US20020119009A1

US20020119009A1 - Shoreline reclamation apparatus and method

Info

Publication number: US20020119009A1
Application number: US10/011,255
Authority: US
Inventors: Wallace Hilliard; Jeffrey Allain
Original assignee: Parker Beach Restoration Inc
Priority date: 2000-12-01
Filing date: 2001-12-03
Publication date: 2002-08-29

Abstract

A porous groin and method of use for restoring an eroding shoreline. The porous groin has at least two vertical supports placed in the seabed within the eroding water flow and a porous elongated barrier is attached to the supports such that the barrier is at least partially within the sediment-laden eroding water flow of the shoreline with the water flow passing through at least a portion of the barrier. The endmost seaside support is anchored to the seabed and the barrier has a lower edge which is retained proximate to the seabed. The porous barrier then causes the accretion of suspended solids within the water flow thereby restoring the eroding shoreline.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Serial No. 60/250,628, filed on Dec. 1, 2000.[0001]

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to apparatuses and methods to restore or prevent erosion of shorelines and beaches. More particularly, the present invention relates to an apparatus and method for shoreline reclamation that uses a plurality of stanchions and a porous barrier fastened to the stanchions to create a temporary structure that is placed in the water flow, proximate to the shoreline, and the structure causes accretion of sediment suspended in the water flow.

2. Description of the Related Art

Shorelines on bodies of moving water, such as rivers and oceans, will erode from natural processes removing material from the shoreline. This erosive process is sometimes referred to as “scour, ” and the natural processes of movement of material along a coastal shoreline are referred to as littoral processes. In scour, the moving water suspends the material at one location in the flowing water and then redeposits the material at some other location. Many factors specific to the particular shoreline and water velocities can enhance erosion phenomenon.

One significant factor is the consistency of the material comprising the shoreline. A sandy beach is easily eroded by a slow and steady stream of water, and can be quickly eroded in very turbulent and fast moving water such as the seas associated with a major storm. Conversely, shoreline comprised of mostly rocks or larger sediment will be much less susceptible to erosion.

Shoreline erosion is a serious problem because most of the urban areas of the world are ports having urban development right up to the shoreline. There are often structural improvements present at and near the shoreline, such as private beach homes, hotels, bridges, retaining structures, and the like, and shoreline erosion progressively undermines the foundations thereof and threatens the physical integrity of the structures over time. There are also many regions with beach tourism as their main industry, and thus, beach erosion can cause these regions significant economic harm by removing the main tourist attraction.

There have been many devices and methods of hydraulic and earth engineering employed in the attempt to preserve shorelines or other areas subject to the erosive influence of moving water. The main method of combating erosion is to simply renourish an eroding beach with a fresh supply of dredged sand. This method has many problems associated with it however. The dredged sand often does not match the existing color of sand on the beach and diminishes the aesthetic appearance of the beach. The dredged sand can also contain rocks or other solid objects that can hinder water sports such as swimming or surfing, and can hurt the bare feet of waders upon the renourished beach.

Other methods to prevent shoreline erosion fortify the eroding shoreline with blocks, cement and the like so as to form a prophylactic layer over the region of the shoreline that would otherwise be subject to the erosive effects of the moving water. However, due to the weight and bulk of the fortifying materials, such “armoring” techniques are often difficult to install on the shoreline and adequately anchor the armor to the underlying shoreline, whether beach, bank or both. The armored structures often result in permanent structures that are not easily removed from the shoreline and prevent full enjoyment of the region of the shoreline that they overlay.

Jetties or groins are also known for attempting to control shoreline erosion. As is well known to those skilled in the art, each shoreline has a natural water direction and flow rate in accord with which the erosive flow migrates. In the typical construction, a jetty of stone or other permanent formation is built into the shore so as to form a jetty traverse the natural flow direction of the shoreline. While the jetty has the advantageous effect of promoting local sediment deposition, the jetty has a distinct disadvantage in that it causes downstream and upstream erosion. And if too many jetties are installed along a given region of shoreline, the jetties may alter the dynamic equilibrium of the shoreline and undesirably change the shape of the beach as a whole, especially when the shoreline is subject to a significant erosive event such as a storm or flood.

