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Notice: ©2001 Academy of Sciences, Inc. http://www.floridaacademyofsciences.org/flsci.htm. This manuscript may be cited as: Smith, N. P. (2001). Tides of , Card Sound, Barnes Sound, and Manatee Bay, Florida. Florida Scientist, 64(3), 224‐236. Oceano!?raphic Sciences

TIDES OF BISCAYNE BAY, CARD SOUND, BARNES SOUND, AND MANATEE BAY, FLORIDA

NED P SMITH 1

Harbor Branch Oceanographic Institution, 5600 U.S. Highway', North, Port Pierce. FL 34946

ABSTRACT: Water level data fronl a 1997-9~ .field SfIU!.V conducted in the coastal bays at the southeast tip qj'the Florida penin."'lda are co/nhined with H-'ater le\'el records from earlier .field studies to characteriz.e sernidiurHal and diurnal period tidal constituents in Bisca)'Ju! Ba.v, Card Sound, Little Card Sound. Barnes ..~'ound llnd Manatee Btl.v. Re,\'ults indicate un~f()nn arnplitudes and rapid .tillin!!, and draining through J11uch (~/ the northern part (~llhe study area.

Semidiurna[ M 2 constituent umplitudes are approxiJnate!.v 30 on; N"2 and S: constituent (lJnpli­ ~ tudes are approximate!:),' alld 5 Clfl, respective!.v. The diurnal K I {lnd O[ constituenfs have amplitudes (~l ahout 3 cnl. In the southern part (~f the study area, a series (~f shallo'vt' hanks reduces the arnplitudes qf all tidal constituents. III Barnes 5;oUJld and Manatee Bay, My- ampli­ tudes are ahout 5 cm, l-vhile all other constituents have amplitudes Oil the order (~l 1 Cln. Calculations t?l bu.v volume relative to fJleafl Sf?{/ level illdicate that 85(j, (~l all.flood tide....' and 870/0 (~l all ehb tides transport fronl 20() to 350 X /(/' Jn 3 (~l wllter into or out (~l the Bisca.vne (~l134.(), Bay Sysfern. l11e M 2• S:!, N 2• K 1 and 0 1 tidal constituents hllve amplitudes /9.3. 26.2, 17.2 and 13.6 X 10(' rn" respectively. Under neap lllld spring tide cOllditions..flood and ehh intertidal volun1es can he as little a.\· /64 X IO() or as 11111Ch as 394 X I ()I' ,n~. Acoustic DO/Jpler pT(~filer data from two locations in central and southern Bisco.vne Ba)' indicate a south-south­ I westward tide-induced residual transport .fi~01Jl Biscayne Bay info Card Sound.

I ! BISCAYNE Bay, Card Sound~ Little Card Sound~ Barnes Sound and Man­ atee Bay, referred to here as the Biscayne Bay SystelTI, lie at the southeastern tip of the Florida Peninsula (Fig. I). The combined surface area of the bays between 25° 55.7'(North Miami Beach) and 25° J 1.7'N (Jewfish Creek) is 2 approximately 703 km • A series of banks and causeways defines the indi­ vidual basins, and these topographic features may have a significant effect on the exchange of water between basins. Within Biscayne Bay, Featherbed Bank separates a slightly larger northern basin frOITI a smaller southern basin. Cutter Bank separates Biscayne Bay from Card Sound., and Card Bank sep­ arates Card Sound from Little Card Sound. A causeway, broken by the , separates Little Card Sound from Barnes Sound. Wa­ ter depth is highly variable. Channels in northern Biscayne Bay are dredged to depths of lOin to accommodate cruise ships, while large parts of southern Biscayne Bay, Card Sound., Little Card Sound., Barnes Sound and Manatee

1 [email protected]

224 No. 32001] SMITH-TIDES IN SOUTH FLORIDA COASTAL BAYS 225

Safdy Valve

o' o' ./t B:iB,5caync°,t" • " a~ Caesar Creek Card S~L1nd~ ~Broad Cree', Littll2 Card Sound""Y' Angelfish Creek Barnl25 Sound[' . lVIanal"l2 Bax~

Jewlish Creek

FIG.!. Maps showing (left) locations of Biscayne Bay, Card Sound, Little Card Sound, Barnes Sound and Manatee Bay; and (right) locations of water level recorders used for calcu­ lating co-amplitude and co-phase charts, and for calculations of bay volume. Closed circles show locations of water level recorders. Open circles west of the Safety Valve and in southern Biscayne Bay show locations of acoustic Doppler profilers. The solid square on the western shore of southern Biscayne Bay indicates the location of the weather station. Insert shows the study area at the southern end of the Florida Peninsula.

