deriving mechanisms and thresholds for cliff retreat in soft rock cliffs under changing climates rapidly retreating cliffs of the suffolk coast uk abstract understanding changing thresholds and mechanisms for retreat in soft rock cliffs is important under changing climates this can be achieved through combining detailed field observation long term process and morphological monitoring and numerical modelling the cliffs of the suffolk coast southern north sea have exhibited long term 1883 2010 recession rates of 3 5 m a 1 rising to 4 7 m a 1 in the period 1993 2010 annual to biannual ground survey data and the application of gis techniques to digitised records of changing shoreline position from historic maps and aerial photography reveal considerable decadal scale variations in cliff recession within which are nested inter annual fluctuations in rates of retreat archival datasets on significant periods of onshore winds and their interaction with high water levels including the incidence of storm surges and rainstorm events are used to determine thresholds for cliff base erosion and its propagation upwards through the cliff profile in addition the geo slope dynamic coupled hydrology stability model is used to establish thresholds for cliff face failures driven by variations in rainfall inputs retreat mechanisms are complex governed by cliff geology both as a primary control on suction loss and through its interaction with basal marine conditions the study allows a general model of cliff retreat for soft rock cliffs to be put forward whereby a resistant basal platform is overlain by more erodible weakly and moderately cemented sands and gravels in this model the varying balance between marine and terrestrial forcing factors are reflected in low 7 m a 1 modes of cliff retreat

a methodology for the study of the relation between coastal cliff erosion and the mechanical strength of soils and rock masses abstract a methodology is proposed to make approximate estimates of the destructive force of waves at the bottoms of cliffs where no accurate bathymetric data are available by means of correlation between the erosion rate of rocky coasts and the mechanical strength of soils and rock masses the correlation used makes it possible to obtain a linear semi logarithmic expression between the long term average erosion rate from an engineering standpoint of coasts consisting of different lithologies wave energy and the uniaxial compressive strength of soils and rock masses forming the cliffs the uniaxial compressive strength of soils consisting of landslide debris was measured using a pocket penetrometer and the rock mass index rmi method was used for rock masses these methods were chosen after critical analysis of the methodologies currently available the proposed approach was tested in the cilento area of southern italy and in particular along a 6 km stretch of coast typified by rock masses and landslide debris that are particularly susceptible to erosion this coastline is exposed to south westerly waves which in deep water reach significant heights between 1 and 3 m and significant wave periods between 4 and 7 s estimates of the coastal erosion rates were made by studying the variations especially in restricted headland areas occurring over two time spans 30 and 45 years respectively by comparing topographic maps and aerial photographs taken at different times these comparisons give approximate indications of retreats of 15 m over the time span of 30 years average erosion rate of 0 5 m year 1 and of 35 m over the time span of 45 years average erosion rate of ca 0 8 m year 1 these data do have a local significance but clearly show how quick these processes sometimes are lastly the study of a notch incised by wave action on a concrete sea wall built to protect a terrace made it possible to quantify the impact of erosion on concrete it was possible to obtain rmi values through field observations furthermore it was possible to obtain the constants of the hoek and brown failure criterion using rmi on the basis of rmi values the rock masses studied were defined as moderately strong to strong and according to the hoek and brown criterion as poor to fair a semilogarithmic linear relation was found between the strength of landslide debris rock masses and concrete as well as their respective long term erosion consequently a rough estimate of the destructive force of waves ca 24 mpa was calculated this value is given by the product of the mean value of their hydraulic pressure for a non dimensional constant which in turn takes into account the sandy pebbly beach sediment at the foot of the cliffs that acts as an abrasive on the rock mass

sea cliff erosion as a function of beach changes and extreme wave runup during the 1997 1998 el nino abstract over time scales of hundreds to thousands of years the net longshore sand transport direction along the central california coast has been driven to the south by north pacific winter swell in contrast during the el nino winter of 1997 1998 comparisons of before and after airborne lidar surveys showed sand was transported from south to north and accumulated on the south sides of resistant headlands bordering pocket beaches this resulted in significant beach erosion at the south ends of pocket beaches and deposition in the north ends coincident with the south to north redistribution of sand shoreline morphology became prominently cuspate with longshore wavelengths of 400 700 m the width and elevation of beaches were least where maximum shoreline erosion occurred preferentially exposing cliffs to wave attack the resulting erosional hotspots typically were located in the embayments of giant cusps in the southern end of the pocket beaches the observed magnitude of sea cliff retreat which reached 14 m varied with the number of hours that extreme wave runup exceeded certain thresholds representing the protective capacity of the beach during the el nino winter a threshold representing the width of the beach performed better than a threshold representing the elevation of the beach the magnitude of cliff erosion can be scaled using a simple model based on the cross shore distance that extreme wave runup exceeded the pre winter cliff position cliff erosion appears to be a balance between terrestrial mass wasting processes which tend to decrease the cliff slope and wave attack which removes debris and erodes the cliff base increasing the cliff slope

