Atlas of U.S. Army Corps of Engineers Historic Daily Tide Data in

Atlas of U. S. Army Corps of Engineers
Historic Daily Tide Data in Coastal Louisiana
Abstract: The U. S. Army Corps of Engineers New Orleans District has historically collected
water level data of various water bodies, rivers, and streams throughout southern Louisiana.
Some of these gages have collected data in tidal areas and have long periods of record with some
exceeding 50 years of collected data. Data Stored in MVN databases may contain unpublished
adjustments to compensate for datum shifts, settlement, to correct leveling errors, or other
reasons. There has been increased interest in determining rising sea level trends in the coastal
areas of Louisiana which has some of the highest Relative Sea Level Rise rates in the United
States. In an effort to disseminate the Corps data referenced to a common gage datum, the data
has been analyzed and known shifts have been removed. Where the shift information was not
available, other means were taken to bring the data back to a common reference elevation,
generally that is the datum to which the gage was originally established. Where the data may
have been influenced by variable river discharge, efforts were taken to remove the portion of the
stage influenced by river discharge and provide a truer tidal record for analysis. Finally, simple
linear trends were applied to the data and the observed trends were summarized.
Introduction
In recent years, a growing public interest has developed regarding the substantial rates of land
loss in coastal Louisiana, especially since Hurricanes Katrina and Rita devastated the Louisiana
coastal marshes and communities. An understanding of the contributions of land subsidence
(isostatic) and global sea level rise (eustatic) to Louisiana’s wetland loss is crucial to the success of
any plan designed to protect coastal communities (Gonzalez and Tornqvist, 2006). The Louisiana
coast’s geography makes it especially vulnerable to the effects of relative sea level rise (Figure 1 ).
The U. S. Army Corps of Engineers, New Orleans District has historically collected water level
data of various water bodies, rivers, and streams throughout southern Louisiana. Some of these
gages have collected data in tidal areas and have long periods of record with some exceeding 50
years of collected data. In order to develop estimates of relative sea level rise for coastal Louisiana
projects, the New Orleans district has engaged in a study of stage data compiled at various coastal
data collection sites.
Relative Sea Level Change
Relative mean sea level change at a particular location considers the cumulative effects of the
global change (eustatic) and any local change in land elevation (isostatic). The long-term causes of
relative mean sea level change are sixfold and include eustatic rise, crustal subsidence, seismic
subsidence, auto-subsidence, man-made subsidence, and variations due to climatic fluctuations
1
(NRC, 1987). Coastal Louisiana has been shown to be subject to some of the highest regional
subsidence rates in the United States and consequently is subject to some of the highest rates of
relative sea level rise.
The data presented here are intended to represent the total relative mean sea level rate
experienced at a particular location. No attempt is made to extract the various components
comprising relative sea level change or to provide further analysis of the data other than what was
recorded at the sight. Estimates of vertical land movement may be made by subtracting the
eustatic sea level rise rate from the data. However, due to the inherent temporal and regional
variability of the eustatic sea level rise rate, that attempt is not made here.
Figure 1. Map of the Coastal Vulnerability Index (C.V.I.) for the U. S. Gulf Coast. The C.V.I.
shows the relative vulnerability of the coast to the changes due to the future rise in sea-level.
Areas along the coast are assigned a ranking from low to very high risk, based on the analysis of
physical variables that contribute to coastal change. (Source: http://pubs.usgs.gov/of/2000/of00179/).
Estimates of historic eustatic sea level rise rates may be found in the literature, for example, the
IPCC Fourth Assessment Report: Climate Change 2007 suggests a rate of +1.8 ± 0.5 mm yr-1 for
the period 1961 to 2003 and +1.7 ± 0.5 mm yr-1 for the 20th century. However, the data upon which
these estimates are based is highly variable by decade. For example, a rate of 3.1 ± 0.7 mm yr-1
2
has been estimated for the period 1993 to 2003, which is significantly higher than the suggested
rate for the 20th century. However, it is unknown whether the higher rate observed in 1993 to
2003 is due to decadal variability or an increase in the longer-term trend. Figure 2 shows the
high variability in global sea level change over time.
