Determining potential for pollutant impacts in dynamic coastal waters: comparing morphological settings

The coastal focus and beach culture of Australia’s population in general, and the people of New South Wales in particular, mean that coastal systems are both highly prized and subjected to great pressures. The vast majority of the wastewater generated by the 7.3 million people of New South Wales is discharged directly to the ocean. The dispersion and fate of waterborne pollutants and their potential to impact coastal ecosystems are fundamentally determined by the dynamics of the coastal boundary layer (CBL). This turbulent interface between the coastline and the deep oceans is defined and classified for the first time in this thesis. Coastal morphologies and changes in the orientation of the coastline promote turbulence and strong gradients with extreme variability and heterogeneity over a broad range of scales. Conceptual models are presented to characterise New South Wales coastal boundary layer processes. The broad aims of this thesis are to investigate the coastal boundary layer processes that affect dispersal and advection of pollutants, and to develop conceptual models and tools to facilitate coastal management. Remote sensed ocean colour and sea surface temperature observations define meso-scale CBL phenomena, and this study demonstrates their application to support management decisions in relation to marine algal (phytoplankton) blooms. However, considerable scope exists to improve regional algorithms to deliver better ocean colour products for the optically complex (Case 2) waters of the inner coastal boundary layer. Past failures to consider the CBL (morphological) settings of pollutant discharges to coastal waters have led to inefficient pollutant discharge systems and potential environmental impacts. Two case studies, investigate the principal forcing mechanisms and demonstrate the importance of morphology in controlling the dispersion and retention times of pollutants. The first case study is focused on Sydney coastal waters where pollutant loadings are greater in magnitude and different in character than elsewhere in New South Wales. Here population pressures generate large wastewater loadings but the distances to offshore discharge locations are large compared to the scale of coastal roughness (headlands and bays) and the water is deep, thus reducing the risk of local retention of pollutants and increasing the potential for rapid dilution. By considering simulations of near field effluent plume behaviour in relation to long term ambient nutrient patterns specific periods of the year and depth intervals have been identified when outfalls would have an increased opportunity to influence bloom development, especially the upper half of the water column during late summer. However, algal blooms appear to be principally driven by seasonal oceanic nutrient enrichment. The research presented in this thesis, together with companion research previously published by the author and routine ongoing monitoring, indicate the viability of disposal of the Sydney’s excess sewage effluent (after source control and re-use options have been exhausted) via existing deepwater outfalls. In contrast, inner CBL settings with coastal irregularities (e.g. headlands and bays) have a greater propensity to trap pollutants. A new hydrodynamically relevant morphological classification of New South Wales bays, headlands and islands provides both broad context for case studies and guides preliminary assessments for other locations. This classification reveals a borderline propensity for flow separation and re-circulation in the lee of Corambirra Point which is the focus of the second case study off Coffs Harbour in northern NSW. Direct observations and 3D finite difference hydrodynamic (Eulerian) and particle tracking (Lagrangian) model simulations quantify transient re-circulation associated with local current accelerations and a persistent shear zone located in the wake to the south of Corambirra Point. The flux of ambient water across the prescribed outfall alignment increases eighteen fold, over a shear zone spanning a cross-shore distance of just 1.4km (from 1.6km to 3km offshore). In contrast, the potential for re-entrainment and trapping of effluent in transient re-circulation cells was demonstrated to be insignificant. The proposed location of the outfalls was 1.5km offshore whereas the greatest gain per unit extension of the proposed discharge point coincides with the centre of the shear zone located ~2km offshore. These case studies illustrate specific coastal boundary layer effects and indicate how an understanding of the spatial and temporal scales of these effects can be used to target more specific assessments of potential pollutant impacts. Simple morphological risk assessment tools are also presented to identify factors and processes which limit the exposure of sensitive environments to high pollutant concentrations and loads. Eddy retention effects are generally not incorporated in existing near field models but potential re-entrainment effects in wake zones can be assessed through the eddy retention value, which is introduced in this thesis. Although the approach presented here is focused on New South Wales coastal waters, the framework serves as a basis for general application elsewhere, and as a foundation for further refinement for application to NSW coastal waters. Existing scientific literature indicates that coastal boundary layer processes also shape the distributions of the biological species and communities. This further motivates the development of a process based understanding of coastal boundary layer dynamics as a fundamental platform to support environmental protection and biodiversity conservation initiatives

