GB2529207A

GB2529207A - Flood defence

Info

Publication number: GB2529207A
Application number: GB1414366.3A
Authority: GB
Inventors: Andrew Charles Tune; Kurt Daniel
Original assignee: Jackson H S & Son Fencing Ltd; H S JACKSON AND SON FENCING Ltd
Current assignee: Jackson H S & Son Fencing Ltd; H S JACKSON AND SON FENCING Ltd
Priority date: 2014-08-13
Filing date: 2014-08-13
Publication date: 2016-02-17
Also published as: GB201414366D0

Abstract

A flood defence1 in the form of fencing substantially constructed from timber and concrete in which a waterproof membrane 15 is sandwiched between two wooden panels (5 & 6 figure 6), the membrane extending below the lower edges of the panels in use and embedded in a concrete base (3 figure 1a). The panels may be constructed from horizontal layers of tongue and groove boards 10 placed back to back, wherein the membrane may be a damp course membrane. The panels (5 & 6 figure 6) may be staggered vertically relative to each other so that the lower edge of the panel nearest the flood risk is higher than the lowest edge of the panel furthest from the flood risk. The panels may be supported in an upright position by posts (7 & 8 figure 6). A later embodiment relates to a method for constructing said flood defence. The flood defence provides effective flood defence qualities whilst having aesthetic appeal.

Description

Flood Defence The present invention relates to a defence against flooding, in particular a defence in the form of fencing.

Floods are caused by many factors including heavy rainfall, highly accelerated snowmelt, severe winds over water, unusual high tides, tsunamis, or failure of dams, levees, retention ponds, or other structures that retained the water. Flooding may be exacerbated by increased amounts of impervious surface or by other natural hazards such as wildfires, which reduce the supply of vegetation that is able to absorb rainfall.

Periodic floods occur on many rivers, forming a surrounding region known as the flood plain. During times of rain, some of the water is retained in ponds or soil, some is absorbed by grass and vegetation and some evaporates, while the rest travels over the land as surface runoff. Floods occur when ponds, lakes, riverbeds, soil and vegetation cannot absorb all the water. Water then runs off the land in quantities that cannot be carried within stream channels or retained in natural ponds, lakes and man-made reservoirs. About thirty percent of all precipitation becomes runoff and that amount might be increased by water from melting snow or unusually heavy rainfall. River flooding is often caused by heavy rain, sometimes increased by melting snow.

Coastal areas are sometimes flooded by unusually high tides, such as spring tides, especially when compounded by high winds and storm surges.

Flooding has many impacts. Particularly, it damages property and endangers the lives of humans and other species. Rapid water runoff causes soil erosion and concomitant sediment deposition elsewhere, such as further downstream or down a coast. The spawning grounds for fish and other wildlife habitats may become polluted or completely destroyed. Some prolonged high floods may delay traffic in areas which lack elevated road-and railways. Floods may interfere with drainage and economic use of lands, such as interfering with farming. Structural damage may occur in bridge abutments, bank lines, sewer lines and other structures within flood ways. Waterway navigation and hydroelectric power are often impaired. Financial losses due to floods are typically millions of pounds each year.

A flood wall (or floodwall) is a permanent flood defence structure that prevents floodwater getting into a protected area. It is primarily a vertical artificial barrier designed temporarily to contain the waters of a river or other waterway which may rise to unusual levels during seasonal or extreme weather events. Flood walls are mainly used in locations where space is scarce, such as cities, or where building levees or dykes would interfere with other interests, such as existing buildings, historical architecture or commercial use of embankments.

A flood defence is any structure that is designed (or by virtue of its nature and location is able) to contain floodwaters and reduce the probability of flooding in the defended area. In the UK, such defences rarely exceed 5m in height and more commonly are 1-3m high.

A floodwall may be constructed from brick, masonry, concrete, sheet piling or a combination of these materials, usually as pre-fabricated units. Steel is the most common material for sheet piles, though the alternative of plastic may be used for situations where a lower inherent strength is acceptable. As a result, permanent flood walls are rarely aesthetically pleasing. Often it is appropriate to clad or treat a wall surface in some way to integrate it into the surroundings. Landscape character assessment can help to determine the appropriate type of finish. For example, the incorporation of flood defences into private gardens calls for imaginative design.

The secret of successful integration is to create a floodwall that does not look like a floodwall. The present invention seeks to achieve this by providing a flood defence that is effective in its purpose while being aesthetic. As such, it finds particular use in areas where aesthetics are important and flood protection is required to be discrete, for example in gardens and residential areas.

