History,Geomorphological Problems and Effects of Dredging in Cleveland Bay,Queensland

The history of dredging is examined for Cleveland Bay, 1883–1988, as the port of Townsville developed. Between 1883 and 1964 only intermittent data exist on localities, depths and quantities dredged but later much more detailed records are available for analysis. Geomorphological problems emerged and are considered with particular reference to material forming the seabed, the sediment yield from the coastal catchments and its seasonally and annually irregular delivery to the coast by the rivers, and sediment movement within the bay in response to wind, wave and tidal processes. Analysis of aerial photographs, 1941–1988, has enabled some dredging effects to be studied, especially relating to localised land reclamation and more widespread probable effects on seagrass beds and mangroves.     

An Examination of Vertical Accretion of Floodplain Sediments in the Labasa River Sugarcane Belt of Northern Fiji: Rates,Influences and Contributing Processes

The ¹³⁷Cs (caesium‐137) method was used to investigate medium‐term rates of sediment deposition on the floodplain of the Labasa River, on Vanua Levu island in northern Fiji. The Labasa basin is commercially important for sugarcane farming, which provides much revenue and sustains the economy in the greater Labasa area. Alluvium was sampled at three riverbank sites in vertical increments of 30 mm. Measured net vertical accretion rates, based on analysis of depth‐profiles of ¹³⁷Cs activity, ranged from 10 mm yr^?1 at a low‐lying site near a tributary confluence with the main river, to 60 mm yr^?1 on a levée that was elevated slightly above the adjacent floodplain. These rates of accretion are high, but in general agreement with rates recorded using similar methods in other tropical Pacific island river systems. Soil erosion under sugarcane on hilly parts of the lower Labasa basin is an important factor in rapid floodplain development. Observations made during Cyclone Ami, which traversed Vanua Levu island in early 2003, illustrate the major contribution of severe storm events to floodplain sediment supply, by triggering numerous landslides on catchment slopes and in‐channel debris floods, and by generating large‐magnitude overbank floods.     

Symbionts in a stromatoporoid-chaetetid association from the Middle Devonian Burdekin Basin,north Queensland

A spectacular association between a chaetetid, a stromatoporoid (Salairella sp.), and straight, vertical tubes interpreted to have housed symbiotic worms is reported from the Givetian Burdekin Formation, Burdekin Basin, north Queensland. The final growth surface of Salairella sp. shows skeletal distortion characterised by long, rather continuous coenosteles and coenostroms with upturned edges. This distorted interface was probably the result of spatial competitive interaction between the encrusting chaetetid and the underlying stromatoporoid. Neither sediment infilling, erosion or surface breakage occurs on the final growth surface of the stromatoporoid skeleton. As such, the growth of the Salairella sp. specimen appears to have been supressed by the encrusting chaetetid. Worm tubes are continuous through the distorted interface without interruption. The skeletal association also suggests that the round, straight, vertical tubes had a symbiotic intergrowth relationship initially with the stromatoporoid and, subsequently, the chaetetid.     

Rugged Plateaus and Extensive Floodplains — Modelling Landform Evolution in a Northern Australian Catchment

Medium to large natural catchments are often more spatially heterogeneous than small catchments or single landforms. Attempting to model landform evolution of large areas is consequently more complex. This paper demonstrates that modelling landform evolution in medium to large catchments can be improved by calibrating the model to smaller, more geomorphologically homogenous sub‐catchments. The paper investigates landform evolution in the Ngarradj catchment in the Northern Territory of Australia (a medium scale catchment of approximately 67 km²). The catchment is complex and contains two distinct landform regions; an upland plateau region with highly dissected sandstone and shallow, sandy soils, and a lowlands region with gentle, wooded slopes and floodplains with deep, sandy soils. The SIBERIA landform evolution model is calibrated and applied to the Ngarradj catchment. The complexity of the Ngarradj catchment is incorporated into the modelling by dividing the catchment into three sub‐catchments (Swift Creek (SC), Upper Main (UM) and East Tributary (ET)) which are relatively homogeneous and for which hydrology and sediment transport data are available. A discharge‐area relationship and long‐term, sediment loss rates for the catchment are derived based on an annual series flood frequency analysis of a 20 year runoff record predicted in a previous study. Sediment transport modelling incorporates both suspended and bedload sediment loss. The denudation rates derived using these data are 37, 63 and 77 mm kyr^?1 for the SC, UM and ET sub‐catchments, respectively. Model predictions indicate that the UM sub‐catchment will have the greatest mean erosion. This is balanced by the large amount of deposition that will occur in the upper Ngarradj valley of the UM sub‐catchment. Further deposition occurs on the floodplain of Ngarradj, with the area between the SC and ET/UM (up‐stream) sub‐catchments experiencing a small net accretion of sediment (15 mm kyr^?1).     

