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7 Conclusions and Recommendations GENERAL FINDINGS Beach nourishment projects can be used effectively to provide a broader beach, which affords protection from storm and flooding damage within human time scales (decades, not centuries) when: stood, · projects are carried out on sites at which the erosion processes are under · uncertainties in design and prediction are accounted for realistically, and · state-of-the-art engineering standards of planning and design are used. Well-designed, -constructed, and -maintained projects provide the storm damage reduction and erosion protection for which they are intended. Beach nourishment may not be technically or economically justified for some sites, particularly those with high rates of natural erosion. RECOMMENDATION: Federal, state, and local authorities with responsibility for coastal protection should view beach nourishment as a viable alternative for providing shore protection and for restor- ing lost recreational beach assets. The planning and execution of successful beach nourishment projects can best be accomplished through a broadly based coalition of disciplines and inter- ests that brings together all the scientific, engineering, economic, and governance knowledge and experience available. Narrowly developed projects have resulted 140
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CONCLUSIONS AND RECOMMENDATIONS 141 in technical, environmental, or economic deficiencies. All project planning should recognize the need for maintenance. RECOMMENDATION: Federal, state, and local agencies in- volved with beach nourishment projects should require multidisci- plinary project planning, design, monitoring, and evaluation. The methodology employed should: . establish the goals and expectations of the project and its con- tinuation as a long-term program; establish clear and quantifiable measures of success; establish and maintain an effective monitoring program that supports the management, design, and execution of subsequent nourishment cycles; develop and maintain a public awareness program; and account for the uncertainties implicit in shore protection mea- sures through the implementation of contingency planning and the identification of future sources of both renourishment material and project funding. SPECIFIC FINDINGS Design The design of a successful beach nourishment project depends on an under- standing of the underlying causes of erosion at the site and a capacity to model or evaluate quantitatively the coastal processes, such as wave climate variations and the cross-shore and alongshore transport rates of sediments. Deficiencies exist in our understanding of many of these processes and adversely affect our ability to predict the evolution and fate of nourishment fill; even when the basic processes are understood, large uncertainties can remain in numerical evaluations. Further, there are significant differences among coasts' geological settings, geomorpholo- gies, sand sources and sinks, sediment characteristics, and physical forces, such as waves, tides, currents, and winds. The great diversity of conditions and the mix of coastal processes result in major regional differences that make it neither practicable nor desirable to establish a national standard design for beach nour- ishment projects. Each must be designed to satisfy the conditions at its location. Nourished beaches usually experience significant spatial alongshore varia- tions that range from high rates of erosion to accretion. When locations erode faster than anticipated (erosional hot spots), reserve protection capacity may be lost and the design compromised along a portion of the beach. The reflourished beach will require more sand than the net background erosion from the project
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142 BEACH NOURISHMENT AND PROTECTION because erosional hot spots require overfill. In addition, accretional areas store advanced fill, and the accretion should not be deducted from the estimated ero- sion. Designers underestimate renourishment needs when they base their esti- mates solely on net erosion projections. A potential savings can be realized when the initial renourishment interval is shortened and less advanced fill is placed in the first renourishment in order that fine tuning of the project to address erosional hot spots can be implemented at an early stage. RECOMMENDATION: The design methodology for beach nour- ishment projects should include the following: · design profiles based on natural profiles at the site suitably adjusted for nourishment grain size rather than straight line segments or other unrealistic approximations; spreading losses owing to the nourishment project accounted for explicitly in the design; volumes adjusted to account for rock outcrops and seawalls in order to provide sufficient volume to nourish the entire profile from the berm or dune to the seaward limit of the active pro- file and avoid underestimating fill requirements; sediment performance characteristics included in the analysis of sediment considered for use as beach nourishment material, with specific attention to the equilibrium shape of the profile, the transportability of the sediment alongshore, and the erod- ibility of the material during a storm; these factors used at first in conjunction with overfill and renourishment factors and later as a substitute for these factors as more experience is gained; the possibility of erosional hot spots recognized in the design; analytical and numerical models used to estimate end losses that will be caused by spreading of the fill material to adjacent . beaches; the Blrst renourishment time interval shortened to allow for uncertainties in alongshore erosion rates, thus enabling cor- rection of erosional hot spots before the design is compro- mised and avoiding overbuilding of accretional areas; and safety factors developed to account for variability and uncer- tainty and applied appropriately to both design volumes and advanced-fill volumes. Although technologically outdated, the Shore Protection Manual published by the U.S. Army Corps of Engineers (USAGE) in 1984 is the de facto standard for coastal engineering throughout most of the world. Strong legal constraints and liability considerations reinforce its continued use in the United States by