Figure 2. Reproduction of IPCC 2007 figure showing decadal variability in eustatic sea level rates.
(Source: Intergovernmental Panel on Climate Change (2007), IPCC Fourth Assessment Report:
Climate Change 2007 (AR4), http://www.ipcc.ch/index.htm).
Methodology
The purpose of the analyses conducted for this study was to determine the relative sea level
change at particular gage sites. This necessitated having all recorded stages for the gages in a
common vertical datum. However, records for all shifts and corrections applied to the gage records
were not always available. In those situations, vertical shifts in the data had to be determined by
other means.
One technique used to determine vertical gage adjustments was by comparison of the data with
data recorded at a nearby gage site that was not shifted during the time frame of the shift applied
at the original gage site. Plotting the two gage records together provided a means to determine
significant shifts by visual estimation.
3
Some gage shifts were estimated by determining the linear trend of the data sets before and after
the shift was applied, usually during a protracted period of missing data and adjusting the data
after the data gap so that the linear trends matched through the data gap. In other words, the
linear equations of the two trends were solved for the variable y using the same variable x
representative of the time (or year) when the shift was thought to have been applied. The
resulting difference is the value of the vertical shift applied at time x (see Figures 3 and 4 for
example).
Gage 85800, Mississippi River - Gulf Outlet at Shell Beach daily stage data
1961 MSL and 1978 NGVD datums
(meters)
3
2
y = 0.0115x - 22.243
y = 0.008x - 15.531
1
0
2003
2004
2005
2006
2003
2004
2005
2006
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
1987
1986
1985
1984
1983
1982
1981
1980
1979
1978
1977
1976
1975
1974
1973
1972
1971
1970
1969
1968
1967
1966
1965
1964
1963
1962
1961
1960
1959
-1
Figure 3, Example of record with unknown gage shift
Gage 85800, Mississippi River - Gulf Outlet at Shell Beach daily stage data with shift removed
1961 MSL NGVD datums (meters)
3
2
1
0
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
1987
1986
1985
1984
1983
1982
1981
1980
1979
1978
1977
1976
1975
1974
1973
1972
1971
1970
1969
1968
1967
1966
1965
1964
1963
1962
1961
1960
1959
-1
Figure 4, Example of record with gage shift removed
A portion of the Mississippi River gage stage records is a result of the variable River discharge. In
order to extract that portion of the stage record that is due to tidal effects only, a special analysis
was conducted on the Carrollton, West Pointe a la Hache, and Venice gages. The analysis
consisted of subtracting a 6-year moving linear stage relationship to River discharge measured at
Tarbert’s Landing near the Old River Control complex. Adjustments were made to the flow data to
account for withdrawals at Bonnet Carre and Morganza as well as temporal shifts applied to
account for travel time from Tarbert’s Landing to the gage site being analyzed.
As an example, the procedure is shown here for the Carrollton gage analysis. First Tarbert
discharges were translated to the Carrolton gage site by accounting for any withdrawals made at
4
Bonnet Carre and Morganza Floodways and the discharges are shifted one day ahead to account
for some travel time. Daily stage/discharge relationships were developed using a moving ± 3 years
moving linear trend, the resultant stage/discharge points are shown in Figure 5 for 1 July 1975.
