An Alluvial Fan, near Field, in British Columbia

1908 ◽  
Vol 40 (6) ◽  
pp. 340
Author(s):  
Fred H. Lahee
Keyword(s):  
British Columbia ◽  
Near Field ◽  
Alluvial Fan

scholarly journals Over 16,000 Years of Fire Frequency Determined from AMS Radiocarbon Dating of Soil Charcoal in an Alluvial Fan at Bear Flat, Northeastern British Columbia

Radiocarbon ◽  
2006 ◽  
Vol 48 (3) ◽  
pp. 435-450 ◽  
Author(s):  
A J Timothy Jull ◽  
Marten Geertsema
Keyword(s):  
British Columbia ◽  
Radiocarbon Dating ◽  
Large Scale ◽  
Fire Frequency ◽  
Alluvial Fan ◽  
Before Present ◽  
Ams Radiocarbon Dating ◽  
Soil Charcoal ◽  
Large Fires ◽  
Millennial Time Scale

We present results of radiocarbon dating of charcoal from paleosols and buried charcoal horizons in a unique sequence, which potentially records the last 36,000 yr, from a fan at Bear Flat, British Columbia (BC) (56°16'51’N, 121°13'39”W). Evidence for forest-fire charcoal is found over the last 13,500 ± 110 14C yr before present (BP) or 16,250 ± 700 cal BP. The study area is located east of the Rocky Mountains in an area that was ice-free at least 13,970 ± 170 14C yr BP (17,450–16,150 cal BP) ago. The latest evidence of fire is during the Medieval Warm Period (MWP). The charcoal ages show a periodicity in large fires on a millennial scale through the Holocene—an average of 4 fires per thousand years. Higher fire frequencies are observed between 2200 to 2800 cal BP, ∼5500 and ∼6000 cal BP, ∼7500 to 8200 cal BP, and 9000 to 10,000 cal BP. These intervals also appear to be times of above-average aggradation of the fan. We conclude that fire frequency is related to large-scale climatic events on a millennial time scale.

scholarly journals Detecting Near-Field Tsunamis off the Coast of British Columbia

Eos ◽  
2014 ◽  
Vol 95 (37) ◽  
pp. 336-336
Author(s):  
Tania Lado Insua ◽  
Kate Moran
Keyword(s):  
British Columbia ◽  
Near Field

scholarly journals Modeling the Transport and Fate of Sediments Released from Marine Construction Projects in the Coastal Waters of British Columbia, Canada

2018 ◽  
Author(s):  
David B. Fissel ◽  
Yuehua Lin
Keyword(s):  
British Columbia ◽  
Numerical Methods ◽  
Environmental Assessment ◽  
Coastal Waters ◽  
Construction Projects ◽  
Numerical Models ◽  
Near Field ◽  
Suspended Sediments ◽  
Initial Dilution ◽  
Resolution Model

Major marine construction projects, resulting in the release of sediments, are subject to environmental assessment and other regulatory approval processes. An important tool used for this is the development of specialized numerical methods for these marine activities. An integrated set of numerical methods addresses four distinct topics: the near-field release and mixing of suspended sediments into the water column (i.e. the initial dilution zone); the transport of the suspended sediments under the influence of complex ocean currents in the far-field; the settling of the transported suspended sediments onto the seabed; and the potential for resuspension of the deposited sediments due to sporadic occurrences of unusually large near-bottom currents. A review of projects subjected to environmental assessment in the coastal waters of British Columbia from the year 2006 to 2017, is presented to illustrate the numerical models being used and their ongoing development. Improvements include higher resolution model grids to better represent the near-field, the depiction of particle size dependent vertical settling rates and the computation of resuspension of initially deposited sediments, especially in relation to temporary subsea piles of sediments arising from trenching for marine pipelines. The ongoing challenges for this numerical modeling application area are also identified.

scholarly journals Last Interglacial Muir Point Formation, Vancouver Island, British Columbia

2007 ◽  
Vol 44 (3) ◽  
pp. 337-340 ◽  
Author(s):  
Stephen R. Hicock
Keyword(s):  
British Columbia ◽  
Alluvial Fan ◽  
Last Interglacial ◽  
Modern Pollen ◽  
Pollen Rain ◽  
Stratigraphic Position ◽  
Normal Polarity ◽  
Tidal Stream ◽  
Exposed Part ◽  
Study Sites

ABSTRACT The Muir Point Formation probably represents the last interglacial and climatic maximum of the Late Pleistocene in southwest British Columbia. It comprises estuarine, floodplain, fluvial, alluvial fan, and debris flow lithofacies. The lower exposed part of the formation is normally magnetized and probably formed during the Brunhes Normal Polarity Chron (<790 ka BP). On the basis of similar polarity, palynology, lithologies, and stratigraphic position, the Muir Point Formation is correlated with the Whidbey Formation of northwest Washington State. It probably also correlates with the Highbury Formation under the Fraser Lowland of mainland British Columbia.These formations may be remnants of shallow marine or subaerial sediment shelves which once rimmed ancestral Strait of Georgia and Puget basins over 100 ka, but were mostly removed by later glaciations. During this time sea level may have been 10 m higher than today. The middle floodplain unit contains five pollen zones whose differences can be explained mainly by shifts in a meandering tidal stream. Throughout most of this record Douglas fir pollen is more abundant than in modern pollen rain around the study sites which indicates that paleoclimate was at least as warm and dry as present.

Bar evolution and development of stratification in the gravelly, braided, Kicking Horse River, British Columbia

1977 ◽  
Vol 14 (4) ◽  
pp. 562-570 ◽  
Author(s):  
Frances J. Hein ◽  
Roger G. Walker
Keyword(s):  
British Columbia ◽  
Current Velocity ◽  
Near Field ◽  
Spring Flood ◽  
Velocity Increase ◽  
Late Afternoon ◽  
Discharge Fluctuations ◽  
Evolution And Development ◽  
Braided Stream ◽  
Shielding Effects

The Kicking Horse River is a gravelly, braided stream characterized by very low winter discharge, a peak spring flood (70 m3s−1 in 1973), and summer diurnal discharge fluctuations (from 18 to 44 m3/s−1 in 1973) related to daily melting on the glaciers that supply the river. The reach studied, near Field, B.C., is characterized by abundant braid bars, and was subdivided into three parts.The upstream reach is characterized by only one major channel, with few unit bars within it. Clast movement takes place at peak flood stages, and the clasts move in 'diffuse gravel sheets' on the channel floor. These sheets are only one to two clast diameters in thickness, and when the clasts stop rolling, the sheet becomes a coarse lag. By contrast, in the midstream and downstream reaches, the channel is more anastomosing, and there are many in-channel bars, mostly transverse and diagonal unit bars. The diagonal bars mostly lack foreset slopes at their downstream margin, and it is suggested that massive to crudely horizontally stratified gravels would be deposited. Transverse bars normally have a foreset slope, giving rise to cross-stratified gravels.Several bars were monitored continuously at their active stages during the diurnal rise in discharge in the late afternoon – evening. Measurement of water slope, current velocity, depth, clast sizes, and rate of bar migration were made every 15 minutes at each of the stations on each bar. The bars tended to advance episodically during periods of velocity increase, as recorded at the upstream monitoring station. However, clast size at the bar front does not seem to increase as velocity increases, possibly due to shielding effects of the largest, stationary, clasts on the bed. This effect made existing initiation-of-bedload-movement equations difficult to apply, and of severely limited use with respect to the poorly sorted gravels.Stratification could not be directly observed in the bars, but we suggest that upstream, the diffuse gravel sheets would form crudely horizontally stratified gravels, probably with a long-axis-transverse imbrication. In the midstream and downstream reaches, in finer gravels, more cross-stratification would be present, related to migration of transverse bars.

The Stratigraphy and Morphology of Para-glacial Alluvial Fans in South-central British Columbia

1971 ◽  
Vol 8 (2) ◽  
pp. 279-298 ◽  
Author(s):  
J. M. Ryder
Keyword(s):  
British Columbia ◽  
Volcanic Ash ◽  
Alluvial Fan ◽  
Alluvial Fans ◽  
River Terraces ◽  
South Central ◽  
Multi Level ◽  
Local Base

Alluvial fan construction within the interior valleys of southern British Columbia was dependent upon temporary conditions resulting from deglaciation. Glacial drift was reworked by streams and mudflows to form fans whose composition is dependent upon the nature of the drift supply and the hydrologic character of the parent basin.Stratigraphic evidence suggests that fan building commenced soon after valley floors became ice-free, continued during post-glacial aggradation by major rivers and for some time after wards. Most recently, fans were built upon degradational river terraces. Mazama volcanic ash within fans indicates that their construction continued until after 6600 years B.P. After deposition ceased many fans were dissected either as local base-levels were lowered under the control of degrading major rivers or by fan-head trenching initiated as the debris supply declined. Where fan building persisted during degradation, multi-level fans were constructed.

