formation of coastline features by large scale instabilities induced by high angle waves along shore sediment transport that is driven by waves is generally assumed to smooth a coastline this assumption is valid for small angles between the wave crest lines and the shore as has been demonstrated in shoreline models but when the angle between the waves and the shoreline is sufficiently large small perturbations to a straight shoreline will grow here we use a numerical model to investigate the implications of this instability mechanism for large scale morphology over long timescales our simulations show growth of coastline perturbations that interact with each other to produce large scale features that resemble various kinds of natural landforms including the capes and cuspate forelands observed along the carolina coast of southeastern north america wind and wave data from this area support our hypothesis that such an instability mechanism could be responsible for the formation of shoreline features at spatial scales up to hundreds of kilometres and temporal scales up to millennia

the impact of north atlantic storminess on western european coasts a review abstract instrumental and documentary records of storminess along the atlantic coast of western europe show that storm activity exhibits strong spatial and temporal variability at annual and decadal scales there is evidence of periods of increased storminess during the little ice age lia ad 1570 1990 and archival records show that these periods are also associated with sand movement in coastal areas independent evidence of sand movement during the lia is derived from dating the coastal sand deposits using luminescence or radiocarbon methods the holocene record of sand drift in western europe includes episodes corresponding to periods of northern hemisphere cooling particularly at 8 2 ka and provides the additional evidence that these periods like the lia were also stormy

depositional evidence for the kamikaze typhoons and links to changes in typhoon climatology in the late 13 th century kublai khan ruler of the mongol empire launched one of the world s largest armadas of its time in an attempt to conquer japan early narratives described the decimation and dispersal of these fleets by the kamikaze of 1274 ce and 1281 ce a pair of intense typhoons divinely sent to protect japan from invasion these historical accounts are prone to exaggeration and significant questions remain regarding the occurrence and true intensity of these legendary typhoons to provide independent insight we present a new 2000 yr sedimentary reconstruction of extreme coastal flooding from a coastal lake near the location of the mongol invasions two marine sourced flood deposits date to the kamikaze typhoons and are the events of record in the reconstruction the complete reconstruction indicates periods of greater flood activity relative to modern beginning ca 250 ce and extending past the timing of the kamikaze events to 1600 ce comparisons with additional reconstructions are consistent with greater regional typhoon activity during the mongol invasions due to the preferential steering of storms toward japan and driven by greater el nino activity relative to modern results are consistent with the paired kamikaze typhoons being of significant intensity and support accounts of them playing an important role in preventing the conquering of japan by mongol fleets the kamikaze typhoons may therefore serve as a prominent example for how past increases in severe weather associated with changing climate have had significant geopolitical impacts

identifying storm impacts on an embayed high energy coastline examples from western ireland abstract large sections of the western irish coast are characterised by a highly compartmentalised series of headland embayment cells in which sand and gravel beaches are backed by large vegetated dune systems exposure to modally high energy swell renders most of these beaches dissipative in character a mesotidal range c 3 5 4 5 m exists along much of the coast analysis of instrumental wind records from three locations permitted the identification of a variety of storm types and the construction of storm catalogues few individual storms were recorded at all three stations indicating a lack of regional consistency in storm record of the total storms recorded only a small percentage are potentially damaging onshore directed and even fewer span a high tide and thus potentially induce a measurable morphological response at the coast through a combination of historical records meteorological records field observations and wave modelling we attempt to assess the impact of storms quantifiable records of coastal morphology maps air photos and beach profiles are few in number and do not generally record responses that may be definitely attributed to specific storms numerical wave simulations and observations at a variety of sites on the west irish coast however provide insights into instantaneous and medium term decadal storm responses in such systems we argue that beaches and dunes that are attuned to modally high energy regimes require extreme storms to cause significant morphological impact the varying orientation of beaches a spatially nonuniform storm catalogue and the need for a storm to occur at high water to produce measurable change impart site specific storm susceptibility to these embayments furthermore we argue that long period wave energy attenuation across dissipative shorefaces and beaches reduces coastal response to distant storms whereas short period locally generated wind waves are more likely to cause major dune and beach erosion as they arrive at the shoreline unrefracted this apparently variable response of beach and dune systems to storm forcing at a decadal scale over a coastline length of 200 km urges caution in generalising regarding regional scale coastal responses to climatic change

