The case studies presented here illustrate successes and failures in marine habitat management. The examination begins with several cases of substantial damage of human origin within and to marine ecosystems. Incomplete environmental assessments led to destruction of valuable overwintering habitat for shrimp in Tampa Bay. Faulty waterway design for the Savannah River estuary led to alteration of hydraulics (since corrected) that was detrimental to navigation and estuarine ecology with adverse impacts to vegetation and certain fish species that required landscape scale restoration. These two case studies point up the need for multidisciplinary, holistic planning and implementation of engineering projects in the coastal zone insofar as they might impact marine (and other) habitats. The examination then shifts to initiatives with primarily positive results: enhancement, restoration, and creation projects for the Chesapeake Bay region, Tampa Bay, San Francisco Bay region, and Kiawah and Seabrook islands in South Carolina. The need for a multidisciplinary approach again stands out. Additionally, these case studies demonstrate the fact that protection and restoration work, when properly designed and implemented, can lead to physical and biological performance that meets project objectives. Indicated in some of these studies is the need for public involvement in order to build public understanding and support for marine habitat protection and restoration. It can also build support for economically essential but environmentally sensitive industrial and commercial development within the marine environment. Use of dredged material was fundamental in several cases as well. Its use for creation and restoration of marsh, creation of sea bird and wading bird nesting islands, and creation of underwater berms is examined in three additional case studies. The
discussion of nesting islands identifies the competing habitat interests of agencies responsible for habitat management because of differing client species. Then follows a case study on bioengineering applications for habitat restoration. Artificial reef technology is presented in a separate case study. Many artificial reefs have been constructed in U.S. waters and on the continental shelf. Although artificial reef design is quite advanced, most applications in the United States are low-technology projects that are not designed to support specific fish species. The appendix concludes with consideration of the application of Geographic Information Systems GIS to marine habitat management, for example, in wetlands delineation.
HABITAT ASSESSMENTS USING SPECIES LIFE HISTORIES
The complex life history of many marine species often depends on multiple habitats whose use may vary by life cycle phases and seasons. The loss or degradation of critical habitat, because it may not be recognized as important to the life cycle, can devastate a species or a local population. The life history requirements of the commercially harvested white, brown, and pink shrimp (penaeids) illustrate several valuable points for managing coastal resources:
Habitat requirements vary throughout the life cycle, even among similar species.
Production varies by habitat.
Local knowledge is an important management tool.
The range of salinities, temperatures, substrates, and vegetation that shrimp pass through in one year is prodigious. Penaeid shrimp cycles generally begin in the open sea (35 parts per thousand [ppt]) as eggs that mature through naupliar, protozoeal, and zoeal stages. Following the pelagic larval drift, the postlarvae enter estuarine areas on flood tides and seek substrates until the next tide change, when they successively penetrate deeper into the estuary (down to 0 ppt). Eventually they live a benthic existence while they grow in the estuary, an environment that offers food and refuge from predators. After several weeks or months, they move back into the ocean, generally in shallow zones (<50 meters). Fishermen harvest them from the estuaries as postlarvae (for stocking ponds) and as subadults and adults in coastal waters. Most commercially important penaeid shrimp are considered estuarine dependent. Students of shrimp life cycles generally agree that recruitment of larvae into estuaries from the spawning sites offshore is high, so high that postlarval growth and survival in the estuary are probably the most important factors affecting the harvestable adult population size. Mortality with age. Recruitment success depends on climate, predation levels,
food supply, and habitat quality. Of these, what constitute high quality habitat are not precisely known.
Although estuarine salinity and temperature changes affect the annual potential for postlarval survival, the long-term yields are strongly related to both the quantity and quality of intertidal habitat. There are several known examples of this relationship throughout the world. A species may use both emergent wetlands and submerged grassbeds in the same estuary. The commercial harvest of penaeid shrimp per area of estuarine vegetation peaks at the equator and falls to nearly zero north of North Carolina (presumably because of temperature limitation).
The anatomical differences between brown and white shrimp are almost indistinguishable; even the color differences are not strong soon after harvest. But their habitat requirements are quite different. Compared to white shrimp, brown shrimp are generally more numerous in brackish waters and they prefer higher salinities (10–20 ppt). Most brown shrimp spawn in offshore marine water in the spring and early summer, but some also spawn in the fall; white shrimp spawn from the spring to fall. Brown shrimp move into estuaries from offshore sooner than white shrimp (spring and summer) (Turner and Brody, 1983). White shrimp may overwinter in the estuary, whereas brown shrimp do not. Several investigators have observed that the two species use different parts of the marsh during flood cycles, that fish predation varies by species, and that substrate preferences vary. Both species use the edge of the wetland extensively as food-rich refuge from predators. The elimination of this habitat (through construction of a bulkhead, for example) drastically reduces population densities. Even with apparently similar habitat quality, seasonal use may vary because of differences in migration and emigration patterns. This is not to say that the interior marshes are unimportant to the survival of transient estuarine-dependent organisms. The importance of emergent marshes as a source of detritus for shrimp is well documented. The small resident fishes and grass shrimp that utilize the interior marshes are an important food source for larger estuarine-transient carnivores (such as spotted seatrout and red drum), especially in the fall and winter, when cold fronts cause extremely low tides, forcing these forage species into open waters.
The broad patterns of the pink shrimp life history and habitat use are documented fairly well, but important specific information is often missing. Knowledge of pink shrimp seasonal distributions and habitat use within specific estuaries is often not known, but it can be acquired from local experts and additional sampling. The consequences of not doing so are illustrated by the inadvertently validated construction of two 600-acre diked areas for dredged material disposal in Tampa Bay (Figure B-1). The new placement sites destroyed some of the most important deep overwintering mud bottoms for pink shrimp. The overwintering population had not been previously identified through scientific sampling during normal fisheries surveys. However, a small commercial fishery did exploit
that over wintering population for profit. These fishermen did not divulge the pink shrimp habitat use because of financial competition. Fishing vessels were occasionally observed working the proposed permit area, but apparently no one investigated. Thus serious gaps in knowledge of the species' life history were not detected and tidal waters were converted in industrial use under an erroneous assumption. The lesson here is that more complete knowledge of species' life histories can be obtained through site-specific and seasonally varying sampling as well as from local experts' knowledge (Turner and Boesch, 1988).
