Howe Sound Research Articles

Younger Dryas readvance in Squamish river valley, southern Coast mountains, British Columbia

Stratigraphy and landforms in the Brohm Creek basin and lowermost Mamquam River valley provide evidence for a readvance of a valley glacier in the southern Coast Mountains of British Columbia during the Younger Dryas interval. At Brohm Creek, till containing wood 10,500 and 10,700 14C yr old (ca 12,500–12,900 cal yr old), overlies an ice-contact terrace that is correlative with similar terraces at the mouth of Mamquam River, 11 km to the south and 900 m lower in elevation. A line linking the two sites has a slope of 5°, which is similar to slopes of termini of present-day valley glaciers in the southern Coast Mountains. We used these observations to reconstruct the Younger Dryas glacier in Squamish valley at the head of Howe Sound. The glacier deflected landslide debris, derived from steep slopes at the head of Cheekye River basin on the west flank of Mt. Garibaldi, southward to an ice-marginal lake at the mouth of Mamquam River. Foreset-bedded sediments in the core of a large fan at the mouth of Cheekye River indicate the glacier terminus had retreated up Squamish valley beyond Cheekye and Mamquam rivers by 10,200 14C yr BP (11,900 cal yr old). Radiocarbon ages on the oldest postglacial sediments in a kettle on the landslide debris show that stagnant ice in the study area had melted before 10,000 14C yr BP (11,500 cal yr BP). The readvance of the Squamish valley glacier during the Younger Dryas Chronozone was probably driven by a regional climate reversal.

Investigation, Remediation and Cost Allocation of Contaminants from the Britannia Mine in British Columbia: A Case Study

This case study, from the province of British Columbia, is described to illustrate the use of environmental forensic techniques. The study involves acid rock drainage (ARD) from the Britannia Mine, a mine located in southwestern British Columbia, that has been closed for approximately 25 years and discharges between 4 and 40 million litres of ARD, depending on the time of year into nearby Howe Sound every day. The ARD occurs as an oxidation of sulphide mineralization exposed to air and water. The sources of ARD contamination from this site are copper, aluminium, iron, zinc and manganese. Current copper concentrations discharging from the 4100 Portal Level range from 40 to 100 mg/L. Environmental forensic techniques are applied to describe the origin of the contaminant release, the timing of the release, the distribution of the contamination, finding the responsible parties and allocating remediation costs for cleanup. Other forensic techniques described include the use of geochemistry to determine contaminant degradation.

Readvance of glaciers in the British Columbia Coast Mountains at the end of the last glaciation

Late Quaternary sediments and landforms at the head of Howe Sound, a fjord in the British Columbia Coast Mountains, provide a detailed record of final decay of the southwestern sector of the Cordilleran ice sheet at the end of the Pleistocene. The upper reaches of Mamquam River valley, a mountain valley at the head of the fjord east of the town of Squamish, were ice free and locally treed as early as 14000 years ago (11900 14Cyr BP). Folding and faulting of late-glacial lacustrine sediments in Mamquam valley may record a glacier readvance, correlative with the Sumas event in the Fraser Lowland to the southeast. By 12900 years ago (10690 14Cyr BP), the trunk glacier in Howe Sound had retreated from a Sumas-age moraine at Porteau Cove, 15km south of Squamish. By 12800 years ago (10650 14Cyr BP), the glacier terminus stood near the present fjord head with the sea at an elevation of about 40–50m a.s.l. Shortly after 12800 years ago, during the Younger Dryas chronozone, the trunk glacier in Squamish valley readvanced a short distance and then retreated for a final time. Tributary valleys were probably completely deglaciated by 11300 years ago (9920 14Cyr BP), and certainly by 10600 years ago (9360 14Cyr BP). Relative sea level fell as deglaciation progressed; however, it did not fall below its present datum in the Squamish area until after 11200 years ago, at least 1300 years later than in the Fraser Lowland.

