EP0551353A1

EP0551353A1 - A method to prevent erosion or injurious influence of erosion and an arrangement for carrying out the method

Info

Publication number: EP0551353A1
Application number: EP19910917470
Authority: EP
Inventors: Ulf Karlsson
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-10-03
Filing date: 1991-10-03
Publication date: 1993-07-21
Also published as: NL9120021A; DE9190136U1; AU8642191A; SE9003180D0; CA2093323A1; WO1992006249A1; SE9003180A0; DE4192413T1; JPH06504334A

Abstract

Méthode et dispositif destinés à prévenir l'érosion ou l'effet nocif de l'érosion dans des zones situées entre la terre (1) et l'eau (2), telles que des zones de littoral, de rives et de berges ; ladite méthode et ledit dispositif sont utilisables dans les cas où l'on cherche à accroître les zones de terre ou de rives. Des dispositifs de guidage (4) sont disposés dans l'eau (2) en contact avec la terre (1), à une certaine distance du rivage (3). Les dispositifs de guidage (4) comprennent des éléments de guidage (16) ayant la forme d'un mur et des dispositifs d'ancrage pour ancrer les dispositifs de guidage et/ou les éléments de guidage dans le fond. Chaque dispositif de guidage (4) et chaque élément de guidage (16) est monté de manière à se prolonger à un certain angle en direction du rivage (3) à partir du fond en direction de la surface de l'eau.Method and device for preventing erosion or the harmful effect of erosion in areas between land (1) and water (2), such as areas of coastline, shores and banks; said method and said device can be used in cases where it is sought to increase the areas of land or banks. Guide devices (4) are arranged in the water (2) in contact with the earth (1), at a certain distance from the shore (3). The guide devices (4) include guide elements (16) in the form of a wall and anchoring devices for anchoring the guide devices and / or the guide elements in the bottom. Each guide device (4) and each guide element (16) is mounted so as to extend at a certain angle towards the shore (3) from the bottom towards the surface of the water.

Description

A METHOD TO PREVENT EROSION OR INJURIOUS INFLUENCE OF EROSION AND AN ARRANGEMENT FOR CARRYING OUT THE METHOD

This invention relates to a method to prevent erosion or injurious influ¬ ence of erosion in areas between land and water, such as in shore areas, and caused of for example a sea. The invention also relates in applicable cases to produce an enlargement of land or shore.

As is well known erosion causes in many places devastation of land within defined or more spread areas, why it exists a need of being able to prevent erosion or injurious influence of erosion in such areas which are exposed for erosion and where no natural means can be brought to prevent erosion or its injurious influence on the surface of the ground. Thus, within cer¬ tain areas erosion, its spreading or injurious influence on the surface of the ground can be prevented by supplying a protective covering of vegetat¬ ion or another plantation binding the surface of the ground, as in deflat¬ ion. In other places it is more difficult or almost impossible to prevent damage or ruin caused by erosion, as in so-called abrasion or in for exaπtp- le unsheltered seashores or other shore areas. On at least such areas as beaches having a surface layer of sand deflation will probably also often have an injurious effect. Besides to be able to prevent and stop spreading of erosion there is a need to be able to recreate eroded areas and if poss¬ ible an enlargement of land. At this it would be an advantage if such steps could be taken without the need of making cuts in the surface of the ground and also in other places, such as when filling materials must be picked out, etc. It would be a considerable .Improvement if rebuilding of land and in applicable cases an enlargement of land could be done with the same or at least some of the means causing erosion in a certain area, as at shore areas or on coast areas. Perhaps, it should also be mentioned the need of preventing fluvial erosion and in that respect principally a washing of slopes and descents and in the ground contained water.

In attempts to prevent or at least mitigate the injurious effect of erosion cxi shore and coast areas one has built moles or similar and often of stones which have been placed on the bed seawards. In recent times there have been made attempts with gabions or wire hampers of steel which have been filled with stones and also cloth bags filled with sand which have been placed on the bed. Corrπ ily for these methods are that there are loadings on the bottom, whereby one yet gets erosion. Thus, the bottom is going to be hollowed out by scouring where such shore protections are arranged, whereby they are going to sink. Other methods to effect shore protections have con¬ sist of mattresses filled with concrete, which have been placed on beach slopes and also to place stones of different dimensions along a beach and sometimes also in the beach-line, which methods are intended for making a barrier to waves and give resistance to waves. When using the latter method an erosion will gradually occur behind the stone protection by the fact that the waves force air through the slots in the stone protection, which air in turn makes a pressing action on the ground surface and erosion occurs, for exaπple by the fact that sand are forced away. It has also been proposed to join concrete tiles to larger units, which are placed in the water. However, it has been shown that known methods does not have been able to prevent erosion or till now have shown that erosion certainly can be prevented.