There are other shore and bank protection techniques and devices known in the art that attempt to control erosion by attenuating the energy, velocity, and/or direction of a potentially erosive water flow with the use of temporary structures placed on the shoreline. Several of these devices are porous groin structures using either flexible or rigid nets, screens, or filters placed on the shoreline substantially perpendicularly to the shoreline and extending into the surf. The porous groins are placed in the tidal and longshore currents and function much in the same way as a jetty to causes sand to accrete around the porous groin. The porous groin must be constantly moved or removed from the accreting sand or else extreme force must be used to dislodge the porous groin from the accreted sediment. Further, the forces of the surf can often dislodge portions of the groin that are constantly impacted by the water flow.

Accordingly, it would be advantageous to provide a device and method for shoreline restoration that uses temporary structures to renourish the beach. Such device and method should renourish the beach without adversely altering the surrounding shoreline, and should use such temporary structures as are not significantly dislodged from the wave action and current. It is thus to such a shoreline reclamation device and method that the present invention is primarily directed.

SUMMARY OF THE INVENTION

The disadvantages of the prior art are overcome by the present invention which, in one aspect, is an apparatus for use in restoring an eroding shoreline. The eroding shoreline having an eroding water flow impacting thereon and the eroding water flow including suspended solids therein. The apparatus includes a plurality of spaced vertical supports, and a porous elongated barrier suspended from the supports which causes the accretion of the suspended solids within the eroding water flow. The vertical supports have a lower portion which is placed in the seabed within the eroding water flow, and an upper portion which extends above the seabed within the water flow. The plurality of vertical supports terminate in an endmost shoreline and seaside vertical support. The end most seaside vertical support is anchored to the seabed. The porous elongated barrier is suspended from the plurality of vertical supports within the eroding water flow. The barrier has a top edge and a bottom edge, the barrier bottom edge is retained proximate to the seabed. The porous elongated barrier causes the accretion of the suspended solids within the water flow, thus restoring the eroding shoreline.

In another aspect, the endmost seaside vertical support is anchored to the seabed by a cable extending from the upper portion of the support to an anchoring means in the seabed. The anchoring means may be at least one Danforth anchor. The anchoring means may also be a weight resting upon the seabed. The endmost seaside support may also be anchored by driving the support substantially deeper into the seabed than the remaining plurality of spaced vertical supports. To retain the porous elongated barrier against the vertical supports, the porous elongated barrier may be held to the upper portion of the vertical support by an elastic member.

In yet another aspect, the porous elongated barrier is comprised of a flexible mesh that is reefable so that the bottom edge of the barrier is raised in the vertical direction. To aid in reefing, the flexible mesh barrier preferably has at least one intermediate reefing line extending substantially horizontally along the barrier length. The flexible mesh barrier may also be repositioned upon the vertical supports so as to raise the barrier bottom edge in the vertical direction. The flexible mesh barrier has a plurality of weights affixed to the mesh and at least one of the spaced vertical supports has a rope cleat for attachment of the barrier to the vertical support.

The porous elongated barrier preferably has a weighted bottom edge to retain the bottom edge proximate to the seabed. Alternatively, the bottom edge of the barrier may be retained proximate to the seabed by staking the bottom edge to the seabed in at least one location between the vertical supports, or both a weighted bottom edge and staking may be used. To enhance the performance of the device, the porous elongated barrier can be embodied with a porosity that varies in a vertical direction. Further, to increase the visibility and safety of the device, at least one of the plurality of spaced vertical supports preferably has a high visibility coating upon the support upper surface, and at least one of the endmost vertical supports preferably has a light reflective material, or a light affixed to the support. Finally, to protect indigenous birds, at least two of the vertical supports preferably have a monofilament line stretched between them above the porous elongated barrier, wherein birds are discouraged from sitting upon the apparatus.

