3
The State of Engineering Practice in Marine Habitat Management

Whether marine habitats can be protected or restored has stimulated considerable debate; so too has the application of technology in protection and restoration. Major issues include the functioning of habitats following application of protection or restoration technology, dredging impacts, the efficacy of using dredged material in restoration work, and the placement of dredged material. These issues introduce our examination of the state of engineering in marine habitat management, followed by an examination of the application of technology in various marine habitat settings (Box 3-1). Dredging and dredged material placement technologies and their application in marine habitat protection and restoration are reviewed, as are alternative approaches and technologies that have been or could be used to establish marine habitats or to minimize or prevent deleterious impacts from human activities. The chapter concludes with an overview of various factors that affect the use of technology for habitat protection and restoration. A categorized list of major references is included as Appendix C. A summary of regional perspectives on the state of practice is provided in Appendix D.

RESTORATION TECHNICAL ISSUES

Functionality Following the Application of Technology

The technology to enhance, restore, or create the physical or three-dimensional structure of marine habitats is generally well developed. (For marine wetlands see Kirkman, 1992; Kusler and Kentula, 1990; Landin et al., 1989b; Seneca



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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology 3 The State of Engineering Practice in Marine Habitat Management Whether marine habitats can be protected or restored has stimulated considerable debate; so too has the application of technology in protection and restoration. Major issues include the functioning of habitats following application of protection or restoration technology, dredging impacts, the efficacy of using dredged material in restoration work, and the placement of dredged material. These issues introduce our examination of the state of engineering in marine habitat management, followed by an examination of the application of technology in various marine habitat settings (Box 3-1). Dredging and dredged material placement technologies and their application in marine habitat protection and restoration are reviewed, as are alternative approaches and technologies that have been or could be used to establish marine habitats or to minimize or prevent deleterious impacts from human activities. The chapter concludes with an overview of various factors that affect the use of technology for habitat protection and restoration. A categorized list of major references is included as Appendix C. A summary of regional perspectives on the state of practice is provided in Appendix D. RESTORATION TECHNICAL ISSUES Functionality Following the Application of Technology The technology to enhance, restore, or create the physical or three-dimensional structure of marine habitats is generally well developed. (For marine wetlands see Kirkman, 1992; Kusler and Kentula, 1990; Landin et al., 1989b; Seneca

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology and Broome, 1992; Simenstad and Thom, 1992; and Zedler, 1992. For coral reefs see Maragos, 1992. For artificial reefs see Lewis and McKee, 1989; Seaman and Sprague, 1991; Sheehy and Vik, 1992. For shallow water submerged seagrass see Fonseca, 1990, 1992; Lewis, 1987; Lewis et al., 1985. For kelp forests see Schiel and Foster, 1992. For mangrove systems, see Cintron-Molero, 1992; Hamilton et al., 1989; Lewis, 1982.) Technology also exists for shore protection and water quality control, although its application by coastal managers and the engineering community is not uniform (Crewz and Lewis, 1991; Roberts, 1991). Regardless of the technology used, the capacity of enhanced, restored, or created structural components to function as refugia or filter contaminants or to serve as sources of carbon and food for marine organisms is seriously debated (NRC, 1992a). For example, Lewis (1992) and Landin et al. (1989c) support the hypothesis that restored marine habitats can function as if they had not been disturbed or altered from preexisting natural conditions; the Pacific Estuarine Research Laboratory (PERL, 1990) disagrees. There is a general acknowledgement that use of existing protection and restoration technology and regulatory enforcement to offset or mitigate permitted losses of marine wetlands has not resulted in "no net loss" of ecological functions (Lewis, 1992; Redmond, 1992; Roberts, 1991). In light of continuing loss of aquatic habitat, the NRC encouraged a dedicated program to reverse historical and current loss of wetlands. The NRC recommended that inland and coastal wetlands be restored at a rate that offsets any further loss of wetlands and contributes to an overall gain of 10 million wetland acres by the year 2010. … In the broadest terms, aquatic ecosystem restoration objectives must be a high priority in a national restoration agenda; such an agenda must provide for restoration of as much of the damaged aquatic resource base as possible, if not to its pre-disturbance condition, then to a superior ecological condition that far surpasses the degraded one, so that valuable ecosystem services will not be lost. (NRC, 1992a) Despite of the controversy over how fruitful marine habitat projects are, they continue to be launched and implemented, and technology continues to be applied. From a coastal engineering perspective, capabilities for dredging and placement of dredged material are important resources that may be used in marine habitat management in conjunction with other important engineering capabilities. These include design expertise, predictive tools, and practical experience with a wide array of engineering technologies and structures. These capabilities may be used for integrating marine habitat objectives into coastal development, improving channel design to reduce dredging requirements, control of hydraulic conditions and sedimentation, planting marsh and submerged vegetation, stabilizing and restoring beaches, and designing and operating sewage and other waste disposal facilities to minimize environmental impacts. It is with this range of tools that the coastal engineering profession can aid in the

