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NEARSHORE TIDAL AND
NONTIDAL CURRENTS,
VIRGINIA BEACH, VIRGINIA

by

W.Harrison, Morris L.Brehmer, and Richard B. Stone

TECHNICAL MEMORANDUM NO.5

April 1964

Material contained herein is public property and not subject to copyright. Reprint or re-publication of any
of this material shall give appropriate credit to U.S.Army Coastal Engineering Research Center

LIMITED FREE DISTRIBUTION OF THIS PUBLICATION WITHIN THE UNITED STATES IS MADE BY THE U.S.ARMY
COASTAL ENGINEERING RESEARCH CENTER, 5201 LITTLE FALLS ROAD, N. W., WASHINGTON D.C. 20016

FOREWORD

The importance of current patterns in coastal waters to submarine
sewage outfalls has been repeatedly emphasized in the literature as
has been, to a lesser degree, the importance of nearshore circulation
to problems of beach erosion and inlet stability. In either case,
precise information relative to the horizontal and vertical velocity
characteristics of the nearshore system is required at several points
in the area, Current measurements and precision estimates of mixing
and diffusion are needed not only at or near the surface but also
simultaneously at several depths.

This Technical Memorandum presents the results of measurements
made by the Virginia Institute of Marine Science and the U. S. Coast
and Geodetic Survey in the nearshore area off Virginia Beach, Virginia.
The data permit resolution of the general circulatory system, as well
as partial separation of tidal and non-tidal currents. Specific in-
formation on the characteristics of turbulent diffusion in one of the
tidal currents is also presented,

This report was prepared by Dr. Wyman Harrison, Associate Marine
Scientist, Virginia Institute of Marine Science, in pursuance of Con-
tract DA-49-055-CIV ENG-63-6 with the Beach Erosion Board and in
collaboration with Dr. M. L. Brehmer, Senior Marine Scientist, and
Mr. R. B. Stone, graduate student at the Institute. Funds for the
drift bottle and dye study portions of this study were provided by
the Hampton Roads Sanitation District Commission and the Virginia
Institute of Marine Science. Precision monitoring of the currents
using Roberts Radio Current Meters was conducted by the U. S. Coast
and Geodetic Survey in a cooperative study requested by the Virginia
Institute of Marine Science.

This report is published under authority of Public Law 166, 79th
Congress, approved July 31, 1945, as supplemented by Public Law 172,
88th Congress, approved 7 November 1963.

CONTENTS

ABS IDRA Clases

INTRODUCTION

RESULTS OF DRIFT BOTTLE RELEASES

RESULTS OF DETAILED SURVEY .

Tidal and nontidal currents
Longshore currents
Diffusion measurements
Clockwise eddy movement

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REFERENCES! 5

Figure
it

2

10

LIST OF FIGURES

Locality Map
Results of Drift Bottle Releases South of Cape Henry

Results of Drift Bottle Releases off Little Creek
Harbor

Tidal and Nontidal Currents Vectors at Three Stations
South of Cape Henry, July 30 - August 5, 1962

Wind Data, July 30-August 5, 1962

Wind, wave, and current data off Virginia Beach
July 31 - August 3, 1962

Dye and Drifter Observations, August 1-3, 1962

Dye Concentration Ratio versus Distance along
Plume Axis

Dye Concentration versus Distance Perpendicular to
Plume Axis

Inferred Mean Position and Extent of Nontidal
Drift System

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18

19

20

NEARSHORE TIDAL AND NONTIDAL CURRENTS, VIRGINIA BEACH, VIRGINIA
by

W. Harrison, Morris L. Brehmer, and Richard B. Stone
Virginia Institute of Marine Science
Gloucester Point, Virginia
and
School of Marine Science, College of William and Mary
Williamsburg, Virginia

ABSTRACT

Simultaneous measurements by Eulerian and Lagrangian
methods were made continuously between 30 July and 5 August
1962. The survey zone extended southward along the shore 11.5
km (7.2 mi.) from the Cape Henry Light and offshore for a
distance of 1.4 km (0.87 mi.). Three Roberts Radio Current
Meter Stations were established along the seaward margin of
the zone; five stations were established on shore for longshore-
current and wave measurements.

