GB2466978A

GB2466978A - Gate for controlling the flow of water through a flood defence

Info

Publication number: GB2466978A
Application number: GB0900716A
Authority: GB
Inventors: Michael Charles Williams; Stephen David Kingett
Original assignee: ENVIRONMENT AGENCY
Current assignee: ENVIRONMENT AGENCY
Priority date: 2009-01-16
Filing date: 2009-01-16
Publication date: 2010-07-21
Also published as: GB0900716D0; WO2010082068A1

Abstract

The invention relates to a self regulating gate or valve 10 for controlling the flow of tidal waters. The gate or valve allows overflow water through a flood defence i.e. a barrage and also allows controlled inundation of defended land behind the flood defence to maintain fragile. The gate or valve 10 comprises a flow housing 12 defining at least one flow aperture, a gate 14 mounted about a pivotal axis 22 and movable across the face of the flow aperture for interrupting the flow of tidal water through the flow aperture. A flotation device 36 is connected to the gate 14 and adapted to rise and fall with tidal waters to control the position of the gate 14. The pivotal axis of the gate 14 is disposed at least substantially perpendicular to the face of the flow aperture such that water flow does not affect the operation of the gate.

Description

Gate for Controlling a Flow of Water The invention relates to a gate for controlling a flow of water and particularly to a gate for controlling tidal flows through flood defences.

Background to the Invention

A self regulating tide gate is a valve or gate, which allows outflow through a flood defence, but also allows controlled inundation of defended land behind the flood defence.

Until now, particularly in the UK, it has been usual to provide a flap valve, ie a flap hinged at its upper edge, in flood defences to allow outflow from defended land, but there has been no self regulating system for allowing controlled inundation of defended land from a rising tide. A typical flap valve, also known as a flapped outfall, is arranged to close under pressure of the rising tide, thus preventing flow of water to the defended land.

It allows free outflow and prevents backflow. A flap valve does not allow intertidal habitat creation because it prevents tidal ingress. It also prevents the passage of fish.

In locations where pedestrian access is required, water-tight floodgates can be fitted in embankments. These gates do not operate automatically and must closed manually when high tides are predicted. Floodgates are not suitable for intertidal habitat creation because they are either open or closed. They also require accurate tide predictions and manpower for their successful operation.

A self regulating tide gate allows the creation of inter-tidal habitats behind existing flood defences whilst maintaining a specified level of protection and enables habitats to be created in locations where removal of flood defences, for example, embankments, outfalls and other structures, is not possible.

In some high-risk locations it is known to provide automatically controlled penstocks to prevent tidal ingress. A processor monitors tide height using signals from a pressure transducer or float switch and closes the penstock using an electric motor at a pre-determined level. It is believed that such a system could be used to control tidal ingress for habitat creation by using numerous sensors to close or open the penstock to different degrees as required. However, this technology is expensive to install, requires regular maintenance and is prone to failures, It therefore requires an on-call workforce for safe operation. It also requires a power supply, which is not always available or desirable, particularly in remote locations.

A self regulating tide gate has been proposed in which a pivoting flood gate, pivoted from its upper edge in the manner of a flap valve, is connected to a buoyancy device or float by a mechanical linkage. The float and linkage control the rate of closing of the gate. When the tide is out, the float is in its lowest position and the gate is open, allowing free outflow. As the tide rises, the float rises causing the gate to close, but complete closure may not be attained until the tidal level is above the water level behind the defence, thus allowing for some limited backflow.

A problem of this type of arrangement is that it is difficult to adjust the position at which the gate opens and closes, and the rate of closing and the range of adjustment for closure at different water levels is limited. The linkage is complicated because in order for the gate to operate as desired, the flotation or buoyancy created by the float has to be magnified by the linkage to be sufficient to actuate the gate. The linkage is also prone to wear and requires maintenance, because it has many moving parts.

Another significant problem is that the force of water of a rising tide also acts against the opening face of the gate and in a direction to force the gate closed. This force may also be counter-balanced to some extent by outflow acting against the rear of the gate and therefore it is difficult to control the gate. It has been found in testing, that the gate closes suddenly with a bang, rather than closing gradually, and this shock loading could damage the device or the headwall over a period of time. Furthermore, due to tidal changes and the continuously changing level of outflow, which is usually highly weather dependent, the gate may need continuous adjustment to open and close as desired.

It is an object of the invention to provide a tidal gate which is self regulating and which reduces or substantially obviates the aforementioned problems.

Summary of the Invention

According to the present invention there is provided gate for controlling a flow of water comprising a flow housing defining at least one flow aperture, a gate mounted about a pivotal axis and movable across the face of the flow aperture for interrupting the flow of water through the flow aperture, a flotation device connected to the gate adapted to rise and fall with water level and to control the position of the gate, the pivotal axis of the gate being disposed perpendicular to, or substantially perpendicular to the face of the flow aperture.

