River Restoration on the River Cam

Our approach

The solution

This project formed part of our WINEP AMP7 into AMP8 river restoration framework with Affinity Water.

As part of this design and build contract we completed a catchment scale scoping stage in 2022 identifying suitable restoration and enhancement areas along the catchment, before a shortlisted optioneering report was completed, where the River Cam was spilt into suitable reaches. This restoration project focuses on reach 2.

Reach 2 had a longlist of six possible river restoration options presented to Affinity Water and key stakeholders. At concept stage, budget construction costs were provided for two options. These were then progressed to outline design for in-channel enhancements and tree thinning.

When proposing options and concept designs, it was important that we engaged with key stakeholders to ensure they were on board, as well as giving an opportunity to obtain feedback from them. During our design phase we carried out multiple stakeholder engagement session over teleconference calls, as well as through site visits.

To inform our designs the following surveys and assessments were completed:

• A River Condition Assessment was undertaken which produced a score of moderate and under WFD is classified as heavily modified.
• A Preliminary Ecological Appraisal (PEA) was also undertaken to identify any ecological constraints and considerations, it concluded that the works are unlikely to pose a risk.
• Topographic Surveys were completed to understand the bank and bed levels, along with silt depth.
• Hydraulic Modelling was commissioned to understand the flood impact

Appropriate permitting and consents were obtained – including a Flood Risk Activity Permit (FRAP).

During the construction phase, we utilised the innovate spider excavator to complete works due to the high embankments. The works completed included: bed raising through riffle installation, woody debris through hinged and pinned site won trees, bank regrading, spoil and brushwood berms. We were able to clean up and the historic dredgings to reinstate the river bed to its natural condition.