Wave heights for the 7-day period ranged between 0.3 and
O.5 m, wave lengths between 14 and 159 m, and wave energies
between 6.3 and 553 kg-m/m. Winds were less than 16 mph during
the period, total wind movements being greatest from the east
and southeast. Shoaling waves made angles with the shore line
that should have resulted in a southward longshore current
during 48 of 69 observations, on a coast uninfluenced by other
currents. Direction of longshore current movement was measured
as northerly, however, in 55 instances, owing to tidal and non-
tidal currents.

Current meter observations at Cape Henry and just south
of Rudee Inlet revealed semi-diurnal tidal currents that were
roughly reversing on the flood and rotary on the ebb, at the
surface. A meter midway between the Cape Henry and Rudee Inlet
meters indicated reversing currents at the surface, as did all
intermediate depth and near-bottom meters. When 280 returns of
neutrally-buoyed drift bottles, released over a year's period,
are integrated with detailed current-survey data, a circulation
model can be constructed. This model confirms earlier specula-
tion that the nontidal drift describes a clockwise eddy movement
south of Cape Henry. The southern limit appears to be near Rudee
Inlet.

Diffusion was investigated in one of the tidal currents
during ebb flow by continuous tagging with rhodamine-B dye
at the rate of 0.7 g/sec and by monitoring dye concentrations
with fluorimeters. A log-log plot of a "concentration ratio,”
c-M-!-D vs x, for values of x between 800 and 3800 m, fitted
an x-l relationship where c equals peak dye concentration, M
equals rate of dye discharge (g/sec), D equals layer depth (m)
and x equals distance along the axis of the plume. Neighbor
diffusivity, F (2) had a minimum value of 316 cm2/sec and the
coefficient e€ , in F (£) = 67/3 had the minimum value of 0.062.

INTRODUCTION

Circulation along the ocean flanks of the mouths of. large estuaries
has been studied little. Our attempts to understand the circulation in
the vicinity of the southern flank of the entrance to Chesapeake Bay
(Figure 1) have been prompted by the practical considerations involved
with locating submarine sewage outfall pipes and the recommendation of
beach protection measures along the shore line of Virginia Beach, Virginia
(Figure 1). The sum of previous work in the area known to us consists of
current observations from lightships by Haight (1942, Figure 15), of
measurements of the U. S. Coast and Geodetic Survey summarized in Special
Publication 162, of drift bottle surveys mentioned by Joseph et al. (1960)
and Norcross et al. (1962), and of casual observations reported in a beach
erosion study by the U. S. Army Corps of Engineers (U. S. Congress, 1953,
p. 15). In combination, these sources suggest that the offshore shelf
waters exhibit a dominantly southerly drift, but that the inshore waters
south of Cape Henry, to an unknown distance seaward of the shore, describe
a clockwise eddy movement extending “approximately 3 to 4 miles south of
Cape Henry" (U. S. Congress, 1953, p. 15). Our examination of the grosser
aspects of the circulation began with the drift bottle releases described
below.

RESULTS OF DRIFT BOTTLE RELEASES

A total of 898 drift bottles were released at the five stations
shown on Figure 2, during the months of April, May, June, July, August,
and October 1962. Results of the releases are summarized in Table 1
and Figure 2.

TABLE 1
RESULTS OF DRIFT BOTTLE RELEASES AT STATIONS OF FIGURE 2

TIDAL CONDITIONS AT RELEASE

Slack Both Slack Slack
Before Ebb Before Before
and Flood Ebb Flood
Number bottles released 898 450 448
Percent recovered 38.9 - -
Percent recovered in 10 days 24.6 16.4 Se
Average time out (days) 552 4.6 6.4
Averxge distance traveled (km) 34.5 34.0 36.0
(Naut. mi. ) 18.6 SES 19.4
Release months May, June, October,
July, April
August

The general picture is one of southward-moving water that has moved out

of Chesapeake Bay impinging upon the shore line to the south of Cape Henry.
That the outflow should take such a course in the northern hemisphere is
predicted by theory (cf. Defant,1961, Figure 25la). Because of a pre-
vailing southward movement of shelf water beyond the bay mouth (Norcross
et. al., 1962), however, the magnitude of the right hand deflection in the
direction of movement is increased. Additional drift bottle returns from
a release point off Little Creek Inlet (Figure 3) on Chesapeake Bay may

be cited here. Of interest are the seeming "depositories" of drift bottles
south of Cape Henry indicating, among other things, the considerable in-
fluence of southward moving shelf waters beyond the bay entrance.