In particular, the invention resides in a flood defence substantially constructed from timber and concrete, in which a waterproof membrane is sandwiched between two wooden panels, the membrane extending below the lower edges of the panels in use and embedded in a concrete base.

Thus, the flood defence of the present invention combines effective flood defence qualities with essential perimeter protection whilst still delivering aesthetic appeal.

The flood defence of the invention is ideally placed to protect residential properties built on higher risk flood sites, or for homeowners whose properties are located within areas prone to occasional flooding.

In a particular embodiment, the flood defence is constructed from two panels arranged back to back. Each panel is constructed from vertically stacked rows of tongue and groove boards running horizontally, in which the lowest row of boards is constructed from base boards. To withstand being in a damp environment, it is advisable if the base boards are treated to Use Class 4 of British Standard 8417.

It is advantageous if the base boards of the panel that faces the flood risk are vertically offset from the base boards of the panel furthest from the flood risk. A vertical offset of about 50mm above the lower edge of the base boards of the panel furthest from the flood risk is found to be appropriate.

While any waterproof membrane may be used, it is advantageous if the membrane is typically used as a damp course membrane.

In use, the waterproof membrane is sized to extend below the bottom of both panels and it has been found that a depth of at least 100mm is suitable. The membrane turned to form a horizontal portion of a minimum of 100mm that turns away from the flood defence towards the flood risk.

It is ideal if the flood defence of the invention provides a barrier to flood water up to a height of at least about 600mm above ground level.

Ideally the flood defence has a witness-tested leakage rate of less than 1 litre per hour per metre base length of barrier, in accordance with PAS1 188-3 standard.

The present invention will now be described by way of example with reference to the figures, in which: Figure 1 is a schematic illustration of a complete flood defence of the invention in situ, in which Figure 1 a is a partial cut-through view of the flood defence and Figure lb is a plan view of the flood defence from above; Figure 2 illustrates the first phase of construction of the flood defence, in which Figure 2a is a cut through view of a trench and tall posts viewed from the flood side, and Figure 2b is a view of the trench and posts from above; Figure 3 illustrates construction of the first panel of boards, in which Figure 3a is a cut through view from the flood side, and Figure Sb is a view from above; Figure 4 illustrates attachment of the membrane to the flood defence, in which Figure 4a is a cut through view from the flood side, Figure 4b is a view from above, and Figure 4c is a partial cut through view from one end of the defence; Figure 5 illustrates the beginning of construction of the second panel of boards, in which Figure 5a is a cut through view from the flood side, Figure 5b is a view from above, and Figure 5c is a partial cut through view from one end; and Figure 6 illustrates the completed barrier, in which Figure 6a is a cut through view from the flood side, Figure 6b is a partial cut through view from above, and Figure 6c is a partial cut through view from one end.

As illustrated in Figures 1 a and 1 b, the flood defence 1 has two parts: a timber fence 2 and a concrete base 3.

As shown in Figure 1, the timber portion 2 of the flood defence 1 comprises two wooden panels 5, 6 arranged back to back and supported by upright wooden posts 7, 8. Each panel 5, 6 is made up of a number of tongue and groove boards 10 orientated horizontally and layered one on top of another to impart vertical height to the panel 5, 6. Each board 10 has a face height of approximately 124mm and length of 4700mm. Each panel 5, 6 is formed from six boards 10 arranged lengtbways horizontally and stacked one on top of each other with the tongue extending from the upper edge of one board 10 fitting snugly into a groove formed in the lower edge of the board 10 above. The lowest board 10 (in use) at the bottom of the panel 5, 6 is a base board 11 having the same dimensions of 124mm in height, 20 mm in width and a length of 4700mm. It has a flat base and a tongue along its upper edge. A base board is made from a specific type of timber that, when intensively treated to Use Class 4 of British Standard 8417, is ideal for areas of a fence that are in constant ground contact. As a result, base boards are particularly suitable for withstanding prolonged exposure to damp and water.

A continuous waterproof membrane 15 is sandwiched between the two panels 5, 6.

The membrane 15 may be any suitable membrane that is used for damp courses, such as Visqueen ZedexTM damp course membrane. The membrane 15 is typically manufactured from polyethylene co-polymer containing standard additives including UV stabiliser, organic and inorganic pigment additives and fillers, with or without aluminium foil. The membrane 15 is sized to extend below the bottom of each panel 5, 6, by a depth of at least 100mm. At the bottom of the membrane drop, the membrane is folded to form a horizontal portion of a minimum of 100mm. This horizontal portion extends away from the flood side 30 of the panel 5 and towards the flood risk.

