The Mississippi River Chenier Plain is a shore parallel landform (down-drift from the Atchafalaya distributary of the Mississippi River) consisting of an alternating series of transgressive sand-shell ridges and regressive, progradational mudflats. The late 1940s shift of 1/3 of the flow of the Mississippi to the newly developing Atchafalaya delta complex to the west has resulted in injection of the river waters and suspended sediment into the westward flowing currents of the coastal current system. This has reactivated the dormant processes of mud accumulation along this coast. These environmental circumstances have provided the opportunity to: (1) investigate the depositional processes of the prograding, fine grained, mud flat facies of the open Chenier main coast and (2) to test the hypothesis that the impacts of the frequent cold front passages of fall, winter and spring exceed those of the occasional and more localized hurricane in shaping the coast and powering the dominant sedimentary processes. We conducted field investigations with the benefit of multi - scale, time series environmental surveillance by remote sensing systems, including airborne and satellite sensors. These systems provided invaluable new information on areal geomorphic patterns and the behavior of the coastal waters. This is a classic case of weather impacting inner shelf waters and sediments and causing the development of a new landform. It is clear that mud flats of the eastern chenier plain are prograding seaward, as well as progressively growing in a westerly direction.
The optically stimulated luminescence (OSL) dating method was used to determine the geochronology of seven relict beach ridges that sit immediately behind the modern beach at Beachmere, a low-energy sandy coast within Moreton Bay, Queensland. Between 2600 +/- 400 and 1700 +/- 130 years ago, the shoreline eroded and foreshore sediment was deposited over the older beach deposit. Subsequently, there was a 1500-year period of shoreline progradation: the shoreline advanced 0.16 m/y between 1700 +/- 130 and 1140 +/- 80 years ago; and 0.41 m/y between 1140 +/- 80 and around 200 years ago. Shortly after 690 +/- 60 years ago, a series of well-developed regularly spaced beach ridges gave way to an intertidal flat and then deposition of a set of lower amplitude, closely spaced beach ridges. The younger ridges were deposited between 230 +/- 40 and 140 +/- 50 years ago, at a rate of around 1.06 m/y. During the last several decades, much of the Beachmere shoreline has eroded into these younger relict ridges. Drivers of these changes in shoreline sedimentary regime are yet to be accurately determined; however, it seems likely they are related to switches that occur in the nearshore sand transport pathway. Our results demonstrate the utility of the OSL method for providing insights into coastal change that occurred in the historical and recent geological period. Better understanding the tempo of shoreline change in the recent past is particularly relevant for assessments of vulnerability to erosion of rapidly developing, low-lying sandy coasts such as northern Moreton Bay. Yes Yes
The coastal zone of Sagar Island, West Bengal, India, is subjected to various cyclic and random processes that continuously modify the region. The shoreline and land-use/land cover changes have been studied using Indian Remote Sensing Satellite IC (IRS IC) linear imaging self-scan sensor (LISS) III satellite data from 1998 and 1999. A comparison between a topomap of 1967 and satellite data of 1999 established that during these years about 29.8 km of coastline was eroded, whereas the accretion is only 6.03 km sup(2). A comparison of satellite data from 1998 and 1999 showed that the island had undergone severe erosion of about 3.26 km sup(2), while the accretion was just about 0.08 km sup(2). Change detection studies based on land-use patterns of the region revealed that the areal extent of mangrove vegetation of the island during 1998 and 1999 was 2.1 km sup(2) and 1.3 km sup(2), respectively. The areal extent of agricultural fields during these periods was 130.4 km sup(2) and 118.6 km sup(2), respectively. These results can be used to develop an index for temporal land-use changes in the region as an aid to quantify the extent and nature of the development change and to understand the surrounding environment, which in turn may help the planning agencies to develop sound and sustainable land-use practices.
In this paper, the 1D unsteady, nonlinear groundwater flow through porous media, corresponding to flood in an aquifer between two reservoirs, is studied by mass conservation equation and Forchheimer equation instead of Darcy's law. The coupling nonlinear equations are solved by homotopy analysis method (HAM), an analytic, totally explicit mathematic method. The method uses a mapping technique to transfer the original nonlinear differential equations to a number of linear differential equations, which does not depend on any small parameters and is convenient to control the convergence region. Comparisons between the present HAM solution and the numerical results demonstrate the validity of the HAM solution. It is further revealed the strong nonlinear effects in the HAM solution at the transitional stage. Yes Yes
A three-dimensional numerical model is developed to investigate the water quality within a harbor under the influence of a pollutant source near the harbor entrance. The numerical model contains two components: a hydrodynamic model that simulates the tide-induced currents and dispersion model which simulates the pollutant transport around the harbor. By solving continuity and momentum equations, the hydrodynamic model generates a three-dimensional flow field for dispersion model to calculate the pollutant dispersion using mass conservation law. The 3D model is tested against analytical solutions for the time series of the central contaminant concentration in an open basin for verification. The model is then applied to the varied breakwater layout of harbors with different locations of pollution sources. For a surface discharge pollutant source under the same tidal condition, the further the distance of the discharge to the harbor entrance, the less impact to the quality of the water in the harbor. Numerical results also show that the effect of the surface discharge was more significant to the water quality in the harbor than a submerged discharge at the same horizontal distance away from the harbor entrance.
A 1.15 m long core collected from 20 m water depth off Karwar on the western continental shelf of India was studied to reconstruct the paleomonsoonal, precipitational history during the recent past with fine time resolution by exploiting foraminifera as proxy. These established parameters (indicating salinity fluctuations, thus runoff from rivers due to the monsoonal precipitation over catchment area) are an angular-asymmetrical morpho-group, directly proportional to salinity. The mean proloculus size of Rotalidium annectens (Parker and Jones), is inversely proportional to salinity and an abundance of indicator species R. annectens is directly proportional to salinity. These parameters show considerable fluctuations in the core (representing about 450 years) indicating variations in paleomonsoons in a cyclic manner (around 77 years). Attempts to establish correlation between inferred paleomonsoonal precipitation with known climatic cycles affecting the earth's climate suggest a possible link with the Gleissberg solar cycle of around 80 + or - 10 years, which is already noted in various other climatic records
In the Wadden Sea, an increasing area of the man-made tidal marshes, which cover over 17,000 ha, are becoming nature reserves or parts of national parks. Consequently, management aims altered from reclaiming land towards restoring natural-like marshes. Within this scope, maintenance of the drainage system was discontinued in a 460-ha nature reserve in man-made tidal marshes in the Ems Dollard Estuary, the Netherlands. We collected elevation data in four sections of the nature reserve to study vertical accretion rates and to evaluate marsh-profile changes. Elevations were surveyed in 1984 and in 1991/1992 along transects with a total length of 9,700 m. Generally, vertical accretion rates were negatively correlated with (a) marsh elevations of 1984, (b) distance from the intertidal mudflats, (c) distance from main creeks, and (d) in many cases, distance from minor creeks. At most of the transects that ran from the seaward marsh edge to the inland seawall, distance from the intertidal mudflats affected vertical accretion rates more than did the 1984 marsh elevation. As a consequence of a gradient in grazing intensity, vegetation structure (density and height) decreased inland and was probably an important auxiliary factor in determining vertical accretion patterns. After abandonment of the drainage system in 1984, the number of levees increased along minor creeks (former ditches), as did elevation differences at many existing levees. Levee development was more pronounced inland, which may be explained by the greater differences in vegetation structure between inland levees and marsh interiors (between minor creeks) as a result of the gradient in grazing intensity. Levee development, together with formation of badly drained depressions, increased elevation differences and abiotic and biotic diversity in the marshes. Vertical accretion rates in the Dollard marshes ranged from 6.6 mm/yr to 11.4 mm/yr among the four marsh sections. These values are relatively low compared to those of other man-made marshes, which might be a consequence of abandoning the drainage system.