Ground penetrating radar facies of the paraglacial Cheekye Fan, southwestern British Columbia, Canada

Abstract Ground penetrating radar (GPR) surveys have been carried out in order to characterise reflection patterns and to assess the method's potential for imaging alluvial fan sediments in southwestern British Columbia, Canada. The results from Cheekye Fan show that GPR achieved over 40 m penetration with the 50 MHz antenna and provided data that allowed identification of 10 radar facies. Glacial till produces a reflection free configuration and bedrock radar facies is characterised by a hummocky pattern often with stacked macro-scale diffractions. Four subaerially deposited alluvial-fan facies were identified. Radar facies of the nearby meandering Squamish River are characterised by a complex, sigmoid oblique pattern that is clearly different from any configuration observed on Cheekye Fan. Based on the analysis of over 27 km radar data, the large-scale internal architecture of Cheekye Fan was reconstructed. Fan sediments are underlain by till and hummocky bedrock in the northern and eastern portion of the fan. Sedimentation was initiated by subaqueously deposited delta foresets following deglaciation of Upper Howe Sound. Subaerially deposited sediments can be divided into: (a) massive, matrix-rich diamicton that appears predominant at the core of the fan and at lower stratigraphic horizons, suggesting bouldery rock-slide or debris flow origin; and (b) horizontally-bedded sheetflood gravel dominating the upper 20–25 m of the stratigraphic column.

The effects of surface area, grain size and mineralogy on organic matter sedimentation and preservation across the modern Squamish Delta, British Columbia: the potential role of sediment surface area in the formation of petroleum source rocks

Surface sediment samples were collected from the Squamish River Delta, British Columbia, in order to determine the role of sediment surface area in the preservation of organic matter (OM) in a paralic sedimentary environment. The Squamish Delta is an actively prograding delta, located at the head of Howe Sound. Bulk total organic carbon (TOC) values across the Squamish Delta are low, ranging from 0.1 to 1.0 wt.%. The carbon/total nitrogen ratio (C org/N) ranges from 6 to 17, which is attributed to changes in OM type and facies variations. The <25-μm fraction has TOC concentrations up to 2.0 wt.%, and a C org/N ratio that ranges from 14 to 16. The 53–106-μm fraction has higher TOC concentrations and C org/N ratios relative to the 25–53-μm fraction. The C org/N ratio ranges from 9 to 18 in the 53–106-μm fraction and 5.5–10.5 in the 25–53-μm fraction. Surface area values for bulk sediments are low (0.5–3.0 m 2/g) due to the large proportion of silt size material. Good correlation between surface area and TOC in bulk samples suggests that OM is adsorbed to mineral surfaces. Similar relationships between surface area and TOC were observed in size-fractionated samples. Mineralogy and elemental composition did not correlate with TOC concentration. The relationships between surface area, TOC and total nitrogen (TN) can be linked to the hydrodynamic and sedimentological conditions of the Squamish Delta. As a result, the Squamish Delta is a useful modern analogue for the formation of petroleum source rocks in ancient deltaic environments, where TOC concentrations are often significantly lower than those in source rocks formed in other geological settings.

Effects of acid mine drainage from an abandoned copper mine, Britannia Mines, Howe Sound, British Columbia, Canada, on transplanted blue mussels ( Mytilus edulis)

Juvenile mussels ( Mytilus edulis) were transplanted to Howe Sound, British Columbia, Canada, along an apparent pollution gradient of acid mine drainage (AMD) from an abandoned copper (Cu) mine. Cages containing 75 mussels each were placed at a total of 15 stations and were exposed to concentrations of dissolved Cu in surface waters ranging from 5 to 1009 μg/l for a period of 41 days. Mussels located at stations closer to the source of AMD at the mouth of Britannia Creek bioaccumulated higher concentrations of Cu and zinc (Zn) in their tissues. Mussel growth was adversely affected by Cu tissue concentrations above 20 μg/g dry wt., while declines in survival and condition index occurred in mussels that bioaccumulated greater than 40 μg/g dry wt. Cu. Tissue Zn concentrations (117–192 μg/g dry wt.) were likely not high enough to have a direct impact on mussel health. Reduced survival of transplanted mussels was supported by an absence of natural mussels in contaminated areas. Phytoplankton was also severely reduced in areas contaminated by mine waters. Based on the weight of evidence, AMD from the Britannia mine had a deleterious impact on mussel survival in a zone extending at least 2.1 km to the north and 1.7 km to the south of Britannia Creek on the east shore of Howe Sound.

