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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology 2 Scientific and Engineering Perspectives To assess coastal engineering practice in marine habitat management, a scientific understanding of marine habitats as ecosystems and as components of larger ecosystems is essential. Just as essential are the engineer's tools, practices, and techniques through which this scientific knowledge can be intelligently applied. These two broad fields—science and engineering—each multidisciplinary, come together as the twin pillars of effective and environmentally sound practice in marine habitat management. The social sciences, including law, economics, and management are also important, but sound science and engineering is fundamental to a habitat project's actual performance. The term multidisciplinary, as used here, includes all the disciplines that contribute to either understanding the ecological setting or providing the techniques used in engineering in the coastal zone. The first two sections of this chapter introduce basic themes from these two fields that resonate through the rest of the report. The third section sketches the too frequent situation where technology, including engineering technology, has intruded on marine habitats, uninformed or unconcerned about the consequences for their ecological functioning. ECOLOGICAL SETTING An ecosystem has numerous components that are all interdependent to some degree. Coastal habitats and ecosystems are prime areas for marine and estuarine organisms. Some of these organisms are fixed in place for some or all of their life cycle; others are capable of spontaneous movement, moving from one habitat
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology to another between birth and their juvenile and adult stages. Both types of organisms are present within any marine habitat. The basic underlying questions relate to the degree to which one component of the ecosystem affects or depends on the others and to the density-independent environmental variables necessary for an ecosystem to function. Interrelationships among biological and physical processes are particularly apparent for marine and estuarine ecosystems. Water is a transport medium for plants, larvae, animals, nutrients, and pollutants. Because of this, there are no closed or isolated ecosystems. Some fish, for example, may spawn offshore and move in and out of coastal areas at various frequencies. Some shrimp species spawn within 50 kilometers of the coast, migrate to the estuary mouth, and then move within the estuary for several months before migrating offshore again. Commonly, larval and juvenile fishes migrate into an estuary for further development after spawning offshore. Some fishes also move into estuaries to spawn. Seasonal migrations and changes in habitat use patterns also occur, such as over wintering in bottom sediments by non-migrating shrimp in some estuaries. Organism movement within an estuary may also include daily travels among seagrass beds, muddy bottoms, salt marshes, and other coastal habitats. For birds and other terrestrial animals, coastal habitat includes brackish marsh, maritime forests, and coastal islands. Such movements represent the evolutionary adaptations of species for optimal growth, survival, and reproduction as affected by competition, predation, and food limitations. Adult population size is often determined during the posthatching stage of a species' life cycle. The movements from one habitat to another often depend on physical factors including salinity gradients, tidal movement, wind and wave energy, and temperature. These factors can help or hinder an organism's ability to optimize or balance energy expenditures for food capture during early life history stages and during old age or sickness. For example, fisheries populations are sometimes dependent on estuarine conditions, such as salinity, temperature, and currents, during the early life history stages. Natural processes and human activities that affect commercially valuable fish and shellfish species also affect the less conspicuous species that provide food, influence habitat, and decompose and recycle nutrients in a given system. With the interdependencies of ecosystems in mind, it is clear that human activities that degrade or destroy any marine habitat affect the whole marine ecosystem in the area that is influenced. At the same time, it is difficult to detect the effect caused by incremental degradation and cumulative loss, even while it is occurring. A degraded salt marsh, for example, may appear healthy while its biological production has been severely disrupted. Water quality degradation below the water's surface is difficult to detect without sophisticated analysis or continuing monitoring programs. Overall, the cumulative effect on the ecosystem can be substantial. The stresses that challenge an organism's growth, survival, and reproductive potential can sometimes bring about adaptive change over time. Organisms live
