03-20-65 M~RCH 20, !965
A~mee~ing Of the City Council' together with the Beach Erosion Com-
mitte~ Was held in the Council Chambers at 9=30 a.m., to provide
lO, preSentation by Glees Engineering Corporation of an engineering
re/~Ort concerning the City's beach erosion problems. Members of the
council present were~ Mayor Al. C. Avery, Vice-Mayor Jack L. Saunders,
and Councilmen J. LeRoy Croft, James H. Jurney and George Talbot, Jr.
Me~bers of the Beach Erosion Committee present~ Chairman Talbot,
Me~srs. Persifor Frazer, Herbert Moffitt, Charles Robertson, J. D.
T~ller, James Wilson, Ac L. Greenwood and T. M. O~Neal, and City
Engineer Mark C. Fleming.
MaYor Avery stated that this meeting was the culmination of the ef-
forts of the City Council in taking a positive approach to the Cityts
beach erosion problem, as a result of which, Glace Engineering Cor-
po=ationwas hired to prepare a feasibility study, which would be
presented today, and Dr. Per Bruun, a world authority on beach erosion,
was employed as a consultant. He commended the Beach Erosion Commit-
tee, with Councilman Talbot as Chairman, on their efforts, and intro-
duced each member.
Following the invocation by Acting City Manager R. D. Worthing, and
the Pledge of Allegiance to the Flag of the United States of America,
the meeting was turned over to Mr. Talbot, who introduced Mr. Harold
Radcliffe, President of Glace Engineering Corporation, and Dr. Per
Bruun. He welcomed the Beach Erosion Committee and said that in all
the meetings the Committee had held, the members had been most faith-
ful in attendance~ further, that City Engineer Mark Fleming has worked
diligently on this project, and, as a whole, the Cormnittee has had the
cooperation of everyone. Mr. Talbot then turned the meeting over to
Mr. Radcliffe.
Mr. Radcliffe stated that a rough draft of the report was being pre-
sented today, on which Dr. Bruun has consulted with Glace Engineering,
and that following the meeting today, it will be printed, copies to
be available to the City in approximately two weeks. He continued as
follows= "This report ~ill cover a number of factors. It is going to
have background in it, rather briefly. There is a tremendous amount
of literature on record, a great deal of it prepared through Dr. Bruun,
who is head of the Coastal Engineering Laboratories at the University
of Florida, incidentally, and we have endeavored in this report to
avoid being repetitious. We have had to, of course, put information
in here which is pertinent, we feel, and informative, but we have kept
it rather brief to keep the report from getting too voluminous. It
is fairly thick, as it is. Today, I am not going to go over the back-
ground information. Z'll Just tell you briefly what we have covered
and then go right into Delray~s situation.
"In the report, we will have the usual background and source of data,
and the introduction, etc., and our general plan of approach. We are
covering in it the factors affecting erosion so that those who care to
read it, and I hope all of you do, will understand some of the natural,
as well as the man-induced factors which cause erosion. We have then
gone into a review of various types of erosion control structures and
erosion control measures, which have been used not only in this coun-
try, but also overseas. As you probably are aware, in countries such
as Holland and Denmark on the North Sea, and England, there have been
tremendous erosion problems there. Ours is just a drop in the bucket
compared to what they run into with those tremendous storms, and they
have gone ahead on very extensive and, of course, very expensive works
that are required to protect the shore lines. We have tried to con-
dense very briefly in this report some of the various types that have
been covered, without going into any detail, because they are really
not germane to what can be applied to Delray.
"After that background, we then get into those ~dt~S:'~£~ctlng
the design of erosion control studies. These are such t~s as t~des,
waves, soil conditions, usage of the beach, aesthetics involved, the
effect on adjacent areas up and down the beach, and the economics of
the problem, and those are discussed herein. At that point, we then
get into the problems at~Delray Beach and our recommendations for
them."
He went on to say that there are four possible t~pes of corrective
measures that could be used to solve Delray's problem, two of which
he would mention briefly and two he would discuss. The first of these
is a breakwater, which is a device of very heavy construction, usually
large blocks of very dense stone, built in the form of a continuous
bar with calculated slopes on the sides and a proper foundation.
These are used normally to protect entrances to harbors, as they take
the brunt of the waves, absorbing the energy so the water behind them
is reduced to a fairly calm state. Theoretically, it would be pos-
sible to build a line of offshore breakwaters here in Delray Beach.
However, that approach has been discarded, as the cost would be pro-
hibitive. These structures must be built offshore and as the water
gets deeper, the wall has to be high enough that it won't be over-
topped in the severe storms that cause the most damage. From an
aesthetic standpoint, there would be a stone wall across the whole
front of the beach.