Bay are less than I m deep. The Intracoastal Waterway, running north-south through the bays, is dredged to a depth of 2.1 m. Growing population pressures and a concern for water quality have prompted a series of studies over the past three decades to characterize flow patterns and especially flushing rates in the Biscayne Bay System (Lee and Rooth, 1973; 1976). Studies have emphasized computer modeling for the most part (Miller, 1984; Wang and van de Kreeke, 1986; Wang et aI., 1999), and the observational data base needed to characterize tidal conditions is restricted largely to that needed for model validation (see Taylor, 1971; Swa­ kon and Wang. 1977; Wang and van de Kreeke, 1986). For the most part, tidal ranges are presented without regard to individual constituents, and phase angles are referenced to a primary coastal station. Extensive field studies were conducted by the National Ocean Service (NOS) in the early 1970s. Numerous study sites were maintained along both 226 FLORIDA SCIENTIST [VOL. 64 the eastern and western shores of the Biscayne Bay System for tinle periods ranging from one 29-day synodic month to one year. Hannonic analysis of these water level records provided the hannonic constants needed for tidal predictions for the Miami Harbor entrance at Governlnent Cut, and for cor­ rections for other locations within Biscayne Bay and Card Sound. More recent fieJd studies have improved station density and contributed bottom pressure records from several locations in the interior of the bays. Data from a one-year study by the Army Corps of Engineers Waterways Experilnent Station (WES) and National Park Service (Pratt, 1999) are an important supplement to the earlier data collected from shore-based stations. The purpose of this paper is to combine results of earlier and more recent studies into a data base of harmonic constants suitable for describing tidal conditions within the Biscayne Bay System and tidal exchanges between the bays and adjacent inner shelf waters. Results of this study provide an im­ proved picture of tides in the Biscayne Bay System and a nl0re complete data base for vaJidating tidal transport and flushing models.

DATA COLLECTION-Harmonic constants (arnplitudes and local phase angles) calculated from historical NOS water level data are £Ivai lable rrOnl 23 locations throughout the Biscayne Bay Systeln (Lyles. 1999). Seventeen of the record~ are one synodic Inonth long. and six are one year long. Twenty of the 23 NOS record~ were obtained froln studies conducted between 1970 and 1975. Conlbining harmonic constants frorn earlier and Inore recent studies assunles that harmonic constants have not changed in the past JO years. In northern Biscayne Bay. however. amplitudes may have increased sornewhat as a result of dredging activitie~. The NOS water level records were collected with Stevens tide gauges which use a float and counterweight to follow the rise and fall of the water surface. Conlparisons of tide staff and chart values in studies using the same recording instrumentation (Slnith, 19X7) suggest that the accuracy of the hourly values is ::!:O.5 cnl. and the precision of the readings is 0.3 cln. The WES field study (Pratt, 1999) produced water level data froln 12 locations using YSII Endeco Model 6000 pressure recorders. Hourly bottorn pressure readings have an accuracy of ].8 cm. For the purpose of characterizing the rise and fall or the tide. the ability of a recorder to sense the height of the overlying water colulnn is of less ill1portance than its ability to resolve hour-by-hour changes in water level. The resolution of the pressure recorders provides water levels to within ::!:O.03 cnl. according to instrulnent specifications. The Model 6000 is not vented to the atmosphere. and it interprets changes in air pressure as changes in water depth. This is of significance in a tide study only insofar as surface air pressure changes associated with atmospheric tides can perturb the water pressure changes associated with oceanic tides. The WES field study included a weather station on the western side of Biscayne Bay (Fig. ]). Air pressure was recorded hourly to the nearest nlillimeter of nlercury for a 355-day period fronl July 18, 1997 to July 7. 1998. Water level records were available also fronl a South Florida Water Management District study at Thursday Point on the southeast shore of Barnes Sound. and frorn Harbor Branch studies in Jewfish Creek and in shelf waters northeast of the nl0uth of Caesar Creek. Using data from al I sources. harmonic constant~ are avai lable frolll 3X locations for constructing co­ ampl itude and co-phase charts and from 33 locations for calculating intertidal volunles. The WES field study included acoustic Doppler profilcr (ADP) data fronl (lve locations. two of which (shown by the open circles in the right-hand rnap of Fig. I) were well positioned for characterizing tidal transport along the axis of Biscayne Bay. The ADP recorded currents in 4-10 layers, depending on tnean water depth and tidal and nontidal changes in water level. The speed and direction accuracy of the ADP are :!: I C'j{' of the indicated speed and :±:: 1°. re- No.3 20011 SMITH-TIDES IN SOUTH FLORIDA COASTAL BAYS 227 spectivcly (SIOCUlll, 1(99). Bottoln pressures recorded by the ADP indicated water levels to the nearest 10 Clll, and they were used for calculating surface-to-botton} transport but not for quantifying tidal hannonic constants.

