Evidence for current-controlled morphology along the western slope of Hatton Bank (Rockall Plateau, NE Atlantic Ocean)

A multibeam bathymetric and high- (airgun and sparker) to very high-resolution (Topas) seismic study of the western slope of Hatton Bank (NE Atlantic), located between 600 m and 2,000 m water depth, has revealed a highly variable range of current-controlled morphological features. Two major seabed areas can be distinguished: (1) a non-depositional area corresponding to the top of the bank and (2) a depositional area in which the Hatton Drift has developed. Both areas are characterised by distinct morphologies associated either with rock outcrops and rocky ridges or with smooth surfaces, slides and bedforms controlled mainly by bottom currents interacting with the topography of the bank. The water depth separating the morphological areas probably coincides with the boundary of the Labrador Sea Water and the Lower Deep Water. Morphological features identified in the study area include contourite channels (moats, furrows and scours), fields of sediment waves, edges of contourite deposits, ponded deposits, scarps, gullies, ridges, depressions, slides and slide scars. These morphological features do not necessarily reflect present-day conditions but may have been associated with past current events, consistent with earlier interpretations.     

Introduction of a new friction routine into the SWAN model that evaluates roughness due to bedform and sediment size changes

The significant loss of wave energy due to seabed interaction in finite depths is a known effect and bottom friction terms are used in the wave models to account for this dissipation. In this paper, a new bottom-interaction function is tested by means of the SWAN model, based on measurements at two field sites, Lake George and Lakes Entrance, both in Australia. The function accounts for dependence of the friction on the formation process of bottom ripples and on the grain size of the sediment. The overall improvement of the model prediction both for the wave height and wave period is demonstrated.     

A Typology of Shared Service Provision in Australian Local Government

Disappointment with the results of forced amalgamation programs across almost all Australian local government jurisdictions has created great interest in shared service models as an alternative method of improving the operational efficiency of local councils, while at the same time preserving local democracy and local autonomy. While an embryonic literature on shared service provision in the Australian municipal milieu does exist, much remains to be done. This paper seeks to contribute to this nascent literature in two main ways: (a) to locate shared services in local government within broader global trends and theoretical disputations on devolution and local economic development, highlighting the importance of political geography in these debates; and (b) in the light of this complexity and ambiguity, develop a new typology of local government shared service provision to inform public policy making on real-world problems in Australian local government.     

An interdisciplinary approach to the collapse of the port and degradation of freshwater resources at Panama Viejo (Panama), 1519–1671

The Archaeological Site of Panama Viejo (Panama) comprises a protected area of 28 km² within present-day Panama City, on America's Pacific coast. In 1519, the Spaniards founded the city of Panama Viejo to secure a natural port in an area inhabited by indigenous peoples since at least the eighth century CE. The site, along the coastline and between two rivers, became a principal gateway for goods and people travelling between Europe and Pacific settlements to the east (Realejo) and the west (Trujillo, Lima, Arica). Within one century, however, Panama Viejo's natural port and freshwater infrastructure collapsed, leading to the city's relocation after corsairs attacked it in 1671. This study combines archaeological, geographical and historical analyses to explain how and why human interactions with the local environment made the settlement increasingly untenable.     

Optical properties of Titan and early Earth haze laboratory analogs in the mid-visible

Scattering and absorption of sunlight by aerosols are integral to understanding the radiative balance of any planetary atmosphere covered in a haze, such as Titan and possibly the early Earth. One key optical parameter of an aerosol is its refractive index. We have simulated both Titan and early Earth organic haze aerosols in the laboratory and measured the real and imaginary portion of their refractive index at λ = 532 nm using cavity ringdown aerosol extinction spectroscopy. This novel technique allows analysis on freely-floating particles minutes after formation. For our Titan analog particles, we find a real refractive index of n = 1.35 ± 0.01 and an imaginary refractive index k = 0.023 ± 0.007, and for the early Earth analog particles we find n = 1.81 ± 0.02 and k = 0.055 ± 0.020. The Titan analog refractive index has a smaller real and similar imaginary refractive index compared to most previous laboratory measurements of Titan analog films, including values from Khare et al. (Khare, B.N., Sagan, C., Arakawa, E.T., Suits, F., Callcott, T.A., Williams, M.W. [1984]. Icarus 60, 127-137). These newly measured Titan analog values have implications for spacecraft retrievals of aerosol properties on Titan. The early Earth analog has a significantly higher real and imaginary refractive index than Titan analogs reported in the literature. These differences suggest that, for a given amount of aerosol, the early Earth analog would act as a stronger anti-greenhouse agent than the Titan analog.     