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology improved stewardship of vital coastal resources. Dredging and the placement of dredged material, although important, are also the source of much controversy, whether applied in marine habitat management or more traditional coastal engineering work. Use of Dredging and Dredged Material in Restoration Dredged material (see Box 3-1) is used in constructing many marine habitat management projects. Thus, in practice, marine habitat management depends heavily on its availability and suitability. Material is obtained either through dredging or water control structures that regulate the natural movement of suspended sediment. In some cases, shore structures have been modified, such as breaching levees (creating artificial crevasses) to reestablish or improve water transport of sediments into areas where they will settle to the bottom and accrete to form emergent wetlands. Substantial quantities of sediments are dredged to maintain federal navigation projects (shipping channels). Disposal of material dredged from such projects is often complicated by controversy over placement because of potential environmental impacts. Lesser quantities of sediments are moved for private navigation projects, such as maintenance of marinas but can still result in a placement problem. Dredging is also conducted during construction of new navigation projects and port facilities and for some commercial and residential developments in shore areas either to provide or improve water access or for fill, although this latter activity is less common today. The placement or disposal of dredged material often creates considerable controversy, regardless of its source (Hamons, 1988; Kagan, 1990; Lethbridge, BOX 3-1 COMPOSITION OF DREDGED MATERIAL Dredged material varies substantially in composition. It may be clean or may contain pollutants (NRC, 1985d, 1989a), affecting its potential use as a resource in marine habitat management. There are five general categories: rock, gravel and sand, consolidated clay, silt and soft clay, and mixtures of the four. Silt and soft clays are of particular interest for use in marine habitat restoration. They form much of the material obtained through maintenance dredging and are potentially useful for habitat development in and out of marine settings. Also of interest are gravel and sands that may be used to stabilize or improve turtle nesting beaches, construct bird nesting islands, and provide elevations necessary for restoring wetlands (Herbich, 1992b; Landin, 1992b; PIANC, 1992a). Rock and consolidated clay obtained through dredging have potential applications as well as construction material for offshore berms and artificial reefs (PIANC, 1992a), for example.

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology 1988; Stromberg, 1988). Dredged material is treated as a resource or a spoil, depending on one's point of view. Concerns over use of dredged material outside its natural marine environment include the chemical changes that occur when marine sediments are exposed to oxygen and contamination of sediments by pollutants (Davies, 1988; Engler et al., 1991a,b; Herbich, 1985; Lee and Jones, 1992; NRC, 1985d, 1989a; 1992a; USACE, 1984). Relatively few navigation project areas are heavily contaminated by pollutants that typically have emanated from nonpoint sources into affected ecosystems. These occur near major coastal cities (Robertson and O'Conner, 1989; Zarba, 1989). About 95 percent of all dredged material is classified by the U.S. Army Corps of Engineers as suitable for open water disposal, although some materials with small amounts of pollutants may require capping, depending on the nature and level of contaminants present. Much of this material is therefore potentially suitable for use as a nourishment and construction resource for habitat enhancement, restoration, and creation projects (Engler, 1988; Landin and Smith, 1987; Murden, 1989b; OTA, 1987) (see Box 3-2). Another relevant concern is the fact that organic and inorganic materials are lost to the dredged material in varying degrees when BOX 3-2 THE ARMY CORPS OF ENGINEERS APPROACH TO USING DREDGED MATERIAL Historically, the Army Corps of Engineers was concerned primarily with the disposal of dredged material. In the past two decades, applied research and dredging interests within the Corps have emphasized dredged material as a resource for habitat protection, enhancement, restoration, and creation (Landin et al., 1989c; PIANC, 1992a; USACE, 1986, 1989a). This approach is referred to as the beneficial uses of dredged material. Such uses primarily involve one or more habitat types: upland meadows and woodlands, marshes and wooded wetlands, wildlife islands, and estuarine and marine habitats. For island design and management, all four are often included. The environmental and engineering technology for using dredged material for habitat purposes has been developed, published, examined in conferences, demonstrated through field applications, and monitored since the 1970s by the Corps of Engineers. Landin (1992a) and Landin et al. (1989c) found that the performance of projects using dredged material can be predicted reliably for salt and fresh marshes. Where feasible, USACE regulations now encourage inclusion of wetland restoration and creation in dredging projects under Section 150 of the Water Resources Development Act (WRDA) of 1986, 1990, and 1992. The Corps has not widely implemented regulations based on these acts; the acts authorize regulations but did not include appropriations to enable widespread implementation. Further, the acts only regulation of wetlands, thereby excluding all the other habitats associated with natural progression in a coastal ecosystem. Another limitation on the use of dredged material is the Army Corps of Engineers policy requiring least-cost, environmentally acceptable placement.

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology sediments are disturbed, depending on compaction and local conditions. This affects its quality for use in habitat restoration. The nation's ports are vast economic engines and access by modern ships is fundamental to their efficient operation. Despite economic and environmental controversy over dredging issues, as discussed in the preceding paragraph (Kagan, 1990; NRC, 1985d, 1992b), past history has shown that bottom sediments will continue to be moved to maintain federally authorized navigation channels as an economic necessity. When this occurs, environmental objectives established by law and regulation need to be met constructively and responsibly (Hamons, 1988; Harr, 1988; Murden, 1989b; NRC, 1985d, 1992b; Rhodes, 1988; Stromberg, 1988). For example, dredging operations could be planned and conducted to disrupt ecosystems as little as possible, such as by maintaining biologically active shallow water and intertidal areas where feasible. In some cases, this might even reduce the amount of material to be moved and the costs of construction and maintenance, all of interest for improving waterway design (NRC, 1992b). Nevertheless, the materials obtained from dredging can provide the very resource needed to reduce or reverse habitat losses. In fact, in the Mississippi River delta region of Louisiana, the controversy is not over whether to use bottom sediments as a resource but about how to overcome federal policy and budgets that constrain wider productive use. Such use, however, may be more costly than least-cost, environmentally acceptable placement options (Landin, 1993a, in press-b). Under current national policy, who should pay for increased costs if use of dredged materials in marine habitat management is not the least-cost alternative becomes an issue. APPLYING TECHNOLOGY This section reviews the general ecological settings within which the various technologies are often applied; it is intended to be illustrative but not exhaustive. The discussion begins with an examination of the relationship between the ecology of barrier islands and estuaries and traditional coastal engineering practices and includes problem areas affecting the application of coastal engineering technology. A similar treatment of marine wetlands follows, including seagrass meadows and tidal marshes. The role of coastal engineering is not as well defined for these habitats. The section concludes with a summary of artificial reef technology. Shoreline Engineering An almost continuous chain of barrier islands, and in some areas beaches extending from headlands, stretch along the Atlantic and Gulf Coasts. When undisturbed, these areas develop complex, dynamic ecosystems. Barrier islands are especially dynamic, shifting and migrating in response to tidal, wind, wave,