identifying the behavioural characteristics of clay cliffs using intensive monitoring and geotechnical numerical modelling abstract coastal monitoring is routinely undertaken to provide an archival record of cliff line movement that can be used in the development and validation of predictive coast retreat and evolution models however coastal monitoring is often purely quantitative in nature and financial necessity requires deployment over extensive coastal sections as a result for local site conditions in particular only limited geomorphological data are available or included during the development of such predictive models this has resulted in many current models incorporating a simplistic or generalised representation of cliff behaviour an approach that progressively loses local credibility when deployed over extensive heterogeneous coastlines this study addresses this situation at a site of extreme coastline retreat holderness uk through the application of intensive monitoring of six representative cliff sections nested within a general geomorphological appraisal of the wider coastline as a whole the data from these surveys have been used to validate a finite difference based geotechnical modelling assessment of clay cliff stability once validated the geotechnical model was used to simulate a range of scenarios that were sufficient to represent the range of topographic hydrogeological geological and littoral conditions exhibited throughout the region our assessment identified that the cliff retreat occurs through the combined influence of direct marine erosion of the cliff with shallow structurally controlled failures or substantial mass failures critically the predisposition to any one of these failure mechanisms arises principally as a result of initial cliff height the results of the numerical modelling have been combined into an empirical slope model that derives the rate of landslide induced retreat that would arise from mass failures under various future scenarios results of this study can be used in the selection and development of retreat models at coastlines of similar physiographic setting to that found at holderness the results represent a key step in linking material deformation properties to the processes of cliff change and the subsequent range of landforms found on clay cliffs as such the results could also be used more generally to illustrate the likely cliff behaviour of other soft rock coastlines

statistical analysis of recent mediterranean sea level data abstract the global rate of sea level rise during the 20th century is generally agreed to be 1 2 5 mm year an examination of the four sea level data series available for the mediterranean shows a sea level rise of a similar rate a statistical analysis based on linear regression reveals this trend to be inconsistent over the century the four time series were divided into two different sets the first consists of records prior to 1960 when sea level was rising consistently and the second from 1961 and onward when there was no significant sea level trend dividing these two data sets into shorter time periods by using additional data from 41 tide gauging stations in the mediterranean showed a consistent trend prior to 1960 between 1961 and 1989 the records show no significant trend this can be due to a rise in mean surface atmospheric pressure of 1 74 3 31 hpa during that period rather than an eustatic decrease in the rate of sea level rise from 1990 onward the sea level recorded in most mediterranean tide gauges indicates a rise in sea level at a rate 5 10 times higher than the 20th century mean rate while this trend should be regarded with some caution because of the relatively short data series the trend observed coincides with the increase in global land and marine surface temperatures during the 1990s and it is important to note that no other short sub period in the data sets shows such an extreme trend

estimation of rev for fractured rock masses based on geological strength index abstract the representative elementary volume rev of fractured rock masses is a significant index to investigate the rock mass behaviors in the continuum mechanics in this research a new indicator to estimate the rev size of fractured rock masses based on the geological strength index gsi is proposed for this purpose a new method that combines the pfc based synthetic rock mass srm model with the hoek brown hb failure criterion is proposed to investigate the strength and deformation properties of fractured rock masses under biaxial stress conditions extensive numerical analyses are carried out to estimate variation of the uniaxial compression strength ucs deformation modulus e and gsi of the brunswick mine rock mass with increasing the size of the srm models up to a rev size results show that the gsi based indicator gives relatively larger rev size compared with the traditional ucs or deformation modulus e based indicators compared with the traditional indicators the proposed gsi based indicator has merits of not only reflecting the geometrical characteristics of rock structures but also containing both geometrical and mechanical properties of discontinuities

short and long term erosional processes affecting the stability of the mediterranean coastal cliffs of israel abstract the destructive processes affecting the coastal cliffs of israel are seen as time dependent processes acting in two independent zones at the top and bottom of the cliffs at the top of the cliff these processes are classed as short term phenomena that may be seen as seasonal changes or those initiated by man two main phenomena are recognized as multiple sliding at the contact of hamra clay and kurkar sandstone horizons and collapse of an overlying hard calcarenite layer high water content is by far the most significant contributor to instability which is aggravated by excessive watering of gardens near the cliff edge other factors contributing to instability are grain size and lack of cementation at the bottom of the cliff these processes are classed as long term phenomena where several climatic seasons to a number of years may pass between events these processes are mainly dependent on the abrasive action of waves and to a lesser extent on wind stability is dependent on factors such as grain size distribution of particles cross bedding and degree of cementation of the sandstone the factor of safety f for kurkar slopes ranges from f 1 29 1 78 and that of hamra slopes from f 0 59 0 60 recognition of the active processes causing instability in the different parts of the cliffs and the factors controlling them is essential for the design and remedial measures required for controlling the continued destruction of the cliffs