RESULTS OF DETAILED SURVEY

Tidal and Nontidal Currents. At the request of the Virginia Institute
of Marine Science, the U. S. Coast and Geodetic Survey established three
Roberts Radio Current Meter Stations at the points shown on Figure 4. Data
were gathered continuously from eight meters at the three stations, for
between 9 and 13 tidal cycles, during the period July 30 - August 5, 1962.
These data were reduced by personnel of both organizations, according to
the methods described in U. S. Coast and Geodetic Survey Special Publica-
itlon\e2 son

Winds (Figure 5) and waves (Figure 6) during the 6-day period were
subdued. Although runoff in the Chesapeake Bay drainage basin was below
average for that time of year (F. J. Flynn, 1963, written communication)

and the tide ranges were slightly below average, we believe the observed
current vectors of Figure 4 to be a reasonable representation of the
expectable tidal and nontidal currents in the area. Wind data were
obtained from the hourly records of the U. S. Weather Bureau Station
(Figures 6 and 7) at Cape Henry. Wave heights, periods, and approach
angles were obtained at 4-hour intervals at the end of the 15th Street
fishing pier (the station on Figure 6 just north of the inlet). Heights
were estimated by an observer, in water depths estimated at 3.0 m (or
about 10 feet).

Surface currents appear to be roughly reversing on the flood and
rotary on the ebb at the northern and southern Roberts Meter stations,
while they are reversing at the middle station (Figure 4). Mid-depth and
bottom currents are generally reversing (Figure 4) for both flood and ebb
currents.

Current drogues consisting of weighted plywood crosses attached to
buoyed and flagged spars were released at slack before ebb and traced on
31 July and 1 August (Figure 6). Accurate positioning was accomplished
by means of transit fixes from three shore stations in radio communication
with each other. Drogue movements at the three depths indicated on Figure
6 corresponded well with current tendencies indicated by the Cape Henry
Roberts Meters when the drogues were in their immediate vicinity. A
clockwise, ellipsoidal movement of the drogue at 6.1 m on 31 July (Figure
6) is of interest. The excursion of this drogue over the ebb tidal flow
approximates that predicted by theory (Haight, 1942, p. 7).

A number of plastic, umbrella-shaped, very slightly negatively-buoyant
bottom drifters (Woodhead-Bumpus Sea Bed Drifters) were released at slack
water before ebb on 31 July at the point shown on Figure 7 (Release Point).
Recovery of 80 percent of the drifters was made a few hours later at 21st
Street (Figure 7) some 5 km south of the release point. Four bottom
drifters also were released on 1 August at 0800 (Figure 7) at a time
indicated in tide tables as that of slack water before flood. A flood
current never developed and one of the drifters was recovered the next
day (Figure 7) some 3.7 km (2 mi.) south of its release point.

Longshore Currents. Detailed studies of the velocities and
directions of these currents were made at five stations (Figure 6) on
four successive days, in conjunction with the Roberts meter observations.
The timed movement of fluorescein dye patches within the breaker zone was
used to measure longshore current drift. Measurements were hampered at
times by the narrowness of the breaker zone, low breaker heights (Hp, Fig.
and the consequently weak current flow. Dye patches at times spread un-
avoidably into the water just seaward of the breaker zone. Water movement
thus traced was possibly the movement induced by winds or by the prevailing

6),

tidal or nontidal currents. At any rate, it was observed that although
shoaling waves made angles with the shore line that should have resulted
in a southward longshore current during 48 of 69 total observations, the
direction of longshore flow was measured as northerly in 55 instances.

