shear strength estimation for aknes sliding area in western norway abstract this paper deals with the unstable rock slope at aknes sliding area located in the county of more and romsdal in western part of norway the sliding body has a complex geometry with several sliding planes at different levels involving unfilled joints gouge material brecciated material as well as bridges of intact rock stability of the rock slope strongly depends on the shear strength of the sliding plane s and this paper discusses the shear strength of the materials present ranging between the strength of intact rock and crushed clay containing gouge material estimation of the in situ shear strength at the aknes sliding area is discussed on the basis of triaxial test results and the barton bandis empirical method triaxial tests have been carried out on samples of gouge material from a potential sliding plane and intact rock specimens while the empirical method has been applied for rock joints in the area comparison and correlation with experimental results found in literature have also been made the resultant shear strength range for the zone of sliding has been found to be in the range of 0 5 1 3 mpa depending on the normal stress and the composition of the sliding zone

role of geological inheritance in australian beach morphodynamics the australian coast contains 10 685 beaches which occupy 49 of the 30 000 km coast and average 1 37 km in length their relatively short length is largely due to the presence of bedrock calcarenite and laterite which form boundaries to many of the beaches as well as occurring as rocks reefs and islands along and off the beaches this geological inheritance plays a major role in australian beach systems determining their length and through wave refraction and attenuation influencing beach location shape type morphodynamics and circulation which in turn influence sediment transport and the backing dune and barrier systems this paper uses a database covering every australian beach to review the role of headlands rocks and reefs on australian beaches major effects are the short average beach length reduction in breaker height resulting in lower energy beach types wave refraction resulting in increased beach curvature the presence of topographic rips on moderate and higher energy beaches and megarips during high wave conditions and the interruption of and or trapping of longshore sand transport leading to beach rotation

rock slope instabilities in sogn and fjordane county norway a detailed structural and geomorphological analysis rock slope failures form a frequent hazard to many populated mountain regions especially in western norway the topographical and meteorological characteristics increase the vulnerability for rock slope failures a major focus for studies in norway is to eciently nd and investigate possible future rock slope failures in order to prevent extensive humanitarian disasters the determination of the critical parameters involved in the development of rock slope failures is crucial in order to optimize hazard recognition in addition a better understanding of the spatial and temporal variability of prehistoric and historic rock slope failures as well as present day rock slope instabilities will optimize monitoring and further research on the susceptibility for future rock slope failures the primary aim of this study is to investigate the spatial and temporal distribution of rock slope instabilities within western norway it is further aimed to determine the controlling parameters on the development of rock slope instabilities within the study region the implemented approaches range from regional scale statistical analyses towards site specic numerical modelling while a focus is set on quantitative analyses within this thesis the main controlling parameters are dened for rockfalls and rock slope instabilities on a regional scale for the entire county of sogn fjordane western norway it is demonstrated that always a combination of several parameters is necessary to destabilize a mountain side rockfalls have the strongest spatial relation to the presence of bare rock as well as landslide deposits the degree of tectonic deformation and the geological lineament density large rock slope instabilities develop preferentially within relatively weak rock units such as phyllites or weathered mac gneisses and at convex slope breaks looking more into detail a strong structural control is conrmed by numerical modelling for the unstable rock slope at stampa susceptibility and hazard are assessed at dierent scales and with dierent measures quantitative rockfall susceptibility is mapped on a regional scale for the entire county of sogn fjordane based on the statistical analysis of a set of controlling factors in addition this statistical susceptibility model is combined with a physically based model restricting the susceptibility map to areas that are steep enough to represent a potential rockfall source this combination allows using road inventories with registered impact points instead of release areas for susceptibility modelling in contrast relative susceptibility and also hazard are assessed locally for single parts of the unstable rock slope at stampa based on morphology and past activity present day annual expectable frequencies for rock slope failures of certain volume classes are determined for the storfjord region in western norway based on magnitude frequency analyses furthermore a semi quantitative hazard estimation is obtained for each potential instability based on a qualitative susceptibility assessment of each instability in this region this phd thesis presents results of the rst attempts of quantitative statistical analyses of dierent inventories covering rock slope instabilities in norway it is shown that susceptibility and hazard can be assessed with dierent measures forming the basis for further decisions regarding risk assessment and mitigation

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

numerical modeling of low frequency wave dynamics over a fringing coral reef abstract low frequency infragravity wave dynamics on a fringing coral reef were investigated using the numerical model xbeach roelvink et al 2009 first the skill of the model was evaluated in one and two dimensions based on its predictions of short waves 0 04 0 2 hz infragravity waves 0 004 0 04 hz and water level measurements tidal and wave setup obtained during a 2009 field study at ningaloo reef in western australia the model calibration was sensitive to friction coefficients for short waves and current infragravity bed friction which were assumed independent in this model study although the one dimensional cross shore model captured the gradients in the dominant hydrodynamic processes at the site a high current ig bed friction coefficient was required this resulted in an overestimation and a phase lag between the observed and predicted wave setup signal in the two dimensional model a lower more realistic current infragravity wave friction coefficient was required to achieve optimum performance due to the presence of significant reef and lagoon mean flows in the model which led to reduced setup across the reef the infragravity waves were found to propagate from the surf zone across the reef in a dominantly cross shore direction towards the shore but with substantial frictional damping the infragravity waves were strongly modulated also over the reef by tidal depth variations primarily due to the variability in frictional dissipation rates when the total water depth over the reef varied two mean wave driven circulation cells were observed in the study area with cross shore flow becoming more alongshore dominated before exiting the system via the two channels in the reef the results reveal that short waves dominated bottom stresses on the forereef and near the reef crest however inside the lagoon infragravity waves become increasingly dominant accounting up to 50 of the combined bottom stresses