METHODs-Water level records frolll the WES field study that were longer than 180 days were analyzed with a NOS least squares harmonic analysis conlputer progranl. "LSQHA." to quantify the harl110nic constants of the principal tidal constituents (Schurelnan. 1958). The saine progranl was used by the NOS to analyze the one-year records collected in their field studies. Excluding the long-period tidal constituenl~. only five constituents were found to have ampli­ tudes greater than I Cl11 throughout nl0st of the Biscayne Bay Systenl. The M 2• S2' N 2• K 1 and 0, constituents eillerged as those having a significant ilnpact on hay-shelf exchange calculations. LSQHA was u~ed also to quantify surface air pressure variations associated with atlno­ ,-;pheric tides. Results indicated that only the S~ atrnospheric tide is large enough to influence significantly the S~ ocean tidal constituent calculated froll1 bottOll1 pressure records. The S~ atrnospheric tide has an alnplitude of 0.72 111111 of 111ercury and a phase angle of 293°. This is

I X tirnes larger than the an1plitude of the 0 1 atlllospheric tide, the next largest. A pressure change of 0.72 l11rn of Inercury is interpreted hy the pressure recorder as a water level change of 0.96 C111. Hanllonic constants calculated froln the 12 WES bottonl pressure records were corrected hy vector-suhtracting the S2 atll10spheric tide frorn the S ~ oceanic tide. The result is a closer approxinlation of the aillplitudc and phase angle that would have been obtaincd from a float-and-counterweight tide gauge. By adjusting harlllonic constants through vector-subtrac­ tion, results of the LSQHA analyis of the air pressure record can be used to correct bottom pressure records collected fronl any nearby study site and for any tilne period. The importance of the correction varies inversely with the ~lInplitude of the ocean tide. In Barnes Sound, where the cffect wa~ largest. the correction increased S.: all1plitudes by about I cm, and phase angles were advanced by ahout J(f. The NOS analyzed synodic 1l10nth water level records using their 29-day harmonic analysis c(lInputer progranl, "CURAN:' CURAN analyzes five tidal constituents directly, the san1e five that ell1erged as principal tidal constituents in the Biscayne Bay Systcln. To quantify the un­ certainty in the hannonic con~tants obtained frolll a single 29-day hannonic analysis. the much longer WES tin1e series were hroken into 29-day seglnents and used for multiple CURAN analyses. For each of the live principal constituents. hannonic constants from multiple CURAN analyses were vector-averaged. and the root-nlean-squared (RMS) deviation froln the vector average was calculated for both alnplitudes and phase angles. Results suggest that the RMS deviation of CURAN alnplitudes, RMSt\. and phase angles. RMS p • as a function of the LSQHA anlplitude. AI' decrease approxilnately exponentially according to

RMSI\ = 0.4276 Exp( -0.00347AI)' and (1)

RMSI' = 10.32 Exp(-O.OXJ 14A[). (2) Thus, for exall1ple. when an LSQHA alnplitude calculated froln a one-year tinle series is on the order of 1-2 C111, the RMS deviation or a CURAN <1lnpJitude calculated from a 29-day subset of the longer record will he approxinlately 0.5 Cln. Silnilarly, the RMS deviation of the CURAN phase angle will be approxilllatcly 10°. Larger ~unplitude constituents are affected less. For the M.: tilial constituent. with arnplitllde~ near :30 Cln in northern Biscayne Bay, the CURAN amplitudes and phase angles should be within ±0.4 em and:!: 1°. Harlllonic constant~ froln all JX locations were used to construct co-anlplitude and co­ phase charts of the principal tidal constituents. Isoplcths of anlplitudes and phase angles in ~ollthern Biscayne Bay. Card Sound and Barnes Sound arc the combined response to tidal wave~ entering directly horn shelf waters and waves Inoving slowly southward into Barnes Sound. For the sen1idiurnal M.:. S] and N) constituents. co-phase charts were contoured at intervals of .10°, hecause a 30° phase difference represents an approximately one-hour difference chart~ in the tilne of high or low water. Co-phase for the diurnal K 1 and 0 1 constituents were contoured at 15° intervals for the san1e reason. 228 FLORIDA SCIENTIST [VOL. 64

Thirty-three of the 3X study sites were within the Biscayne Bay System. The surface areas 2 they represent varied fronl I.X to 54.7 k111 . The tidal rise and fall in water leveL 11. at a station rcpresenting scglnent In. was estitnated by sunlming the contributions of each of the five prin­ cipal tidal constituents

::; 11m = L. 1111\,1" (3) I I

The volulne of water in segn1cnt n1. VIII' relative to the tidal datum is obtained from the product of the predicted water level and the surface area of the seglnent, Sm' This assunles that the surface area of the segnlent does not vary with changes in water level. These products are then Slll1Ulled to obtain the hour-by-hour variation of the volume of the bay systenl relative to the datUl11.

n V I -= L. 'YJIllSlll' (4) III I

The intertidal volulne associated with the flood or ebb phase of the tidal cycle is calculated fr0l11 successive tnaXilnurll and nlininlunl bay volutnes. ADP data included east-west (u) and north-south (v) components of the current at each level. The local surface-tn-bottonl transport was calculated from

11 n T,~ w = L 1l,Llz, TN S = L vlLlz, (5) I I I I where n is the titne-varying nU111ber of layers in the profile. Tidal transport was isolated by using predicted tidal currents and a nunlbcr of layers based on predicted water levels. Quarter­ hourly transport wa~ accurnulatcd in tilllC. and the resultant transport vector was used to quantify the 11lagnitude and direction of the tide-induced residual flow.

RESULTs-eo-amplitude and cO-jJhase charts-Amplitudes of the M 2 constituent are approximately 30 cm in coastal waters (Fig. 2)~ and ampli­ tudes at the northern end of Biscayne Bay are similar to those found over the shelf. Amplitudes decrease only slightly in southern Biscayne Bay. The most rapid decrease occurs between southern Biscayne Bay and Card Sound. An additional decrease of 5 cm occurs between Little Card Sound and Barnes Sound.

The M 2 co-phase chart indicates phase lags of less than 30° throughout the northern half of Biscayne Bay. The 260 and 290° phase angles indicate that M 2 high and low tides in Biscayne Bay occur about an hour later south of Featherbed Bank than in the northern part of the bay. Within southern

Biscayne Bay, M 2 waves moving southward from the Safety Valve interact with M 2 waves entering through Caesar Creek. Phase angles indicate that

M 2 high and low tides in Barnes Sound occur approximately three hours later than in southern Biscayne Bay.

The co-amplitude chart for the N 2 constituent (Fig. 3) shows that am­ plitudes are on the order of 7-8 cln in shelf waters, and they are only slightly less throughout northern Biscayne Bay. Significant damping occurs within and south of Card Sound as a result of the shallow banks and causeway constrictions. Stnallest amplitudes are on the order of 1 em in Barnes Sound. pattern~ The N 2 co-phase chart reveals a complex but most of the complexity No. 32001] SMITH-TIDES IN SOUTH FLORIDA COASTAL BAYS 229

