• TABLE OF CONTENTS
HIDE
 Cover
 Title Page
 Foreword
 Table of Contents
 List of illustratioins and...
 Introduction
 Florida field investigations
 Shore protectioni methods...
 Laboratory investigations
 Dimensional analysis and simil...
 Future laboratory investigatio...
 Proposed wave tank at the University...
 Literature cited
 Bibliography
 Back Cover














Title: Beach erosion studies in Florida
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Table of Contents
    Cover
        Cover 1
        Cover 2
    Title Page
        Page 1
        Page 2
    Foreword
        Page 3
        Page 4
    Table of Contents
        Page 5
    List of illustratioins and tables
        Page 6
    Introduction
        Page 7
        Page 8
        Page 9
        Page 10
    Florida field investigations
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
    Shore protectioni methods and materials
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
    Laboratory investigations
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
    Dimensional analysis and similitude
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
    Future laboratory investigations
        Page 64
    Proposed wave tank at the University of Florida
        Page 65
    Literature cited
        Page 66
    Bibliography
        Page 67
        Page 68
    Back Cover
        Page 69
        Page 70
Full Text
Beach Erosion Studies in Florida
by
Howard J. Hansen
Associate Professor of Civil Engineering
FLORIDA ENGINEERING AND INDUSTRIAL EXPERIMENT STATION College of Engineering University of Florida Gainesville
Bulletin No. 16 June, 1947


THE FLORIDA ENGINEERING AND INDUSTRIAL
EXPERIMENT STATION
The Engineering Experiment Rial ion was first approved by the Board of Control at its meeting on May 18, 1929. Funds for fhc Florida Engineering and Industrial Experiment Station were appropriated by the Legislature of the State of Florida in 1941. The Station is a Division of the College of Engineering of the University of Florida under the supervision of the State Board of Control of Florida. The functions of the Florida Engineering and Industrial Experiment Station are:
a) To develop the industries of Florida by organizing and promoting research in those fields of engineering, and the related sciences, bearing on the industrial welfare'of the State.
b) To survey and evaluate the natural resources of the State that may be susceptible to sound development.
c) To contact with governmental bodies, technical societies, associations, or industrial organizations in aiding them to solve their technical problems. Provision is made for these organizations to avail themselves of the facilities of the Engineering and Industrial Experiment Station on a co-operative financial basis. It is the basic philosophy of the Station that the industrial progress of Florida can best be furthered by carrying on research in those fields in which Florida, by virtue of its location, climate, and raw materials, has natural advantages.
d) To publish and disseminate information on the results of experimental and research projects. Two series of pamphlets are issued: Bulletins covering the results of research and investigations by staff members; and Technical Papers, reprinting papers or reports by staff members which have been published elsewhere.
For copies of Bulletins, Technical Papers or information on how the Station can be of service, address:
The Florida Engineering and Industrial Experiment Station College of Engineering University of Florida Gainesville, Florida
Joseph Weil, Director


Beach Erosion Studies in Florida
by
Howard J. Hansen
Associate Professor of Civil Engineering
FLORIDA ENGINEERING AND INDUSTRIAL EXPERIMENT STATION College of Engineering University of Florida Gainesville
Bulletin No. 16 June, 1947


Permission is given to reproduce or quote any portion of this publication providing a credit line is given acknowledging the source of the information.


POKKWOKD
This bulletin is the first of a scries pertaining to beach erosion problems in Florida. As additional data are developed and experimental results are obtained, they will be published.
The purpose of this bulletin is to review beach erosion problems in Florida, to discuss present methods and materials used in the design of shore protection structures, to review previous laboratory investigations, and to present a plan for future investigation of the factors contributing to beach erosion phenomena.
A typical field investigation that has been made at a particular site on the coast of Florida has been reviewed. This investigation illustrates the vast amount of data required to make an intelligent study of an erosion problem; but, in addition, it is evidence of the need for basic research which will provide a core of fundamental knowledge. The art of shore protection is still in its infancy and considerable research and study arc necessary before the problem of beach protection can be reduced to an exact science.
At present there is probably no limit to the types of design that can be used in shore protection structures, but it must be remembered that there are no two localities with exactly the same conditions and no stereotyped designs which will apply to all localities in the Slate of Florida.
In addition to a discussion of general and specific laboratory investigations that have been made, dimensional analysis and similitude as applied to beach erosion model studies are presented.
Finally, a list of future general investigations of beach erosion problems pertaining to beach erosion as a science, and the proposed wave tank at the University of Florida are discussed.
Joseph Weil. Director


ACKNOWLEDGEMENT
The author is grateful for the criticisms and suggestions offered by Messrs. Robert M. Angas, M orris N. Lip]), and F. C EIIhh in their review of the contents. The illustrations representing typical cases of beach erosion along Florida shores and shore protective structures were provided by Mr. Angas and Mr. Lipp. The pictures were taken at sites where these men were making beach erosion studies and are typical of conditions in Florida. This bulletin would not be complete without these illustrations and the author is grateful for the use of the originals.
H 1


CONTENTS
Pajyo
Foreword....................................................................................... 3
Acknowledgement ............................................................. 4
Introduction ........................ 7
Florida Field Investigation ......................................................... 11
Beach Erosion Study at Hollywood Beach. Florida............ 11
Beach Erosion Study at Daytona Beach. Florida .............. 33
Shore Protection Methods and Materials ................................. 34
Protective Structures ............................................................. 34
Location and Design of Protective Structures .................... 35
Materials .................................................................................. 42
Conclusions............................................................................. 49
Laboratory Investigations .................................................... 50
Wave Studies ............................................................................ 51
Abrasion of Beach Sand ..................................................... 54
Shore Currents and Sand Movement.................................... 55
Model Studies of Particular Sites ........................................ 57
Dimensional Analysis and Similitude...................................... 58
Future Laboratory Investigations .............................................. 64
Proposed Wave Tank at the University of Florida ................. 65
Appendix A. Literature Cited .......................................... 66
Appendix B, Bibliography ............................................................ 67
[53


ILLUSTRATIONS
Figure Page
1. Septic Tank at Fernandina Beach Which Was Buried
in the Sand .......................................................................... 7
2. Erosion at Fernandina Beach 8
A. Water Works at Vilano Beach ......................................... 0
1. Houses Being Moved Back from Encroaching Water
at Vilano Beach ................................................................ 9
5. Erosion on Jupiter Island .................................................... 10
6. Permeable Concrete Groin near Palm Beach ..... 35
7. Typical City of Miami Beach Groin .............................. 36
8. Typical Groin 37
9. Percentage Losses in Weight Due to General Corrosion
of Steel and Copper-Steel Bars After 10-Year Exposure.. 44
10. Abrasive Action on Concrete Sea Wall South of
Boynton Inlet ....... 45
11. Beach at Hollywood, Florida ........................................ 46
12. Abrasion of Steel Groins at Palm Beach ........................ 46
13. Untreated Timber Groins at Palm Beach ...................... 48
14. Groin System for City of Miami Beach ............................ 48
15. Typical Groin at City of Miami Beach .............................. 19
16. Abrasion of Steel in Groin at Baker's Haulover 50
TABLES
Number Page
I. Measured Thickness of Steel Sheet Piling in
Bulkheads .............................................................................. 43
II. Observations on Pitting of Steel and Cooper-Steel
Bars after 10-Year Exposure ........................................... 43
III. Observation on General Corrosion of Steel and Copper-Steel Bars after 10-Ycar Exposure .................................. 44
IV. Dimensions of Physical Quantities .................................... 59


Beach Erosion Studies in Florida
INTRODUCTION
The Slate of Florida has 1,277 miles of tidal shore line. This figure does not include the coastal islands, for with these added the shoreline is approximately 2,'MW miles. Of the 1,277 miles of shoreline around the mainland of Florida, 778 miles are sandy beach, which is one of the main attractions of tourists. Many beach investments contribute one of the most highly valued assets to the State. Yet, these very assets are in great danger of being partially or fully destroyed unless the erosive forces of waves and currents are properly checked by the installation of suitable control works. Much damage has already been done and a recent erosion investigating committee of congressmen has received first hand evidence of serious damage to Florida West Coast waterfront properties. In observing several beaches this committee witnessed the following:
Pip. 1. Septic lark at Fernandina Beach which was buried in the sand.
1. Miles of beach frontage from which hundreds of houses have been moved during the past few years. The steadily encroaching water was threatening to undermine these houses.


Fijr. 2.Erosion at Fernandina Bench.
2. Beach front properties which may soon be in deep water unless some means is found to stop the wearing away of existing frontage.
S. A highway which was at one time separated from the beach by a row of houses is now crumbling in the water and big trees that once lined it on both sides have been uprooted and lie dead in the water.
4. A wide expanse of shifting channels separating Anna Maria Island and Longboat Key, which a few years ago were joined by a bridge that was weakened by erosion and destroyed by storm.
5. Piles that once supported homes sticking out of the water in the Gulf and an artesian well pouring fresh water into the Gulf, that was drilled a few years ago on dry land to supply a beach community.
(J. Rows on rows of waterfront lots on which the water had broken through retaining walls and now threatens to undermine the houses.
The Manatee County Commission, early in 1945, raised funds, which were matched by the Federal Government, to start a survey to determine the best method of preventing further
I 8 1


Fig. 'i.Water works at Vilano Beach.
V\g. I. Houses beinn moved back from encruuehinjf water at Vilano [Beach.
erosion and to stabilize the beaches. In the past several years other Communities and Agencies in Florida have requested the Shore Protection and Beach Erosion Boards of the War De-parlment to make similar studies of beach erosion problems. These requests are further evidence of the need for protective measures against the destructive forces set-up by waves and currents. The Shore Protection Board has made studies at Atlantic Beach, St. Augustine Inlet, Matanzas Inlet, Clearwater Beach and Madiera Beach; and the Beach Erosion Board has made studies at Daytona Beach, Blind Bass, Hollywood Beach, Balm Beach, Miami Beach, and Haiilover Inlet.
Mr. F. C. Elliot, Engineer and Secretary for the Trustees of the Internal Improvement Fund of the State of Florida, recently
[!)]


FiR. 5.Erosion on Jupiter Island.
made a report on whether or not material may he taken from bottoms seaward of Virginia and Biscayne Keys without damage to the beaches in this area of Dade County. Additional evidence for the need of protective measures to arrest the damage being done to beaches in this area by erosion is contained in the following statements from Mr. Elliot's report. "In my judgment the continued artificial removal of material from the bottoms off shore from the two Keys inside of the 12-foot contour would aggravate beach erosion. The trilling amounts of sand removed under permits granted by the Trustees of the Internal Improvement Fund has been insufficient to have measurable effect on the beaches. Both Keys suffered serious erosion long before permits for sand removal were granted. On Virginia Key the beach is receding landward at the relatively rapid rate of twenty to forty feet yearly. In thirty-three years the sea has wrested from the land of Virginia Key some 130 acres of ocean front property. If it is worthwhile for the State to refrain from selling sand from the seaward bottoms to avoid danger of aggravating beach erosion it is likewise worthwhile for local interests to take remedial measures against the sea in its everlasting assault upon the land".
From all of the foregoing examples and evidence of beach erosion and the resulting damage in the State of Florida, it is apparent that something ought to be done. The main question is, "What is the proper procedure and what are the best methods for preventing beach erosion?" Too often, in the past, there has been a lack of uniformity of field and office data secured and in methods of making studies at particular beaches before designs of protective works were begun. In many cases struc-
f 10 1


turcs designed to eliminate beach erosion have proved effective, but some have proved useless and others have done more harm than good. Throughout the majority of beach erosion investigations it is evident that little is known concerning the individual factors which contribute to beach erosion. The problem is very complex, but until the effect of all the variables which cause beach erosion is known, the best means of controlling erosion will remain a mystery. Beach erosion control is a scientific and engineering field in which there is a definite need for basic research. Research has found the scientific means to control or check the destructive fury of rampaging rivers, and similar studies providing a core of fundamental knowledge and principles with a view to preventing erosion of shores by waves and currents are necessary.
Beach erosion studies in Florida may be divided into four general classes; i.e., experimental investigations to check or develop theoretical laws governing the action of wind, waves, and currents, and the relationships between these forces; series of studies on the effect of wind, waves, and currents on sand beaches; proper method of conducting field investigations and data to be secured for any particular area; model studies of a particular beach or harbor and the effect of artificial and natural protective structures on the shoreline of beaches.
FLORIDA FIELD INVESTIGATIONS
A review of a typical beach erosion study made in Florida should provide valuable information on the preservation of our beaches, and illustrate the vast amount of data needed to make an intelligent study. The studies that have been undertaken in Florida were field and office investigations of specific problems in beach erosion at a specific site. It must be remembered that each locality presents a different problem and that it is inadvisable to prescribe a particular plan for the protection of a beach just because it has proven effective elsewhere.
IKA< H KKOSION STI'IIY AT HOLLYWOOD HKACII, I LOKIDA
An investigation and study of the problem of beach erosion at Hollywood Beach, Florida, was made in lfl:Jfi-l!):V7. This cooperative study was made by the United States (acting through the Chief of Engineers, the Beach Erosion Board, and the District Engineer, Jacksonville, Florida) and the state of Florida (acting through the Engineering Experiment Station,
I 11 I