Marine ecosystems are severely affected by water pollution originating from coastal catchments, while these ecosystems are of vital importance from an environmental as well as an economic perspective. To warrant sustainable economic development of coastal regions, we need to balance the marginal costs from coastal catchment water pollution abatement and the associated marginal benefits from marine resource appreciation. Water pollution abatement costs are, however, not equal across industries and, consequently, the question arises to what extent marine water quality improvement can efficiently be pursued across industries. In this paper we develop an optimal control approach to explore, analytically as well as quantitatively, social welfare maximizing rates of water pollution abatement across industries. For a case study of Dissolved Inorganic Nitrogen (DIN) water pollution in the Great Barrier Reef region of Australia, water pollution abatement cost functions for two agricultural industries are estimated to, in turn, explore social welfare maximizing rates of water pollution abatement per industry. Results for the Tully-Murray catchment show that DIN water pollution can be reduced by about 25% through the adoption of win-win management practices in the sugarcane industry. However, when taking into account the benefits from reduced DIN water pollution in the downstream marine environment, this study shows that maximum social welfare gains can be obtained by reducing DIN water pollution through a reduction in the agricultural production area in combination with the adoption of lose-win management practices in the sugarcane as well as the grazing industry.
The distinctive blue hole terrains of the Houtman Abrolhos reef complex have been previously interpreted as the result of karst processes controlling Holocene reef growth and morphology. The apparent intensity of karst modification,indicated by the abundance and density of blue holes, steered the general perception of the reef complex as one that was stressed and marginal for Holocene coral growth. This view is commensurate with the high-latitude location (288298 S) of the reefs. Through an investigation of the reef morphology, litho and seismic stratigraphy, and the growth chronology of these reef complexes, we demonstrate that the blue hole terrains of the Houtman Abrolhos are not karst features but are growth forms that are characteristic of these reefs.
In past decades, considerable effort has been devoted to the phenomenon of wave-induced liquefaction, because it is one of the most important factors for analysing the seabed and designing marine structures. As waves propagate and fluctuate over the ocean surface, energy is carried within the medium of the water particles. This energy could be transmitted into the seabed, which results in the rather complex mechanisms of soil behaviour and significantly affects the stability of the seabed. The prediction of wave-induced seabed liquefaction has been recognised by coastal geotechnical engineers as an important factor when considering the design of marine structures. All existing models have been based on conventional approaches of engineering mechanics with limited laboratory work. In the authors' previous study, a Single Artificial Neural Network (SANN) was applied for the prediction of wave-induced seabed liquefaction. It had been demonstrated that SANN model's performance can be accepted in engineering practice with large liquefaction depth. However, it failed if the liquefied depth is very small such as less than 1 m. Therefore, in the present study, the Multi Artificial Neural Network (MANN) model was introduced. The simulation results indicate that the MANN model can provide more accurate prediction of the wave-induced maximum liquefaction depth between 0 to 1m. This study has shown the capacity of the proposed MANN model and provides coastal engineers with another effective tool to analyse the stability of the marine sediment.
Coastal processes have been monitored for the Tugun desalination plant for over a year by attaching a 1 MHz Sontek Argonaut ADCP and a YSI 6600 CTD to an in-house designed seabed platform with data being downloaded every two weeks by raising the instruments to the surface, manually transferring the data via an interface cable to a laptop computer and re-deploying the system to the seabed. Analysis of the results indicate sporadic internally trapped waves travelling northward along the East Australian coast may be the “cold dirty water” described by local fishermen and whose sediment transport budget impact may be under-estimated by current coastal hydro-dynamic models. Further investigations are underway. The system being discussed and described in this paper upgrades this labour intensive methodology as it allows for data downloading to be undertaken leaving the instruments in-situ. By including an acoustic modem between the seabed unit and a surface buoy and with the addition of a Campbell Scientific CR1000 and wireless modem link a mesh radio network can be established linking the seabed unit to the shore. Real-time interrogation of the unit can then occur allowing for immediate confirmation of the equipment functioning correctly and for management decisions to be made using current and up to date data. Whilst the fundamentals of this system are not new, the novel capability is the addition of additional units into the monitoring area which are immediately picked up and added to the mesh network. Utilising this capability, a series of monitoring stations can be daisy chained away from the shore based receiver station allowing for a comprehensive array of sensors covering a wide area. Furthermore, the system is modular in construction and can be utilised for many other coastal applications that require remote sensing and data recording with the added advantage of a real-time display back to a central command node or WWW. Yes Yes
We describe a novel in situ measuring drogue device developed for the investigation of near-surface sediment and flow dynamics in an estuary. The Lagrangian Acoustic Drogue (LAD) comprises a unique configuration of instruments including a downward-facing 600 kHz Broadband Acoustic Doppler Current Profiler mounted on a Lagrangian float; a Differential Global Positioning System; and a (Conductivity, Temperature, Depth sensor. Open ocean studies have revealed the necessity of understanding the Lagrangian nature of the drifter or drogue. As the ocean and estuarine systems are two vastly distinct environments, a separate study was conducted using the LAD in an estuarine environment. The main objective of this study was to directly quantify the LAD's ability to track and monitor a Lagrangian parcel of water over a slack-water period. It was found that the LAD confidently tracked a parcel of water to a depth of 4.5 m. It was also found that the water tracking ability (slippage) was directly related to the magnitude of tidal velocity. This study also revealed characteristics about the physical state of the estuary itself, and gave positive outlook for the future of drogue-based studies in estuaries. Yes Yes
Much is known about wave attenuation across sandy nearshore environments or coral reef platforms. Limited field work has aimed to measure and assess attenuation across rock platforms. We designed and implemented a field experiment at Belinho, Portugal, to address this need. Field work was conducted in June, 2006, over a sequence of five tidal cycles. We deployed a shore-normal array of seven KPSI pressure transducers, installed 0.15 m above the bed and spaced between 10 and 15 m apart, to measure surface water levels. When all instruments were submerged by the rising tide, they were sampled at 20Hz.. The instrument array spanned the inter-tidal platform composed of schist. The surface, about 70 m wide, is irregular and cut by many shore perpendicular channels. To assess the attenuation and transformation of waves across this surface as a result of shoaling and breaking, we derived spectral estimates of wave height and period through each high tide series. Wave heights at the outermost PT ranged between about 0. 4 to 0.9 m. At the innermost PT, corresponding values were 0.5 to 1.14 m. Wave periods averaged about 10 s through the study. Our results showed that a breaking criterion of 0.42 + c fit our data.
