ALMQVIST, Jan-Erik (Allégatan 23, Boden, S-961 67, SE)
CLAIMS
1. A fish migration device (1) for a road culvert (2), characterised in that it comprises a movable part (3) which in a first position (11) retains an amount of water (4) and in a second position (12) retains a smaller amount of water.
2. A fish migration device as claimed in claim 1 , characterised in that the part (3) retains a smaller amount of water at high water flows than at low water flows.
3. A fish migration device as claimed in claim 1 or 2, characterised in that the part (3) is movably arranged to decrease its surface area facing the water flow at high water flows in order to retain less water.
4. A fish migration device as claimed in claim 3, characterised in that the part
(3) is movably arranged to increase its surface area facing the water flow at low water flows.
5. A fish migration device as claimed in any one of the preceding claims, characterised in that the part (3) comprises a flexible sheet (10) which is arranged on a support part (13).
6. A fish migration device as claimed in claim 5, characterised in that the flexible sheet (10) bends at high water flows to make way for more water and rises when the water flow decreases to retain water.
7. A fish migration device as claimed in claim 5 or 6, characterised in that the support part (13) comprises two parallel elements directed along the road culvert, for instance pipes (14) or wires (15).
8. A fish migration device as claimed in any one of the preceding claims, characterised in that the device comprises a rubber sheeting (16) arranged between the part (3) and the road culvert (2) for sealing purposes.
9. A fish migration device as claimed in any one of the preceding claims, characterised in that the device comprises a connection device (17) for a fish ladder (20) arranged outside the road culvert.
10. A fish migration device as claimed in claims 6 and 7, characterised in that the fish ladder (20) comprises a fastening device (21) for the rubber sheeting (16) to prevent water leakage.
11. A fish migration device as claimed in any one of claims 5-7, characterised in that the fish ladder (20) comprises one or more sheets (22) arranged between two parallel longitudinal carrier elements (22), preferably pipes.
12. A fish migration device as claimed in any one of claim 5-7, characterised in that the sheet (10) comprises a recess (5) arranged in the centre of the sheet as an outlet for water.
13. A fish migration device as claimed in any one of the preceding claims, characterised in that the device comprises a heating device for melting ice in the road culvert (2).
14. A fish migration device as claimed in claim 13, characterised in that the heating device comprises an electric heating cable (18) arranged along the culvert.
15. A fish migration device as claimed in any one of claims 1-4, characterised in that the part (3) comprises a hinged rigid sheet which is arranged to bend at the hinge at high water flows.
16. A fish migration device as claimed in claim 15, characterised in that the hinged sheet is manually bent back to its original position.
17. A fish migration device as claimed in claim 15, characterised in that the hinged sheet is bent back to its original position by spring force. |
MIGRATORY FISH DEVICE FOR A ROAD CULVERT
The invention relates to a fish migration device for a road culvert.
When building motor roads, railways and the like, it is common to arrange a bank as a stable base for the road. If a watercourse is to be crossed, a bridge is built over the watercourse or the water is conducted through a road culvert under the road. The road culvert is dimensioned so that also a high water flow, for instance a great spring flood, can pass without causing flooding or damaging the road. Fish migrating upstream in a watercourse to spawn, however, sometimes experience problems in the road culvert. The outlet may be located high up from the road culvert, or it may be difficult for the fish to pass through the road culvert. The most frequent problems for the fish swimming through the road culvert is that the culvert contains too little water, or the velocity of the water is too great for the fish to manage. The velocity of the water usually increases through the road culvert.
A prior solution to this problem is to place stones in the road culvert. The stones are placed so as to create a number of dams on the way through the road culvert. In this manner, there is always a certain minimum amount of water while at the same time it is possible for the fish to rest on their way through the road culvert. The drawback of this solution is that the stones also reduce the flow through the road culvert in case of a high water flow, for instance spring flood and heavy rain, that is to say times when the fish do not migrate anyway. This means that a larger road culvert is necessary to manage the peaks at a high water flow and prevent flooding or damage to the road. It is expensive to replace previously installed road culverts, and installing a larger drum than necessary also results in extra costs and additional work.
The invention solves the above problem by a fish migration device which retains a certain amount of water at low and normal water flows and makes way for a large amount of water at high flows.
Fig. 1 shows the invention in a road culvert.
Fig. 2 shows an embodiment of the invention.
Fig. 3 shows the invention at a high water flow. Fig. 4 shows a sheet.
Fig. 5a shows a support part pipes.
Fig. 5b shows a support part wires. Fig. 6 shows a connection to a fish ladder. Fig. 7 shows a heating device. Fig. 8 shows a connection at a difference in altitude.
Fig. 1 illustrates a fish migration device (1) for a road culvert (2). The device (1) is arranged in the road culvert (2) which is mainly arranged horizontally or with a minor inclination. With fish migrating upstream in the road culvert, there must be a certain amount of water for the fish to continue. In addition, the water is not allowed to flow too rapidly over a long distance for the fish to manage through it.
The fish migration device comprises a movable part (3) which in different positions retains a varying amount of water (4). The movable part (3) is arranged to decrease its surface area facing the water flow at high water flows in order to retain less water and make way for more water, and to increase its surface area facing the water flow at low water flows in order to decelerate and retain a sufficient amount of water. The movable part can be made of a flexible material which bends when subjected to a sufficient pressure in order to decrease its surface acting against the pressure or a spring-loaded plate which bends about an axis when the pressure exerted by the water flow increases. In a further variant, the movable part decreases and increases its surface area facing the water flow in a manual process.