The effect just mentioned seemed to be most readily exhibited when waves
of low energy, with fronts nearly parallel to the shore (Figure 6, 3
August) were common. Longshore current velocities ranged from nearly
zero to 0.3 m/sec (0.6 kn). Rip currents (Figure 6, 2 August, 1200 hours)
were rarely observed. ‘

Diffusion Measurements. Studies of turbulent diffusion in estuarine
and inshore waters have given recent impetus to the development of a
Superior technique for tagging water masses and detecting the decrease in
concentration of the tag through time. Independent research by scientists
of the Japanese Governmental Agencies (1958) and the Chesapeake Bay In-
stitute (Pritchard and Carpenter, 1960) led to the selection of rhodamine-
B dye, an organic pigment, as a tagging agent, and to the development of
fluorescence analysis as a detecting technique. The fluorescence spectrum
of rhodamine-B has a maximum at 575 millimicrons and use of a Turner Model
III fluorometer permits detection to 0.02 - 0.004 ppb. A review of the
technique and its limitations has been presented by Pritchard and Carpenter
(1960). Studies by the Virginia Institute of Marine Science have utilized
their experimental techniques.

Okubo (1962) has made a comprehensive analysis of the recent theoret-
ical treatments of diffusion in the sea and of the results of experimental
studies. He proposes a solution to the diffusion equations (1962, p. 56)
that involves an "energy dissipation" parameter having the dimensions
cm2/3/sec.

On August 1, 1962, between 0800 and 1400 hours, personnel of the
Virginia Institute of Marine Science and the U. S. Coast and Geodetic
Survey initiated, maintained, and monitored a continuous release of dye
from a point approximately 800 meters off Cape Henry (Figure 7). The rate
of release of rhodamine-B was 0.7 g/sec and the vehicle solution was
adjusted to the density and temperature of the surrounding water (1.01 g/cc
and 25°C, respectively). Release was from a point source at approximately
4 meters depth. In addition, a small number of surface and bottom drifters
were introduced at the point of dye release (Figure 7) to gain a crude
measure of neighbor diffusion, in the event that the dye study should fail
in some respect.

Tide tables had indicated that slack water before flood would occur
at 0800 hours on 1 August 1962. Thus, it was expected that the dye would
be carried into the bay on the flood current. The flood current did not
develop, however, and an ebb outflow began about 0900 hours. This led to
an unusually long southward flow. (This flow was induced by an unusually
heavy rainfall in the vicinity of Chesapeake Bay entrance on the previous
day.)

Wind, current, and wave data for portions of the release period are
shown in Figure 7, The average current velocity, Uv, integrated along the
axis of the dye plume, was 0.30 m/sec (0.54 kn) during the period of moni-
toring (1130 - 1230 hours) upon which the results below are based.

Neighbor diffusivity, F (2) was calculated from returns of drift
bottles. FE (4) had a minimum value of 316 cm2/sec and the coefficient e .
in F (2) = ef£ /3 had the minimum value 0.062. This last value was calcu-
lated using Stommel's (1949) expression,

Gein?) . (Gn = ie
Ree Nan Care| ene aL eee an OT Pano

for the reduction of the experimental observations, where £ is initial
neighbor separation (cm), £1; is separation after time T (sec), and the
bars denote averages. The minimum value of ¢ falls within the range of
values (0.006 - 0.08) that have been determined (cf. Pearson, 1956, Table
10; Harrison, 1963, Table 1) for other oceanic areas subject to tidal cur-
rents of variable strength. A calculation that allows for the turning of
the drifters as they enter the longshore current system shows that a maxi-
mum value for e€ would not exceed 0.075.

Additional diffusion values were calculated from measurement of dye
concentration along the axis of the steady state plume (Figure 7). A
log-log plot (Figure 8) of a "concentration ratio", c-M -.D versus x, for
values of x between 800 and 3800 meters, fits an xl relationship where c
equals peak dye concentration, M equals rate of dye discharge (g/sec), D
equals layer depth (meters) and x equals distance in meters along the axis
of the plume. Thus, there was a decrease in dye concentration downstream
from the discharge point proportional to the minus one power of the
distance.