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology in an environment that changes each year through the accumulation or loss of sediments, seasonal variation in climate, and changes in hydrology. Yet all can survive as long as these changes are within their range of tolerance. For example, the rate of global sea level rise has been slow, and impacts are not readily discernible in the near term, except where relative sea level rise has been accelerated, as when subsidence is also occurring. The effects are cumulative over a prolonged period. Complicating these ecological stresses are the increased human uses of the coastal zone, uses that sometimes exceed the ability of some marine organisms to adjust. Human activity has modified marine habitats in ways that science is just beginning to understand; the most conspicuous is habitat loss. For example, eutrophication has altered algal communities or species, increased occurrences of algal blooms, and created oxygen deficits in some waters. These changes may greatly decrease the shellfish population or make them unfit for human consumption. Although much is known, the effectiveness of management of the coastal zone is still limited by an incomplete understanding of the habitat requirements of species. The EPA and the NOAA have undertaken research monitoring programs to identify and assess indicators of ecological health. Nevertheless, it is very difficult to establish definitive cause and effect relationships, especially for marine ecosystems. Comprehensive ecosystem-based predictors of the effect of change on catches of commercially important fisheries species are generally absent or underdeveloped. The best predictors are often based on a hindsight system measured in previous landings, fishing effort, or surveys of abundance. This problem is widespread, making the success of coastal engineering projects dependent on less-than-certain environmental assessments. Science cannot predict with much certainty, for example, the consequences of seagrass losses or gains to sea trout, shrimp, and oysters in any estuary of the northern Gulf of Mexico. Further, most widely used population models exclude interactions between competing species (USFWS, 1980). The present distribution and abundance of species are not understood in sufficient detail to answer many key management questions. The management of a species often focuses on specific habitats rather than on a comprehensive evaluation of the range of habitats used by a species over its life cycle. This approach could adversely affect successful management of the target species as well as policy and management decisions regarding the importance of marine habitat and the funding of protection and restoration work. It is widely recognized that natural habitats serve society in a variety of ways. Less recognized is the broader alternative view that human society and these habitats are already functioning together. As a result of heightened environmental consciousness, society has begun to embrace this alternative view and improve its management of natural ecosystems, but public appreciation of the extent to which society and the natural world depend upon one another is limited. The importance of these ecological relationships is not clearly defined in
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology terms of goods and services. For example, although the important role of wetlands in supporting commercial shrimp populations is frequently cited as a clearly valuable function, other benefits are not well appreciated. These include the capacity of wetlands to control greenhouse gases that contribute to global warming, act as critical components of the life cycles of animals and fish, buffer storm surges, improve water quality, reduce flooding, and reduce the national export-import debt by supporting valuable fisheries. The adverse impacts on fishery resources caused by habitat degradation and loss are further complicated by overexploitation of some fish stocks by recreational and commercial fishing (Stroud, 1992). When species diversity and abundance change as a result of habitat degradation and loss or from over exploitation, it logically follows that human society will need to change its approach to prevent habitat and species losses. Modern society does not understand or fully appreciate the degree of destruction and alteration that is occurring and does not realize what changes are needed to prevent loss or how to achieve them. A particularly important problem lies with not knowing how to assign a precise value, economic or otherwise, to a particular habitat. Establishing a defendable value of habitat in natural versus converted uses is a challenge. This is a daily task for managers of coastal resources. The only value assessments that can be given within the current state of knowledge and practice are incomplete, resulting in highly subjective decision making on the fate of valuable natural resources (Water Quality 2000, 1992). The lack of acceptable valuation regimes complicates efforts to protect, enhance, restore, and create coastal habitats. The challenge to scientists and engineers is to overcome the past narrow views about the value of habitats, learn more about what makes them important, and interpret and then communicate that information for intelligent decision making and the public's information. THE SCOPE OF COASTAL ENGINEERING Engineering practice in the coastal zone has several general objectives including prediction of sediment transport, movement of surface water and groundwater, and shore evolution and to development and implementation of structural or other means to alter coastal water movement and shore evolution (Mehta, 1990). In addition to engineering activities that are conventionally considered within the domain of coastal engineering, these general objectives encompass relevant aspects of dredging technology, soil and geotechnical engineering, water resource engineering including wastewater treatment and disposal, and civil construction practices related to soils and structures. Coastal engineering practice is conditioned by six factors: habitat management objectives (including physical, chemical, biological, and ecological components);
