Title. Shore protection manual: Volume I and II. Author. Anonymus, A. Date. Abstract. Design manual for coastal structures. Note that this manual is. Shore Protection Manual Vol 2 - Ebook download as PDF File .pdf), Text File .txt ) or read book online. shore protection manual. VOLUME I. CHAPTER. 1. 2. 3. INTRODUCTION TO THE SHORE PROTECTION MANUAL.
|Language:||English, Spanish, Dutch|
|ePub File Size:||23.48 MB|
|PDF File Size:||11.11 MB|
|Distribution:||Free* [*Regsitration Required]|
SHORE PROTECTION. MANUAL. VOLUME II. (Chapters 6 Through 8; I- Introduction, page ; II-Wave Mechanics, page ; III-Wave Refraction, page 2- 60;. U.S. Army Coastal Engineering Research Center () Shore Protection, (1) A lessening of the amplitude of a wave with distance from the origin. (2). SHORE PROTECTION. MANUAL. VOLUME I. (Chapters 1 Through 5) . of Coastal Engineering and the SPM, page ; II —The Coastal Area, page ;.
Selecti on of Type. Plants should be cleaned of most dead vegetation and trimmed to a length of about 50 centimeters 20 inches to facilitate mechanical transplanting. At Haulover Beach Park the planprovided a level berm 15 meters wide at elevation 3 meters above MLW withnatural slopes. For most of the Redondo Beach project it was possibleto excavate to to meters to feet with a cutback of 6 to 9meters 20 to 30 feet. Core Banks, North Carolina Sea oats dune.
The joint of the shiplap type provides a mechanical interlock with adjacent blocks. There are two types of revetments: Dimensions and conditions. This is true for the quarrystone or riprap revetment and to a lesser extent for the interlocking concrete block revetment. Three structural types of bulkheads concrete. Walls of soldier beams and lagging have also been used at some sites. Excessive scouring can endanger the stability of the wall. When vertical or nearly vertical bulkheads are constructed and the water depth at the wall is less than twice the anticipated maximum wave height.
Rubble-mound seawall typical stage placed. Bulkheads are generally either anchored vertical pile walls or gravity walls. A rigid concrete revetment provides excellent bank protection..
Virginia Beach. Virginia Mar. Steel A splash apron may be added next to coping chonnel to Dimensions and details to be determined by particular site conditions reduce damage due to overtopping. Steel sheet-pile bulkhead.
Massachusetts photo. Nantucket Island. Timber sheet-pile bulkhead. Figure New Jersey Sept. Concrete revetment. Maryland before photo. Pioneer Point. Chesapeake Bay. Maryland Topsoil and Seed 0. Grovel BlonKet 0. Quarrystone revetment. Concrete Cap 1. Interlocking concrete-block. Florida photo. Jupiter Island. Interlocking concrete-block revetment. The of type 2.
Selection of Structural Type. Maryland Finished Grade i Major considerations for selection of a structural type are as follows: These are the hopper dredge with pump-out capability and the hydraulic pipeline dredges.
Availability of Materials. Section III. Wave exposure may control the selection of both the structural type and the details of design geometry. This factor is related to construction maintenance costs as well as to structural type. Army Corps of Engineers a. Planning analysis for a protective beach is described in Chapter 5. One of the earliest uses of a hydraulic pipeline dredge in an exposed high-wave energy offshore location was at Redondo Beach.
A discussion of the above dredges and their application to beach nourishment is presented by Richardson and the U. This dredge was held in position by cables and anchors rather than spuds and used a flexible suction Because of wide variations in the initial cost and maintenance costs.
Two basic types of floating dredges exist that can remove material from the bottom and pump it onto the beach. The best structure is one that provides the desired protection at the lowest annual or total cost. Foundation conditions may have a significant a. Random stone or some type of flexible not suitable stone or geotextile filter could be used on a soft structure using a mat sheet-pile structure might be used under although a cellular-steel bottom.
In areas of severe wave action. Foundation Conditions. This has resulted in specially equipped dredges and new dredging techniques. If materials are not available near the construction site. Exposure to Wave Action. The two primary methods of placing sand on a protective beach are by land-hauling from a nearby borrow area or by the direct pumping of sand through a pipeline from subaqueous borrow areas onto the beach using a floating dredge.
Cost promise may have to be made or a lesser degree of protection provided. California in see Ch. Hydraulic pipeline dredges are better suited to sheltered waters where the wave action is limited to less than 1 meter 3 feet but many of the recent nourishment projects have used an offshore borrow source. Where waves are high. Malaga Cove. This method was tested successfully in at Sea Girt. Borrow sources in bays and lagoons may become depleted.
Florida Cape Canaveral to Palm Beach. Dredges with a rigid ladder and cutterhead were used on beach fills at Pompano Beach and Fort Pierce.
Texas Cape May. Region Palm Beach to Miami. It is now necessary to place increased reliance on offshore sources. New Jersey South Lake Erie. Equipment and techniques are currently capable of exploiting offshore borrow sources only to a limited extent. The choice of borrow method depends on the location of the borrow source and the availability of suitable equipment.
Table Sand from offshore sources is frequently of better quality for beach fill because it contains less finegrained sediments than lagoonal deposits. New Jersey Mauriello. After Some hopper dredges are now available with pump-out capability. CERC reports on the geomorphology.
As offshore borrow areas in the immediate vicinity of protective beach projects become scarce. Army Engineer District. As previously mentioned. For planning. Florida see Ch. Subsequent erosion south of Carolina Beach Inlet and accretion north of the jetty at Masonboro Inlet. Exi s ting Protective Beaches. This estimate assumed that 40 percent of the borrow material was finer in size characteristics than the existing beach material. North Carolina. North Carolina Vallianos.
