typhoon induced highly nonlinear internal solitary waves off the east coast of korea 1 highly nonlinear internal solitary waves isws propagating both onshore and offshore were detected in a sar image taken approximately 19 hours after typhoon maemi s passage across the east coast of korea analysis of ocean buoy data suggests that the isws were generated by near inertial waves in response to typhoon wind the near inertial waves can propagate seaward due to a downwelling coastal jet positive relative vorticity offshore of the jet and interact with sharply varying topography producing the isws the area of sharply varying topography approximately 28 km off the coast is suggested as a source region for the isws simple calculations of wave speed based on the two layered korteweg devries kdv equation with upper layer thickness and densities at both layers fixed indicate that the isws were generated 6 hours prior to the time of the acquisition of the sar image approximately 13 hours after the typhoon passage consistent with simultaneous buoy measurements

optimization of the hydrodynamic characteristics of a karst conduit with cfpv2 coupled to ostrich the final publication is available at elsevier via https dx doi org 10 1016 j jhydrol 2018 10 050 2018 this manuscript version is made available under the cc by nc nd 4 0 license https creativecommons org licenses by nc nd 4 0

salman farsi dam reservoir a successful project on a karstified foundation sw iran the salman farsi dam is constructed on the ghareh aghaj river at the northern limb of changal anticline sw iran the anticline is composed of the calcareous asmari formation af sandwiched between two marly formations the pabdeh gurpi pgf and razak rf the af is divided into three units lower laf marl and limestone middle maf karstified limestone and upper uaf marl and marly limestone the dam is constructed on the maf and the reservoir is in direct contact with the maf uaf and rf a huge relict cave was discovered during excavation of grouting galleries in the maf in this research the potential leakage passage plp is defined as parts of the karst aquifer located lower than the normal water level nwl of reservoir in which the reservoir water has potential to be leaked toward downstream assuming no grout curtain construction the plp is composed of the inlet windows transfer passage and discharge zones at the salman farsi dam the plp is determined by three alternative schematic models considering hydrogeological and geological settings at this dam site the grout curtain was properly designed from the maf toward the downstream laf at the narrowest part of the plp and bypassing the huge cave the grout curtain was successful in blocking the plp based on the negligible leakage and high differences between water level in the pair piezometers at the upstream and downstream sides of the grout curtain it is recommended to determine the plp in future dam construction in karst terrains

on the response of the ocean to a moving storm the nonlinear dynamics abstract a novel and efficient numerical method is used to investigate the nonlinear equations of motion for the upper layer of a two layer ocean in which the lower layer is infinitely deep and at rest the efficiency is achieved by seeking solutions that are in a steady state translating in equilibrium with the storm oscillations are found in the wake of the storm two features of the response are attributed to the nonlinear terms in the equation of motion 1 a rapid transition from a maximum in the downwelling phase to a maximum in the upwelling phase of each oscillation followed by a gradual relaxation to the next downwelling maximum and 2 a displacement of the maximum response usually to the right of the storm track by 40 km it is shown that the horizontal pressure gradient terms can be neglected from the momentum equations for fast large storms in which case a lagrangian integration can be performed following fluid particles this enables feature 1 to be attributed to the along tra

effect of topography and mixing parameterization upon the circulation in cold water domes 1 the influence of bottom topography and the parameterization of subgrid scale mixing upon the steady state circulation in a cold water bottom dome was examined using a three dimensional prognostic model in cross sectional form initially the circulation due to a specified bottom dome and surface frontal system associated with observed domes are considered in isolation calculations revealed a cyclonic anticlockwise circulation in the surface layer with an anticyclonic clockwise circulation in the near bed layer associated with an isolated bottom dome in the case of the surface frontal system calculations showed surface and near bed circulations in the opposite directions to those found for a bottom dome for the surface frontal case the maximum current occurs at the sea surface with a weak current at the bed calculations showed that topography had little effect in subsequent calculations surface front and bottom dome in combination were examined in this case their form was not specified but was generated by solar heating and calculations showed that topography had an important role the opposing nature of the circulations associated with the surface front and bottom dome leads to a dominant near surface cyclonic current circulation at the edge of the dome with weaker secondary circulations beyond this cross frontal circulation cells were generated in the vertical the strength and exact form of these circulations depended upon the topography and parameterization of mixing