University of Florida, and the City of Hollywood Beach, Florida). The study involved an investigation of the conditions causing erosion and changes in the beach at Hollywood Beach, Florida, from the southern limits of the city northward to Port Everglades, a distance of about 6.2 miles. The study was made to determine the best methods of preventing erosion and the changes which were taking place on the beach.
The following is extracted from the report of the Beach Erosion Board:
"7. Location and descriptionHollywood Beach is a South Florida seashore resort situated on the Atlantic coast about 17 miles north of the entrance to Miami Harbor. The location is shown on Plate 1 herewith on United States Coast and Geodetic Survey Chart No. 3260. The city limits extend from a point about 2,100 feet south of the Hollywood Beach Hotel northward to Port Everglades, a distance of about 6.2 miles. The resort is attractively laid out, with modern public-service facilities. It has a normal population of about 5,000 inhabitants. During the winter season the population is increased by approximately 15,000. The main highway from Miami to points north passes through the city as do the Florida East Coast Railroad and the Inlracoastal Waterway. New River empties into the ocean through New River Inlet within the limits of this study.
"8. Present structures.A portion of the beach is partially pi'otected by a steel sheet pile bulkhead 1,380 feet long built in 1925. The bulkhead extends northward along the highwater line from near the north end of the Hollywood Beach Hotel and is backed by a light wood boardwalk 30 feet wide with the outer edge on top of the bulkhead. Three short groins of wood construction were built in 1935 in front of the hotel. There are 10 groins 50 feet to 120 feet long spaced about 150 feet apart along the bulkhead and 8 more with the same spacing beyond the north end of the bulkhead. These latter groins constructed of untreated timber in 1927 are now generally in very poor condition. Some of the groins have their inshore ends in fairly good condition and those portions of the groins .appear to be holding the beach sand to some extent. All existing groins along this beach appear to be too short, and they are not properly spaced.
"9. A concrete walk about 1% miles long was constructed along this beach in 1925. It was completely destroyed and washed away during the great storm of 192fi. Some of the con-


crete slabs from the structure were found on the west side of the Intracoastal Waterway which runs parallel with the beach and about 900 feet therefrom. Sometime after the 102(5 storm the municipality constructed a wooden boardwalk about seven-eighths of a mile long. In November, 1935, all of this structure except the portion along the steel sheet pile bulkhead was destroyed. The destroyed sections of the boardwalk have not been rebuilt. An improvised pavement has been constructed to serve until some dependable protection is provided for the beach.
"Hi. At an inspection in April, 1930, the entire length of Hollywood Reach showed evidence of recent erosion in the form of a scarp S to 11 inches high. At limes erosion permits waves to reach the bulkhead for half its length and cause additional scour.
"11. The present beach front buildings are principally located behind the steel sheet pile bulkhead which has provided protection during times of the tropical storms. It is believed locally that the unoccupied areas both north and south of the present bulkhead would be built up rapidly if they were protected against erosion during storms.
"12. Shore line changes.A study was made of all available maps showing the location of the high water shore line. The high water shore lines from surveys made by the United States Coast and Geodetic Survey In 1883 and 1927 and by the United States Engineer Department in 1930 were compared by superposing them as shown on Plate 2.
"19. The net change between 1883 and 1930 has been erosion in the northern half of the beach of from 0 to -100 feet, and a fill along the south half of about 700 feet tapering down to no change at the Hollywood Reach Hotel, thence erosion of about 10 feet to the southern limits of the city.
"20. Changes in offshore depths.The fi-, 12-, and 18-foot depth curves from hydrographic surveys made by the United States Coast and Geodetic Survey in 1883 and 1928, and by the United States Engineer Department in 1930 are shown superposed on Plate 3. By comparing the location of these curves the underwater changes may be ascertained.
"21. The net changes in the olfshore depths may be summarized as follows: The 6-foot curve has moved shoreward except at the southern end where a seaward movement is shown ;


the 12-foot curve has moved shoreward along ihe north half of the beach and seaward along the south half; the 18-foot curve moved shoreward along the north half and seaward along the south half. These movements of the depth curves show a progressive erosion of the underwater area along the northern section of the beach and a prograding at the south end.
"25. A comparison of profiles of the bottom was also made from surveys of 1883 and 1928 by the United States Coast and Geodetic Survey extending from the shore line seaward for a distance of approximately 2 miles. The location of the profiles selected were as follows: "A", at the southern extremity of Hollywood Beach ; "B", a point about half way hetween point "A" and the jetties at the entrance to Port Everglades; and "C", a point just north of the 1936 location of Dania Inlet. These profiles are shown superposed on Plate 4. The three profiles for each survey were averaged and the average or composite profiles thus obtained for each survey were also superposed as shown by the lower figures on Plate 4.
"26. A comparison of the profiles at "A" shows a considerable shoaling from the water line out for a distance of 2,000 feet. From this point seaward for about 3,500 feet there are alternate areas of accretion and erosion. Beyond this last point there is a considerable erosion for 2,500 feet, then accretion to the limit of the profile at a depth of 110 feet where there appears to be no change1.
"27. On line "B" there was erosion from the shore line to a point about 1,000 feet seaward followed by alternate fill and erosion for the next 1,500 feel. From this last point the profiles show fill to a distance of 7,000 feet from shore. Beyond this there was first approximately 500 feet of erosion, then 1,700 feet of fill followed by 1,300 feet where there had been erosion.
"28. On line "C" there was a slight accretion from the shoreline for a distance of 2,000 feet. Beyond this the changes were quite irregular and followed in general the changes noted at "B".
"29. The composite profiles show that on the whole for the entire area there has been a general fill or shoaling over the offshore area from the shore line for a distance of about 7,000 feet, where the; depth of water is 40 feet and the depths of the
I M 1


till varying from 0 to 8 feet. There was a slight deepening from 0 to 5 feet for a distance of about 600 feet, thence a shoaling from 0 to 4 feet for about the same width where the depth of water is 68 feet. Beyond this point there was a continued deepening for a width of about 1,500 feet to the outer limit of the comparison.
"30. Hydrography.A hydrographic survey was made in connection with this study in May, 1036, covering the offshore area to a depth of about 20 feet below mean low water between the southern limits of Hollywood Beach and the south jetty at Port Everglades. The results are shown on Plate 5. The under-water terrace was found fairly uniform out to the 12-foot curve, which lies from 900 to 1,000 feet from the shore line. Beyond this there is a longshore channel enclosed by a reef lying roughly parallel to the shore line, being 1,500 feet therefrom at the north end of Hollywood Beach and 2,500 feet at the south end. The depths on the crest of this reef vary from 9.6 feet at the northern end to 18.5 feet at the south end. The bottom outside the 12-foot curve is interspersed with rock areas. All rock in these offshore areas is believed to be limestone formed of consolidated shell fragments, subject to slow disintegration through severe disturbances by storm waves.
"31. Profiles were made from certain sounding lines of this survey and are shown on Plate 6. These show height of the berm varying from 6 to 10 feet above mean low water, the slope of the foreshore from 1 on 6 to 1 on 30, averaging about 1 on 17. They reveal also the longshore channel and the reef at the outer edge of the channel between 1,500 and 2,500 feet from the shore line.
"32. Ocean currents.The velocities of the ocean currents were measured by means of subsurface floats. The observations covered one complete tidal cycle. The area within which the float observations were made is shown on Plate 5. During the time of the observations the winds were from the southeast, east, and northeast, with velocities of from 7 to 10 miles per hour.
"33. Plate 7 shows the plotted curves of velocities over the area and the approximate location of the crest of the offshore reef in that area. These curves show that the current velocities are generally greater inside the reef than outside. The velocities
I ir. |


outside the reef varied from 11 to 33 feet per minute while those inside the reef were from 10 to 63 feet per minute. While the results of these limited observations are not conclusive, it appears that the direction of the Hood flow is normally south along the beach and that of the ebb is in the opposite direction, north along the beach.
"34. Beach material.The beach material is not compact. It is composed of comparatively fine sand mixed with a large amount of finely broken shell which gives it a dark yellow color. Samples of the beach materials were obtained from points 1,000 feet to 1,500 feet apart, at about the elevation of midtide and the median diameters, the percentage of voids, and the amount of shell particles were determined. It was found from the 23 samples analyzed that there is neither uniformity in the size of the material nor in the ratio of sand to shell in the mixtures. The median diameter varied from 0.466 to 1.741 millimeters, but there is no uniformity in increase or decrease in the median diameters from one end of the beach to the other. Large-sized grains were found adjacent to samples composed of finer grains.
"35. As with the median diameters of the sampled sand, the amounts of shell in the beach samples also varied regardless of the location from which the samples were taken. The shell content of the beach material varies from 44 to 94 per cent. On account of the predominance of the shell content, and the various degrees of fineness of the broken shell, the median diameters of the samples were very irregular. The average shell content in the 23 samples analyzed was 64.5 per cent.
"36. The porosity, or the percentage of voids in the beach material, was more constant. It varied from 30 to 42 per cent and averaged 36 per cent for the 23 samples. The sample containing the least voids, 30 per cent, was that which has the greatest amount of sand, 56 per cent. The sample containing the least amount of sand had 38 per cent voids, slightly above the average of all samples analyzed.
"37. The Twenty-FirstTwenty-Second Annual Report of the Florida State Geological Survey, 1931, contains the results of an investigation of the shell content of the sands on the Atlantic coast of Florida. It was found at that time that generally the shell content of the beach material increases as one goes south along the beaches. The following table, copied from


that report, shows the per cent of shell in the material composing the beaches from Amelia Island to the Upper Matecoml>o Key.
Location Percentage of siiki.i.
Amelia Island, '-j mile south of St. Marys River 1.26
Near St. Johns River Jetty.................. ...... 0.59
3 miles south of Mineral Citv ................... 0.18
Flagler Beach ... '........ 50.90
0.3 miles south of Flagler-Volusia County line 22.31
Daytona Beach .............. 1.43
Cocoa Beach ........ ..... 7.25
(ndiatlantic Beach .............. 23.39
Fort Pierce .................. ......... 16.07
Olympia Bench 41.86
13.2 miles north of Palm Beach ............ 45.68
Rivera.......................... ......... 42.70
Lake Worth ..... 43.6
Boca Raton ....... 41.64
Hollywood ....................................53.40
Miami Beach, 10 miles north of channel at south end 73.85 Miami Beach, 5 miles north of channel at south end 40.36
Islemorada .............................. ....... 97.45
Upper Matecombe Key 97.52
It appears that the above determination of the shell content of the different beaches was made from one sample from each beach. The amount of shell found in the Hollywood Beach sample at that time was 53.4 per cent. From the 23 samples analyzed for the present investigation the average shell content was found to be 61.5 per cent. It is not believed that the average shell content has increased since the time of the State Geological Survey investigation, but it is probable that the difference is duo to the selection of the samples analyzed.
"38. Wash borings were made along the foreshore for the full length of the beach under investigation to determine the character of the underlying materials and the depths at which bedrock is found. Sixty-four borings were made at 200-foot intervals and 12 typical borings, with their respective locations, are shown on Plate 8. In general, there is a layer of beach sand and shell from 2 to 11 feet thick underlain with beds of shell, line sand, muck, conglomerate, and bedrock. Bedrock was found in all the borings and at various elevations from 5.5 to 16.1 feet below mean low water.
"39. Wind and weather.A wind diagram, constructed from wind data of record at Fort Lauderdale, Fla., for the period August 1, 1931. to June 30, 1935, is shown on Plate 5. The winds from the east predominate, with the southeast winds and the
I. it ]