Sinks of agriculturally derived nitrogen in estuarine and coastal lagoon ecosystems

Increased nutrient runoff from mismanaged agricultural farming results in excess inputs of nutrients to coastal ecosystems, which can increase primary productivity causing eutrophication. Estuarine sediments provide the ecosystem service of nutrient cycling; one of the most important of which is denitrification. Denitrification is a key process of the nitrogen cycle which occurs at the interface of oxic/anoxic sediments, where bioavailable nitrate is converted to nitrogen gas and released into the atmosphere. This process filters excess nutrients, reducing bioavailable nitrogen before export to the ocean. However, the process of denitrification is still a limited area of research in New Zealand. This thesis aims to elucidate some of the drivers of spatial and seasonal variability of denitrification predominantly focussing on a unique type of estuary, intermittently closed and open lake lagoons (ICOLLs). Firstly, the seasonality of nutrient inputs is investigated, to see what role that may play in shaping the denitrification potential of the microbial community across two contrasting ICOLLs using denitrification enzyme activity (DEA) (Chapter 2). Secondly, spatial and seasonal variability of denitrification is assessed using novel flexible chambers in situ, under pulses of labelled nitrate (K15NO3-) which was identified to occur in the second chapter (Chapter 3). As well as seasonality in temperature, seasonality in the abundance of dominant macroinvertebrates also changes, and the impacts of bioturbation on denitrification was assessed in situ over a year-long seasonal study in a small ICOLL (Chapter 4). As many estuarine ecosystems are beginning to show eutrophication symptoms (such as a decrease in stable rooted macrophytes and an increase in bloom forming macro- and micro- algae), the effects of changing organic detritus on net nitrogen fluxes was examined in a low nutrient estuary, which periodically experiences blooms of algae (Chapter 5). These results are synthesised and discussed in Chapter 6. The two studied ICOLLs (Ellesmere and Tomahawk) periodically received large inputs of nitrogen (>0.3 mg L-1 NO3-), which mostly occurred during spring and winter. Denitrification potential in the ICOLLs was strongly correlated with the sediment grain size, rather than near these large nutrient inflows as hypothesised. Denitrification potential was greater in sediments with higher sand content. A hierarchy of factors limited denitrification in situ. Primarily, temperature inhibited denitrification at low temperatures, occurring between 8.6 - 12°C. Following this the availability of organic matter, shallow water depth and macroinvertebrate abundance supported increased denitrification rates. Macroinvertebrate communities supported enhanced denitrification and sediment oxygenation. Potamopyrgus antipodarum provided bulldozing of the upper sedimentary layers, and burrowing chironomid larvae increased the extent of the oxic/anoxic sediment interface for denitrification in deeper sediment layers. The lability of various forms of organic carbon played an indirect role in regulating the switch between net N2 removal through denitrification, or nitrogen retention through nitrogen fixation. Cockles reduced nitrogen and sulfur enzyme activity, through changing oxygen conditions and increasing substrate supplies to denitrifying microorganisms. Minimising anthropogenic stressors such as sedimentation, managed ICOLL opening regimes, and nitrogen loading during cooler months will support positive ecosystem processes and the preservation of our unique estuarine ecosystems for future generations

Science-based restoration monitoring of coastal habitats, Volume Two: Tools for monitoring coastal habitats

Healthy coastal habitats are not only important ecologically; they also support healthy coastal communities and improve the quality of people’s lives. Despite their many benefits and values, coastal habitats have been systematically modified, degraded, and destroyed throughout the United States and its protectorates beginning with European colonization in the 1600’s (Dahl 1990). As a result, many coastal habitats around the United States are in desperate need of restoration. The monitoring of restoration projects, the focus of this document, is necessary to ensure that restoration efforts are successful, to further the science, and to increase the efficiency of future restoration efforts

A geomorphological interpretation of saltmarsh channel network morphology and function