FIG. 2. (Left) Co-amplitude and (right) co-phase charts for the M 2 tidal constituent. Am­ plitudes are in em; local phase angles are in degrees. is restricted to the southern part of the study area. North of central Biscayne Bay, all phase angles are between 210 and 240°, indicating that high or low tide conditions are reached within a one-hour period of time. In southern Biscayne Bay, co-phase lines represent the local influence of N2 waves mov­ ing in through Caesar Creek and perhaps Broad Creek. Phase angles increase by approximately 60° through Card Sound and Barnes Sound, indicating that high or low tides are delayed by an additional two hours relative to southern Biscayne Bay. S2 tidal amplitudes are somewhat smaller than N2 amplitudes in northern Biscayne Bay, but amplitudes are similar in Card Sound and Barnes Sound (Fig. 4). In northern Biscayne Bay, phase angles at aU study sites are within 30° of 270°, indicating a nearly in-phase relationship for the rise and fall of the tide. The local influence of direct exchanges with the inner shelf through Caesar Creek and Broad Creek appears in southern Biscayne Bay. Phase 230 PLORIDA SCIENTIST IVOL.64

~ j I I I I

270,

>'360 .~~;~·'Y.-<'J

FIG. 3. Sanle as Fig. 2, except for the N:, constituent. angles increase southward by as much as 60°, indicating an approximately two-hour delay in times of high and low water at the southern end of the study area. Diurnal tidal constituents produce simple co-arnplitude charts, but co­ phase charts are more complex than those representing selnidiurnal tidal constituents. The small number of isopleths on the co-amplitude charts is due to the fact that diurnal constituents have low amplitudes, even in shelf waters. Amplitudes in northern Biscayne Bay are just over 3 cm for both the K 1 (Fig. 5) and 0, (Fig. 6) constituents. Amplitudes decrease by only about ] em through Card Sound and Barnes Sound. The cOlllplexity in the co-phase charts is largely restricted to the southern part of the study area, where waves moving southward through Biscayne Bay interact with waves entering through Caesar Creek, Broad Creek and Angelfish Creek. Diurnal constituent phase angles are similar throughout northern Biscayne Bay. In No. 32001] SMITH-TIDES IN SOUTH FLORIDA COASTAL BAYS 231

FIG. 4. Same as Fig. 2, except for the S2 constituent. the southern part of the bay differences of approximately 60° are equivalent to a time delay of about four hours.

Intertidal volumes-Harmonic constants for the five principal tidal con­ stituents and from the 33 study sites within the Biscayne Bay System were used to make calculations of the hour-by-hour rise and fall in water level, and thus the tidal increase and decrease in volume. Histograms constructed from the 705 semidiurnal flood and ebb tide cycles that occurred during a one-year tidal prediction are approximately mirror images of each other (Fig. 7). The ebb tide histogram has a slightly higher peak, with the 275-300 x 106 m3 bin accounting for 19.6% of the observations. The same bin in the flood tide histogram contains 18.7% of the observations. Both histograms are skewed slightly toward higher intertidal volumes. Flood and ebb tide volumes range between 164 and 394 X 106 m 3. Eighty-five percent of the flood intertidal volumes and 87% of the ebb intertidal volumes are between 232 FLORJDA SCIENTIST [VOL. 64

,, , , ,, ,'/ .~ , \3-."';:' "'~J ...t·

"····2 .... \@7 ,~W

FIG. 5. Same as Fig. 2, except fat the K, constituent.

200 and 350 X 106 mJ . The spread of the histograms is a result of the interaction of individual tidal constituents (Table I). As constituents cycle in and out of phase, they are alternately additive and subtractive, producing diurnal inequalities, and both fortnightly and monthly cycles.

Residual tidal transport-Acoustic Doppler profiler data are available from a study site in central Biscayne Bay, just west of the Safety Valve, and a second study site in southern Biscayne Bay. Combining the tidal rise and fall of water level with the ebb and flood of the current, one can quantify the local vertically-integrated residual transport. Results (not shown) indicate a south-southwestward transport at both locations. The tide-induced transport through central Biscayne Bay has a magnitude of 8.3 X 10-3 m2 S-I along a heading of 208°, and the transport past the station in southern Biscayne Bay has a magnitude of 7.8 X 10-3 m 2 s- [ with a heading of 207°. Results from both locations are consistent with the paradigm of a net inflow through No.3 2001] SMITH-TIDES IN SOUTH FLORIDA COASTAL BAYS 233

FIG. 6. Same as Fig. 2, except for the 0, constituent. the Safety Valve and a net outflow through the tidal channels In southern Biscayne Bay and Card Sound.

