The present invention relates to a flood defence dam structure that can be used to assemble an entire flood defence dam. Such dam stnicture can be filled with water or other liquid, and can be used in case of an expected flood, for example caused by heavy rain falls or increase of sea (or river) water level.

In practice, sand bags are used to protect a house or a dyke in case of an expected flood. Such sand bags are relatively expensive and require a large amount of labour for filling and positioning the sand bags. Also known are box barriers that can be positioned such that a dam is provided. In addition to the relatively high costs associated with these barriers, also storage room is required.

NL2011435 discloses a flood defence dam stnicture from a flexible material having an inlet configured for filling a chamber with a liquid such as water. Such individual dam stnicture comprises different parts or elements that require assembly. Individual dam stmctures need to be positioned carefully to provide an effective flood defence dam. This requires careful operation under difficult circumstances when a flood is expected or when there are heavy rain falls, for example.

The objective for the present invention is to provide a flood defence dam stnicture that obviates or at least reduces one or more of the above stated problems and particularly provides a dam structure that is easier to use when assembling a flood defence dam and provides an effective dam.

This objective is achieved with the flood defence dam stnicture according to claim 1. The liquid chamber of the dam structure can be filled with a liquid, such as water. This chamber extends between two ends of the dam structure in a lengthwise direction thereof. When filled with water the dam structure provides a dam element. Several dam elements can be connected together to achieve a flood defence dam.

By providing the chamber from a flexible material, the required storage room or storage space can be kept to a minimum when the flood defence dam structure is not required. This reduces the storage costs of the dam structure according to the present invention. By providing an inlet that is configured for filling the chamber with a liquid, such as water, the chamber of the flexible material of the dam structure can be easily filled with a liquid to reach its desired shape and mass.

According to the present invention a connecting element is provided at or close to at least one of the first and second ends of the chamber. The connecting element is configured for connecting the flood defence dam stnicture to another adjacent flood defence dam stnicture. This enables building or assembling an entire flood defence dam from a number of individual flood defence dam structures. The length of an individual dam stnicture may vary between the length similar to a door opening and a length of up to 1000 meters or even more.

The connecting element comprises a connecting surface area. On this area the adjacent flood defence dam stnicture can be placed. This provides an effective means to place ends of adjacent dam structures close to each other, with die respective ends engaging each other. This prevents leakage between two adjacent dam stnictures. The connecting surface area preferably comprises anti-slip material or elements. This further improves the connection of two adjacent dam structures.

Preferably, the dam stnicture comprises a bottom surface that acts as a specific floor element of the dam stnicture. Such bottom stnicture contributes to maintain the position of the dam structure, also in case forces are acting on the dam stnicture. Furthermore, twisting of the dam stnicture is prevented.

In a presently preferred embodiment according to die invention, the dam structure comprises two liquid chambers tiiat extend substantially parallel to each other along a longitudinal axis from the first to the second end, wherein the liquid chambers are spaced apart from each other in a direction substantially perpendicular to a longitudinal axis, and wherein the liquid chambers are both connected to a common bottom wall.

Having two liquid chambers that are spaced apart from each other while sharing a common bottom wall has several advantages over the prior art. First of all, manufacturing the dam stnicture having two chambers that are connected via a common bottom wall is more cost-effective and efficient than manufacturing a dam stnicture having a single chamber. Furthermore, providing two separate chambers that are connected via a bottom wall provides additional stability and strength compared to a dam stnicture having a single chamber or a dam stnicture having an internal separation wall. Even if one of the chambers is damaged and leaking, the other chamber remains operational to provide time for switching or repairing the dam structure.

In an embodiment having two parallel spaced apart chambers, each of the chambers is provided with an inlet configured for filling the chamber with a liquid, wherein the connecting element is a single element connected to both chambers.

In an embodiment according to the invention, the dam stnicture is manufactured from a single piece of material, preferably a single piece of material from which the chamber or chambers are folded.

The dam stnicture according to the invention can advantageously be manufactured from a single piece of material to reduces manufacturing costs and time. Additionally, less raw material is required to manufacture the dam stnicture, since the material is more efficiently used. Preferably, the single piece of material is folded into a chamber, after which the walls are connected to each other, for example using welding, glueing, stitching or any other suitable method. Especially advantageous is to manufacture the dam stmcture from Ethylene Propylene Diene Monomer (EPDM), which can easily be folded and welded into the desired shape of the dam stmcture.