constraints on ocean volume change since the archean water may be added to earth s surface by the bombardment of large numbers of small comets increasing free water on earth s surface deepening the oceans continental freeboard is tied to the ocean surface because of the balance between erosion mountain building addition of water will also affect continental thickness area i calculate the effect of increasing ocean volume on the balance between continental oceanic area one model also includes crustal volume growth significant oceanic depths are known to exist during the archean because sulphide deposits requiring deep oceans occur in greenstone belts these observations prohibit the constant addition of large quantities of water comparable to the present day ocean volume throughout earth history but smaller quantities could be added

sediment transfer from beach to shoreface the sediment budget of an accreting beach on the danish north sea coast abstract the sediment budget along the southern part of the exposed danish north sea coast was assessed through a combination of cross shore profile analysis numerical modeling and field measurements of cross shore and longshore sediment transport at the boundary between the upper and the lower shorefaces the beaches along this coast are accreting but observed sediment storage is far smaller than sediment supplied by southerly directed wave driven currents the excess sediment volumes are transferred seaward across the shoreface by systematically offshore migrating nearshore bars that deliver sediment to the lower shoreface from where it is eventually removed by northward directed wind generated currents in the geological past sediment storage rates were much larger than at present and it is likely that the rate of storage along this coastline decreased as shoreface geometry adjusted towards equilibrium associated with shoreface steepening

coastal storm characterization and morphological impacts on sandy coasts the present work deals with storm classification using the storm power index and beach morphological response to storm events in the gulf of cadiz sw spain over the 1958 2001 period 377 events divided into five classes ranging from weak to extreme were characterized classes i weak and ii moderate accounted for 60 and 23 of events respectively class iii significant were 9 of the recorded events and classes iv severe and v extreme accounted for 5 and 2 respectively the probability of storm occurrence per year ranged from 93 for class i to 15 for class v in order to characterize beach response to storm events 214 beach profiles carried out with a monthly periodicity over the 1996 1998 period along the chipiona rota littoral were analysed as well as published data different beach types were observed i intermediate beaches underwent important vertical relief changes ranging from 0 3 m to 1 33 m associated with average slope changes from tan 0 06 to tan 0 03 ii the dissipative beaches were characterized by smaller and homogeneous foreshore vertical changes from c 0 36 m to 0 65 m according to the parallel retreat mechanism characterized by small slope variations from tan 0 025 to tan 0 035 and iii intermediate with rock shore platform experienced small morphological and foreshore slope variations related to both beach pivoting and parallel retreat mechanisms the most important morphological changes were due to the impact of usually weak and moderate events during october and november that produced berm erosion and upper foreshore lowering and the impact of severe significant and extreme events in december and january which produced dune escarpment overwash and or damage to coastal structures copyright 2011 john wiley sons ltd

the sedimentary architecture of a holocene barrier spit sylt german bight swash bar accretion and storm erosion abstract the southern german north sea coast was shaped by the last post glacial sea level rise that caused a significant retreat of the coastline approximately 5 ka bp the rate of sea level rise decreased providing space for the formation of the frisian islands which line the coast this study is focused on the island of sylt located at the german north sea coast close to the danish border here two sandy spit systems developed during the holocene combining ground penetrating radar studies and sedimentological investigations based on shallow cores new aspects on the sedimentary history of this holocene spit system have been revealed the data indicate that strong erosional events alternated with phases of progradation and growth the welding of swash bars is shown to be the predominant process during progradational phases of the spit system during these periods progradation was not restricted to linear growth along the spit axis but also included a seaward directed component major erosion surfaces which delimit progradational sediment packages are interpreted to reflect exceptionally severe storms the fossilization potential of this sedimentary record was controlled by a positive net long term sediment balance and the position of the ground water table which controlled eolian deflation only with a stable or rising sea level and associated ground water table position are sediments protected from deflation the proposed sedimentary model may serve as a template for interpretation of comparable settings in the geological record

