54 MANUAL OF CURRENT OBSERVATIONS 
(2) The time midway between the ends of the horizontal chord which 
represents one-half the largest observed velocity. 
(3) The time of the largest observed velocity, or if the largest velocity 
was observed more than once the time midway between the first and 
last observations of that velocity. 
The three times are readily determined by the use of spacing dividers. The 
average of the three times is the time of current strength sought. 
143. The time selected for each current strength is indicated on the curve sheet 
by a check mark placed just above the flood loop or below the ebb loop of the velocity 
curve. The times thus marked should be scanned for validity by an experienced worker 
and any necessary adjustments made before tabulating. The intersection of the curve 
Form 451 
Rov. Sept., 1931 
DEPARTMENT OF COMMERCE 
U. S. COAST AND GEODETIC SURVEY 
CURRENTS: FLOOD, EBB, AND SLACK 
Lat,_52° 05,2'°N 
Savannah (0.5 Mi. N 42° W of City Hall Dome), Savannah Re, Gae Long. 81° 05.9'9 
Station: 
Acc. No. 1863 Party of E. Fe Hicks, Jr. Plotted on Chart No. 440 _ Siat'on No. 19 
Times referred to sea Tides at Tybee Light, Gae —— Time Meridians: (This Stat) an cn 
Velocities corrected for eee ance at Tybee Light, Ga. f = 6 80/6 .87 2 0.99 (Ref. Sta) 76° Wo 
DATE TIME OF— CURRENT INTERVALS STR.OF FLOOD] STR. OF EBB 
if 
“| Slack Sueagth Slack Strength | Slack Strength Slick Direct | Verse; Direct | Vetocis 
Baore F. | cl Floud | Eeloze E. | of Ebb LDefore F. | cf Ficod | Before E. hieg. Tue CICNY | Moog. True OCuy, 
—+— i— ——— 
h. h. i h. h. he h R o knots 5 | Knota 
May 7/228 ‘(8.0 (140)! (128) 
de9 Ze2| on= [1307 | 1665/1962 43 | 2.0 
Po lene 8 9e7]| 0.0 | 204 5.0! 89 141 | 2,0 
Average BeO ed! 1205 2 | 176 | 2094 142 | 2,0 
Depth lel | 3.2 6e2/1001 145 | 2.0 
1525 | 1828/2220 140 | 2.0° 
T feet 
: 2el| 4.3 | 7.0! --- 
rare Cae 
this station : 1.950 
i 
(MCH) 
computation of mean current hour 
Slack before flood 9241 + 3210 = 12.51 hours 
Strength of flood 21171 " 
Slack before ebb 2009 = 3010 + 12642 = 11.41 " 
Strength of ebb 6046 + 6621 = 11.67 ®* 
SEM o00000000000000R0000000000000 © ET) @ 
n 
Mean current houreescevcccccecor 11.82 
Velocity reduction 
Best known mean range of tide at reference statiOnecccccesccceccssecece 6030 foat 
Range for observational period at reference stationesscccccccsersecsee 5087 
Reduction factor for tidal currentecscccccccscccee f = 680/687 = 0.99 
Observed tidal current at this station = 4(1.43 + 1.97) = 1.70 knots 
Corrected tidal currentercccecssecccce * lelO X 0099 = 1.68 " 
Nontidal currentecseccocscccccccccccce = S(1eA5 — 1.97) = 0.27 ” 
Corrected flood currenteccesscorccecce 2 1e58 = 0e27 = 1.4lo * 
Corrected ebb currentecssccesccscccecce = 1063 + 0027 = 1.950 ® 
FIGURE 28.—Form 451, Flood, ebb, and slack referred to tides. 