a three dimensional baroclinic model of the irish sea formation of the thermal fronts and associated circulation a high resolution three dimensional baroclinic shelf sea model is developed and applied to the determination of the various processes influencing the generation and position of thermal fronts and the associated circulation in the irish sea the model has a horizontal grid resolution of approximately 3 6 km by 3 0 km and can resolve the thermal fronts in the region in particular in the western irish sea although the grid is not sufficiently fine to resolve small scale features along these fronts produced by baroclinic instabilities using meteorological forcing from dublin airport located close to the center of the region and tidal forcing a series of numerical experiments were performed to examine the processes influencing the location and dynamics of thermal fronts and associated circulation in the irish sea the results show a reasonable qualitative agreement with observations of the thermal stratification and the associated circulation in the western irish sea the ability of the model to reproduce the main features of the frontal structures in the region having been established it is used to examine the interannual variability of the density flow field calculations using meteorological forcing from different years show that the western irish sea fronts and the associated cyclonic circulation are persistent features although exact details of the fronts and their times of formation and breakdown show a large interannual variability model results also reveal a patch of thermal stratification in the northern part of the eastern irish sea with northward thermal density driven currents in this region

coastal stratigraphies of eastern bonaire netherlands antilles new insights into the palaeo tsunami history of the southern caribbean abstract a sediment record of three alluvial sites along the east and northeast oriented shore of bonaire netherlands antilles provides evidence for the recurrence of several extraordinary wave impacts during the holocene the interpretation of onshore high energy wave deposits is controversially discussed in recent sedimentary research however it represents a powerful tool to evaluate the hazard of tsunami and severe storms where historical documentation is short and or fragmentary a facies model was established based on sedimentary and geochemical characteristics as well as the assemblage and state of preservation of shells and shell fragments radiocarbon data and the comparison of the facies model with both recent local hurricane deposits and global tsunami signature types point to the occurrence of three major wave events around 3300 2000 1700 and shortly before 500 bp since i the stratigraphically correlated sand layers fulfill several sedimentary characteristics commonly associated with tsunamis and ii modern strong hurricanes left only little or even no sediment in the study areas they were interpreted as tsunamigenic however surges largely exceeding the energy of those accompanying modern hurricanes in the southern caribbean cannot entirely be ruled out the results are partially consistent with existing chronologies for holocene extreme wave events deduced from supralittoral coarse clast deposits on aruba bonaire and curacao as well as overwash sediments from cayo sal venezuela

advective spreading of storm induced inertial oscillations in a model of the northwest atlantic ocean the spreading of inertial oscillations induced by the passage of hurricane juan 2003 across the gulf stream and the scotian shelf is examined using a regional model of the northwest atlantic ocean it is found that surface intensified inertial oscillations develop at locations remote from the storm track after a period of 5 10 days a diagnostic technique reveals the importance of advection by the background geostrophic flow for explaining this effect the results suggest that advection by mean circulation can play a role in redistributing near inertial energy in the ocean we argue that advective redistribution could have important consequences for understanding diapycnal mixing in the ocean

a 1900 year paleohurricane record from wassaw island georgia usa we present here the first paleotempestology record from wassaw island on the georgia bight located in the south atlantic coast of the united states in the historical period the georgia bight has experienced less frequent hits by hurricanes than other locations along the us gulf and atlantic coasts the 1900 year record inferred from the overwash sand layers from a back barrier marsh on wassaw island suggests that the island was directly struck by major storms on nine occasions during this interval the wassaw island record shows alternating regimes with periods of increased activity from 2000 a bp until 1100 a bp and 100 a bp until the present sandwiching a quiet period from 1100 to 250 a bp storm deposits from the most recent active period are perhaps amalgamated indicating that site specific conditions may result in event undercounting and suggests that the relative thickness of sand layers in the sedimentary record is not always indicative of hurricane strength copyright 2011 john wiley sons ltd

strike slip faulting rotation and along strike elongation in the kopeh dagh mountains ne iran summary the kopeh dagh is a linear mountain range separating the shortening in iran from the stable flat turkmenistan platform in its central part is an array of active right lateral strike slip faults that obliquely cut the range and produce offsets of several kilometres in the geomorphology and geological structure they are responsible for major destructive earthquakes in the 19th and 20th centuries and represent an important seismic hazard for this now populous region of ne iran these strike slip faults all end in thrusts revealed by the uplift and incision of late quaternary river terraces and do not continue beyond the atrak river valley which forms the southern margin of the kopeh dagh the cumulative offset on these strike slip faults and their associated rotation about vertical axes can account for 60 km of n s shortening this value is similar to estimates of the late quaternary n s right lateral shear between central iran and afghanistan which must be accommodated in ne iran the strike slip faults also require 30 km of along strike extension of the kopeh dagh which is taken up by the westward component of motion between the south caspian basin and both eurasia and central iran it is probable that these motions occurred over the last 10 ma