Impacts of acid mine drainage on juvenile salmonids in an estuary near Britannia Beach in Howe Sound, British Columbia

The abandoned copper mine at Britannia Beach, British Columbia, has been releasing acid mine drainage (AMD) into Howe Sound for many years. To assess the impacts of AMD on juvenile salmonids in the Britannia Creek estuary, we compared fish abundance, distribution, and survival at contaminated sites near the creek with uncontaminated areas in Howe Sound. Water quality near Britannia Creek was poor, particularly in spring when dissolved Cu exceeded 1.0 mg·L-1 and pH was less than 6. Beach seine surveys conducted during April-August 1997 and March-May 1998 showed that chum salmon (Oncorhynchus keta) fry abundance was significantly lower near Britannia Creek mouth (0-1.2·100 m-2) than in reference areas (11.5-31.4·100 m-2). Laboratory bioassays confirmed that AMD from Britannia Mine was toxic to juvenile chinook (Oncorhynchus tshawytscha) and chum salmon (96-h LC50 = 0.7-29.7% in freshwater and 12.6-62.2% in 10 ppt water). Chinook salmon smolts transplanted to surface cages near Britannia Creek experienced 100% mortality within 2 days. These results demonstrated that juvenile salmonids are vulnerable to AMD from Britannia Creek: their abundance peaks during spring when Cu concentrations are highest and toxicity is greatest in surface freshwater, which matches their preferred vertical distribution.

Impacts of acid mine drainage on juvenile salmonids in an estuary near Britannia Beach in Howe Sound, British Columbia

Impacts of acid mine drainage on juvenile salmonids in an estuary near Britannia Beach in Howe Sound, British Columbia

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

Cheekye fan, a large (~25 km2) 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.

Differentiation of polychlorinated dibenzo‐p‐dioxin and dibenzofuran sources in coastal British Columbia, Canada

AbstractMultivariate pattern analysis techniques, principal components analysis, and polytopic vector analysis (PVA) were used to apportion sources of dioxins and furans to Howe Sound and the lower Strait of Georgia marine ecosystem, British Columbia, Canada, based on deposition in recent sediments. In sediment cores collected in 1990, differences between congeners in the depth of maximum concentration suggested the influence over time of several different sources. Those with a predominance of hexachlorinated dibenzodioxins and 2,3,7,8‐tetrachlorodibenzofuran comprised one of the major contributions to the sediment core samples and surficial samples collected from Howe Sound, consistent with past inputs of pulpmill effluent. For most sediment samples, however, over 50% of the composition was attributable to a separate source with octachlorodibenzo‐p‐dioxin (OCDD) as the dominant congener, followed by heptachlorodibenzo‐p‐dioxins with small amounts of heptachlorodibenzofuran and octachlorodibenzofuran (OCDF). This source signature is consistent with the composition of dioxins/furans in formulations of pentachlorophenol‐based wood preservatives, which were used extensively in British Columbia, Canada prior to the mid‐1980s. This major input signature to the greater Strait of Georgia cannot be unequivocally ascribed to PCP use and disposal, however, since several other dioxin/furan sources also exhibit a highly similar composition, one dominated by OCDD. For example, source signatures similar to PCP formulations include those from diesel emissions, coal combustion, municipal solid waste, or other incineration stack emissions (fly ash, in particular), chimney soot from oil central heating, black‐liquor recovery furnace flue gas, and scrap wire and car incineration. Further research is required to discriminate among the OCDD‐containing sources and, hence, provide for improved future source management.