The fish migration device (1) shown in Figs 2-3 comprises a movable part (3) which retains a certain amount of water (4) in the road culvert (2). The movable part (3) comprises a flexible sheet (10). In long road culverts, a plurality of sheets (10) in succession are suitably used in order to also create calmer zones where the fish can rest before passing the next sheet. A sealing part (9) is also arranged on the sheet (10). The sealing part (10) seals against the bottom of the culvert. The sealing part
(9) is suitably made of a material which can seal against concrete or corrugated sheet metal, for instance a softer form of rubber. Fig. 3 shows how the flexible sheet
(10) bends away from a first normal position (11), which retains a certain amount of water (4), to a second downwardly bent position (12). The downwardly bent position (12) is provided by the pressure exerted by the water flow. In the downwardly bent position (12), the surface area of the sheet facing the water flow is smaller and more water is allowed to pass. Once the high flow has decreased, the sheet springs back to its normal position (11).
Fig. 4 shows the sheet (10) arranged on a support part (13). The support part (13) is arranged between two parallel longitudinal carrier elements (14, 15). Figs 5a and 5b illustrate different alternatives of carrier element, such as pipes (14) and wires (15). In the alternative shown in Fig. 5a, the support part (13) is attached to the pipes (14) by a coupling part (19). The coupling part (19) is used to connect the carrier elements (14) to additional carrier elements (14) (see Fig. 2). In this manner, it is easy to make a fish migration device with more sheets, when required. If the inclination of the road culvert is great, more sheets may be required, whereas if the difference in altitude is small, one or two sheets may be enough to decelerate the water. Fig. 5b shows the alternative involving a wire as carrier element (15). Here the support part (13) is attached to the wire using, for instance, a clamp. If several sheets are required, several support elements are attached along the wire. No matter which alternative of carrier element is used, they are attached in a suitable manner to the road culvert or to the inlet and/or the outlet.
The sheet (10) comprises an outlet in the form of a recess (5). The recess (5) concentrates the water flow to a smaller part and thus creates a flow which often is sufficient for the fish to migrate upstream. In the Figures, the outlet is arranged alternately laterally offset like in a fish ladder. Another alternative is to arrange the recess in the centre of the sheet, which would result in more uniform stress in the sheet and a more uniform water flow as the sheet bends.
The flexible sheet (10) is suitably made of a material which is strong enough to retain an amount of water and at the same time sufficiently flexible to be able to bend at high water flows, such as spring flood and heavy rain, so as then to resume its original retaining shape. Besides, the material should preferably also manage both summer and winter temperatures and other season-dependent stresses. Suitable materials are, for instance, plastic and/or rubber.
Road culverts are usually made of interconnected concrete pipes or corrugated metal pipes. Both variants have their advantages and disadvantages. Road culverts of corrugated metal make it difficult to establish a good seal against the inner wall of the road culvert. Road culverts in the form of concrete pipes often meet with displacements between the pipe sections, in particular between the outermost part/parts and the rest. This results in leakage in the joints and water leaking out,
which means that the culvert can become dry. Moreover, the water leakage may cause erosion, which may affect both road and culvert, with the ensuing expensive repairs.
To prevent this, the device according to the invention comprises a sealing sheet (16), preferably a rubber sheeting, arranged between the wall of the road culvert and the movable part (3). In most cases, the rubber sheet (16) need not be used along the entire road culvert, but above all at the outlet, in order to seal between pipe sections, if any, and also to seal in the transition to a possible fish ladder located outside.
Fig. 6 shows a connection (17) to a fish ladder (20) arranged outside the road culvert. A seal is arranged between the connection (17) and the fish ladder (20) to prevent water leakage. The seal may comprise, for example, a sealing sheet in the road culvert which is attached to the fish ladder. The Figure shows that the fish ladder (20) comprises a fastening device (21) for a sealing sheet arranged in the road culvert.
Fig. 7 shows a heating device arranged along the road culvert. The heating device comprises an electric heating cable (18) and is used to melt ice in the road culvert (2).
Fig. 8 shows how the invention can be used as a fish ladder in case of a difference in altitude between the bottom of the road culvert and the bottom of a ditch. The fish ladder (20) comprises a plurality of sheets (22) arranged in a duct (24). The fish ladder (20) also comprises fastening means (25) for a fish migration device as described above.
The Figures illustrate an embodiment of the invention. Other embodiments are conceivable. In another embodiment, the movable part comprises one or more hinged rigid sheets. When the sheet is in its upright position, it retains an amount of water. If the water pressure exerted on the sheet is too great, it bends at its hinge, thus decreasing its surface area facing the water and making way for more water. When the water flow decreases, the sheet can rise again to its upright position, for example, by spring force. In a further embodiment involving a hinged rigid sheet, the sheets are manually pivoted between their two positions. This can take place, for example, by a wire attached to the sheet. If this solution is applied, a supervisor must
pivot the sheets downwards and enable a greater water flow in the autumn and, after the spring flood, raise the sheets to their retaining position.
Prior-art solutions involving stones in the road culvert cause a number of further drawbacks. For instance, it is heavy work to carry the stones and arrange them in the road culvert. Mud and rubbish easily get stuck among the stones and must be removed at regular intervals. Today this occurs by the stones being removed, cleaned and put back. In contrast, the invention is easy to arrange in the road culvert and easy to remove for cleaning and also to be used again in another culvert in case of alteration.
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