WATER WAY DEVELOPMENT IMPACTS IN THE SAVANNAH RIVER ESTUARY
Two strongly conflicting demands have been made on the Savannah River estuary: to develop it as an industrial center and to preserve its natural resources. Historically, the estuary supported commercial fisheries and navigation, provided valuable wetland habitat for small mammals, and served as breeding, feeding, and resting grounds for indigenous and migratory birds.
Over the years, the Savannah waterfront was developed as an industrial center, deep seaport, and tourist attraction, and maintaining the port complex in view of its important economic contributions to the region is of continuing interest. When the channel was deepened for large oceangoing ships, most shallow water areas where aquatic organisms fed and many lived and bred were eliminated. The estuary's potential to support a well-balanced aquatic ecosystem with the fisheries was substantially reduced.
The upper estuary is divided by a series of islands creating two waterways: the Front and Back channels. The industrially developed Front Channel borders Savannah. The tidal prism is mostly broad and shallow. Intertidal flats and shallow water habitats are found on either side except in areas of industrial development. The cross section is about 10 feet deep across the middle except in the navigation channel. The river flow comprises the rest of the water entering the estuary. The less saline upper estuary formerly supported striped bass, sturgeon, and shad migration and spawning. It was a nursery for larvae development; the Back Channel was especially important as a striped bass and shad nursery.
Over time, runoff and point and nonpoint source pollution from industrial and shipping developments in and above Savannah led to increased organic loading within the estuary. Flushing time increased and sloughing of the banks occurred, increasing navigation maintenance requirements. The U.S. Army Corps of Engineers (USACE) determined that physical modifications were necessary to improve system hydraulics. A tidal curtain was placed in the Back Channel to increase the flow through the Front Channel and lessen sloughing and sediment deposition. Canals were cut through the islands to increase high tide water flushing in the Back Channel. These measures achieved results opposite to those intended.
The cross sectional area of volume of the estuary was increased by deepening and widening without an equal increase in the volume of water entering the estuary. This situation slowed rather than increased flushing times within the estuary. Sloughing of the banks increased and the scouring effect decreased. Sedimentation increased as well, creating greater oxygen demand, particularly at greater depths. Below the tidal curtain, oxygen demand increased, and above the curtain, salinity increased, killing the larvae and freshwater grasses there.
Project design did not adequately accommodate the effect of physical modifications on the tidal prism and associated hydraulic effects. Changes in salinity
and oxygen demands greatly impaired the estuary's capacity to support valuable commercial fisheries and degraded wildlife habitat. Neither navigation nor environmental objectives were served.
Substantial efforts have been made to restore the natural functioning of the estuary. The tidal curtain was removed to restore a more natural hydraulic regime (Georgia DOT, 1989; Pearlstine et al., 1989). Reciprocal transplanting was used to restore vegetation. Good localized results were expected based on extensive field research. The marsh is recovering on a landscape scale, and a fresh water tidal system has been reestablished (Latham et al., 1991; Pearlstine et al., 1990, 1993a,b). The estuary appears to again have the capability to support stripped bass and the bass have been restocked. The fish are rapidly approaching the age class for spawning. The interested agencies have planned a joint sampling effort to determine and assess the spawning when it occurs, and to further assess the estuaries capability to support the bass (W. Kitchens, personal communication, March 15, 1994).
The lower Savannah River situation represents perhaps both worst and best case scenarios. Physical and biological attributes of the estuary were greatly affected by faulty hydraulic design. The resulting damage to the ecosystem exemplifies the unfortunate results of designers' either not understanding or not adequately accommodating the many factors that interact to preserve the essential ecological attributes of an estuarine system. The result was all the more tragic because the estuary appeared to have the capability of supporting waterway improvements without altering basic estuarine ecology. On the other hand, the restoration program is reported to be working remarkably well with respect to hydraulics, water quality, and vegetation. Stripped bass have been reintroduced to the ecosystem and spawning of missing age classes is anticipated.
CHESAPEAKE BAY PROTECTION AND RESTORATION INITIATIVES
The Chesapeake Bay has been under extreme environmental stress for many years as a result of human activity, particularly pollution from point and nonpoint sources within the estuary and its watershed. Many multijurisdictional and private efforts are underway to improve water quality throughout the region in order to improve the health of the ecosystem, restore important commercial and recreational fisheries, and mitigate the effects of erosion. Over the past 20 years, numerous restoration and enhancement projects have involved the Army Corps of Engineers, the U.S. Fish and Wildlife Service (USFWS), the National Marine Fisheries Service (NMFS), the Environmental Protection Agency (EPA), state agencies of Maryland and Virginia, including port authorities, and private organizations.
Windmill Point, Virginia
The Windmill Point habitat restoration project was the first of its type designed and constructed by the Army Corps of Engineers. Experience with construction techniques and monitoring provided information about physical energies and colonization that were useful in later projects (Boesch et al., 1978; Lunz et al., 1978).
Fifteen acres of fresh intertidal marsh were created with dredged material at Windmill Point in the James River. The site was agreed upon by an interagency state and federal working group. Both dredged sand and silt from maintenance
dredging were used in construction. Local physical energy sources included strong river and flood currents, 3-foot tides, and fetches of several miles for westerly winds. A temporary sand dike serving as a breakwater provided site protection. It was breached to allow intertidal exchange. Vegetation planted on the dike enhanced its stability. Natural colonization occurred quickly on the interior protected area of the confinement, but when breaches in the temporary dike washed out, the project failed. The island broke in two in 1983 and most of the marsh washed out. A protected shallow water habitat suitable for fish spawning and a remnant island habitat for wildlife were created in the process. Lessons from this project include:
Project placement must be suitable for local conditions.
Strong riverine woody shrubs and trees may be needed to stabilize dikes in similar conditions rather than herbaceous material.
Dike breaches for intertidal exchanges need to be protected from physical energy that could cause their failure.
Deliberate dike breaches need to be carefully placed.
Intertidal wetlands have been restored within the estuary using sandy dredged materials. Examples include 4 acres on the Honga River and 6 acres on Slaughter Creek in 1974 and 55 acres at Barren Island in 1982 and 1985. Periodic monitoring indicates that use of sandy materials in this environment is a viable restoration technique. However, an experimental seagrass planting near Slaughter Creek in 1989 failed because of poor water quality and current action despite efforts to provide protection from physical energies until the site was established in early 1993. Additional wetlands restoration projects were in progress or in planning at Eastern Neck National Wildlife Refuge, Kenilworth Marsh, and Bodkin Island (Maynord et al., 1992).