Another possibility would be groins, either permeable or imper-
meable, permeable meaning open so that water and sand can pass through
them. These are used to slow the water down, changing the pattern so
that sand will drop out, yet let some of the water surge through the
groin. An impermeable groin is solid, similar to a breakwater, but
extending out from the shore, and just absorbs the energy of the
waves.
There are numerous problems with groins as they cannot, in them-
selves, manufacture sand~ they can only hope to trap it. The source
of sand here comes from the littoral drift, which is sand that drifts
southerly throughout the winter season and northerly during the sum-
mer. It is caused by the action of the wind and water bouncing off
the shoreline at an angle, stirring up sand and moving it out and down
a little at a time. If a groin is installed, it will trap sand at
that particular point, but it causes damage downstream from it.
Therefore, if groins were constructed to stop this littoral drift,
they would have to be continued the whole length of the coast line,
as wherever they are stopped, the areas to the south would lose their
beach. They are also undesirable from an aesthetic standpoint. There
are some places where they are essential, if there is a very narrow
beach to be conserved, but that is not the case in Delray Beach.
On this coast, the greatest intensity of wind and the most severe
weather comes out of the northeast during the winter season and causes
the most beach erosion damage. Of course, hurricanes cause damage
wherever they hit, but these are individual cases. Long term erosion
is f~ndamentally caused by the northeast winds, and if.that is taken
into consideration when protective devices are constructed, the great-
est possibility of protection will be afforded.
The approach to erosion control is twofold - first, as a defensive
measure to protect what already exists, such as buildings, roads, etc.,
and secondly, to retain the beach and even gain sand to provide a good
beachfront.
In i9S7, the Corps of Engineers began a study, on which they sub-
mitted a report in 1961, concerning beach erosion in Pa/m Beach County.
They recommended a program of artificial nourishment, widening the
beach by about 100 feet at a level of 10 feet above sea level. The
total cost of this program was estimated at over three million dollars,
of which the Federal government would pay about 4%, making it neces-
sary for local interests to raise 96%, so as yet this program has not
proceeded.
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Glace Engineering, in their study, have considered the entire
beach from the north City limits to the south City limits, both the
public and privately owned beach, totaling approx/mately 13,000 feet.
Beginning at the north City limits and extending southerly for a
distance of approximately 1,100 feet, there is a series of vertical
sea walls, the southern end of which turns into the shore near the
edge of the road. This will be referred to as Section I.
From the southern end of the sea wall to the north end of the
public beach, an area approximately 1,300 feet long, in which there
are a great many large boulders placed along the edge of the road,
is Section II. Sections I and II are privately owned. Section III
is the entire length of the public beach, which is approximately one
mile long. Section IV begins at the southern end of the public beach
and extends southerly approximately 6,500 feet to the south City
limits, which area is all privately owned, and consists for the most
part of apartments, seasonal rental units and large private homes.
The vertical sea walls in Section I have a very high incidence of
reflection of waves in storms, meaning that as a storm wave hits them,
the energy of the wave is directed in two ways - up in a spray over
the top of the wall, and down in a jet of water on the face of the
wall, which causes the sand at the tow of the wall to be churned up
and carried back out with the undertow action of the wave. With each
wave, more sand is carried out until the wall becomes farther and far-
ther exposed. The effect then is that the normal slope of the sand is
changed and flattaned and there is no longer any beach there, and no
long slope on which the waves can break and dissipate their energy.
All the force of the waves is on the wall and sooner or later, failure
is bound to occur. The vertical walls also change the contour of the
beach so that the erosion to the south is exaggerated.
There is a device know~ asa sloping revetment, which is a form'of
sea wall, but instead of reflecting waves, it is set at a long gradual
angle so that it will absorb the energy of the waves. This revetment
is composed of individually poured, heavy, thick, concrete blocks,
which are interlocked into a design and integrated into a complete
plan sloping down at a reasonable angle. Every other block is five
inches higher than the one next to it, to provide a rough surface so
that when the waves roll over it, they will tend to break up, and any
sand carried along will be deposite~ on the beach. At the tow end of
the revetment, which is down about mean sea level, is a wall, which
can be either poured concrete or sheet piling. This is inserted deep
down into the sand, holding the blocks in place and preventing the
sand from washing out from beneath the blocks. Under the whole struc-
ture is a bed of crushed stone and a filter. At the top is a wave
screen, which is a low wall extending about two feet above the top
of the blocks, which prohibits the splashing or uprush of the waves.
The entire revetment is built in a continuous section, and where it
is terminated depends upon the erosion conditions.
