Vol. 6

DEPARTMENT OF THE ARMY
CORPS OF ENGINEERS

BULLETIN | °c:

‘ COL Li LEC TION

OF THE

WOODS HOLE

BEACH EROSION BOARD OCEANOGRAPHIC InSTITATION
JUL 16 195}
OFFICE, CHIEF OF ENGINEERS wooDs HOLE, MASS.

WASHINGTON, D.C.

VOL. 5 JULY 1, 1951 NO.3

TABLE OF CONTENTS

By-Passing Littoral Drift at a Harbour Entrance .....0¢.

Calculation of Diffracted Wave Height Behind a Semi

Infinite Jetty gQ°o00200008 e@ooo00en00o00009009000 007n0.908008090000000

Beach Erosion Studies ..ccovc. O9000000000 900000000000000

Beach Erosion Literature ..... s00000baD00000 FOSOOUaOODS
Wahine

wey

Page

al

NO.

Booster Pumping
Station

Future Alignment
Of Coast

Drag Line

REPAIR BASE

CUSTOMS PORT FREE PORT

a

Dredge Pipe
Swing Span

ANCHORAGE

FIXED
DREDGE

OPERATION OF THE FIXED DREDGE
AT SALINA CRUZ, MEXICO

FIGURE |

400 METERS

BY-PASSING LITTORAL DRIFT AT A HARBOUR ENTRANCE

FOREWORD

The problem of maintaining coastal harbors at locations
where the rate of littoral drift is large is encountered often.
Employment of fixed dredging plant to by—pass littoral
accumulations across the harbor entrance has been considered
at several localities in this country. Because of the large
cost of initial installation and the lack of assured design
eriteria, no major installation of the fixed type has been
attempted in the United States. In addition to the obvious
benefit to navigation which would be achiaved by intercepting
littoral mterial before it can reach and form shoals in
navigation channels, by—passing of the material to the dowm-
drift shore would prevent costly erosion problems which
sometimes result from interference with littoral processes,

A relatively small fixed dredge has been employed
intermittently with some success at South Lake Worth Inlet,
Florida. Application of the by—passing principal by employ-
ment of a conventional floating dredge has been successfully
accomplished at Santa Barbara, California, where the zone of
littoral accumulation is suitable for that method, and is
now a routine biennial operation.

The following article is abstracted from a pamphlet
titled "Draga Fija" (Fixed Dredge) published in November 1950
by "Junta Directiva de Puertos Libres Mexicanos" (Translation
by William H. Vesper of the Beach Erosion Board Staff). It
is understood that the Salina Cruz installation described
therein has not been in operation sufficiently long to es—
tablish conclusively its adequacy and economic value. An
early difficulty encountered, and the remedial means employed,
is described in the following extract from a letter 8 May
1951, received from the Secretaria de Marina Mexico:

"The fact that the arms of the dredge are not long
enough to open a channel in the beach that would permit the
free entrance of the sand to the dredges, the Office of
Mexican Free Ports has found it necessary to install a power
shovel to open this channel and bring the sand to the dredge.
The scoop is hung from a cable supported by two posts lo-
cated as shown on the attached plan. This scoop is moved
by a motor and capstan. Before the installation of the
scoop it was thought necessary to bring the sand to the dredge
by some means but it was not thought that the scoop would
necessarily be the solution to the problem.!

ka

*edpeip
ayy 07 KTQOeITp TetseqeW Zutaq 04 ueeD0 eyy 4twased [ [TM puno.za
-yoerq 64 UT pues JO pUNoW e844 Jo [eACWeY “piemees ZUTYOOT espeud % ° Std

nthe installation complete, it will begin operating
at full capacity during the present month."

: The Port of Salina Cruz.is completely artificial. It consists
of a repair and maintenance basin and an anchorage area separated
by two large wharves on which are-six doublé warehouses. Originally,
it was intended to build only one breakwater which would extend from
the lighthouse bluff along the entire length of the wharves so as to
protect them from the waves and wind from the south, thus furnishing
an anchorage whose entrance would be to the East. While the break-
water was under construction, it was observed that after stormy days.
with large waves from the south, sand filled the region between the.
partly constructed breakwater and the wharves, that is, the area
which will be the harbor. The engineers then discovered the enormous
importance of the transport of sand which was constantly being
brought from the west.

The direction of the breakwater was immediately changed and
turned more seaward and another had to be constructed to the east
so as to form the actual harbor. There was then an accretion of
sand from the lighthouse to the end of the breakwater. This large
area was Quickly filled with sand, covering depths of 15 fathoms.
When this area was filled, sand began to enter the harbor, It has
been necessary to maintain a dredge for more than forty years to
remove the sand that had been deposited and is still being deposited.
This work has cost the government more than 50,000,000 pesos, (at
the present rate of exchange, 8.65 Mexican pesos equal one U. S.
dollar), and the bay is still in the same danger, the channel shoals
constantly and there are large deposits of sand inside the harbor
making navigation of the channel from the harbor entrance to the
repair basin difficult.

In later years, dredging has been very intermittent. This has
been a great factor in the loss of prestige of the port of Salina
Cruz, large ships have not been able to call, thus paralyzing
commerce in this region. The fact that Salina Cruz and Puerto
Mexico are at the terminus of Tehuano Railroad make them strategic
points and a very important means of increasing the commerce with
the United States. The obstruction of the bay by sand carried
from the west, remained a great engineering problem.

This sand which is brought from the west is not carried by
littoral currents but by the dynamic action of the waves which strike
the coast at an acute angle for the entire year, in such a manner as
to carry the sand up on the shore and toward the east and then back
down on the inclined plane of the beach where it is caught by the
surf. This continual rtse and fall, always with a force toward the
east, causes the eternal voyage of the sand that moves along the
whole coast to the region of Chiapas, where the wave attack is

Fig. 3 Pumps of the main plant and their
connecting hoses to the suction
tubes.

parallel to the shore and the sand ceases its journey.

This continuous wave action would cause the sand to fill the
whole western area between the western breakwater and the lighthouse
point and on occasions it would fill the anchorage and close it
completely. This same wave action which causes the continuous
journey of the sand has formed bay-mouth bars in front of Juchitan,
isolating thsse lakes from the sea, there remains only a small exit,
maintained by the tidal cwrents and also by the rivers which flow
into the lakes.

In Salina Cruz Bay there is not a strong tidal current but only
a weak one that flows into the harbor and this cwrent has not been
able to maintain a channel. The sand which arrives from the west
would obstruct the harbor and completely block the entrance.

This problem was studied by the commissioners of Free Ports
and after much thought it was decided to build a firmstructure
near the end of the western breakwater on the side where sand ac-—
cumulates and to install powerful suction pumps to take up the
sand and pump it around the harbor along the wharves, to the other
side of the eastern breakwater where it would be deposited on the
shore. The sea will continue to force the sand toward the east
as it has done up to now.

Careful studies were made and capable contractors of the United
States were consulted and finally enough money was obtained from the
Mexican Government to complete the structure. It consists of three
large sections each one being twenty meters long and twelve meters
wide. These sections were placed on a line parallel with the break-
water near the end of a protective rubble mound. The sections with
walls one and a half meters thick and transversal partitions of the
same thickness were lowered into position, using their own weight
to force the sand out of the interior. This procedure was called
"Chinese Pit" and we believe that this is the first time an operation
of this nature has been attempted on such a large scale in either
Mexico or America. This operation was accomplished, and though
laborious, the sections were lowered in perfect alinement. The base
of these sections rest 15 meters below low tide.