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CONCLUSIONS AND RECOMMENDATIONS engineers in private practice, even though it by the USACE. 143 is no longer the design standard used RECOMMENDATION: The U.S. Army Corps of Engineers should publish detailed and comprehensive state-of-the-art engi- neering guidance on the design of beach nourishment projects, ei- ther as part of the planned Coastal Engineering Manual or in a separate document. Differences exist in the planning and design methodologies used by the USACE field offices. Some of these differences relate to regional differences in the beaches that have been designed (South Atlantic barrier islands versus West coast bluff-backed beaches). Design approaches must therefore vary to account for regional differences. However, other differences in designs are a result of the methodologies selected, some of which do not employ state-of-the-art practices realistically. This situation results in uneven effectiveness in project design and contributes to less than optimum solutions. RECOMMENDATION: The U.S. Army Corps of Engineers should develop and implement a consistent methodology for beach nourishment design while retaining sufficient flexibility to accom- modate regional variations in physical conditions. Structural Alternatives Fixed Structures Fixed (hardj structures, when appropriately designed and placed at suitable locations, can improve the performance of some beach nourishment projects. These structures may be perpendicular to the shore, to reduce end losses (e.g., jetties and groins); offshore and shore parallel, to reduce local wave intensity (e.g., detached breakwaters); and onshore and shore parallel (e.g., seawalls), to provide a reserve capability to prevent flooding and wave attack where dunes cannot or do not exist, especially in areas like the Pacific coast, where storm surges are small and to reduce wind-blown losses to the land. Broad prohibitions on the use of fixed structures in conjunction with beach nourishment projects can contribute to suboptimal project performance where fixed structures can provide secondary storm damage reduction or are needed to anchor the ends of projects. RECOMMENDATION: Agencies should modify their prescrip- tive laws, regulations, and management plans for the coast to allow the use of fixed structures in conjunction with beach nourishment projects where project performance can be significantly improved, out-of-project negative effects are acceptably small or are mitigated as necessary, and beach access or use is not impaired. The costs of
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44 BEACHNOURISHMENT AND PROTECTION the structures should not exceed the savings achieved by increasing the level of protection or the times between successive renourish- ments. Environmental impacts should also be considered. Structures do not increase the volume of sand in the littoral system; they simply rearrange and control the movement of the sand that is placed or is already there. Failure to provide fill along with the structures often results in erosion of the beach system at another location. Even when a groin field is filled to its holding capacity, localized erosion effects may nevertheless occur. These effects need to be addressed more effectively and accommodated in project design and construction. RECOMMENDATION: Each fixed structure that is used in con- junction with a beach nourishment project should be filled to the upper limit of its holding capacity if it would otherwise accumulate sand. Where uncertainties exist, fill should exceed the calculated upper limit of the holding capacity of the structure. If a beach nour- ishment project is not maintained, adverse effects of any structure should be mitigated or the structure should be removed. Nontraditional Shore Protection Devices The techniques used in conventional shore protection have had the benefit of decades of field performance and the development of demonstrated design mod- els to predict that performance. This experience has clearly shown that there are no cheap and easy solutions to the difficult and expensive process of protecting the shore while maintaining its environmental assets. The use of nontraditional shore protection devices needs to be approached carefully because of uncertain- ties about their performance and beneficial value relative to traditional technol- ogy, for which performance capabilities are established. The Committee on Beach Nourishment and Protection is concerned that some nontraditional devices that involve large structures placed near the shore may cause unfavorable conditions that will be difficult and expensive to correct. At the same time, the committee believes that technical innovation should be encouraged and that entrepreneurs should have access to the marketplace in this field. Evaluation of any beach protection system is expensive because of the size of any meaningful experiment and is time consuming because of concerns for testing under a full set of climate conditions. It is prudent to consider as experi- mental new approaches that purport to be low-cost solutions until their perfor- mance has been adequately demonstrated. Further, unconventional approaches that do not involve addition of sand to the littoral system from outside sources and that involve the trapping or rearrangement of sand must be recognized as providing local improvement only at the expense of neighboring areas that lose this material. A uniform and effective methodology consisting of a performance
