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UFL/COEL-2002/001
HYDROGRAPHIC MEASUREMENTS AT ST. ANDREW BAY
ENTRANCE AND EAST PASS, BAY COUNTY, FLORIDA
PART I
by
Mamta Jain
Vladimir A. Paramygin
and
Ashish J. Mehta
Submitted to:
Coastal Technology Corporation
Destin, FL 32541
March 2002
UFL/COEL-2002/001
HYDROGRAPHIC MEASUREMENTS AT ST. ANDREW BAY ENTRANCE
AND EAST PASS, BAY COUNTY, FLORIDA, PART I
By
Mamta Jain, Vladimir A. Paramygin and Ashish J. Mehta
Submitted to:
Coastal Technology Corporation
Destin, FL 32541
Coastal and Oceanographic Engineering Program
Department of Civil and Coastal Engineering
University of Florida
Gainesville, FL 32611
March 2002
SUMMARY
Hydrographic measurements were carried out on December 18-19, 2001 in two
channels in Bay County, Florida: St. Andrew Bay Entrance (also known as Panama City
Harbor Entrance) and the newly opened East Pass, both connecting the same bay waters
to the Gulf of Mexico. The measurements included four flow cross-sectional surveys -
three in St. Andrew Bay Entrance and the fourth at East Pass, and vertical profiles of
flow velocity across these cross-sections. These data were used to determine the
corresponding time-variation of flow discharge in each channel. The discharge variation
was in turn used to calculate the associated tidal prisms.
We report the following characteristic values. St. Andrew Bay Entrance: (flood)
tidal prism 6.0x107 m3, cross-section (at mean tide) 5,210 m2 and peak flood (cross-
sectional mean) velocity 0.68 m/s. East Pass: (flood) tidal prism 2.3x106 m3, cross-section
300 m2 and peak (flood) velocity 0.50 m/s.
At the cross-section close to the channel throat in St. Andrew Bay Entrance, the
tidal prism was compared with the prism obtained in September 2001, when East Pass
was closed. A credible trend of the effect of East Pass opening on the tidal prism at St.
Andrew Bay Entrance could not be established from this comparison. This observation is
not surprising, especially considering that the prism at East Pass was an order of
magnitude smaller than at St. Andrew Bay Entrance.
TABLE OF CONTENTS
SUMMARY ........................................................................................ 2
TABLE OF CONTENTS........................................................................3
LIST OF FIGURES...............................................................................5
LIST OF TABLES.................................................................................7
ACKNOWLEDGMENT.... ................................................................. 8
SECTION A: ST ANDREW BAY ENTRANCE ...... ......................9
A-i INTRODUCTION........................................................................9
A-2 MEASUREMENTS.....................................................................12
A-2.1 Cross-Sections...................................................................... 12
A-2.2 Tide Level.............................................................................14
A-2.3 Current and Discharge.................................................................14
A-3 TIDAL PRISM...........................................................................20
A-3.1 Calculation of Tidal Prism.......................................................... 20
A-3.2 Comparison with O'Brien Relationship......................................... 20
SECTION-B: EAST PASS....................................................................22
B-i INTRODUCTION......................................................................22
B-2 MEASUREMENTS......................................................................23
B-2.1 Cross-Sections.....................................................................23
B-2.2 Tide Level.............................................................................24
B-2.3 Current and Discharge............................................................. 24
B-3 TIDAL PRISM........................................................................... 26
B-3.1 Calculation of Tidal Prism......................................................... 26
B-3.2 Comparison with O'Brien Relationship.........................................26
CONCLUDING COMMENTS................................................................27
REFERENCES.................................................... ..............................28
LIST OF FIGURES
Fig A-1.1 St. Andrew Bay Entrance, Florida in 1993. Jetties are -430 m apart............10
Fig. A-1.2 St. Andrew Bay Entrance bathymetry and current measurement
cross-sections A' B' and C'. Depths are in feet below MLLW. Measurements
at cross-sections A and B were conducted in September 2001 and are reported
by Jain and M ehta (2001)......................................... ......... .... ....... ........11
Fig A-2. la Cross-section A' measured and compared with 2000 bathymetry.