Redondo Beach. Carolina Beach. The long-term average annual deficiency in material supply for the area was estimated in the basic report at about 10 cubic meters per linear meter 4 cubic yards per linear foot of beach.
Figures to illustrate details of these projects with before-andTable presents a fairly complete listing of beach restoraafter photos. Texas U. A protective beach was part of the a. The predominant direction of longshore transport is from north to south. This conclusion was based on southerly growth of an offshore bar at Carolina Beach Inlet and on shoaling at Cape Fear.
Restoration and widening of beaches have come into increasing use in Examples are Corpus Christi Beach. The method of Krumbein and James was considered for determining the volume of fill to be placed. Beach Inlet. New York Nerseslan. Army Engineer recent years. This estimate was based on the rate of loss from to Carolina Wrlghtsvllle Beach and Carolina Beach. Protective beach. Corpus Christi.
Wrightsville Beach. June Sixteen years after restoration 5 5 10 mi Figure New York. Rockaway Beach. In April The fill consisted of a dune having a width of 7. This resulted in an excess of 1. Using the beach as the native beach. Initial adjustments were expected based on the use of a fill factor of 2.
In the first 2 years. Figure shows the before-and-af ter conditions of the beach. By the end of the second year. Although samples taken from the beach after construction may not be entirely indicative of the characteristics of the native sand.
Following construction. During the period Samples taken from the original borrow material and from the active beach profile in May were therefore used to estimate the amount of material lost from the original fill as a result of the sorting action.
Using the older method of Krumbein and James Although this loss was about 43 percent of the total original fill placed. Beach changes resulted in a 25meter foot recession of the high water line HWL and the loss of the horizontal berm of the design profile.
The erosion along the southern 3. Because the native beach material was not adequately sampled to develop the characteristics of the grain-size distribution. The shoreline and the loss of emergency fill stable. In the first 2 years after the initial placement of The rate of shoreline recession dropped to 1.
Survey records from to reported in the original project report show that the average annual recession rate was about 0. By March During the periods April to April and April to April the shoreline receded 20 and 5 meters 67 and 15 feet. The north end of Carolina emergency measures were taken. Rapid recession of the Carolina Beach shoreline during the first 2 years was a result of the profile adjustment along the active profile which terminates at depths between -7 and -9 meters and feet MLW.
April to April The photo in Figure shows the condition of Carolina Beach in The view is facing southward from the northern fishing pier approx An analysis of the core samples verified an offshore sand source of acceptable quantity and quality. An additional 1. A meter 1. Work on the southern section was completed in May An authorized beach restoration project at Redondo Beach. The first stage. This was followed up by the placement of Los Angeles.
This work was scheduled for spring Progressive erosion along the north end of the project and the occurrence two "northeasters" during December resulted in the partial destruction and condemnation of about 10 homes immediately south of the southern end of the seawall.
This feet southward.
In the second stage. This source covered an area 2. The availability of sand below the 9-meter contour immediately seaward of the project was investigated in two stages. Non-Federal interests placed large sandfilled nylon bags emergency protection devices along meters feet of the shoreline to prevent any further damage to upland property. California photos courtesy of Shellmaker Corporation The contractor used a modified centimeter-diameter 16inch hydraulic pipeline dredge with a water.
Although the water. A contract was awarded to obtain the sand from the ocean source. The offshore sand was considered an excellent source of material for beach replenishment. Several land sources were also investigated and found suitable in quantity and quality for the project. The median diameter of the beach sand was 0. Map of protective beach. As the beach fill rubber hose. A substantial reduction in beach width occurred during the first year. The force to cutting combination head that provided both well.
The dredge was held in position with its beam to the sea by an arrangeOn the end of the dredge ladder was a ment of the stern and bowlines.
By alternating between the two advanced. No additional maintenance material of the fill material at Redondo Beach. The system consisted The fill was accomplished by a double-pipe system. The sand slurry was transported ashore through a combination pontoon and The pontoon line was a centimeter-diameter pipe supported submerged line. This area is subject to high-energy waves with These waves can quickly exceed the operating little advance warning. Of particular interest in this project is the use of a pipeline dredge in a high wave energy coastal area.
The submerged steel pipeline was in meter lengths by steel pontoons. As pipeline that was towed to the next discharge the pipeline filled and sank to the bottom. In July Florida U. The plan called for an initial placement of The experience gained on this project and the hopper-dredge operation at Sea Girt.
During this time. The project includes about The position of the borrow zone. NourThe estimated ishment would be scheduled at 5-year intervals.
At Haulover Beach Park the plan provided a level berm 15 meters wide at elevation 3 meters above MLW with natural slopes. Because of the project size. This was the first project in the United States where a hydraulic pipeline dredge was operated successfully in a high wave energy coastal Although highly successful in this project. In addition. The nourishment requirements are estimated to be at the annual rates of View of protective beach facing north from 48th Street. Dade County.
Project area depicting five phases of beach restoration. A booster pump was necessary because of the long distance between the borrow and the fill areas and the utilization of the rock screening device.
The phase IV contract called for placement of 1. The phase II contract covered the 2. The screened beach-fill material was then punjped to the dredge slurry. The phase III contract involved the placement of 2.
The dredging associated with this contract began in May and was completed Approximately 1. June The phase V contract called for the placement of 1. Sensibar Sons. The remaining sections beach included under this contract had been placed. To accomplish this. Work began on material was placed. The contract was completed winter season and was again resumed in July County has purchased one of these machines and also two smaller versions for conducting an active beach maintenance program.
When wave conditions exceeded 1 to 2 meters. Several methods are being used to relieve this problem. For these reasons. Dade designed for clearing stones. Shells and coral fragments gravel size to cobble fines generally present.
The silty fines size present The quartz is usually of fine-grain size while the acceptable limits. One problem area encountered during the project was the existence of a small percentage usually less than 5 percent of stones in the beach-fill material.
