Asymmetrical deltas below wave base: Insights from the Fraser River Delta, Canada

Sedimentology ◽  
2015 ◽  
Vol 63 (3) ◽  
pp. 761-779 ◽  
Author(s):  
Korhan Ayranci ◽  
Shahin E. Dashtgard
Keyword(s):  
River Delta ◽  
Fraser River ◽  
Fraser River Delta

Seismic site response in the greater Vancouver, British Columbia, area: spectral ratios from moderate earthquakes

1999 ◽  
Vol 36 (2) ◽  
pp. 195-209 ◽  
Author(s):  
John F Cassidy ◽  
Garry C Rogers
Keyword(s):  
Site Response ◽  
Strong Motion ◽  
River Delta ◽  
Data Sets ◽  
Fraser River ◽  
Spectral Ratios ◽  
Data Set ◽  
Seismic Site Response ◽  
Fraser River Delta ◽  
S Period

Three-component, digital recordings of two recent moderate earthquakes provide valuable new insight into the response to seismic shaking in the greater Vancouver area, particularly on the Fraser River delta. The 1996 M = 5.1 Duvall, Washington, earthquake (180 km southeast of Vancouver) triggered strong-motion seismographs at seven sites and the 1997 M = 4.3 Georgia Strait earthquake (37 km west of Vancouver) triggered instruments at 13 sites in the greater Vancouver area. The latter data set is especially important because it contains the first three-component recordings made on bedrock in greater Vancouver. Both data sets represent weak ground motion, with peak horizontal accelerations of 0.5-1.5% gravity (g) for the Duvall earthquake, and 0.2-2.4% g for the Georgia Strait earthquake. Using the method of spectral ratios, we estimate the site response for each of the strong-motion instrument soil sites. On the Fraser River delta amplification is observed over a relatively narrow frequency range of 1.5-4 Hz (0.25-0.67 s period), with peak amplification of 4-10 (relative to competent bedrock) for the thick soil delta centre sites, and about 7-11 for the delta edge sites. Relative to firm soil, the peak amplification ranges from 2 to 5 for the thick soil delta centre sites, and 2 to 6 for the delta edge sites. At higher frequencies, little or no amplification, and in many cases slight attenuation, is observed.Key words: seismic site response, Fraser delta, earthquakes.

scholarly journals Seabed slope instability on the Fraser River delta

1998 ◽  
Author(s):  
H A Christian ◽  
D C Mosher ◽  
J V Barrie ◽  
J A Hunter ◽  
J L Luternauer
Keyword(s):  
River Delta ◽  
Slope Instability ◽  
Fraser River ◽  
Fraser River Delta

Using hedgerow biodiversity to enhance the carbon storage of farmland in the Fraser River delta of British Columbia

2015 ◽  
Vol 70 (4) ◽  
pp. 247-256 ◽  
Author(s):  
B. Thiel ◽  
S. M. Smukler ◽  
M. Krzic ◽  
S. Gergel ◽  
C. Terpsma
Keyword(s):  
British Columbia ◽  
Carbon Storage ◽  
River Delta ◽  
Fraser River ◽  
Fraser River Delta

Short-term effects of grassland set-asides on soil properties in the Fraser River delta of British Columbia

2019 ◽  
Vol 99 (2) ◽  
pp. 136-145 ◽  
Author(s):  
Jason M. Lussier ◽  
Maja Krzic ◽  
Sean M. Smukler ◽  
Art A. Bomke ◽  
Drew Bondar
Keyword(s):  
Soil Properties ◽  
Bulk Density ◽  
Crop Production ◽  
Soil Aggregates ◽  
Negative Relationship ◽  
River Delta ◽  
Fraser River ◽  
Cost Share ◽  
Mean Weight Diameter ◽  
Fraser River Delta

Grassland set-asides (GLSA) in the Fraser River delta are fields that are taken out of crop production and seeded with a mixture of grasses and legumes for 1–4 yr. During this time, the farmer is compensated with a cost-share payment to recover a portion of the financial returns that could have been earned from cash crops. The objectives of this study were to (i) evaluate the effects of GLSA on soil properties during the initial two seasons of enrollment, (ii) determine how GLSA effects differ between fields that were considered productive and unproductive, and (iii) identify soil baseline indicators and preliminary soil thresholds for predicting GLSA vegetation responses. Out of eight fields entering the program, two were considered to be unproductive and exchangeable sodium had the strongest negative relationship to GLSA aboveground biomass (r = −0.61, P = 0.0002). During the second season of GLSA establishment, the mean weight diameter of water-stable soil aggregates was consistently higher in productive GLSAs than paired annual crop rotation (ACR) fields, being 21% higher in April, 14% in July, and 19% in September after crop harvest. After two seasons of GLSA enrollment, both aeration porosity and bulk density were improved by GLSA relative to ACR fields with aeration porosity being 24% greater and bulk density 7% lower in GLSA. The results suggest that GLSA rotations in productive agricultural fields within the Fraser River delta provide an alternative to continued ACR that can improve soil structure and reduce compaction after only two seasons of establishment.

scholarly journals Are Lesser Snow Geese, Chen caerulescens caerulescens, Exceeding the Carrying Capacity of the Fraser River Delta's Brackish Marshes?

2006 ◽  
Vol 120 (2) ◽  
pp. 213 ◽  
Author(s):  
Mike W. Demarchi
Keyword(s):  
Carrying Capacity ◽  
Pacific Salmon ◽  
River Delta ◽  
Fraser River ◽  
Snow Goose ◽  
Chen Caerulescens ◽  
Snow Geese ◽  
Brackish Marshes ◽  
Fraser River Delta ◽  
Chen Caerulescens Caerulescens

Brackish marshes of the Fraser River delta provide important habitats for such high-profile animals as White Sturgeon (Acipenser transmontanus), Pacific Eulachon (Thaleichthys pacificus), Pacific salmon (Oncorhynchus spp.), Western Sandpiper (Calidris mauri), and Lesser Snow Goose (Chen caerulescens caerulescens), the latter comprising the “Fraser-Skagit” segment of the Wrangel Island (Russia) population. This study assessed whether the current numbers of Snow Geese are exceeding the carrying capacity of brackish marshes in the Fraser River delta. Simulation modelling predicts that those marshes are presently capable of supporting ~17,500 Snow Geese—a value that is greatly exceeded by the numbers of geese that have over-wintered there in recent years (~80,000 in 2004-2005). The Pacific Flyway Council’s target 3-y average population and segment sizes of 120,000 and 50,000 - 70,000, respectively, were set without considering the carrying capacity of natural wintering habitats, the potential impacts of too many geese on upland agriculture, or implications for hazards to civilian aircraft at Vancouver International Airport. The modelled results of the present study suggest that the Fraser River delta can sustain the current numbers of Snow Geese that stage or winter there only if those birds also forage in agricultural and refuge fields—a relatively recent phenomenon that likely bolstered the Snow Goose population. Over-use by Snow Geese can degrade the productivity and habitat quality of marshes. There is documented evidence that some key plant species (e.g., Scirpus americanus) of the brackish marshes of the Fraser River delta are well below their biomass potential (~15%), primarily because of grubbing by Snow Geese. Other species that depend on this brackish environment as well as human interests in the Fraser River delta may be adversely affected by an overabundance of Snow Geese. The future effectiveness of hunting as a primary means of population regulation is questioned.

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