Mitigating Shore Erosion Along Sheltered Coasts (2007)

Approaches for mitigating erosion on sheltered coasts have not been subject to the high level of scrutiny and national debate devoted to erosion on open coasts. Although erosion on sheltered coasts is not always analogous, state and local strategies for addressing erosion on ocean shorelines provide context for discussing new approaches to managing erosion on sheltered shorelines. In the 1980s to 1990s, appropriate options for managing erosion on ocean coasts formed the focus of national debate. Opinions ranged from “Properly engineered seawalls and revetments can protect the land behind them without causing adverse effects to the fronting beaches,” (NRC, 1990) to “Hard stabilization may be the best way to save buildings, but retreating from the problem by removing buildings is the best way to save the beach” (Pilkey and Dixon, 1996). From these diverse views among coastal experts, improved approaches for managing ocean shorelines emerged based on studies of erosion processes and ocean front dynamics. One example, the regional sediment budget studies conducted by the U.S. Army Corps of Engineers (USACE, 2005), will be described in this chapter.

The current regulatory structure and prevailing erosion management approaches for sheltered shorelines have favored structures that harden the shoreline with the often unintended consequences of habitat loss, diminished resources, and recreational values. Implementation of a new management approach for sheltered shorelines could minimize further loss of the benefits associated with maintaining more natural shorelines. The prevailing practice of installing bulkheads and similar structures to combat real and perceived erosion problems is, for the most part, the inadvertent result of policies and regulations intended to protect upland property. Unfortunately, these policies sometimes do not give adequate consideration of the

consequent loss of public trust resources such as beaches, wetlands, navigable waters, and submerged tidelands. Erosion mitigation measures have been developed that protect upland property and provide habitat and could be employed in a regional context to avoid undesirable cumulative impacts. A regional approach would help to account for the scale of erosion processes and facilitate exchange of information, technology, and experience gathered at the local level. More proactive planning for shoreline management will require the participation of local decision-makers in addition to state and federal agency partners. This chapter presents the components of a new regional framework for managing shore erosion, with recommendations based on the findings from this study.

The term “regional” is used in this report to reflect an area of shoreline that is defined by some functional physical or ecological parameters such as littoral cells. Several examples of regional proactive planning already exist for shorelines: the USACE Regional Sediment Management approach, the USEPA National Estuary Program, and some special area management plans approved by state coastal management programs. Some aspects of all these experiences offer guidance for proactive regional planning for shoreline erosion control.

The U.S Army Corps of Engineers Regional Sediment Management (RSM) approach provides a model and framework that could be adapted to address sheltered shoreline erosion problems within a regional context. The RSM approach originated as a method for optimizing both economic and ecological resources. For decades, state and local managers of beach shorelines have been at odds with the U.S Army Corps of Engineers over navigation projects and the management of sediment. A demonstration program in 1999 in the northern Gulf of Mexico began a shift towards collaboration among federal, state, and local officials (Box 6-1). The RSM approach of the U.S Army Corps of Engineers has been essential to the agency’s consideration of shoreline management at the regional scale. There are many factors in addition to sediment budgets to consider in the development of regional shoreline management plans. These factors include socioeconomic considerations as well as a broad range of habitat and other ecological issues. Regional plans facilitate the assessment of cumulative impacts and could be informed by credible monitoring of project performance and experience within and without the region of interest.

Environmental planning involves several coordinated steps. The initial phase requires coordination and involvement of all affected decision-makers at the

local, state, and federal levels. Although there are many factors that influence the state of a shoreline ecosystem, human activities are the most readily controlled and most easily planned. The degree to which human activities are controlled depends upon the development of a shared vision for the shoreline. This shared vision should include a long-term perspective consistent with the lifespan of the structures and activities to be governed by the plan. This vision is the first and most essential step in creating a regional plan and includes consideration of the economic, esthetic, and ecological values provided. Development of a shared vision will also incorporate the views of local property owners and users of the shoreline. In the absence of a vision to describe the desired shoreline, the future of sheltered shorelines will be decided through individual permitting decisions that may not reflect the values of the affected communities.

Establishing specific goals that are consistent with the shoreline vision is important to help guide decision-making and monitoring requirements, and provide a means to measure progress over time toward achieving the vision. The following are just some examples of shoreline management goals:

• Prevent loss of taxable land. Protect landward improvements and provide for personal safety.

• Enhance water quality by managing upland runoff and groundwater by maintaining wetland habitat and/or bioengineering of the bluff.