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology FIGURE 2-1 The domain and role of coastal engineering. the physical environment; level of technology; institutional constraints; professional capabilities; and cost. The interactive relations among these factors (Figure 2-1) cannot be overemphasized. Unless the management objectives for a habitat are set in harmony with the other five factors, the overall management program will be missing or incomplete and its efficacy jeopardized. Of these six factors, habitat management objectives are in the committee's experience the least coordinated and developed but are nonetheless important for coastal engineering applications. In particular, the complexities of natural systems make it difficult to predict accurately the final form and function of habitat in any coastal engineering project. Thus, in addition to engineering considerations, setting habitat management objectives is conditioned by scientific and societal factors as well. These factors are a challenge to the engineer. For example, although the functions of a salt marsh are known (see Box 3-3), there is no consensus on what constitutes a fully functional salt marsh. Incomplete scientific knowledge about the biological processes that characterize the functions of a marsh continues to foment debate (NRC, 1992a). There are also philosophical and practical concerns regarding standards of comparison for physical and ecological
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology factors and the time frame necessary to assess success in habitat restoration. Contentious issues are the preexistent conditions that should serve as standards of comparison and the time scales that should be used to assess whether or to what extent full natural functionality has been achieved. For example, physical alterations within watersheds might preclude restoration to pristine conditions prior to all human activity. If degraded or converted habitat is subsequently reconverted to a form of habitat different or less functional than the habitat that predated human or natural alterations, is the result restoration? Some would say it is not. A related view is that all dredged material is waste and that construction of wetland habitat with such material is not restoration regardless of the result, even when the material is used in its native environment (NRC, 1992a). The view of the committee is that most dredged material is nontoxic in its environment and is a valuable resource that can potentially be effectively used to support habitat protection and restoration. Many completed habitat restoration and creation projects constructed with dredged material are functioning to design specifications (Landin et al., 1989c; USACE, 1986). It is clear, however, that despite the successful use of marine sediments in well-founded marine habitat restoration projects, many marine habitat management projects are likely to stimulate controversy. Substantial debate can be anticipated over definitions, natural functions, and with regard to contaminants, the quality of dredged material. As a consequence, habitat protection and restoration using dredged material may continue to be treated by some individuals and organizations as purely experimental into the foreseeable future, although the potential for effective utilization is appropriate. Disagreements over definitions do not mean that less than fully functional modifications or restoration, including those involving dredged material, should not be attempted. For example, while it may not be possible to recreate a fully functional natural wetland, it may be possible to create some habitat characteristics of these wetlands that will in turn support colonization by some animal and fish species. In some cases, partially restored natural functions may nevertheless help maintain the functions of the ecosystem of which it is a part. The diversity of physical settings for habitats requires the use of wide-ranging engineering principles for feasibility studies, design, and application of technology. The physical principles of some coastal processes, such as hydrodynamics and sediment transport, are sufficiently established to enable universal application. However, the technology needed for predicting, developing, and maintaining habitat varies with the physical setting. The maturity and sophistication of technologies for these purposes differ widely and are not as far advanced as the understanding of the underlying physical principles. The engineering profession typically must conform to institutional constraints; principal among them are time, cost, and project specifications. Institutional culture and accountability can be less obvious but still powerful constraints. The time required to obtain approval for projects affecting marine
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology habitat, particularly those involving dredging and dredged material, can be prolonged (Kagan, 1990; NRC, 1985d). This is attributable to fragmented and multitier decision making and regulatory processes at the state and federal levels as well as competing objectives (and conflict over them) among the interested parties. These factors affect not only the interested parties but also the federal, state, and local agencies responsible for decision making and permitting. Although conflict over project goals and specifications can result from economic and sociopolitical factors, it can also result from limited scientific knowledge of the effects of various engineering actions. The engineer is responsible for informing the client of the possible risks involved in a particular project and for providing a reasonable success rate. These are daunting tasks considering the fact that it is often difficult to predict the effects of engineering operations on ecological functions. When possible and feasible, a cautious, phased approach to design and implementation