[From the U.S. Government Printing Office, www.gpo.gov]









                                    Coastal Protection


                                       A White Pape@r on
                                  Engineering Approaches
                                                 to
                                   Shoreline Management









                                            Prepared by

                                         Janice McDonnell
                                        Dr. Michael Bruno
                                        Dr. Norbert P. Psuty
                                        Thomas Harrington



                                New Jersey's Shoreline Future Project
                               Institute of Marine and Coastal Sciences
                             Rutgers - The State University of New Jersey




                                   Coastal Hazard Management Plan
                                  Office of Land and Water Planning
                         New Jersey Department of Environmental Protection







                                      Coastal Protection                                      49V

                                             A White Paper
                                                      on
                                       Engineering Approaches
                                                       to
                                        Shoreline Management









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                                                               Coastal Hazard Managgement Plan
                                           New Jersey Department of Environmental Protection

                                                         In.stitute of Marine and Coastal Sciences
                                                     Rutoers the State University of New Jersey
                                                                                  Summer, 1996








                                     Coastal Protection

                                            A White Paper
                                                     on
                                     Enaineering Approaches
                                                     to
                                      Shoreline Managernent




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                                                             Coastal Hazard Mana-ement Plan
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                                         New Jersev Department of Environmental ProtectIO11

                                                      Institute of Marine and Coastal Sciences
                                                   Rutgers the State University of New Jersey
                                                                               SLIninicr. 1996











                                                                                                            DRAFT




                   DEFENDING THE NEW JERSEY SHORELINE


                   A Review of Shore Protection Approaches and Strategies Utilized in New Jersey



                   Introduction


                          The New Jersey shoreline is an area of continuous and sometimes dramatic change.
                   Atmospheric disturbances generate winds, which in turn cause waves to break on the shoreline
                   resulting in a great release of energy. Shorelines composed of loose sediments are washed in
                   the direction of the waves' advance. If the sediment'is replaced with equal quantities of beach
                   sand from other areas, or returns from the same area with no change in sand volume, then the
                   beach is said to be in "dynamic equilibrium." Dynamic equilibrium can be created either as
                   cross-shore input or longshore replacement of the sand that is lost. On the other hand, if less
                   sand replaces that which is lost in natural coastal proces'ses, erosion occurs leading to an
                   overall loss of sand volume. Erosion is a natural process that shoreline communities have
                   attempted to slow or arrest for the last century. As a result of the desire to protect private
                   beachfront homes or businesses, beach communities have responded to erosion with structural
                   engineering approaches to attempt to retain the sand or with non-structural solutions such as
                   beach nourishment or simple replacement of the sand fill. These structural and non-structural
                   protection strategies have been applied independently and in combinations in attempts to
                   counter, or balance, erosional losses.


                          This report addresses the characteristics of structural and non-structural strategies
                   used to manage shoreline erosion problems in New Jersey. Each strategy is discussed in terms
                   of (1) its location on the shoreline, (2) a physical description (3) short-term positive and
                   negative impacts, (4) long-term positive and negative impacts, (5) associated cost's and
                   benefits, and (6) the life expectancy of the method. The cost and the longevity estimates
                   assess the range of costs associated with structural approaches and the average life expectancy
                   of the unit, respectively. A multitude of factors affect the short-term and long-term benefits
                   of any structural approach, including regional weather conditions, storm events, and the
                   maintenance schedule adopted by the community for the up-keep of the unit. Structural
                   approaches are only short-term adjustments to nature's continual erosional loss of sediment.
                   They do not add new sand to the beaches. They either attempt to reduce the rate of loss or to
                   cause sand to concentrate in one location at the expense of another. The changes to the
                   shoreline's sediment budget can create both positive and negative consequences for the host
                   community and its neighboring shoreline communities.

                          This information is intended as a guide to identify and compare structural and non-
                   structural approaches for shoreline management, and is directed at local and state officials, to










                                                                                                     2 - DRAFT
                   assist in the selection of responses under pre- and post-storm conditions. Existing shore
                   protection strategies in New Jersey are used to- illustrate the engineered structures and non-
                   structural approaches outlined in the paper.


                   1. Engineered Approaches

                   A. Shore Parallel Approaches / Sand Retaining and Stabilizing Approaches

                           Three approaches are used to armor the coast against wave action. These include
                   revetments, bulkheads and seawalls. In each approach, various construction materials are used
                   to form a hard shoreline structure which is placed parallel to the coast.


