Gotowa bibliografia na temat „Fitzroy River estuary (Queensland)”

Environmental Context. The Fitzroy River Basin constitutes a major source of suspended sediment and nutrient fluxes to the southern Great Barrier Reef. Improved land management practices to ameliorate these catchment loads require an understanding of the sediment sources and dynamics. This multidisciplinary geochemical and modelling study provides for the first time a quantitative estimate of sediment sources delivered to, and their degree of retention in, the Fitzroy River Estuary. Abstract. Sources of sediment deposited in the Fitzroy River Estuary (FRE) have been identified and quantified using an integrated geochemical, modelling and reconnaissance soil sampling approach. A companion paper (this volume) identifies the major sources of sediments in impoundments on the major river systems and sediment sampled from flood events in the Fitzroy River Basin (FRB). Sediment within the FRE may display distinct longitudinal variation with little basaltic material retained. Sediments derived from the Bowen Basin, which occupies the greatest portion of the FRB, and from the Surat Basin display the greatest longitudinal variation. All FRB soils have a similar total phosphorus (P) concentration. Thus, in considering P export from the catchment it is the total sediment flux which is of major importance, rather than the relative proportions of individual catchment soils. This research provides crucial new regional scale information on the sediment sources deposited within the FRE.

Environmental Context. The Fitzroy River Basin is a major contributor to the loads of suspended sediment and nutrients reaching coastal areas in the southern Great Barrier Reef. Cost-effective investment in improved land, vegetation, and water management to lower these loads requires an understanding of the sources and movement of sediments within the basin. This multidisciplinary geochemical and modelling study provides for the first time a quantitative estimate of sediment sources and spatial and hydrology-related variation within the Fitzroy River Basin. Abstract. An integrated geochemical, modelling, and reconnaissance soil sampling approach has been used to identify the sources of sediment in the Fitzroy River Basin (FRB). The composition of sediment in weirs and dams within the FRB indicate that in the southern and central FRB the Dawson River contributes only a small basaltic component and the inputs are dominated by soils from the Surat and Bowen Basins. Rivers from the central FRB carry variable amounts of basaltic soils. In contrast, basaltic soils constitute the majority of sediment transported during flood events. Surat Basin soils form a minor component of flood events with little contribution from soils of the Bowen Basin despite it constituting the majority of the area of the central FRB. Soils from the Thomson Fold Belt constitute a substantial proportion of the sediment transported by, and retained in, impoundments in the central FRB and also dominate sediment delivered from the western FRB. This study will inform cost-effective investment by government to target remedial actions to reduce sediment and nutrient loads within the FRB that may be ultimately transported via the Fitzroy River Estuary to the southern Great Barrier Reef.

Environmental context. The Fitzroy River Basin is a major source of suspended sediment and nutrients to the southern Great Barrier Reef lagoon. A reduction in sediment and nutrient loads is necessary to protect coastal reefs and this requires an understanding of the sediment sources. The present geochemical and modelling study provides a quantitative estimate of the spatial and temporal variations in the sources of sediment deposited in the Fitzroy River coastal zone. Abstract. Sediment sources to the Fitzroy River coastal zone have been identified and quantified using an integrated geochemical and modelling approach. The coastal sediments display little geochemical variation as a result of substantial homogenisation during hydrodynamic processes and indicate a sediment composition consistent with derivation from mixed catchment sources. A lack of substantial temporal geochemical variation in the sediment records indicates weathering regimes and hydrodynamic transport have been relatively consistent throughout the Holocene. Despite this apparent geochemical homogeneity, a modelling approach using a Bayesian statistical model revealed changes in catchment sediment sources over time. Variations in the occurrence and intensity of rainfall events in different parts of the catchment as well as land-use changes following European settlement are likely to have had a substantial effect on the relative contributions of the catchment sources delivered to and deposited in the coastal zone. Additionally, large variations in flow events and variable estuary hydrodynamics result in different catchment soil types being delivered and deposited under different conditions. The present study found that basaltic material is the dominant catchment source in the coastal surface sediments with an estimated enrichment of ~3 relative to catchment and estuary abundances. Basaltic soils present as a more recent and extensive, weathered surficial cover are more readily mobilised than other catchment soils and will be transported further within freshwater flood plumes. It is likely that in large flood events, this basaltic material may reach the coral-dominated outer shelf. Improved land management practices to reduce sediment loads can be targeted to the areas supplying the majority of sediment to the coastal zone.