• Protect, maintain, enhance, or create wetlands and other intertidal habitat.

• Provide public access and create recreational opportunities by maintaining or creating beaches.

• Provide a sustainable coast that maintains existing uses in the face of rising sea level.

• Address potential or existing ecological impacts within the management area.

• Align costs with expected benefits to ensure the costs of shoreline management options are carefully analyzed in relation to their expected benefits.

The goals that are agreed upon apply within the context of a shoreline reach or littoral cell. Otherwise, not all mechanisms that could be contributing to the erosion problem will be addressed. Like creating the vision, it is important for all affected parties to work together to identify goals so that differences and potential conflicts can be resolved. Even if all goals are taken into account, different priorities will be given to different goals. It may not be possible to satisfy everyone if some of the goals for a given reach are mutually exclusive (Byrne and Zabawa, 1984).

There are many ways to define the scope of the region of shoreline management plans. Typically erosion processes do not stop at political boundaries and may include two or more localities. Therefore, the preferred option for the geographic scope of the plan is to define the region based shoreline reach (shoreline segment) or littoral cell basis. This accomplishes two objectives: (1) it provides a focus on the erosion problem as opposed to political boundaries, and (2) it improves the ability to assess cumulative impacts. In cases where the physical setting spans political jurisdictions it obviously requires cooperative planning across these boundaries.

A well thought out regional plan is based on the best system-wide information available on the social, economic, physical, and ecological resources of the area. High quality information also facilitates the selection of the most appropriate erosion control alternatives. Maps of the region that illustrate shoreline trends and describe key features (e.g., currents, man-made structures, wetlands, sediment sinks and sources) provides a visual presentation of information that is usually easier for the general public to understand. The location of land and marine resources is also needed for decision-makers when contemplating whether to avoid, minimize impacts, or enhance important resources. Good quality maps also provide a better context and overview of the system, indicating trends of shoreline development over time. Historical wind and water level data with statistical return frequencies are also critical in assessing the wave climate and the level of protection.

A regional shoreline management plan presents a thorough discussion, including cost and effectiveness, of the techniques and technologies available for addressing erosion (i.e., land use management, vegetate, harden, and trap or add sand). A “no action” alternative is also included. This is an important alternative to consider, especially when assessing potential benefits such as sand supply to shallow ecosystems. Many state or region-specific documents already provide a sound foundation of information, but to include the full array of proven, available options would require compilation and expansion. These summary documents would need to be routinely updated to reflect knowledge gained from monitoring and research activities for revisions of regional plans.

Erosion mitigation measures typically affect aquatic resources, landforms, property values, private or public infrastructure, regional sediment supplies, critical habitats on private properties, public property, or on property held in public trust. Therefore, some level of monitoring is required to measure and evaluate the effects on uplands and resources. Effective monitoring occurs at both the individual project level (preconstruction baseline and more detailed assessments after project implementation) and the regional level covered by the plan. Individual monitoring is typically the responsibility of project proponents while regional monitoring is the responsibility of the management plan authority.

In addition to being consistent with the goals of the management plan, proponents, regulators and interested parties need to agree on “criteria for success” that apply to project-level and regional-level activities. The monitoring plan is then based upon these goals and criteria and the results of the monitoring are

used to measure progress toward the goals and criteria. Examples of “criteria for success” are presented in Box 6-2. Guidelines for selecting success criteria are available from U.S. Geological Survey (USGS, 1999), USACE (2002a), and previous National Research Council studies (2003, 2004b, 2005, 2006). Generally, success criteria are measurable, consistent with the purpose and goals of the project, and achievable by the end of a reasonable monitoring period (2-10 years). For example, success criteria in compensatory wetland mitigation projects have included percent canopy cover, percent plant survival, plant vigor, percent of native species, period of inundation, stability of designed hydrologic features, wildlife usage, and plant heights (USACE, 2004).

The following sections describe goals and provide recommendations for developing management approaches consistent with the unique ecological and physical processes of sheltered coasts.

GOAL: Maintaining natural features on sheltered coasts.

FINDING: The current regulatory framework for sheltered coasts contains disincentives to the development and implementation of erosion control measures that preserve more of the natural features of shorelines, mainly as a result of the combined lack of knowledge, vision, and planning. The existing system presents two main obstacles:

• Obstacle 1: General lack of knowledge and experience among decision-makers regarding alternative options for shoreline erosion response, the relative level of erosion mitigation afforded by the alternative approaches and their expected life time, and the nature of the associated impacts and benefits. This unfamiliarity with alternative engineering approaches has resulted in disinterest, concern, or disagreement among regulators regarding the ecological consequences of alternative shoreline stabilization measures.