DISCUSSION-With the integration of harmonic constants from historical and recent water level records, the Biscayne Bay System can be character­ ized as microtidal, with amplitudes well below 1 m everywhere, and just a few centimeters in the more isolated, sOllthern part of the study area. Co­ amplitude charts show that the M2 constituent is dominant, with amplitudes about five times greater than those of the N2 and S2 constituents throughout the study area. Amplitudes of the M2 constituent are ten times those of the

K[ and 0 1 constituents in Northern Biscayne Bay, but only 3-5 times as large in Barnes Sound. Co-phase charts indicate a nearly simultaneous rise and fall in water level in the northern part of the Biscayne Bay System, but significant phase differences in the southern part. This is especially true where tidal waves cross shallow banks, or where waves moving southward 234 FLORIDA SCrENTIST [VOL. 64

20 -

~ Ebb - Flood ~

15 ~ I- - ~

~ c f- Q) ~ 10 ~ Q) 0... f-

f-

5 ~

~ I- - ~ n I o I I I -400 -300 -200 -100 o 100 200 300 400 Intertidal Volumes, in 106 m3

FIG. 7. Histograms of ebb tide (left) and flood tide (right) intertidal volumes. in 106 m" computed from a one-year simulation using the M 2• S2. N2, K 1 and 0, tidal constituents. Bin size is 25 x 106 m'. out of Biscayne Bay interact with tidal waves entering through Caesar Creek, Broad Creek and Angelfish Creek. The semidiurnal variation in bay volume varies considerably as tidal constituents cycle in and out of phase. The interaction of the M 2 and S2 constituents alone produces spring tide bay intertidal volumes of 316 X 106 m3 and neap tide intertidal volumes of 238 X 106 m3 every 14.8 days. The interaction of the M 2 and N2 constituents result in bay volume changes of between 222 and 332 X 106 m3 every 27.55-day anomalistic month. The

TABLE l. Harmonic constants of the principal tidal constituents of the total volume of Biscayne Bay. Card Sound. Little Card Sound, Barnes Sound and Manatee Bay. Amplitudes, 3 Amp. in 10" m ; local phase angles. Pha. in degrees.

Amp Pha a. Semidiurnal Constituents

M2 134.0 271.7 S2 19.3 308.2 N2 26.2 252.7 b. Diurnal Constituents K, 17.2 211.4 0, 13.6 231.0 No.3 2001] SMITH-TIDES IN SOUTH FLORIDA COASTAL RA YS 235

combined effect of the M 2 , S2 and N2 constituents result in significant dif­ ferences in successive spring and neap tides. Every second spring tide is reinforced, and every second neap tide is ditninished. As a result spring tide intertidal volumes can be as large as 368 X 10(l m 3 and neap tide intertidal volumes can be as small as 186 X 106 m-'. The addition of diurnal constituents produces an even greater range in spring-neap extremes. Cal­ culations using all five of the principal constituents indicate that neap tide intertidal volumes can be as small as 164 X 10(1 In \ while spring tides can 6 J be as large as 394 X 10 In . Co-an1plitude and especially co-phase charts contain a degree of uncer­ tainty when single 29-day water level records are used in Inicrotidal envi­ ronnlents. In the Biscayne Bay Systenl study, 17 records were one synodic Inonth long. rrhe ilnpact on the M2 co-phase chart wilJ be minimal because all M 2 amplitudes are 5 cln or greater. But in the southern part of the study area the other four tidal constituents have amplitudes of 1-2 em. In Card Sound, Little Card Sound, Barnes Sound and Manatee Bay, even a deviation of ±O.5 em can significantly change the position of an isopleth of amplitude. For the co-phase charts, the effect will be especially pronounced for the diurnal constituents. A 10° change in phase is a significant fraction of the 15° spacing of the isopleths. Although the RMS deviations can alter the co-phase and co-amplitude charts significantly, uncertainty arising from single 29-day analyses has little effect on intertidal volume calculations. Most of the hour-by-hour change occurs fronl the rise and fall of the tide in the northern part of the bay systeln, where anlplitudes are largest and RMS deviations are least. To quan­ tify the effect of using results frorn single 29-day time series, bay volumes were recalculated, raising and then lowering amplitudes and phase angles by RMS values obtained from Equations (I) and (2). Adjustlnents were nlade only at the J 7 stations for which harmonic constants were obtained from single 29-day harmonic analyses, and all amplitudes and phase angles were raised or lowered by the RMS value appropriate for the tidal constit­ uent in question. Bay-shelf exchanges were largest when amplitudes were increased and phase angles were decreased, however the increase was only 0.35%. Exchanges were reduced by 0.4% when amplitudes were decreased and phase angles were increased. The picture that elnerges froIn this study is one of tidal waves entering the Biscayne Bay System primarily through the Safety Valve, but interacting with tidal waves entering through the three channels in southern Biscayne Bay and Card Sound to produce loca) perturbations in amplitude and phase angle. Spring tide intertidal volumes can be 2.4 tilnes greater than neap tide values as the principal tidal constituents cycle in and out of phase. The 33 study sites within the 703 kn1 2 area of the Biscayne Bay System provide good spatial resolution for constructing co-amplitude and co-phase charts and especially for quantifying bay-shelf exchanges. Harmonic constants used in this study must be treated as at least slightly variable, however, and thus 236 PLORIDA SCIENTIST rVOL.64 the co-alnplitude and co-phase charts are subject to change as additional infonnation beconles available.

