Bevere Fish Pass

Bevere Fish Pass – Facts & Figures

Bevere is the second fish pass that twaite shad and other migratory fish meet on their way upriver. It is located in the village of the same name, 4 km northwest of Worcester city centre.

Construction work on the fish pass began in May 2019, just three months before work started at Diglis. It was the first fish pass to be completed out of the four built along the River Severn. In September 2020, Bevere fish pass was opened to the river.

The 100m long fish pass was designed by FishTek and Kier was the main contractor for the build. Scroll down to watch videos on how the fish pass was designed.

Bevere was most affected by flooding of all the fish pass sites. In 2019, record breaking floods shut the site down all winter and work could only resume in the spring, once the weather started to cooperate!

Why is Bevere the odd one out?

You might notice that Bevere looks a bit different compared to the other fish passes. Whereas Diglis, Holt and Lincomb fish passes are all deep vertical slot fish passes, Bevere fish pass is called a ‘nature-like bypass channel’.

It is so named because the shape of the fish pass and speed of the water running through it are designed to be similar to those of a natural river channel. Due to its rural location, there was enough land alongside the weir to create a long, low gradient channel, which rejoins the main river above the weir. This provides a gradually sloped ramp that fish can swim along to get past Bevere weir.

Having four nature-like bypass channels, like the one at Bevere, would have been the ideal solution at each of the 4 weirs. It is the preferred type of fish pass, as it mimics a river channel. However the space to build one wasn’t available at Diglis, Holt and Lincomb. Deep-vertical slot fish passes were the best option for these three sites. You can find out more about how a deep vertical slot fish pass works in our Understanding Fish Passes blog.

Slowing the flow

The gradient of Bevere fish pass is around 1.6%. Although this about 50% lower than the gradient of a deep vertical slot fish pass (such as at Diglis, Holt and Lincomb), compared to a natural river it is still quite high. So we needed a way to slow down the flow of the river even further, without compromising a fish’s ability to swim through the channel.

You will notice that there are a number of concrete blocks positioned in the fish pass. These blocks were cast into the base of the channel to slow the water down and break up the flow. This creates near-natural varied flow conditions, that fish, including the endangered twaite shad, can comfortably swim through.

The boulders create friction as water flows past it. The friction causes the water to slow down. The water drops around the boulder and energy is dissipated around the structure.

Other features of Bevere fish pass

Bevere fish pass was built with a lateral gradient, i.e. a deeper side and a shallower side. This mimics the river going around a bend. A river is always deeper around the outside of the bend, as the faster flow causes erosion, and shallower on the inside of the bend due to deposition.

The fish pass has a ‘reno mattress’ base. These are rocks encased in a wire metal frame, which create a rough riverbed at the base of the fish pass. Over time, the gaps in the rocks will have filled with sediment and vegetation. This will improve the habitat within the fish pass.

A special fabric was used to cover the side slopes adjacent to the fish pass, as a short term protection against bank erosion. Grass then grew through the fabric, and the roots of the vegetation helped to stabilise the banks.

Archaeology at Bevere

The fish pass and the access road (which was used to get materials and personnel to site) were built on a site of important archaeological interest. So all the excavation works were supervised by a team of specialist archaeologists. Satellite and aerial photographs indicated that there was evidence of Roman features in this field, so surveys were completed and great care was taken during excavations.

Sadly no dinosaur bones or lost treasure were discovered. But archaeologists did confirm a Roman ditch, which probably part of a stock enclosure; and interesting timbers were found which were likely related to the construction of Bevere weir in the 1840s.

Bevere Fish Pass – Facts & Figures

Why is Bevere the odd one out?

Slowing the flow

Other features of Bevere fish pass

Archaeology at Bevere

How this pass was designed

How this pass was built

Volunteering