Distance is measured from point A'-2. The datum is mean tide level. Measured area
= 5,210 m2 .......................... .. ........ .............................. .. 12
Fig A-2.1b Cross-section B' measured and compared with 2000 bathymetry.
Distance is measured from point B'-2. The datum is mean tide level. Measured area
= 5,640 m 2............................................... .. ..... ...... ......... ...............13
Fig A-2.1c Cross-section C' measured and compared with 2000 bathymetry.
Distance is measured from point C'-2. The datum is mean tide level. Measured area
= 5,220 m2....................... ........ . ..........................13
Fig. A- 2.2a NOS predicted tide at St. Andrew Bay Entrance on
December 18, 2001. The datum is MLLW ........................................................14
Fig. A-2.3a Cross-sectional mean current variation at cross-section A' on
December 18, 2001 ........... ..... ................ ....... ....... ........... 15
Fig. A-2.3b Cross-sectional mean current variation at cross-section B' on
December 18, 2001 .................................................... ........ ....... .. .. ....... ...15
Fig. A-2.3c Cross-sectional mean current variation at cross-section C' on
D ecem ber 18, 2001..................................................... ........................ 15
Fig.A-2.4a Discharge variation at cross-section A' on December 18, 2001............... 16
Fig.A-2.4b Discharge variation at cross-section B' on December 18, 2001............. 16
Fig.A-2.4c Discharge variation at cross-section C' on December 18, 2001 ................16
Fig. A-2.5a Ebb velocity structure at cross-section A' on December 18, 2001
at 16:49. Vertical axis represents current speed in m/s. Depth and width axes
are in meters. Origin of width is point A'-2................................................... 18
Fig. A-2.5b Ebb velocity structure at cross-section B' on December 18, 2001
at 16:47. Vertical axis represents current speed in m/s. Depth and width axes
are in meters. Origin of width is point B'-2...................................................18
Fig. A-2.5c Flood velocity structure at cross-section C' on December 18, 2001
at 09:40. Vertical axis represents current speed in m/s. Depth and width axes
are in meters. Origin of width is point C'-2.......................................................19
Fig. A-2.5d Ebb velocity structure at cross-section C' on December 18, 2001
at 16:00. Vertical axis represents current speed in m/s. Depth and width axes
are in meters. Origin of width is point C'-2. A data anomaly is evident close
to the origin ........... ........................ ....... .. ....... .................... 19
Fig B-1.1 East Pass channel in 1997............................................. ................22
Fig. B-1.2 Location of East Pass current measurement cross-section E on USGS
topographic map: left portion 1994; right portion 1982.......................................23
Fig B-2.1 Cross-section E measured by ADCP. Distance is measured from
2
point E-1. The datum is mean tide level. Area = 300 m2.......................................24
Fig. B-2.2 Cross-sectional mean current variation at East Pass December 19, 2001.......24
Fig. B-2.3 Discharge variation at East Pass on December 19, 2001.......................25
LIST OF TABLES
Table A-1.1 Locations of St. Andrew Bay Entrance cross-sections.........................9
Table A-2.1 ADCP measurement sequence at St. Andrew Bay Entrance................ 14
Table A-2.2 Characteristic peak velocities and discharges at cross-sections A', B'
and C' at St. Andrew Bay Entrance ............................................................ 17
Table A-2.3 Characteristic slack water time at cross-sections A', B' and C'
at St. A ndrew B ay Entrance..................................................................... .17
Table A-3.1 Tidal prism values for St. Andrew Bay Entrance...............................20
Table B-1.1 Location of East Pass cross-section E.............................................23
Table B-2.1 ADCP measurement sequence at East Pass........................... ........24
Table B-2.2 Characteristic peak velocity and discharge at East Pass cross-section E.....25
Table B-3.1 Flood and ebb tidal prisms at East Pass.......................................26
Table B-4.1 Comparison of prisms measured at St Andrew Bay Entrance ..............27
ACKNOWLEDGMENT
This study was carried out for the Coastal Technology Corporation, Destin,
Florida. Assistance provided by Michael Dombrowski of Coastal Tech is sincerely
acknowledged. Field work was performed by Sidney Schofield and Vladimir Paramygin
of the Department of Civil and Coastal Engineering, University of Florida.