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CONCLUSIONS AND RECOMMENDATIONS 145 based specification is needed for evaluating the effectiveness of nontraditional shore protection and beach stabilization and restoration devices so that any inter- ested agency or private buyer can be more fully informed before committing to their use. RECOMMENDATION: The performance of nontraditional shore protection and beach stabilization and restoration devices should be successfully demonstrated under a performance-based specification before these devices are used in lieu of conventional shore protec- tion and beach stabilization and restoration alternatives, including beach nourishment. A performance-based specification should be developed by the U.S. Army Corps of Engineers for nontraditional devices to guide their application in projects in which there is fed- eral involvement. This specification or a similar procedure devel- oped objectively by qualified coastal engineers acting in a third- party role should be used to guide the application of nontraditional devices in nonfederal projects. Adequate studies and engineering analyses of borrow sites are critical to the success of a nourishment effort. In particular, the impacts of creating a local depression in the sea bottom on offshore sand movement from the nourished beach need to be assessed in order to determine the effects on the littoral system and any mitigation measures that need to be implemented. It is necessary to avoid dredging within the depth of active sediment transport and minimize wave modi- fications that would adversely affect the nourishment project. RECOMMENDATION: Sponsors of beach nourishment projects should use a methodology for selecting borrow sites that assesses: · the required quality and quantity of sand, · the effect of borrow sites on adjacent beaches when these sites are located within the closure depth of the beach profile or are part of a shoal that normally feeds the downdrift beach, and · the need for, and negative and positive effects of, bypassing sand. If sand must be taken from borrow sites located within closure depths, it should be done as a planned sand bypass operation that is designed specifically to mitigate the effects of a feature or structure that interrupts the littoral movement of sand. Relevance of Sea-Level Rise Relative sea-level changes are occurring along most U.S. coasts. The effects of sea-level rise are particularly important along the Atlantic and Gulf coasts with
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46 BEACHNOURISHMENT AND PROTECTION low-lying topography. Erosion or beach recession, which is the result of current relative sea-level rise, is incorporated into the background erosion rate. The overall effect of a gradual relative sea-level rise at the present rate will not be detectable in the rate of beach loss. If the relative sea-level rise accelerates, the beach loss also will accelerate. Because beach nourishment programs consist of a series of projects, and because reevaluation of erosion rates is included in the design of projects, no additional considerations are necessary to account for erosion that is induced by relative sea-level rise. Sea-level change, however, is just one of many factors impacting beach behavior. Its magnitude and relative importance are difficult to ascertain because changes are masked by more dramatic near-term fluctuations caused by other physical forces. Relative sea-level rise will probably remain a minor factor af- fecting replenished beach durability during the next several decades. Major Management Issues Public Involvement Before a beach nourishment project begins, there is a compelling need to inform the public about: · the anticipated time frame of the program (e.g., a 20-, 30-, or 50-year program); the nourishment intervals and especially the beach state or condition (e.g., width of dry beach) that will trigger renourishment; the timing and extent of the expected profile adjustment and its impact on . beach widths; the possible impacts of major storms on beach character and on projected costs, sand volumes, and the timing between renourishment projects; the potential occurrence of erosional hot spots and the requirements for corrective action; and the adjustment from the temporarily wider and steeper construction pro file to the expected equilibrium profile. Inadequacies in public involvement and information programs have exacer- bated public controversy over beach nourishment. Measures to inform the inter- ested and affected publics about beach nourishment projects have been inad- equate with respect to design expectations for beach behavior and costs, uncertainties in the design process, prediction of project performance, future environmental conditions, and replenishment cycles. The promulgation of infor- mation essential to public support of programs described in technical and design manuals is not an effective substitute for well-designed and -executed public involvement and information programs.