numerical analysis of initiation and progressive failure in natural rock slopes the 1991 randa rockslide the 1991 randa rockslide in the swiss alps involved several complex mechanisms relating to geological mechanical and hydrological processes for which no clear trigger can be asserted this paper investigates the concept of progressive failure and the numerical modelling of rock mass strength degradation in natural rock slopes using the randa rockslide as a working example results from continuum i e finite element modelling are presented to illustrate a hypothesis suggesting that initiation of a progressive rock mass degradation process ultimately leading to failure began following deglaciation of the valley below discontinuum distinct element modelling is then applied to investigate the underlying mechanisms contributing to the episodic nature of the rockslide finally the use of a hybrid method that combines both continuum and discontinuum techniques to model fracture propagation are discussed in the context of modelling progressive slide surface development linking initiation and degradation to eventual catastrophic failure

analyses of past and present rock slope instabilities in a fjord valley implications for hazard estimations abstract for quantitative hazard assessment it is necessary to define the magnitude frequency distribution and a temporal model of the landslide frequency this is often complicated for large rock slope failures due to the lack of significant numbers of large rock slope failures in inventories of a given homogeneous region or sparse information about the timing an inventory of 108 rock slope failure deposits within the fjords of the storfjord region including a relative rockslide chronostratigraphy was available for this study the temporal distribution of rock slope failures is characterized by a rapid response with a high frequency of failures directly after deglaciation followed by a lower constant frequency since 9 000 years bp for the entire storfjord region the largest recorded volumes failed directly after deglaciation volumes larger than 5 10 6 m 3 have not been recorded within the last 9 000 years in addition 17 rockslide scars and on the other hand 17 potential rock slope instabilities have been mapped at the northeastern flank of tafjord which is a branch of the storfjord volume frequency relations have been developed for the three inventories from tafjord comprising i fjord deposits ii rockslide scars and iii potential instabilities they result in very similar distributions over the entire volume range all three inventories are underlying the same processes that lead to destabilisation and finally failure additionally the compilation of the three inventories is independent and based on different methodologies the similarity of the volume frequency distributions is thus verifying the different inventories hence the obtained volume frequency relation can be used to assess the rockslide hazard for the study area present day annual expectable frequencies for different volume classes have been assessed based on the obtained volume frequency relation of the fjord deposits for example the average annual frequency for rock slope failures of v 1 10 6 m 3 originating from the northeastern flank of tafjord is 1 1670 based on a lognormal distribution this regional hazard can be used to improve previously existing qualitative susceptibility rankings for potential unstable rock slopes within the tafjord region the resulting probabilities are very low however the uncertainties of all hazard estimates are very high

analyzing complex rock slope deformation at stampa western norway by integrating geomorphology kinematics and numerical modeling abstract the unstable rock slope stampa above the village of flam norway shows signs of both active and postglacial gravitational deformation over an area of 11 km 2 detailed structural field mapping annual differential global navigation satellite system gnss surveys as well as geomorphic analysis of high resolution digital elevation models based on airborne and terrestrial laser scanning indicate that slope deformation is complex and spatially variable numerical modeling was used to investigate the influence of former rockslide activity and to better understand the failure mechanism field observations kinematic analysis and numerical modeling indicate a strong structural control of the unstable area based on the integration of the above analyses we propose that the failure mechanism is dominated by 1 a toppling component 2 subsiding bilinear wedge failure and 3 planar sliding along the foliation at the toe of the unstable slope using differential gnss 18 points were measured annually over a period of up to 6 years two of these points have an average yearly movement of around 10 mm year they are located at the frontal cliff on almost completely detached blocks with volumes smaller than 300 000 m 3 large fractures indicate deep seated gravitational deformation of volumes reaching several 100 million m 3 but the movement rates in these areas are below 2 mm year two different lobes of prehistoric rock slope failures were dated with terrestrial cosmogenic nuclides while the northern lobe gave an average age of 4 300 years bp the southern one resulted in two different ages 2 400 and 12 000 years bp which represent most likely multiple rockfall events this reflects the currently observable deformation style with unstable blocks in the northern part in between joasete and furekamben and no distinct blocks but a high rockfall activity around ramnanosi in the south with a relative susceptibility analysis it is concluded that small collapses of blocks along the frontal cliff will be more frequent larger collapses of free standing blocks along the cliff with volumes 100 000 m 3 thus large enough to reach the fjord cannot be ruled out a larger collapse involving several million m 3 is presently considered of very low likelihood

time dependent modelling of a mountain front retreat due to a fold to fault controlled lateral spreading abstract the eastern betic cordillera spain exemplifies at the sierra de aitana an impressive case of lateral spreading which involves a mountain anticline ridge dislodged by a post orogenic extensional tectonic the deep trenches testify the ongoing gravitational slope deformation featured by a rock mass lateral spreading the sierra de aitana anticline ridge was dislodged along a normal fault zone which generated a scarp with a kilometric lateral continuity the lateral spreading originated because eocene limestone overlays eocene marls inducing a continuous evolution over time due to visco plastic deformations and isolating huge prismatic blocks to quantify the creep driven stress strain effects at sierra de aitana ridge the mechanical and rheological parameter values of the involved rocks were quantified through field and laboratory tests which allowed to constrain an engineering geological model based on equivalent continuum approach a stress strain numerical modelling aimed at back analysing the sequential morpho structural evolution of the sierra de aitana anticline ridge was performed by reproducing the retreat of the ridge front and the time succession of faults re activations a time dependent solution was approached by assuming a time dependent creep configuration of the modelling and a parametric solution adopted to calibrate rock mass rheology also taking into account tectonic displacement due to the aitana normal fault system by simulating these element as interface in the discretized domain influence of pre existing joint sets by assuming a main anisotropy in the elasto plastic failure solution admissible variations of the regional stress field related to compressive and extensional phases and a generalised visco plastic behaviour representing the ductile marls the numerical modelling outputs that the lateral spreading mainly evolved as a creep driven process while stress release induced by tectonic activity is not sufficient to justify the observed landforms the obtained results highlight a not negligible role of inherited structural elements for regulating the time evolution of the ongoing gravitational process at the sierra the aitana anticline

