NL2007193C2

NL2007193C2 - A fish passage.

Info

Publication number: NL2007193C2
Application number: NL2007193A
Authority: NL
Inventors: Alex Peter Loon
Original assignee: Enrin Environmental Res Instr
Priority date: 2011-07-28
Filing date: 2011-07-28
Publication date: 2013-01-29

Description

A fish passage

Many waterways contain artificial barriers such as dams, locks and weirs. These barriers are typically in place 5 to alter the flow characteristics of a waterway, for example to prevent flooding. A disadvantage to their use is that they prevent the migration of native fish, which in turn can lead to a decline in fish stocks and/or reduced biodiversity. One way to overcome these problems is through the use of fish pas-10 sages.

Fish passages are structures on or around barriers (such as dams, locks and weirs) to allow fish to overcome the barrier and facilitate their natural migration.

The present invention relates to a fish passage com-15 prising at least a plurality of linear segments comprising at least a U-form construction of a base and a first and a second side wall, and a partition provided with a slot.

Such a fish passage is known in practice and is commonly referred to as a 'de Wit' type fish passage.

20 The original 'de Wit' fish passage comprised a metal box divided into compartments by a series of partitions; the compartments being interconnected by openings alternately on the left and right of the partitions.

More recent incarnations of the 'de Wit' fish passage 25 are composed of prefabricated concrete segments.

It is an object of the invention to provide a fish passage with an improved design compared to the fish passages of the prior art in accordance with one or more of the appended claims.

30 It should be noted that in addition to the linear segments, the fish passage of the invention optionally further comprises corner segments useable in combination with the linear segments to allow the direction of the fish passage to be altered, for example turning it through 90 degrees.

35 In a first aspect of the invention, at least a top surface of the base is at an angle relative to an imaginary line perpendicular to the partition; this provides a gradual and natural slope to the bottom surface of the fish passage, which improves its passability for fish.

40 Preferably the top surface of each base lines up with 2 those of its neighbours such that a continuous slope is formed running the length of the fish passage.

It is advantageous to have a continuous slope in order to maintain a uniform depth of water and to minimise tur-5 bulence inside the fish passage. A layer of gravel or similar may additionally be provided on the upper surface of the base in order to modify frictional resistance and/or to make the fish passage more easily passable for small fish. Frictional resistance is defined as the retarding effect that a particu-10 lar surface has on the velocity of water passing over that surface.

In a preferred embodiment, at least the U-form construction of each of the linear segments that form the fish passage are similar in shape i.e. they vary only in length or 15 height; this is advantageous since, for example, the same mold can be used for their production.

In a preferred embodiment, at least the U-form constructions of each of the linear segments that form the fish passage are equivalent, thus simplifying manufacture and mini-20 mising costs.

It should be noted that the velocity of water passing through the slots of the fish passage should preferably be in the range of 0.5 to 1.5 m/s, more preferably about 1 m/s. If the velocity of water passing through the slots is too great 25 fish will not be able to ascend the fish passage; if the velocity of the water passing out of the fish trap is too low, certain fish will not be attracted to the fish passage.

Factors that determine the average velocity of water passing through the slots of the fish passage are the drop be-30 tween bodies of water above and below a barrier; the number of partitions through which the water must flow; frictional losses as water passes along the fish passage (frictional resistance) and acceleration due to gravity.

Features of the fish passage that can be tuned to ob-35 tain a suitable average velocity include the length of the linear segments i.e. the distance between adjacent partitions, the relative vertical displacement of two adjacent linear segments and the angle of the slope of the top surface of the base relative to an imaginary line perpendicular to the parti-40 tion.

3

The base should preferably be at an angle of between 2 and 5 degrees, more preferably between 2.3 and 4 degrees, most preferably about 3.5 degrees relative to an imaginary line perpendicular to the partition.

5 The average vertical displacement between pairs of adjacent linear segments should preferably be in the range of 40-110 mm, more preferably 40-90 mm, most preferably 50-80 mm.

The average linear segment length should preferably be in the range of 570-1700 mm, more preferably 700-1500 mm, 10 most preferably 800-1300 mm.

In a second aspect of the invention, an inside surface of each of the first and second side wall are angled such that a channel formed between the first and second side wall has non-uniform width. Preferably such that an inside surface 15 of each of the first and second side walls is at angle of between 2 and 3 degrees, more preferably between 2.2 and 2.4 degrees, and most preferably about 2.3 degrees relative to an imaginary line perpendicular to the partition.

With the U-form construction and preferably also the 20 partition being composed of a material that can be molded, such as concrete, it is advantageous to angle the first and second side walls of the U-form construction in order that at least the U-form construction can easily be removed from a mold during manufacture.