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CONCLUSIONS AND RECOMMENDATIONS 147 After a beach fill has been completed, there is a continuing need to regularly update the public on its progress, including reports on the sand volumes and beach widths remaining, the nature and extent of erosional hot spots, the condi- tion of the storm berm, and the implications of this information. RECOMMENDATION: Sponsors of beach nourishment pro- grams should establish public information and involvement pro- grams as an integral component of each beach nourishment project, beginning with the design phase and continuing through the mainte- nance stage. Commitments for Long-Term Project Maintenance The long-term financial commitment required to maintain a beach replenish- ment program effectively is generally recognized by communities involved in these projects but is not always incorporated into the planning process. The 50- year life cycle for a typical USACE beach nourishment program is rarely, if ever, paralleled by similar long-term planning by the public and local project sponsors. In particular, an existing beach nourishment program may not be backed by dedicated sand resources for the projected life of the program or for supplemental renourishments that may be necessitated by severe storms or other factors. It is inaccurate to characterize planned beach nourishments as a bona fide program unless long-term planning and commitments to maintain a program are in place. RECOMMENDATION: Given the long-term sand commitments necessary to ensure sufficient sand for the planned life cycle of a nourishment program, federal and state agencies should investigate mechanisms that would help sponsors identify and, where feasible, contract for or secure mineral rights to sources for long-term sand commitments. These mechanisms may include the use of unconven- tional sources for later cycles of nourishment so long as the pro- jected costs are reflected in the cost-benefit analyses. Sand deposits that are located in state waters and that are free to publicly funded within-state beach nourishment projects are often not sufficient in quality or quantity to sustain beach nourishment over a program's life. Sand sources under federal jurisdiction on the continental shelf and administered by the Miner- als Management Service of the U.S. Department of the Interior will become increasingly important for the continued maintenance of some beach nourish- ment programs. Existing mechanisms for allocating these mineral resources through competitive bidding, and by negotiated agreement between the USACE and the Minerals Management Service for projects involving federal cost sharing, do not incorporate provisions for contracting forward for sand resources. Proce- dures for allocating sand resources to accommodate long-term needs merit fur- ther investigation.
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48 BEACH NOURISHMENT AND PROTECTION RECOMMENDATION: When future renourishment sand sources cannot be identified with certainty, each construction project should independently meet the tests for economical viability. Emergency Maintenance and Contingency Plans The need for rapid emergency restoration of a beach or dune system can be created by severe storms that exceed design criteria. When emergency restoration is warranted, procedural delays caused by locating appropriate sources, obtaining permits, and contracting for construction can further jeopardize endangered build- ings and infrastructure. Contingency plans and arrangements are needed to facili- tate the timely implementation of emergency restorations. RECOMMENDATION: Program sponsors should develop con- tingency plans for emergency repair of beach and dune systems necessitated by severe storm damage as part of the beach nourish- ment program at each site. Emergency-use borrow sites should be identified as a minimum and the necessary permits obtained and held in reserve when possible. Sponsors should investigate the feasi- bility of and plan appropriately for expedited procurement proce- dures to identify and secure dredging services from U.S. contrac tors. Project Scope Beach nourishment programs are often undertaken without due consider- ation for their relationship to and impact on other portions of the littoral cell that often cross political boundaries. Most programs encompass only a portion of an area that can be considered a littoral geographic region or littoral cell. However, actions in one area of a littoral cell have generally affected other areas in the cell and, in some cases, areas in adjacent littoral cells. The length of a project has typically been prescribed as the minimum design needed to protect an arbitrarily specified shoreline sector without regard for uncertainties. The program scope has not been adequately recognized by policies governing USACE beach nour- ishment project planning, design, and approval. It is recognized that tough, less- than-ideal choices must be made during the evolution of a project because of jurisdictional, budgetary, and time constraints. RECOMMENDATION: Beach nourishment programs should be planned as part of an overall regional beach management plan. All involved participants should take action to ensure that the process used for planning, design, and approval of beach nourishment pro- grams achieves this objective.