Oyster beds were created using dredged material at Twitch Cove (Smith Island) and Slaughter Creek. The Army Corps of Engineers, in collaboration with the NMFS, used sandy dredged material to raise a deeper area of bay bottom to approximate intertidal conditions that would encourage oyster colonization. The projects achieved design objectives, providing both motivation and justification for similar projects.
At Twitch Cove, 4-foot diameter Longard tubes were used to construct an underwater containment site. The tubes were fabric capsules filled with sediments on-site and placed in predetermined configurations. Dredged material was placed inside the containment area until elevations suitable to oyster production
were reached. The dredged material was then capped with substrate that was also suitable for oyster production. The Slaughter Creek project involved construction of a 2.1-acre dredged material mound at an open water placement site. The mound was located near an area that had once been a productive oyster bar but no longer had substrate favorable for colonization of oyster spat (Earhardt et al., 1998).
Maryland Shore Erosion Control
In response to marine habitat losses resulting from extensive shoreline erosion, mostly in Chesapeake Bay, the Maryland General Assembly established the Shore Erosion Control Program (SECP) in 1968. Housed within the Maryland Department of Natural Resources, the SECP set out to protect and improve the quality of Chesapeake Bay and its tributaries through marine habitat protection, enhancement, restoration, and creation. Having gained renewed force in 1985 as part of the state's Chesapeake Bay initiatives, the SECP is an example of a program that, through coordinated, interdisciplinary efforts has consistently and successfully achieved project objectives.
Some of the program's responsibilities include:
periodic assessments of shoreline erosion in Chesapeake Bay;
provision of technical and other assistance to private and municipal landowners with erosion problems;
evaluation of new technologies and methods to control shore erosion;
design and implementation of shore erosion control projects; and
periodic inspection and monitoring of completed projects in order to recommend preventive and corrective maintenance to property owners.
The program is successful in part because it relies on the participation of citizens, mainly landowners. The state provides matching funds for citizen restoration and protection initiatives. The program also has a revolving loan fund to provide interest-free loans for qualified applicants who wish to undertake restoration/protection projects.
One important feature is the program's emphasis on and encouragement of vegetative nonstructural solutions to shore erosion. To date, more than 10 miles of shoreline in the Chesapeake Bay and its tributaries in Maryland have been protected by the planting of protective vegetation. More than 1.1 million square feet of new wetlands have been created as well.
Recent coordination between Maryland and Virginia and the Norfolk and Baltimore districts of the USACE has given rise to the Chesapeake Bay Shoreline Protection Study. The study will be used to identify critically eroding areas of the bay in an effort to acquire federal funds for important restoration and
protection projects. The success of the SECP derives from innovative and coordinated planning and implementation practices (Zabawa, 1990).
Although not a marine habitat project per se, the Hartmiller Island confined disposal facility project near Baltimore provides useful insights into the difficulties of obtaining approval for projects using dredged material, even if environmental objectives are an element of the project.
The Port of Baltimore is a huge economic engine for the state. It is responsible for as many as 150,000 jobs and has an economic value of $4 billion. To maintain and improve navigation channels to the port, extensive dredging is required. Development of a confined disposal facility was proposed in 1960. Extensive planning and assessments were conducted and an 1,100-acre site was selected in 1971. But the general public was not involved until its approval was needed. The port's proposal was to reconnect Hart and Miller islands (formerly Hartmiller Island) with dikes to form a confined disposal facility. The site was evaluated at low biological productivity, its good sheer strength would support the dike's weight, and dike construction materials were available at the site. The port determined that with proper planning and implementation, the site could be established as a wildlife habitat and recreational area (Hamons, 1988).
Substantial opposition developed over environmental and economic concerns. Additionally, under Maryland law, dredged material above a certain point in the channel is considered contaminated without regard to actual chemical composition. Although the port had conducted extensive internal planning, it did not demonstrate its credibility or build public support through public involvement measures. A resulting lawsuit was finally settled in the port's favor by the Supreme Court of the United States. Construction began in 1981, but by the time the facility was completed in 1985, costs had soared from the 1971 estimate of $11.5 million to $58 million. The nonavailability of the confined disposal facility delayed work on other channel improvement projects, substantially increasing costs to the local port owing to federal policy changes that increased the costshare requirements of local project sponsors (Hamons, 1988).
The project was completed in 1985. Freshwater wetlands are developing rapidly and recreational facilities and upland parkland are available. The freshwater wetlands have attracted large concentrations of waterfowl (Hamons, 1988). Sea birds nest on the dike, and herons, egrets, and other water birds feed inside the facility.
TAMPA BAY WETLAND RESTORATIONS
Tampa Bay is a 400-square mile estuary surrounded by a 2,400-square mile highly urbanized watershed. The cities of Tampa, St. Petersburg, and Bradenton
border the bay. Over time, 44 percent of the tidal marshes and mangroves and 75 percent of the submerged aquatic vegetation (seagrasses) were lost (Lewis and Estevez, 1988).
The state recognized the need to arrest losses and restore wetlands through passage of The Surface Water Improvement and Management (SWIM) Act in 1987. Implementation of SWIM Act measures in Tampa Bay has focused on physical restoration of lost habitats, such as wetlands and seagrass beds, to demonstrate the feasibility of such efforts. Research on restored habitat functional equivalency is in progress. Because SWIM program staff were not sufficiently experienced to design and supervise construction of restoration projects, program managers contracted with a multidisciplinary professional team to perform these functions. Its comprehensive planning, design, and implementation resulted in credible restoration work.
The multidisciplinary team included a restoration biologist, engineers, and surveyors. It was responsible for designing projects, obtaining permits, and implementing each project. As of February 1992, nine projects had been completed (Figure B-1). Each required approximately 1 year from design through construction. All nine, totaling 93.1 acres (37.7 hectares) of enhanced or restored habitat, achieved performance objectives. Another 21 projects are planned for 1992 through 1994 (Lewis, 1992; SWFWMD, 1992).
Results of a similar restoration effort by the Florida Department of Environmental Regulation (FDER) in the Tampa Bay area (using pollution fine funds for habitat restoration) are not similar to those of the SWIM initiative. The FDER decided to use its professional staff instead of an experienced multidisciplinary restoration team. Only two projects have been completed in 3 years. Slow progress in using funds for restoration resulted in diversion of accumulated interest to nonrestoration efforts. In the absence of a well-planned restoration program, pressures are building for diversion of additional funds for nonrestoration projects (Garrity, 1992).