Mr. Radcliffe then showed a cross section of the beach, covering
the area from the beach up to the center line of Ocean Boulevard,
with the revetment in place, and explained how it works. This revet-
ment is recommended for all of Section II, which is from the vertical
sea wall to the north end of the public beach, and on down the public
beach a distance of approximately 1000 feet. It is proposed to ter-
minate this wall at that point and smooth it into the beach on the
south end. In the future, if necessary, it can be extended merely by
adding the desired number of sections. At present, it appears that
if the north end can be stabilized with some nourishment, the erosion
condition can probably be satisfied.
In designing a structure of this type, it wo~ld not be practical
to design something that would prevent all damage and all erosion
100 per cent, as it would have to be so strong and heavy in order to
eliminate all future maintenance that the initial cost amortized
would be more than the maintenance cost on a lesser structure. The
recommended design will be a permanent structure, but every 10, 15
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or 20 years, there will be storms that will cause some damage to the
structure. It is a flexible device, however, and if part of it washes
out, the area in back will still have been protected.
To integrate this structure so as to have the optimum value, it
is necessary to make some improvements to the north. The private pro-
perty owners to the north have already begun by dumping rubble in front
of the vertical sea wall and around the southern end of it. Proposed
in Glace's report are two alternates - one, to continue the rubble
north of the public beach on up to the vertical sea wall, matching as
closely as possible the shape of the revetment that will lie to the
south so there will be a fairly smooth transition. As an alternate,
the owners could use this same t~pe of structure, but this has been
discussed with Dr. Bruun and he feels it would not be as desirable as
the rubble. There are several technical reasons for this, in addition
to which, the rubble is somewhat less expensive, so it appears that the
appropriate thing to do would be to continue the rubble protection,
reshaping it a little to conform with the revetment to the south, to
tie it in. It would have been preferable to lay this rubble on a
filter to reduce sinking and future maintenance, but Dr. Bruun will
have to decide whether or not it would be worth taking it out and
putting in a filter.
The beach is losing sand which is drifting southerly by littoral
drift~ it is also losing sand based on the fact that the sea level is
rising annually. It has been calculated at one quarter inch per year
for the past twenty years. This apparently happens in cycles and
there is no way of predicting it. This slight rise over the entire
bottom, going out from a half mile to a mile, causes a change in the
configuration of the ocean bottom. This brings the water up and
causes a rather dramatic effect on the beach. It requires quite a
quantity of sand on the beach level to offset this, as that sand ul-
timately drifts back down to spread over that wide slope. The ratio
commonly used as a rule of thumb is 100 to 1~ in other words, an inch
out in the water requires 100 inches from the beach, by virtue of dif-
ferent widths and slopes. Dr. Bruun has suggested that in addition
to the protective measures already discussed, an annual maintenance
program be initiated with this construction, adding sand in Sections
II and III, to offset this annual loss through sea level. It would
require roughly 20,000 yards of sand the first year, and in subsequent
years, it would probably be reduced to half of that. It would then
have to be watched and sand added as necessary to maintain stability
down the beach. In the long run, this would not be very expensive -
probably about $10,000 or $15,000 per year, but it would be money
well spent as these structures are very expensive and have to be pro-
tected. Since the littoral drift is to the south, by applying in
September or October the quantity of ssnd Dr. Bruun has recommended
in Sections II and III, the northeasterlies will tend to carry this
sand south, and it will improve all the rest of the beach.
Mr. Radcliffe stated the type of program Glace has recommended
will do the job for Delray Beach in that first, it will give the City
the protection factor, which has been mentioned. Secondly, it would
re-establish a uniform and attractive beach, and third, it would be
poss/ble to maintain the beach at a very reasonable cost per year.
The maintenance of this system would have to be taken into considera-
tion in the City's annual budget, just as the City appropriates funds
for maintenance of streets, etc.
Dr. Bruun has made another suggestion, which would not only im-
prove this revetment hydraulically, but would also be good from an
aesthetic standpoint. The blocks of the revetment come up to a ver-
tical wall. This wall would normally be covered with sand. Dr. Bruun
suggests that this wall or wave screen be moved back about 10 feet
and a promenade be built between it and the top of the blocks. This
promenade would be made of concrete slabs and sloped so that most of
the energy of the waves would be dissipated on it and would not splash
over the wave screen on to the landscaped area. The wave screen could
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then be an attractive, narrow brick wall about two fe~t high' This,
of course, will increase the cost, but it would only amount to the
cost.of a ten foot sidewalk.