northeast winds second and third respectively. The direction of the coast line at Hollywood Beach is almost north and south. Northeast, east, southeast, and south winds produce onshore winds while all others are offshore winds. The following table shows the average percentages of time, during the year, that the wind blows from the different directions:
Per Cent Per Cent
North. 19 days.......
Northeast, 45 days East, 116 days Southeast, 85 days
5.2 12.3 31.8 23.3
South, 22 days........
Southwest, 15 days West, 26 days Northwest, 37 days.
(5.0 4.2 7.1 10.0
This summary shows that 73.4 per cent of the winds are onshore and only 26.5 per cent of the winds are offshore and do not affect the shore line.
"40. The vicinity of Hollywood Beach is subjected to the effects of tropical hurricanes which come from the general region of the Caribbean Sea. These storms produce high wind velocities and high tides accompanied by heavy wave action which greatly damages the coast line and structures thereon as well as inland areas lying within or near their paths. Hurricanes along this area usually occur in the summer and fall, during the months of July, August, September, and October. The hurricanes and other east and northeast storms that occur along the Atlantic seaboard cause rapid changes along unprotected beaches. The hurricanes or cyclonic storms approach from the southeast and their winds may be from any direction dependent upon the location of the storm center. The maximum wind velocity of the 1926 hurricane (the most destructive storm to the Florida coast in recent years) was 99 miles per hour, from the northeast.
"11. Tides.The range of normal ocean tides along this section of the coast is 2.5 feet, but this is materially increased during severe storms. The height of water recorded here during the 1926 hurricane was 10.6 feet above mean low water.
"44. Improvement desired.Local interests desire to provide an adequate bathing beach along the city front and to protect the beach so as to prevent serious erosion or recession in the future.
"45. In view of the great cost of forming and protecting a wider beach suitable for bathing over the entire 6.2 miles of ocean front the local interests have requested that for the pres-
[ IK 1


ent study the area to be considered for immediate protection should be the southern 10,000 feet of the frontage studied. This frontage covers the area which is most extensively developed.
"16. Discussion.The results of the field and ollice studies indicate that the shore line of Hollywood Reach has undergone periods of erosion followed by accretion. The resultant changes within the period of record as shown by the shore line locations, Plate 2, has been a recession of beach, except along the middle third where the shore line advanced along the south point of Dania Inlet in 1883. Both north and south of this pro-grading portion there has been recession except along the steel sheet pile bulkhead where there has been no material change since its construction.
"47. The shore line changes along this beach have not been continuous. The greatest changes occur during the tropical storms at which times high tides and high water work together to attack points at higher elevations than are affected by the usual storm conditions. The city engineer of Hollywood Beach stated that during the 1926 hurricane the sand in front of the steel sheet pile bulkhead was completely washed away exposing the underlying rock. These rapid erosions are usually followed by accretions at a much slower rate and occasionally the beach is attacked by a second erosive storm before the filling processes have completely restored the beach fill to its former extent. There has been a gradual and permanent recession of beach.
"is. The study of the underwater changes off this shore shows a general deepening along the north half of the beach and a shoaling along the south half. Although these changes do not fully correspond to or account for the changes that have taken place in the shore line, they show that there is material moving along the underwater teirace which might, if caused to deposit on the shore, assist in restoring the lost l>oach material.
19. The composite profiles show that there has been a fill on the offshore area out to a distance of about 7,000 feet.
"50. The borings show that the beach is underlaid with solid rock and the rock areas which were noted during the sounding for the hydrographic survey indicate that the underlying- rock extends to the offshore reef which is also believed to be composed of rock. This reef, lying roughly paraKed to the shore line and 1,500 to 2,500 feet therefrom, encloses a long-


shore channel through which the ocean currents How north or south, according to the tides and winds. The rock is a shell conglomerate, the gradual disintegration of which supplies the large local quantities of broken shell.
"51. The ocean currents in this longshore channel were found to have generally higher velocities at the time of observation than those outside the reef. During the violent storms which occasionally occur along this section of the South Atlantic coast (par. 40) it is believed that the velocities of the currents in this longshore channel may be increased materially. The beach material with its large percentage of broken shell, is coarse and forms uncompacted deposits which are readily swept away during the storms unless protected against the eroding forces.
"52. Hollywood Beach is inadequately protected against erosive forces by the short steel bulkhead and light wooden groins, most of them in a dilapidated condition. It is particularly exposed at those times when the beach material is completely removed by storms leaving the underlying rock almost bare. There is a section along the developed portion in the vicinity of Hollywood Beach Hotel where the shore was reduced in level from 3 to 5 feet by the developers of the resort, in order to permit a view of the ocean from the boulevard which runs parallel to the shore line and about 800 feet therefrom. High storm tides cause water to flow across this low area and into the Inland Waterway at times, depositing beach material atid debris in the canal.
"53. The Board is of the opinion that in general the thorough and substantial development of a length of beach sufficient to serve the needs of the tributary population and to protect valuable property is preferable to makeshift methods having in view only immediate expediency. The Hollywood Beach Hotel property is of such value as to justify thorough protection. High grade permanent or semipermanent buildings at other portions of Hollywood Beach are not financially justifiable until a fixed line of defense against waves has been provided, preferably with a reasonable expanse of sand in front of them. Without such a line of defense, builders are inclined to erect cheap structures near the shore or to take unwarranted risk in constructing more expensive buildings. A fixed line of defense adequately


designed is essential to a high grade seashore resort along this portion of the coast.
"54. To provide such a line of defense, and to render the beach readily accessible to the public, the Board considers it desirable to have an expanse of sand of reasonable width in front of a promenade or marginal street with suitable bulkheads and groins.
"55. 1'roposed plan of improvement.To meet the desires of the local interests and the needs of the locality, the Board has designed a bulkhead and groin system which will in time arrest enough of the sparsely moving sand and shell to provide the protective beach desired. If it is the desire of the local community to secure an expanse of sand immediately without awaiting the slower natural accumulations, it will be necessary to nil the area between the groins by pumping into these areas sand dredged from the bottom of the inside waterways.
"56. The general arrangement of the recommended protective structures is shown on Plates 9 and 10. The proposed bulkhead extends northward, a distance of 10,000 feet, along the high water line from the southern extremity of Hollywood Beach. From this bulkhead, extending perpendicular thereto, 11 steel sheet pile groins arc to be constructed, 300 feet long and spaced approximately 770 feet apart.
"57. The steel sheet-pile groins are supported by creosoled wood piles. They are securely attached to the face of the bulkhead by interlocking with special T-section piles driven in the wall of the bulkhead at the proper location for the groins. The groins have a level inshore section, 75 feet long, with its top at 5 feet above mean low water, thence an intermediate section sloping down to mean tide elevation (1.25 feet above mean low water) 1J2.5 feet long, thence a level seaward section, 112.5 feet long with its top at moan tide elevation. All groins are of 18-foot steel sheet piles and 24-foot creosoted round wooden piles through out.
"59. The beach (ill, which may be, if desired, pumped in from the bottom of the inside water area, is designed to fill completely the spaces between the groins for the full width of the level inshore section. This will provide promptly a beach with a berm 75 feet wide and 5 feet above mean low water. The estimated slope of the foreshore of the artificially made beach is 1 on 20.
flit 1


"60. Estimate- of cost.
10,000 linear feet bulkhead, at $44.77 per foot................$117,700
14 groins, 300 feet long, at $39.80 per foot ..................... 167,160
Beach fill, 221,600 cubic yards, at $0.10 per cubic yard 22,160 Back fill for bulkhead, 28,800 cubic yards, at $0.10 per
cubic yard ........................................................... 2,880
Engineering, contingencies, and overhead (15 percent) 95,200
TOTAL COST .............................................................$735,000
"61. If the local interests do not require the full width of beach immediately, the above estimate may be reduced by omitting the item for beach fill, reducing the cost to $710,000. It is the opinion of the Board that in time the groin system will accumulate and retain the sand moving southward along the beach to form the beach desired by local interests. If this smaller plan is adopted the groin construction should begin at the southern end of the area and be carried progressively northward."
The foregoing report by the Beach Erosion Board on the beach erosion study at Hollywood Beach, Florida, has been quoted in considerable detail to illustrate the vast amount of field data and office correlation required to make an intelligent field investigation of an erosion problem. All of the items included in the study at Hollywood Beach are not necessarily required for every beach erosion study. However, some studies may require additional information. A comprehensive outline1 covering data to be considered in formulating a plan for a beach erosion study is given below:
I. Past History
a. Geomorphology
b. Tides and other periodic fluctuation in water level
1. Tides
2. Variations in lake levels
c. Winds and storm
1. Local wind records
2. Wind conditions offshore
d. Ice conditions
e. Shore line changes


BOCA R ATOM!
FORT LAUDERDALE
POMPANO VH\
CALVE STON
r.AL
8S
SAVANNAH / ,0
NEW -,t> JU06ILE f ,y V
taupaI > \ ~
c0 \ HOLLY WOOD RlO grahde \J BEACH
/ /'LOCALITY MAP" t_5
I iff o n 140 mi mi
HOL LYYYOOD
/Vf''' ^
.([PORT EVERGLADES
I
l^oahia inlet
HOLLYWOOD BEACH
bakers hau lover
(j
BEACH FR05I0N BOAHO
HOLLYWOOD BEACH, FLA
VICINITY MAP i i o t ? i v ; mi
WA4HIN61 ON ,P^C~" N^Bft
f*'i ........if t
%0I l^.-, .j* 1MT ^*


LEGEND -
H.W. SHORELINE IBBJ US.CICS.
" I8i7----- "
!-u.SEO.
BEACH EROSION BOARD HOLLYWOOD BEACH,FLA.
HIGH WATER SHORELINE CHANGES
KM-) C IOO0 WO MQg WW ft
WASHINGTON. CJX-" NiP*>2.iOJ<


28* 0 '
26 OV
28*01'
I
o c c a h
PORT EvERGlaOES
TRUE MERIDIAN_
LEGEND -
6 F T CURVE 1665
U5C1GS.
6 6 12 12 12" IS" i8 18
ize
1956.......
168S-----
1926 <
i3 ' -
'663-----
428 >J*------
USED U 5 C 4G S
USED U SC AG 5
USED
H W SHORELINE I9J&
BEACH EROSION BOARD HOLLYWOOD BEACH,FLA.
CHANGES IN OFFSHORE DEPTHS
1000 o roco *ooo 40CO "r.
WASHINGTON,0 W^-l.l?J


PORT """ EVERGLADES
PLAN
LOCATIONS OF PROFILES
r i
OCEAN
TRUE MERIDIAN YTfr V^"7 551
= llHOLLYWOOO/
LOCATIONS OF PROFILES /<">
SHOWN THUS-
DISTANCE IN FEET FROM SHORELINE .OmLWIOOO 2000 5000 4OOP SQQQ 6000 7000 8000 tOOO 10000
LEGEND -
1883 USC ICS. 1926
SEACH EROSION BOARD
HOLLYWOOD BEACH, FLA.
COMPOSITE OFFSHORE PROFILES
SCALES AS SHOWN
wamiin^T0i4.C. MtBI. 2.I9J6
. . -i h a. t
rut M >o >C<*Mm HffOM -'' i: ATM.