Some human-altered habitats such as saltfields support significant numbers of shorebirds and waterbirds, but their values in tropical eastern Australia are poorly understood. With the continuing loss of shorebird habitats in the East Asian-Australasian Flyway, identification of important habitats and management is important for their conservation. The habitat value of two saltfields associated with the Fitzroy River estuary, Queensland (23.520S, 150.860E) was evaluated by monthly surveys over 33 months and by comparison to previous surveys of nearby natural wetlands. Saltfields supported as many waterbirds and species as freshwater and naturally saline lagoons. Numbers of migratory shorebirds peaked during the southern migration period (September to November), when wetlands in tropical northern Australia are at their lowest extent, thus elevating the conservation value of tropical saltfields to shorebirds. Sharp-tailed Sandpipers were regularly present in numbers exceeding international levels for staging, while Red-necked Stints were just below the staging criterion. Salinity regime was found to influence waterbird communities associated with saltfield pools: piscivores dominating metasaline pools, and shorebirds hypersaline pools. A seasonal pattern of occurrence occurred in some guilds with greatest numbers in the drier months (cormorants, pelicans, ducks and egrets, all significantly negatively correlated with the previous month’s rainfall), most of which bred in nearby natural wetlands during the wet season. Furthermore, cormorants were abundant in the saltfields and fluctuated less compared with natural lagoons during the critical drier months. Overall, saltfields are an integral component of the ecology of the landscape, providing complementary resources to that of the natural wetlands.

Environmental context. During flood events, the Fitzroy River is a major contributor to the loads of suspended sediment and nutrients to the southern Great Barrier Reef. The present geochemical and modelling study provides for the first time a quantitative estimate of the temporal variation in sediment sources over an entire flood hydrograph. Basaltic soils are substantially enriched in this flood event relative to their catchment abundance. Abstract. Suspended sediment collected over a complete flood hydrograph in the Fitzroy River provided an insight into the origin and transport of sediment in this system. Strong temporal trends are evident in the proportions of catchment soil types estimated using a Bayesian mixing model in the fine (<10 μm) fraction of the suspended sediment. These temporal trends were also manifested in changes in mineralogy, major and trace element and Nd–Sr and C–N isotope geochemistry. Tertiary Basaltic soils were the most abundant catchment soil type transported in the flood event studied here, constituting 39% of the <10-μm sediment fraction, but varied between an estimated 20 and 50% of the suspended solids over the course of the flood event. The techniques used here allow quantification and comparison between flow and suspended sediment sources and are widely applicable to other river systems.

Understanding spatial patterns in demographic parameters of exploited fish species is of critical importance to effective fisheries management. In the present study, patterns in demography of a large, protandrous, estuarine teleost, king threadfin, Polydactylus macrochir, were compared among three estuaries on the eastern coast of Queensland, Australia. Significant variation in age and growth was observed between fish from the Fitzroy River and those from the Mary and Brisbane Rivers, with Fitzroy River fish living longer (22 years v. 10 and 14 years, respectively), reaching a greater asymptotic length (1222-mm fork length (FL) v. 975- and 1047-mm FL, respectively), and attaining greater length-at-ages of 6 years and beyond. No difference in growth was detected between Mary and Brisbane River fish, or in total mortality among any of the sites. Fitzroy River fish were generally found to mature and change sex at greater lengths and ages than those from the Mary and Brisbane Rivers. The observed variability suggests that spatially segregated populations of P. macrochir may respond differently to fishing pressure and highlights the importance of understanding the spatial patterns in demography of exploited estuarine fish populations.

The Burnett River snapping turtle (Elseya sp.) from the Burnett, Mary and Fitzroy river systems is an undescribed Australian freshwater turtle, of which very little ecological information is known. This paper describes the dietary ecology of the species in the Burnett River catchment. Stomach and faecal samples were collected from turtles and an index of relative importance was used to rank food items found in stomach samples. This index indicated that algae and aquatic ribbon weed (Vallisneria) were the dominant food items consumed. No difference in diet was found between males and females. Although the sample size was small, diet appeared to vary slightly seasonally, with Elseya sp. selectively feeding on the flower buds of the Chinese elm tree (Celtis chinensis) and the seeds of the blackbean tree (Castanospermum australe) when these food items were seasonally available. Faecal samples suggest that the most ingested foods (algae and aquatic ribbon weed) were also the most digestible. Although predominantly herbivorous, Elseya sp. was seen to eat carrion once in the wild.

