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The River Murray is Australia’s largest and most important river. It carries water for irrigation and city supply from the mountains in the east, semi-arid west. The river crosses a series of low-angle alluvial fans (distributive fluvial systems) in its 1500 km path. The Barmah Choke is a narrow section of the River Murray’s channel, formed by a Holocene river avulsion, that restricts flow capacity from the upper to lower Murray River. The flow capacity of the Choke has declined nearly 20% since the 1980s, which imposes a constraint on regulated flows supplied down-valley, and is constraining economic development downstream. Whilst there could be multiple geomorphic factors explaining the decline, we demonstrate that the most likely cause is a sheet of coarse sand shallowing the river, much of which originated from historical gold mining and catchment erosion in late 1800s. The sheet of sand is reducing depth diversity, filling pools up to 5m deep, and degrading the ecological and cultural values of the river. The whole length of the river through the Barmah Forest has shallowed over the last 30 years, aggrading by 1.9 m at the upstream end and 0.70 m in the most downstream section of the Choke (about 10% decrease in area). The total volume of sand stored between Yarrawonga and Barmah is over 20 million m3, and the average total annual sand load transported into the 82km long Choke ranges between 130,000 m3 in a normal flow year to 500,000 m3 in a flood year (which translates into 2 – 9 cm of aggradation per year). Surprisingly, overall, long-duration regulated irrigation flows have decreased the rate of sand transport through the Choke. Decreasing downstream flow capacity across the Barmah Fan is a natural characteristic of this type of distributive fluvial system, but the sand sheet is accelerating the rate of decline. Without intervention, conveyance through the Choke will inevitably continue to decline until the river avulses into a new channel. A range of solutions are explored, but all are extremely expensive.

Bucket dredging to mine and extract gold and tin from rivers is a global industry that has had a range of negative effects on physical environments. These include the destruction of riparian soil profiles and structures, artificial channel straightening and loss of in-stream biodiversity. In this paper we evaluate the immediate effects and long-term consequences of bucket dredging on rivers in Victoria and New South Wales during the period 1900–1950. High quality historical sources on dredge mining are integrated with geospatial datasets, aerial imagery and geomorphological data to analyse the scale of the dredging industry, evidence for disturbance to river channels and floodplains and current land use in dredged areas. The study demonstrates that the environmental impact of dredging was altered but not reduced by anti-pollution regulations intended to control dredging. An assessment of river condition 70–100 years after dredge mining ceased indicates that floodplains and river channels continue to show the effects of dredging, including bank erosion, sediment slugs, compromised habitat and reduced agricultural productivity. These findings have significant implications for river and floodplain management.

People and water intersect in the movement of sediment downstream in rivers. Social processes and geomorphological processes become entangled as each system moves in ways that trigger corresponding responses from the other. Long-term dialectical relationships emerge that span multiple human generations. The power of sediment and water to change physical environments is in constant tension with the power of human actions informed by social, cultural, legal, economic and engineering imperatives. The Pacific Rim gold rushes that began in the mid-nineteenth century provide an opportunity to examine how the interplay of people, water and sediment unfolds over historic time. The mass discharge of mining sediment in California and Victoria that began over 150 years ago was a catastrophic human alteration of river systems. Subsequently, mining sediment has had a long and complex entanglement with society and rivers in both regions and continues to be an active agent in reshaping riparian environments. Mining sediments also have a toxic legacy as associated contaminants, including mercury and arsenic, that are discharged into waterways and dispersed in windblown dust. The changes to river systems caused by gold mining committed societies and rivers to new trajectories of mutual engagement. Anthropogenically induced sedimentation that resulted from mining is an issue that will continue to impact watersheds for generations to come.

European settlement has led to increased loads of fine suspended sediment (SS) entering the River Murray, Australia's largest, and arguably, most important river. The River Murray's anthropogenic sediment history can be divided into four periods with varying source areas, sediment loads, and seasonal patterns. The Aboriginal period (before 1840) was characterized by clear water at summer low-flows in the River Murray and its southern tributaries, with more sediment coming from the northern catchment than the southern, and the Darling River being turbid at all flows. There is little evidence that Aboriginal burning resulted in any measurable increase in SS. SS loads peaked in the 1870s and 1880s (the gold and gully period, 1850–1930) as valley floors were incised by gullies (mostly in northern tributaries), and gold sluicing flushed huge amounts of sludge into southern tributaries. Sedimentation in wetlands and on floodplains increased by 2–10 times in this period, and the biota in wetlands switched from clear water to turbid water communities. In the hiatus period (1930–1960) sediment supply from gullies and gold mining waned and low flow SS concentrations returned to low levels. Dam construction through the 1960s and 1970s (the regulation period, 1960 on) disconnected the River Murray from catchment derived sediment. Despite this, SS levels increased again: now largely derived from instream sources including bank erosion from long duration summer irrigation flows, the spread of bottom-feeding carp (Cyprinus carpio), and wave erosion from boats. Erosion switched from winter to summer dominated. Significant investment in securing water for the environment in the Murray-Darling Basin could be complemented by addressing in-channel sediment sources in the River Murray itself to reduce turbidity. Overall, European era SS concentrations remain relatively low with small sediment delivery to the ocean (0.1 Mt per annum), despite high catchment erosion rates. This is due to poor sediment delivery efficiency through the low-gradient landscape.

Mobilisation of large volumes of bedrock, regolith and soil has long been a characteristic feature of metal mining. Prior to the 20th century this was most efficiently achieved through harnessing the motive power of water. Large-scale water use in mining produced waste sands, gravels and silts that were flushed downstream, triggering changes in stream and floodplain morphology and function. During the 19th century the shift from artisanal to industrialised mining resulted in a rapid increase in the scale and extent of environmental change. This paper presents results from a multi-disciplinary research program investigating the environmental effects of 19th-century gold mining on waterways in south-eastern Australia. Archaeological and geospatial landscape survey are combined with historical data modelling and geomorphological analysis to examine the extractive processes that produced sediment in headwater regions and how this influenced fluvial processes operating on downstream waterways and floodplains. Our case study of the Three Mile-Hodgson Creek system on the Ovens (Beechworth) goldfield in north-east Victoria indicates that miners mobilised up to 7.3 million m3 of sediment in this small catchment alone. Results of the research suggest that tailings dams and sludge channels in this catchment are important archaeological evidence for early attempts to manage industrial waste.

The Victorian gold rush began in 1851, resulting in massive demographic, land use, and social changes (Serle 1968). Rivers, during much of the gold mining history of Victoria, were used as a “free” resource, both to extract and process sediment. The effect on river systems around the state was catastrophic. A quarter of the length of the main streams was damaged. Even though the devastating environmental impact of Victorian gold mining was recognised at the time, it appears to have been forgotten today (Figure 1). This is despite extensive documentation of the number of mining operations, methods used, resultant environmental impacts and consequent legislation. The ARC discovery project “Rivers of gold” set up a multi-disciplinary team to try and reconstruct the historical development of mining across the state of Victoria, and to determine the legacy of this mining.

A growing worldwide body of literature is demonstrating the geomorphic and ecological roles played by wood in rivers. After more than a century of removing wood from rivers in many parts of the world, researchers and managers are now interested in returning the load of wood back to a more natural condition. The mechanical placement of wood in rivers is expensive, and so it is useful to know how long it will take for in‐stream wood loads to passively recover a target load by recruitment from riparian forests. Of fundamental interest to managers and researchers alike are the questions: (1) can a river passively recover to a preremoval load of wood, and (2) if so, how long will recovery take? We address these questions using the example of the anabranching King River, Northeast Victoria, Australia, which was desnagged twice: once in 1957 and again in 1980. We predict a recovery time of 255 ± 23 years using a complete census of recovering wood loads to develop and parameterize a mass balance delivery model run in a Monte Carlo simulation. Our results indicate that with a healthy supply of riparian vegetation and minimal interference from managers, rivers are likely to passively recover natural wood loads at least two and a half centuries after desnagging. Using the data and methods described in this paper, we develop a theory of recovery, conceptually describing the recovery process as a sequence of five stages that can be used to monitor and track wood loads through time.

A significant but previously unquantified factor in anthropogenic change in Australian rivers was the release of large volumes of sediment produced by gold mining in the 19th century. This material, known historically as ‘sludge’, rapidly entered waterways adjacent to mining areas and caused major environmental damage. We interrogate detailed historical records from the colony of Victoria spanning the period 1859 to 1891 to reconstruct the temporal and spatial distribution of sediment volumes released by mining activity. Based on these records, we estimate that at least 650 million m3 of material was released into rivers in the 19th century, exceeding natural sediment yield to rivers by an average 140 times. Although the sediment yield per river is not high when compared with examples around the world, the widespread impacts of sludge distinguishes the case of Victoria. The sludge affected three-quarters of catchments in the state due to the large number of small mining operations spread over hundreds of creeks and gullies across the colony. The impacts of sludge to rivers and farmland filled newspapers for more than 50 years and generated numerous parliamentary inquiries. Today, the impacts are largely forgotten and unrecognised, as are the continuing impacts on aquatic systems. The estimates generated in this study provide a basis for understanding the continuing impact of historical mining on Victorian rivers.

