argus eyes on benson beach mouth of the columbia river - north head lighthouse
DESCRIPTION
Argus Eyes on Benson Beach Mouth of the Columbia River - North Head Lighthouse. Sponsored by: USACE Portland District. Proving Argus Quantitative Accuracy: Where are the White Rocks?. After installation, USACE Portland District asked, - PowerPoint PPT PresentationTRANSCRIPT
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Argus Eyes on Benson BeachMouth of the Columbia River - North Head Lighthouse
Sponsored by: USACE Portland District
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Proving Argus Quantitative Accuracy: Where are the White Rocks?
• After installation, USACE Portland District asked,– “where are these two
rock fall in State Plane coordinates”
– (We want to verify your claim that Argus provides quantitative information)
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Proving Argus Accuracy: Comparing MHW
Alongshore (m)
Cro
ss-s
hore
(m)
Jul. 28, 2004
1000 1500 2000 2500 3000
300
350
400
450
500
550
BuggyArgus
Argus/AREand
WA DOE “Buggy Surveys” (RTK GPS)
Special processing:1) Collect
shorelines during flood tide only
2) Recalculate shoreline Z using foreshore slope from a first pass
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200m
500m
Submerged sandbars
N
630m
MHW Shoreline
Meso-tidal beach
Hsig: 1m – 13m
Foreshore slopes: 0.01 – 0.06
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Background: Argus at Benson Beach since Feb 2004
• Severe winter of 2005/2006– Erosion of grass dunes behind beach– Weakened offshore bar system
• Followed with two years of erosion– Extreme shoreward shift of MHW shoreline– North Jetty foot weakened
• 125k yd3 placed along jetty in 2008• 367k yd3 placed on beach in 2010
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Benson Beach Sediment SystemInterpreted from 7+ years of Argus Eyes
• Observed seasonal changes:– MHW shorelines, sandbar movement, and
foreshore slopes suggest -• interdependency between offshore sandbar
morphodynamics and foreshore change• Differences in foreshore change from one
year to the next are a result of difference in the:– strength and intensity of the winter waves– morphology and health of the offshore
sandbars
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Argus Eyes• Imagery
– Snaps, timex, variance, brightness - hourly– Sandbar location tracking maps – 2x/month
• MHW (2.0 NAVD88) Shorelines– Shoreline location maps – 2x/month– Dry-beach acreage graphs – 2x/month
• Foreshore (1.5-2.5m NAVD88) Bathymetry– Foreshore volume graphs – 2x/month
• A proxy for foreshore beach slopes
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200m
500m
Middle bar
N
630mDry-Beach Acreage
Inner bar
MHW
Foreshore sand volume
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Sandbar Maps – bars moving shoreward
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Thu.Mar.03.18.20.00.GMT.2005
1000 1500 2000 2500 3000 3500 4000 4500
-200
0
200
400
600
800
1000
1200
1400
1600
outer sand barmiddle sand bar
MHW shoreline
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Mon.May.16.23.20.00.GMT.2005
1000 1500 2000 2500 3000 3500 4000 4500
-200
0
200
400
600
800
1000
1200
1400
1600
The middle bar attaches to the shoreface, moving the 2.0m
shoreline seaward
N
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Tue.Jul.26.19.00.00.GMT.2005
1000 1500 2000 2500 3000 3500 4000 4500
-200
0
200
400
600
800
1000
1200
1400
1600
The summer intertidal terrace incorporates the middle bar
Middle bar moving onshore
March 2006 April 2006
May 2006 July 2006
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Sept 2010
Oct 2006
(bold lines mark early March MHW shorelines)
N
OCEAN
BEACH
630m
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Man-made salientSW WA LDR dredge material
placement – Sept 2010
Natural salientSummer following severe 2005/2006
winter
