Urban hailstorms: a view from Alberta

Urban hailstorms are rarely studied in detail. This work documents five urban storms in Alberta where damage has, on three occasions, set the record for Canada's most costly natural disaster. Information from newspapers, insurance companies, and disaster assistance programs was utilized to supplement meteorological records and information obtained from public surveys.The record-breaking hail swath which accompanied the 1987 Edmonton tornado was mapped using over 800 responses to an unprecedented newspaper survey. Tennis ball sized hail struck 125 km² of the city. Record-sized hailstones for Alberta were collected. Citizens' measurements of giant hailstones were compared to laboratory measurements. The rural storms were tracked using lightning detector information and damage was mapped using crop insurance and disaster assistance claims. The tornado-bearing storm was found to have a unique track.A late-season hailstorm which struck Calgary in 1991 was mapped using homeowner insurance claims organized by postal areas. Nine out of thirty areas had claims rates exceeding 50%, mainly for shingle replacement. Experiences of claims adjustors and an informal public survey were also utilized. Rural storms were mapped using weather radar and crop losses. The radar beam was strongly attenuated when it passed through hail-bearing storms and, thus, its ability to detect large hail was compromised.Weather conditions, urban and rural damaged areas, and insurance payments were compared for all five local hailstorms. These storms were discussed within the context of the long history of Alberta hail research and current trends in technology implementation. Forecasting of these hailstorms using conventional severe weather indicators was difficult in Calgary because of that city's proximity to the mountains. Hailstorms that struck Munich, Denver, and Toowoomba (Australia) were also discussed, and the hailstones collected from the great Munich storm were compared to those collected from the Edmonton storms.     

Not a “forever model”: the curious case of graduation in Housing First

This article investigates how Housing First (HF) is practiced in Alberta, Canada, with a focus on the concept of graduation. The dominant HF model, Pathways, holds that client support should be time-unlimited. However, HF is highly mobile and increasingly characterized by ambiguity and drift away from Pathways principles. In Alberta, one prominent example of drift is the notion that clients can and should graduate – that is, “exit” HF programs after a certain time. Interviews conducted with 45 participants in three Alberta cities in 2014–15 revealed commonplace, but contested, graduation practices. Interviewees noted that graduation can be necessary to make room for new clients, and may be expected and encouraged by coordinating organizations. They expressed varied concerns about graduation, and the negative influence it could have on client relationships and housing stability. In particular, they emphasized clients’ ongoing dependence on rental subsidies, and the risk of relapse into homelessness.     

The identification of 9-n-alkyl fluorene-9-ols in the Alberta oil sands

Homologous series of 9-n-alkyl fluorene-9-ols and their nuclear methylated derivatives have been detected in the Alberta oil sands and their structure identified by infrared, field ionization and capillary gas chromatography-mass spectrometry and by comparison with synthetic standards.     

Extracting ecological information from oblique angle terrestrial landscape photographs: Performance evaluation of the WSL Monoplotting Tool

While aerial photography and satellite imagery are the usual data sources used in remote sensing, land based oblique photographs can also be used to measure ecological change. By using such historical photographs, the time frame for change detection can be extended into the late 1800s and early 1900s, predating the era of aerial imagery by decades. Recent advancements in computing power have enabled the development of techniques for georeferencing oblique angle photographs. The WSL Monoplotting Tool is a new piece of software that opens the door to analyzing such photographs by allowing for extraction of spatially referenced vector data from oblique photographs. A very large repeat photography collection based on the world's largest systematic collection of historical mountain topographic survey images, the Mountain Legacy Project, contains >6000 high resolution oblique image pairs showing landscape changes in the Rocky Mountains of Alberta between ca. 1900 – today. We used a subset of photographs from this collection to assess the accuracy and utility of the WSL Monoplotting Tool for georeferencing oblique photographs and measuring landscape change. We determined that the tool georeferenced objects to within less than 15 m of their real world 3D spatial location, and the displacement of the geographic center of over 121 control points was less than 3 m from the real world spatial location. Most of the error in individual object placement was due to the angle of viewing incidence with the ground (i.e., low angle/highly oblique angles resulted in greater horizontal error). Simple rules of control point selection are proposed to reduce georeferencing errors. We further demonstrate a method by which raster data can be rapidly extracted from an image pair to measure changes in vegetation cover over time. This new process permits the rapid evaluation of a large number of images to facilitate landscape scale analysis of oblique imagery.     

Water balance of a burned and unburned forested boreal peatland

We examined the water balance of a forested ombrotrophic peatland and adjacent burned peatland in the boreal plain of western Canada over a 3‐year period. Complete combustion of foliage and fine branches dramatically increased shortwave radiation inputs to the peat surface while halting all tree transpiration at the burned site. End‐of‐winter snowpack was 7–25% higher at the burned site likely due to decreased ablation from the tree canopy at the unburned site. Shrub regrowth at the burned site was rapid post‐fire, and shading by the shrub canopy in the burned site approached that of the unburned site within 3 years after fire. Site‐averaged surface resistance to evaporation was not different between sites, though surface resistance in hollows was lower in the burned site. Water loss at both burned and unburned sites is largely driven by surface evaporative losses. Evaporation at the burned site marginally exceeded the sum of pre‐fire transpiration and interception at the unburned site, suggesting that evapotranspiration during the growing season was 20–40 mm greater at the burned peatland. Although the net change in water storage during the growing season was largely unchanged by fire, the lack of low‐density surface peat in the burned site appears to have decreased specific yield, leading to greater water table decline at the burned site despite similar net change in storage. Copyright © 2013 John Wiley & Sons, Ltd.     

The controls on boreal peatland surface water chemistry in Northern Alberta,Canada

Spatial and temporal variability in surface water chemistry, organic soil chemistry and hydrologic indicators were investigated at three poor‐fen complexes in two boreal catchments in Northern Alberta to provide insight into the dominant controls on surface water chemistry. Improved understanding of these controls is required to enable prediction of runoff chemistry in the region under changing atmospheric deposition conditions. Surface water chemistry exhibited considerable variability; within each fen conductivity, dissolved organic carbon (DOC), and Cl⁻ tended to decrease and pH tended to increase with increasing distance from the lake edge. Variations in evaporative isotopic enrichment in ²H and ¹⁸O, expressed as deuterium excess, were used to distinguish between throughflow waters and those that were more evaporatively enriched. Throughflow surface waters were more acidic primarily due to higher concentrations of DOC and NO₃⁻. Exchangeable base saturation and pH of organic soils were strongly related to surface water chemistry at two of the fen complexes, demonstrating the capacity for cation exchange to influence surface water chemistry. Fen surface water concentrations of most elements and DOC increased during the summer period (between June and August), while pH of water decreased. Evaporative concentration of the surface waters was a dominant driver, with surface water temperature increasing at both catchments. Localized groundwater discharge was an important contributor of base cations to the fens, while the organic soils are sinks for atmospherically deposited SO₄²⁻, N and Cl⁻. Copyright © 2010 John Wiley & Sons, Ltd.     

Precipitation variability and its relationship to hydrologic variability in Alberta

By applying wavelet‐based empirical orthogonal function (WEOF) analysis to gridded precipitation (P) and empirical orthogonal function (EOF) analysis to gridded air temperature (T), potential evapotranspiration (PET), net precipitation (P‐PET) and runoff (Q), this paper examines the spatial, temporal and frequency patterns of Alberta's climate variability. It was found that only WEOF‐based precipitation patterns, possibly modulated by El Nino Southern Oscillation (ENSO) and Pacific Decadal Oscillation(PDO), delineated Alberta into four major regions which geographically represent northern Alberta Boreal forests, southern Alberta grasslands and Aspen Parklands and the Rocky Mountains and Foothills. The leading mode of wavelet‐based precipitation variability WPC1 showed that between 1900 and 2000, a wet climate dominated northern Alberta with significant 4–8, 11 and 25‐year periodic cycles, while the second mode WPC2 showed that between 1960 and 2000, southern Alberta grasslands were characterized by decreasing precipitation, dominated by 11‐year cycles, and the last two modes WPC3 and WPC4 were characterized by 4–7 and 25‐year cycles and both delineated regions where moisture from the Pacific Ocean penetrated the Rocky Mountains, accounted for much of the sub‐alpine climate. These results show that WEOF is superior to EOF in delineating Alberta precipitation variability to sub‐regions that more closely agree with its eco‐climate regions. Further, it was found that while WPC2 could not explain runoff variations in southern Alberta, WPC1, WPC3 and WPC4 accounted for runoff variability in their respective sub‐regions. Copyright © 2009 John Wiley & Sons, Ltd.     

Acid-gas injection at West Stoddart, British Columbia: An analogue for the detailed hydrogeological characterization of a CO2 sequestration site

Geological sequestration of CO₂ is an option for significantly reducing emissions into the atmosphere. Various hydrocarbon companies in western Canada are currently injecting acid-gas (CO₂ and H₂S) into deep subsurface formations. At West Stoddart, in northeast British Columbia, acid-gas has been injected since 1998 at 1600 m depth into sandstones of the Triassic Halfway Formation, which forms a regional aquifer. A comprehensive subsurface characterization was conducted of the regional and local-scale geology, reservoir characteristics, mineralogy, in situ fluid properties, and hydrogeology. Preliminary results from geochemical and numerical multi-phase flow modelling suggest that the majority of the injected acid-gas will dissolve in the formation water and remain within a radius of a few kilometres of the injection well. The experience with the acid-gas injection at West Stoddart and other operations in the Alberta Basin has shown that the process of large-scale CO₂-injection into deep aquifers is technically feasible.     

Modeling an Exhumed Basin: A Method for Estimating Eroded Overburden

The Alberta Deep Basin in western Canada has undergone a large amount of erosion following deep burial in the Eocene. Basin modeling and simulation of burial and temperature history require estimates of maximum overburden for each gridpoint in the basin model. Erosion can be estimated using shale compaction trends. For instance, the widely used Magara method attempts to establish a sonic log gradient for shales and uses the extrapolation to a theoretical uncompacted shale value as a first indication of overcompaction and estimation of the amount of erosion. Because such gradients are difficult to establish in many wells, an extension of this method was devised to help map erosion over a large area. Sonic t values of one suitable shale formation are calibrated with maximum depth of burial estimates from sonic log extrapolation for several wells. This resulting regression equation then can be used to estimate andmap maximum depth of burial or amount of erosion for all wells in which this formation has been logged. The example from the Alberta Deep Basin shows that the magnitude of erosion calculated by this method is conservative and comparable to independent estimates using vitrinite reflectance gradient methods.     

Revised identification of a reported Iguanodon-grade ornithopod tooth from the Scollard Formation, Alberta, Canada

An isolated tooth from the late Maastrichtian strata of the Scollard Formation of Alberta, Canada, has been identified as the only record of a non-hadrosaurid hadrosauriform from the Maastrichtian of North America. Here, we demonstrate that this identification is in error and that the tooth pertains to an indeterminate ceratopsid. In addition, we provide full documentation of the published collection of Scollard Formation fossils from which the tooth was originally derived.