The Rush, Sheep’s Green

Background: The Rush

 

Background: The Rush, as it is known locally, is a meandering watercourse that flows through Sheep’s Green nature reserve under the Fen Causeway and then into Coe Fen nature reserve, finally flowing into the Mill pond. It indicates the original meandering course of the river Cam, prior to it’s canalising to the feed the three Mills of the eighteen hundreds, which were situated where the Mill pub is presently. Over the years this stream had become mostly redundant for species due to extreme siltation. However it still had potential, if reinstated, it could become a route for fish to use to avoid the weir system thus increasing the biodiversity of the river.

This idea was championed by the Cam Valley Forum, funding was then secured through Cambridge City Council ( by using the ‘development contributions for informal public open space’ fund) and combined with a grant from the Environment Agency (Environment Programme to support England’s Biodiversity 2020 Strategy). The project was then delivered by the City Council in partnership with the Environment Agency, the aim to restore this neglected watercourse and let the fish do the rest!

The project:

Firstly the original sluice gate was replaced with a more up to date and eco-friendly model which secured increase year round flow. This increased and regular flow would help to reduce silt build up, increase the oxygen levels but also would in time expose the stream bed gravels. These gravels are vital spawning grounds for many fish species and an important element of a river system’s ecology.

 

There is a drop of level from the upper section of the river to the mill pond which had to be reduced and incorporated into the design of the Rush. This was accomplished by including two natural ramps, connected by pools, this spacing would allow fish to navigate safely and successfully up the stream. The rate of flow has to be managed in this way to create the right amount of volume to initially attract the fish but not too much to actually stop or hinder them. Not all fish species require the same conditions therefore a happy balance was needed to be made to encourage and support the widest group of species possible.

Digger digging river channel

This picture shows the specialist river contractors beginning the work. The original channel bed had to be raised to provide a suitable gradient for the fish to move upstream and through the existing pipe into the upper river section.

Sluice gate installed

This is the new automated sluice control structure being installed. This allows fish passage and can maintain a constant flow of water in the channel should the river level drop.

Dry river channel

Newly created channel prior to switch on. The logs protect against erosion by cattle, whilst the boulders provide slack water for fish to rest. Original bed gravels have been placed on top of the imported material.

Hazel faggots directing flow

Hazel faggots installed to concentrate the down stream flow and clear gravels for spawning fish.

Impacts:

Baseline ecological surveys have been undertaken throughout, including plants, invertebrates, fish and water voles. This helped to ensure species were protected during construction and then to monitor the continuing impact of the development.

 

electro fishing

The Environment Agency have monitored The Rush in 2016 and 2019 using the electro-fishing technique. Many fishes have been recorded; Pike, Dace and Chubb plus 13 other species of fish but also more significant species such as Brown Trout, Spined Loach and Eels. Their presence demonstrating that the conditions created had been a success.

Pike and Chubb fish

Pike and Chubb

 

 

Spined loach fish

The Spined loach.

 

grass snake in water

A Grass snake was spotted hunting the abundant fish fry in the newly wetted margins along with King Fishers, Grey Heron and Little Egrets.

Eel swimming

 

Eels have declined by 95% over the last 25years and therefore they were a welcome sight moving up the opened fish pass, this photo was taken within minutes of the water flowing.

automated sluice gate

 

The solar powered automated sluice gate. This inlet pool now supports a shoal of Dace and is now beginning to naturally soften and vegetate. Further down stream, locally sourced Crowfoot has been planted into the bed of the stream to provide cover for fish and invertebrates.

The margins allow water to escape from between the log reinforced banks to establish a more diverse marginal wetland flora.