Although tidal channel networks are a near-ubiquitous feature of saltmarsh environments developed on the marine sedimentary shores of Britain, only limited progress has been made towards achieving a scientific understanding of their morphological characteristics and the physical functions that they perform. Based on data acquired from a combination of high resolution aerial photography and field survey, a range of descriptive indices and morphometric measures are used to characterise planimetric, longitudinal and cross-sectional adjustment in saltmarsh channel networks from 29 localities around England and Wales. In accordance with the extensive methodological approach employed during this exploratory phase of the study, regularities and distinguishing features of the selected formations are interpreted in terms of broad-scale environmental controls, which represent the relative intensity of erosional versus resistive forces. While statistical analyses suggest that creek morphology reflects a multiplicity of influences, the strongest bivariate associations, between tidal prism and cross-sectional geometry, are consistent with the finding of earlier process studies that creek morphology is principally adapted to perform a conveyance function. Theoretically-based mathematical models are employed to more fully elucidate relations of causality between creek morphology and function. This intensive investigation utilises Brancaster Marsh, Norfolk as an illustrative case study. The availability of airborne laser altimetry (lidar) for this site facilitates the evaluation of alternative models of channel function. Optimality models of angular geometry are implemented at a network-scale, and cross-sectional adjustments are modelled with reference to the concept of stability shear stress. While of interest from a geomorphological perspective, the insights offered into creek morphology and function are also relevant to the field of coastal engineering. Here, they provide an empirical basis for post-project appraisal, and may lead to theoretical guidelines for the design of tidal channel networks, as an integral component of saltmarsh restoration and flood defence realignment schemes

Estuary – coast interaction and morphodynamic evolution: a comparative analysis of three estuaries in southwest England

Investigations of geomorphology and morphodynamics within the coastal zone have tended to treat the open coast as an independent system to that of any neighbouring estuaries. This separation is also evident within shoreline management, which has traditionally been undertaken within the context of coastal cells or estuarine valleys. The focus of this research is a comparative analysis of morphodynamic behaviour and sedimentary characteristics of connected open-coast – estuary systems. The north coast of Cornwall, southwest England, is notably indented and dominated by bedrock cliff and shore platforms. However, it also comprises some broad embayments that accommodate estuarine valleys and open coast, typically sandy beaches. The region provides an ideal environment within which to assess broad-scale coastal change and the association between estuarine and open-coast morphodynamics. Furthermore, it provides an opportunity to consider regional coherence in coastal behaviour and to evaluate the relative importance of local physical context vs. regional climate forcing. The Hayle, the Gannel and the Camel estuaries that are located within St Ives, Crantock and Padstow bays respectively, have received considerable attention in terms of the impacts of mining on estuarine sedimentation. The impacts on sediment supply, sedimentology and mineraology have been explored extensively in these past studies, however, very little consideration has been given to the nature of coastal geomorphology and coastal system dynamics. This PhD research explores mesoscale coastal dynamics, and evaluates coastal behaviour over decades to centuries in the context of climate and sea-level change. Historical geomorphological evolution of these estuaries and their adjacent shorelines are examined to evaluate morphodynamic connectivity through the application of shoreline analysis tools (such as Digital Shoreline Analysis System (DSAS) and Location Probability Analysis). This study showed that low shoreline recession along the north Cornwall coast, where sediments are present, has attributed most to the significant sea-level rise in this region (no significant change was observed on rocky low water shorelines). The high water shoreline imposes a different pattern of change in response to constraining factors which are triggered by both environmental factors and historical human activities. Changes over contemporary time scales are focused on bedform movement into, within and landward of inlets and are primarily driven both by waves in the outer estuary/ebb delta region and by tides in the channels/flood delta region. The inlets, however, are largely fixed in position by the bedrock valley, and channel dynamics within the estuary are dependent on the accommodation space provided by the valley. Sedimentary linkages are also explored through the sedimentological and geochemical analysis of sediments sampled from the intertidal zone of these systems. Based on grain-size parameters, there is considerable homogeneity in the sediment populations specific to the sub-environments sampled and analysed. There is evidence of sediment mixing between estuarine and beach environments. Geochemical (XRF) and mineraological composition of sediment indicate contamination by mine waste tailings in the estuaries resulting from major historical mining activities in the region with Sn, Cu, As and Zn as predominant in the Hayle, Pb and Zn in the Gannel and Sn, W, and Zr in the Camel estuaries. This research presents a multidisciplinary approach that employs a range of computer and lab-based analyses to integrate geospatial resources (including published maps, chart archives, etc) and sedimentological characteristics (including grain size and XRF analyses). The thesis is the first comprehensive comparative investigation of the morphodynamic behaviour and sedimentology of these north Cornwall estuaries