in projects involving marine habitat is normally the best option. Engineering technology could benefit from development of techniques that minimize perturbations to natural systems along with careful documentation of the effects through post project monitoring of both physical and ecological parameters. Indefinite approaches are not standard engineering practice; they also add costs to habitat projects, for which funds are always limited. Comprehensive monitoring regimes also drive up project costs and are not a routine practice. Good monitoring regimes have been applied in some of restoration projects (Clarke and Pullen, 1992; Landin et al., 1989a,c). However, monitoring is more often cursory and sporadic, failing to provide an opportunity to learn from the successes and failures of the projects being monitored. A particular problem with the creation or modification of marine habitats is the lack of consensus on criteria to determine project success (Westman, 1991; Zentner, 1982). Criteria are available (Landin, 1992b,c) and discussed in Chapter 6, although all interested parties may not accept them. The practicing engineer prefers that success be practical and determinant, and not relative to competing perspectives and subjective. Engineering success is defined as meeting project goals and objectives that were agreed on prior to construction. If project goals do not effectively address habitat needs and issues of scale in space and time, the result may or may not be a fully functioning marine habitat or, more realistically, a product positioned to achieve functional objectives over an agreed-to time scale (Risser, 1988; Westman, 1991). The product is also dynamic rather than fixed, a nontraditional engineering result that not only makes determination of success more difficult but also runs counter to predominant engineering approaches to problem solving. To the degree that natural functions and ecosystem needs are project objectives, the involvement of marine biologists, coastal geologists, ecologists, and other scientists in the early stages of project development is fundamental to developing sound project specifications. But again the result may be something less than restoration to natural conditions that preexisted human
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology effects on the environment. Thus, the time factor is a definitional issue in project objectives, and prospective project outcomes can pit theory and philosophy against practical application. Disagreements in these areas might make multidisciplinary collaboration among the scientific and engineering disciplines difficult at times. Advances in technology and heightened societal concerns mean that team effort is increasingly required to address problems. The need for team effort is well recognized by leading practitioners involved in creation or restoration of coastal wetlands and of shallow water and intertidal marine habitats; the coastal engineer typically works with a wet-soil scientist, a sedimentologist, a hydrologist, a biologist, and a systems ecologist, among others. For engineers specializing in environmental work, the multidisciplinary nature of the work requires general familiarity with a broad range of topics across and outside the engineering disciplines. The growing need for interdisciplinary and multidisciplinary perspectives in engineering work generally is one of the reasons why some schools still offer a 5-year degree as an option and why some 4-year undergraduate engineering curricula in the United States have stretched to almost 5 years (NRC, 1985a,b). Yet, a sense of disciplinary dichotomy between science and engineering continues to exist in academic curricula. The engineer often has limited exposure to other disciplines. On the other hand, coastal scientists often do not take advantage of available coastal engineering expertise. Education that is scientifically and technically more integrated without diluting essential engineering or scientific principles would benefit individuals interested in marine habitat management following undergraduate study. This is difficult to achieve under existing curricula requirements, but could be a long-term objective for engineering schools. Because coastal engineering principles and practices are rooted in civil engineering, many coastal engineers recognize and understand civil engineering design principles. But on a global scale, coastal engineering design is not always carried out, permitted, or implemented by engineers who are specialists in this field. Civil construction along the shore often suffers from this lack of expertise. Although this issue is perhaps more institutional than educational, the results have been quite positive where coastal construction was carried out with due regard for coastal hazards through improved coastal engineering design practice and its codification. For example, soon after Hurricanes Elena in 1985 (Hine et al., 1987), Hugo in 1989 (Davison, 1991; NRC, 1990a), and Andrew in 1992 (Schmidt and Clark, 1993), fairly extensive field inspections of the coasts of eastern, southern, and western Florida, Cancun in Mexico, South Carolina, and Louisiana were carried out to document erosion and structural damage. Structures built to modern coastal engineering design standards were found to have weathered the storms, generally without major damage (Dean, 1991), although repairs were necessary in a few locations to correct displacement damage (of
