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Rex J.F.,University of Northern British Columbia | Rex J.F.,British Columbia Ministry of forests | Petticrew E.L.,University of Northern British Columbia | Albers S.J.,University of Northern British Columbia | Williams N.D.,URS Infrastructure and Environment UK Ltd
Earth Surface Processes and Landforms | Year: 2014

Pacific salmon are biogeomorphic agents shown to induce positive feedbacks on their natal watersheds. However, the literature documenting their ecological effects on in-stream natal environments is more divisive. The disturbance salmon create during redd construction has the potential to reduce stream productivity. The pulse of salmon organic matter (SOM) and marine derived nutrients (MDNs) released during carcass decay has been reported as either stimulating in-stream productivity or having no local effect. To evaluate the ecological costs and benefits of salmon spawning events, MDN delivery and storage processes need to be identified and quantified. A simulation was conducted in three flow-through flumes (2m×2m×30m) over a 33-day period (consisting of 15 baseline, four MDN exposure, and 14 post-exposure days) to assess near-field sediment and organic matter dynamics during active and post-spawn simulations. The objective of the study was to measure changes in the amounts and particle sizes of suspended and gravel-stored fine sediment, in order to elucidate the process and significance of SOM recruitment to the gravel bed via sedimentation. Gravel beds in all flumes were enriched with SOM following treatments but the response was highest in the active spawn simulation. The more effective delivery in the active spawn simulation was attributed to its higher inorganic sediment concentration, which is known to enhance floc formation. Although the active spawn simulation delivered more SOM to the gravel bed, the post-spawn phase may be equally important to natural streams because its decay phase is longer than the active spawn and consequently can provide SOM to the streambed as long as carcasses remain in-stream. The delivery, and potential retention, of SOM to spawning streambeds and the intergravel environment may be particularly important for interior streams, which experience low flow conditions during the spawning phase and accordingly have the potential for hyporheic nutrient recruitment and storage. © 2014 John Wiley & Sons, Ltd. Source


Peay S.,URS Infrastructure and Environment UK Ltd | Peay S.,University of Leeds | Dunn A.M.,University of Leeds | Kunin W.E.,University of Leeds | And 2 more authors.
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2015

Invasive crayfish exert adverse impacts on native biodiversity in Europe. This field study investigated the scope for use of electric shock treatment to eradicate signal crayfish in a small headwater stream. High intensity (96kW, direct current 1600V, 57.8 A, at 7Hz) repeated shocks were delivered via electrode tapes to two sections of stream. Both had 98min as 2-min shocks. Section 2 had additional 15-min shocks to a total of 308min. Crayfish mortality was 86% and 97% in the two sections respectively, based on the number recovered when the channel was subsequently dewatered. The survivors found were in the banks. Mark-recapture indicated that 72% of the total population was captured, hence the minimum mortality was 77% of the total population after the longer treatment. All sizes of crayfish were affected, but small individuals (<30mm carapace length) were more susceptible. Test cages showed increasing mortality with exposure. A fitted model showed 50% mortality with 17min shock time, 75% mortality with 30min (distance to electrode in the range 10-50cm). The treatment is a possible non-selective method of control for invasive crayfish in small watercourses, rather than an eradication method, because some crayfish survived in the stony banks. Periodic treatment downstream of a physical barrier would potentially keep the crayfish density low and may therefore reduce the risk of the barrier being overcome by upstream invasion. Options for further investigation to improve the method are discussed. © 2015 John Wiley & Sons, Ltd. Source


Dehdezi P.K.,URS Infrastructure and Environment UK Ltd
Journal of Materials in Civil Engineering | Year: 2014

This paper considers the effect of the thermophysical properties of concrete on temperature distributions and stresses developed in concrete pavements. The temperature distributions in concrete pavements, composed of different thermophysical properties, were calculated using a finite-difference model. These temperatures were then fed into a finite-element model as thermal loads in order to calculate tensile stresses in the concrete. It was found that the thermophysical properties of concrete can significantly influence the magnitude of tensile stresses and, subsequently, the thickness of the concrete slab. Concrete with higher thermal conductivity and diffusivity (e.g., incorporating high conductive aggregates and/or metallic fibers) will experience much more uniform temperature and, as a result, a smaller tensile stress will be developed in the concrete. Increasing the thermal conductivity of concrete from 1.2 W=mK (concrete containing limestone aggregates) to 3.6 W=mK (concrete containing quartzite aggregates and 1% metallic fibers) could result in a 25% reduction of the concrete slab thickness. © 2014 American Society of Civil Engineers. Source