The conceptual development, design, ground test, and flight test of a novel weapons-cavity acoustics store separation pod led to several positive outcomes to aid in the understanding of cavity–stor...

Reporting uncertainty in environmental measurements and estimates is important for cross-comparison and inter-comparison of sites and other spatial units. One such measure is the load of large in-stream wood in river systems. In this paper we propose the use of the Weibull distribution to describe the central tendency and variability of wood loads along a river reach. We illustrate the link between the average wood load and the central tendency or scale parameter of the Weibull distribution. The shape of the Weibull distribution is strongly related to the ability of rivers to transport and rearrange the wood in a reach. We use six Victorian rivers to test the fit of the Weibull distribution, showing that the Weibull is a useful and flexible distribution that provides common reporting metrics useful for future studies. Using common reporting metrics provides a stronger tool for comparisons of wood loads between rivers and with reaches. Copyright © 2016 John Wiley & Sons, Ltd.

A channel evolution model (CEM) represents stages of channel development in response to specific types of disturbance. In recent years, classic incised/disturbed CEMs have provided process-based understanding of channel adjustment and formed the cornerstone for river restoration and rehabilitation. While broadly applicable to alluvial systems in temperate and semi-arid regions, these models cannot be assumed to be universally applicable. Lockyer Creek in South East Queensland, Australia, has notable macrochannel morphology and is subject to high hydrological variability typical of many subtropical climates. The aim of this paper is to present a case study of channel adjustment and evolution in lower Lockyer Creek, to determine if existing CEMs adequately describe processes of channel adjustment and the associated trajectories of change typical of river systems in subtropical settings. Lockyer Creek has recently been subjected to a spate of flooding resulting in significant channel erosion. This offers an ideal opportunity to investigate the nature and rate of channel adjustment processes and place them in context of longer-term geomorphic adjustments in these systems. Specifically we address two questions. Firstly, do the classic incised/disturbed CEMs adequately represent the observed macrochannel adjustment? Secondly, if current CEMs are inadequate, what is the channel evolution model for these systems, of which lower Lockyer Creek is an example? Results show that these are non-incising systems where wet-flow bank mass failures (WBMFs) are the dominant process of channel adjustment. They occur within the channel bank top boundary resulting in no change to overall bank-top width. Furthermore, subsequent floods deposit sediment in the failure scars and failure headwalls generally do not retreat beyond channel bank-top. Channel adjustment has not followed the evolutionary stages for incised/disturbed channels and a new four stage macrochannel CEM is outlined for these subtropical systems. The proposed CEM illustrates a cyclical pattern of erosion by channel bank WBMF followed by re-aggradation, through deposition and oblique processes, contributing to bank rebuilding. This CEM provides sufficient information to determine the stage of macrochannel adjustment, enabling decisions to be made over whether intervention is required or will be successful.

Open cavities exposed to a grazing flow can exhibit large pressure fluctuations, which may result in damage to stores or components carried within a weapon bay. This study investigates the use of passive resonant absorbers based on Helmholtz resonators to attenuate the problematic pressure fluctuations that arise in cavity flows, under both transonic (0.80

A growing body of field, theoretical and numerical modelling studies suggests that predicting river response to even major changes in input variables is difficult. Rivers are seen to adjust rapidly and variably through time and space as well as changing independently of major driving variables. Concepts such as Self-Organized Criticality (SOC) are considered to better reflect the complex interactions and adjustments occurring in systems than traditional approaches of cause and effect. This study tests the hypothesis that riverbank mass failures which occurred both prior to, and during, an extreme flood event in southeast Queensland (SEQ) in 2011 are a manifestation of SOC. Each wet-flow failure is somewhat analogous to the 'avalanche' described in the initial sand-pile experiments of Bak et al. (Physical Review Letters, 1987, 59(4), 381-384) and, due to the use of multitemporal LiDAR, the time period of instability can be effectively constrained to that surrounding the flood event. The data is examined with respect to the key factors thought to be significant in evaluating the existence of SOC including; non-linear temporal dynamics in the occurrence of disturbance events within the system; an inverse power-law relation between the magnitude and frequency of the events; the existence of a critical state to which the system readjusts after a disturbance; the existence of a cascading processes mechanism by which the same process can initiate both low-magnitude and high-magnitude events. While there was a significant change in the frequency of mass failures pre- and post-flood, suggesting non-linear temporal dynamics in the occurrence of disturbance events, the data did not fit an inverse power-law within acceptable probability and other models were found to fit the data better. Likewise, determining a single 'critical' state is problematic when a variety of feedbacks and multiple modes of adjustment are likely to have operated throughout this high magnitude event. Overall, the extent to which the data supports a self-organized critical state is variable and highly dependent upon inferential arguments. Investigating the existence of SOC, however, provided results and insights that are useful to the management and future prediction of these features.

