Rock ramp construction
The Sussex Ouse splits at Sharpsbridge

The project at Sharpsbridge saw the construction and installation of a rock ramp in the western arm of the Ouse as it passes through the road bridge. This rock ramp serves to slightly raise water levels through the western culvert with the effect of ‘drowning out’ the downstream drop in water through the bridge, allowing passage for a far greater variety of fish species in a far greater amount of flows. The rocks themselves break up the flow of water, slowing it down through this section and creating broken water which will act as an attractant flow to fish species

The project team were keen to use locally sourced material, not only to fit in with the surroundings but also to keep the carbon footprint of the project as low as possible. Unfortunately the closest quarry couldn’t provide the material within the tolerances required to ensure the long term stability of the structure. Eventually we found a quarry in Kent who could provide ragstone within the specifications required and this formed the basis of the structure.

Kent ragstone was fixed in place and surrounded by smaller rock to create a more natural effect. Approximately 50% of each stone is buried to withstand the forces present within the river. In order to place the rocks the western channel was blocked using aquadams and pumps to move water through the eastern side of the bridge. Due to the wet weather throughout this project it was necessary to remove these dams on occasion to prevent flooding before waiting for water levels to drop again. Luckily the period of in-channel construction tied in to a period of dry weather and the project was completed without incident.

Following the completion of the project work was undertaken to rectify areas which have been used for access and the site compound. In addition signs were erected within the channel to advise canoeists of the rock area and divert them through the eastern culvert which remains as it was.

Jim the Fish

Jim's Diary

Country ramblings from OART field officer Jim Smith

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