Webster T.L.,Applied Geomatics Research Group
Remote Sensing | Year: 2010
A significant portion of the Canadian Maritime coastline has been surveyed with airborne Light Detection and Ranging (LiDAR). The purpose of these surveys has been to map the risk of flooding from storm surges and projected long-term sea-level rise from climate change and to include projects in all three Maritime Provinces: Prince Edward Island, New Brunswick, and Nova Scotia. LiDAR provides the required details in order to map the flood inundation from 1 to 2 m storm surge events, which cause coastal flooding in many locations in this region when they occur at high tide levels. The community of Annapolis Royal, Nova Scotia, adjacent to the Bay of Fundy, has been surveyed with LiDAR and a 1 m DEM (Digital Elevation Model) was constructed for the flood inundation mapping. Validation of the LiDAR using survey grade GPS indicates a vertical accuracy better than 30 cm. A benchmark storm, known as the Groundhog Day storm (February 1-3, 1976), was used to assess the flood maps and to illustrate the effects of different sea-level rise projections based on climate change scenarios if it were to re-occur in 100 years time. Near shore bathymetry has been merged with the LiDAR and local wind observations used to model the impact of significant waves during this benchmark storm. Long-term (ca. greater than 30 years) time series of water level observations from across the Bay of Fundy in Saint John, New Brunswick, have been used to estimate return periods of water levels under present and future sea-level rise conditions. Results indicate that under current sea-level rise conditions this storm has a 66 year return period. With a modest relative sea-level (RSL) rise of 80 cm/century this decreases to 44 years and, with a possible upper limit rise of 220 cm/century, this decreases further to 22 years. Due to the uncertainty of climate change scenarios and sea-level rise, flood inundation maps have been constructed at 10 cm increments up to the 9 m contour which represents an upper flood limit estimate in 100 years, based on the highest predicted tide, plus a 2 m storm surge and a RSL of 220 cm/century. © 2010 by the authors.
van Beest F.M.,University of Saskatchewan |
Uzal A.,University of Saskatchewan |
Vander Wal E.,Universite de Sherbrooke |
Laforge M.P.,University of Saskatchewan |
And 3 more authors.
Journal of Animal Ecology | Year: 2014
Density is a fundamental driver of many ecological processes including habitat selection. Theory on density-dependent habitat selection predicts that animals should be distributed relative to profitability of habitat, resulting in reduced specialization in selection (i.e. generalization) as density increases and competition intensifies. Despite mounting empirical support for density-dependent habitat selection using isodars to describe coarse-grained (interhabitat) animal movements, we know little of how density affects fine-grained resource selection of animals within habitats [e.g. using resource selection functions (RSFs)]. Using isodars and RSFs, we tested whether density simultaneously modified habitat selection and within-habitat resource selection in a rapidly growing population of feral horses (Equus ferus caballus Linnaeus; Sable Island, Nova Scotia, Canada; 42% increase in population size from 2008 to 2012). Among three heterogeneous habitat zones on Sable Island describing population clusters distributed along a west-east resource gradient (west-central-east), isodars revealed that horses used available habitat in a density-dependent manner. Intercepts and slopes of isodars demonstrated a pattern of habitat selection that first favoured the west, which generalized to include central and east habitats with increasing population size consistent with our understanding of habitat quality on Sable Island. Resource selection functions revealed that horses selected for vegetation associations similarly at two scales of extent (total island and within-habitat zone). When densities were locally low, horses were able to select for sites of the most productive forage (grasslands) relative to those of poorer quality. However, as local carrying capacity was approached, selection for the best of available forage types weakened while selection for lower-quality vegetation increased (and eventually exceeded that of grasslands). Isodars can effectively describe coarse-grained habitat selection in large mammals. Our study also shows that the main predictions of density-dependent habitat selection are highly relevant to our interpretation of RSFs in space and time. At low but not necessarily high population size, density will be a leading indicator of habitat quality. Fitness maximization from specialist vs. generalist strategies of habitat and resource selection may well be apparent at multiple spatial extents and grains of resolution. © 2013 British Ecological Society.