salt marsh stability and patterns of sedimentation across a backbarrier platform abstract long term observations of clay thicknesses from 1949 to 2007 and measurements of the bulk dry density of salt marsh on the backbarrier of skallingen west denmark formed the basis of constructing a space distributed model of salt marsh deposition the deposition potential an empirical constant was measured at 32 locations across the studied salt marsh platform it was found to correlate with two independent variables 1 distance to marsh edge and 2 distance to creeks of 2nd or higher order they explained in combination 71 of the variation the derived algorithms for estimating the salt marsh deposition made it possible to tune in a model in a 4 by 4 m grid covering the studied salt marsh area of app 3 km 2 this was used to describe the general pattern of deposition on the salt marsh platform running the model with a constant sea level revealed that balance between the inner and the outer salt marsh deposition cannot be achieved within a time scale of 1000s of years modeling salt marsh sedimentation under rising sea level scenarios revealed that only one specific sea level rise provides equilibrium for a given location with a higher sea level rise the marsh at the specific location will eventually drown whereas it with a sea level rise below this level will grow towards the top of the rising tidal frame short term scenarios 100 years showed that the skallingen salt marsh will survive a sea level rise of 4 mm yr 1 and become unstable in the inner part with a sea level rise of 6 mm yr 1

natural groundwater recharge in an upland area of central north dakota u s a abstract the magnitude of groundwater recharge to coal aquifers in a 150 km 2 area in west central north dakota was determined using three separate approaches 1 the net water level rise in water table wells 2 calculations of the fluid flux between nested piezometers using the darcy equation and measured values of hydraulic conductivity and vertical gradients and 3 evaluation of the inputs to and outputs from the coal aquifer using a steady state control volume approach in which the aquifer was divided into semi rectangular cells bounded by equipotential lines and flow lines measurements of potential gradients and hydraulic conductivity permitted indirect determination of all components of flow into and out of the cell except the recharge input which was determined by difference all methods yielded consistent results on the order of 0 04 0 01 m yr 1 these values which represent 2 9 of the annual precipitation are consistent with results of other studies on recharge throughout the prairies of north america evaluation of site hydrology and stable isotope data indicates that recharge is restricted in both time and place most recharge occurs in late spring and in the fall following heavy rainfall events during these seasons the ground is not frozen and vegetation is not transpiring large amounts of water some recharge may occur during very heavy localized summer storms but it is not considered volumetrically significant major permanent depressions on the site are a source of significant recharge in addition the extensive area of ephemeral standing water bodies that result from snowmelt can produce significant amounts of infiltration over the entire site

southern north sea storm surge event of 5 december 2013 water levels waves and coastal impacts the storm surge event that affected the coastal margins of the southern north sea on 5 6 december 2013 produced the highest still water levels on record at several tide gauges on the uk east coast on east facing coasts south of the humber estuary and north facing norfolk water levels were higher than in the twentieth century benchmark surge event of 31 january 1 february 1953 maximum significant wave heights were highest off the north norfolk coast peak hs 3 8 m offshore 2 9 m inshore and lowest off the suffolk coast hs 1 5 1 8 m inshore comparable offshore wave heights in 1953 were 7 8 m and ca 3 m the lower wave heights and their short duration in 2013 explain both localised breaching overtopping and back barrier flooding associated with gravel ridges and relatively low earthen banks as well as the lack of failure in more highly engineered coastal defences on barrier coasts and within estuaries the signal of maximum runup was highly variable reflecting the modification of the tide surge wave signal by inshore bathymetry and the presence of a range of coastal ecosystems the landscape impacts of the december 2013 surge included the notching of soft rock cliffs and cliffline retreat erosion of coastal dunes and the augmentation or re activation of barrier island washover deposits whilst surge event related cliff retreat on the rapidly eroding cliffs of the suffolk coast lay within the natural variability in inter annual rates of retreat the impact of the surge on upper beach sand dune margins produced a pulse of shoreline translation landwards equivalent to about 10 years of normal shoreline retreat the study of east coast surges over the last 60 years and the identification of significant phases of landscape change such as periods of rapid soft rock cliff retreat and the formation of new gravel washovers on barrier islands points to the importance of high water levels being accompanied by high wave activity future developments in early warning systems and evacuation planning require information on the variable impacts of such extreme events

