Determinants of the tailed frog's range in British Columbia, Canada

The tailed frog is the only stream-breeding frog in Canada. Due to its highly specialized habitat requirements and its vulnerability to habitat degradation, it is of concern through much of its range in the Pacific Northwest. The purpose of this study was to determine the range of the tailed frog in British Columbia, and to generate hypotheses for its current distribution. The tailed frog is resident of steep mountain streams. Along the coast, other than its absence from Vancouver Island and Haida Gwaii, the tailed frog's distribution coincides closely with the Coastal Western Hemlock (CWH) biogeoclimatic zone. In the interior, an area with a continental climate, its distribution is allied with the Engelmann Spruce/Subalpine Fir (ESSF) biogeoclimatic zone. However, streams in the ESSF are likely only suitable to tadpoles if a thick blanket of snow buffers them from winter freezing. Thus, drier subzones of the ESSF are less likely to support tailed frogs. This close association with moist biogeoclimatic zones may reflect the species preference for a humid temperate climate regime. The tailed frog's distribution may also be associated with geology: in contrast to streams underlain by competent plutonic rocks (e.g., granite), which typically have coarse gravel beds with locked boulder steps, areas with highly fractured or weak rock types (e.g. shale) have a finer and more mobile stream bedload, leading to unstable channel conditions. These streams provide less favorable habitat for tadpoles. Along the coast, the presently documented northern distribution lies at the Nass River, and the factors limiting northward dispersal are not apparent. In the interior of British Columbia, northward advancement appears to be limited in part both to underlying rock type and climat

Influence of a large debris flow fan on the late Holocene evolution of Squamish River, southwest British Columbia, Canada

Cheekye Fan is a large paraglacial debris flow fan in southwest British Columbia. It owes its origin to the collapse of Mount Garibaldi, a volcano that erupted in contact with glacier ice near the end of the Pleistocene Epoch. The fan extended across Howe Sound, isolating a freshwater lake upstream of the fan from a fjord downstream of it. Squamish River built a delta into this lake during the Holocene. We use 28 radiocarbon dates to describe the final infilling of the lake and the subsequent evolution of the Squamish River floodplain over the past 3300 years. These events are recorded in fine-grained lacustrine, wetland, river channel and overbank sediments exposed in the banks of Squamish River over a distance of more than 10 km upstream of the fan. We link these deposits to construction, persistence, and eventual degradation of the dam formed by Cheekye Fan and a smaller inset fan formed by Cheakamus River, into which Cheekye River flows. The coupled Cheekye Fan â Squamish River floodplain system is similar to the low-gradient valley floors upstream of fans in California and the Canadian Rocky Mountains. Future debris flows and landslides in the headwaters of Cheekye River are likely to continue to affect base level along lower Squamish River. We speculate that future aggradation of Cheekye Fan would cause increased flooding and sediment deposition upstream of this barrier. These landscape linkages should be included in future land-use planning in lower Squamish River valley.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Evolution of Cheekye fan, Squamish, British Columbia: Holocene sedimentation and implications for hazard assessment 1