"7P77"
AREA COVERED BY 0 c e CURRENT OBSERVATIONS-)
26ob
26 Oi
n
ec'ce'
n
_ I > 3 1
PORT EvEROLACES
ift tffacoas ta
DlSECT'ON :0 VLCCiT Y CF WINDS AT FORT L AUDERDAl.r FLA.
YiA=L? AVERAGE AUG 1.1931 TO JUNE S0.I93S
TRUE MERIDIAN
LEGEND -
MEAN LOW WATER CFT CURVE 12 IB"
BOTTOM CHARACTERISTICS-
] HOLLYWOOD
IT* ^rlttHiri
p ROC K
LEGEND 10 M PH. OR LESS 10 TO 20 M P.H. 20 M P H. OR MCR E
s-SAND
NOTES-
SOUNDINGS ARE SHOWN IN FEET AND TENTHS AND REFER TO MEAN LOW WATER
MEAN R^NGE OF TIDE IS 2.5 FT.
SURVEYED MAY l3$
CURRENT MEASUREMENTS. BY FLOATS. yllp.z MACE OVER SHADED AREA ON AUGUST 12,1923.
BEACH RC SIGN BOARD HOLLYWOOD BEACH,FLA. HYDROGRAPHY
cAFt CC**"1 c> (.Mas
CCeftBfc*
"it o iX-17-5
SChiM ml MBit


A L N T ,
PORT EVERGLADES
PLAN
LOCATIONS OF PROFILES
l0O O 20M M*tl n,rr
HOLLYWOOD
1000' 2000' 300y 4000'
1
\ MLW
V 1

,_ Ml W 1
\ i

ML*.
\
\
r M.I r.w.


0) U\ w.
,s
i
ML.W.

* \j

N
J i
+10'
+ s'
0
- S'
\
ML.W.

\
1 r Ml _W.
1
\ 1 |
,_ \ \ M LW.

\ .
Ml w.
\
v (io) >
Ml ..w

Sjj?
> 4 M .w.
v
1



BEACH EROSION BOARD
HOLLYWOOD BEACH, FLA.
PROFILES
SCALES AS SHOWN
WASHINGTON, 0,
2. IMC
NOTE-PROFILES FROM SURVEY MAY I9J6
can coino'ocu vmumi 'co...co*r6# EMM . I MM
flic t-C 17-12 tO k.CCmmm* (rOI ftttfO AM.l^rllT


DISTANCE IN 1200 i&OO
FEET FROM SHORELINE 2000 2400 2600
TiOt AND w AT H f R AUfcuST I
141 w HO T DS
t flCH TO C' ft tffL
1 JOA 1 QUI 5 I 7 M P M EBB o 1
9 OO 30 1 ~*9 1
a io 1 CO a I
3 00 3 30 - -Ji i
0 10 i 2 OO 5 -0.1
O Of 18 JO~ f L OOO 1 1
io >q II OO 3 0
n oo I" SO ~ 3 - t 0.1
ti 30 1) oo 0.1
12 60 K ij jap >
ii :op i oo 0
\ oo i 30 ft * I 1
1 10 00 1 A
2 CO 2 J - 7
2 30 1 oo .0 - > 1.0
y oo 1 30 I
i 10 f> oo T ? 2 3
4 00 10 H E *; *
- 10 00 9 ? 2 *
i 00 36 10 Ebb ? i \
5 K> 00 to - *
00 20 10 - '2 1
C 30 09 '0 - I .
? C3 10 lO - I
NOTE: ALL TIDE
RUNS MADE AUG.12,1936 HEIGHTS REFER TO M L.W
NO t.

l 7 H s
2 9 10 10 3
3 10 LI II 40
S l.kkP 2 52 P
< 2 56 3 59
7 L 03 l SO
3 6 25 i 15
BEACH EROSION BOARD
HOLLYWOOD BEACH. FLA.
OCEAN CURRENTS
SCALES AS SHOWN
WASHINGTON. D C---2.1936
rut .c 12-12-7 T< acco-... RlfCuT e.TCs APR 2i.r7


-T-FT
XJL % n *****
PORT EVERCLAOES
PLAN
LOCATIONS OF BORINGS
loot 0 10O l0 MtUT
J @0
' '^Iiui^i7i|r--*
INDICATES LOCATION Of BORINGsjp^ JJJJl^
+ 4
+ 2
StLSi-Or-
_TRUE MERIDIAN
-0-
HOLLYWOOD
-0-
$3

_0_
BEACH EROSION BOARD
HOLLYWOOD BEACH, FLA.
WASH BORINGS
SCALES AS SHOWN
WASHINGTON, D.C^_ NflV 1.1936
NOTE -
BORINGS MADE APRIL 1936
rill ho I5-IJ-S


ATLANTIC OCEAN
COPING CHANNEL STEEL SHEET PILING
IB"*- N eiocr.3- 6'KIO 1V-0' 10.
C-C
PLAN
I *, HI I 7
COPING CHANNEL-,
U ._ 2O--0"-------
t+10.0' TOP OF BULKHEAD PROPOSED SAND FILL
I 4>T,| ,01. / 1 "/""' R.' "
---/.--J. ^ ,|\ .UM
rr." 8" XB" STRUT Xl,. r TYPICAI
SLOPE I ON 20
WA.I
CAL SECTION
BEACH EROSION BOARD
HOLLYWOOD BEACH, FLA.
PROPOSED BULKHEAD
NOTE
ALL TIMBER TREATED ELEVATIONS REFER TO ML.W.
SCALES AS SHOWN
WASHIhC-TOH.D^p-- APpL 9,1317
rut nr 10 tiroi Wio AM 24.1937


L_ a t l antic
ocean C-C-
TRUE MERIDIAN
LOCATION PLAN
ft*_0_1503 iooom
7 ; 7 ) 1
W O I o 0
K.
!0
I ON 20 f!'0'+--7S'-0"~
300'-0" 112- 6"-
EL.+.IOO'_TOP OF_BULKHEAD
1 i2'-e--
_1 mm
EL-I6.7S
A
J--S'-"-
NOTE:
ALL TIMBER TREATED ELEVATIONS REFER TO MLW
IL'ft, M L
TOP 01 pu SM<0. >*l
ectM rtoem
ft
ji nisi
1LU.
PLAN
0 1 1 I**'1
BEACH EROSION BOARD
HOLLYWOOD BEACH, FLA.
PROPOSED GROINS
SCALES AS SHOWN WOShinCIOK.DC. ^- **tv.i>T
SECTION A-A
I O I 1 1 T
it 13-H 5
HMM1 9a>(C AM


f. Offshore changes
1. By comparison of depth curves
2. By comparison of long profiles
g. Effect of protective structures
11. Direction, amount, and character of littoral drift i. Conclusions
II. Present Conditions
a. Horizontal and vertical control
b. Topography
1. Complete to|M>graphic survey
2. Location of present shorelines
3. Shore line changes during study I. Dune elevations
5. Elevations on buildings
c. Hydrography
1. I lydrographic surveys
2. lleach and offshore profiles
:i. Underwater changes during the study
d. Airplane photographs
e. Tides
f. Waves
g. Currents
1. Offshore currents
2. Currents causing beach drift
h. Sand in suspension
i. Materials
1. Sand samples from the beach
2. Bottom samples offshore ... Probings and borings
4. Petrographic study j. Stream detritus
k. Inlet investigation
1. Volume of accretion or erosion.
KKAi'H EROSION STUDY AT DAYTOXA BEACH, FLORIDA
An investigation and study of beach erosion and changes between Ormond Beach and New Smyrna Beach, Florida, was made by the United States (acting through the Chief of Engineers, the Beach Erosion Board, and the district engineer, Jack-
t 88 1


sonville, Florida) and the State of Florida (acting through the Engineering Experiment Station, University of Florida, and the City of Daytona Beach, Florida). The purpose of the study was to determine (1) the causes of erosion of the beach south of Ponce de Leon Inlet and of the erosion and changes in character of the beach at Daytona Beach which have prevented its use for the extreme high speed reached in recent speed tests for automobiles, and (2) the best method of controlling and preventing these changes. The area covered by the study included the beach from a point north of Ormond Beach to a point 5 miles south of Ponce de Leon Inlet, a total distance of 30 miles.
A synopsis of the report of the Beach Erosion Board on the study of beach conditions at Daytona Beach has been published as Bulletin No. I of the Engineering Experiment Station, University of Florida, by Professor W. W. Fineren.
SHORE PROTECTION METHODS AND MATERIALS
PROTECTIVE STRUCTURES The installation of protective works may have one of several objectives, and the selection of the type of structure to use is governed by the purpose for which it is intended. In general, protective structures are designed to accomplish one of the following objectives:
1. Stabilization of a particular beach,
2. Creation and stabilization of artificial beaches.
3. Restoral ion of depleted beaches.
1. Protection of property without regard to the beach.
Offshore breakwaters have two purposes, i.e., to provide a sheltered harbor or area for shipping, and to prevent destructive wave action from reaching the shore. In accomplishing the latter objective offshore breakwaters may cause a cessation of littoral drift with resultant starvation of beaches to the leeward.
Sea walls are used primarily to protect property in rear of a beach against heavy storm wave action and they have no value in stabilizing a beach that is meant for bathing purposes.
Bulkheads are used for the same purpose as sea walls but where the wave action is less severe. By themselves they contribute little to the stabilization of a hathing beach but may be
I 94 I


used to advantage in this respect when employed with a system of groins.
Groins, which are structures projecting from the shoreline, have proved the most effective type of protective structure for stabilizing loaches, but their installation does mar the beauty of a beach and may often prove dangerous to bathers.
Fiji. l>. Permeable eonrrc'iu groin near Palm Beach.
Jetties are similar to groins except that they are larger and considerably more massive. They are used at inlets to prevent the movement of sand into the channel, to regulate the How of tides and rivers and to protect ships entering the inlet from beam seas. In order to accomplish their purpose, jetties are built much higher than groins and because of their height they interfere with the normal process of littoral drill.
LOCATION AMI DKSKJN OK i'KOTK< TIVK STRICTl'KKS
This bulletin is primarily concerned with the location and design of a system of protective works for a beach which is eroding, and from this standpoint the types of structures to be considered are groins or a combination of groins with a seawall or bulkhead. These structures are those which are known at the present time to produce satisfactory results when properly designed. The purpose of a system of groins is to entrap the sand from littoral drill, which will build up a satisfactory beach. The system must be designed so that the profile of tlie groins tends to restore natural conditions and at the same


Fin. " Typical City of Miami Beach groin.
time allows the surplus sand from littoral drift to pass over the groins and feed the beach to the leeward. Groins may be used without seawalls or bulkheads when the property in the rear of the beach is sufficiently high and the land is well consolidated, the average storm action is not severe, and there is sufficient littoral drift to fill the space between the groins. If 1he bulk-
i 36 1


heads are omitted the groins must be securely keyed back into the high land in the rear of the beach.
The detail design of a groin system, whether or not it is used with a bulkhead, depends on the exposure to wave action and the material used. Regardless of the material used, groins must be strong enough to resist the wave forces against them. Once the type of material is decided upon the design is relatively simple, providing certain well accepted rules as to the general profile and spacing of the groins are followed.
The Beach Erosion Board has developed2 a typical profile for groins after an exhaustive examination of beach profiles measured during normal conditions (See Figure 8). Normal beach profiles show a flat horizontal bertn above the high water line, a sloped section extending from this upper berm to a point below low water line, and then a gentle slope underwater. From these observations the profile of a groin is divided into three parts, i.e., an inner horizontal section, a connecting slope, and an outer horizontal section. Recommendations by the Beach Erosion Board as to the height and length of each section of a groin are as follows:
Fijf. H.Typical groin.
"The top of the inner section is at the average elevation of the natural berm over the entire area to be protected. This Is obtained from the topographic survey or profiles. The length


of the horizontal inner section is determined by the requirement of providing an adequate recreation area for the number of people expected to use the beach. If the demand is for an upper beach or berm wider than may be expected from natural accumulation, artificial filling of the groins by sand pumped from rear or offshore areas or transported from a selected source will be required.
"The angle of slope of the intermediate section is made slightly less than the average natural slope of the beach in order to encourage as flat a beach as possible. The slope to be used is determined from the profiles made during the course of the study. The length of this section is fixed by its slope and the difference in elevation between the inner and outer horizontal sections.
"The top of the outer section is usually fixed at the elevation of mean sea level. This is a compromise with the ocean forces and the difficulties of construction. So far as the ocean forces are concerned, it would be desirable to keep the top of the outer section of the groin below mean low water in order to check the wave currents but not to oppose directly the maximum force of the wave exerted above still water level. The practical difficulty of construction below the low water line in the ocean makes this uneconomical. Several of Palm Beach, Florida, groins have alternate piles driven to mean low watei with the top of the others at mean high water. This may prove a workable solution.
"The length of the outer horizontal section depends on offshore conditions. If there is a reef or bar a reasonable distance" offshore the groin should extend inside the reef or bar and end on the crest of the reef or outer face of the bar in depths about 6 feet. Since about 80 per cent of the littoral drift during normal weather conditions is shoreward of the (5 foot depth curve, the 6-foot contour seems to be the proper place to end groin."
From observations made by the Beach Erosion Board of successful groin systems the ratio of the length of a groin to the spacing of the groins should be between 1:1 and 1:3. Spacing groins closer than 1:1 does not injure the beach but will prove uneconomical while a spacing greater than 1:3 will be ineffective in holding a good beach. Within these limits, the Beach Erosion Board recommends the following:
"The spacing is determined by the volume of littoral drift
f 1


and the direction of approach of the storms causing the most severe erosion on the beach. After the length of groin has been fixed by offshore conditions, draw a line through the end of the groin parallel to the direction of storm approach. The projection of this line on the line of the bulkhead will determine the proper space to be allowed between groins in so far as storms are concerned. The spacing thus determined does not always fall within the limits previously set. If it does not, the nearer limit should be used. This method of determining spacing while empirical, is not haphazard. The more directly onshore the wave action the less will be the littoral movement of sand under the influence of the wave forces and the less serious the erosion. In the case of storm action parallel to the coast the resulting waves do not travel parallel therewith but the shoreward ends are retarded so that the wave reaches the shore at an angle of about 16". If there is a large volume of littoral drift, groins may be spaced farther apart. Since it is often impossible in a study to determine the amount of littoral drift, groins should be spaced as described for storm action with the plan of inserting intermediate groins if littoral drift is insufficient to fill them between storms."
Observations' in Florida have corroborated most of the recommendations of the Beach Erosion Board. Statements by Morris V. Lipp in his discussion of Col. Earl I. Brown's paper in the ASCE Proceedings are as follows:
"Colonel Brown cites the necessity for geological studies and establishes vital points in his discussion of littoral drift. Once (he direction of drift is determined an improvement barrier is hurdled. It is now accepted as true that the general movement of sand along the Florida east coast is in a southerly direction. This principle was established by the Florida State Geological Division. Analyzing sand at various points along the coast, and tracing the sand to its source of supply, entered into its studies. The engineer, as Colonel Brown points out, sees evidence of (he direction of drift at jetties.
"Colonel Blown states that the progressive reduction in length of groins toward the ends of a protective system has proved successful in some instances, whereas in other cases it has not been effective at all. In South Florida attempts have been made toward progressive reduction, but they have not been successful. It should be realized that after a system of


protective works has been constructed on the east coast of Florida its extension to the south will be required eventually.
"The requirement advocated by Colonel Brown that a groin be sand tight is correct. This type has proved to be the most successful in Florida. Permeable groins have been constructed, but there have been instances in which they have been converted to solid ones.
"To adopt a ratio between the length of the groin and spacing of 1 to 'A, which is one limit of Colonel Brown's suggested spacing, would be a radical change from the ratio now used in southeast Florida where an economical length of groin is approximately two-thirds of the spacing.
"The length of a groin plays a large part in the extent to which a beach will build up. At Miami Beach, where approximately 9000 ft. of ocean front are protected by city-constructed works, groins in one system have a length of 170 ft., in a second a length of 200 ft., and in a third a length of 250 ft. More extensive lengths of beach have been built up in the areas having longer groins. In all these systems the two-thirds rule has been followed. Naturally, in many instances, such considerations as depth of water, wave action, and structural stability will determine the length.
"Other factors such as wave height and life of the structure should be considered, in addition to those mentioned by the author, to determine the profile of a groin. The inshore end of a groin should be above normal wave height, not only because it is desirable to have an available beach at high tides, but so that such a beach will be formed that ordinary waves will break on it, and not against the bulkhead. The backlash of waves breaking against a seawall and meeting the incoming waves will not only retard the building up of a beach, but may prevent the making of one. Where it is desired that the beach be made naturally, it woidd not be necessary to construct the inshore groin elevation above a point where occasional heavy storms would deposit sand."
When groins are used in combination with bulkheads, the design details of the groins are the same as though they were used without the bulkhead, except, of course, the groins must be securely attached to the bulkhead. Recommendations as to height, and the forces to be considered in the design of bulkheads by the Beach Erosion Board are as follows:
I 40 1


"With a groin system,Determination of the proper height for a sea wall or bulkhead requires consideration of four factors: The character and extent of the development in the area to be protected; the elevation and character of the ground in the rear; the maximum heights and frequency of storm tides and waves; and the probable effect of the groin system in accumulating sand. In this discussion relative to bulkheads it is assumed that the development warranted protection against ordinary storm tides only and that the land in rear was comparatively low. In determining the proper bulkhead height the probable effect of the groin system in accumulating sand to act as a buffer to storm waves should be considered. If there is a large amount of sand moving along the shore to be trapped by the groins this accumulation will act as a buffer to trip the storm waves and prevent their breaking over the bulkhead. The average frequency, duration, and direction of storms should be studied to determine whether one storm might be expected to remove all of the sand accumulated during normal conditions and whether recurrence of storm conditions might be expected before normal conditions have restored a sand supply between the groins. Where littoral drift is meager or storms frequent, the sand accumulation cannot be counted upon to act as a buffer to the storm waves. The top of the bulkhead should lx> placed at an elevation equal to the average height of the highest yearly storm tides plus wave heights, omitting from consideration extremely infrequent hurricane tides. If the sand accumulation can be counted on to trip the waves before they reach the bulkhead, the bulkhead height may be reduced by the average wave height. Where groins may be expected to trap sand to form a beach, the bulkhead is simply a last line of defense and an insurance against serious property loss during exceptional storms,
"Without a groin system.The details of design of the seawall or bulkhead will depend upon the character of the subsurface material and on the probability of exposure to the direct force of the breaking wave. The length of piles should be such that they will have two-thirds penetration when the beach is cut down to the point where the low water is at the foot of the wall. Piles should be tied back to insure against failure by pressure on the land side when exposed to low water on the ocean face. It is important in the design to insure impervious-ness to protect the backfill. The leaching of the backfill through
i 41 I


a bulkhead is a common cause of failure. Consideration should be given to providing release for the water topping the bulkhead during storms so that property in the rear is not damaged."
Consideration should be given to the possibility of using partially submerged bulkheads to protect a beach from erosion. This type of structure' has proved successful in Lake Michigan at Chicago, Illinois. Instead of constructing a bulkhead at the shore end of the gi-oins the bulkhead was placed at the lakeward end. The advantages of this type of construction are:
1. Cheaper than a shore bulkhead.
2. Effectively holds the sand behind it.
The important characteristics of this type of bulkhead are its effect on the waves and the stilling action of the undertow at the wall. The portion of the bulkhead above the water impedes the waves, and the water passing over the bulkhead returns in the form of an undertow along the bottom. When this undertow reaches the wall it rises to the surface, encounters the sea coming in and creates a stilling action at the wall. Although this type of structure may be considered cheaper than a shore bulkhead in regard to the actual cost of construction, the function is not the same; and where it is necessary to build a shore bulkhead also, the total cost may be prohibitive.
MATERIALS
The three basic materials, concrete, steel, and wood have been used extensively in the construction of shore protection structures. While no attempt will be made to discuss the relative advantages or disadvantages of these materials, observations and recommendations of the effectiveness of certain types of structures will be given. Whether a bulkhead or bulkhead and groin system is constructed of wood, steel, or concrete, it should be expected to have a reasonably long life; but due to the destructive forces that these structures are subjected to, this has not always been the case in the past.
SteelIn order to determine the extent of deterioration in the beach protection works at Miami Beach, Florida, an extensive survey'' of existing structures was conducted by measuring at regular intervals the web thickness of the steel at the pulling holes in the bulkhead sheets. The results of this investigation are given in Table 1.


Table i. Measured thickness or Stkki. Sheet Piling in Bulkheads
(Civil Engineering).
1927 Construction 1930 Construction
Original Thickness Original Thickness
0.407 in. 0.407 in.
Average maximum thickness.............. 0.380 in. 0.404 in.
Average minimum thickness. 0.322 0.370
General average thickness................. 0.351 0.387
Since the original thickness was 0.407 in., the figures in Table 1 show that a loss of 11 per cent occurred over a period of eight years in the case of the 1927 construction, and a loss of 5 per cent in a five year period for the 1930 construction.
Additional information on losses in weight due to the general corrosion of steel and copper-steel bars is given in the results of 10-year tests completed by the Committee on Deterioration of Structures in Sea Water of the Institution of Civil Engineers of (beat Britain. Mann0 has presented a summary of this data as given in Tables 2 and 3, and Figure 9.
Tabi>: II. Observations of Pittinc; ok Stkki. and Copper-Stkei. Bars After 10-Yeak exposure
Locvtion Steel designation
Plymouth. England Steel E
Steel D Copper Steel G
Halifax. N. S.
Auckland N. 7.
Colombo. Covlon
Copper Steel H Steels E and D Copper Steel (J
Copper Steel H
Steel E
Steel D Copper Steel C
Copper Steel H
Steel E
Steel D Copper Steel C5
Copper Steel If
Remarks At half-tide, heavily pitted all over At half-tide, deeply pitted At half-tide, circular pits, edges
severely attacked Creen color, circular pits No comments
At half-tide, uniform attack; submerged, surface rough and pitted
Submerged, steel H was similar to
G. but more severely attacked,
edges corroded Submerged, attacked all over.
widespread deep pitting Submerged, the same as E Submerged, the same as E; at
half-tide, tendency to pit Submerged, the same as E. at
half-tide, a tendency to pit At half-tide, honeycomb corrosion.
bottom of bar to a knife edge;
submerged, heavy pitting At half-tide, covered with pits.
edges corroded away At hnlf-tido, very deeply pitted;
submerged, edges corroded
away; covered with pits, some
very deep At half-tide, perforated, very
deeply corroded; submerged.
edges corroded away, covered
with deep pits
1 4--i 1


S 10
i
20
'./I AIR.EXPOSURE 10 YEARS
_---__ , r.Urd. Nil
*-*>-*CV^^**^ Plymouth 1 nn'jnd
1 i ; 1 / /


(tiHALF TIDE EXPOSURE 10 YEARS

***-__- . ------ r-w., OM"2,-^
----- ItoM n. n s * 5^1
1%
Fig. II.--Percentage losses in weight due to general corrosion of steel and copper-steel bars after 10-year exposure.
Table Hi. observations on General Corrosion of Steel and Copper-Steei. and copper-Steel Bars After 10-Year Exposure
Steel Designation Exposure Per Cent Loss of Wt. Reference
Plain steel In air 3.85 to 54 , .
Copper steel In air 2.10 to 53.4 9,a'
Plain steel At half-tide 3.80 to 42.8
Copper steel At half-tide 3.20 to 37.2 iun. ."/
Plain steel Submerged 12.70 to 20.0 . . .
Copper steel Submerged 12.20 to 21.1 '* * The steel product particularly adapted to the construct;on of bulkheads, groins, and sea walls is interlocking sheet steel piling'. The greatest amount of steel has been used in bulkheads; and when used in this type of structure, the usual con-


struction is a simple wall of piling backfilled with earth and anchored at the top with steel tie rods. The anchorage may l>e either a short sheet piling wall, a batter pile structure or reinforced concrete deadman. Between the tie rods wales are bolted to the piling on the back of the wall. The top of the wall may be capped with timber, reinforced concrete, or a steel channel section. Sheet steel piling has been used extensively for groins and as such are usually simple cantilever walls with steel or timber wales on each side of the top. Additional stability may be obtained by using timber bearing piles at intervals along both sides.
The abrasive action of sand in moving water has a serious effect on any material. The deterioration caused by this abrasive action in sheet steel piling has been studied by the Beach Erosion Hoard on four test groins constructed at Palm Beach. Florida. Different types of sections, deep arch and straight web. were used, but a recent report shows that the shape of the section has little effect on abrasion. In deep arch sections and straight web sections with a web thickness of % in., the abrasive action was sufficient to cause small holes through the unprotected piling in slightly over three and four years respec-
Kijr. 10. Abrasive action on concrete sea wall south of Boynton Inlet.


tively. The report indicates that the steel groin sheathed with creosoted timber planking is probably the best method of resisting abrasion. Comprehensive tests on protective coatings for steel subjected to sea water exposure indicate that the fol-
Kig. 11. Beach at Hollywood, Florida.
Fig. 12.Abrasion of steel groins at Palm Beach. I 46 |


lowing coatings provide the t>ost protection against corrosion in the order named :
1. A thick coat of coal tar pitch enamel applied hot over a priming coat of coal tar pipe line primer.
2. A priming coat of zinc chromate iron oxide paint having a Bakelite vehicle and two additional coats of aluminum paint having a Bakelite vehicle.
ConcreteBoth plain and reinforced concrete have been used extensively for all types of shore protection structures. The important factors to consider in the design of a concrete structure for beach protection are the proportions of the concrete mixture and the placing of the concrete". Only aggregates that are known to be physically sound under the exposure of sea action should be used and these aggregates should be mixed with a watertight paste. A low water-cement ratio of T) to 51/2 gallons of water per sack of portland cement is commonly used. This ratio makes it difficult to place the concrete properly unless high frequency vibration is used. Proper curing is essential to securing a watertight paste, and concrete beach protection structures should be kept wet for a week or ten days at a temperature above 50 degrees prior to exposure. In order to eliminate joints, particularly at the tidal zone, the concrete should be placed in a continuous operation. When reinforcement is required it should have a minimum of 3 in. of protective concrete covering, except at the cornel's where the cover should be 4 in.
Permeable groins of precast concrete units which can be designed to present as much or as little obstruction to the littoral currents as the designer wishes have proved successful. Groins of this type have been built at Palm Beach, Florida, and consist of large precast hollow units placed about 10 ft. apart around si eel sections in line with sheet piling driven into the rock. The space in each pier is filled with concrete and the precast concrete notched members are set in grooves provided in the piers.
WoodPressure creosoted timber has been used for water front structures for over a hundred years-'. Such structures include various types of bulkheads, jetties and groins, docks and piers, and pile foundations supporting masonry walls. The most effective and economical utilization of treated timber involves the proper selection of grades and species, designation of the


proper preservative, and specification of the correct retention of the preservative in the timber.
Fig-. 14.Groin system for City of Miami Beach. I 18 |


The species and grade of wood to use depend upon the type of structure contemplated. Douglas fir and the southern pities are the most common species used and these are available in a variety of grades covering practically every conceivable use.
Vig. I!>. Typical groin at City of Miami Iteai'h.
Timber for use in shore protection structures should be treated by the full-cell process with the maximum practicable absorptions of creosote. Southern pine timbers in salt water are usually treated with 1(5 pounds of creosote per cubic foot and Douglas Fir with 12 pounds per cubic foot. Final retentions of 20 pounds per cubic foot for southern pine piles and M pounds per cubic foot for Douglas fir piles are standard requirements.
CONCLUSIONS
There is probably no limit to the ty|x>s of design and combination of materials that can be used for shore protection structures, and the engineer responsible for the design of these structures may wish to refer to the items covering this phase of beach erosion given in the bibliography in the appendix. In considering the design and selection of a material for any par-


Fig. 1G.Abrasion of steel in groin at Baker's Ilaulover.
ticular structure, it must be pointed out that there are no stereotyped designs which will apply to all localities in the State of Florida. Since any beach protective structure is expensive, the designer must select the materials with care, giving due consideration to their ability to withstand corrosion, abrasive action, marine borers, and wave impact.
LABORATORY INVESTIGATIONS
Before discussing various forms of laboratory investigations it should be noted that the science or art of shore protection is still in its infancy and that considerable research and study is necessary before the problem of beach protection can be reduced to an exact science. There is further need for experiments in the field on the action of currents, waves, and sand movements, and for investigations of materials used in shore protection structures. In addition, present structures should be observed continually and reports made concerning their effectiveness.
Laboratory investigations of beach erosion problems will yield reliable data and a solution to many of the complicated
I so I


problems that are not solvable in the field. It should be pointed out that laboratory investigations are not necessarily studies of a reduced scale model of a particular situation in nature. In beach erosion studies the laboratory investigations may be divided into live general classes:
1. Studies to verify existing mathematical theories concerning all the characteristics of wave motion
a) Velocity of waves
b) Internal motion in waves
c) Energy of waves
d) Shape and changes in shape of waves
2. Studies on the generation of waves
a) Generation of waves by wind
b) Effect of local winds on waves
'\. Studies of the effect of winds and waves and their relationship to the following:
a) Various grades of l>each material
b) Supply of beach material
c) Various shore slopes
d) Littoral currents and drifts
e) Various angles of approach
f) Tidal phenomena
4. Model studies of natural and artificial protective structures on the shoreline of beaches
5. Model studies of particular beaches or harbors.
A number of laboratory investigations concerning the primary variables in beach erosion problems have been made and numerous model studios of particular sites have been conducted in wave tanks. The laboratory studies that have been made are indicative of the value that may be derived from a systematic and exhaustive series of laboratory investigations.
WAVE STUDIES
Before discussing particular laboratory wave studies it will be well to define the various types and characteristics of waves.
A deep water wave is usually defined as a wave travelling in a depth of water greater than half of its wave length. From this definition it is apparent that a shallow water wave is one travelling in a depth of water less than half its wave length. The wave length is the distance from crest to crest of the wave


and the wave height is the vertical distance from the top of the crest to the bottom of the wave trough. Oscillatory waxes are classified as waves with a periodic wave motion. They are characterized by alternate crests and troughs and by the fact that as the wave form progresses the water particles move forward on the crest and backward in the trough. The oscillatory waves under consideration here are those of such height and period as to break on a sloping shore. When the oscillatory wave breaks, a wave of translation is formed and continues forward in the direction of wave propagation. In this type of wave the surface particles rise, move forward, descend and come to rest in an advanced position; there is no corresponding backward motion of the water particles.
One of the most recent and significant experimental studies of wave motion is that contained in the Beach Erosion Board's Technical Report No. 1 entitled, A Study of Progressive Oscil-liatory Waves in Water. Prior to this study the knowledge of the motion of oscillatory waves in water consisted, for the most part, of theoretical studies made by mathematicians. These classical studies have resulted in two general theories for waves of finite amplitude. These are the irrotational theory of Stokes, Levi-Civita, and Struik, and the trochoidal theory of Gerstner and Laplace-Airy. The irrotational theory for waves of finite amplitude in deep water is based on the fact that the waves are not sinusoidal in form and that there is an induced drift or mass transport in the direction of wave motion which modified the wave velocity and orbital motion. When the water depth is great in comparison to the length of the wave the equations based on the irrotational theory are:
Wave v
elocity, Ojft (
Waveform, Z = dCOS
where 0 =
-iL_ 3ELU 73nV 2 16 U 96L'


Mass transport, \J=4BJti Ce^_ QflC.
L Ld
For shallow water waves the above equations become:
Wave velocity,
C=
, 2nd 2nd.
2n 2o3 .2nd
od .and 4nd _4nd ^
r nnjj 2ndi \L /
2nd2nd> -g "
Wave Conn,
, 2nd .and 4rjd .4nd
2nd iind end end -and nd 2nd
|(CL+gL |-f!4(gL + gM-H9(gTr+ a1^
1 + 32
(a a~LJ
Mass transport, (J= 4rjjPc u _. n
2arj .2nd
( d|TAN2nd
The trochoidal theory is based on rotational flow, and does not consider the possibility of the wave movement being accompanied by a mass transport in the direction of wave travel. The formulas derived from this theory are as follows:
Deep Water Waves:
Wave velocity, C= |jf" Wave form, X = R e r SIN O
Z,= R-r cos-e-
Shallow Water Waves:
Wave velocity, r l|SL tan
Waveform, 2 =Z cos & s
Xs= Re-x sino


The nomenclature used in the foregoing formulas are defined as follows:
a a function of the wave height, ft.
C velocity of wave propagation, ft. per sec.
d = still water depth, ft.
e base of natural logarithms
g = acceleration due to gravity, ft. per sec. per sec.
h wave height, ft.
h1 = depth below still water level, ft.
L = wave length, ft.
U velocity of mass transport, ft. per sec.
X = horizontal axis of reference
Z vertical axis of reference
R = radius of rolling circle (L = tt R)
r = radius of tracing circle (h 2r)
The subscript s denotes a value at the water surface.
In the published results, Technical Report No. 1 of the Beach Erosion Board, of experimental studies of progressive oscillatory waves in water all of the characteristics of the oscillatory wave in deep or shallow water required by the irrotational wave theories were reproduced in the wave tank, with the exception of the wave profile. It was shown that mass transport as indicated by the theories of Stokes does exist. This has also been found true experimentally by C. F. Mitchim, Oscillatory Waves in Deep Water, the Military Engineer, March-April, 1940. The report also shows that the magnitude of the difference in value of the wave characteristics, other than mass transport, defined by the rotational and irrotational theories is smaller than the experimental error associated with the tests. From the results of this very valuable report have come suggestions and methods for additional studies vital to beach erosion problems. These will be indicated later.
ABRASION OF BEACH SAND
One of the factors that has been proposed as contributable to beach erosion is the loss of sand due to abrasion. The movement of beach material by waves and currents does result in abrasion and sorting of the material, but the importance of abrasion in beach erosion studies depends on the rate of loss due to abrasion and the rate of loss or gain of beach material by the action of other forces. The Reach Erosion Board, Tech-


nical Memorandum No. 2, lias made a study of the abrasion of beach sand for the purpose of ascertaining the rate of loss by abrasion and the importance of abrasion in beach erosion studies. As a result of this study the following conclusions have been made: "The product of abrasion of beach material is smaller than 0.07 mm. particle diameter; that such particles are subject to removal and loss from the beach by transportation; that the magnitude of such loss cannot be stated exactly but it is probably a function of the mobility of the beach; and that abrasion of particles in the sand size range proceeds very slowly. It is therefore concluded that the loss of beach material ascribable to abrasion is of very minor importance as compared to the losses and gains ascribable to littoral movement".
SHORE CURRENTS AND SAND MOVEMENT
Iiitloral drift is one of the most important factors involved in beach erosion and shore protection studies. Any structures thai completely arrest the material carried by littoral currents should not be permitted because the neighboring shores would be denuded of their sand. All structures perpendicular to the shoreline will arrest the drift somewhat; but when they impound all of the sand on one side, they invariably cause serious erosion on the adjacent side.
As oscillatory waves approach a sloping shore the crests become higher and closer together until they break in water that is approximately equal in depth to the height of the waves. When the oscillatory waves break they become waves of translation with an energy in the horizontal direction proportionate to their mass and the square of their velocity. In addition, currents are set up across the waves and material is carried across in suspension and traction, and ripples on the surface form and carry material with them. When a shore has been eroded during storm, a number of projections may form due to the differences in the depth of water along the shore, shape of the bottom, and shore material. As such projections take form the sediment of the beach builds up more rapidly on the windward side than on the leeward and the littoral currents are directed offshore carrying the material with it. Although wave currents set up the most powerful forces governing the movement of coastal material, the effect of tidal and rip currents should be taken into consideration. Considerably more information is


needed concerning the rate of movement of sediments and the subsurface movement of water under all conditions. Because the factors that contribute to beach erosion are very complex and are constantly changing with respect to each other, it seems necessary to obtain a knowledge of what actually happens beyond the shore line during all conditions of weather before any beach protection structure may be assumed adequate.
A step in this direction is a laboratory investigation on Shore Currents and Sand Movement on a Model Beach by W. C. Krum-bein, Beach Erosion Board Technical Memorandum No. 7. The purpose of this study was to explore some of the relations between waves breaking at an angle to a beach, the currents generated, and the amount of sediment transported. These variables made the problem complicated because the strength of the shore currents depend upon the wave characteristics and the angle of approach, while the amount of sand transported depends directly upon the velocity and degree of turbulence of the current and ultimately upon the wave characteristics. Thus, the study was actually two studies: (1) the velocity of the shore currents under given conditions of wave character and angle of approach, and (2) the mass transport of sand under the same conditions. The study was made with an angle of approach of 15. As an example of the results obtained in the model, and in accordance with scale-model theory, a deep water wave of length about 200 ft., period of about 6.3 seconds, and height of about 1 feet approaching the shore at an angle of 15 would generate a maximum shore current of about 2 feet per second. Additional results showed that a wave 250 feet long, nearly 4 ft. high and with a period of 7 seconds would generate a maximum shore current of nearly 2 ft. per sec. along the shore and would move about 2 cu. ft. of sand per sec, providing the angle of approach was 15. The conclusions of this study clearly show that additional studies should be made with varying angle of wave approach and varying characteristics of sand used. The study illustrates the fact that a number of related problems can be attacked which depend ultimately upon wave characteristics and angle of approach. The results of this experimental study afford a basis for approximating the order of magnitude of natural shore currents under like conditions, and suggest lines of attack on field problems designed to study natural beaches or to control beach erosion.