Rainfall,floods and river channel changes in the upper Hunter

Since 1946, there has been a significant increase in annual rainfall in the Hunter Valley, especially for stations in the western sector. Contemporaneous increases in rainfall intensities of frequent storms and flood peaks have also been recorded. From analyses of the data, together with a review of recent environmental changes in the Hunter Valley, it is concluded that human disturbance of the catchment has played no significant part in the increase in flood magnitude. Instead, the change in floods may be completely attributed to the variation in rainfall regime. The altered hydrologic regime combined with a decrease in sediment yield from extra-channel sources appears to be the primary cause of recent river channel changes.     

A Comparison of Holocene and Historical Channel Change along the Macdonald River,Australia

Changes in channel morphology that occurred along the Macdonald River between 1949 and 1955 are often cited as an example of catastrophic channel change. However, the question of whether these changes represented one component of a cyclical evolutionary pattern, or a systematic and persistent shift to a new morphologic state remains to be clearly defined, as does the significance of these dramatic channel changes when viewed against the river's longer‐term Holocene history. In this paper, new measurements of the Macdonald River's channel morphology are used to resolve the river's evolution in the ～50 years since these major channel‐altering floods. By 2002, the Macdonald River's bed had narrowed considerably from its 1955 post‐flood maximum due to the construction of a new floodplain surface within the widened channel. In some locations, the 2002 bed width is comparable to that of the pre‐1949 channel. This aspect of the river's evolution follows models of cyclical channel evolution proposed for the region. However, in light of recent research into the river's longer term Holocene evolution, it is clear that other channel changes that occurred in response to the 1949–1955 floods, particularly the 2 metres of river bed aggradation and 7 kilometres down‐valley shift in the thalweg's intersection with mean sea level, are less cyclic in nature. The capacity of coastal rivers to prograde into estuaries, which in turn induces river bed aggradation, can be seen in this case to counteract the incisional tendencies associated with post‐flood channel contraction, such that persistent river bed aggradation occurs.     

An Initial Analysis of River Discharge and Rainfall in Coastal New South Wales,Australia Using Wavelet Transforms

In many coastal catchments of south eastern New South Wales, Australia, changes in river morphology are a response to human impact superimposed on spatial and temporal patterns of variability in precipitation and discharge. Understanding, and preferably quantifying, spatial and temporal patterns of hydrologic variability are essential to understanding natural changes, and to separate these from artificial changes in river systems. Prediction and management of water resources are also dependent upon this understanding. We assess the variability in precipitation and discharge using the wavelet transform which projects the time series of data into a three dimensional surface of frequency, amplitude and time. The analysis reveals that changes across time often reflect changes in individual seasons and may be linked to changes in particular seasonal atmospheric circulation systems. Strong perturbations in the analysis of one catchment are consistent with documented, geomorphically‐effective, flooding sequences. The characteristics of the series in the transformed data reveal interesting differences at certain times and scales which may be a reflection of changes in larger scale atmospheric processes.     