HYDROGRAPHIC MEASUREMENTS AT ST. ANDREW BAY ENTRANCE
AND EAST PASS, BAY COUNTY, FLORIDA
SECTION A: ST. ANDREW BAY ENTRANCE
A-1. INTRODUCTION
Hydrographic measurements were carried out on December 18-19, 2001 in two
channels in Bay County, Florida: St. Andrew Bay Entrance (also known as Panama City
Harbor Entrance) and the newly opened East Pass, both connecting the same bay waters
to the Gulf of Mexico. The measurements included: 1) four flow cross-sectional surveys
three in St. Andrew Bay Entrance and the fourth at East Pass, and 2) vertical profiles of
flow velocity across these cross-sections. These data were used to determine the
corresponding time-variation of flow discharge in each channel. The discharge variation
was in turn used to calculate the associated tidal prisms.
Figure A-1.1 is an aerial view of the St. Andrew Bay Entrance channel and Fig.
A-1.2 is a bathymetric survey based largely on measurements carried out in 2000. The
three cross-sections (A' B' and C'), where currents were measured on 12/18/2001 with a
vessel mounted Acoustic Doppler Current Profiler, or ADCP (Workhorse 1200 kHz, RD
Instruments, San Diego, CA), are as marked. The coordinates of end-points A'-l, A'-2,
B'-1, B'-2, C'-l and C'-2 are given in Table A-1.1.
Table A-1.1 Locations of St. Andrew Bay Entrance cross-sections
Section Side Latitude Longitude Northing Easting
A' A'-1 3007.18 -85 43.72 409256.63 1611563.75
A'-2 3007.40 -8543.91 410626.10 1610534.09
B' B'-1 3007.43 -8543.30 410766.60 1613757.91
B'-2 3007.68 -8543.44 412309.71 1613034.11
C' C'-1 30 07.06 -85 43.90 408542.02 1610606.43
C'-2 30 07.27 -85 44.01 409822.96 1610030.59
Fig A-1.1 St. Andrew Bay Entrance, Florida in 1993. Jetties are -430 m apart.
.met.
^i
412000.00 4 9
411000.00
8 -^ 6 -5.00
S. .-.^ B,.
B-
410001:D CO c-.2
409000.00 A'-1
5.00 8
C'-1
1610000.00 1611000.00 1612000.00 1613000.00 1614000.00 1615.' ,)
Fig. A-1.2 St. Andrew Bay Entrance bathymetry and current measurement cross-sections
A' B' and C'. The tide level recorder was located northward of the area shown. Depths
are in feet below MLLW. Measurements at cross-sections A and B were conducted in
September 2001 and are reported by Jain and Mehta (2001).
___
A-2. MEASUREMENTS
A-2.1 Cross-Sections
Cross-sections A', B' and C' measured by the ADCP are shown in Figs. A-2.1a,b.
These have been compared with the bathymetric survey of 2000. The trends in the two
sets of depths are qualitatively (although not entirely) comparable. As far the velocity
measurements given later are concerned, the ADCP based values must be treated as
having a good degree of accuracy because they were obtained at the precise times and
locations of profiling for velocity. On the other hand, the bathymetric data are likely to be
less accurate, given that they were not synchronous.
0 -- 1 1 I I
-50 50 150 250 350 450 50
-5
S -10
-15
-20
Distance(m)
.--ADCP -- Bathymetry
Fig A-2.la Cross-section A' measured and compared with 2000 bathymetry. Distance is
measured from point A'-2. The datum is mean tide level. Measured area = 5,210 m2.
100 200 300 400 600
-5
-10
-15
-20
Distance(m)
Bathymetry --ADCP
Fig A-2.1b Cross-section B' measured and compared with 2000 bathymetry. Distance is
measured from point B'-2. The datum is mean tide level. Measured area = 5,640 m2.
-20
500
Distance(m)
-- Bathymetry -- ADCP
Fig A-2.1c Cross-section C' measured and compared with 2000 bathymetry. Distance is
measured from point C'-2. The datum is mean tide level. Measured area = 5,220 m2.