extreme erosion on high energy embayed beaches influence of megarips and storm grouping abstract megarips have long been recognised as an important yet poorly documented mechanism of beach erosion on high energy embayed beaches the persistence and cumulative effect of megarips during storm groups are described from three embayed beaches arrifana mt clerigo and amoreira exposed to high energy wave conditions in the mesotidal bedrock dominated southwestern coast of portugal morphological changes determined by topographic monitoring and supplemented by interpretation of digital imagery over two years revealed the development of storm induced megarips which exerted a major influence on beach erosion differences in megarip influence within and between beaches are related to embayment geometry and orientation which significantly influence the nearshore wave field rip location is topographically controlled being determined by alongshore variations in breaking wave height and obliquity along with interaction of wave driven circulation patterns and embayment nearshore topography moderate beach sand loss during individual storms was linked to the development of megarips with associated rip neck and feeder channels extreme erosion however occurred when megarips and feeder channels persisted during successive storms promoting continued erosion and seaward sediment export observations show that once initiated megarip channels persist for several months and continue to act as conduits for offshore sediment transport under non storm conditions the maintenance of such rip circulation systems driven by morphodynamic feedback reduces beach recovery ability until the rip neck and feeder channels are infilled

structural constraints on deep seated slope deformation kinematics abstract a significant sackung type deep seated slope gravitational deformation dsgsd was recognised for the first time by the authors in the middle part of valfurva east of bormio rhaetian alps italy the reconstruction of its kinematics age and state of activity is presented through a detailed description of its morphological geomechanical and structural features an integrated multi disciplinary approach was performed to achieve a clear comprehension of the phenomenon field surveys and aero photo interpretation were carried out in order to clarify the structural geological and geomorphological setting in which the dsgsd developed a kinematic conceptual model of the slope deformation was developed through the analysis of morpho structures of their significance and relationships with lithological markers and quaternary deposits after a geomechanical characterisation of the rock mass involved in the slope deformation numerical modelling was performed to verify the hypotheses made on kinematics and driving factors of the phenomenon the sackung affects pre permian metapelites metabasites and marbles belonging to the upper austroalpine basement of the campo nappe as well as late pleistocene and holocene glacial and rock glacier deposits the deformation started after the late wurmian age 15 000 11 000 years b p and continued until few centuries ago not excluding a present day low rate activity deformation consists in a large oblique sagging along a deep confined sliding surface associated with gravitational reactivation of pre existing late alpine and recent tectonic brittle structures leading to the formation of n s and wnw ese trending gravitational morpho structures the evolution of the wnw ese trending system resulting in asymmetric trenches led to progressive failure of the lower part of the slope during the last 10 000 years as testified by large paleo landslide accumulations and it is still in progress numerical modelling indicates post glacial unloading as the main triggering factor of the slope deformation the importance of this deep seated slope deformation is enhanced by the occurrence of the 30 mm 3 active ruinon landslide in the lower part of the slope such landslide is subjected to rapid evolution and threatens the valley floor establishing an important risk factor connected to human lives and socio economic activities

geological model of the aknes rockslide western norway abstract aknes is known as the most hazardous rockslide area in norway at present and is among the most investigated rockslides in the world representing an exceptional natural laboratory this study focuses on structural geology and the usage of geophysical methods to interpret and understand the structural geometry of the rockslide area the interpretations are further used to build a geological model of the site this is a large rockslide with an estimated volume of 35 40 million m 3 derron et al 2005 defined by a back scarp a basal shear zone at about 50 m depth and an interpreted toe zone where the sliding surface daylights the surface the rockslide is divided into four sub domains experiencing extension in the upper part and compression in the lower part structural mapping of the area indicates that the foliation of the gneiss plays an important role in the development of this rockslide the upper boundary zone of the rockslide is seen as a back scarp that is controlled by and parallel to the pre existing steep foliation planes where the foliation is not favourably orientated in regard to the extensional trend the back scarp follows a pre existing fracture set or forms a relay structure the foliation in the lower part dipping 30 to 35 to s sse seems to control the development of the basal sliding surface with its subordinate low angle trust surfaces which daylights at different levels the sliding surfaces are sub parallel to the topographic slope and are located along mica rich layers in the foliation geophysical surveys using ground penetrating radar gpr refraction seismic and 2d resistivity profiling give a coherent understanding of undulating basal sliding surface in the subsurface the geophysical surveys map the subsurface in great detail to a depth ranging from 30 40 m for gpr to approximately 125 m for refraction seismic and 2d resistivity profiling this gives a good control on the depth and lateral extent of the basal sliding surface and its subordinate low angle thrusts drill cores and borehole logging add important information with regard to geological understanding of the subsurface fracture frequency fault rock occurrences geophysical properties and groundwater conditions both in outcrops and or drill cores constrain the geometrical and kinematic model of aknes rockslide