The object with the method in accordance with the invention is to effect a method preventing erosion or injurious influence of erosion in areas where land and water are met, as in shore or coast areas. According to an embodiment of the method in accordance with the .invention, the object is not only to prevent or stop erosion but instead to produce an addition of land or shore. Thus, one should when using the method in accordance with the invention be able to fulfil the requirements made, whereby the disadvantages of the known methods are el-uninated. Furthermore, a method in accordance with the invention can be produced without visual interfer- ence on nature. Used devices when enlarging land can, without any negative effects on the environment, be allowed to be buried in the newly created ground and will thus become totally invisible and inaccessible. The method in accordance with the invention is characterized in that in connection or relatively close connection with land, as a distance from the shoreline or shorestrip and in the water, guiding devices are arranged to extend from the bottom or its surface and in the direction of the surface of water and in applicable cases holder elements are arranged into or on the ground in the water and/or on land.

According to an embodiment of the method in accordance with the invention the guiding devices are arranged in such a way that their weight or load does not load or principally load the bottom or its surface. In another ernbodiment of the method in accordance with the invention one end of the guiding devices is arranged at a distance from the shoreline, whereby holder elements are arranged between the guiding devices and the shoreline or to the area for the shoreline. The task of the holder eleiients are to catch particles or sand in the water and keep the particles or the sand and in applicable cases to drain or facilitate drainage of ground.

According to still another embodiment of the method in accordance with the invention two guiding devices are arranged at a distance from each other along a shore area influenced by erosion, whereby the guiding devices are arranged for co-operation with each other and in applicable cases, when the affected shore area is of some length, one or more units of guiding devices are arranged at a distance from the first mentioned unit of guiding devices, whereby the guiding devices' relative angle, i.e. directions towards land, in respective unit of guiding devices can vary or be different depending on local conditions.

In an additional en±icdiment of the method in accordance with the invention measurings are carried out of certain parameters, registration of the mea- surement results and evaluation before that the guiding devices and in applicable cases also the holder elements are arranged or put in position, whereby the direction or extension of the guiding devices is settled with regard to the measurings made, etc.

Further characteristics of and advantages with the method and the arrange¬ ment in accordance with the invention will in the following description of the invention be apparent by an embodiment example, whereby reference will partially be made to the accompanying schematic drawings, of which Fig. 1 shows from above schematically an example of an arrangement to effect a method according to the invention, Fig. 2 shows in cross-section an example of a device in form of a guiding device, Fig. 3 shows from above part of a guiding device, Fig. 4 shows from above an additional example of a method and an arrangement according to the invention, Fig. 5 shows from above a method according to the invention and adopted in a arrangement or a part of an arrangement according to the invention, Fig. 6 shows in section a part of an arrangement, Fig. 7 shows in a perspective view a holder element in the course of joining to another holder element and which holder ele¬ ments can be included in a method and be part of an arrangement according to the invention, Fig. 8 shows from above a number of individual holder elements according to Fig. 7 and arranged into a unit of holder elements and Fig. 9 shows from above an arrangement according to the invention and used in a test.

In previous arranging of shore protection one has often placed some kind of obstacle in the water, as a mole of stone, whereby its direction has been decided upon visual impressions or supposed conditions. In more elaborated studies one has made geotechnical measurements in the water 50 metres from the shoreline and on land also 50 metres from the shoreline but never in the strip bordering the body of water, i.e. in the real area where erosion is in progress or perhaps has the strongest influence. Further, one has totally avoided studying the phenomena taking place under the surface of water and down to the bed.

In the method in accordance with the invention one uses guides in the water 2 in form of guiding devices 4 and in applicable cases holder elements 5, which also can be used on land 1 and in the shoreline 3, see for exaπple Fig. 1.