SAN FRANCISCO BAY WETLANDS RESTORATION
Land subsidence in the San Francisco Bay system, including the Sacramento-San Joaquin River delta, is a result of extensive diking and pumping to create farmlands over the years. The area's peaty substrate, formed from thousands of years of coastal and riverine wetlands evolution, has largely been farmed. In peat soils, tillage, draining, and fertilization hastened the process of subsidence and degradation. Some bay area lands in the deltas are now as much as 15 feet below the surrounding water levels. As marginal lands (such as subsided farmlands) and other open lands become available, state and federal organizations have joined (within the limit of available resources) to acquire and restore such lands to use as natural habitat. The industrial, commercial, and residential development that has occurred generally precludes full restoration to predisturbed conditions.
Thus much of the work consists of partial restoration that focuses on a few indigenous plant species and a few target species that the site may be able to support.
Several wetland restoration projects have used sediments dredged from the bay to restore intertidal elevations (Figure B-3). Four completed projects include Salt Pond Number 3 in south San Francisco Bay (1972), Muzzi Marsh near Tiberon (1978), and Donlan Island and Venice Cut in the San Joaquin River (1983). All have been monitored by the Army Corps of Engineers, the California Coastal Conservancy, and researches from the University of California at Davis (England and Nakaji, 1990; Landin et al., 1990b). The Salt Pond Number 3 site was compared to three nearby natural salt marshes. All four wetlands achieved goals and objectives established when they were built and are considered successful by project sponsors and monitoring organizations (England and Nakaji, 1990; Landin et al., 1989c, 1990b). All four also continue to be monitored under long-term plans. These projects in turn are being used to guide additional wetland restoration projects that are in planning or already underway in the San
Pablo Bay area (north portion of San Francisco Bay) at Hamilton Antenna Field, Sonoma Baylands, and Cullinan Ranch (Landin, 1991).
The conceptual design of the completed and planned projects and those in progress involve leaving the dike or its remnant intact until dredged sediments are placed. In the completed projects, the dike remnants provided the confinement necessary to hold placement materials until intertidal elevations were established under site-specific tidal conditions. One suitable elevations were attained, the dike was breached to allow intertidal flow. At Salt Pond Number 3 and Muzzi Marsh, tidal channels were also cut into the heart of the marshes to provide better intertidal flow throughout the site. Both sites were planted with two indigenous dominant plant species to provide habitat attractive to the endangered species (in California) clapper rail and the salt marsh harvest mouse.
The two intertidal river sites (Donlan Island and Venice Cut) were allowed to colonize with typical wetland vegetation following placement of dredged material. Because the dikes at these sites had been compromised prior to construction, dredged material was placed at the point farthest away from the dike opening. This measure was necessary to allow as much time as possible for the sediment to drop out suspension before the effluent could move back into an already highly turbid river.
Sonoma Baylands, which is being restored by the state, includes an intertidal marsh using sediment from the Petaluma River, a marsh managements unit for waterfowl, and open natural land. Hamilton Antenna Field is planned to become a 300-acre intertidal salt marsh. Construction is projected for completion in 1994 using dredged material to restore intertidal elevations. Cullinan Ranch is a 2,200-acre site owned by the U.S. Fish and Wildlife Service which plans to fill cells with dredged material to restore wetlands. All seven projects discussed were expensive compared to similar-scale projects in other areas of the United States. Yet these costs do not appear to be extreme in relation to typical California land values and construction costs.
ENVIRONMENTALLY SENSITIVE DEVELOPMENT OF KIAWAH ISLAND, SOUTH CAROLINA
In the early 1950s, a family purchased Kiawah Island to harvest pine timber. The family subsequently used the island as a modest personal retreat, selling one lot each year to pay property taxes. When the property was reassessed in 1974, its classification was changed from agricultural to residential, and the resulting tax increases made it economically infeasible to maintain the largely undeveloped island as a private retreat. It was sold to the Kiawah Development Corporation, a Kiawah government investment unit for residential development. The corporation established a development strategy that emphasized long-term planning.
Initial project design activities included a comprehensive multidisciplinary
environmental assessment. The assessment was performed through separate development and construction contracts by a carefully composed team that was given wide latitude and status. The study encompassed climatology, archeology, history, shallow water physical oceanography, estuarine and freshwater sediments, benthic fauna within the sediments, fisheries, phytoplankton and zooplankton, birds, mammals, herpetology, forest and dune vegetation, coastal processes, oyster populations, and marine turtle nesting. The final report discussed each component in detail and synthesized the results as a holistic view of the island in its ecological surroundings.
The development corporation used the environmental assessment as a primary basis for project planning. The assessment began before and then ran concurrently with project planning. During this period, the environmental assessment research team met with corporation development and planning staff to answer specific environmental concerns. Thus the planners could work with their engineering staff to develop environmentally acceptable policies and procedures. Coastal processes information, for example, resulted in removal of a highly dynamic terminal sediment deposition site for the island (recurved spit) from residential development plans. Information on wetland processes was used by the civil engineers to design drainage systems that would use natural runoff to collect rainwater and hold it in ponds. These measures were also intended to maintain the freshwater lens and inhibit salt water intrusion. Plans were also made to maintain a native wetland vegetation border on wetlands for filtration and as wildlife habitat. Architects used biologists knowledge of sea turtles in designing lighting systems that would protect hatchlings. Climatology was used to develop structure height limits to protect forest vegetation. Knowledge of the sensitivity of dune vegetation assisted in developing self-imposed setback lines for ocean-front structures. Power transmission lines would be placed underground, and roads would avoid specimen trees and sensitive wetland areas. In the development and subsequent implementation of these plans, numerous meetings were held so that the scientific team understood the engineering issues and needs and the constraints of the permitting agencies, planners, and marketing staff. In turn, the planners and engineers gained practical insight on environmental considerations and could refine designs to accommodate them.
Integration of the scientific components with the engineering considerations at the outset enabled the scientists to collect the data and develop the environmental information that was most useful for project development. Kiawah Island is now recognized as one of the most environmentally sensitive coastal developments. It is also one of the most financially successful. It has weathered extreme episodic storms; for example, during recent hurricanes, no services were lost and no flooding occurred on the island. Eighteen years after project initiation, the management team reported that it is still using the original reports and planning documents, testifying to the quality and soundness of multidisciplinary planning.