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology rubblemound groins) and damage to armor stone and foundations [USACE and Florida DNR, 1993]. IMPACTS OF TECHNOLOGY IN THE COASTAL ZONE Although an activity may be sound from an engineering perspective, it may not be sound for the organisms living in the area affected. Such is the case where engineering practices and technological developments have intensified human habitation and use of the coastal resources. The coastal habitats that existed naturally in the absence of roads, culverts, flood protection, and urban runoff have been stressed in often unpredictable and consequential ways. These responses are frequently unpredictable because methodologies have not yet been developed to predict changes that will occur, particularly those that are subtle or take a long time for their effects to become visible. The application of engineering and technology in the coastal zone has both directly and indirectly influenced coastal habitats. The visible results, such as habitat conversion or loss caused by port development or oil and gas exploration, can often be readily discerned. Documented examples of habitat destruction and adverse effects of human-related activity include seagrass habitat losses from changes in water quality and from propeller damage from recreational and commercial craft, coral reef damage and loss from ship groundings and propeller strikes; species decline from pollutants and impoundments, wetland losses from disruption of sediment transport and from construction of bulkheads; loss of intertidal flushing, and waterlogging following hydrologic impoundment. The full ecological impacts are usually less obvious, especially in the near term, and are subject to intense debate. Focusing the debate over ecological impacts is complicated by the limitations of accepted data and analysis, a lack of consensus among decisionmakers and regulators, limited long-term monitoring, and disciplinary perspectives that are too narrow for holistic problem solving. For example, the large-scale physical impacts of constructing navigation channels, underwater berms, and flood protection levees are easier to predict than the ensuing and perhaps long-lasting effects of the hydraulic and hydrologic modifications that affect sedimentation rates and turbidity, water quality, fish and wildlife use, and endangered species. The problems associated with this uncertainty often result in and are compounded by contradictory project objectives. In another example, objectives for the protection of a ''client species" may indirectly and unintentionally overlap with objectives affecting a large part of society. In hindsight, project participants may recognize the interdependencies between ecosystems and the human activities that alter them, but it is difficult to incorporate these realizations into project planning. First of all, the relationship between incremental habitat loss and degradation and human activities is difficulty to quantify. Engineering and scientific capabilities to quantify interdependencies in ecosystem functioning and the critical
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology nature of natural functions is not fully developed (Cairns and Niederlehner, 1993). Further, those who would convert marine habitat to other uses can bring their resources quickly to bear while the regulators and managers who are the overseers of change and the stewards of natural resources generally have less flexibility and resources. Less appreciated but substantial roles for technology in coastal habitat management include recently developed capabilities to manage information, habitats, and communications through both remote sensing, both computer simulations and ecologic-economic-physical models, and graphic display capabilities for training and monitoring. Geographic information systems (GIS) are powerful organizers of data. For example, GIS can provide overlays of spatial data sets accumulated in one location for nearly instant analysis of habitat changes and landscapes for use in permit evaluations. OBSERVATIONS ON THE IMPLICATIONS OF SEA LEVEL RISE TO THE APPLICATION OF PROTECTION AND RESTORATION TECHNOLOGY Plant and animal communities are generally resilient, being capable of relatively rapid response to ecological changes—if there is a place with suitable conditions that supports migration and there is sufficient time for migration to occur (Daniels et al., 1993; NRC, 1987a; Ross et al., 1994). A global eustatic rise of relative mean sea level (RMSL) at many shores could potentially eliminate vast and presently extant habitat areas while creating new ones upland (NRC, 1987a), and changes in the character of species can occur as compression of habitat takes place (Titus, 1988). Although the full extent of sea level is not known, the apparent eustatic rise in sea level places a demand on the scientist and the coastal engineer to reconsider fundamental approaches to protecting, improving, and creating wetlands (NRC 1987a, 1989b, 1990a, 1990c; Titus, 1988). Both coastal development and marine habitat management have often assumed a relatively stable RMSL except in coastal Louisiana where the rate of change is obvious and subsidence is also a factor. Even without a drastic eustatic rise, the RMSL rise in coastal Louisiana has created a situation wherein cost considerations may limit engineering responses to protecting those areas that are vital to the state's and the nation's economy. In other areas, an RMSL rise may mean that costs could preclude any defense, and abandonment may be the only outcome. Although abandonment may not be a humanistic policy option, defending the coast at any cost may prove unrealistic (NRC, 1987a; Roy and Connell, 1991). Shoreline recession is one indicator of sea level rise. A common method of calculating the recession of sandy shoreline owing to sea level rise is a simple mathematical relationship known as the Bruun Rule (Bruun, 1962, 1981, 1988).
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology The basis for this relationship does not include any net gain or loss of sand from the beach profile but considers only sediment shifted seaward to maintain a profile in equilibrium with the wave climate. This relationship dictates that doubling the rate of sea level rise doubles the rate of recession. Calculations based on this relationship and/or other sources suggest, for example, that the majority of the shoreline of the east coast of Florida is suffering from moderate to severe erosion (Williams et al., 1990). This situation may be a harbinger of what may occur as a result of greater RMSL rise than in the recent past, but careful calculations based on measured shore profiles along Florida's east coast over the past century indicate otherwise. Although the shoreline has indeed receded locally (quite drastically in some places, especially near inlets), on average, the shoreline has actually advanced at the rate of 0.16 meters per year over more than 100 years (Grant, 1992). Further, the application of the Bruun Rule to shorter-term changes in the shoreline to corresponding changes in the sea level for the same shoreline shows no significant correlation (Grant, 1992; SCOR, 1991). Shore processes other than a transitory rise in sea level have evidently had a dominating effect on the shoreline position. Transport of sediment from offshore as well as local biogenic production of carbonaceous sediment may be important factors affecting RMSL. Because simple computational procedures such as the Bruun Rule are often based on basic assumptions and can easily be misapplied, future predictions will depend on carefully defining the applicability of such procedures. On the other hand, computational procedures can be modified, where feasible, to broaden their use (NCR, 1987a). These facts argue for the initiation of both short-and long-term strategies to perfect restoration technology and apply it aggressively to the problem of historical wetland loss and the future threat of accelerated sea level rise. Further, they dramatize the challenges and limitations of restoration; a system cannot be restored in a context that requires continual, intensive subsidy. Those engaged in enhancement, restoration, and creation efforts need to consider four approaches: enhancement or restoration of individual sites that were damaged as the result of human influence; large-scale ecosystem approaches (referred to as landscape ecology) to maintain and enhance habitat while remaining cognizant of the implications of sea level rise, including spatial relationships. long-term needs for shoreline protection measures; and in the extreme, retreat or abandonment. DEFINING SUCCESS A successful track record is necessary for building and sustaining public and private support for more widespread use of protection and restoration technology. This record is especially needed to establish the credibility of restoration
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology technology and of practitioners where protection or restoration is used as mitigation in exchange for coastal development. Despite the importance of defining and achieving success, there are no universally accepted measures for gauging project performance or guiding evolving practices. One school of thought, the ecological viewpoint, is that success should be principally defined as the ability to fully reproduce natural processes, although social and economic values should be considered to some extent (Cairns, 1988; Erwin, 1990; Josselyn et al., 1990; NRC, 1992a). Goals (that is, expected results) focus on natural functions (Zedler and Weller, 1990) to the exclusion of social (including economic) interests in a restoration project. Determining whether predisturbed natural conditions have been restored requires rigorous, long-term monitoring that can strain the limits of scientific knowledge to interpret the results (D'Avanzo, 1990) and increases project costs. Each can be a problem for project sponsors, engineers, and regulators, who prefer more quantifiable measures. Returning a disturbed ecosystem to its predisturbed condition is generally preferred but is not always feasible. However, enhancement or partial restoration is often possible (Landin, 1992c; Sheehy and Vik, 1992). Then the environmental or social value can be produced even when nature is not fully replicated. But from a purely ecological perspective, the projects would not be considered successful. A second school of thought, reflected in this report, defines success as achieving project goals and objectives. This viewpoint considers natural functions important but does not give them status as exclusive parameters for defining success (Berger, 1991; Clark, 1990; Garbisch, 1990; Landin, 1992c; Lewis, 1990a; Westman, 1991). Thus both environmental and social (including economic) factors can be accommodated in project goals and objectives. This approach provides a more traditional format for compatibility with regulatory processes, economic reality, and engineering practice. Establishing project goals and objectives, implementing the project, and measuring performance in relation to the objectives remain challenges regardless of how success is defined. SUMMARY Concomitant application of scientific knowledge of marine habitats as ecosystems and coastal engineering capabilities is needed to produce effective and environmentally sound human interactions with coastal resources, but this is not common practice. The ecological setting is not widely understood or accommodated in human activities that impact marine habitat. The application of coastal engineering capabilities and technologies may be sound from an engineering perspective but not beneficial to organisms affected by engineering work. Habitat management objectives are not well developed from an engineering perspective and are also conditioned by societal and scientific factors, including the effects of relative sea level rise. Interdependencies in the functions of coastal
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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology habitats are not fully understood and are therefore difficult to restore to a natural state. Standards of comparison for determining the performance of habitat restoration projects are a source of substantial debate. Use of dredged material in habitat restoration work, concern over the chemical properties of sediments, and questions over natural functioning stimulate considerable controversy. But some dredged material is also a resource that is needed for constructing habitat projects in coastal ecosystems. Even if not fully functional, habitats based on dredged materials may help maintain the natural functioning of the coastal ecosystems of which they are a part. How well areas restored using dredged material mimic habitats that have been converted is an issue. Controversy over these issues may continue use of dredged material in restoration as an experimental rather than proven application. Coastal engineers have traditionally not always adequately prepared for multidisciplinary design and construction of protection and restoration projects. Where scientific knowledge and engineering capabilities were not in harmony, the result was often adverse consequences to affected coastal ecosystems. To avoid these consequences, a conservative and multidisciplinary approach is essential whenever engineering activities may impact marine habitat. Project objectives need to adequately incorporate both scientific and engineering principles as well as social factors to enhance their prospects for successful performance and to ensure their broad acceptability. Project performance to these objectives provides a practical measure that can be used to determine success.
Representative terms from entire chapter: