It is known to provide flood walls adjacent to water courses, such as rivers or streams, where there is a risk of an increase in water level following heavy rainfall, and a consequent risk of damage to adjacent buildings if the water level were to rise above the level of the banks of the water course. Such flood walls may take the form of in situ concrete walls or earthwork structures such as bunds. Such flood walls suffer from the disadvantage that they are permanent walls and can be visually obtrusive when the water course is at its normal level. In particular large exposed areas of concrete wall can be unsightly.

Flooding can be a localised problem, and in many areas such as central Scotland it is known for extensive flooding to result from excessive build up of uncleared rubbish which blocks culverts which under normal circumstances carry water courses underneath

obstructions such as roads, buildings and other structures. The blocking of a single culvert can cause a water course upstream of the blocked culvert to burst its banks over a limited length, but because the water course is in a built up area the damage caused to adjacent buildings can be extensive. Such localised flooding can have disastrous consequences, costing millions of pounds. The problem of flooding risks arising from uncleared debris in streams, culverts, water courses and rivers is one that affects built up areas everywhere. However it is in such built up areas that intrusive permanent flood walls are detrimental to the environment, since in a built up area the water course may be an environmental feature, and may have local landscaping around it.

It is an object of the present invention to provide a visually unobtrusive apparatus in which a flood retaining barrier will rise as the level of water in a water course rises, thereby preventing the rising water from flowing out into the surrounding area.

According to the present invention there is provided a flood prevention apparatus to be used on a water course, comprising one or more flood prevention barriers, each barrier comprising a buoyant wall section movably supported such that as the level of said water course rises beyond a predetermined level, said wall section rises under the action of buoyancy with the level of the water course, such as to retain the water in the water course.

According to a first preferred embodiment of the present invention each barrier further comprises: a trough, having first and second substantially vertical outer walls;

the buoyant wall section being an inner wall section located between the first and second outer walls of said trough, and slidably attached to said trough for movement in a substantially vertical plane; further comprising sealing means for sealing between said trough and said inner wall.

Preferably said sealing means comprises one or more rollers mounted on said inner wall. Said sealing means may comprise one or more rollers mounted on said trough.

Preferably the first outer wall is provided with one or more apertures adapted to communicate with the water course, such that water may pass between the interior of the trough and the water course.

Preferably the flood prevention apparatus comprises a plurality of flood prevention barriers, whereby the troughs of the flood prevention barriers are arranged in end to end contact. Preferably sealant is provided between adjacent troughs.

Preferably the end face of each inner wall is provided with sealing means adapted to seal with the end face of the inner wall of the adjacent flood prevention barrier.

In a particular embodiment there is provided a support arm member attached to said inner wall section, to provide support for said inner wall section when in an elevated position.

Preferably, said support arm comprises an arm member and a sleeve member, said arm member being slidably attached to said sleeve member for movement in a

substantially vertical plane. Preferably, said sleeve member is structurally connected to said container portion.

According to a second preferred embodiment of the present invention each barrier comprises: a pivotally supported wall element comprising said buoyant wall section and a base section; a foundation; and a hinge pivotally connecting the wall element and the foundation and extending substantially parallel to the water course; said wall element being substantially L shaped in section, whereby the angle between the wall and base sections is between 80° and 150°, the wall element being proximate the water course.

Preferably the angle is between 105°and 140°. The buoyant wall section may be planar or curved about a substantially horizontal axis. Preferably the wall element and foundation are shaped such it can rotate between a first position in which the buoyant wall section is supported in a lowered position and a second position in which the buoyant wall section is in a raised position and the base section is held against a restraining means by water pressure on said buoyant wall section. Preferably the restraining means comprises the foundation.

Preferably the hinge is provided with a sealing flap which prevents ingress of water through the hinge.

Preferably the wall element comprises a sealing element on at least one end face, adapted to form a seal with the end face of an adjacent wall element.

The present invention will be described, by way of

example only, with reference to the accompanying drawings in which: Fig. 1 shows a transverse section through a flood prevention apparatus according to a first embodiment of the present invention under normal water level conditions; Fig. 2 shows a transverse section through the flood prevention apparatus of Fig. 1 under flood conditions ; Fig. 3 shows a plan view of the apparatus according to Fig. 1; Fig. 4 shows a sectional view of the apparatus of Fig.