The knowledge and understanding of sediment transport is essential for the development of effective management strategies for nutrient and sediment loading in estuarine systems. Estuarine suspended sediment (in high concentrations), has the ability to adversely impact upon surrounding ecosystems, such as the Great Barrier Reef, Australia. Due to a recent decline in water and sediment quality, it has recently been mandated that a number of tropical, coastal estuarine systems in Queensland, such as the Fitzroy River estuary, have their sediment loading reduced. In order to meet these requirements, a greater understanding of the sediment transport dynamics and driving processes (such as flocculation and settling velocity) needs to be achieved, and the accuracy of estimation improved. This research project was motivated by the need to improve the general accuracy of field measurements for estuarine suspended sediment transport and dynamics. Field-based measurements (especially settling velocity) are necessary for the parameterisation of sediment transport models. The difficulty in obtaining accurate, in situ data is well documented and is generally limited to methods that isolate a water sample from its natural environment, removing all influences of estuarine turbulence. Furthermore, the water samples are often extracted from points (Eulerian) where the history of the suspended particles is generally unknown. These sampling methods typically contain intrinsic errors as suspended sediment transport is essentially Lagrangian (i.e., flows with the net motion of flow-field) in nature. An investigation into different drogue systems conducted in parallel with a study into the tidal states of the Fitzroy River estuary led to the development of a novel Lagrangian drogue device, the LAD. Additionally, the water-tracking ability of the LAD was tested and found to accurately follow a parcel of estuarine water over a slack water period. Therefore the LAD was deployed in the Fitzroy River to assist in the further understanding of complex sediment transport processes such as flocculation and settling velocity in a natural estuarine flow field. The final device (the LAD - Lagrangian Acoustic Drogue) was developed, utilizing the principals of acoustic backscatter intensity-derived SSC measurements. The investigation of a series LAD deployments (during slack water) in the Fitzroy River estuary, revealed the dominant suspended sediment processes and also gave an insight into the prevailing flow-patterns. Results showed the presence of a settling lag mechanism between low and high tide, which can initiate a net sediment flow upstream with each flood tide. The bulk settling velocity showed comparable results at both low and high water. The LAD derived bulk settling velocity as a function of concentration (SSC), yielding a strong positive correlation (r2 = 0.73). Also the importance of flocculation in the bulk settling and clear up of the water column during periods of still water (high and low tide) was demonstrated as all in situ settling velocities (0.33 - 1.75 mm s-1) exceeded single grain approximations (0.47 mm s-1). This research demonstrates the potential for Lagrangian drogue studies as an effective measuring platform for the accurate quantification of estuarine suspended sediment dynamics. The application of the LAD in the Fitzroy River has lead to a significant improvement in the understanding of the system's real sediment transport processes. This research has provided an effective and accurate technique for measuring real settling velocities for input into numerical models or for the validation of existing model outputs. Furthermore, this technique shows great potential for application in other estuarine systems.

The knowledge and understanding of sediment transport is essential for the development of effective management strategies for nutrient and sediment loading in estuarine systems. Estuarine suspended sediment (in high concentrations), has the ability to adversely impact upon surrounding ecosystems, such as the Great Barrier Reef, Australia. Due to a recent decline in water and sediment quality, it has recently been mandated that a number of tropical, coastal estuarine systems in Queensland, such as the Fitzroy River estuary, have their sediment loading reduced. In order to meet these requirements, a greater understanding of the sediment transport dynamics and driving processes (such as flocculation and settling velocity) needs to be achieved, and the accuracy of estimation improved. This research project was motivated by the need to improve the general accuracy of field measurements for estuarine suspended sediment transport and dynamics. Field-based measurements (especially settling velocity) are necessary for the parameterisation of sediment transport models. The difficulty in obtaining accurate, in situ data is well documented and is generally limited to methods that isolate a water sample from its natural environment, removing all influences of estuarine turbulence. Furthermore, the water samples are often extracted from points (Eulerian) where the history of the suspended particles is generally unknown. These sampling methods typically contain intrinsic errors as suspended sediment transport is essentially Lagrangian (i.e., flows with the net motion of flow-field) in nature. An investigation into different drogue systems conducted in parallel with a study into the tidal states of the Fitzroy River estuary led to the development of a novel Lagrangian drogue device, the LAD. Additionally, the water-tracking ability of the LAD was tested and found to accurately follow a parcel of estuarine water over a slack water period. Therefore the LAD was deployed in the Fitzroy River to assist in the further understanding of complex sediment transport processes such as flocculation and settling velocity in a natural estuarine flow field. The final device (the LAD - Lagrangian Acoustic Drogue) was developed, utilizing the principals of acoustic backscatter intensity-derived SSC measurements. The investigation of a series LAD deployments (during slack water) in the Fitzroy River estuary, revealed the dominant suspended sediment processes and also gave an insight into the prevailing flow-patterns. Results showed the presence of a settling lag mechanism between low and high tide, which can initiate a net sediment flow upstream with each flood tide. The bulk settling velocity showed comparable results at both low and high water. The LAD derived bulk settling velocity as a function of concentration (SSC), yielding a strong positive correlation (r2 = 0.73). Also the importance of flocculation in the bulk settling and clear up of the water column during periods of still water (high and low tide) was demonstrated as all in situ settling velocities (0.33 - 1.75 mm s-1) exceeded single grain approximations (0.47 mm s-1). This research demonstrates the potential for Lagrangian drogue studies as an effective measuring platform for the accurate quantification of estuarine suspended sediment dynamics. The application of the LAD in the Fitzroy River has lead to a significant improvement in the understanding of the system's real sediment transport processes. This research has provided an effective and accurate technique for measuring real settling velocities for input into numerical models or for the validation of existing model outputs. Furthermore, this technique shows great potential for application in other estuarine systems.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Engineering
Full Text

