Influence of vertical channel change associated with wood accumulations on delineating channel migration zones, Washington, USA

We combine hydraulic modeling and field investigations of logjams to evaluate linkages between wood-mediated fluctuations in channel-bed-and water-surface elevations and the potential for lateral channel migration in forest rivers of Washington state. In the eleven unconfined rivers we investigated, logjams were associated with reduced channel gradient and bank height. Detailed river gauging and hydraulic modeling document significant increases in the water-surface elevation upstream of channel-spanning wood accumulations. Logjams initiated lateral channel migration by increasing bed-or water-surface elevations above adjacent banks. Because the potential for a channel to avulse and migrate across its floodplain increases with the size and volume of instream wood, the area of the valley bottom potentially occupied by a channel over a specified timeframe — the channel migration zone (CMZ) — is dependent on the state of riparian forests. The return of riparian forests afforded by current land management practices will increase the volume and caliber of wood entering Washington rivers to a degree unprecedented since widespread clearing of wood from forests and rivers nearly 150 years ago. A greater supply of wood from maturing riparian forests will increase the frequency and spatial extent of channel migration relative to observations from wood-poor channels in the period of post-European settlement. We propose conceptual guidelines for the delineation of the CMZs that include allowances for vertical fluctuations in channel elevation caused by accumulations of large woody debris.     

Learning Conservation: the role of conservation covenants in landscape redesign at Project Hindmarsh,Victoria

Biodiversity decline continues apace across the Australian landscape with a pressing need to redesign land use to address this situation. The significance of private land increasingly is recognised for the protection and enhancement of biodiversity as landholders inevitably make decisions that affect environmental quality. Biodiversity conservation is as much a social process as a physical one. Conservation covenants are perpetual agreements under which landholders choose to conserve land voluntarily, primarily for conservation purposes. The role covenants might play in landscape-scale conservation was investigated in north-western Victoria. In-depth interviews with a range of participants were undertaken, with an emphasis on the role covenantors might play as social learning and cultural change agents. Analysis of these interviews offers useful perspectives for understanding socio-cultural dimensions of landscape change and exploring the differing values of production farmers and nature conservation landholders. Consideration is then given to approaches to engaging local production farmers in nature covenants and promoting communication between this group and the largely non-production conservationists who currently form the mainstay of conservation covenants.     

Community and Nostalgia in Urban Revitalisation: a critique of urban village and creative class strategies as remedies for social ‘problems’

We examine how normative constructions of ‘the creative city’ have entered into Australian planning discourses. Although welcoming a place-based approach, critical consideration is given to how the misappropriation of ‘place making’ in creative city revitalisation plans may enhance rather than address processes of social marginalisation. A Foucauldian framework is employed, exploring the notion of the social production of power through discourse. We draw on a case study of Wentworth Street, a key urban space in Port Kembla, the industrialised district of Wollongong, New South Wales. The study focuses on various ideas of a common place-making theme of the ‘urban village’ evoked by planners, the media and a targeted local resident group (here elderly Macedonians) for a street positioned in ‘crisis’ because of declining infrastructure, services and its association with crime, drugs and prostitution. The case study demonstrates that marginalisation and exclusions are products of creative city strategies and wider, more oppressive urban discourses. But we also demonstrate that despite becoming normative in the texts of planning policies, discourses of place and identity always remain multiple, negotiated, and contradictory.     

Episodic shear zone associated fluid flow in the Curnamona Province, South Australia

Two distinct generations of fluid flow associated with shear zone activity have been identified in Willyama Supergroup rocks of the southern Curnamona Province in northeastern South Australia. Fluids in the first event are inferred to have been sourced from the devolatilisation of Willyama Supergroup metasedimentary rocks during prograde metamorphism associated with the (1.61–1.58 Ga) Mesoproterozoic Olarian Orogeny. The second episode of fluid flow occurred during the (c. 500 Ma) Cambrian Delamerian Orogeny and resulted in localised rehydration of the Willyama Supergroup. Fluids were isotopically light and most likely sourced from prograde Delamerian metamorphism and dehydration of fault rocks and entrained meteoric waters that originally were involved in (c. 700 Ma) Neoproterozoic Adelaidean rifting. A key outcome of this study is the identification of this previously unrecognised fluid flow system that was active during the Delamerian Orogeny.     

