• TABLE OF CONTENTS
HIDE
 Half Title
 Title Page
 Summary
 Table of Contents
 List of Figures
 List of Tables
 Acknowledgement
 Introduction
 Measurements
 Tidal prism
 Concluding comments
 Reference














Group Title: Hydrographic measurements at St. Andrew Bay entrance, Florida
Title: Interim Report
ALL VOLUMES CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00091376/00001
 Material Information
Title: Interim Report
Series Title: Hydrographic measurements at St. Andrew Bay entrance, Florida
Physical Description: Book
Language: English
Creator: Jain, Mamta
Publisher: Coastal & Oceanographic Engineering Dept. of Civil & Coastal Engineering, University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: November 2001
 Record Information
Bibliographic ID: UF00091376
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Half Title
        Half Title
    Title Page
        Page 1
    Summary
        Page 2
    Table of Contents
        Page 3
    List of Figures
        Page 4
    List of Tables
        Page 5
    Acknowledgement
        Page 6
    Introduction
        Page 7
        Page 8
        Page 9
    Measurements
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
    Tidal prism
        Page 18
        Page 19
    Concluding comments
        Page 20
        Page 21
    Reference
        Page 22
Full Text




UFL/COEL-2001/014


HYDROGRAPHIC MEASUREMENTS AT ST. ANDREW BAY
ENTRANCE, FLORIDA






by



Mamta Jain
and
Ashish J. Mehta



Submitted to:

Coastal Technology Corporation
Destin, FL 32541


December 2001









UFUCOEL-2001/014


HYDROGRAPHIC MEASUREMENTS AT ST. ANDREW BAY ENTRANCE,
FLORIDA





By






Mamta Jain 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


December 2001








SUMMARY

Hydrographic measurements were carried out in St. Andrew Bay Entrance (also

known as Panama City Harbor Entrance) connecting St Andrew Bay to the Gulf of

Mexico, Florida between 09/18/2001 and 09/19/2001. The measurement included: 1)

Two flow cross-sectional surveys one being in the entrance channel vicinity of the

throat where the jetties are located and the other towards St. Andrew Bay, 2) vertical

profiles of flow velocity across these two cross-sections and 3) 2-day record of tidal

variation in the channel. These data were used to determine the corresponding time

variation of flow discharge in the channel. The discharge was in turn used to calculate the

flood and ebb tidal prism through the throat cross-section.

We report the following approximate values: tidal prism 7.0x107 m3 (from peak

discharge), tidal range 0.17 m, representative cross-section (mid-tide) 6,365 m2 and peak

(cross-sectional mean) flood/ebb velocity 0.63 m/s.









TABLE OF CONTENTS

SUMMARY .................................................. ................ ...................2

TABLE OF CONTENTS.....................................................................3

LIST OF FIGURES.................................................... .......................4

LIST OF TABLES...................................... ............... .........................5

ACKNOWLEDGMENT...... .......... ............................................................6

1. IN T R O D U C TIO N .........................................................................7.

2. MEASUREMENTS.................................................... ....................10

2.1 Cross-Sections ................................. ........... ......... ...........10

2.2 Tide L evel............................................. ......... ............ .... .. .. 11

2.3 Current and Discharge................................................................13

3. TIDAL PRISM..................................................... .........................18

3.1 Calculation of Tidal Prism.............................................................18

3.2 Comparison with O'Brien Relationship...............................................18

4. CONCLUDING COMMENTS..................................................... .......20

R EFE R EN C ES .................................... ........................................22









LIST OF FIGURES


Fig 1.1 St. Andrew Bay Entrance, Florida in 1993. Jetties are -430 m apart ............8

Fig. 1.2 St. Andrew Bay Entrance bathymetry and current measurement cross-sections.
The tide level recorder was located northward of the area shown...........................

Fig 2.1a Cross-section A: measured and compared with 2000 bathymetry. Distance is
measured from point A-1 ................................................................ .... 10

Fig 2.1b Cross-section B: measured and compared with 2000 bathymetry. Distance is
m measured from point B ......................................................................... 11

Fig. 2.2a Measured tide in the channel vicinity on September 18-19, 2001. The datum is
M L LW ..................................................... ........................................12

Fig. 2.2b NOS Predicted tide at the entrance on September 18-19, 2001. The datum is
M LLW ..................................................... .......................................12

Fig. 2.3a Cross-sectional mean current variation at cross-section A on September 18,
2001................................ ......................................13

Fig. 2.3b Cross-sectional mean current variation at cross-section B on Septemberl9,
2001 .......... .. ............... ...... ............. ...................... 14

Fig. 2.4a. Discharge variation at cross-section A on September 18, 2001................ 14

Fig. 2.4b. Discharge variation at cross-section B on September 19, 2001 ................ 15