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology and storm energies. These coastal barriers are a first line of defense for back bay areas and uplands against winter storms and hurricanes. The beaches serve to dissipate storm wave energy. The sand dunes protect against storm surges, and when breached, result in overwash that naturally raises upland elevations behind the dune line. The stability and health of barrier island ecosystems depends on this flexibility (Amos and Amos, 1985; Mendelssohn, 1982; Perry, 1985; Platt et al., 1992; Rose et al., 1878; Weber et al., 1990; Williams et al., 1990). However, human activity has disturbed the physical processes that caused barrier islands to shift and migrate by replacing sand dunes with homes and commercial properties, and through construction of shoreline protection and beach and inlet stabilization structures. Nevertheless, barrier beaches continuously respond to the influence of waves, currents, and wind. The net effect has often been erosion that threatens both fragile barrier island ecosystems and shore-front properties (NRC, 1987a, 1989a,b). Faced with a challenge from the sea to coastal development, there is strong public interest in stabilizing eroding shorelines. Several strategies are used in shoreline management. Permanent structures (''hard" projects), such as seawalls, groins, jetties, and offshore parallel breakwaters have been used for many years. They create an effective barrier between the sea and land but interrupt the littoral flow of sediment (Charlier et al., 1989; USACE, 1991, 1992). This change perpetuates erosional problems in some instances and creates new ones in others, such as accelerated erosion on downdrift sides of jetties. In extreme cases where the barrier island is forced landward, marshlands behind the island are lost. Permanent shoreline protection structures, although popular in the past, are used less extensively except to protect harbor entrances and port facilities because of actual and perceived adverse effects on erosion (Charlier et al., 1989; Hall and Pilkey, 1988; Pilkey and Wright, 1988; USACE, 1994). Some coastal engineers have concluded that properly engineered seawalls and revetments can protect the land behind them without adversely affecting the fronting beaches (NRC, 1987a, 1990a). There is evidence that beach change near seawalls is like that on beaches without seawalls in both magnitude and variation (Kraus, 1988; NRC, 1990a). Hardened structures technology is well advanced and could potentially be applied in some circumstances to protect marine habitat (Bruun, 1989a,b; Herbich, 1990, 1991, 1992a; USACE, 1984). For example, breakwaters could be constructed to dissipate wave energy that threatens wetlands in large estuaries. However, effects on sediment transport would need to be considered. An increasingly popular shoreline engineering technique is to nourish an eroding beach by adding sand of suitable size and quality. In the United States, normally dredged material is used. The main purposes of beach nourishment are to increase the capability of beaches to act as storm buffers to protect structures in the coastal floodplain and on barrier islands and peninsulas and to provide attractive recreational "habitat" (Anderson, 1980). Periodic replenishment is needed to maintain the desired beach platform and profile. Secondary benefits

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology include possible locations for placement of beach-quality material dredged from some navigation channels (presently institutionally constrained) and enhancement of nesting beaches for sea turtles. Improving the performance of beach nourishment projects is sometimes attempted by anchoring the beach with terminal structures such as groins. Some practitioners prefer beach nourishment as a preferred management solution from an environmental perspective; nonstructural ("soft") measures could replace hard structures (Charlier et al., 1989). Beach nourishment is a nonstructural measure with some potential for use in marine habitat management. However, much remains to be learned about the physical performance of these projects, and whether they can be effectively considered a long-term solution to shoreline erosion (USACE, 1994). Another aggressive approach is to dredge and fill, or dike and pump, thereby altering the configuration and characteristics of estuaries. This approach is practiced most extensively in the Netherlands (Charlier et al., 1989; Verhagen, 1990). Beach nourishment involves excavating large quantities of sand from one site (usually offshore or from ebb tide shoals, but the source could be sand deposits in an estuary, for example, a flood tide shoal). The sand is placed on an existing beach to advance the shoreline seaward. The beach is essentially moved back in time so that an earlier sequence of shoreline change can be repeated (O'Brien, 1985). Beach nourishment projects are typically site-specific. Although some projects have covered 10 or more miles of shoreline, most are much smaller. Landscape (regional) perspectives have generally not been employed in planning and design to address effects on downdrift beaches or on sand budgets for long-term maintenance including periodic renourishment. However, it is recognized that the greater the length of the beach segment that is nourished, the longer will be the duration of retention of the placed sand (Dean and Yoo, 1993). Another approach to beach nourishment is sand bypassing. Sand is artificially transported from one side of a shoreline protection or inlet stabilization structure or from a sand deposit in an inlet to the other side of the structure or inlet in order to restore the sand budget for the downdrift beach. Typically, special pumping systems are installed to dredge the sand and transport it by pipelines to downdrift beaches. The few applications of this technique in the United States have been principally for beach nourishment purposes. The beach nourishment projects have used hydraulic pumping systems for sand transport and are used intermittently as needed. Special pumping systems have recently been developed for continuous bypassing. However, these are currently being tested at only a few locations. Data on their efficiency and effectiveness are minimal (Mehta, 1993). The sand bypassing technique appears to have only very limited potential for application in marine habitat management projects. The efficacy of beach nourishment projects and their relation to structural protection is controversial; some projects have been considered successful, others not (NRC, 1987a, 1990a; Pilkey, 1989). Success is determined by the

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology volumetric loss, loss rates, planned versus actual renourishment intervals, and project objectives, including whether a project was designed as direct nourishment or to serve as a feeder beach for natural nourishment of other beaches. Some coastal engineers trace failures to inappropriate siting (such as attempting projects where there are high background erosion rates) or inappropriate application of the technology (such as less than optimal design) (NRC, 1990a). Critics attribute failures to gaps in knowledge of shoreline processes and consistent underestimation of the volume of sand required to maintain beaches near their design dimensions (Pilkey, 1989). The technical controversy is fed by the fact that shoreline processes are complex, and their effects are highly site specific, making case histories difficult to apply to broader applications; data interpretation methods are not consistent, so that what appears to one person as erosion may appear as accretion to another; and arguments are sometimes advanced to support a point of view. Decision making about beach nourishment is undergoing major change. Recent changes include a 50 percent cost-share requirement by local sponsors for shoreline improvements. As a result, states and municipalities now have a substantial and direct interest in the cost and performance of shoreline projects. Further, the Water Resources Development Act (WRDA) of 1990 [Public Law (P.L.) 101-640] linked federal participation in the planning, implementation, or maintenance of any beach stabilization or nourishment project with a state's establishment of or commitment to a beach front management program. The act accentuates the controversy over beach nourishment. The cost-share requirement may hinder use of beach nourishment technology to benefit marine habitat management (in the absence of a residential or commercial tax bases that benefits from a project), except where marine life uses the nourished beaches or the objective is to protect parks or preserves. Some nourished beaches along the South Atlantic have enhanced sea turtle nesting habitats. This result was effected by placement of dredged sand in advance of turtle migration to the beach for reproduction. Timing is critical so that sorting and settling of materials occur before the migration. Improving turtle habitat was unanticipated but has now been incorporated in beach nourishment project planning and implementation (Nelson, 1985; Nelson and Dickerson, 1988). Typically, material is placed in late fall or early winter to satisfy nesting requirements. Costs of placement may increase if more sturdy equipment is required or if placement is hampered by environmental conditions in the winter months. Although knowledge of project performance has improved considerably over the past few decades, prediction of the loss rates associated with a beach nourishment project is still probably no better than about 30 percent (NRC, 1990a).

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology However, the associated design methodology and placement technologies continue to evolve in an effort to improve the longevity of fill. Although potentially negative environmental impacts may result from beach nourishment, they may be offset by implementing management techniques, such as relocation of nests, tilling of compacted sand, use of compatible sand, smoothing of scarps, and placement of dredged material prior to the nesting season (Nelson and Dickerson, 1988). These techniques are prime examples of a conscious effort to improve marine habitat management through the use of beach nourishment technology. Estuaries The nation's estuaries are of great value as breeding and nursery grounds for post-larval fishes as well as feeding grounds for many young adult oceanic fishes. The estimated value of estuary-based commercial fisheries in the late 1980s was $5–6 billion. The recreational fishing industry generated more than $8 billion in 1986. Recreational fishing activities are believed to have increased an estimated 40 percent since then (Bell et al., 1989; Brown and Watson, 1988; Kelley, 1991; Water Quality 2000, 1992; Weber et al., 1990). The importance of estuaries and the need to preserve and improve those that remain were recognized in 1987 when Congress established the National Estuary Program (NEP) as part of Clean Water Act amendments. The NEP builds on earlier and continuing programs for the Great Lakes and Chesapeake Bay ecosystems. Twenty-one major estuary projects are in progress under the program (EPA, 1992). Estuarine health depends on complex interactions among physical, chemical, geological, and hydrological factors. These interactions are not fully understood, and they differ among estuaries and within specific locations of an estuary. Process-oriented and empirically based predictive models are available, but not well developed (Bell, 1989; NRC, 1983a). Salinity gradients are important to marine and estuarine life in associated marshlands. Any engineering practice that alters estuarine salinity patterns can severely impact the functioning of the ecosystem. For example, altered by hydraulics and salinity in the Savannah River estuary related to channel maintenance adversely impacted some fish species and invertebrates (Weber et al., 1990). Water diversion (that is, removal from the system) also threatens the health of estuaries. Fresh water removal alters the salinity gradient, making the area that is affected unsuitable for fresh water vegetation, fishes and other organisms that are suited to fresh or low salinity waters. For example, dams and water diversions have eliminated 80–100 percent of fish migration and spawning areas in northern California rivers. In the Sacramento River, Columbia River, and Chesapeake Bay systems, dams have eliminated hundreds of miles of anadromous fish spawning areas in the main streams and eliminated access to tributaries; hatchlings are not able to successfully migrate downstream (NRC, 1992a; Stroud,

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology 1992; Williams and Tuttle, 1992). Effects of water wells and diversions, particularly in times of low rainfall in the watershed, are being felt in the Delaware River system as well. Salinity in the estuary has increased because the salt water wedge penetrates more deeply into groundwater and freshwater marshes. The oxygen content of the estuary water has changed substantially. The severity of effects on marine life depends on the amount of water removed from the system, particularly on a continuing basis. Flushing time is an important factor in maintaining a favorable oxygen concentrations in an estuary. Any activity that slows the flushing rate probably will decrease the oxygen supply when all plants are macrophytes (that is, large plants), and thus produce conditions deleterious to aquatic life. Restoration efforts require comprehensive assessments of flushing times to ensure that oxygen demands are identified and accommodated. Seagrass Meadows Submerged seagrass beds are highly productive habitats that are often found in estuaries and are associated with tidal salt marshes and mangrove swamps (Hamilton et al., 1989; Weber et al., 1990). Eelgrass (a macrophyte) dominates the more northern coasts, and turtle grass dominates the coast of Florida and isolated places on the Gulf Coast. Seagrass beds may develop from coral or rock reefs or from sand and mud substrates. Many species of invertebrates, such as crabs, mollusks, and shrimp, and also larval and juvenile fish, use seagrass beds for habitats and nursery grounds. Turtles also use these areas extensively. Because submerged seagrass beds hold sediments in place, their removal or loss can lead to severe erosion. The restoration of seagrass habitat has grown increasingly important, and considerable experimentation has been attempted (Merkel, 1990a,b, 1991; Phillips, 1990; Thorhaug, 1990). Seagrass restoration includes plantings using plugs, tufts, seeds, grids, or sprigs. Thorhaug (1990) identified the literature available on specific projects. Successes have been achieved with lessons learned reported by Hoffman (1990), Merkel (1990a, 1991), and Nitsos (1990) for seagrass restoration work performed in southern California. Evidence shows that simply installing seagrass sprigs on an unvegetated bottom or bare spot in an existing seagrass meadow does not usually work (Fonseca, 1990; Lewis, 1987). Seagrass meadows require good water quality characterized by low dissolved nutrient and suspended sediment levels, and high light transparency. The increasingly eutrophic conditions in coastal waters have caused major declines in the areal cover of extant seagrasses in the Chesapeake Bay (Orth and Moore, 1983), Tampa Bay (Lewis et al., 1985), and Galveston Bay (Pulich and White, 1991), among other water bodies. The precise mechanisms causing these losses may vary somewhat among estuaries, but without significant improvements in existing water quality, the planting of seagrasses could fail. Many losses are due to an increase in nutrients and sediments from point

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology and nonpoint sources, causing eutrophication and increased turbidity. The subsequent reduction in light penetration has eliminated many seagrass beds. Dredging activities for developing and maintaining ports and navigation channels have mechanically removed many acres of seagrass beds and increased turbidity. When water quality management improves conditions appropriate for natural seagrass recolonization, planting efforts often succeed (Johansson and Lewis, 1992; Merkel, 1990a). Intertidal Marshes Intertidal salt marshes occur along all U.S. coasts, particularly along the Atlantic and Gulf Coasts (Amos and Amos, 1985; McConnaughey and McConnaughey, 1985; Perry, 1985; Weber et al., 1990). Intertidal marshes are among the most productive vegetative areas in the world, supporting abundant fish and wildlife populations. Their great value in protecting the shoreline, providing fish and wildlife habitat, filtering pollutants, and providing nutrients to adjacent estuaries was not generally appreciated until the latter half of this century. Despite their critical importance in providing marine habitat, salt marshes and other coastal wetlands were drained and filled to provide more coastal land for development, an important economic consideration in earlier times when natural areas were far more plentiful and seemingly inexhaustible. Water diversion projects and other activities upstream from estuaries have degraded or destroyed intertidal marshes as well (Brown and Watson, 1988; GAO, 1991; Gooselink and Baumann, 1980; Kusler, 1983; OTA, 1984). Ecological Considerations Intertidal marshes usually develop on coasts with low physical (wave and current) energy; accordingly, they are frequently within the protected confines of estuaries or on the landward side of barrier islands or barrier beaches extending from headlands. Mature coastal intertidal marshes have many functions (Box 3-3) and are complex ecosystems that usually developed over long periods. They are the result of a wide range of chemical, biological, and physiological processes, including sediment deposition and erosion, nutrient and other organic cycles, and tidal energies. These forces define the structure of marsh ecosystems. Tidal energies are particularly important. The diversity of species depends a good deal on the individual marsh characteristics and, in the long term, on marsh stability. Intertidal marsh typically has a much higher primary productivity rate than the higher marsh, which is less frequently inundated. These grassy marshlands are also important in the production and export of detritus to coastal areas, where it comprises a main portion of food available to many invertebrates and fish. These marshes are also effective in removing excess nutrients and in the production of oxygen.

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology the offshore underwater berm at Norfolk, Virginia, south of the entrance of Chesapeake Bay, primarily for its physical performance and, as an adjunct, for fisheries production (Clarke et al., 1988; Langan, 1988). To date, data from these three berms indicate that the deep water berm off Mobile Bay is stable and, in effect, is providing artificial reef-like fisheries habitat and a refuge for numerous species of several age classes; the nearshore berm off Mobile Bay, consisting of beach-quality sand, is slowly moving with the current to nourish the beach; and the Norfolk berm is providing habitat to over wintering blue crabs from the Chesapeake Bay, among other fisheries benefits (Clarke and Pullen, 1992). Shallow Water Vegetated Habitats The most difficult habitats to establish using dredged material are shallow water vegetated habitats, such as seagrass meadows. Seagrass species have precise requirements with respect to current action and water quality. With few exceptions, mitigation and restoration of seagrasses have not been successful. In Mission Bay near San Diego, a dredging project provided ideal habitat conditions. Eelgrass plantings there established and multiplied extensively around lagoons (Merkel,1991; Merkel and Hoffman, 1990). This area might have recovered on its own over time. Based on observations of seagrass restoration efforts, a rule of thumb is that seagrasses will become established in areas where they had previously occurred naturally regardless of whether dredged material is used (USACE, 1986). Dredged material can be used in seagrass restoration projects to provide elevations suitable for seagrass recolonization and to construct berms to provide protection. Oyster Beds One recent application of dredged material involves raising bottom elevations and covering the new areas with suitable culch or gravel to provide oyster beds. These habitats were built both accidentally and intentionally in Galveston Bay. The USACE and the NMFS cooperated in building similar habitats in Chesapeake Bay. Early findings of ongoing research indicate that intentionally built oyster bed habitats are achieving project objectives (Earhardt et al., 1988). The overall effect of these projects on function and balance within the ecosystem has not been determined.