The coastal city of the Gold Coast, Australia is the first of eighteen sub-domain studies within South East Queensland (SEQ) that has been measured using the index of sustainable functionality (ISF). As a quantitative definition of sustainability, the ISF offers an adaptive method of measurement. It does so based on an engineering standpoint that institutes stable energy and mass transfer indicates longevity over spatial and temporal scales. Sustainability trends are measured using adaptive sustainability which incorporates complex interactions by making use of a matrix-based approach. Twenty-three functions were utilised in the study and measured against a total of 53 indicators. The span of the research is between the years 2000 to 2005. The results of the study indicate that the ISF of the Gold Coast can assist in improving the overall sustainability of the region. The overall result shows sustainability trends have slightly improved and are heading toward a sustainable blueprint for rapidly developing regions. Monitoring of trends would reduce future unsustainable action and optimise the ISF to the region and beyond. Yes Yes
Field measurements of tidal current velocities are used to infer sediment transport characteristics in the lower section of a large, tidally dominated estuarine system at Whangarei Harbour, New Zealand. Recent (2002) developments at the harbour entrance included a 32.6 ha intertidal reclamation and a 31.8 ha dredged turning basin. Residual distance vectors indicate that the postdevelopment, large-scale pattern of sediment transport dynamics remains consistent. Minor, localised modification of transport potentials has been observed immediately adjacent to the developments, however. These modifications include a slight realignment of current flows near the reclamation wall and some leakage from a previously identified transport loop near the dredged basin. The potential for scour is identified along the eastern margin of the dredged basin, which could act to remove material moving downslope into the basin from its western edge. These data are consistent with numerical model results that predicted minimal consequences resulting from the developments. Lower harbour sediment dynamics are consistent with established patterns for tide-dominated inlets, with separation of the channel into areas of ebb and flood dominance, and typical transport patterns over the flood tidal delta. Broad-scale inlet geomorphology has been maintained, which is consistent with other dredged tidedominated inlets.
This paper reports results from a field experiment at Esposende Beach, Portugal, conducted in May/June, 2006. The purpose of the experiment was to measure characteristics of the aeolian saltation system, including sand transport rates, vertical distribution of mass-flux, and the associated wind speeds. The measurements were made on a sand flat, near the top of a parabolic dune flat. The mean grain size of the surface sediments was 0.32 mm. There was an unobstructed fetch exceeding 60 m in length and sloping at approximately 10°. Sand transport was measured with vertical stacks of hose-type traps and wind profiles were measured with a vertical array of three or four, Gill-type, cup anemometers. The transport rate data are compared to predictions made with the BAGNOLD (1936), KAWAMURA (1951) and ZINGG (1953) models. Vertical flux profiles were analyzed using a geometrically-weighted, trap centering method; using 1 mm as an estimated apparent roughness length, and by fitting a non-linear least-squares curve to find the empirical constants to describe the exponential decay of saltation intensity away from the sand surface. For the 13 data runs that we examined, α averaged 18.663 and fi averaged -0.016. These constants yielded an r2 of 0.992 and an error sum of squares of 1.897 for our data.
In support of the Texas Seagrass Monitoring Program, remote sensing research is underway to evaluate automated methods for monitoring landscape changes in seagrass beds related to human and/or natural disturbances. This paper discusses the integration of high resolution aerial color film photography, color space transformation, pixel threshold models, and geographic information system technology to detect, assess, and monitor 1-m ground feature changes and disturbance areas within a Texas, United States, shallow seagrass bed over 3 site years. The procedure entails transforming digitized, aerial color film transparencies from red, green, and blue color space to intensity, hue, and saturation color space; analyzing the saturation and/or intensity imagery and their histograms to identify bare areas; and developing threshold models to separate bare areas from vegetated areas employing the results obtained in the previous step. Maps created with this semiautomated approach had classification accuracies ranging from 75% to 100%. We used geographic information system tools to quantify landscape feature changes occurring at the shallow test site for 3 consecutive years. The overall findings indicate that the semiautomated approach described in this study can be used as an efficient protocol to accurately map changes in bare and vegetated areas within this Texas seagrass bed, and suggest that the techniques would have high potential for other similar seagrass areas.
The Mas alomas dune field and adjacent beaches are the most extensive coastal sedimentary environment on the island of Gran Canaria. This area is very important from both a natural and an economic perspective. The analysis of aerial photographs and satellite images from recent decades does not show important shoreline changes for the El Ingles and Maspalomas beaches, which can be considered, consequently, in a state of equilibrium. However, the Maspalomas dune field presents several modifications, such as aeolian corridors associated with beach kiosks, a significant reduction in thickness of the aeolian deposits, and an increase of deflation areas in the underlying substratum. All these are proof of a drastic reduction in sediments. Sediment transport pathways obtained from the grain size parameters of beach samples show an input of sediments from El Ingles beach to Maspalomas dune field, whereas longshore drift is predominant on Maspalomas beach. This grain-scale analysis agrees with previous geomorphologic and wind studies. Foraminiferal content analysis also confirms the input of sediments from El Ingles beach to the dune field, as well as indicating the lack of inputs across Maspalomas beach, on which only seaward fluxes from closer dunes can be expected. Input and sinking areas of the system have been confirmed as well as a notable lack of sediments in the dune area, which is suffering severe erosion because of the shortage of sediment supplies from El Ingles beach.
The coastal-tract approach to coastal morphodynamics, described in the companion paper (The Coastal-Tract Part 1), provides a framework for aggregation of process and spatial dimensions in modeling low-order coastal change (i.e., evolution of the shoreline, continental shelf and coastal plain on time scales of 102 to 103 years). Behavior-oriented, coastal-change models encapsulate aggregate dynamics of the coastal tract. We apply these models in a coastal-tract framework to illustrate the use of the concept, and to explore low-order morphological coupling under different environmental settings. These settings are characterized by data-models that we have constructed from four contrasting continental margins (NW Europe, US Pacific, US Atlantic, and SE Australia). The gross kinematics of the coastal tract are constrained and steered by sediment-mass continuity. The rate of coastal advance or retreat is determined quantitatively by the balance between the change in sediment accommodation-space, caused by sea-level movements, and sediment availability. If the lower shoreface is shallower than required for equilibrium (negative accommodation), then sand is transferred to the upper shoreface (NW Europe, US Pacific, and SE Australian cases modelled) so that the shoreline tends to advance seaward. This tendency also occurs when relative sea level is falling (coastal emergence). Coastal retreat occurs when the lower shoreface is too deep for equilibrium (positive shoreface accommodation). This sediment-sharing between the upper and lower shoreface is an internal coupling that governs first-order coastal change. The upper shoreface and backbarrier (lagoon, estuary or mainland) also are coupled in first-order coastal change. Sediment accommodation-space is generated in the backbarrier by sea-level rise (and reduced by sea-level fall), but the amount of space is also moderated by influx of fine sediments from the coast, or sand and mud from fluvial sources. Remaining space can then be occupied by sand transferred from the upper shoreface causing a retreat of the latter (transgressive phases modelled for NW Europe, US Atlantic, and SE Australian cases).
