32 results on '"Terry R. Healy"'
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2. Littoral Drift Gradient
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Terry R. Healy
- Subjects
Longshore drift ,Oceanography ,Geology - Published
- 2018
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3. Reliability of Geomorphic Indicators of Littoral Drift: Examples from the Bay of Plenty, New Zealand
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Terry R. Healy and Willem P. de Lange
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geography ,geography.geographical_feature_category ,Ecology ,Range (biology) ,Sediment ,Estuary ,Longshore drift ,Tectonics ,Oceanography ,Harbour ,computer ,Bay ,Sediment transport ,Geology ,Earth-Surface Processes ,Water Science and Technology ,computer.programming_language - Abstract
Healy, T. and de Lange, W., 2014. Reliability of geomorphic indicators of littoral drift: Examples from the Bay of Plenty, New Zealand. The net direction of littoral drift can be evaluated by multiple lines of evidence, including a range of geomorphic indicators and trends in sediment characteristics. In this article, the processes that influence the longshore transport of sediment are reviewed and assessed by the types of geomorphic indicators and sediment trends that can be expected. Various proxies for measured littoral drift are used to evaluate the littoral drift in the Bay of Plenty, New Zealand. Previous studies, utilising geomorphic indicators and, to a lesser extent, sediment characteristics and simple models of longshore sediment transport, developed a conceptual model of two main littoral drift systems starting at the western and eastern margins of the Bay of Plenty and converging in the vicinity of Ohiwa Harbour, an estuary enclosed by two opposing spits within the bay. Comparison of ...
- Published
- 2014
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4. Debris dispersal modeling for the great Sumatra Tsunamis on Banda Aceh and surrounding waters
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Jose C. Borrero, Terry R. Healy, Gegar Prasetya, Kerry P. Black, and Willem P. de Lange
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Atmospheric Science ,Oceanography ,Hydrogeology ,Culvert ,Natural hazard ,Earth and Planetary Sciences (miscellaneous) ,Biological dispersal ,Environmental science ,Banda aceh ,Particle (ecology) ,Submarine pipeline ,Debris ,Water Science and Technology - Abstract
The Great Sumatra Tsunami on 26 December 2004 generated large amounts of debris and waste throughout the affected coastal region in the Indian Ocean. In Banda Aceh—Indonesia, the tsunami flows were observed carrying a thick muddy sludge that mixed with all kinds of debris from the destroyed buildings, bridges and culverts, vehicles, fallen trees, and other flotsam. This waste and debris was mostly deposited inland, but traveled both onshore and offshore. Numerical dispersal modeling is carried out to simulate the transport of debris and waste produced by the tsunamis during the event. The model solves the Lagrangian form of the transport/dispersion equations using novel particle tracking techniques. Model results show that understanding the pathway and distribution of the suspended materials and flotsam caused by tsunamis is important for a proper hazards mitigation plan and waste management action, and to minimize serious long-term adverse environmental and natural resources consequences.
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- 2011
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5. Modeling of inundation dynamics on Banda Aceh, Indonesia during the great Sumatra tsunamis December 26, 2004
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Jose C. Borrero, Terry R. Healy, Gegar Prasetya, Willem P. de Lange, and Kerry P. Black
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Atmospheric Science ,Oceanography ,Natural hazard ,Earth and Planetary Sciences (miscellaneous) ,Banda aceh ,West coast ,Surface runoff ,Geology ,Water Science and Technology - Abstract
The tsunami inundation flows on Banda Aceh, Indonesia reached 5 km inland during the December 26, 2004, event and devastated most of the houses, buildings, and infrastructure along the coast and killed more than 167,000 people. The overland flows from the northwest coast and the west coast collided at Lampisang village approximately 3.7 km from Ulee Lheue (northwest coast) and 6.8 km from Lhok Nga (west coast) as reported by survivors. Inundation modeling based on the nonlinear shallow-water wave equations reproduces the inundation pattern and demonstrates a colliding of the overland flows. The model suggests that wave characteristics on the northwest coast of Banda Aceh were different from those on the waves that impacted upon the west coast. The areas, which experienced higher inundation levels, did not always experience greatest overland flow speeds, and the damage areas mostly coincide with the flow speed distribution rather than the runup and inundation depth.
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- 2011
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6. Establishment of a Dredged Material Disposal Site in the Exclusive Economic Zone: New Zealand
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Bryna K. Flaim, Phillip Weir, and Terry R. Healy
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geography ,geography.geographical_feature_category ,Flat surface ,Continental shelf ,Exclusive economic zone ,Cultural significance ,Oceanography ,Environmental protection ,Benthic zone ,Dumping ,Territorial waters ,Environmental Chemistry ,Environmental science ,Environmental impact assessment ,General Environmental Science - Abstract
Disposal options for muddy dredged material, especially if lightly contaminated, is an issue facing many countries, particularly if environmental protection and adherence to the Protocols of the London Dumping Convention is a regulatory requirement. For the case of the oceanic islands of New Zealand, disposal of muddy dredged material has become an issue for the prime city of Auckland. Accordingly, it has been necessary to investigate a suitable marine disposal site outside of the territorial seas in the exclusive economic zone (EEZ). Ideal properties for such a disposal site include a near flat surface on the continental shelf, with sediments of similar textural characteristics to the material being disposed, a site of non-critical benthic ecology, water depths sufficient to enable the disposal site to be monitored (as required under the London Dumping Convention), a site experiencing low shelf currents, not affected by significant wave agitation, and a site not of cultural significance. The approach for...