                                   1. Revethwnts


                           Revetments are the simplest structures of the three. These structures are placed on the
                   seaward face of a slope and are designed to stabilize an eroding shoreline in areas of light wave
                   action. Revetments are made of interlocking concrete blocks or stone interlocking blocks,
                   called rip-rap and are generally built on a slope (Figure 1). The short-term positive impacts of
                   revetments are that they stabilize the slope and they reduce wave run-up, thereby reducing the
                   risk of direct wave attack on the landward infrastructure. However, an increase in wave
                   reflection associated with an increase in local erosion may threaten the long-term survival of
                   the structure. Local beach dynamics and storm events also affect the life expectancy of
                   revetments. With careful thought in the structural design, a revetment may last an average of
                   thirty years or more. The cost of a revetment is approximately $500- 1000 per linear foot and
                   varies based on the materials used and the elevation.


                                  Z Bulkheads


                           Bulkheads are vertical walls constructed of steel or concrete sheet piling, creosote-
                   treated lumber, aluminum, plastic, or timber (Figure 2.) These structures extend from below
                   low water to above high tide and usually do not experience direct wave action except during
                   storms or other high water events. The short-term positive impacts of bulkheads are that
                   they preserve the landward property and generally improve access to the water. However,
                   direct wave action can undercut and undermine the bulkhead and lead to the construction
                   seawalls in their place. The cost of constructing bulkheads is dependent on the chosen
                   material. Materials such as aluminum and creosote cost approximately $ 600-1000 per linear
                   foot (S50-1 00 per ton). The life expectancy of the bulkhead is dependent on the material and
                   local conditions.   Material such as creosote-treated lumber has been recorded- to last
                   approximately 30 years if maintained properly. Aluminum also has been used experimentally
                   in bulkhead construction and is thought to have an extended life expectancy.














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                                                                                                  headland,


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                                                                                                  F-un@ 2. Vertical
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                                                                                                  Fiuwre  Seawall
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                                                                                                          3 - DRAFT
                                    3. Seawalls


                            Seawalls may be constructed of stone or concrete, and are sometimes built with a
                    curved face. to dissipate wave energy and prevent undermining (Figure 3). Seawalls are
                    designed to sustain the full force of wave action, and are often used in conjunction with other
                    structures described previously. Bulkheads and seawalls are designed to protect only the land
                    immediately behind them. Beach erosion continues in front of and downdrift of the structure,
                    and may intensify erosion. This can result in scour and eventual collapse of the structure.
                    Costs of constructing seawalls are variable depending on the material but generally range from
                    $ 500- 1000 per linear foot ($50- 100 per ton). Seawalls may be expected to last depending on
                    the construction, maintenance schedule, and local conditions on the order of 50 -100 years.

                            B. Shore Perpendicular Approaches / Intercepting Shoreline Transport


                                    1. Groins


                            A groin extends from the backshore area into the water at right angles to the shoreline
                    (Figure 4). Its function is to slow the rate of littoral drift of sand and to capture sand along the
                    updrift side causing accretion or accumulation of sand. They are constructed of stone,
                    concrete, steel, or timber and are built to varying lengths and with a r-ange of profile shapes
                    (e.g., constant top elevation or sloping top elevation - low profile groin). Groins initially trap
                    sand moving along the shore, creating a pocket of sediment on the updrift side. In the short-
                    term, groins accrete on the updrift side and cause erosion or shoreline displacement on the
                    downdrift side. However, a groin may also accelerate erosion in the downdrift direction to
                    such an extent that it may become necessary to construct a second groin, then a third, and so
                    on. Downdrift erosion may become an urgent problem requiring more elaborate protective
                    measures. Groin installations do not create new sand but are intended to slow the rate of loss
                    created by alongshore transport of sand. Groins function best when there is an adequate
                    supply of sand and are not effective where the littoral or nearshore materials are finer than
                    sand.    The problems associated with downdrift erosion may be partially ameliorated by
                    notching the groin, thereby allowing some of the sand to pass across the structure. The top
                    elevation of the groin also may designed so that the seaward end slopes downward or is lower
                    allowing some sand to pass across. When constructed and maintained properly, these
                    structures may last 30 - 40 years at a cost of $1000-2000 per linear foot ($75-100 per ton).
                    Most of the New Jersey shoreline has groins, especially Monmouth County.

                                    2. Inlets and Sand Bypassing

                            Jetties at inlets are larger structures used primarily to confine tidal flow at an inlet, and
                    to prevent littoral drift from shoaling the channel (Figure 5). Jetties are often constructed in
                    pairs and are designed to help stabilize the depth and location of channels. By their nature and
                    definition, inlets are directly at odds with beach stabilization. A stable, jetty-protected










                                                                                                       4       DRAFT
                    navigational channel prevents or minimizes shoaling of the channel, creating a barrier to littoral
                    transport. This creates accretion on the updrift and erosion on the downdrift sides of the
                    channel. Natural (uncontrolled) inlets will exhibit natural sand exchange across an ebb tide
                    shoal. Most often, controlled inlets (with/jetties) do not exhibit this behavior. This problem
                    can be addressed by transforming the accumulated sediment mechanically, or sand bypassing,
                    via dredge or periodic truck fill, thus minimizing erosion on the downdrift side (Figure 6). Sand
                    bypassing may be conducted at an estimated cost of $2 per cubic yard, excluding capital costs.
                    Sand bypassing is conducted at Indian River Inlet, Delaware, where the capital costs (above
                    annual maintenance costs) of constructing the sand bypassing system were approximately
                    $1.7 million dollars.


                                    3. Breakwaters


                            Breakwaters are offshore structures constructed of stone and /or concrete armor units
                    (CAU). They are designed to protect shore areas from direct wave action and to create littoral
                    sand traps. In a detached breakwater, or a structure riot connected to the mainland, sand
                    accumulates behind the breakwater forming a seaward projection of the shoreline (Figure 7).
                    This structure shields a portion of the beach, but often leads to erosion. These structures are
                    used on the West Coast of the U.S. and more commonly, in the Mediterranean and Australia.


                            The attached breakwater, which is connected to the mainland, ftmctions slightly
                    differently. Its objective is to shield an area from direct exposure to waves (Figure 8).
                    However, it also intercepts longshore sediment transport, causing accumulation on the updrift
                    side and accelerates loss downdrift.


                            The long-term positive effects of breakwaters are an increase in beach accretion, and
                    shore protection immediately landward of the structure. However, breakwaters accumulate
                    sand at the expense or sand starvation of the downdrift area.           Attached and detached
                    breakwaters can be installed at a cost of approximately $1000 per linear -foot and may be
                    expected to last an average of 30 years with proper maintenance.

                    11. Non-Structural Approaches

                            A. Beach Augmentation Methods


                                   1. Beach nourishment


                            Beach nourishment involves bringing quantities of sand from an outside source onto an
                    eroded beach area (Figure 9). This activity can range from periodic replacement of sand lost
                    by erosion to extensive placement of sand for construction of beach areas. Sand may be
                    pumped from an offshore location or may be trucked in and dumped on the beach.              Beach
                    scraping, or the mechanical movement of sand from the high water line to dry beach areas, also




















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                                                                                                       seaward from
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                                                                                                       Indian River Inlet,
                                                                                                       Delaware.










                                                                                                      5       DRAFT
                    is practiced along the New Jersey shoreline.

                           fn the short-term, beach nourishment creates a large beach berm, and provides for
                    better shore protection and recreational use. However, beach nourishment is a comparatively
                    short-term solution to erosion; sand fill must be replaced periodically to maintain a shoreline
                    position. There are many factors to consider in a nourishment project, including: rate of loss
                    of beach material in the region; predominant direction of littoral drift and its interaction with
                    all existing protective structures; availability and suitability of beach fill material; method of
                    beach fill placement; and effects of removal if from an offshore location. It is important to
                    select fill that closely matches the natural grain size frequency of the beach. Sources of fin
                    which are too fine, as from the back bays, will be rapidly eroded from the beach. Upland
                    sources tend to have a silt component that will wash out quickly and may create a yellowish
                    stain for a short time.


                           The use of nourishment as an erosion control measure generally requires a continuous
                    commitment to its financial and material maintenance. The costs associated with beach
                    nourishment are generally balanced against the value in protection of infrastructure, property
                    and development. Sand fill may cost $600 per linear foot ($2-8 cubic yard) and usually is
                    replaced on a 2-6 year cycle. The fill cycle is highly dependent on the location and resulting
                    beach dynamics. Ocean City and Avalon, NJ have perhaps the longest running beach
                    nourishment projects in the State. Beach scraping is an alternative beach nourishment practice
                    that moves beach sand one position in the beach profile to another. This process may,
                    however, be detrimental if the beach slope is altered greatly or is scraped too deeply, creating
                    steep slopes or pools in the beach. Seaside Heights and Manasquan both practice beach
                    scraping.