The two panels 5, 6 are supported in an upright position and held together by vertical posts 7, 8. In the particular example illustrated, tall and intermediate posts 7, 8 are alternated. The tall posts 7 have a height of 1500mm and square sides each of about 91mm. The intermediate posts 8 are rectangular with approximate dimensions of 120mm by 34mm and a height of 900mm, of which 750mm is above ground and 150mm is buried below ground level.

In situ, the concrete base 3 is the lower part of the defence 1, the top of which is level with the Finished Ground Level (FGL) 20. Turning to Figures 2a and 2b, initially a trench 21 is dug, 300mm deep and 300mm wide, along the desired line of the flood defence 1. This depth is the minimum and may have to be increased in soft or permeable ground. Square holes 22 of size 300mm by 300mm are then dug to a further depth of 500mm (800mm below FGL), the centres of each hole being spaced apart by 1880 mm. The holes 22 are positioned along the wall of the trench 21 that lies furthest from the flood side 30. The bottom of each hole 22 is covered with a 50mm layer of gravel and/or ballast 23. A tall wooden post 7 is located substantially in the centre of each of the square holes 22 so that the side of each post that faces away from the flood side 30 is in the same horizontal plane as the wall of the trench 21 that is furthest from the flood side 30. Concrete 24 is poured into the holes 22 up to and level with the base of the trench 21.

As shown in Figure 3a and Figure 3b, a single layer of wooden base boards 32 is fixed between the tall posts 7 using 60mm screws (not shown) so that the bottom of the base boards is below FGL 20 by about 100mm. The base boards 32 are fixed to the flood side 30 of the posts 7. Five layers of tongue and groove boards 10, topped with a cover board 33, are then installed on top of the base boards 32 to build the panel 5 vertically. All boards 10 are fixed (screwed) at each end to the tall posts 7.

Turning to Figures 4a, 4b and 4c, the waterproof membrane 15 is temporarily attached by clamps to the uppermost edge of the top board 33 so that the membrane hangs down the flood side 30 of the panelS. The membrane 15 has a drop that allows it to hang below the bottom edge of the base boards 32 and into the trench 21 below FGL 20. The membrane 15 extends by about 250mm, of which a minimum of 100mm is folded horizontally, parallel to the base of the trench 21 and extending away from the flood side 30 of the panel 5, toward the flood risk. The membrane 15 is a continuous layer extending along the line of the flood defence 1.

As shown in Figures Sa, Sb and Sc, the second panel 6 is built up from the bottom of the barrier 1 in the same way as the first panel 5. Base boards 40 are fixed at the bottom of the barrier 1 but offset from the bottom edge of base boards 32 by 50mm.

Post sides 41 having dimensions of 900mm by 120mm by 34mm are placed on the flood side 30 of the base boards 40 and held in place by wooden blocks 42 sized to fit between the post sides 41 and the edge of the trench 21 nearest the flood risk.

The remaining tongue and groove boards 1 Oa are installed on top of base boards 40 before the post sides 41 and boards 40, iDa are fixed to the tall posts 7 using timber lock screws (not shown). The timber lock screws are fixed at least 600mm above FGL 20 to ensure that the membrane below this level is not compromised, 600mm being the effective height of the flood defence 1.

Finally, as illustrated in Figures 6a, 6b and 6c, the intermediate posts 8 are fixed in between tall posts 7 so that the centres of the tall posts 7 and intermediate posts 8 are 940mm apart. The intermediate posts 8 are fixed using timber lock screws (not shown), again above the effective height of the defence 1 (i.e. 600mm above FGL 20). Finally, the trench 21 is filled with concrete 24 up to FGL 20 to complete the assembly, making sure that the lower edge of the membrane 15 is held horizontally and in position while the concrete is poured.

The example illustrate and described above has a fence line of about 4151mm but it will be appreciated that the defence 1 may be extended to the required length. The defence 1 need not be extended in whole units, as described, but boards 10, 1 Oa may be cut to a shorter, intermediate, length if required.