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CONCLUSIONS AND RECOMMENDATIONS 149 It is common for economic analyses to show that a broad range of potential projects produces positive and comparable cost-benefit ratios, but the single project beach width that provides maximum net benefits is selected as the federal National Economic Development (NED) plan. Because of uncertainties in both the design and the physical processes, selection of a plan larger than the NED plan would provide a safety margin against uncertainty and variability. In many cases, the larger project selection would not significantly change the cost-benefit ratio but would significantly increase the margin of safety for reducing storm damage. RECOMMENDATION: The federal government should modify its policies to allow for the selection of a project larger than the National Economic Development plan as long as it provides a posi- tive cost-benefit ratio and is within the financial capability of the local sponsor. A sensitivity analysis should be performed for each prospective and existing program for which one has not been done in order to identify the scope of a more inclusive program that would reduce the risks of excessive damage. The sensitivity analysis should be applied to both the advanced-fill and design beach com- ponents. Measures of Success There is no single measure of success for beach nourishment programs be- cause programs usually serve a variety of objectives. Therefore, various mea- sures of success need to be defined for beach nourishment programs. A program may or may not be successful in meeting all objectives underlying its establish- ment. Some of the performance measures may occur in the near term, such as a program's response to physical forces. Other objectives may occur over a much longer term for example, the realization of related shore community economic development goals and reduction of shoreline retreat. Effective program perfor- mance from an engineering perspective may or may not change the economic conditions that motivated local support for a beach nourishment program because socioeconomic conditions can change over the life of a program. The fundamental measure of success is the life span of the beach fill and how nearly actual performance conforms to predicted performance. Success in enhancing recreation can be related to the width of the dry beach, whereas success in shore protection is better evaluated in terms of the total sand volume (subaerial and subaqueous) remaining in the program area and the protec- tion it provides during storms. Two simple measures of a successful beach nour- ishment program are the dry beach width and the volume per unit length of shoreline remaining in the program area during its design life. Two more com
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150 BEACH NOURISHMENT AND PROTECTION plex measures are the assessment of property damage avoided and the remaining level of protection. RECOMMENDATION: Sponsors of beach nourishment pro- grams should quantify and report on four measures of performance of beach nourishment projects. The measures are: · dry beach width, · total sand volume remaining, poststorm damage assessments, and residual protection capability. The federal process for renourishing a beach from the reconnaissance study through the first nourishment typically takes 10 to 15 years. On authorized projects that require only preconstruction engineering, design, and real estate (or right-of-way) acquisition, the process takes 5 to 6 years. These long planning times burden the local sponsor with years of uncertainty about storm damage. Some of the delays are caused by the rigid and sequential federal process, which includes detailed agency reviews and waiting times for next-phase funding. Other delays are caused by slippage in USACE planning schedules. To speed the plan- ning process, the federal approval process can be streamlined and delays mini- mized through contracting technical services. The Water Resources Develop- ment Act of 1992 enabled local governments to undertake the planning process for authorized projects to reduce schedule slippage. That authority has not been exercised because local governments are required to finance the federal share of project costs until after project construction and acceptance by the USACE. RECOMMENDATION: The federal government should reduce the time now needed to process a beach nourishment project. The following steps should be taken: revise the federal approval process to streamline approvals and funding time frames, increase the level of contracting for technical services by con- sultants to the USACE, and · modify the laws and regulations to make federal funding for locally constructed federal projects available upon approval of preconstruction engineering and design by the Assistant Secretary of the Army for Civil Works. Environmental and Monitoring Issues Most beach nourishment programs are inadequately monitored following construction. Monitoring of the physical environment and the performance of the fill material is often too limited in scope and duration to quantify project perfor- mance adequately. Comprehensive assessments of the effects on biological re