A method in accordance with the invention can start with ireasurements of certain parameters, as currents in the water and in that respect not only surface currents but also bottom currents and sand movements on or near the bottom. Further, measurements of wave motions and that consideration can be taken to latitude with other centrifugal forces, ebb and flood, tempera- ture, atmospheric pressure and specific weights, the slope of the bottom, depth of water, etc. The most important groups of calculation are the direction and force of sand and water and the earth-layer along the shore. The said -neasurernents are carried out at depression and high pressure. After that registration of the measurement tests and evaluation of these are done, which give a basis for the arrangement of guides 4 and holder elements 5, if any and in that respect patience, strength or resistance of the devices used, size and directions for preventing or stop erosion. Place of reference can at this be the direction of shore and the direction from land and towards the water. If an enlargement of the shore is desired it can also be attained by calculations based upon the measurement results. Thus, the direction and dimension of the guides 4 are accurately settled by such preparations and examinations for just that place in question. Geotechnical measurements give a basis for subsoil and surface water on land and by that it can be calculated necessary protection to prevent erosion from land 1. Measurements in water 2 give basis for control of sand movements and reduction of the influence of water force motions on the shore or shoreline 3. In other words measuring and evaluation of sur¬ face currents, bottom currents and sand movements and in applicable cases wave motions are necessary to bring about effects instead of only study motions of the water from above the surface of the water plus any geotech^¬ nical measurements far from the shore 3 or shoreline. Thus, it is estab¬ lished any drainage and stabilization of ground towards land 1, directions of guiding devices 4 in the form of protective guide elements and their dimensions and beach locks in the form of the said holder elements 5 and their dimensions and possible directions.

Through other or further parameters, as movements of air masses, densities, i.e. the salinity of the water, etc., a fine adjustment can be realized of said directions and classification of the power, whereby an improved effect is attained to keep the beach or sand and collection of sand for addition of the beach.

The rotation of the earth has a certain influence but above all the cori- olis power has such an influence that one must take that fact into consid¬ eration when using the method and the arrangement in accordance with the invention. Thus, on the northern hemisphere the sand in the waves, for example, are transported to the right or anti-clockwise. It is on the contrary on the southern hemisphere. Sand removal or sand movements in the water or along the bed are one and the same on a certain place and are done without any influence of water currents and waves and happen also in calm weather. Sand transfer is also done by the influence of low pressure and high pressure and pressure differences into .and at wave motions. Certain sand transfer is also done at low pressure because of intensity. Further, the movements or the bottom currents are fluctuating dependent on low pressure and high pressure and different or contrary at low pressure and high pressure respectively. Wind affects the height of waves but not or only to some extent the direction of waves, i.e. surface currents. Certain effect or erosion is obtained owing to the force of impact. However, it is particles and means in the water giving the real erosion. High salt content gives increased erosion.

The reference designation 1 in Figs. 1, 4, 5 and 9 shows land and the refe¬ rence designation 2 in Figs. 2 and 6, as well, water, whereby the shore or the shoreline between land 1 and water 2 is shown by the reference design¬ ation 3. In order to stop or prevent erosion or injurious influence of erosion in an area, as on beaches, and in applicable cases to produce an enlargement of land 1 or shore 3, guiding devices 4 are arranged in the water 2 in that area and in the form of guides in connection or relatively close connection with land 1, as a distance from the shoreline 3 or strip of shore and in that respect principally two by two and in areas of some length more guiding devices 4 or at a distance from one another units of guiding devices 4 in pairs. In applicable cases there are also arranged holder elements 5 into or on the bed or bottom 12 and in the water 2 and/ or on land 1, as between the ends 6 of the guiding devices 4 directed to¬ wards the shore or shoreline 3 and the shore or shoreline 3, between the guiding devices 4 in the shoreline 3 and in applicable cases on land 1, for example, in banks, in the water 2 on shallow water and perhaps between or in connection with sandbanks, etc.