sediment supply from shoreface to dunes linking sediment transport measurements and long term morphological evolution a significant problem in current coastal research is the understanding of linkages between morphological phenomena occurring on different temporal and spatial scales morphodynamic processes in the nearshore typically exhibit nonlinear behaviour and consequently phenomena which occur on short temporal event scales as e g observed during field experiments have generally been difficult to upscale to provide an understanding of the long term behaviour of the coast on the time scale of seasons or decades this paper documents a persistent onshore migration of nearshore bar features over a period of 3 decades using a set of cross shore profile surveys from a barrier on the danish north sea coast the observed behaviour is consistent with experimental data obtained during weeklong field campaigns when sediment transport and bar migration were found to be landward directed during high energy dissipative conditions hydrodynamic and sediment transport processes leading to onshore bar migration and eventually welding of the bars are documented to provide an explanation for the observed long term evolutionary trends in addition bar welding and the resulting intertidal bar formation represent an onshore sediment storage which is subsequently available for aeolian transport observations on aeolian sediment transport indicate that transport rates and sediment supply to the foredunes critically depend on the presence of dry sand sources as represented by well drained intertidal bars measurements of long term accretion rates in foredunes indicate that volumes deposited on the crest and lee slope of the dunes are in reasonable correspondence with volumes supplied to the subaerial beach through the process of bar welding hence the data suggest that a persistent onshore directed sediment supply occurs from the shoreface across the surf and intertidal zones and into the dunes of the investigated barrier

stratigraphical evidence of late holocene barrier breaching and extreme storms in lagoonal sediments of ria formosa algarve portugal stratigraphical sedimentological and paleoecological studies undertaken in lagoonal sediments of the ria formosa barrier lagoon indicate that a number of present day aligned beaches outcropping within the marsh and detached from mainland marsh detached beaches mdb represent the remnants of former ephemeral flood deltas which established following barrier breaching induced by extreme storms from circa 1270 bc onwards dating of these beaches suggests that they resulted from multiple events of flooding separated both in time and space repeated emplacement of tidal deltas following overwash of the same location of the barrier is represented in the stratigraphical record by buried and partly overlapping marsh beaches it is suggested that further refinement of the data presented in this paper and the extension of the stratigraphic survey to the entire lagoonal space will substantiate the usefulness of the stratigraphic record as a proxy to hindcast a time series of extreme storminess extending far beyond the instrumental and historical records

persistent non solar forcing of holocene storm dynamics in coastal sedimentary archives considerable climatic variability on decadal to millennial timescales has been documented for the past 11 500 years of interglacial climate1 2 3 this variability has been particularly pronounced at a frequency of about 1 500 years with repeated cold intervals in the north atlantic1 3 however there is growing evidence that these oscillations originate from a cluster of different spectral signatures4 ranging from a 2 500 year cycle throughout the period to a 1 000 year cycle during the earliest millennia here we present a reappraisal of high energy estuarine and coastal sedimentary records from the southern coast of the english channel and report evidence for five distinct periods during the holocene when storminess was enhanced during the past 6 500 years we find that high storm activity occurred periodically with a frequency of about 1 500 years closely related to cold and windy periods diagnosed earlier1 2 3 we show that millennial scale storm extremes in northern europe are phase locked with the period of internal ocean variability in the north atlantic of about 1 500 years4 however no consistent correlation emerges between spectral maxima in records of storminess and solar irradiation we conclude that solar activity changes are unlikely to be a primary forcing mechanism of millennial scale variability in storminess

