Private rights,public benefits: Industry-driven seabed protection     

Jeremy Helson  Stefan Leslie  George Clement  Richard Wells  Ray Wood 《Marine Policy》2010

New Zealand has a large exclusive economic zone (EEZ) that contains a variety of marine habitats and commercially-important species. The commercial fishing industry operating within New Zealand's EEZ is of significant value to the economy and fisheries resources are managed through the extensive use of Individual Transferable Quotas (ITQs). One of the benefits of ITQs has been to better align some of the private incentives of quota owners with the public interest. These incentives contributed to an initiative proposed by the fishing industry to close large areas of New Zealand's EEZ to protect the seabed from trawling. These closed areas are termed benthic protection areas (BPAs) and protect the benthic biodiversity of about 1.1 million square kilometres of seabed—approximately 30% of New Zealand's EEZ. A significant proportion of New Zealand's known seamounts and active hydrothermal vents are protected by these closed areas. We describe and discuss the criteria used to select BPAs and some of the criticism of this marine protection initiative. We argue that the assignment of strong property rights in fishing resources was an important precondition to an industry initiative that has a significant public benefit. Where private and public interests are well aligned, government can adopt an enabling and facilitation role, ceding direct control of processes in order to get the results the align with the public interest.  相似文献   

A comparison of the main methods for estimating probabilities of extreme still water levels     

Ivan D. Haigh  Robert Nicholls  Neil Wells 《Coastal Engineering》2010

Sea-level return periods are estimated at 18 sites around the English Channel using: (i) the annual maxima method; (ii) the r-largest method; (iii) the joint probability method; and (iv) the revised joint probability method. Tests are undertaken to determine how sensitive these four methods are to three factors which may significantly influence the results; (a) the treatment of the long-term trends in extreme sea level; (b) the relative magnitudes of the tidal and non-tidal components of sea level; and (c) the frequency, length and completeness of the available data. Results show that unless sea-level records with lengths of at least 50 years are used, the way in which the long-term trends is handled in the different methods can lead to significant differences in the estimated return levels. The direct methods (i.e. methods i and ii) underestimate the long (> 20 years) period return levels when the astronomical tidal variations of sea level (relative to a mean of zero) are about twice that of the non-tidal variations. The performance of each of the four methods is assessed using prediction errors (the difference between the return periods of the observed maximum level at each site and the corresponding data range). Finally, return periods, estimated using the four methods, are compared with estimates from the spatial revised joint probability method along the UK south coast and are found to be significantly larger at most sites along this coast, due to the comparatively short records originally used to calibrate the model in this area. The revised joint probability method is found to have the lowest prediction errors at most sites analysed and this method is recommended for application wherever possible. However, no method can compensate for poor data.  相似文献   

Interactions between submarine channel systems and deformation in deepwater fold belts: Examples from the Levant Basin, Eastern Mediterranean sea   总被引：1，自引：0，他引：1  

Ian R. Clark  Joseph A. Cartwright 《Marine and Petroleum Geology》2009,26(8):1465-1482

Submarine channel levee systems form important hydrocarbon reservoirs in many deep marine settings and are often deposited within a structurally active setting. This study focuses on recent submarine channels that developed within a deepwater fold and thrust belt setting from the Levant Basin, eastern Mediterranean Sea. Compressional deformation within the study area is driven by the up-dip collapse of the Nile cone above the ductile Messinian Evaporites. Structures such as folds and strike slip faults exert a strong control on channel location and development over time. From this study four end-member submarine channel–structure interactions can be defined: Confinement, diversion, deflection and blocking. Each of these channel–structure interactions results in a distinct submarine channel morphology and pattern of development compared to unconfined channel levee systems. Each interaction can also be used to assess timing relationships between submarine channel development and deformation.  相似文献   

The divergent environmental characteristics of permanently-open,seasonally-open and normally-closed estuaries of south-western Australia     

Benjamin M. Chuwen  Steeg D. Hoeksema  Ian C. Potter 《Estuarine, Coastal and Shelf Science》2009