On these sections, a room 60 meters long was built to house
the dredge equipment which included the pumps and their motors,
generators, electric motors, and pumps for refrigeration, vaccum,
etc., but care had to be taken to get duplicate machinery in order
to maintain a reliable operation at all times. The pumps pick up
the sand from the seaward side through six suction tubes which are
moved by special apparatus, up, down and to the sides like a fan.
The movement of the six tubes cover the entire area along the front
of the structure making a large pit 10 meters deep. Sand arriving
from the west continually falls into this pit. “This is a real sand
trap." The suction tubes are moved by cranes operated from a booth

Fig. 4 Winches which operate
the suction tubes.

in the main room. The motion of the tubes, up, down, and to the
sides is accomplished by three electric winches which are con-
trolled by an operator stationed at the central window between the
suction tubes. The sand is pumped out through a pipe that runs
between the dredge and the breakwater on a straight line to the
beginning of the wharves, where a sub-station has been constructed
with motors and pumps the same as in the main station. The pipe
runs along the wharves across the entrance to the repair area of
the harbor and discharges on the shore east of the eastern break-
water. A removable pipe section is used in crossing the entrance.
The sand is pumped a distance of 2,200 meters. When the traffic
of the port increases, it will be necessary to run the pipe on
land from the sub-station around and in back of the repair basin
thus eliminating necessity of uncoupling the pipe at the entrance
to the harbor.

The fact that this efficient dredge, which does the same work
as one afloat, has its machinery in a fixed edifice induced us to
nam it "Draga Fija". (Fixed Dredge).

The operation of this dredge is very simple and very cheap,
costing little more than 20 centavos a cubic meter to pump the
sand to the beach, as against a cost of two or three pesos a cubic
meter for boat dredging.

A dredge operator and an electrician with their helpers are
all that is needed for the operation of the dredge.

The dredge will not pump all of the required sand from the
bay but when this new equipment is functioning normally there will
be time to check its condition. Not less than 2 or 3 million
cubic meters of sand will have to be removed in order to put the
port in a reasonable condition.

Without the fixed dredge, the removal of the sand by floating
dredges would be an impossible operation, as has been shown by 40
years experience.

The fixed dredge conceived by us is progressing very well. It
furnishes a new method of resolving many of the obstacles encountered
in the control of littoral drift. If the expected success is obtained,
there will be international reprecussions for there are many ports in
the same condition, and the cause of Commerce and World production
will be benefited.

The dredge has cost about 10 million pesos of which 6 million was
used to purchase machinery. The machinery was purchased from the
Wert Conrad Company who specialize in the construction of dredges,
and was paid for in sugar. The civil engineering was done by the

*(punousyoeq UT JJnTQ ssnoyqyst, jo 4yooy ye Aq,ef) *uoTQonI4s
—u0d suUTINp UeeDO ely WoIs esperp eyy SuTQoeZoId JeTaseq pues ¢ - Sta

Fig. 6 Interior of the booster pumping
station showing the pumps, motors,
and intake and discharge pipes.
The top pipe is the by-pass.

*uotatsod uedo ut
eouei4uUe uUTseq Itedei eyy ssoroe edtd eyg sutéaseo ueds durms Sul *L ° STA

Obras Portuarias Company, South America, whose diligent and constant
struggle against the sea brought this work to a successful end.

THE MACHINERY OF THE DREDGE
The machinery of the dredge consists of the following:

1. 2 Superior Diesel engines, 450 h.p. American make
which operate the two dredge pumps.

2. 2 Chicago Pneumatic diesel engines with generators,
200 hep. These produce the energy to operate the
auxiliary motors and winches.

3. Strong pumps for water pressure, vacuum refrigeration,
lubrication, etc.

4e Bilge pumps.
5. Hlectrical distribution panel.

On the outside of the engine room there are six pipes which
connect to the suction tubes of the dredge. Each pump is coupled
to each of these pipes by a flexible hose. Water at high pressure
is injected separately into each of the suction tubes by the water
pressure pump to agitate the sand and facilitate its removal. The
suction tubes are on the seaward side of the dredge.

The base of these tubes are fastened to large brackets which
are securely attached to the wall of the structure. They can be
swung in a manner that will permit the pumping of sand from the area
along the front of the dredge and even from in between the tubes
themselves.

The vertical and lateral motion of the tubes are controlled by
cables which run in front of the operators booth and along the roof
of the main room. There are three winches for each tube or a total
of eighteen winches.

The movement of each suction tube is controlled electrically by
an operator stationed at a window between each pair of tubes.

From two discharge tubes of the dredge, a pipe line runs direct
to the sub-station located at the foot of the wharves, It then
continues along wharves cross the entrance to the repair basin and
terminates on the seaward bank of the eastern breakwater. At the
repair basin entrance there is a draw which can be opened for the
passage of ships.

11

12

General view of the pipe bridge in operating position.

Fig. 8

*pesperp eq 07 [eT Jequ Jo yUNoWe eYy4 eoNpar pue 4JTIp [e1099TT
qselie 04 JJNTQ ssnoy_qUstT ey. JO 4OOT 4e UOTZONAYGSUOD JepuN A49QeP

13

SUB-STATION

The sub-station (booster pumping plant) was built to aid the
dredge pumps in moving the dredge material. At the sub-station there
are two pumps each run by a 450 h.p. electric motor similar to those
on the dredge. Aliso at the sub-station there are duplicate pumps
for refrigeration, fuel, etc. The motors which operate this auxiliary
equipment are run by electricity supplied at the rate of 40 h.p. at
400 volts through a transmission line from the dredge. Three #00
copper Wires are used for the transmission line.

All of the pipe is 18 inch diameter steel and is run exposed 50
that it may be inspected at any time. In the beginning the practica-
bility of laying the pipe along the bay and crossing the repair
basin entrance by means of a siphon was considered. This however was
discarded in favor of the present method due to the possibility of
deteriation of the submerged pipe.

At the foot of the lighthouse bluff, west of the fixed dredge,
a jetty is being constructed at the least possible cost. With it,
it is hoped to impound the littoral drift from the west, forming
a bank of sand that will not have to be dredged, thus prolonging
the useful life of the Draga Fija.

Eventually the sand that collects at the end of the jetty will
be in a depth less than five or six meters. When this occurs,
the action of the surf will be capable of lifting the sand and
starting it on its eastward journey. This is the only sand that
the fixed dredge will have to pump.

It has been calculated that a jetty five or six hundred meters
long will impound sand for two hundred years. However, when a beach
is formed near the end of the jetty surf action will cause the sand
to be transported to the east. This is the limiting point of the
jetty's effectiveness.

As yet it is not known whether or not it would be more economical
to construct such a jetty or to pump sand that would be trapped by
it, nor is it known which method would be the more effective. The
answer to these questions can be resolved only through experience.
For the present the littoral drift will be allowed to go directly
to the dredge.

However, it would be well to consider the construction of this
jetty for though it might cost a little more to retain the sand
than to pump it, the jetty would prolong the life of the dredge.
In either case, whether by the joint.function of the jetty and the
dredge or by the operation of the dredge alone, sand will be pre-
vented from entering the Bay of Salina Cruz.

14

CALCULATION OF DIFFRACTED WAVE HEIGHT BEHIND A
SEMI INFINITE JETTY

by

C. Carry and E. Chapus
La Howille Blanche, Jan-Feb 1951

FOREWORD

Wave diffraction is the phenomenon in which water
waves are propagated into a sheltered region formed by a
breakwater, island, or similar barrier which interrupts
a portion of an otherwise continuous wave train. The
ability to predict wave diffraction obviously has
important application in the planning and design of harbor
works where wave action is involved.

A theory of the diffraction of water waves passing
a breakwater has been adapted from theories of physical
optics. Putnam and Arthur investigated the theory ex-—
perimentally for deep water waves approaching a break-
water with angles of incidence of 45°, 90°, and 135°,
measured at distances varying from 3.38 to 17.85 wave
lengths from the breakwater and compared results both
with the somewhat complicated rigorous theory and a
Simplified solution employing approximations (Trans—
actions, American Geophysical Union, Vol. 29, No. 4,
August 1948). The application of diffraction theory
to water waves passing through a breakwater gap, for
both deep and shallow water waves in uniform depth, has
been investigated experimentally by Blue and Johnson.
(Transactions, American Geophysical Union, Vol. 30,
No. 5, October 1949). Experiments reported in the follow-
ing translation supplement the work of Putnam and Arthur,
covering diffracted shallow water wave heights along the
breakwater itself in the sheltered region, for angles of
incidence corresponding to those tested by Putnam and
Arthur.

This article has a double objective: first, to translate into
curves or asymptotic formulae(1) results derived by the method
developed by Messrs. Putnam and Arthur for the calculation of the
diffracted wave height behind a semi-infinite jetty; second, to
report certain experiments which had as their objective the
verification of this theory.

