Observations of Saltwater Intrusion into the Atchafalaya Bay

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Observations of Saltwater Intrusion into the
Atchafalaya Bay
Chunyan Li, Harry Roberts, Eddie Weeks, Greg
Stone, Zhixuan Feng Coastal Studies
Institute Department of Oceanography and Coastal
Sciences Louisiana State University
Ecosystem Functions and the Dynamic Atchafalaya
River, Baton Rouge, Jan 10-11, 2008
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Objectives
Catch the dynamical processes of cold front
passages for a better understanding of the delta
hydrodynamics that is important to the evolution
of the delta.
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Study Area
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Mooring Site
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Weather Stations
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Sontek
Tripods
W117
W118
Nortek
W137
W129
W130
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Instrument Setup
Instruments Start Time (UTC) MAB (m) dt (s)
Data Pts Sontek PADP 3/25/2006 1900
0.89 0.5 3921371 OBS1 3/25/2006
1900 0.345 OBS2 3/25/2006 1900 0.725
SBE16p 3/25/2006 2210 0.973 600 3581 Wet
labs 3/25/2006 1920 0.78 Wadar (1) 3/25/2006
1919 0.275 60 44769 Wadar (2) 3/25/2006
1916 0.812 60 44776 Wadar (3) 3/25/2006
1926 1.157 60 44677 Nortek 3/25/2006
2300 1.23 600 4720 CSI Wave Gauge 3/25/2006
2300 Wadar (1) 3/20/2006 1919 0.17 60 55929
Wadar (2) 3/20/2006 2022 1.19 60 55954
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Method of Analysis
? Filtering using a Lowpass Filter Butterworth
Filter cutoff at 0.6 Cycle per Day (CPD),
equivalent to a 40 hour in period ? Power
Spectrum Analysis, identifying major frequencies.
filter
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wind
discharge
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water T
tide
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power spectrum for tide
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air T
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Salinity, DO, and Tide
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ADP Pressure and Salinity
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North Wind and Salinity
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EasyQ East Flow
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Pressure from ADP
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ADP North Flow
ADP East Flow
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Future Studies

• More observations
• Modeling

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Conclusion
A few cold front events are captured by multiple
parameters between Mar 26 and April 20,
2006 Response of the cold front passage includes
a wind-surge (setup and set-down of surface
elevation from tidal records), and saltwater
intrusion prior to the cold front passage. DO
goes to a minimum when salinity reaches its
peak. The peak of the salinity spike occurs
before the north wind decreases and it occurs at
or right after the peak of tidal records.