from deep seated slope deformation to rock avalanche destabilization and transportation models of the sierre landslide switzerland abstract sackung is a widespread post glacial morphological feature affecting alpine mountains and creating characteristic geomorphological expression that can be detected from topography over long time evolution internal deformation can lead to the formation of rapidly moving phenomena such as a rock slide or rock avalanche in this study a detailed description of the sierre rock avalanche sw switzerland is presented this convex shaped postglacial instability is one of the larger rock avalanche in the alps involving more than 1 5 billion m3 with a run out distance of about 14 km and extremely low fahrboschung angle this study presents comprehensive analyses of the structural and geological characteristics leading to the development of the sierre rock avalanche in particular by combining field observations digital elevation model analyses and numerical modelling the strong influence of both ductile and brittle tectonic structures on the failure mechanism and on the failure surface geometry is highlighted the detection of pre failure deformation indicates that the development of the rock avalanche corresponds to the last evolutionary stage of a pre existing deep seated gravitational slope instability these analyses accompanied by the dating and the characterization of rock avalanche deposits allow the proposal of a destabilization model that clarifies the different phases leading to the development of the sierre rock avalanche

adsorption as a methane storage process in natural lake sediment 1 methane stored in a natural lake sediment was investigated fresh sediment 8 25 cm in sediment depth taken from lake biwa japan contains 2 6 mol g d s dry sediment of ch4 on average the sediment retained 0 31 mol g d s of ch4 even after air drying which is 12 of the total ch4 in the fresh sediment the higher the temperature for drying of the sediment the smaller the amount of ch4 retained the result of an adsorption experiment indicated that dried and completely degassed lake sediment adsorbs ch4 clay particles in the sediment are possibly responsible for the adsorption of ch4 methane observed in the fresh lake sediment was probably produced by bacteria in the past then adsorbed on the sediment particles adsorption is another form of storage of ch4 in lake and ocean sediments in addition to the well known forms of dissolved bubble and hydrate ch4

the biogeochemistry of sorbed methane in marine sediments abstract sorption of volatile hydrocarbon gases vhcs to marine sediments is a recognized phenomenon that has been investigated in the context of petroleum exploration however little is known about the biogeochemistry of sorbed methane and higher vhcs in environments that are not influenced by thermogenic processes this study evaluated two different extraction protocols for sorbed vhcs used high pressure equipment to investigate the sorption of methane to pure clay mineral phases and conducted a geochemical and mineralogical survey of sediment samples from different oceanographic settings and geochemical regimes that are not significantly influenced by thermogenic gas extraction of sediments under alkaline conditions yielded higher concentrations of sorbed methane than the established protocol for acidic extraction application of alkaline extraction in the environmental survey revealed the presence of substantial amounts of sorbed methane in 374 out of 411 samples 91 particularly high amounts up to 2 1 mmol kg 1 dry sediment were recovered from methanogenic sediments carbon isotopic compositions of sorbed methane suggested substantial contributions from biogenic sources both in sulfate depleted and sulfate reducing sediments carbon isotopic relationships between sorbed and dissolved methane indicate a coupling of the two pools while our sorption experiments and extraction conditions point to an important role for clay minerals as sorbents mineralogical analyses of marine sediments suggest that variations in mineral composition are not controlling variations in quantities of sorbed methane we conclude that the distribution of sorbed methane in sediments is strongly influenced by in situ production

a review of the geochemistry of methane in natural gas hydrate the largest accumulations on earth of natural gas are in the form of gas hydrate found mainly offshore in outer continental margin sediment and to a lesser extent in polar regions commonly associated with permafrost measurements of hydrocarbon gas compositions and of carbon isotopic compositions of methane from natural gas hydrate samples collected in subaquatic settings from around the world suggest that methane guest molecules in the water clathrate structures are mainly derived by the microbial reduction of co2 from sedimentary organic matter typically these hydrocarbon gases are composed of 99 methane with carbon isotopic compositions 13cpdb ranging from 57 to 73 in only two regions the gulf of mexico and the caspian sea has mainly thermogenic methane been found in gas hydrate there hydrocarbon gases have methane contents ranging from 21 to 97 with 13c values ranging from 29 to 57 at a few locations where the gas hydrate contains a mixture of microbial and thermal methane microbial methane is always dominant continental gas hydrate identified in alaska and russia also has hydrocarbon gases composed of 99 methane with carbon isotopic compositions ranging from 41 to 49 these gas hydrate deposits also contain a mixture of microbial and thermal methane with thermal methane likely to be dominant published by elsevier science ltd

detailed dem analysis of a rockslide scar to characterize the basal sliding surface of active rockslides 1 the basal sliding surfaces in large rockslides are often composed of several surfaces and possess a complex geometry the exact morphology and location in three dimensions of the sliding surface remains generally unknown in spite of extensive field and subsurface investigations such as those at the aknes rockslide western norway this knowledge is crucial for volume estimations failure mechanisms and numerical slope stability modeling this paper focuses on the geomorphologic characterization of the basal sliding surface of a postglacial rockslide scar in the vicinity of aknes this scar displays a stepped basal sliding surface formed by dip slopes of the gneiss foliation linked together by steeply dipping fractures a detailed characterization of the rockslide scar by means of high resolution digital elevation models permits statistical parameters of dip angle spacing persistence and roughness of foliation surfaces and step fractures to be obtained the characteristics are used for stochastic simulations of stepped basal sliding surfaces at the aknes rockslide these findings are compared with previous models based on geophysical investigations this study discusses the investigation of rockslide scars and rock outcrops for a better understanding of potential rockslides this work identifies possible basal sliding surface locations which is a valuable input for volume estimates design and location of monitoring instrumentation and numerical slope stability modeling