contribution of spectral coherency analysis and tracer test to study leakage at the doosti dam reservoir iran and turkmenistan the doosti dam was built across the harirood river on the border between turkmenistan and iran during the reservoir impounding leakage occurred as new springs through the sandstone layers of the pesteleigh aquifer and limy sandstone and limestone layers of the neyzar kalat aquifer at the right abutment of the dam to evaluate the grout curtain operation a tracer test was carried out by injection of uranine in a borehole located at the upstream of grout curtain in the pesteleigh aquifer tracer test results demonstrated a diffuse flow component through the grout curtain in the pesteleigh aquifer but no tracer was detected at the main leakage point sp1 spring emerged downstream of grout curtain from the neyzar kalat aquifer using the spectral coherency function the lag time between changes in the water level of the injection borehole and water level in the tracer detected boreholes or discharge of the tracer detected springs was determined linear regression analyses indicated that the estimated lag time by the time series analysis was close to the first arrival time of the tracer therefore the estimated velocities based on the lag time of time series could be considered close to the calculated velocities based on the first arrival time of the tracer the estimated groundwater velocities based on the time series analysis ranged from 3 91 to 20 31 m h 1 showed that diffuse flow dominated pathways from the reservoir toward the downstream boreholes in the neyzar kalat aquifer while conduit flow was present within the pathways toward the sp1 spring regarding the reservoir volume the negligible amount of leakage at the maximum water level of the reservoir confirmed well overall operation of the grout curtain at the dam site

sequential tracer tests for determining water seepage paths in a large rockfill dam nakdong river basin korea the rockfill dam of this study has a clay core filter zone and sandy gravel shell and it is located in the nakdong river basin in korea filling the reservoir began in august 1994 and it was full by april 1998 when the reservoir level was approximately 150 m three settlement holes were found in the dam crest to determine possible seepage paths and potential damaged areas within the rockfill dam 15 tracer tests were performed during two periods during the two test periods six and nine tracer tests were conducted when the average water levels of the reservoir were 145 m and 142 m respectively rhodamine wt rwt and bromide ion were used as tracers for each test 1800 to 4000 l of tracer solution were injected into the riprap for about 5 h the 15 injection points were uniformly distributed from the right to left sides of the embankment and the two tracers were injected alternately tracer concentrations were monitored at 26 observation wells which were divided into four groups by their geographical positions right side of the crest left side of the crest right side of the dam toe and left side of the dam toe for each tracer test more than 30 water samples were taken during a period of 96 h at each observation well based the breakthrough curves obtained from the sequential tracer tests it was inferred that the most probable seepage paths and potential damaged area were in the left side of the crest tongue wing zone and to a lesser extent in the right side of the dam abutment

processes influencing the non linear interaction between inertial oscillations near inertial internal waves and internal tides 1 a numerical model of the hebrides shelf edge represented by a cross section is used to examine the non linear interactions producing energy at the fm2 frequency calculations show that in the near coastal ocean this is primarily due to coupling between wind induced inertial oscillations although near inertial internal waves are present and the m2 internal tide the major non linear interaction and hence largest fm2 currents occurs in the region of the thermocline and is associated with shear in the inertial oscillation and the vertical velocity due to the internal tide this non linear process represents an important contribution to the energy cascade from the wind and tide into higher frequency waves and eventually mixing the fm2 current is shown to be a maximum in the shelf edge region and hence measurements in this area will be particularly valuable in determining the extent to which models can represent non linear processes

the relation of near inertial motions observed in the mixed layer during the jasin 1978 experiment to the local wind stress and to the quasi geostrophic flow field abstract oscillations with near inertial frequencies were an energetic component of the upper ocean velocity field observed at each of two moorings separated by 44 km during the joint air sea interaction jasin experiment during the late summer of 1978 at each mooring the amplitude of the inertial motion was highest in the mixed layer where it was nearly depth independent previous work pollard and millard 1970 pollard 1980 had found that the amplitude and phase of inertial motion in the mixed layer was related to the local wind stress in this case the loacal winds measured at each mooring were coherent but the time series of mixed layer near inertial motion at one mooring bore little resemblance to that at the other mooring during jasin 1978 the differences in the inertial response at the two moorings coincided with differences in the quasi geostrophic flow field in the vicinity of the two moorings inclusion of the horizontal gradients of the quasi geostrophic flow in model equations prov

water leakage paths in the doosti dam turkmenistan and iran the doosti dam with a reservoir capacity of 1 250 million cubic meters was constructed on the harirood river at the border of turkmenistan and iran the reservoir is in direct contact with permeable formations on the right abutment of the dam including the neyzar sandstone the kalat limestone and the pesteleigh alternative layers of marlstone and sandstone after the reservoir impoundment several new springs and seepages emerged from these formations and the alluvium the amount of leakage increased with the rise in reservoir water level fifteen kilograms of sodium fluorescein were injected into a 113 m deep borehole intersecting three permeable sandstone layers of the pesteleigh formation dye was detected downstream of the grout curtain in boreholes and springs that were in direct contact with parts of the pesteleigh formation having the same sandstone layers as the injection borehole the dye velocity was in the range of diffuse flow confirming the good performance of the grout curtain in the pesteleigh formation no dye was detected in the other formations because the injection borehole was not in direct contact with these formations the hydraulic relation of the other formations with the reservoir was determined by considering direct contact of the formations with the reservoir emergence of new springs and seepages after reservoir impoundment correlation of time variations of the springs discharge and the borehole s water level with the reservoir water level and in some cases the hydrochemistry of the water the results show that the kalat and neyzar formations are hydraulically connected to the reservoir but the small amounts of leakage from these formations at a hydraulic gradient of 24 indicates good performance of the built grout curtain the total reservoir leakage at maximum reservoir water level was 100 l s which is insignificant compared with the 15 m3 s average annual release of the reservoir

