RESEARCH NEEDS OF THE OFFICE OF BEACHES AND COASTAL SYSTEMS FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION
Robert G. Dean
Office of Beaches and Coastal Systems Florida Department of Environmental Protection Marjory Stoneman Douglas Building 3900 Commonwealth Boulevard Tallahassee, Florida 32399-3000
OFFICE OF BEACHES AND COASTAL SYSTEMS FLORIDA DEPARTMENT OF ENVIRONMENTAL
Office of Beaches and Coastal Systems
Florida Department of Environmental Protection Marjory Stoneman Douglas Building
3900 Commonwealth Boulevard
Tallahassee, FL 32399-3000
Robert G. Dean
Department of Civil and Coastal Engineering
University of Florida
Gainesville, FL 32611-6580
TABLE OF CONTENTS
1. INTRODUCTION ....................................................... I
(1) Limited Quantities of Quality Sand Resources ............................. 1
(2) The Presence of Many Stakeholders ..................................... 2
(3) Increasing Sophistication of Coastal Residents and Governmental Entities ....... 2 (4) The Continued Impact of Inlets on the Adjacent Beaches ..................... 3
(5) Increasing Environmental Concerns ...................................... 3
(6) The Availability of Significant Funding to Accomplish the Beach
M anagem ent M ission ................................................. 3
2. THE PROCESS EMPLOYED IN THIS REPORT ............................ 3
3. ORGANIZATION OF THIS REPORT ..................................... 4
4. RESEARCH NEEDS .................................................... 4
4.1 Research Needs Identified ............................ ;,****- *- 4
4.2 Construction of a "Turtle Friendly Beach Nourishment Project ............... 6
4.3 Addressing Problems at Inlets .......................................... 6
4.4 Sea Level Change .................................................... 6
4.5 Comprehensive Review of Beach Nourishment Projects in Florida ............. 7
4.6 Instrumentation of a Beach Nourishment Project ........................... 7
4.7 Native Sand Characteristics ............................................ 7
4.8 Erosional Hot Spots .................................................. 8
4.9 Sand Transfer Technology ............................................. 8
4.10 Use of Groins or Detached Breakwaters .................................. 8
4.11 Laser D ata .......................................................... 8
4.12 Establishment of a Data Base on Bluff Line Positions ....................... 9
4.13 Statistics of Shoreline Change .......................................... 9
4.14 Prediction of Near Real-Time Erosion .................................... 9
4.15 Performance Differences of Quartz and Calcareous Nourishment Materials ..... 10 4.16 Criteria for Experimental Projects on Erosion Control ...................... 10
4.17 W ave Inform ation ................................................... I I
A CONSTRUCTION OF A "TURTLE FRIENDLY" BEACH ................. A-1
A 1 D iscussion ...................................................... A -1
A .2 Reference ....................................................... A -2
B ADDRESSING PROBLEMS AT INLETS ................................. B-1
B I G eneral .......................................................... B -1
C SEA LEVEL CHANGE ................................................ C-1
C I G eneral .......................................................... C -1
C .2 Reference ........................................................ C-3
D COMPREHENSIVE REVIEW OF BEACH NOURISHMENT PROJECTS IN
FL O R ID A ........................................................... D -1
D I G eneral ......................................................... D -1
D.2 Recommended Plan ............................................... D-1
D.2.1 Task 1: Performance Evaluation .............................. D-1
D.2.2 Task 2: Evaluation of Models and Available Information for Design D-2
D.2.3 Task 3: Identification of Needed Improvements in Data and Beach
Nourishment Design Methodology ..................... D-2
D .3 References ...................................................... D -2
E INSTRUMENTATION OF A BEACH NOURISHMENT PROJECT .......... E-1
E. I G eneral Plan ...................................................... E-1
E.2 Selection of Project for Detailed Field Monitoring ........................ E-1
E.3 Instrumentation and Data Collection Plan ............................... E-1
EA Data Reduction .................................................... E-2
E.5 Comparison With Current Design Methodology .......................... E-2
E.5.1 Volume Remaining Within the Nourished Area .................... E-2
E.5.2 Plan Area Within the Nourished Area ............................ E-2
E.5.3 Volume Changes Adjacent to the Project Area ..................... E-2
E.5.4 Detailed Profile Adjustment .................................... E-2
E.5.5 Sediment Sorting Across the Profile ............................. E-2
E.5.6 Profile Form as a Function of Size Characteristics of
Nourishment Sediments ....................................... E-3
F NATIVE SAND CHARACTERISTICS ................................... F-1
F. I G eneral .......................................................... F-1
F.2 Reference ........................................................ F-1
G EROSIONAL HOT SPOTS ............................................ G-1
G I G eneral ......................................................... G -1
G.2 Recommended Field Program ....................................... G-1
G .3 Reference ....................................................... G -1
H SAND TRANSFER TECHNOLOGY .................................... H-1
H 1 Introduction ..................................................... H -1
H.2 Sand Transfer Around Inlets ........................................ H-1
H.3 Sand Transfer Over Long Distances ................................... H-1
H A Reference ....................................................... H -1
GROINS OR DETACHED BREAKWATERS ............................. 1-1
1. 1 G eneral .......................................................... I-1
EVALUATION OF LASER DATA ....................................... J-1
J. I Introduction ...................................................... J-1
J.2 Recom m endation .................................................. J-1
K ESTABLISHMENT OF A DATA BASE ON BLUFF LINE CHANGE ........ K-1
K 1 Introduction ..................................................... K -1
K .2 M ethodologies ................................................... K-1
K.2.1 Statistical Distributions ...................................... K-1
K.2.2 Correlation With Other Indicators of Bluff Line Change ............ K-1
K.3 Additional Comments .............................................. K-1
L STATISTICS OF SHORELINE CHANGE ................................ L-1
L. I Introduction ...................................................... L-1
L.2 Discussion and M ethodology ......................................... L-I
M PREDICTION OF NEAR REAL-TIME SHORELINE EROSION ........... M-1
M I Introduction ..................................................... M -1
M .2 M ethods ........................................................ M -1
* PERFORMANCE DIFFERENCES BETWEEN QUARTZ AND
CALCAREOUS NOURISHMENT MATERIALS ......................... N-1
N 1 Introduction ..................................................... N -1
N .2 A pproach ....................................................... N -1
N .3 Reference ....................................................... N -1
* CRITERIA FOR EXPERIMENTAL PROJECTS ON EROSION CONTROL 0-1
0 1 Introduction ..................................................... 0 -1
0.2 Recommended Program ............................................ 0-1
0.2.1 Compilation of Previous Experience With Innovative Methodology ... 0-1
0.2.2 Criteria For Evaluating the Suitability of Proposed
Approaches for Testing ...................................... 0-2
0.2.2.1 Uniqueness, i.e. The Same or
Essentially Similar Concept Has Not
Been Tested Under Similar
Conditions Without Success .......................... 0-2
0.2.2.2 Inherent Supporting Physical
Principles ......................................... 0 -2
0.2.2.3 Very Low Potential for Adverse
Effects to Adjacent Beaches......................... 0-2
0.2.2.4 Very Low Potential for Adverse
Environental. Effects .............................. 0-3
0.2.2.5 Aesthetics ...................................... 0-3
0.2.2.6 Acceptable Monitoring Plan......................... 0-3
0.2.2.7 Pre-testing Development of Criteria Against Which the Success of the
Testing Will Be Judged ............................. 0-3
0.2.2.8 Evaluation by a Third Party Reviewer ..................0-3
P DEVELOPMENT OF WAVE INFORMATION.......................... P-1
P.1I Introduction .................................................. P-1
P.2 Recommendation............................................... P-2
P.2.1 General ................................................ P-2
P.2.2 Establishing the Need for Additional Wave Information .............P-2
P.2.3 Possible Scopes of Programs to Develop Wave Information ..........P-2
P.2.3.1 Sustained Measurements at Selected Locations and Duration Limited
Measurements at Other Selected
Locations ....................................... P-3
P.2.3.2 Limited Duration Measurements at Selected Locations with Correlations to and Later with Greater Reliance on Hindcasts and Buoy Data .......................... P-3
LIST OF FIGURES
B-1 Port of Palm Beach Entrance, February 11, 1991 ............................. B-1
C-1 Locations of Long-term Tide Gages in Florida ............................... C-1
C-2a Relative Sea Level Changes at Pensacola, FL ................................ C-2
C-2b Relative Sea Level Changes at Juneau, AK .................................. C-2
I-1 Adjustable Groin Which Was Used Extensively in Florida in the 1960's to 1970's ... 1-2 L-1 Hypothetical Shoreline Changes .......................................... L-1
L-2 Shoreline Changes at Three Locations in St. Johns County Based on Aerial
Photographs .......................................................... L-2
P-1 Locations of Wave Buoys in the Vicinity of Florida ........................... P-1
LIST OF TABLES
I Research N eeds ......................................................... 5
RESEARCH NEEDS OF THE
OFFICE OF BEACHES AND COASTAL SYSTEMS
FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION
The landscape of beach management in Florida has changed significantly over the past few decades and continues to evolve rapidly. Some of these changes are favorable to appropriate beach management and others represent significant challenges which if not addressed early in the process, could impede the State's beach management program significantly, The causes of the changes include: (1) Limited quantities of quality sand resources, especially in the southeast region of the State, (2) The presence of many stakeholders along the coastline, usually with a wide and sometimes conflicting range of objectives, (3) Increasing sophistication of coastal residents and governmental entities, (4) The continued impact of inlets on the adjacent beaches, (5) Increasing environmental concerns, and (6) The availability of increased funding to accomplish the beach management mission. Each of these elements is discussed in this section to provide a basis for development of research needs. It is noted that research can contribute to reducing some of the potential impediments to appropriate beach management, but not to others. Also, it is appropriate to observe that the beach management program in Florida is far advanced relative to those in other coastal states; however, in order to maintain the program and use limited resources effectively, it is essential to anticipate emerging problems and needs and to conduct the required research in advance to meet these needs.
(1) Limited Quantities of Quality Sand Resources
The quantities of high quality sand available from conventional nearby offshore resources are becoming more scarce in some locations. This problem is expected to increase and to become more geographically broad in the future. Suitable sand resources immediately offshore Dade County are considered nearly exhausted. The limited quality sand resources are in close proximity to environmental resources which limits the potential for their future extraction. Elsewhere, sand resources may contain too much rock or the color may not be suitable. Rock present in a sand body can be removed at a cost. Although in many cases, the sand color immediately after dredging may improve with exposure to sun and rain, in other cases, an undesirable color may be permanent or may improve on a much longer time scale.