15

It should be recalled that the theory consists in applying the
rigorous theory of diffraction of light, or of sound, behind a
semi-infinite screen to the diffraction of a water wave in constant
depth behind a semi-infinite jetty; if the application is limited to
the terms of the first order for this latter problem the equations
and the limiting conditions are in effect the same for the two cases.

The ratio of the amplitude of the diffracted wave at a polar
coordinate point (r, 9) to the amplitude of the incident wave is
given by the modulus of the following complex function:

— { 8% cos(a-e)
F (r,0) = f(u,)e L
ay See cos (8,46)

ae if (Beko

where

x !
ode 2, oe ~ip eS @

v

eh) = —\ [82 sin G — 6

AL IL 2

Up - —\[& sin +e
UE 2

Note that F(r,@) may also be written in the form

F(r,0) =0(7r, @)e’ 6M
whe re

e (r,@) is the modulus of the function F and determines the re-
lative height of the wave and

¢(r,0), the argument of the function F, determines the plan of
the wave distribution, or in other words, ¢(r,0) = const. is, in

(1) Putnam and Arthur: Diffraction of water waves by breakwaters.
Trans. Am. Geophy. Union, Aug 48). Note that this method of calcula-
tion was proposed previously by Mr. Iarras in the French publication
"Travaux" for June 1942.

16

polar coordinates, the location of points of equal phase. Our pur-
pose is to calculate the wave heights, that is to calculate Qe .

It is convenient to define the geometric shadow as the zone
situated behind the jetty corresponding to the geometric shadow of
optics.

I. GRAPHS

Figures 1, 2, and 3 show three series of curves corresponding
to the following wave incidences:

1. direction of propagation normal to the jetty, i.e.,
normal incidence;

2. direction of propagation makes an angle of 45° with
the jetty;

3. direction of propagation makes an angle of 135° with
the jetty.

For each angle of incidence we have drawn curves showing the
distribution of wave height on the radius vectors drawn from the end
of the jetty and making a certain angle with the direction of the
jetty. The curves are draw to r = 51, beyond that one my utilize
the asymptotic formulae.

It is necessary to distinguish several zones;

a.) within the geometric shadow, (i.e., 9<@ ) the height
decreases in a uniform fashion as one moves along the radius vector.
One my interpolate without difficulty between the different curves,

b.) outside the geometric shadow, (i.e., 0< O< 7m), the
height presents a series of mxima or minima, as functions of r/L
and 9. These mxima and minima may be very sharp and very close for
certain values of the angle 0; for other values they are not so
evident or are quite separated. As an example of the first case we
may cite the curve corresponding to a value of @ = 56° for an incidence
of 45°; as an example of the second case we my cite the curve correspond-
ing to 0 = 67° for an incidence angle of 45°. For these reasons the
drawing of the curve is very laborious and presents great difficulty,
and for the same reason it is impossible to interpolate between curves.
It may be states however, that in the neighborhood of the origin there
exists a minimum which may be very sharp. When r increases indefinite—-
ly the ratio of the amplitude to the amplitude in the open sea
approaches unity.

ce) on the geometric shadow the amplitude decreases
regularly to a value 0.5;

Ibi

“Aq9ef & putyeq eAem & Jo UCTIOeITIJIG °T emsty

epniijduy 434044 dae
PDNLUGWI7

Amplitude
Deep Water Amplitude

ce Jetty
Origin of angle

Direction of
propagation

Figure 2. Diffraction of a wave behind a jetty.
Amplitude7- wo :
Sea Oy i

Amplitude A)
90

Figure 3. Diffraction of a wave behind a jetty.
19

d.) on the prolongation of the jetty the height ratio is
almost unity.

Il. ASYMPTOTIC FORMULAE

1. In the geometric shadow one may substitute for f(u) the
following equivalent expression when Uy and Uy are smaller than -2
1 —tr(l4g+urzy)

Placa =
Tue

or

ment ve
at rr (1/q+ ue) a

i Sana 3 cade fe Piss ame
fF sin 9 + 6.
Age 2

In this case
~ 7 47r cos (8, — @)

f(%)e
d ;
A —~¢ £22 cos(a +6)
f (42)e
have the sams phase; the relative height then becomes:
Bon et Pali sale i ps SN
4r ff Sin GarO sin 2=@
ib 2 2 (3)
Along the jetty where 9 = O one has
BO es ath 1
P 0 FG
Zia a Mis (4)

2. On the geometric shadow, where u, = 0, then f(u,) = 1/2,
and starting at uo <— 2, the relative height of the wave is
furnished by the modulus of the complex expressfon

= BE,
A =0.5+ 1 e 4
4n Ve sin @,

3e. Outside the geometric shadow:

(a) when u, is greater than 2, one may write
Be ed ne) is,
eae

20

(b) when u,; is greater than 2 and up less than -2 the
amplitude has as its asymptotic value the modulus of the following
complex expressions

cos_2 Sin Se SS BURRS i) HE

cos @ — COS,

=)
ao bs
|s

In this zone it does not appear that the variation of the second
term of A can be greater than + 0.16.

(c) when uj is smaller than 2 it is necessary to expect in
general a maximum of amplitude on the curve

6 © Oc W963 By

and a minimun on the curve

. [_——2
Ove 0.924+2yY

the axis Ox being the perpendicular of the polar angle 8, and the
axis Oy the perpendicular of the polar angle Q@ + eS

We must now examine in what measure the preceding theory re—
presents the real phenomena.

In the article cited above Messrs. Putnam and Arthur give the
results of experiments made at the University of California. They
were conducted in deep water, i.e. ina depth greater than L/2 and
they include angles of incidence of 45°, 90° and 135°; the height
of the diffracted wave was measured along parallels to the jetty and
compared to the corresponding theoretical curve. These parallels were
Situated at distances from the jetty varying from 3.38L to 17.85L,
with however, a predominance for the larger distance. The agreement
was good between thsory and experinent within the geometric shadow.

In a thesis submitted to the Faculty of Science of Grenoble, in
July 1949, and prepared in the Laboratoire Dauphinois d!Hydraulique
Neyrpic, Mr. Dixon studied the same problem for normal incidence
in a zone which had not been studied by Messrs. Putnam and Arthur.
The lines on which Dixon measured the height were situated at
distances from the jetty varying from 0.41%, to 3.35L. Furthermore,
the study was conducted in shallow water, i.e. in a depth smller
than one-half wave length (depth of 12 cm. for a wave length of
60 cm). The agreement with theory was good in the interior of the
geometric shadow and in the neighborhood of the jetty end.

Finally, in the course of studies on diffraction now under

way in the Eaboratoire Dauphinois d'Hydraulique Neyrpic we have
made measurements along the jetty itself for incidences of 45°,

ails

Ob 6 8 Z 9 S

"Aqqgel ayy suoTe oAcM
pepoerTsFtp eyy JO opnqttdwe eatyepsey

°7 a|InsT a

OPN HOW JHO/ daeq

apnys/duiy

02'0

22

90° and 135° with the objective of verifying Equation 4. The test
basin, the same which was utilized by Mr. Dixon, was 25 meters
(82.5 feet) long by 4 meters (13.2 feet) wide, and 0.5 meter

(1.65 feet) deep. Since mritime ports are established always in
relatively shallow depths, we limited ourselves to the case of
diffraction in shallow water. Although very simple in appearance,
this condition necessitates the use of a basin with an absolutely
horizontal bottom, which was not easily obtained. It is known,

in fact, that in shallow water the wave refracts and reflects in
relation to the bottom that it encounters, The modifications in
propagation which result may cause, sometimes at large distances
from their original topographic cause, notable wave reinforcenent
and interference resulting in augmentation or diminution of the
instantaneous height. We think however, that we have limited this
cause of error because the difference in elevation between any two
points of the bottom of the basin was, on the average, of the order
of a 0.5 mm. and never exceeded 1.5 mm.