MODEL STUDrES OF PARTICULAR SITES
Numerous model studies have been made for the purpose of studying wave action as related to harbor and breakwater construction, but few studies have been made considering the movement of bed materials. The majority of studies on harbor protection have been carried on at the U. S. Waterways Experiment Station at Vicksburg, Miss. An outline of the model study procedure for this type of investigation is as follows1".
1. A definition of the problems to be studied and the establishment of a general criterion for determining the effectiveness of a given plan.
2. Securing of accurate and sufficiently detailed hydro-graphic and topographic surveys of the problem area.
Securing of sufficient wave data to define the characteristics of the primary ocean or lake waves, i.e., the height, direction of approach, and period of the waves in the ocean or lake before reaching the problem area.
1. Selection of a series of test waves described in (3). The waves should provide a thorough test of the protective ability of the various plans tested in the model. They should include large, intermediate, and relatively small waves, as the small or intermediate wave may under certain conditions be more destructive than the large ones.
">. Selection of model scale to insure a model large enough for an accurate production and an accurate measurement of the wave action over the problem area.
(>. Construction of the model and its appurtenances.
7. Adjustment of the wave reproducing apparatus to produce the primary waves selected as test waves under (4).
X. Study of wave action in the model under existing conditions.
9. Study of effects in the model resulting from the installation of improvement works designed to accomplish the desired changes in wave action in the problem area.
A model study of beach erosion problems at a particular site should follow a procedure similar to the foregoing, but, in addition, detailed information must be obtained on the beach and bottom material, the offshore currents and currents causing beach drift, the volume of accretion or erosion, winds, storms, and tides.


Interesting and valuable wave tank experiments have been conducted by the Chicago Park District concerning the movement of sand in Lake Michigan; and the development of a submerged bulkhead to protect their beaches has been mentioned previously.
DIMENSIONAL ANALYSIS AND SIMILITUDE
In any model study it is necessary to know the variables involved in the investigation. Depending upon the type of beach erosion study the variables may involve two or more force properties, such as weight, viscosity, and surface tension. Since the fluid used in the model is the same as that in the prototype, true similitude can only be obtained when one force property is acting; and the determination of the exact model scale for beach erosion studies is impossible. From purely a practical standpoint it is illogical to seek strict similitude, but the model should be designed so that the salient features of flow are similar. When more than one problem is involved in a study, such as that mentioned previously, Shore Currents and Sand Movements on a Model Beach, dimensional analysis may be used to advantage and the scale factor is largely eliminated. For any model study, however, the use of dimensional analysis has many advantages.
Dimensional analysis is a mathematical tool used in predicting the general form of physical equations. The dimensions of length, time, and either mass or force are sufficient for the solution of problems encountered in fluid flow. The dimensions of quantities concerning fluid flow in terms of LMT arc given in Table IV.
In using dimensional analysis it is first necessary to arrange the several variables dimensionally in the smallest number of significant parametric groups. The principal tool for accomplishing the organization of the variables is known as the tt theorem". This theorem states that any variable V, depending on the independent variables V... V3 . V. and no others, may be expressed as follows:
V, f(V,, V:, . .V)
and furthermore, since there is mathematical equilibrium between the dependent and indepedent variables the function maybe written in the form


If all of these n variables may be described in m fundamental units, then they may be grouped into n-m dimensionless terms, so that
P{*u 77,, 77, . .....) -.0
in which each of the variables ?r represents a dimensionless product of m 1 V- terms, and n is the number of kinds of quantities and m is the number of independent variables needed in specifying the dimensions of n quantities. Since length, mass, and time are sufficient for the solution of problems in fluid flow, m is equal to three.
table IV. Dimensions or Physical Quantities
Quantity Symbol Dimensions
Geometric: LMT
Length ............... ............................. L L
Area................. A La
Volume V L
Kinematic:
Time.................. T T
Velocity...................... .......... V LT'
LT-
Discharge.................. ......... Q L'< T->
Kinematic Viscosity La T-a
Dynamic;
Mass ............... ....................... M M
Force......................... .................................. F ML T-1
Density................. V ML-'
Specific Weight...... ............... w ML-'j T--'
Dynamic Viscosity ML-' T-i
Surface Tension MT--
Volume Elasticity ................................ K ML-i T--
Pressure Intensity ............... P MIj-' T--
Momentum Impulse I (Mi ML T-1
Energy and Work E I w) ML- T--
Power...................... ................................. P ML T-
It should be noted that the variables influencing fluid How may be divided info three classes as follows:
1. Linear dimensions, which describe the boundary conditions.
2. Kinematic and dynamic characteristics of fluid flow, such as mean velocity or a pressure increment.
3. Physical properties of the fluid.
As an application of the tt -theorem, which combines the variables into a set of physically signicant non-dimensional parameters, consider the problem of determining an equation for the energy, E, per wave length per unit breadth of water
I fni |


waves. The variables involved are the properties of the fluid, the characteristics of the waves, and the energy of the waves. These variables are:
L = wave length
h = wave height
T wave period
< specific weight of the fluid
ft density of the fluid
n = dynamic viscosity of the fluid
E = energy of the wave
In choosing repeating variables for the application of the tt theorem, L may be taken as the geometric term, t> as the dynamic term, and the ratio of h, which has the dimensions of a
velocity, as the kinematic term.
We have seven quantities and two of these, L and h, are of the same type. Three fundamental dimensions are needed to describe the variables so there will be 6-3 3 r- -terms plus a ratio of the height, h and length L. If we use four tt terms it will be shown that the ratio, h, is equal to one of the w terms.
T
L
Then, each term is as follows:
Substituting the dimensions LMT in t, we have
n,
= L.It^M L L
Since tt, is dimensionless x + y 3z +
3z + 1 = 0 y = 0 z = 0
[fio]


from which x -1. Substituting the values x, y, and z in the original expression for w,
TV L> Similary the value for t2, its and r, are found to be
The general equation for the problem may now be written as
If we solve the equation for we will obtain an expression for the energy, as follows:
It will be noted that tt, which is in the form of a Froude number, F, and ir which is in the form of a Reynolds number, R, both contain a ratio of a dynamic force and density, which means that each term has a kinematic significance. In applying the principles of dimensional analysis to model studies, it is necessary to decide which of the dynamic forces is dominant and design the model in accordance with this force. In wave studies the force of gravity is considered dominant and the model and prototype must, therefore, have the same Froude number. If we let the subscript m denote quantities referred to the model and the subscript p denote the prototype, equating the Froude numbers gives the following equations and scale ratio:
C c' _r a i_.g.
Lpg0 Lg C* LgM
For all practical purposes g,.;gM, so that
>> M
[1 1


The equation for energy, E, previously given, is similar to that derived theoretically, if we neglect Reynolds number. The theoretical equation is
=^(,-4.93 ')
If the model is designed in accordance with the Froudian principle, then the scale ratio for energy, which is a function of the ratio of h, can only be determined by making the horizontal L
and vertical scales of the model the same. In this manner the term 11-493 j will have the same value for model and prototype and the energy ratio becomes:
.assuming ^
JL-- u
In considering the velocity of deep-water or shallow-water waves, the formula used for obtaining the scale ratio may be based on either the trochoidal or irrotational theory if the horizontal and vertical scales of the model are the same. For deep water-waves, then
9z c.
2n 1^ l,
gl i l.
cr = flr
For shallow-water waves, the velocity
reduced to
Jak TAK,
c || fn TAN .
\2U as
where b. is the vertical displacement of a water particle at the surface or the vertical axis of the elliptical surface orbit of the wave, and a is the horizontal displacement. The scale ratio becomes:


llgLp. b= rr- (K <2rr Qp
Cp l2n dp t|J=^r I_Op. Un art
In order, then, for shallow water waves to have the same velocity scale ratio as deep water waves, Q ="^~ the waves in the model and prototype must be geometrically similar. This
means that the expression "ji^r must be unity and the horizontal
and vertical scales of wave form in the model must be the same.
The velocity of translatory waves may be derived from the expression for the velocity of shallow-water waves. In this
expression the TAN approaches -2112. because the wave
length of a translatory wave is large as compared to the depth. The velocity of a translatory wave becomes:
c-W~-W-ffi
The scale ratio for prototype and model becomes:
In order for this ratio to agree with the previous scale ratios, Cr- fL7r the scale of depth must also equal the scales of wave length and wave height.
Kinematic similarity as well as dynamic, similarity involves
C I t
consideration of time periods. Since = y-M the time scale becomes:
a t l.
t- ^
and since Q=
[G3]


From the foregoing discussion it is evident that a wave model may be constructed to attain dynamic similarity providing the Froudian principle is followed, the model is undistorted as to the bottom configuration and wave form, the time velocity and time scales are equal to the square root of the linear scale, and viscosity, surface tension, and bed roughness are neglected. The effect of viscosity may be disregarded because its effect is small compared to other factors. As surface tension increases, the velocity of propagation of a train of capillary waves also increases and since any surface disturbance contains the effects of gravity and capillarity the true wave velocity is the sum of the velocities due to these two independent relationships. Since the equations of motion of the two wave types are different the problem of attaining complete similarity is very complex. Fortunately, however, capillary effects are not noticeable until the wave length becomes very small which may be seen from the equation for the velocity of a capillary wave.
Surface tension may be neglected for waves whose length is greater than two inches.
Bed roughness has a minor effect on the action in a model and for practical reasons may be neglected except for shallow water and then the model can he made to conform approximately to the prototype.
In addition to model studies of a particular problem at a particular site, numerous general investigations of beach erosion problems pertaining to beach erosion as a science are necessary. Laboratory investigations of beach erosion problems require a systematic and exhaustive series of studies. The progress that has already been made is indicative of the results that may be obtained in the laboratory in furthering the understanding of the basic principles involved in beach erosion phenomena. A partial list of future general investigations is as follows:
1. Additional studies to seek experimental confirmation of wave theories.
2. Qualitative and quantitative verification of the theory of mass transport.
c =
, where a-
FUTURE LABORATORY INVESTIGATIONS
I C>4 1


3. Verification of the existence or nonexistence of rotation in wave motion.
4. Investigation of the details of the mechanism of how a small wave builds up to a large one.
5. Effect of local winds on waves and swells.
6. Are the present wave theories applicable to a sloping bottom ?
7. Effect of surface tension on waves.
8. Establish lower limit of size at which model waves break in a manner similar to natural waves.
9. Investigation of the possibility of predicting wave heights based on the energy concept.
10. How much energy is dissipated by internal and bottom friction before a wave reaches outer breakers?
11. Investigation of development of shore currents and their effects on beach erosion.
12. Investigation of the movement of sand by shore currents with waves approaching the shore at any angle.
13. Determination of sand transport for various bottom slopes and supply of beach material.
II. Study of the origin of sand beaches and the sources of sand.
Io. Study of the effect of artificial and natural structures on sand movement.
PROPOSED WAVE TANK AT THE UNIVERSITY OF FLORIDA
The proposed wave tank in the Civil Engineering Department of the University of Florida is essentially two tanks in one. It is planned to build two adjoining tanks with the same water supply and recirculation systems. One tank, which will be similar to that adopted by the Beach Erosion Board, is 14 ft. wide, 80 ft. long and 4 ft. deep. This tank will be used primarily for basic research in an attempt to solve some of the problems of beach erosion phenomena. It will be fitted with glass sides for visual and photographic observations on vertical sections of flow occurrences. The wave machine will be of the plunge)- type; and in addition to waves, the tank water supply system will be designed with inserts on each side of the tank
1 65 1


to permit the flow of water across the tank in any direction at most any velocity. Thus, it will be possible to study the effect of littoral currents. An apparatus will be provided that can constantly change the water surface elevations and velocities in accordance with tidal curves.
The second tank will be 40 ft. wide, 80 ft. long and 2 ft. deep. Although it will be used for a few basic research projects, it is primarily intended for model studies of particular localities in Florida. Thus, the coastal cities of Florida will now have an opportunity of studying their beach erosion problems in the laboratory; and before undertaking the construction of expensive protective structures they may be able to test the effectiveness of any proposed plan in this wave tank.
APPENDIX A
LITERATURE CITED
1 Manual of Procedure in Beach Erosion Studies, Beach Erosion Board. Dec. 1. 1938, U. S. Government Printing- Office. Washington. D. C.
2 Beach Erosion Studies, by Earl I. Brown. A.S.C.E. Proceedings. Vol. 65, January, 1939
3 Beach Erosion Studies, Discussion, by Morris N. Lipp, A.S.C.E. Proceedings, Vol. 65, April, 1939
4 Beach Erosion Studies, Discussion, by James J. O'Rourke, A.S.C.E., Proceedings. Vol. 65, May, 1939
5 Some Data on Beach Protection Works, by M. N. Lipp, Civil Engineering, Vol. 6, No. 0, May, 1936
6 Deterioration of Structures in Sea Water by Ralph H. Mann, Civil Engineering, Vol. 6, No. 8, August, 1936
7 Steel Sheet Piling for Shore and Beach Protection Structures, by R. J. Mcintosh, Shore and Beach, October, 1944
R Concrete Shore Protection Structures, by L. H. Corning, Shore and
Beach, October, 1944 9 Pressure Creosoted Timber for Shore and Beach Protection Structures.
by R. H. Mann, Shore and Beach, October. 1944
10 The Experiment Station Hydraulic Bulletin, No. 1, Vol. 4, May 15, 1941. U. S. Waterways Experiment Station, Vicksburg, Miss.
11 Model Experiments and the Forms of Empirical Equations. E. Buckingham. A.S.M.E. Trans., Vol. 37, 1915
I 66 J


APPENDIX B
BIBLIOGRAPHY
Beach Erosion Board
a Study of Progressive Oscillatory Waves in Water. Tech. Report No. 1, U. S. Gov't. Print. Off., Wash., D. C 1041
A Summary of tile Theory of Oscillatory Waves, Tech. Report No. 2 U. S. Gov't. Print. Off., Wash., F>. C., 1942
Abrasion of Beach Sand. Tech. Memo. No. 2. U. S. Gov't. Print. Off. Washington, D. C., 1042
Shore Currents and Sand Movement on a Model Beach, Tech. Memo. No. 7, War Dept. U. S. Engineers, 1944
Manual of Procedure in Beach Erosion Studies, U. S. Gov't. Print Off.. Washington, D. C., 1938
Brown, E. I.
Studies of Beach Erosion, Engineering News-Record, Vol. 120, No. 8, 1938
Beach Erosion Studies. A.S.C.E. Proa, Vol. 65, No. 1, 1939; Discussions, Vol. 65, No. 4, 5, and 6, and Vol. 66, No 2. and 3, 1940
Case. G. O., Causes of Coast Erosion and Accretion, Surveyor i London), Vol. 69, No. 1777, 1926
Converse, J. B Shore and Storm Protection on the Gulf Coast, American Concrete Institute Journal, Vol. 1, No. 6, 1930
Corning, L. H.. Concrete Shore Protection Structures, Shore and Beach, Vol. 12, No. 2, 1944
Cram. C. M,, Beach Erosion in Southern California, Civil Engineering Vol. 6, No. 12, 1936
Dakers, J., Suffolk County Beach Rehabilitation, Shore and Beach, Vol. 8, No. 1, 1940
Dent. E. J., New Study of Beach Erosion, Military Engineer, Vol. 23, No. 129, 1931
Evans, O. F., Wave Action and Movement of Beach Sediments, Shore and Beach, Vol. 9, No. 4, 1941
Fellows, C. E., Coastal Protection, Civil Engineering (London), Vol. 39, No. 45fi, 1944
Galllard, D. D,, Wave Action in Relation to Engineering Structures, Engineering School, Fort Belvoir, Va., 1935
Grant, U. S., Waves as Sand Transporting Agent, American Journal of Science, Vol. 241, No. 2, 1943
Waves as Sand Transporting Agent, Shore and Beach, Vol. 11, No. 2 1943
Hall, W, C, Beach Protection Measures, Military Engineer, Vol. 34, No. 200. 1942
Hennebique, J. J., Littoral Drift, Civil Engineering. Vol. 4, No. 3, 1934
Howard, E. A., Permeable Groins of Concrete Check Beach Erosion, Engineering News Record, Vol. 114, No. 17, 19.15
Irminger, J. O. V., Formation of Waves, Engineering, Vol. 119, No. 3080, 1925
Jeffreys, H., Formation of Water Waves by Wind, Royal Soc. Proc, Vol. 107. No. A-742, 1925
Formation of Water Waves by Wind, Royal Soc, Proc., Vol. 110, No. A-754, 1926
I M I


Johnson, A. G., Beach Protection Erosion. Pollution Mar Shores, Western Construction News, Vol. 18, No. 6, 1943
Keay. T. B., General Question of Coast Erosion and Measures Desirable for Prevention of Damage Caused Thereby; arid Drainage of Low-Lying Lands, Instr. Mun. and County EngineersJ, Vol. 67, No. 6, 1940
Kingman. J. J., Shore Protection Methods and Materials, Shore and Beach, Vol 12. No. 2, 1944
Urge Concrete Sheetpiles for Beach Protection, Concrete, Vol. 52, No. 7. 1944
Kressner. B.. Hydraulic Experiments with Models on the Effect of Currents and Surf Breakers Upon a Sandy Sea Beach, Bnutcchnik. Vol 6, No. 25. 1928
Leypoldt. H.. Shoreline Formation by Currents, Shore and B.^ach. Vol. 9, No. 1, 1941
Lipp. M. N., Some Data on Beach Protection Works, Civil Engineering, Vol. 6. No. 5 and 8. 1936
Mackenzie, A. D., Coastal Erosion in Victoria, Australia, Dock and Harbor Authority, Vol. 20, No. 236, 1940
Mann, Ft. H, Pressure Creosoted Timbers fur Shore and Beach Protection Structures. Shore and Beach, Vol. 12, No. 2, 1944
Mcintosh, K. J., Steel Sheet Piling for Shore and Beach Protection Structures. Shore and Beach, Vol. 12. No. 2, 1944
Mitchim. C. F.. Oscillatory Waves in Deep Water. The Military Engineer, March. April. 1940
Mobbs. W. S.. Sea Defences: Erosion and Protection on a Sanely Coast. Surveyor (London). Vol. 72. No. 1871. 1927
Molitor, D A.. Wave Pressures on Sea-Walls and Breakwaters. A.S.C.E. Proceedings, Vol. 60, No. 5, 7, and 10, 1934
O'Brien. M. P., Transportation of Sand by Wind. Civil Engineering, Vol. 6, No. 12. 1936
Ripley. II. C. Beach Erosion, Its Causes and Cure, A.S.C.E. Proc, Vol. 50, No. 1, 1924. Discussions, No. 4 and No. 5, 1924
Stratton, A. C, Reclaiming North Carolina Banks. Shore and Beach. Vol. 18. No. 6. 1943
Taylor. L. B.. Sea Walls and Groins of Steel Sheeting Stabilize Miami Beach. Engineering News-Record. Vol. 106. No. 19, 1931
Trotman. E. E. R.. Submerged Barriers for Shore Protection, Engineer, Vol. 169. No. 4391. 1940
U. S. Waterways Experiment Station. Hydraulics Bulletin. Vol. 4, No. 1
Vander Burgt, .1. H.. Coast Protection on North Sea Coasts of Holland, France, Belgium, and Germany, Royal Engineers J.. Vol. 51, 1937
Warburton, W., Bulkheading Expands Miami's Shore. Earth Mover, Vol. 27, No. 12. 1940
Weatherwax. H. E., Protecting North Carolina Reaches against Wind and Wave Action, Engineering News-Record, Vol. 118, No. 9, 1937
Youngberg, G. A.. Conservation of Florida Beaches and Waterways, Fla. Engineering Society. Bulletin No. 10, 1936


PUBLICATIONS OF THE FLORIDA ENGINEERING AND INDUSTRIAL EXPERIMENT STATION
Ah long as the supply is adequate, copies of available publications are free for general distribution. Address all requests to: The Director, Florida Engineering and Industrial Experiment Station, University of Florida, Gainesville, Florida.
BULLETIN SERIES
No. 1 "The Mapping Situation in Florida", by William L. Sawyer.
No. 2 "The Electrical Industry in Florida", by John W. Wilson. No. 3 "The Locating of Tropical Storms by Means of Associated Static", by Joseph Weil and Wayne Mason. No. 4 "Study of Beach Conditions at Daytona Beach, Florida,
and Vicinity", by W. W. Fineren. No. 5 "Climatic Data for the Design and Operation of Air
Conditioning Systems in Florida", by N. C. Ebaugh
and S. P. Goethe. No. 6 "On Static Emanating from Six Tropical Storms and its
Use in Locating the Position of the Disturbance", by
S. P. Sashoff and Joseph Weil. No. 7 "Lime Rock ConcretePart 1", by Harry II. Houston
and Ralph A. Morgen. No. 8 "An Industrial Survey of Hides and Skins in Florida",
by William D. May. No. 9 "Studies on Intermittent Sand FiltrationPart I", by
D. L. Emerson, Jr.
No. 10 "Florida Spray Gun for Pine Tree Gum Stimulation", by Norman Bourke ami K. W. Dorman.
No. 11 "Developments of Ceramic Compositions Suitable for the Production of Porcelain Type Artware", by B. W. Thorngate.
No. 12 "Mold and Mildew Control for Industry and the Home", by S. S. Block.
No. 13 "Engineering and Industrial Research at the University of Florida."
No. 14 "Reverse Cycle of Refrigeration for Heating in the South", by S. P. Goethe.
No. 15 "Analysis of the Two Span Rigid Frame Highway Bridge", by C. D. Williams.


TECHNICAL PAPER SERIES
No. 1 Heats of Solution of the System Sulfur Trioxide and Water, by Ralph A. Morgen.
No. 2 The Useful Life of Pyro-Meta and Tetraphosphate, by Ralph A. Morgen and Robert L. Swoope.
No. 3 Florida Lime Rock as an Admixture in Mortar and Concrete, by Harry H. Houston and Ralph A. Morgen.
No. 4 Country Hides and Skins, by William D. May.
No. 5 Empirical Correction for Compressibility Factor and Activity Coefficient Curves, by R. A. Morgen and J. H. Childs.
No. 6 Crate Closing Device, by William T. Tiffin.
No. 7 The System Sodium Acetate-Sodium Hydroxide-Water, by R. A. Morgen and R. D. Walker, Jr.
No. 8 Patent Policies for Sponsored Research, by Ralph A. Morgen.
No. 9 Conservation of Municipal Water Supplies in Air Conditioning Systems, by N. C. Ebaugh.
No. 10 Florida Scrub OakNew Source of Vegetable Tannin, by H. N. Calderwood and William D. May.
No. 11 Protein Feed from Sulphite Waste Liquor, by R. D. Walker, Jr., and R. A. Morgen.
No. 12 Effect of Moisture on Thermal Conductivity of Lime-rock Concrete, by Mack Tyner.
No. 13 Insect Tests of Wire Screening Effectiveness, by S. S. Block.
No. 14 Properties of Limerock Concrete, by Mack Tyner.
No. 15 Scrub Oak as a Potential Replacement for Chestnut, by H. N. Calderwood and W. D. May.


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