The derived shell and coral fragments. The average daily yield was about The sand size ranges from fine to coarse.
During this phase a June and was 80 percent completed by December The phase IV contract requirement to remove all stones larger than 2. The water depth in the borrow area is 12 to 18 meters 40 to 60 feet and the excavation was accomplished primarily by either centimeter 27inch diesel-electric dredges or by an centimeter 32 inch electric dredge These large dredges excavate material at depths running off land-based power.
Until the phase IV contract. Sand Movement. The completed part of the beach has functioned effectively for years. Foredune system. Winds with sufficient velocity to move sand particles deplete the exposed beach by transporting sand in the following three ways.
Padre Island. They function as a reservoir of sand nourishing VI and Ch. Plastic fabrics have been investigated for use as sand fences Savage and Woodhouse. Jagschitz and Bell. Various mechanical methods. Current dune construction methodology is given by Knutson and Woodhouse In this manner. Foredunes are often created and maintained by the action of the beach grasses. Although most sand particles move by saltation.
As the dune builds. The following are guidelines and suggestions based on these tests and observations recorded over the years: Open and closed areas should be smaller than 5 Sand particles are carried by the wind in a series of b Saltation short jumps along the beach surface. Core Banks. Larger particles remain on the Medium-sized particles form the foredunes. Surface Creep as a result of wind particles c: Particles are rolled or bounced along the beach forces or the impact of descending saltating These natural transportation methods effectively sort the original beach material.
Smaller particles are removed from the beach and dune area.
Although dunes can be built by use of structures such as sand fences. Foredunes may be destroyed by the waves and high water levels associated with severe storms or by beachgrass elimination induced by drought. Dune building begins when an obstruction on the beach lowers wind velocity causing sand grains to deposit and accumulate.
Field tests of dune building with sand fences under a variety of conditions have been conducted at Cape Cod. Relatively inexpensive. Fence construction with side spurs or a zigzag alinement does not increase the trapping effectiveness enough to be economical Savage.
The dune slopes will The dune will be about as high as the fence. Lateral spurs may be useful for short fence runs of less than meters feet where sand may be lost around the ends Woodhouse. With sand moving on the beach. Efforts have been most berm crest to be away from frequent wave attack. Erecting snow-type sand fencing. The standard wooden snow fence appears to be the centimeters in width.
It need not be The fence should parallel the shoreline. Fences may remain empty for months following installation. Snow-type sand fencing filled to capacity. Usually where appreciable sand is moving. In order to take full advantage of the available sand. The dune may either landward or seaward in this way if the dune is i Accumulation of sand by fences is not constant and varies widely with the location.
Single rows of fencing are usually the most cost-effective. Sand accumulation by a series of four single-fence lifts. North Carolina Savage and Woodhouse. Junk cars mar the beauty of a beach and create a safety hazard. Outer Banks. They are more expensive and less effective than fencing Gage.
Harvesting and Processing. To reduce weight during transport. Most plants may be stored several weeks if their bases are wrapped with wet burlap. Department of Agriculture. Table is a regional summary of the principal plants used for dune stabilization.. Kidby and Oliver. Brown and Hafenrichter Sand fence deterioration due to exposure and storms. Woodhouse and Hanes. The plants should be dug with care so that most roots remain attached to the plants.
The clumps should be separated Into transplants having the desired number of culms stems. Survival of sea oats is reduced if stored more than 3 to 4 days. Plants should be cleaned of most dead vegetation and trimmed to a length of about 50 centimeters 20 inches to facilitate mechanical transplanting. Celsius may be at to 3 storage 1 in cold and held while dormant winter used in late spring plantings.
Steep and irregular slopes see Fig. Table by slopes must be planted beach grasses. Transplanting and Planting for recommended is Transplanting developed. A mechanical transplanter mounted on a tractor is successful stabilization. Plants dug Plants may be kept longer if refrigerated. Mechanical transplanting of American beachgrass. Rates of fertilizer are provided in Table Where field tested. Species Planting and fertilization summary by regions. Only American beachgrass should be routinely fertilized the second growing season with 56 kilograms per hectare 50 pounds per acre of fertilizer nitrogen in April and again in September.
Other species should be fertilized if overall This in turn provides greater sand-trapping capacity. Beach-grass seeds are not generally available from commercial sources. Seeding is practical only when protection can be provided from eroding and drying winds by mulching or frequent irrigation. American zone Nags Head. South Campbell and Fuzy. During fertilization.. Plant spacing and sand movement must be considered e. Planting Width.
Deteriorating stands of American exposure to sandblasting is reduced. In general. American beachgrass typically spreads outward by rhizomatous underground growth.
South of Virginia. The spacing and pattern should be determined by the characFunctional planting teristics of the site and the objective of the planting.
Plantings a species cold. The following example illustrates the interrelationship of the planting American beachwidth.
Seaward movement of the dune crest in North Carolina stem When little sand is moved for trapping. The slow natural invasion 6 to 10 years of sea oats to American beachgrass dunes Woodhouse. Thus a dune can build toward the beach from the original planting. North Carolina Figure shows an experiment to test the feasibility of increasing the dune base by a sand fence in a grass planting.
This phenomenon has not occurred with the North Carolina Fig. Texas Fig. The fence was put in the middle of the meter-wide foot planting. The seaward edge of the dune trapped nearly all the beach sand during onshore winds. Some sand was trapped while the American beachgrass began its growth.
The landward edge of the dune trapped the sand transported by offshore winds blowing over the unvegetated area landward of the dune. The rate of spread of sea oats is considerably less. It is essential that part of the strip be planted at a density that will stop sand movement sometime during the first year.
Another meterwide strip may be added immediately seaward 4 to 5 years later if a base of 30 meters has not been achieved by natural vegetative spread. The initial planting should be a strip 15 meters wide. The rates are averaged over a number of profiles under different planting conditions.