In a preferred embodiment, in which the dam stmcture has two separate chambers having a common bottom wall, it is even more preferable to manufacture the dam stmcture from a single piece of material. Outer ends of the single piece of material are folded inward and shaped to form of the chambers, after which the outer end is connected to the common bottom wall, for example using welding, glueing or another suitable connecting means that provides a durable sealed connection. By providing a space between the two chambers the chambers can be formed, shaped and subsequently connected to the common bottom wall more easily. In addition, the space provides for a more stable and resilient dam stmcture.

Both the single chamber embodiment and the dual chamber embodiment of the dam stm cture according to the invention can be combined with embodiments of the invention as described below.

In an embodiment of the invention in which the dam stmcture comprises two liquid chambers, a distance between oppositely positioned side walls of adjacent liquid chambers may be in the range of 0,05 meter to 2,00 meter, and may preferably be in the range of 0.05 meter - 1,00 meter, and may more preferably be in the range of 0,25 meter to 0,50 meter.

Providing a specific distance between the opposite walls of two adjacent liquid chambers has several advantages. Preferably the distance is adapted to the (other) dimensions of the dam stmcture and/or to the specific user demands of the dam stmcture. A larger distance between the two chambers reduces the amount of material that is required for manufacturing the dam stmcture, w hereas an increasing distance may also lead to a dam stmcture that is insufficiently strong and resilient for the required function. Therefore, the distance should preferably be adapted to the otlier dimension of the dam stmcture, such as the length, height and width as well as the intended use. Preferably, the distance is chosen to be in the range of 0.05 meter to 2,00 meter when the width of the dam stmcture is between 1,33 and 2,66 meters, although other dimensions of both the distance between the chambers as well as the dam stmcture as a whole fall within the scope of the invention as well.

In a presently preferred embodiment of the invention the at least one of the first and second ends is provided at an angle to a vertical plane.

By providing at least one end of the dam stmcture at an angle to a vertical plane the watertight engagement of two adjacent ends is significantly improved. In one of the presently preferred embodiments the angle is in the range of 1° to 15°, more preferably in the range of 1.5° to 10° and most preferably the angle is about 5°. Experiments have shown that such angle significantly contributes to the perfonnance of the dam and the dam structures. It will be understood that the actual angle may depend of the overall size of the dam structure. In one of the presently preferred embodiments the upper surface of the flood defence dam stmcture has a length extending between the first and second end of the chamber that is larger as compared to the length of the low er surface of the flood defence dam stmcture that in use rests on a ground surface. This assures an effective engagement of two adjacent ends of two adjacent dam structures. Experiments showed that the watertight connection when providing this angle is significantly improved, thereby improving the overall protection achieved with the flood defence dam stmcture.

In the presently preferred embodiment of the invention the connecting element comprises a fastening element that is configured for releasable connection of the flood defence dam stmcture to an adjacent flood defence dam stmcture.

By providing a releasable fastening element the connection can be improved, thereby improving the aforementioned effects of an improved w atertight connection between individual flood defence dam structures.

In one of the embodiments of the invention, the fastening element comprises Velcro to enable an effective and easy to implement connection between two adjacent flood defence dam stmctures. In an alternative embodiment, the fastening element may comprise a number of grommets or eyelets. This enables fastening the connecting element using a rope, cord, cable or other element. In a presently preferred embodiment the dam stmcture comprises both fastening elements.

In a further preferred embodiment according to the present invention the dam stmcture comprises a partition wall dividing at least two sub-chambers in the liquid chamber.

By providing a partition wall the effect of the dam stmcture is improved. Preferably, the partition wall extends in a substantially lengthw ise direction of the flood defence dam stmcture, more preferably in a substantially vertical plane. This improves the stability and strength of the flood defence dam stmcture.

Optionally, in one of the preferred embodiments of the invention the partition wall is provided between two sub-stmctures that are U-shaped. Preferably, open sides of the U-shaped sub-stmctures or sub-chambers are directed towards each other and the partition wall separates the two sub-stmctures. The components of such dam stmcture are preferably sealed against each other, for example involving a hot-bonding process or other suitable process.

In a further preferred embodiment according to the present invention the inlet comprises a non-return valve. By providing a non-return valve filling the chamber of the dam stmcture is made easier and it is prevented that a liquid leaves the chamber in an uncontrolled manner. This improves the filling process when installing the dam stmcture according to the present invention. Preferably, the non-return valve can be manipulated to enable removing the liquid from the chamber. Alternatively, or in addition thereto, a separate outlet can be provided .

In a presently preferred embodiment the flexible material comprises Ethylene Propylene Diene Monomer (EPDM). Experiments showed that this material is effective, relatively easy to repair, not very sensitive for UV, and requires minimal maintenance. Alternatively, or in additional thereto, other materials can be used, such as PVC or TPE for example. Also, inserts or filaments of another material such as polyester can be included in the EPDM material or alternative material to improve the tensile strength. This further improves the overall performance of the dam structure.

In a further preferred embodiment of the invention the flood defence dam structure is provided with a ratio between a height of the structure and a width of the structure that is in the range of 1 :4 to 2: 1, and preferably is about 1 :2. In experiments it is shown that this ratio provides an effective dam structure.

In an embodiment according to the invention, a height of the dam structure is in the range of 0,50 to 2,00 meters, preferably in the range of 0,67 to 1,33 meters.

The dam structure can be provided in different heights to accommodate for different situations. Moreover, the available heights are preferably chosen to be multiples, i.e. having a dam structure of 0,67 meters and a different one of 1,33 meters. These particular dimension provide a relatively easy to handle dam structure that can be relatively quickly filled and is even usable for small floodings. By combining multiple dam structures, the dam structures can also be used in larger floodings.

In an embodiment according to the invention, a w idth of the dam structure is in the range of 1,00 to 4,00 meters, preferably in the range of 1,34 to 2,66 meters.

The width of the dam structure is preferably adapted to the expected use of the dam, such as the expected water pressure that will be exerted on the dam and dam structures.

In an embodiment according to the invention, a length of the dam structure is in the range of 1,00 to 10,00 meters, and is preferably substantially 5,00 meters.

It is found that a length of the dam structure of substantially 5 meters is effective in that it is relatively easily transportable and fillable.

In an alternative embodiment according to the invention, a length of the dam structure is in the range of 10 to 10.000 meters .

For specific situations, for example protection against flooding of a river or sea coast, it is preferred to have longer dam structures, which can be placed quickly, such as by rolling it out along a river bank or sea coast.

In an embodiment according to the invention, the inlet is flush-mounted with respect to the surface of the dam structure in which it is placed. The advantage of having a flush-mounted inlet is that damage to the inlet from placing adjacent dam structures is substantially prevented. Furthermore, an improved connection between adjacent dam structures can be obtained when the inlet is flush-mounted.

In an embodiment according to the invention, the dam stmcture is provided with an outlet that is positioned in a bottom surface of the dam stmcture and that is connectable with an inlet of a second dam stmcture on which the dam stmcture is placed such that both dam structures are simultaneously fillable. It may also be possible to provide a dam stmcture having two outlets, wherein each outlet is connectable to an inlet of a different second dam stmcture that is placed underneath the dam stmcture.

The dam stmcture according to this embodiment is configured to provide a dam that the number of filling operations can be reduced due to the fact that multiple dam structures are in fluid connection with each other. This also makes it possible to connect the inlets and outlets of a number of unfilled dam structures in a stack to each other and subsequently fill that stack with liquid in a single operation. As a result, the filling time of the dam is reduced.

In an embodiment of the dam stmcture, the dam stmcture comprises one or more of a number of sensors configured for measuring physical parameters within the chamber, a transmitter for sending and/or receiving signals to an external transmitter and a chip, preferably a computer chip, for providing geolocation and/or for processing signals from and to the sensors and/or transmitter.

In use, especially during emergency situations, it is preferred that the operational status of the dam stmcture is measurable. This may for example include measuring a fill level and/or a pressure within the chamber to detect leakage and may also include providing a geolocation of the dam stmcture. Preferably, the dam stmcture is provided with multiple sensors for measuring a diversity of physical parameters indicating the operational status of the dam stmcture, which information is processed and subsequently provided to an external receiver for processing. This allows continuous remote monitoring of larger numbers of dam structures, for example dam structures in an emergency dam. As a result, a leak or failure of a dam stmcture, for example in a dam, may be detected at an early stage such that the leak can be repaired and damage to the surroundings may be diminished. The present invention also relates to a flood defence dam comprising a number of flood defence dam structures as described herein.

The flood defence dam provides the same advantages and effects as described for the flood defence dam stmcture. Especially the connecting elements achieve a watertight connection of two ends of two adjacent dam stmctures engaging each other. This effect is further increased by providing one or both edges at an angle relative to the vertical. In an embodiment of the flood defence dam according to the invention, it may comprise a number of drive plates that are positioned on an upper surface of the dam for providing an emergency walk- or driveway.

The flood defence dam according to the invention can advantageously used to provide both a flood defence dam as well as an emergency road or path along which people may be evacuated. The flood defence dam only needs to be provided with drive plates, which are placed on an upper surface of the dam structure.

Moreover, if the dam structures forming the dam are filled w ith another fluid, for example a gas or a liquid that floats on water, the dam can also be used to form an (emergency) bridge to cross bodies of water. This may for example be used in a situation in w hich a flood defence dam according to the invention is used, after which a number of dam structures is filled w ith air, provided with drive plates and is subsequently connected to the flood defence dam to fonn a bridge to allow ^r the evacuation of people and/or other living beings.

The bridge as described above may also be used alone and without a combination with a flood defence dam according to the invention as described above. As such, the invention therefore also relates to a dam-bridge structure for providing a fillable modular bridge, and a bridge being formed using flood defence dam structures, dam-bridge structures or a combination thereof.

The invention also relates to a dam-bridge structure, the dam-bridge structure comprising: a fluid chamber from a flexible material that is fillable with a fluid, preferably a gas, the chamber having an inlet configured for filling the chamber with a fluid, the chamber extending between a first end and a second end of the dam-bridge structure; a connecting element for connecting the dam-bridge structure to an adjacent dam- bridge structure for forming a bridge support.

The dam-bridge structure according to the invention provides the same effects and advantages as the flood defence dam stmcture and the flood defence dam according to the invention as described above. The dam-bridge structure according to the invention may be used in conjunction with one or a combination of the embodiments that are disclosed in reference to the flood defence dam structure.

In an embodiment of the dam-bridge stmcture, the connecting element comprises a connecting surface area, whereon the adjacent dam-bridge stmcture is placeable.

On this area the adjacent dam-bridge stmcture can be placed. This provides an effective means to place ends of adjacent dam-bridge structures close to each other, with the respective ends engaging each other. This prevents leakage between two adjacent dam-bridge stmctures. The connecting surface area preferably comprises anti-slip material or elements. This further improves the connection of two adjacent dam-bridge stmctures. Preferably, the dam-bridge structure comprises a bottom surface that acts as a specific floor element of the dam-bridge stmcture. Such bottom stmcture contributes to maintain the position of the dam-bridge stmcture, also in case forces are acting on the dam-bridge stmcture. Furthermore, twisting of the dam-bridge stmcture is prevented.

In an embodiment of the dam-bridge stmcture, the dam-bridge stmcture further comprises a drive-deck connecting element for connecting drive plates to the dam-bridge stmcture.

Preferably, the dam-bridge stmcture is configured with a drive-deck connecting element for securing drive-plates to the upper surface of the dam-bridge stmcture to provide increase the safety of the driveway on the bridge.

As mentioned above, the invention also relates to a bridge comprising a number of connected flood defence dam structures or dam-bridge structures according to the invention.

The bridge according to the invention provides the same effects and advantages as the flood defence dam stmcture, the flood defence dam and the bridge dam stmcture according to the invention as described above.

In an embodiment of the bridge according to the inv ention, the modular bridge may further comprise a driving deck comprising a number of drive plates that are placed on and/or connected to an upper surface of the bridge.

The present invention further also relates to a method for providing a flood defence dam, the method comprising the steps of:

- providing a flood defence dam stmcture comprising:

a liquid chamber from a flexible material having an inlet configured for filling the chamber with a liquid, with the chamber extending between a first end and a second end of the dam stmcture;

a connecting element provided at or close to at least one of the first and second ends of the chamber and the connecting element configured for connecting the flood defence dam stmcture to an adjacent flood defence dam stmcture, wherein the connecting element comprises a connecting surface area whereon the adjacent flood defence dam stmcture can be placed;

- filling the chamber with a liquid; and

- connecting two adjacent flood defence dam structures with the connecting element.

Such method provides the same effects and advantages as described for the flood defence dam stmcture and/or flood defence dam.

The method according to the invention preferably comprises the additional step of providing at least one of the ends of the dam stmcture at an angel to the vertical and/or the additional step of fastening the connecting element to improve the connection between two adjacent dam stmctures. The present invention also relates to a method for providing a modular bridge, the method comprising the steps of:

- providing a dam-bridge structure comprising:

a fluid chamber from a flexible material that is fillable with a fluid, preferably a gas, the chamber having an inlet configured for filling the chamber with a fluid, the chamber extending between a first end and a second end of the dam- bridge structure;

a connecting element for connecting the dam-bridge stmcture to an adjacent dam-bridge stmcture for fonning a bridge support.

- filling the chamber with a fluid, preferably a gas, more preferably air;

- connecting two adjacent dam-bridge structures with the connection element; and,

- optionally placing drive plates on an upper surface of the dam structures to provide a driveway.

Such method provides the same effects and advantages as described for the flood defence dam stmcture and/or flood defence dam and/or the dam-bridge stmcture and/or the modular bridge according to the invention. Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings in which:

- figure 1 A-B shows a first embodiment of the dam stmcture according to the invention with a connecting surface element;

- figure 2 A-B show s an alternative embodiment of the invention with a fastening element;

- figure 3 A-B shows a dam that assembled from dam structures of figure 2;

- figure 4 A-B shows an alternative dam with a further alternative dam stmcture;

- figure 5 A-B show s an alternative application as a dam-bridge with the dam stmcture; and

- figure 6 A-B shows an alternative embodiment of the dam stmcture according to the

invention having two spatially separated chambers.

Flood defence dam stmcture 2 (figures 1 A-B) comprises first U-shaped chamber 4 and second U-shaped chamber 6 that are oriented with their open ends tow ards each other and are separated by partition wall 8. Dam stmcture 2 comprises upper surface or top surface 10. Defence stmcture 2 comprises sides 12. bottom surface 14, first end or edge 16, second end or edge 18, and inlet 20. Inlet valve 20 is provided with a non-return valve or check valve. In the illustrated embodiment of dam stmcture 2 side edges 16, 18 are provided at an angle a to the vertical (figure IB). Sub-chambers 4, 6 extend between ends 16, 18.

In the illustrated embodiment defence dam stmcture is provided with dimensions Li of 5050 mm, L ₂ of 5000 mm, H] of 670 mm, width W] of 1340 mm and distance h _L of partition wall 8 that extends above upper surface 10 of about 50 mm. It will be understood that other dimensions are also possible. For example, H, and Wj of an alternative dam structure can be 1000 mm and 2000 mm respectively, or in another embodiment 1330 mm and 2660 mm respectively. It will be understood that other dimensions can also be envisaged in accordance with the present invention. In the presently preferred and illustrated embodiments the ratio of Hi to Wi is 1 :2. It is shown that this ratio provides an effective dam structure.

Alternative dam structure 102 (figures 2 A-B) comprises first sub-chamber 104, second sub-chamber 106, partition wall 108, top surface 1 10, side surfaces 1 12, bottom surface 1 14, first end or side edge 1 16, second end or side edge 1 18, inlet 120. connecting flap 122 of connector 124. Connector 124 further comprises sides 126 and flaps 128 with fastening surface 130 made of Velcro. Dimensions L], L ₂ , Hj, Wj and hi can be similar as for the other illustrated embodiment of dam stmcture 2. In the illustrated embodiment width si of flap 128 is about 750 mm and the length of flap 128 ranges between 670 and 1330 mm and is preferably similar to i. In the illustrated embodiment, the width Di of the fastening surface 130 is about 200 mm. Also in the alternative embodiment 102 side edges 1 16, 1 18 are provided at an angle a to the vertical. Also in relation to alternative dam stmcture 102 other dimensions can be envisaged, for example similar to the dimensions described for dam stmcture 2.

Flood defence dam 202 (figures 3A-B) comprises a number of adjacent dam structures 102 with connecting elements 124 in an open position (figure 3A) or in a closed position (figure 3B). Ends or side edges 1 16 of dam stmcture 102 engage ends of adjacent dam structures 102.

In an alternative flood defence dam 302 (figure 4A-B), further alternative dam stmcture

402 is provided that is based on dam stmcture 102 with connecting elements 124. In addition, the further alternative dam stmcture 102 comprises alternative connecting elements 404 with a number of grommets or eyelets 406 that can be connected with rope 408 that binds flaps 410 of connecting elements 404 together. In the illustrated embodiment there is also provided Velcro attachment surface 412 to further improve the connection between two adjacent dam structures 402.

In use, dam structures 2, 102, 402 are brought from a storage position into a use position. Bottom surfaces or floor elements 14, 1 14 are positioned at the desired position on the ground surface or floor. Chambers 4, 6, 104, 106 are filled with liquid and individual dam structures 2, 102, 402 are connected with connections 22, 124, 404 after placing side elements 16, 18, 1 16, 1 18 to each other.

In the illustrated embodiments, dam structures 2, 102, 402 are designed considering the specific desires of the user. Preferably, EPDM is used as material and partition wall 8, 108 is sealed by hot-bonding to substructures 4, 6, 104, 106. The thickness of the material is in the illustrated embodiments about 1.2 mm.

Dam structures 2, 102, 402 can also be applied as bridge 502 (figures 5 A-B). Dam structures 2, 102, 402 are provided parallel to river/ditch 504 to connect sides 506 of river/ditch 504. Optionally, road or drive plates 508 are provided over dam structures 2, 102, 402. This improves the stability of bridge 502 for enabling vehicle 510 to cross river/ditch 504. In the illustrated embodiment dam structures 2, 102, 402 are filled with air and tied together. It will be understood that also other filling gases and/or liquids can be applied as an alternative or in combination with air. Bridge 502 can be used as a quick emergency bridge, for example. Also, more structural application can be envisaged. Bridge 502 may also partially or completely be applied using dam-bridge structure according to the invention. Preferably, bridge 502 is fonned from dam structures having two separate chambers as shown in the examples of figures 1-4 and 6. Furthermore, it is preferred that a number of dam structures and/or dam bridge structures is connected with each other during manufacturing. More preferably, the number is three and/or the connection is made using welding.

In use, dam structures 2, 102, 402, 602 are filled with a gas, such as air. Subsequently, outwardly facing side walls 12, 112, 612a, 612b are placed contiguous to each other, after which dam structures 2. 2012, 402, 602 are connected to each other. In this example, dam structures 2, 201, 402, 602 are connected to each other using ropes or wires that are connected to eyelets on dam structures 2, 102. 402, 602. Other methods of connecting dam structures 2, 102. 402, 602 are possible as well. Subsequently, dam structures 2, 201, 402, 602 are placed in the stream or river 504 with side walls 2, 112, 612a, 612b extending substantially parallel to the river bank 506. In some situations, it may be preferred to place dam structures 2, 102, 402, 602 in stream or river 504 before connecting the dam structures 2, 102, 402, 602 with each other. After connecting dam structures 2, 102, 402, 602 to each other and to sides 506 of the stream or river 504, optionally drive plates 506 are placed on top of the bridge to form a more stable surface for transporting people and/or vehicles over the bridge. Preferably, especially when having to bridge larger streams or rivers, dam structures 1, 102, 402, 602 are manufactured and delivered in units fonned of three already interconnected dam structures 2, 102, 402. 602 to reduce the installation period required for building bridge 502.

In another example of the dam structure according to the invention, dam structure 602 is provided with two liquid chambers 604, 606 that are spatially separated from each other by distance W2, which is less than total width Wl of dam structure 602. Liquid chamber 604 is provided with upper surface 610a, end walls 616a, 618a, outwardly facing wall 612a and inwardly facing wall 613a that extends substantially parallel with and spatially separated from inwardly facing wall 613b of second chamber 606. As such, inwardly facing chamber walls 613a, 613b are positioned opposite each other and form a slot-formed opening. Similarly, chamber 606 is further provided with upper surface 610b, end walls 616b, 618b, and outwardly facing wall 612b.

Chambers 604, 606 are connected to each other with bottom wall 614, which in this example is an integral part of both chambers. Each chamber 604. 606 is provided with its own respective liquid inlet 620a, 620b. Dam structure 602 is also provided with a connector 124 for connecting dam structure 602 with an adjacent dam stmcture 602. In this example connector 124 is formed as a foldable flap that extends from end walls 616a, 616b outwardly (see figure 6b). Connector 124 may be an integrally fonned flap or may be a separate flap that is connected to dam structure 602 A second dam structure 602 can be placed in the U-shape form of connector 124 after which the end parts of connector 124 are folded around dam second stmcture 602, thus forming a solid and substantially water-tight connection that substantially prevents water from flowing or seeping through the connected dam structures. The present invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.