25 In a third aspect of the invention, at least a por tion of an edge of the partition having the slot of all but the last segment, be it a linear or corner segment, is rounded on an outlet side. Preferably this rounding is provided on the outlet side only. The effect of rounding at the outlet side of 30 the slot is to promote spreading of a stream of water as it passes out of the slot; consequently the energy of the stream and hence also its velocity is damped. Preferably the radius of the rounding at the outlet side of the slot is in the range 40 - 50 mm.

35 Conversely, at least a portion of an edge of the par tition having the slot of a segment (be it a linear or a corner segment) at an outlet of the fish passage is rounded at an inlet side only while the outlet side of the slot has sharp edges. This is in order to ensure that the stream of water ex-40 iting the fish passage is as compact as possible.

4

In a fourth aspect of the invention, the height and/or the width of the slots are selected at predetermined differing values. Thus after construction of the fish passage, not all slots are identical in shape and/or dimensions, but 5 preferably have equivalent surface areas through which the water is flowing so that it maintains the same speed. It should be noted however that it is equally in keeping with the spirit of the invention that each slot is embodied either as a doorway of fixed height that in use remains entirely submerged, or 10 as a vertical slot of fixed height that in use is not entirely submerged. The design is thus flexible and suitable for a broad range of applications.

In a fifth aspect of the invention, the fish passage further comprises a coupling element for coupling the segments 15 (linear and/or corner segments) together wherein the coupling element provides a means for staggering the segments such that they form a series of steps.

The coupling elements are preferably mountable between the segments in multiple orientations or vertical dis-20 placements, each orientation or vertical displacement providing a particular step size to the said series of steps.

In a sixth aspect of the invention, values for (i) the angle of a top surface of the base relative to an imaginary line perpendicular to the partition, and/or (ii) the step 25 size, and/or (iii) a length of each linear segment, and/or (iv) dimensions of the slot, are chosen such that the total average speed of water passing through each slot of the fish passage remains in the range of 0.5 to 1.5 m/s and preferably does not exceed about 1.00 m/s. This is in order to ensure 30 that the velocity of water passing through each doorway of the fish passage is great enough to attract fish to the fish passage, but not be so great that fish become washed back downstream or become exhausted to the point of inability to continue their journey through the fish passage and onwards. A 35 proper selection of said values as well as choosing the value of the angle of an inside surface of each of the first and second side walls relative to an imaginary line perpendicular to the partition, further contribute to the simple and inexpensive manufacturing and installation of the fish passage 40 according to the invention.

5

In a preferred embodiment other parameters that may be tuned to limit the flow of water through the slots of the fish passage include: the nature of at least a surface of the segments that in use is water contacting; the depth of water 5 in the segments; the form of the slots.

In a seventh and final aspect of the invention, the fish passage preferably further comprises two series of piles in the ground, each series of piles supporting one of two girders, and said two girders supporting the segments (linear 10 and/or corner segments) mounted thereon. Piles are particularly advantageous for use in areas where the ground is soft such as in wetland areas where other types of foundation would not be able to provide sufficient support. The girders are preferably provided with steps at their upper surface, wherein 15 said steps have preselected stepsizes. By providing steps having preselected stepsizes coupling of the segments (linear and/or corner segments) during construction of the fish passage is greatly facilitated; the stepped girders further serve to strengthen the fish passage.

20 The invention will hereinafter be elucidated with reference to the drawing of Figures 1-9 showing an exemplary embodiment which is not limiting of the appended claims.

In the drawing:

Figure 1 shows a fish passage.

25 Figure 2 shows a front view of a linear segment of the fish passage;

Figure 3 shows a cross-section of a linear segement of the fish passage;

Figure 4 shows a top view of a linear segment of the 30 fish passage;

Figure 5 shows a view of the slots;

Figure 6 shows an example of a coupling element;

Figure 7 shows an example of the compling element in use; 35 Figure 8 shows a side view of a number of linear seg ments arranged to form part of a fish passage;

Figure 9 shows a top view of a linear segment mounted on girders.

Whenever in the figures the same reference numerals 40 are applied, these numerals refer to the same parts.

6

With reference first to Figure 1, a view of a preferred embodiment of a fish passage (1) is shown comprising both linear segments (2) and corner segments (2'). Fish are able to enter the fish passage via the outlet (0) from a first 5 body of water (X), ascend the fish passage by passing through the series of slots (8) to emerge via an inlet (I) into a second body of water (Y) above the barrier.