• Obstacle 2: The current legal and regulatory framework discriminates against innovative solutions because of the complex and lengthy permitting process that almost always considers these options on a case-by-case basis.

Overcoming these obstacles would require a change in the current shoreline management framework. Decision-makers who are responsible for managing sheltered shorelines will need to become more educated about the potential solutions to shoreline erosion problems and take proactive steps to encourage approaches that minimize habitat loss and, if possible, enhance natural habitats. In addition, decision-makers will need to evaluate potential cumulative impacts of mitigation measures on shoreline features, habitats, or other amenities, but individual permit review, as currently practiced in most locales, does not include consideration of cumulative effects.

Virginia is implementing one example of a new proactive approach to managing sheltered coasts in the Chesapeake Bay. Virginia has established a permitting process that encourages alternatives to the use of vertical structures to stabilize shorelines if they are properly designed and installed.

This management change came in the form of a revision to an existing Virginia state statute to achieve no net loss of tidal wetlands. In May 2005, the Virginia Marine Resource Commission (VMRC) adopted a revised policy that, in part, removed the previous threshold of 1,000 square feet (approx. 90 square

meters) for noncommercial projects (revised Wetland Mitigation-Compensation Policy and Supplemental Guidelines; Regulation 4 VAC 20-390-10 et seq.). These revisions address compensation for impacts of proposed bulkheads and revetments to vegetated and nonvegetated wetlands. As revised, any proposed impact to tidal wetlands will be addressed by compensation through mitigation, wetland banking, or use of in-lieu fees, in that order. The use of properly engineered and installed marshes and beaches for shore stabilization may be deemed acceptable onsite compensation or mitigation by VMRC.

FINDING: Development of an integrated plan for management of shore erosion will require improvements in the scope and accessibility of the available information, including the nature of the erosion problem at specific sites and the overall patterns of erosion, accretion, and inundation in the broader region (estuary, lagoon, littoral cell). Many areas lack geospatial information on estuarine erosion zones and rates despite the relevance to coastal planning and its importance in the assessment of vulnerability to natural hazards. For example, although the National Flood Insurance zone maps indicate high hazard flood zones, they do not consider shoreline erosion trends. As a result, property insurance premiums paid into this federal program do not reflect the risk of loss from shoreline erosion, thereby underestimating the actual risk of flooding. This, in effect, subsidizes and encourages the development (or rebuilding) of structures in high-risk areas.

RECOMMENDATIONS:

• State and federal agencies (EPA, USACE, and NOAA) need to convene a working group to evaluate the decision-making process used for issuing permits for erosion mitigation structures to revise the criteria for sheltered coasts, including consideration of potential cumulative impacts.

• Proactive erosion mitigation plans should be implemented to avoid the unintended consequences from hardened shorelines that reduce the recreational, esthetic, economic, and ecological value of sheltered coastal areas. The regulatory preference for permitting bulkheads and similar structures could be changed to favor more ecologically beneficial solutions that still mitigate erosion.

• Long-term shoreline erosion information should be gathered and included in publicly available maps, such as flood insurance rate maps, to more accurately reflect the risks and potential costs of building on erosion-prone shorelines. These maps would provide better information for property buyers and insurers and could guide localities in establishing land use and zoning policies.

• The USGS should include data collection and reporting on sheltered shorelines as part of their National Assessment of Coastal Change program

GOAL: Understanding sheltered shoreline processes and ecological services.

FINDING: Decision-makers need adequate information on the effectiveness of new techniques for addressing erosion and the effects of various mitigation strategies on the physical and biological characteristics of the affected areas to achieve a more balanced approach to erosion along sheltered coasts.

Although there are a few good examples of publications that address the physical process of sheltered coast systems (Finlayson and Shipman, 2003; Jackson et al., 2002; Riggs, 2001), overall, less is known about these systems than about open coasts. Basic information, such as resource characterization, shoreline change analysis, sediment transport patterns, habitat function, and ecological services, is available for only a portion of the nation’s sheltered shorelines and few programs address these knowledge gaps. States have not committed the resources necessary to periodically collect and analyze data for a comprehensive assessment of affected shorelines as would be necessary for effective regional planning.