The apparatus used in the basin was the same as that used by
Mr. Dixon. The wave generator was a three-—section paddle driven by
a 2 HP AC motor and gear box. Absorbent beaches of round gravel
were used to surpress reflection at the basin end and along the
wall of the basin sheltered by the jetty. A straight jetty with
vertical walls was milt from one of the jongitudinal walls of the
basin at a distance of 9 meters (29.7 feet) from the wave generator,
leaving an opening of 1.2 meters (3.96 feet) minimum width. To
avoid reflection of the incident wave on the jetty an absorbent
beach was built in front of its; a flat guide of sheet mtal 0.5
meters (1.65 feet) long, placed perpendicular to the extremity of
the jetty avoided any lateral reduction of the wave penetrating
into the opening. Wave heights were measured by means of a resistance
gauge; the variations of voltage at the electrodes of the sounding
gauge as a function of the depth of immersion of the points of the
electrodes were registered photographically through the medium of
a cathode oscillograph.

The results obtained with a wave 76 cm. long in a depth of
water of 13 cm. are represented by points on Figure 4. The curves
of this figure correspond to equation 4 for the angles of incidence
Q@, = 45°, 90°, and 135°. The portions of the curves that are
dotted correspond to the region where

hy mann
L 2 sin® $e

i.e. where the approximation of Equation 2 is no longer valid. The
curves give values that are greater than true values in this region.

23

Note that the preceding theory concerns a semi-infinite screen,
infinitely thin, and perfectly reflecting; on our model the problem
studied differed slightly from the theoretical problem but was
nevertheless very nearly the same in the zone where we have made
our measurements.

aT sas reac

Note: The curves given in this paper were calculated before the
appearance of the approximate theory of diffraction developed
by Mr. Lacombe in the Hydrographique Annalsx. This fact
explains why we have not shown the corresponding curves of
which the interest is obviously apparent.

Sn

* Editors Note: Note sur la diffraction de la houle en incidence
normale, Henri Lacombe, Annales Hydrographiques Paper No.
1363, 1949.

Translated by Dr. Martin A. Mason, Beach Erosion Board.

24

BEACH EROSION STUDIES

The principal types of beach erosion control reports of studies
at specific localities are the following:

a. Cooperative studies (authorization by the Chief of
Engineers in accordance with Section 2, River and
Harbor Act approved on 3 July 1930).

b. Preliminary examinations and surveys (Congressional
authorization by reference to locality by name).

co Reports on shore line changes which may result from
improvements of the entrances at the mouths of rivers
and inlets (Section 5, Public Law No. 409, 74th
Gongress).

d. Reports on shore protection of Federal property
(authorization by the Chief of Enginesrs).

Of these types of studies, cooperative beach erosion studies
are the type most frequently made when a community desires investi-
gation of its particular problem. As these studies have greater
general interest, information concerning studies of specific
localities contained in these quarterly bulletins will be confined
to cooperative studies. Information about other types of studies
can be obtained upon inquiry to this office.

Cooperative studies of beach erosion are studies made by the
Gorps of Engineers in cooperation with appropriate agencies of the
various States by authority of Section 2, of the River and Harbor
Act approved 3 July 1930. By executive ruling the cost of these
studies is divided equally between the United States and the co.
operating agency. information concerning the initiation of a co-
perative study may be obtained from any District Engineer of the
Gorps of Engineers. After a report on a cooperative study has been
transmitted to Congress, a summary thereof is included in the next
issue of this bulletin. Summaries of reports transmitted to Congress
since the last issue of the Bulletin and lists of completed co~
operative studies and those now in progress follows:

SUMMARIES OF REPORTS TRANSMITTED TO CONGRESS
QUINCY SHORE, MASSACHUSETTS

The area studied is located in the City of Quincy, Massachusetts,
at the head of Quincy Bay in Boston Harbor, 6 miles southeast of the

25

City of Boston. It comprises the southerly 6700 feet of the publicly
owned Quincy Shore Reservation which is under the jurisdiction of the
Metropolitan District Gommission. The Reservation comprises a marrow
public beach which is generally undér water at high tide, seawalls
and riprap shore protection, parking areas, and a boulevard. The
shore of the study area is lined with concrete seawalls except at ths
southerly end where 400 feet of riprap have been placed. The beach
consists of coarse sand and gravel above mean tide level and mud
below that elevation. The offshore area is very flat and shoal, ex-
cept in the dredged yacht channel, and at low tide large calm flats
and other areas are exposed,

The land immediately adjacent to the boulevard which traverses
the reservation is used for commercial purposes. The adjacent area
is a densely populated, urban, middle class residential area which
extends back across the City of Quincy. Two yacht clubs, the
Wollaston Yacht Club and the Squantum Yacht Club are located on
the bay sise of the reservation boulevard. Hach club maintains a
pier which projects 350 feet into the bay to the head of a yacht
basin and channel which are maintained by the Commonwealth of
Massachusetts.

Free public parking is provided along the entire length of the
beach on a parking strip between the highway and the seawall. Bus
service is provided within 800 feet of the beach by a system serving
the area south of Boston and connecting with the Metropolitan Transit
Authority system of Boston. Ths beach is open to the public free
of charge. There are no public bathhouses in the study area, but ex-
tensive use is made of the beach by bathers from nearby homes and
by those who travel to the beach attired in bathing mits. The daily
summer attendance is estimated to average 1000, Sunday and holiday
attendance 3000 to 5000.

The existing beach in the study area was artificially developed
and resulted from the realignment of the shores of Quincy Bay by
construction in 1905 of a highway over beaches and marshes. The
highway was built on an embankment, the seaward face of which within
most of the length of the study area is now protected by a low
concrete stepped seawall which was constructed in 1926. The present
beach is the result of wave and tidal action on the highway embank-
ment. The stepped seawall is too low to provide adequate protection
to the highway and adjacent property and is, furthermore, presently
in need of extensive repairs. In 1948 a reinforced concrete parapet
wall was added to the top of the northerly 1130 feet of the stepped
seawall, The parapet wall has since been extended about 1000 feet
in a southerly direction.

In furtherance of the general purpose of the study, specific

problems at Quincy Shore Beach were found to require determination
of the most suitable measures to provide adequate protection to the

26

highway and adjacent property from high tides and storm wave action
and to provide a more suitable recreational beach.

The division engineer considered the desires of the cooperating
agency, studied the existing structures, the sources and movement of
beach material, the changes in the shore line and offshore bottom,
the effects of winds and storms, developed plans for protecting and
improving the shore of the study area, and made an economic analysis
of proposed new protective and improvement construction for Quincy
Shore Beach. He found that prospective benefits warrant construction
of these measures and that the public interest therein justifies
Federal participation to the extent of one-third of the total cost
of the recommended new work, in accordance with the policy established
by Public Law 727, 79th Congress.

The division engineer recommended, subject to certain conditions,
adoption of a project authorizing Federal participation in an amount
equal to one-third of the first cost of protecting and improving the
shore of the Metropolitan District Commission Quincy Shore Reserva—
tion, Massachusetts, by:

a. Placing approximately 126,000 cubic yards of sand and
gravel, and 221,500 cubic yards of sand on the beach between Hovey
Street, and Rufe's Hummock Sea Wall, a distance of 8500 feet, to
provide a backshore elevation of 15.0 feet above mean low water;

b. Constructing a concrete-encased steel sheet-pile
bulkhead with a top elevation of 18 feet above mean low water
between the parapet wall, near Hollis Avenue, and the National
Sailor's Home Hill Sea Wall, a distance of 4750 feet;

ec. Constructing a concrete sea wall, with a top elevation
of 19.2 feet above mean low water, in extension of the existing
parapet wall to high ground at Billings Street, a distance of 325
feet:

d. Constructing two impermeable stone groins each 350
feet long, with tops generally 2 feet above the highest adjacent
fill, one 200 feet north of the Squantum Yacht Club, the other 200
feet south of the Wollaston Yacht Club; and

e. Constructing a culvert at Sachem Creek, and extending
existing drains across the beach to discharge seaward of the recommend—
ed fill.

The Beach Erosion Board carefully considered the report of the

division engineer and concurred generally in his conclusions and
recommendations, subject to the following comments.