The late Holocene evolution of the former coastal lagoon of Vilamoura was reconstructed according to sediment cores and geophysical profiles. According to sedimentological analyses of the cores, five palaeoenvironmental stages were defined. (1) The pretransgression stage is represented by an erosive surface formed during incision of the river into the basement because of a lower sea level. This palaeosurface was retraced by refraction seismic profiles, showing that the marine transgression took place on a wide plain with several incised channels. (2) The development of an estuary started by transgression into the river valley corresponding to the postglacial sea level rise. Radiocarbon dating indicates a sea level not lower than -4 m at a minimum age of 4716 +/- 72 Cal BP. After the transgressive maximum, infilling of the estuary started, beginning with (3) subtidal infilling related to the formation of a sandy barrier followed by (4) supratidal infilling with further accretion of the barrier, changing the previous open bay into a coastal lagoon. (5) Finally, the lagoon was fluvially filled with terrestrial sediments, changing the marine to a fluvial milieu with floodplain deposition. Analysis of benthic foraminiferal and ostracod assemblages revealed additional information about the environmental conditions during evolution of the estuary, which led to a further subdivision of the marine facies into stages with mainly estuarine, lagoonal, or marine influence. The end of the marine stage was dated at 2895 +/- 48 Cal BP, indicating a pre-Roman onset of human-induced soil erosion.
MARAQA, M. A., ALI, A. and KHAN, N., 2007. Modelling Selected Water Quality Parameters at Jebel Ali Harbour, Dubai-UAE. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 794 - 799. Gold Coast, Australia, ISSN 0749.0208 Jebel All Free Zone in Dubai has the largest man-made harbour in the world. Several factors may affect water quality in the harbour, including discharge of treated wastewater, navigational activities, and nearby projects in the Arabian Gulf. The main objective of this study was to simulate the level of BOO and some nutrients in the harbour water under existing and potential future conditions. Modeling of water quality was carried out using the ECO Lab coupled with the advection-dispersion modules in the MIKE21 modeling system. The results showed that the input rates of BOO, ammonia, nitrate and phosphate associated with the discharged treated wastewater are not sufficient to simulate the observed levels of these parameters in the harbour water. Additional input rates of 600 times for BOO and 144 times for nitrate are needed to adequately describe the observed levels of these parameters. An assimilation capacity analysis of BOO in the harbour water revealed that the BOO starts to build up when the BOO loading rate reaches 2.88 g/m(2)/d, which is about 20% higher than the estimated loading rate under the current conditions. Simulations further showed that increasing the organic loading into the harbour will reduce DO and increase ammonia, but will not significantly affect nitrate and phosphate levels in the harbour water.
In the Mediterranean sea tides oscillate only-a few meters and water displacement is mainly due to the influence of winds and changes in atmospheric pressure. This makes Mediterranean estuaries an unpredictable system for shorebirds. The causal mechanisms on habitat selection of Dunlin was studied in such system at Ebro Delta, where littoral and rice field habitats were available for shorebirds. Dunlins choose to forage littoral habitats where prey are more abundant showing higher intake rate in this habitat, however, this species also uses rice fields. No differences in microhabitat use and foraging technique was found between habitats. Intake rate and searching speed were lower when high bird density was present in littoral but not in rice fields. Therefore, the use of both habitats can be explained by a combination of density-dependent effects following the ideal free distribution model and the unpredictability of water movements that reinforce that effect. The study suggests the importance of rice fields as alternative habitats and that the availability of these alternative habitats could contribute significantly to the maintenance of wintering populations of shorebirds in Mediterranean estuaries Peer reviewed
Ammophila arenaria (L.) Link (marram grass) is the most important sand-fixing plant species along the northwestern European and Mediterranean coast, and it is also planted worldwide for sand dune stabilization. In spite of the intense use of this species in foredune restoration and stabilization programs, little is known about the genetic diversity within and between populations. We analyzed the genetic diversity of seven European populations of A. arenaria using inter-simple sequence repeats (ISSR) markers. The studied populations were selected in Wales, England, Belgium, the Netherlands, Portugal, and France. One half of the populations showed similar values of genetic diversity. The lowest values (Nei's index =0.17) were found in the population from the Netherlands, which had been established after a foredune reinforcement project, and in a declining population in the south of Portugal. Statistical and phylo-genetic analyses revealed genetic differences between populations, and northern and southern clusters that corresponded to the two subspecies of A. arenaria. We propose that plant material for dune vegetation re-establishment programs should be collected locally rather than from remote populations that might be less well adapted to the local conditions of the planting site. However, when using local clonal plant material, care should be taken to collect the plant material from a number of sampling sites in order to ensure the genetic diversity of the new stands.
Modelling of tide-induced watertable fluctuations in coastal unconfined aquifers has, for many years, been based on the assumptions of one-dimensional shallow flow and a vertical beach face. This approach is based on the Boussinesq equation, neglecting variations in the coastline and beach slope. Here, a closed-form analytical solution for a two-dimensional unconfined coastal aquifer, taking account the sloping and variable coastline, is derived. In the appropriate limits, this new solution reduces to the vertical beach, one-dimensional solution. The effects of different beach slopes and the coastline variability for a typical sandy beach environment are investigated. The results indicate that both the coastline shape and beachface slope are important parameters affecting the solution for tide-driven coastal groundwater fluctuations.
A comparison has been made of sand, silt, and clay percentage of 118 samples from the Ayeyarwady continental shelf, northern Andaman Sea, measured by the sieve-laser diffraction technique and by classical sieve-pipette methods. Clay and silt percentages determined by Malvern Mastersizer 2000 Laser Particle Size Analyzer are 37% and 157% of pipette clay and pipette silt percentages, respectively. Clay particles separated by the settling technique and having an apparent size of less than 2 mu m when measured with laser diffraction show that 99% of the particles have an upper size range between 4.8 and 7.7 mu m. A calibration relationship between pipette and laser diffraction techniques has been developed for the northern Andaman Sea. A clay particle size of 2 mu m defined by the pipette technique corresponds best to a size of 6.2 mu m defined by laser diffraction. For the laser data, when 6.2 mu m is taken as the boundary between silt and clay, the results are comparable to pipette analysis. Use of the calibration relationship enables one to make use of the rapid laser diffraction size analysis technique for routine sediment texture analysis with high precision.