                    B. Shoreline Stabilization Techniques


                                   1. Dunes


                           Dunes are a part of the natural shoreline and are the product of many years of
                    interaction between waves, wind, and sand. They create a protective buffer that exchanges
                    sand with the beach to reduce rates of shoreline displacement and may act as a barrier to storm
                    surge, thereby offering protection to properties inland of the dune zone. A common dune-
                    building method consists of erecting wind obstructions, such as picket-style sand/snow fewFs-
                    which break the wind and capture sand particles (Figure 10). Another approach is to create a
                    dune ridge by direct placement of sand on the upper beach, as a short-term stop gap. There are
                    many materials that are used as wind flow barriers along the shore to trap the sand in
                    transport across the beach such as fences of cloth or plastic. Old Christmas trees are often
                    recycled as brush in the dune to help trap sand. The trees can be unsightly and trashy if they
                    are not buried, or if they are uncovered. Sand fencing is inexpensive at $ 1 per linear foot.














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                                                             -41
                                                                                               s
                                                                                                 d dune. created
                                                                                               an
                                                         44
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                                                                                               E tiuc I
                                                                                               autmented by samd
                                                                                               fences, stabilized
                                                                                               by plant vegetation.
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                                                                                               dunc.Tude is a type
                                                                                               of' seawall Protectill"
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                                                                                               Atlantic OtN. N









                                                                                                      6       DRAFT


                                   2. Dune Stabilization


                           Any artificial or natural dune may be somewhat stabilized with vegetation (Figure 10).
                    Dune vegetation has specific adaptations to the harsh beach environment such as long stems
                    and roots, resistance to salt spray, and tolerance of low nutrient levels. The most common
                    plant used in dune stabilization in New Jersey is American beach grass (Ammophila
                    breviligulata). Dune vegetation costs approximately $2 per square yard and can be expected
                    to survive 5-10 years, depending on weather conditions and nutrient supply.

                           Some dune stabilization projects have included excavation of the area below elevation
                    and the application of a clay fill called 1-5. The area is then retopped with sand at a cost of
                    $ 6-120 per linear foot. Some dunes are fortified. with a structural core such as a geotube
                    (Figure 11). These geotubes are large filled bags, which are covered with sand to create a dune.
                    Geotubes may be constructed at an average cost of $60-70 per linear foot (9.5 foot diameter,
                    hydrologically-filled with local sediment) and may be expected to survive 5-10 years.

                           Ideally, dunes must be located above the spring high water line and sufficiently far
                    inland (100-150 feet) of this line to be out of the reach of storm high tides.              Many
                    communities enlist the support of their residents for dune grass planting and dune fencing
                    projects. Examples of an on-going artificial dune projects occur throughout the State.



                    Prognosis

                           The long-term trend of the shoreline position is an inland displacement accompanied
                    by loss of sediment and drowning of the coastline. The major factors leading to this situation
                    are the general absence of new sediment replacing the material that is being eroded, and the
                    slow drowning of the shore associated with sea-lev@el rise.          Several of the engineering
                    approaches discussed in these pages have been applied as an attempt to stabilize portions of
                    the New Jersey shore. The hard structures approach defines a line and holds the ocean back.
                    The soft non-structural approach moves sand to problem areas, and creates a temporary beach
                    with a limited life. All of the approaches outlined in this paper are costly and may not be
                    appropriate in all situations. Choosing an appropriate solution to shoreline problems depends
                    on the location, severity of the erosion problem, availability of materials, associated costs, a@s
                    well as environmental, esthetic, and social concerns. It is imperative that local resource
                    managers throughout New Jersey have access to accurate, current information on the
                    appropriate strategies to manage the effects of severe storms and erosion on the shoreline.










                                                                                                                     7       DRAFT
                      Summary


                               All of these methods have been used along the New Jersey shoreline, with varying
                      degrees of success. Table I summarizes the physical description of various approaches, the
                      associated costs/benefits, and the life expectancy of the shoreline strategy.


                        METHOD                     PHYSICAL DESCRIPTION                            COSTS                 LIFE
                                                                                                   (linear foot)         EXPECTANCY
                                                                                                                         (YRS.)