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CONCLUSIONS AND RECOMMENDATIONS 151 sources have been limited, especially at sand borrow sites. Resources associated with beach habitats are affected both positively and negatively, with negative effects generally of short duration relative to the expected renourishment interval. Alterations to biological resources in the sand borrow areas are generally of longer duration, and the consequences of those changes have not been well de- fined. RECOMMENDATION: Sponsors of all beach nourishment projects and programs should establish adequate monitoring pro- grams to evaluate changes in the physical and environmental condi- tions. The scope of the monitoring program should be appropriate to the scale of the nourishment program, and the monitoring design should recognize how the data will be used to make project-related decisions. Monitoring data should be analyzed in a timely manner and used to make management and operational decisions regarding continuation of the beach nourishment project or program. RECOMMENDATION: Project sponsors should plan beach res- toration programs so as to avoid significant long-term degradation of the biological resources that are affected, either directly or indi- rectly by construction activities. Emphasis should be on monitoring resources and habitats of greatest concern, including the borrow areas. The appropriateness of the dredging equipment to be used and the manner in which dredged materials will be discharged should also be considered. Where feasible, construction projects should incorporate design features that would enhance biological resources of concern. Costs and Benefits Assessing and Allocating Costs and Benefits Beach nourishment programs result in economic benefits in a variety of forms and to a variety of recipients. Cost-share ratios arbitrarily mandated by Congress do not necessarily reflect the actual distribution of benefits; nor do these ratios take into account the impact of navigation projects on nearby and downdrift shores. RECOMMENDATION: The full range of benefits that accrue from a beach nourishment program should be assessed and quanti- fied. Cost sharing should more accurately reflect the spread of ben- efits that stem from a project.
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52 BEACH NOURISHMENT AND PROTECTION RECOMMENDATION: The federal government should bear an appropriate share of beach nourishment project costs when it can be clearly established that federal navigation projects have exacer- bated the erosion problems on adjacent or downdrift shores, even when these projects were not the only or even the primary cause. Cost-benefit Analysis Although the theory and methodology for conceptualizing and measuring costs and benefits are well developed, the valuation of beach nourishment pro- grams does not take full advantage of these capabilities. As a result, social costs and benefits are not always fully represented in the analysis used to determine whether a program should be undertaken or in the choice among alternative project designs and implementation strategies. The procedures for calculating costs and benefits are overly restrictive, al- lowing only storm damage reduction and limited recreational benefits. There is a wide range of potential costs and benefits that are not currently counted, such as the full complement of recreation benefits and the beneficial effects to adjacent beaches outside a project's domain. RECOMMENDATION: The U.S. Army Corps of Engineers should modify the rules governing both its cost-benefit analysis and its choices among alternative project design and implementation strategies so that the true social costs and benefits provided to the entire coastal region are captured. In particular, the policy should recognize the storm damage reduction and recreational values to the total area affected and account for the benefits of sand transport to adjacent areas. Because only limited postconstruction assessment of beach nourishment pro- grams has taken place, there is little information about the types of costs and benefits (beyond storm damage reduction and recreation) that might accrue from these projects and might be sufficiently significant to warrant measurement. RECOMMENDATION: The U.S. Army Corps of Engineers should conduct postconstruction economic evaluations to identify and measure the wide range of costs and benefits that actually result from beach nourishment programs. A particular focus of this effort should be reassessment of the categories of costs and benefits that should be included in future cost-benefit analysis procedures. The procedures used for calculating the benefits that are allowed under cur- rent cost-benefit guidelines do not uniformly reflect state-of-the-art methodol- ogy. This point applies to assessing recreational benefits and may apply to other areas as well.
