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The 2017 areas of operations focuses on
the South Channel. Prior to 2009, this channel terminated in
~120m of water and distributed sediment as a splay deposit
on a proximal lobe just downstream. Between 2009 and 2011,
the South Channel first developed an extension onto that
lobe. Since then it has grown over 2 kilometres and deepened
the past 6 years. As a result of redirection of the delta
top river channel talweg since 2011, the off-delta sediment
flux has migrated away from the North and Central channels
and is now predominantly feeding the South Channel.
The aim in 2017 was to monitor flow events in that 2 km
section of the South Channel, particularly the transition
from channelized to unconstrained flow. To that end, a 600
kHz ADCP has been suspended 15 m off the bottom close to the
channel termination. The plan is to collect a total of 12
weeks of data. In the first 6 weeks (the data
recovered so far), approximately 15 flows, ranging from 0.3
m/s to 2.5 m/s have been detected.
Complimenting the flow information, updated bathymetric and
backscatter surveys in April, May and June (and upcoming
July) have been performed to measure the morphological
change. As part of the June update, a 1.5 m/s flow was
caught in real time, with surveys immediately before, during
and after.
A new focus in 2017, is to look at the backscatter image
changes. Normally, when running directly on top of the
channels, little could be discerned that was not
contaminated by seabed slope signatures. This year, offset
lines looking obliquely into the channel allow far better
delineation of changes in the surficial backscatter
signature.
The ExxonMobil funded component addresses the idea of
having sensors in the flow that would be capable of
reporting in real time. This year, the viability of leaving
pressure sensors on seabed moorings along the channel is
being investigated. Should they prove viable (if they
survive the high velocity flows), the intent is to use them
to trigger acoustic links to turn on high sampling rate data
downstream. Acoustic links have not been tested this year
due to delays in funding schedule.
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