Physical modeling of an outflow event in Howe Sound, British Columbia

Outflow winds occur when differing air masses are separated by a coastal mountain barrier. In extreme cases the cross‐barrier pressure gradient and the high degree of stratification (often approaching a distinct layered structure) result in channel winds which exhibit hydraulic features. We present a study of outflow winds in Howe Sound, British Columbia. A field investigation, aimed specifically at locating and quantifying hydraulic effects, was undertaken during the winter months of 1992/1993. Microbarographs positioned in the region recorded pressure changes at discrete locations in the streamwise direction. The pressures obtained during a severe outflow wind event, which occurred from December 27, 1992 to January 1, 1993, show a highly variable lower‐layer depth suggestive of hydraulic control. Experiments were conducted with a three‐dimensional physical model that is geometrically and kinematically similar to Howe Sound. Synoptic conditions recorded during the outflow wind event in Howe Sound in December 1992 were used to determine appropriate model flow forcing. The expanse of supercritical flow area was observed to be relatively sensitive to changes in along‐channel pressure gradient and downstream depth, when compared to changes in discharge. Channel sinuosity and local topography appeared to force critical conditions at specific locations. For example, a channel bend combined with headlands was observed to force a situation where subcritical and supercritical streams flow side by side. Flow separation, resulting in lateral shear discontinuities, produced similar conditions. These effects are discussed and put into context with field observations. Field and model results show good agreement.

A biological index to predict pulp mill pollution levels

The species diversity of mid to low rocky intertidal beaches along the protected coast of British Columbia, Canada, increases significantly as exposure to pulp mill effluent decreases. Species were categorized according to hardiness and ranked as either pollution tolerant, sensitive, or intolerant. Indicator species whose presence or abundance is highly correlated to exposure to mill effluent were discovered. A biological index (Bioindex) was developed to predict a rocky shore's exposure to mill effluent by analyzing the hardiness of the resident biota. The Bioindex is useful to evaluate the environmental stress from pulp mills, to pinpoint depleted beaches for cleanup, and to evaluate pristine areas to be protected. The Howe Sound mills were found to have the most detrimental and widespread effect on rocky shore beaches of all regions surveyed, followed, in order of decreasing severity, by the Crofton mill, the Prince Rupert mill, and the Powell River mill.

工場紹介 （５７） ハウサンド・パルプ・アンド・ペーパー社

工場紹介 （５７） ハウサンド・パルプ・アンド・ペーパー社

Surface winds during an intense outbreak of arctic air in Southwestern British Columbia

Abstract An outbreak of arctic air which occurred from 30 January to 2 February 1989, plunging southwestern British Columbia (as well as most of western North America) into extreme cold, is examined and put in context by reference to similar events reported in the literature. Emphasis is placed on the resulting wind fields in Howe Sound and the Lower Fraser Valley. The wind speed in these topographically confined channels during arctic outbreaks is found to be related to the down‐channel pressure gradient. Three simple steady‐state models of wind speed are suggested whose results are compared to observed winds. It is found that the Friction model, representing a balance between friction, acceleration and horizontal pressure gradient, compares best with observations in the Lower Fraser Valley. Hydmod, a hydraulic model of wind flow performs reasonably well, with previous work indicating it produces more realistic along channel flow variability in Howe Sound.

Hydraulic Physical Modeling and Observations of a Severe Gap Wind

Abstract Strong gap winds in Howe Sound, British Columbia, are simulated using a small-scale physical model. Model results are presented and compared with observations recorded in Howe Sound during a severe gap wind event in December 1992. Hydraulic theory is utilized to explain along-channel variation in wind. Field observations affirm the findings of the physical modeling with both, indicating the presence and location of controls and hydraulic jumps in the wind layer. Hydraulic behavior is found to change as the synoptic pressure gradient and the flow rate increase. In particular, field results indicate two distinct hydraulic situations: one during relatively weak wind, the other, which is more strongly controlled, during the period of peak wind. An additional comparison is made with output from the computer model hydmod of Jackson and Steyn. Numerical simulations, configured for the conditions present in Howe Sound during the December 1992 event, indicate channel hydraulics (and thus spatial wind spee...