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- 2010
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7. Quantitative experimental comparison of single-beam, sidescan, and multibeam benthic habitat maps
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Dirk Immenga, David Linton Johnson, Terry R. Healy, and Alexandre C. G. Schimel
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Ecology ,Backscatter ,Mosaic (geodemography) ,Aquatic Science ,Oceanography ,Sonar ,Echo sounding ,Acoustic seabed classification ,Remote sensing (archaeology) ,Statistics ,Segmentation ,Cartography ,Ecology, Evolution, Behavior and Systematics ,Geology ,Seabed - Abstract
Schimel, A. C. G., Healy, T. R., Johnson, D., and Immenga, D. 2010. Quantitative experimental comparison of single-beam, sidescan, and multibeam benthic habitat maps. – ICES Journal of Marine Science, 67: 1766–1779. Map comparison is a relatively uncommon practice in acoustic seabed classification to date, contrary to the field of land remote sensing, where it has been developed extensively over recent decades. The aim here is to illustrate the benefits of map comparison in the underwater realm with a case study of three maps independently describing the seabed habitats of the Te Matuku Marine Reserve (Hauraki Gulf, New Zealand). The maps are obtained from a QTC View classification of a single-beam echosounder (SBES) dataset, manual segmentation of a sidescan sonar (SSS) mosaic, and automatic classification of a backscatter dataset from a multibeam echosounder (MBES). The maps are compared using pixel-to-pixel similarity measures derived from the literature in land remote sensing. All measures agree in presenting the MBES and SSS maps as the most similar, and the SBES and SSS maps as the least similar. The results are discussed with reference to the potential of MBES backscatter as an alternative to SSS mosaic for imagery segmentation and to the potential of joint SBES–SSS survey for improved habitat mapping. Other applications of map-similarity measures in acoustic classification of the seabed are suggested.
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- 2010
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8. Ebb-Jet Dynamics and Transient Eddy Formation at Tauranga Harbour: Implications for Entrance Channel Shoaling
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Terry R. Healy, Christian Winter, and Kyle C. Spiers
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Rip tide ,geography ,geography.geographical_feature_category ,Ecology ,Sediment trap (geology) ,Shoaling and schooling ,Inlet ,Current (stream) ,Longshore drift ,Oceanography ,Eddy ,Sediment transport ,Geology ,Earth-Surface Processes ,Water Science and Technology - Abstract
In 1992 the entrance channel through the tidal inlet to Tauranga Harbour, which is located along the Bay of Plenty littoral drift system, was deepened from 10 m to 14 m. The deepened channel has become a sediment trap for littoral drift bypassing and tidal current driven sediment transport through the inlet. Since 1992, there has been an increase in maintenance dredging requirements at the inlet, because of sand accumulation along the southeastern border of the entrance channel. Previous studies have identified an ebb tide–induced eddy operating on the eastern side of the ebb-jet as it exits the tidal gorge. In this article, the eddy system has been simulated with a validated two-dimensional hydrodynamic model, detailing time-varying current patterns over the ebb-tidal delta. Particular emphasis is placed on defining the trajectory of the eddy and evaluating its influence on the observed sedimentation patterns. The model results indicate the formation of opposing eddies on either side of the entr...
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- 2009
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9. Modelling of wave climate and sediment transport patterns at a tideless embayed beach, Pirita Beach, Estonia
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Jüri Kask, Tarmo Soomere, Terry R. Healy, and Andres Kask
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geography ,geography.geographical_feature_category ,Sediment ,Aquatic Science ,Oceanography ,Spatial distribution ,Waterline ,Wave model ,symbols.namesake ,Beach ridge ,symbols ,Bathymetry ,Sediment transport ,Ecology, Evolution, Behavior and Systematics ,Geology ,Seabed - Abstract
Nearshore sand transport patterns along the tideless, embayed Pirita beach, Tallinn, Estonia, have been investigated utilizing high-resolution modelling of wave processes combined with bathymetric surveys and sediment textural analyses of the nearshore sea floor. Textural analysis showed the mean grain size is about 0.12 mm. Fine sand (0.063–0.125 mm) accounts for about 77% of the sediments. Coarser-grained sand (0.28 mm) dominates along the waterline. Based upon the spatial distribution of the mean grain size and basic features of the local wave activity, properties of the Dean Equilibrium Beach Profile were determined. Alongshore sediment transport was calculated based upon a long-term time series of wave properties along the beach, and the CERC formula applied to about 500 m long beach sectors. The time series of wave fields and the properties of the local wave climate were modelled using a triple nested WAM wave model with an extended spectral range for short waves. The model is forced by open sea wind data from Kalbadagrund for the years 1981–2002. Results indicate that typical closure depth at Pirita is 2.5 m. The width and mean slope of the equilibrium profile are 250 m and 1:100, respectively. Southward transport dominates in the northern sections of the beach whereas no prevailing transport direction exists in the southern sections. This pattern has several nontrivial implications for the planning of beach protection activities.