Six Year Stage Discharge Curve Centered Around 1 July 1975
25
Observed River Stage (feet)
20
6 year Observed stage record
15
Expected Stage corresponding to 562K
cfs
10
Stage corresponding to 100K cfs
8.76
Linear (6 year Observed stage record)
5
1.04
0
0
200
400
600
800
1000
1200
1400
Translated Tarbert Landing Computed Discharges to Carrollton gage site (1000 cfs)
Figure 5, Example plot demonstrating procedure to extract tidal signal from observed River
stages
The expected stage from this linear stage/discharge relationship for the corresponding Carrollton
discharge on 1 July 1975 of 562K cfs was 8.76 feet. The stage corresponding to a base flow of 100K
cfs, or 1.04 feet was subtracted from this stage to get a stage adjustment of 7.72 feet, which is
considered to be an estimate of that portion of the stage record attributable to River discharge
variance. The use of 100K cfs as the base flow was selected because that is the lowest computed
discharge on the Mississippi River during the period of record. The daily stage adjustment is then
subtracted from the observed stage to build the daily synthetic tide record, i.e. for 1 July 1975, the
result is 9.78 feet minus 7.72 feet or 2.06 feet. The slope of this synthetic tide record is considered
to represent the Relative Sea Level change rate for that particular gage. The resultant synthetic
tide is shown in Figure 6 for a portion of the Carrollton stage record.
5
Mississippi River at Carrollton, LA. daily 8 AM stages with corresponding synthetic tide signal
(Gage ID no. 01300)
6
5
Stage (meters)
4
3
2
1
0
-1
1970
1971
1972
1973
1974
1975
Observed Stage
1976
1977
1978
1979
1980
Synthetic Tide
Figure 6, Example stage record and resultant synthetic tide from the tide extraction process for a
portion of the Carrollton daily stage record
Results
The results of the linear trend analyses performed on the daily tide data recorded at 19 USACE
gages is summarized in Table 1 and on Figures 7 and 8. Appendix A contains graphs of the
daily tide data used in the analyses along with the linear trend lines developed for each gage site.
6
Table 1, Summary Table of Relative Sea Level Trends for U. S. Army Corps of Engineers
Gages
USACE
Gage ID
number
Latitude
and
Longitude
Mississippi River at New Orleans
(Carrollton)
Mississippi River at West Pointe a la Hache
01300
Mississippi River at Venice
01480
Southwest Pass at East Jetty
01670
South Pass at Port Eads
01850
Calcasieu River and Pass at Lake Charles
73550
Calcasieu River and Pass near Cameron
73650
Bayou Petit Caillou at Cocodrie
76305
Freshwater Canal at Freshwater Bayou
Lock (South)
Intracoastal Waterway at Calcasieu Lock
(West)
Bayou Lafourche at Leeville
76593
Bayou Barataria at Barataria
82750
Lake Pontchartrain at Frenier
85550
Lake Pontchartrain at Mandeville
85575
Lake Pontchartrain at West End
85625
Rigolets near Lake Pontchartrain
85700
Bayou Terre Aux Boeufs at Delacroix
85780
Mississippi River Gulf Outlet at Shell Beach
85800
East Cote Blanche Bay at Luke’s Landing
88800
29-56-05
90-08-10
29-34-16
89-47-49
29-16-33
89-21-10
28-55-38
89-29-12
29-00-53
89-09-57
30-13-05
93-15-12
29-46-30
93-20-46
29-14-43
90-39-48
29-33-09
92-18-21
30-05-19
93-17-40
29-14-52
90-12-32
29-44-29
90-07-56
30-06-22
90-25-17
30-21-31
90-05-45
30-01-18
90-06-57
30-10-02
89-44-13
29-45-50
89-47-32
29-51-00
89-41-00
29-35-48
91-32-35
Gage Name
01400
76960
82350
Jan 1950 – Dec 1998
Linear
Trend for
Entire
Period of
Record
(mm yr-1)
18.6 (9.2)*
Jan 1950 – Dec 2009
12.6 (13.1)*
Jan 1953 – Aug 2005
21.8 (23.0)*
Jan 1953 – Jan 2004
25.7
Jan 1953 – Dec 2004
25.5
Jan 1950 – Jul 2003
6.1
Jan 1950 – Aug 2005
3.9
Mar 1969 – Aug 2009
6.4
Jul 1968 - Aug 2009
5.4
Jan 1951 – Dec 2009
5.2
Nov 1955 – Apr 2000
10.8
Jan 1950 – Nov 1992
7.0
Jan 1950 - Dec 2002
8.4
Aug 1957 - Jul 2002
6.6
Jan 1950 – Dec 2009
9.1
Jan 1950 – Aug 2001
4.7
May 1975 – Aug 2005
6.1**
Jun 1961 - Dec 2002
10.2
Feb 1957 – Oct 2002
13.3
Period of Record
Analyzed
* The Carrollton, West Pointe a la Hache and Venice River stage records were analyzed to account for River
discharge stage influences. Estimates of the Relative Sea Level Rise using only the extracted tidal portion of
the records are shown in parentheses.