The Andaman Sea is known for the genesis of many severe cyclones that traverse the Bay of Bengal. The Andaman Islands face the surge disaster threat as their north-south orientation comes across the eastward path of severe cyclones moving from the Andaman Sea and western Pacific Ocean. In this study, we investigated the potential of a storm-induced surge - a natural disaster due to short-duration sea-level rise to affect the Andaman Islands. A two dimensional hydrodynamic model was employed to simulate storm surge characteristics and demarcate the coastal flooding extent of the highly inhabited Port Blair region of the Andaman Islands in the case of the severe cyclone of November 1989. A storm surge disaster mitigation plan is also proposed for the group of Andaman Islands.
A 3-year study of water density anomalies within a conventional tide-well indicated that the average water density within the well was consistently lower than that of the external ambient waters. The tide-well at Marmugao, Goa, India is situated at the mouth of the Zuari estuary, and anomalies were reported at all periods except during peak summer and the onset of the summer monsoon. These anomalies lead to an over-estimation of sea level by a tide-well based gauge. The density difference, delta p, between waters inside and outside of the tide-well had a significant dependence on local rainfall and wind. This trend was noticed throughout the 3 years observation period, with the minimum (0.001 g cm sup(-3)) difference corresponding to maximum (approx. 6 m s sup(-1)) winds and maximum (approx. 350 mm) rainfall. The monthly-mean over-estimation in sea level (delta h), was a minimum (2 mm) during the summer monsoon, rose rapidly to over 22 mm after the monsoon, and remained around this peak value for approx. 3 months before slowly decreasing to approx. 4 mm by peak summer. The yearly-mean over-estimation in the mean sea level (MSL) was 11.3 mm. The limitation of the conventional tide-well could be minimized by incorporation of arrays of perforations on its entire submerged portion. The observed annual repeatability of the density difference pattern indicates that it might be possible to correct the historical sea level records, obtained from tide-well-based gauges, for the observed systematic over-estimation of sea levels, from measurements of density differences inside and outside of tide-wells over a period of one year. This would be a practical way to go back to what is in the archives and recover the absolute sea level. In this paper a feasible solution is addressed to the lower density water-trapping problem suffered by the guided-air-acoustic gauges, wherein a long and narrow tube is used to guide the acoustic pulse between the acoustic head and the water surface.
Here, for the first time, fluorescence microscopy (FM) was coupled with leaf autofluorescence to visualize and track trace levels of anthracene (An) in living Kandelia candel (L) Druce leaves, without destructive chemical extraction techniques The experimental results revealed that, after tracking over 96 hours, An adsorbed onto the leaf surface was moved through the upper cuticle and through the stomata of the lower side into the internal leaf tissues An was identifiable in six separate locations within the K candel leaves the first hypodermis, the second hypodermis, and the upper palisade tissue moving from the upper cuticle, the lower hypodermis and the lower palisade tissue moving from the stomata of the lower side, and the spongy mesophyll moving from both sides Under the same exposure conditions, the impact of An adsorbed at the center of the upper side of the leaf surface was much less than that at the edges of the leaf surface However, after 96 hours of exposure to An, the amount of An transferred into the inner leaf tissues at the center of the leaf was higher than at the edges, which might provide important new information concerning how An enters, is moved, and is distributed within the K candel leaves Furthermore, this FM technique provided us with a noninvasive tool for visualizing and tracking the movement and storage locations of PAHs within K candel leaves based only on the autofluorescence of leaf tissues as revealed by fluorescence microscopy National Natural Science Foundation of China [20777062, 40521003]; SRFDP 
Biogenic sulphides, particularly pyrite and hydrated iron- monosulphides, are common in sediments in mangrove ecosystems where they may provide a geochemical trap for heavy metals. However, oxidation of the sulphides can lead to remobilisation of metallic species and the development of acid sulphate soil conditions. In this paper the effects of prolonged dry conditions on the metal binding capacity of sediments in a mangrove forest are investigated. Data from 1989 show that the mangrove forest is acting as a buffer between a domestic garbage tip and the open waters of Moreton Bay. However, prolonged dry conditions during 1991 removed much of this buffering capacity and some metals were mobilised to deeper layers in the sediment or transported down the hydraulic gradient until chemical conditions more favourable for metal trapping were encountered. This study shows that understanding the transient nature of geochemical conditions in natural environments is important in environmental management because: (a) consideration needs to be given to how environmental data collected at one time may be affected by natural changes (commonly cyclic) in geochemical conditions; (b) consideration needs to be given to how human activities may have affected natural changes in geochemical conditions; and (c) planned development or environmental remediation work will need to anticipate the consequences of natural changes in geochemical conditions.
A sequence of at least three Late and Middle Pleistocene coral reef terraces (Lower Terrace, Middle Terrace I and II), which are uplifted up to 45 m a.s.l., is conserved on Curaçao. The less uplifted Lower terrace (elevation 6 to 12 m above sea level) consists of two different coral reef formations: the Hato unit and the underlying Cortalein unit. The discontinuity between these two superimposed units is typically marked by a strong difference in the degree of weathering. Samples of coral in growth position were collected from the Lower Terrace (Hato and Cortalein unit) and the Middle Terrace I. ESR ages indicate a Last Interglacial age of the Hato unit of about 122 ky BP, and a correlation with the Last Interglacial sea level maximum (stage 5e). The ESR age of the underlying Cortalein unit is about 216 ky BP (stage 7). Palaeo sea level calculations imply a correlation with the youngest of three Penultimate coral reef terraces located on the island of Barbados, which was uplifted more strongly than the island of Curaçao. No equivalents of older Penultimate Interglacial coral reefs and of the Interglacial stage 9 were found. Middle Terrace I could be at least as old as stage 11 (approx. 400 ky BP), however, it could also be more than 500 ky old.
Situated just north of the Venezuelan coast around 12° to 13° N, the Netherlands Antilles are normally well outside the hurricane belt. Nevertheless, some of these powerful storms sent waves and swell of significant size to these islands, strong enough for impacts on the coastal geomorphology. Hurricane Ivan of September 2004, with Saffir–Simpson category 5 and around 250 km/h sustained winds less than 150 km north of Bonaire, was the most recent and one of the strongest of these events in history. Waves along the rocky eastern coastline reached heights of >12 m. Our observations during the days of Hurricane Ivan on Bonaire Island include impacts on exposed and sheltered shorelines, transformation of beaches and cliffs, sediment movement on higher terraces, as well as boulder transport. The latter is important to distinguish storm wave-induced boulder movement from boulder movement by tsunami, which have affected Bonaire several times during the Younger Holocene.
