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Part I

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Title:
Part I
Series Title:
Hydrographic measurements at St. Andrew Bay entrance, Florida
Creator:
Jain, Mamta
Place of Publication:
Gainesville, Fla.
Publisher:
Coastal & Oceanographic Engineering Dept. of Civil & Coastal Engineering, University of Florida
Publication Date:
Language:
English

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University of Florida
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University of Florida
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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 6.0x 107 in3, cross-section (at mean tide) 5,210 M2 and peak flood (crosssectional mean) velocity 0.68 m/s. East Pass: (flood) tidal prism 2.3x 106 Mn3, 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
S U M M A R Y ........................................................................................... 2
TABLE OF CONTENTS ........................................................................... 3
LIST OF FIGURES ................................................................................. 5
L IST O F T A B L E S ................................................................................... 7
ACKNOWLEDGMENT ........................................................................... 8
SECTION A: ST ANDREW BAY ENTRANCE .............................................. 9
A-] INTRODUCTION .......................................................................... 9
A-2 MEASUREMENTS ........................................................................ 12
A-2.1 Cross-Sections ........................................................................... 12
A -2.2 Tide L evel ................................................................................ 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 L evel ................................................................................ 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 (200 1) ........................................................................... 11
Fig A-2.l a Cross-section A' measured and compared with 2000 bathymetry. Distance is measured from point A'-2. The datum is mean tide level. Measured area
2
- 5 ,2 10 m ....................................................................................... . .. 12
Fig A-2. lb 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. lc 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 m 2 ........................................................................................ . 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 D ecem ber 18, 200 1 ............................................................................... 15
Fig. A-2.3b Cross-sectional mean current variation at cross-section B' on D ecem ber 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 mis. 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 mis. 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.l1 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 point E-1. The datum is mean tide level. Area = 300 m .............................. 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. A ndrew 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-i. 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'-I, A'-2, B'-I, B'-2, C'-I 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'-I 3007.18 -8543.72 409256.63 1611563.75
A'-2 3007.40 -8543.91 410626.10 1610534.09
B' B'-I 3007.43 -8543.30 410766.60 1613757.91
B'-2 3007.68 -8543.44 412309.71 1613034.11
C C'-1 3007.06 -8543.90 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.




B --2 Q
412000.00
411000.00
o o A'
410000.00 V-2'-2
4109000,00 R~ A- AI
5.00
1610000.00 1611000.00 1612000.00 1613000.00 1614000.00 161500'0.00
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.l a,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.
I 0WI I 1 I 4 -* I
-50 50 150 250 35050
-5
S -10
0
-15 -20
Distance(m)
--ADCP -- Bathymetry
Fig A-2.1 a 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.




0 1
100 200 300 400 600
-5
E
.- 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 -u-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
E0.2 0.1
0 0
0 LO r- 04' Lo 00 "1 C0
-0.1 o-04 '4\ 0P04
- 0N W M ,. r-- 04 04
-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. A2.4a,b, c.




0.8
0.6
0.4
0.2
E
0
_0 (0 't~ 00 ( C\j CO 0
-0.2
a, -0.4 \- j 0qt O Y ItO r
0V CO 0)5 CD ) D V
-0.6 6
-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
o
0
2 -0.2 D D C
0 MO r- w 0 N 0 CO 0)
Time (hrs) Fig. A-2.3b Cross-sectional mean current variation at B' on December 18, 2001.
0.8 0.6
0.4
0 0.2
E
0
E0
" -0.2 q- co O O o LO N CO
S -0.4 o a a -' o ,
-0.6 6 6 cm as 6c q- o a0 N
-0.8
-1
Time(hrs)
Fig. A-2.3c Cross-sectional mean current variation at C' on December 18, 2001.




