River Rib Bengeo Fish Passage Restoration

This project looked to restore a stretch of the River Rib Bengeo, an iconic chalk stream in Hertfordshire. With limited fish passage, degraded habitat, and the presence of manmade impoundments, our project aimed to enhance the overall fish passage and habitats along the stretch. 

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RJBull Ltd were tasked with restoring the River Rib Bengeo, an iconic chalk stream in Hertfordshire. With the proposed reach facing numerous challenges, including limited fish passage, degraded habitat, and the presence of manmade impoundments, our project aimed to enhance fish migration, establish riparian vegetation, increase sinuosity, remove barriers to flow, and engage the public in the preservation of chalk stream ecosystems.

The AIM?

  • Improve overall fish passage to facilitate the migration of native fish species.

  • Establish riparian and marginal vegetation to stabilise banks, reduce erosion, and provide habitat for aquatic and terrestrial species.

  • Increase sinuosity to promote natural channel dynamics.
  • Remove impoundments to restore natural flow regimes and improve riverine habitat conditions.
  • Educate the public about the ecological importance of chalk streams and the need for conservation efforts.
  • Create a more diverse and sustainable habitat.
  • Regrade riverbanks to improve flood storage capacity by reconnecting the flood plain.

What were the challenges?

  • Significant shading along the river channel
  • A lack of vegetation both on banks and within the river
  • The presence of a large artificial impoundment beneath a footbridge
  • Undercut manmade features below a steep bank
  • Straightened river channel
  • Heavy public foot traffic in the project area
  • Overcome challenges related to limited site accessibility
  • Implement measures to mitigate sedimentation risks
  • Address concerns related to bank instability and erosion rates
  • Manage biosecurity risks posed by non-native invasive species

Before: Poor flow and habitat quality

During: Building of banks and improving flow

What were the results?

RJBull Ltd worked in collaboration develop a comprehensive restoration plan that integrated ecological principles with innovative fish easement solutions. The project site presented multiple complexities, including poor access, which limited/hindered logistical operations and biosecurity concerns related to invasive species, such as Himalayan Balsam and Signal Crayfish.

Our primary objective was to remove the weir under the footbridge and constructing a fish-friendly rock ramp, providing fish easement and linking them to the upper reaches of the river rib. The concrete removed from the weir was repurposed to protect a failing gabion wall, which had been built to try and prevent bank erosion on a sharp meander.

Selective tree coppicing opened the canopy to increase sunlight penetration, while hessian matting and the establishment of native marginal vegetation stabilised banks and enhanced the habitat. River restoration techniques, including bank regrading, woody structure placement, the creation of pool riffle sequences and bed reprofiling helped naturalise fluvial processes.

Heavy public foot traffic had to be managed to remove negative impacts on restoration efforts and the habitat itself. We used signage, site barriers and open correspondence with, the local community and Hertfordshire and Middlesex Wildlife Trust members, throughout the works to maintain a safe working environment and raising awareness about the importance of chalk streams and the need for conservation efforts. Temporary exclusion fencing was also put in place across sensitive areas throughout the project and following its completion to allow vegetation establishment and prevent further habitat damage.

Through innovative restoration methods, RJBull Ltd revitalized the River Rib Bengeo, creating a more sustainable ecosystem. The project demonstrates effective river restoration and the importance of holistic conservation approaches.

During: Developing habitats along the river utilising natural materials

After: Healthy flowing river with diverse ecosystem