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CONCLUSIONS AND RECOMMENDATIONS RECOMMENDATION: To improve the basis for policy analysis and decision making, the U.S. Army Corps of Engineers should become aware of and employ the methodological progress that has been made in economic valuation, especially in measuring nonmarket benefits such as recreation. The guidelines for measur- ing benefits should be updated and applied consistently throughout all U.S. Army Corps of Engineers divisions and districts. RECOMMENDATION: The U.S. Army Corps of Engineers should improve the basis for economic valuation of beach nourish- ment projects by: · reassessing the categories of costs and benefits included in evaluating a project, · incorporating uncertainties in assessing uncertain costs and benefits both with and without the project, · investigating behavioral responses stimulated by beach nour- ishment projects; and their policy ramifications, and · coupling projects with local growth and land-use plans to in- crease the net benefits of projects and designing financing schemes that provide efficient incentives. Coordination of Navigation and Shore Protection Projects 153 The USACE constructs and maintains both navigation and beach nourish- ment projects. The implementation of one type of project can have significant impacts on the other; yet the costs and benefits of the two types of activities have not been considered jointly insofar as the committee can determine. Construction and maintenance of navigation projects that result in the trap- ping of sand from adjacent beaches often cause erosion of those beaches. A1- though the USACE has authority to address cause and effect on specific projects, current practice does not encourage coordination and correlation of the effects of navigation projects with the erosion mitigation and nourishment needs of nearby beaches. The occasional placement of beach-quality sand obtained from naviga- tion projects on eroding beaches is more a matter of economic convenience as a least-cost disposal option rather than a planned action to minimize disruption of the littoral system. The many instances in which dredged beach-quality sand has been disposed of offshore rather than on adjacent beaches does not recognize the economic value of the sand. The cost of offshore disposal is greater than esti- mated in the past when only the direct cost of offshore disposal was considered. RECOMMENDATION: Beach-quality sand dredged from federal navigation projects should be used for beach nourishment projects where the benefits to the latter exceed the extra direct costs to the
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154 Role of Beach Nourishment BEACHNOURISH1tIENT AND PROTECTION navigation projects Implementing such an approach requires that a navigation project be "charged" the cost of any sand budget deficit that it might impose on the adjacent shoreline. RECOMMENDATION: The U.S. Army Corps of Engineers should modify its policies to require both consideration of the eco- nomic value of the sand and the placement of beach-quality sand dredged from federal navigation projects in the littoral system from which it was removed. The U.S. Army Corps of Engineers should coordinate and correlate the construction and maintenance of coastal navigation projects with erosion mitigation along adjacent beaches. RECOMMENDATION: The U.S. Army Corps of Engineers should revise its procedures for cost-benefit analysis of navigation and beach nourishment projects in which there is federal involve- ment to require calculation of both the benefits provided and the costs that one type of project imposes on another. Flood Protection A beach nourishment program located seaward of upland buildings or infra- structure provides storm damage reduction relative to the level of protection that would exist if there were no program. Adequate methods exist for approximating the damage reduction owing to a beach nourishment program; however, there is significant uncertainty about the frequency of storm conditions that could com- promise project performance. Nevertheless, the increase in the level of protection provided by beach nourishment projects and programs supports a finding of reduction in flooding risk, which would merit a reduction in insurance premiums. RECOMMENDATION: The Federal Emergency Management Agency should weigh the effect of an adequately designed, con- structed, and maintained beach nourishment program on flooding risk and hence on flood insurance premiums. Qualification of Engineered Beaches for Disaster Assistance Under the disaster assistance program administered by the Federal Emer- gency Management Agency, the definition of an engineered beach that is used to qualify for payment of sand losses from a beach nourishment program does not provide sufficient specific criteria to define the engineering adequacy of pro- posed programs.