Calculation of the so-called "diffusion velocity" yielded a value of
2x 1073 m/sec. This value was computed from a relationship proposed by
Schonfeld (1959) and expressed by Okubo (1962) as:

m/U w x/U
ur GYfty? © ye

where S (x,y) equals the mean concentration at some point (x,y) in the
plume, x being in the direction along the axis of the plume and y the
direction perpendicular to the axis of the plume, m equals the number

of particles released per unit time, U equals the mean flow, and W equals
the "diffusion velocity". When solving for w, S (x) is expressed as the
concentration ratio (mentioned above), in order to correct for depth-
dependent variations in dye concentration along the axis of the plume,
The approximate value for diffusion velocity(2 x 10-3m/sec) found in this

study has been found also by Pritchard and Carpenter (1960) in some of
their experiments with continuous dye releases in waters influenced by
currents. Figure 9 is a plot of dye concentration versus distance from
the plume axis, showing lateral distribution of dye concentration.

Clockwise Eddy Movement. The following quote is taken from the
Virginia Beach, Virginia, Erosion Control Study (U. S. Congress, 1953,
, LS)He

"A review of Special Publication No. 162, titled ‘Tides
and Currents in Chesapeake Bay and Tributaries’, prepared by
the United States Coast and Geodetic Survey, indicates that
the tidal flow through the Virginia Capes probably affects the
erosion forces at work on the shore at Cape Henry and vicinity.
The observations by that agency indicate that the tidal current
strikes northwest and southeast on flood and ebb tides, respec-
tively, when passing a line joining the two capes at the bay
entrance; that about 10 to 12 miles east of this point the
general trend of the current is due east; and that 18 to 20
miles east of the bay entrance the trend of the current is
toward the northeast. Coast and Geodetic Chart No. 1222 in-
dicates that the deeper water in the bay entrance lies close
in to the Cape Henry shore and follows a southeast course for
4 or 5 miles past the cape. It is, therefore, apparent that
the greater portion of the ebb flow through the Virginia capes,
particularly that confined to the deeper water, initially strikes
to the southeast, then recurves and eventually moves off to the
northeast, due probably to the influence of the northward move-
ment of the Gulf Stream and prevailing ocean currents. It is
believed that a minor part of the ebb flow, particularly that
moving over the shallow areas near the bay entrance, is diverted
to the south by the prevailing northward oceanic currents, with
a subsequent recurving clockwise movement. This clockwise eddy
movement apparently extends approximately 3 to 4 miles south of
Cape Henry and tends to partially explain the forces at work to
preserve the northern section of the beach, where some accretion
has been observed, as against the south end of the beach, where
advanced erosion has occurred,"

Confirmation of this inferred clockwise eddy movement is apparent
from (1) the nontidal current values (Figure 4) that indicate northerly
water movements at the central Roberts Meter Station and (2) those drift
bottle strandings from the Little Creek and Cape Henry release points
(Figures 2 and 3), that are for bottles that had been out long enough to
have come under the influence of the nontical drift. The inferred north-
eastwardly recurving movement of the Chesapeake Bay outflow, however, has
not been confirmed by other drift bottle studies in that area (Norcross
et.al., 1962, Figure 1), a prevailing southerly drift having been observed
whose velocity approximates 10 to 14 miles per day (Joseph et. al., 1960).

An apparent dividing zone for nearshore nontidal drift currents
moving to the north- induced by the outflow from Chesapeake Bay striking
roughly southeast (Figure 4)- and nontidal drift to the south induced by
the prevailing oceanic currents from the north, is found in the vicinity
of Rudee Inlet (Figure 4). This inference seems to explain the scarcity
of drift bottles recovered in the vicinity of Rudee Inlet (for bottles
out long enough to be influenced by the nontidal drift) and the longer
residence time in the sea of most of the bottles released near Rudee
Inlet (that were recovered from 2 to 10 days after their release).

Figure 10 shows the inferred average nontidal circulation as based
on these measurements. Although the center of the clockwise eddy is by
no means known, it is believed to be placed here (Figure 10) in its most
logical position. Additional measurements, perpendicular to shore, would
be of great value in this area. The presence of Rudee Inlet in the area
of diverging currents may be additional confirmation of the validity of
this circulation model (Figure 10), for currents transport sand across
mouths of inlets and close them. The sand deposits at Cape Henry that
are indicated by the bottom contour shown on the nontidal drift diagram
(Figure 4) similarly reflect the area of converging currents shown in our
model (Figure 10).

The dimensions, position of the center, and rates of water movement
in the eddy system will all vary as the pressure gradient undergoes
modifications by runoff variations and/or the frictional drag of winds
(especially from the north) and longshore and nearshore currents.

Tidal currents in the area are generally moderate to strong, maximum
velocities of 1.6 m/sec (3.0 kn) having been noted on the ebb and 0.87
‘m/sec (1.7 kn) on the flood, at the Cape Henry station. The characteristic
of the ebb tidal current to sweep surface water southward and toward the
shore between 3 and 9 hours after flood at nearly all three stations has
been observed (Figure 4). Bottom water, however, tends to move directly
onshore or northward and obliquely toward the shore between 8 hours after
flood and flood, and between flood and one hour after flood, in the central
portion of the area (Figure 4).

The detailed current data and inferred circulation model presented
here are being used for prediction studies of the inshore transportation
of sediment and the design and positioning of sewage outfall structures.
It is hoped that the techniques and findings presented will provide some
guidance to other workers planning similar investigations of nearshore
currents and circulation at the mouths of estuaries.

ACKNOWLEDGMENTS

Cooperation of the U. S. Coast and Geodetic Survey, especially
Commander Jones and the crew of the C. & G. S. S. MARMER, and members
of the Tides and Currents Branch, is gratefully acknowledged, Funding
of part of the study was provided by the Hampton Roads Sanitation
District Commission of Virginia. Preparation of illustrations was.
supported by the Beach Erosion Board, U. S. Army Corps of Engineers.

ILO),

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14.

REFERENCES

Defant, A., Physical Oceanography. Pergamon, New York, Vols. 1 and 2.

Coastal Currents along the Atlantic Coast of the United

Haight, F 5
CAS GASES DeCep aU be NOS OFNWiSis Den mLOAge

su Vo
Siaikelsein Ukr

Harrison, W., Diffusion in a Low-velocity, Inshore Tidal Current off
Virginia Beach, Virginia. Va. Inst. Mar. Sci. Spec. Sci. Rept. (mimeo),
Chipa aL ose

Japanese Governmental Agencies, Oceanographic Research on Waste
Disposal. Proc. 2d Intern. Conf. Peaceful Uses of Atomic Energy in
Caneves We LS, fo SSS, LYS.

Joseph, E. B., W. H. Massmann and J. J. Norcross, Investigations of
Inner Continental Shelf Waters off Lower Chesapeake Bay, Part I -
General Introduction and Hydrography. Chesapeake Sci., v. 1, pp.
15> —O3h) LOO;

Norcross, J. J., W. H. Massmann and E. B. Joseph, Data on Coastal
Curren\t'soriiChesapelaker Baym Viale insite Malcew tS Gill S De Chums Clay ReIpi
Gnaimecio) BNORESIEy aos per loge

Okubo, A., A Review of Theoretical Models of Turbulent Diffusion in
thes sea Chesapeake Bayurinsitey Lech Re piteusOLeElW Si oer OlOZe

Pearson, E. A., An Investigation of the Efficacy of Submarine Outfall
Disposal of Sewage and Sludge. Calif. State Water Pollution Control
Board eubA NOM ela e ws) bi peal SIOr

Pritchard, D. W., and J. H. Carpenter, Measurements of Turbulent
Diffusion in Estuarine and Inshore Waters. Bull. Intern. Assoc. Sci.
HyGiolt No cOn sp pe =a OOF

Stommel, H., Horizontal Diffusion Due to Oceanic Turbulence. J. Mar.
REISE AVE On DDEmlOO— 22 seo 4OR

Schonfeld, J. C., Diffusion by Homogenous Isotropic Turbulence.
Rept. FA-1959-1, Rijkswaterstaat, Netherlands, 1959.