dynamics of rip currents associated with groynes field measurements modelling and implications for beach safety abstract rip currents can occur around groynes and other coastal structures e g breakwaters and geological headlands which provide a boundary to the wave induced flow field and present a hazard to water users worldwide shore normal groynes are common along drift aligned coasts in northern europe these are often low energy fetch limited environments that are dominated by locally generated wind waves the presence of boundary controlled rip currents due to groynes is supported anecdotally in literature but few field measurements of their presence and dynamics exist this study provides new quantitative scientific understanding of the dynamics of boundary controlled rip currents within this setting a 10 day field experiment at boscombe beach on the south coast of england measured rip currents and nearshore hydrodynamics around an impermeable groyne field observations from both fixed instruments wave tide and current metres and gps drifters confirmed the presence and characteristics of hazardous topographic rip currents around a groyne structure during a number of oblique wave events and drift reversals the strongest offshore directed rip velocities of up to 1 m s 1 10 min average and 2 m s 1 instantaneous were measured on the updrift side of the groyne where the longshore current generated within the embayment was deflected offshore these strong rip flows were measured under relatively small wave heights hs

structural analysis of turtle mountain alberta using digital elevation model toward a progressive failure abstract in 1903 the eastern slope of turtle mountain alberta was affected by a 30 m m 3 rockslide named frank slide that resulted in more than 70 casualties assuming that the main discontinuity sets including bedding control part of the slope morphology the structural features of turtle mountain were investigated using a digital elevation model dem using new landscape analysis techniques we have identified three main joint and fault sets these results are in agreement with those sets identified through field observations landscape analysis techniques using a dem confirm and refine the most recent geology model of the frank slide the rockslide was initiated along bedding and a fault at the base of the slope and propagated up slope by a regressive process following a surface composed of pre existing discontinuities the dem analysis also permits the identification of important geological structures along the 1903 slide scar based on the so called sloping local base level slbl an estimation was made of the present unstable volumes in the main scar delimited by the cracks and around the south area of the scar south peak the slbl is a method permitting a geometric interpretation of the failure surface based on a dem finally we propose a failure mechanism permitting the progressive failure of the rock mass that considers gentle dipping wedges 30 the prisms or wedges defined by two discontinuity sets permit the creation of a failure surface by progressive failure such structures are more commonly observed in recent rockslides this method is efficient and is recommended as a preliminary analysis prior to field investigation

a reevaluation of coastal embayment rotation the dominance of cross shore versus alongshore sediment transport processes collaroy narrabeen beach southeast australia 1 over 30 years of wave and beach survey data at collaroy narrabeen beach in southeast australia are analyzed to investigate the extent to which shoreline variability within this coastal embayment is dominated by shoreline oscillations due to cross shore sediment exchange or shoreline rotations due to alongshore exchange between the beach s extremities offshore wave data are derived from both buoy measurements and era 40 reanalysis data eof analysis of the monthly shoreline data suggests that the dominant mode of shoreline variability 60 of variability is an onshore offshore sediment exchange that is greater at the more exposed northern end of the beach than at the predominantly sheltered southern end this mode is primarily associated with variability in wave energy storms which by the nature of the wave climate of this region chiefly occurs from the south southeast the secondary mode of shoreline variability 26 of variability is a rotational signal between either end of the beach which coincides with 24 of the offshore wave climate shifting between the south southeast and east as well as changes in the wave period and wave energy storms a distinct annual cycle is identified in this rotation signal it is concluded that alongshore sediment transport processes associated with embayment rotation is more subtle than previously thought and a refined conceptual model of coastal embayment variability in this region is presented highlighting the dominance of cross shore sediment exchange processes

nearshore circulation over transverse bar and rip morphology with oblique wave forcing there is a paucity of field data to describe the transition in nearshore circulation between alongshore meandering and rip current systems a combination of in situ current meters and surf zone drifters are used to characterize the nearshore circulation over a transverse bar and rip morphology at pensacola beach florida in the presence of relatively low energy oblique waves current speeds vary in response to the relative wave height ratio hs h which defines the degree and extent of breaking over the shoal in the absence of wave breaking the nearshore circulation was dominated by an alongshore current driven by the oblique waves as waves begin to break across the shoal 0 2 0 5 the meandering current is replaced by an unsteady rip circulation that moves offshore between the shoals before turning alongshore in the direction of wave advance outside the surf zone the increase in wave dissipation is associated with an increase in very low frequency vlf variations in the current speed across the shoal and in the rip channel that caused the circulation to oscillate between an offshore and an alongshore flow the unsteady nature of the nearshore circulation is responsible for 55 of all surf zone exits under these more dissipative conditions in contrast only 29 of the drifters released from the shoal exited the surf zone and bypassed the adjacent shoal with the alongshore meandering current while the currents had a low velocity maximum of 0 4 m s 1 and would not pose a significant hazard to the average swimmer the results of this study suggest that the transverse bar and rip morphology is sufficient to create an alongshore variation in wave dissipation that forces alongshore meandering and low energy rip circulation systems under oblique wave forcing copyright 2013 john wiley sons ltd

dynamic distinct element analysis of the 800 m high aknes rock slope dynamic analysis of the 800m high aknes rock slope using udec dynamic distinct element analysis of the 800 m high aknes rock slope