B-Spline impulse response functions (BIRF) for transient SSI analysis of rigid foundations

This work presents a simplified, yet accurate model of rigid foundation-soil systems for the dynamic analysis of structures including SSI effects. The simplified model is based on closed form solutions that reproduce the characteristic B-spline impulse response functions (BIRF) of 3D continuous soil-foundation systems, as obtained from rigorous boundary element method (BEM) analysis. The proposed simplified model is used within the framework of B-spline impulse response techniques and can be coupled directly to other solution techniques, such as the finite element method (FEM). Validation and application studies demonstrate the accuracy and versatility of the simplified model for the direct time domain solution of dynamic SSI problems involving rigid square surface foundations of any size. The proposed model, although simplified, demonstrates similar high accuracy to that of more rigorous solutions based on domain discretizations.     

Dating ancient wood by high-sensitivity liquid scintillation counting and accelerator mass spectrometry—Pushing the boundaries

It is critical that a comprehensive terrestrial radiocarbon (¹⁴C) calibration curve is developed beyond 26 ka for high-precision calibration and correlation of climatic, environmental and archaeological records. Abundant sub-fossil New Zealand kauri (Agathis australis) wood, preserved in Oxygen Isotope Stage-2 and 3 peat swamps, provides an important resource for ¹⁴C calibration; nowhere else in the world does such an extensive collection of ancient wood exist. Although finite ¹⁴C ages beyond 50 ka are becoming routinely reported, few attempts have been made to demonstrate their accuracy or precision. Finite ages beyond 50 ka require optimization of all elements involved in sample preparation and ¹⁴C analysis. Here we discuss the methodology employed for optimizing the ¹⁴C dating of near-background wood samples by both benzene synthesis for liquid scintillation counting (LSC) or graphite synthesis for accelerator mass spectrometry (AMS). We report the mean background blank activities for both methods and present a statistical model for assigning blank standard errors when blank activity variation is over and above counting statistics. We also present duplicate analyses (using LSC and AMS) of nine successive samples of wood obtained from a sub-fossil kauri log near-background in age to investigate the significance of the measured blank levels and variability.     

Gaussian plume modeling of contaminant transport

A technique for modeling contaminant transport based on Markov process theory is developed. Transport is quantified by summing the first two moments of independent random displacements and applying the central limit theorem (CLT) to obtain solute distributions of a Gaussian nature. For non-uniform flow fields the CLT is applied in a streamfunction/equi-travel time space and transforms are used to give concentrations in Cartesian coordinates. Simulations in uniform, radially converging and circular flow fields show the method to be two to three orders of magnitude faster than modeling with the advection-dispersion equation, using a control volume technique.     

Cosmogenic 10BE Age Constraints for The Wester Ross Readvance Moraine: Insights Into British Ice-Sheet Behaviour

This study presents the first absoluteage constraints from a palaeo‐ice‐sheet margin in western Scotland. Cosmogenic ¹⁰Be from four Lewisian gneiss boulders on the Gairloch Moraine in NW Scotland have yielded reliable exposure ages. Three of these dates, taken from a single moraine ridge, cluster around c. 15.5–18 ka BP, with a weighted mean of 16.3 ± 1.6 ka BP. These findings indicate that the last British Ice Sheet had retreated to the present‐day coastline in NW Scotland by this time. It is suggested that the Wester Ross Readvance represents an ice‐sheet oscillation during, or in the immediate aftermath of, Heinrich Event 1 (c. 17–18 ka BP).