27

The beach under study, located at the head of Quincy Bay is =
partially protected against wave action during the dominant north-~
east storms by islands and by extensive shoal areas in front of the
beach. Littoral currents are relatively weak in the study area. The
shore consists of a highway embankment located over former beach and’
marsh areas. The seaward face of this embankment along most of the
length of the study area is protected by a low stepped concrete wall
which is in need of repair. During storms accompanied by extreme
high tides, storm waves break over this wall flooding the highway and at
adjacent low-lying residential areas, Fronting the seawall is a
narrow public beach which is mostly under water at high tide, The
lowering of this beach by erosion has exposed the toe of the seawall
to incipient undermining at a number of points. The water is now ©
polluted by raw sewage discharged into Boston Harbor. However,
sewage treatment plants now under construction or proposed, will
materially reduce and probably ultimtely eliminate the existing
pollution. In spite of the present undesirable characteristics of
the existing beach, it is now used extensively as a recreational
bathing beach.

ast

The division engineer recommended the construction of a concrete
encased steel sheet pile bulkhead immediately seaward of the existing
seawall throughout the greater portion of its length and the back-—
fill of the space between the two structures to an elevation of +15 feet.
No provision was made for tie-backs, presumably because the sand fill
seaward of the bulkhead will also have an elevation of +15 feet or
3 feet below the top of that structure. The Board nevertheless believed
that tie-backs should be included in the bulkhead design as a measure
of reasonable prudence and recommends that they be so included when
the detailed design of the structure is undertaken.

The artificial sand fill proposed by the division engineer will
raise and widen the beach thereby constituting a material improvement
of the beach as a recreational facility. The Board was of the
opinion that this fill is also an essential part of the plan for the
protection of this shore and the installations immediately behind it.
Without this protective fill the proposed bulkhead would be in-
adequate to withstand the direct attack of storm waves. The alterna-—
tive would be the construction of an expensive seawall with a
foundation level considerably below sea level and with adequate pro-
vision for protection at its toe. Such a seawall would probably
hasten the present processes of erosion which would in turn result
in the ultimate loss of the existing beach with consequent increased
cost of maintenance of the wall itself.

The Beach Erosion Board noted that the recommended plan includes
two impermeable stone groins adjacent to the yacht club area. The
stated purposes of these groins are to maintain a steeper beach slope
in the area between them, and preyent the movement of beach mterial

28

into the yacht club area and the dredged yacht basin. The Board was
of the opinion that these groins, as designed, will be inadequate
to accomplish these purposes in their entirety, and that groins
properly designed to accomplish the intended purposes would of
necessity be larger and more costly. The Board recommended that
the proposed groins be eliminated from the plan as unnecessary and
undesirable features. The Board recognized that this elimination
will require that the shore line in the immediate vicinity of the
yacht clubs be advanced to correspond with the proposed beach al-
ignment throughout the remainder of the area. This change will
eliminate the cost of the groins but will necessitate an increase
in the length of the Sachem Creek conduit and an increase in the
Quantity of sand fill. The net effect will be an increase in the
total estimated cost of the plan from $849,000 to $897,000.

The Board was of the opinion that the recommended plan of pro—
tection and improvement as modified by the above comments will pro-
vide needed protection to the shore of the publicly owned Metro—
politan District Commission, Quincy Shore Reservation and adjacent
privately owned property and will promote and encourage une heaith—
ful recreation of the people.

In accardance with existing statutory requirements, the Board
stated its opinion that;

a. It is advisable for the United States to adopt a pro—
ject authorizing Federal participation in the cost of protecting
and improving the publicly owned shore of the Metropolitan District
Gommission Quincy Shore Reservation, Massachusetts.

b. The public interest involved in the proposed measures
for the publicly owned shores is substantial. It is associated with
prevention of direct damages to public property, increased tax
revenue resulting from increased earning power of adjacent property
and recreational benefits to the public;

co The share of the expense which should be borne by the
United States is one-third of the first cost of the proposed work
for publicly owned shores. The estimated amount of this share is
$299,000.

The Board recommended that a project be adopted by the United
States authorizing Federal participation by the contribution of
Federal funds in an amount equal to one-third of the first cost of
protecting and improving the shore of the Metropolitan District
Gommission Quincy Shore Reservation, Massachusetts, bys

a. Placing approxi mately 126,000 cubic yards of sand and

gravel, and 253,000 cubic yards of sand on the beach between Hovey
Street and Rufe's Hummock Sea Wall, a distance of 8500 feet, to provide

29

a back shore elevation of 15 feet above mean low water;

b. Gonstructing a concrete-encased steel shest—-pile bulk-—
head with a top elevation of 18 feet above mean low water between the
parapet wall, near Hollis Avenue, and the National Sailor's Hom Hill
Sea Wall, a distance of 4750 feet;

ce. Constructing a concrete sea wall with a top elevation
of 19.2 feet above mean low water, in extension of the existing
parapet wall to high ground at Billings Street, a distance of 325
feet;

d. Constructing a culvert at Sachem Creek, and extending
existing drains across the beach to discharge seaward of the
recommended fill.

Federal participation was recommended subject to the conditions
that the Commonwealth of Massachusetts will:

a. Adopt the project named herein;

b. Submit for approval by the Chief of Engineers prior to
the commencement of work, the plans and specifications for the project
and also the arrangements for prosecuting the work.

co Assure maintenance of the protective and improvement
measures during their useful life as my be required to serve their
intended purposes:

d. Provide at its own expense, all necessary lands, ease-
ments, and rights—of-way;

e. Hold and save the United States free from all claims
for damages that may arise either before, during, or after pro-
secution of the work3

f. Assure that water pollution that would endanger the
health of bathers will be eliminated;

g. Assure continued public ownership of the shore and its
administration for public use only.

The estimated amount of Federal participation in accordance with
the foregoing recommendations is $299,000.

30

REVERE BEACH, MASSACHUSETTS

Revere Beach is located in the Gity of Revere, 5s miles north-
east of the City of Boston. It is a barrier beach which extends a
distance of 34 miles northward from Roughan's Point to the mouth of
Saugus River, separating the Lynn marshes from Broad Sound. The
southern half of Revere Beach has been developed as a large amusement
area; the northern half as a residential area. The shore is publicly
owned and comprises the Metropolitan District Commission Revere Beach
Reservation for a length of 3 miles between Point of Pines at the
north end and Roughan's Point at the south end. The reservation con-
sists of the beach, a wide boulevard, sidewalks, a series of seawalls,
pavilions and retaining walls along the seaward edge of the boulevard.
Excellent highways and the Metropolitan Transit Authority transporta—
tion system connect the study area with all sections of Metropolitan
Boston. Revere Beach is open to the public without charge. A
nominal fee is charged for use of the public bathhouse. The daily
attendance at Revere Béach during the summer season is estimated at
150,000 to 200,000, Sunday and holiday attendance at 400,000 to
500,000.

Point of Pines, north of the Revere Beach Reservation, is a
densely populated, permanent residential area bounded by a paved
town road paralleling the privately owned shore. The road is partially
protected by miscellaneous walls, bulkheads and riprap revetments.
Roughan's Point, south of the Reservation, is a summer and year-round
residential area protected by a sea wall constructed by the Massachusetts
Department of Public Works.

The beach fronting the Metropolitan District Commission Reserva-
tion consists of firm sand with deposits of stones in the backshore
area. The width of beach above the mean high water line varies from
50 feet to 100 feet for most of the length and increases to more than
200 feet at the ends. The position of the beach is stabilized by
Roughan's Point, Cherry Island Bar, Oak Island, and the Saugus River.
Although the beach is exposed to waves from the open ocean with
directions of approach between southeast and east, direct wave attack
during the dominant northeast storms is prevented by Nahant, Little
Nahant and the tombolos connecting them to the minland. Waves
approaching the coast from the northeast reach Revere Beach only
after being refracted around the outer end of Nahant. Shore protection
works along the coast have cut off all onshore sources of beach
building materials. Since 1900, the date of the earliest profile
surveys, accretion has occurred along 2000 feet at the southerly end,
erosion along the remaining 12000 feet of the Reservation. Since
1932, stones have appeared on the beach in large quantities inter—
fering with recreational use of the beach. During severe storms
seawalls have been overtopped and the adjacent road flooded, but
structures along the beach have not, as yet, suffered great damege.
Gontinued erosion will, however, endanger existing protective
structures.