An examination of a rectangular cavity with a length-to-depth ratio of 5.67 was tested at Mach 0.7 and 1.5 with corresponding Reynolds numbers of 6.49×106 and 7.35×106/m, respectively. High-speed shadowgraph movies were simultaneously sampled with dynamic pressure sensors at 75 kHz. From the high-speed shadowgraph movies, observations of the cavity flowfield indicate that linear models like Rossiter’s equation and Helmholtz resonance may be too simplistic to correctly model rectangular cavity flow physics. Some of the observations are as follows. In the cavity’s shear layer, large-scale vortices have been found to be nonperiodic. The shear-layer convection velocity was determined to be 0.6U∞ at both Mach numbers, which is significantly higher than Rossiter’s equation predicts for correct peak frequency matching. Shear-layer entrainment of freestream flow starts and feeds the acoustic cycle inside the cavity. There are more acoustic wave in the cavity at any one time than has been considered before, which ...

A rectangular cavity with an L/D of 5.67 was tested at Mach 1.5 with a corresponding Reynolds number of 7.35 × 106/m. High speed shadowgraph movies were simultaneously sampled with dynamic pressure sensors at 75 kHz. Fourier analysis was performed on the high speed movies as well as the dynamic pressure data, which resulted in the determination of spatial and temporal characteristics of the dominant cavity frequencies in the flow field. Four passive flow control devices were tested, two of which have historically performed well at reducing the acoustic tones and broadband noise levels. The other two devices were less effective. Flow physics based on the detailed analysis of the high speed shadowgraphs and dynamic pressures sensors is presented.

Wet-flow river bank failure processes are poorly understood relative to the more commonly studied processes of fluvial entrainment and gravity-induced mass failures. Using high resolution topographic data (LiDAR) and near coincident aerial photography, this study documents the downstream distribution of river bank mass failures which occurred as a result of a catastrophic flood in the Lockyer Valley in January 2011. In addition, this distribution is compared with wet flow mass failure features from previous large floods. The downstream analysis of these two temporal data sets indicated that they occur across a range of river lengths, catchment areas, bank heights and angles and do not appear to be scale-dependent or spatially restricted to certain downstream zones. The downstream trends of each bank failure distribution show limited spatial overlap with only 17% of wet flows common to both distributions. The modification of these features during the catastrophic flood of January 2011 also indicated that such features tend to form at some ‘optimum’ shape and show limited evidence of subsequent enlargement even when flow and energy conditions within the banks and channel were high. Elevation changes indicate that such features show evidence for infilling during subsequent floods. The preservation of these features in the landscape for a period of at least 150 years suggests that the seepage processes dominant in their initial formation appear to have limited role in their continuing enlargement over time. No evidence of gully extension or headwall retreat is evident. It is estimated that at least 12 inundation events would be required to fill these failures based on the average net elevation change recorded for the 2011 event. Existing conceptual models of downstream bank erosion process zones may need to consider a wider array of mass failure processes to accommodate for wet flow failures.

Traditionally, in rectangular cavity research the fundamental physical understanding of cavity resonance is a handful of empirical equations. The authors have recently derived the cavity acoustic wave equation and the cavity hydrodynamic wave equation from Lighthill’s and Curle’s acoustic analogy wave equations. By changing the cavities boundary conditions with half span doors, in both doors open and one door closed configurations, the resulting pressure spectrum changes are attributable to the boundary condition changes and can capture the large frequency shift differences due to the door configuration changes. These results suggest these derived cavity wave equations are correct.

While the impacts of regulation on river systems have been investigated, the main focus of the research has been on ecological and in-channel impacts. An understanding of the impacts of regulation on floodplain geomorphology is needed in order to inform management actions, in particular environmental flows. Concurrently with a traditional literature review on the effects of river regulation on floodplain geomorphology, we undertook a systematic review of the evidence using causal criteria analysis. The causal criteria approach tested evidence from multiple studies against a ‘checklist’ of criteria, constructing an argument for causality by combining a number of pieces of evidence into a single coherent argument. The causal criteria analysis only found support for one hypothesized cause-effect linkage in the conceptual model. In contrast, after discussing many of the conceptual model linkages, the traditional review provided a series of eight hypothesised scenarios to highlight the different possibilities for floodplain geomorphic change resulting from regulation. The difference was partly as a result of the time taken to enter studies into the Eco Evidence Database, but mainly because of the quality of evidence from geomorphic studies. Low statistical rigour in study designs meant that many papers were inadmissible as evidence. Thus, the causal criteria analysis made transparent the quality of data used in a traditional literature review that might subsequently be used to justify costly management recommendations.