It should be appreciated that a fish passage (1) comprising only linear segments (2) is also completely in keeping 10 with the spirit of the invention and that for many applications a fish passage comprising only linear segments (2) is preferred. An embodiment of the fish passage (1) of the invention as shown in Figure 1 comprising two corner segments (2') does however offer a number of advantages, namely: such a fish 15 passage can be constructed almost entirely on land i.e. in the dry; the fish passage (1) does not need to pass through the barrier; the distance between an inlet (I) and an outlet (0) of the fish passage (1) can be shorter than for a fish passage composed only of linear segments (2). In the case that the 20 fish passage (1) comprises only linear segments, the fish passage (1) passes either through or alongside the barrier such that it does not adversely affect the function of the barrier.

With reference to Figures 2-4 alternative views of a linear segment (2) of the fish passage (1) of the invention 25 are shown comprising at least (i) a U-form construction (3) of a base (4) and a first (5) and a second (6) side wall, and (ii) a partition (7) provided with a slot (8). In this embodiment the slot (8) is shown as a doorway, however in alternative embodiments that are equally in keeping with the spirit 30 of the invention the slots are embodied as vertical slots of fixed height, or as slots whose height and/or width is selected at a predetermined variable value. In this preferred embodiment, the first and second side walls (5,6) are further provided with threaded screw holes (9) and channels (10) that 35 run the length of the linear segment; the threaded screw holes (9) and channels (10) are provided for the purpose of coupling the segments (2 and/or 2'); the first and second side walls (5,6) must be sufficiently thick to house the channel and to give the structure sufficient strength. The U-form construc-40 tion (3) is further provided with a projecting lip (11) for 7 ensuring a seal between two adjacent segments (2 and/or 2’) of the fish passage (1) and a grid (12) or a solid lid as a cover for the fish passage (1). The linear segments are preferably molded as a single piece comprising the U-shape construction 5 (3) and the partition (4) from a moldable material such as concrete. The seal is completable by filling spaces between two adjacent segments with a sealant, for example grout.

A top surface (13) of the base (4) is declined at an angle (0) relative to an imaginary line (A) perpendicular to 10 the partition (7). The length of the linear segment (B) and the step size (C) is also shown. The step size (C) is the relative vertical displacement of two neighbouring segments (2 and/or 2') and is preferably equivalent to the product of the length of the linear segment (B) and tan 0. The angle (0) , the 15 length of the segment (B) and the step size (C) are equivalent for each of the linear segments forming the fish passage (1) of this preferred embodiment of the invention. Whilst infinite combinations of values for these parameters are possible that would result in an average flow velocity in the range of 0.5-20 1.5 m/s through the slots (8) of the partitions (7), only lim ited ranges are acceptable in practice. These relate both to ease/practicality of manufacture and cost. A balance needs to be drawn between having as few segments (2 and/or 2') as possible and the total span of the fish passage. Suitable values 25 are for: 0 - any value between 2 and 5 degrees, more preferable between 2.3 and 4 degrees, but most preferably 3.5 degrees; C - any value in the range of 40-110 mm, more pref-30 erably 40-90 mm, most preferably 50-80 mm.

B - any value in the range of 570-1700 mm, more preferably 700-1500 mm, most preferably 800-1300 mm.

In Figure 4, it is shown that an inside surface of each of the side walls (5,6) of each linear segment (2) are 35 angled such that a channel formed between the first and second side wall (5,6) has non-uniform width. In particular, an inside surface of each of the first and second side walls (5,6) is at angle (¢)) of between 2 and 3 degrees, more preferably between 2.2 and 2.4 degrees, and most preferably about 2.3 de-40 grees relative to an imaginary line (A) perpendicular to the 8 partition (7).

Figure 5 is a view of a linear segment (2) at an outlet (0) of the fish passage showing slots SI and S2. A fish entering the fish passage must pass through slot S2. Partition 5 PI (7) is rounded on the outlet side such that water passing through the slot disperses; in contrast, partition P2 is rounded only on an inlet side in order that the outflow of water from the fish passage is as uniform as possible.

Figure 5 shows further that the vertical upstanding 10 walls of the slots are parallel to each other and at their exit side perpendicular to the partition to optimize the attraction of fish.

Figures 6-8 show a preferred embodiment of the coupling element (14) and an example of its use for coupling lin-15 ear segments (2). The coupling element comprises two elliptical holes (15, 17) through which for example a bolt (18) or bar (19) may be passed and securedly fixed with a correspondingly sized nut (20), and a nut (16) that forms a part of the coupling element. At least a portion of the bar is threaded 20 and should preferably have the same diameter and thread size as the bolt (18) .