A paleo-ecological reconstruction of long-term changes in the distribution of submersed aquatic vegetatioin (SAV) in a Chesapeake sub-estuary was made using dated sediment cores on transects going from shallow (< 0.5 m) to deep (> 2 m) waters. Maynedier and Saltworks Creeks, branches of the Severn River, have had substantial losses of SAV, similar to many parts of the upper Chesapeake Bay. Dating via 210Pb established that sediment accretion rates were 0.5-0.7 cm yr-1 in these two systems, double the rate of sea level rise in this region. Seeds of only two SAV species were found in the sediments despite evidence others were present at one time or another in other tributaries of the Severn Estuary. Of the two species found, Zannichellia palustris seeds were much more abundant than Ruppia maritima seeds, reflecting the high dispersibility of the former species. The vertical pattern of seed distribution in these cores indicates that over the past 100 years, SAV (particularly Z. palustris) has been increasingly confined to shallower water depths. Although there is less riverine pulsing in the two study creeks, than at the head of the Bay (where previous seed records are available), both data sets are consistent with the hypothesis that decreasing light availability due to eutrophication and sediment erosion has been a problem for SAV in Chesapeake Bay, particularly over the last several decades. Furthermore this study suggests that historically low species diversity may be attributable to more chronic and longer term stress in the shallows of the Severn River than present in SAV beds at the head of the Bay.
In the present study, Artificial Neural Networks (ANNs) are adopted to simulate groundwater table fluctuations. A multilayer feed-forward neural network model has been developed and trained using a back-propagation algorithm. The training data was based on field measurements (KANG et al., 1994) from five different locations down the east coast of Australia. The data included information on watertable, tide elevation, beach slopes and hydraulic conductivity at each beach. The results from the developed model show that the artificial neural network model is very successful in terms of the prediction of a target that is dependent on a number of variables. Sensitivity analysis was undertaken which confirmed that a variation in tide elevation is the most important parameter to use for simulating groundwater levels in coastal aquifers. Yes Yes
The prediction of the wave-induced liquefaction potential is particularly important for coastal engineers involved in the design of marine structures. An artificial neural network (ANN) model is used to estimate the waveinduced liquefaction in terms of wave and seabed sediment conditions. The sensitivity of wave and seabed sediment parameters is extensively investigated to get the most accurate results. The deterministic wave and liquefaction models are used to explain the parameter features physically. Numerical examples demonstrate the capacity of the ANN modelling approach in simulating complex mechanisms such as wave-induced liquefaction with adequate information. Yes Yes
Seagrass bed habitat is an important biotic community in decline worldwide. Boat damage has long been recognized for its negative impacts on shallow-water seagrass beds, with those along the Florida coast particularly vulnerable in the face of a large human population possessing a large number of boats. Boat scars to seagrass beds recover slowly, resulting in new damage that often outpaces recovery of existing damage. We examined the rate of accumulation of total area composed of boat scars from 1994 to 2005 at Lignumvitae Key Submerged Land Managed Area, an area containing approximately 3400 ha of seagrass beds. We found the total area of damage increased from 1994 to 1997 by an average of 27.1 ha/y and from 1997 to 2005 by an average of 10.8 ha/y. This most recent rate of damage increase represents an additional $1,523,819 annual loss in habitat value using cost figures based on costs from restoration attempts permitted by the Environmental Protection Agency. Severe groundings investigated by law enforcement officers showed increasing trends over time in the average amount and severity of damage. The size of the boat inflicting the damage was more closely related to the severity of damage than to the amount of damage. The most immediate and practical measures for preventing damage include increasing signage to warn boaters to avoid seagrass beds and increasing law enforcement staff. Signage is a relatively low-cost, long-term investment that becomes cost-effective even if only 0.03 ha of seagrass bed damage is averted over the life of the signs. Each patrol staff member added becomes cost-effective even if only 0.42 ha of damage is averted annually. Holding the total area of damage constant for 1 year (new damage = recovery) would represent a benefit-cost ratio of 25.71 if accomplished with only one additional law enforcement officer.
Erosion of unprotected levee banks decreases their structural integrity and increases the likelihood of failure. Several types of restoration structures for levee protection and stabilization have been used in the Sacramento San Joaquin River Delta, California, to reduce erosion. The purpose of this paper is to describe the results of a field experiment designed to measure the effectiveness of organic restoration structures (brush bundles) in altering the hydrodynamic regime in the vicinity of levees, with specific focus on changes in boat wake energy. Two simple hypotheses were tested: 1) restoration structures reduce boat wake energy, and 2) energy reduction is dependent on water depth. Field work was conducted August 29-31, 2000 on Georgiana Slough, which is a tidally influenced (spring tidal range of 2 meters) distributary of the Sacramento River. Pressure sensors were deployed offshore and landward of the restoration structures. Data collection occurred with the bundles in place and with them removed. Boat wakes were generated during rising and falling tides to capture the effects of fluctuating water levels. Wakes were characterized by index wave height, period and energy. Comparing sample means of normalized energy with the bundles removed and with the bundles in place revealed a 60% reduction of energy by the bundles. It was also determined that energy reduction was tidally, or depth dependent. The reduction of energy by the structures indicates that they are an effective method to protect against boat-wake induced, levee erosion.
Although, a variety of methods have been employed to determine sediment transport along Goa coast, India, the results differ in some sections. Fifteen studies have been reviewed, compared, re-assessed and a corrected shore drift map of the Goa coast is prepared and presented. Advantages and limitations of these methods are discussed. The present review and re-assessment confirms that, though sediment transport is bi-directional, the long-term net shore drift direction along Calangute and Colva beaches is southward. The overall net shore drift direction along Goa coast is also towards south. It is qualitatively determined that except for 3 short drift cells, shore zone has long-term stability. Finally, it is concluded that landform indicator study using remote sensing can be an effective method for determining long-term net shore drift along the coast.
The Benthic Ecological Assessment for Marginal Reefs (BEAMR) method is a universal assessment procedure which helps to quantify the “health” condition of a coral reef habitat over time. Coral reefs, due to their complexity as an ecosystem, have presented problems in the past to marine researchers trying to assess the performance of the habitat through statistical evaluation. Previous methodologies such as the Atlantic and Gulf Rapid Reef Assessment method and the Caribbean Coastal Marine Productivity Program, while being useful, were created specifically for reefs within the Caribbean Sea and are biased toward one or two main indicator organisms (e.g., stony corals). However, given that most reefs worldwide are considered marginal habitats, which describes them as having an impoverished community condition with biogeographic limits, the BEAMR method offers a more comprehensive analysis of all benthic functional groups defining the reef. Assessments and analysis using the BEAMR method provide marine researchers with accurate in situ documentation of all aspects within benthic coral communities, allowing conservation managers to more effectively protect these marine habitats. Coral reef resources are under a constant threat from both human and natural forces, making habitat assessment protocols, such as the BEAMR method, an important tool in the worldwide conservation of coral reef communities.