A-2.2 Tide Level
Tide variation reported in Fig. A-2.2a is the predicted National Ocean Service
(NOS) tide at St Andrew Bay Entrance channel based on reference station at Pensacola.
The record indicates a (spring) range of 0.51 m on December 18, 2001. It appears that
the record has been filtered to emphasize the diurnal signature (presumably for navigation
purposes), inasmuch as the current data described next showed semi-diurnal oscillations.
To that extent, Figure A-2.2a should be treated as a severe approximation of the actual
tidal variation on 12/18-19/2001.
0.4 -
0.3
0.2 -
= -0.1 -
0 0 .
O r- 'i- c o' C 0 'o CV)
-0.1 o ',- O o
-0.2
Time (hrs)
12/18/01 12/19/01
NOS Tide -- Mean tide
Fig.A- 2.2a NOS predicted tide at St. Andrew Bay Entrance on December 18, 2001. The
datum is MLLW.
A-2.3 Current and Discharge
The sequence of ADCP measurements is as given in Table A-2.1.
Table A-2.1 ADCP measurement sequence at St. Andrew Bay Entrance
Cross Date Time Date Time No. of transects
section starting starting ending ending
A' 12/18/2001 09:27 12/18/2001 19:31 20
B' 12/18/2001 09:04 12/18/2001 19:15 22
C' 12/18/2001 09:41 12/18/2001 18:17 15
The time-variation of the cross-sectional mean current at A', B' and C' is plotted
in Figs. A-2.3a,b,c, respectively. The corresponding discharges are given in Figs. A-
2.4a,b, c.
0.8
0.6
0.4
0.2
o -0.2 'I O
-0.4 N t It O O LO l
,- i (D
-0.6 U) 1
-0.8
-1
Time(hrs)
Fig. A-2.3a Cross-sectional mean current variation at A' on December 18, 2001.
0.8
0.6
0.4
E 0.2
0. 0
Fg A 3 CD Mc ma CM CNi o a B CeJ e C1 0)0
-0.2 .0 -r .. 0 .o ..- . o o. 9
> -0.4 o \o C o o
a) 0 0 T CqJ CO to l --
-0.6 -
-0.8
Time (hrs)
Fig. A-2.3b Cross-sectional mean current variation at B' on December 18, 2001.
0.8
0.6
0.4
2 0.2
E 0
-0.2 - co o o in o i- n M co
-0.6 oa C CO CO CD CO r .-
-0.8
-1
Time(hrs)
Fig. A-2.3c Cross-sectional mean current variation at C' on December 18, 2001.
4000 -
3000 -
- 2000 -
C 1000 -
E
0)
z -1000
5 -2000 -
.c
0 -3000 -
-4000 -
-5000 -
(0 0 CC N CO Oin (D
LO tCY )
NM N 0 LO MLO L
0) In C In
0) 0; -1 i i (0r N-
Time(hrs)
Fig. A-2.4a. Discharge variation at cross-section A' on December 18, 2001.
5000 ,
4000 -
-.3000 -
C')
c 2000 -
E 1000 -
p 0 -
O -1000 -
n -2000 -
o -3000 -
-4000-
-5000 -
C.0 (0 M) CO) N 0) N (0 CO 0M
CO NO)
m L crN CLO O N)
0 0 N. CO 6 I,- c 6
0 9 -N) 0)
0) 0 -l M W 0 N
Timefhrs)
Fig. A-2.4b Discharge variation at cross-section B' on December 18, 2001.
4000 -
3000 -
2000 -
m 1000 -
E 0
0)
F -1000 -
5o -2000 -
o -3000 -
-4000 -
-5000
st O(D CO CO O 19t (N CO
6- 66 U 66
0 T- M
Time(hrs)
Fig. A-2.4c Discharge variation at cross-section C' on December 18, 2001.
Based on the data in Figs. A-2.3a,b,c and A-2.4a,b,c, Table A-2.2 provides
characteristic velocity- and discharge-related times and magnitudes.