Southern Moreton Bay and the adjacent continental shelf have provided a natural laboratory in which to describe the sedimentology, sequence stratigraphy and coastal evolutionary processes of a wave dominated coastline. Sequence stratigraphy has become a routine tool for Earth Scientists in the exploration of hydrocarbons and as such detailed studies in Quaternary depositional environments are required to provide analogues for ancient environments. The Quaternary has a well documented sea level curve which when used in combination with high resolution seismic, drill core and age dating provides the opportunity to derive accurate and detailed depositional scenarios for various stages of sea level. This study has established that the southeast Queensland coastal prism is an example of a relatively sediment deficient margin as a result of the low gradient of the regional topography and the low flow rate of the fluvial systems. This differs dramatically from the regions from which most of the generic sequence stratigraphic models have been derived (ie. North America and Europe) where major fluvial systems have high flow rates and generally greater topographic relief Consequently the system described herein provides an important variation on generic sequence stratigraphic models, particularly in the way a fluvial system responds to periods of low sea level. The incision of the Logan/ Albert fluvial system has been mapped across the coastal plain, through the lagoon and under the inner to mid-continental shelf The valley system is not apparent on the outer shelf. This may primarily be a function of stream gradient. The gradient of the incised valley is approximately 0.002 in the coastal prism, the outer continental however is 10 km wide with a relief of 2-3m giving a gradient of 0.00025. This essentially flat shelf area coincides with the lack of incision on the shelf. As a result of the extremely low gradient of the outer shelf area in combination with potentially hard substrate and a reduced stream power during glacial periods, it is unlikely that the Logan/ Albert Pluvial system incised to the shelf edge. The low gradient of the exposed shelf during glacial lowstands therefore resulted in the over extension and loss of stream power (reduced transport efficiency) of the Logan/ Albert flu vial system. The area that is now the outer shelf was most likely occupied by single channel thick shelf bypass channels (c.f. Posamentier & Allen, 1999) or became a low-lying fluvial shallow braid plain. The earliest deposition in the study took place on the continental shelf where three sequences are dominated by transgressive and lowstand systems tracts with highstand systems tracts not being readily recognised. On the coastal plain, three sequences have been cored and described in the Logan River incised valley. These sequences have been dated in this study at 40,000 yBP and 25,000 yBP and <18,000 yBP. This indicates that the Logan River incised valley can be classified as a compound valley fill (Zaitlin et al., 1994) characteristic of a relatively long lived fluvial system. Seismic mapping indicates the first sediment deposited in southern Moreton Bay was related to late lowstand conditions (the first onset of sea level rise and the creation of sufficient accommodation to allow for vertical aggradation), and was confined to the thalwegs of incised valleys. Seismic geometries suggest that deposition took place in fluvial point bars and therefore is most likely gravel and sand dominated. A transgressive surface separates these late lowstand fluvial sediments from an early to mid transgressive unit. The early to mid transgressive sediments are characterised by h high amplitude continuous reflectors and are generally confined within the wider valley walls, and are interpreted to have been deposited in a quiet estuarine setting. After the peak at 1OOkyBP, sea level began to fall into the next glacial maximum at 18 kyBP. This sea level fall was not smooth and was punctuated by a number of transgressive-regressive cycles. As a consequence three force regressive shelf perched early lowstand wedges are recognised on the continental shelf adjacent to the southern Moreton Bay area. These wedges have been grouped as sequence set C and represent subsequences within the overall early lowstand or falling stage systems tract associated with this punctuated falling sea level. Each of these sequences represent coastal plain deposits forming at a stage of sediment by-pass in the upper reaches of the fluvial valleys creating minor but significant sequence boundaries. The main sequence boundary GL is related to incision associated with the major