The invention further provides a method of restoring an eroding shoreline having an eroding water flow impacting thereon, the eroding water flow including suspended solids therein, the method including the steps of placing a plurality of vertical supports in the seabed in the eroding water flow, with an endmost seaside vertical support being anchored in the seabed, suspending from the vertical supports a porous elongated barrier having a top edge and a bottom edge, the bottom edge retained proximate to the seabed, and the porous elongated barrier in the eroding water flow, accreting the suspended solids from the eroding water flow with the elongated barrier, and periodically raising the bottom edge of the elongated barrier out of the accreted solids by partially extracting the plurality of vertical supports from the seabed.

These and other aspects of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the following drawings. As would be obvious to one skilled in the art, many variations and modifications of the invention may be effected without departing from the spirit and scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side-perspective view of the apparatus for shoreline reclamation installed on a shoreline. [0019]
FIG. 2 is a side-perspective view of a section of the apparatus for shoreline reclamation installed on the shoreline, and particularly illustrating the supports driven into the seabed and end support anchored to the seabed. [0020]
FIG. 3 is a side-perspective view of one embodiment of the invention, and particularly illustrating an elastic member used to hold the webbing against the stanchions. [0021]
FIG. 4A is the beach restoration apparatus within a sediment-laden water flow [0022]
FIG. 4B is the beach restoration apparatus of FIG. 4A, within a sediment-laden water flow in the direction of Arrow F through the porous elongated barrier, and the barrier is causing sediment to accrete from the water flow onto the seabed. [0023]