a dye tracing test as an aid to studying karst development at an artesian limestone sub aquifer zagros zone iran a dye tracing test is employed to study the karst development and flow regime at an artesian limestone sub aquifer the khersan3 dam site zagros zone iran tracer breakthrough curves showed an early dominant peak followed by a pronounced tailing effect the peak concentration was a response to induced pressure during dye injection the results suggest that the dye was pushed into the small pores and fissures around the injection point during dye injection hence the dye moved out as a result of matrix and fissure diffusive processes and created a long pronounced tailing the maximum flow velocity in the upper artesian sub aquifer ranged from 0 97 to 2 9 m h however the mean tracer velocity ranged from 0 19 to 0 51 m h based on the mean residence tracer time consequently the flow regime in the artesian sub aquifer was determined to be mainly diffusive the results reveal 1 a low hydraulic gradient from upstream of the dam axis to downstream consequently there is no considerable flow 2 poor karst development and diffuse flow at the tracing test area 3 a discharge zone at a location downstream of the dam axis which is the main terminal of general flow direction at the dam site

influence of coastal fronts on near inertial internal waves 1 a numerical model with a coastal boundary and near shore surface or bottom front is used to examine the role of the coast and front upon the generation and propagation of wind induced near inertial internal waves when stratification extends to the coast near inertial internal waves are produced at the coastal boundary however when the near shore region is well mixed the source of near inertial internal wave production is the front near inertial internal waves generated on the positive vorticity side of the front propagate away in the horizontal those generated on the negative vorticity side are trapped although some vertical propagation occurs when a coastal boundary is included significant inertial currents are found at depth phase shifted by 180 from the surface this goes some way to explain the recent observed distributions of inertial energy found in near coastal measurements

lake sediment record of late holocene hurricane activities from coastal alabama coastal lake sediments contain a stratigraphically and chronologically distinct record of major hurricane strikes during late holocene time frederic a category 3 hurricane that struck the alabama coast on the gulf of mexico in 1979 left a distinct sand layer in the nearshore sediments of lake shelby as a result of storm tide overwash of beaches and dunes sediment cores taken from the center of lake shelby contain multiple sand layers suggesting that major hurricanes of category 4 or 5 intensity directly struck the alabama coast at ca 3 2 3 0 2 6 2 2 1 4 and 0 8 ka 14 c yr with an average recurrence interval of 600 yr the alabama coast is likely to be struck by a category 4 or 5 hurricane within the next century

wind induced motion in the vicinity of a bottom density front response to forcing frequency 1 a numerical model is used to examine the influence of nonlinear processes in the vicinity of a shallow sea bottom density front upon the depth of penetration of the wind s momentum at both superinertial and subinertial frequencies calculations show that nonlinear effects associated with differences in vorticity across the frontal jet significantly influence the depth of penetration of the wind s momentum and internal wave propagation differences in wind induced current amplitude and phase at depth due to nonlinear effects give rise to substantial vertical velocity in the frontal region which drives near bed currents and forces internal waves at superinertial frequencies internal waves propagate away from the positive vorticity side of the front however at depth internal waves are generated and current amplitude increases in the region of sloping density surfaces associated with the front on the negative vorticity side due to an effective inertial frequency below inertial the wind s energy can propagate deeper into the water column wind forcing at subinertial frequencies does not lead to internal wave propagation on the positive vorticity side of the front the wind s momentum cannot diffuse to depth due to turbulence suppression by stable stratification the ability of the wind s momentum to penetrate to a greater depth in a frontal region through nonlinear effects suggests that these may be important processes influencing wind mixing in frontal regions