holocene sea level changes along the mediterranean coast of israel based on archaeological observations and numerical model local sea level curves reflect global eustatic changes regional isostatic adjustments of the crust to changing ice and ocean volumes and tectonically controlled crustal movements in this study we evaluate the relative contribution of each of these factors to the holocene sea level curve of the mediterranean coast of israel we use archaeological data as constraints on palaeo sea levels and we then compare the observational limits with isostatic models for sea level change across the region the isostatic model includes the contribution arising from the relative minor increase in ocean volumes for the past 6000 years due to residual melting of ice sheets the effect of the changing shape of the ocean basin the time dependence of shorelines as sealevel changes and the changing surface area occupied by ice sheets differences if significant between the observed and predicted change are interpreted as being of tectonic origin the archaeological observations and the model sea level curve along the mediterranean coast of israel were found to be generally consistent and any discrepancies lie within the uncertainties of both values our model predicted that 8000 years ago sea level at the israel coast was at about 213 5 2 m whereas the archaeological data place it at 216 5 1 m by 7000 bp the predicted level has risen to about 27 1 m consistent with the archaeological evidences according to both observations and predictions sea level was still lower than 2 3t o24 5 m at 6000 bp and remained below its present level until about 3000 2000 bp the comparison between the model sea level curve and the archaeological observations also enable to conclude that the average rate of vertical tectonic movement for the last 8000 years at the carmel coast israel has been less than 0 2 mm year q 2001 elsevier science b v all rights reserved

erosional processes in the hard rock coastal cliffs at staithes north yorkshire the processes of change on near vertical coastal cliffs have been quantified using terrestrial photogrammetry and laser scanning the approach allows discrete rockfall geometry to be measured and source located in three dimensions this paper presents the analysis of an inventory of over 100000 discrete rockfalls recorded from the liassic coast at staithes north yorkshire uk where a rock face area of over 16000 m 2 has been monitored over a 20 month period the data obtained on three dimensional scar geometry and source position give an insight into rockfall characteristics from a range of rock types cliff heights and geometries multiple failure mechanisms such as overhang collapse constant spalling fragmentation and large scale coherent rockfalls have been observed and related to rock type controlled processes on the rock face the spatially referenced rockfall scar data are used to assess the influence of environmental controls on variable rock mass properties such as rock type structure and cliff geometry analysis of rockfall magnitude frequency reveals notable similarities between coastal rockfalls and inventories from non coastal environments the resolution of the monitoring data allows quantification of rockfalls down to volumes of 1 25 x 10 4 m 3 to be consistently sampled and measured this complete magnitude frequency relationship suggests that rather than evolving exclusively through isolated sporadic losses coastal cliff geomorphology reflects interconnected processes in which each rockfall is part of a continuum of change to the rock face further detailed assessment of the rock face reveals the control of the pre failure morphology on subsequent failure patterns for example the quantity of rock protrusion from the cliff is positively correlated with subsequent failure volume the continuum of activity and the controls on failure identified within these data suggest that the episodic behaviour of coastal cliffs previously assumed may have been overstated by coarser resolution monitoring data the findings improve our understanding of the evolution of coastal cliffs and highlight areas for further research into both cliff processes and the character of rock slope failures in general

effect of the development of notches and tension cracks on instability of limestone coastal cliffs in the ryukyus japan abstract notches cut by waves are currently developing at the base of vertical coastal limestone cliffs in okinawa japan the cliff height varies from 3 0 22 1 m and the maximum notch depth is 8 8 m many rectangular or cubic blocks which appear to have originated from cliff failures are found on platforms in front of the cliffs on the flat top surface of the cliff tension cracks often run parallel to the cliff face the vertical face of the cliffs displays small undulations but no sliding striation suggesting that cliff failures have been caused by toppling rather than by shearing or sliding we use slope stability analysis to determine the critical condition for toppling failure physical and mechanical properties of the cliff material were first obtained from laboratory tests the results indicate that the strength of limestone shows a scale effect such that the strength decreases with increasing size of the test specimens based on this result we estimated the strength of a rock mass corresponding to the size of the coastal cliff cliff stability was then analyzed using a cantilever beam model comparison of the stability analysis and the dimension of fallen blocks indicates that toppling failure is strongly associated with the development of notches and tension cracks