The holder elements 5 can be in form of individual elements 20, which are arranged to be able to be joined together or the like to form an unit of holder elements 5, see Figs. 1, 7 and 8 and the arrow 21 in Fig. 7. As is evident from said figures, the holder elements 5 show rectangular shape and can be made as a plastic construction consisting of a central rectangle surrounded by several or e.g. ten equal squares. Further, the individual elements 20 show drain channels 22 within the walls 23 allowing drainage in four directions. When elements 20 are linked together the drain channels are automatically aligned allowing unimpended flow. The units are easily laid and linked without the aid of tools and can be anchored by means of anchoring devices 7 or cables. Further, the material can be made of a chem¬ ically inert and harmless material when in contact with food, vegetables, etc. and allowing trees and vegetation to follow their normal growing cycle. It is not essential to have level foundation as the element 20 can be flexible and allows it to settle according to the ground contour. Thus, the elements 5 involve also to construct steeper slopes thus saving on land utilization and avoiding the need to level out. The elements 20 can either be linked side by side or corner to corner.

With further reference to Fig. 2 it is shown a guiding device 4 comprising guiding elements 16 in form of a wall, embankment or another guiding ele¬ ment. The guiding device 4 is meant for being arranged on the bottom 12 and follow the bed without loading or essentially loading the bottom 12 or the surface 14 of the bottom with its load and extend from the bottom 12 or its surface 14 and in the direction towards the surface 15 of the water.

The guiding devices 4 or the guiding element 16 can be formed of for exa p- le a Nylon mattress, which is filled with a fine concrete mixture and is then formable until the concrete stiffen. Such a shaping of the guiding devices 4 lead to tight and durable guiding devices, which can resist pressure. The guiding devices 4 can be adapted in dimensions according to the local circumstances. Further, the guiding devices 4 are meant for being anchored into the ground or bottom 12. As is evident from Fig. 3 the guid¬ ing devices 4 or the mattress are shaped or being shaped with an edge port¬ ion 17, which is folded in order to connect with the bed or bottom 12. That edging 17 can be utilized for the anchoring of the guiding device 4 or the guiding element 16 or wall or the guiding elements or walls comprised by the guiding device. At this one uses the anchoring devices 7, which show a proportionately small cross-section in at least that part breaking through the surface 14 or the surface layer of the bottom 12 and preferably with engagement devices 19 loading the load of the guiding devices 4 a distance below the surface 14 or surface layer of the bottom 12. The anchoring devices 7 are thus arranged besides to anchor the guiding devices 4 .and the guiding elements 16 to transfer the load of the guiding devices and the guiding elements a distance below the surface of the bottom and can by this show engagement devices, which are arranged to be able to engage the bottom a distance below the surface of the bottom.

According to the embodiment examples shown the guiding devices 4 show a cross-section mainly of a V or U turned upside down, whereby one or both legs form such a said wall 16 or similar. The arrangement comprises sup¬ ports 8 for the support and bearing of the guiding device 4, whereby the guiding device 4 rests against the upper part of the support by the fact that the guiding device lie against the support 8 in the angle between the legs of the guiding device or the area for the connection of the legs with each other and the support is anchored preferably by means of such a said anchoring device 7, which transfer the load of the guiding device 4, the support 8, etc. to a distance below the surface 14 or surface layer of the bottom 12.

The support 8 comprises besides an anchoring device 7 a carrier 9, for example in form of a tube and a spacer 10, which according to the embodi- ment exaπple extends between the carrier 9 and the anchoring device or to the surface 14 of the bottom 12. The support 8 can be shaped in such a way that the anchoring device 7 forms an extension of the support 8 or the spacer 10.

The guiding devices 4 will be totally concealed in the water 2, i.e. will not or does not need to be visible, as they only will extend fifty centi¬ metres from the surface 14 of bed. According to one embodiment the guid¬ ing devices 4 reach to just under the surface 15 of the water and by that stop all movements in the water 2, which in turn i.a. give less or elimin¬ ate the force of impact of waves against the shore and spread the force exposed to the coast of especially the pressure of the sand. Foremost shall the guiding devices 4 or the guiding elements 16 guide bottom currents 11 and break waves 18, see Fig. 6. Thus, one can with the guiding devices 4 or the guiding elements 16 guide sand movements and the sand transfer and get the sand directed towards the shore 3 for addition 25 of land and shore, i.e. one captures and directs the sand towards the shore and addition is done. The use of beach locks or holder elements 5 create a more rapid addi¬ tion, as they capture, keep and stabilize the ground so that the sand have time to settle and in applicable cases drain the surface water and subsoil water, which is lead off to the water 2. The holder elements 5 or the indi¬ vidual elements 20 are shaped in such a way that they does not stem the water but the water shall be able to pass, why holder elements 5 or indi¬ vidual elements 20 are arranged between the guiding devices 4 or the end 6 of them and shore 3 or shoreline, see the arrows 24 in Fig. 5.

The relationship between sand transfer and bottcm currents in water and surface currents in water relate to movements in water at high and low pressure at the place in question. With reference to Fig. 9 the movaπents at high and low pressure are shown by the arrows 26 and 27 respectively. Sand is added when currents in the water 2 are influenced by high pressure, as it is forced towards land 1. Sand is torn off the shore 3 by the cur¬ rents at low pressure. In change of currents can, for example, refilling 25 of sand decrease or deteriorate. Thus, according to the method in accor- dance with the invention one takes up the sand currents 11 and the bottom currents by guiding devices 4 and direct the currents towards land 1 for addition 25 of shore. At reverse pressure (low pressure) the sand is caught so it does not is swept into the water 2. The erosion system can thus be based on the factors: a) No load on bottom/bed. b) The protective guidings are underneath the surface of water in order to direct sand and bottom currents. c) The protective guidings are in a direction from the shore so that the waves are broken in the middle of a trough of a wave or so when normal water level and normal waves exist, approximately 0,5 to 1 metre in height. d) The beach locks are attached in the direction from the protective guid- ings and towards the shore and between the guidings perpendicularly to the shore. e) The beach lock is applied to the shoreline with excavation and is filled up.

In tests one installation was arranged, as shown in Fig. 9, whereby the result was amazing with an -immediate stop for continued erosion and with rapid addition of shore. At this guiding devices 4 were arranged in the shown manner as shown in the installation and at shown angles and distances according to the local conditions which was ruled.

Along a shore line it is arranged at least two guiding devices 4 at a dis¬ tance from one another, whereby two adjacent guiding devices are arranged for an united action with each other, of which one guiding device is arranged at an angle preferably below 90 to land or shoreline and the other guiding device is arranged at an angle preferably exceeding 90° to land or shoreline, i.e. at an angle below 90 but seen from land in a divergent direction to the first mentioned guiding device. Along one of erosion influenced shore area two guiding devices 4 are arranged at a distance from each other for co-operation with each other and in applic- able cases, when the affected shore area is of some length, one or more units of guiding devices 4 are arranged at a distance from the first mentioned unit of guiding devices, whereby the relative angle of the guid¬ ing devices, i.e. directions towards land, in respective unit of guiding devices can vary or be different depending on local conditions.

Without exceeding the scope of the concept of the invention, modifications of the method and the arrangement in accordance with the invention should be possible. Thus, the guiding devices can be of another construction and shape, the directions and the number of guiding devices can vary, as well as the location and the number of holder elements. Materials and shape of guiding devices and holder elements can be another. The anchoring devices can also be of another type or shaping but should fulfil the demands of a small cross-section in the area of the ground, bed or in the breaking through of the surface or surface layer of the ground or bed and transfer¬ ring of the load from the arrangement and/or the protective guidings to a distance below the surface of the ground or bed. The method and the arran¬ gement are also applicable for the intended purpose or purposes in other areas between land and water than the exemplified, as in lakes, streams, rivers. Further, the method and the arrangement are applicable in the cases where foremost erosion or injurious influence of erosion shall be prevented or be stopped, whereby perhaps foremost guiding devices are utilized, while the holder elements in applicable cases are formost utili¬ zed for anchoring the shoreline or banks. The method and the arrangement in accordance with the invention are thus not restricted to what has been shewn and described in the en-bodiment exaπples, but soley by the following claims.

Claims

Claims:

1. A method to prevent erosion or injurious influence of erosion in areas between land (1) and water (2) , such as in shore areas, and caused of, for example, a sea and in applicable cases to produce enlargement of land or shore, characterized in that in connection or relatively close connection with land (1), as a distance from the shoreline (3) or shorestrip and in the water (2), guiding devices (4) are arranged to extend from the bottom (12) or its surface (14) and in the direction towards the surface (15) of the water and in applicable cases holder elements (5) are arranged into or on the ground in the water (2) and/or on land (1) .