Abstract: Cheekye fan, a large (~25 km 2 ) fan located at the head of Howe Sound, southwestern British Columbia, has its origins in the collapse of the western flank of Mount Garibaldi onto a waning Late Pleistocene glacier, followed by post-glacial redistribution of colluvial-glacial sediments. Reconstruction of internal fan architecture allowed characterization of the rapid decline in sediment delivery to the lower fan through the paraglacial period, a result holding important implications for hazard assessment. A ground penetrating radar profile on lower Cheekye fan has reflectors with a steep (25°), westerly dip lying between 48 and 26 m above sea level, which are interpreted as foreset beds. Radiocarbon ages from marine deltaic deposits at the head of Howe Sound indicate that the sea stood at about 45 m above sea level at 10 200 BP. Together, the data indicate that the head of Howe Sound was deglaciated by 10 200 BP, that the fan had prograded 2.5 km into the fjord by this time, and continued to prograde as relative sea level fell. Reflectors at -10 m above sea level with a steep southerly dip along the southern edge of the lower fan, and radiocarbon ages in this vicinity, indicate it had reached close to its modern extent by 8000-9000 BP. Calculation of the volume of sediment stored in the lower fan indicates that at least 90% of the material was deposited before 6000 BP. This indicates that the Cheekye fan is largely a relict feature, putting its large size into context for future hazard assessments. Résumé : Le cône alluvial de Cheekye, un grand cône (~25 km 2 ) à pente douce localisé à la tête du bras de mer Howe, dans le sud-ouest de la Colombie-Britannique, doit son origine à l'affaissement, au Pléistocène tardif, du flanc occidental du mont Garibaldi sur un glacier en décrépitude, suivi de la redistribution postglaciaire des sédiments colluviaux-glaciaires. La reconstitution de l'architecture interne du cône permet de préciser le déclin rapide de l'approvisionnement en sédiment du cône inférieur durant le paraglaciaire, un résultat qui procure des enseignements importants pour évaluer un tel risque naturel. Une image radar du profil de terrain du cône inférieur de Cheekye montre des horizons réflecteurs avec inclinaison abrupte (25°) vers l'ouest, apparaissant entre 48 et 26 m au-dessus du niveau marin, interprétés comme étant des lits de progradation inclinés. Les âges au radiocarbone des dépôts deltaïques marins à la tête du bras de mer Howe indiquent, qu'il y a 10 200 ans avant le Présent, la mer se trouvait à environ 45 m au-dessus du niveau marin actuel. Ensemble, ces données révèlent, qu'il y a 10 200 ans avant le Présent, le glacier était déjà retraité de la tête du bras de mer Howe, et qu'à cette période le cône avait pénétré 2,5 km dans le fjord, et que sa progradation continuait au fur et à mesure que s'abaissait le niveau marin. Les réflecteurs à -10 m audessus du niveau marin, avec une forte inclinaison vers le sud qui longent la bordure méridionale du cône inférieur, couplés aux âges radiocarbone des sédiments des environs, indiquent que le cône alluvial avait presque atteint sa position actuelle vers 8000-9000 ans avant le Présent. Le calcul du volume de sédiment stocké dans le cône inférieur indique qu'au moins 90% du matériel avait déjà été déposé 6000 ans avant le Présent. Ce qui indique que la portion principale du cône de Cheekye représente un phénomène relictuel, et que sa grande taille peut servir d'exemple dans un contexte analogue pour estimer les risques naturels futurs. [Traduit par la Rédaction] Friele et al. 203

Structure from Motion used to revive archived aerial photographs for geomorphological analysis: an example from Mount Meager volcano, British Columbia, Canada

High resolution topographic modeling has become more accessible due to the development of Structure from Motion (SfM) image matching algorithms in digital photogrammetry. Large archival databases of historical aerial photographs are available in university, public, and government libraries, commonly as paper copies. The photos can be in poor condition (i.e. deformed by humidity, scratched, or annotated). In addition, the negatives, as well as metadata, may be missing. Processing such photos using classic stereo-photogrammetry is difficult and, in many instances, impossible. SfM can be applied to these photosets to access the valuable archive of geomorphic changes over the past century. In this paper, we illustrate the utility of the SfM technique using 568 digitized vertical aerial photographs of Mount Meager volcano, located in southwest British Columbia, Canada. We use the aerial photographs, which span the period from 1947 to 2006, to track glacier and glacier-landslide interactions on the volcano. Over this period, glaciers have thinned and retreated, interrupted by minor advances in the 1960s and 1970s. Landslides are frequent on the volcano and contribute to debris cover on the glaciers affecting the ablation process. SfM processing of the aerial photographs allowed us to unlock geomorphic information and reconstruct landscape change that would otherwise have been impossible. The results from SfM provide a visually effective way of presenting landscape change to a broad public audience, as a form of virtual geoheritage. The approach can thus be broadly applied in scientific and professional practices for improving land planning and hazard management.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author