If a natural vegetation or foredune line is not evident. Foredune restoration is most likely to succeed when the new dune coincides with the natural vegetation line or foredune line.
Sea oats dune. Table presents comparisons of annual sand accumulation and dune growth rates. Where beach recession is occurring. The European beachgrass annual trapping rate on Clatsop Spit. European beachgrass 0. Mass American beachgrass American beachgrass Sea oats and 0.
The storm surge at the location of the experimental dune building site has been estimated to be between 2 and 3 meters 8 and 10 feet Although a substantial part of the dunes had eroded. Small plantings of 10 meters square feet square of American beachgrass that trap sand from all directions have trapped as much as 40 cubic meters per linear meter 16 cubic yards per linear foot of beach in a period of 15 months on Core Banks.
The survival rate of transplants may be increased by C ost Fa ctors. While this figure may exaggerate the volume of sand available for dune construction over a long beach. The average annual vertical crest growth. This increase in survival rate It is does not offset the increase in cost to harvest multiculm transplants. Commercial nurseries are now producing American Some States provide and European beachgrasses.
These rates are much less than the rates of vigorous grass plantings. Using a mechanical transplanter.
The Soil Conservation Service routinely compiles a list of commercial producers of plants used for soil stabilization. SAND BYPASSING The construction of jetties or breakwaters to provide safe navigation conditions at harbor entrances or tidal inlets along sandy coasts usually results in an interruption of the natural longshore transport of sand at the entrance or inlet.
For example. This suggests that dune growth in most areas is limited by the amount of sand transported off the beach rather than by the trapping capacity of the beach grasses. Nursery production of transplants is recommended unless easily harvested Nursery plants are easier wild plants of quality are locally available. The resulting starvation of the downdrift beach can cause Descriptions of selected plants.
Both were located at South Africa U. During the next 3 years than kilometer downcoast. The Salina Cruz plant breakwaters on the updrift sides of harbor entrances. F lorida Watts.
Mexico U. Army Beach Erosion Board. The plant consisted of a centimeter 8-inch suction line. South Lake Worth Inlet. In the past. Sou th Lake Worth Inlet. The dredged The jetties caused erosion of the channel was stabilized by entrance jetties. Fixed bypassing plants have been used at South Lake Inlet. Several techniques of mechanical sand bypassing have been used where The most suitable method is jetties and breakwaters form littoral barriers.
Army Corps of Engineers. Jones and Mehta. Virginia type V inlet improvement. Florida both type I inlet improvements. The five types of littoral barriers for which sand transfer The basic methods of systems have been used are illustrated in Figure Fixed Bypassing Plants. The original plant.
The resumed No apparent cient littoral drift reaching the plant. Lake Worth Inlet. The channel immediately began to shoal with littoral material. After removal of the groin. The original intent of the groin was to prenorth of the plant was removed.
In addition to the fixed bypassing plant. A meter section of the submerged discharge line can be removed The system was during maintenance dredging of the navigation channel. Rudee Rudee Inlet. A complex emergency plant to a depth of The average annual amount of bypassed material between and was In the groin to the Virginia Richardson.
This plant yielded an average discharge of 75 The remainder of the littoral drift cubic meters cubic yards per hour. The Design capacity was about cubic meters cubic yards per hour. The estimated discharge is cubic meters cubic yards of sand per During the period to Jones b. In the north jetty was extended and the bypassing plant was moved The current plant consists of a pump.
In addition to the fixed plant. Florida Zermuhlen. Fixed bypassing plant. Florida Fig. Florida Since late the system has been owned and operated by local authorities who estimate the pumping capacity at 38 cubic meters 50 cubic yards The per hour and the effective pumping time at about hours per month. Using these two estimates as limits and assuming yearmonths of operation. Floating Bypassing Plants.
Inlet sand trap locations at Jupiter b Type II: Sand bypassing has been achieved by floating plants at all five types of Those operations that are discussed and illuslittoral barriers Fig. During the first 6 months of operation. By California Fig. This enables the pumps to reach a large area of the cables from the shore. The fixed plant was destroyed by a storm pipeline dredge was added in This system consists of two jet pumps attached by flexible rubber hoses the steel pipes.
The weir jetty impoundment basin was never fully dredged initially. Jettied inlet — location — at Port Hueneme. Rudee Inlet. Type V: Murrells Inlet. New York Fig. Californ ia Savage. Port Hueneme. Jettied inlet and offshore c Type III: Channel Islands Harbor. Oceanside Harbor.
Herron and Harris. East Pass. Ventura Marina. In sand impounded by the updrift jetty was pumped across the harbor South Carolina.
Perdido Pass. North Carolina Fig. Florida channel dredging. Sand bypassing. Alabama Fig. Masonboro Inlet. Type III: Boca Raton Inlet. Jupiter Inlet. Florida Jones and Mehta. Sebastian Inlet. Photo was taken just after 2.
Santa Barbara. Fire Island Inlet. Hillsboro Inlet. Direction of Net Longstiore Tronsport Sand bypassing. Ponce de Leon Inlet. The unique entrance to the downdrift beach through a submerged pipeline. After completing the phase I dredging see Fig. Maintenance dredging of the inlet has been performed since the early ' s.
Channel Islands Harbo r. Since it was necessary to close the dredge entrance channel to prevent erosion of the protective strip. In dredging of the sand trap.
Since most maintenance dredging of The general plan is shown in Figure Between and dredging of the inlet produced approximately The Since the initial dredging. The sand-bypassing dredging operation transfers sand a across both the Channel Islands Harbor entrance and the Port Hueneme entrance to the downdrift beaches U.
It mound structure with a crest elevation 4. Ca lifornia Herron and Harris. Land equipment excavated a hole in the beach. The type II sand Jupiter Inlet. Jupiter Inlet is an improved natural inlet located in the northern part Palm Beach County.