depositional controls on a hypertidal barrier spit system architecture and evolution pointe du banc spit north western france physical stratigraphy architecture and evolution of barrier systems in hypertidal environments tidal range above 6 m are understudied and depositional controls are poorly understood compared with wave dominated barrier systems and barrier spits in microtidal mesotidal and macrotidal settings based on vibracores ground penetrating radar radiocarbon and optically stimulated luminescence age data the formation and evolution of the hypertidal barrier system of pointe du banc north western france has been reconstructed the study shows that the barrier spit has a complex composite sedimentary architecture consisting of wave dominated and tide dominated sedimentary bodies a morpho sedimentary model is presented that demonstrates how barrier spit progradation resulting from littoral drift was the main manner of spit elongation whereas sediment convergence caused by landward migration of swash bars and seaward migration of tidal dunes caused the spit terminus to grow in height and width these results suggest that long term accretion rates varied considerably in response to changes in sediment supply variations in storminess together with the large scale topography of the coast controlled the sediment supply and thus the evolution of the barrier system during latest holocene despite architectural complexity hypertidal barrier systems preserve records of past climate changes

numerical simulation of a low lying barrier island s morphological response to hurricane katrina abstract tropical cyclones that enter or form in the gulf of mexico generate storm surge and large waves that impact low lying coastlines along the gulf coast the chandeleur islands located 161 km east of new orleans louisiana have endured numerous hurricanes that have passed nearby hurricane katrina landfall near waveland ms 29 aug 2005 caused dramatic changes to the island elevation and shape in this paper the predictability of hurricane induced barrier island erosion and accretion is evaluated using a coupled hydrodynamic and morphodynamic model known as xbeach pre and post storm island topography was surveyed with an airborne lidar system numerical simulations utilized realistic surge and wave conditions determined from larger scale hydrodynamic models simulations included model sensitivity tests with varying grid size and temporal resolutions model predicted bathymetry topography and post storm survey data both showed similar patterns of island erosion such as increased dissection by channels however the model under predicted the magnitude of erosion potential causes for under prediction include 1 errors in the initial conditions the initial bathymetry topography was measured three years prior to katrina 2 errors in the forcing conditions a result of our omission of storms prior to katrina and or errors in katrina storm conditions and or 3 physical processes that were omitted from the model e g inclusion of sediment variations and bio physical processes

response of wave dominated and mixed energy barriers to storms wave dominated and mixed energy barriers are extremely dynamic landforms responding to processes operating over a spectrum of time scales ranging from daily to monthly fluctuations related to storm and post storm conditions to century to millennium scale evolution driven by relative sea level change two types of storms are of particular relevance warm core tropical and cold core extratropical cyclones both are responsible for generating very large waves highly energetic surf zone dynamics and sediment transport elevated inshore water levels and extensive morphological responses all cyclones are affected by climate change which governs their frequency intensity and tracks barrier storm response is primarily governed by maximum storm runup and barrier morphology as conceptualised in abby sallenger s storm impact scale model sallenger 2000 this model defines four storm impact regimes and includes erosive as well as accretionary responses on the erosion side the swash regime drives bar and berm flattening the collision regime is marked by dune scarping and beach lowe the overwash regime leads to dune scouring and channel incision and the inundation regime may result in barrier destruction on the deposition side storm berms and beach ridges may form and accrete in the swash and collision regimes localised vertical beach and barrier accretion are associated with the collision and overwash regimes and washover deposition takes place in the overwash and inundation regimes site specific factors play a key role in moderating the morphological response and include storm characteristics type duration and track longshore sediment supply upwelling downwelling currents coastal setting and inner shelf topography the response of a barrier to a tropical or extratropical cyclone can however not be considered in isolation and has to be appreciated in a longer temporal context involving morphological preconditioning due to antecedent wave and water level conditions additionally a simple process response approach of the cause and effect type is inappropriate and a more complex conceptual framework involving thresholds feedbacks resilience and vulnerability will need to be adopted a useful way to visualise and conceptualise more complex storm behaviours and the longer term vulnerability of barriers is the resilience trajectory which maps out the changes in barrier geometry elevation and width over various time scales from weeks to years or even longer and under varying forcing conditions including changes in storminess and sea level rise an increased understanding of barrier response to storms and sequences of storms is required to better quantify long term barrier response to climate change high resolution and comprehensive decadal records of barrier response to storms are a prerequisite to achieve this ambition linking site specific coastal settings hydrodynamic drivers and morphological responses and allowing the recognition of recovery and impact dominated phases the enhanced insights in barrier response to extreme events must then be incorporated into improved coastal response models to help predict the impacts of future climate change on wave dominated and mixed energy barriers around the world 2013 elsevier b v