stability of steep slopes in cemented sands the analysis of steep slope and cliff stability in variably cemented sands poses a significant practical challenge as routine analyses tend to underestimate the actually observed stability of existing slopes the presented research evaluates how the degree of cementation controls the evolution of steep sand slopes and shows that the detailed slope geometry is important in determining the characteristics of the failure mode which in turn guide the selection of an appropriate stability analysis method detailed slope profile cross sections derived from terrestrial lidar surveying of otherwise inaccessible cemented sand cliffs are used to investigate failure modes in weakly cemented unconfined compressive strength ucs30 kpa and moderately cemented 30ucs400 kpa sands and their role in the evolution of the geometry of the slopes the results show that high resolution slope topography such as can be obtained with terrestrial lidar is essential for identifying altogether different failure modes in weakly cemented shear mode and moderately cemented tensile mode sand slopes analyses show that the standard culmann method for steep slopes is inappropriate for modeling the stability of cemented sand slopes since it tends to overpredict expected crest retreat and underestimate failure plane angle instead a simplified analysis using infinite slope assumptions but applied to a slope with finite dimensions subject to changing geometric conditions such as toe erosion and slope steepening is suggested for analysis of weakly cemented sand slopes for moderately cemented sand slopes a limit equilibrium analysis directly comparing the cliff tensile stress and cemented sand tensile strength is shown to reasonably predict failure conditions and timing as a result of either slope steepening or tensile strength loss presumably from wetting in most cases doi 10 1061 ascegt 1943 5606 0000396 ce database subject headings slope stability sand soil type limit equilibrium tensile strength failure modes author keywords slope stability cemented sand limiting equilibrium tensile strength lidar cliffs failure mode

a predictive model for wave induced cliff erosion with application to pacific coasts of japan a model for predicting the rate of short term bluff recession originally derived from wave tank experiments is tested under field conditions the fundamental equation is dx dt k c ln gh sc where dx dt is the recession rate h is the wave height at the cliff base sc is the compressive strength of the cliff forming material is the density of water g is the acceleration due to gravity c is a nondimensional constant and k is a constant with units of lt 1 the critical wave height to initiate erosion hcrit is given by hcrit sce c g this model is applied to two eroding tertiary cliffs in japan both facing the pacific ocean results show that 1 the larger but rarer waves only cause cliff erosion compared with the smaller but more common waves and 2 the erosion rate at each site is greatly affected by the occurrence frequency of waves higher than hcrit

ancient coastal wells of caesarea maritima israel an indicator for relative sea level changes during the last 2000 years abstract during the detailed excavations of ancient caesarea israel east mediterranean 64 coastal water wells have been examined that date from the early roman period with the oldest occurring in the 1st century ad up to the end of the crusader period mid 13th century ad the depths of these coastal water wells establish the position of the ancient water table and therefore the position of sea level for the first century ad up to 1300 ad the connection between the coastal water table and changes in sea level has been established from modern observations in several wells on time scales of days and months and this is used to reconstruct sea level during historical time the results indicate that during the byzantine period sea level at caesarea was higher by about 30 cm than today the late moslem and crusader data shows greater fluctuations but the data sets are also much smaller than for the earlier periods the consistency of the data indicates that the near coastal well data from caesarea provides a reliable indicator of sea level change with an accuracy of about 10 15 cm these results are consistent with observations for earlier periods and with comparisons to model predicted glacio hydro isostatic sea level change indicate that ocean volumes have been constant for much of the past 2000 years the well data is also consistent with an absence of significant vertical tectonic movement of the coast at caesarea over about 2000 years

a new process response coastal recession model of soft rock cliffs abstract the development of cliff erosion predictive models is limited by the complex interactions between environmental processes and material properties over a range of temporal and spatial scales current models incorporate a stochastic representation of cliff behavior based on assumptions regarding the magnitude and frequency of events in a probabilistic framework the new model presented here has been developed to incorporate the behavioral and mechanical characteristics of coastal cliffs which are dominated geologically by overconsolidated clays tills and an associated protective colluvial wedge this model is capable of providing precise and stable responses to some of the inherent uncertainties in cliff recession processes including those caused by different failure mechanisms e g colluvium generation groundwater and erosive tidal cycles material strength is incorporated using the unconfined compressive strength of the material that composes the cliff unlike previous models a calibration parameter is restricted to account for uncertainties linked to marine processes the mechanisms of cliffline retreat have been identified as slump and topple landslides once cliff material has fallen colluvium formation at the cliff foot is incorporated into the model using three different procedures according to the geomechanical characteristics of the debris the model is validated through profile evolution assessment at various locations of coastline retreat on the holderness coast uk higher groundwater content also produces an increase in the number and size of the slope failures the results represent an important step forward in linking material properties to the processes of cliff recession

