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Modeling network‐scale sediment (dis)connectivity and its response to anthropic pressures provides a baseline understanding of river processes and sediment dynamics that can be used to forecast future hydro‐morphological changes in river basins. However, this requires a solid understanding of how a system is currently operating, and how it operated in the past. We present the basin‐scale, dynamic sediment connectivity model D‐CASCADE, which combines concepts of network modeling with empirical sediment transport formulas to quantify spatiotemporal sediment (dis)connectivity in river networks. D‐CASCADE accounts for multiple factors affecting sediment transport, such as spatiotemporal variations in hydrological regime, different sediment grain sizes, sediment entrainment and deposition. Add‐ons are included in D‐CASCADE to model local changes in river geomorphology driven by sediment‐induced variations in features such as channel width. We apply D‐CASCADE to the well‐documented Bega River catchment, NSW, Australia, where significant geomorphic changes to rivers have occurred post European colonization (after 1850s), including widespread channel erosion and sediment mobilization. The Bega catchment provides a useful case study to test D‐CASCADE, as original source data on the historical sediment budget are available. By introducing historic drivers of change in the correct chronological sequence, the D‐CASCADE model successfully reproduced the timing and magnitude of major phases of sediment transport and associated channel adjustments over the last two centuries. With this confidence, we then ran the model to test how well it performs at estimating future trajectories of basin‐scale sediment transport and sediment budgets at the river reach scale. Key Points: We present the new dynamic D‐CASCADE model for network‐scale river sediment (dis)connectivity modelingD‐CASCADE successfully reproduced major historic geomorphological changes observed in the Bega river network after European settlementD‐CASCADE is used to test future trajectories of basin‐scale sediment transport and reach‐scale sediment budget in the Bega river system [ABSTRACT FROM AUTHOR]

The extent to which Aboriginal Australians used fire to modify their environment has been debated for decades and is generally based on charcoal and pollen records rather than landscape responses to land-use change. Here we investigate the sensitivity of in-situ-produced 10Be, an isotope commonly used in geomorphological contexts, to anthropogenic perturbations in the southeastern Australian Tablelands. Comparing 10Be-derived erosion rates from fluvial sediment (8.7 ± 0.9 mm k.y.-1; 1 standard error, SE; n = 11) and rock outcrops (5.3 ± 1.4 mm k.y.-1; 1 SE; n = 6) confirms that landscape lowering rates integrating over 104-105 yr are consistent with rates previously derived from studies integrating over 104 to >107 yr. We then model an expected 10Be inventory in fluvial sediment if background erosion rates were perturbed by a low-intensity, high-frequency Aboriginal burning regime. When we run the model using the average erosion rate derived from 10Be in fluvial sediment (8.7 mm k.y.-1), measured and modeled 10Be concentrations overlap between ca. 3 ka and 1 ka. Our modeling is consistent with intensified Aboriginal use of fire in the late Holocene, a time when Aboriginal population growth is widely recognized. [ABSTRACT FROM AUTHOR]

The concept of the geomorphic cycle is a foundational principle in geology and geomorphology, but the topographic evolution of a single landscape from inception to maturity has been difficult to demonstrate in nature. The onlapping dunes of the Cooloola Sand Mass (CSM) in eastern Australia provide an ideal chronosequence to evaluate landscape evolution. Here commonly assumed properties on which landscape models are based (i.e., conservation of mass and major factors contributing to landscape change) can be physically measured and accounted for. Our field based measurements and forward numerical models demonstrate that dunes, like other landscapes, relax in an exponential manner. The emplaced dunes evolve through an initial phase of rapid topographic adjustment associated with the dominance of landsliding. This phase continues for ∼1 kyr until hillslope gradients are lowered below their angle of repose (0.65 m m−1 or 33°). Once sufficiently lowered, the dunes evolve through slow, soil creep processes. These findings of dual transport regimes are validated by stratigraphic records at all excavated dune foot-slopes and we propose that this evolution can be measured by the distribution of curvature (C) of a landform, specifically its standard deviation (σ C), as a measure of surface roughness. Surface roughness smooths with time through diffusional sediment transport that lowers local relief. The value and its rate of smoothing can define the stage in evolutionary development and help infer processes, which makes it an important morphometric tool for understanding landscapes. These observations highlight that under stable evolutionary conditions, the development of the landscape is governed by the physical properties of the dune's parent material. In addition, our findings support landscape evolution inferences from numerical and physical models and the coupling of granular material physics with landscape change. • Measured evolution of a natural dune landform from emplacement to maturity. • Episodic mass-movement dominates slope evolution on young emplaced dunes. • Soil creep processes controls slope evolution on older emplaced dunes. • Angle of repose defines the transition from non-linear to linear slope processes. • Surface roughness is directly related to variability in erosion rates. [ABSTRACT FROM AUTHOR]