INLET ENGINEERING SEABROOK ISLAND AT SOUTH CAROLINA
Tidal inlets play an important role in the evolution of nearby shorelines and backbay areas, particularly in areas with tide ranges of 2–4 meters with relatively low wave energy, where large ebb-tidal deltas occur. Sediment management in these settings is complex and often depends on knowledge of inlet movement, the timing and rate of sand bypassing, and quantitative sediment budgets. But such information is lacking in many areas or cannot be generalized from one place to another. Interactions between humans and nature at Seabrook Island illustrate both the role of an unstable tidal inlet in the management of adjacent shorelines and incorporation of inlet dynamics into a nonstructural solution to beach erosion. To the degree that beaches are stabilized naturally, associated marine habitat may benefit as well.
Many up-to-date geological, hydrographic, and coastal engineering studies were available, providing details of the area. Seabrook is an accreting beachridge island that derives its sediment from Kiawah Island and Stono Inlet to the north. Captain Sams Inlet, at the northern end of Seabrook, undergoes a natural cycle of inlet migration and spit breaching at 40- to 80-year intervals. The result is active erosion of the Seabrook beach. This situation did not impact human interests until the island was developed during the 1960s. Early shore protection measures included sandbag revetments and groins, riprap, and eventually larger rock, but storms continued to destroy the structures and properties. By 1982, an 8,000-foot section of shoreline was armored with a revetment composed of riprap or larger rock. Continued erosion and lowering of the beach in front of the revetments made the structures vulnerable to wave damage, and sustained maintenance was needed to preserve structural integrity.
Coastal geology and engineering studies indicated that inlet relocation was an affordable alternative to existing practices (Kana, 1989). The project was approved and funded by the Seabrook Island Property Owners Association and the Seabrook Island Company. The plan required soft engineering solutions that did not depend on physical structures at the project shoreline. After much review and many appeals before the South Carolina Coastal Council and Army Corps of Engineers, the necessary permitting bodies, the project was approved with specific design features, objectives and a monitoring process. Completed in March 1983, the project cost approximately $350,000. About $175,000 cubic yards of sand were moved. Unit costs were approximately $0.50 per cubic yard, compared with direct nourishment by dredging sand from offshore at a cost of $1.75–5.25 per cubic yard.
The project has resulted in active accretion of the beaches on Seabrook Island. The relocation of Captain Sams Inlet demonstrated that cost-effective management of a migrating tidal inlet is possible under the physical conditions at the site. The project was both environmentally sensitive and cost effective, indicating
the benefits of combining fundamental research on coastal processes with coastal engineering practices. Monitoring demonstrated the fact that only short-term adverse environmental impacts resulted from the disturbances caused by project construction. New dune habitat was established within 1 year. Sediment transport rates suggest that the inlet will return to its 1982 position by the turn of the century. The capability to engineer environmentally acceptable modifications to inlets is potentially adaptable to other barrier island locations.
MARSH RESTORATION AND CREATION USING DREDGED MATERIALS
In some restoration projects there are multiple users to be satisfied, and therefore a multiple-use project results.
Pointe Mouillee, Michigan
The 4,600-acre Pointe Mouillee wetland restoration project in western Lake Erie has many goals:
containment of dredged materials from Lake Erie;
restoration of an eroded barrier island;
enhancement and management of the point as habitat and recreational area;
improvement of water quality;
removal and isolation of contaminated sediments from Lake Erie;
establishment of a nature education program and visitor center;
establishment of biking, hiking, and jogging trails;
establishment of fishing grounds and hunting areas;
provision of a boat harbor and marina;
support for natural resource activities;
provision of fish spawning areas, nurseries, and habitats;and
provision of habitat for wildlife, resident and migratory birds, and small mammals.
The Pointe Mouillee confined disposal facility was built by the USACE to protect and stabilize the area's rapidly eroding shoreline and wetlands. Wetland restoration was encouraged through a slowing of the water flow. Dredged material was used to create waterfowl nesting islands, feeding areas for water birds, and nesting areas for sea birds. Natural resource recreation (that is, fishing, hunting, bird watching, boating, and nature trails) was incorporated in the design. The USACE and the Michigan Department of Natural Resources (DNR) developed a cooperative 30-year management strategy. The DNR is responsible for management of the site's natural resources. The Waterways Experiment Station of the USACE monitors (since 1979) the site for the Corps' Detroit District.
Sediments dredged from Lake Erie contain contaminants and thus must be carefully place. The dredged materials that were placed at Pointe Mouillee consisted primarily sand and therefore leach rapidly. Earlier deposits at the site with high ambient levels of contaminants were covered under substantial layers of cleaner material that was placed in subsequent years. Rigorous monitoring conducted at the site indicates that contaminants remaining in the sediments have not resulted in environmental problems.
The success in meeting project objectives has stimulated requests to the Detroit district for additional use of disposal sites to provide wetland and shoreline protection in other areas of Lake Erie. Similar projects have been constructed at Monroe Harbor and Sterling State Park, once primarily recreational beach and park areas (Landin 1984, 1993b; Landin et al., 1989b,c).
Miller Sands Island, Oregon
Three habitats were developed at Miller Sands Island: an intertidal freshwater marsh, a grass/legume meadow for waterfowl nesting and Columbia white-tailed deer habitat, and dunegrass plantings to stabilize sandy dredged material and protect intertidal marsh.
The wetland and dune plantings have spread from an initial 300 square meter area to encompass over 5 square kilometers, and is providing water bird nesting and feeding habitat. The wetland has changed and increased in size considerably owing to annual additions of dredged material, but it largely maintains itself. Monitoring was done by the Waterways Experiment Station and the engineering work by the USACE Portland district. When compared to three reference areas nearby, wildlife use was dramatically greater on Miller Sands Island, and aquatic invertebrate and fish use of the wetland was equal to the reference areas. Several endangered species now use Miller Sands for migratory or year-round habitat (Landin, 1993c; Landin et al., 1988). The island has been designated as critical habitat for endangered salmonoid species.