                        Shore Parallel Approaches
                        Revetment                  Interlocking concrete blocks     or rip- rap    $500-1000             30
                                                   built on a slope.
                        Bulkheads                  Vertical walls constructed' of steel,           $600-1000             30
                                                   concrete sheet piling, creosote-treated
                                                   lumber, aluminum, plastic or timber.

                                                                                                           000            0-100
                                                   with a curved face) of stone or concrete.
                        Seawalls                   Vertical wall constructed (sometimes            $500-1


                        Shore Perpendicular Approaches
                        Groins                     Concrete blocks, steel, or timber built to      $1000-2000            30-40
                                                   varying lengths with a range of profile
                                                   shapes (constant top or sloping top
                                                   low profile groin).
                        Sand Bypassing             Mechanically passing sand across an             $2/yd. and cost       sand is transferred
                                                   inlet with a dredge or periodic trucked         of pump station       periodically
                                                   fill.

                        Detached/ Attached         Offshore structures constructed of stone        $1000                 30
                        Breakwaters                and/or concrete armor units (CAU).
                        Beach Nourishment          Process of bringing quantities. of sand         $600;                 2-6
                                                   from an outside source onto an eroding          $2-8 cu.yd.
                                                   beach area.
                        Dune Stabilization         Creation and stabilization of artificial        $2 / sq. yd.          5-10
                                                   dunes with natural dune vegetation, or 15        (vegetation);
                                                   fill, or sand fences.                           $6-12)0 (15 fill)
                                                                                                   $1 (sand fencing)
                        Geotubes                   Large filled bags covered with sand to          $60-70                5-10
                                                   create a dune/dike ridge.




                      Acknowledgements
                               Much of the information on costs of operations was supplied by Mr. John Garofolo
                      of the Coastal Engineering Division of NJDEP. Other sources on costs and life expectancy










                                                                                           8 - DRAFT
                 were John Tunnell and Ted Keon, Philadelphia District, U. S. Army Corps of Engineers.
                 Dery Bennett, American Littoral Society, and Robert Mainberger, Killam Associates -
                 Constulting Engineers, provided review of an earlier draft. Elizabeth Haynes contributed
                 greatly to an early draft of this document. All of the photographs were, taken by N. P. Psuty
                 and Susane Pata. Michael Padulo digitized the photos and created the photo-templates for
                 this report.










                                                                                                  9       DRAFT
                   Glossary


                   Adapted from the U.S. Army Corps of Engineers report Low Cost Shore Protection... A
                   Property Owners Guide.

                   Accretion - Accumulation of sand or other beach material due to natural action of waves,
                   currents and wind. A build-up of the beach.

                   Alongshore - Parallel to and near the shoreline: same as longshore.

                   Beach fill - Sand or gravel placed on a beach by mechanical methods.

                   Breakwater - Structure aligned parallel to the shore, sometimes connected to the shore, that
                   provides protection from waves.

                   Bulkhead - Vertical structure that retains or prevents sliding of land or protects land from
                   wave action.


                   Current, Longshore - Current shoreward of the breaker zone moving essentially parallel to
                   the shore and usually caused by waves breaking at an angle to the shore. Also called
                   alongshore current.


                   Downdrift - Direction of alongshore movement of littoral materials.


                   Dune - Hill, bank, ridge, or mound of loose, wind blown and water deposited material, usually
                   sand.


                   Dynamic Equilibrium - Cross -shore exchange or longshore replacement of sand.

                   Ebb tide- Part of the tidal cycle between high water and the next low. The falling tide.

                   Erosion - Wearing away of land by action of natural forces.

                   Groin - Shore protection structure built perpendicular to the shore and designed to trap
                   sediment and slow the rate of shore erosion.


                   Groin field - Series of groins placed along a stretch of beach to trap sediment and slow shore
                   erosion.


                   Littoral Material - Sediments moved in the LITTORAL ZONE by waves and currents.
                   Also called littoral drift.









                                                                                               10 - DRAFT
                  Littoral Transport - Movement of LITTORAL MATERIAL by waves and currents.


                  Littoral Zone - Area extending from the shoreline to just beyond the breaker zone.

                  Nourishment - Process of replenishing a beach either naturally by longshore transport or
                  artificially by delivery of materials dredged or excavated elsewhere.


                  Revetment - Facing of stone, concrete, etc. built to protect a embankment, or shore structure
                  against erosion by waves or currents.

                  Seawall- Parallel structure separating land and water areas primarily to prevent erosion and
                  other damage by wave action.

                  Updrift - Direction opp  .osite the predominant movement of littoral materials in longshore
                  transport.







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