ACKNOWLEDGMENTS-My thanks to Steve Lyles for providing the harnlonic constants from the early NC)S studies. Thank~ also to Patrick Pitts, who put a considerable effort into editing and renloving tillling error~ in thc data fr0l11 the WES field study. Support for this work was provided hy the Arrny Corps of Engineers and the National Park Service through Cooperative Agreenlcnt No. 5250-9-9020. Harhor Branch Oceanographic Institution Contribution Number 139<).

LITERATURE CITED

LEE, T. N. /\Nn C. G. H. ROOTH. 1971. Water n10venlent~ in shallow coastal bays and estuaries. University of Mianli Sea Grant Coastal Zone Managen1cnt Bulletin No.3. --- 1976. Circulation and exchange processes in southeast Florida's coastal lagoons. Pp. 51-63 In: THORIlAUC" A. (cd.). Biscayne Bay: Past, Present and Future, Univ. of Miami Sea Grant Special Report. No.5. LYLES, S. 1<)99. National Ocean Service. Silver Spring, MD. Personal communication. MILLER. H. P 19R4. NUlnerical three-din1ensional free surface circulation model for the South Biscayne Bay. Florida. Appl. Math. Model. R:313-318. PRATI. T. 1999. Biscayne Bay Field Data. Technical Report CHL-Ol. U.S. Army Corps of Engineers. Waterway~ Experilnent Station. Vicksburg, MS. SCHlIREMAN. ~ 195X. Manual of harrnonic analyses and prediction of tides. Spec. Publication No. 98, rev. cd .. U.S. Govt. Printing Office. Washington. D.C., 317 pp. SLOCl:M. D. Sonlek Inc.. San Diego, CA. Personal cotnrnunication. SMITH. N. R 1987. An introduction to the tides of Florida's Indian Ri vel' lagoon. I. Water levels. Florida Scient. 50:49-6 I. SWAKON. JR., E. A. AND J. D. W ANCi. 1977. Modeling of tide and wind induced flow in South Biscayne Bay and Card Sound. Sea (,rant Tech. Bulletin No. 17. TA YLOR. III, R. B. 1971. Nutnerical rnodcling of tidal circulation of inlet systen1s as applied to the Broad Creek, Angel1ish Creek and Old Rhodes Channel cOTnplex in South Florida. Univ. or Miallli Tech. Rept. ML 71034, Miatni, FL. WANG,.I. D. AND J. VAN DE KREEKE. 19R6. Tidal circulation in North Biscayne Bay. J. Waterway. Port. Coastal Ocean Eng. 112:615-631. ---. .I. S. AULr, B. K. HAllS, J. Luo. AND J. RIVERA. 1999. Modeling the Southeast Florida coastal ecosysten1-hydrodynalnic transport, salinity and trophodynamics. Pp. 208- 210 Ill: Prograrn and Abstracts. 1999 Florida Ray and Adjacent Marine Systems Science Conference. , FL.

Florida Scient. 64(3): 224-236. 2001 Accepted: January 30. 2(0).