Table A-2.2 Characteristic peak velocity and discharges at cross-sections A', B' and C' at
St. Andrew Bay Entrance
Cross-section A' Cross-section B' Cross-section C'
Quanty Value Time Value Time Value Time
Flood velocity (m/s) 0.68 09:32:15 0.69 09:04:36 0.67 09:44:16
Ebb velocity (m/s) 0.73 15:37:42 0.66 16:22:52 0.77 16:00:14
Flood discharge (m3/s) 3620 09:32:15 4061 09:04:36 3480 09:44:16
Ebb discharge (m3/s) 3920 15:37:42 3876 16:22:52 3750 16:00:14
Examples of measured flood and ebb velocity structures over cross-section A' are
shown in Figs. A-2.5a,b,c,d for illustrative purposes. From Table A-2.2 we note that for
each flow phase (flood and ebb), peak (cross-sectional mean) velocities were of
comparable magnitudes at the three sections as were the corresponding discharges, within
the typically expected accuracy of data. (See comments by Jain and Mehta, 2001 relative
to limitations of the ADCP measurements). As seen from Table A-2.3, slack water times
(after flood) at the three cross-sections were close to each other as would be expected in a
short channel.
Table A-2.3 Characteristic slack water time at cross-sections A', B' and C' at St. Andrew
Bay Entrance
Cross-section A' B' C'
Slack water time (h) 12:48 12:49 12:51
Ichiye and Jones (1961) reported 0.52 m/s peak flood velocity and and 0.61 m/s at
peak ebb close to cross-section A'. Lillycrop et al. (1989) measured 0.68 m/s peak flood
and 0.73 m/s at peak ebb. Note that during both of those studies East Pass was open. Jain
and Mehta (2001) reported 0.63 m/s at flood and 0.62 m/s at ebb, respectively, when East
Pass was closed.
2
S700
-2 ,
500
6 \ 400
300
8 200
100
10 0
Fig. A-2.5a Ebb velocity structure at cross-section A' on December 18, 2001 at 16:49.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of width is point A'-2.
F',g.5 veloci*t .tr r at c' o
o...dt.., .:, ., ,,B -
2 .,.
"-"\ .-!\ ",,
S 500
4 *' .'* \"' ,;" .'. .-"
: .- ; "- 400
6 300
S" 200
100
10 0
Fig. A-2.5b Ebb velocity structure at cross-section B' on December 18, 2001 at 16:42.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of width is point B'-2.
2
0\
250
,-i """ 200
8 100
10 0
Fig. A-2.5c Flood velocity structure at cross-section C' on December 18, 2001 at 09:44.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of width is point C'-2.
10
0
0
L^p- ----""
\ 100
0 0 5
10 0
Fig. A-2.5d Ebb velocity structure at cross-section C' on December 18, 2001 at 16:00.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of width is point C'-1. A data anomaly is evident close to the origin.
A-3. TIDAL PRISM
A-3.1 Calculation of Tidal Prism
In general, tidal prism over flood (which is the characteristic prism per definition)
or ebb is obtained by integrating the discharge curve, from slack to slack, for flood or ebb
flow, respectively. When a complete discharge curve for that purpose is not available, the
following formula yields an approximate value of the prism, P:
QmT
P = (A-3.1)
nCK
where Qm is the peak discharge (Table A-2.2), T is the (semi-diurnal, M2) tidal period
(12.42 h) and the coefficient CK = 0.86 (Keulegan, 1967).
Table A-3.1 Tidal prism values for St. Andrew Bay Entrance
Tidal prism Cross-section
(m3) A' B' C'
Flood 6.0x107 6.7x107 5.8x107
Ebb 6.9x107 4.9x107 6.4x107
A-3.2 Comparison with O'Brien Relationship
The O'Brien (1969) relationship between the throat area Ac and the tidal prism P
on the spring range for sandy inlets in equilibrium is:
Ac = a Pb (A-3.2)
For inlets with two jetties, a = 7.49x104 and b = 0.86 (Jarrett, 1976). Now,
considering cross-section A' to represent the throat section, Ac = 5,210 m2 at mid-tide
level. Thus, from Eq. A-3.1 we obtain P = 9.0x107 m3, which may be compared with the
measured (flood) value of 6.0x107 m3. The latter value is 30% less than the former. It is
uncertain if this difference is has significance in relation to the stability of the channel,
since Eq. A-3.1 merely provides an estimate.