holocene relative sea level change isostatic subsidence and the radial viscosity structure of the mantle of northwest europe belgium the netherlands germany southern north sea abstract a comprehensive observational database of holocene relative sea level rsl index points from northwest europe belgium the netherlands northwest germany southern north sea has been compiled in order to compare and reassess the data collected from the different countries regions and by different workers on a common time depth scale rsl rise varies in magnitude and form between these regions revealing a complex pattern of differential crustal movement which cannot be solely attributed to tectonic activity it clearly contains a non linear glacio and or hydro isostatic subsidence component which is only small on the belgian coastal plain but increases significantly to a value of ca 7 5 m relative to belgium since 8 cal ka bp along the northwest german coast the subsidence is at least in part related to the post glacial collapse of the so called peripheral forebulge which developed around the fennoscandian centre of ice loading during the last glacial maximum the rsl data have been compared to geodynamic earth models in order to infer the radial viscosity structure of the earth s mantle underneath nw europe lithosphere thickness upper and lower mantle viscosity and conversely to predict rsl in regions where we have only few observational data e g in the southern north sea a very broad range of earth parameters fit the belgian rsl data suggesting that glacial isostatic adjustment gia only had a minor effect on belgian crustal dynamics during and after the last ice age in contrast a narrow range of earth parameters define the southern north sea region reflecting the greater influence of gia on these deeper older samples modelled rsl data suggest that the zone of maximum forebulge subsidence runs in a relatively narrow wnw ese trending band connecting the german federal state of lower saxony with the dogger bank area in the southern north sea identification of the effects of local scale factors such as past changes in tidal range or tectonic activity on the spatial and temporal variations of sea level index points based on model data comparisons is possible but is still complicated by the relatively large range of earth model parameters fitting each rsl curve emphasising the need for more high quality observational data

metamorphism denudation and sea level in the archean and cooling of the earth abstract over long enough time scales an antagonistic balance acting between tectonics uplift and rifting and the sedimentary cycle erosion and deposition probably keeps continental surfaces close to sea level we argue that this balance constitutes the primary mechanism for keeping long term continental freeboard constant by regulating the continental thickness an important implication is that the long term uplift or down warp history of ancient continental segments provides direct information on secular changes in the isostasy of the adjacent ocean basins through time the amount of uplift can be estimated from the regional metamorphic grade the burial pressures at present exposure of ten undisturbed archean granite greenstone segments are estimated to be 1 5 0 5 kb from this we infer a maximum long term uplift and erosion of 5 2 km for stable continent since 3 0 ga implying a mean continental thickness of 46 km at the time of crustal stabilization for a constant mean ocean depth isostasy requires a palaeo oceanic crust 14 2 km thick in the middle archean alternatively if little continent existed then the oceans would have been shallower and the palaeo oceanic crust 21 2 km thick assuming plate spreading did occur in the archean potential temperatures in the shallow mantle at 3 ga were 90 30 c or 170 20 c for no continent hotter than those prevailing today these temperatures translate into time averaged cooling rates for the shallow mantle of 57 c ga 1 and are comparable to estimates of the present day cooling rate for the whole earth the low burial pressures are a strong argument against the existence of catastrophic mantle flush events in the geological past which have been predicted by some mantle convection models taken together these constraints suggest a plume related geological setting i e oceanic plateau like flood basalt for the initial stage of greenstone belt evolution