** The trend computed for this gage is based on a period of record that is less than the duration of two tidal
epochs or about 40 years.
7
Figure 7. Observed Relative Sea Level Trends for USACE gages in West Louisiana
8
Figure 8. Observed Relative Sea Level Trends for USACE gages in Southeast Louisiana
Conclusion
Historic daily tide measurements of USACE gages have been analyzed to determine relative sea
level trends that are representative of the gage sites. This data is provided to supplement relative
sea level rates provided by other sources (see http://tidesandcurrents.noaa.gov/ for example) and
may be used to assist in the estimation of the components of relative sea level rise (eustatic and
isostatic) in order to conduct analyses of future projections of sea level trends for project planning
purposes.
9
References
http://pubs.usgs.gov/of/2000/of00-179/
Gonzalez, J. L. and T. E. Tornqvist (2006), Coastal Louisiana in Crisis: Subsidence or Sea Level
Rise?, Eos, Transactions, American Geophysical Union, Vol. 87, No. 45, 7 November 2006.
National Research Council (1987), Responding to Changes in Sea Level, Engineering Implications,
National Academy Press, Washington D. C.
Intergovernmental Panel on Climate Change (2007), IPCC Fourth Assessment Report: Climate
Change 2007 (AR4), http://www.ipcc.ch/index.htm.
Acknowledgements: This report was funded by the Louisiana Coastal Area Science
and Technology Office ( http://www.mvd.usace.army.mil/lcast ) which is supported by both the Corps
of Engineers and CPRA.
10
Appendix A
USACE Gages Daily Stage Graphs and Linear Trends
11
Mississippi River at Carrollton, LA. daily 8 AM stages
(Gage ID no. 01300)
8
7
y = 0.0186x - 34.46
Stage (-0.01524 meters MSL, 1950 datum)
6
5
4
3
2
1
0
-1
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
1990
1995
2000
Mississippi River at Carrollton, LA. Extracted Daily Tidal Stages
3.0
2.5
y = 0.0092x - 17.859
2.0
Stage (meters)
1.5
1.0
0.5
0.0
-0.5
-1.0
1950
1955
1960
1965
1970
1975
12
1980
1985
Mississippi River at West Pointe a la Hache, LA. daily 8 AM stages
(Gage ID no. 01400)
5
Stage (0.00 meters MSL, 1950 datum)
4
y = 0.0126x - 23.603
3
2
1
0
-1
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
Mississippi River at West Pointe a la Hache, LA. Extracted Daily Tidal Stages
3.0
2.5
2.0
y = 0.0131x - 25.432
Stage (meters)
1.5
1.0
0.5
0.0
-0.5
-1.0
1950
1955
1960
1965
1970
1975
1980
13
1985
1990
1995
2000
2005
2010
Mississippi River at Venice daily 8 AM stages
(Gage ID no. 01480)
3.0
y = 0.0218x - 42.054
2.5
Stage (0.00 meters MSL, 1953 datum)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
1995
2000
2005
2010
Mississippi River at Venice Extracted Daily Tidal Stages
3.0
2.5
y = 0.023x - 44.703
2.0
Stage (meters)
1.5
1.0
0.5
0.0
-0.5
-1.0
1950
1955
1960
1965
1970
1975
1980
14
1985
1990
Southwest Pass at East Jetty daily 8 AM stages
(Gage ID no. 01670)
3.0
2.5
Stage (0.00 meters MLG, 1953 datum)
y = 0.0257x - 49.68
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
1990
1995
2000
2005
South Pass Port Eads daily 8 AM stages
(Gage ID no. 01850)
3.0
2.5
y = 0.0255x - 49.237
Stage (0.00 meters MLG, 1953 datum)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1950
