Hydraulic and earth engineering – Fluid control – treatment – or containment – Flow control
Reexamination Certificate
1999-03-31
2001-04-03
Lillis, Eileen D. (Department: 3673)
Hydraulic and earth engineering
Fluid control, treatment, or containment
Flow control
C405S028000, C405S092000, C405S113000
Reexamination Certificate
active
06210072
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of protecting part of a coastline against erosion, by placing in a wave breaking zone, a device to dampen water flow generated by the breaking waves.
The invention also relates to an arrangement for protecting a part of a coastline against erosion. The arrangement includes a device being placed in a wave breaking zone and adapted to dampen water flow generated by the breaking waves.
In a zone where the water is so shallow that waves have an influence on the sea bed, sea-bed material will be suspended by waves and transported inwards and outwards perpendicular to the coastline, this material settling at roughly the same rate as it was suspended, thereby leaving the coastline more or less intact. However, the water flow will often have a flow component along the coastline. Such a flow component occurs when waves are angled to the coastline in the breaking zone. This results in sand and other erosion material/beach and coast material being moved along the coastline. Sand that is washed away along the coast from one place to another is not always replaced to the same extent from a part of the coast located upstream. Thus, sandy beach can be washed away or built-up and extended even in the case of relatively small changes in the direction of the incoming waves at the part of the coast in question. This phenomenon whereby a sand beach is washed away and re-built can be amplified by general water flows in the coast region.
Such coast erosion is a well known problem and proposed solutions include the use of beach facings, wave breakers, groynes, artificial reefs, pneumatic wave dampers, artificial “seaweed” (bottom-secured oil-filled hoses) among other things.
One problem with these known solutions, however, is that they are very expensive to construct and are either built to provide the intended function for a specific predominant wave direction or to dampen incoming waves. None of the solutions is aimed at actively influencing the coast-parallel net loss of sediment along a heavily eroded coast section.
In reality, however, wave direction varies in a manner that cannot be fully anticipated, and consequently fixed structures along the coastline can sometimes give a less desirable result.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a method that can be carried out effectively at low cost, and to provide an effective arrangement that can be manufactured and mounted at a relatively low cost and which will function effectively in the case of differing wave directions, and which is able to adjust automatically to an optimal setting with respect to variations in wave direction, such as variations that have been observed over long periods of time.
One object of the invention is therewith also to provide a corresponding method.
This object is achieved by using a device in the form of an elongated fin with a longitudinal axis lying in a horizontal plane. The method includes the step of providing a support for the fin so that it can swing in the horizontal plane. This is accomplished by adjusting the longitudinal axis of the fin in the horizontal plane. The fin deflects, from the water flow, a component that counteracts with a generally coast-parallel water flow component that originates from the water flow and/or from a wave that is not parallel with the coastline. This occurs when the angle of the wave direction relative to the coastline increases. Alternatively, when the angle of the wave direction relative to the coastline decreases, the suspension arrangement decreases the fin angle relative to the coastline.
The method is also achieved with the arrangement according to a device which is an elongated fin. The longitudinal axis of the fin is orientated in a chosen first fin orientation such as to cause the fin to deflect from the water flow a first flow component. The first flow component counteracts a coast-parallel water flow component originating from a general water flow and/or from a wave that is not parallel with the coastline. The fin is carried by a suspension arrangement which enables the fin to swing in the horizontal plane. The suspension arrangement is constructed to increase the fin angle relative to the coastline when the angle of the waves relative to the coastline increases, and when the angle of the waves relative to the coastline decreases, the suspension arrangement decreases the fin angle.
Further embodiments of the invention will be evident from the dependent claims.
The inventive arrangement can be considered fundamentally to include an elongated fin having a longitudinal direction that generally lies in the horizontal plane. The fin also suitably has a generally vertical extension, such as to be able to capture and dampen water flows that derive from the breaking waves. The fin is conveniently constructed from a buoyant material, so that the upper edge of the fin will lie essentially at the surface of the water. The fin is supported so as to be able to swing in the horizontal plane. The longitudinal axis of the fin is set in the horizontal plane to a selected orientation in which the fin deflects from the water flow a flow component along the fin. This current component gives rise to a coast-parallel, water-flow component that serves to counteract an undesired coast-parallel water flow, for instance a water flow that transports sand away from the coast section concerned. This undesired coast-parallel water flow may consist of a general water flow and/or of a flow component generated by a wave that falls obliquely to the coastline. The orientation of the fin relative to the coastline is then changed in dependence on changes in wave direction relative to the coastline, so that the current component, or rather the component parallel with the coastline, deflected by the fin is given a desired value for different angles defined by the waves with the coastline.
The fin suspension can be controlled by sensing, or detecting, the direction of incoming waves, and using the sensed wave direction to control setting means/suspension arrangements coupled to the fin. In preferred embodiments of the invention, the suspension may be designed to enable incoming waves themselves to set the fin to those directions permitted by the suspension arrangement. According to one embodiment of the invention, the suspension arrangement may include a mechanism that has two anchoring points that are mutually spaced along the coastline, two coupling points spaced along the fin, and two links which are each connected between an anchoring point and a coupling point so as to intersect one another. The anchoring points may, for instance, comprise sea anchors, i.e. anchoring devices that are embedded in the sea bottom.
Alternatively, the suspension arrangement may include a fixed post, a fixed block or like element, and a centered U-shaped element on the rear side of the fin, wherein the post extends through the U-shaped element and wherein the U-shaped element is constructed to allow the fin to self-adjust in accordance with the abovementioned pattern for waves incoming in different directions.
A system for protecting a coastline or beach against erosion may include a plurality of protective arrangements mounted along the coastline.
When applying the inventive technique, a reduction in erosion can be expected by virtue of the fact that the invention retards the coast-parallel transportation of erosion material or sand, wherewith this erosion limiting effect can also result in a build-up of the coastline concerned, because the sedimentation possibilities with respect to coast-parallel material transportation are favoured. The invention can therefore also be applied to build-out or extend a coastline that would otherwise be kept constant or be eroded due to coast-parallel water flows and currents.
The fins will preferably be placed in the water in the coast zone where the incoming waves are broken, i.e. where the incoming waves generate water flows that cause erosion
Jacobson Price Holman & Stern PLLC
Lillis Eileen D.
Mayo Tara L.
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