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- 2008
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10. Transient wind‐driven coastal upwelling on a shelf with varying width and orientation
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Kerry P. Black, Peter C. Longdill, and Terry R. Healy
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Ecology ,Outcrop ,Wind stress ,Aquatic Science ,Algal bloom ,Current meter ,Oceanography ,Downwelling ,Upwelling ,Satellite ,Bay ,Ecology, Evolution, Behavior and Systematics ,Geology ,Water Science and Technology - Abstract
Cross‐correlations between along‐shelf wind stress and both along‐ and cross‐shelf currents within the central Bay of Plenty, New Zealand show the circulation during spring‐summer to be highly responsive to wind events. Current meter records indicate that upwelling‐favourable wind stresses generate upwelling dynamics in both mean and fluctuating senses. Both thermistor moorings and satellite inferred temperature data record the outcropping of this cool water following upwelling‐favourable wind stresses. The upwelling circulation provides an efficient mechanism for the periodic delivery of cool (c. 80 μg litre‐1) water to the coastal zone during spring. Historical wind forcing data suggest that the wind‐forced dynamics described were responsible for a major toxic algal bloom within the Bay of Plenty during 1992–93.
- Published
- 2008
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11. Theoretical post-glacial sedimentation rates for a semi-enclosed sea; example of the Kieler Bucht, Western Baltic
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Kyaw Winn, Friederich Werner, Terry R. Healy, and Helmut Erlenkeuser
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Archeology ,geography ,geography.geographical_feature_category ,Geology ,Sedimentation ,Sedimentary basin ,Deposition (geology) ,Oceanography ,Sedimentary rock ,Glacial period ,Bay ,Ecology, Evolution, Behavior and Systematics ,Holocene ,Marine transgression - Abstract
The theoretical rates of deposition for fine sediments over the last 10 ka have been deduced and plotted for the Kieler Bucht. Assumptions are that the bay has remained as a closed sedimentary system, and that the fine sediments deposit in water deeper than 10 m. A sharp peak of sedimentation activity is indicated between 7.5 and 8.5 ka B.P. with low rates prior to 9.5 ka and since 6 ka. Comparison of rates obtained from dated cores extracted from different parts of the Kieler Bucht with the theoretical curve shows general conformity, and confirms that peak sedimentation rates exceeding 3 mm/a, as averaged over 100–200 years, occurred between 8 and 9 ka, with the suggestion of a minor activity peak between 3 and 4 ka. The overall consistency supports the view that the bay has acted essentially as a closed sedimentary basin during the Holocene marine transgression and subsequently.
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- 2008
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12. Submarine terraces and morphology in the Kieler Bucht, Western Baltic, and their relation to late Quaternary events
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Terry R. Healy
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Archeology ,geography ,geography.geographical_feature_category ,Submarine ,Geology ,Present day ,Sedimentation ,Hypsometric curve ,Oceanography ,Sea-level curve ,Cliff ,Quaternary ,Bay ,Ecology, Evolution, Behavior and Systematics - Abstract
From analysis of the densest network of echogrammes yet available for the Kieler Bucht, Western Baltic, the submarine erosional terraces have been mapped. In general these correlate well with the features mapped and described by Kolp (1976) for the adjacent Mecklenburger Bucht. The lower terraces are at - 30 m and may reach 2100 m in broadness. Compared to present day conditions, the rates of cliff retreat at the time of formation were evidently much accelerated, due possibly to harsher climatic conditions including a greater intensity of winter lake ice, frosts, wind and rain. Other terraces at - 27, - 24, - 19, and - 14 m were identified, and these are related to syngressions in the various eustatic curves applicable to the Western baltic. A hypsometric curve for the submarine terrain of the Kieler Bucht, when compared to the relative sea level curve shows that 65% of the bay was transgressed in only 700 years. Maximum sedimentation rates in the Kieler Bucht should have occurred at this time, and independent data from dated cores from Vejsnas Rinne support this prediction.
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- 2008
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13. An integrated GIS approach for sustainable aquaculture management area site selection
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Terry R. Healy, Kerry P. Black, and Peter C. Longdill
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Geographic information system ,biology ,business.industry ,Environmental resource management ,Site selection ,Management, Monitoring, Policy and Law ,Aquatic Science ,Diversification (marketing strategy) ,Oceanography ,biology.organism_classification ,Geography ,Aquaculture ,Environmental protection ,Constraints accounting ,Sustainability ,business ,Perna canaliculus ,Bay - Abstract
Within New Zealand, growth in the aquaculture industry has led to the diversification of aquaculture sites from more sheltered bays and harbours toward open coast locations. Coastal zone managers, along with the aquaculture industry, aim to ensure the long-term sustainability of any ‘new’ sites selected. Through targeted data collection programmes and the subsequent implementation of Geographic Information System (GIS) based models, the most suitable and sustainable locations for Aquaculture Management Areas (AMAs) can be identified. This approach is applied within the Bay of Plenty, New Zealand, with specific reference to suspended mussel (Perna canaliculus) aquaculture. Within the region, areas where maximum sustainability may be achieved make up 18% of the total area considered, with conflicting uses and other constraints accounting for 46%. Whilst further site and development specific studies are required to determine explicit carrying capacities, the effort required has been considerably reduced by eliminating unsuitable locations and identifying those where sustainability can be maximised. 2008 Elsevier Ltd. All rights reserved.