Fig. 2.5a. Flood velocity structure at cross-section A on September 18, 2001 at 09:25.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of w idth is point A -1 ........................................ .. ..................... ... ........ 16

Fig. 2.5b. Flood velocity structure at cross-section A on September 18, 2001 at 17:18.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of w idth is point A ............................................................................ .. 16

Fig. 2.5c. Ebb velocity structure at cross-section A on September 18, 2001 at 15:55.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of width is point A-2.................................... ........................... ....... 17

Fig. 2.5d. Flood velocity structure at cross-section A on September 18, 2001 at 20:48.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of w idth is point A ...................... ..................... ........ ........ ................. ...17











LIST OF TABLES


Table 1.1 Locations of channel cross-sections................................................7

Table 2.1 ADCP measurement sequence.................................................... 13

Table 2.2 Characteristic peak velocity and discharge values at cross-sections A and B.15

Table 3.1 Flood and ebb tidal prism s.......................................................... 18









ACKNOWLEDGMENT


This study was carried out for Coastal Technology Corporation, Destin, Florida.

Assistance provided by Michael Dombrowski of Coastal Tech is sincerely acknowledged.

Field work was performed by Sidney Schofield and Vic Adams, both of the Coastal and

Oceanographic Engineering Laboratory of the Department of Civil and Coastal

Engineering, University of Florida.









HYDROGRAPHIC MEASUREMENTS AT ST. ANDREW BAY ENTRANCE,

FLORIDA


1. INTRODUCTION

Hydrographic measurements were carried out in St. Andrew Bay Entrance (also

known as Panama City Harbor Entrance) connecting St Andrew Bay to the Gulf of

Mexico in Bay County, Florida between 09/18/2001 and 09/19/2001. The measurements

included: 1) Two flow cross-sectional surveys one being in the entrance channel

vicinity of the throat where the jetties are located and the other towards St. Andrew Bay,

2) vertical profiles of flow velocity across these two cross-sections and 3) 2-day record of

tidal variation in the channel. Results and analysis based on these measurements are

described in this report.

Figure 1.1 is an aerial view of the St. Andrew Bay Entrance channel and Fig. 1.2

is a bathymetric survey based largely on measurements carried out in 2000. The two

cross-sections (A & B) where currents were measured with a vessel mounted Acoustic

Doppler Current Profiler, or ADCP (Workhorse 1200 kHz, RD Instruments, San Diego,

CA) and the location of an ultrasonic tide level recorder (Model #220, Infinities USA,

Daytona Beach, FL) are as marked. The coordinates of end-points A-1, A-2, B-1 and B-2

are given in Table 1.1. The tide gage was located in waters (Grand Lagoon) close to the

entrance channel, at Lat: 30 07.9667, Long: -85 43.6667.

Table 1.1 Locations of channel cross-sections
Section Side Latitude Longitude Northing Easting
A A-1 30 07.7086 -85 43.3667 412452.6240 1613441.9000
A A-2 30.07.4492 -85 43.2846 410875.8000 1613857.6000
B B-1 3007.3508 -8543.9159 410315.8300 1610524.0000
B B-2 30 07.1753 -85 43.7126 409240.0000 1611584.6000

































. I


Fig 1.1 St. Andrew Bay Entrance, Florida in 1993. Jetties are -430 m apart.


INl>:.* 7
O 'k
'^ ?Y
btl'ii^B,


* J

























-55.00

-45.00



-ra


* I


-5.03


1610000.00 1611000.00 1612000.00 1613000.00 1614000.00 1615000.00


Fig. 1.2 St. Andrew Bay Entrance bathymetry and current measurement cross-sections A
and B. The tide level recorder was located northward of the area shown. The datum is
MLLW.


4120C0'1 ,10


411000.00






410000.00






409000.00


111 I __ ~________~______lyl_










2. MEASUREMENTS

2.1 Cross-Sections

Cross-sections A and B measured by the ADCP are shown in Figs. 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 measured at the precise times and

locations of acoustic profiling for current data. On the other hand, the bathymetric data

are likely to be less accurate, given that they were not synchronous.








Batymetry side-A
Side-A-1 Side- A-2


0 100 200 300 400 500 600
-2 -
-4
-4 -

-6
E -8 -
r-
a) -10 -

-12

-14-

-16

-18
ADCP -U- Bathymetry chart Distance (m)






Fig 2.1 a Cross-section A: measured and compared with 2000 bathymetry. Distance is
measured from point A-1. The datum is MLLW.









Batymetry side-B
Side-B1 Side-B-2

2 50 100 150 200 250 300 350 400 450 500



-6
-8 -
-10 -
-12

-14 -
-16 -
-18
-- ADCP -U- Bathymetry chart Distance (m)


Fig 2.1b Cross-section B: measured and compared with 2000 bathymetry. Distance is
measured from point B-1. The datum is MLLW.


