TY - CHAP
T1 - Imaging active mass-wasting and sediment flows on a fjord delta, Squamish, British Columbia
AU - Hughes Clarke, John E.
AU - Vidiera Marques, Carlos R.
AU - Pratomo, Danar
N1 - Publisher Copyright:
© Springer International Publishing Switzerland 2014.
PY - 2014
Y1 - 2014
N2 - An active fjord head delta in Squamish British Columbia, was selected as the location for a repetitive multibeam survey program to monitor temporal evolution of the prodelta morphology. Daily resurveys in 2011 established the style and extent of submarine mass movements, their typical periodicity and the conditions associated with the most active periods. This has now been followed by an hourly resurvey program in 2012 during those most active periods to actually witness the progression of activity immediately preceding, during and subsequent to a singular event. The delta front in depths of 20–50 m is often the apparent start point for trains of sequential erosive and depositional events associated with upslope bedform migration along prodelta channels. Heavy targets on the channel floors were monitored in 2011 and indicated rare, abrupt down channel displacements of a few hundred metres, indicating that a small subset of events involved bulk translation of the seabed. In 2011, a bottom-mounted ADCP beyond one channel mouth recorded clear turbidity current events for a subset of the channel bedform migration periods. In 2012, using multibeam water column imaging and a rapidly dipping towed optical backscatter probe, the evolution of a descending suspended sediment plume below the overlying river plume was monitored on an hourly basis. Towards low water, that descending plume was seen to occasionally feed a near seabed higher suspended sediment layer. On the development of this layer, the water column imaging revealed a thin basal flow that lasted about an hour and corresponded directly with the period ofmigration of the channel floor bedforms.Delta-lip failures are associated with the upslope end of about half of the bedform trains suggesting an alternate initiating mechanism.
AB - An active fjord head delta in Squamish British Columbia, was selected as the location for a repetitive multibeam survey program to monitor temporal evolution of the prodelta morphology. Daily resurveys in 2011 established the style and extent of submarine mass movements, their typical periodicity and the conditions associated with the most active periods. This has now been followed by an hourly resurvey program in 2012 during those most active periods to actually witness the progression of activity immediately preceding, during and subsequent to a singular event. The delta front in depths of 20–50 m is often the apparent start point for trains of sequential erosive and depositional events associated with upslope bedform migration along prodelta channels. Heavy targets on the channel floors were monitored in 2011 and indicated rare, abrupt down channel displacements of a few hundred metres, indicating that a small subset of events involved bulk translation of the seabed. In 2011, a bottom-mounted ADCP beyond one channel mouth recorded clear turbidity current events for a subset of the channel bedform migration periods. In 2012, using multibeam water column imaging and a rapidly dipping towed optical backscatter probe, the evolution of a descending suspended sediment plume below the overlying river plume was monitored on an hourly basis. Towards low water, that descending plume was seen to occasionally feed a near seabed higher suspended sediment layer. On the development of this layer, the water column imaging revealed a thin basal flow that lasted about an hour and corresponded directly with the period ofmigration of the channel floor bedforms.Delta-lip failures are associated with the upslope end of about half of the bedform trains suggesting an alternate initiating mechanism.
KW - Bedform translation
KW - Cyclic steps
KW - Prodelta mass wasting
KW - Surface differences
KW - Turbidity current
KW - Water column imaging
UR - http://www.scopus.com/inward/record.url?scp=84908421416&partnerID=8YFLogxK
U2 - 10.1007/978-3-319-00972-8_22
DO - 10.1007/978-3-319-00972-8_22
M3 - Chapter
AN - SCOPUS:84908421416
T3 - Advances in Natural and Technological Hazards Research
SP - 249
EP - 260
BT - Advances in Natural and Technological Hazards Research
PB - Springer Netherlands
ER -