coastal cliff retreat rates at beit yannay israel in the 20th century research indicates that the aeolianite kurkar cliffs along the israeli mediterranean coastline have continuously retreated eastward during the last few decades there seems to be no dispute among earth scientists regarding the general trend of cliff retreat however the majority of papers displaying cliff retreat rates are based upon comparison of aerial photographs their lack of advanced geometric measurement methods causes a high margin of error public attention is focused upon the beit yannay coastal cliff since private homes are located along the southern section of the cliff crest the current research compares the historic location of the cliff crest edge at beit yannay as observed in a series of aerial photographs taken during the period 1918 2000 quantitative measurement methods included applications of satellite geodesy and digital photogrammetry and mapping research results offer quantitative consecutive and highly accurate data regarding retreat rates over a relatively long period of 82 years it is concluded that 1 annual average cliff retreat rates of the cliff crest is 20 cm year 2 categorization of the study time span reveals periods displaying varying retreat rates such as 27 cm year during 1918 1946 21 cm year during 1946 1973 and 10 cm year during 1973 2000 3 maximum retreat distances of the cliff crest over the study period were found to be approximately 25 m along the northern lowest section of the cliff minimum distances of 11 m were identified at the highest southern section of the cliff 4 the eolianite kurkar cliffs along the israeli mediterranean coast throughout the 20th century have been an important source of sediment contributing approximately 24 10 6 m 3 of sediments to the sediment balance of israeli beaches copyright 2004 john wiley sons ltd

landslides in vibrating sand box what controls types of slope failure and frequency magnitude relations abstract although landslides are a worldwide significant natural hazard their physics is not well understood here landslides were induced in a vibrated box filled with wet practically cohesive sand simulating natural slope failure the questions addressed were a what controls the type of slope failure and b what controls frequency magnitude relations of landslides in the experiments two end member slope failure types were obtained during application of only horizontal acceleration a failure plane rapidly developed followed by a box sized slump in contrast under application of only vertical acceleration mode i fractures formed slowly dissecting the slope into blocks the fractures caused a strength heterogeneity and were followed by block sliding in the vertical shaking experiments a power law size distribution of slide blocks was measured controlled by the fracture distribution the experiments suggest that heterogeneity may be a major control on the size distribution of natural landslide inventories in a homogeneous environment the landslide will have a characteristic size of the whole system in a heterogeneous slope sizes of landslides will reflect the heterogeneity following the above experimental observations our hypothesis is that natural landslides may be divided into two groups small and large the processes controlling their formation are different i the smaller natural landslides occur as slumps within the unconsolidated rather homogeneous sediments typical of the upper few meters close to the surface the size of these slumps is determined by the dependence between failure depth constrained to be the depth of the unconsolidated sediments and area ii in contrast to the homogeneous upper layer rock mass below the unconsolidated sediment is always heterogeneous due to fractures layers and bedding this preexisting heterogeneity is the source of the power law decay observed for the large landslide portion in natural landslide distributions finally in light of these insights in hazard evaluation it is advised to fit a regression line to the power law decay of the large landslide inventory only and consider the characteristic landslide separately

temporal and spatial variations in recession rates and sediment release from soft rock cliffs suffolk coast uk high rates of coastal retreat characterise the weakly cemented plio pleistocene rocks and sediments which form much of the cliffed coastline of east anglia southern north sea the accurate establishment of sediment losses from these cliffs has a regional significance as these sediments are important in maintaining beaches and nearshore bank systems and in feeding nearshore sediment transport pathways however the high spatial and temporal variability of cliff failure processes in such materials necessitates fine scale integration of alongshore variations in cliff retreat over a series of well established time periods to accurately define cliffline recession rates and sediment volume inputs to the nearshore system this study applied the dsas digital shoreline analysis system within the gis software package arcmap to digitised georeferenced positions of former shorelines obtained from historic maps and aerial photographs after 1992 for the sections of benacre southwold and dunwich minsmere on the suffolk coast of east anglia uk transects were cast every 10 m alongshore producing very high spatial resolution upon which to assess shoreline retreat over 1000 transects along 11 km of shoreline long term 1883 2008 mean shoreline retreat rates varied between 2 3 3 5 m a 1 benacre southwold and 0 9 m a 1 dunwich minsmere for six cliffed subunits within these larger coastal sections spatial variations in cliffline recession rates for shorter time intervals at ca 20 year intervals within this longer 125 year period were established the combination of recession rates with photogrammetric methods of obtaining cliff top elevation at the same spatial resolution available using aerial photographs and digital terrain models along with cliff sediment composition allowed the calculation of sediment volumetric inputs from cliff retreat in the period 1992 2008 re assessment of the magnitude and location of sediment inputs into the nearshore zone their interaction with regional sediment transport and the growth of inshore bank systems as well as the implications for contemporary and near future coastal management strategies are discussed with reference to this section of the suffolk coast