Empirical and theoretical solutions to predict acoustic tones inside a rectangular cavity have been proposed throughout the years and can result in inaccurate frequency prediction depending on mode number. A new theoretical approach has been developed to explain acoustic wave formation and motion inside the cavity. The derived frequencies from this new approach match to within the uncertainty error of the experimental data that is used for comparison. Using the same physical and fluid properties, a simulation of the acoustic wave formation and motion inside the cavity results in an acoustic frequency spectrum that compares extremely well with the experimental acoustic frequency spectrum.

The summer discharge pattern of the Skeldal River, which drains a 560 km2 partly glacierized catchment in north-east Greenland, is dominated by diurnal oscillations reflecting variations in the melt rate of snow and ice in the basin. Superimposed on this diurnal pattern are numerous short-lived discharge fluctuations of irregular periodicity and magnitude. The larger fluctuations are described and attributed to both rainfall events and periodic collapse of the glacier margin damming flow from beneath the Skelbrae glacier. Other minor fluctuations are less readily explained but are associated with changes in the channelized and distributed reservoirs and possibly temporary blockage of subglacial conduits caused by ice melt with subsequent damming. Fluctuations in suspended sediment concentration (SSC) are normally associated with discharge fluctuations, although examples of ‘transient flushes’ were observed where marked increases in SSC occurred in the absence of corresponding discharge variations. A strong relationship between the event discharge increase and event SSC increase for rainfall-induced events was established, but no such relationship existed for non-rainfall-induced events. There is some evidence for an exhaustion effect in the SSC patterns both at the event time-scale and as the month proceeds. A mean suspended sediment load of 1765 ± 0·26 t day−1 was estimated for the study period, which would be equivalent to a suspended sediment yield of 732 ± 4 t km−2 year−1. Copyright © 2001 John Wiley & Sons, Ltd.

The eastern Badia of the Hashemite Kingdom of Jordan is a landscape developed predominantly on late Tertiary and Quaternary basalt lava flows, which vary in age between 8.9 million and 0.1 million years. Pyroclastic deposits are associated with remnant volcanic cones. There is limited, seasonal rainfall. Natural vegetation regenerates during cool, damp months. Slopes, which range from concave to convex forms and have varying relief, can be related to different basalts and the time since emplacement. Much of the ground surface is mantled with boulders. In many places the continuity of boulder cover produces a desert pavement. Clasts show differing degrees of burial or exhumation, depending on the surrounding topography. Water and sediment movement are important to landscape development. Much sediment is deposited in pans, which evolve at topographic lows. The pans, known locally as Qa, vary in form depending on drainage network development. Transitional forms, known as Marab, develop where wadis widen out and sediments are deposited along ephemeral channels. Groundwater is significant, with three aquifers beneath much of the eastern Badia. Recharge of the upper aquifer is predominantly on the footslopes of the Druze Mountains, with north to south flow. Groundwater extraction has resulted in the expansion of agriculture, with consequent changes in soil and water quality.

Few studies have considered downstream changes in bank erosion rates and variability along single river systems. This paper reports some preliminary results of an intensive and direct field monitoring exercise of bank erosion rates on 11 sites along 130 km of the 3315 km2 Swale-Ouse river system in northern England over a 14·5 month period. Data were collected at active sites using grid networks of erosion pins read at c. 18–30 day intervals and bank-line resurveys. Erosion rates were relatively high for a river of this scale: spatially averaged bank erosion magnitudes over the 14·5 months varied from 82·7 mm to 440·1 mm, although at one highly mobile reach retreat of 1760 mm was recorded over 4 months. Bank erosion rates tended to peak in mid-basin, possibly because of an optimum combination there of high stream powers and erodible bank materials, as predicted theoretically by Lawler (1992, 1995). The piedmont (upland–lowland transition) zone was especially active. Graphical erosion representations for specific periods, however, showed that bank retreat was often highly localized within individual sites. Strong seasonal variations in erosion rate were also observed with a significant winter (December–March) peak. A novel finding, however, was the apparent downstream increase in the length of the erosion ‘season’, with measurable retreat occurring at the lower sites from September to July. This is interpreted as a reflection of a richer mix of bank erosion processes at the downstream sites, where mass failure, fluid entrainment and weathering processes are all active, with each process group having its own, but overlapping, temporal (seasonal) domain. Copyright © 1999 John Wiley & Sons, Ltd.