As assessments of long-term coastal erosion and inundation hazards become more widespread due to observations of climate change impacts, the methods used to make these assessments are coming under increased scrutiny. Using observations from the Languedoc-Roussillon region of southern France, this study estimates errors associated with the evaluation of potential coastal erosion and inundation due to sea level rise. Three independent error analyses are completed addressing the impacts of variability in sea level rise predictions, evaluations of long-term coastal evolution, and the quality of available topographic data. The results are presented for the Languedoc-Roussillon site, demonstrating the need for high resolution topographic data, estimations of a range of probable sea level rise values, and expert evaluation of probable coastal evolution scenarios. The applied methods are generalized to be applicable at additional study sites.
Harmonic analysis of the observed and simulated tides in the Mandovi and Zuari estuaries along the west coast of India was carried out. Tidal constituents derived from this process were analyzed to study the tidal asymmetry in these estuaries. Sea level observations during March-April 2003 at 13 stations in the Mandovi and Zuari estuaries were used for the harmonic analysis. Simulations of tides were carried out using a hybrid network numerical model. The model could well simulate the amplitude and phase of five major tidal constituents (K sub(1), O sub(1), M sub(2), N sub(2), S sub(2)) in almost all stations in the Mandovi and Zuari estuaries. Both observations and simulations show that the amplitude and phase of major diurnal and semidiurnal constituents increase toward the upstream regions. The increase of this predominant species toward the upstream regions shows that the Mandovi and Zuari estuaries are not frictionally dominated estuaries because amplification due to geometrical effects cancels the decay in amplitude due to friction. The rapid increase of the first and second harmonics of M sub(2) and compound tides inside the estuaries shows the nonlinear response of the Mandovi and Zuari estuarine systems to tidal forcing. The M sub(4)/M sub(2) amplitude ratio indicates that the tide is subjected to more asymmetry in the Zuari than that in the Mandovi estuary. The increase of the first harmonic of M sub(2) and decrease of relative surface phase (2M sub(2) - M sub(4)) inside the Mandovi and Zuari estuaries show that these estuaries are flood dominant estuaries.
Between June 1995 and November 1998, eight Patagonian rivers were sampled for the suspended and dissolved loads delivered to the SW Atlantic. The most important rivers (Negro and Santa Cruz) jointly deliver ;90% of the total Patagonian freshwater budget (;60 km3 y21). Of the total sediment load (;1.7 1012 g y21), 2.8% was accounted for by particulate organic carbon (POC), 0.9% by inorganic particulate carbon (PC), 0.7% by particulate nitrogen (PN), and 0.7% by particulate phosphorus (PP). The mean dissolved organic carbon (DOC) yield was ;0.50 g m22y21, and POC ;0.3 g m22y21. Nitrogen is the limiting nutrient in all rivers; the mean molecular C:N:P ratio is 37:1:1. POC:PN ratios (4.4–10) indicate an autochthonous origin for the organic matter in suspended particulate matter (TSS). Many factors, such as proglacial oligotrophic lakes, coal-bearing strata, wetlands, aridity, as well as various human impacts, suggest a complex typology. The analysis (Euclidean distance cluster analysis) of biogeochemical variables [SiO2, NO3 2, PO4 32, DOC, POC, PC, PP, PN, C:N, DOC:POC, PC:POC, POC (%)] indicates that runoff, superimposed on biogeochemical variables, plays an important role in Patagonian riverine typology: a) Low runoff rivers (,100 mm y21): the Chubut, Chico, Deseado are characterized by low yields and POC:PN ratios; the Coyle River, by high DOC:POC; b) Medium discharge rivers (100–300 mm y21): the Negro River has high dissolved yields and high POC(%TSS); the Colorado is distinguished by high PP and PC specific yields, and POC:PN ratio; c) High runoff rivers (.1000 mm y21): Santa Cruz and Gallegos rivers, are both characterized by above-average specific yields; the Gallegos has high POC(%TSS), POC:PN and DOC:POC.
Although being more biohermal in form, the Pliocene reef system under Miami appeared to have distinct zonation, with evidence of 4 ecological zones being collected at the sampling sites. Based upon both the extent of the Atlantic Coastal Ridge and the implied faunal zonation of the reefs, it is conjectured that the Pliocene reef tract produced the original topographic high along the SE coast of Florida. This was later covered by a crust of oolitic limestone and sand in the late Pleistocene to produce the Atlantic Coastal Ridge. Together, the atoll-like Pliocene reef tracts and the central lagoon-like basin laid down the geomorphological framework for the formation of the Everglades in the Holocene.-from Author
With the potential threat of global climate change leading to sea-level rise, policy makers and engineers are looking towards managed realignment as a genuine attempt to provide a more sustainable coastal defence strategy. Public perceptions and attitudes towards this approach have generally indicated that it is not a favoured defence option as local residents often view managed realignment as 'giving in to the sea'. Brancaster West Marsh is the first of three ongoing studies that will attempt to identify changes in public acceptance of managed realignment and the Environment Agency (the main statutory body responsible for these works). It is hypothesised that local residents will show the most support for this type of strategy once it is fully established rather than at the inception or during the construction phases. A postal questionnaire, composed mainly of attitude statements was used to elicit resident perceptions and attitudes on the local environment, coastal flooding, coastal defence and managed realignment. Findings from the current Brancaster scheme suggest that residents who have a higher regard for the Environment Agency are generally more accepting of the scheme, however, the results could not conclusively determine whether the majority of the respondents support the scheme. Qualitative data also highlighted conflicting views among residents on the issues of sustainability, hard and soft defences, economics, the environment and consultation. This was thought to have resulted from information feedback deficiencies between the public and operating authorities. The study concludes that the information needs of local residents and access to information are integral components in the process of public understanding and should be addressed and assessed on a case-by-case basis.
There is an increasing demand for knowledge about hydrodynamic, morphological and water quality processes within the estuarine waterways of the Gold Coast. This study describes the development of a suite of hydrodynamic, sediment transport and water quality models for the Gold Coast tidal waterways. The modeling framework described was developed to provide a strategic understanding of waterway behaviour at a level appropriate for planning and environmental impact assessment in addition to guiding strategic decision making. The model simulations are based on DHI's two-dimensional flexible mesh code, MIKE21 FM. The hydrodynamic equation is linked to a set of transport-dispersion (transport module) equations that are solved using the flow field generated by the hydrodynamic model. This transport module establishes connection between heat, salinity, tracers and turbulence parameters and hydrodynamic. It also provides a base for water quality and sediment transport modeling. Water quality modeling is achieved through development of required process module. Process module is constructed using templates that the ECOLab interface provides. The process module describes the flow of N, P and C between the various trophic forms. The external factors, such as salinity and temperature, which govern the variations of the components in time and space, are made available to processes through a link with the hydrodynamic module. The current induced sediment transport and the associated morphological evolution in the study area were simulated by the sediment transport module of the software. The transport rates and the morphological evolution are calculated on the same flexible mesh that was used for hydrodynamic and water quality modeling. The resulting estuarine model framework has been applied to a number of specific issues such as recycled water discharge and waterway assimilative capacity. Future applications include modeling of extreme events under climate change.