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology ALTERNATIVE APPROACHES AND TECHNOLOGIES FOR MINIMIZING OR AVOIDING IMPACTS TO MARINE HABITAT Adverse impacts on coastal habitats may be minimized or avoided through use of non-traditional and innovative methods for dredging and minerals exploitation. Some alternatives are: refinement of channel design and maintenance operations to minimize impacts to marine habitat and, if possible, to improve existing habitat; directional drilling (drilling several oil or gas wells from one location instead of dredging individual canal slips for each drilling location); spray dredging (spraying the dredged material over the wetland in layers under hydraulic pressure so that no spoil bank is formed); hovercraft (use of air-cushion vehicles (ACVs) to lift seismic or drilling equipment over the wetland on a cushion of air, thus eliminating the need for dredging). However, this technique is very expensive in comparison to traditional technology; use of oil and gas pipelines to distribute sediment (Suhayda et al., 1991); and use of coastal engineering capabilities to assist in the management of wastewater and storm water (including the use of natural marsh functions to treat sewage and wastewater and concurrently develop marine habitat). Improving Channel Design and Maintenance The principal objective of channel design is to provide for safe and efficient transits by vessels. The design vessel is, in effect, the largest vessel that the channel is designed to accommodate safely. Channel cross sections are based on engineering guidelines and rules of thumb for design, which are sometimes supplemented by physical scale modeling or computer-based shiphandling simulations. The latter offer more precise channel dimensions required for design vessels. This precision may reduce requirements for dredging and placement of dredged material. Shiphandling simulations are also used to address environmental concerns about channel adequacy for tankers and other large vessels (NRC, 1992b). Potentially, reduced dredging requirements could reduce turbidity and impacts on shallow water and intertidal habitats. Sedimentation of navigation channels is a continuous process that is traditionally addressed through dredging to maintain project depths necessary to support marine commerce. Each port and waterway system is unique, necessitating site-specific examinations to determine the sources and extent of sedimentation, requirements for channel maintenance, and the potential effects of dredging operations on the local environment. Alternatives that potentially could be used to reduce sedimentation include stopping or diverting sediments before they reach

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology navigation channels or keeping material in suspension as it passes through. These alternatives could be employed to reduce sedimentation from many existing facilities, although such action would be costly. Alternately, sediment management could be incorporated into the site selection, design, construction, and maintenance of new waterway projects and facilities. More complete and accurate hydrographic data would be needed than are normally available (NRC, 1987b). Attempts to manage sedimentation need to be carefully formed to avoid unintended side effects (Appendix B). Physical scale modeling has been done for both channel design and environmental purposes. Cross sections could be modeled to determine their effects on an estuary's hydraulics. If the cross sections create an area of greater volume than the tidal prism, then the water flow through the system is reduced, changing the salinity, temperature, oxygen content, and sedimentation rates. A better understanding of these effects and their accommodating design could potentially lead to a reduction of impacts on existing marine habitat. Shiphandling simulation technology has apparently not been used to determine whether equivalent safety performance in maneuvering could be achieved using cross sections designed to (1) mitigate wave or current action on contiguous habitats, (2) serve as habitat for vertebrates and invertebrates, or (3) provide migration routes for various species. It may be possible to provide cross sections that support all three uses. For example, it may be feasible in some areas to provide a substantial deep to shallow water intertidal habitat from the 25-foot depth contour to the shoreline. Although scale modeling and computer-based shiphandling simulations potentially could be employed to help improve channel design relative to marine habitat needs, counter pressures could reduce design effectiveness for this purpose. For example, channel improvements lag years behind changes in ship technology. The result is that channel configurations are routinely stressed well beyond design ship parameters because of economic pressures and competition between ports. Even where improvements are authorized, there is great pressure to minimize costs because of increased cost sharing responsibilities of local sponsors (NRC, 1992b). Thus, sloping a channel wall to the 25-foot depth contour could increase dredging requirements, increasing project cost. Other alternatives to modify channel design to satisfy habitat objectives would be subject to similar pressures. Another issue is who would pay for the added modeling, simulation, or construction costs associated with the marine habitat objectives. Alternatives to Access Canals for Mineral Exploration and Production in Coastal Marshes The construction of access canals for oil and gas exploration and production in coastal marshlands results in significant direct and indirect losses of marine habitat. Canals can also lead to salt water intrusion in estuaries and blockage of

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology natural channels. Alternatives for substantially reducing the need for canals and reducing the impacts of those that are constructed include directional drilling, spray dredging, and the use of air cushion vehicles. Directional Drilling Directional drilling is a subsurface mineral-recovery process that usually creates a nonlinear wellbore track from the surface to a recovery zone beneath, occasionally several miles from the drill site. Directional drilling is often used in coastal Louisiana to avoid disturbing sensitive environmental features (such as barrier islands, endangered species, or wetlands). This technology could also reduce the number of drilling sites needed in a given field. Directional drilling is more complex than drilling straight downward because of the increased and variable pressures on the subsurface equipment, loss of lubricants, and increased chances of well blowout. Drilling angles are usually less than 30° (<2° per 30-meter change in the vertical) for vertical drilling and less than 20° with multiple curvatures (<1.5° per 30-meter drop). Directional drilling is generally 15–70 percent more costly than conventional methods (Louisiana's average cost is 30 percent or more). The technical feasibility and safety of using directional drilling for certain oil and gas wells have been evaluated in Louisiana since mid-1982; the procedure, known as a geological review, involves a state petroleum geologist and petroleum engineer. Its purpose is to minimize the area and number of dredging access canals and well slips in wetlands (Scaife et al., 1983). A geologic review meeting can reduce adverse impacts on vegetated wetlands by shortening access canal or access road lengths by directional drilling to proposed bottom hole locations or to geologically equivalent strata; eliminating proposed access canals/well slips and board roads/ring levees by directional drilling from open water or from existing slips or ring levees within the directional drilling radius of the proposed bottom hole location; and allowing advance planning of field-wide exploration from one central drilling location instead of random canal or board road dredging to individual locations. Directional drilling engineering practices succeed because an appropriate technology is applied in a mixed institutional setting of environmental managers, geologists, and permit applicants; the additional costs of directional drilling assumed by the permit applicant are generally known and acceptable to the applicant; and knowledge of the coastal ecosystem affected (primarily wetlands and barrier islands) is sufficiently understood to be persuasively applied as a management and regulatory tool.

