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  
       [0001]    This application claims the benefit of U.S. Provisional Application Serial No. 60/250,628, filed on Dec. 1, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    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.  
           [0004]    2. Description of the Related Art  
           [0005]    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.  
           [0006]    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.  
           [0007]    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.  
           [0008]    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.  
           [0009]    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.  
           [0010]    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.  
           [0011]    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.  
           [0012]    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  
         [0013]    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.  
           [0014]    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.  
           [0015]    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.  
           [0016]    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.  
           [0017]    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.  
           [0018]    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  
       [0019]    [0019]FIG. 1 is a side-perspective view of the apparatus for shoreline reclamation installed on a shoreline.  
         [0020]    [0020]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.  
         [0021]    [0021]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.  
         [0022]    [0022]FIG. 4A is the beach restoration apparatus within a sediment-laden water flow  
         [0023]    [0023]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.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    With reference to the figures in which like numerals represent like elements throughout, FIGS. 1 and 2 show a first embodiment of the 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 .  
         [0025]    The 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 .  
         [0026]    As further shown in FIG. 2, the 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 .  
         [0027]    The 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.    
         [0028]    The 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 .  
         [0029]    As shown in FIG. 2, stabilizing 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 .  
         [0030]    Within the 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.  
         [0031]    As shown in FIG. 3, an alternative embodiment for the connection of the 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.  
         [0032]    The 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 .  
         [0033]    Once the 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 .  
         [0034]    In operation, as shown in FIGS. 4A and 4B, the 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.  
         [0035]    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.