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- 2008
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14. Mapping the Morphology of a Dredged Ebb Tidal Delta, Tauranga Harbour, New Zealand
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Terry R. Healy and J. C. Kruger
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Delta ,Rip tide ,Ecology ,Ocean current ,Sedimentation ,Sonar ,Dredging ,Oceanography ,Sonar imagery ,Harbour ,computer ,Geology ,Earth-Surface Processes ,Water Science and Technology ,computer.programming_language - Abstract
The morphological units of an ebb tidal delta were mapped and results used to evaluate the relationship between morphology and hydrodynamics, as part of an investigation into the sedimentation at the Entrance Channel at Tauranga Harbour, New Zealand. Four end-member map units (shell lag, coarse sand, medium sand, and fine sand) were identified from the sidescan sonar imagery, which was verified using seabed sediment samples and SCUBA diver observations. These four units were used in a classification scheme that consisted of 10 composite map units. The use of standardized map units helped to reduce the subjectivity involved in sidescan sonar image interpretation. The mapping scheme was used to assist in the understanding of the impact of capital dredging on the morphological evolution of an ebb tidal delta. Observed morphological changes over the ebb tidal delta were attributed to possible changes in the asymmetry of the vertical tide and residual eddy currents.
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- 2006
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15. An experimental investigation of the burrowing behaviour ofPaphies australis(bivalvia: Mesodesmatidae)*
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Terry R. Healy, Penelope J. Hull, Robert G. Creese, and Russell G. Cole
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geography ,geography.geographical_feature_category ,biology ,Physiology ,Mesodesmatidae ,Sediment ,Estuary ,Aquatic Science ,Oceanography ,Bivalvia ,biology.organism_classification ,Paphies australis ,Burrow - Abstract
Laboratory and field experiments examining the burrowing behaviour of the estuarine infaunal bivalve Paphies australis (Bivalvia: Mesodesmatidae) were conducted in two areas of northeastern New Zealand. Field experiments examining reburial showed that when exposed on the sediment surface most P. australis were able to bury within 40 min. Slightly fewer pipi buried during high‐tide trials than during mid‐tide trials. Laboratory experiments established the ability of P. australis of various sizes to burrow up to the sediment surface after being inundated with sediment to a depth of up to 40 cm. P. australis buried under 10 cm of sediment burrowed to the surface at a slower mean rate than those buried under lesser depths of sediment, and variability in ascension rates increased with increasing burial depth. P. australis with an initial upright orientation burrowed and ascended at a greater rate than P. australis placed laterally or inverted. Though capable of ascending through as much as 50 cm of sand in lab...
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- 1998
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16. Holocene sediment lithofacies and dispersal systems on a storm-dominated, back-arc shelf margin: The east Coromandel coast, New Zealand
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Campbell S. Nelson, Paul M Dell, Barry E. Bradshaw, Willem P. de Lange, and Terry R. Healy
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geography ,Upper shoreface ,geography.geographical_feature_category ,Continental shelf ,Geology ,Oceanography ,Paleontology ,Geochemistry and Petrology ,Back-arc basin ,Sedimentary rock ,Siliciclastic ,Quaternary ,Holocene ,Marine transgression - Abstract
Holocene sediment lithofacies and dispersal systems on the east Coromandel shelf, New Zealand, are mainly characterised by an accommodation-dominated regime in which autochthonous siliciclastic sediments were reworked through erosional shoreface retreat during the post-glacial marine transgression (12.0–6.5 ka). Stabilisation of sea level at its present position ca. 6.5 ka initiated onshore reworking of the autochthonous deposits into fine-grained regressive barrier and shoreface sands, while coarser sands remained offshore to form an erosional-lag inner-shelf deposit. Modern episodes of shoreface erosion rework fine and coarse autochthonous sands offshore and northwards into very large (η = 0.5–2.5 m; λ = 250–1500 m) submarine dunes. The submarine dunes are similar in form to sand ridges on the North American Atlantic shelf, but with crests striking perpendicular to both the shoreline and generating flows. Allochthonous siliciclastic lithofacies are also important aspects of east Coromandel shelf sedimentation, and are transported offshore from infilled estuary systems to form very fine-grained upper shoreface and muddy mid-shelf sands. The regional geology has a strong influence on shelf lithofacies and dispersal systems off the east Coromandel coast. Southern shelf regions are associated with deep back-arc basins which have formed major late Cenozoic depocentres for sediments sourced from the Taupo Volcanic Zone. Further north, a shallow volcanic platform extends out across the shelf and forms a barrier to any large-scale along-shelf dispersal of sediments. Consequently, lithofacies in northern shelf regions tend to be highly variable and reflect local catchment lithologies.
- Published
- 1994
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17. Holocene coastal depositional sequences on a tectonically active setting: southeastern Tauranga Harbour, New Zealand
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Terry R. Healy and Richard A. Davis
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geography ,geography.geographical_feature_category ,Pleistocene ,Stratigraphy ,Fluvial ,Geology ,Sedimentary depositional environment ,Headland ,Paleontology ,Oceanography ,Sedimentary rock ,Radiometric dating ,Quaternary ,Holocene - Abstract
More than 70 cores, a high-resolution seismic survey, and SCUBA observations provide the basis for the interpretation of depositional environments that accumulated during the Quaternary in the southeastern Tauranga Harbour area of the North Island, New Zealand. Three lithofacies comprise this sequence; in ascending order they are pumiceous sand and gravel, shelly mud and shelly sand. The pumiceous sand is interpreted as fluvial and fan deposits of Pleistocene to early Holocene age with a radiometric date of 9420 ± 100 yr BP near the top of the unit. The shelly mud represents low-energy estuarine deposition of essentially normal marine salinity in a valley-like setting. This unit dates at 8100 ± 80 yr BP. The extensive overlying shelly sand thickens seaward and represents wave-dominated shoreface conditions much like the present nearshore environment. Radiometric dating of samples within the present harbor are all between 6000 and 7000 yr BP and those seaward of the spit to Mt. Maunganui are less than 3370 ± 100 yr BP. The barrier spit that has attached to the volcanic headland began accumulating about 4000–5000 years ago.