Late Quaternary sediments and geomorphic history of northern Vancouver Island, British Columbia

1983 ◽  
Vol 20 (1) ◽  
pp. 57-65 ◽  
Author(s):  
D. E. Howes
Keyword(s):  
British Columbia ◽  
Late Quaternary ◽  
Mass Movement ◽  
Vancouver Island ◽  
Alluvial Fan ◽  
Eastern Coast ◽  
Sedimentary Environments ◽  
History Of ◽  
Floodplain Deposits ◽  
Organic Deposits

Materials from two glacial intervals and one nonglacial interval have been identified on northern Vancouver Island, British Columbia. The oldest Pleistocene unit, termed "older drift," consists of glaciomarine silt and clay >38 000 years BP in age that overlie a till that has only been recorded in well logs. "Older drift" is tentatively correlated with Dashwood drift of the Semiahmoo Glaciation (early Wisconsin or older). No sediments of the succeeding Olympia nonglacial interval (mid-Wisconsin) have been found in the area. It is thought that this interval was characterized by a period of degradation in which Olympia-age sediments were deposited in transient sedimentary environments and subsequently eroded, in part during the Fraser Glaciation (late Wisconsin). The youngest Pleistocene unit, termed Port McNeill drift, includes advance deposits, till, and deglacial sediments, all deposited during Fraser Glaciation. Ice of this glaciation did not cover most of northern Vancouver Island until after 20 600 ± 330 years BP. At the maximum, which probably occurred about 15 000 years ago, Coast Mountain ice coalesced with and overrode Vancouver Island ice, and flowed in a westerly to northwesterly direction across northern Vancouver Island. Deglaciation commenced prior to 12 930 ± 160 years BP and possibly as early as 13 630 years ago on the eastern coast. Maximum sea level during and immediately following deglaciation was about 92 and 20 m elevation on the east and west coasts, respectively. This suggests that ice thickness at the Fraser maximum decreased westward across the study area. Deposits of Recent time include colluvial sediments formed by weathering and mass movement processes, alluvial fan and floodplain deposits, eolian sands associated with active beaches on the west coast, and organic deposits.

scholarly journals Reconnaissance sediment budgets for Lynn Valley, British Columbia: Holocene and contemporary time scales

2003 ◽  
Vol 40 (5) ◽  
pp. 701-713 ◽  
Author(s):  
David Campbell ◽  
Michael Church
Keyword(s):  
British Columbia ◽  
Drainage Basin ◽  
Mass Movement ◽  
Alluvial Fan ◽  
Stream Channel ◽  
Sediment Sources ◽  
Stream Channels ◽  
Photographic Analysis ◽  
Sediment Transfer ◽  
Channel Degradation

Volumes of erosional and depositional landforms were estimated by reconnaissance methods in a steep, forested drainage basin in the Coast Mountains, British Columbia, to examine what insight might be gained into the sediment budget in the absence of direct measurements of sediment transfer processes. Sediment transfers in postglacial and contemporary time were inferred on hillslopes, from hillslopes to stream channels, and within stream channels. Data were collected by aerial photographic analysis and field observation. Postglacial sediment sources are major gullies created by debris slides and flows, failures in glaciolacustrine terraces, and stream channel degradation. Depositional landforms consist of talus slopes and colluvial and alluvial fans. Contemporary sediment sources include debris slides and flows in established gullies and minor processes on hillslopes. Debris slide and debris flow volumes were calculated, and other processes were estimated from regional values. Erosion rate averaged over postglacial time is 276 t·km–2·a–1 (0.15 mm·a–1 surface lowering), with gullies and stream channel degradation contributing 170 and 82 t·km–2·a–1, respectively. A terminal alluvial fan provides an independent check of the results. In contemporary time, erosion rates are calculated to be 350 t·km–2·a–1, with debris flows and slides contributing nearly all of this sediment. The contemporary rate is probably perturbed by recent land use history. Mass-movement processes appear to be the dominant mechanism of sediment transfer and, contributions from Pleistocene valley deposits have declined significantly during Holocene time.

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