Semi-automated generation of depth contours for ENCS

This note presents a largely automated method to create bathymetrically safe,legible, scale appropriate depth contours for Electronic Navigation Charts (ENCs)using the CARIS BASE Editor version 4.4 software installed in the AustralianHydrographic Office (AHO). The method is suitable for contouring modern high densitymulti-beam survey data as well as sparser single beam data (or a combination ofboth). Being a largely automated process, the time required to incorporate newbathymetric data into navigation products is significantly reduced. The methodfacilitates finer resolution depth encoding within ENCs and therefore a more realisticportrayal of safe water to the mariner

Holocene valley aggradation driven by river mouth progradation: examples from Australia

Since the end of the post-glacial sea level rise 6800 years ago, progradation of river mouths into estuaries has been a global phenomenon. The responses of upstream alluvial river reaches to this progradation have received little attention. Here, the links between river mouth progradation and Holocene valley aggradation are examined for the Macdonald and Tuross Rivers in south-eastern Australia. Optical and radiocarbon dating of floodplain sediments indicates that since the mid-Holocene sea level highstand 6800 years ago vertical floodplain aggradation along the two valleys has generally been consistent with the rate at which each river prograded into its estuary. This link between river mouth progradation and alluvial aggradation drove floodplain aggradation for many tens of kilometres upstream of the estuarine limits. Both rivers have abandoned their main Holocene floodplains over the last 2000 years and their channels have contracted. A regional shift to smaller floods is inferred to be responsible for this change, though a greater relative sea level fall experienced by the Macdonald River since the mid-Holocene sea level highstand appears to have been an additional influence upon floodplain evolution in this valley

Synoptic-scale climate pattersn associated with rainfall δ 18 O in southern Australia

A detailed examination of the relationship between synoptic patterns and the oxygen isotopic composition (δ 18O) of rainfall is made using a 5-year long dataset of daily-event based rainfall samples from Tasmania, southern Australia. Rainfall δ 18O var

Bankfull discharge and recurrence intervals in Irish rivers

Different definitions of the bankfull condition in rivers are based on morphological characteristics, boundary conditions and geometrical properties. Consequently, the magnitude and associated return period of the bankfull discharge can be ambiguous. Knowledge of this discharge is important in index flood estimation and subsequent regional flood frequency analysis. This study investigates bankfull discharges and recurrence intervals at 88 locations in the Irish river network using a combination of surveyed bankfull levels, rating curves and equations and photographic records at the sites in question. Catchments ranged in area from approximately 23 km2 to 2778 km2. Recurrence intervals were determined by fitting generalised extreme value (GEV) distributions to the annual maximum flow series at the sites investigated. These intervals were found to be less than 2 years (the median annual flood) at 42 stations (48%) and less than 2·33 years (the mean annual flood assuming a GEV type 1 distribution) at 47 stations (53%). Higher return periods of between 2·33 and 10 years and 10 and 25 years were observed at a further 20% and 6% of locations respectively. Using multivariate regression analysis, the computed bankfull discharges are correlated with catchment descriptors and three expressions are presented for estimating bankfull flows.Deposited by bulk importPermission granted to archive the final PDF (the version used for publication that subscribers gain access to) but this not available yet. On the webpage that the file is hosted on, please reference the journal homepage (www.geotechnicaljournal.com) and including the text “Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.”TS 01.03.1

Potential effects of climate change on Australian estuaries and fish utilising estuaries: a review

Estuaries are especially vulnerable to the impacts of climate change because changes in climatic and hydrologic variables that influence freshwater and marine systems will also affect estuaries. We review potential impacts of climate change on Australian estuaries and their fish. Geographic differences are likely because southern Australian climates are predicted to become warmer and drier, whereas northern regions may see increased precipitation. Environmental factors, including salinity gradients, suspended sediment, dissolved oxygen and nutrient concentrations, will be influenced by changing freshwater input and other climate variables. Potential impacts will vary depending on the geomorphology of the estuary and the level of build-up of sand bars across estuarine entrances. Changes to estuarine fish assemblages will depend on associated changes to salinity and estuarine-mouth morphology. Marine migrants may be severely affected by closure of estuarine mouths, depending on whether species 'must' use estuarine habitat and the level of migratory v. resident individuals. Depending on how fish in coastal waters locate estuaries, there may be reduced cues associated with estuarine mouths, particularly in southern Australia, potentially influencing abundance. In summary, climate change is expected to have major consequences for Australian estuaries and associated fish, although the nature of impacts will show significant regional variation

The Anthropocene: a geomorphological and sedimentary view

The ‘‘Anthropocene’’, as used to describe the interval of recent Earth history during which humans have had an ‘‘overwhelming’’ effect on the Earth system, is now being formally considered as a possible new geological Epoch.Such a new geological time interval (possibly equivalent to the Pleistocene Epoch) requires both theoretical justification as well as empirical evidence preserved within the geological record. Since the geological record is driven by geomorphological processes, geomorphology has to be an integral part of this consideration given that it is Earth-surface processes that produce terrestrial and near-shore stratigraphy. This paper sets a priori considerations concerning the possible formalisation of the Anthropocene from a geomorphological perspective, including the recognition of human dominance in sedimentary transport systems, the boundary problem, and the spatial diachrony of ‘‘anthropogenic geomorphology’’

Bayesian geomorphology

The rapidly growing amount and diversity of data are confronting us more than ever with the need to make informed predictions under uncertainty. The adverse impacts of climate change and natural hazards also motivate our search for reliable predictions. The range of statistical techniques that geomorphologists use to tackle this challenge has been growing, but rarely involves Bayesian methods. Instead, many geomorphic models rely on estimated averages that largely miss out on the variability of form and process. Yet seemingly fixed estimates of channel heads, sediment rating curves or glacier equilibrium lines, for example, are all prone to uncertainties. Neighbouring scientific disciplines such as physics, hydrology or ecology have readily embraced Bayesian methods to fully capture and better explain such uncertainties, as the necessary computational tools have advanced greatly. The aim of this article is to introduce the Bayesian toolkit to scientists concerned with Earth surface processes and landforms, and to show how geomorphic models might benefit from probabilistic concepts. I briefly review the use of Bayesian reasoning in geomorphology, and outline the corresponding variants of regression and classification in several worked examples. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Lt