BL

In furtherance of the general purpose of the study, specific
problems at Revere Beach were found to require determination of the
most suitable measures for protecting and improving the beach in
the Metropolitan District Commission Reservation and for preventing
flooding in the Point of Pines area.

The Division Engineer considered the desires of the cooperating
agency, determined the character, source, and movement of beach
material, studied the existing structures, the changes in the shore
lines and offshore bottom, the effects of winds and storms,
developed plans for protecting and improving the shore of the area,
and made an economic analysis of proposed new protective and improve-
ment construction for the publicly owned shore in the study area,

He found that the estimated benefits warrant construction of certain
masures for the protection and improvement of the publicly owned
shore and that the public interest therein justifies Federal parti-
cipation to the extent of one-third of the total cost of recommended
new work, in accordance with ene policy established by Public Law
Weis 79th Congress.

The Divisien Engineer recommended, subject to certain conditions,
adoption of a project by the United States authorizing Federal parti-
cipation in an amount equal to one-third of the first cost of pro=
tecting and improving the beach of the Metropolitan District Commission
Revere Beach Reservation for a length of 13,700 feet between Northern
Girecle and a point near Shirley Avenue by placing theraen §22 ,00%)
cubic yards of sand fi11 te provide a backshore elevation of 13.0
feet above mean low water, except at the northern end of the beach
where local conditions require backshore elevations between 16.8 and
17,3 feat above man low water.

The Division Ingineer also recommended that the Commonwealth

of Massachusetts, if it considers the work justified, (a) construct

a concrete-encased steel sheet pile sea wall having a top elevation
of 18.0 feet above mean low water in tha Point of Pines area between
the General Edwards Bridge and Northern Circle, a distance of 4500
feet; (b) periodically level the top of the stone ridge at the
southerly end of Revere Baach Reservation when it reaches an
elevation higher than that of the adjacent road; (c) seal openings
in the existing Roughan's Point sea wall and extend it to Eliot
Gircle. Federal contrition to items (b) and (¢c) would not be in
accordance with the policy stated in Public Law 727, 79th Gongress.
tudy of item (a), not originally included in the scope of the
investigation, was not sufficiently extensive to determine the extent
of Federal aid to be recommended in accordance with existing statutes.
The Division Engineer was of the opinion that Federal participation
in this item that might be recommended as a result of further study
would not exceed 9 per cent of the total cost,

The Beach Erosion Board carefully considered the report of the
Division Engineer. It concurred generally in his conclusions and
recommendations.

The beach under study is protected from the dominant storm waves
by Nahant, Little Nahant and the tombolos connecting them to each
other and to the mainland. The publicly owmed portion, the Metropolitan
District Commission Reservation, has not yet suffered severe storm
damages, although the highway is occasionally washed over. The recent
history of the beach of the Reservation indicates a greater amount of
erosion than accretion and interference with recreational use of the
beach by exposure of increasing numbers of stones on the backshore
areas. Continued erosion will endanger many structures, but, since the
rate of erosion is relatively low, only a small portion of the exist-
ing structures are in imminent danger. The natural rate of supply of
beach material is insufficient to permit its entrapment to create a
stable beach of satisfactory composition. The Board therefore con—
curred in the plan of the Division Engineer to provide protection and
improvement of the beach by artificial placement of sand fill. The
improved wider beach will provide more effective shore protection.
Furthermore, as the backshore beach areas are stony and unsatisfactory
for recreational use, the recommended wider and improved beach will
provide, in addition to other benefits, very large recreational
benefits which provide economic justification for the wrk. The
Board concurred in the opinion of the Division Ingineer that pro-
spective benefits warrant the proposed expenditure for an improved
protective beach.

The Board noted that the volume of sand necessary to maintain
the artificial fill in its original condition was estimated by the
Division Engineer at 5,000 cubic yards per year. The Board believed
that this figure will be found to be too small in practice and there-
fore that the cost of maintenance will probably be somewhat higher
than estimated in the report. However, it is apparent that no reason-
able increase of mintenance cost from this cause will appreciably
disturb the present economic justification.

In accordance with existing statutory requirenmnts, the Board
stated its opinion that:

a. It is advisable for the United States to adopt a pro—
ject authorizing Federal participation in the cost of protecting and
improving the publicly-owned shore of the Metropolitan District
Commission Revere Beach Reservation, Massachusetts;

b. The public interest involved in the proposed measures
for the publicly owned shores is substantial. It is associated
with prevention of direct damages to public property, increased tax
revenue resulting from increased earning power of adjacent property,

33

and recreational benefits to the general public. Private benefits
will also result in lesser amount from increased earning power of
adjacent lands;

c. The share of the expense which should be borne by the
United States is one-third of the first cost of the proposed work for
publicly owned shores. The estimated amount of this share is $337,300.

The Board recommended that a project be adopted by the United
States authorizing Federal participation by the contribution of
Federal funds in an amount equal to one-third of the first cost of
works for the protection and improvement of the shore of the Metropolitan
District Commission Revere Beach Reservation, Massachusetts, con-—
sisting of the placement of 522,000 cubic yards of sand fill between
Northern Circle and Profile 13 near Shirley Avenue, a distance of
about 13,700 feet, to provide a backshore elevation of 18.0 feet
above mean low water, except at the northern end of the beach wheres
local conditions require backshore elevations between 16.8 and 17.3
feet above mean low water.

Federal participation was recommended subject to the conditions
that responsible local interests will:

a. Adopt the project named herein;

b. AsSSure maintenance of the improvement during its use-
ful life as may be required to serve its intended purpose;

c. Provide, at their own expense, all necessary lands,
easements, and rights—of-way;

d. Hold and save the United States free from all claims
for damages that may arise either before, during, or after pro-
secution of the works

e. Assure that water pollution that would endanger the
health of bathers will not be permitted;

f. Assure continued public ownership of the shore and
its administration for public use only.

The estimated amount of Federal participation in accordance
with the foregoing recommendations is $337,300.

Opes pide rate SRS

LYNN — NAHANT BEACH, MASSACHUSETTS

The beach referred to herein as Lynn-Nahant Beach comprises
portions of the shore in the towns of Swampscott and Nahant and the
City of Lynn, a total length of about 2-3/4 miles. The area is
located 7-1/2 miles north of the main entrance channel to Boston
Harbor and 9 miles northeast of the City of Boston. Th shore is
publicly owned between the privately owned headlands, Blaney Rock
and Little Nahant, respectively at the north and south ends of the
beach. The publicly owned reservations are under the control of
the Metropolitan District Commission. Good roadsfollow the shore
for the length of the study area. Public parking areas have been
provided. All parts of the beach are open to the publie without
charge. A nominal fee is charged for use of the public bathhouse.
The Swampscott and Lynn portions of the area are extensivély
developed for year-round residential use.

The northern section of the area studied is the mainland head-
land consisting of moderately high bluffs composed of a thin veneer
of till over bed rock. Rock outcrops occur at Blaney Rock and
Red Rock in this section. The southern end of the area is the
former island of Little Nahant, which also consists of bluffs of
till with rock outcrops. Between these headlands a narrow tombolo
has been formed, which separates Lynn Harbor from Nahant Bay, the
latter being a broad open arm of the Atlantic Ocean. The tombolo
averages about 350 feet in width and its crest is 15 to 20 feet
above mean low water. The narrow beaches fronting the headlands
on the miinland and Little Nahant are generally of hard-packed
sand with some stones and boulders. Nahant Beach on the tombolo
is composed generally of sand on the flat foreshore, with con~-
siderable stone backed by low dunes on the backshore.

The headlands on the mainland and on Little Nahant have been
protected by substantial seawalls. Most of the wall on the mainland
was constructed 40 or 45 years ago and is now in poor condition.
Erosion of the beach at the base of the wall has necessitated the
construction of toe walls to prevent undermining.. Although the
tombolo between the mainland and Little Nahant has been reasonably
stable, a storm in 1945 eroded the dunes where they were not pro-
tected by riprap revetment.