Handbook of Mathematical Geosciences

This Open Access handbook published at the IAMG's 50th anniversary, presents a compilation of invited path-breaking research contributions by award-winning geoscientists who have been instrumental in shaping the IAMG. It contains 45 chapters that are categorized broadly into five parts (i) theory, (ii) general applications, (iii) exploration and resource estimation, (iv) reviews, and (v) reminiscences covering related topics like mathematical geosciences, mathematical morphology, geostatistics, fractals and multifractals, spatial statistics, multipoint geostatistics, compositional data analysis, informatics, geocomputation, numerical methods, and chaos theory in the geosciences

Littoral sediment budget and beach morphodynamics, Pukehina Beach to Matata, Bay of Plenty

The Pukehina-Matata coastal sector is one of the least studied parts of the Bay of Plenty coastline. Currently this section of coast is in a stable, tending towards erosive, condition, with historical erosion of 0-0.2 m/year. Sediment mineralogy reflects the high input of quartzo-feldspathic material into the beach-dune-nearshore system. For the Otamarakau-Matata sector much of the sediment is provided from fluvial sources, predominantly the Waitahanui, Pikowai, and Herepuru streams, although the total stream input in this area is only 3,000 to 7,000 m³ per year. The sources of beach sand from Town Point to Otamarakau includes some erosion of catchment material, supplemented by littoral drift, erosion of submarine rock outcrops in the Town Point-Otamarakau region, and possible onshore reworking of pre-Holocene sediments. The greywacke gravels present within the littoral system, especially between Rodgers Road and Pukehina, are relict deposits, which are presently active within the beach-dune-nearshore system due to the small volume transfers of sandy sediments. Their original source, is suggested as from marine erosion of Castlecliffian sediments, such as exposed in the coastal cliffs at Matata. Net littoral drift is suggested as bi-directional from a centre-point near Otamarakau, to both the north-east along Pukehina Spit, and to the south-west towards Matata. Some counter-drift occurs between the Tarawera River mouth and Matata, and along the tip of Pukehina Spit, with nourishment of this area by the Waihi estuary. Nearshore sedimentary-morphodynamic units show that the nearshore and inner-shelf at Town Point, and from southern Pukehina Beach to Otamarakau, is characterised by the presence of numerous rock outcrops, which are responsible for the coarse sands and relatively higher carbonate abundances in this area. Sediment volumes within the beach-nearshore system, and alongshore transfers between sectors of the coast are small, with annual net littoral drift estimated as 15,000 m³ at Matata. Diabathic processes are considered to dominate, with the limit of significant onshore-offshore sediment transport no more than 12 m, and a parabathic limit of less than 6 m. The net change in sediment volume for the entire beach system within the Pukehina-Matata coastal sector between 1989 and 1993, produced a calculated deficit of sediment of 90,570 m³. In comparison a longer-term change, between 1978 and 1993, showed a sediment surplus of 218, 560 m³. Over the Pukehina-Matata coastal sector these volume changes are reasonably small and their variability reflects both the dynamic nature, and the delicate state of equilibrium, of the beach-dune-nearshore system. The derived littoral sediment budget shows that in order to balance the inputs and outputs within the system approximately 27,400 m³ of annual onshore sediment transport must occur. Current sand extraction at Otamarakau has resulted in a decline in the beach sediment volumes between Otamarakau and Pikowai, with this sector in a sediment deficit. Although natural processes mask the true impacts, the increased sand extraction rate of 36,000 m³ per year is liable to further deplete the beach-dunenearshore system. However, in the short-term these effects are unlikely to be immediately noticeable

Study on orthogonal basis NN-based storage modelling for Lake Hume of Upper Murray River, Australia

The Murray-Darling Basin is Australia's most iconic and the largest catchment. It is also one of the largest river systems in the world and one of the driest. For managing the sustainable use of the Basin's water, hydrological modelling plays important role. The main models in use are the mathematical represented models which are difficult of containing full relationship between rainfall runoff, flow routing, upstream storage, evaporation and other water losses. Hume Reservoir is the main supply storage and one of the two major headwater storages for the River Murray system. It is crucial in managing flows and securing water supplies along the entire River Murray System, including Adelaide. In this paper, two Orthogonal Basis NN-Based storage models for Hume Reservoir are developed by using flow data from upstream gauge stations. One is only considering flow data from upstream gauge stations. Another is considering both upstream flow data and rainfall. The Neural Network (NN) learning algorithm is based on Ying Li's previous research outcome. The modelling results proved that the approach has high accuracy, good adaptability and extensive applicability