Gap Winds in a Fjord. Part I: Observations and Numerical Simulation

Gap winds in Howe Sound, British Columbia, are described and placed in context by reviewing studies of similar phenomena in other locations. An observational program consisting of a surface mesonetwork and vertical soundings shows that gap winds vary considerably along and across the channel, as well as vertically. Wind strength generally increases down channel, and strongest winds are found below 1000-m depth. Results from application of a 3D mesoscale numerical model to a gap wind case compare reasonably well with observations. Model output reveals more details of horizontal and especially vertical flow structure than is possible from observations. Model vertical cross sections and Froude number output indicate similarity with hydraulic flow. This is further substantiated by a force-balance analysis of model output.

A three‐dimensional numerical model of suspended sediment transport in Howe sound, British Columbia

Abstract Numerical models of the hydrodynamics of Howe Sound and of the transport and deposition of suspended sediment from the Squamish River entering Howe Sound are described. Two different versions of a three‐dimensional hydrodynamic model of Howe Sound have been developed. One is a fine‐grid model employing a 390‐m grid size, the other a coarse‐grid model with a 1.95‐km grid size. In the present implementation, both models have 9 layers in the vertical, and calculate the three components of the velocity field as well as the time‐varying density field. The models are forced at their open boundaries by a larger three‐dimensional model of the Strait of Georgia, by surface wind stress and by the Squamish River flow. The coarse‐grid model is computationally less demanding and is used for long‐term simulations, whereas the fine‐grid model is used for detailed simulations for shorter time periods. The sediment model derives its velocity field from the coarse grid three‐dimensional hydrodynamic model. Sedimen...

Debris Torrents and Professional Responsibilities

There have been several debris torrents down steep creeks along Howe Sound, near Vancouver, British Columbia, Canada. A debris torrent is a rapid surge of water, mud, and rocks down a steep creek. Debris torrents only occur under special circumstances and are not yet fully understood, although knowledge about them has been growing rapidly. The way in which the professionals who are responsible for public safety responded to the growing knowledge about debris torrents and the risks that they pose is examined. Civil engineers are used to uncertainty and deal with it by using a variable safety factor that depends on the level of uncertainty and the consequences of failure. This approach worked well in the case of the Howe Sound debris torrents, but did not in those cases where the engineers felt little sense of direct responsibility.

Contemporary Squamish River sediment flux to Howe Sound, British Columbia

Squamish River drains 3600 km2 in the southern Coast Mountains of British Columbia to Howe Sound at Squamish, some 50 km north of Vancouver. This study uses differencing of digitized bathymetric surfaces based on the Canadian Hydrographic Services surveys of 1930, 1973, and 1984 at the head of Howe Sound to yield a long-term sedimentation rate for Squamish River delta. The sediment flux from Squamish River to Howe Sound is determined to be 1.29 × 106 m3 a−1 or 1.81 × 109 kg a−1, rates consistent with loads calculated from flow and sediment-concentration regimes measured in the estuary in 1973 – 1975 and 1987 – 1988. The latter data indicate that the modal discharge-effectiveness class is 600 – 700 m3 s−1, moving 13% of the annual suspended-sediment load. Discharges up to 1400 m3 s−1 constitute 99.8% of all flows and are responsible for transporting 81.5% of the annual load. A very significant 18.5% of the load is moved by large-magnitude floods (&gt; 1400 m3 s−1), which occur less than 0.2% of the time.Squamish Delta is prograding downfjord at an average rate of 3.86 m a−1 although local extensions of the delta front in a given year may approach 20 m. Some of the geomorphic implications of extrapolating these contemporary rates of fjord infilling over the Holocene are discussed briefly.

A model for debris accumulation and mobilization in steep mountain streams

Previous work on the initiation of debris flows has emphasized the roles played by material strength, stream gradient, and fluid pressure, but in most published models the friction angle (φ′) of the channel material is assigned some characteristic or constant value. The model presented here retains gradient and pressure as variables, and considers the probable changes in φ′ and hydraulic conductivity, K, of channel debris over time. Preliminary results from the Howe Sound area in southwest British Columbia suggest that stream reworking may lead to small increases in φ′ and large increases in K, rendering channel debris more stable with time. This is partially offset by a local increase in channel gradient as debris accumulates. These factors favour the growth of large, marginally stable debris deposits, and may lead to high-magnitude, low-frequency debris torrents in channels not steep enough to produce torrents directly from hillslope failure events.