DETAILED DESCRIPTION OF THE INVENTION

With reference to the figures in which like numerals represent like elements throughout, FIGS. 1 and 2 show a first embodiment of the [0024] apparatus 10 for shoreline reclamation. As shown in FIG. 1, a plurality of stanchions 20 are driven into the seabed 15, and webbing 30 is fastened therebetween. The stanchions 20 and webbing 30 extend into the surf of the shoreline from the high tide water line 34 to the low tide water line 36. The stanchions 20 can be made of any rigid material such as Schedule 80 PVC, galvanized steel channels, or molded or cast polyethylene (PET). One preferred construction of the stanchions 20 is the use of 2 lbs/ft galvanized, rib-back u-shaped channels (not shown) that average 12 feet in length. If portions of stanchions 20 are required, the channel can be cut in half or to any desired length, and if longer stanchions are required, sections may be bolted together using stainless steel fasteners. Further, it is preferable that the top of each stanchion 20 is marked with international orange paint 26 or other bright paint and a caution light 40 is placed on the top of the end stanchion 24 to make the apparatus 10 highly visible to boaters and beachgoers. To protect the indigenous bird population, it is preferable that a monofilament line 28 stretch across the top of the stanchions 20 to deter birds from attempting to land on the apparatus 10.
The [0025] webbing 30 is preferably made from a flexible material, such as nylon, and can have various sizes of meshes, depending upon the sediment grain size and other factors specific to project location. The mesh size may also vary between different vertical locations within the same webbing. The variable mesh size will be chosen to compliment the different dynamic surf conditions experienced by the webbing 30 at different elevations over the seabed 15 and will optimize the sand accretion rate generated by the apparatus 10. Various colors of webbing 30 can be used according to existing factors at project location, such as brackishness of water and indigenous wildlife populations. The webbing 30 can be attached to the stanchions 20 in individual segments or alternately, one contiguous piece of webbing 30 can be connected to stanchions 20 at various points in the length of the webbing 30.
As further shown in FIG. 2, the [0026] webbing 30 is held up by a suspension line 42 strung between the upper ends of the stanchions 20, and secured to the stanchions with rope cleats 44. The suspension line 42 keeps the webbing 30 stable and taut within the water of the surf. Any slack in the suspension line may be removed by coiling excess cable upon the rope cleat 44 and stanchion 20. The suspension line is preferably comprised of twisted rope, either of nylon or another flexible and durable material. At the webbing bottom edge 46 preferably is a chain 48 to keep the webbing 30 proximate to the seabed 15. The chain 48 can run the entire length of the apparatus 10, or alternately, can be cut into separate segments and attached at the bottom edge 46 of each segment of webbing 30 and secured to bottom of each stanchion 20 by a movable tie such that the segment of webbing 30 can be individually raised as sand and sediment is accreted on the bottom of the webbing 30.
The [0027] webbing 30 is preferably attached to a top reefing line 50 comprised of {fraction (5/16)}″ twisted rope, either of nylon or another flexible and durable material. The top reefing line 50 will be woven through the top course of the webbing 30, and is preferably segmented between stanchions 20. The segmentation of the top reefing line 50 is advantageous because in the event of failure in any one top reefing line 50, the integrity of the remaining reefing lines 50 and of the entire suspension line 42 will not be jeopardized. The webbing 30 and top reefing line 50 are affixed to the suspension line 42 preferably by orange wire ties 54. Such attachment method facilitates installation and replacement of any segment of the webbing 30 and the adjustment of slack in the webbing 30.
The [0028] webbing 30 is connected to the stanchions 20 preferably through connector rings 58 which encircle a stanchion 20 and secure the webbing 30 to ensure it remains taut, also allowing the webbing 30 to be reefed by sliding the connector rings 58 up the stanchion 20 as sand is accreted. Alternatively, the webbing 30 may be held to the stanchions 20 by attaching wire ties down the length of each stanchion 20 and through the webbing 30. The wire ties can be adjusted as necessary to ensure tautness of the webbing 30 between the stanchions 20. If it is necessary to weight down the webbing 30 due to the force of the water, snap-on lead weights 64 can be attached within the webbing 30 along with the chain 48 at the bottom. In very strong surf, it is preferred that the webbing 30 have weights 64 attached throughout its lower portion at about every six inches. The bottom edge 46 of the webbing 30 can also be pinned to the seabed 15 with stakes 68 driven at intermediate points between stanchions 20 in addition to the chain 48, or the stakes 68 can solely be used to hold the bottom edge 46 proximate to the seabed 15. The stakes 68 immobilize the bottom edge of the webbing 30 between stanchions 20 and thus reduces the compliance of the webbing 30 as a whole as the surf impinges upon the apparatus 10.
As shown in FIG. 2, stabilizing [0029] cables 70 anchor the end stanchions 24,74 of the apparatus. The end stanchions 24,74 are under the greatest pressure from the tension of the suspension line 42 and webbing 30, and also due to the forces exerted by moving water on the apparatus 10. The preferred stabilization occurs from two cables 70 that are attached at the top of each end stanchion 24,74 and extend down to anchors 78 embedded in the seafloor. The anchor 78 can be a traditional sea-floor anchor such as a Danforth Anchor, a weight such as a mobile home tie (which is made of galvanized steel), or the end stanchion 24,74 can be fastened to another fixed structure that may be present in proximity to the end stanchion. As also shown in FIG. 2, the end stanchions 24,74 may be driven substantially deeper into the seabed 15 than the intermediate stanchions 20, in which case the end stanchions 24,74 are proportionately longer so as to achieve the same exposure above the high tide water line 34 as the intermediate stanchions 20. When viewed from the side, each stanchion-stabilizing cable 70 should be positioned at approximately a 45-degree angle from the anchor 78 to the top of the end stanchions 24,74 to which they are attached. In a top view, the two stabilizing cables 70 should extend to either side of the long axis of the apparatus 10. Turn-buckles 82 are preferably used in the stanchion stabilizing cables 70 to make minute adjustments to tension on the length of the apparatus 10.