2.2 Tide Level

Tidal variation in the channel was measured and compared with the predicted

National Ocean Service (NOS) tide at St Andrew Bay Entrance channel based on

reference station at Pensacola. The measured tide is shown in Fig. 2.2a and the

corresponding NOS tide in Fig. 2.2b. Both show general similarities, although the

measured one should be deemed more accurate. The record began on 09/18/01 at 9:00:00

and ended on 09/19/01 at 20:15:00. The measured data indicate a weak semi-diurnal

signature with a range variation of 0.11 to 0.17 m.












Tide at St Andrew Bay Entrance
-Tide at St Andrew Bay Entrance


0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
S0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
--N -- J 0o0 0 0 (O-
^',^^ Time (hrs)


UY ]?IU]


10/91/90
U/ /UI
--- --


Fig. 2.2a Measured tide in the channel vicinity on Septemberl8-19, 2001. The datum is
MLLW.


NOS Tides


0.45
0.4-
E 0.35
S0.3
> 0.25 -
S0.2-
( 0.15 -
0.1 -
0.05 -
0 -


-- In 00 00 C,


S09/18/01 Time (hr:min

-Y


- Tides


0 In 9o

09/19/
Y-


Fig. 2.2b NOS predicted tide at the entrance on Septemberl8-19, 2001. The datum is
MLLW.


""""""""""""""""""""










2.3 Current and Discharge

The sequence of ADCP measurements is as given in Table 2.1.



Table 2.1 ADCP measurement sequence
Cross Date Time Date Time No. of transects
Section starting starting ending ending
A 09/18/2001 09:25 09/18/2001 09:02 84
B 09/19/2001 09:10 09/19/2001 20:05 70



The time-variation of the cross-sectional mean current variation at A and B is

plotted in Figs. 2.3a,b, respectively. The corresponding discharges are given in Figs.

2.4a,b.



Velocity Profile side-A

0.80

0.60

0.40

S0.20


ID O It L 6
S 0.0 . .. .V O C
-V -0O -PCM0TC N 0 0 U) 0 NM 00

-0.40

-0.60

-0.80
-4--velocity Profile on side A Time (hrs)


Fig. 2.3a Cross-sectional mean current variation at A on September 18, 2001.












Velocity profile side B


S0.1


Q 0 o
"> o o)
-0.1 ,
cD ri


i- CO C
0 0) .-
.- 0 <
0 T


-0.4
--- Velocity profile side B Time (hrs)


Fig. 2.3b Cross-sectional mean current variation at B on September 19, 2001.




Discharge Profile side A


5000


4000


3000


2000
C,)

E 1000



c co cO o o 0 .- co - Ao c Nt- co co to ~t


-2000


-3000


-4000


0) ~ ~0 N ~ 0 )LA-0
0) 0 0 C) C)


CmOCON........


-- Total discharge Time (hrs)


Fig. 2.4a. Discharge variation at cross-section A on September 18, 2001.


0 wO (0 0
uri *4f 4? LA
M Lo C O

N C C C







Discharge profile side B


4000

3000

2000

E 1000

-- 0 o o
0
So C' Un N- C C to LC J cC t (N
S i 00*i V : C) M o V) 0 ) U) 0 6i U W i 0 C) L 0
-1000 !t 9 5 "In" A 9 N '!t 7: q! I 0 C' 7


-2000

-3000
Time (hrs)
-U- "Total discharge"
Fig. 2.4b. Discharge variation at cross-section B on September 19, 2001.

Based on the data in Figs. 2.3a,b and 2.4a,b, Table 2.2 provides characteristic

velocity and discharge related times and magnitudes.

Table 2.2 Characteristic peak velocity and discharge values at cross-sections A and B.
Cross-section A Cross-section B
Quantity Peak Time Peak Time Peak Time Peak Time
flood Ebb flood ebb
Velocity (m/s) 0.63 09:25 -0.62 17:18 0.45 10:37 -0.34 18:32
Discharge (m3/s) 4200 09:25 -3620 17:18 2980 10:37 -2250 18:32



Lillycrop et al. (1989) measured 0.70 m/s peak flood velocity and -0.84 m/s at ebb

close to cross-section A. Ichiye and Jones (1961) reported 0.52 m/s and 0.61 m/s,

respectively. During both studies East Pass, a second entrance to the bay, was open.

During the present study it was closed.

Examples of measured flood and ebb velocity structures over cross-section A are

shown in Figs. 2.5a,b,c,d for illustrative purposes. From Table 2.2 we note that at each

section, peak (cross-sectional mean) flood and ebb velocities were of comparable

magnitude. On the other hand, the ebb discharge was lower than flood, at A by 14% and











at B by 24%. Assuming the validity of the data, one must attribute this difference


between flood and ebb prisms to the temporary storage of water in St. Andrew Bay, in the


absence of any other openings.