2. A method in accordance with claim 1, characterized in that the guiding devices (4) are arranged without to load or substantially load the bottom (12) or its surface (14).

3. A method in accordance with claim 1 or 2, characterized in that one or more guiding devices (4) are arranged at angle to land (1) or shoreline (3).

4. A method in accordance with claim 1 or 3, characterized in that along a shore area is arranged at least two guiding devices (4) at a distance from one another, whereby two adjacent guiding devices are arranged for an uni¬ ted action with each other, of which one is arranged at an angle prefer¬ ably below 90 to land or shoreline and the other is arranged at an angle preferably exceeding 90 to land or shoreline, i.e. at an angle below 90° but seen from land in a divergent direction to the first mentioned guiding device.

5. A method in accordance with claim 1 or 4, characterized in that said holder elements (5) preferably are arranged in connection or close connect¬ ion with land (1) or the area for the shoreline (3) and/or between the land (1) end of guiding devices (4) and in the direction towards land and between adjacent and co-operating guiding devices.

6. A method in accordance with claim 1, characterized in that along one of erosion influenced shore area two guiding devices (4) are arranged at a distance from each other for co-operation with each other and in applic¬ able cases, when the influenced shore area is of some length, one or more units of guiding devices (4) are arranged at a distance from the first mentioned unit of guiding devices, whereby the guiding devices relative angle, i.e. directions towards land, in respective unit of guiding devices can vary or be different depending on local conditions.

7. A method in accordance with any of the preceding claims, characterized in that before the arrangement of the guiding devices (4) measurings are carried out in the water (2) of at least bottom currents, surface currents and sand currents .and preferably also wave motions or their direction to¬ wards land (1) or shoreline (3) and preferably at low pressure as well as at high pressure conditions and in applicable cases also geotechnical mea¬ surements in the shore area, i.e. in the area of the shoreline (3) and towards and/or on land (1) or shore and/or towards the water (2) , which measurement results are registered and evaluated for calculation of i.a. the direction or extension towards or from land of the guiding devices, which then are arranged, and in applicable cases also power of resistance or strength and size or dimensions.

8. A method in accordance with claim 1, 5 or 7, characterized in that the holder elements (5) are arranged to collect particles or sand in the water (2) and keep such particles or sand and/or for drainage of water.

9. An arrangement for carrying out a method in accordance with any of the claims 1 - 8 for preventing erosion or injurious influence of erosion in areas between land (1) and water (2), such as in shore areas, and in appli- cable cases to produce an addition of land or shore, whereby the arrange¬ ment comprises guiding devices (4) and/or holder elements (5), characteri¬ zed in that guiding devices (4) comprise a wall (16), embankment or another guiding element, which is meant to be arranged in or substantially in water (2) bordering to land (1), extend fran the surface (14) of the bottom (12) and in the direction towards the surface (15) of the water and be anchored into the bottom (12) a distance underneath its surface (14) so that the load of the guiding devices does not or essentially does not load the bottom (12), the surface (14) or surface layer of the bottom but the load is absorbed of the bottom (12) a distance underneath its surface (14) or surface layer, whereby anchoring devices (7), for anchoring of said guid¬ ing devices (4) or the wall (16) or the walls comprised by the guiding devices, show a proportionally small cross-section in at least that part breaking through the surface (14) or the surface layer of the bottom (12) and engagement devices (18) loading the load of the guiding devices (4) a distance below the surface or surface layer of the bottom (12) and in that in applicable cases existing holder elements (5) in form of individual elements (20), which are meant for being arranged in the water (2) and/or on land (1) and in that respect i.a. in connection with one end of a wall (16) or the walls (16) in case of many guiding devices (4) and in the direction towards land (1) or the shoreline (3) and preferabbly also bet¬ ween two adjacent, co-operating guiding devices (4).

10. An arrangement in accordance with claim 9, characterized in that the guiding devices (4) show a cross-section mainly of a V or U turned upside down, whereby one or both legs form such a said wall (16) or similar and arranged to rest against a support (8) and at this with the angle between the legs or the area for the connection of the legs with each other, where¬ by the support is anchored by means of a said anchoring device (7) , which transfer the load from the guiding device (4), the support (8), etc. to a distance underneath the surface (14) or surface layer of the bottom (12).