Southwest Pass, Lower Mississippi River, Louisiana
Marsh development in southern Louisiana is a dynamic process that can be viewed as a battle to stave off some of the shoreline erosion, subsidence, and sediment starvation from levee systems and navigation channels that are resulting in the annual conversion of about 30 square miles per year of Louisiana wetlands, depending on the estimates used, into shallow water habitats (see Figures 3-1 and 3-2) (Turner and Cahoon, 1988). The USACE New Orleans district is developing up to 35,000 more acres of intertidal marsh by deepening and widening the lower Mississippi River, including Southwest Pass, the main outlet to the Gulf of Mexico. Southwest Pass and the Atchafalaya Delta in Louisiana are the two largest new wetlands constructed of dredged material in the United
States. The Atchafalaya Delta is also being reformed from sediments channeled through the Old River Control Structure on the Mississippi River.
Unconfined dredged material disposal was used to nourish, restore, or create (as determined by site conditions) intertidal marsh on the western side of the Southwest Pass. The dredge pipe was generally placed over the river berm in shallow water areas and slurry pumped through until intertidal elevations were reached. The dredge outfall was progressively moved to other shallow water areas to achieve the same result. Natural colonization occurred in 2–5 years.
Wildlife use of project sites is diverse, and wetland response to the placements is mixed. Some created marsh was destroyed when pipes were not moved soon enough. Subsidence in the area is so rapid that some of the marsh created during the 1970s has already subsided back into shallow water (Landin et al., 1989c)
CREATION OF SEA AND WADING BIRD NESTING ISLANDS IN NORTH CAROLINA
Since the 1890s, the Army Corps of Engineers has used dredged material to construct more than 2,000 islands in U.S. waterways; prior to 1970 virtually all were originally intended as disposal sites. Most were built when the Intracoastal Waterway System was established in the late 1940s and most of the islands are coastal.
At the same time that these islands were being built, coastal populations were increasing vastly. Natural habitats used by water birds were converted for urban and suburban development. The dredged material islands were isolated, unused, and similar to natural beaches and sand bars that are attractive as habitat for colonial water birds. As a result, sea and wading bird colonies relocated to these artificial islands in large numbers. More than 1 million water birds nest on the dredged material islands annually.
These islands have been carefully studied by the Waterways Experiment Station in conjunction with university and private contractors since 1975. Their objective is to determine the design and construction criteria that provide the best conditions for nesting colonies. Results of these studies have been published in government reports, scientific engineering journals, and dredging textbooks and are now used worldwide (Buckley and McCaffrey, 1978; Chaney et al., 1978; Landin, 1978, 1992b; Parnell et al., 1978; Peters et al., 1978; Scharf et al., 1978; Schreiber and Schreiber, 1978; Soots and Landin, 1978; USACE, 1986). The primary factors for sea and wading bird colonization are isolation, location within the waterway, size (more than 10 acres is best), configuration, elevation, presence or absence of dikes, slope of dikes, and substrate (Parnell et al., 1988).
The cost of constructing dredged material islands has risen from $0.50 to more than $4.00 per cubic yard. But costs are not the dominant factor in determining whether to repair and restore an existing island or to build a new one.
The principal factor is the competing habitat objectives of federal agencies with habitat management responsibilities for different client species. The issue is not technical—but is one of discord over use of water resources and lands.
Intense opposition to fishery habitat interests is often associated with proposals to repair or build new dredged material islands. Further, because the placement of any structure, including islands, in shallow waters affects or replaces other habitats, it stimulates controversy. Thus restoration of dredged material islands has been erratic and is often delayed until water bird nesting has declined markedly, usually owing to loss of or natural changes to nesting habitat. Especially in Louisiana and North Carolina, state and federal agencies responsible for habitat management have improved their flexibility and willingness to consider the needs of diverse coastal species. But the optimal approach to nesting islands is unresolved.
UNDERWATER FEEDER AND STABLE BERMS DAUPHIN ISLAND, MOBILE
Many feeder and stable berms have been constructed in the coastal zones in the United States, South Africa, the Netherlands, and Australia (Langan, 1988). That dredged material could be used effective for the construction of underwater berms to reduce beach erosion by dissipating wave energy and improve habitat for marine life was a major conclusion of Section II, Subject 3, Engineering on Sandy Coasts of the XXVI International Navigation Congress, held in Brussels, Belgium, June 17–21, 1985.
The two viable approaches to the design and construction of underwater structures apply: the feeder and stable berm concepts. Feeder berms (for beach nourishment) involve the placement of beach-quality sand in relatively shallow water, 16–18 feet deep, by small hopper dredges. The objective is to add suitable sand to the nearshore system in a manner similar to the natural bypassing of material that occurs at tidal inlets (Richardson, 1986). Stable berms involve the placement of dredged material in deeper water areas, up to 40–42 feet, using a variety of dredged material: silt and fine-grained sand and clay particles.
In 1982, the USACE Norfolk district began a pilot study of stable berms in the Dam Neck placement site off Virginia Beach. Construction drew on maintenance dredged material from the Thimble Shoal channel serving the ports of Hampton Roads (Murden, 1989a,b). Monitoring confirmed that the material was undisturbed even though a series of storms and three hurricanes had struck the area. Based on this study, the Corps proceeded with a national demonstration project offshore of Dauphin Island, Mobile, Alabama.
The plans and objectives for the construction of a feeder berm and a stable berm offshore of the badly eroded strand of Dauphin Island were coordinated extensively with members of Congress, the local sponsor of the Mobile harbor navigation project, and several environmental groups to ensure that the concept
was fully understood prior to construction. Further, an extensive monitoring program was planned in consultation with concerned parties to determine success or failure in meeting project objectives and to determine whether or to what degree marine habitat could be created using underwater berms an artificial reef. If adverse impacts to the marine environment were detected, then the dredged material would be transported to a historical placement area under contingency plans developed for this purpose (Clarke et al., 1988; Murden, 1988).
During February 1987, about 450,000 cubic yards of beach-quality sand were excavated from the entrance channel to the Port of Mobile and placed along the 18- to 20-foot depth contours. The material was placed parallel to the Dauphin Island shoreline about 3.5 miles offshore and 1.5 miles downdrift from the entrance channel.
The long-term monitoring program, initiated in 1987, includes precision bathymetric surveys before, during, and after construction. It is currently in progress. Monitoring includes fathometer and sidescan sonar surveys, wave and current data compilation, and soil sample analyses. It is intended to identify any adverse impacts on the marine habitat from construction of the nearshore feeder berm and any movement of the berm material (Hands, 1991; Poindexter-Rollings, 1990).