Ho inte cae Dithiusinvatyi seu Glophyise eReSe si VinlOlen DD:
3187-3199, 1962.

U. S. Congress (83rd, 1st Session), Virginia Beach, Virginia, Beach
Erosion Control Study. House Doc. No. 186, U.S.G.P.0O., Washington,
Ds Coo MAIS [Ia bh) LOSS.

U. S. Department of Commerce, Coast and Geodetic Survey, Manual of
CunnentObsenvaititonsma Specs shubll 2 lop UN Ss GuPeOn an Washiineonym Daan Gee
87 je, L950.

Lai 76°
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Cape Henry

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FIGURE |. LOCATION MAP

RELEASES AT
SLACK WATER
BEFORE FLOOD

Chesapeake Bay

1% (8) -—®@
3% (9) ~—&

TRIVE

KEY
2 %(3)... Two percent of all bottles
recovered within 10 days after release,
from all release points, were recovered
in this area ofter being three days out

SYMBOL EXAMPLES:
0 Release point
® Recovery point
<—@ Recovery out of map area

SCALES:

i (eo) i 2 3.4 5
Cece = ]
Miles
10) 4 8
————S—S_S_Sa
Kilometers

Cape Henry

VIRGINIA

3% (7)
15% (2-9) f 17(7)
t | i
e2¢
A
3% (9) & © 1% (9)

BEACH

3% (2)

ATLANTIC

4

Sand Bridge

1% (10)

OCEAN

1% (2)

@\ 5% (7-10)
w\ 34 % (6-10)

FALSE

CAPE 4\ 4% (7-10)

VIRGINIA

FIGURE 2.

\ 1% (4)
18 % (2-9)

NORTH CAROLINA

RESULTS OF DRIFT BOTTLE RELEASES SOUTH OF CAPE HENRY

RELEASES AT
SLACK WATER
BEFORE EBB

2% (5)
1% (6-7) |

hod

11% (9-10)

a\ 3%(0-10)

11% (0-10)
7 % (O-10)

1% (1)

A\ 3% (4-9)

@\ 3% (1-8)

1% (8) &
7% (1-9) @

Gt
o \ 11% (8-10)
| 9% (7-9)
9% (4-9)

CHESAPEAKE BAY

mm 1%(3) @

i

3% (1-4)

Little Creek
Harbor 3% (1)
5 1% (1) @
VIRGINIA
BEACH ATLANTIC
TRIVE
Rudee Inlet
1% (1)
@\ 3% (1-9)
OCEAN

@\ 16% (1-9)

Total released: 75 (high slack water)
Total recovered: 43
Total recovered within 10 days: 40

Sand Bridge
KEY:
2 %(3)....Two percent of all bottles
recovered within 10 days after release
were recovered in this area after being

three days out. @\ 15% (3-10)

Q Release point
@ Recovery point
<— @ Recovery out of map area

SCALES:

Miles
0 4 8
anys sass
Kilometers

1% (7)

4

VIRGINIA
4 ate 8% (3-9)

“NORTH CAROLINA

FIGURE 3. RESULTS OF DRIFT BOTTLE RELEASES OFF LITTLE CREEK HARBOR

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15

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67"
13.3"

313° 1.29 KN
258° 90 KN

6.7' 118° 30 KN
13.3’ 138° .40 KN

Hy2.2'

12.5! 338° .89 KN
iN 19.0" 338° 65 KN

12.5! 193° .21 KN
if 19,0' 173° 32 KN

1300)

80% BOTTOM DRIFTER
RECOVERY — 21 ST,

VEL, 1,02 KN
AT (848

1619

6.7’ 078.63 KN
13.3) 103° 29 KN

0900

Hy=19"

6.7' 128° 35 KN
13.3' (08° .40 KN

Bakr)

5.0' 008° .90 KN
12.5) 348° 1.09 KN
19,0' 353° ,00 KN

oor

1300 5.0' 278° .04 KN

+ — 15.0! 088° .09 KN

t

Hp 2.1"

\

Hyz1.9

‘

6.7' 103° 3,00 KN
13,3' 103° 2.10 KN

1650

Hz.