The majority of the world's floodplains are dammed. Although some implications of dams for riverine ecology and for river channel morphology are well understood, there is less research on the impacts of dams on floodplain geomorphology. We review studies from dammed and undammed rivers and include influences on vertical and lateral accretion, meander migration and cutoff formation, avulsion, and interactions with floodplain vegetation. The results are synthesized into a conceptual model of the effects of dams on the major geomorphic influences on floodplain development. This model is used to assess the likely consequences of eight dam and flow regulation scenarios for floodplain geomorphology. Sediment starvation downstream of dams has perhaps the greatest potential to impact on floodplain development. Such effects will persist further downstream where tributary sediment inputs are relatively low and there is minimal buffering by alluvial sediment stores. We can identify several ways in which floodplains might potentially be affected by dams, with varying degrees of confidence, including a distinction between passive impacts (floodplain disconnection) and active impacts (changes in geomorphological processes and functioning). These active processes are likely to have more serious implications for floodplain function and emphasize both the need for future research and the need for an “environmental sediment regime” to operate alongside environmental flows.

Iwao’s mean crowding-mean density relation can be treated both as a linear function describing the biological characteristics of a species at a population level, or a regression model fitted to empirical data (Iwao’s patchiness regression). In this latter form its parameters are commonly used to construct sampling plans for insect pests, which are characteristically patchily distributed or overdispersed. It is shown in this paper that modifying both the linear function and statistical model to force the intercept or lower functional limit through the origin results in more intuitive biological interpretation of parameters and better sampling economy. Firstly, forcing the function through the origin has the effect of ensuring that zero crowding occurs when zero individuals occupy a patch. Secondly, it ensures that negative values of the intercept, which do not yield an intuitive biological interpretation, will not arise. It is shown analytically that sequential sampling plans based on regression through the origin should be more efficient compared to plans based on conventional regression. For two overdispersed data sets, through-origin based plans collected a significantly lower sample size during validation than plans based on conventional regression, but the improvement in sampling efficiency was not large enough to be of practical benefit. No difference in sample size was observed when through-origin and conventional regression based plans were validated using underdispersed data. A field researcher wishing to adopt a through-origin form of Iwao’s regression for the biological reasons outlined above can therefore be confident that their sampling strategies will not be affected by doing so.

Riverbank erosion is a major contributor to catchment sediment budgets. At large spatial scales data is often restricted to planform channel change, with little information on process distributions and their sediment contribution. This study demonstrates how multi-temporal LiDAR and high resolution aerial imagery can be used to determine processes and volumes of riverbank erosion at a catchment scale. Remotely sensed data captured before and after an extreme flood event, enabled a digital elevation model of difference (DoD) to be constructed for the channel and floodplain. This meant that: the spatial area that could be assessed was extensive; three-dimensional forms of bank failures could be mapped at a resolution that enabled process inference; and the volume and rates of different bank erosion processes over time could be assessed. A classification of riverbank mass failures, integrating form and process, identified a total of 437 mass failure polygons throughout the study area. These were interpreted as wet flow mass failures based on the presence of a well defined scarp wall and the absence of failed blocks on the failure floor. The failures appeared to be the result of: bank exfiltration, antecedent moisture conditions preceding the event, and the historic development of the channel. Using one-dimensional hydraulic modelling to delineate geomorphic features within the main boundary of the macrochannel, an estimated 1 466 322m2 of erosion was interpreted as fluvial entrainment, occurring across catchment areas from 30 to 1668 km2. Only 8% of the whole riverbank planform area was occupied by mass failures, whilst fluvial entrainment covered 33%. A third of the volume of material eroded came from mass failures, even though they occupied 19% of the eroded bank area. The availability of repeat LiDAR surveys, combined with high-resolution aerial photography, was very effective in erosion process determination and quantification at a large spatial scale

An examination of a rectangular cavity with an L/D of 5.67 was tested at Mach 1.5 with a corresponding Reynolds number of 2.3x106/ft. High speed shadowgraph movies were simultaneously sampled with dynamic pressure sensors at 75 kHz. Fourier analysis was performed on the high speed movies as well as the dynamic pressure data, which resulted in determining the locations of dominant cavity frequencies in the flow field. Four passive flow control devices were tested, two of which have historically preformed well, while two neither reduced the main acoustic tones nor reduced the broadband levels. From the high speed shadowgraph movies, observations are made in the changes in the cavity flow physics when the passive flow control devices are used, and will be discussed.