role of hurricanes in the holocene stratigraphy of estuaries examples from the gulf coast of florida abstract sarasota and little sarasota bays are shallow coastal bays located landward of a holocene barrier inlet complex on the west central microtidal gulf coast of florida sediments presently accumulating in the bay consist of 1 fine to very fine quartz sand contributed from the gulf shoreline during storm generated washover through tidal inlets and from reworking of older deposits 2 fine sand to pebble sized quartz and phosphatic sediment contributed by tertiary and pleistocene deposits 3 biogenic carbonate debris which is produced within the bays and or derived from the gulf of mexico 4 clay minerals derived from weathering of tertiary and pleistocene carbonates and clays and 5 particulate organic debris interpretations from 51 vibracores from throughout the bays have enable delineation of four major depositional sedimentary facies resulting from specific environmental conditions protected bay open bay tidal delta washover and storms bedrock in the area ranges from 0 to about 8 m msl and is largely responsible for the areal configuration of the bay and the location of the barrier islands the holocene stratigraphy of both bays has been greatly influenced by the passage of major hurricanes which carried large volumes of sand and shell gravel into the bays at least four of these storms are documented in these cores three storm units from sarasota bay have been radiocarbon dated at 2 270 1 320 and 240 years before present ybp historically documented severe hurricanes influenced this coast in 1848 and 1921 hurricanes interrupted the normal low energy slow deposition in the bays and caused inlets to open and close three storm generated sedimentary facies are identified 1 a graded storm facies which is composed of conspicuously fining upward units ranging from sandy shell gravel to slightly shelly quartz sand 2 a homogenous storm facies consisting of homogenous and relatively thin shelly sand and gravel units and 3 a fluvial storm facies which is muddy and generally free of shells representing terrigenous influx from runoff

a sedimentary based history of hurricane strikes on the southern caribbean coast of nicaragua abstract multi millennial hurricane landfall records from the western north atlantic indicate that landfall frequency has varied dramatically over time punctuated by multi centennial to millennial scale periods of hyperactivity we extend the record geographically by presenting a paleostrike record inferred from a four core transect from a marsh on the caribbean coast of nicaragua fossil pollen indicates that the site was a highly organic wetland from 5400 4900 cal yr bp at which time it became a shallow marine lagoon until 2800 cal yr bp when it transitioned back into swamp marsh freshening over time with the present fresh to brackish typha marsh developing over the very recent past hurricane joan 1988 is recorded as a distinctive light colored sand silt clay layer across the top of the transect identifiable by abrupt shifts in color from the dark marsh deposits increased grain size and two upward fining sequences which are interpreted as representing the storm s traction and suspension loads the six layers identified as hurricane generated display temporal clustering featuring a marked increase in landfall frequency 800 cal yr bp this pattern is anti phase with the activity pattern previously identified from the northern caribbean and the atlantic coast of north america thereby opposing the view that hyperactivity occurs simultaneously across the entire basin

forest changes in the amazon basin during the last glacial maximum we report here the discovery of forest beds in the amazon basin radiocarbon dated to the wisconsin wurm glaciation these are the first dates from the last glaciation determined on amazonian samples the locality is in ecuador at 1 100 m elevation near the upper limit of the present amazonian rainforest both pollen spectra and podocarpus wood in the deposits suggest that vegetation comparable to the present andean forest grew at least 700 m lower than it does now suggesting a temperature depression of at least 4 5 c for the amazon lowlands

palaeohurricane reconstructions from sedimentary archives along the gulf of mexico caribbean sea and western north atlantic ocean margins hurricanes annually threaten the atlantic ocean margins historical hurricane records are relatively short and palaeohurricane sedimentary archives provide a geological and climatic context that sheds light on future hurricane activity here we review palaeo trends in hurricane activity elucidated from sedimentary archives we discuss dating methods site selection and stat istics associated with previously published records these archives have been useful for under standing the long term evolution of coastal systems and the response of intense hurricane activity to climatic changes regional shifts in hurricane overwash on centennial to millennial timescales have been linked to various climatic modes of variability including el nino southern oscillation and the north atlantic oscillation but could also reflect regional scale controls on hurricane activity

modelling the depth of penetration of the wind s momentum at super inertial frequencies due to non linear effects in frontal regions 1 a numerical model with a coast and density front is used to examine the influence of the front upon the depth of penetration of the wind s momentum we find that non linear processes associated with spatial variations in vorticity play an important role in driving wind induced currents at depth internal wave generation and propagation also occur in the frontal region for a bottom front the downward propagation of internal waves in the frontal region is inhibited by the presence of sloping isotherms and a region of enhanced current magnitude develops at depth at the front s edge on the stratified side for a surface front the presence of enhanced surface vorticity on the well mixed side of the front means that the wind s energy is trapped in the surface layer these calculations help to explaining the large spatial variability of wind forced energy found in observations

mangrove dynamics in the southwestern caribbean since the little ice age a history of human and natural disturbances relatively little is known about the long term response of caribbean mangroves to human and natural disturbances during the little ice age lia we present new palynological information on the dynamics of the bahia honda mangrove from the eastern coast of san andres island in the southwestern caribbean for the late holocene major changes in the bahia honda pollen record show the combined effects of natural events strong storms and sea level rise and human disturbances these changes are supported by 14c dates sedimentological and palynological information a storm most probably a hurricane was recorded around ad 1600 caused sediment reworking and the subsequent loss of about 2000 years of the vegetation record the devastation of tree vegetation by this event allowed the expansion of heliophytic vegetation e g grasses and vines mangroves and coastal vegetation started to recover at ad 1700 reaching their maximum extent within a few decades when microforaminifera shells became abundant at