It is an advantage of the invention that pressure of water against the gate does not affect the position of the gate because the gate moves substantially perpendicular to the direction of flow through the aperture.

Preferable and/or optional features of the invention are described in the appended claims 2to 13.

The gate can be used in a tidal position to allow limited back flow for the creation of intertidal habitat creation. It can be adjusted to suit different tidal ranges and can be opened and closed at different tide levels, within a given tidal range. The gate moves in an arc about a pivot perpendicularly to the flow of water and so the control of the gate is not substantially affected by flow acting against the gate. The incorporation of a conventional flapped valve enables the gate to be retro-fitted to any existing flapped valve outflow.

DeserIpfionoftheDrawIn For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way example, to the accompanying drawings, in which: Figurelshowsaschematicfintviewofaflmmbodimentofgate,withthegateinan open position Figure 2 shows a schematic front view of the gate of FIgure!, with the gate between the open and closed positions; Figure 3 shows a schematic perspective view of the gate of FIgure 1 from the rear, with thegateintheopenposition Figure4showsapluralityofschematicfrontviewsofthegateofFigurelinasequence, showing the opening and closing of the tide gate with the tide; Figuie5showsaplumlityofschematicfrontviewsofthegateofFigure 1 inasequence, showing the opening and closing of the tide gate with the tide, the gate being adjusted to operate at a different tidal range; Figure 6 shows a schematic front view of a second embodiment of gate, with the gate in a closedpositionatlowtide; Figure7showsaschematicfrontviewofthegateofFigure6,withthegateinanopen position between low and high tide; Figure 8 shows a schematic schematic front view of the gate of Figure 6, with the gate in a closed position at high tide; and Figure 9 shows a plurality of schematic front views of the gate of Figure 6 in a sequence, showing the movement of the tide gate with the tide.

Description of Preferred Embodiment(s)

Referring firstly to Figures 1 to 3, a first embodiment of self regulating tidal gate is indicated generally at 10. The tidal gate 10 includes a flow housing 12 for mounting to the tidal side of a flood defence and a gate 14, pivotally mounted to the flow housing 12 for controlling the flow of tidal waters through the housing 12. The housing 12, best seen in Figure 3, includes a substantially tubular member 16, which in the embodiment shown is cylindrical. First and second circumferential flangesl8, 20 are provided around the distal ends of the tubular member 16 and project upwards of the tubular member to form a mounting point for the gate 14.

An axle or shaft 22 is mounted between the upper ends of the first and second flanges 18, 20, and extends through the first flange 18 to provide a mounting for the gate 14. A reinforcing web 24 is disposed between the flanges 18, 20 and extends axially of the flow housing 12. The second or rear flange 20 can be used to mount the tidal gate 10 to an existing outflow.

The gate 14 is substantially shaped as a circular sector and is pivotally mounted at its upper end to the shaft 22. The gate 14 is free to swing across the face of the end of the flow housing 12, adjacent the first flange 18. Stop members (not shown) may be mounted to the sides of the gate 14, which act against the sides of the flange 18, to limit the movement of the gate 14, as required. A circular aperture 26 is provided through the gate 14 and is the same size as the central aperture, or flow aperture through the flow housing 12. The aperture is set to one side of the gate 14 and is positioned to be aligned with the flow aperture of the housing 12, as shown in Figure 1.

A control arm 26 is also pivotally mounted to the shaft 22 and extends to one side of the gate 14. A locking arm 28 extends perpendicularly downwards from the pivotal mounting of the control arm 26 and is braced to the control arm with a diagonal brace 30. An aperture 32 in the locking arm 28 is in radial alignment with a plurality of spaced apertures 34 in the gate 14. The lock member 28 can be fastened to the gate 14 by passing a bolt through the aperture 32 and any one of the apertures 34. By locking the control arm 26 in different positions relative to the gate 14, the gate 14 can be made to open and close in different tidal ranges, as explained further below.

A float or buoyancy device 36 is attached to the distal end of the control arm and is pivotally mounted to enable the float to maintain a constant orientation in the water. The float 36 is typically a polyethylene foam filled buoy.

Referring in particular to Figure 3, a further aperture 38 is provided in the side of the flow housing 12, which is covered with a pivotally mounted flap 40. The flap 40 is a typical flap valve hinged along its upper edge and allows outflow of water through the tidal gate in conventional manner.