An examination of a rectangular cavity with an L/D of 5.67 was tested at Mach 0.7 with a corresponding Reynolds number of 2x10 6 /ft. High speed shadowgraph movies were simultaneously sampled with dynamic pressure sensors at 75 kHz. Fourier analysis was performed on the high speed movies as well as the dynamic pressure data, which resulted in determining the locations of dominant cavity frequencies in the flow field. Five passive flow control devices were tested, three of which have historically preformed well, while two neither reduced the main acoustic tones nor reduced the broadband levels. From the high speed shadowgraph movies, observations are made in the changes in the cavity flow physics when the passive flow control devices are used, and will be discussed.

An examination of a rectangular cavity with an L/D of 5.67 was tested at Mach 0.7 and 1.5 with corresponding Reynolds numbers of 2x10 6 /ft and 2.3x10 6 /ft, respectively. High speed shadowgraph movies were simultaneously sampled with the dynamic pressure sensors at 75 kHz. Fourier analysis was performed on the high speed movies as well as the dynamic pressure data which resulted in determining the locations of dominant cavity frequencies in the flow field. From the high speed shadowgraph movies, observations of the in the cavity flow physics are discussed. Several cavity related issues are examined e.g. How do vortices form in the shear layer? What is the actual starting mechanism for these cavity acoustic tones? How do the cavity acoustic tones affect the shear layer?

A new optical turbulence reduction cavity model has been built and tested in the Trisonic Gasdynamic Facility (TGF) at Air Force Research Laboratory (AFRL). The new model replaces the 1970’s era model and has optical quality fused silica windows that will allow non-intrusive flow field measurements to be made. The results presented in this paper compare the current optical turbulence reduction cavity model with the historic data from the old turbulence reduction cavity model and examines some passive flow control devices.

The combined trends toward internal carriage of weapons in modern aircraft and the design of new weapons to be neutrally stable for in creased performance have increased the probability that unsteady aerodynamics will effect store separation trajectories. Reports from time accurate computational fluid dynamics trajectory simulations have shown trajectory sensitivity to time of weapon release. Typical wind tunnel data collected to support store separation analysis cannot detect thi s effect since the data collected consists of time averaged store loads. Flight testing to inves tigate effects of bay unsteadiness has not been done since it is expensive and typically there are insufficient funds to conduct repeated store drops at identical flight conditions. Carefu lly designed and conducted small scale drop testing in wind tunnels provides a means to identif y the effect of unsteady weapons bay aerodynamics on store separation trajectories. Time accurate computational fluid dynamics trajectory analysis results on the Small Smart Bomb separating from an F-111 aircraft and a GBU-12 separation from the B-52 aircraft are reviewed. Small scale drop test data from a generic 10% scale rectangular cavity in a flatplate and from a 6% scale B-1B are introduced to provide experimental evidence of the effect of u nsteady flow on the store separation trajectory.

Stream bank erosion often isolates the root plate of a riparian tree on a pedestal of sediment jutting out from the stream bank. To our knowledge, these root-plate abutments have not been formally described. Apart from being a landform in their own right, abutments are of interest because their morphology integrates the complex effects of trees on bank erosion processes. From measuring seven abutments formed along the Acheron River in southeastern Australia, we conclude the following: (1) Roots from a single tree increase the resistance of impinging banks in a semi-circle centered on the trunk. The abutment has a radius that is always smaller than (usually less than half) the canopy radius. This relationship holds for four dominant riparian tree species along the Acheron River, situated on gravel and sandy-loam banks that are from 1 m to 4 m high. (2) All abutments are deeply undercut, with most of the abutment formed of a 0.5 m to 1 m thick overhanging plate of finer sediments reinforced by roots. The deviation of the curve of the concave stream bank, at the bank toe below trees, indicates that trees provide some bank toe strengthening, even when the bank is nearly 4 m high. However, the strengthening from single trees is not enough to materially alter the migration rate of a meander bend. (3) The bed is deepened at the tip of the abutment by up to 30% of the bank height. Thus the abutments have a secondary effect on channel morphology. © 2004 by the American Geophysical Union.

One objective of the USAF/RAAF F-111G flight test was to capture and compare separation trajectory differences of the generic Small Smart Bomb (SSB) weapons from a modified Royal Australian Air Force (RAAF) F-111 weapons bay, with and without the Active Separation Control (ASC) blowing device activated. The ASC blowing device acts like a “virtual spoiler” at the leading edge of the weapons bay to both reduce weapons bay acoustics and enhance weapon separation characteristics. Flight test trajectory data was captured with cameras mounted on the inboard wing pylon and aft fuselage centerline of the RAAF F-111G. The flight test separation data was compared with 1/15 scale F-111 wind tunnel data obtained in the USAF AEDC 4T wind tunnel. This paper will present and compare wind tunnel and flight test separation and acoustic data with and without bay leading edge blowing utilizing the ASC device.