inertial oscillations on the continental shelf of the gulf of lions observations and theory abstract observations in the gulf of lions northwestern mediterranean sea in summer have shown that gusts of wind lasting a few days generate transient upwellings and inertial motions oscillations at the inertial frequency were observed in current meter data near the shore and at a frequency 10 greater in the temperature data vertical coherences in current meter data show a strong baroclinic mode at frequencies greater than inertial frequency a simple one dimensional two layer transient model suggests that these motions are associated with two different physical processes the first process describes the local response of the ocean to meteorological forcing the second is associated with the propagation of long internal waves generated in the transient phase of the geostrophic adjustment process as suggested by the model the direction of propagation of the internal waves is computed from current and temperature data measured at one point and it is found that the shore is the source zone

a 3000 yr paleostorm record from st catherines island georgia abstract tropical cyclones hurricanes in the northern hemisphere are amongst the most devastating of the world s natural disasters and cause billions of dollars in damage every year data on the likelihood of a coastal site being struck by a major hurricane strike can potentially aid in planning and mitigation efforts that could save money and lives however forecasting requires data that are currently insufficient for the georgia bight this study provides information to enhance the paleohurricane record by analysis of a 467 cm thick vibracore raised from st catherines island ga sediment geochemistry and foraminiferal assemblages indicate deposits attributable to seven paleohurricane events five of which were likely major hurricanes when they made landfall on st catherines magnitudes were estimated by comparison to the overwash deposit left by the sea islands hurricane of 1893 a major hurricane recorded by the recent sediment of st catherines island the st catherines record also shows a change in the activity levels on the georgia coast with two distinct activity regimes over the past 3000 years

model studies of near inertial waves in flow over the oregon continental shelf abstract two dimensional primitive equation model studies of wind forced flow over a continental shelf show that under upwelling conditions high levels of near inertial wave energy are found in the interior over the shelf the regions of elevated wave energy with maximum wave amplitudes of around 0 2 m s 1 persist for up to two weeks and have spatial scales of 20 40 m vertically and 5 20 km horizontally relatively high dissipation levels are associated with these concentrations of wave energy when forced with downwelling favorable winds model results show very little subsurface inertial energy on the shelf a comparison of inertial wave propagation using the primitive equation model and a linearized version of the model demonstrates strong dependence on the background flow field the behavior of inertial waves using the linearized model is completely different very little subsurface inertial energy is seen on the shelf in either upwelling or downwelling conditions except where the bottom slope

hydrogeological characterization of dasht e arjan lake zagros mountains iran clarifying a long time question dasht e arjan lake is located in the southern zagros mountain ranges of iran it is a tectonic karst polje fed by a single spring plus local surface runoff and drained by a single ponor the fate of sinking water from the ponor had not been determined before this study previous investigations suggested two alternatives 1 underground flow 24 km southwest to parishan lake and or springs in the kazeron area and 2 underground flow 20 km southeast to springs at domeasb gorge to clarify this question an integrated hydrogeological study including a dye tracer test was undertaken comparison of the discharge into the arjan ponor and the discharge of the domeasb springs shows a reliable correlation further annual water balance analysis reveals that the discharge at the domeasb springs is too great for its topographic catchment requiring a major additional source the dye tracer test using 5 kg of uranine was detected only at the domeasb springs flow through time after the dye injection was 210 h the tracer breakthrough curves are very simple and sharp with a clear peak concentration of 7 ppb the total tracer mass recovery and groundwater flow velocity were estimated to be 58 and 105 m h 1 respectively the results indicate a simple and direct limestone karst hydraulic connection along the geologic strike between dasht e arjan lake and the domeasb springs the results clearly suggest the possibility of designing a dam around the ponor to protect drying up the lake during drought periods

reconstruction of prehistoric landfall frequencies of catastrophic hurricanes in northwestern florida from lake sediment records abstract sediment cores from western lake provide a 7000 yr record of coastal environmental changes and catastrophic hurricane landfalls along the gulf coast of the florida panhandle using hurricane opal as a modern analog we infer that overwash sand layers occurring near the center of the lake were caused by catastrophic hurricanes of category 4 or 5 intensity few catastrophic hurricanes struck the western lake area during two quiescent periods 3400 5000 and 0 1000 14 c yr b p the landfall probabilities increased dramatically to ca 0 5 per yr during an hyperactive period from 1000 3400 14 c yr b p especially in the first millennium a d the millennial scale variability in catastrophic hurricane landfalls along the gulf coast is probably controlled by shifts in the position of the jet stream and the bermuda high