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- 1993
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18. A 'blind-folded' test of equilibrium beach profile concepts with New Zealand data
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Terry R. Healy, Albert P Dommerholt, and Robert G. Dean
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Sand mining ,Hydrology ,Shore ,Plage ,geography ,geography.geographical_feature_category ,Disequilibrium ,Sediment ,Geology ,Oceanography ,Geochemistry and Petrology ,Granulometry ,Clastic rock ,medicine ,Stage (hydrology) ,Physical geography ,medicine.symptom - Abstract
Methodology for calculating equilibrium beach profiles for uniform sand size characteristics is extended to the case of an arbitrary distribution of sediment characteristics across the profile. The application of this method and comparison with actual profiles is posed as a means of interpreting whether the profile contains a deficit or excess of sediment and thus whether long-term shoreline recession or advancement can be anticipated. Various types of profile disequilibrium are reviewed and the significance discussed. The methodology is applied using measured profiles, sediment sizes and beach face slopes for ten sites on the Northern Island of New Zealand. One profile was documented in this study, whereas the data for the other nine were obtained from published sources. The number of sediment samples available for each profile varied from three to twelve. The agreement between the actual and calculated profiles differs considerably for the ten sites. The degree of disequilibrium is quantified by calculating the shoreline adjustment, Δy , required for the actual profile to equilibrate for depths less than 7 m, which represents the near-maximum depth available on all profiles. These shoreline adjustments ranged from − 105 m (recession) to + 159 m (advancement) with four of the ten sites having positive values. Three of the sites with negative shoreline adjustment have been, or are presently, sites of substantial sand extraction from the beach or in the nearshore waters. However, the differences between the actual and equilibrium profiles are not consistent with anticipated profile forms and/or volumes and it is thus concluded that sand mining is not responsible for most of the observed deficits. At this stage, it is not possible to state with confidence whether differences between actual and (calculated) equilibrium profiles are due to true disequilibriums or to limitations in the equilibrium beach profile methodology. Studies of the type reported here when applied to many different areas will advance the methodology and contribute to the confidence in the resulting interpretations.
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- 1993
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19. Coastal oceanography and sedimentology in New Zealand, 1967–91
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Terry R. Healy, Terry M. Hume, D.Murray Hicks, Willem P. de Lange, Robert G. Bell, and R. M. Kirk
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geography ,Plage ,geography.geographical_feature_category ,Ecology ,Storm surge ,Estuary ,Aquatic Science ,Physical oceanography ,Coastal erosion ,Longshore drift ,Oceanography ,Sedimentology ,Ecology, Evolution, Behavior and Systematics ,Geology ,Beach morphodynamics ,Water Science and Technology - Abstract
This paper reviews research that has taken place on physical oceanography and sedimentology on New Zealand's estuaries and the inner shelf since c. 1967. It includes estuarine sedimentation, tidal inlets, beach morphodynamics, nearshore and inner shelf sedimentation, tides and coastal currents, numerical modelling, short‐period waves, tsunamis, and storm surges. An extensive reference list covering both published and unpublished material is included. Formal teaching and research programmes dealing with coastal landforms and the processes that shape them were only introduced to New Zealand universities in 1964; the history of the New Zealand Journal of Marine and Freshwater Research parallels and chronicles the development of physical coastal science in New Zealand, most of which has been accomplished in last 25 years.
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- 1992
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20. Definition and physical characteristics of the world's enclosed coastal seas
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Terry R. Healy and Kenichi Harada
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Computer Science::Graphics ,Oceanography ,Semi-major axis ,Computer Science::Computational Geometry ,Aquatic Science ,Spatial distribution ,Pollution ,Bay ,Geology ,Term (time) - Abstract
Definitions of the geomorphic term “enclosed sea” are imprecise. Some available definitions are presented and reviewed. Based upon a quantitative morphometric ratio of {major axis length within the enclosed sea} to {entrance width}, fully “enclosed” seas are defined as having a ratio exceeding 4. If there is more than one entrance, the sea is defined as “semi-enclosed”. Those seas with major axis length to the entrance width ratios less than 4 are defined as “enclosed bays”, except if they have multiple entrances, in which case the term “semi-enclosed bay” is appropriate. Data from the world's coastal enclosed seas, defined according to the new morphometric criterion, are presented. We identify 22 enclosed seas, 6 semi-enclosed seas, 9 enclosed bays and 5 semi-enclosed bays.
