70 indicates that a net southward sand movement of 144 000 m3 occurred comparison of this rate with beach sediment input rates along the whole coast backed by till cliffs suggests a sediment deficit at the northern end and a surplus towards the southern end this conclusion is supported by an overall increase in beach sediment volume southwards from barmston within this longshore sediment transport system the ords migrate southwards from their point of origin in the barmston skipsea area without losing their identity until reaching the tip of spurn head