This b.. Surveys showed that this sand was not moved to the beach. The next bypassing was done in by a pipeline dredge. This has because the sides of the channel are cut into rock formations. The top elevation of the wall is 3 meters 10 feet above MLLW. The trap was enlarged to 15 hectares 37 acres in when In This initial dredging produced This feeder beach was successful in reducing erosion downdrift of the harbor.
The breakwater resulted in accretion on the updrift side west and erosion on the downdrift side east. In the city of Santa Barbara decided not to remove the shoal at the seaward end of the breakwater because it provided additional protection for the inner harbor.
Between and has taken place in the sand trap area see Fig. A total of This inlet differs from most inlets on sandy coasts tion occurred in In a sand trap was excavated in a region where the inlet widens and the currents decrease sufficiently to drop the sediment load see Fig.
In order to reduce the overwashing of the shoal. Since that time an estimated Bypassing was started in by hopper dredges which dumped about A part of this This caused the littoral drift to move laterally along the shoal until it was deposited adjacent to and into the navigation channel. A small floating dredge was used to maintain the channel and the area leeward of the shoal. The Santa Barbara sand-bypassing operation was necessitated by the construction of a meter 2.
Wave and weather conditions limited the dredging operations to 72 percent of the time. Without the south jetty. It is projected that It is expected that the south jetty will prevent the navigation channel from migrating into the deposition basin.
In the south jetty see Fig. The jetty consisted of an inner section the north jetty and deposition basin. Rayner and Magnuson. Southward-moving littoral sand is washed across the reef and settles in the sheltered impoundment area where it is dredged and bypassed to the south beaches. A centimeter hydraulic dredge. This inlet is the Army Engineer District. The rock reef and jetties form what is called a sand spillway. The total quantity of sand bypassed between and was This sand-bypassing operation is the origianl the basis for the type V bypassing concept.
The north and south jetties were rebuilt and extended during An improvement to southern limit of Wrightsville Beach. Flori da Hodges.
North Carolina Magnuson. The elevation of the weir section about midtide level was established low enough to pass the littoral drift. Hillsboro Inlet is a natural inlet in Broward County. The basin was this location where the mean tidal range is about 1. The first redredging of the basin occurred in This material formed into bars that reduced in size as they moved shoreward.
While this method provides some nourishment and protection to the beach. Three shorter trestles were built north of the inlet where the sand was dumped on the beach. This weir-jetty project was completed in h. Land-based vehicles were used in a sand-bypassing operation at Shark River Inlet.
The diurnal tidal range is about 0. These figures indicate that approximately In Hurricane Frederic dislodged three sections of the concrete sheet piling in the weir and cut a channel between the weir and the beach. Several other methods of bypassing sand at littoral barriers have been tested. Augustine Beach. This method is limited by the fuel expense and by the requirement for an easy access across the inlet and to the loading and unloading areas.
The project consisted of removing Perdid o Pass. A test of this method was conducted at New River Inlet. The structural types of revetments used for coastal protection in exposedand sheltered areas are illustrated in Figures to There are twotypes of revetments: A rigid concrete revetment provides excellentbank protection, but the site must be dewatered during construction so thatthe concrete can be placed. A flexible structure also provides excellent bankprotection and can tolerate minor consolidation or settlement withoutstructural failure.
This is true for the quarrystone or riprap revetment andto a lesser extent for the interlocking concrete block revetment. Both thearticulated block structure and the quarrystone or riprap structure allow forthe relief of hydrostatic uplift pressure generated by wave action. Theunderlying geotextile filter and gravel or a crushed-stone filter and beddinglayer relieve the pressure over the entire foundation area rather than throughspecially constructed weep holes.
Interlocking concrete blocks have been used extensively for shore protec-tion in Europe and are finding applications in the United States, particularlyas a form of relatively low-cost shore protection. Typically, these blocksare square slabs with shiplap-type interlocking joints as shown in Figure The joint of the shiplap type provides a mechanical interlock withadjacent blocks.
Virginia Beach, Virginia Mar. Concrete slab and king-pile bulkhead, Nantucket Island, Massachusetts photo, courtesy of U. Steel A splash apron may be added Dimensions and details to benext to coping chonnel to determined by particular sitereduce damage due to overtopping. Steel sheet-pile bulkhead, Avalon, New Jersey Sept. Figure Timber sheet-pile bulkhead. Concrete revetment, Chesapeake Bay, Maryland Topsoil and Seed 0.
Quarrystone revetment. Concrete Cap1. Interlocking concrete-block, revetment. Cedarhurst, Maryland Finished Grade i Interlocking concrete-block revetment.
However, prototypetests at the U. Army Engineer Waterways Experiment Station Coastal Engineer-ing Research Center CERC , on blocks having shiplap joints and tongue-and-groove joints indicate that the stability of tongue-and-groove blocks is muchgreater than the shiplap blocks Hall, An installation of the tongue-and-groove interlock block is shown in Figure Selection of Structural Type.
Major considerations for selection of a structural type are as follows: Foundation Conditions. Foundation conditions may have a significantinfluence on the selection of the type of structure and can be considered fromtwo general aspects. First, foundation material must be compatible with thetype of structure.
A structure that depends on penetration for stability isnot suitable for a rock, bottom. Random stone or some type of flexiblestructure using a stone mat or geotextile filter could be used on a softbottom, although a cellular-steel sheet-pile structure might be used underthese conditions.
Second, the presence of a seawall, bulkhead, or revetmentmay induce bottom scour and cause failure. Thus, a masonry or mass concretewall must be protected from the effects of settlement due to bottom scourinduced by the wall itself. Exposure to Wave Action. Wave exposure may control the selection ofboth the structural type and the details of design geometry. In areas ofsevere wave action, light structures such as timber crib or light ripraprevetment should not be used.