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- 1991
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21. Beach Renourishment through Spoil Disposal Downdrift of a Dredged Entrance Channel
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Kyle C. Spiers and Terry R. Healy
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Dredging ,Delta ,geography ,Oceanography ,geography.geographical_feature_category ,Berm ,Beach nourishment ,Bathymetry ,Downdrift ,Inlet ,Geology ,Accretion (coastal management) - Abstract
The offset configuration of Tauranga tidal inlet delta system, in combination with the dredged entrance channel, hinders sediment supply to the down-drift beaches. Maintenance dredging of the entrance channel provides suitable sediment to be deposited as a nearshore berm, downdrift of the entrance channel, as a means to artificially bypass the tidal inlet and renourish the beaches of Mt Maunganui. During April and May of 2004, ∼112,000 m 3 of dredged medium sand was deposited between two nearshore dump grounds (Sites B and C), under the assumption that onshore transport would occur and act to renourish the beaches shoreward of these sites. Bathymetric and side-scan sonar monitoring showed erosion of the mounds at both sites and significant onshore dispersal at Site B clearly evident after disposal. Sub-aerial beach profile monitoring from 1999 to 2005 shows continued accretion of the sub-aerial beach from 2001 to 2005, partially in response to ongoing beach nourishment. This suggests that any reduction in sediment supply to the down-drift beaches is being successfully alleviated.
- Published
- 2007
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22. Chapter Fourteen Muddy coasts of mid-latitude oceanic islands on an active plate margin—New Zealand
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Terry R. Healy
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Graben ,Tectonic uplift ,Tidal range ,Oceanography ,biology ,Subduction ,Pacific Plate ,Intertidal zone ,Zostera ,biology.organism_classification ,Deposition (geology) ,Geology - Abstract
Publisher Summary This chapter describes the muddy coasts of mid-latitude oceanic islands on an active plate margin in New Zealand. The oceanic islands, comprising New Zealand, lie astride the boundary between the Australian-Indian and the Pacific plate. These large islands are subjected to the geological processes of an active subduction zone, including volcanism, seismic instability, and rapid tectonic uplift of the plate marginal on-lapping soft tertiary deposits. This hilly-to-mountainous unstable setting is a precondition for remarkable regolith instability, allowing exceptional erosion rates of the resulting steepland catchments. Special cases of muddy deposition in the New Zealand coastal zone occur within embayments of structural origin. The largest contiguous intertidal muddy coastal deposition in the country occurs in the headwaters of the Firth of Thames, a shallow semi-enclosed sea within a structural graben, and with a relatively large meso tidal range, into which flows the Waihou river. Distinctive vegetative features of the muddy coast are the occurrence of the seagrass macrophyte Zostera beds. These are often associated with topographic mounds in the generally flat tidal flats, and are recognized as providing a nursery for many organisms.
- Published
- 2002
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23. Chapter Five Relative sea level changes and some effects on muddy coasts
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Eduardo Marone, Terry R. Healy, and Saskia Jelgersma
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Sedimentary depositional environment ,geography ,Oceanography ,geography.geographical_feature_category ,Sediment ,Global change ,Last Glacial Maximum ,Estuary ,Future sea level ,Sedimentation ,Sea level ,Geology - Abstract
Summary Sea level changes since the last glacial maximum may be identified by three intervals. From 18 Ka-6 Ka sea level rose rapidly and was controlled mainly by the melting of continental ice caps. From about 6 Ka sea level rise reduced, and locally sea level rise history was influenced by pre-existing topography and regional and local tectonics. Projections of future global sea level rise between 1990 and 2100 from the latest IPCC assessment, range from 0.09 m to 0.88 m, with a central value of 0.48 m. The impact of future sea level rise on muddy coast depositional environments is primarily dependent upon the available sediment input, and the magnitude and frequency of the hydrodynamic forcing processes as agent for sediment redistribution. Where sediment deposition rates exceed the sea level rise rate, or where there is a balance of sediment deposition accompanying the sea level rise, effects on muddy coast morphodynamic environments may not be detectable. In muddy coasts of low sedimentation rates the relative sea level rise may result in depth increases of a few cm, which would only be relevant in shallow harbours. Increased intensities of storms as a result of global change will likely increase sediment load and turbidities in estuaries and semi-enclosed seas. These effects are likely to induce change to the muddy coast ecology over time, but distinguishing the effects from human impacts will be difficult.
- Published
- 2002
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24. Chapter Ten Typhoon storm surge and some effects on muddy coasts
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Chenglan Bao and Terry R. Healy
- Subjects
Shore ,Oceanography ,Geography ,geography.geographical_feature_category ,Typhoon ,Climatology ,Extratropical cyclone ,Wind stress ,Cyclone ,Storm surge ,Tropical cyclone ,Sea level - Abstract
Publisher Summary This chapter describes the typhoon storm surge and some effects on muddy coasts. Storm surge is an anomalous phenomenon of short-term rise in sea level caused by low atmospheric pressure and strong atmospheric disturbances, such as tropical cyclones or extra-tropical cyclones. It is of short time scale of between 1 and 100 h, usually half a day. The sustained shoreward hurricane wind stress, concomitant with abnormally low atmospheric pressure, forces seawater to the shore, causing water level to suddenly rise by up to 7 m. It is found that if storm surge is superimposed upon the astronomical high tide, it may cause disastrous impacts, especially to the low-lying land of muddy coastal regions. Tropical cyclones of the Bay of Bengal are typically not as intense as in the western North Pacific. Generally, the maximum wind speed is wind force 10–11. It is observed that, because of the funnel shape of the coastal outline, with shallow water near the apex of the bay, the strong southerlies to the east side of a tropical cyclone that are often sustained for several days, force vast quantities of surface sea water to be driven onshore, thereby generating an extremely high storm surge, and inundating the low muddy coast of Bangladesh.