SECTION-B: EAST PASS
B-1. INTRODUCTION
Hydrographic measurements were carried out at East Pass on 12/19/2001. The
aim was dual: 1) to determine the tidal prism of this new cut as a record of its incipient
stability, and 2) to examine the effect of this inlet on St Andrew Entrance, by comparing
the measured prism with that at St. Andrew Bay Entrance. The measurements included a
flow cross-sectional survey and vertical profiles of flow velocity that cross-section.
Figure B-1.1 is an aerial view of the East Pass before it was opened along the
designed configuration. Cross-section (E) where currents were measured is marked in
Fig. B-1.2. The coordinates of end-points E-1 and E-2 are given in Table B-1.1.
Fig B-1.1 East Pass channel in 1997.
Table B-1.1
Section
E
E
Location of channel cross-section at East Pass
Side Latitude Longitude Northing
E-1 30 03.78 -85 37.07 388325.56
E-2 3003.79 -8537.12 388371.27
Easting
1646376.03
1646103.36
S-s
1 I '
*s--^
,;1 r
y\-
2'
)
iras Endr
A -
ZA 4
2
1 .
4,
..1
/
Reopened
IEast Pass
mouth
Fig. B-1.2 Location of East Pass current measurement cross-section E on USGS
topographic map: left portion 1994; right portion 1982.
B-2. MEASUREMENTS
B-2.1 Cross-section
The bottom track of cross-section E obtained by the ADCP is shown in Fig. B-
* Lia
0 I I I I
-0.5 ) 20 40 60 80 100
-1
E -1.5
_ -2
a)
-2.5
-3
-3.5 -
-4
Distance(m)
Fig B-2.1 Cross-section E measured by ADCP. Distance is measured from point E-1. The
datum is mean tide level. Area = 300 m2.
B-2.2 Tide Level
Tidal variation in the channel on 12/19/01 was predicted NOS tide at St Andrew
Bay channel (Fig.A-2.2a). The record indicates a range of 0.45 m on December 19, 2001.
B-2.3 Current and Discharge
The sequence of ADCP measurements is as given in Table B-2.1.
Table B-2.1 ADCP measurement sequence at East Pass
Cross Date Time Date Time No. of
section starting starting ending ending transects
E 12/19/2001 10:30 12/19/2001 18:49 92
The time-variation of the cross-sectional mean current at E is plotted in Figs. B-
2.2. The corresponding discharge variation is given in Fig. B-2.3.
0.60 -
0.40 -
4 0.20
E
0.00
0
a) -0.20
>
-0.40 1
-0.60
It I0 10 O0 CO ) 0 (0 0 I
)n Co 0 cV m T (QA CM '0 i- CIn '- 0NI rin
q 0) '- f CO O- PI' CM 0O
- ) t0 t o o 0 C o t r t C0 0i p '. 0
I L O N C. c o 6
Time(hrs)
Fig. B-2.2 Cross-sectional mean current variation at E on December 19, 2001.
200.00 -
150.00 -
- 100.00 -
E 50.00 -
V-
2 0.00
S-50.00
_ -100.00
-150.00
-200.00 -
3 I CC) LO LO 00 T) 0 (D (0 rli It CO
Ia LO a 0- ci co ~ c0 o
S 6 i Time hrs
Time(h rs)
Fig. B-2.3 Discharge variation at cross-section E on December 19, 2001.
Based on the data in Figs. B-2.2 and B-2.3, Table B-2.2 provides characteristic
velocity and discharge-related times and magnitudes.
Table B-2.2 Characteristic peak velocity and discharge at East Pass cross-section E
Cross-section E
Quantity Flood Time Ebb Time
Velocity (m/s) 0.51 11:16:11 0.49 15:29:58
Discharge (m3/s) 139 11:16:11 165 15:29:58
From Table B-2.2 we note that peak (cross-sectional mean) flood and ebb
velocities were of comparable magnitude. On the other hand, the ebb discharge was
greater than flood by 19%.