Finnie S.B.,URS Infrastructure and Environment UK Ltd
7th International Conference on Maintenance and Rehabilitation of Pavements and Technological Control, MAIREPAV 2012 | Year: 2012

Road authorities are currently faced with the challenge of reducing their carbon footprint in response to Climate Change at a time when many also have to cope with reduced capital and maintenance budgets due to the economic climate. When considering alternative maintenance options, those strategies with the lowest capital or whole life cost are not always those with the lowest carbon footprint. This gives the road authorities a dilemma when it comes to selecting the optimum maintenance option to meet their business objectives. Understanding the relative cost and carbon impact of alternative design options is, therefore, critical to managing these competing demands. URS has developed an application (app), branded WLCO2T, which measures the whole life cost and whole life carbon footprint of alternative maintenance strategies for pavement assets over a 60-year analysis period. WLCO2T includes a database of maintenance activities for flexible, composite and rigid pavements that contains cost data and greenhouse gas emissions factors. The User builds a maintenance strategy by allocating maintenance activities to a specific year. WLCO2T then calculates the: capital cost, operational cost, whole life cost, capital carbon footprint, operational carbon footprint and whole life carbon footprint. The outputs of the app provides road authorities with high-level decision making information which is intended to be used at preliminary design stage to select the preferred option or several options for further design development. The app can also be used to determine the optimum year in which to carry out the maintenance. Source


Owens P.N.,University of Northern British Columbia | Blake W.H.,University of Plymouth | Giles T.R.,British Columbia Ministry of forests | Williams N.D.,URS Infrastructure and Environment UK Ltd
Journal of Soils and Sediments | Year: 2012

Purpose: Wildfires represent one of the major natural disturbances within forested landscapes and have potential implications for the quality and function of downstream aquatic ecosystems. This study aimed to determine if a wildfire in a mountainous, forested watershed in British Columbia, Canada, caused a change in the dominant sediment source in the immediate 1-2 years following the wildfire, and if the sediment sources changed over the medium term (3-7 years) as the landscape recovered. Materials and methods: Source materials (surface soil, subsurface soil and channel bank material) and fluvial (suspended and channel bed) sediment samples were collected over the period 2004 to 2010 from a watershed burnt by a wildfire in 2003, and from an adjacent watershed that was not impacted by the fire. Samples were analysed for the fallout radionuclides (FRNs) caesium-137 (137Cs) and unsupported lead-210 (210Pbun). An unmixing model was used to calculate the relative source contributions of the fluvial sediment samples. Results and discussion: 137Cs and 210Pbun were concentrated in the upper layers of surface soils in both watersheds and were statistically different to concentrations in subsurface and channel bank material. In the burnt watershed, FRN concentrations were greatest in the ash layer. Sediment sources as determined by the unmixing model were 100 % subsurface/channel bank material in the unburnt watershed, while in the burnt watershed 8.5 ± 2.5 % was derived from surface soils. In both watersheds, there were no major changes in the relative contributions from surface soil and from subsurface/channel bank material over the period 2004 to 2010. Thus, while the wildfire did cause a change in sediment sources, it was fairly subtle and did not conform to the effects following wildfire described for other studies in contrasting environments, which typically document a major increase in hillslope contributions relative to channel bank sources. Conclusions: There was a limited response in terms of fine-grained sediment sources (and also sediment fluxes) in the burnt watershed. The reason for this muted response to a severe wildfire is likely to be the lack of precipitation, especially winter precipitation and the associated snowmelt, in the first year following the wildfire. Thus while the landscape was primed for erosion and sediment transport, the lack of a driving force meant that there was a limited immediate post-fire sediment response. © 2012 The Author(s). Source

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