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology Spray Dredging High- and low-pressure spread dredging are the two types of hydraulic dredging being used infrequently in the Louisiana coastal zone to construct oil and gas access canals and well slips. Cahoon and Cowen (1988) provide a comprehensive assessment of these technologies. The advantages of spray dredging over conventional bucket dredging include: It creates no spoil banks, resulting in less wetland habitat destruction. In addition, the method maintains the low elevations prevalent in coastal wetlands throughout the life of an active oil and gas well. Spray dredging may result in less damaging impacts on localized hydrologic conditions. Sheet flow across vegetated wetlands and tidal interchange through surrounding waterways may be less affected by spray dredging. Further, spray dredge barges are usually smaller and require less draft than bucket dredge barges. More remote and shallower areas may be accessed with less disturbance of water bottoms. Spray dredging may result in slower or less compaction of underlying sediments, thereby slowing subsidence rates. The disadvantages of spray dredging include: It is less efficient than conventional dredges, thereby increasing placement costs for dredged material. Costs can be 2–14 times higher than bucket dredging. Pollution risks increase when an oil spill or well failure occurs (the lack of spoil banks may allow contaminants access into surrounding wetlands). It is considerably less effective in aquatic substrates and wetland swamp habitats and where underwater obstructions (such as logs and stumps) are common. Equipment breakdowns are frequent, especially where organic materials occur in the sediments. Options for improving the technology and use of spray dredging include: Spray dredging costs reported during geologic review meetings could be evaluated to determine whether the habitat value and acreage of wetlands to be impacted by a proposed project justify the added costs to the applicants. Additional funding could be provided for scientific research to examine

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology the elements of projects that use spray dredging for the purpose of developing data and analysis to better understand the potential of this technique. Equipment could be more efficient and cost effective. Air-Cushion Vehicles The use of ACVs to avoid long-term impacts on coastal tundra wetlands of the North Slope arctic oil fields has been discussed in both general and technical publications (Sikora [1989] is a substantial review). Both drilling barges and smaller support craft that utilize ACV technology are in regular use in that region. The advantages of the ACV technology are: It would eliminate the majority of the dredging for exploratory wells. The need for maintenance dredging is likely nil. The obstacles to their use are: No demonstration or field tests in other coastal habitats have been conducted for more expensive alternative equipment. No minimal regulatory or economic impetus exists for oil exploration companies to consider their general use. Substantially increased transport and placement costs for the excavated material (the cost per cubic yard is two to five times that of traditional placement technology). Industry practices will likely continue to rely on a proven infrastructure in the absence of a workable and cost-effective or required alternative. One option, therefore, is for states or the federal government to provide an economic incentive grant to a recognized ACV company or petroleum exploration company that would underwrite the costs of drilling and producing an oil or gas well with ACV equipment where marine habitats could be affected. Some expenses (landowner royalties and lease payments) could be minimized by conducting the project on state-owned lands. If a well were productive, then grant expenses could be recouped from production profits. Such a project could provide a unique opportunity for determining the technical feasibility of using ACVs as placement equipment, conducting an in-depth economic analysis of production costs associated with the ACV use, and determining the degree to which impacts on habitat are avoided or mitigated. Management of Wastewater and Storm Water The management of wastewater and storm water, especially in coastal urban areas, is a large and complex problem. Essentially, estuaries and coastal ocean areas are, in effect wastewater and storm water disposal areas. Although considerable

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology efforts have been undertaken to control and treat wastewater including the use of freshwater wetlands for natural treatment of wastewater in some locations (EPA, 1985; Gearheart and Finney, 1982; Gearheart et al., 1982; Reddy and Smith, 1987), these remain major sources of nutrients and sedimentation which affect water quality, and ultimately, the fate or quality of marine habitats. The need for integrated coastal management to systematically and effectively address wastewater and storm water issues was examined by the NRC(1993). Coastal engineering capabilities are resources that could potentially be applied to controlling wastewater and storm water, and thus to improve water quality. Because this report addresses engineering capabilities to restore and protect marine habitat, the use of marine wetlands and engineering capabilities for other purposes, such as treatment of wastewater and storm water, were not assessed. Although there might be potential applications in select locations, perhaps using marine wetlands as a final stage of treatment, there are significant concerns that any pathogens and pollutants that were introduced into an ecosystem could threaten the health of wildlife, fish, and nearby human populations. There are also significant concerns that water quality could be degraded. Therefore, in order for such applications to be environmentally acceptable, they would have to be seriously examined with respect to policy, legal, human and environmental health, scientific, and technical considerations. IMPLEMENTATION FACTORS AFFECTING USE OF TECHNOLOGY The foregoing discussion centered on the present use of technology in marine habitat management as seen by practicing experts (Yozzo, 1991; Appendix D). Several important factors have restricted the use of protection and restoration technology. They include: limited predictive capabilities for shoreline change; poor performance of some projects, including lack of project monitoring, that undermines the credibility of protection and restoration technology, particularly for mitigation projects; lack of evaluation procedures and criteria to determine success of restoration projects, particularly in regard to inherent values of environmental (including ecological) benefits; lack of national policy and commitment to protect and restore marine habitats; uncertain professional qualifications of individuals or organizations engaged in protection and restoration work resulting in a range of technical expertise that affects project performance; a relatively young and rigid regulatory framework in which adaptive management is basically nonexistent;