B-3. TIDAL PRISM
B-3.1 Calculation of Tidal Prism
The flood and ebb prisms given in Table B-3.1 were estimated from Eq. A-3.1
based on the peak discharge values. In addition, the ebb the prism was also estimated by
extrapolation of the ebb portion of the discharge curve in Fig. B-2.3, as the measurement
did not run over the entire tidal cycle. The value thus obtained is given within
parentheses.
Table B-3.1 Flood and ebb tidal prisms at East Pass
Flow Prism
direction (m3)
Flood 2.3x 10
Ebb 2.7x 106 (4.Ox 106)
B-3.2 Comparison with O'Brien Relationship
Relative to Eq. A-3.1, for inlets with no jetty, a = 1.58x10-4 and b = 0.95 (Jarrett,
1976). Now, considering cross-section E to represent the throat section, Ac = 300 m2 at
mean tide level. Thus, from Eq. B-3.1 we obtain P = 4.1x106 m3, which is very close to
the measured 4.0x106 m3 at ebb, but higher than the measured 2.3 xl06 m3 at flood by
78%.
CONCLUDING COMMENTS
From the collected data the following characteristic values are obtained. At St.
Andrew Bay Entrance, selecting A' as the "throat" cross-section, the measurements indicate:
tidal prism 6.0x107 m3, cross-section (at mean tide) 5,250 m2 and peak flood (cross-
sectional mean) velocity 0.68 m/s. The corresponding values for East Pass are: (flood)
tidal prism 2.3x106 m3, cross-section 300 m2 and peak (flood) velocity 0.50 m/s.
It is interesting to compare the flood/ebb tidal prisms at St. Andrew Bay Entrance
measured on 09/18/01-09/19/01 (Jain and Mehta, 2001) with those from the present
study. This is done in Table B-4.1 based on the prism definition according to Eq. A-3.1.
Note that all prisms have been calculated using Eq. A-3.1.
Table B-4.1
Flow
direction
Flood
Ebb
Comparison of prisms measured at St Andrew Bay Entrance
Prism
(m3)
Cross-section Cross-section Cross-section Cross-section
A A' B B'
(09/01) (12/01) (09/01) (12/01)
7.0x107 6.0x107 4.9x107 6.7x107
6.0x107 6.9x107 3.7x107 4.9x107
Cross-section
C'
(12/01)
5.8x 10
6.4x107
Since cross-sections A and A' are close to each other (Fig. A-1.2), and believed to
be close to the channel throat, it is instructive to compare the values obtained there. Note
that there is no discernible trend of the effect of East Pass, which was not open in
September 2001, but open in December 2001. This lack of identifiable is not surprising,
especially considering that the flood/ebb prisms measured at East Pass on 12/19/01 were
only 0.23x107 m3 and 0.40x107 m3, respectively.
REFERENCES
Ichiye, T., and Jones, M. L., 1961. On the hydrology of the St. Andrew Bay system,
Florida. Limnology and Oceanography, 6(3), 302-311.
Jain, M., and Mehta, A. J., 2001. UFL-COEL-2001/000, Department of Civil and Coastal
Engineering, University of Florida, Gainesville, FL.
Jarrett, J. T. Prism-inlet area relationships. G.I.T.I Report No. 3, U.S. Army Engineering
Coastal Engineering Research Center, Ft. Belvoir, VA.
Keulegan, G. H., 1967. Tidal flow in entrances: water level fluctuations of basins in
communication with the seas, Technical Bulletin No. 14, Committee on Tidal Hydraulics,
U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.
Lillycrop, W. J., Rosati, J. D., and McGehee, D. D., 1989. A study of sand waves in the
Panama City, Florida, entrance channel. Technical Report CERC-89-7, U.S. Army
Engineer Waterways Experiment Station, Vicksburg, MS.
O'Brien, M. P., 1969. Equilibrium flow areas of inlets on sandy coasts. Journal of the
Waterways and Harbors Division ofASCE, 95(1), 43-52.
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