Water,Wind, Wood,and Trees: Interactions,Spatial Variations,Temporal Dynamics,and their Potential Role in River Rehabilitation

Recent Australian research has quantified the role of large wood (wood of any origin and length with a diameter greater than 0.1 m) in dissipating stream energy, forming pool habitats by local bed scour, protecting river banks from erosion, and damming rivers with long rafts causing avulsions. Large wood in Australian streams is sourced by a range of processes from the nearby riparian zone which has usually been degraded by post‐European settlement vegetation clearing. Large wood loadings within the bankfull channel are dependent not only on the type and quality of the riparian plant community but also on bankfull specific stream power, channel width, and the processes of large wood delivery to the stream. While bank erosion and floodplain stripping by catastrophic floods are obvious and important delivery mechanisms, treefall and trunk and branch breakage by strong winds during tropical cyclones and severe storms are also significant in the tropics. Furthermore, wood decay and downstream transport produce temporally dynamic large wood distributions. The longevity of natural large wood structures in rivers, such as rafts, debris dams, and log steps, requires determination. River rehabilitation programs need to not only include the reintroduction of large wood, but also carefully plan the spatial distribution of that wood, the most appropriate type and range of large wood structures, and, most importantly, the revegetation of the riparian zone to ensure a natural long‐term source of large wood. Exotic species management is an essential part of river rehabilitation.     

Variation in suspended sediment concentration during storms in five small catchments in southeast New South Wales

Suspended sediment concentrations were determined during storm events for five small catchments in the Wallagaraugh River in southeast New South Wales between July 1977 and June 1978. A total of thirty-nine storm responses were analysed and both storm hydrographs and hysteresis loops were produced. The behaviour of suspended sediment concentration was extremely variable and seven different types of response were recognised. In these catchments there is no simple single constant relationship between discharge and suspended sediment concentration. The free availability of suspendable material appears to be an important limiting control on sediment concentration and this appears to be related to the soil moisture conditions     

International rivers as border infrastructures: En/forcing borders in South Asia

Rivers have long been convenient yet troublesome borders. Inherently itinerant, rivers routinely defy cartographic depictions of borders as static, territorially bounded formations. Such dynamism poses material and conceptual challenges to state regulatory activities, resulting in increasingly heterodox attempts to fix waterbodies through various securitizing mechanisms. I examine the dialectical relationship between rivers and borders through the concept of the river-border complex. I ask how the Ganges River shapes the form and function of the Indo-Bangladeshi border and how, in turn, bordering practices in India regulate flows along the river, which comprises 129 km of India's border with Bangladesh. Drawing on archival records, in-person interviews, and river data, I find that the border and efforts to secure it mediate many flows along the river. The study corroborates previous work within critical border studies that securitizing cross-border flows has the perverse effect of generating greater insecurity in adjoining countries. Crucially, historical analysis of sediment, information, and human flows reveals how international rivers also determine patterns and processes of circulation and thereby warrant reconceptualization as border infrastructures, rather than as merely being subject to them.     

Fluvial Geomorphology and River Management

Australian river landscapes offer many challenges for management. Much Australian river research is novel, but practical concerns have always had an influence on the research agenda. Australia’s distinctive contributions to fluvial geomorphology include recognition of the great age of many fluvially eroded landscapes; understanding complex levee, terrace and valley fill sequences; analysing the impacts of rare major floods; interpreting the effects of impoundment, mining and urbanisation; and understanding the great anastomosing inland river systems. River restoration is now a major theme in the literature of river engineering, fluvial geomorphology and landscape design. Great achievements are occurring in geo‐ecological river management and engineering. Changing people’s thinking is becoming at least as important as gaining new scientific knowledge. The existing understanding needs to be more widely shared and enhanced by greater involvement with Asian countries where river management issues daily affect the lives of millions of people.     

The deserts of the Kashmir‐Tibetan frontier

Abstract

Semi-arid landscapes are vulnerable to cultivation, overgrazing and climate variability, although it is difficult to identify the relative significance of these three factors. In the South African Karoo, the ‘desertification debate' seeks to explain a change to more shrubby vegetation in heavily grazed areas. We examine these issues in catchments where farm reservoirs provide sediment stores with 137Cs, 210Pb, geochemical and mineral magnetic signatures. Rainfall data and stocking numbers are reported and current erosion rates are estimated. Sediment accumulation in the reservoirs increases between 1935 and 1940, probably due to rises in the frequency of rainfall events of >25mm day. Significant increases in sedimentation rates (×8) occur during rain-fed wheat cultivation. In an uncultivated catchment, sediment yields remain relatively high and reflect increases in erosion from hillslopes, colluvial storage, and cultivated land sources. Gully systems have acted as transport routes rather than sediment sources over the last ～70 years. Badland erosion rates average ca. 50t ha^?1 yr^?1. At Ganora, their development in the 1920s strongly influences peak sedimentation between 1970 and 1980. Any delay between badland initiation and increased sediment yield appears to be a function of landscape connectivity. Recovery following disturbance is occurring slowly and is likely to take >100 years. De-stocking and better management systems are reducing erosion rates but may be offset by increases in rainfall intensity.     