Summary: Rainfall patterns have a well recognised effect on erosion, sediment transport and water quality. In recent years, there has been a focus on understanding the impact of changing climate on rainfall and storm patterns both globally and in Australia with research directed to examine how the global hydrological cycle will respond to climate change. This study investigates the effect of different rainfall patterns on erosion and resultant water quality in a small study catchment in the Northern Territory, Australia. Rainfall projections for the study area indicate an increase in storm activity but there has been little assessment of this variability and its impact on resultant water quality. Numerical modelling studies are an essential means of assessing hydrological and geomorphological impacts of changing rainfall patterns resulting from climate variability. Here, a numerical model that simulates erosion, deposition and water quality (CAESAR) is used to assess several different rainfall scenarios over a 1000year modelled period. The model results reveal that increased rainfall amount and intensity increases sediment transport rates but predicted annual sediment concentration (total load) was variable and non-linear but within predicted ranges for the catchment and region. In terms of impact of increased rainfall and storms on sediment output, the more frequent returns of high intensity rainfall increases sediment output but average concentration may reduce as a result of the increased discharge. Subtle thresholds may operate as a result of both external and internal forcings where differences in rainfall events and resultant sediment delivery produce rapid change in erosion rates and patterns producing autogenic adjustments within the catchment. The study provides a sensitivity analysis of both model parameterisation and differing rainfall scenarios on long-term water quality as well as a method for assessing the impact of rainfall variability on catchment scale hydrology. [Copyright &y& Elsevier]

Abstract: We present the most complete and new high-resolution multibeam bathymetry datasets from the shelf to the basin in the Ribbon Reef region, northern Great Barrier Reef (GBR). Analysis of these data, combined with existing side-scan sonar data provides a detailed morphologic framework of the submarine canyon system and other related features, their spatial distribution, controlling factors on their evolution, and evidence of recent sedimentary activity. Two morphologically different submarine canyon types are recognised: 1) shelf-incised canyons whose heads are indented into the shelf-break at shallow-water depths (about 60 to 80m). These canyons can be single-fed or multi-fed depending on the number of tributaries that merge into the main canyon valley. According to the degree of connection with the shelf, these canyons can be reef-blocked, partly reef-blocked or shelf-connected; 2) slope-confined canyons, which are located at deeper waters in the slope and show a different canyon head morphology. Canyon formation and development of the different canyon types is explained according to a four-phase model. In the first phase, localised slope failures and/or sediment gravity flows may lead to the formation of an initial canyon by retrogressive headward or downslope erosion respectively. These processes continue during the second transitional phase, leading to upslope canyon progression. Finally, canyons breach the shelf-break during a mature stage that represents the more active phase in the canyon evolution. The development of an extensive shelf-edge barrier reef (Ribbon Reefs) represents a fourth phase that conditioned the sedimentary dynamics of the canyons. The location and morphology of this reef barrier determine the type and amount of sediment supply by controlling the connection of the canyon head with the shelf drainage system. Recent canyon activity is evidenced by the presence of erosive and depositional features that include submarine landslides, gullies and rills on the canyon walls and slopes, sandwaves migrating along the canyons floors, and sediment gravity flows deposited on the lower canyons and adjacent basin floor. [Copyright &y& Elsevier]

Abstract: Analysis of the changes in rates of catchment sediment storage can provide material evidence of the impact of landscape disturbance on catchment sediment flux. A number of studies have suggested increased sediment yields from the rivers draining to the Great Barrier Reef since European settlement in the mid-nineteenth century. Many of these predictions, which indicate increases between four to ten times the pre-disturbance estimates, are based on large-scale catchment modelling that make some critical assumptions about pre-disturbance erosion rates and/or sediment delivery ratios. In addition, the majority have not been validated by empirical data. This study uses single-grain OSL dating and 137Cs depth profiles to determine pre- and post-floodplain accretion rates in Theresa Creek, a subcatchment of the dry-tropical Fitzroy River basin. We demonstrate that floodplain accretion rates have increased by three to four times since European settlement (ca. A.D. 1850). Decreased rates of floodplain accretion since the mid-twentieth century at sites contributed to by gullied terrain suggest a decrease in the supply of sediment derived from gully networks. In contrast, floodplain accretion rates from areas dominated by cultivation remain high. Widespread in-channel benches deposited since European settlement are stable and appear to be important stores of large volumes of sediment. Low magnitude increases in post-disturbance floodplain sedimentation rates (3 to 4 times), in comparison to those reported from mainly temperate climates (10 to 100 times), are attributed to the naturally high sediment loads typical of dry-tropical catchments. Consequently, previous predictions of large post-disturbance increases in sediment yields from large dry-tropical catchments draining to the Great Barrier Reef are likely to be overestimates. [Copyright &y& Elsevier]

Abstract: This paper describes the “miniphone,” an instrument to measure aeolian saltation. This instrument is a modified electret microphone that detects the impacts of individual grains. The unidirectional miniphone is inexpensive (approximately US$10), small, and poses minimal disruption to the wind field. It can be sampled at rates up to 44,100 Hz using commonly available sound card technology or it can be interfaced with a data acquisition system. Data from deployments on beaches on Marco Island, FL, USA and near Shoalhaven Heads, NSW, Australia using sample rates of 44,100 Hz and 6000 Hz, are presented. An algorithm for identifying discrete impacts of grains is described. The number of saltation impacts was not reduced when sub-sampling a record from 44,100 Hz to 6000 Hz. The most immediate use for the miniphone is for short-term deployments to detect unsteadiness in the saltation field. [Copyright &y& Elsevier]