The feeder berm began to move slowly, as forecasted by the use of coastal engineering technology. A survey in January 1988 indicated that the material had begun to move to the west and farther downdrift from the entrance. By August 1989, portions of the berm had moved both westerly and to the north toward the Dauphin Island shoreline. Although the feeder is still a definable underwater feature, the berm material is beginning to merge with the ebb-tidal delta. Civic organizations and members of the engineering and scientific communities judged the project a success, based on these favorable data. Similar successful berms have since been constructed offshore of New York State, North Carolina, Texas, and California.
The stable berm element was begun in February 1988 and completed in May 1990. About 17 million cubic yards of silt and soft plastic clay particles were placed along the 40- to 45-foot depth contours parallel to the Dauphin Island shoreline about 2 miles downdrift and about 5 miles offshore. Extensive monitoring includes bathymetric, subbottom profile, and sidescan sonar surveys; sediment analyses; wave, wind, and barometric pressure data collection; benthic microfauna and vertical sediment profiling surveys; and fisheries investigations with trawling surveys, feeding analyses, and hydroacoustic surveys. These studies were done to determine whether the underwater feature would remain stable, whether the berm would contribute to wave energy dissipation, and whether the berm would improve the fisheries habitat. Initial dimensions of the stable berm were: elevation about 20 feet above the seabed, width 1 mile, and length 2.5 miles. It is the largest underwater berm constructed to date. Materials were excavated
by a clamshell dredge and transported to the placement area in hopper barges.
Based on the following findings, the USACE considers the project successful (Clarke and Pullen, 1992; Langan and Rees, 1991):
The project was constructed to design specifications with conventional dredging and positioning equipment.
A relatively stable configuration was achieved, albeit with use for a wide variety of fine-grained materials.
Energy of long-period storm waves was reduced by as much as 75 percent (McLellan et al., 1990).
No adverse impacts on biological resources of the area have been indicated.
The berm is serving as a refuge and feeding location for juvenile red snapper, other fish species of various age classes, and shrimp (Clarke and Pullen, 1992).
Additionally, construction costs were lessened because the distance to placement was less than to the historical placement area offshore. Extensive monitoring is providing the engineering and scientific data needed to conclude that underwater berms offer a wide variety of potential benefits. Further monitoring and evaluation at other sites could be used to improve quantification of the berm's response to waves, currents, and other forces; with this information, the design criteria for future berms can be broadened and the potential benefits better understood (McLellan and Imsand, 1989).
To date the demonstration projects indicate that the technology is well suited for shoreline protection and the creation of marine habitat. Benefits of the feeder berms include the introduction of beach-quality sand into the nearshore profile. Over an extended period, the supplemental materials are expected to contribute to the creation of a more gentle underwater slope and corresponding reduction in beach erosion. Research indicates that the cost of nearshore placement can be about one half the cost of beach placement (Juhnke et al., 1990). The stable berms are also providing benefits; they are reducing wave energy and improving fisheries habitat.
The potential benefits of underwater berm construction are summarized by Hands and Bradley (1990) as follows:
enhancement of fisheries;
stockpiling of sand for later use;
reduction wave impact and run-up damages;
augmentation of the sand budget on an eroding coast;
reduction of offshore sand loss through service as an underwater barrier;
bolstered foundations or formed cores of offshore structures;
channelized migration of fluid muds;
reduced hauling distances and placement costs; and
improved monitoring of materials behavior.
ARTIFICIAL REEF TECHNOLOGY AND APPLICATIONS
The construction of artificial reefs has evolved from the dumping of trash, construction materials, tires, automobiles and appliances, and worn-out or excess ships to the sophisticated design structures with specific habitat objectives. The state of the art is highly advanced in Japan, where virtually all coastal habitats have been destroyed or substantially altered. No undisturbed estuaries remain; coastal waters have been heavily polluted by runoff from rivers and discharge from municipalities and industries. As a result, the Japanese government and private interests commit large resources to creating artificial habitat. In the United States, artificial reefs have been constructed in domestic waters and on the continental shelf, primarily as artificial fishing reefs for recreation instead of commercial use. Most of the reefs are unsophisticated in terms of design, construction materials, and placement technology (Bell, 1986; McGurrin et al., 1989 a,b; Seaman and Sprague, 1991; Sheehy and Vik, 1992).
Artificial habitats are constructed from a variety of materials that include bamboo and cork rafts, spheres, midwater fish attraction devices, ballasted trees, plastic seaweed, stones and quarry rock, concrete cubes and culverts, ballasted tires, plastic and concrete blocks (including oil ash stabilized in concrete blocks), derelict and scrap vessels, low- and high-profile steel reefs, and obsolete petroleum platforms (McGurrin et al., 1989; McGurrin and Reeff, 1986; Seaman and Sprague, 1991; Sheehy and Vik, 1992; Shieh et al., 1989). Many reefs are formed simply by dumping or sinking materials and then relying on natural colonization. Except for structures such as ships, control over the form and function of the reef is limited. Designed, prefabricated reefs have some advantages over the less sophisticated reefs; the former can accommodate site-specific and species-specific considerations. This capability permits the use of artificial reefs where other restoration technologies, such as those for restoring seagrass beds, might not be suitable. Although prefabricated artificial reef technology is expensive relative to more traditional techniques, it has more flexibility for use under varying water quality and physical energy conditions. Prefabricated reef technology could also be employed as an interim measure to enhance or provide opportunity for natural recolonization of a damaged site (Sheehy and Vik, 1992).
Artificial Reef Technology in Japan
Comprehensive reviews are available on the evolution and status of Japan's exhaustive efforts to construct and maintain artificial reefs in its nearshore waters (Grove and Sonu, 1991a,b; Sheehy and Vik, 1981a,b). In the 1900s local
practices evolved beyond individuals making their own reefs by pushing shore rocks into coastal waters, for example. As fishermen organized cooperatives, they built larger, more effective structures. Then in the 1950s, designed and prefabricated concrete modules were used to make artificial reefs. At the same time, the Japanese government made matching funds available to prefectural and municipal governments and fishing cooperatives (Sheehy, 1982).
Japan's national program for the creation of artificial reefs has for years involved long-term planning and the expenditure of hundreds of millions of dollars; the reefs have ''altered the nature of coastal fisheries and have contributed to appreciably increasing the incomes of coastal fishermen" (Sheehy, 1982). Grove and Sonu (1991b) reported that the Japanese government spent an average of approximately $100 million to construct 1.4 million cubic meters of habitat annually for the past 12 years. Japan's next 6-year plan (1988–1994) calls for the expenditure of $933 million (1987 conversion rates) to construct 14 million cubic meters of artificial habitat (Grove and Sonu, 1991b).