Adaptive Management for Water Quality Improvement in the Great Barrier Reef Catchments: Learning on the Edge

This paper proposes using an adaptive management approach to achieve water quality improvement in large catchments with multiple diffuse pollutant issues. Adaptive management involves attention to process, and commitment to continually improving knowledge and practice. It also requires an appreciation of differences in understanding of various stakeholders and an ongoing commitment to learning. Based on research with the Burdekin Dry Tropics regional Natural Resource Management group, the paper shows how the acquisition of knowledge about Water Quality Management can be an aim in itself, rather than an activity peripheral to the planning process. To this end, the paper describes the methods used to elicit stakeholders’ understandings, explores the variation in understandings between key stakeholders, and describes a process used to incorporate the various views in an adaptive management framework for managing water quality. The research findings reveal the importance of process and participation for adaptive management and suggest that success can be judged in terms of learning outcomes.     

Paleoenvironmental catastrophies on the Peruvian coast revealed in lagoon sediment cores from Pachacamac

Paleoenvironmental reconstruction combining data from diatom, pollen, macrophytic, and archaeological analyses had not been attempted previously for coastal Peru. We analyzed two radiocarbon-dated sediment cores extracted from the “sacred” Urpi Kocha Lagoon at the pre-Hispanic religious center of Pachacamac (ca. AD 350-1533), near Lima, to characterize the paleoenvironment of the site. The data reveal an environmental history characterized by alternating periods of severe drought and catastrophic flood. Recurrent pulses with distinctive sediment, diatom, pollen, and macrophytic characteristics reflecting variations in water depth, substrate, turbidity and salinity, usually contain a thick basal sandy storm deposit overlain by thin organic accumulations of peat, gyttja, and snails. The most intense of these disturbance pulses, when correlated with pollen, plant macrofossils, radiocarbon dates, and regional proxy data, provide local evidence of four major floods associated with sustained, catastrophic El Niño events, tsunamis and/or severe storms in the Andean highlands over the last 2000 years.     

Hydrogeomorphic Effects of River Training Works: the Case of the Allyn River,NSW

Since 1955 the NSW Department of Water Resources has undertaken extensive river training works on many NSW streams. In the Hunter Valley alone over $23 million have been spent and more than 850 km of channel have been treated Published work suggests that river training works are usually undertaken in response to a pre-existing problem of river instability but can also induce adverse hydrogeomorphic effects. One of the treated streams, the Allyn River, had been supposedly degraded by the constructed works. It was alleged that vegetation clearing, channel excavations, alignment straightening and bank protection works had decreased roughness thus increasing velocity and flood frequency. As a result, what were thought to be relatively moderate floods were eroding the banks and destroying the floodplain. A critical evaluation of the available hydraulic, hydrologic and geomorphic data revealed that the river training works were a response to, rather than a cause of river instability.     

A Role for Geomorphology in Integrated Catchment Management

Catchments (watersheds) are integrated through water movements. Water moves sediments; and the translocation of materials has geomorphic and pedological responses. Fertiliser and pesticide residues and other toxic substances are also transported by water, in solution and attached to sediment particles, affecting various ecological components of catchments. The insertion of pollutants is directly caused by land‐use practices. In turn, land uses are influenced by the pedo‐geomorphology of the catchments (uplands, valley sides, flood plains and terraces, spurs and hollows, convexities and concavities; position in the upper, middle or lower catchment; and by catenary relationships). Therefore catchment management must deal with interrelationships amongst human activities and various geomorphic elements. Several case study examples from southwestern Australia demonstrate the importance of geomorphology in catchment management. They include: rates of hillslope erosion and translocation of P in micro‐catchments within a drainage basin context; stream salinisation; accumulation of heavy metals in stream sediments; geomorphic elements influencing the spread of weeds and the erosion of access tracks; and some relationships between valley‐side land uses and stream morphology. The incorporation of these and other issues in a management strategy is then illustrated. Complex skills are involved in producing and implementing a management strategy, including but extending well beyond those of the geomorphologist.     