Within the [0030] webbing 30 are one or more intermediate reefing lines 86 which assist in reefing the webbing 30 to adjust to accretion and profile changes in the sea-floor bottom. As the webbing 30 is reefed, the bottom edge 46 of the webbing is partially extracted from the accreting seabed. As mentioned above, the top reefing line 50, which is suspended from the suspension line 42, is also used to secure excess webbing 30 which is reefed up as the sediment is accreted around the bottom edge 46 of the webbing 30. The reefing lines 50,86 allow excess webbing to be gathered towards the suspension line 42, and secured with wire ties 54 or other fasteners, which ensures compactness of the webbing 30 and prevention of the bottom edge 46 of the webbing 30 from becoming too enmeshed in the accreting seabed 15. Alternatively, the bottom edge 46 of the webbing 30 may be elevated in the accreting seabed 15 by raising the webbing as a whole by partially extracting the supporting stanchions out of the accreted seabed. The stanchions may be extracted by known methods such as jacking or hydraulic lifting an appropriate amount to elevate the bottom edge 46 in the accreting seabed 15. In this manner, no reefing of the webbing is required and the apparatus 10 is elevated as an assembly as the seabed 15 rises.
As shown in FIG. 3, an alternative embodiment for the connection of the [0031] webbing 30 to the stanchions 20 is the use of bungee cords 60. The bungee cords 60 are secured to the bottom of each stanchion 20 using a connector ring 58. The bungee cords 60 are then stretched and hooked to the rope cleat 44 at the top of each stanchion, with the webbing 30 captured between the bungee cord and the stanchion. The bungee cord 60 then retains the webbing 30 against the stanchion 20 without the chaffing of the webbing material associated with more rigid connection techniques.
The [0032] apparatus 10 is installed by inserting the stanchions 20 into the shoreline and sea-bottom though known methods such as jet-pumping or mechanical driving, to an approximate depth of 50% of overall length. Each end stanchion 24,74 of the apparatus 10 is preferably driven to a minimum depth of 8 ft, and deeper if required due to a significant anticipated load from the surf. When the rib-back u-shaped channels are used, they can be pre-drilled with holes one inch on center to accept the fastening of lights, signs, ropes, wire ties, caution tape, and the like. Further, height adjustments of the stanchions 20 are easily achieved by splicing the channel and bolting with stainless steel bolts. The end stanchions 24,74 may then be additionally braced with stabilizing cables 70 affixed to anchors 78.
Once the [0033] stanchions 20 are secured and placed at the preferred heights, the suspension line 42 is secured to the rope cleats 44 at the top of the stanchions 20, and then the webbing 30 is secured to each stanchion 20, and the reefing lines 50,86 are inserted through the segments of the webbing 30. Once the top reefing line 50 is inserted into the webbing 30, the top reefing line 50 can be secured to the suspension line 42 with wire ties 54. Tightening the reefing lines or fastening additional portions of the webbing 30 to the stanchions can correct any undesired slack within the webbing 30. If the webbing 30 does not have a chain 48 already inserted into its bottom portion prior to attachment to the stanchions 20, the chain 48 is then interwoven into the bottom portion of the webbing 30, either segment by segment or throughout the entire length of the webbing 30. Weights 64 may then be installed along the length of the mesh if required by the prevailing surf conditions at the installation location. The webbing bottom edge 46 may then be pinned to the seabed 15 using stakes 68.
In operation, as shown in FIGS. 4A and 4B, the [0034] apparatus 10 is placed in seabed 15, preferably such that a portion of the apparatus 10 is above the high tide water line 34, so that the apparatus is visible and does not pose a water hazard. The apparatus 10 is also placed in the seabed 15 preferably such that the webbing 30 is generally perpendicular to the direction of the main erosive water flow, which in the case of a coastal shoreline, is typically the longshore transport, but the apparatus 10 will also work with non-orthogonal water flows. In FIG. 4B, once the sediment-laden water flow begins to flow through at least a portion of the webbing 30, the water flow shown in the direction of Arrow F, the apparatus 10 begins to cause the accretion of the sediment suspended in the water, as shown by the accreting sediment 90. The accreting sediment 90 also can cover the bottom edge 46 of the webbing 30, such that the bottom edge of the webbing is entrapped in the accreting seabed 15 to the depth of lower edge 92. The webbing 30 should thus be occasionally pulled out of the accreting sediment 90 such that the covered bottom edge 46 does not become too buried within the accreting sediment whereby extreme force must be used to extract the webbing. As long as the webbing 30 is periodically raised through the methods herein described, the entire apparatus 10 can be easily be removed from the shoreline by detaching the webbing from the stanchions 20 and removing same, and then extracting the stanchions from the beach.
While there has been shown a preferred embodiment of the present invention, it is to be understood that certain changes may be made in the forms and arrangement of the elements and steps of the method for shoreline reclamation without departing from the underlying spirit and scope of the invention. [0035]