Operation of the self regulating tidal gate will now be described with reference to Figures 4 and 5, in which sequences of movement are shown. In Figure 4, the gate 14 is initially shown to be fully open (a) with the tide at its lowest point. In this position the tidal level is below that of the gate 14 and the flap valve 40 operates to allow free outflow from the flow housing 12. As the tide comes in (b to e), the water level rises around the tidal gate until the tubular member 16 of the flow housing 12 is submerged (f). During this time, backflow or tidal ingress can pass through the flow housing to defended land behind. As the tide rises further (g) the upward pressure of the water acts on the float 36, causing the gate 14 to begin to close. The length of the control arm provides mechanical advantage to the upward force of the float 36 and minimally affects the tidal range required to move the gate from an open to a closed position. As the tide rises further (h to j) through a further 1.2m, the gate 14 pivots about the shaft 22 to a closed position. During this closure, the solid part of the gate moves across the flow aperture reducing its size until backflow through the flow housing 12 is prevented. As the tide goes out, the gate 14 moves back through stages (k) to (a) to the open position under its own weight. In order to achieve this, some counter-balancing of the gate 14 may be required.

S Referring in particular to Figure 5, a second sequence of operation is shown over a different tidal range. In this sequence, the control arm 26 has been locked to the gate 14 in a different position, to enable the gate 14 to operate over the different tidal range. At low tide (a) the gate 14 is fully open, and the water level is below the gate allowing free outflow from the flow housing 12. As soon as the tide begins to come in (b), the rising water level begins to act on the float 36, causing the gate to close, The gate 14 gradually closes (c to f) until the gate is fully closed (g) after the tide has risen only 1.Sm. In this arrangement, the amount of back flow through the flow housing 12 is limited, because as soon as the water level begins to rise, the gate 14 begins to close. Nevertheless, because the gate 14 is not fully closed until the tide has reached high tide, some back flow is able to occur, allowing the passage of fish and intertidal habitat creation.

Referring now to Figures 6 to 8, a second embodiment of the tidal gate is indicated at 50.

Features in common with features of the tidal gate 10 are designated with the same reference numerals. The construction of the flow housing 12 is substantially the same as in the previous embodiment, but the size of the gate is increased to facilitate the closing and opening of the gate over different tidal ranges. The connection of the float 36 has also been altered, to facilitate adjustment of the opening and closing of the gate.

In particular, the gate 54 is still substantially shaped as a circular sector and is pivotally mounted at its upper end to the shaft 22. An aperture 56 is disposed centrally of the gate 54, such that when the gate is hanging centrally, then the aperture 56 is aligned with the flow housing 12 and water can pass through the flow housing and gate 54. The aperture 56 is substantially circular, but is restricted by segments on either side, which form part of the solid gate 54. This is necessary, in order to reduce the size of the gate 54. A counter-balance arm 58 is mounted to the gate and extends substantially vertically upwards from the centre of the gate above the shaft 22, when the gate is in its central position, as shown in Figure 7. A counter-balance weight 60 is attached to the distal end of the counter-balance arm.

The float 36 is mounted on a support stem 62, which extends perpendicularly upwards from the control arm 26. The position of the float 36 on the support stem 62 can be adjusted by axially sliding the float along the support stem and fastening it by means of a bolt passing through one of a plurality of apertures 64. Similarly, the support stem is axially adjustable along the length of the control arm 26, and can be fastened in similar manner by passing one or more bolts through a plurality of apertures 66 provided through the control arm 26. The mounting of the control arm to the gate is adjustable in the same way as in the first embodiment, save that first and second plates 68, 70 are mounted on the gate 54 and control arm 26 respectively, there being a plurality of apertures in the plate 68 and one or two apertures in the plate 70, enabling the plates to be attached together in different positions by means of bolts.

The movement of the gate 54 with the rising tide can be seen through Figures 6 to 8. In Figure 6, the gate 54 is shown at low tide in its rest position, and the gate is closed. In this position, the portion of the gate 54 to the right hand side of the aperture 56, as viewed, acts to prevent flow through the flow housing 12 and the portion of the gate to the left hand side of the aperture 56, as viewed, has no effect. Outflow through the flap valve 40 can occur as usual in this tidal position. At mid tide as shown in Figure 7, the gate is fully open and the aperture 56 is aligned with the flow housing 12, and at high tide, as shown in Figure 8, the gate is again closed, but by the portion of the gate 54 to the left hand side of the aperture 56, as viewed.

This will now be described in more detail with reference to Figure 9. At low tide (a), the gate 54 is fully closed in its rest position and the aperture 56 through the gate is disposed to the left hand side of the flow housing 12, as viewed. The gate 54 remains closed until the tide reaches a level where the flow housing 12 is nearly submerged (d). As the tide continues to rise, (e to h) the gate 54 gradually opens, until it is fully open (i). As the tide continues to rise (j to m) the gate 54 gradually closes with the aperture 56 moving to the right hand side of the flow housing 12, as viewed, and the gate 54 is nearly fully closed (n) after the tide has risen 3.0m. Finally as the tide increased to high tide, the gate 54 closes (o) and risk of flooding is prevented. As the tide goes out, the gate 54 swings back through the stages (n to a) passing through the fully open position (i) to the fully closed position(a)underitsownweight In this sequence of drawings, it can be seen that the gate 54 opens and closes through an entirely different tidal range to those of Figures 4 and 5. This movement pennits the creation of a saline lagoon behind a sea defence by using salt water from an estuary. The dense salt water enters the estuary in a wedge underneath outgoing fresh water, and thereforeitisessentialforthegatetoitmainshutuntilthetideispaitwayinandthes alt water is available to be let in behind the flood defence. The gate 54 remains closed until the tide rises to a point (0) where it would pose a risk of flooding. At this point the gate is fully closed.