Cost estimates for this entire project have been based, in part,
on the experience of contractors who have constructed this ty~e of
revetment on the lower east coast, plus an allowance for contingencies.
Estimated cost for Section I, approximately 1,100 feet of rubble con-
struction, is $104,500. Section II, which is a combination of the
fill and revetment for approximately 1,300 feet, estimated cost is
$223,100. For the City property, Section III, if the entire 5,400
feet were done, the cost wo~ld come to approximately $842,000. As
previously indicated, there is a possibility that the public beach
could be done in phases of approximately 1,000 feet or less. This is
a matter that will have to be discussed with the Council and Beach
Erosion Co~mittee, as it depends entirely on the financing. Nothing
has been shown for Section IV as there appears to be no serious ero-
sion at the moment. There is a pocket at the south limits of the
public beach, at the Seagate Club, where there has been damage~ some
of the sidewalk was taken out and the swimming pool at the Club was
undermined. This has since been repaired and filled, and has actually
accreted. It is recommended that this pocket be improved on a nourish-
ment basis, and take a calculated risk that it will hold, with the
other improvements to the north.
There are periodic maintenance costs on this type of structure,
but they would be relatively nominal - for example, Section II is
estimated at about $1,500 per year and the public beach, about $5,800
per year. Of course, this does not include the cost of the artificial
nourishment Dr. Bruun has recommended.
Several possible sources of financing have been investigated, but
they are not likely sources. With regard to the Federal government's
program in 1961~ that is, adding 100 feet to the beach at a ten foot
elevation. On this project, they were willing to pay 4% of the cost.
However, their policy does not allow them to pay for any other type
of work. The solution recommended by Glace Engineering for Delray
Beach is not acceptable for Federal participation. The only way it
could/be made acceptable would be for a request to be made through
the ~ublic Works Committee of the Congress for study of the beach at
Delray only. This would be referred to the Corps of Engineers, who
would estimate the cost for the study, and the Committee would, pre-
sumably, appropriate the funds for said study. The Corps of Engi-
neers' recommendation would be based on the entire coastline, and if
they again recommended nourishment as the only solution, and the City
agreed to proceed on that basis, the government would participate
possibly to the extent of 50%. However, it would have to be done
exactly as the Corps of Engineers recommended and this might or
might not serve Delray Beach's particular interests best. There is
a different philosophy here, based on protection against damage vs.
correcting the erosion of sand.
On the State level, erosion functions have been turned over to the
Board of Conservation. They are to establish funds and a program to
operate a beach erosion program throughout the State. An association
known as the Florida Shore and Beach Preservation Association, which
is composed of interested individuals, members of City and County
governments, etc., a non-profit organization, is endeavoring to get
through the Legislature a substantial sum of money, to be placed in
the Department of Conservation budget for projects such as this.
Their hope is that legislation can be established whereby the State
would ~ay 50% of the non-Federal funds. However, this is a prospect
for the future.
A portion of Section II is State Road Department right-of-way
and has already been protected with rock and rubble, but this is not
necessarily a permanent solution. It is recommended that some effort
be made to ascertain if the State Road Department would be willing to
participate on this project, as concerns the area they are now pro-
tecting.
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The ~!y othek~Way to finance a project of this nature is for the
City of handle it in the same manner as any other large public works
proJect~S~ch as sewer or water. This would have to be done through
a revenue issue of some t~pe and the City is cognizant of what is
involved~
Mr. Radcliffe closed by stating that it appeared necessary to con-
centrate on local efforts for financing, if this project is to get off
the ground.
The meeting was then turned over to Dr. Per Bruun, who stated that
there was no reason for him to review what Mr. Radcliffe had already
said, but that the fact has to be faced that the sea level is rising
and something has to be doneto cope with the problem.
He went on to review the background of the beach erosion problem
on the east coast of Florida. He mentioned the recent hurricane
damage in Jacksonville Beach and stated that this had been declared
an emergency situation and a combination of revetment and beach nou-
rishment had been recommended by the Corps of Engineers. He com-
mented that the revetment could take care of storm tides from hur-
ricanes, as well as northeasters, which are the initiators of beach
erosion. Revetments, therefore, have been recommended for Dural
County and for the rest of Florida, ss well. These are what Glace
Engineering is recommending for Delray Beach. They have been used in
Jupiter Island, some 8,000 feet, and they are now building them in
South Palm Beach. Deerfield Beach is using a combination of revet-
ments, beach nourishment and a special type of groin. As they have
a very small beach with a very steep offshore bottom, it was necessary
to use all three instruments. Here at Delray Beach, he feels two of
these instruments should be used, but not the third - groins, as
groins would not apply on a long stretch of beach. He said he was
in complete agreement with the type of protective device Glace has
recommended for Delray Beach.