The step size between a pair of linear segments (2) joined by coupling element (14) is dependent upon the orientation of the coupling element (14): the step size (C) is either 25 the distance D1 or the distance D2. The sizes of the holes (15, 17) should be equivalent. It is advantageous to provide elliptical holes (15, 17) since they provide more flexibility in terms of the step size (C) between two consecutive segments (2 and/or 2') I.e. some variability is possible in the values 30 of D1 and D2. When D1 and D2 are exactly known it is advantageous for reasons of cost to replace the two elliptical holes (15, 17) with cylindrical holes. Each of the linear segments (2) and preferably also the corner segments (2') when used, should preferably be provided with channels (10) and threaded 35 screw holes (9) as shown in Figure 2.

Figures 8 and 9 show the fish passage further comprising two series of piles (22) in the ground, each series of piles (22) supporting one of two girders (21), and said two girders (21) supporting the segments (2 and/or 2') mounted thereon.

40 The girders (21) are provided with steps (23) at their upper 9 surface; the steps (23) have preselected stepsizes equivalent to the aforementioned step size (C). The piles are driven into the ground in order to provide the fish passage with sufficient support and stability. The segments (2 and/or 2') are 5 preferably fixed to the girders (21), preferably by means of a bolt or bolts (24) passed through the base of the segments (2 and/or 2' ) .

Claims

A fish passage (1) comprising at least a plurality of linear segments (2) with at least one U-shaped structure (3) of a base (4), a first and a second side wall (5,6), and a partition (7) ) provided with a slot (8), characterized in that at least one upper surface (13) of the base (4) of each linear segment (2) is at an angle (0) with respect to an imaginary line ( A) perpendicular to the bulkhead (7).

Fish passage (1) according to claim 1, characterized in that an upper surface (13) of the base is at an angle (0) of between 2 and 5 degrees, more preferably between 2.3 and 4 degrees and most preferably about 3.5 degrees with respect to an imaginary line (A) perpendicular to the baffle (7).

Fish passage (1) according to at least one of the preceding claims, characterized in that the average vertical displacement (C) between adjacent segments is between 40 and 110 mm, more preferably between 40 and 90 mm and with the most preferably between 50 and 80 mm.

Fish passage (1) according to at least one of the preceding claims, characterized in that the sectional section length (B) is between 570 and 1700 mm, more preferably between 700 and 1500 mm and most preferably between 800 and 1300 mm.

A fish passage (1) according to at least one of the preceding claims, characterized in that an inner surface of each pair of first and second side walls (5, 6) is slanted such that a channel that runs between each pair of first and second second side walls is formed has a non-uniform width.

Fish passage (1) according to at least one of the preceding claims, characterized in that an inner surface of each first and second side wall (5, 6) at an angle (<j>) of between 2 and 3 degrees, more preferably between 2.2 and 2.4 degrees and most preferably about 2.3 degrees with respect to an imaginary line (A) perpendicular to the bulkhead (7). 2007193

Fish passage (1) according to at least one of the preceding claims, characterized in that at least a part of an edge of the baffle (7) is rounded off with the slot (8) on an outlet side.

Fish passage (1) according to at least one of the preceding claims 1-6, characterized in that at least a part of an edge of the baffle (7) which connects the slot (8) of a segment to an output of has the fish passage, is only rounded on an input side and is provided with sharp edges on an output side.

Fish passage (1) according to at least one of the preceding claims, characterized in that the height and / or width of the slot (7) is selected for a predetermined variable value.

Fish passage (1) according to at least one of the preceding claims, characterized in that the fish passage further comprises a coupling element (14) for coupling the segments, wherein the coupling element (14) offers the possibility of zigzagging the segments. to form a series of steps.

11. Fish passage (1) according to claim 10, characterized in that the coupling elements (14) are mountable between the segments (2) in multiple orientations or vertical displacements, such that each orientation or displacement gives a certain step height to the series of steps .

Fish passage (1) according to at least one of the preceding claims, characterized in that values of (i) the angle (0) of a surface (14) of the base (4) with respect to an imaginary line (A) ) perpendicular to the bulkhead (7), and / or (ii) the step height (C), and / or (iii) the length of each linear segment (B) and / or (iv) the dimensions of the slot (8) ). chose such that the total average speed of water through each slot (8) of the fish pass does not exceed about 1.00 m / s.

Fish passage (1) according to at least one of the preceding claims, characterized in that it comprises two series of posts (22) in the ground, each series of posts (22) supporting one of two longitudinal beams (21), while the two lance beams support the segments (2) mounted thereon.

A fish pass (1) according to claim 13, characterized in that the longitudinal beams (21) are provided with steps (23) on their upper surface, the steps (23) having a preselected step height (C). 20 07 193