variations in storm response along a microtidal transgressive barrier island arc abstract storm response along the transgressive chandeleur barrier island arc southeast of the mississippi delta plain is variable because of local differences in sediment supply shoreline orientation and barrier morphology a study of the morphological impact of hurricane frederic 1979 affirmed that tropical storms are the primary agents causing erosion and migration of this barrier arc frederic s greatest impact was in the duneless southern chandeleurs where sheet flow overwash caused flattening of the barrier profile destruction of a strip of marsh 50 100 m wide and shoreline retreat of approximately 30 m in contrast overwash in the northern chandeleurs was confined between dunes in channels established by previous storms this channelized overwash breached the northern chandeleur barriers in nineteen places as frederic passed return flow through these channels transported overwashed sediment back to the nearshore zone these ebb deposits were a source for longshore drift sediments which quickly sealed storm channels reestablishing a coherent northern chandeleur barrier arc these storm response patterns may help explain long term changes in barrier morphology during an 84 yr period 1885 1969 the southern chandeleurs decreased 41 in area with an average retreat rate of 9 1 m yr 1 compared to a 15 increase in area and an average shoreline retreat rate of 7 2 m yr 1 for the northern chandeleurs

impacts of storms and evolution of the coastline in western france abstract the morphological impact of storms on coastal accumulations varies considerably in space along the coast of western france at some locations the storm produces erosion whereas at others impacts may vary from erosion to accumulation or no effect this is explained by the variability of incident waves wave amplitude variability cross checked with wave direction variability is presented on a phase diagram and shows that the response of the coast is not linked to the absolute values reached during the storm but to changes in wave patterns that take place during the event the morphology of the bottom skerries banks is greatly forcing these changes because of the high tidal range and the complicated and fast changing patterns of refraction locations with a flat seafloor have an almost predictable response to storms places with a complex submarine morphology have a response characterized by high variability the variability of the wave pattern during a half tidal cycle storm from low tide at 1 m to high tide at 13 m in 6 h is a microscale equivalent of the variability of wave patterns changing during sea level rise in the holocene from 7 to 0 m in 6 ka this fact explains why during the late holocene the same locations 1 have displayed a very chaotic response to sea level rise and 2 are displaying today a highly variable response to storms in that respect seafloor morphology is a mesoscale to macroscale control on beach barrier behaviour

rates of continental erosion and mountain building the first objective of this work was to obtain values for the rates at which continental erosion can smooth out or remove the topographic expression produced by orogeny the dominant part is played by mechanical erosion which acts most strongly in regions of large topographic expression chemical erosion depends strongly on precipitation or runoff in individual river drainage basins but because most continents have very similar average rainfall chemical erosion is fairly uniform for continental sized areas and will succeed in planing down all continents to a level peneplain if given enough time the exception to this rule is australia which has a very low chemical erosion rate because of its dryness the time constants for mechanical and chemical erosion so obtained vary between about 30 and 300 my depending on the continent and the assumptions made mountain building occurs throughout the geological time scale but at a non uniform rate although there will not be a balance between erosion and mountain building over a short time scale due to the non uniform rate of mountain building the long term situation must be that the two phenomena should balance out it is shown that the freeboard of continents will respond to the long term balance between mountain building and erosion an expression has been derived for the average continental elevation in which the rate of mountain building depends on the rate of radiogenic heat production within the earth it is shown that relatively small changes in average elevation above sea level of a few hundred metres are predicted to have occurred since the beginning of the proterozoic as mountain building is predicted to decrease on average with time because of the reduction in internal heat generation and as erosion is dependent on the average elevation this average elevation will decrease slowly through time the opposite of what some workers have predicted a more complicated model of mountain building is then investigated in which one component of mountain building has a sinusoidal signal the oscillations in average elevation depend on the period of the sinusoid being smaller for shorter periods finally an average continental elevation is derived using a list of real orogenic events although this list of orogenies is incomplete there is some indication that the actual continental elevation as seen in the flooding history of the continents is similar to that derived in this paper