sea level fall that peaked at 18 kyBP. This surface is heavily incised in places and formed at stages associated with each of the falls on the overall falling sea level limb. In the southern area incision related to the paleo-Logan Albert system is up to 60m on the coastal plain. The Logan system has re-inherited its main valley, and its position is structurally controlled. The Logan River valley was reincised as a result of the low sea level associated with the last glacial maximum. The first sediments to be deposited within this reincised valley were fluvial point-bar polymictic gravels and quartz-lithic sands these are interbedded with overbank deposits of mud and silt. These deposits are confined to the valley thalwegs. The earliest dateable material sampled by drilling in this study was 13,650 ±60 yBP (Beta-104824), indicating late·lowstand to early transgressive conditions based on the sea level curve of Chappell, et al., (1996). The transgressive surface, which overlies these deposits, is contained within the valleys and is recognised by the input of estuarine fauna! assemblages although the quartz-lithic and poorly sorted character of the sediments does not change. This in turn is overlain by high amplitude, concordant reflectors that are generally confined to the greater valley walls and shown to be laminated estuarine mud by drilling. The thickness and fine grained nature of these sediments in conjunction with a rapid sediment accumulation rate (approximately 11mm/year) indicates extensive creation of accommodation space consistent with the rapid transgression experienced on the east Australian coast at this time (up to 2.5rn/100years. A major tidal ravinement surface overlies the laminated muds of the early to mid transgressive phase of sedimentation. This surface is highly erosive and recognised as an abrupt change from laminated mud to clean well-sorted fine grained quartzose sand in conjunction with a shelly lag. The tidal ravinement surface is often coincident with the GL sequence boundary in areas. The last glacial transgression reached its peak at 6.5kyBP at approximately - 1.5 m higher than present. Age dating shells from a depth of 3m near the +2.5m contour on the coastal plain gave an Amino Acid Ratio consistent with an age of approximately 6.5kyBP. The Pimpama Coastal Plain was inundated at the peak of the transgression. Sediments form a depth of 6.lm were dated at 4780±60 yBP (WK-7663) in LR#3. Given the thickness of the overlying section it is apparent that the area was still part of an active flood tidal delta setting well beyond the peak of sea level at 6.5 kyBP. This is in keeping with a relatively rapid drop in sea level after 3000 yBP as is proposed by Flood, (1983), and explains the virtual absence of regressive bayhead delta sands on the coastal plain. The H4 seismic unit represents the current highstand since the peak of the late transgression. It is generally confined to the immediate vicinity of the Logan River bayhead delta and constrained geographically to the Redland Bay area. Where seen the unit downlaps onto the maximum flooding surface. This maximum flooding surface is coincident with the bay floor in most places of the northern area as a result of insufficient sediment supply to the area either from the Logan River or the tidal delta. When sea level fell by 1-l.5m approximately 3000 yBP, the tidal prism of the southern Moreton Bay area was dramatically decreased. As a result the efficient ancestral tidal inlet which had developed between the newly developed South Stradbroke barrier Island and North Stradbroke Island had to narrow and become shallower until it eventually closed. This period of closure allowed for the tidal circulation to decrease in the vicinity of southern Moreton Bay to virtually nil as that area became a tidal null point for tides now entering the area from South Passage (to the north) and the Nerang Inlet (to the south). Consequently the only sediment input was mud, silt and quartz-lithic sand supplied by the Logan and Pimpama Rivers. As a result, the sand shoals of the previous flood tide delta became relict and colonised by mangroves forming intra-to supra tidal · islands. This situation remained until 1898 when the sea broke through at Jumpinpin. Once this had occurred the regional tidal null point was shifted to become coincident with an area closer to the mouth of the present Logan River and the northern end of Canaipa Passage. The main effect was the scouring of previously inactive abandoned tidal channels to become the deep channels of present day. Quartzose marine sand has entered into the lagoon by a distance of nearly 9krn since 1898.

The coastal region influences many aspects of our lives, including our economy, our quality of life and our safety and security. Many large cities in Australia are located along estuaries and coasts. As a consequence of the growing human population, most coastal areas throughout Australia are now facing threats of over urbanisation, and industrialisation, resulting in significant impacts on the coastal aquatic environments. Additional challenges may also come from more frequent severe flooding resulting to climate changes, which could degrade the environment even further and more rapidly. Sediment accumulation and transport in estuaries and coastal bays is one of major issues, not only impacting on the maintenance of navigation channel but also resulting in ecological problems. For several decades, a large number of investigations of sediment transport have been conducted in Australia, which them mostly addressing conditions of the sediment delivered to the estuary within the dry season. However, a limited number of researches have been done in great detail, focusing on the hydrodynamic and sediment transport in the wet season. In recent years, with the development of computing and satellite technologies, the study on the hydrodynamic and sediment transport has allowed studies to be conducted on large spatial and temporal scales. Additionally, this has meant it is now easier to investigate the event-driven behaviour severe flooding events.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text

Hydraulic lock structures have been used for hundreds of years to control and maintain water levels in waterways. The most common are gated water regulation structures used to catch and divert water, and form an essential and critical part of many flood control and agricultural schemes. Although there are clear economic advantages to building the structures, they can contribute to major water quality problems for the waterways they influence (i.e. increased residence times and a change in mixing ability). Further, in most cases, the methods previously used to assess how the structures and their operations influence the flow regimes between the two connected systems were limited, thus hydraulic designers rely on simple formulations, existing literature and experience. Consequently, the objectives of this thesis were to undertake a detailed field study and develop a methodology and computer simulation tool to calculate the flow through a hydraulic structure connecting two water bodies so that future designs can be undertaken based upon sound knowledge. To demonstrate the outcomes of this thesis, the methodology and model were applied to an existing hydraulic structure (referred to as Structure C). Structure C is used to connect and exchange water between the tidally dominated section of the Nerang River estuary and an artificial lake system (Burleigh Lakes) on the Gold Coast, Australia. The gates of this structure open four times each day (once during each semi-diurnal tidal phase) and remain open for a period of 2 hours, allowing alternative and partial exchange between the two water bodies. To gain a better understanding of the dynamics of each waterbody under the influence of the structure, a series of detailed field experiments were initially undertaken to understand and quantify the exchange of water and its mixing ability. Tide gauges deployed within the lake indicated a water level change during each opening of up to 22 cm, equating to 413,600 m3 of water entering the lake over the 2 hour discharge period. Salinity profiles showed that the structure permitted the exchange of saline and freshwater between the two systems, during each tidal cycle, in turn maintaining the lake system as a saline (brackish environment). However, the field study also revealed that the controlled exchange of water between the systems perpetuated a permanently stratified environment on both sides of the structure. To simulate the flow dynamics influenced by Structure C, new routines were incorporated into an existing hydrodynamic model (BFHYDRO) within the model's grid and computational code, as part of this thesis. To achieve this, the flow in and out of the hydraulic structure cell (used to represent the hydraulic structure's location within the model grid) was calculated entirely from the local water level gradients on either side of the structure at each time-step, and not prescribed. This was found to be essential for complex tidally-dominated systems, such as the Nerang River. Routines were also developed to replicate the opening and closing times of the gates. Following the development of the methodology, the hydraulic structure cells were tested and applied to simulate the flow through Structure C and the complex exchange between the estuary and lake, in 2 and 3-dimensions. Tests indicated that the opening and closing times of the gates and the calibration of the discharge coefficient (which forms part of the broad-crested weir formula) were the most sensitive parameters to ensure the correct volume of water exchange between the two systems. Statistically, the model-predicted results compared very well with available surface elevation data within the estuary and lake, and thus, quantified the ability of the hydraulic structure cells to simulate the flux between the estuary and lake for each opening. Following the model validation process, results from the existing configuration were compared with hypothetical design alternatives and are documented herein. Further, part of the thesis also explored a practical and effective computer based learning strategy to introduce and teach hydrodynamic and water quality modelling, to the next generation of undergraduate engineering students. To enhance technology transfer a computer based instructional (CBI) aid was specifically developed to assist with the setup, execution and the analysis of models' output, in small easy steps. The CBI aid comprised of a HTML module with links to recorded Lotus Screen cam movie clips. The strategy proved to be a useful and effective approach in assisting the students to complete the project with minimum supervision, and acquire a basic understanding of water quality modelling. Finally, it is anticipated that this new modelling capability and the findings detailed herein will provide managers with a valuable tool to assess the influence of these structures on water circulation for present and future operations within the region. This model can also be set up at other sites to pre-assess various design configurations by predicting changes in current flows, mixing and flushing dynamics that a particular design might achieve, and assist with the selection process before the final selection and construction.

