The Tichborne river restoration project, on the Cheriton Stream, was one of the most challenging and diverse of its kind ever to be conceived, designed and delivered by Aquascience. The result was 825m of restored or revived chalk stream habitat and a Highly Commended Certificate at the 2018 River Restoration Centre conference.
The Cheriton Stream is a SSSI/SAC and the historic lake at Tichborne Park was identified as an impoverished chalk stream environment, which was having significant impacts on the SSSI/SAC, such as:
- Obstacles to fish passage
- Reduction in upstream channel gradient
- Disconnection from the flood plain
- Sedimentation and obstructed sediment transportation
- Phosphate enrichment of downstream environments
After originally being contacted to quote for dredging the historic lake however, seeing an opportunity to restore the stream to natural circumstance, Aquascience designed a scheme to reinstate the channel to its natural course through the floodplain. The design included the removal of all three impoundments on the Cheriton Stream and turning the historic lake into a fen meadow and reed swamp, habitats which are features of the SSSI.
Aquascience carefully designed the restored channel, including profiles and gradients, but also encouraged excavator drivers to be inventive and create varied batters for a more natural finish. Introduction of flints and large wood debris into the channel further enhanced the diversity of habitats created in this restoration project.
A project of this size does not come without its challenges of course. Aquascience were not only responsible for the application of complex environmental permits and planning permission, but also thorough archaeological and ecological surveys for the grade II listed manor house and SSSI/SAC, respectively. Sediment mobilisation was also carefully managed throughout the project; managing flows, using sediment traps/barriers and pumping turbid waters onto flood meadows.
On top of the very successful channel reinstatement, Aquascience lined a leaking historic moat at the Tichborne House. The moat had previously been inline, via the lake, and had suffered from sedimentation as a result. In order to maintain the now offline moat, it needed to be drained, dredged and lined to fix the leak, including importing over 100t of stone and concrete to create a level, smooth bed for the liner. This was also completed successfully, and the moat was restored to being sediment and leak free.