Artificial Reef Technology in the United States
Artificial reef technology has largely drawn on available construction materials, such as old ships and rubble. Placement basically involves sinking or dumping materials at a designated site (Bell, 1986; Lewis and McKee, 1989; McGurrin et al., 1989a,b; McGurrin and Reeff, 1986). More recently, efforts have been made to apply more sophisticated design and placement techniques. These include important progress in Louisiana and South Carolina, which is emphasizing design and planning. Programs in both states have significant research efforts to support future artificial development. Specially designed and placed artificial reefs have also been used as a form of mitigation for port development (Sheehy and Vik, 1988b). Private investment in artificial reefs for commercial fishing is constrained by the treatment of artificial reefs and the fishes that inhabit or are attracted to them as common property. Without control of the fishery resources by private companies, for example, commercial investment is unattractive.
Louisiana is converting oil and gas production platforms to artificial reefs when they stop producing and regulations call for their removal from the Gulf of Mexico. Using creative legislation and memorandums of understanding with the state and federal governments, the state has cooperated with the petroleum industry to tip the old structures into the water, remove them as navigation hazards, and mark them for use by anglers. Part of the money saved by the industry is dedicated to research and development in support of the Rigs to Reefs project (Sheehy and Vik, 1982).
South Carolina resource authorities recognized that the state's continental shelf lacks structures that support reef communities. The state became an early proponent of creating artificial habitats to support recreational fishing. Its Wildlife and Marine Resources Department has a section that studies, promotes, and
assists in developing artificial reefs. Section personnel work with fishing clubs and other private groups and use state and federal funds as well as volunteer efforts to create new structures. The legislature has approved a reef management plan. Placement of new artificial reef structures is regulated by the South Atlantic Fishery Management Council.
BIOENGINEERING APPLICATIONS FOR COASTAL RESTORATION
Bioengineering is the use of plants and plant materials for protection and restoration. In Western Europe, resource restoration has applied bioengineering technology for decades, and is so routine that restoration technology, its costs, and monitoring are automatically included in construction designs before they are approved and implemented. Germany routinely uses bioengineering in reservoir, lake, and streambank erosion control, including preventive structure placement prior to water impoundment. Breakwater designs, cribbing, wattling, soil stabilization amendments, and other techniques are available to German engineers (Allen, 1992). On the North Sea coast where 12-foot tides occur, routine application of bioengineering techniques includes grid systems built with light-foot-pressure equipment to trap sediments and create fast land, a remarkably successful technique in the North Sea environment and one that could have direct applications in coastal Louisiana, for example.
In the United States, where resource restoration has used bioengineering technology for the past 20 years, it is still considered an untested technology. Yet there are dozens of examples of success with temporary and permanent breakwaters coupled with plant materials, erosion control fabrics and geotextiles, layering, wattling, bundling, floating islands, and other techniques in the nation's lakes, reservoirs, rivers, and streams and along the coast. Poor technology transfer may be a problem. This technology, although widely used by federal agencies (the USACE and SCS primarily), is not widely known elsewhere; nor is it routinely addressed in academic curricula.
In cost comparisons with traditional engineering structures prepared by the Waterways Experiment Station, these techniques save as much as 90 percent of protection and restoration costs. For example, riprap typically costs approximately $300 per linear foot and erosion control matting (plants included) an estimated $30–40 per linear foot. Bioengineering appears to have little effect on costs in high energy areas. Yet low-to-moderate wave energy sites have been stabilized with little difficulty along the South Atlantic coast and Gulf coast when plant materials were used along with bioengineering technology.
The National Park Service tested bioengineering techniques in restoring Kenilworth Marsh in the Anacostia River in Washington, D.C., and other agencies are considering using these techniques. Technical information is available from the USACE and SCS (Allen, 1990; Allen and Klimas, 1986; Landin, 1991; PIANC, 1992b).
GIS APPLICATION IN MARINE HABITAT MANAGEMENT
GIS are tools for delineating wetlands, evaluating natural resources, predicting impacts on these resources, and helping determine where restoration will be most effective. Several agencies are exploring GIS use in coastal restoration and enhancement, including applications in the Chesapeake Bay region. For example, Maryland already uses GIS for wetlands delineation purposes. Figures 3-1 and 3-2 in Chapter 3 were derived from GIS maps prepared by the USFWS. GIS technology has also assisted in resource evaluation in the Yazoo Basin in Mississippi and Lake Michigan, both discussed below.
In the Yazoo Basin, the USACE Vicksburg district, the Dallas EPA office, the USFWS Vicksburg field office, and the Mississippi SCS office used GIS to advance wetland identification on 3 million acres. The GIS mapping of land use and habitat types was used to determine whether landowners owned wetlands and the implications to the owners. GIS technology has also aided in developing a comprehensive levee and channel system, and, based on hydrology, elevation, and soil types, in predicting restoration mitigation effects for major areas of the Yazoo Basin.
In the Great Lakes, GIS applications are being developed to predict lake level changes and associated wetland and other habitat losses. The information will be used in urban planning, identifying continued habitat changes and losses, identifying potential habitat restoration areas, and predicting achievement of restoration project objectives.
The Army Corps of Engineers funded costs of the Yazoo Basin GIS applications and both the USACE and the EPA funded the Great Lakes GIS applications. Development of the GIS systems used in these two applications cost several hundred thousand dollars; both agencies will bear the GIS maintenance and updating costs (Landin, 1991).
Although substantial amounts can be spent on computer hardware and GIS software, moderately priced GIS software (about $5,000) that can run on desktop computers is available. High-resolution work, depending on the scale and size of the database, may require a computer workstation with active hard drives and a substantial memory capacity. Data acquisition can be expensive; their availability, accuracy, and costs are the limiting factors in use of GIS technology, not the software or hardware, unless a high capacity workstation is needed. Existing databases with potential marine habitat management potential are available or are being developed by some local, state, and federal agencies. In particular, some local taxing authorities have adopted GIS, conducted aerial reconnaissance, and digitized the results to assist in tax assessments. When such data are available, marine habitat management authorities can use them to identify and track changes in habitat profiles, including conversions and alterations of human origin that are not permitted.