These limited quantities of suitable and economically and environmentally retrievable sediments will require that new or previously unrecognized sources be considered. This may require development of new capabilities in the dredging industry to extract sand from deeper water or to transport sand economically over large distances, possibly from inland sources. Additionally, the development and implementation of new methods of sand management may be required in which sand is relocated from beaches that have become wider as a result of transport and depositional patterns while other beaches have become narrower. This "recycling" of sand will require an answer to the often asked question "where does the sand placed in nourishment go?" This question must be considered in much greater detail than in the past in order to convince shore front residents with a wide beach that they should allow their beach to be diminished in width with the sand removed and placed in an area
where the beach is much narrower. In such cases, education of the various stakeholders will play a vital role.
(2) The Presence of Many Stakeholders
The shorelines of Florida are nearly fully developed. Most changes in the form of development that occurs are redevelopment as a result of storm damage or economic incentive. Within this scenario are many and diverse stakeholders often with competing agendas and objectives. The stakeholders in the vicinity of inlets are especially complex and include: boaters, downdraft and updrift property owners, and surfers. The inevitable "tug of war" over often-times inadequate amounts of sand for all perceived needs is obvious. Boaters and surfers are understandably suspicious of any modifications that could alter a perceived "perfect inlet" thereby affecting their uses. Against this backdrop are the substantial natural changes that will occur regardless of whether the inlet is altered or whether the sand transport practices are changed. The recognition that any undesirable occurrence after a physical or operational change will be interpreted as due to the change casts a pall on the regulatory agencies responsible for and/or proponents of the change.
The best strategy in this scenario, and one that OCBS is presently following, is to engage at an early date and throughout the process, all known stakeholders with the hope that by maintaining all interests represented and playing a significant role in the decision making process, that the needed action will be recognized, shaped and accepted by all stakeholders.
(3) Increasing Sophistication of Coastal Residents and Governmental Entities
Coastal residents and governmental entities are becoming increasingly engaged and sophisticated with regard to their beach resources. It is expected that the sand placed in nourishment will provide a near ideal match to the native sand. No longer in most places in Florida is the concern only to provide a beach of adequate width to provide storm protection, but rather to provide a wider beach with nearly imperceptible differences from the native beach characteristics. As a demonstration of the different levels of concerns of the type of material placed on the beach, a resident whose home is threatened will be very appreciative of approval to place, at their own expense, large rocks to provide the necessary protection. The presence of these rocks represents a completely different character to the native beach. If small rocks are placed and scattered during the placement of the larger more stable rocks, the resident who has received the sought after protection is not concerned. However, change this picture to a shorefront community with a reasonable beach that has been experiencing erosion at a relatively slow rate and for which storms have not impacted the area during the experience history of most residents. These shore front residents will examine the character of the nourishment material with much greater scrutiny.
Added to the "mix" above is the role played by the news media in reporting on and amplifying these concerns which might be considered as minor by most. Again, the need for the design engineer to anticipate the types and degree of differences that may occur and to convey these to the sponsoring communities and other agencies in advance is evident. The downside of developing a more complete anticipation of the types and magnitudes of differences by the design engineer are the associated costs to carry out more comprehensive sampling and analysis. There must be an optimum between
the cost of the investigation and the risk that the sponsors and regulatory agencies are willing to accept; however, at present this is not established and represents part of the changing landscape of beach management in Florida.
(4) The Continued Impact of Inlets on the Adjacent Beaches
Inlets continue to impact significantly the beaches of the State of Florida. Of the 56 inlets in the State of Florida, there are now some 35 Inlet Management Studies, completed and 7 additional underway. Many of these studies were or are being carried out under the auspices and partial funding of the OBCS. Additionally, of these 42 studies, Inlet Management Plans (IMP) have been adopted for 16 of these inlets. The significance of adoption of an IMP is that the particular inlet is eligible for State funding in carrying out the provisions of the IMP. The present challenge is to proceed to implement the IMP with the diverse stakeholders represented as discussed earlier and to identify and institute modifications of the IMP as determined as the process unfolds, retaining sufficient flexibility.
(5) Increasing Environmental Concerns
Management of Florida's beaches has the potential to be either environmentally beneficial, neutral, or detrimental. The main environmental concerns have been associated with the effects of beach nourishment on the successful nesting and reproduction of sea turtles. Additionally the covering of hard bottom or sea grasses with nourishment material has been questioned. In some cases, it may be possible to mitigate any potential adverse effects through use of appropriate nourishment materials and designs. Improvements in sea turtle nesting habitat can occur through a wider beach, thereby providing more habitat. These improvements are most significant in locations where potential beach nesting widths have been diminished through beach erosion and the resulting construction of seawalls and revetments. Every reasonable effort should be made to ensure, to the degree possible, that engineering modifications to the shoreline improve the environment or at worst, are environmentally neutral.
(6) The Availability of Significant Funding to Accomplish the Beach Management Mission
The Florida Legislature, in recognizing the value to Florida!s economy of maintaining healthy beaches, established a dedicated finding source of $ 30 million per year for a 15 year period. This dedicated funding carries with it opportunities and responsibilities. The opportunities are the obvious provision of funding to carry out the program mission. The responsibilities are to place on a fast track, the methods of solving the program problems now that the funding resources are available while garnering as much additional funding as possible through cost sharing with local and Federal participants.
2. THE PROCESS EMPLOYED IN THIS EFFORT
The process employed in this report was to conduct interviews of individuals who play a role and/or have a stake in the beach management program in the State of Florida. These individuals included employees of the OBCS of DEP, practicing engineers, local governmental employees and Members of the Coastal Engineering Technical Advisory Committee (CETAC) which includes a cross-section of the above. The interviews with employees of OBCS were carried out while working in Tallahassee during Summer 2000. The communications with the other entities were initially by letter in which recommendations in writing were solicited with an option offered for those wishing to discuss their recommendations in person. These discussions were conducted either at "meetings of opportunity" or, in some cases, special visits were made to the individual's offices. Finally, a draft of this report was reviewed by individuals regarded as having a comprehensive view of the present and future beach program needs in Florida. It is believed that this process employed yielded a fairly complete and thorough view of the State's present and future research needs. However, there will be a need to update this summary of Research Needs as the needs evolve. The prioritization of the sixteen research needs identified was carried out by CETAC and Staff of OBCS and will be presented in Table 1.
3. ORGANIZATION OF THIS REPORT
The remainder of this report is organized as follows in an attempt to ensure that the report is most readable by individuals interested in both an overview of the needs and those interested in the details. Section 4 presents, in reasonably brief form, sixteen individual research needs and a brief discussion of the associated rationale. The more detailed approaches for addressing each of these research needs are presented in individual appendices, one appendix for each research need.
4. RESEARCH NEEDS
4.1 Research Needs Identified
The following sections present descriptions of the sixteen research needs in reasonably brief forms. These needs are also summarized in Table 1 along with indications of whether the needs are short or long-term, a priority ranking and the approach to addressing the needs. The prioritization was based primarily on responses from the Coastal Engineering Technical Advisory Committee and Staff of OBCS. The Reader will recognize that these research needs range from the more basic to the manner of approaching some of the problems with which the OBCS is confronted. Thus the list below encompasses from the basic to the very practical.
OFFICE OF BEACHES AND COASTAL SYSTEMS
________________RESEARCH NEEDS_____ ___Research Need Priority Detailed Method of1
Ranking* IDiscussion Immediacy Addressing
Construction of a "Turtle 5 A Short & Field Tests
Friendly" Beach Long-Term
Addressing Problems at Inlets 2 B Short & Stakeholder
Sea Level Change 9 C Short & Field
Comprehensive Review of Beach 1 D Short & Office
Nourishment in Florida Long-Term Studies
Instrumentation of a Beach 13-15** E Short & Field
Nourishment Project Long-Term Studies
Native Sand Characteristics 7 F Short & Field
Erosional Hot Spots 3 G Short & Office
Sand Transfer Technology 2 H Short & Office/Field
Groins or Detached Breakwaters 4 1 Short & Office
Laser Data 13-15** J Short & Office
Establishment of Data Base on 11 K Short & Office
Bluff Line Changes Long-Term Studies
Statistics of Shoreline Change 8 L Short & Office
Prediction of Near Real Time 12 M Long-Term Office
Beach Erosion Studies
Performance Differences of Short & Laboratory
Quartz and Calcareous 10 N Long-Term Studies
Criteria for Experimental 13-15** 0 Short & Office
Projects on Erosion Control Long-Term Studies
Development of Wave 6 P Short & Office/Field
Information ILong-Term Studies
Lowest Numbers Signify Highest Rankings.
** No Clear Differentiation Emerged For These Needs
Beach nourishment projects are generally designed and constructed with slopes that are steeper than equilibrium. Over several years, the beach profile will equilibrate to a milder slope. Associated with this equilibration which can occur predominantly during storms, is a shoreline retreat which results in a "scarping" of the berm leaving a quite steep portion of the profile which could present difficulties to sea turtles intent on climbing up the berm to excavate a nest chamber and deposit their eggs. Thus there is a desire to construct beaches which will exhibit less profile adjustment and associated scarping, resulting in less impediments to nesting sea turtles.
The detailed approach to addressing this research need is presented in Appendix A.
4.3 Addressing Problems at Inlets
Florida has some 56 inlets located along its some 750 miles of sandy shoreline of the 24 counties in the Coastal Construction Control Line (CCCL) Program. These inlets serve primarily for navigation and water exchange. However, many of these inlets have been shown to have significant adverse effects on the adjacent shorelines. This is primarily the case for the inlets which are located where the net longshore sediment transport is large and which have been established or modified for navigation purposes which usually requires a deepened channel and/or jetties to reduce the sand flow into the inlet.
As noted, of the 56 inlets along the predominantly sandy beaches of Florida, there are now some 35 Inlet Management Studies, completed and 7 additional underway. Many of these studies were or are being carried out under the auspices and partial finding of the OBCS. Additionally, of these 42 studies, Inlet Management Plans (IMP) have been adopted for 16 of these inlets. The challenge is to identify and implement some approach to expediting corrective action at those inlets where such corrective action is feasible.
The detailed approach to addressing this research need is presented in Appendix B.
4.4 Sea Level Change
Relative sea level (RSL) change is extremely relevant to long-term beach management. If the rate of sea level rise increases in the future as predicted by some scientists, the maintenance of fixed shorelines and elevations will become increasingly difficult over the long-term. The central questions here are those of time scales which depend, in part on whether or not RSL rates of rise will increase in the future, and if so, when and at what rate and the associated effect on beach stability. A determination is needed of whether the available rise rates from tide gages are representative of the general Florida coastline.