Also, decision-makers (especially property owners) need assessments of new techniques and materials designed to mitigate shore erosion. Because of the comparatively low energy environments on sheltered coasts, special techniques have been developed to address erosion in these areas. Some techniques, such as the combination of a planted marsh fringe with a sill have been tested and proven effective under well characterized physical settings. However, new techniques (or structural materials) are periodically introduced that require a rigorous process of testing and evaluation to determine their effectiveness in controlling erosion and to evaluate their impacts on the environment.

RECOMMENDATIONS:

• Federal agencies (e.g., USACE, EPA, USGS, NOAA, and NSF), state agencies, and coastal counties and communities should support targeted studies of sheltered coast dynamics to provide an informed basis for selecting erosion mitigation options that consider the characteristics of the broader coastal system rather than simply addressing immediate problems at individual sites. Topics for studies:

  • Identify trade-offs in ecosystem services associated with various mitigation measures,

  • Quantify the costs and benefits of nonstructural erosion control techniques,

  • Document system-wide process and hazard information, including mapping of erosion zones and rates. This information needs to be presented in nontechnical formats such as summary maps that can be readily understood by decision-makers, and

  • Develop models to predict the evolution of coastal features under various scenarios.

• State and federal agencies should ensure that the information obtained from these studies is readily available to decision-makers at all levels of government.

• State and federal regulatory programs should establish a technical assistance function to provide advice on permitting issues and information on types of erosion mitigation approaches and their effectiveness under various site conditions.

GOAL: Improving awareness of alternative measures for addressing erosion.

FINDING: Many decision-makers, particularly homeowners but also some state and federal regulators, are not sufficiently informed about the choices available to them or the short and long term impacts of their choices. Chapter 3 presents many different approaches and technologies that address erosion along sheltered coasts. Inconsistency among states, and even USACE districts, in terms of permitting and the availability of information about various mitigation measures, unnecessarily constrains options and outcomes.

RECOMMENDATIONS:

• The major federal agencies involved in permitting activities (EPA, USACE, and NOAA) should initiate a national policy dialogue on erosion mitigation for sheltered coasts to bring together state and federal decision-makers and share information on the potential application and value of different mitigation approaches.

• The national dialogue should be used to develop guidelines for mitigating erosion on sheltered coasts that give deference to ecologically beneficial measures and ensure consistency of decision-making across regions.

• The national dialogue will require development of handbooks or Web pages with objective information about erosion mitigation techniques, including descriptions of the conditions under which each option would be effective. These handbooks (or Web pages) should be actively distributed to state and local planning and permitting staff; professional associations of environmental consultants, engineers, zoning officials, planners, and building inspectors; and extension agents; and made readily available to property owners and community groups.

• Professional societies and conferences should be utilized as a venue for transferring information to decision-makers such as regulators, engineers, and consultants.

GOAL: Document individual and cumulative effects of erosion mitigation approaches.

FINDING: Cumulative effects of shoreline hardening are rarely assessed and hence are generally unknown. However, an appreciation of the potential cumulative effects will be necessary to prevent an underestimation of the impacts of individual projects. As discussed in Chapters 4 and 5, all shoreline management options have associated costs and benefits. To effectively evaluate these costs and benefits requires delineation of the area of influence of the proposed option and assessment of the associated cumulative impacts. Generally speaking, the physical area influenced by mitigation structures is limited to adjacent properties and their adjoining ecosystems in the case of small structures like bulkheads or to the littoral cell in the case of large structures such as groin fields. The societal area of influence can be much more extensive because armoring projects tend to initiate community trends and preferences for these types of structures along shorelines.

Cumulative impacts encompass legal, social, and physical effects. From a legal or regulatory perspective, issuance of a permit may establish a precedent, potentially facilitating the approval process for future requests for similarly situated structures. This is one form of cumulative impact that often results in similar shoreline structures being constructed throughout a regulatory jurisdiction. Another aspect of cumulative impact is the erosion enhancing effect of structures such as bulkheads on adjoining properties. Flanking property owners are likely to respond by constructing their own bulkheads, with a domino-type effect up and down the shoreline.

Although loss of small parcels of shoreline habitat from hardening may not have a large impact on the ecosystem, the cumulative impact of the loss of many small parcels will at some point alter the properties and composition of the ecosystem. For example, sand- or mud-dependent intertidal species could be replaced by species that favor hard substrates such as rocky revetments. In addition, the economic, recreational and esthetic properties of the shoreline will be altered, with potential loss of public use, access, and scenic values. However, it is difficult to identify the point at which individual projects accumulate to an extent that threatens the valued properties of the shoreline. This requires a determination of the values the affected communities invest in the nonhardened shoreline and an assessment of the value of the ecosystem properties that stand to be lost. Both require a significant amount of information that might not be immediately available to decision-makers. As noted in Chapter 5, regulators are responsible for protecting the public trust values of the ecosystems that are affected by their decisions, and this requires an evaluation of the impact of permit decisions on ecosystem services.