4000 3000 S2000 S 1000E
00 z -1000
-2000 o -3000
-4000 -5000 -

0 i0 N CO t0 r_ O0
IC Itj LO I t CO N~ 0 N~
r .. 9. 6i. .6 6
- N- N) It- O CO ,,- .Om 10 \O 10 10 CO
Time(h rs)

Fig. A-2.4a. Discharge variation at cross-section A' on December 18, 2001.
5000 ,

4000
- 3000 C')
c 2000E 1000
O -1000
c -20000 -3000
-4000 -5000 -

10 1o M CO N 0 N 0 CO 0a
CO 10 CO N 0 10 0 10 0
4 C CO) r_ 6 0 N- Nq 0 CO 0)
O CO 0 CO N
S 0 0 CO <0
Time(hrs)

Fig. A-2.4b Discharge variation at cross-section B' on December 18, 2001.

4000 3000 2000 S1000E 0
- -1000 S-2000
-3000
-4000 -5000 -

v- 4 co .4 .v o 9 9 0
0 0 (N CO C O 0 0 N N
,It -- rT i m e r
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" Quantity 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 ms 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.




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.
N-,,
2
-2
01
2
500
400
6 300
, .. 200
10100
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.




300
4 "250
200
150
50
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
4 300
150
8 100
53
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:
P m (A-3.1)
I"CK
where Q... 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
(in3) A' B' C'
Flood 6.0x 107 6.7x 107 5.8x 107
Ebb 6.9x 107 4.9x 107 6.4x 107
A-3.2 Comparison with O'Brien Relationship
The O'Brien (1969) relationship between the throat area A, 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 = 7.49xl0-4 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.Ox 107 M3, which may be compared with the measured (flood) value of 6.Ox 107 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-i. 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-I 30 03.78 -85 37.07 388325.56
E-2 3003.79 -8537.12 388371.27

Casting 1646376.03 1646103.36

'1

~---- N
N. :~

Lais End

I,

Ii ~
*'\ '~ 11~ K
I.;
I'
/

. E

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-

Reopened East Pass mouth

\




0 I I I I
-0.5 4) 20 40 60 80 100
-1
-1.5
- -2
-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. B2.2. The corresponding discharge variation is given in Fig. B-2.3.




0.60
0.40
0.20
E
S0.00
o
0
a) -0.20
>
-0.40
-0.60

It 00 IO Ur) 00 0) 0 '- (0 (D 0 tC
IL) C~) C\J 7 -C1 O0
2 (0 0) '- C) ,N C'\i
10, O T- C\j ULO Cf) -~ 1 fr
2i 0) 0- L--0-

Time(hrs)
Fig. B-2.2 Cross-sectional mean current variation at E on December 19, 2001.

200.00 150.00 4 100.00 E 50.00
S 0.00
-50.00 I -100.00
-150.00 -200.00 -

" 4 O to to M 0o (0 a 0 M q c cO) I LO CO 0 C1J LO r- 0 O a 66 a 4 0I 1- C\ cil co 6
aaw - M- o o co
Time(hrs)

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 (m 3)
Flood 2. 3xl10
Ebb 2.7x 10' (4.Oxl10)
B-3.2 Comparison with O'Brien Relationship
Relative to Eq. A-3.l1, for inlets with no jetty, a = 1.58x 10-4 and b = 0.95 (Jarrett, 1976). Now, considering cross-section E to represent the throat section, A, = 300 m 2 at mean tide level. Thus, from Eq. B-3.1 we obtain P = 4.xl in 16 3, which is very close to the measured 4.Oxl 16M3 at ebb, but higher than the measured 2.3 X106 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 6.0x 107 in3, 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 6.0x 10 4.9x 10' 6.7x 107
6.0x 107 6.9x 107 3.7x 107 4.9x 107

Cross-section
C'
(12/01)
5.8x107 6.4x 107

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 0.23x 107 m3 and 0.40x 107 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/O00, Department of Civil and Coastal Engineering, University of Florida, Gainesville, FL.
Jarrett, J. T. Prism-inlet area relationships. G.LT.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.
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