This item is not viewable because it is not yet digitized or has special access permissions. Please log in or request access.
Estuarine Sedimentation and Erosion within a Fjord-Head Delta: Squamish River, British Columbia
Academic Work
This study has determined the nature of tidal and riverine control on deposition along the lower 5,500 m estuarine reach of Squamish River; delta and floodplain sediments exposed along channel banks at 42 locations along Squamish estuary were examined. This study has also determined the rate and nature of estuarine channel bank erosion from 1957 to 1990 and has determined the nature and rate of Squamish delta accretion. Erosion rates are calculated from aerial photographs and erosion pins, while accretion data are calculated from deposition stakes.
Analysis of delta and floodplain sediments reveals that estuarine sequences comprise seven distinct facies which record varying degrees of tidal and riverine influence. While most of these facies yield evidence of their estuarine location, only the deposits of intertidal sands and tidal marsh are unequivocally tidal in origin. Sedimentation within this fjord-head environment primarily is driven by gradual channel abandonment and fill. Estuarine sequences produced by this process display a decreasing tidal influence both up estuary and up section, as evidenced by a change in sediment size, structure, and the form of facies contacts. Within this estuary the bayline is located around 3,100 m upstream from the delta front.
Erosion data indicate that the tidal deposits are very unlikely to be fully preserved in sequence because of their low preservation potential. Since 1957 the estuarine channel has shifted considerably, and predicted continued meander migration poses a threat to the future stability of the river training dyke, built in 1972 to isolate Squamish River to the west of the valley. Along certain reaches, rates of channel bank erosion have increased as a result of decreased channel and effective floodplain widths associated with dyke construction. These factors have also led to an increased riverine influence near the river mouth which has in turn led to the formation of an anomalous coarse-grained sedimentary sequence along the lower 800 m of Squamish west delta. Accretion data reveal that Squamish west delta accretion has increased dramatically since dyke construction, and that this accretion is both spatially and temporally variable. This variability reflects the riverine source of sediment, and indicates that depositional processes differ within summer and winter months.
Comparative analysis of sedimentary sequence within fluvial and tidal reaches reveals that fine-grained deposits provide evidence of their environment of deposition. These deposits may be used as environmental indicators based on sediment-size characteristics, facies geometry, organic content, and bedding form.
Analysis of delta and floodplain sediments reveals that estuarine sequences comprise seven distinct facies which record varying degrees of tidal and riverine influence. While most of these facies yield evidence of their estuarine location, only the deposits of intertidal sands and tidal marsh are unequivocally tidal in origin. Sedimentation within this fjord-head environment primarily is driven by gradual channel abandonment and fill. Estuarine sequences produced by this process display a decreasing tidal influence both up estuary and up section, as evidenced by a change in sediment size, structure, and the form of facies contacts. Within this estuary the bayline is located around 3,100 m upstream from the delta front.
Erosion data indicate that the tidal deposits are very unlikely to be fully preserved in sequence because of their low preservation potential. Since 1957 the estuarine channel has shifted considerably, and predicted continued meander migration poses a threat to the future stability of the river training dyke, built in 1972 to isolate Squamish River to the west of the valley. Along certain reaches, rates of channel bank erosion have increased as a result of decreased channel and effective floodplain widths associated with dyke construction. These factors have also led to an increased riverine influence near the river mouth which has in turn led to the formation of an anomalous coarse-grained sedimentary sequence along the lower 800 m of Squamish west delta. Accretion data reveal that Squamish west delta accretion has increased dramatically since dyke construction, and that this accretion is both spatially and temporally variable. This variability reflects the riverine source of sediment, and indicates that depositional processes differ within summer and winter months.
Comparative analysis of sedimentary sequence within fluvial and tidal reaches reveals that fine-grained deposits provide evidence of their environment of deposition. These deposits may be used as environmental indicators based on sediment-size characteristics, facies geometry, organic content, and bedding form.
AW.00167
December 1994
Geography
Copyright is held by the author.
The author has not granted permission for the file to be printed nor for the text to be copied and pasted. If you would like a printable copy of this thesis, please contact summit-permissions@sfu.ca.
The author has not granted permission for the file to be printed nor for the text to be copied and pasted. If you would like a printable copy of this thesis, please contact summit-permissions@sfu.ca.
Thesis / Dissertation
Do you have a comment, story, or something you would like us to know related to this item?