characteristics of sea cliff erosion induced by a strong winter storm in the eastern mediterranean abstract changes in sea cliff morphologies along the 30 km long sharon escarpment segment of israel s weakly cemented mediterranean eolianite cliff line were analyzed to gain quantitative insights into erosion characteristics associated with a high energy winter storm 10 20 year return interval ground based repeat lidar measurements at five sites along the cliff line captured perturbations of cliff stability by basal wave scouring during the storm subsequent post storm gravity driven slope failures in the cliff face above and return of the system to transient stability within several months post storm erosion which amounted to 70 of the total volume of cliff erosion documented resulted in dramatic local effects of up to 8 m of cliff top retreat and yet at the larger scale of the 30 km cliff line examined erosion during the storm and the year that followed affected less than 4 of the cliff length and does not appear to be above the average cliff length annual erosion implied by previously published decadal scale retreat rates along this sea cliff our results do not support a direct association between strong storm events and elevated erosion and retreat at the cliff line scale

active faulting in the western pyrenees france paleoseismic evidence for late holocene ruptures abstract we have identified a 50 km long active fault scarp called herewith the lourdes fault between the city of lourdes and arette village in the french pyrenees this region was affected by large and moderate earthquakes in 1660 io viii ix msk 64 in 1750 io viii msk 64 and in 1967 md 5 3 io viii msk 64 most earthquakes in this area are shallow and the few available focal mechanism solutions do not indicate a consistent pattern of active deformation field investigations in active tectonics indicate an east west trending and up to 50 m high fault scarp in average made of 3 contiguous linear fault sub segments to the north the fault controls quaternary basins and shows uplifted and tilted alluvial terraces deviated and abandoned stream channels of the southern block are likely due to the successive uplift of the northern block of the fault paleoseismic investigations coupled with geomorphic studies georadar prospecting and trenching along the fault scarp illustrate the cumulative fault movements during the late holocene trenches exhibit shear contacts with flexural slip faulting and thrust ruptures showing deformed alluvial units in buried channels 14c dating of alluvial and colluvial units indicates a consistent age bracket from two different trenches and shows that the most recent fault movements occurred between 4221 bc and 2918 bc fault parameters and paleoseismic results imply that the lourdes fault and related sub segments may produce a mw 6 5 to 7 1 earthquake fault parameters imply that the lourdes fault segment corresponds to a major seismic source in the western pyrenees that may generate earthquakes possibly larger than the 1660 historical event

the impact of climatic and seismic events on the short term evolution of seacliffs based on 3 d mapping northern monterey bay california abstract coastal cliff retreat along the central california coast is episodic occurring in response to single large storms or seismic events traditional approaches to the study of long term seacliff retreat utilize historical aerial photography and maps to delineate the landward migration of the top edge of the cliff over periods of tens of years to a century while these methods yield cumulative retreat amounts they provide little or no information on the character of the individual retreat events nor the physical processes of retreat this study addresses the processes of episodic and short term coastal cliff retreat through the analysis of seacliff failure styles and retreat magnitudes the study areas are three 1 km long sections of cliffed coast in northern monterey bay the earliest data set is vertical aerial photography from october 18 1989 taken the day following the magnitude 7 1 loma prieta earthquake more recent photography collected in late january early february and early march of 1998 captured seacliff failure in response to the severe storms associated with the 1997 1998 el nino for each data set high resolution digital photogrammetric techniques are used to identify the top edge of the cliff at each cliff failure location its position failure length and character are documented results suggest that on a regional scale the seacliffs respond to seismic and climatic forcing differently we have found variation in the magnitude of cliff response along the three sections of coast in the study area large scale climatic events such as the 1997 1998 el nino have a greater impact on both the linear extent of seacliff failure and the amount of cliff retreat

instability investigation of cantilevered seacliffs wave action is a fundamental mechanism in seacliff erosion whereby wave undercutting creates an unstable cantilevered seacliff profile and can lead to large catastrophic cliff failures thus threatening coastal infrastructure this study investigated the instability of two such failures that occurred in solana beach california by combining terrestrial lidar scanning cantilever beam theory and finite element analysis each landslide was detected by evaluating the surface change between subsequent high resolution digital terrain models derived from terrestrial lidar data the dimensions of failed cantilever masses were determined using the surface change measurements and then incorporated into failure stress analysis superimposing stress distributions computed from elastic cantilever beam theory and finite element modeling provided a method to back calculate the maximum developed tensile and shear stresses along each failure plane the results of the stress superposition revealed that the bending stresses caused by the cantilevered load contributed the majority of stress leading to collapse both shear and tensile failure modes were investigated as potential cliff failure mechanisms by using a comparison of the back calculated failure stresses to material strengths found in laboratory testing based on the results of this research the tensile strength of the cliff material was exceeded at both locations thus causing the cliffs to collapse in tension copyright 2008 john wiley sons ltd

rain waves and short term evolution of composite seacliffs in southern california abstract a four year time series of nine airborne lidar surveys were used to assess the roles of wave attack and rainfall on the erosion of 42 km of southern california seacliffs nine continuous seacliff sections separated by coastal lagoon mouths all show maximum seacliff erosion in the rainiest time period when wave energy was not particularly elevated and in most sections the squared correlations between rainfall and erosion time series exceeded 0 8 although rain and associated subaerial mechanisms such as groundwater seepage triggered most of the observed seacliff failures wave attack accelerated seacliff erosion with erosion rates of cliffs exposed to wave attack five times higher than at adjacent cliffs not exposed to waves the results demonstrate the importance of both waves and rain in the erosion of southern california seacliffs and suggest that the combined influences of marine and subaerial processes accelerate the erosion rate through positive feedbacks