why did the 1756 tjellefonna rockslide occur a back analysis of the largest historic rockslide in norway abstract on 22 february 1756 the largest historically recorded rockslide in norway took place at tjelle in the langfjord western norway the rockslide created three displacement waves of up to 50 m in height that caused 32 casualties and destroyed most houses and boats along the shores of the langfjord the trigger and contributing factors leading to the tjellefonna rockslide are largely unknown and even seismic triggering has previously been suggested this study provides a thorough back analysis of the tjellefonna rockslide using detailed geomorphological engineering geological and tectonic field mapping in combination with topographic reconstructions bathymetry analysis volume estimations and numerical slope stability analysis the back scarp and eastern flank of the tjellefonna scar form several tens of meter high rock walls while the basal failure surface and other parts of the scar are covered by rock avalanche debris that extend from the back scarp down to the bottom of the langfjord the rockslide occurred in granodioritic gneisses with variably developed metamorphic foliation that is folded and strike parallel to the fjord two prominent fault zones are present in close proximity to the tjellefonna scar one is steeply se dipping tjelle fault while the other one is sub horizontal to shallow se dipping ritlehamran fault both fault zones are linked to the more trondelag fault complex with one of its branches forming the langfjord lineament and probably also the faults at tjellefonna additionally there are four persistent joint sets that together with the metamorphic foliation and the tjelle fault define the back scarp of the rockslide and give a fracturing of the rock mass corresponding to a geological strength index gsi of 45 55 the gsi decreases significantly to 10 20 in the fault zones which form distinct weakness zones in the rock slope volume estimates based on a reconstruction of the ante rockslide topography range from 9 3 to 10 4 million m 3 which is lower than previous volume estimates 12 15 million m 3 large portions of the failed rock mass remained on land and only approximately 3 9 million m 3 entered the fjord the observed discontinuities in the rock mass at tjellefonna do not allow for a simple kinematic failure mechanism due to the lack of moderately se dipping structures the basal failure surface was most likely not composed of a single structure but of a complex interplay of fault zones metamorphic foliation joints and broken rock bridges numerical slope stability modelling highlights that weak fault zones are essential for the development of the failure surface over a long time this progressive failure was likely aided by low to medium magnitude earthquakes that are frequent in the region numerical slope stability modelling and historical accounts suggest however that heavy long lasting rainfall was the triggering factor for the 1756 tjellefonna rockslide rather than an earthquake

nearshore hydrodynamics at pocket beaches with contrasting wave exposure in southern portugal abstract pocket beaches on rocky coasts with headlands that control hydro sedimentary processes are considered to be constrained sedimentary systems generally with limited sediment inputs pocket beaches face severe changes over time under worst case scenarios these changes can result in the loss of the beach causing waves to directly attack adjacent cliffs studies of nearshore hydrodynamics can help to understand such changes and optimise sediment nourishment procedures the present work contributes to the knowledge of hydrodynamic forcing mechanisms at pocket beaches by providing a comprehensive description of the nearshore circulation at two beaches with contrasting wave exposures two pocket beaches in southern portugal were studied by combining field measurements of waves and currents with numerical models stwave and bouss 2d the aim of this analysis was to evaluate nearshore hydrodynamics under different wave exposure forcing conditions e g variable wave heights directions and different tidal levels the results show that the beach circulation can rapidly shift from longshore to rip dominated depending on changes in both the offshore wave direction and tidal levels waves with higher obliquity for both low and moderate wave energy conditions tend to generate longshore circulation in all considered tidal stages while waves with lower obliquity tend to produce rip flow with higher velocity rip currents during low to intermediate tidal stages the results indicate that the location and intensity of rip currents strongly depend on geomorphological constraints that is the control exerted by shore platforms a larger morphological control is observed at mean sea level because most platforms are submerged exposed during high low tide and therefore exert less control on nearshore circulation

rock topography causes spatial variation in the wave current and beach response to sea breeze activity we hypothesized that beach profiles that are perched on natural rock structures would be better protected from waves and currents than profiles that are not fronted by rock in southwest western australia many beaches such as at yanchep are perched on quaternary limestone yanchep lagoon is fronted by a low crested limestone reef that partially encloses a coastal lagoon the spatial variation of waves and currents around the rock structures were quantified during the sea breeze cycle at locations 1 offshore 2 20 m seaward of the reef 3 inside the lagoon and 4 in the surf zone the spatial variation in the beach profile response was measured at two beach profiles 1 the exposed profile that was not fronted directly seaward by outcropping limestone and 2 the sheltered profile which was fronted seaward by submerged limestone at 2 m water depth and that was near the lagoon exit at the end of the limestone reef the sheltered profile had greater volume changes during the cycle of the sea breeze whilst the exposed profile recovered more by overnight accretion when wind decreased the lagoonal current drove the strong response of the sheltered profile and may have contributed to the lack of overnight recovery of the beach together with the seaward rock formation impeding onshore sediment transport the different direction and speed responses of bottom currents in the surf zone fronting the two profiles reflected the local variation in geology the influence of the jet exiting the lagoon and wave refraction around the reef that was measured with gps drifters and wave ray tracing using xbeach major spatial variation in waves currents and beachface behavior at this perched beach shows the importance of the local geological setting

multi stage structural and kinematic analysis of a retrogressive rock slope instability complex preonzo switzerland abstract large catastrophic rock slope failures are difficult to predict because the underlying mechanisms causing slope accelerations are difficult to study under in situ conditions for slope failures with compound basal rupture planes not only fracture propagation and slip in the basal rupture surface but also within the landslide body control the displacement evolution and time to failure the preonzo instability complex in southern switzerland failed several times since 2002 and offers a unique opportunity to study these mechanisms under in situ conditions the largest failure at preonzo occurred in may 2012 and was conditioned by large slope parallel nne ssw fracture zones which are intersected by ne and sw and e w striking faults creating diverging lateral boundaries whereas in the head scarp region oblique and flexural toppling along pre existing fracture sets is the prevailing mechanism sliding of either planar or wedge type is the preferred kinematic mode facilitated by the new discontinuities developed within the basal rupture surfaces these dominating mechanisms leading to a classical rock slope collapse could only be revealed in retrospect we compare fracture patterns in stable ground tectonic and unloading fractures with new fractures related to rock slope failure observed on basal rupture surfaces and in the head scarp simplified mechanical and kinematic analyses show that old pre existing tectonic fractures cannot accommodate substantial deformations under the in situ stress conditions and propagate connect through curved wing cracks forming at high angles this situation favors the development of new nearly slope parallel fractures which are interpreted as synthetic p shears along localized shear zones fractographic markings on these fractures indicate a continuous and relatively fast formation which presumably has taken place during a period of about 60 years prior to catastrophic failure this detailed description of the multi stage evolution of slope failure at preonzo represents a unique data set for future numerical studies of progressive failure in crystalline rocks