This study has compared the environmental characteristics of the basins and saline lower reaches of the tributaries of eight estuaries on the south coast of Western Australia, which differ in their degree of connectivity with the ocean. Although four estuaries between 115.1° and 121.8° E along that coast remain permanently open to the ocean, the others only become open when the volume of river discharge is sufficient to breach the prominent sand bars at their mouths, which occurs annually following heavy winter and early spring rainfall in some estuaries (seasonally open) and infrequently in others (normally closed). Estuaries to the west of 118.5° E are predominantly permanently open, e.g. Oyster Harbour, or seasonally open, e.g. Broke, Irwin and Wilson inlets, whereas those further east, e.g. Wellstead Estuary and Hamersley, Culham and Stokes inlets, where annual rainfall and thus discharge are much lower, only become open after exceptionally heavy discharge. In permanently and seasonally-open estuaries, pronounced haloclines and oxyclines are present in the narrow rivers but not the wide basins where the waters are subjected to wind-driven mixing. The extent of cyclical seasonal fluctuations in environmental conditions differed markedly among the three seasonally-open estuaries and between years in one of those systems. These differences reflected variations in the relationship between the volume of fluvial discharge, which is determined by a combination of the amount of local rainfall, catchment size and extent of clearing of native vegetation, and the amount of intrusion by marine waters, which is largely controlled by the size and duration of the opening of the estuary mouth. The mean seasonal salinities in the basins of the three normally-closed estuaries increased over three years of very low rainfall to 64 in the deepest of these estuaries (Stokes Inlet) to 145 in Hamersley Inlet and to 296 in the shallowest estuary (Culham Inlet). These results demonstrate that the environmental characteristics of estuaries on the south coast of Western Australia differ markedly, even among those of the same type, e.g. seasonally-open estuaries or normally-closed estuaries.  相似文献   

Beach nourishments at Coolangatta Bay over the period 1987–2005: Impacts and lessons     

Bruno Castelle  Ian L. Turner  Xavier Bertin  Rodger Tomlinson 《Coastal Engineering》2009

Erosion of the southern Gold Coast beaches (SE Queensland, Australia) was exacerbated after the extension of the Tweed River training walls in the early 1960s. To achieve the objective of restoring and maintaining beach amenity, significant nourishment works have been undertaken in Coolangatta Bay over the past 30 years. Particularly, under the Tweed River Entrance Sand Bypassing Project (TRESBP) since 1995, a number of nourishment campaigns and the implementation of a permanent sand bypass system in 2001 have resulted in significant changes of Coolangatta Bay morphology. The present case study investigates the influence of both wave climate and nourishment works on the area extending from the updrift Snapper Rocks area to downdrift Kirra Beach. SWAN spectral wave model is implemented at Coolangatta Bay area and forced by the global wave model WW3 to estimate wave forcing and the potential natural longshore drift entering in Coolangatta. Specific transects extracted from accurate bathymetric surveys are used to investigate and quantify Coolangatta Bay sedimentation for the period 1987–2005. A network of Argus video stations provides high sample rate information on the shoreline evolution. Results show that, over the past 10 years, Coolangatta Bay has infilled rapidly. Sedimentation reached up to 6 m in some areas between 1995 and 2005, with beach width increasing by 200 m at Kirra Beach. Rapid seaward shoreline migration is consistent with the intense over-pumping of sand relative to the natural potential to move sand alongshore. The nourishment strategy used during this project has successfully delivered large amounts of sand to the southern Gold Coast embayment, although it has been up to now controversial from many community perspectives. The artificial sand bypassing process proved to be much more efficient than depositing the dredged sand in the nearshore area which requires a significant period of low energy condition in order for the deposited sediment to migrate shoreward and weld to the shore. This case study confirms that, when carefully undertaken, sand bypassing is a sustainable and flexible soft engineering approach which can work in concert with natural processes.  相似文献   

Nearshore suspended sediment variations,central Surinam coast     

John T. Wells  James M. Coleman 《Marine Geology》1977,24(4):M47-M54

Nearshore suspended sediment concentration along the muddy Surinam coast is highly variable; maximum values are many times greater than on other muddy coasts. Water samples taken at four field stations during various stages of the tide range in concentration from 15 to 3,700 mg/l near the surface and from 100 to 30,000 mg/l near the bottom. Highest overall concentrations and greatest variability in concentration occur in water over large banks of fluid mud (thixotropic gel) that extend 2–3 km offshore and 5–10 km along-shore. On both the intertidal and subaqueous portions of these mudbanks highest concentrations are found at low tide. Results provide evidence that an exchange between fluid mud and suspended sediment takes place during each tidal cycle.  相似文献   