Where waves are high, a curved, reentrant facewall or possibly a combination of a stepped-face wall with a recurved upperface may be considered over a stepped-face wall. Availability of Materials. This factor is related to constructionand maintenance costs as well as to structural type.
If materials are notavailable near the construction site, or are in short supply, a particulartype of seawall or bulkhead may not be economically feasible. A cost com-promise may have to be made or a lesser degree of protection provided. Costanalysis includes the initial costs of design and construction and the annualcosts over the economic life of the structure. Annual costs include interestand amortization on the investment, plus average maintenance costs.
The beststructure is one that provides the desired protection at the lowest annual ortotal cost. Because of wide variations in the initial cost and maintenancecosts, comparison is usually made by reducing all costs to an annual basis forthe estimated economic life of the structure. The two primary methods of placing sand on a protective beachare by land-hauling from a nearby borrow area or by the direct pumping of sandthrough a pipeline from subaqueous borrow areas onto the beach using afloating dredge.
Two basic types of floating dredges exist that can removematerial from the bottom and pump it onto the beach. These are the hopperdredge with pump-out capability and the hydraulic pipeline dredges. Adiscussion of the above dredges and their application to beach nourishment ispresented by Richardson and the U.
Army Corps of Engineers a. Hydraulic pipeline dredges are better suited to sheltered waters where thewave action is limited to less than 1 meter 3 feet ,but many of the recentnourishment projects have used an offshore borrow source.
This has resultedin specially equipped dredges and new dredging techniques. One of the earliest uses of a hydraulic pipeline dredge in an exposedhigh-wave energy offshore location was at Redondo Beach, Malaga Cove,California in see Ch. This dredge was held inposition by cables and anchors rather than spuds and used a flexible suction Dredges with a rigid ladder and cutterhead were used on beachfills at Pompano Beach and Fort Pierce, Florida, where the borrow area wasoffshore on the open ocean.
Some hopper dredges are now available with pump-out capability. Afterloading at the borrow site normally offshore , the hopper dredge then movesclose to the fill site and pumps sand from the hoppers through a submergedpipeline to the beach.
This method is particularly applicable to sites wherethe offshore borrow area is a considerable distance from the beach restorationproject. Army Engineer District, Philadelphia, As off-shore borrow areas in the immediate vicinity of protective beach projectsbecome scarce, the use of hopper dredges may become more appropriate.
The choice of borrow method depends on the location of the borrow sourceand the availability of suitable equipment. Borrow sources in bays andlagoons may become depleted, or unexploitable because of injurious ecologicaleffects. It is now necessary to place increased reliance on offshore sources. CERC reports on the geomorphology, sediments, and structure of the InnerContinental Shelf with the primary purpose of finding sand deposits suitablefor beach fill are summarized in Table Hobson presents sedimentcharacteristics and beach-fill designs for 20 selected U.
Sand from offshore sourcesis frequently of better quality for beach fill because it contains less fine-grained sediments than lagoonal deposits. Equipment and techniques arecurrently capable of exploiting offshore borrow sources only to a limitedextent; and as improved equipment becomes available, offshore borrow areaswill become even more important sources of beach-fill material.
Exi s ting Protective Beaches. Restoration and widening of beaches have come into increasing use inrecent years. Figures to illustrate details of these projects with before-and-after photos.
Table presents a fairly complete listing of beach restora-tion projects of fill lengths greater than 1. In , beach widening and nourishmentfrom an offshore source was accomplished by a pipeline dredge at RedondoBeach, California.
As previously mentioned, this was one of the firstattempts to obtain beach fill from a high wave energy location exposedoffshore using a pipeline dredge see Ch. The largest beachrestoration project ever undertaken in the United States was recentlycompleted in Dade County, Florida see Ch.
Carolina Beach, North Carolina. A protective beach was part of theproject at Carolina Beach Figs. The projectalso included hurricane protection; however, the discussion of protectivebeach planning in this chapter includes only the feature that would have beenprovided for beach erosion control.
The report on which the project is basedwas completed in U. Army Engineer District, Wilmington, , and theproject was partly constructed in The predominant direction of longshore transport is from north tosouth. This conclusion was based on southerly growth of an offshore bar atCarolina Beach Inlet and on shoaling at Cape Fear, 19 kilometers 12 miles south of Carolina Beach. Subsequent erosion south of Carolina Beach Inlet andaccretion north of the jetty at Masonboro Inlet, about 14 kilometers 9 miles north of Carolina Beach, have confirmed the direction.
The long-term averageannual deficiency in material supply for the area was estimated in the basicreport at about 10 cubic meters per linear meter 4 cubic yards per linearfoot of beach. This estimate was based on the rate of loss from to, from the dune line to the 7-meter foot depth contour. CarolinaBeach Inlet, opened in , apparently had little effect on the shore ofCarolina Beach before ; therefore, that deficiency in supply was con-sidered the normal deficiency without regard to the new inlet.
For planning, it was estimated that 60 percent of the material in theproposed borrow area in Myrtle Sound behind Carolina Beach would becompatible with the native material on the beach and nearshore bottom andwould be suitable for beach fill. This estimate assumed that 40 percent ofthe borrow material was finer in size characteristics than the existing beachmaterial, and therefore would be winnowed due to its incompatibility with thewave climate.
The method of Krumbein and James was considered fordetermining the volume of fill to be placed. However, insufficient sampleswere taken from the foreshore and nearshore slopes to develop characteristicsof the grain-size distribution for the native beach sand.
Protective beach, Corpus Christi, Texas. Protective beach, Wrightsville Beach, North Carolina. Protective beach, Carolina Beach, North Carolina. June Sixteen years after restoration 5 5 10 miFigure Protective beach, Rockaway Beach, New York. Table Beach restoration projects in the United States.
Project Although samples taken from the beach after construction may not beentirely indicative of the characteristics of the native sand, they do repre-sent to some extent the borrow material after it has been subjected to waveaction, presumably typical of the wave climate associated with sorting on thenatural beach. Samples taken from the original borrow material and from theactive beach profile in May were therefore used to estimate the amount ofmaterial lost from the original fill as a result of the sorting action.
Using the beach as the native beach, the standard deviations, a,,and a, , of the borrow and native materials are 1. Using the older method of Krumbein and James , the upper bound of the fill factor was computed to be 2. Because thenative beach material was not adequately sampled to develop the characteris-tics of the grain-size distribution, no further attempt is made to compare theproject results with the procedures described in Chapter 5, Section III,3,c.
In April , approximately 2,, cubic meters 2,, cubicyards of borrow material were placed along the meters 14, feet ofCarolina Beach Vallianos, Figure shows the before-and-af terconditions of the beach.
The fill consisted of a dune having a width of 7. Along the northernmost 1, meters 3, feet of theproject, Fig. Following construction, rapid erosion occurred along the entire length ofthe beach fill.
Initial adjustments were expected based on the use of a fillfactor of 2. This resulted inan excess of 1,, cubic meters 1,, cubic yards of fill beingplaced on the beach to account for the unsuitability of part of the borrowmaterial.
However, the actual rates of change, particularly those evidencedalong the onshore section of the project, were much greater than was origi-nally anticipated considering that all the fill had not been subjected towinnowing by wave action. In the first 2 years, erosion persisted at Carolina Beach along theentire length of the fill.
The erosion along the southern 3, meters 10, feet of the project was less than that along the northern 1,meters 4, feet. During the period , approximately , cubic meters ,cubic yards of the 1,, cubic meters 1,, cubic yards initiallyplaced on the southern 3,meter section moved offshore to depths seaward ofthe 7-meter contour.
Although this loss was about 43 percent of the totaloriginal fill placed, in terms of fill protection, it was as planned consider-ing the suitability of the borrow material. Beach changes resulted in a meter foot recession of the high water line HWL and the loss of thehorizontal berm of the design profile. By the end of the second year, thesouthern 3, linear meters of project was stabilized. In the first 2 years after the initial placement of , cubic meters , cubic yards of fill along the meter northern section of theproject, beach changes were greater than those in the longer, southern sec-tion.
Although about , cubic meters , cubic yards of fill waslost from the active profile, amounting to a percent reduction in the totalinplace fill, this only exceeded the anticipated winnowing loss by about 9percent. By March , the HWL along this section receded 43 meters feet , resulting in the complete loss of linear meters 1, linear feet of original fill and the severe loss of an additional meters 1,feet of fill.
This erosion progressed rapidly in a southward direction andthreatened the more stable southern section of the project.
In March ,emergency measures were taken. The north end of CarolinaBeach was restored by placing about , cubic meters , cubic yards of fill and by building a meter foot groin near the north end. Thegroin was necessary because there was a reversal in the predominant directionof the longshore transport at the north end.
In the next year, approximately, cubic meters , cubic yards of emergency fill eroded, and mostof the shoreline returned to about normal configuration before the emergencywork.
The shoreline immediately south of the groin, for a distance of about meters feet , remained nearly stable, and the loss of emergency fillalong this small segment was about 42 percent less than the loss along theremaining emergency section. Survey records from to reported in the original projectreport show that the average annual recession rate was about 0. Theannual loss of material for the entire active profile was estimated to beabout 10 cubic meters per linear meter 4 cubic yards per linear foot.
During the 2 years following the fill, the effects of shore processeswere radically different from processes determined from historical records. During the periods April to April and April to April the ,shoreline receded 20 and 5 meters 67 and 15 feet , respectively, withcorresponding losses of , and , cubic meters , and ,cubic yards.
In the third year, April to April , a marked changeoccurred in fill response. The rate of shoreline recession dropped to 1. Surveysin indicated that the project was in nearly the same condition as it wasin Rapid recession of the Carolina Beach shoreline during the first 2 yearswas a result of the profile adjustment along the active profile which termi-nates at depths between -7 and -9 meters and feet MLW, as well asnet losses in volume resulting from the natural sorting action displacing thefine material to depths seaward of the active profile.
The foreshore andnearshore design profile slope of 1 on 20 was terminated at a depth of 1. The adjusted project profile of April showsthe actual profile closing at a depth of about 7 meters below MLW, with acharacteristic bar and trough system. Thus, displacement of the initial fillwith the accompanying reduction of the beach design section resulted from a Further protective action was completed on Carolina Beach in December A meter 1,foot rubble-mound seawall was constructed, extend-ing southward from the northern limit of the project.
At the same time, cubic meters , cubic yards of fill, obtained from the sedimentdeposition basin in Carolina Beach Inlet, was placed along the northern meters of the project. This was followed up by the placement of , cubicmeters , cubic yards of fill along the southern meters 11,feet of beach. Work on the southern section was completed in May , andthe beach-fill material was obtained from a borrow area in the Cape FearRiver.
The rubble-mound seawall was extended an additional meters feet southward, with the work being completed in September Thisbrought the total length of the seawall to meters 2, feet. Progressive erosion along the north end of the project and the occurrenceof two "northeasters" during December resulted in the partial destructionand condemnation of about 10 homes immediately south of the southern end ofthe seawall.
Non-Federal interests placed large sandfilled nylon bags emer-gency protection devices along meters feet of the shoreline toprevent any further damage to upland property. During May , , cubic meters , cubic yards of fill fromCarolina Beach Inlet and 76, cubic meters , cubic yards from theAtlantic Intercoastal Waterway was placed on the northern end of the projectas an emergency measure.