It will be appreciated that the design of tidal gate 10,50 is highly flexible, and in particular, the tidal gate 50 can be fine tuned by careful positioning of the float 36 relative to the gate. For example, adjustment of the support stem along the control arm 26 affects the depth of water at which the gate is closed at low tide but does not haves any effect on the height of the tide required to close the gate at high tide. Adjustment of the float 36 along the support stem does not substantially affect the closure of the gate at low tide, but does alterthe positionofclosureofthe gate athightide. Thepositionofthefloat36 relative to the control arm 26 also affects the rate of opening and closing of the gate 54.

Adjustment to cope with different tidal ranges can also be made by fixing the control arm 26 in a different angular position relative to the gate 54 and the combination of all of these adjustments enables the gate to be adapted to suit any tidal range. Both the tidal gate 10 and the tidal gate 50 are folly self regulating, and do not require any power supply for operation. Furthermore, the tidal gate 50 has a fail safe operation, because should the float 36 become detached from the gate 54 then the gate will return to its closed position as shown in FIgure 6, and the flow housing is closed to prevent any risk of flooding.

The tidal gates 10, 50 are made from 316 grade stainless steel save for the counter balance weights which are made from galvanised mild steel and the float 36 which is made from plastics filled with polyethylene foam. The tidal gates 10, 50 are relatively simple to manufacture and can be fitted to replace existing flapped outfalls, requiring little civil works on site. The tidal gates 10, 50 facilitate fish passage and do not have an adverse effect on ecology or sediment transfer. They permit and control tidal flows through flood defences and allow controlled inundation of defended land thus allowing the creation of inter tidal habitats behind existing flood defences whilst maintaining a specified level of protection. The amount of inundation or backflow can be changed to suit a particular tidal location, not only by the adjustment of the tidal gates 10, 50 described, but also by altering the size and shape of the apertures through the gates 14, 54. Most importantly, the fail safe position of the gate 50, as shown in Figure 6, prevents flooding. Although the gates 10, 50 have been described for use in tidal applications, it is also envisaged that the gates can be used in non-tidal applications, for example, where tributaries meet a river.

Claims

CLAIMS1. A gate for controlling a flow of water comprising a flow housing defining at least one flow aperture, a gate mounted about a pivotal axis and movable across the face of the flow aperture for interrupting the flow of water through the flow aperture, a flotation device connected to the gate adapted to rise and fall with water level and to control the position of the gate, the pivotal axis of the gate being disposed perpendicular to, or substantially perpendicular to the face of the flow aperture.
2. A gate as claimed in claim 1, in which the gate is pivotally mounted to the flow housing.
3. A gate as claimed in claim 1 or 2, in which an aperture is provided in the gate enabling water to flow through the flow aperture when the aperture in the gate and the flow aperture overlap.
4. A gate as claimed in any preceding claim, in which a control arm is connected to the gate, the flotation device being mounted to the control arm.
5. A gate as claimed in claim 4, in which the control aim is pivotally mounted to the flow housing about an axis co-axial with the pivotal axis of the gate, and the control arm is angularly adjustable relative to the gate.
6. A gate as claimed in claim 4 or claim 5, in which the flotation device is pivotally mounted to the control arm.
7. A gate as claimed in claim 4 or 5, in which the flotation device is mounted on a support stem, the support stem extending perpendicularly away from the control arm.
8. A gate as claimed in claim7, in which the position of the flotation device is axially adjustable along the support stem.
9. A gate as claimed in claim 7 or claim 8, in which the position of the support stem is axially adjustable along the control ann.
10. A gate as claimed in any preceding claim, in which a counter-balance arm is mounted to the gate and extends substantially to the other side of the pivotal axis.
11. A gate as claimed in claim 10, in which a counter-balance weight is mounted to the counter-balance-anm
12. A gate as claimed in any preceding claim, in which the flow housing is a substantially tubular member having first and second flanges at the distal ends thereof, and an axle extending between the flanges.
13. A gate as claimed in any preceding claim in which a hinged flap valve is provided in the side of the flow housing, for allowing egress of water from within the housing when the water level external of the flow housing is substantially below the level of the flap valve.
14. A gate substantially as described herein with reference to and as illustrated in Figures 1 to 5 and 6 to 9 of the accompanying drawings.