Appendix C presents the recommended detailed approach to addressing this research need.
4.2 Construction of a "Turtle Friendly Beach Nourishment Project"
4.5 Comprehensive Review of Beach Nourishment Projects in Florida
To date, there have been more than 40 beach nourishment projects constructed along Florida!s beaches and beach nourishment is clearly the method of choice for beach erosion control. Only a small percentage (estimated at less than 5% to 10%) of these projects has been analyzed using state of the art methodology in which the performance was compared with design predictions and different available design methodologies; no attempt has been made to evaluate quantitatively the remainder of the projects. There is a substantial variation in the quality and adequacy of the monitoring data for the various projects which represents a serious limitation in the use of the same degree of evaluation and comparison for all projects. Additionally, there are significant differences in the performances of the various projects. A comprehensive review and documentation of the performance of all beach nourishment projects constructed in Florida would provide an invaluable resource and should lead to a greatly improved basis for design and confidence in performance of future projects.
Appendix D presents the recommended detailed approach to addressing this research need.
4.6 Instrumentation of a Beach Nourishment Project
All modem beach nourishment projects in Florida are monitored to some degree. Usually, the performance of the project is documented through surveys, sand sampling and aerial photographs. No recent projects have included the measurement of waves and tides which are the most dominant "forces" causing the project evolution. This situation leaves open interpretation of any less than expected project performance as "due to a severe storm" and prevents the quantitative evaluation of design methodologies. In order to evaluate existing design capabilities, to identify specific deficiencies in existing capabilities and to establish a basis for improving design capabilities, instrumentation of a beach nourishment project is required, including the measurement of waves and tides.
Appendix E presents the recommended detailed approach to addressing this research need.
4.7 Native Sand Characteristics
Guidelines should be developed for the characterization of the native sands in a format that would be readily usable for preliminary beach nourishment design purposes. A provisional guideline could be the method recommended in a report by Dean (2000) in which samples across the profile are characterized by the composite weighted mean of the individual sample grain size characteristics and the cross-shore distances represented by the individual samples. These composite grain size characteristics could be represented in an idealized form, by their individual means and standard deviations or by the detailed grain size distributions.
Appendix F presents the recommended detailed approach to addressing this research need.
Erosional Hot Spots (EHS) occur on natural or nourished beaches, but of course are of primary concern to the OBCS program when their occurrence is unexpected in a beach nourishment project and which can require early mobilization of a dredge to address the EHS and also which is perceived unfavorably by the general public. Studies have shown that some EHSs can be caused by the nourishment operations and can be due to the borrow area characteristics and/or to the placement methods. In such cases, it should be possible to avoid or reduce the EHS through proper anticipation and design.
Appendix G presents the recommended detailed approach to addressing this research need.
4.9 Sand Transfer Technology
There is a need to transfer sand around many of Florida's inlets that have been either excavated or modified for navigational purposes. Of the total of 56 tidal entrances, there is effective sand transfer at approximately six. In some cases, political difficulties may preclude such transfer. For other inlets, there is a need to identify appropriate sand transfer technology for inlets with various characteristics. In addition to the sand transfer need posed by inlets, if inland sources are accessed for beach nourishment purposes, there may be a need to transfer sand over long distances.
Appendix H presents the recommended detailed approach to addressing this research need.
4.10 Use of Groins or Detached Breakwaters
There is interest in employing coastal structures for control of the flow of sands and for shoreline stabilization. The three generic locations where structures are being employed include erosionally stressed areas immediately downdraft of inlets, in the vicinity of erosional hot spots, and at the ends of nourishment projects to limit losses. The two types of structures which can be applied for the purposes discussed include groins and detached breakwaters which function differently and are aesthetically quite different. A feature of many structures is that they are not readily adjusted and, once installed, they are difficult to remove regardless of their performance. Thus, it is important to ensure that appropriate types and designs of structures are employed for the particular application under consideration.
Appendix I presents the recommended detailed approach to addressing this research need.
4.11 Laser Data
The Office of Beaches and Coastal Systems has now accumulated considerable laser data obtained by two types of systems: (1) Those which only determine land elevations, and (2) Systems which also measure underwater elevations. Plans include the collection of more laser data, including poststorm surveys. Laser data appear to have significant potential for the survey needs confronting OBCS, including collecting pre-and post- storm data rapidly, possibly project monitoring and periodic documentation of the entire shoreline of the State. However, at present there are questions regarding the accuracy of these surveys, suitability (if found to be accurate) and limitations.
4.8 Erosional Hot Spots
Because of the plans to acquire more of this type of data, there is a need to develop an early understanding of the accuracies and limitations of the data as the capabilities and uses of laser survey technology increases.
Appendix J presents the recommended detailed approach to addressing this research need.
4.12 Establishment of a Data Base on Bluff Line Positions
The OBCS has established and maintains an exceptional shoreline position data base, encompassing from the 1800's to recent times. This data base lists the Mean High Water (MHW) positions at times for which they are available. For purposes of evaluating applications for armoring, the Office requires estimates of the bluff line positions that would occur due to certain levels of storms. One approach that has been used is through numerical dune erosion models which simulate the effects of storm surges and waves on the cross-shore sediment transport processes. This approach has proven effective in some portions of the State's shoreline, but not as effective in others. The development of a data base of bluff line positions would only be possible from surveys that documented the above water portion of the profile and would thus be limited to the last 20 years or so, depending on the particular county. This data resource would serve as a direct means of calculating expected bluff line recessions due to a particular return period storm event and as a basis for calibration/evaluation of numerical models developed for this purpose.
Appendix K presents the recommended detailed approach to addressing this research need.
4.13. Statistics of Shoreline Change
Shorelines change in response to waves and tides on a range of time and space scales. In developing rational and appropriate shoreline management policies, it is essential to understand the short and long term dynamic characteristics of the shoreline of interest. Such an understanding will be invaluable in interpreting occurrences of unusual erosion events or periods of shoreline advancement. Although the causes of shoreline fluctuations are recognized qualitatively, because there are no validated procedures for calculating long-terrn shoreline response, the only way in which these characteristics can be established is empirically, that is, through analysis of historical data. Although the shoreline position data base maintained by OBCS is of excellent quality, the average number of shoreline positions at a particular location is 8 or so over a time span of approximately 120 years and is thus not of sufficient frequency to quantify the shoreline fluctuations of interest. The program to establish the statistics of shoreline change would require use of aerial photographs to supplement the OBCS data base.
Appendix L presents the recommended detailed approach to addressing this research need.
4.14 Prediction of Near Real-Time Beach Erosion
During extreme events that can affect their well being and security, coastal residents are understandably interested in up to date estimates of future conditions which can pose threats, including flooding and beach erosion. Indeed, the availability of good estimates can contribute to
orderly planning by individuals and by those responsible for emergency operations. The threat of coastal flooding is addressed and distributed to the general public by popular media through models which employ state of the art calculation procedures which incorporate various uncertainties (for example, in the hurricane path) in a probabilistic manner. Similar accessibility by the general public to the results of the best available erosional models should be established.
Appendix M presents the recommended detailed approach to addressing this research need.
4.15 Performance Differences of Quartz and Calcareous Nourishment Materials
Sand sampling along the east coast of Florida has established that many of the profiles are characterized by a berm composed of coarse material with a high calcareous (shell) content and a finer quartz sediment seaward. Often when conducting a "sand searcW' for beach nourishment material similar to the native, several potential sources of suitable material will be located. In some projects currently in the design stages, potential borrow areas have been located that are composed primarily of quartz and others containing predominantly coarser calcareous materials. A relevant question relates to which of these materials is more suitable for nourishment. Concern has been expressed that although the available calcareous materials may have the greater fall velocities, since the quartz sand comprises a greater portion of the active native profile, the quartz sand may be more suitable. This question is expected to arise more frequently in the future.
Appendix N presents the recommended detailed approach to addressing this research need.
4.16 Criteria for Experimental Projects on Erosion Control
There will undoubtedly always be projects proposed using methods which are "innovative" or "nontraditional" in their approach to erosion control. The interest in development of improved methodology for erosion control is healthy and is due, in part, to the inquisitiveness and creativity of interested individuals and in part to the relatively high cost of traditional methods of erosion control. It is expected that, with the increased emphasis on erosion control and the availability of expanded programs and funding, the interest in innovative methods will increase in the future. The process of evaluating whether these projects warrant permits for field testing and the conditions for such testing should be formalized to the degree possible and be available for potential individuals seeking permits. Additionally, it would be desirable for OBCS to establish and maintain a document which records the history of such efforts carried out in the State and elsewhere including the project outcomes. The general criteria governing whether or not a new approach should be permitted for field testing should include, but perhaps not be limited to: (1) Uniqueness, i.e. the same or essentially similar concept has not been tested under similar conditions without success, (2) The existence and description of inherent supporting physical principles, (3) Very low potential for adverse effects to adjacent beaches, (4) Very low potential for adverse effects to the environment,
(5) Aesthetics, (6) Acceptable monitoring plan, (7) Pre-testing development of criteria against which the success of the testing will be judged, and (8) Evaluation by a third party reviewer.
Appendix 0 presents an expanded discussion of the recommended process including each of the above eight criteria.
4.17 Wave Information
The areas of responsibility of the OBCS require access to a range of quantitative wave information. These requirements can include average wave height information for design of some beach nourishment projects on the open coast and wave height and direction for nourishment projects in the vicinity of structures. In cases of interpretation of storm effects, time varying wave characteristics as well as water level information are required. These examples represent only a portion of the needs. Wave information can be developed by wave hindcasts, installation of wave gages or a combination. Additionally, four wave buoys currently operate off the Florida coast, the Corps of Engineers has developed hindcast data and there are some wave measurements available from a previous wave gaging program.
Appendix P presents a discussion of possible approaches to satisfying this research need.
CONSTRUCTION OF A "TURTLE FRIENDLY" BEACH
CONSTRUCTION OF A "TURTLE FRIENDLY" BEACH
The development of procedures to construct a "turtle friendly beach" was identified as a significant research need. The rationale for this need is presented in Trindell, et al (1998) in which turtle hatching success results are reported from the monitoring of 24 beach nourishment projects. Nest relocation was not allowed in these projects and it was found that the nesting/hatching success was decreased relative to control locations monitored during the first year after nourishment. An interpretation of the lower nesting success during the first year is that the relatively rapid profile adjustment during this first year with the associated shoreline retreat causes those nests within this retreat zone to be lost. Of course, one approach would appear to be the relocation of those nests considered to be in jeopardy due to profile adjustment. Lacking the option to relocate nests, it is desirable to construct the beach so as to minimize profile adjustment. In fact, the sand could be placed such that the profile adjustment would be an associated shoreline advancement rather than a retreat. Details are discussed below.