seepage problems in the karstic limestone foundation of the kalecik dam south turkey abstract seepage phenomena through the karstic limestone foundation of kalecik dam are investigated the dam designed as a rock fill dam with a height of 77 m is already used for irrigation the foundation consists of mesozoic ophiolite paleocene allochthonous units composed of different lithologies and miocene conglomerate the conglomerate lies unconformably on the other units quaternary basaltic lava patchily covers the others seepage from upstream to downstream occurs through the allochthonous karstic limestone this limestone which is overlain by conglomerates has a thickness increasing towards the right abutment to prevent seepage at the right abutment a 200 m long and 60 m deep grout curtain along the dam axis was constructed after the impoundment some springs occurred downstream and for this reason extra grouting was performed however the seepage problem could not be solved in order to determine the seepage direction and karstification pattern hydrological studies have been done additional investigation boreholes have been drilled to observe fluctuations of the groundwater level and to analyze hydrochemistry also dye tracer tests have been carried out as a result of these hydrogeological studies seepage paths were observed in the karstic limestone located between the dam and the spillway as those carbonate rocks continue beneath the spillway the seepage problems are enjected to continue

on the nature of internal wave spectra near a continental slope 1 amongst the most energetic motions in the deep ocean are internal waves supported by stable vertical stratification in density previously these waves were considered freely propagating as described by a smooth continuum internal wave band iwb frequency spectrum we studied details of the iwb using yearlong current observations from the bay of biscay instead of observing continuum iwb spectra near a continental slope we show that at least the first half decade of the iwb is dominated by motions at localized frequencies determined by strong non linear interactions between waves at the fundamental semidiurnal tidal and atmospherically induced inertial frequencies

on the influence of a surface coastal front on near inertial wind induced internal wave generation 1 a numerical model is used to examine the wind induced near inertial internal waves in the coastal region in the presence of a surface front initial calculations with the front separating a well mixed coastal region from a stratified offshore area in an infinite sea domain showed that away from the front surface inertial oscillations are dominant near the front on the positive vorticity side superinertial internal waves are generated and propagate offshore in an analogous manner to that found when stratification intersected a coastal boundary however in the case of a coastal boundary the no flow condition at the coast produced inertial oscillations at depth phase shifted by 180 from those at the surface on the negative vorticity side of the front internal waves at the subinertial frequency are trapped between the well mixed region and the front some inertial energy is found at depth in the frontal region although the large scale features of the distribution of inertial energy are independent of vertical eddy viscosity parameterization its magnitude depends upon it in the case of a stratified nearshore region and an offshore front near inertial waves generated at the coast were trapped between the coastal boundary and the front which results in a surface region of enhanced inertial energy this gradually decreased with time as inertial energy diffused to depth this timescale depended upon vertical eddy viscosity magnitude

the lar dam an example of infrastructural development in a geologically active karstic region abstract the problems associated with the construction of the lar dam iran provide a classic example of problems that can result from infrastructural development in an active geological terrain which includes the regional carbonate units the lar dam lies in a heavily faulted and fractured region close to the active damavand volcano the fracturing has enhanced the production of karst and sinkholes in the limestone below the dam and acidic ground water run off from the damavand volcano increases the dissolution of the carbonate beds along the fractures to produce sinkholes below the dam the initial problem of building the dam in such a region is compounded by the relationship between water loss due to enhanced sinkhole development and the remedial measures being taken to lessen this leakage drainage of the sub reservoir caverns through leakage along fractures can lead to loss of hydrostatic support for the developing sub reservoir caverns and their consequent collapse furthermore rapid changes in subterranean water levels would lead to rock shattering hammer effects particularly during rapid rises in water level

quantitative tracing of the maligne karst system alberta canada abstract early dye tracing studies on the large maligne karst aquifer in the canadian rocky mountains gave indeterminate results and low tracer recoveries in contrast a recent series of tests using high precision field fluorometry gave well defined breakthrough curves and far higher but variable recovery low recovery in one test may be accounted for by hydraulic switching or interaction with an alluvial aquifer which buries the principal conduit outlets a 16 km long karst conduit averaging between 90 and 170m 2 in cross sectional area drains the principal sinking lake to a group of karst springs a 14 km tributary conduit linking a high karst valley to the major conduit both drains and feeds the karst lake although during winter it has flows transitional between laminar and turbulent regimes a strong nonlinear relation between travel time and discharge suggests a partly vadose system that is little influenced by unsteady flow static and maximum dynamic conduit storage were estimated to be 1 95 and 0 76 10 6 m 3 respectively

detection of leakage paths at the wanyao dam body in southwest china by hydrochemical analysis and tracer testing leakage at the wanyao dam body was studied using a combined approach of field exploration hydrochemical analysis and tracer testing the objective of study was to determine the location of the water leakage paths at the dam a hydraulic connection was observed between exploration boreholes of dam crest and drain holes at drainage gallery during the period of drilling this connection shows that there were some defects in the dam the hydrochemical compositions and characteristics of the water samples involved the main anions and cations total dissolved solids electrical conductivity ph and water temperature which were analyzed and evaluated by correlation and cluster analysis the results indicated that a close hydraulic connection existed between water from the dam body and reservoir water particularly reservoir water from sections iii and ix tracer testing results demonstrated further existence of leakage paths between reservoir water and sections iii and ix also there were multiple leakage paths in section ix compared with a single path of section iii furthermore the leakage location of upstream concrete faces in the vertical and horizontal directions was determined accurately with the measured electrical conductivity of receiving points the experimental data provide a strong foundation and basis for maintaining and reinforcing the dam