an introductory review on gravitational deformation induced structures fabrics and modeling abstract recent studies have pointed out a similarity between tectonics and slope tectonic induced structures numerous studies have demonstrated that structures and fabrics previously interpreted as of purely geodynamical origin are instead the result of large slope deformation and this led in the past to erroneous interpretations nevertheless their limit seems not clearly defined but it is somehow transitional some studies point out continuity between failures developing at surface with upper crust movements in this contribution the main studies which examine the link between rock structures and slope movements are reviewed the aspects regarding model and scale of observation are discussed together with the role of pre existing weaknesses in the rock mass as slope failures can develop through progressive failure structures and their changes in time and space can be recognized furthermore recognition of the origin of these structures can help in avoiding misinterpretations of regional geology this also suggests the importance of integrating different slope movement classifications based on distribution and pattern of deformation and the application of structural geology techniques a structural geology approach in the landslide community is a tool that can greatly support the hazard quantification and related risks because most of the physical parameters which are used for landslide modeling are derived from geotechnical tests or the emerging geophysical approaches

surf zone flushing on embayed beaches 1 using a numerical model we show that the surf zone of embayed beaches systematically flushes out more floating material simulated using passive tracers than on open beaches with most exits occurring through the headland rips for obliquely incident waves a headland rip acts as a persistent conduit for transporting floating material out of the surf zone and into the inner shelf region wave angle and embayment size determine which headland rip upwave or downwave flushes out more the surf zone material for narrow embayed beaches passive drifters exit the surf zone through the upwave headland rip for wider embayed beaches the longshore current has enough room to develop and is further deflected against the downwave headland where most drifters exit the surf zone our results indicate that wave exposed rugged coasts strongly enhance exchange of floating matter e g pollutants and nutrients at the ocean continent interface

how multiple foliations may control large gravitational phenomena a case study from the cismon valley eastern alps italy abstract the right slope of the high cismon valley trento province italy carved into the poly deformed phyllites of the south alpine basement shows evidence of differential quaternary slope evolution which highly depends on how the slope intersects the inherited structures in the study area the regional schistosity outlines a kilometer scale nnw sse trending fold with close flanks and an axial plane dipping to the ne the structure obliquely intersects the nne ssw trending slope so that the northern part of the slope follows the upper limb of the fold and the southern sector coincides with the lower limb and the hinge the secondary axial plane foliation is typically incipient at the fold flanks and much more pervasive and fan shaped near the hinge zone this foliation as well as the asymmetric polyharmonic secondary folds has significant consequences on rock mass mechanical properties and on mechanisms and timing of the gravitational phenomena developed along the slope in particular the joint compressive strength jcs and the geological strength index gsi obtained on stable outcrops outside the deforming area display a decrease from north to south this points to a progressive deterioration of the rock mass strength which directly reflects the influence of the pre existing fabric the results obtained by the analysis of lidar derived digital elevation model show evidence of two different gravitational movements located in the northern and southern sectors of the slope respectively the northern side is characterized by an ongoing deep seated gravitational slope deformation dsgsd likely triggered by post glacial unloading derived from the retreat of the ice tongue that filled the cismon valley during the last glacial maximum lgm conversely the southern part of the slope is the expression of a fully evolved pre lgm gravitational collapse this heterogeneous behavior of the slope is most likely controlled by the secondary foliation and asymmetric polyharmonic folds the former being of paramount importance for the release of the mobilized mass at the crown area and the latter easing or impeding the downslope movement although it is widely accepted that the regional foliation is the dominant controlling factor of dsgsds on poly deformed and highly foliated metamorphic basement our work suggests that the secondary foliation as well as parasitic folds may also have remarkable effects on slope evolution if favorably oriented and sufficiently pervasive

morphodynamics of structurally controlled headland bay beaches in southeastern brazil a review abstract this paper presents a comprehensive review on the interaction between hydrodynamic processes beach morphology and sedimentology at large scale coastal behaviour along the coastline of santa catarina between laguna and sao francisco island a microtidal east coast swell environment with headland and bay geomorphologies the parabolic bay shape equation has proven to be a convenient and practical tool for studying the stability of the headland bay beaches tombolos and salients in santa catarina the beaches exhibit different patterns of sediment removal as a function of the degree of beach curvature in highly curved beaches there is a well developed shadow zone and a range of morphodynamic conditions from a sheltered low energy beach adjacent to the downdrift headland to a high energy exposed beach on the straight end of the headland bay beach the less curved beaches instead tend to show more uniform behaviour since they are directly exposed to incident waves there is no obvious relationship between average wave height and mean grain size showing the importance of sediment source to characterize the sedimentary distribution patterns in the study area the analysis of beaches showed that beach morphodynamics and sequence profiles for a bay headland coast in a microtidal east coast environment is a function of geological inheritance e g distance between headlands and orientation nearshore and inner shelf morphology coastal plain morphology and sediment source and hydrodynamic factors wave conditions oceanic wave exposure and relative tidal range