1955
1960
1965
1970
1975
15
1980
1985
Calcasieu River and Pass at Lake Charles, LA. daily 8 AM stages (Gage ID no. 73550)
3.0
y = 0.0061x - 11.258
Stage (-0.1810512 meters MLG, 1950 datum)
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
Calcasieu River and Pass, Cameron, LA. daily 8 AM stages
(Gage ID no. 73650)
3.0
y = 0.0039x - 7.1055
2.5
Stage (0.00 meters MLG, 1950 datum)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1950
1955
1960
1965
1970
1975
1980
16
1985
1990
1995
2000
2005
2010
Bayou Petit Caillou at Cocodrie, LA. daily 8 AM stages
(Gage ID no. 76305)
3.0
Stage (0.048768 meters MSL, 1969 datum)
2.5
y = 0.0064x - 12.211
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
2005
2010
Freshwater Canal at Freshwater Bayou Lock, LA. daily 8 AM stages
(Gage ID no. 76593)
3.0
2.5
y = 0.0054x - 10.113
Stage (0.00 meters MLG, 1968 datum)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
1965
1970
1975
1980
1985
17
1990
1995
2000
Intracoastal Waterway at Calcasieu Lock, LA. daily 8 AM stages
(Gage ID no. 76960)
3.0
Stage (-0.2469 meters MLG, 1951 datum)
2.5
y = 0.0052x - 9.373
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Bayou Lafourche at Leeville, LA. daily 8 AM stages
(Gage ID no. 82350)
3.0
2.5
y = 0.0108x - 20.947
Stage (meters MSL, 1956 datum)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1955
1960
1965
1970
1975
1980
18
1985
1990
1995
2000
2005
Bayou Barataria at Barataria, LA. daily 8 AM stages
(Gage ID no. 82750)
3.0
2.5
y = 0.007x - 13.127
Stage (0.00 meters MLG, 1951 datum)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
Lake Pontchartrain at Frenier, LA. daily 8 AM stages
(Gage ID no. 85550)
6.0
5.5
y = 0.0084x - 13.08
Stage (0.00 meters MLG, 1951 datum)
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1950
1955
1960
1965
1970
1975
19
1980
1985
1990
1995
2000
2005
Lake Pontchartrain at Mandeville, LA. daily 8 AM stages
(Gage ID no. 85575)
6.0
Stage (-3.048 meters MSL, 1957 datum)
5.5
y = 0.0066x - 9.5892
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
Lake Pontchartrain at West End, LA. daily 8 AM stages
(Gage ID no. 85625)
6.0
y = 0.0091x - 14.417
Stage (-3.048 meters MSL, 1950 datum)
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1950
1955
1960
1965
1970
1975
1980
20
1985
1990
1995
2000
2005
2010
Rigolets near Lake Pontchartrain, LA. daily 8 AM stages
(Gage ID no. 85700)
6.0
Stage (Zero of gage, -3.048 meters MSL, 1955 datum)
5.5
y = 0.0047x - 5.8139
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
Bayou Terre Aux Boeufs at Delacroix, LA. daily 8 AM stages
(Gage ID no. 85780
3.0
2.5
y = 0.0061x - 11.787
Stage (meters MSL, 1975 datum)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1975
1980
1985
1990
1995
21
2000
2005
2010
Mississippi River - Gulf Outlet at Shell Beach, LA. daily 8 AM stages
(Gage ID no. 85800)
3.0
y = 0.0102x - 19.746
2.5
Stage (0.00 meters MSL, 1961 datum)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
East Cote Blanche Bay at Luke's Landing, LA. daily 8 AM stages
(Gage ID no. 88800)
3.0
2.5
y = 0.0133x - 25.883
Stage (0.00 meters MSL, 1957 datum)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1955
1960
1965
1970
1975
1980
22
1985
1990
1995
2000
2005