S200
10 '
S100

15 0


Fig. 2.5a. Flood velocity structure at cross-section A on September 18, 2001 at 09:25.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of width is point A-1.


2

0

-2
0


S* o




10 21 *
150


50
20 0


5 300
250


Fig. 2.5b. Ebb velocity structure at cross-section A on September 18, 2001 at 17:18.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of width is point A-1.






















:
i
~
~ ; 1
:b


20 0


Fig. 2.5c. Ebb velocity structure at cross-section A on September 18, 2001 at 15:55.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of width is point A-2.












''~


5 '. '. '25


5250
200
10
150

15\ 100
50
20 o







Fig. 2.5d. Flood velocity structure at cross-section A on September 18, 2001 at 20:48.
Vertical axis represents current speed in m/s. Depth and width axes are in meters. Origin
of width is point A-1.








3. TIDAL PRISM


3.1 Calculation of Tidal Prism

The flood and ebb tidal prisms were estimated as follows. Referring to Fig. 2.4a,

the flood tidal prism was estimated by extrapolation of the starting point of the discharge

curve, as measurement did not run over the entire flood cycle. However, from Fig. 2.2a

we note that the tide is measurably semi-diurnal (M2), so the tidal period is 12.42 h.

Hence, by extending the flood tide curve (to a comparatively minor extent, on the order

of 1 hour) to the previous slack water, the flood tidal prism (equal to volume of water

entering the channel) is found to be 9.2x107 m3. In Table 3.1 flood and ebb prisms

obtained from Figs. 2.4a,b are given.

When a complete discharge curve for that purpose is not available, the following

formula yields an approximate value of the prism, P:

QT
P = (A-3.1)
1rCK

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). Values are given in Table 3.1.

Table 3.1 Flood and ebb tidal prisms
Cross-section A (09/18/01) Cross-section B (09/19/01)
Method Flood Ebb Tide range Flood Ebb Tide range
(m3) (m3) ( (m) ((m3) (m3) (m)
Area 9.2x107 3.4x107 0.17 7.7 x107 1.7 x107 0.16
Peak 7.0x107 6.0x107 0.17 4.9x107 3.7x107 0.16


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


For inlets with two jetties, a = 7.49xl04 and b = 0.86 (Jarrett, 1976). Now, considering

cross-section A to represent the throat section, Ac = 6,365 m2 at mid-tide level. Thus,

from Eq. 3.1 we obtain P = 11.4x107 m3, which may be compared with the measured

9.2x107 m3. The latter value is 19% less than the former; however it is uncertain if this

difference is has significance in relation to the stability of the channel, since Eq. 3.1

merely provides an estimate. Overall we may surmise that the measured value is a

reasonable estimate of the prism, given that the value obtained from Eq. 3.1 is not

drastically different.


(3.1)











4. CONCLUDING COMMENTS

We note that the discharge measurements by the ADCP model used are

constrained by the acoustic black zones at the top and the bottom, as well as the inability

of the vessel (make, draft) to traverse near-bank depths less than the vessel draft plus

required underkeel clearance. The blank zone limitations led to the need to the need to

extrapolate the velocity data in order to calculate the cross-sectional mean velocities and

corresponding discharges.

Built-in routines in the instrument calculate the measured discharge and convert

to total discharge. At sections A and B the total discharge was typically greater than the

measured discharge by 13% and 23%, respectively.

No correction was applied for the loss of data due to vessel limitation close to

channel banks. One may expect that, typically, the discharge not accounted for in this

way would be less than -5% at this entrance as a result of this limitation.

Finally, we note that the backscatter signals were not corrected for any effects due

to salinity induced stratification in the channel, instrument. During the study period at

this entrance, the error from this source is likely to have been secondary to that due to

above-mentioned limitations.

By definition, the tidal prism characteristic of an entrance is that during flood

flow (at spring tide). Accordingly, and based on the reported measurements, we report the

following approximate values for St. Andrew Entrance: tidal prism 7.0 m3, tidal range

0.17 m, representative cross-section (mid-tide) 6,365 m2 and peak (cross-sectional mean)

flood/ebb velocity 0.63 m/s.









While the tidal prism is seemingly reasonable, an unquantified degree of

uncertainty in its value exists due to: 1) lack of full coverage of the flood cycle and 2) the

inevitable presence of acoustic blank zones with the device used. It is our

recommendation that if available resources allow for monitoring only two tidal cycles,

monitoring should be carried out across a single cross-section over two tidal cycles, as

opposed to one cycle at two sections. Presently, more efficient devices are being

developed to reduce the blank zone. These should find considerable use in Florida's

shallow coastal environment.








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.

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.

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.




University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs