FAU Institutional Repository http://purl.fcla.edu/fau/fauir This paper was submitted by the faculty of FAU’s Harbor Branch Oceanographic Institute. Notice: ©2001 Florida Academy of Sciences, Inc. http://www.floridaacademyofsciences.org/flsci.htm. This manuscript may be cited as: Smith, N. P. (2001). Tides of Biscayne Bay, 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 Intracoastal Waterway, 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.