In furtherance of the general purpose of the study, specific
problems at Lynn—Nahant Beach were found to require determination
of the most suitable measures for insuring the stability of the
existing mainland seawalls, for protecting and improving the
tombolo beach in the vicinity of the bathhouse and for protection
of the tombolo from erosion and the possibility of breaching.

35

The Division Engineer considered the desires of the cooperating
agency, determined the sources and movement of beach material, the
changes in the shore line and offshore bottom, the effects of winds,
storms and of existing structures, developed plans for protecting
and improving the shores of the area, and made an economic analysis
of proposed new protective and improvement construction for Lynn-Nahant
Beach. He found that prospective benefits warrant construction of
these measures and that the public intsrest therein justifies ‘
Federal participation to the extent of one-third of the total cost
of recommended new work, in accordance with the policy established
by Public Law 727, 79th Gongress, o

The Division Engineer recommended, subject to certain conditions, |
adoption of a project by the United States authorizing Federal
participation in an amount equal to one-third of the first cost of
protecting and improving the beach between Woodbury's Point and the
dune on Nahant tombolo, a distance of about 2,600 feet, by placing
172,000 cubic yards of sand thereon to perce a ‘sepleehnone elevation
of 18 feet above mean low water, and constructing a stone mound having
a top elevation of 18 feet above mean low water along the tombolo
from the improved beach to Little Nahant, a distance of 6,250 feet..

The Division Engineer also recommended a plan for insuring the ..
stability of existing seawalls on ths mainland shore between Blaney —
Rock am Wocdbury's Point, consisting of the construction of steel
pile cut-off walls at those places where tue walls do not extend
below elevation 6 feet above mean low water, and refacing the exist-
ing wall. The entire cost of this maintenance work should be borne .
by local interests as it is not eligible for Federal assistance
under the policy established by Public Law 727, 79th Congress.

The Beach Erosion Board carefully considered the report of the
Division Engineer. It concurred generally in his conclusions and,
recommendations »

The beach under study, lying at the head of Nahant Bay, is pro-
tected by the headlands at Philips Point and those of Nahant and
Little Nahant. As a result, the beach is reasonably stable. Material
is moved by wave action back and forth within the area, but the rate
of loss of material from the area is low. The headlands have been
protected by seawalls, most of which are 40 to 45 years old and now
in poor condition, The Beach Erosion Board is of the opinion that
the storm damage to these conerete seawalls described by the Division
Engineer can be attributed largely to the deteriorated condition
of concrete 40 to 45 years old. Mcedern seawalls of concrete properly
designed and constructed will certainly withstand similar exposure
to wave action with little or no damege.

In connection with the recommendation of the Division Engineer
for armoring the existing concrete wall between Blaney Rock and

36

Woodbury's Point, the Board believed that although it may not be the
most economical, reinforced concrete facing is the most satisfactory,
and feasible method. Gareful treatment will be required to avoid
infiltration of water, either from wave action or precipitation, into
any exposed joint.

Largely as a result of protection of the headlands against erosion
there is now no apparent natural source of new mterial to replace
losses. In view of the lack of natural replacement material, breach-
ing of the tombolo is possible, if low places are allowed to develop
where storm waves can wash across the tombolo. The Board therefore
concurred in the plan of the Division Engineer to build up the crest
of the tombolo to elevation 18 feet above mean low water.

The Board noted that the recommended method of protection of the
shore in the vicinity of the Metropolitan District Commission bath-
house results in an improved beach. The Board concurred in the opinion
that the improved wider beach will provide more effective shore
protection. As the backshore beach area in the vicinity of the bath—
house is stony and unsatisfactory for recreational use, the proposed
wider and improved beach will provide, in addition to other benefits,
recreational benefits which increase the economic justification of the
work.

The Board also noted that the benefits evaluated for the pro-
tection and improvement of Lynn-Nahant Beach apply principally to the
shore from Woodbury's Point to and including the recreational beach
in the vicinity of the Metropolitan Bistrict Commission bathhouse.
However, the Board believed that the unevaluated benefits consisting
of prevention of indirect damages that would result to the Little
Nahant and Nahant area from breaching of the tombolo amply justify
the proposed stone mound construction from south of the bathhouse to -
Little Nahant, the annual charges on which are estimated at $4,860.

In accordance with existing statutory requirements, the Board
stated its opinion that:

a. It is advisable for the United States to adopt a project
authorizing Federal participation in the cost of protecting and im—
proving the publicly owned shores at Lynn and Nahant, Massachusetts;

b. The public interest involved in the proposed measures
for the publicly owned shores is substantial. It is associated with
prevention of direct damages to public property, indirect damges
prevented, and recreational benefits to the general public.

¢. The share of the expense which should be borne by the
United States is one-third of the first cost of the proposed new
construction for publicly owned shores. The estimted amount of
this share is $154,670.

37

The Board recommended that a project be adopted by the United
States authorizing Federal participation by the contribution of
Federal funds in an amount equal to one-third of the first cost of
the following measures for the protection and improvement of the
shores of Lynn and Nahant, Massachusetts, as follows:

a. Artificial placement of approximtely 172,000 cubic
yards of sand on the beach for a distance of 2,600 feet south of
Woodbury's Point, to provide a backshore elevation of 18 feet above
mean low waters:

b. Gonstruction of a stone mound with a top elevation of
18 feet above mean low water along the tombolo from the foregoing
improved beach to Little Nahant, a distance of about 6,250 feet.

Federal participation was recommended subject to the conditions
that responsible local interests will:

a. Adopt the project named herein;

b. Assure maintenance of the improvements during their
useful life as may be required to serve their intended purpose:

c. Provide, at their oWm expense, all necessary lands,
easements, and rights-of-way;

d. Hold and save the United States free from all claims
for damages that may arise either before, during, or after prosecution
of the work;

e. Assure that water pollution that would endanger the
health of bathers will not be permitted;

f. Assure continued public ownership of the shore and
its administration for public use only.

The estimated amount of Federal participation in accordance
with the foregoing recommendation is $154,670.

RE SR eat

COMPLETED COOPERATIVE BEACH EROSION STUDIES

Location

Qld Orchard Beach

Hampton Beach

South Shore of Cape Cod
(Pt. Gammon to Chatham)

Salisbury Beach

Winthrop Beach

Lynn=-Nahant Beach

Revere Beach

Nantasket Beach

Quincy Shore

South Shore
(Town of Narragansett,
South Kingstown,
Gharlestown & Westerly}

Compo Beach, Westport

Hawk's Nest Beach, Old Lyme
Ash Creek to Saugatuck River

Hammonasset River to East
River

Jacob Riis Park, Long Is.

Orchard Beach, Pelham Bay,
Bronx

Niagara County

South Shore of Long Is.

Completed
MAINE

20 Sep 35

NEW HAMPSHIRE

15 Jul 32

MASSACHUSETTS

26 Aug 41
26 Aug 41
12 Sep 47
20 Jan 50
12 Jan 50
12 Jan 50

2 May 50

RHODE ISLAND

4 Dec 48

CONNECTICUT

18 Apr 35
21 Jun 39
29 Apr 49
29 Apr 49
NEW YORK

16 Dec 35
30 Aug 37

27 Jun 42
6 Aug 46

39

Published in

House Doc. Congress

764

490

239
454
47h,

Boi

450
271

80

81

74
81
81

74

75
78

NEW JERSEY

Wanasquan Inlet & Adjacent

Beaches 15 May 36 ail om
Atlantic City 11 Jul 49 538 81
| VIRGINIA.
Willoughby Spit, Norfolk 20 Nov 37 482 75
Golonial Beach, Potomac
River 24 Jan 49 333 81

NORTH CAROLINA

Fort Fisher 10 Nov 31 204 72
Wrightsville Beach 2 Jan 34 218 UW
Kitty Hawk, Nags Head &

Oregon Inlet 1 Mar 35 155 74
State of North Carolina 22 May 47 763 80

SOUTH CAROLINA

Folly Beach 31 Jan 35 156 74
GEORGIA
St. Simon Island 18 Mar 40 820 76
FLORIDA
Blind Pass {Boca Giega) 1 Feb 37 187 15
Miami Beach. - 1 Feb 37 169 UD
Hollywood Beach 28 Apr 37 253 75
Daytona Beach 15 Mar 38 Syak UE
Bakers Haulover Inlet 21 May 4$ Da Ue
Anna Maria & Longboat Keys 12 Feb 47 760 80
Jupiter Island 13 Feb 47 765 80
Palm Beach (1) 13 Feb 47 772 80
MISSISSIPPI
Hancock County 3 Apr 42
Harrison County—Initial 15 Mar 44
Harrison GCounty—Supplement 16 Feb 48 682 80
LOUISIANA
Grand Isle 28 Jul 36 92 75

(1) A cooperative study of experimental steel pile groins was also made,
under which-methods of improvement were recommended in an interim report
dated 19 Sep 40. Final report on experimental groins was published in
1948 as Technical Memorandum No. 10 of the Beach Erosion Board.