Present plans call for placement of 2,, cubicmeters 3,, cubic yards of fill to be obtained from an upland borrowarea adjacent to the Cape Fear River. This work was scheduled for spring The photo in Figure shows the condition of Carolina Beach in The view is facing southward from the northern fishing pier approx-imately the same as Fig.
Anauthorized beach restoration project at Redondo Beach, California, providedanother opportunity to use an offshore sand source see Figs. The availability of sand below the 9-meter contour immediately seawardof the project was investigated in two stages.
The first stage, a geophysicalsurvey with an acoustical profiler indicated that enough sand was availablefor the project. In the second stage, core samples were obtained from theocean by use of a vibrating core-extraction device.
An analysis of the coresamples verified an offshore sand source of acceptable quantity and quality. This source covered an area 2. It would produce1,, cubic meters 2,, cubic yards of sand if it could be workedto a depth 16 meters 52 feet below mean low low water MLLW between the 9-to meter-depth to foot contours. An additional 1,, cubicmeters of sand could be recovered by extending the depth of the excavation to Map of protective beach, Redondo Beach, California.
The median diameter of the beach sand was 0. The offshore sand was considered an excellent source of material forbeach replenishment. Several land sources were also investigated and foundsuitable in quantity and quality for the project. A contract was awarded to obtain the sand fromthe ocean source.
The contractor used a modified centimeter-diameter inch hydraulic pipeline dredge with a water- jet head on the end of a ,meter foot ladder. Although the water- jet technique had been used inexcavating channels, filling and emptying cofferdams, and prospecting forminerals in rivers, its application to dredging in the ocean appears to be Ultimately, the dredge operated in seas up to 1.
Of particular interest in this project is the use of a pipeline dredge in ahigh wave energy coastal area. This area is subject to high-energy waves withlittle advance warning.
These waves can quickly exceed the operatingconditions of the dredge. The dredge was held in position with its beam to the sea by an arrange-ment of the stern and bowlines. On the end of the dredge ladder was acombination head that provided both cutting and suction action. The force tolift the suspended material was provided by a suction pump in the dredge well,assisted by water jets powered by a separate k.
Sand was removed by working the head down to the bottom of the cut andkeeping it in that position until the sandy material stopped running to thehead. The head was then raised, and the dredge would pivot about 12 meters 40 feet to the next position in the cutting row, where the process would berepeated. The dredge could cut a row 76 meters feet wide. At thecompletion of a row, the dredge was moved ahead on its lines about 12 metersfor the next row cut.
For most of the Redondo Beach project it was possibleto excavate to to meters to feet with a cutback of 6 to 9meters 20 to 30 feet. This is desirable for high production because itminimizes moving and swinging of the dredge. The sand slurry was transported ashore through a combination pontoon andsubmerged line.
The pontoon line was a centimeter-diameter pipe supportedin meter lengths by steel pontoons. The submerged steel pipeline wasjoined to the floating line by a flexible rubber hose. As the beach fillprogressed, the submerged line was moved by capping the shore end of thedischarge and then pumping water out of the line. This created a floatingpipeline that was towed to the next discharge position.
As pumping resumed,the pipeline filled and sank to the bottom. The fill was accomplished by a double-pipe system. The system consistedof a yoke attached to the discharge line and, by use of a double-valvearrangement, the discharge slurry was selectively distributed to either onepipe or the other, or to both pipes simultaneously. By alternating between the two discharge lines, the beach width of60 meters feet was built to the full cross section as they advanced. The final placement see Fig. Between and 11,cubic meters 4, and 15, cubic yards per day were placed on the beach,averaging 6, cubic meters 8, cubic yards per day.
The work wascompleted in October A substantial reduction in beach width occurred during the first year. More material was transported offshore. While theseinitial changes did reduce the beach width, they also increased beach stabil-ity, and the rate of retreat dropped significantly in subsequent years. Arecent study Hands, in preparation, documents the long-term stabilityof the fill material at Redondo Beach.
No additional maintenance materialhas been placed on the beach to date , and after 12 years much of the During this time, the artificial borrow pit, which parallels the beach about meters 1, feet from shore, has shoaled to about half its original depth with sand moving infrom deeper water.
The position of the borrow zone, just seaward of the 9-meter MLLW contour, was thus well chosen for this site as it is beyond thezone of cyclic onshore and offshore sand transport of beach material. Largevolumes of sand are transported offshore at Redondo Beach during storms andparticularly during the winter season, then returned by natural onshore trans-port during summer swells. The offshore borrow pit is far enough seaward sothat it does not trap this beach sand or interfere with its cyclic exchangebetween the beach and the nearshore profile.
This was the first project in the United States where a hydraulicpipeline dredge was operated successfully in a high wave energy coastalarea. Although highly successful in this project, this procedure has a —critical limitation the necessity for a nearby harbor.
Army Engineer District, Philadelphia, providedthe techniques for many subsequent beach nourishment projects that utilizedoffshore sand deposits.
Dade County, Florida U. Army Engineer District, Jacksonville, The Dade County Beach Erosion and Hurricane Protection Project, whichincludes Miami beach, was designed to provide beach nourishment and stormsurge protection for one of the most highly developed beach-front areas onthe Atlantic coast.
Erosion, greatly accelerated by manmade structures andmodifications, had reduced the beach along this part of the barrier island tothe point where ocean waves often reached the many protective seawalls builtby hotel and private property owners. The project includes about The plan called for an initial placement of This placement provided adune 6 meters wide at 3. At Haulover Beach Park the planprovided a level berm 15 meters wide at elevation 3 meters above MLW withnatural slopes.
In addition, the project provides for periodic beach nourish-ment to compensate for erosion losses during the first 10 years following theinitial construction. The nourishment requirements are estimated to be at theannual rates of , cubic meters , cubic yards of material. Nour-ishment would be scheduled at 5-year intervals, or as needed.