- Published
- 2002
- Full Text
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25. The sediment threshold over tidally induced megaripples
- Author
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Kerry P. Black and Terry R. Healy
- Subjects
Bedform ,integumentary system ,Field (physics) ,Plane (geometry) ,Flow (psychology) ,Sediment ,Geology ,Mechanics ,Oceanography ,body regions ,Physics::Fluid Dynamics ,Geochemistry and Petrology ,Parasitic drag ,Geotechnical engineering ,Shear velocity ,human activities ,Sediment transport - Abstract
Formulae to predict the initiation of sediment transport over bedforms are derived and field tested. Unlike a Shields-type curve which is valid only for plane beds, both the form drag and skin friction are accounted for. The method relies on successful isolation of the skin friction component of the flow energy losses from the total loss which includes an ineffective form drag component. This is achieved using the Vanoni and Hwang equation for form drag losses while the skin friction is taken from the Yalin sediment threshold curve for plane beds. In conjunction, formulae are derived for the total friction velocity and the speed at 1 m above the bed at the sediment threshold. The theory is tested using thresholds measured in mesotidal estuaries.
- Published
- 1986
- Full Text
- View/download PDF
26. Sediment and hydrodynamics of the Tauranga entrance to Tauranga harbour
- Author
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R. J. Davies‐Colley and Terry R. Healy
- Subjects
Delta ,geography ,geography.geographical_feature_category ,Ecology ,Continental shelf ,Sediment ,Aquatic Science ,Inlet ,Swell ,Physics::Geophysics ,Physics::Fluid Dynamics ,Oceanography ,Wind wave ,Astrophysics::Earth and Planetary Astrophysics ,Geomorphology ,Sediment transport ,Bay ,Astrophysics::Galaxy Astrophysics ,Physics::Atmospheric and Oceanic Physics ,Ecology, Evolution, Behavior and Systematics ,Geology ,Water Science and Technology - Abstract
To relate the textural characteristics of the bottom sediments of a tidal inlet to hydrodynamics, 45 sediment samples from the Tauranga Entrance to Tauranga Harbour were analysed for textural parameters, and tidal currents and waves were monitored. Tidal currents dominate sediment transport processes near the Tauranga Entrance although swell waves are significant on the ebb tidal delta, and wind waves may influence intertidal sediments within the harbour. The bulk of the sediment is probably derived from marine sand from the Bay of Plenty continental shelf, but tidal currents and waves have changed its textural character. In areas of swift tidal currents, particularly in the inlet channel itself, sediment is coarser, more poorly sorted, and more coarsely skewed than that in areas of slower currents.
- Published
- 1978
- Full Text
- View/download PDF
27. Beach erosion at Waihi Beach Bay of Plenty, New Zealand
- Author
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K. G. Harray and Terry R. Healy
- Subjects
geography ,geography.geographical_feature_category ,Ecology ,Aquatic Science ,Storm beach ,Coastal erosion ,Shingle beach ,Longshore drift ,Oceanography ,Beach ridge ,Erosion ,Beach nourishment ,Sedimentary budget ,Ecology, Evolution, Behavior and Systematics ,Geology ,Water Science and Technology - Abstract
Since the 1940s, severe dune erosion has threatened property at Waihi Beach. This paper investigates beach erosion and dune recession in relation to wave climate, sedimentoldgy and mineralogy of the beach sediments, cyclical beach changes and sediment budget, and the littoral drift. Average dune recession along the entire beach between 1948 and 1977 was 27 m, although maximum recession recorded to 1977 was 83 m. Sand loss rates 1948–1977 average 3.4 m3 per metre of beach per year. The sediment budget of the entire beach is about 850 × 103 m3 and up to 74% of this was recorded as being ‘cut’ from the beach in one erosive episode. The cut and fill cycles are dominantly controlled by wave steepness, which has a critical value of 2.1 × 10−3 for breaking waves on Waihi Beach. Net littoral drift is towards the south‐east, and the basic reason for beach erosion at Waihi Beach is the lack of sediment to supply the littoral drift.
- Published
- 1978
- Full Text
- View/download PDF
28. First approximation sea-level dependent mathematical model for volume eroded and submarine profile development in a semienclosed sea: Kiel Bay, Western Baltic
- Author
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A. D. Sneyd, F. Werner, and Terry R. Healy
- Subjects
Shore ,geography ,geography.geographical_feature_category ,Lithology ,Submarine ,Structural basin ,Abrasion (geology) ,Mathematics (miscellaneous) ,Oceanography ,Sea-level curve ,Earth and Planetary Sciences (miscellaneous) ,Bay ,Geology ,Sea level - Abstract
Given a marine basin of near homogeneous lithology, a known sea level curve, and known submarine abrasion rates, a model is developed to estimate the volume of material eroded by marine action. Assumptions of the model are that erosion is effected solely by submarine abrasion, which is assumed known and uniform through time, and that the volume eroded is small relative to the total volume of the basin. The basis of the model is that the volume eroded V, between time limits t1 andt2,is essentially a function of the perimeter length l of the basin, which in turn is time-dependent on the sea level curve, so that $$V = k\int_{t1}^{t2} {l(t)dt} $$ where k is an abrasion rate constant. The model was tested on Kiel Bay, Western Baltic, a shallow semienclosed, essentially nontidal sea, for which considerable data is available. Critical for numerical integration of the model is the k value, representing the volume eroded from the shore normal profile per unit length of shoreline per year. A number of possible k values were utilized, the most likely realizing a total volume eroded over the past 9000 y, since the sea first entered Kiel Bay, of 2.60×109m3. From this model, long-term average vertical submarine abrasion rates for Kiel Bay can be deduced as being between 0.001 and 0.0004 m/y.