RECOMMENDATIONS:

• The decision-making process should account for ecosystem services when permitting coastal shoreline stabilization projects. Decision-makers

require objective, quantifiable methods for evaluating specific ecosystem services as one of the criteria in permit decisions.

• The economic, recreational, and esthetic properties of the shoreline should be evaluated to assess potential loss of public use, access, and scenic values.

• Cumulative effects should be considered in shoreline management plans, both for the values invested by the affected communities in non-hardened shorelines and the value of ecosystem properties that stand to be lost with shoreline hardening. Although it may not be possible to identify the threshold beyond which cumulative impacts become unacceptable or irreversible, anticipation of the problem allows prioritization of projects in areas unsuited to nonstructural alternatives or sites where structures are predicted to have less impact.

• In the absence of a comprehensive assessment of the cumulative impacts of erosion mitigation measures, a precautionary approach should be used to prevent the unintentional loss of shoreline features and significant alteration of the coastal ecosystem.

GOAL: Proactive shoreline management planning.

FINDING: The current permitting system fosters a reactive response to the problem of erosion on sheltered coasts (see Chapter 5). Decision-making is usually parcel-by-parcel and based on little or no physical or ecological information. The path of least resistance drives choices through a rigid decision-making process, with inadequate attention to the cumulative effects of individual decisions.

Creating a more proactive “regional approach” to shoreline management could address the unintended consequences of reactive permit decisions.

RECOMMENDATIONS:

• The development of regional shoreline management plans for sheltered coasts should occur at the state and local level in partnership with the federal government. Plans should be proactive and comprehensive in scope, and should be scaled to the estuary, bay, or littoral cell as appropriate.

• Regional shoreline management plans should include the following essential elements: (1) a shared vision and goals for the future shoreline of the water body through stakeholder collaboration, (2) analysis of regional sediment budgets and the cumulative effects of existing shoreline management activities, (3) the mechanism for turning the vision into reality through consistent permitting provisions, (4) implementation, and (5) performance evaluation and monitoring requirements (adaptive management).

• Plans should be considered “living documents” and updated every 5 to 10 years as new information (e.g., monitoring data, research results) becomes available.

• Each regional shoreline management plan should describe the physical and hydrodynamic settings, including the location and type of existing shoreline structures in a GIS format. The plan should describe the available mitigation options and discuss the applicability, relative cost and benefit, and effectiveness of each option.

• Monitoring should include both a preconstruction baseline and more detailed assessments after project implementation, both at the individual project level and for the entire region covered by the plan. Individual monitoring should be the responsibility of project proponents while regional monitoring should be the responsibility of the management plan authority.

• Information obtained from monitoring programs should be incorporated in subsequent planning activities to support adaptive management as a mechanism to consistently evaluate and refine regional plans.

Regional planning generally takes place at the state and local level in partnership with the federal government. To be effective, these planning efforts should involve property owners and other stakeholders early in the process. The programs most suited to undertake planning for regional shoreline management are the state coastal zone management programs. Shoreline management plan development could be an eligible activity under Section 309 of the Coastal Zone Management Act and could be effectively implemented as Special Area Management Plans (SAMPs). Creating regional shoreline management plans under the auspices of SAMPs would also provide an opportunity to employ the federal consistency provisions of the Coastal Zone Management Act (CZMA) to ensure that federal permitting actions are consistent with the plan (see Box 6-3).

Applying principles of adaptive management to regional shoreline management plans will allow these plans to be continually updated and improved as new information becomes available. Adaptive management acknowledges the uncertainty of systems; therefore, it integrates monitoring and evaluation into an iterative decision-making process for management. Essential elements of an adaptive management plan can be found in Adaptive Management for Water Resources Project Planning (NRC, 2004a).

Overcoming the obstacles associated with the existing management framework will require a number of societal and institutional changes: (1) better understanding of sheltered shoreline processes and ecological services; (2) improved awareness of the choices available for erosion mitigation; (3) documentation of individual and cumulative consequences of erosion mitigation approaches; (4) proactive shoreline management planning that takes into consideration the

unique ecological and physical processes of sheltered coasts; and (5) a permitting system with incentives that support the goals of the shoreline management plan. The objective is an erosion mitigation decision-making process that helps achieve the shoreline management plan.