The application of remote sensing to environmental archaeology     

Daniel Donoghue  Ian Shennan 《Geoarchaeology》1988,3(4):275-285

An area in the Fenlands of Eastern England was used to assess the spectral, spatial, and seasonal requirements of airborne multispectral data for identifying wetland archaeological features by detecting crop and soil marks. Ordination of data from a scanner with 11 spectral channels was achieved using the Sheffield method, which calculates the wavebands that produce a 3 band composite image with optimum contrast using band variances and interband correlations. the spatial detail requirements for multispectral data were investigated by applying an edge enhancing filter to single waveband images. the loss of feature clarity with increased levels of spatial smoothing is visually apparent. Seasonal variation in crop mark visibility was quantified by cross tabulating feature visibility in fields known to contain features with time period and sensor type. If remote sensing is to be used for repeated operational archaeological survey then the quality and quantity of information which can be gained from the data must be evaluated. This study attempts to define some of the necessary operational requirements for the use of multispectral data for archaeology.  相似文献   

The age,extent and geomorphological significance of the Sassafras basalt,south‐eastern New South Wales     

R. W. Young  Ian McDougall 《Australian Journal of Earth Sciences》2013,60(4):323-331

Basalt at Sassafras was erupted in the Middle Eocene. The K‐Ar ages average 45.3 ± 4.9 Ma on whole rock and 48.4 ± 1.9 Ma on plagioclase. The basalt is not limited to a plateau capping, but extends 150 m down into adjacent valleys. Comparison with nearby Eocene basalts shows that there was in excess of 250 m of local relief in the central Shoalhaven valley by the Early Tertiary. The basalts were extruded at high elevation, and denudation of the coastal margin of the upland was already well advanced. Post‐basaltic denudation has been very slow, and the Early Tertiary landscape is well preserved.  相似文献   

Late Holocene vertical land motion and relative sea‐level changes: lessons from the British Isles     

Ian Shennan  Glenn Milne  Sarah Bradley 《第四纪科学杂志》2012,27(1):64-70

Vertical land motion caused by continuing glacial isostatic adjustment is one of several important components of sea‐level change and is not limited just to previously glaciated regions. A national‐scale analysis for the British Isles shows an ellipse of present‐day relative uplift (relative sea‐level fall), ～1.2 mm a^?1, broadly centred on the deglaciated mountains of Scotland. The pattern of three foci of relative subsidence, ～1 mm a^?1, results from the additional interactions of the deglacial meltwater load on the Atlantic basin and the continental shelf, and the signal due to far‐field ice sheets. At a local scale, sediment compaction can more than double the rate of relative land subsidence. Relative land‐level change (the negative of relative sea‐level change) is not the same as vertical land motion. There is a spatial pattern in the difference between relative land‐level change and vertical land motion, with differences at present of approximately ?0.1 to ?0.3 mm a^?1 around the British Isles and +2.5 to ?1.5 mm a^?1 globally. For the wider scientific and user community, whether or not the differences are considered significant will depend upon the location, time frame and spatial scale of the study that uses such information. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Epikarst hydrology and implications for stalagmite capture of climate changes at Grotta di Ernesto (NE Italy): results from long‐term monitoring     

Renza Miorandi  Andrea Borsato  Silvia Frisia  Ian J. Fairchild  Detlev K. Richter 《水文研究》2010,24(21):3101-3114

Grotta di Ernesto is a cave site well suited for palaeoclimate studies because it contains annually laminated stalagmites and was monitored from 1995 to the end of 2008 for microclimate, hydrology and hydrochemistry. Long‐term monitoring highlighted that cave drips show three different hydrological responses to rainfall and infiltration: (1) fast seasonal drips in the upper part of the cave, which are mostly fed by fractures, (2) slow seasonal drips, located at mid‐depth in the cave characterized by mixed feeding and (3) slow drips, mostly located in the deeper gallery, which are fed by seepage flow from bulk porosity with a minor fracture‐fed component. The slow drips display daily cycles during spring thaw. Monitoring also indicated that drip waters are only slightly modified by degassing within the soil zone and aquifer and by prior calcite precipitation. Hydrochemical studies show a clear seasonality in calcite saturation index, which results in most cave calcite precipitation occurring during late autumn and winter with similar amounts of precipitated calcite on most stalagmites, regardless of drip rate (discharge) differences. Drip rate, and drip rate variability, therefore, has a minor role in modulating the amount of annual calcite formation. In contrast, drip rate, when associated with moderate reduction in calcite saturation index, clearly influences stalagmite morphology. Increasing drip rate yields a passage from candle‐, to cone‐ to dome‐shaped stalagmites. Very high drip rates feed speleothems with flowstone morphology. In summary, monitoring provides information about the karst aquifer and how hydrology influences those physical and chemical characteristics of speleothems which are commonly used as climate proxies. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献