Claims

CLAIMS: 1. A flood defence substantially constructed from wood and concrete, in which a waterproof membrane is sandwiched between two wooden panels, the membrane extending below the lower edges of the panels in use and embedded in a concrete base.
2. A flood defence as claimed in Claim 1, wherein the wooden panels are constructed from horizontal layers of tongue and groove boards.
3. A flood defence as claimed in Claim 2, wherein the lowest layer of boards is constructed from base boards.
4. A flood defence as claimed in Claim 3, wherein the base boards are treated to Use Class 4 of British Standard 8417.
5. A flood defence as claimed in any one of Claims 1 to 4, wherein the lowest edge of the panel nearest the flood risk is vertically offset from the lowest edge of the panel furthest from the flood risk.
6. A flood defence as claimed in Claim 5, wherein the vertical offset is about 50mm above the lower edge of the panel furthest from the flood risk.
7. A flood defence as claimed in any one of Claims 1 to 6, wherein the waterproof membrane is a damp course membrane.
8. A flood defence as claimed in any one of Claims 1 to 7, wherein the waterproof membrane is sized to extend below the lowest edge of the panels by a depth of at least 250mm.
9. A flood defence as claimed in Claim 8, wherein the waterproof membrane extends below the lowest edge of the panels by a depth of at least 100mm before the membrane turns to form a horizontal portion of a minimum of 100mm that extends away from the flood defence towards the flood risk.
10. A flood defence as claimed in any one of Claims ito 9, wherein the flood defence provides a barrier to flood water up to a height of at least about 600mm above ground level.
11. A flood defence as claimed in any one of Claims 1 to 10, wherein flood defence has a witness-tested leakage rate of less than 1 litre per hour per metre base length of barrier.
12. A method for constructing a flood defence as claimed in any one of Claims ito ii, wherein the method comprises the steps: i) excavating a trench; U) digging at least two holes along the wall of the trench that lies furthest from a flood risk, optionally covering the bottom of each hole with gravel and/or ballast; Ui) locating a first wooden post in the centre of each hole and filling each hole with concrete up to and level with the base of the trench; iv) fixing a wooden base board to the posts on the side furthest from the flood risk; v) fixing to the base board two or more vertical layers of tongue and groove boards, optionally including a cover board as a final layer, and fixing all layers to the posts to form a first panel; vi) fixing a waterproof membrane to the highest board on the first panel so that the membrane covers the boards on the side facing the flood risk, the membrane having a drop that allows it to hang below the bottom edge of the base boards and into the trench below finished ground level; vU) folding the lowest edge of the waterproof membrane horizontally away from the panel towards the flood risk; vUi) constructing a second panel with a lowest layer being a base board and at least two vertical layers of tongue and groove boards above the base board, and attaching the second panel to the first posts to sandwich the membrane between the two panels; ix) fixing second posts at a distance that substantially bisects the distance between the first posts; and x) filling the trench with concrete up to a finished ground level.
13. A method according to Claim 12, wherein the trench has a width of about 300mm, a depth of at least about 300mm and a length of at least about 1880mm.
14. A method according to Claim 12 or Claim 13, wherein the at least two holes are dug to a depth of about 500mm below the trench.
15. A method according to any one of Claims 12 to 14, wherein the centre of each hole is spaced apart by about 1880mm.
16. A method according to any one of Claims 12 to 15, wherein the bottom of each hole is covered with gravel and/or ballast to a depth of about 50mm.
17. A method according to any one of Claims 12 to 16, wherein the first wooden post has a height of about 1500mm, of which about 750mm is located below finished ground level.
18. A method according to any one of Claims 12 to 17, wherein the lowest edge of the base boards is located about 100mm below finished ground level.
19. A method according to any one of Claims 12 to 18, wherein the membrane extends by about 250mm below the lowest edge of the base boards.
20. A method according to Claim 19, wherein the lowest at least about 100mm of the waterproof membrane is folded horizontally away from the base boards towards the flood risk.
21. A method according to any one of Claims 12 to 19 wherein the base board of the second panel is vertically offset from the lowest edge of base board of the first panel.
22. A method according to Claim 21, wherein the base board of the second panel is vertically offset from the lowest edge of base board of the first panel by about 50mm.
23. A method according to any one of Claims 12 to 22, wherein the second panel is fixed to the first posts by post sides located on the flood side of the base boards.
24. A method according to Claim 23, wherein the post sides have dimensions of 900mm by 120mm by 34mm.
25. A method according to Claim 23 or Claim 24, wherein the post sides are held in place by wooden blocks.
26. A method according to Claim 25, wherein the wooden blocks are sized to fit between the post sides and the edge of the trench nearest the flood risk.
27. A method according to any one of Claims 12 to 26, wherein second posts have a height of about 900mm, of which about 150mm is located below finished ground level.
28. A flood defence substantially as described herein.
29. A flood defence substantially as illustrated in Figures 1 and 6.
30. A method for constructing a flood defence substantially as illustrated in Figures 2 to 6.