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200m
500m
Middle bar
N
630mDry-Beach Acreage
Inner bar
MHW
Foreshore sand volume
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4/1/200410/1/2004
4/1/200510/1/2005
4/1/200610/1/2006
4/1/200710/1/2007
4/1/200810/1/2008
4/1/200910/1/2009
4/1/201010/1/2010
350000
400000
450000
500000
550000
600000
sum
mer
sum
mer
sum
mer
sum
mer
sum
mer
sum
mer
win
ter e
rosi
on
extre
me
win
ter
win
ter
win
ter
win
ter
win
ter
win
ter
sum
mer
acc
retio
n
Dry-Beach Acreage (m2)
12.3 acres
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144/1/2004
10/1/20044/1/2005
10/1/20054/1/2006
10/1/20064/1/2007
10/1/20074/1/2008
10/1/20084/1/2009
10/1/20094/1/2010
10/1/2010 700,000
750,000
800,000
850,000
900,000
950,000
1,000,000 2004-2011 Foreshore (1.5-2.5m NAVD88) Volumes (m3)
sum
mer
sum
mer
sum
mer
win
ter
win
-te
r
win
ter
sum
mer
sum
mer
sum
-m
er
win
-te
r win
-te
r
win
ter
sum
mer
sha
llow
slo
pe
win
ter
stee
p sl
ope
Stee
per
(a proxy for beach shape - steep, shallow, plane, concave, convex)
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154/1/200410/1/2004
4/1/200510/1/2005
4/1/200610/1/2006
4/1/200710/1/2007
4/1/200810/1/2008
4/1/200910/1/2009
4/1/201010/1/2010
350000
400000
450000
500000
550000
600000
win
ter e
rosi
on
win
ter
win
ter
win
ter
win
ter
win
ter
win
ter
sum
mer
acr
etio
n
Dry-Beach Acreage (m2)
Extreme 05-06 Win-ter
North Jetty berm repair – 125k yds3
Healthy 3-bar system
Greatest north & south shore-
line retreat
SW WA LDR 367k yd3
First 4-bar system observed
Weak 2-bar system
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Argus Eyes on the SW WA LDRDredge Material Beach Placement
• 1 Aug - 22 Sept 2010– 367k yd3 (281 m3) placed on Benson Beach– First storm in the last week of Sept
• Argus foreshore (1.5-2.5m NAVD88) volume measurements– capture the material placement & movement
(reshaping of the foreshore)• Argus sandbar maps reveal the creation of
a fourth sand bar by Spring 2011
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NN of
DS
N of DS
N DS
S DS
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160,000
180,000
200,000
220,000
240,000
260,000
280,000
South Disposal Site
North Disposal Site
North of DS
North North of DS
AlongshoreRange
Volume (m3)Jetty
Lighthouse
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First observed 4-bar system
Dec 2010
March 2011
Oct 2010
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Benson Beach Sediment SystemInterpreted from 7+ years of Argus Eyes
• Interdependency of offshore sandbar morphodynamics and foreshore change– Winter storms >> swash bar pulled offshore
>> steep foreshores– Summer calm >> swash bar attaches to
shoreface >> shallow foreshores– Health of sandbars affect how much sand is
pulled from the foreshore during storms• Feed the bars, save the beach
– OR! starved bars feed on beaches
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What’s Next?• Quantifying the “health” of a sandbar
– The volume/linear-meter of sand in the bar may be a metric of health and behavior (Russeinik et al, 2009)
– Kaminsky’s and Ruggiero’s jet ski bathymetry surveys of Benson Beach can provide volume information!
• Imagine! We may be able to identify the presence of a “weak” bar system – before a winter of extreme erosion and jetty
damage
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Argus at North Head Lighthouse would not have been possible without funding from USACE and the joint cooperation of Washington State
Parks, Coast Guard, and USACE/Portland District
A collaborative effort with WA DOE (Kamininsky), OSU (Ruggiero, Ozkan-Haller, Haller), USGS (Gelfenbaum), Golder (Osborne)
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NorthWest Research Associates (NWRA)
Redmond, WA
NWRA is a scientific
research group, owned
and operated by its
Principal Investigators,
with expertise in the
geophysical and related
sciences.