Time series analysis and model simulations defined dynamics of coastal boundary layer formation off Coffs Harbour based on four deployed acoustic Doppler current (ADCP) meters and wind data from Coffs Harbour airport. Variance preserving spectra revealed peak energies at 7.8, 3.9 and 2.5 days plus ~24 and ~12 hours consistent with dominant forcing by winds. At inshore sites the highest energy levels occurred at the surface and decrease uniformly with depth at all frequencies with local peaks centred at exactly 24 hours, corresponding to peak local wind energy. In contrast, offshore sites showed depth dependency in the peak spectral energy with evidence of regional influences and wave-guide effects due to density stratification. Hydrodynamic simulations using the 3-dimensional explicit finite difference model 3DD revealed local bathymetric controls on circulation. A coastal boundary layer, delineated by a shear zone ~2km offshore in the lee of Corambirra Point, south of Coffs Harbour, was associated with formation of transient eddies. Model simulations and independent ADCP data identified 3 dimensional flow structures typified by clockwise rotation of flows down through the water column at all sites except for the quiescent, shallow water site in the headland wake south of Corambirra Point. The area south of Corambirra Point was predisposed to clockwise eddy rotation while offshore flows were generally shore-parallel. Pollutant dispersal was shown to be significantly less within this coastal boundary layer thus highlighting the need to consider effects of coastal boundary layers when locating discharges such as ocean outfalls.
Saltwater Creek and Coombabah Creek are branches of the Coomera River estuary situated within the subtropical Gold Coast City region, Australia, where fresh water flushing occurs during the wet season. The two creek systems are physically adjacent to each other and join at a confluence before connecting to the lower Coomera River. Saltwater Creek is 17 km long and is joined again halfway up its tidal section, via an anabranch, to Coomera River. Coombabah Creek leads upstream to Coombabah Lake, a large shallow lake ringed by mangrove swamps. In order to develop an understanding of how these systems interact with each other, in particular their salinity dynamics, at time scales ranging from tidal to annual, three field studies were undertaken. Field measurements confirmed that the salinity dynamics of these systems were dominated by rainfall and tidal events, typical of estuaries during the 'wet season' in subtropical environments. In contrast, the studies found that hypersaline conditions (salinity as high as 42 psu) developed upstream during the 'dry season' within Coombabah Lake due to the evaporative effects of its large shallow area and adjoining mangrove swamps. Further, the data also revealed that during the dry season, Saltwater Creek's high frequency salinity fluctuations were in-phase with tidal oscillations while Coombabah Creeks' were out-of-phase despite their close proximity. The mechanism for this was attributed to ebb tidal currents in Coombabah Creek which flushed hypersaline water out of the lake past the confluence, and the following flood tidal currents bringing that water into Saltwater Creek. The studies also identified a low Yes Yes
Low Isles Reef is the most southerly located of 46 coral reef platforms unique to the inner shelf of the northern Great Barrier Reef Province, Australia, which support both sea grass and mangrove growth. Such reefs develop in areas that are influenced by river flood plumes and where interreef sediments are dominated by terrigenous mud. Low Isles Reef has long been a popular tourist destination. Informal reports of decreasing visibility, a decline in scleractinian corals, and increases in soft coral and macroalgae have sparked speculation that agricultural activities in coastal catchments are affecting the reef. Comparison of the modern surface of Low Isles Reef with historical surveys and photographs dating back to 1928 allows quantification of modern sedimentary processes, rates of change, and factors influencing reef development. Results indicate that changes on Low Isles Reef are related to remobilization of coarse sediment during storm events and gradual shoreline retreat associated with rising sea level. Retreat of shingle ramparts and elongate ridges of coral debris toward the reef interior has led to the infilling of subtidal ponds on the reef top, which supported hard coral colonies in 1928. The gradual development of a composite shingle rampart along the windward margin has promoted an increase (;150%) in the area of the reef top covered by mangroves. On the leeward margin, a decrease in hard corals since 1950 may reflect a rising contribution of organic debris from the expanding mangrove swamp. Results suggest that recent changes on Low Isles Reef can be explained in the context of natural processes. Further study is needed before the effects of agricultural activities in coastal catchments on reef health can be confirmed.
The Seaway entrance is a tidal inlet located on the Gold Coast (Queensland, Australia). Before the 80s, the entrance was highly variable in terms of inlet location and sand bar characteristics. The Seaway stabilisation with two training walls combined with an artificial sand bypassing system were completed in 1986 with the aims of fixing the entrance, maintaining a safe navigable channel, preventing shoreline erosion to the north and a buildup of sand to the south. Despite these training works, the dynamics of the Seaway is still poorly understood: channel infilling problems and navigation issues remain. For these reasons, the present study aims to develop a comprehensive model of the entrance to be used for further dredging and training work issues. The present investigation is carried out in two stages. The first stage is based on historic aerial photograph analysis of the Seaway before training works. It shows that the mouth was periodically driven northward by the longshore drift, with an average cycle time of 10 years. The second stage is based on numerical modelling after training works. Refined Delft3D modelling is undertaken with a 2DH approach on the Seaway area, taking into account the training walls and the sand bypassing system. This local model is coupled with MIKE21 implemented on a regional scale to provide accurate tide and flow forcing at the boundaries. After calibration, the analysis of flow patterns shows that the Gold Coast Seaway is ebb-dominated and that the more intense flow velocities are observed in the northern channel. Morphological evolution of the inlet is also investigated with a qualitative approach. Results indicate the pathways and rate of the sand movement within the tidal inlet in its current configuration and provide information about a planned 400 m extension of the southern training wall. A significant calibration work, involving sediment transport and bathymetry measurement, is required for the model to be used as a comprehensive tool for further dredging and dumping strategies within the entrance. Yes Yes
Coastal wetlands and estuaries are important environments providing significant habitats for flora and fauna species - often supporting commercial and recreational fisheries. These systems also act as filters for contaminants and sediments, and the absorption of wave energy. As a consequence of the ecological significance and the potential for anthropogenic disturbances and inputs into Coombabah Lake estuary (Australia), the lake and surrounding wetlands have been the focus of recent scientific study efforts. This estuarine lake (~2 km2 in size) is a very shallow (mean depth < 1 m) estuarine system that experiences a tidal range of 1.2 m, thus resulting in the continual exposure of large mud flats at low tide. Variations in water column physio-chemical and biological parameters and nutrient concentrations of the benthic sediments have previously been attributed to the hydrodynamic regime, hydrologic events, and sediment sources. In this study, a three-dimensional (3D) hydrodynamic model with unstructured mesh is setup to simulate the hydrodynamic regime and Bottom Boundary Layer (BBL) properties. In particular, the sensitivity of calibration parameters for a very shallow estuarine model is investigated. Model results are verified by recent intensive measurements. The hydrodynamic regime of the lake was found to be favorable for settlement of suspended sediments. The results reveal the necessity to correctly measure and use the appropriate bathymetry and bed roughness conditions in the numerical scheme for very shallow environments. Yes Yes