morphological records of storm floods exemplified by the impact of the 1872 baltic storm on a sandy spit system in south eastern denmark beach ridge systems are important geo archives providing evidence for past wave climate including catastrophic storm flood events this study investigates the morphological impacts of the 1872 baltic storm flood on a beach ridge system sandy spit in south eastern denmark and evaluates the frequency of extreme storm flood events in the area over a longer time perspective this paper combines field studies of morphology and sedimentary deposits studies of historical maps digital terrain model ground penetrating radar profiles and luminescence dating sea water reached 2 8 m above mean sea level amsl during peak inundation and based on studies of the morphological impacts of the 1872 storm flood the event can be divided into four phases phase 1 increasing mean water levels and wave activity at the beach brought sediments from the beach intertidal bars and normal berm higher up in the profile and led to the formation of a storm berm phase 2 water levels further increased and sediment in the upper part of the profile continued to build up the storm berm phase 3 water levels now reached the top of the dune ridge and were well above the storm berm level sea water was breaching the dune ridge at several sites and wash over fans were generated until a level where the mean water level had dropped too much phase 4 the non vegetated wash over fans functioned as pathways for aeolian sand transport and relatively high dunes were formed in particular along the margins of the fan where aeolian sand was trapped by existing vegetation the studied beach ridge system records about 4500 years of accumulation the storm flood sediments described are unique suggesting that the 1872 baltic storm flood event was an extreme event thus studies of beach ridge systems form a new source for understanding storm surge risk copyright 2013 john wiley sons ltd

sedimentary records of intense storms in holocene barrier sequences maine usa coastal morphological geophysical ground penetrating radar gpr and sedimentological data document extreme storm events along the sandy barriers of maine s south central hunnewell and flat point barriers and southwestern saco bay barriers coastal compartments the hunnewell barrier contains four equally spaced buried storm scarps behind the exposed scarp of the blizzard of 1978 a 100 year storm that eroded more than 100 m of shoreline causing extensive property loss these scarps dip 3 5j steeper than the normal beachface slope and consist of sands with more than 50 heavy minerals the heavy minerals produce distinct subsurface reflections that facilitate the location of buried supratidal parts of storm scarps and the mapping of ancient poststorm shoreline positions the imaged scarps likely formed within the past 1 5 2 0 ka bp the flat point barrier consists of a prograded sequence overlain by a laterally extensive seaward thinning layer of freshwater peat and capped by aeolian sands this stratigraphy suggests that the bog varied in size through time contracting during overwash events and aeolian deposition and expanding across washover sheets during extended periods of barrier stability the main overwash event accompanied by barrier planation and wetland expansion may be linked to the first historical storm in new england the great colonial hurricane of 1635 evidence of near modern and mid holocene storm events along saco bay includes washover units and marsh ridges washovers interfinger with saltmarsh peat that ranges in age from 4 5 ka bp to modern the presence of isolated sandy ridges behind existing and former tidal inlets reflects overtopping of marshes and high intertidal mudflats during major storms radiocarbon ages indicate that this process took place at different locations along the saco bay barrier complex from 3 to 1 ka bp d 2004 elsevier b v all rights reserved

sandy berm and beach ridge formation in relation to extreme sea levels a danish example in a micro tidal environment abstract the formation of berms and their transformation into beach ridges in a micro tidal environment is coupled to wave run up and overtopping during extreme sea levels a straight forward comparison between extreme sea levels due to storm surges and active berm levels is impossible in the semi enclosed bays along the baltic sea quite often the maximum water levels do not coincide with the maximum intensity of the wave driven processes because of seiches in the baltic in this paper we look into the joined distribution of extreme water levels and high energetic wave conditions at feddet a sandy prograding spit on the south eastern baltic shores of zealand denmark the modern sandy beach at this location consists of a beachface with a shallow incipient berm a mature berm and a dune covered beach ridge it borders a beach ridge plain to the west where more than 20 n s oriented beach ridges and swales are present measured water level data from 1991 to 2012 and topographical observations carried out during fair weather period and during a storm event provided the basis for a conceptual model exhibiting berm formation and transformation into the local beach ridge system the character of extreme sea level events is identified using thirty three well described extreme events throughout a period of 15 years analysis of the meteorological conditions during these events revealed that berm formation only occurred during 20 of all extreme events when onshore winds high energy wave action and elevated water coincided these berm forming events had a mean return period of once every three years the average age between successive beach ridges on the beach ridge plain was about 180 years which means that the transformation of a berm into a single beach ridge is the result of a large number of storm episodes with high energy waves and extreme water levels