Hopkinson C.,Applied Geomatics Research Group |
Chasmer L.,Wilfrid Laurier University |
Munro S.,University of Toronto |
Demuth M.N.,Geological Survey of Canada
Hydrological Processes | Year: 2010
The influence of digital elevation model (DEM) resolution to modelled glacier melt during peak melt production was evaluated by performing a clear sky GIS radiation simulation over the Peyto Glacier in the Canadian Rockies. DEMs were generated at eight resolutions ranging from 1 m to 1000 m grid spacing from airborne lidar data. When applied to the planar area (PA) of the terrain, it was found that total melt increased with DEM resolution (r2 = 0.63) by 4% over 3 orders of magnitude. This systematic scaling-effect was mitigated at the basin scale, however, when the DEM slope variant area (SVA) was used to account for the increased divergence from PA as resolution increases. However, even after the inclusion of SVA in glacier surface melt simulations, localized melt variations with scale were still evident in the ablation and accumulation zone observations. In the ablation zone, there was a systematic increase in simulated melt (~4%) as resolution decreased from 1 m to 1000 m (r2 = 0.89), with the opposite effect in the accumulation zone (r2 = 0.81). DEM resolution also affected the diurnal melt cycle, such that for the entire glacier there was a tendency for a morning over-estimation and afternoon underestimation of melt rate with decreasing resolution. For the accumulation zone, there was an increased melt rate at low resolutions occurring in the afternoon, while in the ablation zone there was a tendency for increasing melt rates with decreasing resolution throughout the day. These localized spatio-temporal variations in simulated melt are largely due to the lowering of ridges and raising of valley floors that occur as resolution decreases. This scale dependence in the representation of terrain morphology directly controls the pattern and relative proportion of direct beam shadowing over actively melting surfaces and thereby has a systematic influence on the grid cell-level hydrological balance. It is recommended that GIS-based glacier melt modelling routines take into account the slope area of grid cells, while noting that the choice of DEM scale can have a discernible and systematic influence on modelled runoff magnitude. It is important to note that while higher grid resolutions mitigate the effect of terrain smoothing on spatio-temporal melt patterns, lower resolutions actually mitigate the systematic error associated with assuming all surface areas are planar. © 2010 John Wiley & Sons, Ltd and Her Majesty the Queen in right of Canada.
Hamilton J.M.,Bedford Institute of Oceanography |
Collins K.,Applied Geomatics Research Group |
Prinsenberg S.J.,Bedford Institute of Oceanography
Journal of Geophysical Research: Oceans | Year: 2013
A decade of instrumented mooring data from Barrow Strait in the eastern Canadian Arctic Archipelago reveals connections between sea ice, water characteristics, and zooplankton dynamics on interannual time scales. On the North side of the Strait, the timing of breakup is positively related to the timing of freezeup in the previous year and negatively related to spring water temperature. This suggests that an early freezeup insulates the ocean from a cold autumn atmosphere, allowing heat to be retained until spring when it contributes to early sea ice erosion. There is also a very strong negative association between the timing of freezeup and late summer salinity, suggesting that monitoring of salinity in real time could be used to predict freezeup. A zooplankton biomass index derived from acoustic Doppler current profiler echo intensity data is used to demonstrate that on the North side there are also strong connections between early summer water temperature and the start, length, and productivity of the zooplankton growth season. On the South side of the Strait where currents are stronger, the relationships seen on the North side were not observed. But here integrated zooplankton biomass index and measured currents are used to identify interannual variability in the zooplankton biomass being delivered downstream into Lancaster Sound. Also on the South side, two yearlong records of daily fluorescence profiles reveal a large difference in the phytoplankton biomass being delivered downstream between years and demonstrate a strong relationship between the timing of the spring phytoplankton bloom and that of breakup. © 2013. American Geophysical Union. All Rights Reserved.
Hill R.A.,Bournemouth University |
Boyd D.S.,University of Nottingham |
Hopkinson C.,Applied Geomatics Research Group
Remote Sensing Letters | Year: 2011
This letter investigates the influence of within-pixel variation of canopy height on the spectral response recorded in Landsat Enhanced Thematic Mapper (ETM+) data for tropical rainforest. Forest canopy height is derived from airborne, smallfootprint LiDAR data acquired using a Leica ALS50 II system. The field site is in the Tambopata National Reserve, in Peruvian Amazonia, where forest types include regenerating, swamp, floodplain and terra firme. For individual Landsat ETM+ bands, the strongest correlation for maximum, mean and standard deviation of canopy height occurred with ETM+ Band 4 (near infrared) for regenerating, floodplain and terra firme forest, and with ETM+ Band 5 (middle infrared) for swamp forest. For normalized difference band indices, ND42 and ND43 (i.e. the Normalized Difference Vegetation Index, NDVI) showed strong correlation with both mean and maximum canopy height for regenerating and terra firme forest, and with maximum and standard deviation of canopy height for floodplain forest. The palm-dominated swamp forest showed weaker relationships, with the strongest occurring for ND45 and ND52 with mean canopy height. Many papers have identified middle-infrared bands as being most sensitive to tropical rainforest structure, although these have often focussed on young regenerative forests. By focussing on older regenerative forest (of > 25 years since land abandonment) and mature rainforest types, this work has shown that there is considerable variation with how structure may influence spectral reflectance and lends support to the hypothesis that canopy height distribution and shadowing effects caused by canopy complexity and the presence of emergent trees is what most significantly influences spectral response for tropical rainforests. © 2011 Taylor & Francis.