40

Galveston
Galveston Bay, Harris Cty.

Santa Barbara - Initial
Supplement
Final

Ballona Creek & San Gabriel

River (Partial)

Orange County

Coronado Beach

Long Beach

Mission Beach

PENNSYLVANIA

Presque Isle Peninsula,
Erie (interim)
(Final,)

Erie County-Vicinity of
Huron

Lake Erie Shore-Michigan
Line to Marblehead

Cities of Cleveland &
Lakewood

Lake County

Chagrin River to Fairport,
Vermillion to Sheffield
Lake Village, Lorain Cty.

State of Illinois

Milwaukee County

Punta Las Marias, San Juan

TEXAS

10 May 34
31 Jul 34

CALIFORNIA

15 Jan 38
18 Feb 42
22 Nay 47
ll May 38
10 Jan 40
4 Apr 41
3 Apr 42
4 Nov 42

3 Apr 42
23 Aug 49

OHIO

26 Aug 41
30 Oct 44
22 Mar 48
22 Nov 49
24 Jul 50
ILLINOIS
8 Jun 50

WISCONSIN

21 May 45

PUERTO RICO

5 Aug 47

4l

400
74

552

761

637
636

220
177

502
596

526

769

(3
74,

WD

80

76
Wil

719
ug,

81
81

19

80

COOPERATIVE BEACH BHOSION STUDIES IN PROGRESS
NEW HA MPSHIRE

HAMPTON BEACH. Cooperative Agency: New Hampshire Shore and Beach
Preservation and Development Commission.

Problem: To determine the best method of preventing further
erosion and of stabilizing and restoring the beaches,
also to determine the extent of Federal aid in any
proposed plans of protection and improvement.

MASSACHUSETTS

PEMBERION POINT TO GURNET POINT. Cooperating Agency: Department of
Public Works, Commonwealth of Massachusetts.

Problem: To determine the best methods of shore protection
prevention of further erosion and improvement of
beaches, and specifically to develop plans for pro-
tection of Crescent Beach, The Glades, North
Scituate Beach and Brant Rock.

CONNECTICUT

STATE OF CONNECTICUL. Cooperating Agency : State of Connecticut
(Acting through the Flood Control and Water Policy
Commission).

Problem: To determine the most suitable mthods of stabilizing
and improving the shore line. Sections of the coast
will be studied in order of priority as requested by
the cooperating agency until the entire coast is in-
cluded.

JONES BEACH. Cooperating Agency: Long Island State Parks Gommission
Problem: To determine behavior of the shore during.a 12-month
cycle, including study of littoral drift, wave re-
fraction and movement of artificial sand supply
between Fire Island and Jones Inlets.
NEW JERSEY
OCEAN CITY. Cooperating Agency: City of Ocean City.
Problem: To determine the causes of erosion or accretion and
the effect of previously constructed groins and

structures, and to recommend remedial measures to
prevent further erosion and to restore the beaches.

42

VIRGINIA
VIRGINIA BEACH. Cooperating Agency: Town of Virginia Beach.

Problem: To determine the methods for the improvement and
protection of the beach and existing concrete sea
wall.

SOUTH CAROLINA

STATE OF SOUTH CAROLINA. Cooperating Agency; State Highway
Department o

Problem: To determine the best method of preventing erosion,
stabilizing and improving the beaches.

FLORIDA
PINELLAS COUNTY. Cooperating Agency: Board of County Commissioners.

Problem: To determine the best methods of preventing further
recession of the gulf shore line, stabilizing the
gulf shores of certain passes, and widening certain
beaches within the study area.

LOUISIANA

LAKE PONTCJARTRAIN. Cooperating Agency: Board of Levee Commissioners,
Orleans Levee District.

Problem: To determine the best method of effecting necessary
repairs to the existing sea wall and the desirability
of building an artificial beach to provide protection
to the wall and also to provide additional recreational
beach area.

TEXAS

GALVESTON COUNTY. Cooperating Agency: County Commissioners Court
of Galveston County.

Problem; To determine the best method of providing a permanent
beach and the necessity for further protection or ex-
tending the sea wall within the area bounded by the
Galveston South Jetty and Eight Mile Road.

To determine the most practicable and economical
method of preventing or retarding bank recession on
the shore of Galveston Bay between April Fool Point
and Kemah.

43

CALIFORNIA

STATE OF CALIFORNIA. Cooperating Agency. Division of Beaches and
Parks, State of California. i

Problem: To conduct a study of the problems of beach erosion
- and shore protection along the entire coast of
California. The initial studies are being made in
the Ventura-Port Hueneme area, the Santa Monica Bay
area and the Santa Cruz area.

WISCONSIN
RACINE COUNTY. Cooperating Agency; Racine County.

Problem: To prevent erosion by waves and currents, and to
determine the most suitable methods for protection,
restoration and development of beaches.

Kenosha. Cooperating Agency: City of Kenosha.

Problem: To determine the best method of shore protection
and beach erosion control.

OHIO

STATE OF OHIO. Cooperating Agency: State of Ohio (Acting through
the Superintendent of Public Works).

Problem: To determine the best method of preventing further
erosion of and stabilizing existing beaches, of re-
storing and creating new beaches, and appropriate
locations for the development of recreational
facilities by the State along the Lake Erie shore
line.

TERRITORY OF HAWAII

WAIKIKI BEACH:
WAIMEA & HANAPEPE, KAUAI. Cooperating Agency: Board of Harbor
Commissioners, Territory of Hawaii.

Problem: To determine the most suitable method of prevent—
ing erosion, and of increasing the usable recreational
beach area, and to determine the extent of Federal
aid in effecting the desired improvement.

A4

BEACH EROSION LITERATURE

There are listed below some recent acquisitions to the Board's
library which are considered to be of general interest. Copies of
these publications can be obtained on 30-day loan by interested
official agencies.

"Observations of Echo Signals Obtained Using Variable Frequency Trans-
mission," Edwin M. WeMillan, July 4, 1942.

In dealing with the problem of large amplitude fluctuations
in underwater echoes, the frequency modulation offers very
considerable improvement in the distinguishability of echoes
from reverberation; for listening, the signal frequency sweep
is preferable because of the ability of the ear to differentiate
a tone, or sequence of tones, froma toneless background and
for presentation on a cathode ray screen, rapid modulation by
a Sine wave or by noise is preferable because it gives more
effective smoothing of the reverberation.

"Model Study of Sand Transport Along an Infinitely Long, Straight,
Beach ,* Thorndike Saville, Jr., Trans. AGU, Vol. 31, No. 4, 1950

This paper describes a small-scale tank study of the rate
littoral transport of sand induced by wave action ona straight
beach inclined to the direction of wave crest.

"Notes on the Studies of Dam Problems Carried Out in the Laboratorio
de Engenharia Civil," Lisbon, 1950.

The Laboratorio de Engenharia has made numerous studies of
problems related to the building of large dams. This paper
discusses studies of materials, cements, concretes and soils
together with studies of mechanical properties of the founda-
tion rock and observations of the dams during and after con—
struction.

"Report of Sedimentation Surveys, Denison Dam (Lake Texoma) Red
River, Texas and Oklahoma," June 1950, Tulsa District.

This report presents the results of the first resurvey
of sedimentation-in Lake Texoma. Data relative to changes in
the river below the dam are also presented. The purpose of
the investigation was to determine the effect of the operation
of the project upon the channel of the Red River downstream
from the dam.

45

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