- Published
- 1987
- Full Text
- View/download PDF
29. Pockmark-like structures on the Poverty Bay sea bed — possible evidence for submarine mud volcanism
- Author
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Campbell S. Nelson and Terry R. Healy
- Subjects
Pockmark ,Geochemistry ,Geology ,Diapir ,Geophysics ,Oceanography ,Subaerial ,Earth and Planetary Sciences (miscellaneous) ,Prospecting ,Submarine pipeline ,Paleogene ,Bay ,Mud volcano - Abstract
Side-scan sonographs of the shallow (2–22 m) sea floor off Gisborne Harbour, northern Poverty Bay, New Zealand, include areas of scattered to locally prominent, subcircular, flat-floored depressions, resembling pockmarks, typically 5–20 m across and 0.3–0.5 m deep, in muddy very fine sands. Because of their geologic setting, it is speculated that the structures are exhalative pits for ascending streamers of mud, water, and/or natural gas from underlying diapiric intrusions of predominantly Paleogene shale, and that they may be submarine equivalents of the subaerial quiescent mud volcanoes occurring in the Gisborne district. Because of their possible significance in hydrocarbon prospecting, tsunami generation, and siting of subsea cables, pipelines, and offshore structures, they require further research.
- Published
- 1984
- Full Text
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30. New Zealand tsunamis 1840–1982
- Author
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W. P. de Lange and Terry R. Healy
- Subjects
geography ,geography.geographical_feature_category ,Continental shelf ,Magnitude (mathematics) ,Submarine ,Geology ,Volcanism ,law.invention ,Richter magnitude scale ,Geophysics ,Oceanography ,law ,Epicenter ,Earth and Planetary Sciences (miscellaneous) ,Bay ,Slumping ,Seismology - Abstract
An extensive search of newspaper reports, archival material, and the literature has revealed that many more tsunamis have affected the New Zealand coast than hitherto realised. 32 tsunami events are listed, including their probability of occurrence, the maximum runup height, as well as the epicentre and Richter magnitude for those events associated with earthquakes. Most coastal regions of New Zealand are reported as experiencing tsunamis. Generally these events have been associated with earthquakes, although the tsunami source mechanisms have also been attributed to large rotational slumps, submarine slumping along the Chatham Rise, and submarine mud volcanism associated with diapiric intrusions on the continental shelf off Poverty Bay. Tsunami waves and seiching accompanying the Krakatoa eruption of 1883 appear to have been induced by pressure coupling between the atmosphere and oceans. Most tsunamis have affected the east coast. This largely reflects both exposure to pan-Pacific origins and th...
- Published
- 1986
- Full Text
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31. Sedimentology and evolution of Ohiwa Harbour, a barrier‐impounded estuarine lagoon in Bay of Plenty
- Author
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Bruce M. Richmond, Terry R. Healy, and Campbell S. Nelson
- Subjects
geography ,Provenance ,geography.geographical_feature_category ,Ecology ,Terrigenous sediment ,Shoal ,Aquatic Science ,Oceanography ,Salt marsh ,Harbour ,Sedimentology ,Tephra ,computer ,Bay ,Ecology, Evolution, Behavior and Systematics ,Geology ,Water Science and Technology ,computer.programming_language - Abstract
Ohiwa Harbour is a 24 km2 estuarine lagoon impounded by the 6 km long Ohope spit in the west and the 0.7 km long Ohiwa spit in the east. These barrier sand spits are presently separated by a c. 340 m‐wide inlet channel where the maximum harbour depth of 14 m occurs. Seventy percent of the harbour consists of tidal flats supporting a rich shelly benthos and diversified by stands of mangrove and backed locally by salt marsh. Lower harbour sediments in barrier beach, dune, and entrance shoal and channel environments are well sorted, negatively‐skewed, medium to fine sands. In contrast, upper harbour sediments are poorly to very poorly sorted, positively‐skewed, medium to very fine (silty) sands, the coarser of these deposits occurring in channel and restricted harbour beach environments, and the finer in inter‐tidal flat, creek, and channel bank areas. The terrigenous mineralogy is consistent with a dominantly acid volcanic provenance, directly from the tephra mantle of the catchment and, most impor...
- Published
- 1984
- Full Text
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32. Progradation at the Entrance, Tauranga Harbour, Bay of Plenty
- Author
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Terry R. Healy
- Subjects
Oceanography ,Geography, Planning and Development ,Harbour ,General Earth and Planetary Sciences ,Progradation ,computer ,Bay ,Geology ,computer.programming_language - Published
- 1977
- Full Text
- View/download PDF
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