River Test and Floodplain Lake and River Restoration

For this project we were tasked to construct an enriched biodiverse lake, along with rejuvenating a 900-meter stretch of the adjacent River Test. The site had significant scientific interest, so maximum habitat quality and biodiversity was the aim.

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We were tasked with constructing an enriched biodiverse lake spanning 15,000 square meters, with more than 60,000 m3 of material being moved, along with rejuvenating a 900-meter stretch of the adjacent River Test. Situated within a floodplain of significant scientific interest, this endeavour aimed to increase biodiversity, maximise habitat quality, and restore natural processes.

The Aim?

  • Cultivate biodiversity by establishing a vital wildlife habitat in the form of a lake.
  • Improve water quality through the strategic establishment of wetlands for contaminant filtration.
  • Reuse riparian and marginal turfs to support habitat restoration.
  • Utilise efficient material transportation techniques to navigate challenging terrain.
  • Enable access to previously inaccessible areas with minimal environmental impact.
  • Optimise ecosystem functionality by restoring and naturalising the river’s fluvial forms.
  • Construct a bridge and access platform to connect with an island within the lake.
  • Install a hatch system to regulate water outflow from the lake.

What were the challenges?

  • Address the previous habitat monoculture of the non-native poplar plantation
  • Navigate challenges posed by a high-water table and deep peaty soil
  • Work within the floodplain while considering adjacent Sites of Special Scientific Interest (SSSIs)
  • Resolve issues related to straightened and over-widened sections of the river, as well as shear undercut riverbanks
  • Navigate high vole activity in the project area
  • The need to establish clear communication channels for effective project coordination and completion
  • Be aware of public oversight of project activities
  • Manage diverse and large quantities of materials with specialized machinery
  • Overcome challenges related to poor accessibility on-site

During: Digging the lake

During: Freelands river restoration

What were the results?

Following the removal of over 300 non-native poplar trees, and the coppicing and relocation of native trees located on the site of excavation construction of the lake could begin. The site was partially located on the floodplain, therefore excavated material was to be tipped along a designated stretch of higher ground along the site boundary.

Due to the high-water table and poor ground conditions we opted to dig the lake wet, this meant using a long reach excavator and low ground pressure tracked machinery all running on biooil. The use of hardwood matts and construction of tracks using dug gravels meant we were able transport materials and machinery around site efficiently whilst reducing disturbance to the SSSI and surrounding habitats.

We utilized existing riparian and marginal vegetation turfs from the excavated area to reinstate lake margins, while selectively reintroducing native aquatic and riparian plant species to stabilize banks and filter pollutants. This also increased the rate of repopulation and provided a bridge from existing environments into the new lake.

The construction of natural features like wetlands, swales, and kingfisher banks enhances water filtration, recycles nutrients, and provides a more diverse habitat. Additionally, the large variation in bank and bed topography throughout the lake integrate habitat features such as shallow-water zones, vegetated margins, and submerged habitats to provide refuge, spawning grounds, and foraging areas for wildlife enhancing biodiversity and ecological resilience.

Lake Infrastructure Enhancements

The addition of an island connected to the lake edge by a bridge along with a the installation of an access platform, provide visitors with immersive experience and vantage points to appreciate the natural surroundings.

The deck and bridge structures were designed to seamlessly blend with the natural landscape while providing durability and safety, with tropical hardwood piles and beams being selected for their strength and resilience in aquatic environments, ensuring longevity and stability.

Innovative Hatch System

As previously mentioned within our lake construction project, we strategically incorporated a hatch system, designed to facilitate outfall into the constructed wetland system.

A reinforced cast concrete structure was chosen for its durability and resilience in aquatic environments, providing a sturdy foundation for the hatch system. User-friendly wooden hatch boards were fitted securely within the concrete body, allowing for easy adjustment of water levels as needed.

River Restoration

The 900m river restoration was essential to improve the over widened and slow flowing stretch. There was also a large vole population and heavily undercut banks in places along with neighbouring landowners and the SSSI status. To minimise disturbance to sensitive habitats and species we used hardwood matts to access the river in three points.

We implemented diverse river restoration techniques, including channel re-meandering, bank stabilisation, the introduction of berms using lake-excavated gravels and small woven willow toes, transplanting turfs for instant vegetation, riparian and marginal planting, and bed reprofiling to improve fluvial forms and overall river ecology. Furthermore, due to the large vole population along the reach, berms were only connected onto the existing banks at either end creating back waters further increasing habitat diversity and greatly reducing the impact of the restoration on the surrounding environment.

Conclusion

In conclusion, our team executed the ambitious project of constructing an enriched biodiverse lake and restoring a 900-meter stretch of the adjoining river with precision and environmental sensitivity. By integrating innovative techniques and adhering to sustainable practices, we created a valuable wildlife habitat, restored degraded river conditions, and contributed to biodiversity enhancement. This project underscores our expertise in geomorphology, river restoration, and habitat creation, showcasing our commitment to environmental stewardship and sustainable management practices.

During: Freelands deck, bridge and hatch system