He then discussed the various types of revetments. In some places
in Holland and England, a revetment has been used that is built in the
form of steps. German revetments are very similar to the checkerboard
design recommended here. He said there is one advantage in the check-
erboard design in that the step type revetments, instead of being one
vertical wall, are perhaps 20 vertical walls, whereas the checkerboard
tends to buildup the sand over it.
The first checkerboard revetment in the United States was built
at Jupiter Island and completed on September 9, 1960. It was bap-
tized by Hurricane Donna the following day and there was no damage
to it.
In the some 10,000 feet of revetment constructed in Florida, there
has been about 160 feet, a very small percentage, that has had some
sinking. This was ~ue to the sheet piling not being as adequate as
it should have been. This difficulty has since been corrected in new
construction an~ they are being made stronger by the use of further
reinforcement between the concrete slabs. He strongly recommended
that the City not hesitate in taking steps to provide for this pro-
tection for its beach.
He went on to explain his method of computing the amount of sand
required in the nourishment portion of the program and discussed his
reasons for recon~nending that a ten foot promenade be built on top of
the revetment.
Mr. Talbot asked about the source of sand for the nourishment, and
Dr. Bruun replied that one source has been from the ocean itself, but
that this type of operation provided hundreds of thousands of yards,
and it wouldn't be sensible to into that type of program, such as the
operation at Jupiter Island, for only 20,000 yards of sand, which is
recommended here. It would probably be more economical to find some
land source, which is available in this area.
Dr. Bruun was asked whether Delray ~each receives any benefit
from the sand that is being dumped on the beach at Bo~nton Inlet, and
he replied that because of the groins, sea walls an~ reefs between
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the Inlet and Delray, Delray gets hardly any benefit from the opera-
tion.
Col. Dugal Campbell asked if Delray Beach could substitute arti-
ficial nourishment, as the government recommends, for this revetment,
as it would be much cheaper and would not require a revenue bond is-
sue. Dr. Bruun stated that the program the government recommended
probably would not take place for some years and if the City did this
work on its own, the neighboring properties to the south would even-
tually get the benefit from it, rather than the City.
Mr. Saunders asked if all the phases of this program are very
much intertwined; in other words, if the private owners in Section I
and the County in Section II to not wish to participate in the pro-
gram, would the City be able to proceed with Section III. Mr. Rad-
cliffe stated that this was one of the basic reasons for having the
program set up in four sections. The recommended improvement for
Section I would very definitely be desirable and help Section I, but
it can be dropped and the program started at Section II. The same
thing applies to Section IV. However, Sections II and III, while
they are separate, are integrated and tied together, and have to be
considered as a whole.
Mr. Radcliffe was asked how the financing could be worked out in
the areas the City does not own, and he replied that projects of this
type have been financed, on the west coast at least, by assessing the
benefitted properties. Naturally, Section III, the public beach, is
owned solely by the City, but in Section II, the detailed ownership
would have to be developed. There would be a legal problem that
would have to be referred to City Attorney Adams. The land in Section
II has eroded naturally. If the property line is now below the high
water mark, that property has been lost to the owners, under the laws
of accretion and (reduction). If the City artificially restores the
land, there would have to be a legal determination as to who owned
that restored land. If all the land is Section II is privately owned,
a program of assessment against the benefitted properties could be
established. He said there are a lot of legal details to be worked
out in this section, but he felt it would be proper to make some sort
of assessment against the private property owners.
Someone asked if the revetment could be built a section at a time,
year by year, in perhaps 200 foot sections. Mr. Radcliffe stated
this could be done, but the length of section suggested was about
1,000 feet. He pointed out that where this revetment is terminated,
there must be a very strong cut off wall well in back of the revet-
ment, to prevent storms from washing out in back of it, along with a
rubble protection. This is quite expensive. If the sections are too
small, there will be a series of very heavy, expensive construction
that, the following year, will be just wasted. In other words, the
investment in the cut off walls would be good only for one year.
Mr. Radcliffe was asked to again point out on the drawing the
boundaries of the different sections of the program.
As there were no further questions, Mr. Talbot thanked Dr. Bruun
for his interesting discussion; also Mr. Radcliffe for his excellent
presentation. He then turned the meeting back to the Mayor, who
thanked the Beach Erosion Committee and said that today's meeting
shows what can be acoomplished when a Committee really functions,
that the Committee members have donated hundreds of man hours to
bring the project to this point. He stated the next step in the pro-
ject is for the Erosion Committee to meet and bring to the City
Council a positive recommendation.
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