3 along the line IV-IV; Fig. 5 shows a transverse section through a flood prevention apparatus according to a second embodiment of the present invention; Fig. 6 shows a plan view of the apparatus of Fig. 5; Fig. 7 shows a plan view to an enlarged scale on the joint between two units of the apparatus of Fig. 6; Fig. 8 shows a partial elevation view on Arrow VIII of the apparatus of Fig. 6; Fig. 9 shows a transverse section through a flood prevention apparatus according to a third embodiment of the present invention; Fig. 10 shows a partial elevation view on the hinge of the apparatus of Fig. 9;

Fig. 11 shows a partial plan view on a sealing roller used in the apparatus of Fig. 5; Fig. 12 shows an elevation on a flood prevention apparatus according to a fourth embodiment of the present invention; Fig. 13 shows a plan view of the apparatus of Fig. 12; Fig. 14 shows a section on Line XIV-XIV through the apparatus of Fig. 12 when the water is at its normal level; and Fig. 15 shows a section on Line XIV-XIV through the apparatus of Fig. 12 when the water is at its flood level.

In Figures 1 to 4 there is shown in schematic form only a first embodiment of the present invention, wherein a number of individual flood prevention barrier units 1 are arranged on either side of a water course 6. Each unit has an open-ended trough 2, a buoyant inner wall 3, and a supporting arm 4. The trough 2 is partly submerged at the bank 5 of a water course 6, and comprises a pair of opposed outer walls 7,8. The trough is provided with a capping member 11 at its upper end. The outer wall 7 nearest the water course 6 has slots or apertures 9 located therein to allow water to flow through from the water course to the interior of the trough 2.

The inner wall 3 may be a hollow wall of steel, GRP or similar, or may be cast from lightweight concrete. It is connected, by bolting, welding or any suitable method, to the supporting arm 4, so that the supporting arm 4 may provide rigidity when the inner wall 3 is

raised. Two or more supporting arms 4 may be provided for each inner wall. Typically the supporting arms may be of steel or a lightweight GRP composite. The inner wall 3 is located in a guide slot 10 in the cover 11 of the container portion 2 in order to allow the inner wall C to be raised or lowered. The supporting arm 4 slides vertically in an anchor sleeve 12, typically a tubular pile member, so that it may rise or fall with the inner wall 3, according to the level of water in the water course. As the water level rises, so buoyancy of the inner wall 3 forces both the inner wall 3 and arm 4 to rise.

The slot 10 is provided with a seal, for example a rubber strip, to prevent water leaking when the inner wall is in the flood position shown in Fig. 2.

The trough 2 may be anchored to the ground of the bank 5 by means of ground anchors 13, shown schematically only in the Figures. These may take the form of steel bars or composite rods or strips attached to the rear outer wall 8 of the trough and secured by the weight of material placed behind the trough during backfilling.

As can be seen from Figs. 3 and 4, a number of barrier units 1 are joined together to form a continuous flood protection barrier. The inner walls may be aligned with the trough sections, or they may be staggered as shown in Figs. 3 and 4. Adjoining troughs 2 are sealed to each other using conventional elastomeric seals at the rear wall 8 to ensure that the water course cannot leak through the troughs. Adjoining inner walls 3 are also sealed to each other so that leakage through the barrier is minimised when the water is at its flood level it. This sealing may be accomplished by securing rubber or elastomeric seals to the end faces of the

inner walls 3. Figs 3 and 4 show the water level 20 under flood conditions and the water level 21 under normal conditions. The support arms 4 are omitted from Fig. 3 for clarity. A drain system 22 may be provided behind the units 1 to cater for any leakage through the barrier.

Referring to Fig. 1, when the water level in the water course 6 is at the"normal"level 21, the water flows through the apertures 9 in the outer walls 7 of the troughs 2 and is thus contained within the boundaries of the barriers 1. However, as the level in the water course 6 rises, the buoyant inner wall 3 will rise at the same rate as the water level in the water course 6.

Thus the buoyant inner wall 3 will rise, and with the support of the supporting arm 4 will prevent the rising water level from flooding the surrounding area. As the water level decreases, the inner wall 3 will also descend until it reaches its lowest position again.

Figs. 5 to 8 show a second embodiment of the present invention, in which each flood prevention barrier unit 31 comprises a buoyant wall 33 which is free to rise and fall within its own trough 32. The trough has closed ends and is preferably made of GRP or steel.

The trough is installed by excavating a trench 34, placing the trough 32 in the trench 34 and surrounding concrete 35. The outside faces of the trough 32 may be provided with ribs (not shown) which extend into and engage with the concrete to provide stiffness to the trough walls 36, 37 and to ensure that the trough is not subject to uplift due to flotation arising from surrounding ground water. The front wall 36 is provided with an aperture 38, to which is connected a pipe 39 in communication with the water course 6.

The buoyant wall 33 may be formed of lightweight concrete, such as Litecrete (TM), or may be formed as a hollow moulding or hollow steel fabrication. The wall 33 is free to float in the trough 32. Rollers are provided on all four faces of the wall to allow vertical movement of the wall, but to prevent lateral movement and to allow the wall to resist lateral loading from flood water when it is in the raised position 33', while maintaining a seal between the wall 33 and trough 32. The rollers 41,42 on the front face are attached to the wall, so that they rise to the positions 41', 42'when the wall rises to position 33'.

The rollers 43 on the end face are also attached to the wall. The roller 44 on the rear face is a free roller, and rolls with the wall 33 to position 44'as the wall rises. Its extent of movement is limited by stops 45 at the top of the trough and at an intermediate position on the trough. The roller 44 rolls in contact with the wall 33 and trough 32 as the wall rises and falls. Alternatively the rear roller 44 may be anchored in the position 44'to the rear wall 37 of the trough 32.

A hinged cover member 46 may be provided at the top of the trough 32. When the wall is in the lowered position the member 46 covers the trough and prevents debris falling between the wall and the trough and interfering with the operation of the roller seals 42, 44.

A typical method of fixing a roller to the trough wall is shown in Fig. 11. A number of rings 51 are secured to the wall, typically by threaded shafts 52 and nuts 53,. The roller 44 has a steel spindle 54 which is rotatably supported by the rings 51. A sleeve 55 of rubber or elastomeric material surrounds the spindle

54, with cutaway portions to allow the spindle to be supported in the rings 51. The rollers 41,42, 43,44 can extend along the complete length of the side of the wall 33, or a number of abutting rollers can be provided on each side of the wall 33. The arrangement for securing rollers 41,42 to the wall 33 can be similar to the arrangement shown in Fig. 11, but instead the rings 51 may be provided on anchors which (not shown) are cast into the wall 33.

At the front vertical corner edges of the wall there are provided rubber or elastomeric seals 60, which extend over the full height of the wall. These seals 60 serve to prevent water passing through the gap between the end face 63 of the wall 33 and the end wall 64 of the trough 32. The seals 60 may be attached to the wall 33 by anchors 61. The seals should be resilient and flexible enough such that they expand to seal between adjacent wall units 33 when the walls are in a raised position, and contract to seal between the wall unit 33 and the end wall 64 of the trough when the walls are in a lowered position. The seals 60 may also be positioned at the rear vertical corner edges 65 of the wall 33 if required.

Adjacent troughs 32 may be placed next to each other to form a continuous flood barrier, similar to the barriers shown in Figs. 3 and 4. To accommodate curves in the barrier, adjacent troughs may be placed at a small angle, typically less than 5°, to each other.

The seals 60 should be sufficiently resilient to accommodate the slightly larger gap between wall units which may arise from placing the trough units at an angle. If angle is such that there is a larger gap at the front of the trough 32, then the seals 60 should be provided on the rear vertical corner edges 65 of the

wall 33. If angle is such that there is a larger gap at the rear of the trough 32, then the seals 60 should be provided on the front vertical corner edges 66 of the wall 33.

The troughs 32 may be of lightweight GRP, and may be factory fabricated and delivered to site for installation. During backfilling with concrete 35 the troughs 32 should be propped so that they do not deflect inwardly. The invention relies on a uniform gap between the trough 32 and the wall unit 33. The walls 33 may be cast on site from lightweight concrete using a prefabricated mould.

Figs. 9 and 10 show a third embodiment of the present invention, in which each flood prevention barrier unit 71 comprises a buoyant wall element 72 rigidly attached to a base element 73, which may be of denser material than the wall element, the unit being rotatably connected by a hinge 75 to a foundation 74. The unit 71 is free to rotate under the action of rising and falling water in the water course 6, so that the wall 72 moves between a lower position 72a, in which the weight of the wall causes the unit 71 to rotate in the direction of arrow 90 until the wall 72 rests on foundation 74, and a raised position 72b, in which the weight of the base element 73, the buoyancy of the wall 72 and water pressure on the wall 72 cause the unit 71 to rotate in the direction of arrow 91 until the base element 73 rests on foundation 74.

The wall element 72 is made of lightweight concrete or a hollow moulding, while the base unit 73 may be made of the same material, or of a denser concrete. The respective weights of the wall and base elements 72,73 are selected so that the unit will readily rotate under

buoyancy action of rising water, but will swing back to the lower position when the water level subsides.

As the water 6 rises from the normal water level 21 to the flood water level 20, the buoyant wall 72 floats from its equilibrium position 72a and rotates in the direction of arrow 91 to retain the flood water. The hinge 75 is shown in Fig. 10 and comprises a pin 80 which passes through lugs 81,82 of corrosion-resistant material mounted in the base element 73 and the foundation 74. Resilient seals 77 in the form of foldable membranes are secured to the wall element 72 by fixings 78, so that under the action of water pressure they are held in front of the hinge 75 to minimise leakage of water through the hinge when the water level in the water course is higher than the hinge.

Adjacent barrier units 71 may be placed next to each other to form a continuous flood barrier, similar to the barriers shown in Figs. 3 and 4. To accommodate curves in the barrier, adjacent units may be placed at an angle to each other, in which case it will be necessary to place a vertically moving barrier, such as shown in Fig. 5, between two hinged units, to prevent interference of the hinged barrier units during rotation. Rubber or elastomeric sealing strips (not shown) may be provided on the end faces of adjacent barrier units, similar to those strips 60 shown in Figs. 7 and 8. Alternatively a flexible membrane (not shown) spanning between adjacent barrier units 31 may be sealed and fixed to each of the two opposing end faces. Small angles between adjacent units 71 may be accommodated by the provision of a sufficiently large and flexible membrane.

A channel 76 may be provided in the top of the foundation 74 to allow debris which may collect on the foundation to be carried away and not to interfere with the closure of the base element 73 on to the foundation 74 when the wall 72 is in its fully raised position.

The top surface of the foundation 74 may slope away from the hinge 75, to discourage the collection of debris on the top surface.

Figs. 12 to 15 show a fourth embodiment of the present invention, in which the flood prevention barrier 101 comprises a number of buoyant wall units 102, each of which is rigidly connected at each end to a float 103, which is free to rise and fall within a casing 104.

The float and casing are preferably cylindrical. The casing 104 is preferably made of GRP or steel, and is founded in the river bed 105. The front face of the casing 104 is provided with an aperture 106, so that the interior of the casing 106 is in communication with the water course 6.

The buoyant wall 102 may be formed of lightweight concrete, such as Litecrete (TM), or may be formed as a hollow moulding or hollow steel fabrication. If the floats are sufficiently buoyant the wall 102 does not need to be buoyant itself. The wall 102 passes through slots 107 in the casing 105 and is free to float as the water level rises. A coping beam 110 is fixed to the bank 111 of the water course, preferably by bedding in concrete. The front face 113 of the coping beam is provided with a low friction sealant, such as a PTFE coated elastomer, so that when the water level rises from the normal level 21 to the flood level 20, water pressure pushes the wall 102 against the front face 113 to seal the wall and prevent water leaking between the back of the wall 102 and the coping beam 110. The

coping beam 113 may be secured to the top of a retaining wall 114 of sheet piles or similar, marking the edge of the water course.

Seals (not shown) may also be provided along the edges of the slots 107 and between the float 103 and the casing 104, similar to the seals 60 described earlier with reference to Figs. 7 and 8.

The apparatus according to the invention will be of great benefit to local authorities and those having responsibility for water courses and flooding, as well as to manufacturing, industrial, agricultural and other organisations responsible for land or property with a water course running through. The apparatus of the invention will prevent local flooding and consequent building damage and pollution of the surrounding environment. Many authorities around the world are introducing flood prevention legislation which puts the responsibility for maintaining culverts and water courses in the hands of those whose land the culvert passes through. Responsibility will also lie with those who produce the debris which clogs up culverts and water courses, and as a result many parties will be open to risk of huge claims from flood damage if they do not take active steps to prevent flooding.

The apparatus of the invention will also find application in areas subject to risk of flooding from the sea.

Reflective strips or similar may be provided on the tops of the floating walls, to warn users that the wall is in a raised position. Other suitable materials may be used, such as timber, hollow concrete, hollow metal, glass fibre reinforced plastic, lightweight aggregate

concrete, as appropriate, providing the necessary buoyancy is achieved.

These and other modifications and improvements can be incorporated without departing from the scope of the invention.