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Sediment Trapping and Dredging Systems
Trap support frames and degrees of freedom
TR-01-22
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Design
of
Sediment
Trapping
System
Sediment
traps
The
sediment
traps
are
located
at
the
downdrift
end of
the
facility,
and
are
positioned
within
the
flow
channels,
as
illustrated
in
Figure
20.
A sediment
trap
is located in
each
flow
channel
starting
with
Channel
No.
1
(the
most
shoreward
flow
channel)
and
extending
offshore
to
flow
Channel
No.
17.
Additionally,
a
sediment
trap
is located in
flow
Channel
No.
19.
The
decision
to
eliminate
traps
in
flow
Channels
No.
18 and 20
was
determined
based
on
cost
considerations and
the
expected
low
rates
of
longshore
sediment
transport
in
the
offshore
region.
Based
on
the
fall
velocity
of
the
sediment
used
to construct
the
moveable-bed
beach,
and
the
magnitude
of
the
longshore
current
in
the
flow
channels,
the
decision
was
made
to
maximize
the
length
of
these
sediment
traps.
Each
trap
is
approximately
6.0
m
long
and
0.6
m
wide.
In
addition,
two
shorter
traps
are
located
landward
of
flow
Channel
No.
1
with
the
objective
of
quantifying
the
longshore sediment transport
rate
near
the
still-water
shoreline
and in
the
uprush
zone.
Each
"uprush-zone
"
trap
is
approximately
2.5
m
long
and
0.5
m
wide.
These
two
traps
were
added
to
the
design
after
qualitatively
observing
the
magnitude
of
longshore
sediment transport in
the
swash
zone
as
well
as
the
morphologic
changes
that
occurred in
this
region
during
some
preliminary
moveable-bed
experiments.
Figure
20.
Twenty
sediment
traps
are
located
inside
downdrift
flow
channels
The
dimensions and
capacity
of
each
of
the
traps
are
tabulated
in
Table
2,
based
on
the
as-built
inside
dimensions of
each
trap
and
assuming
that
the
traps
can
be
completely
filled
with
sand
along
the
entire
length
of
the
trap
(a
very
extreme
case).
The
last
column
lists
the
capacity
of
each
trap
in
terms
of
the
36
Chapter
4
Sediment
Trapping
and
Dredging
Systems
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