Over several years, a nourished profile will approach equilibrium, the geometry of which depends on a number of factors with the grain size of the nourishment sand being the most significant. In order to minimize profile adjustment after nourishment, the nourished profile could be placed in a reasonably near equilibrium configuration. Most beach nourishment project specifications call for planar design slopes and the Contractor is paid based on meeting these specifications. These planar slopes are on the order of 1: 10 to 1:20 and may extend out to water depths ranging up to 10 to 15feet. In contrast, the average slope for typical Florida natural profiles out to a water depth of 10 feet is approximately 1:50. For a typical Florida beach nourishment profile in which the nourishment density (volume placed per unit length) is 100 yds'/ft, the total shoreline adjustment may be on the order of 3 0 ft to 40 ft. In all cases in which a slope of 1: 10 to 1:20 is specified, the Contractor places sand outside of these limits for which payment is not received. This is especially the case for the finer nourishment materials placed hydraulically which tend to "run" beyond the construction template. Estimates of this component of overfilling range up to 25% to 30% above quantities required to fill the construction template. The modification of the usual specification from a planar beach slope to one that requires placement over a greater portion of the active profile and altering the basis for payment to quantities based on surveys and found within a reasonable distance from shore should improve this problem greatly. Additionally, the Contractors should welcome this change as they would receive payment for all of the material which they place in the profile and the bid prices should be reduced accordingly. Concurrently with the placement of the underwater portion of the profile in a form more toward equilibrium, the elevation of the berm should be addressed. Ideally, the berm should be at a natural elevation, so as to minimize impediments of turtles to crawl onto the berm. In contrast to the underwater portion of the profile, the specifications for the berm elevation should be maintained fairly "tight" and could be specified at 0.5 feet below the natural berm elevation with subsequent high tides and waves carrying out the final deposition of sand to the natural berm elevation.
There are two potential "downsides" to the placement of material in a form more representative of an equilibrium profile. The first is that the "pay" surveys will be somewhat more complex although certainly within the state of the art in surveying. The second concern is that by placing more material directly in the water, the potential for greater turbidity is increased.
To evaluate the possibility of designing and constructing a "turtle friendly" beach nourishment project, it is recommended that a full scale test project be conducted. The project should be reasonably long so as to highlight the cross-shore processes of concern here rather than the longshore "spreading out" of the project sediments. A project should be selected for this test for which the borrow area has a relatively small silt and clay content (say 3 to 5 %) to ensure that turbidity due to direct placement of sediments in the water will not be a concern. If the area is one of low wave activity, it might be possible to place the sand by either the "Rainbow Method" in which the slurry mixture is placed as a high pressure jet from the dredge to the shore/shallow water area or by relatively small split hull barges. The latter could result in a somewhat "uneven" placement of the material underwater which would place greater demands on the survey; however, with the availability of wave runner survey capabilities, this is not expected to present a problem. Of course, this test project should include greater documentation than is associated with a typical nourishment project.
Trindell, R., D. Arnold, K. Moody and B. Medford (1998) "Post-Construction Marine Turtle Nesting Monitoring Results on Nourished Beaches", Proceedings, 1 lth National Conference on Beach Preservation Technology, pp. 77- 92.
ADDRESSING PROBLEMS AT INLETS
ADDRESSING PROBLEMS AT INLETS
Natural entrances modified for navigational purposes or new inlets constructed for this purpose along with the past management of the sand resources at these entrances have taken their toll on the adjacent beaches. As an example, Figure B-1 presents a photograph of Lake Worth Entrance (also called the Port of Palm Beach Entrance) which was cut in 1917 with jetty construction completed by 1925. The net longshore sediment transport in this area is toward the South at a rate of approximately 200,000 cubic yards per year. As can be seen from Figure B-1, there is a substantial offset from the north to the south side due to the jetties acting as a barrier to the natural flow of sand.
Figure B-1. Port of Palm Beach Entrance, February 11, 1991.
present, the shoreline offset at this entrance is some 1,200 feet and the more seaward structures on the updrift (north) side of the entrance have been built on some of the accumulated sediment. Thus this sand is no longer available for bypassing as would have occurred if this navigational entrance had not been constructed. Additionally, it is estimated that approximately 3 million yards of sand has been dredged for maintenance purposes at this entrance and disposed of in deep water and a similar quantity has been placed as "spoil" on Peanut Island located immediately inside the entrance. This sand, which was removed from the active beach system, is also not available for placement on the beaches; however, its removal has impacted the beaches to the south. Using standard coastal engineering principles to estimate the erosional effect of the removal of some 6 million cubic yards of quality sand on the 15 mile barrier island comprising Palm Beach Island extending from Port of Palm Beach Entrance to South Lake Worth Inlet yields an average shoreline recession of approximately 100 ft (corresponding to 76 yd'/ft)!
As noted earlier, to date the OBCS has co-sponsored the development of approximately 40 Inlet Management Studies (IMS). Of these, 16 have been adopted as Inlet Management Plans (IMP). An IMP is a rather brief document which usually summarizes and adopts, on a provisional basis, the more salient results of the IMS and, perhaps, more importantly, qualifies the inlet for State funding. Since the adoption of these 16 plans, the OBCS has altered their strategy for the remaining inlets which are now being integrated into Strategic Beach Management Plans, which are more regional in scope and incorporate the inlets as well as the beaches in the particular region. Regardless of the approach for a particular inlet, the most significant challenge is that of proceeding to implementation of corrective action for the inlets. The approach being followed by OBCS has been to commence efforts on a number of inlets and some success has been realized. For these entrances, a Technical Review Group (TRG) has been formed with an attempt to invite representation from all stakeholders. During meetings of the TRG the issues are identified and attempts are made to establish approaches acceptable to all which will represent progress toward reinstating the natural sand flows past the entrance. For the case of St. Lucie Inlet in Martin County, which is certainly one of the most impactive inlets in Florida, this approach has been effective and resulted in the removal in 1999 of 800,000 yd' of sand from the flood tidal shoals, the transport of this sand some 8 miles by barge south through the Intracoastal Waterway and placement on the eroded beaches of the Town of Jupiter Island, thus alleviating both the shoaling problem in St. Lucie Inlet and the severe erosion problem on the beaches of the Town of Jupiter Island.
An alternate more "focussed" approach to that which is being followed would be to: (1) Screen the inlets for the combination of factors which are conducive to addressing effectively and expeditiously, the severe impacts to the State's shorelines. This would include, based on consideration of all factors, the likelihood of success in correcting the impact in several years, and (2) Adopt a schedule for the measures required to correct the impact. Each year, the process would be repeated with a different inlet selected based on the above criteria and a schedule adopted for the new inlet, etc. Additionally, after each year, a review of progress toward the objectives for those inlets for which schedules had been established would be conducted and adjustments made as necessary.
The screening process would include, but not be limited to: (1) Review of the engineering feasibility of corrective measures, (2) Adverse impacts of the inlets, and (3) Preliminary meetings with stakeholders to determine their general commitment to pursue corrective action.
SEA LEVEL CHANGE
SEA LEVEL CHANGE
Relative Sea Level (RSL) rise rates in Florida are based on the seven long-term tide gages shown in Figure C-1 and indicate a RSL rate of approximately 20 cm/century, some 67 % more rapid than the world-wide rate of 12 cm/century. This difference, which could be due to local or regional effects, is central to the type and timing of long-term beach management strategies. In the paragraphs below, some background on RSL is first presented followed by a recommended program in Florida to quantify relevant rates more accurately.
Fernandina Beach Mayport
Cedar Key St. Petersburg
Figure C-1. Locations of Long-term Tide Gages in Florida
As noted, on a world-wide basis, sea level is rising at an average rate of approximately 12 cm/century; however, there are very substantial local deviations from this rate (termed the "eustatic rate"), ranging from areas where the land is sinking at more than 10 times this world wide rate to areas where the land is rising at more that 10 times this rate. There are numerous causes of these deviations, including natural and human related. The most predominant natural causes include tectonic activity due to long-term uplift of geologic formations, and the rebound in the higher latitudes (for example in Alaska) due to the unloading associated with the melting of the large glaciers formed during the last ice age. Connected with this rebound in the higher latitudes is an associated subsidence in the lower latitudes such as those in Florida. The increase of the available
RSL values in Florida above the eustatic values could be due predominantly to the adjustment of the earth's sphere as a result of the glacier unloading at the higher latitudes. Figure C-2 presents the RSL changes, based on long-term tide gages for Pensacola, Florida and Juneau, Alaska. It is seen that the RSL is rising in Pensacola, FL at a rate of somewhat less than 1 foot/century and falling in Juneau, AK at an approximate rate of 4 feet/century. These large scale regional causes cannot be controlled.
Yearly Mean Sea Level
Station No. 8729840 Pensacola, FL
8.2 Trend Line of
1 ft Per Century i8~ 1865(for comparison purposes)
101851880 1895 1910 1965 19Q40 19'56 1970 1985
Figure C-2a. Relative Sea Level Changes at
13.8 13.4 -
Yearly Mean Sea Level Station No. 9452210 Juneau, A
Trend Line of40
Mt Per Centtry
(for comparson purposes:\
13.0. A A
1850 1865 1880 1895 1910 1925 1940 1955 1970 1985
Figure C-2b. Relative Sea Level Changes at
The quantification of a possible second and local human related cause, discussed below, is relevant to the appropriate long-term strategy adopted by the State of Florida for the management of its beaches. A concern with the seven long-term Florida tide gages is that they are all located near reasonably densely populated areas (usually ports) and thus may not be representative of conditions along the main portion of the Florida shoreline. The reason is that it has been determined in many locations that the extraction of large quantities of ground fluids (water, hydrocarbons, etc) can result in substantial ground subsidence. The most celebrated case is at Terminal Island, CA where the extraction of large quantities of hydrocarbons resulted in a relatively rapid subsidence in excess of 20 feet before the effect was recognized (National Research Council, 1987). As a result of that occurrence, for every barrel of hydrocarbons extracted, it is now required that a barrel of salt water be pumped into the aquifer as a volumetric replacement for the removed hydrocarbon. A second example is at Niigata, Japan, where, during the second World War, large quantities of groundwater were extracted for industrial purposes resulting in a subsidence of some 6 feet.
In order to establish whether, and if so, to what degree the Florida tide gage results are influenced by the local extraction of ground water near the gages, it is recommended that GPS technology be used to determine whether: (1) Subsidence is occurring at the locations of the tide gages (Based on the data, it appears that these areas are subsiding, on an average at 8 cm/century), and (2) Other coastal areas, distant from locations of ground water extraction are subsiding. This effort would require a "test of concept phase" in which GPS receivers would be installed to determine their capabilities. GPS should be able to establish absolute elevations at sub millimeter accuracy if allowed to remain on station for a sufficiently long time.
