River Cam restoration project

River Cam Restoration project

A group of 20 members and guests visited this project on 12 May 2010.  Our guide was Rob Mungovan, Ecology Officer of South Cambridgeshire District Council, who had developed the restoration plan.  The project has developed as part of the plan to build 1200 new houses nearby on the edge of Trumpington and create a 60 ha Community Park.  The aim is to provide an amenity, improve water quality and diversify the flow characteristics to improve biodiversity and enjoyment by visitors.  

This part of the river has a history of dredging, which has created artificial levees.  The river has become degraded by reduced water flow, following abstraction, which has allowed silting in some parts of the bed.  Water quality has recently improved slightly.  

The project has developed in collaboration with land owners following initial site investigation and hydraulic modelling.  We were shown breaches in the levees to allow flood water to spread over adjacent re-established meadows, an important part of the flood prevention part of the scheme which also aims to recreate water meadows and reed beds.   The river banks have been regraded in places and new gravel beds created adjacent to some of the breaks in the levees.  In addition, artificial gravel riffles have been positioned to raise the river bed and increase flow locally.  The river has also been reintegrated with the existing ditch system to create contrasting backwater habitats.  

This part of the river, just above Grantchester, is relatively slow flowing, so deflectors have been positioned on some bends to diversify flow and assist in silt scouring.  In contrast wooden revetments and debris have been placed along parts of the bank to provide shelter for fish from predators and high flows.

This was an especially interesting time to visit the project as some planting remains to be completed.  Most of the amelioration work has not yet had a chance to become fully integrated into the riparian ecology, although benefits of the project are already visible in variation of flows.  Some of the benefits of the scheme were already apparent with newly established water crowfoot and kingfisher seen by the group.