Claims

What is claimed is:

1. An apparatus for use in restoring an eroding shoreline, the shoreline having an eroding water flow impacting thereon, the eroding water flow including suspended solids therein, the apparatus comprising:

a plurality of spaced vertical supports each having a lower portion placed in the seabed within the eroding water flow and an upper portion of the support extended above the seabed within the water flow, and having an endmost shoreline vertical support and an endmost seaside vertical support, the endmost seaside vertical support being anchored to the seabed;

a porous elongated barrier having a top edge and a bottom edge, the barrier being suspended from the plurality of vertical supports within the eroding water flow;

the barrier having the bottom edge retained proximate to the seabed; and

wherein the porous elongated barrier causes the accretion of the suspended solids from the water flow thereby restoring the eroding shoreline.

2. The apparatus of claim 1, wherein the endmost seaside vertical support is anchored by a cable extending from the upper portion of the vertical support to an anchoring means in the seabed.

3. The apparatus of claim 2, wherein the anchoring means comprises at least one Danforth anchor.

4. The apparatus of claim 2, wherein the anchoring means comprises a weight on the seabed.

5. The apparatus of claim 1, wherein the endmost seaside vertical support is anchored by driving the endmost seaside vertical support substantially deeper into the seabed than the remaining plurality of spaced vertical supports.

6. The apparatus of claim 1, wherein the porous elongated barrier is held to the upper portion of the vertical support by an elastic member.

7. The apparatus of claim 1, wherein the porous elongated barrier is comprised of a flexible mesh.

8. The apparatus of claim 7, wherein the porous elongated barrier is reefable so as to raise the barrier bottom edge in the vertical direction.

9. The apparatus of claim 7, wherein the porous elongated barrier has at least one intermediate reefing line extending substantially horizontally along its length.

10. The apparatus of claim 1, wherein the porous elongated barrier is repositionable upon the vertical supports so as to raise the barrier bottom edge in the vertical direction.

11. The apparatus of claim 1, wherein the porous elongated barrier has a plurality of weights affixed thereto.

12. The apparatus of claim 1, wherein at least one of the spaced vertical supports has a rope cleat for attachment of the porous elongated barrier.

13. The apparatus of claim 1, wherein the barrier bottom edge is retained proximate to the seabed with a weighted barrier bottom edge.

14. The apparatus of claim 1, wherein the barrier bottom edge is retained proximate to the seabed by staking the bottom edge to the seabed in at least one location between the vertical supports.

15. The apparatus of claim 1, wherein the porous elongated barrier has a porosity that varies in a vertical direction.

16. The apparatus of claim 1, wherein at least one of the plurality of spaced vertical supports has a high visibility coating upon the upper portion thereof.

17. The apparatus of claim 1, wherein at least one of the endmost vertical supports has a light reflective material affixed thereto.

18. The apparatus of claim 1, wherein at least one of the endmost vertical supports has a light affixed thereto.

19. The apparatus of claim 1, wherein at least two of the vertical supports have a monofilament line stretched therebetween above the top edge of the porous elongated barrier.

20. A method of restoring an eroding shoreline having an eroding water flow impacting thereon, the eroding water flow including suspended solids therein, the method comprising the steps of:

placing a plurality of vertical supports in the seabed in the eroding water flow, with an endmost seaside vertical support being anchored in the seabed;

suspending from the vertical supports a porous elongated barrier having a top edge and a bottom edge, the bottom edge retained proximate to the seabed, and the porous elongated barrier in the eroding water flow;

accreting the suspended solids from the eroding water flow with the elongated barrier; and

periodically raising the bottom edge of the elongated barrier out of the accreted solids by partially extracting the plurality of vertical supports from the seabed.

21. An apparatus of for use in restoring an eroding shoreline, the shoreline having an eroding water flow impacting thereon, the eroding water flow including suspended solids therein, the apparatus comprising:

a supporting means for supporting a barrier in the eroding water flow; the supporting means anchored in the seabed;

an accreting means for accreting sand suspended within the eroding water flow as the flow impacts the barrier, the accreting means supported on the supporting means within the eroding water flow; and

whereby the accreting means causes the accretion of the suspended solids from the water flow.