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology lack of technical qualifications needed for decision making about and oversight of restoration technology applications among regulatory personnel (discussed in Chapter 5); limited information transfer and training for practitioners (discussed in Chapter 5; and cost. Shoreline Change Predictive Capabilities The capability for predicting shoreline change relative to temporal (time) and spatial process scales is limited, and confidence levels tend to be low. Research that enabled even those accuracies that are attainable is are only about a decade old. Limited prediction capabilities are directly related to limitations in the knowledge of coastal processes, discussed in Chapter 2. Time Scale Predictions Storm-related dune erosion can occur in a single day. Localized beach erosion may take a month to a year. Effects of sea level change can take on the order of 10–100 years or longer. The predictive capability (and confidence in the result) decreases as the time scale increases. In coastal engineering, 30–50 years is generally used as the project life span. Predictions of project performance beyond this time scale have little utility within the present state of knowledge of coastal processes. The traditional coastal engineering time scale is unrealistic for marine habitat projects because of their dynamic nature. The understanding of their natural functioning relative to coastal processes is even less well developed. Although near-term predictions are possible for some marine habitat protection and restoration, their appearance and performance much beyond the near term cannot be estimated with reasonable confidence. Spatial Scale Predictions Predicting spatial scales is problematic. Coastal engineers deal with orders of magnitude ranging from 10 meters to 10 kilometers. Generally, predictions with moderate confidence levels relative to coastal processes can be made on the 1-kilometer scale relative to specific structures, such as a groin. Broad predictions on any scale have relatively low confidence levels and are particularly difficult on the 10-meter scale. For example, it is difficult to determine if, when, or where a barrier island will move over the long term. With the exception of beach habitat that coexists with traditional coastal engineering work, the coastal engineering profession has not focused much attention on spatial relationships between coastal processes and marine habitat or ecosystem dependencies. Spatial scale relationships are being vigorously developed within an emerging

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology discipline referred to as landscape ecology (Turner, 1989). Ecologists have achieved moderate confidence levels in predicting habitat change in the near term on a small scale. Spatial relationship predictions for areas over the 1-meter scale are less reliable. Mathematical models and simulations are just beginning to be developed. Performance of Habitat Protection and Restoration Projects In the absence of reliable predictive capabilities for all time and spatial scales, project performance, from an applied technology perspective, is the single most important factor in determining the appropriateness and effectiveness of protection and restoration technology. Failure of a project to achieve its objectives does not establish the track record or credibility needed to advance the state of practice, although lessons can be learned through careful documentation and analysis. Inadequate performance of mitigation projects, in particular, has resulted in challenges to mitigation as an environmentally acceptable approach to destruction of habitat in return for a promise of full restoration of a degraded habitat elsewhere (NRC, 1992a). Views on mitigation range from stopping all wetland impact permitting and the associated required mitigation to requiring full execution of all permitted marine wetland restoration (for mitigation) projects prior to authorizing the activity for which mitigation was the tradeoff. Because success in marine habitat protection and restoration is critical to advancing the state of practice, an approach to attaining project goals and objectives is described in Chapter 6. Professional Qualifications of Practitioners The qualifications of individuals and organizations performing habitat protection and restoration work directly influence the effective application of scientific knowledge and engineering capabilities and, ultimately, project performance. Application by less than fully qualified individuals compounds problems associated with limitations in knowledge and capabilities. Identification of individuals and organizations qualified to perform marine habitat management work can be difficult. Although all states have license requirements for professional engineers, only about one third of practicing engineers are licensed (Anderson, 1992). Few licensing requirements pertain to environmental work; those that do have been enacted by local jurisdictions often lacking the professional expertise necessary to operate a credible specialty licensing program (Anderson, 1992; Eisenberg, 1992). A recent explosion in the number of voluntary registration and certification programs, including some with no professional credibility, has undermined the perception of certification as a means of identifying qualified practitioners (Eisenberg, 1992). These issues are discussed in Chapter 5.

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology Regulation of Restoration Projects Based on practical experience, regulatory programs have not been particularly successful in ensuring project performance to design objectives. This situation is attributed in part to the cost of conducting monitoring to determine project performance, the cost of enforcement, the relatively young status of regulatory programs directed toward habitat protection and restoration, and turnovers in federal and state regulatory enforcement personnel. These factors make it difficult to maintain a cadre of qualified regulators. General Status of Restoration Regulation The U.S. Fish and Wildlife Service, Forest Service, Soil Conservation Service, and Army Corps of Engineers have been conducting nonregulated habitat restoration for more than 70 years. Regulations governing the type of habitat restoration permissible and its design are less than two decades old. As with most new regulations, permitting issues have dominated the concerns of regulators, regulated industries, and third-party interests (such as environmental groups). Recently several ad hoc and regulatory agency-sponsored wetland mitigation permit compliance reviews in Florida, Oregon, Louisiana, and New England, received wide notice and third-party comments. All these compliance reviews involved a nonrandom selection process based on projects that could be easily identified and located. Because the criteria used were not part of the original project goals and objectives, a percent failure figure or percent success is meaningless. It is generally accepted that problems exist in most permitted marine wetland habitat restoration projects. No other habitat types were reviewed. SUMMARY A broad range of technology has been applied over a wide variety of habitat projects. Although there are some gaps in technical capabilities, they are not limiting factors for most projects. The more constraining factors in technology application relate to an incomplete understanding of the ecological functions of marine habitats relative to habitat enhancement, restoration, and creation. A substantial body of literature is available describing marine habitat management projects, technologies, and monitoring regimes. Valuable lessons can be learned from both successful and unsuccessful projects when comprehensive monitoring is planned and executed. These lessons can be applied in subsequent project planning, design, and implementation. The major gaps in scientific knowledge and engineering practice and predictive capabilities are known. Research can be conducted to establish the informed basis needed to overcome scientific and technological impediments to marine habitat management projects. In the absence

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Restoring and Protecting Marine Habitat: The Role of Engineering and Technology of suitable predictive capabilities, project performance is the principal technical factor in determining the appropriateness of restoration technology. This does not provide a suitable basis for resolving uncertainties. Application of the technology is impeded by inadequate professional qualifications of some practitioners and regulators and by the regulatory process itself.