Hydraulic lock structures have been used for hundreds of years to control and maintain water levels in waterways. The most common are gated water regulation structures used to catch and divert water, and form an essential and critical part of many flood control and agricultural schemes. Although there are clear economic advantages to building the structures, they can contribute to major water quality problems for the waterways they influence (i.e. increased residence times and a change in mixing ability). Further, in most cases, the methods previously used to assess how the structures and their operations influence the flow regimes between the two connected systems were limited, thus hydraulic designers rely on simple formulations, existing literature and experience. Consequently, the objectives of this thesis were to undertake a detailed field study and develop a methodology and computer simulation tool to calculate the flow through a hydraulic structure connecting two water bodies so that future designs can be undertaken based upon sound knowledge. To demonstrate the outcomes of this thesis, the methodology and model were applied to an existing hydraulic structure (referred to as Structure C). Structure C is used to connect and exchange water between the tidally dominated section of the Nerang River estuary and an artificial lake system (Burleigh Lakes) on the Gold Coast, Australia. The gates of this structure open four times each day (once during each semi-diurnal tidal phase) and remain open for a period of 2 hours, allowing alternative and partial exchange between the two water bodies. To gain a better understanding of the dynamics of each waterbody under the influence of the structure, a series of detailed field experiments were initially undertaken to understand and quantify the exchange of water and its mixing ability. Tide gauges deployed within the lake indicated a water level change during each opening of up to 22 cm, equating to 413,600 m3 of water entering the lake over the 2 hour discharge period. Salinity profiles showed that the structure permitted the exchange of saline and freshwater between the two systems, during each tidal cycle, in turn maintaining the lake system as a saline (brackish environment). However, the field study also revealed that the controlled exchange of water between the systems perpetuated a permanently stratified environment on both sides of the structure. To simulate the flow dynamics influenced by Structure C, new routines were incorporated into an existing hydrodynamic model (BFHYDRO) within the model's grid and computational code, as part of this thesis. To achieve this, the flow in and out of the hydraulic structure cell (used to represent the hydraulic structure's location within the model grid) was calculated entirely from the local water level gradients on either side of the structure at each time-step, and not prescribed. This was found to be essential for complex tidally-dominated systems, such as the Nerang River. Routines were also developed to replicate the opening and closing times of the gates. Following the development of the methodology, the hydraulic structure cells were tested and applied to simulate the flow through Structure C and the complex exchange between the estuary and lake, in 2 and 3-dimensions. Tests indicated that the opening and closing times of the gates and the calibration of the discharge coefficient (which forms part of the broad-crested weir formula) were the most sensitive parameters to ensure the correct volume of water exchange between the two systems. Statistically, the model-predicted results compared very well with available surface elevation data within the estuary and lake, and thus, quantified the ability of the hydraulic structure cells to simulate the flux between the estuary and lake for each opening. Following the model validation process, results from the existing configuration were compared with hypothetical design alternatives and are documented herein. Further, part of the thesis also explored a practical and effective computer based learning strategy to introduce and teach hydrodynamic and water quality modelling, to the next generation of undergraduate engineering students. To enhance technology transfer a computer based instructional (CBI) aid was specifically developed to assist with the setup, execution and the analysis of models' output, in small easy steps. The CBI aid comprised of a HTML module with links to recorded Lotus Screen cam movie clips. The strategy proved to be a useful and effective approach in assisting the students to complete the project with minimum supervision, and acquire a basic understanding of water quality modelling. Finally, it is anticipated that this new modelling capability and the findings detailed herein will provide managers with a valuable tool to assess the influence of these structures on water circulation for present and future operations within the region. This model can also be set up at other sites to pre-assess various design configurations by predicting changes in current flows, mixing and flushing dynamics that a particular design might achieve, and assist with the selection process before the final selection and construction.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Engineering
Full Text

Land use practices over the last 200 years have dramatically altered the distribution and amount of riparian vegetation throughout many catchments in Australia. This has lead to a number of negative impacts including a decrease in water quality, an increase in sediment transport and a decrease in the quality of terrestrial and aquatic habitats. The task of restoring the functions of riparian zones is an enormous one and requires spatial and temporal prioritisation. An analysis of the existing and historical functions of riparian zones and their spatial distribution is a major aid to this process and will enable efficient use of remediation resources. The approach developed in this thesis combines remote sensing, field measurement and terrain analysis to describe the distribution of five riparian zone functions: sediment trapping, bank stabilization, denitrification, stream shading and large woody debris production throughout a large semi-arid catchment in central Queensland.

This research contributed to the rather limited knowledge on the transport of organic contaminants in estuarine environments from South-East Queensland. Modelling studies were conducted to assess the fate of some current-use pesticides and pharmaceuticals in the Brisbane River estuary. The vertical transport of per- and polyfluoroalkyl substances (PFASs) in soils from a previous firefighting training ground was also assessed. The outcomes of this study contribute to the global stock taking of organic contaminants in the environments and are expected to be useful in designing effective containment or remediation strategies for organic contamination.

The seasonal periodicity of hydrology, physical and chemical water quality parameters and phytoplanktonic assemblages was studied at two sites in a large tropical Australian riverine impoundment. This study, the first in the lower Fitzroy River at Rockhampton, occurred between August 1990 and November 1993. It covered extremes in riverine flow conditions including major flooding and drought.

The annual flow regime was characterized by major flows in the "wet" season (summer and autumn) and greatly reduced or no flow in the "dry" season of winter, spring and sometimes early summer. Consequently, the thermal regime at both of the study sites was divided into two phases. The first was a phase of water column heating in the late winter to early summer. Features of this heating phase were long term stratification with progressive epilimnetic deepening, high pH, regular occurrence of epilimnetic oxygen supersaturation and decreased or undetectable levels of oxidized nitrogen in the surface layer. Hypolimnetic anoxia was recorded late in this phase. The second, between substantial wet season inflows and late winter was characterized by nutrient rich inflows and water column cooling and mixing.

Distinct interannual differences occurred in the volume, source and timing of inflows and subsequent water chemistry. In 1991, conductivity, water clarity, filterable reactive phosphorus (FRP) and pH increased markedly following major flooding from northern tributaries, while oxidized nitrogen decreased. This was in marked contrast to the drier years of 1992 and 1993 where turbidity and oxidized nitrogen were higher during the initial post-flood period and conductivity and FRP were lower. Extremes of mostly abiogenic turbidity (range 1.6 to 159 NTU) were a feature of the light climate. Ratios of euphotic depth/mixing depth below 0.3 occurred in early 1992 and 1993.

Steep gradients in the physical and chemical environment were paralleled by variations in the phytoplankton. Algal biomass (as chlorophyll a) at Site 1, midstream opposite the water intake for the city of Rockhampton, ranged from 1.5 to 56.6 ug L-1. The vertical water column distribution of chlorophyll was variable with assemblages normally dominated by phytoflagellates and various species of cyanoprokaryotes. There was also higher relative abundance of chlorophyll a (reflecting increasing dominance of cyanoprokaryotes) in the latter half of the year and at the lower end of light availability. The specific vertical water column positioning with respect to light and temperature is shown for assemblages dominated by the genera Anabaena, Aphanizomenon and Cylindrospermopsis.

The most striking aspect of the phytoplankton was the long term dominance of cyanoprokaryotes and the species richness (particularly that of cyanoprokaryotes) when compared with the dearth of information to date on other tropical rivers. Seasonal successions were varied. Regularly occurring assemblages were cyanoprokaryotes (Oscillatoriales), euglenophytes or non-flagellated chlorophytes during flows followed by flagellated chlorophytes and then cyanoprokaryotes (Nostocales) during the dry season. Genera present indicated highly eutrophic conditions. Hierarchical agglomerative clustering of phytoplankton data and comparison with a principal components analysis of corresponding environmental data were used to demonstrate the linkage between steep environmental gradients and variation in the phytoplankton assemblage. The specific environmental conditions associated with the success of various species were also analysed and presented. Using the above information, a two-part model was proposed which predicts the most likely genera of phytoplankton with respect to multidimensional environmental gradients. This model covers a wide gamut of conditions varying from highly variable lotic to lentic environments.

As Cylindrospermopsis raciborskii was considered a most important species in relation to the quality of the water supply for Rockhampton, the physical, chemical and biotic conditions prior to and during a bloom of this species are described. A number of possible grazers of C. raciborskii were identified with a view to future biomanipulation. One of these, the large ciliate, Paramecium cf. caudatum was found to be an effective grazer of toxic straight C. raciborskii in the laboratory.

This study is unique in that it analyses the impact of episodic events (eg. major flooding) on the subsequent phytoplankton in the lower Fitzroy River. The model relating phytoplankton to multidimensional environmental gradients provides great information for use in management, particularly in relation to the prediction of toxic algal blooms.

<i>Abstract</i> .—Central Queensland in Australia already has a highly variable rainfall and streamflow pattern. River flows of the largest local river, the Fitzroy, are seasonal and ephemeral and, between 1976 and 2008, varied in magnitude from around 349,677 to 22,903,390 ML per annum. Predictions of local climate change effects suggest that rainfall and streamflows will become more variable with less frequent but larger flood events and extended, more severe drought periods. SUNTAG is a program that has recorded details of tagged and recaptured fish in Queensland since 1986. CAPREEF is a community-based program that has collected catch-and-effort data from recreational fishers across Central Queensland since 2005. The SUNTAG and CAPREEF programs act as a long-term central repository to collect recreational fish tagging and catch information. The goal of this paper was to examine two models predicting changes associated with rainfall and streamflow, the first examining changes in barramundi <i>Lates calcarifer </i> recruitment in a wetland system and the second predicting changes in recreational catch rate of sand whiting <i>Sillago ciliata </i> and red throat emperor <i>Lethrinus miniatus</i> . Catch rates of young barramundi recruiting to a wetland in the Fitzroy River delta between 1985 and 2008 varied between 0 and 37 fish/d. The median catch rates of fishing clubs also varied widely, being highest in years following wet season flooding.