long term cliff retreat and erosion hotspots along the central shores of the monterey bay national marine sanctuary abstract quantification of cliff retreat rates for the southern half of santa cruz county ca usa located within the monterey bay national marine sanctuary using the softcopy geographic information system gis methodology results in average cliff retreat rates of 7 15 cm yr between 1953 and 1994 the coastal dunes at the southern end of santa cruz county migrate seaward and landward through time and display net accretion between 1953 and 1994 which is partially due to development in addition three critically eroding segments of coastline with high average erosion rates ranging from 20 to 63 cm yr are identified as erosion hotspots these locations include opal cliffs depot hill and manresa although cliff retreat is episodic spatially variable at the scale of meters and the factors affecting cliff retreat vary along the santa cruz county coastline there is a compensation between factors affecting retreat such that over the long term the coastline maintains a relatively smooth configuration the softcopy gis methodology significantly reduces errors inherent in the calculation of retreat rates in high relief areas e g erosion rates generated in this study are generally correct to within 10 cm by removing errors due to relief displacement although the resulting root mean squared error for erosion rates is relatively small simple projections of past erosion rates are inadequate to provide predictions of future cliff position improved predictions can be made for individual coastal segments by using a mean erosion rate and the standard deviation as guides to future cliff behavior in combination with an understanding of processes acting along the coastal segments in question this methodology can be applied on any high relief coast where retreat rates can be measured

luminescence chronology of aeolianites from the section at givat olga coastal plain of israel abstract the eastern mediterranean coastal plain of israel is composed mainly of loam sand and gravel of pleistocene to holocene age indicating an alternation of marine coastal and continental environments owing to the complexity of the numerous exposures of aeolianites kurkar and soils hamra in the elongated ridges along the coastal plain it is difficult to set up a reliable stratigraphy a systematic luminescence dating study was carried out on loose sand kurkar and hamra deposits in the coastal plain between netanya and haifa sixteen samples were taken and investigated from the section at givat olga the chronological results show excellent agreement between the infrared optically stimulated luminescence irsl and thermoluminescence tl techniques indicating that the former sand dunes were well bleached prior to deposition the irsl and tl age estimates range from about 75 3 ka for the aeolianites indicating that this kurkar ridge formed during an older period of the last glaciation likely before 50 ka

luminescence chronology of upper pleistocene and holocene aeolianites from netanya south sharon coastal plain israel abstract the coastal cliff at netanya south in the sharon coastal plain of israel was investigated with luminescence dating methods twenty four samples were taken from the exposed aeolianites and intercalated paleosols the 24 irsl and 24 tl age estimates suggest that the lower 45 m of the section were deposited in oxygen isotope stage 3 the uppermost 7 m of the section are of holocene age and clearly separated by a hiatus of 20 30 ka from the lower part

critical notch depths for failure of coastal limestone cliffs case study at kuro shima island okinawa japan development of a notch at the base of a cliff reduces cliff stability and often induces a collapse pleistocene limestone coastal cliffs of elevation 5 m in kuro shima ryukyu islands have a prominent notch with a depth of 3 4 m at their bases around these coastal cliffs collapses different from previous studies of cliff collapses in the ryukyu islands were found collapses in kuro shima have a horizontal failure surface the horizontal failure surface situated at the height of the failure surface corresponding to the retreat point of the notch is bounded by vertical joints cutting the whole cliff and the reef flat in front of the cliff two types of horizontal failure surface were found triangular and quadrangular the distinction appears to depend on the angle between the vertical joints and the front face of the cliff prior to collapse these cliffs appear to have been separated from the adjacent cliffs by the development of vertical joints consequently a cliff that will collapse can be identified in advance cliff instability is strongly dependent on the development of a notch to study the effect of notch development on cliff collapse the notch depth at which collapse occurs was calculated using stability analysis instability of a cliff increases with notch depth collapse occurs at the horizontal failure surface when the ratio of the notch depth to the seaward length of the cliff is approximately 0 5 0 7 for a triangular failure surface and 0 7 0 9 for a quadrangular failure surface copyright 2010 john wiley sons ltd