The Palaeoenvironmental Implications of the Distribution of Intertidal Foraminifera in a Tropical Australian Estuary: a Reconnaissance Study

Modern intertidal foraminifera were investigated in a mangrove‐lined microtidal distributary channel of the Barron River Delta (Cairns, Queensland, Australia). A monospecific assemblage of Trochammina inflata characterises saltmarsh environments (Biozone 1), whilst the more regularly inundated tidal flat is dominated (≥55%) by Ammonia beccarii (Biozone 2). Within the tidal flat environment, two foraminiferal subdivisions can be recognised; a high tidal flat assemblage (Biozone 2a) characterised by ≥70% Ammonia beccarii and low diversity, and a low tidal flat assemblage (Biozone 2b) with 55–65% Ammonia beccarii and high diversity (due to the settling out of small allochthonous species transported into the estuary from shelf environments). Foraminiferal distributions are also compared with tide levels estimated in the field. It appears approximately that Biozone 1 occurs between High Water and Mean High Water (MHW), Biozone 2a between MHW and Mean Tide Level (MTL), and Biozone 2b between MTL and Low Water. From this preliminary study, it is concluded that foraminifera possess significant potential in palaeoenvironmental studies of tropical Australian estuaries as indicators of intertidal environments, and also tidal levels.     

The haves and have nots in Australia's Tropical North – New Perspectives on a Persisting Problem

There is significant confluence in the literature that leads one to expect groups of haves and groups of have nots in socio‐economic systems within common spatial contexts. Several economic theories suggest economic activity to be concentrated in a few core areas with geographically large ‘peripheries’ relying on one or two industries for employment and income. In the context of the north of Australia, issues of disparities in socio‐economic status between the region and elsewhere in Australia, and also within the region have been highlighted in the literature for some time. This paper discusses the contemporary situation using customised data collected and analysed for 55 river‐basin catchments in the Tropical Rivers region of northern Australia to highlight the extent of the haves and have nots problem. A range of spatial economic theories are discussed as theoretical bases for the present day situation and as pointers to revisionist approaches which may address it. Transforming the have nots to improved states of well‐being will be a costly and difficult process. Consequently, we argue that factors other than raw incomes and economic production should be reconsidered and re‐prioritised by governments as redress to the ongoing ‘problem’ of the North.     

Reconstruction of the landscape history around the remnant arch of the Klidhi Roman Bridge,Thessaloniki Plain,North Central Greece

This paper deals with the palaeoenvironmental reconstruction of the area surrounding the remnant arch of the ancient bridge of Klidhi, Thessaloniki Plain, Greece. 19th century travellers and 20th century historians discussed the age of the monument and concluded that it was built during Late Roman Times (3rd Cent. AD) and supported a branch of the Via Egnatia road. However, few studies have considered the environmental context of the construction of the bridge, and until now, only two hypotheses have been presented: The bridge was built on or over a junction of the Aliakmon and Loudias Rivers, or on a coastal barrier. Within the framework of a geoarchaeological project developed in April 2008, five boreholes were drilled and the sediment cores analysed for microfauna and sedimentology. Seven ¹⁴C AMS dates provided a chronostratigraphic sequence and helped to define the geomorphological evolution of the area. Spatial interpretation of the results was possible using a Landsat TM image (False Colour Composite – FCC). Our data indicate the gradual transition of the site from a marine to a terrestrial environment during Ancient Times. Lagoonal conditions dominated during the construction of the bridge and the presence of a palaeochannel of the Aliakmon River was later revealed (transition from Byzantine and Ottoman periods), overlying sediments of a coastal barrier.