‘

12.5! (73° ,
19.0' 198°

30 KN
29 KN

Hpz2.t Hye le" Hy=12
cALM CALM
(RAIN) (RAIN) H=.94 H=.92 0
T=7.3 SEC. T=7,8 SEC. 7.0 SEC
5.0' 206° 60 KN 5.0/ 118° 48 KN
Rudee Inlet { 12.5' 130° .57 KN 12.5’ 163° 29 KN
o
5.0' 328° .20 KN
12.5! 018° .20 KN i» -
Hye 9 19.0' 348° 39 KN Myeh.3 HL?! Hpel.7"
x x Vy x
31 JULY 31 JULY 31 JULY 1 AUG | AUG | AUG
0700-1000 1200-1420 1200-1230, 0700-1000 1200-1420 1600-1800
1630-2030
TIMES IN SLANTED LETTERS. Wind direction and J Roberts meter station and OROGUES:
6 KN velocity. average current bearing. 6 =o (Sm)
(Ba CSR Mas Roberts meters and current a —!5) (4.6m)
group readings 7 bearings! © —20' (6.1m)
LONGSHORE CURRENTS
i n F 5 average) current veloclty, Se
ep - 9 \ 0-.2 KN
NouticolIM jes Hp=l.5' Breaker height mM 2-.4 KN
' Oo 1 2 3 4 5 4-—.6KN
BESE a = H = Est. wave height in feet in 10° depth NW his
Kilometers

T= Period

6.7' 103° 92 KN
13.3' 108° 66 KN

12.5, 34

—36°55'-+-

Rudee Inlet

— 76° 00'

we

2 AUG
0700-1000

5.0° 028° .60 KN
19.0 338°.76 KN

2 KN]

6.7" 103° 2.17 KN

7 KN
~

Hp: 1.6

1300 5.0' 343° .49 KN
12,5' 348° .70 KN

19.0' 018° .51 KN

B°.BOKN

5.0 023° 30 KN
12.5) 343° 43 KN
19,0 293° 46 KN

2 AUG
1200-1420

(84 KN)

83’ 18° 1.52 KN

2
1600-1800

5.0 163° 1,07

12.5) 168° 80 KN

19.0' 153° 50

AUG

6.7" 093° 1,00 KN
13.3! 073° .41 KN

f 13.3 008° 60 kn

0900 5,0) 013° 55 KN
12.5! 348° .43 KN

4 19.0" 343° 40 kN

46 KN]

KN

KN

{

Hy: 1.6"

12.5! 353° 30 KN
19.0° 318° 26 KN

3 AUG
1200-1420

5,0' 008° .79 KN
12.5 353° .40 KN
19,0' 338° 23 KN

[a7 KN)

5.0°, 353° 42 KN
12.5' 348° .30 KN
19,0' 163° 14 KN

\

FIGURE 6.

WIND, WAVE AND CURRENT DATA OFF VIRGINIA BEACH
JULY 3] — AUGUST 3, 1962

@ RELEASE POINT, August |, 1962
Continuous dye release (0.7 g/sec))
Twelve drift bottles -
at O800 hrs (1=150 cm)
Four bottom drifters
at O800 hrs

FORT STORY

— 36°55’
Dye concentration
homogeneous,
surface to |O m
depth, 1140 hrs.

|< axis of dye plume

SEASHORE

\ °
One bottom 2
drifter recovery —.y
August 2
\

Recovery of \
STATE PARK 9 drift bottles,
1130 hrs, Aug. |.

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lek) (ABE V DEPTH CONTOURS

| KILOMETER

Two drift bottles
recovered, Aug. 2&3,
5.0 & 10.5 km to south.

FIGURE 7. DYE AND DRIFTER OBSERVATIONS-AUGUST I-3, 1962

x10
x (meters)

FIGURE 8. DYE CONCENTRATION RATIO VERSUS DISTANCE
ALONG PLUME AXIS

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FIGURE 10. INFERRED MEAN POSITION AND EXTENT OF
NO

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