A dual-porosity model for the study of chemical effects on the swelling behaviour of MX-80 bentonite

Significant chemical influence on the swelling potential of MX-80 bentonite was observed during swelling tests where specimens were hydrated with highly concentrated brine. The maximum swelling pressure for specimens hydrated with brine was about 30% of the maximum swelling pressure for the same specimens hydrated with de-ionized water. The maximum swelling pressure was attained within tens of hours of brine infiltration and further decreased by half within a year. A fully coupled hydro–mechanical–chemical (HMC) dual-porosity model is proposed in this paper to interpret the swelling behaviour of MX-80 when infiltrated with brine. The dependence of hydraulic and mechanical properties on such factors as porosity, salinity and water content was investigated. A nonlinear elastic constitutive model was proposed to correlate the swelling pressure with the variation in the microporosity. The chemical effects on the mechanical behaviour were coupled at the micropore level. A number of relationships have been developed for MX-80, i.e. micropore permeability as a function of void ratio, water retention characteristics of micropores and macropores, micropore dependence on water content and the diffusion coefficients of the two types of pore structure. The proposed model was successful in reproducing both quantitatively and qualitatively the experimental results from two sets of infiltration experiments on compacted MX-80 bentonite.

     

Relative size of fluvial and glaciated valleys in central Idaho

Quantitative comparisons of the morphometry of glaciated and fluvial valleys in central Idaho were used to investigate the differences in valley relief and width in otherwise similar geologic and geomorphic settings. The local relief, width, and cross-sectional area of valleys were measured using GIS software to extract information from USGS digital elevation models. Hillslope gradients were also measured using GIS software. Power-law relationships for local valley relief, width, and cross-sectional area as a function of drainage area were developed. Local valley relief in glaciated valleys relates to drainage area with a power-law exponent similar to fluvial valleys, but glaciated valleys are deeper for a given drainage area. Local valley width in glaciated valleys is greater than in fluvial valleys, but the exponent of the power-law relationship to drainage area is similar in both valley types. Local valley cross-sectional area in glaciated valleys increases with drainage area with a power-law exponent similar to fluvial valleys, however, glacial valleys have roughly 80% greater cross-sectional area. Steep valley walls in glaciated basins increase the potential for bedrock landsliding relative to fluvial basins. Both the Olympic Mountains of Washington and valleys in central Idaho show relationships in which glaciated valleys are up to 30% deeper than fluvial valleys despite differences in lithology, tectonic setting, and climate.     

Deep Injection of Waste Water in the Western Canada Sedimentary Basin

Injection of wastes into the deep subsurface has become a contentious issue, particularly in emerging regions of oil and gas production. Experience in other regions suggests that injection is an effective waste management practice and that widespread environmental damage is unlikely. Over the past several decades, 23 km³ of water has been injected into the Western Canada Sedimentary Basin (WCSB). The oil and gas industry has injected most of this water but large amounts of injection are associated with mining activities. The amount of water injected into this basin during the past century is 2 to 3 orders magnitude greater than natural recharge to deep formations in the WCSB. Despite this large‐scale disturbance to the hydrogeological system, there have been few documented cases of environmental problems related to injection wells. Deep injection of waste appears to be a low risk activity based on this experience but monitoring efforts are insufficient to make definitive statements. Serious uncharacterized legacy issues could be present. Initiating more comprehensive monitoring and research programs on the effects of injection in the WCSB could provide insight into the risks associated with injection in less developed sedimentary basins.