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CONCLUSIONS AND RECOMMENDATIONS RECOMMENDATION: The Federal Emergency Management Agency should revise its definition of and requirements for an engi- neered beach to consist of technical criteria, monitoring require- ments, and measures to promote accountability for program perfor- mance. · The technical basis for certification should be the establish- ment of a design level of storm and flood protection, including the level of protection provided by the design beach and the advanced-fill section seaward of the design portion. The Fed- eral Emergency Management Agency should establish a stan- dard risk factor and then contract for engineering studies to establish return periods or other appropriate design standards that will result in the establishment of standard risk for each of the major coastal regions. Designs for beaches intended to qualify for engineered beach status should meet the joint storm and flood levels appropriate to these return periods or design standards. An assessment of the capacity of a beach to protect against storms should be updated through periodic surveys conducted at least annually to document the evolution of the beach and to determine any change in storm and flood damage reduction potential. Identification of sources of emergency nourishment material should be made well before the need arises. 155 There are two mechanisms for the Federal Emergency Management Agency to participate in emergency actions following a severe storm. If there is a disaster declaration by the President, public assistance funds may be used to support the costs of replacing sand lost to an engineered beach. Second, mitigation funds may be used to restore beach and dune dimensions as soon as possible to protect against subsequent storm damage. At present, these are the only standing emer- gency assistance programs available at the federal level for shore protection and are relied on by coastal communities following damaging storms. RECOMMENDATION: Beach and dune dimensions lost as the result of a severe storm should be restored as quickly as possible to protect against subsequent storm damage. The Federal Emergency Management Agency should continue to provide support for these essential activities. Shore Construction Standards Although nourishment offers effective reduction of storm damages to on- shore construction, the level of protection afforded by the fill is subject to rapid
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156 BEACH NOURISHMENT AND PROTECTION reduction during a major storm and will diminish through time if the beach is not maintained by subsequent renourishment. It is not advisable to reduce or elimi- nate construction or location standards based on prefill hazard assessments or dune protection setback requirements because of (1) uncertainties about continu- ing financial means and political will to maintain a beach nourishment program in the absence of a requirement to do so and (2) uncertainties about sediment availability in the absence of dedicated sediment resources. RECOMMENDATION: In recognition of uncertainties in the pre- diction of coastal processes, cognizant government authorities should establish and maintain construction and location require- ments to set construction back from the storm hazard regardless of whether a beach nourishment project is in place. RECOMMENDATION: In recognition of uncertainties in the pre- diction of coastal processes, the Federal Emergency Management Agency should establish and maintain construction standards for buildings or lots within the benefit area of a beach nourishment program and should prepare Flood Insurance Rate maps as if a beach nourishment project were not in place. . Research Needs to Support Design and Prediction Capabilities There is a need for research to better understand the physical, economic, and biological processes associated with beach nourishment programs and to mini- mize uncertainties. Research is needed on a regional basis to accommodate re- gional differences in these processes. In particular, a more complete understand- ing is needed in the following areas to improve the design of beach nourishment programs: . the natural variability of beach profiles and how they respond to changing wave and current conditions and sediment textures; the significance of profile closure depths beyond which the profiles ap- pear to show minimal responses to changing wave conditions, particularly the degree to which sediment exchange occurs between the beach and offshore out to these closure depths and how these depths can be pre- dicted as a function of sediment and wave conditions; · the choice of grain size and other characteristics of the nourishment mate- rial for best retention on the beach and how that choice affects the dynam- ics of the beach profiles and alongshore spreading of the nourishment sediment; · the further development of cross-shore sediment transport models related to profile changes; and
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CONCLUSIONS AND RECOMMENDATIONS 157 · the causes of erosional hot spots occurring on natural beaches and within beach nourishment programs. RECOMMENDATION: An intensive study for a few large-scale beach nourishment programs should be undertaken by a third-party group of investigators under federal sponsorship. The objective of the study should be to test the validity of current predictive methods and design assumptions and improve prediction and design meth- odologies further. The study should include postconstruction assess- ment of the costs and economic benefits of the programs and the overall effects on economic development. Directional Wave Data On a major project, especially at a site with complex bathymetry, directional wave data are essential to verify the design methodology and to improve perfor- ~nance in future beach nourishment. These data are needed to establish the coastal wave climate for the program. Collateral uses of the data should be considered when justifying the cost of measuring waves. RECOMMENDATION: The U.S. Army Corps of Engineers should require the collection, analysis, and dissemination of direc- tional wave data as part of major beach nourishment programs in which there is a federal cost share. Erosion Data There is a need for a uniform, national, reliable data base on historical erosion rates. Erosion rate data based on historical charts collected by the Na- tional Oceanic and Atmospheric Administration and profile data collected by the USACE and some local agencies are uneven and of varying usefulness. RECOMMENDATION: The U.S. Army Corps of Engineers, the National Oceanic and Atmospheric Administration, and the U.S. Geological Survey should undertake a cooperative program to es- tablish standardized decadal rates of erosion or accretion for all U.S. shorelines subject to significant change over this time scale. The detailed data base used in these assessments should be readily available to coastal engineers and scientists.
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Representative terms from entire chapter: