Floodgates (alternatively spelt"flood gates"and"flood-gates", and sometime referred to as"water gates") are defined as gates"designed to regulate the flow of water". In general, flood gates are designed to operate in response to particular water levels or changing water flow circumstances.

One use of flood gates, as described in The Macmillan Encyclopedia, 1998 Edition, is as a movable barrier to control the height of water at dams. That publication describes vertical lift gates"which are raised to permit flow beneath them"and drum gates (solid circular quadrants) which"rotate downwards to allow water to flow over them".

The calibrated rationing of salt water into enclosed natural and artificial drainage systems, such as tidal drainage systems, improves water quality to a standard acceptable for fish habitat, by using the natural carbonate in sea water to neutralize acidic discharge associated with coastal acid sulphate soils. This calibrated flow of sea water is crucial, not only for environmental improvement, but also as security against low level flooding of agriculturally commercial areas.

In many of the tropical regions of the world, where deltas of mangrove swamps occur, there exist formations of marine sediments commonly known as"sulphidic marine sediments"or iron monosulphides. These sediments may be identified by their black"oozy"nature, their sulphurous organic odour, and their general relationship with tropical tidal areas.

These sulphidic black oozes are produced by a chemical reaction involving the sulphur in sea water and dissolved ferric iron, in an anoxic condition which exists in shallow coastal swamps. This reaction is fuelled by organic matter, produced by abundant plant species. The result of these reactions is the vast formation of iron monosulphides or sulphidic sediments.

Once these sulphidic sediments are exposed to atmospheric oxygen, they rapidly oxidize, and sulphuric acid is formed. Accordingly, should the sediments be disturbed, by, for example, construction work for residential projects or to form canals, drainage projects, or by farming practices, bringing them into contact with the atmosphere, as a result of which large scale oxidation of sulphidic marine sediments will occur. Sulphuric acid produced by this oxidation will be discharged, resulting in extreme environmental damage to flora and fauna. By using the naturally occurring and abundant neutralizing carbonates in sea water, sulphuric acid discharges may be economically managed.

Some applications of flood gates are described in the prior art. US-A-6,485, 231 describes a flood gate which is used for flood venting crawl spaces and basements in buildings. WO 01/32991 discloses an automatic water gate which is installed in a canal such as an irrigation canal of a river or a relatively small reservoir so as to maintain a stored water level within a certain extent.

US-A-6,171, 023 relates to a top-hung gate for controlling the flow of water in a waterway. The gate is pivotally mounted on a pair of piers located above an upstream of the gate for allowing the gate to pivot between a closed position, and an open position in which water flows beneath the gate.

US-A-4,349, 296 discloses an irrigation ditch gate with a pair of gates which rotate about a vertical axis, the gate being adjustable so that the pressure required to open the gate of water is varied.

US-A-5,984, 575 describes a gate which is pivotally mounted at its base about a horizontal axis, for movement between a substantially vertical closed position and a substantially horizontal open position.

It is believed that prior art flood gates are not sufficiently capable of permitting accurate calibrated water flow, particularly the flow of sea water back in to tidal drainage systems. Conventional flood gates only let water out of drains.

It is an object of this invention to provide improvements in flood gates, such

improved flood gates being suitable for location in areas with acid sulphate soils.

The invention provides a flood gate characterised by a first element, said first element including at least one aperture for the flow of water therethrough, a second element, said second element including at least one aperture for the flow of water therethrough, said second element being movable relative to said first element such that said or each aperture in said second element may be moved between a first position in which said at least one aperture of said second element is completely out of register with said one aperture or a respective aperture of said first element, and a second position in which said at least one aperture of said second element is in register with said one aperture or a respective aperture of said first element, and by actuating means adapted to move said second element between said first position and said second position ins response to a water level.

Embodiments of the invention will be described hereinafter, with reference to the accompanying drawings, in which:- Fig. 1 is a front elevation of a flood gate in accordance with an embodiment of the present invention; Fig. 2 is a front elevation of the flood gate of Fig. 1, showing the elements of the flood gate-including an additional element not shown in Figs. 1 and 3- separated; Fig. 3 is a section through the flood gate of Fig. 1; and Fig. 4 is a front elevation of part of the flood gate of Fig. 1, showing the float and float arm attached to the rotating valve member.

The calibrated flood gate valve 10 of the present invention has been designed to meet the requirement to facilitate the accurate flow of head water in and out of specified tidal drainage systems. The calibrated rationing of salt water into enclosed natural and artificial drainage systems improves water quality to a standard acceptable for fish habitat, by using the natural carbonate in sea water to

neutralize acidic discharge associated with coastal acid sulphate soils. The calibrated flow of sea water is absolutely necessary not only for environmental improvement but also as security against low level flooding of agriculturally commercial areas.

The flood gate 10 includes a backing plate 12 which is adapted to be installed in an existing flood gate arrangement, or which may be supported by a frame or the like (not shown) to form the basis of a new flood gate.

Backing plate 12 has a central aperture 14 which is intended to be used to provide a pivot point for other elements of the flood gate 10, as will be described later in this specification. Of course, aperture 14 need not be centrally located in backing plate 12, and backing plate 12, shown as square, may be rectangular or may have any other shape.

There are four mounting apertures 16,18, 20 and 22 in backing plate 12, for mounting other elements of flood gate 10. Of course, there may be a different number of mounting apertures, and they may be located in positions on backing plate 12 other than those shown in the drawings.

Flow openings 24,26, 28 and 30 are also located in backing plate 12. These flow openings are for the flow of water through the plate 12, in a manner to be described later in this specification The flow openings are shown as having a round shape, but they may be oval, or may have any other shape. They may also be located in positions on plate 12 other than those shown in the drawings, and there may be a different number of apertures 24,26, 28,30.

A backing plate seal 32 may have the same general shape as main flood gate element 12, although, as shown in the drawings, it may be slightly smaller. Seal 32 is preferably formed from or has a coating of a material such as polytetrafluoroethylene, high-density polyethylene, or a similar material, capable of acting in a sealing manner. Seal 32 has a central aperture 34, and four mounting apertures 36,38, 40 and 42. Aperture 34 is intended, in an assembled flood gate 10, to be in register with aperture 14 in element 12, and mounting apertures 36,

38,40 and 42 are intended to be in register with apertures 16,18, 20 and 22 respectively in backing plate 12. Backing plate seal 32 also has four flow apertures 44,46, 48 and 50, which are intended to be in register with flow apertures 24,26, 28 and 30 respectively in backing plate 12.

A further element, in the form of an adjustable plate 94, may be included in the assembly 10, as shown in Fig. 2. Plate 94 has flow apertures 96,98, 100,102, similar to apertures 64,66, 68, and 70,24, 26, 28 and 30, and 44,46, 48 and 50.

Adjustable plate 94 is preferably rotatably adjustable about shaft 82, which may locate through central aperture 104, relative to backing plate 12, such that the alignment of apertures 96,98, 100,102 in this plate 94 may be adjusted so that even when apertures 64,66, 68, and 70 are completely in register with apertures 24,26, 28 and 30, and 44,46, 48 and 50, complete flow therethrough does not occur, thereby calibrating flow rate. This enables one long-term form of calibration to be effected. An actuating member, arm or lever 106 may be located on plate 94, to facilitate the rotation of plate 94 to a desired position. It may be fixed in that position, relative to plate 12, by any suitable means.

A retaining ring 52 has four mounting apertures 54,56, 58 and 60 arranged around it, which are adapted top be in register with mounting apertures 36,38, 40 and 42 of seal 32, and apertures 16,18, 20 and 22 respectively in backing plate 12. The ring 52 is preferably formed from, or coated with, a material such as polytetrafluoroethylene.

Retaining ring 52 is adapted to retain valve member 62 against sealing plate 32, for rotation relative to sealing plate 32 and backing plate 12. Valve member 62 has four flow apertures 64,66, 68 and 70. A float arm 72 is attached at one end to valve member 62 and at the other end to a float 74, shown in Fig. 4 but not in Figs.

1 and 2. A movement limiter or stroke monitor 80 limits the movement of float arm 72.

Turning now to Fig. 3, which shows a vertical section through an assembled flood gate arrangement 10, seen from the right-hand side of Figs. 1 and 2, bolts or the like 76,78 are shown securing backing plate 12, seal 32 and retaining ring 52

together. To accomplish this, bolts 76,78 extend through apertures 54,36 and 16, and 60,42 and 22 respectively. Similar bolts may be used to extend through apertures 56,38 and 18, and 58,40 and 20 respectively. Of course other means may be used to secure together the elements 12,32 and 52 of the flood gate 10.

In Fig. 3, the flow apertures 24,44 and 64, and 28,48 and 68 are shown in full register, one of the positions made possible by the relative rotation of valve member 62 relative to seal 32 and backing plate 12. A shaft or the like 82 is secured through central apertures 14,34 and 84 in elements 12,32 and 62 and may be secured in element 12 as shown in Fig. 3. Valve member 62 and float arm 72 are adapted to be secured to shaft 82 for rotation about the shaft.

Fig. 4 shows valve element 62 in isolation, but connected through float arm 72 to float 74. The stroke limiter 80 has two control stops 86,88 which provide upper and lower limits to the movement of float arm 72. Also shown are connection points 90,92, which secure arm 72 to valve member 62. Such connection may be by way of bolts, or any other suitable fastening means. Float arm 72 is connected to float 74 in any suitable manner, but is preferably connected in such a way that there is relative rotation between float arm 72 and float 74. One means of achieving this result is for a bolt or the like 108 to connect arm 72 to float 74. The connection between float 74 and valve member 62 may be more complex. For example, it may take the form of a pantograph arrangement, with parallel arms hinged together.

In the arrangement 10, the flow apertures 24,26, 28 and 30,44, 46,48 and 50, 96,98, 100 and 102, and 64,66, 68 and 70, are located at the 12 o'clock, three o'clock, six o'clock and nine o'clock positions, as is also the case for the arrangement 10 of Figs. 2 to 4. The apertures 64,66, 68 and 70 are shown in solid lines, where they are in full register with apertures 24,26, 28 and 30,44, 46, 48 and 50. This corresponds with one extreme position of float arm 72, when it reaches one of the stop members 86,88. Of course, the number of flow apertures, and their positions, may be varied as desired.

The apertures 64,66, 68 and 70 shown in broken lines in Fig. 1, represent the position of those apertures when they are completely out of register with apertures 24,26, 28 and 30,44, 46,48 and 50. This corresponds with the other extreme position of float arm 72, when it reaches the other of the stop members 86,88.

In use, the flood gate 10 is located in a position adjacent to at least one body of water or a waterway or watercourse which is adapted to contain water at some time. Float 74 is intended to float in or on the water, and rise and fall with the level of the water, or in response to the head water situation. The movement of the float 74 controls the movement of the float arm 72, which is able to move between the two stops 86,88. Float arm 72, acting in accordance with the movement of float 74, and constrained by the presence of the stops 86, 88, is able to rotate valve member 62 relative to backing plate 12, about shaft 82.

In one example, as shown in Fig. 1, the arm 72 is at the lower stop position 88, which indicates that the valve member has been rotated such that apertures 64, 66,68, and 70 are completely out of register with apertures 24,26, 28 and 30,44, 46,48 and 50. Thus, the valve member 62 has closed the flood gate, and water cannot flow from one side thereof to the other. As float 74 rises, it actuates float arm 72, which in turn rotates valve member in an anti-clockwise direction, so that apertures 64,66, 68, and 70 are partially in register with apertures 24,26, 28 and 30, and 44,46, 48 and 50. As a result, a partial flow of water is able to flow through the partially aligned apertures. As float 74 rises further, valve member is rotated further anti-clockwise, increasing alignment and water flow, until such time that apertures 64,66, 68, and 70 are completely in register with apertures 24,26, 28 and 30, and 44,46, 48 and 50, and water flow is at a maximum. This preferably coincides with float arm 72 contacting stop 86.