transferability of a calibrated numerical model of rock avalanche run out application to 20 rock avalanches on the nuussuaq peninsula west greenland long run out rock avalanches are one of the most hazardous geomorphic processes and risk assessments of the potential threat they pose are often reliant on numerical modelling of their potential run out distance the development of such models requires a thorough understanding of past flow behaviour inferred from deposits emplaced by previous events despite this few records exist of multiple rock avalanches that occurred in conditions sufficiently consistent to develop a set of more generalised and hence transferrable rules we conduct field and imagery based mapping and use numerical modelling to investigate the emplacement of 20 adjacent rock avalanches on the southern flanks of the nuussuaq peninsula west greenland the rock avalanches run out towards the vaigat strait and are sourced from a range of coastal mountains of relatively uniform geology we calibrate a three dimensional continuum dynamic flow code volcflow with data from a modern well constrained event that occurred at paatuut ad 2000 the best fit model assumes a constant retarding stress with a collisional stress coefficient simulating run out to within 0 3 of that observed this calibration was then used to model the emplacement of deposits from five other neighbouring rock avalanches before simulating the general characteristics of a further 14 rock avalanche deposits on simplified topography our findings illustrate that a single calibration of volcflow can account for the observed deposit morphology of a uniquely large collection of rock avalanche deposits emplaced by a series of events spanning a large volume range although the prevailing approach of tuning models to a specific case may be useful for detailed back analysis of that event we show that more generally applied models even using a single pair of rheological parameters can be used to model potential rock avalanches of varied volumes in a region and therefore to assess the risks that they pose

surf zone dynamics simulated by a boussinesq type model part i model description and cross shore motion of regular waves abstract this is the first of three papers on the modelling of various types of surf zone phenomena in this first paper part i the model is presented and its basic features are studied for the case of regular waves the model is based on two dimensional equations of the boussinesq type and it features improved linear dispersion characteristics possibility of wave breaking and a moving boundary at the shoreline the moving shoreline is treated numerically by replacing the solid beach by a permeable beach characterized by an extremely small porosity run up of nonbreaking waves is verified against the analytical solution for nonlinear shallow water waves the inclusion of wave breaking is based on the surface roller concept for spilling breakers using a geometrical determination of the instantaneous roller thickness at each point and modelling the effect of wave breaking by an additional convective momentum term this is a function of the local wave celerity which is determined interactively the model is applied to cross shore motions of regular waves including various types of breaking on plane sloping beaches and over submerged bars model results comprise time series of surface elevations and the spatial variation of phase averaged quantities such as the wave height the crest and trough elevations the mean water level and the depth averaged undertow comparisons with physical experiments are presented the phaseaveraged balance of the individual terms in the momentum and energy equation is determined by time integration and quantities such as the cross sectional roller area the radiation stress the energy flux and the energy dissipation are studied and discussed with reference to conventional phase averaged wave models the companion papers present cross shore motions of breaking irregular waves swash oscillations and surf beats part ii and nearshore circulations induced by breaking of unidirectional and multidirectional waves part iii

new insights into embayed beach rotation the importance of wave exposure and cross shore processes although embayed beach rotation has been viewed and modeled as an alongshore sediment transport process acting on a uniform beach profile recent research suggests a more complex response whereby alongshore variability in cross shore sediment fluxes may be more significant this study utilizes 5 years of fully three dimensional beach surveys at narrabeen collaroy beach se australia to quantify the control of alongshore nonuniform wave exposure and cross shore processes on embayed beach rotation empirical orthogonal function analysis of the alongshore variability in subaerial beach volume width and berm slope confirms that the dominant mode of subaerial beach variability is an onshore offshore sediment exchange that is strongly controlled r 0 8 by the alongshore gradient in breaker wave height and coincides with a uniform flattening steepening of the berm slope a secondary rotation like signal is observed in both the subaerial beach volume width data and significantly the berm slope this inverse flattening steepening of the berm slope between beach extremities is most likely a proxy for differing cross shore processes within the surf zone between the exposed and sheltered ends of the embayment particularly with regards to dissipation of storm wave energy by offshore sandbars and beach recovery following storms analysis of the corresponding wave data reveals two distinct time scales of wave forcing characteristic of short term erosion and longer term recovery processes a new conceptual model is presented of three differing modes of embayed beach rotation with the newly identified beach rotation mode controlled by offshore sandbars considered of particular importance at embayments where headland sheltering of oblique waves is pronounced

internal structure and deformation of an unstable crystalline rock mass above randa switzerland part ii three dimensional deformation patterns the monitoring of slope displacements over time provides the basis for most rockslide early warning systems yet the prediction of catastrophic failure from these records is highly problematic and tenuous especially if the underlying kinematics and instability mechanism are poorly understood an example is the moving slope above the town of randa in the swiss alps this slope is considered typical of those in crystalline rock that lacks a natural highly persistent weakness plane dipping towards the valley that can serve as a through going detachment surface for kinematic release in part i the companion paper to this the findings from a comprehensive geological and geophysical investigation to image the internal structures of the unstable rock mass were presented in this paper we develop a kinematic model that describes the pattern of displacement vectors for the rock mass along these structures both on surface and at depth the displacements were estimated from 5 years of data from an extensive monitoring system which included surface geodetic and crackmeter measurements borehole inclinometer and extensometer measurements up to 120 m depth and microseismicity the results showed that the displacement field is highly heterogeneous internal deformation is accommodated by both shear and opening mode dislocation of faults and fracture zones which dip moderately to steeply into the slope microseismicity is most intense near the front of the scarp where surface translation in large part reflects the toppling of blocks accommodated by slip along the steeper dipping fractures the small displacement rates at the study site of up to 2 cm year coupled with a modest deviation of up to 15 from vertical of the boreholes posed severe problems for the estimation of horizontal displacements from the inclinometer data we describe the error analysis of these data in some detail since it is relevant for similar installations elsewhere conclusions drawn from this work highlight the importance of integrating various types of data in order to better understand the complex block kinematic processes whose evolution governs the long term progressive failure of unstable rock slopes