Jnce the capability of the GPS methodology was established, receivers would be placed at representative locations along the Florida shoreline to quantify elevations. The receivers could reoccupy these selected locations annually with a fairly low level of effort until the trends became clear. The trends would be analyzed until, based on their variabilities, it was established that a statistically valid estimate of RSL had been established. The locations of the tide gages would also be included in these selected locations. If the results indicated that anomalously high RSL rise rates existed near the tide gages, it would be worthwhile to investigate the cause and, based on the costs and benefits, to consider eliminating or reducing the cause(s). The results from this study would assist the State of Florida in developing a long-term beach management strategy to cope with rising sea levels.
National Research Council (1987) "Responding to Changes in Sea Level: Engineering Implications", National Academy Press, 148 pages.
APPENDIX D COMPREHENSIVE REVIEW OF BEACH NOURISHMENT PROJECTS IN FLORIDA
COMPREHENSIVE REVIEW OF BEACH NOURISHMENT PROJECTS IN FLORIDA
As noted earlier, there have been at least 40 beach nourishment projects constructed in Florida. For some of the long-term projects and most projects constructed in the last 10 to 15 years, reasonably complete and quality monitoring data exist. The settings and design and construction characteristics of the 40 or so projects differed substantially as did many of their performances. Some of these projects were constructed with sand coarser than the native; however, most used sand compatible with or finer than the native. One class of projects is those constructed along long straight beaches, whereas others were constructed in proximity to inlets which could act as sinks or littoral barriers. Some projects encountered storms during construction which could have affected performance. Projects have been designed with different methodologies and a range of renourishment intervals have been predicted. The overall objective of this comprehensive analysis of the performance of many beach nourishment projects is two fold: (1) To evaluate the performance of the projects vis a vis the construction parameters and geographical settings using state of the art methodology, and (2) To evaluate the methods used in design and to compare the actual performance established through monitoring with the predicted performance. Each of these objectives is reviewed below and will require assembly of all design and construction data available for each of the projects.
D.2 Recommended Plan
The recommended plan comprises three tasks over an approximately two year total effort.
D.2.1 Task 1: Performance Evaluation
The performance evaluation will be carried out by employing state of the art methods and models to predict the performance of the individual projects. The most significant design parameters include: sand size, volumetric density of sand added, project length, constructed profile, background erosion rates and geographic setting, in particular whether the project is located on a long unobstructed beach or adjacent to an inlet or near a partial or complete littoral barrier. The predicted renourishment interval will also be included in the evaluation.
With the design information available, the performance will be predicted using state of the art models and pre-established data bases for the design input including wave characteristics, background erosion, effects of nourished and native sediment size and closure depth. The results of these calculations of performance will be compared with the documented performance through monitoring. Three of the main comparison bases will be: (a) The variation of the volume within the nourishment area with time, (b) The variation of the plan area (above NGVD) with time, and (c) The adjustment of the profile toward equilibrium. Additionally, the presence of erosional hotspots will
be noted. It is anticipated that two performance models and data sources will be used for this portion of the effort. These include the numerical model developed by Dean and Grant (1989) described in a report which also presents recommended values of other variables (e.g. wave height, wave period and closure depth) required in design. The second methodology will employ the GENESIS model (Hanson and Kraus, 1989) and the WIS hindeasts for the wave data. It is estimated that this phase of the effort will require approximately I year of intensive effort.
D.2.2 Task 2: Evaluation of Models and Available Information for Design
The results of Task 1 will be evaluated to identify the strengths and weaknesses of the available methodology (models) and data sources and to identify "gaps" in both design methodologies and in data required in design. An effort will be made in the evaluation, to recognize deficiencies and strengths of each method and data source. The weaknesses that could be corrected simply by scaling (for example, the sediment transport coefficient, K) will be differentiated from those that are more endemic. A comparison between the predicted volumetric and plan area changes with time and those documented through field monitoring will be presented in graphical forms. These results will also be presented allowing for a simple scaling of the results, with the scaling based on the entire body of results, rather than on a project by project basis. The differences between the predicted renourishment intervals and those which actually occurred will be summarized.
The results of Task 2 will be a documentation of the strengths and weaknesses of the two methods and data bases employed. This task will require approximately six months and will form the basis for Task 3.
D.2.3 Task 3: Identification of Needed Improvements in Data and Beach Nourishment Design Methodology
Based on the results from Task 2, the weaknesses and limitations of the methodology and data sources will be evaluated and recommendations made to improve the basis for design. The shortcomings and exceedances in performance of individual projects that cannot be explained by the general deficiencies identified in this study will be highlighted. These results will establish a rational basis for improving beach nourishment design capabilities in Florida. Additionally, the overall results will provide, for the first time, a basis for assessing the overall beach nourishment program in Florida comprehensively and will ensure that future investments in improvements in beach nourishment design methodology and/or data are focused appropriately and that future beach nourishment designs are carried out with the best methodology and data available.
It is anticipated that Task 3 will require four months to complete and will set the stage for focused efforts on methodology for design improvements.
Dean, R.G. and J. Grant (1989) "Development of Methodology for Thirty-Year Shoreline Projection in the Vicinity of Beach Nourishment Projects," UFL/COEL-89/026, Coastal and Oceanographic Engineering Department, University of Florida, Gainesville.
Hanson, H. and N.C. Kraus (1989) "GENESIS: Generalized Model for Simulating Shoreline Change, Report 1, Technical Reference," Technical Report No. 89-19, Coastal Engineering Research Center, Waterways Experiment Station, Vicksburg, MS.
INSTRUMENTATION OF A BEACH NOURISHMENT PROJECT
INSTRUMENTATION OF A BEACH NOURISHMENT PROJECT
EA General Plan
Beach nourishment projects can be considered as large scale experiments in nature in which substantial quantities of sediment of generally different character than the native sediments are placed in the nearshore, thus inducing both longshore and cross-shore sediment transport components. Designs of beach nourishment projects must be based on statistically expected storm waves and tides. However, the detailed evolution of a particular project depends on the actual conditions which that project is subjected to after its placement. In order to better understand the relationship between the forcing (waves, tides, etc) and the response longshoree spreading, profile equilibration, etc), of a project, it is necessary to measure the forcing and response. These data would allow existing relationships to be tested and, where found to be necessary, new relationships developed.
The plan is to identify an appropriate scheduled beach nourishment project in advance, to develop a monitoring plan and to document carefully, the characteristics of the borrow material, based on the cores and samples taken during placement and then to establish the as-built project characteristics. The project would be monitored at a level of detail which is considerably greater than occurs for most projects, including more frequent and post-storm monitoring. Each of these monitoring issues is discussed briefly in the following paragraphs.
E.2 Selection of Project for Detailed Field Monitoring
A beach nourishment project would be selected based on the consideration of characteristics which would clarify design questions. At the present stage of detailed understanding of design performance, one main question relates to the performance of nourishment sediments for which the characteristics are not closely matched to the native. In particular, the nourishment sediments could be characterized by a broad distribution or there could be a significant mismatch between the native and nourishment median sizes. Most projects would meet this criterion as it is unusual for the nourishment sediments to provide a close match to the native sediments.
E.3 Instrumentation and Data Collection Plan
The instrumentation plan would include one or two wave gages, a tide gage (the tide gage information could be provided by the wave gage) and a meteorological station. Sediment sampling would be conducted before and after completion of the project and at intervals which would commence at 3 month intervals and then after the first three samplings, the sample frequency including nourishment sand deposited on adjacent beaches could be adjusted depending on the changes observed. Surveys would be carried out to document the project evolution initially at three
month intervals and after significant storms. Depending on the rate of evolution as documented by the monitoring, the monitoring periods may be adjusted. The longshore extent of monitoring will be sufficient to document the full influence of spreading by the project. Thus, it should be possible to document the full fate and pathways of the nourishment material as it spreads including nourishment sand deposited on project adjacent beaches.
E. 4 Data Reduction
The monitoring results will be analyzed to quantify the following: (1) The rates of losses of material from the nourished portion of the project, (2) The rates of volumetric increase of the volume adjacent to the nourished section, (3) The change in plan areas both within the nourished segment and adjacent to the nourished segment, (4) The equilibration of the profile with time, and (5) The changes in sediment characteristics both within and adjacent to the project areas.
E.5 Comparison With Current Design Methodology
Current beach nourishment design methodology will be used to calculate the evolution of the nourishment project. In particular, the following specific features of the evolution will be examined.
E.5.1 Volume Remaining Within the Nourished Area The volume remaining within the nourished area will be calculated on the basis of the measured wave characteristics and compared with the monitoring-based evolution.
E.5.2 Plan Area Within the Nourished Area The dry beach plan area remaining within the nourished area will be calculated based on the measured wave characteristics and compared with the monitoring-based results. This will require adoption of a model for the rate of profile equilibration.
E.5.3 Volume Changes Adjacent to the Project Area The volume changes adjacent to the project area will be calculated and compared with the monitoring-based results. If the nourishment and native sediment characteristics are substantially the same, the distribution of the "spreading out" should be symmetric on the two sides of the project (considering that the platform of the project is initially symmetric). This is the case even if the project is constructed in an area of substantial net longshore sediment transport. If, on the contrary, the nourishment and native sediment characteristics differ substantially, the planforins of the volumetric redistributions on the two sides of the project area should not be the same. Some preliminary calculation methodology has been developed to represent these effects.
E.5.4 Detailed Profile Adjustment This issue has been discussed, in part, in Item E.5.2 above. The focus of this concern will be the determination of the "depth of closure", better stated in this framework as the depth to which the profile equilibrates depending on the wave climate which has occurred prior to the particular monitoring event.
E.5.5 Sediment Sorting Across the Profile Sediment sorting usually causes the finer sands to be transported seaward to less energetic regions where it is stable. In many nourishment projects, the borrow material is bimodal with the finer sands being predominantly quartz and the coarser sediments composed of carbonates (shell and coral). In these cases, the comparison of median or mean grain sizes may not provide an adequate description of the nourished equilibrium profile. If the borrow contains a greater proportion of the finer quartz than the native, the fine material may be transported seaward, forming a larger bar than present in the pre-nourished profiles and a narrower equilibrated beach width than anticipated. The correlation of cross-shore sediment sorting with profiles will provide necessary documentation and guidance on this design issue.
E.5.6 Profile Form as a Function of Size Characteristics of Nourishment Sediments This aspect of beach nourishment project performance is related to Item E.5.5 above. As noted, the distribution of sediments as well as the gross measures (mean, median, sorting, etc.) is relevant to the equilibrium beach profiles, especially bar formation and the amount of sand stored in the bar. Comparison of measured profiles with those calculated based on available methodology will allow assessment and, if necessary, will provide guidance for further research.
NATIVE SAND CHARACTERISTICS
NATIVE SAND CHARACTERISTICS
Accomplishment of this research objective would comprise a two-step process. The first step would be the development of guidelines for the characterization of the native sands with the intent that this characterization would be used for preliminary beach nourishment design purposes. A provisional approach to this characterization could be the method recommended in a report by Dean (2000) in which samples across the profile are composite by the weighted mean of their individual grain size characteristics and the cross-shore distances represented by the individual samples. The grain size characteristics of the individual samples could be represented in an idealized form, by their individual means and standard deviations or by the detailed grain size distributions.
The second step would be to assemble the existing native sand characteristics and, where necessary, supplement these with additional sampling and analysis. These combined results would be summarized and disseminated in a form readily available for preliminary beach nourishment design purposes.
Dean, R. G. (2000) "Beach Nourishment Design: Considerations of Sediment Characteristics", Report No. UFLICOEL 20001002, Coastal and Oceanographic Engineering Program, Department of Civil and Coastal Engineering, University of Florida, Gainesville, FL.
EROSIONAL HOT SPOTS
EROSIONAL HOT SPOTS
Erosional Hot Spots (EHS) occur on natural and nourished beaches, but of course are of primary concern to the OBCS program when their occurrence is unexpected on a beach nourishment project and which can require early mobilization of a dredge to address the EHS and also which is perceived unfavorably by the general public. Studies have shown that some EHSs can be caused by the nourishment operations and can be due to the borrow area characteristics and/or to the placement methods. In such cases, it should be possible to reduce or completely avoid the EHS through proper anticipation, design and construction.
Research on EHS's has been conducted under sponsorship by the OBCS and reported by Dean, et al. (1999). One cause of EHS's, termed "residual bathymetry" is due to the refraction effects of offshore bathymetry in which sediment placed seaward of the closure depth is not smoothed out by the waves and, in some respects, acts as a lens which, through refraction, causes the wave crests to mimic the curvature of the residual bathymetry. Thus, the shoreline will likewise be a reduced form of the offshore bathymetry. This is intuitive as the shoreline tends to mimic the shape of the seaward contours. Regardless of the cause of the EHS, the principles associated with the residual bathymetry mechanisms could be exploited to reduce the transport away from an EHS. Specifically, an offshore (seaward of closure depth) "lens" could be constructed to cause the desired compensation to ameliorate the effect of the EHS. In order to commence a deliberate program to address EHS's, it is recommended that a field experiment be implemented as described below.
G.2 Recommended Field Program
The Captiva Beach Nourishment Project has experienced two EHS's since its first nourishment in the 1980's. These EHS's require earlier renourishments than would otherwise be required even though approximately 85% of the beach length is at the desired width. It is recommended that an offshore nourishment (deposit) be designed to reduce the effect of one of the EHS's. The design would utilize the latest suite of models to: (1) Attempt to determine whether the models can explain why the EHS occurs, and (2) Regardless of whether (1) is successful, develop a design to reduce the effects of the EHS. The response of the beach would be monitored carefully to determine the effects of the measures implemented to reduce the EHS.
Dean, R. G., R. Liotta and G. Simon."Erosional Hot Spots" (1999) UFL/COEL-99/021, Coastal and Oceanographic Engineering Department, University of Florida, Gainesville, FL.
SAND TRANSFER TECHNOLOGY
SAND TRANSFER TECHNOLOGY
There are two classes of sand transfer technology that are central to the mission of the OBCS: (1) Sand transfer around inlets, and (2) Sand transfer over long distances as may be required to access inland resources or to recycle sand from downdrift beaches. Each of these is discussed below.
H.2 Sand Transfer Around Inlets
Inlets which have been improved for navigation by the construction ofjetties and/or the deepening of channels below their natural depths, remain as the principal cause of erosion along Florida's shoreline, especially on the east coast. With a greater number of stakeholders along Florida's shoreline, the difficulties of accessing sand from updrift fillets and transferring this sand to the beaches downdrift of beaches is increasing. South Lake Worth Inlet and Port of Palm Beach Inlet are examples in which the updrift property owners implemented measures to decrease the effectiveness of the transfer capabilities which existed at that time. Other concerns include the availability of the required real estate and the aesthetics of a sand transfer facility. In these cases, the only feasible approach may be to transfer only the sand which accumulates in the channel. It is recommended that those inlets where a sand transfer facility is desirable be reviewed for the feasibility of such construction. Where transfer facilities are not considered feasible, other measures should be sought to maintain the net longshore sediment transport around the inlet.
H.3 Sand Transfer Over Long Distances
As noted, Florida's future beach management program may require sand transfer over long distances for: (1) Accessing inland sources, and (2) Recycling sand from the downdrift ends of beaches to the updrift ends. Slurry transport is well-developed for other purposes than beach nourishment. Wasp et al. (1977) have documented that coal slurries have been transported over distances exceeding 1000 miles! The Black Mesa slurry pipeline which transports coal from the Kayenta Mine in Arizona to a power plant in Nevada is 273 miles long. Iron, copper and limestone are other minerals that have been transported over long distances in slurry pipelines.
It is recommended that a prospectus be developed for the effectiveness of slurry pipelines from sand resources in the interior of Florida and the backpassing of sand from downdrift beaches. This prospects would address issues of costs and pipeline longevity and would include a summary of slurry transport technology and relevant case studies of slurry transport.
Wasp, E. J., J. P. Kenny, and R. L. Gandhi (1977) Solid-Liquid Flow: Slurry Pipeline Transport", Trans Tech Publications, ISBN 0-87849-016-7, Germany.
GROINS OR DETACHED BREAKWATERS
GROINS OR DETACHED BREAKWATERS
Tfhe use of coastal structures to control sediment transport and stabilize shorelines is becoming more prevalent along Florida's shorelines. The three generic areas for which structures are being proposed and have been used include areas immediately downdrift of inlets, at erosional hot spots, and as terminal structures adjacent to beach nourishment projects. South Lake Worth Inlet is an example of the first generic area, the hot spots in the vicinities of 32,d Street and 63rd Street in Miami Beach are examples of the second generic area and the groins near the south end of Amelia Island are an example of the third application.
Technically speaking, coastal structures can be "tricky" with unexpected results and available methodologies and data for predicting their effects are not sufficiently advanced to reliably represent their complete effects. Additionally, should undesirable changes occur in the shorelines adjacent to the structure installation, the perception is usually that the structure is responsible even if this were not the case. Two additional complexities are due to variable wave directions and that numerical models can be "tuned" to predict the desired results.
Groins and detached breakwaters interact with the ambient sediment transport processes differently and the degree of adjustability can differ substantially. Additionally the aesthetics of these two structures types and their effects on beach users are quite different. A comparison of the performance versus prediction of recently installed structures in Florida illustrates the limitations in design and predictability.
The use of a submerged breakwater along the Palm Beach shoreline was not effective and after three years was removed and some of the units were configured into eleven groins in conjunction with a beach nourishment project and the remainder placed as an offshore reef. The detached breakwater at Redington Shores in Pinellas County has maintained a wide beach; however, the shoreline has advanced beyond predictions even after the removal of the top course of breakwater stone. Additionally, there have been at least two drownings at this beach although there is no evidence that the breakwaters were responsible. The groin field near the south end of Amelia Island appears to have stabilized the beach nourishment project to the north, but has also destabilized the State Park beaches to the south.
In order to develop an improved basis for the selection of structures for a particular application, it is recommended that available design guidance be reviewed by or for the OBCS and the results summarized in terms of the project needs. This review should: (1) Capture the design experience in situations and wave climates similar to those for the potential Florida applications, and (2) Evaluate the capabilities to "fine tune" the two types of structures to accommodate differences in expectations and actual performance. One type of structure which appeared to be reasonably effective in Florida
and which has the advantage of fine-tuning is the so-called "adjustable groin", an example of which is shown in Figure I- I and for which there were once Florida groin standards for functional design. Perhaps these research needs could best be met under the aegis of a CETAC effort in which various knowledgeable engineers would be charged with the responsibility of developing the required materials in advance of a workshop and these materials distributed to the Participants in sufficient time before the Workshop to allow their study. These materials would be presented and reviewed at the Workshop and a brief design consensus guidance document written providing recommendations for and benefits associated with the two different types of structures. The workshop effort could also address the documented performance of "T-groins" and their potential areas of application.
FILLED AND STABILIZED PROFILE
4' CONCRETE BASE PANEL-
KING-PILE (PRESTRESSED) 1?'WOODEN PANELS
Figure I 1. Adjustable Groin Which Was Used Extensively in Florida in the 1960's to 1970's.
EVALUATION OF LASER DATA
EVALUATION OF LASER DATA
Examination of some of the comparisons of laser results with those from conventional survey methods raises questions regarding the accuracies of the results in dry sandy beach areas and greater questions where vegetation exists. Even if acceptable accuracies can be obtained only in those areas of no or sparse vegetation, it would appear that this technology would have substantial applications. However, at present the accuracies on dry sandy beaches are in question. The delivery of Shoals data which establishes underwater elevations has apparently been a problem with delivery times greater than six months after the surveys. There is a need for timely delivery of all survey results in accordance with an established schedule. Otherwise both the use of the data and the ability to address uncertainties which arise during analysis and application are compromised. In all cases, the data should be delivered in a timely and agreed upon schedule.
In an attempt to resolve the data quality concerns noted above, a continuing program to ensure that expenditures on laser survey data are effective is recommended. This program need not be onerous but one which is responsive to the needs at the time. In particular, at the present stage, it is recommended that a short meeting be convened to establish a benchmark of the current capabilities, accuracies and concerns of the methodology and plans for a program to remedy or clarify those concerns. With sufficient advance preparation, the workshop objectives could be accomplished in one day. Advance preparation would be the graphical development of comparisons of "problem" profiles obtained by laser technology and conventional survey methodologies. These results would be distributed in advance of the meeting.
The Participants in the meeting would include those responsible for the quality of the data sets being addressed in the workshop. The results of the workshop would be a memorandum describing the agreement(s) reached at the Workshop, the remaining differences and an outline of a program to resolve the differences. To ensure continuing applicability of the laser data, it is recommended that "ground truth" surveys be conducted during each laser survey, the results compared with the laser data and a brief report written describing the comparison results.
ESTABLISHMENT OF A DATA BASE ON
BLUFF LINE CHANGE
ESTABLISHMENT OF A DATA BASE ON
BLUFF LINE CHANGE
Most CCCL Counties have profile data which date back some 20 years or more. On average, approximately four to six surveys are available which span this period. The criteria governing the conditions under which shore protection structures are permittable relate to the recession of the bluff line associated with various return period storms. Thus, it is desirable to develop a data base of bluff line changes to serve as a direct basis for permitting and for calibration of models developed for this purpose. Methodologies are described below.
The extensive profile data base maintained by OBCS would be analyzed to determine the characteristics of bluff change. It is envisioned that the most appropriate manner of characterizing the change would be as a trend and fluctuations about the trend. With the availability of the results, several additional efforts would be possible.
K.2.1 Statistical Distributions With the characteristics of bluff change available, it would be possible to test the type of statistical distribution(s) most appropriate for representing these changes. For, example, are the changes normally distributed or does some other distribution provide the best representation? The utility of this determination would be the application of the results in a parameterized form in which the fluctuations are represented only by a measure of their magnitudes, probably the standard deviation of fluctuations about the trend line. Additionally, knowledge of an appropriate statistical distribution would allow the results to be extended with confidence to greater return periods than represented by the length of the profile survey data.
K.2.2 Correlation With Other Indicators of Bluff Line Change Many of the OBCS profile surveys indicate the location of the vegetation line. Also, aerial photographs are available for approximately the same times for which the surveys were conducted and are available much earlier than the systematic surveying of beach profiles. If a correlation of bluff position (or change) and vegetation line position (or change) could be developed, the use of pre-survey aerial photographs would allow extension of the duration of available bluff line change data.
K.3 Additional Comments
One difference between the determination of the Mean High Water Line statistics and the bluff line statistics is that the appropriate elevation for representing the bluff line will vary from County to County and probably within a county, whereas a similar complication does not exist for the MHW elevation. Perhaps a contour elevation could be taken which is one-half the difference between the Seasonal High Water Line (SHWL) and the top of the bluff and this could be maintained uniform
for a segment of the shoreline for which the bluff elevation is more or less uniform. Another possibility would be to also establish the change characteristics of the SHVVL.
It is recommended that the results be presented in tabular and electronic forms. If it is found that the statistics are well represented by a trend and standard deviation and a particular distribution, it could be adequate to tabulate only the bluff contour change rate and a measure of its variability such as the standard deviation. As noted, the elevation of the selected contour may change along a County shoreline and, of course, the elevation of the reference contour should also be tabulated for each monument.
STATISTICS OF SHORELINE CHANGE
STATISTICS OF SHORELINE CHANGE
Shorelines change on a variety of time scales ranging from daily to seasonal to decadal to millennia. The understanding of these changes is central to the interpretation of occurrences of events and the development of appropriate post-storm response strategies. Appropriate regulation and post-storm response depend on a knowledge of the character and rarity of shoreline position occurrences An example is the case in which a major storm causes severe erosion of a shoreline and damage to the upland structures. Should those structures be allowed to be reconstructed and, if so, should they be reconstructed in the same locations as before? Of course, major storms causing much more widespread damage than has been witnessed in historic times will occur in the future and such questions will be asked and there will be two factions, one favoring the "reconstruction option" and the other the "retreat option". A second example is that in which a particular shoreline advances significantly, perhaps due to an extended period of unusually low storm occurrences. This advancement may occur over a period of decades and lead to the interpretation that it will continue and thus that more seaward locations of planned structures are appropriate. In both of these examples, the knowledge of the rarity of the particular event and the likelihood that the condition is temporary and the particular time scales associated with the event are essential for appropriate decisions.
L.2 Discussion and Methodology
The statistics of shoreline change include the trends, magnitudes of changes and the times over which these occur. Figure L-1 presents hypothetical shoreline positions at a location where a significant erosional trend exists.
0 5 10 15 20 25 Time(years)
" Major Storm Effect
~Major Storm Effect C- Period of
-100 Normal Maj,/ St
C NdtsMajor Storm Effect Peio I ""- rend Line
0.c: ~~~of Mild-I \^ L" ',,
Figure L-1. Hypothetical Shoreline Changes.
In general, the statistics of change are related to both natural and human-induced causes; however, it is believed that while the trend can be due to human causes, the fluctuations about that trend line, of greatest interest here, are predominantly due to natural causes. These natural causes are many and their interaction with the shoreline position complex and poorly known. The primary factors are storm waves and surge levels. The waves provide the energy and the increased water levels result in a disequilibrium of the profile such that the energy can accomplish erosion. Secondary factors include: water table elevations (high water tables within the beach bermi tend to destabilize beaches), onshore winds which result in offshore bottom currents carrying sand seaward, and cooler waters which result in slower fall velocities and thus greater seaward sediment transport by the winter waves. The quantitative significance of these secondary factors is unknown. It is known that the seasonal shoreline changes along the United States shorelines range from 20 feet to 300 feet with those along the Florida shoreline toward the lower end of this range. Seasonal shoreline changes are due primarily to the increased energies (and perhaps higher water levels) due to Winter waves. Thus, if there is an unusual succession of storms, especially those that are accompanied by high water levels, there will be an associated unusual cumulative shoreline recession. What are the magnitudes and frequencies of these more extreme erosional events? This and related questions would be the focus of the study outlined below.
The existing data base on shoreline change maintained by the OBCS is of excellent quality and can contribute to the goals of this effort. However, the frequency of data availability in this source is not sufficient to establish the shoreline changes in the desired detail. Thus, the shoreline positions in the data base should be augmented by those determined from aerial photographs. An example of such results is shown for three locations in St. Johns County in Figure L-2 where the available data extends from 1942 to 1998. At these locations, the MHW receded approximately 140 feet from 1942 to the 1960's and then recovered some from this recessed condition.
ST. JOHNS COUNTY
SHORELINE POSITION (WeIcnIty of R172)
0I 15 go 90oW2
-200 J Var
Figure L-2. Shoreline Changes at Three Locations in St. Johns County. Based on Aerial Photographs.
The recommended approach would be to select a number of locations around the Florida shoreline and, using the OBCS maintained shoreline position data base supplemented by MHW Line positions estimated from aerial photographs, to establish as frequent shoreline positions as possible. The statistics of these positions would be quantified. In particular, the maximum and minimum deviations from the shoreline trend would be established. The durations of the shoreline deviation exceedances would also be quantified. One approach to summarizing the statistical characteristics would be in terms of the lengths of time and return periods of exceedances, for both positive and negative deviations from the trend line.
PREDICTION OF NEAR REAL-TIME SHORELINE EROSION
PREDICTION OF NEAR REAL-TIME SHORELINE EROSION
As a hurricane approaches the Florida shoreline, there is a substantial interest in the impact of that storm on the State and its Residents. The impacts include both flooding and erosion, knowledge of which assists the emergency managers and the general populace in developing their avoidance and response strategies. The flooding aspects of this interest are addressed through a probabilistic type model which considers the uncertainties in the hurricane track and other hurricane parameters including its future strength, etc. These predictions are updated and made available in real time through popular media outlets. The program described in some detail below outlines a parallel effort with the goal of developing and verifying a near real-time probabilistic model for erosion prediction. It is anticipated that this model would use the probabilistic estimates of the storm surge developed by others as input and would disseminate the estimates of erosion along with and in parallel to the storm surge predictions.
Several models for beach and dune erosion have been developed, some under sponsorship of the OBCS. The main ingredients required in beach and dune erosion models are the initial beach and dune profile and the characteristics of the storm induced hydrodynamics, including the time varying waves and storm tides. The available beach and dune erosion models are two-dimensional and thus do not account for waves approaching the shoreline at an angle such that more sand may be transported out of a profile in the longshore direction than is transported into the profile. Thus, these two-dimensional models conserve sand in the profile. For the first phase of this project as discussed here, it is recommended that a two-dimensional model be used.
The most recent beach and dune profiles available would be used as the initial conditions for the area of potential impact by the hurricane. The projected storm surges and their associated probabilities as developed by others (National Hurricane Center (NHC)) and predicted wave heights (developed from the wind fields established by NHC) would be the input to the model. The model would be evaluated/calibrated based on the documented hydrodynamics and erosion associated with several past hurricanes, including the real time phase as the storm approaches landfall. An additional feature of erosion phenomena which is not present in coastal flooding is the local longshore variability of erosion due to various factors. This feature will require an additional probability ingredient in the estimates presented.
In addition to the Public Service benefits of the model, the output could assist the OBCS in developing early strategies in responding to the storm, both in geographic allocation of response resources and in developing an early assessment of the likely magnitude of the impact.
PERFORMANCE DIFFERENCES BETWEEN
QUARTZ AND CALCAREOUS NOURISHMENT MATERIALS
PERFORMANCE DIFFERENCES BETWEEN QUARTZ AND CALCAREOUS NOURISHMENT MATERIALS
With greater amounts of nourishment of Florida's beaches planned and the limitations on ideal sand sources for nourishment, there is a need to evaluate which of the types of available materials are most ideally suited for nourishment. Characteristics relevant to beach nourishment include: physical performance, environmental suitability and aesthetics. This effort will concentrate on the physical performance characteristics of quartz sand and calcareous materials, both with approximately the 'same fall velocity characteristics.
The best approach to address the physical performance characteristics of quartz vis a vis calcareous sediments with approximately the same fall velocity characteristics is through laboratory modeling. A series of two types of tests is recommended as discussed below.
The first series of tests would evaluate the profile characteristics of the two types of materials and would be conducted in a wave tank. In sequential tests, the two types of material would be configured to the same initial slope and the profile adjustment and equilibrium forms would be documented under several wave conditions. Additionally, replicate experiments would be conducted.
The second series of experiments would be carried out in a wave basin and would focus on the longshore sediment transport characteristics of the two materials. The wave basin would be partitioned into two sections. Within each section, one of the two types of material would be prepared as a model beach nourishment project and then subjected to wave action. The configurations of the two segments and the analysis of the data would parallel that of Altman (2000), as shown in Figure N-i. The evolution of the two projects under the same wave action would be monitored and the evolutions compared.
Altman, D. (2000) "Evaluation of the Suitability and Efficacy of Aragonite Sand for Beach Nourishment", Department of Civil and Coastal Engineering, University of Florida, Master of Science Thesis, Report No. UFL/COEL-2000/004.
SNAKE WAVE MAKER WA DWAVE RAY
LITTORAL CELL LITTORAL CELL
Figure N- 1. Wave Basin Layout for Simultaneous Testing of Two Different Nourishment Sediments.
CRITERIA FOR EXPERIMENTAL PROJECTS ON EROSION CONTROL
CRITERIA FOR EXPERIMENTAL PROJECTS ON EROSION CONTROL
The processes of erosion stimulate interests in the development of relatively inexpensive and permanent "solutions" to these erosion problems. Over the years, many such innovative approaches have been tested, both at laboratory and field scales. These attempts include: artificial seaweed which was tested at perhaps 20 locations in the world, beach dewatering at some 5 or 6 locations internationally, submerged breakwaters, underwater stabilizers, etc. Some of these approaches were moderately successful and others failed entirely to provide any of the benefits claimed or caused erosion rather than accretion. In most cases, the benefits did not justify the capital, operation, monitoring and maintenance costs. The real test of the effectiveness of a system is whether, after introduction, the method is still being applied decades later. The conduct of field tests is costly and detracts limited resources from other efforts. Thus, it is imperative to screen future identified approaches to ensure that the method has not been attempted previously without success and, secondly that the approach meets several criteria which support the potential for achieving its claims. The following paragraphs recommend a program to provide a consistent basis and framework by which potential innovative approaches will be evaluated for testing. The purposes of the approach recommended here are to outline for an Applicant, the pathway to a permit, the requirements and criteria, and to ensure that all Applications are judged uniformly and consistently. It is believed that an established framework of this type would reduce political involvement in the decision process.
0.2. Recommended Program
0.2.1 Compilation of Previous Experience With Innovative Methodology
Many laboratory and field tests have been conducted to evaluate the effectiveness of innovative approaches to erosion control. With the documentation of these efforts ranging from cursory to detailed. Taken in aggregate, the results of these tests provide a valuable, but presently an undocumented resource, against which future ideas could be evaluated and possibly improved. The availability of such a document would be of use to those seeking to develop innovative approaches and those responsible forjudging their success potential. Thus, costly testing could be avoided if documentation of previous efforts were available and definitive. As somewhat of an aside, the rhetoric question is asked here of whether the OBCS should be pro-active in the encouragement of innovative approaches that have a high potential of success, for example in prolonging the performance of beach nourishment projects?
It is recommended that a compilation be developed of previously documented laboratory and field efforts to demonstrate the effectiveness of innovative approaches to erosion control. Much of the documentation is in the "gray" literature, that is, in unpublished engineering reports. In other cases, there may be no written documentation. For approaches where there has been more than one effort, all well-documented tests, including laboratory and field sites would be reviewed. Artificial seaweed
and beach dewatering are examples where both laboratory and field tests have been conducted. The effectiveness of some approaches may depend on the geometry of the device and geometric setting of the test. For example, submerged breakwaters induce two effects on the nearshore: wave energy reduction and longshore current enhancement, the first being beneficial and the second detrimental to the beach landward of the structure. Japanese investigators have reported the successful performance of submerged breakwaters with wide crests. Installations with narrow crests have been demonstrated in the laboratory to induce longshore currents and erosion landward of the structure in a field installation. To the degree possible, the compilation should document all relevant characteristics of the approach, including geometry, costs and any environmental information. A standard format should be developed for the compilation with flexibility to tailor the documentation according to the information available for the particular case. Finally, the compilation could be published in a loose leaf notebook and on the WYEB, such that additions could be included as new approaches are documented.
0.2.2 Criteria For Evaluating the Suitability of Proposed Approaches for Testing
The eight criteria discussed below are proposed as "screens", all of which the proposed approach would be required to pass prior to permit approval for field testing.
0.2.2.1 Uniqueness, i.e. The Same or Essentially Similar Concept Has Not Been Tested Un der Similar Conditions Without Success
The compilation of previously tested approaches will assist in determining whether the proposed or
similar approach has been tested and if so, under what conditions and the results of the tests. The Applicants should be encouraged to conduct their own literature search and if results additional to those in the compilation are found, they should be incorporated into the compilation. If the results of review of previous testing do not reveal previous similar testing which found the approach to be unsuccessful, the remaining criteria should be applied.
0.2.2.2 Inherent Supporting Physical Principles
The underlying physical principles which govern the hydrodynamics of and sediment transport within the nearshore are well understood qualitatively, if not quantitatively. Proposed approaches should be screened to ensure that they are consistent with this understanding. The Applicant should be required to enumerate the physical principles which underlie the processes by which the proposed approach would accomplish the objectives of the claims.
0.2.2.3 Very Low Potential for Adverse Effects to Adjacent Beaches
A criterion for installation and testing is that the approach have a very low potential for causing adverse effects to the adjacent beaches. The principles of "sand trapping" devices are well known, and the encouragement/permitting of such devices should be only under rare conditions, such as at the ends of a littoral system, perhaps at an inlet where the natural bypassing is very inefficient due to an artificially deepened entrance or a very low net natural longshore sediment transport.
0.2.2.4 Very Low Potential for Adverse Environmental Effects
The coastal environment including its natural biota is one of the natural 'jewels" of the State of Florida and is thus highly valued. Any approach which does not have an acceptably low potential for adversely affecting the coastal environent should be discouraged.
As the value of the environment is significant, so are the aesthetics of the coastline and nearshore. Past proposed innovative technology has ranged from floating breakwaters to underwater coils of wire. Applicants should recognize the aesthetic value of the coastal area due to the intrinsic value which the residents and visitors place on this attribute. Thus any approach which compromises the aesthetics would have, at best, limited potential for extensive application.
0.2.2.6 Acceptable Monitoring Plan
A monitoring plan should be developed which is acceptable to the OBCS. The Plan should include physical and environmental elements as appropriate and should be of adequate scope and detail to quantify the claims of the Applicant as well as any adverse effects to the adjacent beaches or to the environment. Timeliness of data submission and analysis of results should be addressed.
0.2.2.7 Pre-testing Development of Criteria Against Which the Success of the Testing Will Be Judged
The Applicant should be required to develop in the permit application, claims of the effectiveness of the proposed method. An example could be "The device will accumulate 40,000 cubic yards over a six month field test period without measurable adverse effects on the adjacent shoreline or to the environment. All of the material accumulated will derive from offshore." A second example would be the case where the objective of the approach was to stabilize beach nourishment and could read "The proposed device will reduce the spreading losses from the project by 30% without measurable adverse effects to the adjacent shorelines or to the environment."
0.2.2.8 Evaluation by a Third Party Reviewer
The monitoring results should be reviewed and evaluated by a third party. As appropriate, the "third party" may consist of one or more individuals with expertise in the areas of performance claims (physical and environmental) by the Applicant and of concern by the OBCS.
DEVELOPMENT OF WAVE INFORMATION
DEVELOPMENT OF WAVE INFORMATION
Wave information is a valuable design and interpretative resource for many coastal engineering problems. Depending on the particular problem, the required information may range from the highest wave in 100 years for design purposes to the "effective wave height" for beach nourishment design to the seasonal wave characteristics with a measure of the variability. Wave information may be developed through measurements and/or hindcasts based on weather information.
As for much of the United States, hindcasts are available along Florida's shorelines through the U.S. Army Corps of Engineers "Wave Information Study" (WIS). Additionally, some wave measurements for up to ten locations along the Florida shorelines have been conducted through the University of Florida "Coatsal Data Network" (CDN), which is not presently operational. These data are for various lengths of times and over different time periods. Although the wave instrumentation presently available is significantly advanced compared to that when the CDN data were collected (from approximately 1975 to 1990), these data represent a valuable and unique data resource. There are currently four moored wave buoys off Florida as shown in Figure P-i1; however, none of these gages measure wave direction, yet they represent a valuable resource which has not been fully explored for application to Florida's beach program needs.
Figure P-I. Locations of Wave Buoys in the Vicinity of Florida.
An important difference between this research need and the others presented in this report is the potential magnitude and longevity of the wave information effort. The following section provides recommendations for the determination of the need and, if deemed warranted, possible scopes of a program for the development of wave information.
In view of the aforementioned potential for a continuing dedicated effort to developing wave information, it appears advisable to devote considerable planning to ensure that the program meets the needs and does not consume unnecessary resources. The most sophisticated and successful wave information program in the U. S. is clearly that at Scripps Institute of Oceanography in California. The information products can be accessed at the Web Site "http://cdip.ucsd.edu" and includes up to date measurements from offshore buoys and oil producing platforms, nearshore wave gages and the computational results of transforming the waves to shallow water. Clearly a review of the Scripps program, probably including a visit for detailed discussions, would benefit the planning and scope of a Florida program.
P.2.2 Establishing the Need for Additional Wave Information
Wave information is useful for a variety of engineering, interpretative and regulatory purposes. Beach nourishment design requires a representative wave height and period for those projects placed on long straight beaches and wave direction information for projects constructed adjacent to inlets or partial or complete littoral barriers. Interpretation of storm damage and erosion is an application of wave data. The development of improved beach and dune erosion numerical models will require wave measurements for development and verification. In addition to measuring wave heights, wave gages can also measure tides which are valuable especially during storms. Statistical wave information can also be useful to dredgers, including the average seasonal wave characteristics as well as their variability. Finally, wave information can be useful for particular studies; however, those types of installations would be relatively short term.
Relevant to the previous discussion is that some of the wave data needs have been satisfied through experience since dredgers have been operating in Florida waters for many years and beach nourishment projects have been constructed and monitoring data available for up to 27 years. Thus, there is a need to identify the most critical unmet and future needs in the development of a wave information program.
P.2.3 Possible Scopes of Programs to Develop Wave Information
There is a wide range of possible scopes of programs which the OBCS could implement. These programs could be limited in duration to development of a correlation with hindcast results or could
be planned as a continuing and geographical extensive program. Two possibilities are discussed below; other possibilities include combinations of those described. The discussion will not include wave measurements for a specific limited purpose such as the evaluation of the performance of a submerged breakwater.
P.2.3.1 Sustained Measurements at Selected Locations and Duration Limited Measurements
at Other Selected Locations
One approach would be to plan to maintain a number (say 6) permanent wave gages around the State and, to "fill in" at locations distant from the gages, by the placement of gages for a relatively short time (say one year). The wave characteristics at these short term locations would be correlated with the characteristics at the longer term stations to establish a desired level of confidence in the correlation. The same approach could be employed to use the buoy data. Additionally, the use of wave hindcast models could be used to assist in the correlation and/or extension of wave characteristics to locations other than those at which measurements were available.
P.2.3.2 Limited Duration Measurements at Selected Locations With Correlations to and Later
with Greater Reliance on Hindcasts and Buoy Data
This approach would entail limited duration wave measurements at a number of locations along the Florida coastline followed by later usage of calibrated and verified hindcast models completely or to supplement a smaller number of wave gages and the available buoy data.