The float 74 preferably has an adjustable connection to float arm 72, somewhat more sophisticated than bolt 108, to control the duration of alignment and misalignment of apertures 64,66, 68, and 70,24, 26,28 and 30, and 44,46, 48 and 50. This is one form of calibration for the flood gate 10. Of course, the connection would still allow for movement of the float arm 72 relative to the float 74.

The calibrated flood gate according to the present invention may be duplicated, that is, elements 32,52 and 62, (and 94, if preferred) with their associated peripherals, may be located on the other side of backing plate 12, so that the flow of water is controlled from both sides of the flood gate, in accordance, for example, with water levels on both sides of the flood gate 10.

Conventional floodgates operate in rather crude fashion by flushing everything out of a watercourse such as a drain. The flood gate of the present invention is a more sophisticated piece of machinery.

The flow apertures of the flood gate 10 of the present invention are adapted to move in and out of register according to float 74 height, which is adjustable in accordance with various requirements, which are determined by such matters as local area needs, primary producer requirements, local knowledge, tidal movement, or a combination of one or more of those aspects. Once a limit (stops 86, 88) has been reached, the float arm 72 has rotated valve member 62 to a position in which the flow apertures of the various elements of the flood gate 10 permit maximum flow, or not permitting any flow. Of course, intermediate positions provide flow between those two options, and the use of adjustable plate 94 also allows further calibration.

The flood gate 10 of the present invention may be used in a variety of situations, such as in irrigation (for example, of sugar cane fields), aquaculture, or in a weir- type situation. In aquaculture, the level of water in fish ponds needs to be monitored and adjusted and changed to different levels on certain occasions, and the flood gate 10 of the present invention is adapted to effect such activities. In a weir-type situation, where a certain level is required at certain times and a row or cascade of flood gates 10 may be used in a cascade.

The flood gate 10 of the present invention is adapted to allow a certain (calibrated) amount of water into a canal, trench, drain or river system. This may be required in the following circumstances. Firstly, to help treat acid runoff in a drain.

Secondly, to keep a certain level of water in a drain. If a drain is allowed to dry out, oxidation of the soils could occur, resulting in acid runoff after rain. Thirdly, to

allow fish life to return to a river system. Many fish and other aquatic species begin life in remote parts of a river system. If the system dries out, the breeding cycle stops. The flood gate of the present invention can assist in keeping water in the system.

Fourthly, to keep a certain height of water in a dam or creek system for reasons other than the system drying out, for example to provide water for livestock or for irrigation purposes. Lastly, the heights of two dams may be adjusted in relation to each other. For example, water may only be allowed into one dam if the other dam is at a predetermined height.

If the flood gate of the present invention is fitted to existing flood gate structures, it would normally be located at the arm of a river, stream, drain or the like. It is to be noted that in such a situation the flood gate of this invention does not prevent operation of any conventional flood gate located in the structure. The flood gate of the present invention may also be treated as a fully-adjustable spillway with adjustment of the lever 106 or the float 72.

The float 72 may be placed on either side of the flood gate of this invention, depending on what body of water is used for the reference height or level. The float 72 may be located on either the high water side, or the low water side in a drainage system. For example, in an agricultural drainage system one might wish the flood gate to open in response to tidal movements, or it may be desired to respond to the level of the water already in the drain.

It can be seen that the present invention provides an improved flood gate which is able to be calibrated in order to provide unmanned flood mitigation, to minimise the risk of tidal flooding, and to maximise the passage of fish through the flood gate. The flood gate of the present invention is substantially controlled by head water depth and influence on the flotation device 74. As previously mentioned, conventional flood gates only let water out of drains. The flood gate of the present invention lets calibrated amounts of water, including sea water, back in.

The flood gate of the present invention may be easily fitted to an existing flood gate structure, and may be constructed from a wide variety of materials, including polytetrafluoroethylene, marine plywood, stainless steel, and high-density plastics material.

The claims form part of the disclosure of this specification.