comparison of short term seacliff retreat measurement methods in del mar california article i nfo seacliff retreat has been variously characterized as the recession rate of the cliff top of the cliff base and as the bulk recession rate based on volumetric changes of the entire cliff face here these measures of retreat are compared using nine semi annual airborne lidar light detection and ranging surveys of southern california seacliffs changes in the cliff base location where the steeply sloping cliff face intersects the beach include cliff retreat owing to basal erosion but also reflect changes in beach sand level and basal talus deposits averaged over the 2 5 km alongshore study span the cliff base actually prograded seaward about 12 cm during the 4 year study cliff top change was dominated by few relatively large several meters localized retreats cliff face changes that include failures and deposits anywhere on the cliff profile had a relatively small mean magnitude compared to cliff top changes and were more widely distributed alongshore however the similar alongshore averaged cumulative cliff top and net bulk cliff face end point retreat 14 and 19 cm respectively suggest that mean cumulative cliff top retreat can potentially be a viable surrogate for mean net cumulative cliff wide erosion and vice versa over relatively short time periods cliff face erosion occurred repeatedly at some locations confirming the presence of seacliff erosion hot spots during the study period

processes of coastal bluff erosion in weakly lithified sands pacifica california usa abstract coastal bluff erosion and landsliding are currently the major geomorphic processes sculpting much of the marine terrace dominated coastline of northern california in this study we identify the spatial and temporal processes responsible for erosion and landsliding in an area of weakly lithified sand coastal bluffs located south of san francisco california using the results of a five year observational study consisting of site visits terrestrial lidar scanning and development of empirical failure indices we identify the lithologic and process controls that determine the failure mechanism and mode for coastal bluff retreat in this region and present concise descriptions of each process bluffs composed of weakly cemented sands unconfined compressive strength ucs between 5 and 30 kpa fail principally due to oversteepening by wave action with maximum slope inclinations on the order of 65 at incipient failure periods of significant wave action were identified on the basis of an empirical wave run up equation predicting failure when wave run up exceeds the seasonal average value and the bluff toe elevation the empirical relationship was verified through recorded observations of failures bluffs composed of moderately cemented sands ucs up to 400 kpa fail due to precipitation induced groundwater seepage which leads to tensile strength reduction and fracture an empirical rainfall threshold was also developed to predict failure on the basis of a 48 hour cumulative precipitation index but was found to be dependent on a time delay in groundwater seepage in some cases

coastal cliff recession the use of probabilistic prediction methods a range of probabilistic methods is introduced for predicting coastal cliff recession which provide a means of demonstrating the potential variability in such predictions they form the basis for risk based land use planning cliff management and engineering decision making examples of probabilistic models are presented for a number of different cliff settings the simulation of recession on eroding cliffs the use of historical records and statistical experiments to model the behaviour of cliffs affected by rare episodic landslide events the adaptation of an event tree approach to assess the probability of failure of protected cliffs taking into account the residual life of the existing defences and the evaluation of the probability of landslide reactivation in areas of pre existing landslide systems these methods are based on a geomorphological assessment of the episodic nature of the recession process together with historical records

chronostratigraphy of aeolianites from the sharon coastal plain of israel abstract the sharon coastal plain in israel is composed mainly of sand dune fields and aeolianite ridges three major sand accumulation periods are documented in the terrestrial record along the cliffs of the sharon coastal plain between 65 to 50 ka from 7 to 5 ka and from 5 to 0 2 ka these seem to correlate with the periods of sapropel formation in the mediterranean sea and so with periods of strongly increased african monsoon activity the accumulation of the stratigraphically oldest aeolianite kurkar unit 5 appears to correlate with sapropel s2 formed about 55 ka bp the uppermost aeolianite calcareous sandstone unit 2 seems to correlate with sapropel s1 formed at about 7 8 4 0 ka bp major soil formations occurred between 35 and 25 ka resulting in a rhodoxeralf soil grumusolic dark brown soil and between 15 and 12 ka resulting in a rhodoxeralf hamra soil at least seven weak weathering horizons regosol type soils are intercalated in the aeolianite of unit v and two regosols are present in the holocene aeolian sand of unit i

modeling cliff erosion using negative power law scaling of rockfalls we model cliff erosion using an approach based upon the negative power law scaling properties of rockfall magnitude frequency distributions these are derived from an extensive high resolution rockfall inventory for a series of sea cliffs near staithes north yorkshire a comparison between observed volumetric erosion and that produced by the model yields a statistically significant correlation however we note that the temporal resolution of the inventory can have an influence on results our data indicate that monthly inventories are capable of producing magnitude frequency relations that model erosion in good correlation with observed events however for months that experience high magnitude events seasonal inventories are more appropriate furthermore increasing the return period between surveys has the effect of increasing the superimposition of rockfall events thereby reducing the slope of the power law giving an incorrect picture of the scaling properties of rockfalls at this site applying observed variations in the negative power law scaling parameters to a probabilistic simulation model of cliff retreat provides a new means of assessing the most likely erosional scenarios and indicates that the current dataset may not be indicative of long term cliff evolution this may provide a quantitative means of establishing an appropriate time window for characterizing rockfall erosion over decadal time scales