resonant diurnal oscillations and mean alongshore flows driven by sea land breeze forcing in the coastal southern california bight abstractthis study presents observations of the cross sectional structure of resonant response to sea land breezes slbs off huntington beach hb in the southern california bight scb a resonant response to local diurnal wind stress fluctuations associated with slb forcing occurs intermittently and produces strong diurnal oscillations of flow and temperature resulting from enhanced work of the diurnal local wind on the sea surface at nighttime daytime a coherent cross sectional circulation with offshore onshore currents in the surface layer upper 15 m and onshore offshore currents in the intermediate layer around 20 m are generated with a three layered vertical structure on the outer shelf the authors find a net cross shore eddy heat flux net cooling of nearshore water during the period of strong response to slb that is a rectified mean heat flux and steeper isotherms resulting from the diurnal slb fluctuations the steepened mean isotherms are also found to be in thermal wind balance

particle motion and the theory of charcoal analysis source area transport deposition and sampling principles from particle motion physics were applied to recurring problems of the interpretation of stratigraphic charcoal data 1 fires within catchments of lakes often produce no record in fossil charcoal curves and 2 periods characterized by no local fire e g 20th century fire suppression often display as much charcoal as times when local fire was frequent quantitative theory on source area transport deposition and sampling of charcoal shows the relationship between particle sizes counted by alternative methods of charcoal analysis pollen slides for particles 5 80 m in diameter petrographic thin sections for particles 50 10 000 m diameter and charcoal diagrams the relationship between diameter and critical and deposition velocities results in fundamental aerodynamic differences between the sizes of particles quantified by the two methods charcoal recorded on pollen slides is of a size that is difficult to lift but once entrained it remains in suspension thin section charcoal is lifted at relatively low wind velocities but it is not suspended at normal surface wind speeds thermal buoyancy during fire lofts charcoal above the forest canopy depending on particle size and wind speed pollen slide charcoal sizes are underrepresented near the fire because they remain in suspension and are preferentially exported from the burn area thin section charcoal is convected to lower heights on average and is deposited nearby following fire thin section charcoal is redistributed locally by wind and thus may enter lakes because of cohesive forces and aerodynamics more pollen slide charcoal remains on the ground and less enters lakes source areas for pollen slide charcoal are subcontinental to global and diagrams of pollen slide charcoal are biased toward nonlocal charcoal they can be used to interpret importance of fire for broad spatial and temporal scales thin section charcoal represents the catchment fire regime simulation models that generate charcoal during fire mix sediments and then sample at specified intervals indicate that 1 in the absence of sediment mixing the pollen slide method should consistently resolve individual fires that occur with an expectation of 30 50 yr 2 unless samples are continuous neither method will produce useful estimates of fire frequency and 3 even a modest amount of sediment mixing will obscure the signal

modern pollen spectra from costa rica abstract we analyzed pollen spectra preserved in surface lake and mire sediments and soils to provide information on modern pollen rain across a range of vegetation types in costa rica we collected samples at 29 sites located within ten principal vegetation types mangrove tropical dry forest derived savanna tropical moist forest tropical wet forest lowland freshwater swamp premontane rain forest montane rain forest montane bog and paramo samples from sites with similar vegetation generally had similar pollen assemblages and clustered together in detrended correspondence analysis results indicate that major vegetation types in costa rica have distinct pollen spectra

paleoecological record of hurricane disturbance and forest regeneration in nicaragua studying infrequent phenomena e g hurricanes and slow processes e g forest regeneration greatly challenges the ecological techniques of real time studies by combining the two relatively new approaches of paleotempestology and fine resolution palynology this study provides insight into the impacts of hurricanes and the post hurricane regeneration of forests i analyzed a 5 m sediment core from a swamp lagoon on the caribbean coast of nicaragua that covered the entire 8000 yr history of the swamp urquhart g r 1997 disturbance and regeneration of swamp forests in nicaragua evidence from ecology and paleoecology ph d dissertation the university of michigan ann arbor mi usa x rays revealed a sand layer dating to c 3300 bp of the type deposited by hurricanes pollen analyses showed this sand layer was followed by major changes in vegetation and fires this pattern is identical to the wake of hurricane joan which struck the area in 1988 and left 90 000 hectares of damaged swamp forest that burned shortly after after the prehistoric hurricane forest vegetation did not return until 500 yr later due to repeated burning this parallel event of the past illustrates a possible course for modern forest regeneration as a counterpart to direct ecological analysis fine resolution paleoecological study can provide great insight for the study of rare events and slow processes