Stream bank condition is an important physical form indicator for streams related to the environmental condition of riparian corridors. This research developed and applied an approach for mapping bank condition from airborne light detection and ranging (LiDAR) and high-spatial resolution optical image data in a temperate forest/woodland/urban environment. Field observations of bank condition were related to LiDAR and optical image-derived variables, including bank slope, plant projective cover, bank-full width, valley confinement, bank height, bank top crenulation, and ground vegetation cover. Image-based variables, showing correlation with the field measurements of stream bank condition, were used as input to a cumulative logistic regression model to estimate and map bank condition. The highest correlation was achieved between field-assessed bank condition and image-derived average bank slope (R2 1/4 0.60, n 1/4 41), ground vegetation cover (R2 1/4 0.43, n 1/4 41), bank width/height ratio (R2 1/4 0.41, n 1/4 41), and valley confinement (producer's accuracy 1/4 100%, n 1/4 9). Crossvalidation showed an average misclassification error of 0.95 from an ordinal scale from 0 to 4 using the developed model. This approach was developed to support the remotely sensed mapping of stream bank condition for 26,000 km of streams in Victoria, Australia, from 2010 to 2012.

International audience; Food production in cities has long been a tradition in many countries around the world and a mainstream activity for many developed countries. While urban agriculture plays an important role in increasing food security and social well-being, it comes with significant costs and constraints. Here, we review the growth of urban agriculture throughout the developed world in order to clarify the different benefits, risks, and hindrances associated with the practice. Through this analysis, we identify the need for better understanding of the following five aspects if urban agriculture is to make a meaningful contribution to food security and social well-being in the future: (1) the impacts of continued urban sprawl and loss of peri-urban agricultural land; (2) appropriate government and institutional support at local, regional, and country levels; (3) the role of urban agriculture in self-sufficiency of cities; (4) the risks posed by pollutants from agriculture to urban ecosystems and from urban ecosystems to agriculture; and (5) the carbon footprint of urban agriculture and use of “food miles.” If urban agriculture is to have a legitimate place in resolving the global food crisis as advocates claim, then it is time to take urban agriculture seriously and assess more rigorously both the positive and negative impacts, especially carbon emissions. Only then can the world’s limited resources be properly allocated to the development of urban agriculture.

International audience; Urban agriculture is receiving increasing attention throughout the developing world, but debate rages as to whether it is a blessing or a curse. Some see it as savior for the poor, providing food, and livelihoods, yet to others it is responsible for harboring and vectoring pathogenic diseases and is an archaic practice that has no place along the path toward development. Consequently, the activity receives a mixed reception, and despite much support in many instances, it certainly does not enjoy universal unimpeded progress. Here, we undertake a global tour of urban agriculture throughout the developing world in an attempt to elucidate the various benefits, costs, and hindrances associated with the practice. Through this analysis we identify the need for better understanding of the following six aspects if urban agriculture is to make a meaningful contribution to food security and sustenance of livelihoods in the future: (1) the global and regional extent of urban agriculture; (2) the contribution of urban agriculture to communicable diseases, especially malaria but also diarrheal disease; (3) the role that urban agriculture does and/or could play in abating both malnutrition and obesity; (4) the impacts of urban agriculture on women; (5) appropriate methods of achieving governance and institutional support; and (6) the risks posed by chemical pollutants, particularly as Africa becomes increasingly industrialized. Overlaying these, we suggest that the time is ripe to extend the debate about urban agriculture’s positive and negative environmental impacts—especially in relation to carbon emissions—from primarily a developed world concern to the developing world, particularly since it is the developing world where population growth and consequent resource use is increasing most rapidly.

This report describes the results of the first and second seasons of field work by an interdisciplinary research team studying the landscape history of the upper Orontes Valley near Homs in western Syria. Initial discussions address the value of survey data to Syrian archaeology, the research aims of the project and describe the survey area. The project methodology, which includes a combination of both extensive and intensive survey methods, is outlined, and the use of satellite imagery as a means of site location discussed. Work on geomorphological processes and off-site artefact distributions has facilitated the development of sampling strategies for intensive surface collection planned for 2002 and 2003. A test core has established that pollen is well-preserved in the silts of Lake Qattine, which appear to offer a west Syrian palaeoenvironmental sequence. Preliminary work in the basalt terrain west of Homs has allowed the refinement of methodologies for the mapping and analysis of cairns and field systems which predominate in this area, and has highlighted the threat resulting from current bulldozing. The report concludes with some preliminary observations on the main trends as these are emerging from the data.